COMMERCIAL VEHICLE'S HYBRID POWER STEERING SYSTEM AND METHOD FOR IMPROVING PERFORMANCE AND FUEL EFFICIENCY BY CONTROLLING SAME

摘要

A commercial vehicle's hybrid power steering system of the present invention includes: a motor driven power steering (MDPS) unit (10) for generating motor output torque according to driver steering torque; an electro-hydraulic power steering (EHPS) unit (20) for generating hydraulic output torque considering the motor output torque of the MDPS unit; a ball nut gear box (4) in which the driver steering torque, the motor output torque and the hydraulic output torque are inputted and then are generates as output torque (Tp) operating a tie rod (8) comprising a left wheel (9a) and a right wheel (9b); and two torsion bars (31, 32) which block torque variation rate of a joint (3) by detecting road repulse force delivered to a steering column through the ball nut gear box at least at two different positions. Thus, the system provides steering capacity required in a compact commercial vehicle and also in a medium to large-sized commercial vehicle, and prevents generation of torque variation rate around the joint (universal joint) connecting an MDPS unit mounting part and an EHPS unit mounting part with two torsion bars, and improves catch up performance highly with an assistant EHPS unit (100).;COPYRIGHT KIPO 2014