To provide a power steering device capable of obtaining a stable assist force without deteriorating the return of steering when performing steering assist by driving an electric motor and rotating a pump.
The power steering device is equipped with a torque detection means detecting steering torque, an assist steering control means calculating an assist steering force command value based on the steering torque to be detected and driving the electric motor based on the command value to be calculated, a pump driven by the electric motor, and a steering assist means having a hydraulic system performing the steering assist by introducing the delivery pressure of the pump to two chambers of the power cylinder partitioned by a piston. The power steering device is provided with a power cylinder hydraulic pressure calculation means calculating the hydraulic pressure of power cylinders of the two chambers respectively. The assist steering control means is made to be a means to drive the pump so as to supply hydraulic pressure to the one of the low hydraulic pressure chamber of the two chambers of the power cylinder chambers when the torque to be detected is below the set value to be previously set.
SUGIYAMA YOSHITAKA
Satoru Asakura
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