Patent ID: 7306070
Filing Date: 2007-12-11
Classification: B62D,F15B

Abstract:
1. A variable gear ratio hydraulic power steering device having a variable ratio transmission mechanism for varying the rotation transmission ratio V 2 /V 1 between the rotational angle V 1 of a first steering shaft coupled to a steering handle and the rotational angle V 2 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 which provides an assist force to the steering device, 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 for storing main and secondary flow volume control maps each mapping various flow volume control values for controlling the flow volume control valve, and a detector adapted to detect 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.