JPH08230706A - Power steering device - Google Patents

Abstract

(57) [Summary] [Configuration] A steering assist force is generated by pressure oil from a pump driven by an electric actuator. The electric actuator accelerates the pump to the steering assist speed when the steering assist condition is satisfied, and decelerates to the standby speed when the first steering assist cancellation condition is satisfied. The steering assist speed is changed according to the vehicle speed. When the detected vehicle speed is equal to or lower than the reference vehicle speed, the pump is accelerated even if the steering assist condition is not satisfied, and the steering assist speed is maintained even if the first steering assist cancellation condition is satisfied. If the detected vehicle speed is less than or equal to the reference vehicle speed, the first
The pump is decelerated by satisfying the second steering assist cancellation condition different from the steering assist cancellation condition. The second steering assist cancellation condition is satisfied by not satisfying the steering condition and satisfying the criterion that the steering frequency is lower than when the first steering assist cancellation condition is satisfied. [Effect] It is possible to prevent a delay in steering assistance at a low vehicle speed.

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 In a power steering system including a pump driven by an electric actuator and a hydraulic actuator for generating a steering assist force by pressure oil from the pump, the pump is always operated. If an attempt is made to maintain the speed required for steering assistance, the energy of the battery that will be the power source for the electric actuator will be wasted.

Therefore, a means for increasing the steering assist speed to the steering assist speed when the steering assist condition is satisfied by the electric actuator and decelerating the pump to the standby speed when the steering assist cancellation condition is satisfied is provided. It is attempted to improve energy efficiency by speeding up and decelerating to the standby speed when traveling straight ahead, that is, near the midpoint of the steering angle. Furthermore, increase the steering assist speed at low vehicle speeds,
By decreasing it at high vehicle speeds, the steering assist force can be increased at low vehicle speeds to improve turning performance during garage entry and stationary steering, and at high vehicle speeds the steering assist force can be reduced to improve running stability. (JP-A-56-9985)
9 and JP-A-3-132474).

However, when the pump is accelerated from the standby speed to the steering assist speed by the electric actuator during steering, since the steering assist speed is large at low vehicle speed, the steering assist is delayed due to the response delay of the electric actuator, and the steering assist is delayed. There is a problem that the feeling is deteriorated.

Therefore, in the case of frequent steering such as mountain road traveling, the time for maintaining the steering assist state is lengthened or the voltage applied to the electric actuator in the standby state is increased to prevent response delay, In addition, when the steering frequency is low, such as when traveling on a highway or in an urban area, it has been proposed to shorten the time for maintaining the steering assist state or reduce the voltage applied to the electric actuator in the standby state ( JP-A-3-112777).

However, even when driving in an urban area, steering may be performed at a low speed. In such a case, if the time for maintaining the steering assist state is shortened or the voltage applied to the electric actuator in the standby state is small, the steering operation is performed. The delay will increase.

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

[0008]

SUMMARY OF THE INVENTION The present invention is directed to a hydraulic actuator for generating a steering assist force by pressure oil from a pump driven by an electric actuator, and a steering assist speed for the pump when the steering assist condition is satisfied by the electric actuator. In the power steering apparatus, the power steering device includes means for increasing the vehicle speed and decelerating to the standby speed when the first steering assist cancellation condition is satisfied, and means for changing the steering assist speed in accordance with the vehicle speed. Is equal to or lower than the preset reference vehicle speed, the pump is accelerated through the electric actuator even if the steering assist condition is not satisfied, and the steering assist speed is maintained even if the first steering assist cancellation condition is satisfied. And means.

When the detected vehicle speed is equal to or lower than the reference vehicle speed, the pump is decelerated via the electric actuator by satisfying the second steering assist cancellation condition different from the first steering assist cancellation condition, and the steering assist condition is satisfied. The second steering assist cancellation condition satisfies the criterion that the steering frequency is lower than that when the first steering assist cancellation condition is satisfied and the second steering assist cancellation condition is not in the steering state. It is preferably satisfied.

Means for detecting at least one of the steering angle and the steering angular velocity is provided, and the first steering assist release condition is that at least one of the steering angle and the steering angular velocity is less than or equal to a value continuously set for a set time. The second steering assist release condition is satisfied when at least one of the steering angle and the steering angular velocity is continuously equal to or less than a set value for a set time, and the second steering assist release condition is satisfied. At least one of the set steering angle and steering angular velocity is set to be less than the value set for the first steering assist cancellation condition, and the time set for the second steering assist cancellation condition is set for the first steering assist cancellation condition. It is preferable that the release condition is set to be longer than the set time.

[0011]

In the power steering apparatus to which the present invention is applied, the pump is accelerated by the electric actuator to the steering assist speed only during steering, and decelerated to the standby speed during straight traveling, that is, near the midpoint of the steering angle. By doing so, energy saving is improved. Also, by increasing the steering assist speed at low vehicle speeds and decreasing it at high vehicle speeds, the steering assist force is increased at low vehicle speeds to improve turning performance during garage entry and stationary steering, and at high vehicle speeds. To improve running stability. The steering assist condition is
A criterion for determining whether the vehicle is in a steering state, for example, at least one criterion when the steering angle exceeds a preset value and when the steering angular velocity exceeds a preset value, or the direction indicator operates, etc. , Can be satisfied. The first steering assist cancellation condition is at least one of criteria for determining that the vehicle is not in a steering state, for example, when the steering angle is less than or equal to a preset value and when the steering angular velocity is less than or equal to a preset value. The time that satisfies the criteria can be satisfied by satisfying the time such as the passage of a preset time.

According to the structure of the present invention, in such a power steering system, when the detected vehicle speed is equal to or lower than the reference vehicle speed, the pump is accelerated through the electric actuator even if the steering assist condition is not satisfied. By maintaining the steering assist speed even when the first steering assist cancellation condition is satisfied, the steering assist state can be maintained at a low vehicle speed. This can prevent a delay in steering assistance during steering. The reference vehicle speed is set so as not to be lower than the vehicle speed when the steering force is large, such as when entering the garage or when stationary, and when it does not require a large steering assist force, such as when driving at high speeds. Good.

Further, even if the vehicle speed is lower than the reference vehicle speed, the steering frequency is low when traveling on a road in a traffic jam, for example.
In such a case, steering assist is a waste of energy. Therefore, it is conceivable to decelerate the pump to the standby speed when the steering frequency is low even at the standard vehicle speed or less. Therefore, when the vehicle speed is equal to or lower than the reference vehicle speed, the pump is decelerated by the electric actuator by satisfying the second steering assist cancellation condition different from the first steering assist cancellation condition, and the standby speed is maintained until the steering assist condition is satisfied. By doing so, it becomes possible to improve the energy saving in a situation where the steering frequency is low even at the standard vehicle speed or less.

The fact that the state where the steering angle or the steering angular velocity is equal to or less than the set value continues for the set time is a criterion for judging that the steering state is not established. In that case, the value of the steering angle or the steering angular velocity set under the second steering assist cancellation condition is less than the value set under the first steering assist cancellation condition, and the duration time that is less than or equal to the set value is 2 The steering assist cancellation condition is longer than the first steering assist cancellation condition means that the steering frequency is lower when the second steering assist cancellation condition is satisfied than when the first steering assist cancellation condition is satisfied. It will be the criterion.

[0015]

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 FIG. 1 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. 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. Its output shaft 4
A pinion 7 is formed on the rack, and a rack 8 meshing with the pinion 7 is connected to a steering wheel (not shown). 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. As a result, the rotation of the input shaft 2 due to steering is transmitted to the pinion 7 via the torsion bar 3, the rack 8 moves in the vehicle width direction, and the movement of the rack 8 steers the wheels. Oil seals 14 and 15 are provided between the input / output shafts 2 and 4 and the valve housing 10a. Also,
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.

A hydraulic cylinder 18 is provided as a hydraulic actuator that applies a steering assist force. The hydraulic cylinder 18 includes a cylinder tube configured by the rack housing 10b and a piston 20 integrally formed with the rack 8, and a pair of oil chambers 21 and 22 partitioned by the piston 20 are formed. Each oil chamber 21,
A rotary hydraulic control valve 23 is connected to 22.
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 attached to the output shaft 4 via a pin 26 so as to be rotatable together. The second valve member 25 is integrally formed on the outer circumference of the input shaft 2.

As shown in FIG. 2, a plurality of recesses along the axial direction are formed in the inner circumference of the first valve member 24 and the outer circumference of the second valve member 25 at equal intervals in the circumferential direction. The first valve member-side recesses are four right steering recesses 27 located at equal circumferential intervals, and the four right steering member recesses 4 are provided at equal circumferential intervals.
And two left steering recesses 28. The second valve member-side recesses are arranged at equal intervals in the circumferential direction and the four recesses 29 for supplying pressure oil are located at equal intervals in the circumferential direction.
It is composed of two pressure oil discharge recesses 30. 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. Room 2
1, the left steering recesses 28 are formed by the first valve members 24.
Second flow path 33 and valve housing 10 formed in
hydraulic cylinder 18 through the second port 34 formed in a.
To the other oil chamber 22. Each pressure oil supply recess 29 is
It communicates with a pump 37 as shown in FIG. 1 through a third flow path 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. 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. 2 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 the steering wheel is steered to the right from the midpoint, the torsion bar 3 is twisted according to the steering torque, and the valve members 24 and 25 rotate relative to each other. As a result, the opening degree of the throttle portion A between each right steering recess portion 27 and each pressure oil supply recess portion 29 and the throttle portion B between each left steering recess portion 28 and each pressure oil discharge recess portion 30 are reduced. The opening degree becomes large, and the opening degree of the throttle portion C between each left steering recess portion 28 and each pressure oil supply recess portion 29 and the throttle portion between each right steering recess portion 27 and each pressure oil discharge recess portion 30. The opening degree of the portion D becomes smaller. 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 steering wheel is steered to the left from the midpoint of the steering angle, the throttles A, B, C,
Since the opening degree of D changes in the opposite direction to the case of steering to the right, the steering assist force to the left of the vehicle acts on the rack 8.

As shown in FIG. 1, a sensor 51 for detecting the steering angle of the steering wheel H is connected to a controller 52 composed of a computer. The sensor 51 sends a signal according to the rotation angle of the steering wheel H to the control device 52. For example, a sensor sends a pulse signal according to the rotation angle of the steering wheel H to the control device 52 by a rotary encoder, or a potentiometer. The electric signal corresponding to the rotation angle of the steering wheel H obtained via the A / D converter may be converted into a digital signal and sent to the control device 52. Since the steering angle is an angle with reference to the steering angle midpoint, when the steering angle is detected from a pulse signal corresponding to the rotation angle of the steering wheel H by a rotary encoder or the like, the steering angle midpoint is controlled by the control device 52. Is determined, and the pump 37 is always driven at the steering assist speed until the determination is made. In order to determine such a steering angle midpoint, as disclosed in, for example, Japanese Patent Laid-Open No. 2-197465, the fact that the steering torque becomes small at the steering angle midpoint is used to detect a sensor that detects the steering torque. Provided,
The time when the steering torque becomes smaller than the set value can be determined as the midpoint of the steering angle. Further, as disclosed in Japanese Examined Patent Publication No. 6-43188, it is used that the statistical distribution of the appearance frequency of the pulse signal from the detected sensor is a normal distribution that maximizes at the midpoint of the steering angle. However, the steering angle midpoint may be determined based on the statistical distribution of the appearance frequency of the pulse signal, and the determining means is not particularly limited. Also,
When the steering angle is detected from the electric signal corresponding to the rotation angle of the steering wheel H obtained via the potentiometer, by setting the reference value of the electric signal corresponding to the midpoint of the steering angle when the power steering device is assembled, The steering angle can be detected according to the change from the reference value.

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, the first set value of the steering angle, the second set value of the steering angle, the first set value of the steering angular velocity,
The second set value of the steering angular velocity, the first set time, the second set time, and the reference vehicle speed are stored. Further, the control device 52 detects the steering angular velocity by reading the steering angle of the steering wheel H detected by the sensor 51 in time series according to the control program and calculating the steering angular velocity from the time required for the change of the steering angle. To do.

The controller 52 determines that the detected steering angle is the first
It is determined that the steering assist condition is satisfied when either one of the condition that the value exceeds the set value and the detected steering angular speed exceeds the first set value is satisfied. When the steering assist condition is satisfied, the control device 52 sends a steering assist signal to the motor 50 via a power amplifier (not shown), thereby driving the motor 50 with a control voltage according to the steering assist signal, and the pump 37. Is increased from the standby speed to the steering assist speed. A battery mounted on the vehicle is used as a power source for driving the motor 50. In the relationship between the steering angle and the time in FIG. 3, the broken line A indicates the first set value of the steering angular velocity, and when the steering angular velocity is smaller than the first set value as indicated by the solid line B, the steering angle is indicated by a dashed line. At the time (Ta) at which the first set value θa shown is exceeded, the pump 37 is driven by the motor 50.
Start speeding up. Further, when the steering angular velocity is higher than the first set value as indicated by the solid line C, the motor 50 is detected at the time (Tb) when the control device 52 detects that the steering angular velocity exceeds the first set value. Then, the speedup of the pump 37 is started. The first set value θa of the steering angle is, for example, a play angle from the steering angle midpoint of the steering wheel H. The first set value of the steering angular velocity is, for example,
When the acceleration of the pump 37 is started after the steering angle exceeds the first set value θa, the delay of the steering assist can be set based on the steering angular velocity that does not pose a problem.

The control device 52 changes the control voltage of the motor 50 during steering assist 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. In addition, the motor 5 during standby
The standby speed of the pump 37 corresponding to the control voltage of 0 is shown in FIG.
Is set to the minimum value Nmin at the time of steering assistance as indicated by the alternate long and short dash line L.

When the first set time elapses after the steering angle becomes equal to or less than the first set value θa and the steering angular velocity becomes equal to or less than the first set value, the control device 52 controls the reference vehicle speed described later. Except in the following cases, it is determined that the first steering assist release condition is satisfied. When the first steering assist cancellation condition is satisfied, the control device 52 cancels the steering assist signal sent to the motor 50, and the motor 50 decelerates the pump 37 from the steering assist speed to the standby speed. The first set time can be set empirically by setting so as to reduce unnecessary speedup of the pump 37 as much as possible, and is set to, for example, 1 second.

When the vehicle speed detected by the vehicle speed sensor 53 becomes equal to or lower than the reference vehicle speed, the control device 52 pumps through the motor 50 even if the steering assist condition is not satisfied.
And the steering assist speed is maintained even if the first steering assist release condition is satisfied. The reference vehicle speed is set so as not to be lower than the vehicle speed when the steering force is large, such as when entering the garage or when stationary, and when the vehicle does not require a large steering assist force, such as when driving at high speeds. For example, it is set to 10 km / hour.

When the detected vehicle speed is equal to or lower than the reference vehicle speed, the control device 52 controls the steering angle to be equal to or less than the second set value,
Moreover, after the steering angular velocity becomes equal to or less than the second set value,
When the second set time has elapsed, it is determined that the second steering assist cancellation condition is satisfied. When the second steering assist cancellation condition is satisfied, the control device 52 cancels the steering assist signal sent to the motor 50 to decelerate the pump 37, and keeps the standby speed unless the steering assist condition is satisfied. As shown by the alternate long and short dash line in FIG. 3, the second set value θb of the steering angle is set to be less than the first set value θa. For example, when the first set value is 15 degrees from the steering angle midpoint in each of the left and right steering directions. The two set values are 5 degrees from the midpoint of the steering angle for each of the left and right steering directions. As shown by a chain double-dashed line b in FIG. 3, the second set value of the steering angular velocity is set to be less than the first set value. The second set value is 10 from the midpoint of the steering angle for each of the left and right steering directions.
Degrees / second. The second set time is longer than the first set time. For example, the first set time is 1 second and the second set time is 30 seconds.

The control procedure of the pump 37 will be described with reference to the flowcharts of FIGS. The midpoint of the rudder angle is assumed to be fixed.

First, the engine is started (step 1),
The vehicle speed is detected (step 2), and it is determined whether the detected vehicle speed is equal to or lower than the reference vehicle speed Vb (step 3). If the detected vehicle speed is equal to or lower than the reference vehicle speed Vb, the motor 50 pumps the steering assist speed corresponding to the detected vehicle speed.
Is accelerated and steering assist is performed (step 4). Next, the steering angle is detected (step 5), and it is determined whether the detected steering angle is the second set value θb or less (step 6). If it is not the second setting value θb or less, the process returns to step 2, and if it is the second setting value θb or less, the steering angular velocity is detected from the steering angle detected in time series (step 7), and the detected steering angular velocity is set to the second setting. It is determined whether the value is less than or equal to the value (step 8). If it is not less than or equal to the second set value, the process returns to step 2, and if it is less than or equal to the second set value, it is determined whether or not the second set time has elapsed since it was determined in step 8 that the value was less than or equal to the second set value. Judge (step 9). If it is determined in step 3 that the vehicle speed is not equal to or lower than the reference vehicle speed Vb during the progress of the time measurement for determining whether or not the second set time has elapsed, in step 6, the steering angle is equal to or less than the second set value θb. If it is determined that the steering angular velocity is not equal to or less than the second set value in step 8, the progress of the time counting is canceled, and the steering angular velocity is set to the second setting again in step 8. After it is determined that the value is less than or equal to the value, the time measurement is newly advanced. If the second set time has not elapsed, the process returns to step 2, and if the second set time has elapsed, it is determined that the second steering assist release condition is satisfied, and the motor 50 decelerates the pump 37 to the standby speed. Then, the steering assist is released (step 10).

When it is determined in step 3 that the vehicle speed is not equal to or lower than the reference vehicle speed Vb, and when the steering assist is canceled in step 10 because the second steering assist cancellation condition is satisfied, the steering angle is detected (step 11 ), It is determined whether or not the detected steering angle is less than or equal to the first set value θa (step 12). If it is not less than the first set value θa, it is determined that the steering assist condition is satisfied, the vehicle speed is detected (step 13), the pump 50 is accelerated by the motor 50 to the steering assist speed corresponding to the detected vehicle speed, and steering is performed. Assist (step 14). Next, it is judged whether or not the detected vehicle speed is equal to or lower than the reference vehicle speed Vb (step 15), and if it is not equal to or lower than the reference vehicle speed, the process returns to step 11. If the steering angle detected in step 12 is less than or equal to the first setting value θa, the steering angular velocity is detected from the steering angle detected in time series (step 16), and whether the detected steering angular velocity is less than or equal to the first setting value. Is determined (step 17). If it is not less than the first set value, it is determined that the steering assist condition is satisfied, and the process returns to step 13 to perform the steering assist. If it is less than or equal to the first set value, it is determined whether or not the first set time has elapsed from the time when it is determined in step 17 that the value is less than or equal to the first set value (step 18). When it is determined in step 12 that the steering angle is not equal to or less than the first set value θa during the progress of the time measurement for determining whether or not the first set time has elapsed, in step 17, the steering angular velocity is set to the first set value. When it is determined that the value is not less than or equal to the value, the progress of the time counting is canceled, and the timing is newly advanced after it is determined in step 17 that the steering angular velocity is less than or equal to the first set value. If the first set time has not elapsed, the process returns to step 11, and if the first set time has elapsed, it is determined that the first steering assist release condition is satisfied, the pump 37 is decelerated to the standby speed, and steering assist is performed. Is canceled (step 19) and the process returns to step 11. If the vehicle speed detected in step 15 is equal to or lower than the reference vehicle speed Vb, the process returns to step 5.

According to the above configuration, when the detected vehicle speed is equal to or lower than the reference vehicle speed Vb, the pump 37 is accelerated through the motor 50 and the first steering assist release condition is satisfied even if the steering assist condition is not satisfied. Even if the steering assist speed is maintained, the steering assist speed can be maintained even when the vehicle speed is low. This can prevent a delay in steering assistance during steering. Further, even if the vehicle speed is equal to or lower than the reference vehicle speed, the pump 50 is decelerated by the motor 50 by satisfying the second steering assist release condition, and is kept at the standby speed unless the steering assist condition is satisfied. In such a situation where the steering frequency is low, the pump 37 can be decelerated to improve energy saving. When the pump 37 is decelerated to the standby speed due to the satisfaction of the second steering assist cancellation condition, it is possible that the subsequent first acceleration to the steering assist speed is less than or equal to the reference vehicle speed. The frequency of occurrence is small and practically not a problem.

The present invention is not limited to the above embodiment. For example, the steering assist condition may be satisfied when only the steering angle exceeds the set value, or may be satisfied by the operation of the direction indicator. Also,
The first steering assist cancellation condition and the second steering assist cancellation condition may be satisfied when only the steering angle is continuously maintained for a set time or less than a set value. Further, the values of the steering angle and the steering angular velocity set for each steering assistance condition may be different from the values of the steering angle and the steering angular velocity set for each steering assistance cancellation condition. Further, although the present invention is applied to the rack and pinion type power steering apparatus in the above-mentioned embodiments, it can also be applied to a ball screw type power steering apparatus.

[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 sectional view taken along line II-II of FIG.

FIG. 3 is a diagram showing a relationship between a steering angle and time of the power steering device according to the embodiment.

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 flowchart showing a control procedure of a pump 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 Drive Motor 51 Steering Angle Sensor 52 Control Device 53 Vehicle Speed Sensor

Claims (3)

[Claims] 1. 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 accelerating the pump to a steering assist speed when a steering assist condition is satisfied and first steering. In a power steering device including means for decelerating to a standby speed when the auxiliary release condition is satisfied, and means for changing the steering assist speed in accordance with the vehicle speed, a vehicle speed detection means and a detected vehicle speed equal to or lower than a preset reference vehicle speed. In this case, the power steering apparatus is provided with means for increasing the speed of the pump through the electric actuator even if the steering assist condition is not satisfied, and for maintaining the steering assist speed even when the first steering assist cancellation condition is satisfied. 2. When the detected vehicle speed is equal to or lower than the reference vehicle speed, the pump is decelerated via an electric actuator by satisfying a second steering assist cancellation condition different from the first steering assist cancellation condition, and the steering assist condition is also satisfied. The second steering assist cancellation condition satisfies the criterion that the second steering assist cancellation condition is not in the steering state and the steering frequency is less than when the first steering assist cancellation condition is satisfied. The power steering device according to claim 1, wherein the power steering device is satisfied. 3. A means for detecting at least one of a steering angle and a steering angular velocity, wherein the first steering assist release condition is:
When at least one of the steering angle and the steering angular velocity is continuously satisfied for a set time and is equal to or less than a set value, the second steering assist release condition is that at least one of the steering angle and the steering angular velocity is set. It is satisfied when the time is equal to or less than the set value, and at least one of the steering angle and the steering angular velocity set for the second steering assist release condition is less than the value set for the first steering assist release condition. The power steering device according to claim 2, wherein the time set for the second steering assist cancellation condition is set longer than the time set for the first steering assist cancellation condition.