Variable gear ratio hydraulic power steering device

• US 20050229592A1
• Filed: 04/04/2005
• Published: 10/20/2005
• Est. Priority Date: 04/20/2004
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Toyoda Koki Kabushiki Kaisha
• Inventors: Kobayashi, Yukihiro
• Granted Patent: US 7,306,070 B2
• Time in Patent Office: Days
• US Class Current: 60/387
• CPC Class Codes: B62D 5/008 Changing the transfer ratio between the steering wheel and the steering gear by variable supply of energy, e.g. by using a superposition gear
• CPC Class Codes: B62D 5/065 characterised by specially adapted means for varying pressurised fluid supply based on need, e.g. on-demand, variable assist
• CPC Class Codes: B62D 5/091 Hydraulic steer-by-wire systems, e.g. the valve being actuated by an electric motor
• CPC Class Codes: B62D 5/30 Safety devices, e.g. alternate emergency power supply or transmission means to ensure steering upon failure of the primary steering means
• CPC Class Codes: F15B 2211/30575 in a Wheatstone Bridge arrangement (also half bridges)

Abstract

A variable gear ratio hydraulic power steering device 1 is provided with a variable ratio transmission mechanism 7 for varying the rotation transmission ratio between the rotational angle of a steering handle 31 and the rotational angle of a pinion shaft 33 and a flow volume control valve 40 for controlling the discharge flow volume of an oil pump 10 which circulates operating fluid. The variable ratio transmission mechanism 7 has a lock mechanism 75. A valve controlling controller 50 for controlling the flow volume control valve 40 switches main and secondary flow volume control maps for controlling the flow volume control valve 40, in dependence on the operational state of the lock mechanism 75. Thus, a failsafe function for the variable ratio transmission mechanism 7 is given to the variable gear ratio hydraulic power steering device 1.

Claims

1. 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.

2. The variable gear ratio hydraulic power steering device as set forth in claim 1, wherein the sensing function is constructed to take thereinto a reference signal related to the operational state of the lock mechanism for restricting the relative rotation between the first and second steering shafts and to detect the operational state regarding whether the lock mechanism restricts or permits the relative rotation between the first and second steering shafts, based on the reference signal.

3. The variable gear ratio hydraulic power steering device as set forth in claim 2, wherein the reference signal is a control signal for controlling the lock mechanism.

4. The variable gear ratio hydraulic power steering device as set forth in claim 1, wherein:

the transmission ratio controlling controller is constructed to vary a transmission ratio control target value for the rotation transmission ratio V2/V1 of the variable ratio transmission mechanism within a predetermined range including value 1 in dependence on a traveling state; and

in a control range in which transmission ratio control target values smaller than value 1 are set by the transmission ratio controlling controller, various flow volume control values which are mapped in the secondary flow volume control map are set to more increase the discharge flow volume of the oil pump than various flow volume control values mapped in the main flow volume control map do; and

in another control range in which transmission ratio control target values larger than value 1 are set by the transmission ratio controlling controller, various flow volume control values which are mapped in the secondary flow volume control map are set to more suppress the discharge flow volume of the oil pump than various flow volume control values mapped in the main flow volume control map do.

5. The variable gear ratio hydraulic power steering device as set forth in claim 2, wherein:

the transmission ratio controlling controller is constructed to vary a transmission ratio control target value for the rotation transmission ratio V2/V1 of the variable ratio transmission mechanism within a predetermined range including value 1 in dependence on a traveling state; and

in a control range in which transmission ratio control target values smaller than value 1 are set by the transmission ratio controlling controller, various flow volume control values which are mapped in the secondary flow volume control map are set to more increase the discharge flow volume of the oil pump than various flow volume control values mapped in the main flow volume control map do; and

in another control range in which transmission ratio control target values larger than value 1 are set by the transmission ratio controlling controller, various flow volume control values which are mapped in the secondary flow volume control map are set to more suppress the discharge flow volume of the oil pump than various flow volume control values mapped in the main flow volume control map do.

6. The variable gear ratio hydraulic power steering device as set forth in claim 3, wherein:

the transmission ratio controlling controller is constructed to vary a transmission ratio control target value for the rotation transmission ratio V2/V1 of the variable ratio transmission mechanism within a predetermined range including value 1 in dependence on a traveling state; and

in a control range in which transmission ratio control target values smaller than value 1 are set by the transmission ratio controlling controller, various flow volume control values which are mapped in the secondary flow volume control map are set to more increase the discharge flow volume of the oil pump than various flow volume control values mapped in the main flow volume control map do; and

in another control range in which transmission ratio control target values larger than value 1 are set by the transmission ratio controlling controller, various flow volume control values which are mapped in the secondary flow volume control map are set to more suppress the discharge flow volume of the oil pump than various flow volume control values mapped in the main flow volume control map do.

7. The variable gear ratio hydraulic power steering device as set forth in claim 1, wherein the transmission ratio controlling controller is integrated with the flow volume controlling controller.

8. The variable gear ratio hydraulic power steering device as set forth in claim 2, wherein the transmission ratio controlling controller is integrated with the flow volume controlling controller.

9. The variable gear ratio hydraulic power steering device as set forth in claim 3, wherein the transmission ratio controlling controller is integrated with the flow volume controlling controller.

10. The variable gear ratio hydraulic power steering device as set forth in claim 4, wherein the transmission ratio controlling controller is integrated with the flow volume controlling controller.