Patent ID: 7278512
Filing Date: 2007-10-09
Classification: B62D,F15B

Abstract:
1. A variable gear ratio hydraulic power steering device having a variable ratio transmission mechanism for varying a rotation transmission ratio between a first steering shaft coupled to a steering handle and a second steering shaft coupled to a pinion shaft, a transmission ratio controlling controller for controlling the variable ratio transmission mechanism, a flow volume control valve for controlling a discharge flow volume of an oil pump which circulates operating fluid, a valve controlling controller for controlling the flow volume control valve, and a steering angle sensor for measuring a handle steering angle input to the steering handle, wherein: the variable ratio transmission mechanism is provided with a drive motor having a rotor and a stator combined and a rotational angle sensor for measuring a measured ACT angle which is a motor rotational angle of the drive motor, and is constructed to alter the rotation transmission ratio between the first and second steering shafts in dependence on a rotational operation of the drive motor; the transmission ratio controlling controller is constructed to take therein the handle steering angle measured by the steering angle sensor and to control the variable ratio transmission mechanism in dependence on at least the handle steering angle and a handle angular velocity which is obtained by time-differentiating the handle steering angle; the valve controlling controller is constructed to take therein the measured ACT angle and the handle steering angle and to calculate a target ACT angle which is a control target value of the motor rotational angle of the drive motor, in dependence on the handle steering angle; and the valve controlling controller is also constructed to control the flow volume control valve so that the discharge flow volume is made to be equal to or greater than a predetermined flow volume when a difference ACT angle which is the difference between the target ACT angle and the measured ACT angle is equal to or greater than a threshold value and so that the discharge flow volume is made to be less than the predetermined flow volume when the difference ACT angle is less than the threshold value.