Reduction of Lubrication System Pressure Pulsation due to Oil Foaming in a Double Clutch Transmission

Foaming of Oil is accumulation of air bubbles on the surface. The source of air can be environmental or dissolved air or both. Foaming of Lubricant Oil is an undesired effect which has various reasons to occur- sudden decrease of pressure, contamination, reservoir design, etc. The effects can be pressure pulsation in pump discharge which results in abnormal Noise and Vibration, Cavitation, etc. This paper will describe the mechanical design changes done in a gearbox to guide the Oil flow to a less turbulent passage and to the reservoir. This will allow oil to degas while its flow to the reservoir, largely losing its foamability characteristic. By introducing circular enclosing structure around the rotating Clutch pack, the centrifugally escaping oil is guided and escapes into a collection tray via single point opening. The Oil tray will route the oil back to the reservoir. The enclosing structure around the Clutch pack is a carefully designed two-parts structure with close and calculated proximity to the Clutch body. These two parts were designed as structural parts meant for other system functions and now adopted to also serve the purpose of oil guiding and Clutch pack encapsulation. Before encapsulation of Clutch body, foamed Oil was greatly observed in the reservoir due to erratic oil escaping from the clutch pack and collected in the reservoir. This resulted in main pressure pulsation in the Pump measuring well above the acceptable range of operation. Tests were carried out with above said encapsulated design of clutch pack and less visible foaming of Oil was observed in the reservoir thus reducing the pressure pulsation by 60% to an acceptable range of operation.