Browse Topic: Wet disc clutches

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Modeling and Design of a Wet Clutch Offset Compound Gear Transmission for Dual-Speed Rotorcraft ApplicationsF-0076-2020-1633610/5/2020
This paper develops a lumped-parameter multi-plates wet clutch Offset Compound Gear (OCG) transmission dynamics and its thermal model for dual-speed rotorcraft applications with an active clutch slip-speed control. This model includes the Reynolds equation for the clutch oil film thickness, the clutch thermal model, the clutch transferred torques (viscous and asperity torque) and the clutch disengagement model. The wet clutch/OCG transmission system is implemented in Matlab® Simulink™ to manage the upshift clutch temperature rise, which is a main issue need to handle for a dual-speed helicopter transmission. Here, the clutch temperature rise is treated by injecting a certain amount of coolant during engagement so that the temperature rise for the wet clutch is much lower than that of an dry clutch. In order to transfer a required torque using the available power, the sizing of the wet clutch could be evaluated via the developed wet clutch/OCG transmission model. This study shows that the temperature rise drops as the wet clutch oil flow rate increases adding extra weights compared with the dry clutch. The simulation also captures a phenomenon that a larger clutch engagement pressure might be required for the wet clutch to transfer the same torque since the wet clutch oil viscosity drops as the oil temperature increases during the clutch engagement.
DeSmidt, Hans, Bill, Robert, Su, Xiaowen, Smith, Edward
Coordination Control Strategy for Mode Switching of a Parallel Hybrid Electric System Based on Continuously Variable Transmission02-13-02-00108/11/2020
This study aims to solve the problem of impact in a parallel hybrid electric system based on the continuously variable transmission (CVT) during switching from pure electric mode to engine-driven, power-generating mode. Taking into account the torque response characteristics of the engine and motor and the dynamic characteristics of the wet clutch hydraulic control system, the mode switching process is divided into six stages, namely, pure electric mode, wet-clutch free travel, engine start-up, engine speed synchronization, clutch combination, and engine intervention drive. A coordination control strategy is developed based on the model predictive control algorithm to ensure smooth mode switching. The effectiveness of the control algorithm is verified using Matlab/Simulink and the AMESim co-simulation platform. Results show that with the mode switching coordination control strategy, the components of the system work harmoniously. The maximum impact is reduced by 52.0% at the speed synchronization stage and by 84.3% at the clutch coupling stage compared with the uncoordinated control situation.
Zeng, Xiaohua, Li, Xiaojian, Dong, Bingbing
Development of GM Allison 10-Speed Heavy Duty Transmission2020-01-04384/14/2020
This paper describes the development of the GM Allison 10-Speed Heavy Duty (HD) Transmission. The trend of increased towing capacity and engine horsepower in the automotive heavy-duty truck segment has been steadily climbing for the past 10 years. The development of 10-Speed HD Transmission is designed to be best in class in for towing performance in the 2500/3500 series segment while optimizing fuel economy. The 10-Speed HD Transmission also gives the customers the option to order an integrated power take-off (PTO) unit that benefits downstream installation of utility accessories such as hydraulic pumps, generators, etc.
Lee, Chi Teck, Ames, David, Caldwell, Brett, Knoth, Matthew, Reinhart, Timothy, Kelly, Jeffrey, Kannan, Rajesh, Tanasi, German
Optimized Control of Dynamical Engine-Start Process in a Hybrid Electric Vehicle2020-01-02684/14/2020
Engine start while driving is one of the most typical and frequent work conditions for hybrid vehicles. Engine start has very significant impact on the driving comfort. Engine start, especially a dynamical engine start, have high control requirements regarding control time, torque output and riding comfort. In some hybrid transmissions such as P2, engine is cranked and synchronized through wet clutch slipping. Because clutch pressure control has time-varying delay and estimation precision of engine torque by ECU (Engine Control Unit) is poor, conventional PID controller is unable to meet the high requirements of control quality. A new control algorithm is proposed in this paper to cope with all these challenges. The new control algorithm is based on LADRC (Linear Active Disturbance Rejection Controller) and is improved through combination with Smith predictor and Adaline network. LADRC is adopted to reduce negative effects of poor precision of engine torque. Smith predictor is introduced to compensate the time delay of clutch torque. In addition, the time-varying delay can be estimated by Adaline network and parameters of Smith predictor can also be adaptive adjusted.
Gao, Ji, Lou, Diming, Zhang, Tong
Characterization and Modeling of Wet Clutch Actuator for High-Fidelity Propulsion System Simulations2020-01-14144/14/2020
Innovations in mobility are built upon a management of complex interactions between sub-systems and components. A need for CAE tools that are capable of system simulations is well recognized, as evidenced by a growing number of commercial packages. However impressive they are, the predictability of such simulations still rests on the representation of the base components. Among them, a wet clutch actuator continues to play a critical role in the next generation propulsion systems. It converts hydraulic pressure to mechanical force to control torque transmitted through a clutch pack. The actuator is typically modeled as a hydraulic piston opposed by a mechanical spring. Because the piston slides over a seal, some models have a framework to account for seal friction. However, there are few contributions to the literature that describe the effects of seals on clutch actuator behaviors. In a routine simulation, a spring constant is commonly tuned to match vehicle data, assuming that it captures the effects of seal friction. The validity of this approach is not well established. This article describes the characterization and empirical modeling of a wet clutch actuator. The effect of seal friction is examined in detail during stroking and de-stroking. It is found that the seal friction is highly non-linear and directional. It introduces a significant error in clutch applied force calculation unless seal friction is explicitly accounted for. Propulsion system simulations are conducted to demonstrate the significant impact of seal friction on clutch operation and the quality of simulations. A framework of a new actuator model is proposed to represent seal friction based on empirical observations of its complex behaviors.
Haria, Hiral, McCallum, James, Fujii, Yuji, Tsuchiya, Takahiro, Miyagawa, Masatoshi, Nakamura, Shinji, Wendel, Matthew, Katopodes, Nikolaos
Dynamics and Control of Gearshifts in Wet-Type Dual Clutch Transmission for BEVs2020-01-07674/14/2020
The dual clutch transmission is one of the possible choices for electric vehicle drivelines. The basic principle and control mode of shifting of wet dual clutch transmission are introduced, and the dynamic process of shifting of wet double clutch transmission is studied. Combined with the dynamic model of the wet clutch engagement process, the difference between the dynamic characteristics of the dual clutch transmission modeling using the Coulomb friction model and the dual-clutch transmission model using the average flow model and the micro-convex contact theory is analyzed. The shift control strategy of the dual clutch transmission proposes a correction method to improve the shifting smoothness. Studies have shown that the torque response of the wet clutch has significant hysteresis, and the improved control algorithm can significantly improve the shifting smoothness of the wet dual clutch transmission. Based on the dynamic model of the wet clutch, the torque interruption of the shift control strategy of the dual clutch transmission is studied, and the method of improving the shift smoothness by the correction of the shift control strategy is proposed.
Lou, Zhenxiong, Duan, Yupeng, Zhang, Yunqing
Optimized Wet Clutch Design2019-32-05531/24/2020
Multi-plate wet clutches used in motorbikes transmit the torque by friction under pressure between driving and driven Plates. The life & performance of the clutch for the friction material used, depends on amount of energy generated during clutch slip, amount & uniformity of heat dissipation amongst the plates and surface texture of mating surfaces. Above parameters if not properly considered during design stage may lead to higher temperature of rubbing surfaces. Higher temperature further reduces the friction coefficient and increases the wear rate of friction material leading ultimately to lower torque capacity of clutch. The temperature rise in a wet clutch is the balance between amount of heat generated and the amount of heat dissipated by oil flowing through clutch. The maximum amount of oil is limited by the requirement of clutch drag torque, Which decides the quality of neutral finding and gear shift feel on vehicle. Further, if roughness of rubbing surfaces is not controlled in mass production, it leads to fast wear of friction material during initial operating cycles. The rate of wear is faster if the heights of surface asperities are of high magnitude. This paper explains the design features of clutch developed by Endurance Technologies Ltd., optimized to achieve above aspects, for the engines having clutch cooling oil supply through the gear box input shaft. I. An innovative oil management concept is incorporated which distributes the oil as per requirement amongst the plates. Adequate distribution of oil facilitates to have optimum oil flow with minimum desired drag torque. It also ensures effective heat dissipation throughout the clutch assembly. A part of oil is directed to cool the clutch clamping springs which reduces the clamping load loss. II. The validation procedure to confirm the adequacy of oil flow through the plurality of plates is developed. III. The defined controlled surface texture of steel plates provides consistent and controlled wear rate in mass production. Further, it ensures the dynamic torque capacity within a narrow band over the longer life span. The above two features of multi-plate wet clutch design achieved reduction in wear by 56 % and improved dynamic torque capacity by 16 % at the end of durability tests.
Bhone, Nitin, Thakare, Sachin, Jahagirdar, Ashutosh
Inside Tremec's SUPERCAR DCT20AUTP02_041/1/2020
To polish the 2020 mid-engine Corvette's driving prowess, GM and Tremec engineers joined forces to create a new and better automated transaxle. Explaining Corvette's move to one transmission for all buyers, global chief engineer Tadge Juechter notes, “Our customers began requesting a dual-clutch automatic transmission [DCT] several years ago. Following the introduction of the C7 Corvette in 2014, our take-rate for sticks [manual gearboxes] fell from 50 percent to less than 20 percent this year.” Searching the globe - read Europe - for a suitable DCT, Juechter's team found none with sufficient torque capacity to survive behind the lively LT2 6.2-L V8 planned for the all-new 2020 mid-engine edition of GM's reimagined sports car. To solve that dilemma, discussions began with Tremec, the Mexico City-based manufacturer which has supplied GM, Ford and FCA with manual transmissions for two decades. While Tremec had the expertise to make the mechanical components packed inside a dual-clutch box, the automated half of the equation - mechatronic actuators to engage the clutches and shift the gears - was beyond their ken. Tremec filled that need in 2012 by purchasing Hoerbiger Drivetrain Mechatronics, a Belgium-based supplier of electronic dual-clutch actuators with a customer list including AMG-Mercedes, Ferrari and McLaren.
Sherman, Don
Advanced Bench Test Methodology for Generating Wet Clutch Torque Transfer Functions for Enhanced Drivability Simulations2019-01-234012/19/2019
A wet clutch continues to play a critical role for step-ratio automatic transmissions and finds new utilities in hybrid and electrified propulsion systems. A torque transfer function is often employed in practice for sophisticated clutch slip controls. It provides a simple, yet practical framework to represent clutch torque as a function of actuator force. An accurate transfer function is also increasingly desired in today's vehicle design process to enable upfront assessment of clutch controls through simulations. The most common approach is based on Coulomb's linear friction model, where the coefficients are adaptively identified based on vehicle data. However, it is generally difficult to tune Coulomb's model for hydrodynamic behaviors even if the reference vehicle data are available. It also remains a challenge to produce in-vehicle clutch behaviors on a component test bench to determine realistic transfer function before prototype vehicles are built. SAE#2 test procedure is the industry standard for evaluating clutch frictional behaviors. It is a viable tool for durability assessment, but not designed to characterize hydrodynamic behaviors for clutch controls. This research focuses on the development of a methodology to generate realistic clutch transfer functions using an advanced engagement bench tester. The test stand is equipped with programmable slip and force controllers to replicate both torque phase and inertia phase of gear shifting. It accommodates a clutch module, not only the clutch pack, to reproduce actual in-vehicle lubrication conditions. The clutch behaviors are characterized for various combinations of operating conditions. The bench test data are compared with SAE#2 data to highlight the sensitivity of hydrodynamic behaviors to force and slip profiles. A regression technique is utilized to represent clutch behaviors as a transfer function in non-linear forms using data from the advanced tester. Shift simulations are conducted to demonstrate the value of realistic transfer functions to enable upfront drivability assessment for control development.
Haria, Hiral, Fujii, Yuji, Pietron, Gregory M., Sun, Anna, Tsuchiya, Takahiro, Miyagawa, Masatoshi, Nakamura, Shinji, Wendel, Matthew, Miyoshi, Hiroya, Wang, Pengchuan, Katopodes, Nikolaos
Integrated Multi-Physics Simulation for Full-Vehicle Low Frequency NVH Optimization in HEVs2019-01-14556/5/2019
The recent automotive industry trend towards electrification has created new challenges for NVH engineers. These challenges stem from new powertrain architectures and their complex interactions, the governing control strategies which aim to optimize energy management, and new unmasked sources of excitation. Additionally, vehicle manufacturers are attempting to reduce hardware testing in order to rapidly satisfy increasing production demand and to minimize its costs. Hence, to meet the above-mentioned challenges up front in the development process of Hybrid Electrical Vehicles (HEVs) while balancing competing design objectives of drivability, durability and NVH, a simulation-led design and optimization is required. NVH problems are often the result of mechanisms that originate through complex interactions between different physical domains (flow, electromagnetic, structural/mechanical, control logic, etc.) and the assembly of individual components into a complete system. Therefore, accurate system-level integrated models are becoming a requirement to solve modern NVH problems. Combining the optimal balance between simulation and experimental data, this article describes a joint effort between Ford and Gamma Technologies to develop a general methodology to perform full-vehicle low frequency NVH analysis. Using GT-SUITE software, a non-linear multi-physics simulation model of a rear wheel drive HEV was created. The model was exercised to accurately evaluate the effects of powertrain control strategy and component selection on low-frequency NVH performance during a tip-in regeneration, downshifting and in-gear acceleration maneuvers while minimizing the computational cost.
Gomez, Llorenc Foraste, Zeman, Jonathan, Liu, Jack
Analytical Estimation of Clutch Life for Manual Transmission2019-01-03354/2/2019
The clutch is the connecting link between engine and the power train. It connects and disconnects the engine to the gearbox as per the wish of the driver. Clutch has a friction disc which acts like a fuse wire which wears in the process of the connection. This paper tries to calculate the clutch life analytically (In terms of Kms. run by vehicle), of automotive vehicles having manual transmission. As the clutch engages and disengages the engine to the gearbox, during this time due to slippage, energy is dissipated which results in the wear of the clutch disc. It calculates life based on the volumetric wear of the clutch disc and wear allowance available. The work done by other people in this domain include the empirical estimation of clutch life based on the past data, effect of the surface topography on the friction characteristics of the wet clutches, modeling of clutch housing and facing temperature for the estimation of the clutch life of a manual transmission etc. The present work simplifies the estimation of clutch performance using fundamental principles, without high end analysis software or past data. It helps to estimate the clutch performance in the concept stage itself thereby saving time and labor making the selection of the right clutch at the very first time. The complete work was done in-house and its purpose was to estimate the life of the clutch in terms of vehicle run in Kms. The results estimated were closely compared with respect to the field data of vehicles. This tool will be of immense help in such a fast changing automotive world where competition is cut-throat and product development time is shrinking continuously.
Mishra, Anurag, Chollangi, Damodar
Development of a Low Loss Clutch for CVT Reverse Function2019-01-07744/2/2019
Continuously variable transmissions (CVT) provide superior fuel economy by enabling internal combustion engines to operate at their “sweet spots”. However, there is still potential to improve CVT system’s mechanical efficiency, and further enhance vehicle-level fuel economy. In the past, extensive research work has focused on the core continuously variator unit (CVU) that includes pulleys and a belt or chain. Another thread of research has centered on optimization of CVT clamping force control to reduce hydraulic system loss. Nonetheless, to the best of our knowledge, very little research has looked into the planetary gear sets and clutches that enable the CVT system to switch between forward, neutral and reverse gears. The state-of-the-art reverse clutch usually consists of multiple friction and steel plates, and is normally open during all forward driving maneuvers. The relative speed between friction and steel plates is identical to turbine speed, which generate spin loss. We believe there is an opportunity to improve the CVT system mechanical efficiency by replacing the reverse plate clutch with a low loss clutch, for example a binary clutch. At first, we studied the theoretical spin loss associated with plate clutches. Secondly, we identified the most challenging shifting maneuver using the lever diagram analogy. Thirdly, we proposed a control strategy to address the most critical rolling garage drive-to-reverse shift, and conducted one-dimensional simulation using an AMESim model to validate our strategy by comparing our simulation result with available vehicle data. At last, we obtained spin loss data from dynamometer testing to evaluate the potential fuel economy benefit.
Duan, Chengwu, Lee, Chunhao, Yao, Jian, Samie, Farzad, Huang, Ying
Development of Empirical Asperity Contact Model for Wet Friction Material2019-01-03464/2/2019
A wet clutch couples or decouples gear elements to alter torque paths in an automatic transmission system. During the gear shifting event, the clutch torque is directly transmitted to the output shaft. Hence, clutch torque heavily influences the dynamics of the transmission. In order to evaluate the behavior of the transmission early and efficiently, the development process increasingly relies on high-fidelity transmission system simulations with added complexity. However, a wet clutch continues to be modeled using Coulomb’s friction in a typical shift simulation. Its linear framework does not physically represent non-linear hydrodynamic effects due to the presence of oil layer during clutch engagement. To make up the lack of physics, Coulomb’s clutch model often requires extensive tuning to match actual shift behaviors. Alternatively, a squeeze film based clutch model, coupled with an asperity contact model, can be employed to represent hydrodynamic behaviors and enable the broader use of dynamic simulation models in transmission development. However, while the squeeze film model has been extensively studied over the years, the asperity contact model remains largely unexamined. In this research, the contact behaviors of the asperities are empirically characterized for a wet clutch friction material. The results are compared against the base theory of Greenwood-Williamson asperity contact model (GW model) which is commonly accepted in wet clutch modeling. The analysis shows that the key assumptions of GW model, specifically the elastic deformation of spherical asperity tip and Gaussian distribution of their heights, do not hold for clutch friction materials. A new empirical asperity contact model is developed for wet friction material based on asperity roughness characterization and microscopic contact area measurements. The empirical model provides an accurate representation of asperity behaviors in wet clutch modeling, as an alternative to the conventional GW model, for high-fidelity transmission system simulations. The modeling framework is also applicable to a broad range of friction materials used in dry clutches, brakes and other applications that are characterized with hard constituents embedded in an elastic matrix.
Haria, Hiral, Fujii, Yuji, Pietron, Gregory M., Miyagawa, Masatoshi, Tsuchiya, Takahiro, Nakamura, Shinji, Wendel, Matthew, Miyoshi, Hiroya, Hou, Shiyang, Wang, Pengchuan, Katopodes, Nikolaos
Modeling, Control, and Adaptation for Shift Quality Control of Automatic Transmissions2019-01-11294/2/2019
The parameters determining shift quality control in automatic transmissions are determined as part of the calibration of the transmission control. The resulting control system typically has three components: feedforward control, where the control output is determined before a gearshift; feedback control, where the control output is determined during the gearshift based on sensed feedback; and learning control (adaptation), where the feedforward or feedback controller parameters are modified after the current gearshift has ended and before the next similar gearshift begins. Gearshifts involving the same ratio change are referred to here as similar gearshifts, though such gearshifts may involve differences in other variables such as vehicle speed or engine torque. In most automatic transmissions, gearshifts are controlled by hydraulic clutches, and operating conditions for these clutches may vary widely, requiring a dedicated transmission controller involving significant calibration effort. In the current work, novel model-based methods are used to accomplish feedforward control of gearshifts, involving offline calibration of fill and torque phase control parameters and learning control of the fill phase. Towards this end, a physics-based model of the oncoming clutch involved in an upshift of a production automatic transmission was developed and experimentally validated against test bench experiments for a wide variety of inputs and operating conditions. The resulting model is used to generate a feedforward controller, offline model-based calibration algorithm, and a learning controller that corrects for clutch under-fill and over-fill. The effectiveness of the resulting controller is validated by simulation studies using the experimentally validated transmission hydraulic system model, in conjunction with a powertrain model. In particular, it is demonstrated that the learning controller corrects for initial under- or over-fill error in two to three gearshifts. Convergence and robustness properties, and transient performance of the learning controller are also discussed.
Mishra, Kirti Deo, Cardwell, Gilbert, Srinivasan, Krishnaswamy
Application of Empirical Asperity Contact Model to High Fidelity Wet Clutch System Simulations2019-01-13014/2/2019
Wet clutches are complex hydrodynamic devices used in both conventional and electrified drivetrain systems. They couple or de-couple powertrain components for applications such as automatic shifting, engine disconnect and torque vectoring. Clutch engagement behaviors vary greatly, depending on design parameters and operating conditions. Because of their direct impact on vehicle drivability and fuel economy, a predictive CAE model is desired for enabling analytical design verification processes. During engagement, a wet clutch transmits torque through viscous shear and asperity contact. A conventional Coulomb’s model, which is routinely utilized in shift simulations, is inadequate to capture non-linear hydrodynamic effects for higher fidelity analysis. Extensive research has been conducted over the years to derive hydrodynamic torque transfer models based on 1D squeeze film or 3D CFD. They are typically coupled with an elastic asperity contact model for mechanical torque transfer. However, the recent advancement reveals no significant asperity deformation at the frictional surface during engagement and establishes a new empirical asperity contact model. This paper describes the integration of the empirical asperity contact model with CFD for developing a high-fidelity wet clutch engagement model. The asperity models are examined in detail for four friction materials to highlight distinct contact behaviors. They are coupled with 3D CFD model in OpenFOAM for engagement simulations, demonstrating the importance of selecting the right asperity model for predictive clutch analysis. A breakdown of hydrodynamic and mechanical torques is provided, enabling numerical examination of clutch engagement processes. Simulation results are compared with clutch module test data that is specifically designed to replicate actual shifting conditions. It is found that accurate simulation of a complete clutch system requires not only engagement physics, but also in-depth understanding of actuator characteristics such as seal drag.
Haria, Hiral, Fujii, Yuji, Pietron, Gregory M., Wang, Pengchuan, Katopodes, Nikolaos, Miyagawa, Masatoshi, Tsuchiya, Takahiro, Nakamura, Shinji, Wendel, Matthew, Miyoshi, Hiroya
Necessity of Advance Damper Technology for Future Agriculture Domain2019-26-01931/9/2019
There is an increasing demand from end-users of tractors for longer clutch durability, reduction in driver fatigue and comfort during field operations. Tractor manufacturers are moving towards Wet Clutch Pack with torsion dampers to meet this emerging customer needs. However, in Conventional Torsion Dampers, there is a technical challenge to withstand harsh clutch engagement or high unexpected impacts of agri-implements, which are common in field operations. This is in addition to, torsional vibrations produced by the power-train. There are constraints, to further optimize a conventional damper without compromising important parameters like factor of safety, noise and durability issues. Hence the proposed next generation damper technology can meet all the new technical requirements and can ensure smooth and durable power shift transmission in tractors. This case study has been done with help of SCHAEFFLER’s tailor made “Tornado Instrument” and “Software” by acquiring real time data (directly from agricultural field operations) from several OEMs followed by quantitative analysis of unexpected impacts, and addressing this issue with next generation damper technology.
Bagadekar, Vijaykumar Shankar, Alavilli, Satya Pavan, Kadhar Maideen, Salim Malik, Rajendran, Ashok Kumar, Radhakrishnan, Padmanaban, Soni, Sandeep
The Influence of Friction Modifiers in Fully Formulated Motorcycle Engine Oils2018-32-002410/30/2018
Globally, emissions legislation placed on motorcycles is becoming ever more stringent [1]. One way of meeting these new regulations is to use friction modifiers (FMs) in the engine oil to reduce frictional losses in the engine. This is, however, complicated by the fact that many motorcycles use a common oil sump for both the engine and a lubricated clutch. It is often the case that if a FM reduces friction in a steel/steel contact it will also reduce friction in a steel/friction material contact. Therefore, it is usually viewed that there will be a necessary compromise between maximizing engine efficiency and maintaining efficient clutch performance. In this paper we examine the effect of a range of organic FMs on commercial fully formulated motorcycle engine oils (MCOs) using benchtop tribotests and full-scale rig tests (SAE #2 clutch test machine). The results show that by careful selection of appropriate FM chemistry it is possible to reduce steel/steel friction whilst maintaining clutch performance. To obtain a deeper understanding of the effect of FM chemical structure on the clutch friction performance the friction-speed (μ-v) behaviour of a commercial MCO formulation is investigated. It is found, in agreement with previous studies, that a lower amount of branching in the alkyl tail of an organic FM corresponds to a positive correlation between friction and speed of the type usually desired in an automatic transmission fluid (ATF). This contrasts with the μ-v behaviour of a commercial MCO intended for use in motorcycles with a wet clutch, which shows almost no correlation between friction and speed. This insight could be used to help rational design of new OFMs for motorcycle oils.
Gillespie, David, Moody, Gareth, Viadas, Aitziber
Drag and Cooling Characteristics of Circular Pin-Fin Groove Pattern of a Multi-plate Clutch Pack Using CFD2018-01-03874/3/2018
A numerical analysis of drag torque and cooling characteristics of a Multi-plate clutch pack with a circular pin fin shaped groove pattern is presented in this article. Simulations were performed using Simerics MP® platform to investigate the drag torque and heat transfer under various operating conditions. The performance characteristics of the circular pattern were later compared with various designs from the literature. Some of the groove pattern designs considered have been commonly used in transmission systems and some are from the patent literature. This study compares each design and later proposes the most efficient, that has the least drag and highest heat transfer characteristics.
Yashwanth, Bangalore Lingaraj, Ngo, Dinh, Schroeder, Debera, Hopson, Brian, Wang, De Ming
Electro-Hydraulic Shuttle Transmission and Control for Tractors with Non-Electronic Engine2018-01-03904/3/2018
Recently, emerging technological developments in powertrain were mostly accompanied with electronics for efficient and precise control of various powertrain systems like engine, transmission, hydraulics, etc. Agricultural tractors are of no exception to this context. Most of the higher horsepower tractors above 50 HP are equipped with modern transmission systems such as Power-shuttle, Power-shift etc. having their wet clutch transmission and diesel engine controlled by an Electronic Control Unit. This is possible only with an engine that receives and provides electronic signals. Whereas a tractor with mechanical (non-electronic) engine is of predominant use in the Indian farm lands due to their low cost and immediate availability compared to that of an engine equipped with high-end electronics. Hence, there is a demand for low cost drivetrain with improved controls and without engine electronics. This research work depicts on one such development, where an effective power shuttle transmission system and controls were developed for a non-electronic engine tractor. The multi-plate wet clutch shuttle transmission is electro-hydraulically controlled, thus eliminates the operator fatigue due to frequent clutch pedal application with improved vehicle launch and smooth shuttle shift ability. This research work also address the safety features for protecting and increasing the life of system components like clutch slippage, energy dissipation, power consumption. Additional system protection was also done through fault mode diagnosis via safety features such as anti-stalling, speed cut off shuttling, wrong direction detection, etc with minimal sensors and powertrain components.
Rajagopal, MahendraMohan, M A, Velmurugan
Simulation to Estimate the Output Torque Characteristics and Temperature Rise of a Transmission Wet Clutch during the Engagement Process2018-01-04024/3/2018
During a typical shift event, one or more clutches are brought to engagement while others are released in order to change the torque transmission path. A mismatch in torque level and handshake timing between the off-going and on-coming clutches affects the shift quality. In order to capture the dynamic behavior of the torque response and estimate the temperature rise at the friction disk and separator plate interfaces during the engagement process, several numerical models have been developed. The earliest of these models was presented by Berger et al. which was later modified and enhanced by Natsumeda et al. and Yang et al. However, these models cannot capture the dynamic behavior of grooved clutch disks. Hence, development of a wet clutch engagement simulation model using commercial CFD simulation tool, which can capture the dynamic behaviors of no groove and grooved disks, becomes a pressing need. In this paper, we have presented an engagement simulation model using Star CCM+ simulation software and also discussed our observations from the simulation results. The key input parameters are squeeze velocity of the oil film, oil inlet temperature, initial rotating speed and flow rate. The porosity of the friction materials, friction co-efficient, compressive strain and flow factors are also taken into account. Our simulation model provides a helpful means to realize the influence of oil flow rate, rotating speed, applied pressure and groove patterns on the output torque behavior and temperature rise.
Mahmud, Syeda Faria, Pahlovy, Shahjada A., Ogawa, Makoto
Power Transfer Unit Gear Rattle Assessment Using AMESim-ADAMS Co-simulation2018-01-06794/3/2018
The Power Transfer Unit (PTU) provides full time, part-time or on-demand All-Wheel-Drive (AWD) torque distribution for Front-Wheel-Drive (FWD) based AWD systems. FWD has advantage in drivetrain efficiency and fuel economy, while AWD improves traction to have better acceleration and handling. Part-time and on-demand AWD have all the benefits of AWD and the efficiency of FWD. So AWD vehicle option continues to be popular around the world. However, Noise, vibration and Harshness (NVH) error state called PTU rattle has been detected in FWD mode of AWD systems due to torsional excitation. This study is one of the first to be focused on the PTU gear rattle as a NVH error state so far. We developed an AMESim-ADAMS co-simulation model for understanding PTU gear rattle phenomenon through drivetrain torsional responses (i.e. rotational degree of freedom, DOF) in system and PTU rattle assessment through PTU case vibration. The correlated one-Dimensional (1-D) torsional model simulating the operation condition of PTU rattle provides the torsional input to excite ADAMS three-Dimensional (3-D) PTU model to recover PTU case vibration. Hence, PTU rattle can be assessed in Computer-aided Engineering (CAE) analysis by applying the target defined from test data with respect to PTU case vibration. The critical measurements for correlation are also investigated and treated as indicators. This co-simulation model will be capable of evaluating PTU rattle risk and developing countermeasures. In the future we plan to study the PTU case boundary condition, as an example, to improve the case vibration level of the non-rattle region.
Huang, Hsun-Hsuan, Sun, Wulong, Juang, T. Bin
In-Vehicle Characterization of Wet Clutch Engagement Behaviors in Automatic Transmission Systems2018-01-03954/3/2018
A new generation of a planetary-gear-based automatic transmission system is designed with an increasing number of ratio steps. It requires synchronous operation of one or more wet clutches, to achieve a complex shift event. A missed synchronization results in drive torque disturbance which may be perceived by vehicle occupants as an undesirable shift shock. Accurate knowledge of clutch behaviors in an actual vehicle environment is indispensable for achieving precise clutch controls and reducing shift calibration effort. Wet clutches are routinely evaluated on an industry-standard SAE#2 tester during the clutch design process. While it is a valuable tool for screening relative frictional behaviors, clutch engagement data from a SAE#2 tester do not correlate well with vehicle shift behaviors due to the limited reproducibility of realistic slip, actuator force profiles, and lubrication conditions. Advanced clutch testers with programmable slip and force controller are available for replicating torque phase and inertia phase of shifting. However, it remains a challenge to substantiate bench test data in the absence of actual clutch behaviors observed in a vehicle. This article describes the in-vehicle characterization of wet clutch engagement torque, with a focus on temperature effects during gear ratio changing. Clutch torques are accurately identified based on transmission torque measurements at input and output shafts. The analysis shows that the relationships between actuator force and clutch torque are highly non-linear with respect to transmission oil temperature, demonstrating the importance of in-vehicle clutch characterization for robust shift control. Furthermore, a squeeze film analysis is conducted to provide physical insight into clutch behaviors during torque transfer phase of shifting, where Coulomb’s linear friction model is not applicable.
Haria, Hiral, Pietron, Gregory M., Meyer, Jason, Fujii, Yuji, Wang, Pengchuan, Katopodes, Nikolaos
Electronic Bi-Directional Shift Control Design and Calibration for Farm Vehicle2017-01-220510/8/2017
Agricultural tractors are often subjected to various applications like front end loading work, cultivation work, where frequent forward and reverse gears are needed. Most of Indian agricultural tractors are equipped with mechanical transmission system which demands repeated clutching and de-clutching operation for such applications resulting in increased operator fatigue and lesser productivity. Also need of electronics in Indian agricultural industry for better farm mechanization is growing high. This research work depicts development of electronic bi-directional shifting (power shuttle) control design and calibration for farm vehicle fitted with wet clutch transmission. This research also reduces operator fatigue via frequent directional shift through electronic transmission. The control system is designed without any electronic interfacing with engine and also provides clutch-less gear shifting and auto-launch which offers ease to drive even for novice driver. The power shuttle transmission control system offers more functionality and features in adjunct to in-built safety features without any additional sensors or components. Use of minimal sensor for system control and calibration delivers cost effect solutions. Adaptive control strategy is adopted for achieving efficient and optimal clutch fill modulation which is calibrateable for various climatic zone, vehicle loads, gears etc. Control software is designed by considering the vehicle variants pertinent to clutch load and engine characteristics. Modular control system design is employed in this research which can be extended across all tractor variants.
M A, Velmurugan, Rajagopal, MahendraMohan
Statistical Modeling of Plate Clearance Distribution for Wet Clutch Drag Analysis06-11-01-000710/8/2017
Wet clutch packs are the key component for gear shifting in the step-ratio automatic transmission system. The clutch plates are coupled or de-coupled to alter gear ratios based on the driver’s actions and vehicle operating conditions. The frictional interfaces between clutch plates are lubricated with automatic transmission fluid (ATF) for both thermal and friction management. In a 10-speed transmission, there may be as many as 6 clutch packs. Under typical driving conditions, 2 to 3 clutch packs are open, shearing ATF and contributing to energy loss. There is an opportunity to improve fuel economy by reducing the associated viscous drag. An important factor that directly affects clutch drag is the clearance between rotating plates. The axial position of clutch plates changes continuously during operation. It is known in practice that not only the total clearance, but also its distribution between the plates affects the viscous drag. However, it is very difficult to measure the actual distribution for every clutch in a running transmission. Because of the limited theoretical understanding of plate movement, a fine tuning of clutch clearance design is often conducted based on trial and error during a vehicle’s development process. This article describes a statistical method for modeling the distribution of the plates in a clutch pack. The proposed method employs order statistics to represent dynamically-changing plate positions. A simulation study is conducted to investigate the effects of plate movement on open clutch drag in the slip region where ATF is present at the interface. It is shown that the model can predict the difference in drag torque with or without fixed clutch plates. The simulation results compare satisfactorily with experimental data. The model provides a mathematical insight into complex plate behaviors for open clutch drag torque analysis. The use of such a statistical model improves the fidelity of a drive cycle simulation for up-front examination of drivetrain efficiency, thus practitioners can take the impact of clearance into consideration when calibrating open clutch models.
Wang, Pengchuan, Katopodes, Nikolaos
Combined Spatter and Immersion Type Oil Cooling System for Multi Disc Wet Clutch Transmission in Tractors2017-28-19767/10/2017
The utility of tractors in India has grown and is growing. Other than in agricultural area, it finds use in non-agricultural and construction/ earthmoving applications like loaders, dozers, power source, etc. The tractors that are subjected to heavy duty cycles are mostly with conventional dry type clutches. These types of dry clutch when operated in heavy application generate large amount of heat within shorter period of time on the surface of friction discs. This increase in disc surface temperature weakens the friction material property & bonding element leading to deterioration and decreasing the life of clutch. This curtails the clutch life extensively and is a big challenge to farmers and tractor users. The frequent clutch failures not only increases the operating cost, but also the servicing of clutches in the tractor fitted with heavy attachments leads to a higher downtime and service cost. To overcome this challenge, an innovative solution in the oil spatter concept has been evolved to provide active circulation of oil to the multi disc wet clutch friction discs while in engaged conditions. The system is designed in such a way that it cut-off the oil flow in to the clutch unit while clutch is disengaged. This oil spatter system evenly carries away the heat generated across friction & steel disc surface through the groove patterns in the discs. This combined spatter and immersion type oil cooling provides improved heat removal and significantly reduces the drag torque and reduces power loss. This oil spatter clutch system will provide a fit and forget trouble free clutch system to farmers with significantly higher ROI.
Narayana Rao, Suresh Kumar
Tribodynamics of a New De-Clutch Mechanism Aimed for Engine Downsizing in Off-Road Heavy-Duty Vehicles2017-01-18356/5/2017
Clutches are commonly utilised in passenger type and off-road heavy-duty vehicles to disconnect the engine from the driveline and other parasitic loads. In off-road heavy-duty vehicles, along with fuel efficiency start-up functionality at extended ambient conditions, such as low temperature and intake absolute pressure are crucial. Off-road vehicle manufacturers can overcome the parasitic loads in these conditions by oversizing the engine. Caterpillar Inc. as the pioneer in off-road technology has developed a novel clutch design to allow for engine downsizing while vehicle’s performance is not affected. The tribological behaviour of the clutch will be crucial to start engagement promptly and reach the maximum clutch capacity in the shortest possible time and smoothest way in terms of dynamics. A multi-body dynamics model of the clutch system is developed in MSC ADAMS. The flywheel is introducing the same speed and torque as the engine (represents the engine input to the clutch). The hydraulic pressure is applied behind the piston to initiate the engagement. The angular motion of the plates is supported by friction torque between the plates and friction linings. The conjunctions between paper-based linings and steel plates are designed to be dry. Friction (the most significant tribological feature of the linings in torque transmission) is measured in a pin-on-disc tribometer and mapped into the dynamics model in MSC ADAMS. The pin-on-disc tribometer is able to capture the variation of friction coefficient with contact pressure and sliding velocity. The surface topography is obtained experimentally to examine the consistency of surface properties. The normal pressure and tribology of the contacting components determines the engagement time, clutch capacity and dynamic behaviour of the clutch.
Dolatabadi, Nader, Rahmani, Ramin, Theodossiades, Stephanos, Rahnejat, Homer, Blundell, Guy, Bernard, Guillaume
Traditional and Electronic Solutions to Mitigate Electrified Vehicle Driveline Noises2017-01-17556/5/2017
Hybrid powertrain vehicles inherently create discontinuous sounds during operation. The discontinuous noise created from the electrical motors during transition states are undesirable since they can create tones that do not correlate with the dynamics of the vehicle. The audible level of these motor whines and discontinuous tones can be reduced via common noise abatement techniques or reducing the amount of regeneration braking. One electronic solution which does not affect mass or fuel economy is Masking Sound Enhancement (MSE). MSE is an algorithm that uses the infotainment system to mask the naturally occurring discontinuous hybrid drive unit and driveline tones. MSE enables a variety of benefits, such as more aggressive regenerative braking strategies which yield higher levels of fuel economy and results in a more pleasing interior vehicle powertrain sound. This paper will discuss the techniques and signals used to implement MSE in a hybrid powertrain equipped vehicle. MSE utilizes powertrain signals from the vehicle bus to determine which harmonics need to be veiled and at what output level. By enhancing and complementing the naturally occurring electric propulsion sounds, it’s possible to create a more continuous and rich hybrid powertrain sound through the hybrid transition states. As MSE is adding noise to improve the overall sound in the vehicle, this feature can also be utilized to make the vehicle sound heartier and more refined for acceleration or deceleration events while simultaneously masking unwanted tones. The MSE concepts discussed in this paper are covered under US patent 9237399.
Valeri, Frank C., Lagodzinski, James T., Reilly, Scott M., Miller, John P.
Two-Phase MRF Model for Wet Clutch Drag Simulation2017-01-11273/28/2017
Wet clutch packs are widely used in today’s automatic transmission systems for gear-ratio shifting. The frictional interfaces between the clutch plates are continuously lubricated with transmission fluid for both thermal and friction management. The open clutch packs shear transmission fluid across the rotating plates, contributing to measurable energy losses. A typical multi-speed transmission includes as many as 5 clutch packs. Of those, two to three clutches are open at any time during a typical drive cycle, presenting an opportunity for fuel economy gain. However, reducing open clutch drag is very challenging, while meeting cooling requirements and shift quality targets. In practice, clutch design adjustment is performed through trial-and-error evaluation of hardware on a test bench. The use of analytical methodologies is limited for optimizing clutch design features due to the complexity of fluid-structure interactions under rotating conditions. This article presents a two-phase Multiple Reference Frame (MRF) CFD model for simulating wet clutch behaviors, accounting for detailed design geometry. The model employs the Volume of Fluid (VOF) method to determine the air-fluid interface inside a computational domain. Model setup and simulation parameters, including initial conditions, boundary conditions, and relaxation factors are evaluated in terms of convergence behaviors. The model capabilities are validated against experimental data. Convergence of the CFD solver is demonstrated, capturing peak drag location as a function of rotating speed, until the phase fraction drops to a small value. The CFD model provides analytical insight into complex fluid interactions for grooved rotating plates, complementing hardware-based clutch design processes.
Fujii, Yuji, Wang, Pengchuan, Katopodes, Nikolaos
Development and Challenges of Electrically Selectable One-Way Clutches2017-01-11333/28/2017
This paper discusses new developments in the field of one-way clutches (OWC). These recent developments involve “Selectable OWC (SOWC)” actuating both hydraulically as well as electrically. The primary focus of this paper is a low-current consuming Electrical SOWC (eSOWC) used in hybrid transmission being designed and developed at Ford Motor Company. Other SOWCs currently being utilized across different applications at Ford are also discussed. Clutching devices represent significant cost, weight, size and drag-loss in automatic transmissions. However, implementation of SOWCs offers the potential to reduce transmission cost, size, weight, and spin loss; eSOWCs may also improve shift quality, reduce shift times, improve shift consistency and reduce OWC-related NVH. In Hybrid applications the electric motor(s) and SOWC create a system that is analogous to a manual transmission synchronizer. Similarly, in automatic transmissions SOWC are analogous to pump-solenoid-valve-friction-clutch system. In conclusion, this paper is intended to educate the reader on the development challenges and benefits associated with SOWC using analytical and empirical data.
Bird, Norman J., Bindra, Raunak, Klaser, Jacob
An Advanced Automatic Transmission with Interlocking Dog Clutches: High-Fidelity Modeling, Simulation and Validation2017-01-11413/28/2017
Fuel economy regulations have forced the automotive industry to implement transmissions with an increased number of gears and reduced parasitic losses. The objective of this research is to develop a high fidelity and a computationally efficient model of an automatic transmission, this model should be suitable for controller development purposes. The transmission under investigation features a combination of positive clutches (interlocking dog clutches) and conventional wet clutches. Simulation models for the torque converter, lock-up clutch, transmission gear train, interlocking dog clutches, wet clutches, hydraulic control valves and circuits were developed and integrated with a 1-D vehicle road load model. The integrated powertrain system model was calibrated using measurements from real-world driving conditions. Unknown model parameters, such as clutch pack clearances, compliances, hydraulic orifice diameters and clutch preloads were estimated and calibrated. Simulation results, such as vehicle acceleration, turbine speed, and output shaft speed, are reported and compared with the measured data to validate the transmission model. Subsequently, the transmission model was coupled with internal combustion engine and road load models. This arrangement permitted investigating the dog clutch engagement dynamics under transient conditions. The relative speed of the dog clutch halves was found to be highly sensitive to the transmission input torque, which indicates that a precise engine torque control schemes are necessary for successful engagement.
Alzuwayer, Bashar, Prucka, Robert, Haque, Imtiaz, Venhovens, Paul
Agile and Low-Cost Experimental Evaluation of Fuel Consumption Reduction of a New Electrified Clutch Transmission Virtually Connected to a Vehicle2017-01-10963/28/2017
Automated Manual Transmission (AMT) based on classic electrohydraulic clutch actuation gives high performances and comfort to a recreational vehicle. However, overall power consumption remains high due to the pump efficiency. In addition, the pump is often driven by the vehicle’s engine and thus is continuously working. To address this issue, a new electrified clutch based on electromechanical actuation has been designed and prototyped. In order to evaluate the effective fuel consumption reduction using this new clutch actuator, a low-cost and agile method is presented and used in this paper. Indeed, instead of integrating the clutch actuator in a real vehicle and performing expensive real emission test cycles on a road, this original method proposes to perform accurate semi-virtual emission test cycles. Moreover, the method allows to perform numerous test iterations in a short time. This consists in connecting the prototyped new electric clutch to a virtual vehicle in order to test it as it would be used in a real vehicle. A dedicated real-time rapid prototyping system (Opal-RT) runs the simplified vehicle dynamics and controls clutch algorithms to generate commands for the clutch actuator as a function of the measured clutch responses and as a function of the simulated vehicle dynamics. The method, entitled Actuator-In-The-Loop (AIL), is used to evaluate the fuel consumption of virtual vehicle connected to the prototyped new electric clutch, in compliance with the World-wide Motorcycle Emissions Test Cycle 3.2 (WMTC 3.2). On the same driving cycle, a fuel consumption comparison is achieved with an identical virtual vehicle equipped with a classic electrohydraulic clutch actuator. Finally, this experimental evaluation/comparison by the original AIL method leads to a mean vehicle fuel consumption reduction of 2.95% using the prototyped new electric. For a given vehicle and a given normalized driving cycle, the AIL method allows an accurate, low-cost and agile evaluation of any vehicle’s actuator power consumption.
Temporelli, Robin, Micheau, Philippe, Boisvert, Maxime
A Calibration Optimizer Tool for Torque Estimation of K0 Clutch in Hybrid Automatic Transmissions2017-01-06033/28/2017
Software development for automotive application requires several iterations in order to tune parameters and strategy logic to operate accordantly with optimal performance. Thus, in this paper we present an optimizer method and tool used to tune calibration parameters related to torque estimation for a hybrid automatic transmission application. This optimizer aims to minimize the time invested during the software calibration and software development phases that could take significant time in order to cover the different driving conditions under which a hybrid automatic transmission can operate. For this reason, an optimization function based on the Nelder-Mead simplex algorithm using Matlab software helps to find optimized calibration values based on a cost function (square sum error minimization). This work will present a K0 clutch in a hybrid automatic transmission run under several operating conditions, and the method with which the optimizer aids the parameter calibration process in order to converge to the optimal values. This process also helps in the software development process to identify and include control strategy changes. The simulation environment that will be presented in this paper is based on Simulink/Stateflow Model Based Design (MBD) under Matlab platform. In this environment, the calibration parameters and strategy logic will be loaded to run desktop tests, optimization and further validation. Finally, a quantitative comparison among calibration methods (i.e. with and without the optimization algorithm) will be presented and how this could impact vehicle development processes in terms of test time optimization.
Cuapio Espino, Vicente, Bichkar, Akshay, Osorio, Joycer D.
Effect of Fluid Flow through Clutch Material on Torque Fluctuations in Clutches2016-01-234310/17/2016
Improving vehicle fuel efficiency is a key market driver in the automotive industry. Typically lubricant chemists focus on reducing viscosity and friction to reduce parasitic energy losses in order to improve automotive fuel efficiency. However, in a transmission other factors may be more important. If an engine can operate at high torque levels the conversion of chemical energy in the fuel to mechanical energy is dramatically increased. However high torque levels in transmissions may cause NVH to occur. The proper combination of friction material and fluid can be used to address this issue. Friction in clutches is controlled by asperity friction and hydrodynamic friction. Asperity friction can be controlled with friction modifiers in the ATF. Hydrodynamic friction control is more complex because it involves the flow characteristics of friction materials and complex viscosity properties of the fluid. This paper shows how NVH and torque capacity can be controlled by optimizing the flow characteristics of friction materials and the complex viscosity of fluids.
Devlin, Mark, Williams, Darryl, Glasgow, Michael, Hux, Karen, Whitworth, Aaron, Cameron, Timothy
Fluid Effects on Shifting Clutch Friction2016-01-220610/17/2016
Good shift quality in automatic transmissions is important for fuel efficiency, driver comfort, and performance. Maintaining this performance over the life of the vehicle is also important. Typically lubricant development focuses on reducing viscosity and friction in order to reduce parasitic losses. In an automatic transmission other factors are also important for good performance, primarily due to the shifting clutches and the torque converter clutch. A high level of friction is desirable for torque capacity and a steady decrease in friction as sliding speed (rpm) decreases is necessary for both good shift feel and good friction system durability over the lifetime of the vehicle. Changes in the friction system over time that result in a lowering of the friction level, particularly at higher sliding speeds, compromise the performance of both types of clutches. In this paper, an experimental shifting clutch durability study demonstrates the impact of changes in friction materials on the mu-v curve and how small changes in a fluid can control these changes.
Williams, Darryl, Guevremont, Jeffrey, Perry, John
New Development of a Gas Cavitation Model for Evaluation of Drag Torque Characteristics in Disengaged Wet Clutches2016-01-11374/5/2016
A significant reduction of C02 emission can be achieved by improving the efficiency of transmission of cars. A reduction of drag torque or spin loss of disengaged clutches can improve the efficiency of transmissions. Generally, the drag torque is measured by conducting drag test which needs making samples, manpower, power and wastage of raw materials. In this paper, an analytical model is proposed to predict the drag torque of a disengaged wet clutch at different rotation speeds, clearances, disk sizes and oil temperatures without making any samples and conducting any drag tests. Various assumptions are made from the results of visualization investigations. Visualization results show that the volume of oil existed in between the clutch disk and clutch plate decreases with increasing speed due to centrifugal force. It is also noticed that several visible air bubbles are formed in the oil film at lower speeds and the size of the bubbles increase with increasing speeds. We consider that the gas cavitation has a significant role in air bubble formation. The model is validated with test results and it shows that they are almost coincident with each other.
Pahlovy, Shahjada A., Mahmud, Syeda F., Kubota, Masamitsu, Ogawa, Makoto, Takakura, Norio
Estimation of the Clutch Characteristic Map for an Automated Wet Friction Clutch Transmission2016-01-11134/5/2016
Higher demands on comfort and efficiency require a continuous improvement of the shift process. During the launch and shift process the clutch control is used to get a smooth and efficient behavior. In this short time of acting the shifting behavior can be rated. Many control concepts use a clutch characteristic to calculate the actuator signal based on the clutch torque. Therefore, a high quality of this characteristic is necessary. Because of the dynamic process during clutch engagement the clutch characteristic needs further information to reach a high accuracy for the control algorithm. In this paper an existing clutch torque characteristic is extended to a characteristic map where the clutch torque becomes a function of the current actuator signal of the clutch and the clutch slip. The extension of the torque characteristic describes the slip based dependencies, e.g. the friction coefficient. The model of the characteristic map consists of the multiplication of two separate functions in these two dimensions. The parameters of this model are estimated using different identification algorithms, in this case a non-linear recursive and a non-recursive identification algorithm. Both estimation algorithms result in a characteristic map of the clutch behavior. A further advantage of the presented approach is the normalization during the estimation process of the slip-based function with the cost function. Thus, the original torque characteristic can be used as fallback if the identification of the slip-based part still need reference data to converge or shows an implausible behavior.
Arndt, Thorsten, Tarasow, Alex, Bohn, Christian, Wachsmuth, Guido, Serway, Roland
Lubricants Formulation Technology for Fuel Saving Performance in Automatic Transmissions2015-01-20379/1/2015
The use of Automatic Transmission Fluids (ATFs) with lower viscosity and excellent anti-shudder durability for wet clutch system will be effective for improving fuel saving performance in automatic transmissions. In this study, two ATF formulation techniques were examined. The first trial formulation is to improve fatigue life in gear components even if a lower viscosity ATF is used. The second one is to improve anti-shudder durability for wet lock-up clutch system in AT units. As to fatigue life performance, the relation between molecular weight of Viscosity Index Improver (VII) and film formation property in EHL contact regions were experimentally investigated. ATFs containing VIIs with lower molecular weight tend to increasing EHL film thickness, resulting in a longer gear pitting fatigue life. Calcium detergents and ashless friction modifiers in ATFs were found to give a great impact on the anti-shudder performance. The trial ATF containing these additives demonstrated 1.5 times longer anti-shudder durability compared with a commercial ATF.
Yokomizo, Masato, Iwai, Toshiaki, Narita, Keiichi, Kudo, Mitsugu
Investigation on Torque Jump Up and Vibration at High Rotation Speed of a Wet Clutch2015-01-21846/15/2015
Reduction of the drag torque and longevity of the clutch assembly are the most important factors for vehicle transmission improvement. The decreasing trend of the drag torque with speed after its peak is a common characteristic of the clutch assembly. Several theoretical models have been presented by the researchers describing the drag torque characteristics at lower clutch speed. However, very little study has been made on the drag torque behavior at very high clutch speed (6000∼10000+ rpm). The alarming jump of the drag torque at high speed operating condition remains unexplained till date. In this paper, we investigated the possible reasons of torque jump up at high rotation speed and solution to overcome this problem. We presented an analytical correlation of torque jump up with the excessive decrease of local static pressure and assumed that vacuum formation is the possible reason of high speed torque rising and associated vibration. Result shows that when the separator plates are free, a remarkable torque jump is observed. However the drag torque jump up at higher speed can be eliminated by fixing the separator plates by some means.
Mahmud, Syeda, Pahlovy, Shahjada
Dry Dual Clutch Transmission (DCT) Thermal Model2015-01-11444/14/2015
Dual Clutch Transmissions (DCT) for passenger cars are being developed by OEMs and suppliers. The driving force is the improvement in fuel economy available from manual transmissions together with the comfort of automatic transmissions. A dry clutch system (dDCT) is currently the subject of research, development, and production implementation. One of the key issues in the development of a dDCT is clutch durability. In dry clutches with current linings, above a critical temperature, the friction system starts to suffer permanent damage. In addition, the clutch friction characteristics are a function of the clutch interface temperature. Because a reliable, low-cost temperature sensor is not available for this application, the clutch control engineers rely on a good thermal model to estimate the temperature of the clutches. A thermal model was developed for dry dual clutch transmissions to predict operating temperature of both pressure and center plates during all maneuvers. The model is intended to be used to a) prevent clutch plate over-heating during abusive driving scenarios such as hill holding or multiple GCVW launches in both forward and reverse on grades and b) estimate clutch friction characteristics for control purposes. It is a Simulink based model that is integrated into the transmission controller to notify drivers and take corrective actions in case of overheating. The model also predicts the initial conditions for the temperature of the clutches during engine startups. The thermal model was validated fully in a test cell environment as well as in vehicles using slip ring and telemetry hardware. The thermal model has seven states that include both bell housing air and skin temperatures. Other parameters that affect cooling performance of a dry DCT, such as ambient temperature, and engine coolant and transmission oil temperatures, are also taken into consideration.
Hebbale, Kumaraswamy, Samie, Farzad, Kish, Jonathan
Optimization of DCT Power-On Upshift Control Strategy Based on PSO Algorithm2015-01-11094/14/2015
This investigation presents a methodology to develop and optimize shift process control strategy to improve shift quality as perceived by drivers during power-on upshift events for Dual Cultch Transmission (DCT) vehicles. As part of the first study, the main factors affecting shift quality during shifting process under typical working conditions are analyzed. And taking the power-on upshift as example, dynamic model of DCT shifting process is build. An Integrated control strategy is proposed for power-on upshift, which during torque phase slipping revolving speed controller is adapted to harmonically control two clutches power switching process, and during Inertial phase engine torque is regulated to synchronize with the value of target gear while holding the oncoming clutch pressure. Oncoming clutch oil pressure gradient in torque phase and engine torque reducing target decrement in inertial phase are chosen as controlled quantity. The proximity between actual and ideal shift process is taken as fitness function. Power transmission system simulation model, shift quality evaluation model and Particle Swarm Optimization (PSO) algorithm are integrated based on Maltab/Simulink platform. The proposed integrated control strategy is optimized by PSO algorithm. Through comparison of evaluation indexes before and after optimization, the optimized control strategy could reduce the frictional loss and improve the power performance with no sacrifice of shifting comfort. So the optimized control strategy can improve the shift quality which verifies the feasibility.
Lei, Yulong, Liu, Ke, Fu, Yao, Lin, Ge, Song, Bin
A Three Dimensional Finite Element Analysis for Grooved Friction Clutches2015-01-06884/14/2015
This paper presents three-dimensional thermal model, performed transient thermal analysis for the grooved dry friction clutches. A finite element technique has been used to study the effect of radial and /or circumferential grooves (classic models) on the temperature distribution for dry friction clutch during a single engagement. The friction clutch has been discretised using 20-noded brick elements. The effect of the groove area ratio (G.R=groove area / total contact area), number of grooves and their location are investigated. Furthermore, new groove shapes have been suggested, e.g., curved groove. The response of the new suggested groove has been compared to the already existing shapes. The commercial ANSYS13 has been used to perform the numerical computations in this paper.
Abd Al-Sahb, Wassan, Abdullah, Oday Ibraheem
Optimal Engine Starts of an Input-Split Hybrid Electric Vehicle2015-01-12274/14/2015
Engine start-stop system is one of the main mechanisms for fuel saving in hybrid electric vehicles (HEVs). During those transient events, especially during engine starts, the engine torque pulsations can be an NVH issue if there is direct mechanical coupling between the engine and the driveline. In addition, engine starts may also result in the interruption of driving torque. The fast torque response of the electric machines provides a possible solution to mitigate the output torque fluctuation. But the effect is limited by the capability of these two electric machines due to the three missions they must satisfy simultaneously, i.e., starting the engine, compensating the torque pulsations and providing the demanded driving torque. To thoroughly understand this problem and propose possible solutions, in this study, we developed an input-split HEV powertrain model with a grounding clutch. The Dynamic Programming (DP) technique is adopted as the optimization approach to investigate the maximum output torque we can have without any torque error during engine starts. At the same time, the relationship between these two conflicting goals is achieved and the optimal solutions can be divided into four parts depending on the driver demand torque, from the minimum engine start time solution to the maximum driver torque demand solution. Based on the DP results, a control algorithm is proposed to achieve smooth and quick mode transition from the EV mode to power-split driving while meeting the driver torque demand.
Zhuang, Weichao, Kum, Dongsuk, Peng, Huei, Wang, LIangmo, Li, Daofei
Performance Characterization of Automatic Transmission Upshifts with Reduced Shift Times2015-01-10864/14/2015
As the number of fixed gear ratios in automatic transmissions continues to increase in the pursuit of powertrain system efficiency, particular consideration must continue to be focused on optimizing the design for shifting performance. This investigation focuses on the effect of shift time on the performance attributes of shift quality, durability, on schedule fuel consumption and enablers to further reduce shift time. A review of fundamental design features that enable reduced shift times in both planetary and dual clutch transmissions is presented along with key operating features of both the transmission and engine/prime mover. A lumped parameter metric is proposed to assess and compare the upshift controllability of new transmission architectures and powerflows using simple analysis. The durability of fast shift times during performance maneuvers are quantified through calculation of shifting clutch energy and power from analysis and form measurements on a powertrain dynamometer. In addition to perceived powertrain performance, powertrain dynamometer measurements running the FTP test schedules fuel consumption trends with respect to inertia phase shift time and can provide upwards of 1.25% by optimization of shift times depending on powertrain details. The paper concludes with vehicle measurements comparing part and wide-open throttle shift times for 6 and 8 speed planetary automatics transmissions.
Robinette, Darrell, Gibson, Gabriel, Szpara, David, Tehansky, Eugene
New Development Approach for Wet Motorcycle Clutch System2014-32-013611/11/2014
This paper discusses the design elements for a wet clutch system to successfully meet the requirements of today's motorcycle market. You can find new design ideas regarding how to realize important and critical clutch performance features such as torque boost, coast torque reduction (anti-hopping function), reduced actuation force, reduced drag torque, optimized weight, and/or optimized product cost. Most of these functions and features can be implemented in a modular clutch kit in which many of the parameters can be adapted with a minor design change of just a few components.
Metzinger, Thomas, Raber, Christoph, Wittmann, Christoph
Multiphase Drag Modeling for Prediction of the Drag Torque Characteristics in Disengaged Wet Clutches2014-01-23339/30/2014
The undesired Drag Torque (DT) which is developed due to the shearing of fluid film in between the disk and separator plate reduces the efficiency of a transmission and increases the fuel consumption of a car. In order to minimize the transmission loss, the physics of the fluid flow mechanism inside the clutch should be understood well and the factors influencing the DT should be identified. In this paper, a model is proposed to predict the drag torque of a disengaged wet clutch at different rotation speeds, clearances, disk sizes and oil temperatures. The model explains well how the DT changes for the no groove disk, grooved disk and different ATF properties. The proposed model is validated by several experimental results conducted by a visualization tester and images of the fluid film taken during the test. Results show that there is a good degree of agreement between the DT trends derived from the proposed model and the test results for the same condition.
Pahlovy, Shahjada, Mahmud, Syeda Faria, Kubota, Masamitsu, Ogawa, Makoto, Takakura, Norio
Dynamic Loading Reduction of Multiplate Clutches Lined Plates of the Vehicle Powertrain2014-01-23329/30/2014
The paper presents the findings of the investigation of initiation conditions for parametric resonances in the nonlinear system “Engine unit - Torque Converter - Planetary Transmission Elements (Drum and Lined Plate)”. The mentioned oscillations and resonances form dynamic loading of powertrain lined plates. In terms of the research results the paper validates the ways of tuning parametric oscillations. These ways provide for the increasing of durability of multiplate clutches plates of vehicle powertrain. The evaluation of dynamic stability was performed on the basis of the analysis of Mathieu equation and Ince-Strutt diagram. The restriction of modulation depth parameter is proposed by filtering of high-frequency disturbances which are generated in the nonlinear system by different oscillation sources (power unit - internal combustion engine (ICE) or electric motor (EM), hydrodynamic processes in the hydraulic transformer - torque converter or hydraulic coupling, oil supply pump). The efficiency evaluation of the influence of the developed actions on lined plate's durability was performed.
Taratorkin, Igor, Derzhanskii, Viktor, Taratorkin, Alexander, Kharitonov, Sergey
Study of Power Losses in a Two-Speed Dual Clutch Transmission2014-01-17994/1/2014
This paper mainly studies the power losses in a refined two-speed dual clutch transmission which is equipped in a electric vehicle test rig. Both numerical and experimental investigations are carried out. After theoretical analysis of the power losses original sources, the developed model is implemented into simulation code to predict the power losses. In order to validate the effectiveness of the proposed model, results from experimental test are used to compare the difference the simulation and test. The simulation and test result agree well with each other. Results show that the power losses in the two-speed are mainly generated by multi-plate wet clutch drag torque and gear churning loss.
Zhou, Xingxing, Walker, Paul, Zhang, Nong, Zhu, Bo, Ruan, Jiageng
An Investigation of Heat Generation Due To Friction Using Finite Element Method2014-01-09544/1/2014
Most of failures in automotive friction clutches occur due to the excessive heat generated between the contact surfaces during the slipping period; for this reason, the accurate calculation of the heat generation during the slipping is considered an essential item in the successful design process to avoid the failures due to the high thermal stresses. A finite element technique has been used to study the temperature field, the heat generation and the contact pressure distribution when friction disc slides over the steel disc. Analysis has been completed using a three dimensional model to simulate the thermo-structural coupling in automotive clutches. ANSYS software has been used to perform the numerical calculation in this paper.
Abdullah, Oday Ibraheem, Schlattmann, Josef
A Study on Friction Characteristics at Low Pressure Slip Condition of Wet - Clutch2014-01-17514/1/2014
1 Recently, automatic transmissions (AT) have been developed to have more step numbers to improve their power transmitting efficiency for better fuel consumption. Due to the increased steps, the frequency of engaging and disengaging of wet clutches and brakes in an AT is getting higher. And then the required characteristics for a clutch is not only to make a smooth engagement but also to react smoothly in the process of disengagement, due to the clutch-to-clutch type shift strategy. Although there have been many researches on the engaging process, however, few have been done for the clutch behavior in the disengagement process so far. Regarding the process of disengagement of a clutch, a phenomenon described below has been observed and reported which leads to a kind of shock during a shift. In the process of one clutch disengagement, the clutch starts to be opened with some slipping at very low apply pressure from the cramped state and, during the slipping, sometimes a friction rise in the clutch is observed and recognized as a shift shock by the driver. We would like to call it as “mu-swing.” The purpose of this study is to eliminate or reduce mu-swing under this very low facing pressure in a clutch. In order to investigate factors which influence mu-swing, a series of evaluation with varied conditions has been done, and the important influence of the state of oil film at sliding surfaces was confirmed. The factors which prevent mu-swing were also evaluated, with respect to the friction material type and oil groove patterns.
Okamoto, Daisuke
Simulations of Drag Torque in Multi-Plate Wet Clutch Affecting Synchronizers in a TC+AMT Transmission2014-01-17144/1/2014
Drag torque in multi-plate wet clutch consumes engine energy, but also has significant affect on synchronization process during shifting. The mathematical models of drag torque and shift synchronization process were established, and the results carried out by Matlab/Simulink simulation were compared with experiment results as well. It is demonstrated that the models are correct and accurate. The influences of friction pair gap in multi-plate wet clutch, cooling oil flow and properties of cooling oil under different temperature etc. on drag torque, shift synchronization time and energy were analyzed. The conclusions have certain guiding significance to the multi-plate wet clutch theoretical study and structural design as well as transmission system matching.
Sun, Shaohua, Lei, Yulong, Li, Xingzhong
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