JPH062466B2 - Hydraulic reaction force control device for power steering device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for controlling a steering force of a power steering device by a hydraulic reaction force according to a vehicle speed.

(Prior Art) Conventionally, as shown in Japanese Patent Publication No. 58-19504, the hydraulic pressure on the upstream side of a fixed throttle provided in an oil passage between a discharge port of a pump and a power steering control valve is adjusted to a hydraulic reaction chamber. Guided vehicle speed response hydraulic reaction force control devices are known. Further, it has a first spool valve that changes according to the vehicle speed and a second spool valve that is controlled by circuit pressure, and adjusts the pressure acting on the hydraulic reaction chamber by the displacement of each valve. This spool is controlled by the hydraulic pressure regulated by the vehicle speed using the third spool, and the pressure in the passage connecting the pump and the power steering device is adjusted to improve the rigidity near the center at high speed. It was

However, the control device as described above is extremely complicated in structure and expensive.

(Purpose) An object of the present invention is to significantly reduce the number of parts of the valve structure without lowering the performance and to reduce the cost.

(Structure) In order to achieve the above object, the present invention provides an oil passage connecting an upstream side of a first fixed throttle provided in an oil passage between a discharge port of a pump and a power steering controller valve and a tank or a return passage. A power steering device in which a variable throttle whose opening degree increases with an increase in vehicle speed and a second fixed throttle are arranged in series, and the hydraulic pressure between the variable throttle and the second fixed throttle is guided to a hydraulic reaction chamber. In the hydraulic reaction force control device, the pressure switch is provided in the oil passage between the discharge port of the pump and the power steering control valve,
When the pressure switch detects a predetermined pressure, the opening of the variable throttle is decreased.

A specific description will be given below based on Examples. A fixed throttle 4 for controlling the pump discharge flow rate is arranged in an oil passage 3 between the pump 1 and the power steering control valve 2, and a vehicle speed or a vehicle speed is set in an oil passage 6 connecting the upstream side of the fixed throttle 4 and the tank 5. A step motor 8 is provided which is rotationally controlled by the output of an electronic control unit 7 which is controlled by signals of vehicle sensors such as a steering angle and a pressure switch. Reference numeral 9 is a rotor shaft for variable throttle of the step motor 8 which is decelerated by the reduction gear 10, and variably controls the variable throttle 11 of the oil passage 6. A fixed throttle 12 is arranged in the oil passage 6 in series with the variable throttle 11,
An oil passage 13 branched from an intermediate portion between the variable throttle 11 and the fixed throttle 12 is guided to a hydraulic reaction force chamber 14. Reference numeral 15 is a pressure switch arranged in the oil passage 3.

Next, the operation will be described. When the pump 1 rotates, the oil discharged from the pump 1 has a hydraulic pressure P ₁ generated by the fixed throttle 4. A flow control valve (not shown) acts on this hydraulic pressure P ₁ to determine the amount of oil discharged from the pump 1. This serves as a hydraulic power source for a general power steering apparatus and operates. This hydraulic pressure P ₁ is maintained at about 5 kg / cm ² regardless of the rotation speed of the pump 1.

When the vehicle speed is zero, the step motor 8 is operated so as to fully close the variable throttle 11 by the signal of the electronic control unit 7, the oil passage 6 is cut off, and there is no hydraulic pressure acting on the hydraulic reaction chamber 14. . Therefore, the power steering apparatus has the characteristics as shown in FIG. 3 (a) by the same operation as the conventional apparatus, and the light steering can be performed.

When the vehicle travels straight at medium speed, the step motor 8 operates in response to a signal from the electronic control unit 7 as the vehicle speed increases, and the variable throttle 11 is slightly opened. At this time, between the opening a, the hydraulic pressure P ₁ , the fixed throttle 12, the hydraulic pressure P _{2 of the} oil passage 13, and the tank side back pressure P ₃ , The relationship is established. Since P ₃ is zero because it is atmospheric pressure, It becomes a relationship.

Now, when the opening b of the fixed throttle 12 is much larger than a, P ₂ ≈0. That is, no pressure is generated in the oil passage 13, and there is no steering load near the center of the steering wheel as with zero vehicle speed, and steering can be performed with a light force.

When the steering wheel is steered at a medium speed, the power assist of the power steering device is started and the hydraulic pressure P ₁ increases. Therefore, the increase of P _{1 in} the above equation exceeds the contribution rate of the opening b of the fixed throttle 12, and the oil pressure P _{2 of the} oil passage 13 increases accordingly. The hydraulic pressure P ₂ increases in proportion to the increase of the hydraulic pressure P ₁ . Therefore, the hydraulic pressure P ₂ proportional to the hydraulic pressure P ₁ also acts on the hydraulic reaction force chamber 14 to increase the rigidity at the time of steering and to obtain a characteristic with a sense of cutting as shown in FIG.

However, since the oil forces the extent that very torque as indicated by a dotted line when the hydraulic pressure P ₁ increases further becomes dull handle increases occurs, step by the signal of the pressure switch 15 when the hydraulic pressure P ₁ becomes a constant value the motor 8 Is rotated to control the opening a of the variable throttle 11 and keep the hydraulic pressure P ₂ acting on the hydraulic reaction chamber 14 constant, so that the steering torque does not increase as shown by the solid line and the steering wheel cannot be turned due to the increase in steering torque. There is nothing.

When traveling straight at high speed, the signal from the electronic control unit 7 is received due to the increase in vehicle speed, and the step motor 8 is further rotated to make the variable aperture 1
When the opening a of 1 is set to be sufficiently larger than b, P ₁ ≈P _{2 and} the pressure of the hydraulic pressure P ₁ constantly acts on the hydraulic reaction chamber 14, resulting in the characteristic shown in FIG. The rigidity near the center of the increases. When the steering wheel is steered at this time, as in the case of the medium speed, when the hydraulic pressure P ₁ becomes a constant pressure, the signal of the pressure switch 15 is received and the hydraulic pressure P ₂ acting on the hydraulic reaction chamber 14 is kept constant. The handle will not get stuck.

On the contrary, when the cutting feeling is insufficient in the characteristic shown by the dotted line as the characteristic of FIG. 4, the step motor 8 is rotated by the steering wheel steering angle and the pressure switch to change the opening a of the variable throttle 11. It will be apparent that the hydraulic pressure P ₂ acting on the hydraulic reaction chamber 14 can be increased and the steering torque can be increased as shown by the solid line to increase the feeling of cutting.

As described above, the rate of change of the hydraulic pressure P ₂ acting on the hydraulic reaction chamber with respect to the hydraulic pressure P ₁ changes depending on the vehicle speed, and linearity with respect to the vehicle speed can be obtained.

According to the present invention, the opening degree is increased by increasing the vehicle speed in the oil passage connecting the upstream side of the first fixed throttle provided in the oil passage between the discharge port of the pump and the power steering control valve and the tank or the return passage. In the hydraulic reaction force control device of the power steering device, the variable throttle to be increased and the second fixed throttle are arranged in series, and the hydraulic pressure between the variable throttle and the second fixed throttle is guided to the hydraulic reaction chamber. Since a pressure switch is provided in the oil passage between the discharge port of the pump and the power steering control valve, the opening of the variable throttle is reduced when the pressure switch detects a predetermined pressure. The cost can be reduced by significantly reducing the number of parts of the valve structure without lowering the performance.

Furthermore, the steering wheel does not become stuck due to an increase in steering torque at medium and high speeds.

[Brief description of drawings]

FIG. 1 is a variable throttle and hydraulic circuit diagram of one embodiment of the present invention, and FIG.
FIG. 3 is an overall hydraulic circuit diagram, FIG. 3 is a characteristic comparison diagram of steering torque and steering pressure, and FIG. 4 is a characteristic comparison diagram of steering torque and steering pressure in a comparative example. 1 ... Pump 2 ... Power steering control valve 3, 6, 13 ... Oil passage 4, 12 ... Fixed throttle 5 ... Tank 7 ... Electronic control device 8 ... Step motor 9 ... Variable throttle rotor shaft 11 ... Variable throttle 14 ... Hydraulic reaction chamber 15 ... Pressure switch

Claims (1)

[Claims] Claim: What is claimed is: 1. An opening according to an increase in vehicle speed in an oil passage connecting an upstream side of a first fixed throttle arranged in an oil passage between a discharge port of a pump and a power steering control valve and a tank or a return passage. In the hydraulic reaction force control device of the power steering device, the variable throttle to be increased and the second fixed throttle are arranged in series, and the hydraulic pressure between the variable throttle and the second fixed throttle is guided to the hydraulic reaction chamber. A power steering system characterized in that a pressure switch is provided in an oil passage between the discharge port of the pump and the power steering control valve, and the opening of the variable throttle is reduced when the pressure switch detects a predetermined pressure. Control device for hydraulic reaction force.