JPH10203387A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device by which fuel consumption of a vehicle can be reduced without incurring reduction in a steering feeling and generation of a noise. SOLUTION: A power steering device has a hydraulic actuator 18 to generate steering assisting force by pressure oil supplied through an oil pressure control valve 23 from a pump 37 driven by a motor 50 which is put at steering assisting speed at steering assisting time and is put at standby speed at steering assistance released time. A pressure oil supply pipe to the control valve 23 from its pump 37 has a main pressure oil supply part 82 and an auxiliary pressure oil supply part 83. When rotating speed of its motor 50 is increased to steering assisting speed from standby speed, the auxiliary pressure oil supply part 83 is selected until preset time passes after a speed increase is started, and the main pressure oil supply part 82 is selected after its preset time passes, as a pressure oil supply passage to its control valve 23. A length of a part elastically deformable by oil pressure of its auxiliary pressure oil supply part 83 is set shorter than a length of a part elastically deformable by oil pressure of its main pressure oil supply part 82, or is set to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A pump driven by a motor, a hydraulic control valve for hydraulic oil discharged from the pump, and a hydraulic actuator for generating a steering assist force by the hydraulic oil supplied through the control valve are provided. In a power steering apparatus, if the motor is always maintained at a speed necessary for assisting steering, energy of a battery serving as a power source of the motor is wasted. Therefore, the fuel consumption of the vehicle is reduced by setting the rotation speed of the motor to the steering assist speed only during the steering assist, and to the standby speed when the steering assist is released.

There is also a problem that the noise generated by the pump increases due to the pulsation of the hydraulic oil discharged from the pump. Therefore, at least a part of the pressure oil supply pipe from the pump to the control valve is constituted by a rubber pipe or the like which can be elastically deformed by the applied oil pressure, thereby increasing the noise generated by the pump due to the oil pressure pulsation. The prevention is performed by elastic deformation of the supply pipe.

[0004]

However, in the conventional configuration, when the rotation speed of the motor is changed from the standby speed to the steering assist speed, the pressure oil supply pipe is increased with an increase in the oil pressure of the pressure oil discharged from the pump. Is elastically expanded, a delay occurs until the flow rate of the pressure oil supplied to the hydraulic actuator becomes a value necessary for the steering assist. As a result, there is a problem that the steering feeling is deteriorated due to the delay of the steering assist.

An object of the present invention is to provide a power steering device that can solve the above-mentioned problems.

[0006]

SUMMARY OF THE INVENTION The present invention provides a pump driven by an electric motor, a hydraulic control valve for hydraulic oil discharged from the pump, and a steering assist by a hydraulic oil supplied through the control valve. A hydraulic actuator for generating a force, and a means for setting the rotation speed of the motor to a steering assist speed at the time of steering assist and a standby speed at the time of canceling the steering assist, and providing a hydraulic oil supply pipe from the pump to the control valve. In a power steering device that is at least partially elastically deformable by an applied hydraulic pressure, the pressure oil supply pipe has a main pressure oil supply section and an auxiliary pressure oil supply section, and waits for the rotation speed of the motor. When the speed is increased from the speed to the steering assist speed, the auxiliary pressure oil supply unit is operated until the set time elapses from the start of the speed increase, and after the set time elapses, the main pressure oil supply unit is operated. Oil supply Means for selecting a path are provided, and the length of the portion that can be elastically deformed by the hydraulic pressure in the auxiliary pressure oil supply portion is shorter than the length of the portion that can be elastically deformed by the hydraulic pressure in the main pressure oil supply portion, or It is characterized by being set to zero.

According to the structure of the present invention, the rotation speed of the motor for driving the pump for discharging the pressure oil for generating the steering assist force is set to the steering assist speed only during the steering assist, and to the standby speed when the steering assist is released. By doing so, the fuel efficiency of the vehicle can be reduced. When the rotation speed of the motor is changed from the standby speed to the steering assist speed, the length of the portion that can be elastically deformed by hydraulic pressure is zero or shorter than the main pressure oil supply portion until the set time elapses from the start of speed increase. Pressure oil can be supplied from the pump to the control valve via the auxiliary pressure oil supply section. As a result, the elastic expansion of the pressure oil supply pipe accompanying the increase in the oil pressure at the start of the steering assist can be reduced or eliminated, so that the flow rate of the hydraulic oil supplied to the hydraulic actuator for generating the steering assist force is increased. It is possible to prevent a delay from occurring until the value required for assistance is reached. After the lapse of the set time, by supplying pressure oil from the pump to the control valve through the main pressure oil supply unit, the elastic deformation of the main pressure oil supply unit increases pump noise generated by hydraulic pulsation. Can be prevented.

It is preferable that the set time corresponds to a rising time until the rotation speed of the motor reaches the steering assist speed from the standby speed. As a result, if the rise time is long, by increasing the set time,
Effectively prevent the delay of steering due to the elastic deformation of the main pressure oil supply unit.If the rise time is short, shorten the set time to reduce the increase in pump noise due to hydraulic pulsation. It can be effectively prevented.

[0009]

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

A rack and pinion type power steering device 1 shown in FIG. 1 includes 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. The torsion bar 3 is connected to the input shaft 2 via a pin 5 and to the output shaft 4 via a serration 6. A pinion 7 is formed on the output shaft 4, and a rack 8 that meshes with the pinion 7 is connected to steering wheels (not shown). The input shaft 2 is supported by a valve housing 10 a via a bearing 9, and is supported by an output shaft 4 via a bush 11. The output shaft 4 is supported by the rack housing 10b via bearings 12 and 13. As a result, the rotation of the input shaft 2 due to the steering is transmitted to the pinion 7 via the torsion bar 3, and the rack 8 moves in the vehicle width direction, and the wheels are steered by the movement of the rack 8. Note that oil seals 14, 15 are provided between the input / output shafts 2, 4 and the valve housing 10a. Also,
A support yoke 16 for supporting the rack 8 is provided. The support yoke 16 is pressed against the rack 8 by the elastic force of a spring 17.

A hydraulic cylinder 18 is provided as a hydraulic actuator for applying a steering assist force. The hydraulic cylinder 18 includes a cylinder tube configured by the rack housing 10b, a piston 20 formed integrally with the rack 8, and a pair of oil chambers 21 and 22 partitioned by the piston 20. A rotary hydraulic control valve 23 is connected to each of the oil chambers 21 and 22. The control valve 23 includes a cylindrical first valve member 24 and a second valve member 2 that is rotatably inserted into the first valve member 24.
5 is provided. The first valve member 24 is connected to the output shaft 4
Is mounted so as to be rotatable together with a pin 26 via a pin 26.
The second valve member 25 is formed integrally with the outer periphery of the input shaft 2.

As shown in FIG. 2, a plurality of recesses along the axial direction are formed on the inner periphery of the first valve member 24 and the outer periphery of the second valve member 25 at equal intervals in the circumferential direction. The first valve member-side recess is composed of four right steering recesses 27 located at equal intervals in the circumferential direction and four left steering recesses 28 located at equal intervals in the circumferential direction. The second valve member-side recess is composed of four pressure oil supply recesses 29 located at equal intervals in the circumferential direction and four pressure oil discharge recesses 30 located at equal intervals in the circumferential direction. Each right steering recess 27 and each left steering recess 28 are alternately arranged in the circumferential direction, and each pressure oil supply recess 29 and each pressure oil discharge recess 30 are alternately arranged in the circumferential direction. Each right steering recess 27 is
As shown in FIG. 1, one of the oil chambers 2 of the hydraulic cylinder 18 passes through a first flow path 31 formed in the first valve member 24 and a first port 32 formed in the valve housing 10a.
Lead to 1. Each left steering recess 28 is provided with the first valve member 2.
2 and the second flow path 33 formed in the valve housing 1
Through the second port 34 formed at 0a, the oil port 22 communicates with the other oil chamber 22 of the hydraulic cylinder 18. Each pressure oil supply recess 29
Is a third flow path 35 formed in the first valve member 24 and an inlet port 36 formed in the valve housing 10a.
As shown in FIG. 1, an electromagnetic switching valve 80 to be described later communicates with the pump 37. The pump 37 includes a motor 50
, And can be constituted by a vane pump or a gear pump that discharges pressure oil at a flow rate corresponding to the rotation speed of the motor 50, for example. Each pressure oil discharge recess 30 is formed in the first discharge passage 38 formed in the second valve member 25, the passage 47 between the input shaft 2 and the inner and outer circumferences of the torsion bar 3, and the input shaft 2 shown in FIG. 1. It communicates with the tank 41 via a second discharge path 39 and a discharge port 40 formed in the valve housing 10a. Thereby, the pump 37 and the tank 4
1 and the respective oil chambers 21 and 22 of the hydraulic cylinder 18
The valve member 24 and the second valve member 25 communicate with each other through an inter-valve flow path 42 between the inner and outer circumferences. 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 formed throttle portions A, B, C, D whose opening degree changes due to relative rotation of the two valve members 24, 25. , The apertures A, B, C,
The hydraulic pressure acting on the hydraulic cylinder 18 is controlled by the change in the opening degree of D.

FIG. 2 shows the relative positions of the two valve members 24 and 25 at the midpoint of the steering angle where steering is not being performed. In this state, since each pressure oil supply recess 29 and each pressure oil discharge recess 30 communicate with each other through all the throttle portions A, B, C, and D,
The pressure oil supplied from the pump 37 is directly returned to the tank 41 and does not generate a steering assist force. Therefore, it is not necessary to drive the motor 50 at a steering assist speed required for steering assist.

When the steering is steered rightward from the steering angle midpoint, the torsion bar 3 is twisted in accordance with the steering torque, and the two valve members 2 are turned.
4 and 25 rotate relatively. As a result, each right steering recess 2
The opening degree of the throttle A between each of the pressure oil supply recesses 29 and the throttle B between each of the left steering recesses 28 and each of the pressure oil discharge recesses 30 increases. The opening degree of the throttle portion C between the steering recess 28 and each pressure oil supply recess 29 and the opening degree of the throttle portion D between each right steering recess 27 and each pressure oil discharge recess 30 are reduced. . As a result, pressure oil is supplied from the pump 37 to one oil chamber 21 of the hydraulic cylinder 18, and the pressure oil is returned from the other oil chamber 22 of the hydraulic cylinder 18 to the tank 41, and the steering assist force to the right of the vehicle is provided. Acts on the rack 8.

When the steering wheel is steered to the left from the steering angle midpoint, the degree of opening of each of the throttle portions A, B, C, and D changes in reverse to the case where the steering device is steered to the right. Acts on the rack 8.

A pressure oil supply pipe from the pump 37 to the control valve 23 has a common pressure oil supply section 81 connecting between the pump 37 and the electromagnetic switching valve 80, and an inlet of the electromagnetic switching valve 80 and the control valve 23. A main pressure oil supply unit 82 for connecting between the port 36 and the electromagnetic switching valve 80 and the main pressure oil supply unit 8
2 and an auxiliary pressure oil supply unit 83 connected to the middle part of the second oil supply unit.

The solenoid-operated switching valve 80 includes a spool 80a that can be displaced between a rising position and a steady position, a solenoid 80b for displacing the spool 80a from the rising position to a steady position, and a rising position of the spool 80a. Spring 80c for returning to the raised position and its common pressure oil supply unit 8
1, a connection port 80 e to the main pressure oil supply unit 82, and a connection port 80 f to the auxiliary pressure oil supply unit 83. Thereby, the spool 8
0a is located at the starting position when the common pressure oil supply unit 81
And the auxiliary pressure oil supply unit 83 and the inlet of the main pressure oil supply unit 82 is closed, and when the spool 80a is located at the steady position, the common pressure oil supply unit 81 and the main pressure oil supply unit 82 are connected. At the same time, the inlet of the auxiliary pressure oil supply unit 83 is closed. In other words, the electromagnetic switching valve 80 allows the main pressure oil supply unit 82 and the auxiliary pressure oil supply unit 83 to be selectively selected as the pressure oil supply path to the control valve 23. The main pressure oil supply unit 82 is provided with a check valve 84 for preventing the flow of pressure oil from the auxiliary pressure oil supply unit 83 to the main pressure oil supply unit 82. Note that the common pressure oil supply unit 81 may be omitted, and the pump 37 and the electromagnetic switching valve 80 may be directly connected.

At least a part of the main pressure oil supply section 82 is made of, for example, a rubber pipe, so that it can be elastically deformed by the hydraulic pressure of the pressure oil supplied from the pump 37 to the control valve 23. Have been. The auxiliary pressure oil supply unit 83 is formed of, for example, a metal tube, and has a length that is substantially elastically deformed even when the hydraulic pressure of the pressure oil supplied from the pump 37 to the control valve 23 acts. Even if it is set to zero or has a portion that can be elastically deformed by the action of the oil pressure, it is much shorter than the elastically deformable portion of the main pressure oil supply unit 82.

As shown in FIG. 1, the motor 50 is connected to a controller 60. The controller 60 has a control circuit 61 and a drive circuit 62. The control circuit 6
Reference numeral 1 denotes a main component of a computer, which is connected to a steering angle sensor 51 for detecting the steering angle of the steering wheel H from the steering angle midpoint and a vehicle speed sensor 53, and outputs an instruction signal to a drive circuit 62 according to a stored control program. I do. The drive circuit 62 is connected to the battery power supply 63, the motor 50, and the solenoid 80b of the electromagnetic switching valve 80, and drives the motor 50 and the electromagnetic switching valve 80 with a current corresponding to an instruction signal from the control circuit 61. A well-known power control switching element including a transistor such as an FET can be used.

The control procedure of the motor 50 by the control circuit 61 will be described with reference to the flowchart shown in FIG.

First, the control circuit 61 determines whether or not steering has been performed (step 1). For example, a preset reference steering angle is stored. The reference steering angle is, for example, a play angle from the steering wheel midpoint of the steering wheel H. When the steering angle of the steering wheel H detected by the steering angle sensor 51 is equal to or larger than the reference steering angle, it is determined that steering is performed. When there is no change in the steering angle or when a predetermined time has elapsed after the steering angle returns to the play range, it is determined that there is no steering.

If it is determined in step 1 that steering is performed, the control circuit 61 outputs to the drive circuit 62 an instruction signal for setting the rotation speed of the motor 50 to the steering assist speed. In response to the instruction signal, the drive circuit 62 supplies a current so that the rotation speed of the motor 50 becomes equal to the steering assist speed Na (step 2). The steering assist speed Na is a speed set in advance so that the flow rate of the pressure oil sent from the pump 37 becomes a flow rate necessary for steering assist. The steering assist speed Na of the motor 50 is increased when the vehicle speed detected by the vehicle speed sensor 53 is low, and is decreased when the vehicle speed is high. Thus, at low vehicle speeds, the steering assist force is increased to improve the turning performance of the vehicle, and at high vehicle speeds, the steering assist force is reduced to improve the running stability of the vehicle.

Next, it is determined whether or not a set time has elapsed after outputting an instruction signal for setting the rotation speed of the motor 50 to the steering assist speed (step 3). The setting time is
4 corresponds to a rising time ta until the rotation speed of the motor 50 reaches the steering assist speed Na from the standby speed. The specific value of the set time may be set to be equal to the rising time ta, or set to be longer than the rising time ta if the steering assist is delayed due to the expansion of the main pressure oil supply unit 82 by the hydraulic pressure. As long as the steering assist is not delayed, it may be set as short as possible, and an appropriate value can be obtained by an experiment. The standby speed is a preset speed smaller than the steering assist speed, and is set to zero in the present embodiment, but may be a value larger than zero.

If the set time has not elapsed in step 3, the process returns to step 1. Thereby, the motor 5
When the rotation speed of 0 is increased from the standby speed to the steering assist speed Na, the solenoid 80b of the electromagnetic switching valve 80 is not excited until the set time elapses from the start of the acceleration, and the spool 80a is moved to the start position. Since it is located, the auxiliary pressure oil supply unit 83 is selected as the pressure oil supply path from the pump 37 to the control valve 23.

If the set time has elapsed in step 3, the control circuit 61 sets the spool 8 of the electromagnetic switching valve 80
An instruction signal for displacing 0a to the steady position is output to the drive circuit 62. In response to the instruction signal, the drive circuit 62 supplies an exciting current for the solenoid 80b of the electromagnetic switching valve 80 (step 4), and thereafter returns to step 1. As a result, when the rotation speed of the motor 50 is increased from the standby speed to the steering assist speed, the spool 80a of the electromagnetic switching valve 80 is located at the steady position after a set time has elapsed from the start of the acceleration. The main pressure oil supply unit 82 is selected as a pressure oil supply path from the pump 37 to the control valve 23.

If it is determined in step 1 that there is no steering, the control circuit 61 outputs to the drive circuit 62 an instruction signal for setting the rotational speed of the motor 50 to a standby speed, that is, zero, and the drive circuit 62 outputs (Step 5), whereby the steering assist is released. Further, the control circuit 61 outputs to the drive circuit 62 an instruction signal for displacing the spool 80a of the electromagnetic switching valve 80 to the rising position. In response to the instruction signal, the drive circuit 62 cuts off the current to the solenoid 80b of the electromagnetic switching valve 80, whereby the spool 80a is displaced to the rising position (Step 6). Thereafter, the process returns to step 1.

According to the above configuration, the rotation speed of the drive motor 50 of the pump 37 for discharging the pressure oil for generating the steering assist force is set to the steering assist speed only during the steering assist, and to the standby speed when the steering assist is released. By doing so, the fuel efficiency of the vehicle can be reduced. When the rotation speed of the motor 50 is changed from the standby speed to the steering assist speed, the length of the portion that can be elastically deformed by the hydraulic pressure is zero or the main pressure oil supply unit 82 until the set time elapses from the start of the speed increase. The pressure oil can be supplied from the pump 37 to the control valve 23 via the short auxiliary pressure oil supply unit 83. As a result, the elastic expansion of the pressure oil supply pipe accompanying the increase in the oil pressure at the start of the steering assist can be reduced or eliminated, so that the flow rate of the hydraulic oil supplied to the hydraulic cylinder 18 for generating the steering assist force is reduced. It is possible to prevent a delay from occurring until a value required for steering assist is obtained. After the elapse of the set time, the pressure oil is supplied from the pump 37 to the control valve 23 through the main pressure oil supply unit 82, and the elastic deformation of the main pressure oil supply unit 82 causes the hydraulic pulsation. An increase in pump noise can be prevented. Furthermore, since the set time corresponds to the rise time ta until the rotation speed of the motor 50 reaches the steering assist speed from the standby speed, if the rise time ta is long, the set time is increased by increasing the set time. The delay of steering due to the elastic deformation of the main pressure oil supply unit 82 is effectively prevented, and when the rise time ta is short, the set time is shortened to increase the noise generated by the hydraulic pulsation. Can be effectively prevented.

The present invention is not limited to the above embodiment. For example, conditions for performing the steering assist and conditions for canceling the steering assist are not particularly limited. The steering assist condition is satisfied when the steering angular velocity exceeds a set value or when the direction indicator is activated, or the steering angular velocity is not satisfied. Is less than the set value for the set time, the steering assist release condition can be satisfied. Further, in the above embodiment, the present invention is applied to the rack and pinion type power steering device, but may be applied to, for example, a ball screw type power steering device.

[0029]

According to the present invention, it is possible to provide a power steering apparatus capable of reducing the fuel consumption of a vehicle without deteriorating the steering feeling or generating noise.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a power steering device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a flowchart showing a control procedure of the power steering device according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating a relationship between a rotation speed of a motor and time in the power steering device according to the embodiment of the present invention;

[Explanation of symbols]

 Reference Signs List 1 power steering device 18 hydraulic cylinder (hydraulic actuator) 23 control valve 37 pump 50 motor 60 controller 82 main pressure oil supply unit 83 auxiliary pressure oil supply unit

Claims (2)

[Claims] A pump driven by an electric motor, a hydraulic control valve for hydraulic oil discharged from the pump, a hydraulic actuator for generating a steering assist force by the hydraulic oil supplied through the control valve, Means for setting the rotational speed of the motor to a steering assist speed during steering assist and a standby speed when canceling the steering assist, at least a part of a pressure oil supply pipe from the pump to the control valve is provided with an operating hydraulic pressure. The pressure oil supply pipe has a main pressure oil supply section and an auxiliary pressure oil supply section, and the rotational speed of the motor is increased from a standby speed to a steering assist speed. In this case, the auxiliary pressure oil supply unit is selected as the pressure oil supply path to the control valve after the set time has elapsed since the start of the speed increase, and the main pressure oil supply unit after the set time has elapsed. A step is provided, and the length of the portion that can be elastically deformed by the hydraulic pressure in the auxiliary pressure oil supply portion is shorter than the length of the portion that can be elastically deformed by the hydraulic pressure in the main pressure oil supply portion, or is zero. A power steering device characterized in that: 2. The power steering apparatus according to claim 1, wherein the set time corresponds to a rise time until the rotation speed of the motor reaches a steering assist speed from a standby speed.