JPH08244636A - Power steering system - Google Patents

Abstract

PURPOSE: To overdrive a pump to steering aiding speed only in steering with a motor actuator and moderate the pump to the stand-by speed in the rectilinear motion and to improve an energy saving property by detecting the axial shift amount of a steering member from a mid-point of steering angle to judge whether or not the steering is carried out. CONSTITUTION: Since wheels are steered by the axial shift of a rack 8 due to the steering, whether or not the steering is carried out can be judged by detecting the axial shift amount of the rack 8 from the mid-point of the steering angle. Thus, a pump 37 is accelerated to the steering aiding speed only in the steeling by a motor 50 and decelerated to the stand-by speed in the rectilinear motion to improve an energy saving property. Since an incremental type encoder or the like capable of setting previously a reference point can be used for a shift distance detecting device 51 for detecting the axial shift amount of the rack 8 from the mid-point of steering angle, the determination of the mid-point of the steering angle is not needed and the energy saving property can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering device for generating a steering assist force by pressure oil from a pump driven by an electric actuator.

[0002]

2. Description of the Related Art Power comprising a steering member for steering wheels by axial movement by steering, a pump driven by an electric actuator, and a hydraulic actuator for generating a steering assist force by pressure oil from the pump. In the steering device, if the pump is always kept at a speed required for steering assist, the energy of the battery that is the power source of the electric actuator is wasted.

Therefore, energy saving is achieved by controlling the pump to a steering assist speed only when steering by an electric actuator and decelerating to a standby speed at the time of going straight, that is, at the midpoint of the steering angle. (Japanese Patent Laid-Open No. 56-99859 and Japanese Patent Laid-Open No. 3-1324)
74 publication).

That is, an absolute type rotary encoder or the like is used to detect the steering angle from a pulse signal corresponding to the rotation angle of the steering wheel, and it is determined whether or not the steering is performed from the steering angle from the steering midpoint. It was

The steering angle detected by the pulse signal sent from such an absolute type rotary encoder is relative, and is not absolute with reference to the steering angle midpoint. Had to make a decision. For example, utilizing that the steering torque becomes smaller at the steering angle midpoint, a torque sensor for detecting the steering torque is provided, and the time when the steering torque becomes smaller than the set value is determined as the steering angle midpoint. Based on the statistical distribution of the appearance frequency of the pulse signal, it is used that the statistical distribution of the appearance frequency of the detected pulse signal is a normal distribution that maximizes at the midpoint of the steering angle. It has been proposed to determine the rudder angle midpoint (see Japanese Patent Publication No. 6-43188).

[0006]

However, since it cannot be determined whether or not steering is being performed until the midpoint of the steering angle is determined, the pump must be held at the steering assist speed by the electric actuator. Therefore, there is a problem that wasteful energy is consumed when the vehicle is stopped and the idling state is continued until the decision. Further, if a torque sensor is used to determine the midpoint of the steering angle, the structure becomes complicated and the size becomes large.

Further, when stationary steering or the like is performed with the steering wheel being rotated to the lock position, the steering wheel is held at the lock position, so that it is not necessary to assist the steering, but in the conventional configuration, the pump is used. Was maintained at the steering assist speed by an electric actuator. Therefore, there is a problem that wasteful energy is consumed, seizure of the electric actuator occurs, and the flow noise of the pressure oil increases.

It is an object of the present invention to provide a power steering device which can solve the above problems.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a steering member for steering wheels by axial movement by steering, and a hydraulic actuator for generating steering assist force by pressure oil from a pump driven by an electric actuator. And a means for accelerating the pump to a steering assist speed when the steering assist condition is satisfied by an electric actuator and decelerating the pump to a standby speed when the steering assist cancellation condition is satisfied, in the steering angle of the steering member. A means for detecting the axial movement amount from the point is provided, and it is determined whether or not the steering assist condition is satisfied according to the axial movement amount from the steering angle midpoint of the steering member. .

There is at least two steering assist cancellation conditions, one steering assist cancellation condition is set so that the pump can be decelerated to the standby speed by the electric actuator when the vehicle is traveling straight, and the other steering assist cancellation condition is The pump is preferably set to be decelerated to the standby speed by the electric actuator when the steering member is located at the moving end.

[0011]

According to the structure of the present invention, since the wheels are steered by the axial movement of the steering member due to steering, it is possible to detect the axial movement amount of the steering member from the midpoint of the steering angle. , It is possible to determine whether or not steering is being performed. As a result, the electric actuator increases the pump speed to the steering assist speed only during steering and decelerates to the standby speed during straight traveling, thereby improving energy saving.

To detect the axial movement amount of the steering member from the midpoint of the steering angle, for example, an incremental linear encoder having a lattice scale and a sensor is used, and the lattice scale is on the steering member side and the sensor is on the fixed side. Attached to
This can be done by reading the scale of the scale with a sensor using the midpoint of the steering angle as a reference point in advance. That is, when the steering angle is detected from the rotation angle of the steering wheel as in the prior art, the rotation angle range of the steering wheel exceeds 360 degrees, so use a detection means such as an incremental encoder that can set a reference point in advance. I can't. On the other hand, in the present invention, it is not necessary to determine the midpoint of the steering angle because an incremental encoder or the like that can set a reference point in advance can be used by detecting the axial movement amount of the steering member. As a result, it is not necessary to maintain the pump at the steering assist speed by the electric actuator until the midpoint of the steering angle is determined, and energy saving can be improved. Moreover, the torque sensor for determining the midpoint of the steering angle is unnecessary, and the structure does not become complicated or large.

Further, when the steering member is located at the moving end, that is, when the steering wheel is rotated to the lock position, the pump is decelerated to the standby speed by the electric actuator to rotate the steering wheel to the lock position. When the stationary steering is performed with, the energy saving can be improved, seizure of the electric actuator can be prevented, and the flow noise of the pressure oil can be reduced.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

The rack and pinion type power steering device 1 shown in FIGS. 1 and 2 comprises an input shaft 2 connected to a steering wheel H and an output shaft 4 connected to the input shaft 2 via a torsion bar 3. ing. The torsion bar 3 is connected to the input shaft 2 via a pin 5, and is also connected to the output shaft 4 via serrations 6. A pinion 7 is formed on the output shaft 4, and each end of a rack (steering member) 8 meshing with the pinion 7 has a rack housing 1
It projects from the openings formed at both ends of 0b. Steering wheels (not shown) are connected to each end of the rack 8 via ball joints 19a, 19b, tie rods, and the like. The input shaft 2 has a bearing 9 and a valve housing 10
It is supported by a and is also supported by the output shaft 4 via the bush 11. The output shaft 4 is supported by the rack housing 10b via bearings 12 and 13. Accordingly, the rotation of the input shaft 2 due to the steering of the handle H is transmitted to the pinion 7 via the torsion bar 3, and the rotation of the pinion 7 causes the rack 8 to move in the axial direction. The wheels are steered by the movement of the rack 8. Oil seals 14 and 15 are provided between the input / output shafts 2 and 4 and the valve housing 10a. A support yoke 16 that supports the rack 8 is provided, and the support yoke 16 is pressed against the rack 8 by the elastic force of a spring 17.

As shown in FIG. 2, the rack 8 is provided between the inner circumference of the rack housing 10b and the outer circumference of the rack 8.
A piston 20 is attached to the, and thereby a steering assist hydraulic cylinder (hydraulic actuator) 18 having a pair of oil chambers 21 and 22 partitioned by the piston 20 is configured. On the outer side of the seal member 44 that seals the one oil chamber 21, the rack housing 10b is provided.
An annular stopper 45 is attached to the. The stopper 45 prevents one ball joint 19a from moving inward of the rack housing 10b. Further, a step 10c is formed on the inner circumference of the other opening of the rack housing 10b, and the other ball joint 19b abuts on this step 10c, thereby preventing the rack 8 from moving inward of the rack housing 10b. . As a result, the amount of axial movement of the rack 8 is regulated within a certain range.

Oil chambers 21 and 22 of the hydraulic cylinder 18
Is connected to the rotary hydraulic control valve 23 via pipes 46a and 46b. As shown in FIGS. 1 and 3, the control valve 23 includes a tubular first valve member 24 and a second valve member 25 that is inserted into the first valve member 24 so as to be relatively rotatable. . The first valve member 24 is rotatably attached to the output shaft 4 via a pin 26. The second valve member 25 is integrally formed on the outer circumference of the input shaft 2.

On the inner circumference of the first valve member 24 and the outer circumference of the second valve member 25, a plurality of recesses are formed at equal intervals in the circumferential direction along the axial direction. The first valve member side recesses are composed of four right steering recesses 27 which are located at equal circumferential intervals, and four left steering recesses 28 which are located at equal circumferential intervals. The second valve member side recesses are composed of four pressure oil supply recesses 29 that are located at equal circumferential intervals, and four pressure oil discharge recesses 30 that are located at equal circumferential intervals. The right steering recesses 27 and the left steering recesses 28 are alternately arranged in the circumferential direction, and the pressure oil supply recesses 29 and the pressure oil discharge recesses 30 are alternately arranged in the circumferential direction. Each of the right steering recesses 27 is provided with one oil of the hydraulic cylinder 18 as shown in FIG. 1 via the first flow passage 31 formed in the first valve member 24 and the first port 32 formed in the valve housing 10a. Each of the left steering recesses 28 communicates with the chamber 21 and the other oil chamber 22 of the hydraulic cylinder 18 is provided with a second flow passage 33 formed in the first valve member 24 and a second port 34 formed in the valve housing 10 a. Lead to Each pressure oil supply recess 29 communicates with a pump 37 as shown in FIG. 1 via a third flow passage 35 formed in the first valve member 24 and an inlet port 36 formed in the valve housing 10a. The pump 37 is driven by a motor (electric actuator) 50, and can be configured by, for example, a vane pump that discharges pressure oil at a flow rate according to the rotation speed. An in-vehicle battery is used as a power source for driving the motor 50. Recess 30 for discharging each pressure oil
Is a first discharge passage 38 formed in the second valve member 25,
It communicates with the tank 41 via a passage 47 between the inner and outer circumferences of the input shaft 2 and the torsion bar 3, a second discharge passage 39 formed in the input shaft 2 shown in FIG. 1, and a discharge port 40 formed in the valve housing 10a. As a result, the pump 37,
Oil chambers 21 and 22 of the tank 41 and the hydraulic cylinder 18
Communicate with each other through the intervalve passage 42 between the inner and outer circumferences of the first valve member 24 and the second valve member 25. Between the first valve member side concave portion and the second valve member side concave portion in the inter-valve flow path 42, there are throttle portions A, B, C, D whose opening degree is changed by relative rotation of both valve members 24, 25. , Its aperture A,
The hydraulic pressure acting on the hydraulic cylinder 18 is controlled by the changes in the opening degrees of B, C, and D.

FIG. 3 shows the relative positions of both valve members 24 and 25 at the midpoint of the steering angle where steering is not performed.
In this state, the pressure oil supply recesses 29 and the pressure oil discharge recesses 30 communicate with each other through all the throttles A, B, C, D, so that the pressure oil supplied from the pump 37 is directly supplied to the tank 41.
And the steering assist force is not generated, and therefore the pump 37
Need not be driven at the steering assist speed required for steering assist.

When steering from the midpoint of the steering angle to the right, the torsion bar 3 is twisted in accordance with the steering torque, and both valve members 2 are twisted.
4 and 25 rotate relative to each other. As a result, each right steering recess 2
7 and the opening portions of the throttle portions A between the pressure oil supply recess portions 29 and the left steering portion recess portions 28 and the pressure oil discharge recess portions 30 are increased, and the left portions of the throttle portions B are increased. The opening degree of the throttle portion C between the steering recess portion 28 and each pressure oil supply recess portion 29 and the opening degree of the throttle portion D between each right steering recess portion 27 and each pressure oil discharge recess portion 30 become small. . As a result, pressure oil is supplied from the pump 37 to the one oil chamber 21 of the hydraulic cylinder 18, and the pressure oil is circulated from the other oil chamber 22 of the hydraulic cylinder 18 to the tank 41, so that steering assist force to the right of the vehicle is obtained. Acts on the rack 8.

When the vehicle is steered to the left from the midpoint of the steering angle, the apertures of the throttles A, B, C and D change in the opposite manner to the case of steering to the right. Acts on the rack 8.

As shown in FIG. 2, a moving distance detecting device 51 for detecting the amount of axial movement of the rack 8 from the midpoint of the steering angle.
Is provided. The moving distance detecting device 51 is, for example, a well-known incremental linear encoder, and can be configured by a device having a lattice scale 51a and a sensor 51b for transmitting a reading pulse of the scale of the scale 51a. The scale 51a is the rack 8
The sensor 51b is attached so as to move with
Is attached to the fixed side of the rack housing 10b or the vehicle body. The sensor 51b is arranged with respect to the scale 51a so as to read the reference scale formed on the scale 51a at the midpoint of the steering angle and transmit the reference pulse. As shown in FIG. 1, the sensor 51a is connected to a control device 52 composed of a computer.

The control device 52 includes a vehicle speed sensor 53,
The pump driving motor 50 is connected. The control device 52 stores a control program for the motor 50.
As a part of the control program, one steering assist condition and two steering assist cancellation conditions are stored. Control device 52
Indicates that the steering assist signal is sent to the motor 5 when the steering assist condition is satisfied.
0 via a power amplifier (not shown), which drives the motor 50 with a control voltage according to the steering assist signal and speeds up the pump 37 from the standby speed to the steering assist speed. Further, the control device 52 decelerates the pump 37 to the standby speed by releasing the steering assist signal sent to the motor 50 when the respective steering assist release conditions are satisfied.

The steering assist condition is satisfied when the amount of axial movement of the rack 8 from the midpoint of the steering angle exceeds zero.

The first steering assist cancellation condition is satisfied when the axial movement amount of the rack 8 is zero for the set time. The set time may be set empirically so as to minimize unnecessary speedup of the pump 37, and is set to, for example, 1 second.

The second steering assist cancellation condition is set so that the pump 37 can be decelerated to the standby speed by the motor 50 when the rack 8 is located at the moving end. In this embodiment, the second steering assist release condition is satisfied when the rack 8 reaches a preset position near the moving end.

The control device 52 changes the control voltage of the motor 50 during steering assistance according to the vehicle speed detected by the vehicle speed sensor 53. That is, the steering assist speed of the pump 37 corresponding to the control voltage of the motor 50 during steering assist decreases in proportion to the vehicle speed as shown by the solid line K in FIG. 4, and is set to the maximum value Nmax when the vehicle speed is zero. The minimum value Nmin is set at the set vehicle speed Va or higher. Thus, the steering assist speed of the pump 37 is changed according to the vehicle speed, the steering assist force is increased at a low vehicle speed to improve the turning performance of the vehicle, and the steering assist force is decreased at a high speed to improve the running stability of the vehicle. are doing. Further, the control device 52 drives the motor 50 so that the standby speed becomes the minimum value Nmin during the steering assist as shown by the alternate long and short dash line L. As a result, the flow rate of the pressure oil delivered from the pump 37 reaches the maximum value Qmax until the rack 8 reaches a preset position ± E near the moving end, as indicated by the solid line M in FIG. When the rack 8 reaches a preset position ± E near the moving end, the rack 8 starts to decrease to the minimum value Qmin at the moving end. Further, the pressure oil flow rate during traveling at a constant vehicle speed is set to a value Qn corresponding to the vehicle speed until the rack 8 reaches a preset position ± E near the moving end, as indicated by a solid line N in FIG. , When the rack 8 reaches a preset position ± E near the moving end, the rack 8 starts decreasing and reaches the minimum value Qmin at the moving end. In addition,
At the start of steering assist, as shown by the broken line in the figure, the pressure oil flow rate gradually increases according to the amount of movement of the rack 8 from the midpoint of the steering angle.

Referring to the flow chart of FIG. 6, the pump 3
A control procedure via the motor 50 of No. 7 will be described.

First, the engine is started (step 1),
The pump 37 is set to the standby speed by the motor 50 (step 2). Next, the amount of movement of the rack 8 is detected (step 3), and it is determined whether the rack 8 is located at the midpoint of the steering angle (step 4). If the rack 8 is located at the midpoint of the steering angle, the process returns to step 2, and if it is not located at the midpoint of the steering angle, it is determined whether or not it has reached the vicinity of the moving end (step 5). Rack 8
Has reached the vicinity of the moving end, the process returns to step 2, and if not near the moving end, the motor 37 pumps 37.
Is increased to the steering assist speed (step 6). Next, the amount of movement of the rack 8 is detected (step 7), and it is determined whether the rack 8 is located at the midpoint of the steering angle (step 8). If the rack 8 is located at the midpoint of the steering angle, it is determined whether the set time has elapsed (step 9). When it is determined in step 8 that the rack 8 is not located at the midpoint of the steering angle during the progress of the timekeeping for determining whether or not the set time has elapsed, the progress of the timekeeping is canceled and the step 8 is performed again.
In, the time is newly advanced after it is determined that the vehicle is located at the midpoint of the steering angle. If the set time has not elapsed, the process returns to step 6. If the set time has elapsed, the process returns to step 2, and the motor 50 decelerates the pump 37 to the standby speed. When it is determined in step 8 that the rack 8 is not located at the midpoint of the steering angle, it is determined whether or not it has reached the vicinity of the moving end (step 10). If the rack 8 has not reached the vicinity of the moving end, the process returns to step 6, and if it has reached the vicinity of the moving end, the process returns to step 2, and the pump 50 is decelerated by the motor 50 to the standby speed.

According to the above construction, the wheels are steered by the axial movement of the rack 8 due to the steering, so that the steering is performed by detecting the axial movement amount of the rack 8 from the midpoint of the steering angle. You can judge whether or not. As a result, the energy saving property can be improved by increasing the pump 37 to the steering assist speed only when steering by the motor 50 and decelerating to the standby speed when going straight. A moving distance detecting device 5 for detecting the amount of axial movement of the rack 8 from the midpoint of the steering angle.
As 1, it is possible to use an incremental encoder or the like that can set a reference point in advance, so that it is not necessary to determine the steering angle midpoint, and the pump 37 can be used until the steering angle midpoint is determined.
Is not required to be maintained at the steering assist speed by the motor 50, and energy saving can be improved. Moreover, the torque sensor for determining the midpoint of the steering angle is unnecessary, and the structure does not become complicated or large. Further, when the rack 8 is located at the moving end, that is, when the steering wheel H is rotated to the lock position, the pump 37 can be decelerated to the standby speed by the motor 50, and the steering wheel H is installed in the lock position. When cutting or the like is performed, energy saving can be improved, seizure of the motor 50 can be prevented, and the flow noise of the pressure oil in the control valve 23 can be reduced.

The present invention is not limited to the above embodiment. For example, the moving distance detecting device 51 is not limited to an incremental linear encoder, and an A / D converter converts an electric signal corresponding to an axial moving amount of the rack 8 obtained via a potentiometer into a digital signal. It can be configured by sending to the control device 52. In this case, the reference value of the electric signal corresponding to the steering angle midpoint is stored in the control device 52 when the power steering device is assembled. The amount of axial movement of the rack 8 from the midpoint of the steering angle can be detected according to the change from the reference value without making a determination. In addition, even if the vehicle is traveling straight ahead, when the vehicle responds to unevenness on the road surface or when cornering a gentle curve, the amount of axial movement of the rack 8 exceeds zero in order to improve energy efficiency without steering assistance. The steering assist condition may be satisfied by exceeding the above condition. Further, when the steering assist condition is satisfied because the axial movement amount of the rack 8 exceeds a value exceeding zero, when the axial movement amount of the rack 8 is equal to or less than the value exceeding the zero for a set time, The steering assist cancellation condition No. 1 may be satisfied. Alternatively, the second steering assist cancellation condition may be satisfied when the rack 8 reaches the moving end. The standby speed of the pump 37 may be zero.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a hydraulic power steering device according to an embodiment of the present invention.

FIG. 2 is a front view of the hydraulic power steering device according to the embodiment.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is a diagram showing a relationship between a pump speed and a vehicle speed of the power steering device according to the embodiment.

FIG. 5 is a diagram showing the relationship between the rack movement distance and the pressure oil flow rate of the power steering device of the embodiment.

FIG. 6 is a flowchart showing a control procedure of a pump of the power steering device of the embodiment.

[Explanation of symbols]

 1 Power Steering Device 18 Hydraulic Cylinder 37 Pump 50 Pump Driving Motor 51 Moving Distance Detection Device 52 Control Device 53 Vehicle Speed Sensor

Claims (2)

[Claims] 1. A steering member for steering a wheel by axially moving by steering, a hydraulic actuator for generating a steering assist force by pressure oil from a pump driven by an electric actuator, and an electric actuator for the pump. In the power steering apparatus, a means for increasing the steering assist speed when the steering assist condition is satisfied and decelerating to the standby speed when the steering assist cancellation condition is satisfied,
A means for detecting the axial movement amount of the steering member from the steering angle midpoint is provided, and whether or not the steering assist condition is satisfied is determined according to the axial movement amount of the steering member from the steering angle midpoint. A hydraulic power steering device characterized by making a judgment. 2. At least two steering assist canceling conditions are set, and one steering assist canceling condition is set such that the pump can be decelerated to a standby speed by an electric actuator when going straight, and another steering assist canceling condition is set. The power steering apparatus according to claim 1, wherein the power steering device is set so that the pump can be decelerated to a standby speed by an electric actuator when the steering member is located at the moving end.