JP3198287B2 - Power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic power steering apparatus for assisting a steering operation by using a force generated by a hydraulic actuator disposed in a steering mechanism.

[0002]

2. Description of the Related Art In recent automobiles, power steering devices (power steering devices) have become widespread in order to reduce the labor required for steering (steering wheel) operations for steering and to obtain a comfortable steering feeling. ing. This power steering device is roughly classified into a hydraulic type using a hydraulic actuator as a source of a steering assist force and an electric type using an electric motor.

FIG. 1 is a schematic diagram showing a general configuration of a hydraulic power steering apparatus in a vehicle provided with a rack and pinion steering mechanism. As shown in the figure, the power steering device includes a hydraulic pump 1 serving as a hydraulic pressure generating source, a power cylinder (hydraulic actuator) 2 for generating a steering assist force, and a hydraulic control valve 3 interposed between the two. It becomes.

A rack and pinion type steering mechanism 4 houses a rack shaft 41 slidably in the axial direction in a rack housing 40 extending in the left-right direction of the vehicle body.
Both ends of a rack shaft 41 protruding from both sides of the 40 are connected to knuckle arms 5a, 5a of a pair of left and right steering wheels 5, 5, respectively, and are connected to the middle of the rack housing 40 in such a manner as to intersect therewith. The lower end of a steering wheel shaft (steering column) 44 extending below the steering wheel (steering wheel) 43 is made to enter the inside of the gear housing 42, and a pinion (not shown) fixed to the end portion is inserted in the middle of the rack shaft 41. To be engaged.

The power cylinder 2 is provided with a cylinder chamber in which both sides are sealed in a liquid-tight manner in the middle of the rack housing 40.
A piston fixed to the rack shaft 41 is arranged in the cylinder chamber, and the rack shaft 41 itself is configured as an output rod. Further, the hydraulic control valve 3 is arranged in the middle of the steering wheel shaft 44 so as to perform a hydraulic pressure supply / discharge operation using a twist generated in the steering wheel shaft 44 by a steering torque applied to the steering wheel 43.

The hydraulic control valve 3 is connected to the discharge side of the hydraulic pump 1 via an oil supply path 11 and is connected to the oil tank T via a return oil path 12. They are connected to the left and right oil chambers of the power cylinder 2 via paths 13 and 14, respectively. The hydraulic pump 1 includes an engine E
, The hydraulic oil stored in the oil tank T is sucked through the suction oil passage 10, the operation oil is pressurized and supplied to the hydraulic control valve 3 through the oil supply passage 11.

The hydraulic control valve 3 connects the pressure oil supplied through the oil supply passage 11 to an oil supply passage 13 or an oil supply passage 14 connected to both oil chambers of the power cylinder 2 and an oil tank T, respectively. The power cylinder 2 generates an oil pressure (steering assist force) corresponding to the oil pressure supplied through the oil supply passage 13 or the oil supply passage 14. Is added to the rack shaft 41 inside the rack housing 40, and the rack shaft 41
Of the left and right steering wheels 5, 5 performed by the transmission of the sliding of the knuckle arms 5a, 5a, that is, the steering mechanism 4
Assists the steering operation.

The ratio of the distribution in the hydraulic control valve 3 is determined according to the magnitude of the twist generated in the steering wheel shaft 44, and the distribution to the oil supply passages 13 and 14 depends on the direction of the twist. Is determined. Therefore, when the vehicle is stopped or running at a low speed in which steering is performed against a large road surface reaction force acting on the steered wheels 5, 5, the amount of oil supplied to the hydraulic control valve 3 is large because the torsion of the steering shaft 44 is large. The portion is fed to the power cylinder 2 and a large steering assist force is obtained in the operation direction of the steering wheel 43. On the other hand, when the road surface reaction force acting on the steered wheels 5 and 5 is running at high speed, the torsion of the steering wheel shaft 44 is reduced. Hydraulic control valve 3
Most of the oil supplied to the tank is returned to the oil tank T without being sent to the power cylinder 2, and almost no steering assist force is obtained.

In accordance with the above operation, the hydraulic oil in the other oil chamber of the power cylinder 2 is pushed out into the oil supply passage 14 or 13 and returns to the hydraulic control valve 3, where the hydraulic control valve 3 And returns to the oil tank T via the return oil passage 12, and these reflux oils are sucked into the hydraulic pump 1 again via the suction oil passage 10. Rarely used cyclically.

[0010]

At the time of steering a motor vehicle, the left and right steering wheels 5, 5 are stopped or stopped at a low speed in order to change the position in a limited space, for example, when putting the vehicle in a garage or moving the vehicle sideways. In some cases, a steering operation is performed to obtain a steering angle as large as possible. In this case, the operation of the hydraulic control valve 3 described above causes a sufficient amount of pressure oil to be supplied to the corresponding oil chamber of the power cylinder 2. Although a large steering assist force is obtained by being fed, after the steering mechanism 4 reaches its operating end (lock position), it becomes impossible to receive the pressurized oil into the oil chamber. The entire amount of the pressure oil supplied from 1 to the hydraulic control valve 3 is returned to the oil tank T by the operation of the relief valve attached to the hydraulic pump 1.

At this time, in the inside of the hydraulic pump 1, the oil is returned to the oil tank T via the relief valve, and the circulation is sucked into the hydraulic pump 1 again from the suction oil passage 10, and the steering mechanism 4 is moved to the lock position. If the lock state held by the continuation is continued, various inconveniences such as seizure of the hydraulic pump 1 and oil leaks in various parts of the piping system are caused due to a rise in the temperature of the circulating oil, which lowers reliability. During this time, an unnecessary power burden is imposed on the engine E that drives the hydraulic pump 1, and there is a problem that fuel efficiency is reduced.

In particular, in recent years, in order to reduce the size of a hydraulic actuator (power cylinder 2) serving as a source of a steering assist force, the pressure generated by the hydraulic pump 1 during a steady operation tends to be set higher. The possibility that the above-mentioned inconvenience occurs is increasing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to avoid the occurrence of a high pressure while a locked state is continued, to prevent a decrease in reliability due to this, and to improve fuel efficiency. An object of the present invention is to provide a power steering device that can be obtained.

[0014]

A power steering apparatus according to a first aspect of the present invention supplies a hydraulic pressure generated by a hydraulic pump to a hydraulic actuator by an operation of a hydraulic control valve according to a steering operation, and the hydraulic actuator generates the hydraulic pressure. In a power steering apparatus configured to apply a steering assist force to a steering mechanism of a vehicle to assist the operation of the steering mechanism, a bypass that bypasses a middle of an oil passage from the hydraulic pump to the hydraulic actuator to a low-pressure section. An oil passage, opening / closing means for opening and closing the bypass oil passage, a position sensor for detecting that the steering mechanism is located near its operating end, and an operation sensor for detecting that the steering mechanism is operating. And that the position sensor is in the detection state.
The opening / closing hand when the motion sensor is in a non-detection state.
Open the step and respond to the return of the motion sensor to the detection state.
And a control unit for closing .

The power steering apparatus according to the second aspect of the present invention is the first aspect of the present invention.
, A vehicle speed sensor for detecting a running speed of the vehicle
When the vehicle speed detected by the vehicle speed sensor exceeds a predetermined value.
Means for interrupting the operation of the control unit when the operation is performed .

[0016]

[0017]

[0018]

According to the present invention, a position sensor capable of detecting whether or not the operating position of the steering mechanism is at a specific position, that is, in the vicinity of its operating end (lock position), and whether or not the steering mechanism is operating. And an operation sensor capable of detecting the lock state.Based on the detection results of these sensors, a bypass oil passage that bypasses an oil passage from the hydraulic pump to the hydraulic actuator for steering assistance to the low-pressure section is opened, and the locked state is established. Unnecessary high pressure generated by the continuation is released to the low pressure section, and the occurrence of inconvenience caused by this high pressure is avoided.

By opening and closing the bypass oil passage in response to detection and non-detection by the position sensor, the above-described object is achieved with a simple configuration. In addition, when the detection by the position sensor and the non-detection by the operation sensor are both performed, the bypass oil passage is opened, and when the operation state is detected by the operation sensor, the bypass oil passage is closed, so that the lock state is established. And the return to the unlocked state is more reliably recognized, and the above-described object is achieved with high accuracy and high responsiveness.

[0020]

Further, when the vehicle speed detected by the vehicle speed sensor exceeds a predetermined value, the opening / closing of the bypass oil passage based on the detection result of each sensor is not performed, and the change in the steering feeling during traveling caused by the opening / closing is not detected. prevent.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 2 is a schematic diagram showing the overall configuration of a power steering device according to the present invention (hereinafter referred to as the present device). This drawing is an example of a configuration of a rack and pinion type steering mechanism 4 having the above-described configuration, similarly to the conventional power steering device shown in FIG. 1. The present invention device is a hydraulic pump serving as a hydraulic pressure generation source. 1 and a power cylinder 2 for generating a steering assist force
And a hydraulic control valve 3 interposed between them.

The hydraulic pump 1 is connected to an output end of an engine E mounted on a vehicle via a suitable transmission means such as a V-belt. The hydraulic pump 1 is driven to rotate by the engine E and operates in an oil tank T. The operation of sucking oil through the suction oil passage 10 to increase the pressure and discharging the oil into the oil supply passage 11 connected to the discharge side is performed.

The power cylinder 2 is provided with a cylinder chamber in which both sides are liquid-tightly sealed in the middle of the rack housing 40.
A piston fixed to the rack shaft 41 is provided in the cylinder chamber, and an oil pressure corresponding to the pressure difference generated between the oil chambers on both sides of the piston is generated and applied to the rack shaft 41. An operation of assisting the steering of the steered wheels 5 and 5 caused by the sliding, that is, the steering is performed.

Further, the hydraulic control valve 3 is formed in the middle of a steering wheel shaft 44 provided below the steering wheel 43,
To the discharge side of the hydraulic pump 1 via the return oil passage 12
And connected to the oil tank T via the oil supply passages 13 and 14, respectively. In FIG. 2, the hydraulic control valve 3 is located in the upper half of the steering wheel shaft 44 for convenience of illustration, but the hydraulic control valve 3 is generally mounted on the rack shaft 41 at the lower end of the steering wheel shaft 44. Gear housing 42 that stores the pinion that meshes with
It is configured inside.

The operation of the hydraulic control valve 3 utilizes the torsion generated in the steering wheel shaft 44 in accordance with the operation of the steering wheel 43 to supply the hydraulic oil supplied from the hydraulic pump 1 through the oil supply passage 11 to the power cylinder 2.
The distribution is performed between the oil supply passage 13 or the oil supply passage 14 connected to the two oil chambers and the return oil passage 12 connected to the oil tank T. The ratio of the distribution depends on the magnitude of the twist generated on the steering wheel shaft 44 in response to the operation of the steering wheel 43, and the direction of the distribution,
In other words, which of the oil supply passages 13 and 14 is distributed is determined in accordance with the direction of the twist.

In the apparatus of the present invention shown in FIG. 2, the oil supply passage 11 from the hydraulic pump 1 to the hydraulic control valve 3 is bypassed to the oil tank T maintained at a low pressure state.
Is provided in a manner that branches off the middle of the refueling passage 11,
A solenoid valve 6a is disposed in the middle of the bypass oil passage 6 as an opening / closing means thereof.

Also, a position sensor 7 for detecting that the steering mechanism 4 operating to steer the steered wheels 5 and 5 is located near the operating end thereof, and that the steering mechanism 4 is operating. An operation sensor 8 for detection is provided, and the results of these detections are given to an opening / closing controller 9 which outputs an opening / closing signal for the solenoid valve 6a.

FIG. 3 is a longitudinal sectional view showing the manner in which the position sensor 7 is mounted near one end of the rack housing 40.
As shown in the figure, a seal holder 45 holding an oil seal functioning as a sealing member on one side of the power cylinder 2 is provided at an end of the rack housing 40, and a rack shaft 41.
And the bearing bush 46 for supporting the inner part is fixed inside with the former being the inner side.

At the tip of the rack shaft 41 supported by the bearing bush 46 and protruding from the rack housing 40, a tie rod 47 for connection to the steering wheel 5 on the same side is provided with a ball joint 48.
The outside of the connection portion is connected to a bellows 49 whose both ends are fitted to the vicinity of the base end of the tie rod 47 and the outer periphery of the end of the rack housing 40 in order to prevent dust from entering from outside. Covered by

As shown in the figure, the rack shaft 41 is a hollow shaft, and an air hole 50 is formed at the fitting end of the ball joint 48 so as to penetrate inside and outside. The air hole 50 is formed by sliding the rack shaft 41 with respect to the rack housing
When the rack 49 expands and contracts, it acts to supply and discharge air in the bellows 49 by a synergistic action with an air hole similarly formed at the other end of the rack shaft 41, and the steering caused by sliding of the rack shaft 41 is performed. This is necessary so as not to hinder the operation of the mechanism 4.

The sliding range of the rack shaft 41 (the operating range of the steering mechanism 4) to the right in the drawing is the bearing bush 46.
Range until the end face of the ball joint 48 contacts the end face of
It is limited to the length range of L in the figure. The position sensor 7
Is screwed and fixed to a union 70 projecting from the outer periphery near the end of the rack housing 40, and is provided on the outer periphery of the rack shaft 41 through a through hole 71 that passes through the rack housing 40 and the bearing bush 46 inside the rack housing 40. It is detected through the air hole 50 that the rack shaft 41 is located near the end of the sliding range, that is, the steering mechanism 4 is located near its operating end.

This is realized by determining the fixed position of the position sensor 7 so that the distance between the air hole 50 and the opening position is substantially equal to the length L. The position sensor 7 may be any sensor that can detect the presence or absence of the air hole 50 on the outer periphery of the rack shaft 41. For example, a proximity switch, or the reflection of light projected on the peripheral surface of the rack shaft 41, and the air may be detected. A photo sensor or the like that detects the hole 50 may be used.

As shown in FIG. 2, one position sensor 7 is required on each side of the rack housing 40 to detect the operating ends on both sides of the steering mechanism 4. Further, the detection target by the position sensor 7 is not limited to the air hole 50, but may be a step portion appropriately provided on the outer periphery of the rack shaft 41, or a magnet or the like buried in the outer periphery. The air holes 50 are indispensable for supplying and discharging air in the bellows 49, and it is reasonable to use them as detection targets.

On the other hand, the motion sensor 8 comprises, for example, a potentiometer fixed in the middle of the steering wheel shaft 44 and a differential circuit for the output of the potentiometer, and determines whether or not the steering mechanism 4 is operating as an output of the differential circuit. It is configured to detect the rotation of the steering wheel shaft 44 obtained as a medium. In addition, since the rotation range of the steering shaft 44 extends several rotations from the neutral position to the left and right, when using a potentiometer capable of detecting one rotation, the rotation of the steering shaft 44 is reduced to the outside. It is necessary to add a take-out deceleration mechanism.

The output of the potentiometer indicates the rotational position of the steering shaft 44 corresponding to the operating position of the steering mechanism 4, and this can be used in place of the detection result of the position sensor 7. However, the sliding position of the rack shaft 41 and the rotating position of the steering wheel shaft 44 corresponding to the operating position of the steering mechanism 4 are as follows.
Since there is a gear mechanism between the two, it does not correspond strictly, and in consideration of accuracy, it is desirable to provide a dedicated position sensor 7 having the configuration shown in FIG.

When the steering wheel 43 is operated in the device of the present invention configured as described above, the hydraulic control valve 3 operates according to the twist generated in the steering shaft 44 at this time, and the hydraulic pump 1
The hydraulic pressure supplied to the hydraulic control valve 3 from the oil supply passage 13 or 14
And the return oil passage 12, and the power cylinder 2
The hydraulic pressure supplied to one of the oil chambers via the oil supply passage 13 or the oil supply passage 14 generates a steering assist force corresponding to the operation force in the operation direction of the steering wheel 43, and the operation of the steering mechanism 4, specifically Specifically, the sliding of the rack shaft 41 is assisted.

In accordance with the above operation, the hydraulic oil in the other oil chamber of the power cylinder 2 is pushed out into the oil supply passage 14 or 13 and returns to the hydraulic control valve 3 to be returned to the hydraulic control valve 3. Is returned to the oil tank T together with the working oil distributed to the return oil passage 12 side, and is sucked into the hydraulic pump 1 again through the suction oil passage 10 for circulating use.

The operating state of the steering mechanism 4 generated in this manner is detected by the position sensors 7, 7 and the operation sensor 8, and the opening / closing control section 9 to which the detection results are given.
Operates according to the flowchart shown in FIG. 4, and opens and closes a solenoid valve 6a in the middle of the bypass oil passage 6.

The opening / closing control section 9 starts its operation in response to the operation of turning on the engine start switch of the vehicle, and first issues a closing signal to the solenoid valve 6a to close it (step 1). Next, the outputs of the position sensor 7 and the motion sensor 8 are fetched (step 2), and the input from the motion sensor 8 is examined to determine whether or not the steering mechanism 4 is operating (step 3). As a result of this determination, when it is determined that the operation is being performed, the process returns to step 1 to maintain the closed state of the solenoid valve 6a and newly take in the outputs of the position sensors 7, 7 and the operation sensor 8.

On the other hand, if it is determined that the vehicle is not operating, then the inputs from the position sensors 7, 7 are checked to determine whether any of them is in a detection state, that is, the steering mechanism 4 It is determined whether it is at one of the left and right working ends (step 4). As a result, if it is determined that the actuator is not at the operating end, the process returns to step 1 and the above-described operation is repeated.
An operation is performed to issue a release command to 6a and release it (step 5).

By the operation of the opening / closing control unit 9 as described above, when the steering mechanism 4 is in the non-operating state near the operating end thereof, it is recognized that the steering mechanism 4 is in the locked state, and the solenoid valve 6a which is normally closed is normally closed. Is released. By this opening, the oil supply passage 11 from the hydraulic pump 1 to the hydraulic control valve 3 is connected to the oil tank T via the bypass oil passage 6,
Most of the discharge oil from the hydraulic pump 1 returns to the oil tank T via the bypass oil passage 6 without being supplied to the hydraulic control valve 3, and flows through the suction oil passage 10 into the hydraulic pump 1. Follow and cycle.

Since there is no large resistance element in this circulation path, there is no possibility that high pressure will be generated in the oil supply path 11, the hydraulic control valve 3 downstream of the oil supply path 11, and the oil supply path 13 or 14. And the temperature rise of the circulating oil is also small, and even if the lock state is maintained for a long time,
The risk of various inconveniences, such as seizure of the hydraulic pump 1 and oil leaks from various parts of the piping system, which lowers reliability is avoided. Further, since the power load on the engine E that drives the hydraulic pump 1 is greatly reduced, it is possible to contribute to improving the fuel efficiency of the engine E.

In step 5, the solenoid valve
After issuing the opening command of 6a, the opening / closing controller 9 takes in the output of the motion sensor 8 (step 6), determines whether or not the steering mechanism 4 is operating (step 7), and deactivates it. If it is determined that the vehicle is in the operating state, the process returns to step 6 to take in a new output of the motion sensor 8, and the same determination is repeated. Returning to step 1, a close command is issued to the solenoid valve 6a, and the above-described operation after step 2 is repeated.

That is, the opening / closing control section 9 recognizes the release of the above-mentioned locked state by detecting the return of the steering mechanism 4 to the operating state by the operation sensor 8, and accordingly, the solenoid valve 6a is closed, and as a result, the hydraulic pressure is reduced. The discharge oil of the pump 1 is supplied to the power cylinder 2 via the hydraulic control valve 3, and the normal operation state in which the power cylinder 2 generates the steering assist force is quickly restored.

The unlocking of the locked state may be recognized by returning to the non-detection state by the position sensor 7.
In some cases, an error having a width corresponding to the size of the detection target, such as 50, may occur, and as a result, the responsiveness from the release of the locked state to the return to the normal operation state is slightly inferior.

As a condition for opening the solenoid valve 6a, it is not essential to detect the non-operating state by the operation sensor 8, but by using this detection together with the detection of the operating end by the position sensor 7, it is possible to recognize the locked state. Is performed more reliably.

The bypass oil passage 6 opened and closed by the solenoid valve 6a is not limited to the position shown in FIG.
It may be provided at any position as long as it can communicate the middle of the oil passage from to the power cylinder 2 with the low pressure portion.

FIG. 5 is a schematic diagram showing a second embodiment of the apparatus of the present invention. In this embodiment, a bypass oil passage 6 is provided in such a manner that a pair of oil passages 13 and 14 from the hydraulic control valve 3 to the power cylinder 2 communicate with each other. The operation of opening and closing the solenoid valve 6a interposed in the middle of the oil passage is performed. Furthermore, the bypass oil passage 6 may be provided in a mode that connects the high-pressure portion and the low-pressure portion inside the hydraulic pump 1 or the hydraulic control valve 3.

FIG. 6 is a schematic diagram showing a third embodiment of the apparatus of the present invention. In this embodiment, a pressure sensor 7a for detecting the internal pressure of the oil supply passage 11 is provided instead of the position sensors 7,7.
The output of the pressure sensor 7a is supplied to the opening / closing control section 9 together with the output of the operation sensor 8, and the opening / closing control section 9 determines whether or not the steering mechanism 4 is at the operating end based on the detection result of the pressure sensor 7a. Is determined.

The pressure detected by the pressure sensor 7a is the internal pressure of the oil supply passage 11 as described above. This is the state in which the power cylinder 2 to which the hydraulic pressure is supplied is at the operating end and the pressure oil cannot be received. It is higher when there is. Therefore, the opening / closing control unit 9
When the detected pressure of the pressure sensor 7a exceeds a preset upper limit value, it can be determined that the operating end is present. However, the internal pressure of the oil supply path 11 increases even when the road cylinders 5 and 5 temporarily exert a large road surface resistance during traveling on a rough road and the operation of the power cylinder 2 is hindered. It is necessary to determine whether or not the taking mechanism 4 is at the operating end when the state where the pressure detected by the pressure sensor 7a exceeds the upper limit continues for a predetermined time.

That is, according to the third embodiment, in order to detect the operating end of the steering mechanism 4, instead of the two position sensors 7, 7 on both sides of the rack housing 40, they are provided in the oil supply passage 11. Only one pressure sensor 7a is required, and the pressure sensor 7a does not need to quantitatively detect the internal pressure of the oil supply passage 11 and can detect whether or not it is in a predetermined pressure state. Therefore, an inexpensive sensor such as a pressure switch can be used, and there is no need to modify the steering mechanism 4 itself for mounting the pressure sensor 7a. From these, the effect that the device configuration can be simplified is obtained.

Further, according to the third embodiment, the solenoid valve 6a is opened and closed based on the internal pressure itself of the oil supply passage 11, which is the original purpose of avoiding the generation of high pressure while the lock state is continued. Unnecessary opening and closing operations of the solenoid valve 6a are not frequently repeated, and a stable operation without causing a hunting phenomenon can be performed.

FIG. 7 is a schematic view showing a fourth embodiment of the apparatus of the present invention. In this embodiment, the detection result of the vehicle speed sensor 20 for detecting the traveling speed of the vehicle is given to the opening / closing control section 9 together with the detection results of the position sensors 7, 7 and the operation sensor 8, and the opening / closing control section 9 When the vehicle speed detected by the vehicle speed sensor 20 exceeds a predetermined value, the control operation described above is interrupted.

This means that between the steps 1 and 2 in the flowchart shown in FIG.
Is added by adding a new step of comparing the detection result with the predetermined reference vehicle speed. If the vehicle speed is equal to or higher than the reference vehicle speed, the process returns to step 1, and if the speed is lower than the reference vehicle speed, the process proceeds to step 3. it can. Also, the vehicle speed sensor 20
When the detection result is equal to or higher than the reference vehicle speed, the opening / closing control unit 9
The power supply to the power supply may be stopped.

According to the fourth embodiment, for example, when the vehicle enters or exits a high-rise parking lot, the vehicle travels along a spiral slope while maintaining the steering wheel 43 in the locked position. The steering assist by the cylinder 2 is not performed, and the disadvantage that a large operation force is required to operate the steering wheel 43 is avoided.

In each of the above embodiments, the rack
Although the vehicle provided with the pinion type steering mechanism 4 has been described, the device of the present invention can be applied to a vehicle provided with another type of steering mechanism such as a ball screw type, and the same effect can be obtained. Needless to say.

[0058]

As described in detail above, in the device of the present invention, it is determined whether or not the steering mechanism is locked based on the detection results of the position sensor and the motion sensor. The bypass oil passage that bypasses the oil passage from the pump to the hydraulic actuator for steering assistance to the low-pressure section is opened to release the high pressure generated inside the oil passage. The present invention has excellent effects, for example, there is no possibility that inconveniences such as seizure of the pump and oil leaks from various parts of the piping system, which may cause a decrease in reliability, occur, and the fuel efficiency of the engine that drives the hydraulic pump can be improved. Play.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an overall configuration of a conventional power steering device.

FIG. 2 is a schematic view showing a first embodiment of the device of the present invention.

FIG. 3 is a vertical cross-sectional view of the vicinity of one side end of a rack housing showing a mounting mode of a position sensor.

FIG. 4 is a flowchart illustrating an operation content of an opening / closing control unit.

FIG. 5 is a schematic view showing a second embodiment of the device of the present invention.

FIG. 6 is a schematic view showing a third embodiment of the device of the present invention.

FIG. 7 is a schematic view showing a fourth embodiment of the device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 Power cylinder 3 Hydraulic control valve 4 Steering mechanism 5 Hydraulic control valve 6 Bypass oil path 6a Solenoid valve 7 Position sensor 7a Pressure sensor 8 Operation sensor 9 Opening / closing control unit 10 Suction oil path 11 Oil supply path 12 Return oil path 13 Oil line 14 Oil line 20 Vehicle speed sensor T Oil tank

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeki Shimamura 3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka Inside Koyo Seiko Co., Ltd. (72) Yoshiaki Hamasaki 3-5-minamisenba, Chuo-ku, Osaka-shi, Osaka No. 8 Koyo Seiko Co., Ltd. (56) References JP-A-63-11477 (JP, A) JP-A-3-176280 (JP, A) JP-A-61-115775 (JP, A) 132583 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/00

Claims (2)

(57) [Claims] 1. A hydraulic control valve in accordance with a steering operation to send a hydraulic pressure generated by a hydraulic pump to a hydraulic actuator, and to apply a steering assist force generated by the hydraulic actuator to a steering mechanism of a vehicle. In a power steering device configured to assist the operation of a mechanism, a bypass oil passage that bypasses a middle of an oil passage from the hydraulic pump to the hydraulic actuator to a low-pressure section, and an opening / closing unit that opens and closes the bypass oil passage, A position sensor that detects that the steering mechanism is near its operating end, an operation sensor that detects that the steering mechanism is operating, and a state in which the position sensor is in the detection state.
And when the motion sensor is in the non-detection state,
The opening / closing means is opened, and the operation sensor returns to the detection state.
A power steering device comprising: a control unit that closes when returning . 2. A vehicle speed sensor for detecting a running speed of the vehicle.
And when the vehicle speed detected by the vehicle speed sensor exceeds a predetermined value.
Means for interrupting the operation of the control unit in some cases
The power steering apparatus according to claim 1 , wherein: