Design and Development of Rack and pinion steering gear assembly for passenger car vehicle

Cross-Helical gears are helical gears with non-parallel,non-intersecting axes and their helix angles are not equal and opposite. Profile shift gears are used to balance the strength of the rack and pinion, avoid undercut, and change the center distance as per the requirement of the vehicle. Passenger cars use these gears for maneuvering by converting the pinion rotary motion to rack translation and thereby turning the wheels. This paper discusses the design and development of Rack and pinion steering (RPS) gear assembly in terms of gear calculations, modeling, performance, and strength analysis over various load cases. Design calculations are being done for several parameters- Normal module, helix angle, No. of teeth as per steering gear ratio and shaft angle. A complete CAD geometry of the RPS gear assembly is made in CAD modeling software UG-NX as per vehicle requirements. BIW and its surrounding parts clearance from the RPS assembly are verified for packaging review. Performance study of the assembly includes simulation-based prediction using MSC Adams for estimation of various output parameters like free pinion Torque and its variations over rack travel, Rack force required for rotating pinion, gear ratio, the relation between input torque of pinion and output load to find rack efficiency. Strength tests of the assembly are done to find the areas of stress locations using FE analysis. Rubber boot clearance study with steering gear components is assessed for various tie rod envelope conditions and physical testing for boot wear is also performed. This paper will conclude with experimental testing for performance and strength evaluation to validate the designed Rack and pinion steering gear assembly.