Variable gear ratio hydraulic power steering device

A variable gear ratio hydraulic power steering device having a variable ratio transmission mechanism for varying the rotation transmission ratio V2/V1 between the rotational angle V1 of a first steering shaft coupled to a steering handle and the rotational angle V2 of 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 the discharge flow volume of an oil pump which circulates operating fluid, and a valve controlling controller for controlling the flow volume control valve, wherein:

• the variable ratio transmission mechanism is provided with a lock mechanism for restricting relative rotation between the first steering shaft and the second steering shaft;
• the valve controlling controller is provided with a memory function of storing main and secondary flow volume control maps each mapping various flow volume control values for controlling the flow volume control valve and a sensing function of detecting the operational state of the lock mechanism;
• and
• the valve controlling controller is constructed to control the flow volume control valve by the use of the main flow volume control map when the lock mechanism permits the relative rotation between the first and second steering shafts and to control the flow volume control valve by the use of the secondary flow volume control map when the lock mechanism restricts the relative rotation between the first and second steering shafts.