US 4,730,687 A · Steering force control device for power steering system

Abstract

A working fluid passage supplying a fixed flow rate is divided into passages so that a flow rate ratio between the two passages is varied by a variable orifice valve based on a detection signal of a physical quantity factor which varies depending on travelling and steering conditions of the vehicle. The working fluid from one of the two passages is supplied to a steering assisting force generating mechanism through a changeover valve which changes over the passages in accordance with a direction of steering torque acting on the input shaft steering the vehicle, to generate the steering assisting force. The working fluid from the other passage is supplied to a steering reaction force generating mechanism through the changeover valve, and by generating the steering reaction force to the input shaft, the steering force is controlled to an adequate condition corresponding to the physical quantity factor. Furthermore, the passage of the variable orifice valve at the side of the steering reaction force generating mechanism is connected to a drain through a changeover valve or a pressure regulating valve to thereby control the steering feeling to a more adequate condition, and at the same time, when the vehicle is travelling at a low speed, the generation of the steering reaction force by the steering reaction force generating mechanism is suppressed, or the steering reaction force of the steering reaction force generating mechanism is maintained at a constant value. Moreover, the steering angle ratio is regulated by rotating the input shaft in the same direction as the steering direction by a steering angle ratio varying mechanism in correspondence with the reaction force of the steering reaction force generating mechanism, and thus optimum steering feeling can be obtained. Further, a change in the exciting current due to an internal resistance change of an electromagnetic solenoid is suppressed by a voltage correction circuit provided in a control unit for controlling the electromagnetic solenoid of the variable orifice valve, and an appropriate steering force can be generated.

Claims22

Dependent claims

In a power steering system, which generates a steering assistance force and a steering reaction force in accordance with steering torque acting on an input shaft steering a vehicle, and which includes a control unit for setting a steering force based on a detective signal of detecting means for detecting a physical quantity factor which varies depending on a travelling condition and a steering condition of said vehicle, a steering force control device comprising:

a variable orifice valve for dividing a supply passage from a pump into first and second passages, respectively, for generating said steering assisting force and said steering reaction force, said variable orifice valve selecting a flow rate rates between said first and second passages in accordance with a control signal from said control unit, said variable orifice valve operating such that when a communicating area of one passage of said first and second passages increases, a communicating area of the the other passage decreases;
a passage changeover valve having first and second directional control valves formed in a common rotary valve having a spool interlocked to the input shaft and an outer sleeve secured to the steering members, said first and second directional control valves being connected to said first and second passages of said variable orifice valve, each of said first and second directional control valves changing over a working fluid under a unitary control in accordance with a direction and an amount of the steering torque acting on said input shaft;
a steering assisting force generating mechanism for generating a steering assistance force for said input shaft by the working fluid supplied from said second directional control valve of said passage changeover valve.

In a power steering system which generates a steering assisting force and a steering reaction force in accordance with steering torque acted on an input shaft steering a vehicle, and which includes a control unit for setting a steering force based on a detection signal of detecting means for detecting a physical quantity factor which varies depending on a travelling condition and a steering condition of said vehicle, a steering force control device comprising:

a variable orifice valve for dividing a supply passage supplying a constant flow rate into two passages including first and second passages and for selecting a flow rate ratio between said first and second passages in accordance with a control signal from said control unit, said variable orifice valve operating synchronously so that a sum of areas varying respectively in said first and second passages is equal to or larger than a predetermined value;
a pair of passage changeover valves connected respectively to said first and second passages of said variable orifice valves for changing over the passages in accordance with the steering torque acting on said input shaft;
a steering assisting force generating mechanism for generating the steering assisting force for a steering member by the working fluid supplied from one of said passage changeover valves;
a steering reaction force generating mechanism for generating the steering reaction force for said input shaft by the working fluid supplied from the other of said passage changeover valves;
and
a drain passage having a valve portion connected to said second passage of said variable orifice valve for opening and closing in association with the operation of said variable orifice valve.

3 more elements

In a power steering system which generates a steering assistance force and a steering reaction force in accordance with a steering torque acting on an input shaft steering a vehicle, and which includes a control unit for setting a steering force based on a detection signal of detecting means for detecting a physical quantity factor which varies depending on a travelling condition and a steering condition of said vehicle, a steering force control device comprising:

a variable orifice valve for dividing a supply passage from a pump into first and second passages, respectively, for generating said steering assistance force and said steering reaction force, said variable orifice valve selecting a flow rate ratio between said first and second passages in accordance with a control signal from said control unit, said variable orifice valve operating such that when a communicating area of one passage increases, a communicating area of the other passage decreases;
a passage changeover valve having first and second directional control valves formed in a common rotary valve having a spool interlocked to the input shaft and an outer sleeve secured to the steering member, said first and second directional control valves being connected to said first and second passages of said variable orifice valve, each of said first and second directional control valves changing over a working fluid under a unitary control in accordance with a direction and an amount of the steering torque acting on said input shaft;
a steering assistance force generating mechanism for generating a steering assistance force by the working fluid supplied from said first directional control valve of said passage changeover valve;
a steering reaction force generating mechanism for generating a steering reaction force for said input shaft by the working fluid supplied from said second directional control valve of said passage changeover valve;
and
a steering angle ratio varying mechanism including a resilient body interposed between said input shaft and said passage changeover valve, and including rotational displacement for said input shaft in a direction the same as the steering direction of said input shaft against torsional rigidity of said resilient body the working fluid supplied from said directional control valve of said passage changeover valve.

3 more elements

In a power steering system which generates a steering assisting force and a steering reaction force in accordance with steering torque acting on an input shaft steering a vehicle, and which includes a control unit for setting a steering force based on a detection signal of detecting means for detecting a physical quantity factor which varies depending on a travelling condition and a steering condition of said vehicle, a steering force control device comprising:

a variable orifice valve for dividing a supply passage supplying a constant flow rate into two passages and for selecting a flow rate ratio between said two passages in accordance with a control signal from said control unit, said variable orifice valve operating to increase a communicating area of one passage and to decrease a communicating area of the other passage so that a sum of the communicating areas in said two passages is at least equal to a predetermined value;
a passage changeover valve having first and second directional control valves connected respectively to said two passages divided from said supply passage said variable orifice valve, each of said first and second directional control valves changing over a working fluid in accordance with a direction and an amount of the steering torque acting on said input shaft;
a steering assisting force generating mechanism for generating a steering assisting force by the working fluid supplied from said first directional control valve of said passage changeover valve;
a steering reaction force generating mechanism for generating the steering reaction force for said input shaft by the working fluid supplied from said second directional control valve of said passage changeover valve;
a steering reaction force generating mechanism for generating the steering reaction force of said input shaft by the working fluid supplied from the said second directional control valve of said passage changeover valve;
and
hydraulic pressure regulating means for regulating a pressure of the working fluid supplied to said steering reaction force generating means.

4 more elements

a variable orifice valve for dividing a supply passage supply a constant flow rate into two passages and for selecting a flow rate ratio between said two passages by actuating an electromagnetic solenoid in accordance with a control signal from said control unit, said variable orifice valve operating to increase a communicating area of one passage and to decrease a communicating area of the other passage;
a passsage changeover valve having first and second directional control valves connected respectively to said two passages divided from said supply passage of said variable orifice valve for changing, each of said first and second directional control valves changing over the passages of working fluid in accordance with the steering torque acting on said input shaft;
and
a steering assisting force generating mechanism for generating the steering assisting force by the working fluid supplied from said first directional control valve of said passage changeover valve;
wherein said control unit includes:
frequency-voltage converting means for converting the detection signal of said detecting means to a voltage signal,
means for generating a triangular wave,
comparison means for comparing the output voltage of said frequency-voltage converting means with the output voltage of said triangular wave generating means,
pulse width modulation means for supplying a pulse-shaped exciting current obtained from said comparison means to said electromagnetic solenoid, and
voltage correcting means for correcting either one of the output voltages of said frequency-voltage converting means and said triangular wave generating so that a change in the exciting current due to an internal resistance change caused by a temperature change of said electromagnetic solenoid is suppressed.

7 more elements

Dependencies are inferred from the claim text.

Steering force control device for power steering system

Life of this patent

Steering force control device for power steering system

Life of this patent

Abstract

Claims22