JPS61295172A - Power steering device - Google Patents

Abstract

PURPOSE:To enhance the returning characteristic of a steering wheel, by decreasing the amplification degree of steering force with respect to a manual steering force which is applied with an assist steering force, when steering operation is carried out in the direction in which the absolute value of the steering angle is decreased. CONSTITUTION:A servo valve 56 controls the direction and pressure of hydraulic oil flowing into a hydraulic cylinder 58 for generating an assist steering force, in accordance with a manual steering force inputted to a steering shaft. Further, an amplification degree control device 30 applies a control signal to a variable valve 60 disposed in a bypass pipe line 80 to control the degree of amplification corresponding to the ratio of the assist steering force to the manual steering force. Further, when steering operation is carried out in the direction in which the absolute value of the steering force is decreased, the degree of amplification is lowered irrespective of the steering angle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power steering device for assisting the steering force of an automobile, and particularly to a device that improves the return performance of the steering wheel during cornering.

[Prior Art] 4 Conventionally, a hydraulic power steering device uses a hydraulic cylinder to generate an auxiliary steering force in response to a manual steering force input to a steering shaft. Furthermore, in order to improve the steering feeling, the ratio (amplification degree) of the auxiliary steering force to the manual steering force is changed depending on the vehicle speed, steering angle, steering angular velocity, etc. However, no device is known in which the degree of amplification is changed in accordance with the direction of increase or decrease in the absolute value of the steering angle.

[16 Problems to be Solved by the Invention] When the vehicle is being steered in a direction in which the absolute value of the steering angle is decreasing,
That is, when the steering wheel is moving toward the neutral point, the vehicle is about to return to a straight-ahead state.

When the vehicle returns to a straight-ahead state, a mechanical restoring force is applied from the steering wheels. For example, at the end of a corner, this restoring force causes the steering wheel to return to a neutral point against the driver's light, opposing drag. When a power steering device is not installed, the automatic restoring force of this steering wheel is large, so the restoring operation of the steering wheel is easy, and the feel of the steering wheel operation is also Q. However, in a hydraulic power steering device, the above-mentioned restoring force is attenuated due to fluid resistance in the hydraulic cylinder, conduit, etc., and this has the disadvantage that the steering wheel returns poorly. Furthermore, when the steering wheel returns to the neutral point due to the restoring force alone, a torsional torque in the opposite direction to the torque due to the restoring force is generated on the steering shaft due to the driver's grip force as a reaction. The power steering device uses this torsional torque as an input signal to generate an auxiliary steering force. For this reason, the auxiliary steering force acts in the opposite direction to the restoring force, which further weakens the automatic restoring force, making it difficult for the steering wheel to return. In addition, since it is not enough for the driver to return the handle by the restoring force, the driver rotates the handle towards the neutral point faster than the rotational speed due to the restoring force, and generates torsional torque in the direction of the neutral point to assist the driver in the direction of the neutral point. There were cases where the steering wheel was returned by gaining steering force. These causes lead to a decrease in the feel of the steering wheel restoration operation.

[Technical means for solving problems and their effects] Part 1
The figure shows a block diagram illustrating the concept of the present invention.

The present invention includes a hydraulic cylinder 58 that generates an auxiliary steering force to the steered wheels, and a hydraulic cylinder 58 that controls the inflow direction and pressure of pressure oil flowing into the hydraulic cylinder according to the manual steering force that is input to the steering shaft 52. a servo valve 56 that pumps oil from a tank 67, and a high pressure pipe 65a that is connected to the pump and leads pressure oil to the servo valve.
and a low pressure pipe 65 connecting the servo valve to the tank.
b, and is arranged in a bypass pipe line 80 between both working chambers of the hydraulic cylinder or between the high pressure pipe and the low pressure pipe,
a variable valve 60 that adjusts the pressure of oil applied to the high pressure chamber of the hydraulic cylinder in response to an external signal; and a variable valve 60 that applies a control signal to the variable valve; In a power steering system, the amplification control device 30 includes a steering angle detector 20 that detects a steering angle, and a steering angle detector 20 that detects a steering angle. A direction determining section 37 inputs a signal from the detector to determine the direction in which the absolute value of the steering angle increases or decreases; teeth,
An amplification r! that outputs a signal for setting the amplification degree low to the variable valve regardless of the steering angle. This is a power steering device characterized by having a 1 m joint portion 38.

The variable valve adjusts the pressure difference between the high pressure chamber and the low pressure chamber of the hydraulic cylinder, and the degree of amplification changes depending on this pressure difference. The variable valve can be provided in a pipeline that bypasses the high-pressure piping and the low-pressure piping, between the servo valve 56 and the hydraulic cylinder 58 or between the pump 64 and the servo valve 56, as shown in the figure. The amplification degree control device changes the amplification degree by controlling this variable valve. When the vehicle is being steered in a direction in which the absolute value of the steering angle increases, the auxiliary steering force is generated with an amplification degree that depends on the steering angle or a constant amplification degree that is independent of the steering angle. On the other hand, when the vehicle is being steered in a direction in which the absolute value of the steering angle decreases, the amplification degree is set low regardless of the steering angle. That is, when the steering wheel returns toward the neutral point, generation of auxiliary steering force that opposes the automatic restoring force from the steering wheels is prevented. Furthermore, since the variable valve of the bypass line is opened to lower the amplification degree, the resistance of the hydraulic cylinder is reduced, and it is possible to prevent the restoring force from attenuating.

As a result, the return performance of the steering wheel to the neutral point by the restoring force from the steering wheels is improved.

[Example 1 The present invention will be described below based on a specific example.

FIG. 2 is a block diagram showing the configuration of the device of this embodiment. The rotational force of the steering wheel 500 is transmitted to the input shaft 54 via the steering shaft 52. 56 is a hydraulic cylinder 58 that responds to the rotational force of the input shaft 54.
This is a servo valve that controls the inflow of pressure oil into. Reference numeral 58 denotes a hydraulic cylinder that operates a piston using pressure oil to rotate the steering arm shaft 62 and swing the steering arm 63 connected to the steering arm shaft 62 to increase the steering force. Pressure oil is sent to a pipe line 65a by a pump 64, and is then sent to a hydraulic valve 56, a hydraulic cylinder 58, and a servo valve 5.
6. Return to tank 67 through pipe 65b 3! The pump 64 is connected to an engine drive shaft (not shown) via a pulley 66. 60 is connected to the hydraulic cylinder 5.
This is a variable valve having a solenoid for controlling the opening degree of the valve body of the variable valve provided in a bypass passage that communicates both of the working chambers of No. 8. The opening degree of the variable valve is controlled by the duty control signal (1), the pressure in the high pressure chamber is adjusted, and the degree of amplification of the steering force is controlled.

The speed detector 10 consists of a vehicle speed sensor 11 and a speed counter 12 that counts its output pulses. The vehicle speed sensor 11 detects the rotation of a magnetic pole rotated by a speedometer cable as a pulse signal using a reed switch. The steering angle detector 20 is connected to the steering shaft 52
A photointerrupter 22 that detects the light passing through the slit plate 21, a waveform shaping circuit 23 that shapes the waveform of the signal detected thereby into a pulse waveform, and a rotation direction of the slit plate 21 is determined. It consists of a direction discriminating circuit 24 and an addition/subtraction counter 25 that adds and subtracts the pulse output according to the direction of rotation. Since the slit plate 21 blocks light from the photointerrupter 22 at a frequency corresponding to its rotation speed, the photointerrupter 22 outputs a number of pulses proportional to the amount of rotation of the steering shaft 52. Furthermore, since a pair of photointerrupters 22 are provided with a spatial phase difference of π/2, two-phase pulses A and B having a phase difference of π/2 are output from the photointerrupters 22.
The direction of rotation is determined by the state of the logic level of the phase pulses. The amplification degree control device 30 outputs a signal v1 that controls the variable valve 60 to control the amplification degree of the steering force. The other configuration of the amplification control device 30 is a microcomputer 31.
, memory 32 and input/output interfaces 33 and 34. The direction determining section and the amplification adjusting section of the amplification control device 30 are realized by software of a computer system.

3 and 4 are flowcharts showing the processing of the microcomputer 31. FIG. The direction determination circuit 24 generates an interrupt signal V2 at each minute rotation angle of the steering shaft 52.
is output to the microcomputer 31. The microcomputer 31 executes the process shown in FIG. 3 every time this interrupt signal v2 is input. In step 100, the signal v
Time data is read from the timer to determine the steering speed from the second interrupt interval. In step 102, a timer is reset to determine the time interval until the next interrupt. In step 104, the steering angle θ is read from the addition/subtraction counter 25, and a positive/negative determination is made, that is, it is determined whether the steering shaft is rotated clockwise or counterclockwise.

In the case of clockwise rotation, the process moves to step 106 and the difference from the previous input value Oθ is calculated. If it is determined to be negative, the process moves to step 108. In step 108, it is determined that the vehicle is being steered in a direction in which the absolute value of the steering angle increases, so the parameter NEGA is set to O to store this fact.

Further, if it is positive, that is, if the steering angle is being steered in a direction in which the absolute value of the steering angle is decreasing, NEGA is set to 1. Steering 1
) direction is to the left, it is similarly determined in step 112,
If the vehicle is being steered in a direction in which the absolute value of the steering angle increases, NFGA is set to O in step 116, and if the vehicle is being steered in a direction in which the absolute value of the steering angle is decreasing, step 114.
Set NEGA to 1 with . The processing from step 104 to step 116 corresponds to the direction determining section of the amplification control I device 30. In step 118, the speed of the steering angle is determined using the data of the interrupt interval T measured by the timer. In step 120, the currently input steering angle θ is stored as Oθ.

Next, the processing of the amplification degree adjusting section will be explained using FIG. 4. The process shown in FIG. 4 is executed at regular intervals. In step 200, the vehicle speed is input from the speed counter 12 and the steering angle is input from the addition/subtraction counter 25. In step 202,
The result determined by the direction determining section is determined, and if the steering is being performed in a direction in which the absolute value of the steering angle increases (cutting), the process moves to step 204 to obtain the amplification degree suitable for that mode. The driving current of the solenoid of the variable valve 60 for this purpose is calculated. If the steering is in the direction in which the absolute value of the steering angle decreases (return), the process moves to step 206, where a solenoid drive current is determined to obtain an amplification degree suitable for that mode.

Figure 5 shows the characteristics of the drive current with respect to the absolute value of the steering angle. (a) shows the characteristics when the absolute value increases, and (b) shows the characteristics when the absolute value decreases. The characteristics for the direction are shown. If the driving current of the solenoid of the variable valve 60 is large, the opening degree of the variable valve is large and the degree of amplification can be reduced.

In the case of a deep cut, the further the steering wheel is cut, the smaller the amplification degree becomes, and therefore the auxiliary steering force becomes smaller and the steering wheel becomes heavier. On the other hand, in the case of return, the amplification degree is small regardless of the steering angle.
Therefore, generation of an auxiliary steering force that resists the restoring force from the steered wheels is prevented as much as possible. Also, the variable valve is in the open state at 7C.
Therefore, the fluid resistance of the conduit is reduced and the return of the hydraulic cylinder is improved, so the attenuation of the restoring force is suppressed and the natural return of the handle is improved.

In step 208, the vehicle speed and steering angular velocity are roughly taken into account and the optimum amplification degree of C1 is controlled.

At step 210, a control signal (1) for driving the solenoid is output based on the determined amplification degree.

[Effects of the Invention] The present invention includes a direction determination unit that detects a steering angle and detects the direction of increase/decrease in the absolute value of the steering angle, and an auxiliary An amplification degree adjustment section is provided that reduces the amplification degree of the steering force relative to the input manual steering force.

Therefore, even if reaction torque is generated on the steering shaft in response to the driver's grip force against the restoring force from the steering wheel, it is possible to prevent the generation of auxiliary steering force based on this, so the attenuation of the restoring force is small and the steering wheel is in the neutral position. Go back to the point (
Become. Furthermore, since the variable valve is controlled to be open, the fluid resistance of oil flowing into and out of the hydraulic cylinder is reduced.
Hydraulic cylinder returns better. Therefore, the attenuation of the restoring force is small, and the return performance of the handle is improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the concept of the present invention. FIG. 2 is a block diagram showing the configuration of the device of this embodiment. FIGS. 3 and 4 are flowcharts p-1-, respectively, showing the processing of the micro combi coater used in the same apparatus. FIG. 5 is a characteristic diagram showing the characteristics of a control signal that controls the amplification degree with respect to the absolute value of the steering angle. 10...Speed detector 2o...Steering angle detector 3
0... Amplification degree control device 21... Slit plate 22.
... Photo interrupter 50 ... Steering wheel 52 ... Steering shaft 56 ... Servo valve 60 ... Variable valve 62
...Steering arm shaft 63...Steering arm 64...
・Pump 67...tank patent applicant
Toyoda Machine Tool Co., Ltd., Figure 5, Figure 7J-1+/%S! ■ (a) To t7IsuX; + (b) Also to t”(

Claims (1)

[Claims] (1) A hydraulic cylinder that generates an auxiliary steering force to the steered wheels, and a control system that controls the inflow direction and pressure of pressure oil flowing into both working chambers of the hydraulic cylinder according to the manual steering force that is input to the steering shaft. a servo valve that pumps oil from a tank; a high pressure pipe that is connected to the pump and guides pressure oil to the servo valve; a low pressure pipe that connects the servo valve to the tank; Disposed between the chambers or in a bypass pipeline between the high pressure piping and the low pressure piping,
a variable valve that adjusts the pressure of oil applied to the high pressure chamber of the hydraulic cylinder in response to an external signal; and a variable valve that adjusts the ratio of the auxiliary steering force to the manual steering force by applying a control signal to the variable valve. A power steering device comprising: an amplification degree control device that controls a certain amplification degree; the amplification degree control device includes a steering angle detector that detects a steering angle; A direction determining unit that determines the direction of increase or decrease in the absolute value of A power steering device comprising: an amplification adjustment section that outputs a signal to set the variable valve to a low value.