JP4114449B2 - Hydraulic power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
This invention is mounted on an automobile or the like to a hydraulic power steering apparatus using the damper valves provided in the hydraulic circuit between the hydraulic pump and the hydraulic actuator.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a hydraulic power steering device that assists a steering force with hydraulic pressure is frequently used as a steering device for a vehicle. This hydraulic power steering device outputs a steering assist force by supplying hydraulic oil discharged from a hydraulic pump to a hydraulic actuator such as a hydraulic cylinder or a hydraulic motor. The hydraulic pump, the hydraulic actuator, A hydraulic control valve for controlling the supply of hydraulic oil to the hydraulic actuator according to the steering direction and the steering resistance is interposed between the hydraulic control valves.
[0003]
In this type of hydraulic power steering apparatus, the steered wheel excessively vibrates during traveling due to the accuracy of parts of the steering system, and this vibration is caused by, for example, the steering wheel via the piston rod (rack shaft) of the hydraulic cylinder. The so-called shimmy phenomenon that is transmitted to the camera may occur. In order to suppress such a shimmy phenomenon, for example, by providing a check valve in the hydraulic control valve and sealing the hydraulic cylinder, the hydraulic cylinder can function as a damper against the vibration. It has been broken.
However, when the hydraulic cylinder functions as a damper as described above, the flow of hydraulic oil trying to return to the hydraulic control valve from one of the oil chambers is reversed especially when sudden steering is performed to avoid danger. It is hindered by the stop valve, and the steering assist force is reduced, causing problems such as an abnormally heavy steering wheel. Therefore, a damper valve is interposed in each of the hydraulic circuits that individually connect the hydraulic control valve and the left and right oil chambers of the hydraulic cylinder.
[0004]
This damper valve is described in, for example, Patent Document 1, and as shown in FIG. 7, a valve sleeve 102 is disposed inside a hollow casing 101, and the inside of the casing 101 is placed in the first chamber by the valve sleeve 102. 103 and the second chamber 104. The first chamber 103 is communicated with the hydraulic control valve side via the first port 105, and the second chamber 104 side is communicated with the hydraulic cylinder side via the second port 106.
[0005]
Inside the valve sleeve 102 is provided a check valve 107 that allows the hydraulic oil to flow from the first port 105 to the second port 106 and restricts the flow in the opposite direction. In addition, a plurality of communication passages 109 are formed in the peripheral wall portion of the valve sleeve 102 to communicate the first chamber 103 and the second chamber 104.
A spool 110 is provided in the first chamber 103 so as to be able to contact with and separate from the end surface of the valve sleeve 102, and the spool 110 is urged toward the end surface of the valve sleeve 102 by a spring 111. A valve plate 112 that closes the communication path 109 is interposed between the spool 110 and the valve sleeve 102. The valve plate 112 is a ring-shaped member made of a thin metal, and is elastically deformed by the pressure of hydraulic fluid that is returned from the hydraulic cylinder to the hydraulic control valve through the second chamber 104, the communication passage 109, and the first chamber 103. can do.
[0006]
According to the damper valve, when the piston rod of the hydraulic cylinder vibrates left and right along with the vibration of the steered wheels, the valve is driven by the pressure of the hydraulic oil going from the second chamber 104 to the first chamber 103 through the communication path 109. The plate 112 is elastically deformed according to the amplitude. As a result, the communication passage 109 is opened and the hydraulic oil is recirculated to the hydraulic control valve side through the first chamber 103 and the first port 105. At this time, since the communication passage 109 is throttled by the valve plate 112, a damper effect is exhibited, and vibration from the steered wheels is suppressed from being transmitted to the steering wheel via the piston rod of the hydraulic cylinder.
[0007]
In addition, when the driver suddenly steers, a large amount of hydraulic fluid is recirculated from either the left or right oil chamber of the hydraulic cylinder to the hydraulic control valve side, so that the valve plate 112 is greatly elastically deformed and the spool 110 and the valve sleeve 102 are largely separated from the biasing force of the spring 111. As a result, the communication passage 109 is greatly opened and a large amount of hydraulic oil is recirculated to the hydraulic control valve side. As a result, it is possible to prevent problems such as abnormally heavy steering wheels.
[0008]
Further, in this type of damper valve, when the valve plate 112 adheres to the valve sleeve 102 due to oil film breakage, the driver feels a certain load on the steering until it leaves the valve sleeve 102, which is a steering feeling. May be adversely affected. Therefore, in the conventional example, a plurality of recesses 113 are formed at predetermined intervals on the contact surface of the valve sleeve 102 with respect to the valve plate 112, and the valve plate 112 is caused to contact with the contact surface by the hydraulic oil accumulated in the recess 113. Suppresses sticking to and becoming difficult to leave.
[0009]
[Patent Document 1]
JP 2001-158369 A (page 4, FIG. 4)
[0010]
[Problems to be solved by the invention]
In the conventional hydraulic power steering device described above, since the recesses 113 of the valve sleeve 102 are provided between the communication passages 109, an oil film breakage occurs at an intermediate portion between the recesses 113 and the communication passages 109. It is easy to occur and it is difficult to reliably prevent the valve plate 112 from sticking to the contact surface. Further, when the hydraulic oil is recirculated through the communication passage 109, the hydraulic oil presses only a portion corresponding to the communication passage 109 of the valve plate 112, so that the valve plate 112 is partially deformed and its operation is unstable. As a result, the steering feeling may become worse.
In view of the conventional problems as described above, the present invention can effectively prevent the valve plate from sticking to the contact surface and becoming difficult to separate, and can stabilize the operation of the valve plate. further and to provide a good steering feeling oil pressure power steering system is Ru can be obtained [0011]
[Means for Solving the Problems]
In order to achieve the above object, a hydraulic power steering apparatus according to the present invention includes a hydraulic pump, a hydraulic actuator that outputs a steering assist force by hydraulic oil supplied from the hydraulic pump, and a gap between the hydraulic actuator and the hydraulic pump. A hydraulic power steering device that includes a hydraulic control valve that controls hydraulic oil supply and discharge with respect to the hydraulic actuator according to steering,
A damper valve is provided in a predetermined portion of the hydraulic circuit between the output port of the hydraulic control valve and the hydraulic actuator;
This damper valve
A hollow casing having a first port connected to the hydraulic pump side and a second port connected to the hydraulic actuator side;
A valve sleeve that divides the inside of the casing into a first chamber that communicates with the first port and a second chamber that communicates with the second port, and has a plurality of communication passages that communicate the first chamber and the second chamber. When,
A spool provided on the first chamber side and movable relative to the valve sleeve in the axial direction;
A spring for urging the spool toward the second chamber;
An oil supply passage for supplying hydraulic oil supplied to the first chamber through the first port to the second chamber through the inside of the spool and the valve sleeve;
A check valve that is provided in an oil supply passage in the valve sleeve, allows hydraulic oil to flow from the first port to the second port, and restricts flow in the opposite direction;
A reflux path that guides the hydraulic oil that is refluxed from the second chamber to the first chamber through the communication path to the first port;
In close contact with the opening facing the first chamber of the communication path, the opening is opened by elastic deformation caused by the working oil recirculated from the second chamber to the first chamber, and the working oil is recirculated at a predetermined flow rate or more. and the move with the spool against the biasing force of the spring, and an annular valve plate to open further increase the aperture,
An annular groove communicating with each communication path is provided on an end surface of the valve sleeve facing the valve plate, and the groove width of the annular groove is wider than the opening width of the communication path. There Ru.
[0012]
According to the damper valve configured as described above, the hydraulic fluid that is recirculated from the second chamber to the first chamber through the communication path is guided to the annular groove, and the oil film is cut over the entire circumference of one side surface of the valve plate. Can be prevented from occurring. Further, the valve plate can be pressed over the entire circumference by the hydraulic oil.
[0013]
In the damper valve, the groove width of the annular groove is wider for a than the opening width of the communicating path, it is possible to increase the contact area between the hydraulic oil and the valve plate which is returned to the first chamber side through the communicating path. Therefore, it is possible to more effectively prevent the oil film from being cut and to press the entire circumference of the valve plate over a wide range by the hydraulic oil.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the oil pressure power steering apparatus of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing a hydraulic power steering apparatus according to an embodiment of the present invention. In this figure, the hydraulic power steering apparatus includes an input shaft X connected to a steering wheel (handle) (not shown), a pinion 1 that rotates as the input shaft X rotates, and a rack shaft that meshes with the pinion 1. 2, a housing 5 that covers the rack shaft 2, a hydraulic cylinder 6 as a hydraulic actuator provided inside the housing 5, a hydraulic pump 7 that supplies hydraulic oil to the hydraulic cylinder 6, and the steering wheel A main part is constituted by a hydraulic control valve 8 that controls supply and discharge of hydraulic oil to and from the hydraulic cylinder 6 in conjunction with each other.
[0017]
Both ends of the rack shaft 2 protrude from both end openings 5a and 5b of the housing 5, and ball joints 10 and 11 are integrated with the protruding ends. Tie rods 12 and 13 are attached to the respective ball joints 10 and 11, and both ends of the rack shaft 2 are connected to the steered wheels via the tie rods 12 and 13. Accordingly, the vehicle can be steered by rotating the pinion 1 via the input shaft X and moving the rack shaft 2 in the axial direction (vehicle width direction) by rotating the steering wheel.
[0018]
The hydraulic cylinder 6 includes a cylinder tube 6a formed by the housing 5, a piston rod 6b formed by the rack shaft 2, and a piston 6c integrated with the rack shaft 2, and both sides sandwiching the piston 6c. The space is configured as a first oil chamber 6d and a second oil chamber 6e.
The hydraulic control valve 8 is constituted by a rotary valve, and an input port 8b, a return port 8c, a first output port 8d, and a second output port 8e are respectively formed in the valve housing 8a so as to protrude. The input port 8b is connected to the output port 7a of the hydraulic pump 7 via the first hydraulic pipe T1, and the return port 8c is connected to the reserve tank T via the second hydraulic pipe T2. The first output port 8d is connected to the first oil chamber 6d of the hydraulic cylinder 6 via the third hydraulic pipe T3, and the second output port 8e is connected to the hydraulic cylinder 6 via the fourth hydraulic pipe T4. Is connected to the second oil chamber 6e. The hydraulic control valve 8 supplies the hydraulic oil for assisting the steering force to one of the oil chambers 6d and 6e according to the steering direction and the steering resistance, and simultaneously supplies the hydraulic oil from the other oil chamber to the reserve tank T. To reflux.
[0019]
The third hydraulic pipe T3 and the fourth hydraulic pipe T4 are each constituted by a metal pipe 4, and each of these pipes T3 and T4 is connected to the hydraulic cylinder 6 via a damper valve 20 according to an embodiment of the present invention. It is connected. That is, the third hydraulic pipe T3 is connected to the first input port 6f communicating with the first oil chamber 6d of the hydraulic cylinder 6 via the damper valve 20, and the fourth hydraulic pipe T4 is connected to the first hydraulic chamber 6d via the damper valve 20. The hydraulic cylinder 6 is connected to a second input port 6g communicating with the second oil chamber 6e.
[0020]
Each damper valve 20 has a function as a check valve that allows the flow of hydraulic oil from the hydraulic control valve 8 to the hydraulic cylinder 6 side, and allows the flow of hydraulic oil in the opposite direction with a predetermined resistance. And a function as a throttle check valve.
Referring to FIG. 2, the damper valve 20 includes a hollow casing 21, a cylindrical spool 22 disposed inside the casing 21, a valve sleeve 23 defining the inside of the casing 21, and the valve A check valve 24 provided inside the sleeve 23, a valve plate 25 along one end surface of the valve sleeve 23, and a coiled compression spring 26 that biases the spool 22 are provided.
[0021]
The casing 21 includes a flare pipe 21a, a first connector 21b connected to the flare pipe 21a, and a second connector 21c screwed into the first connector 21b at the distal end side. The inside of the casing 21 is partitioned by the valve sleeve 23 into a first chamber C 1 that communicates with the hydraulic control valve 8 and a second chamber C 2 that communicates with the hydraulic cylinder 6.
The second connector 21c is formed with a first port P1 for communicating the first chamber C1 with the hydraulic control valve 8 through the metal pipe 4, and the flare pipe 21a has the second chamber. A second port P2 for communicating C2 with the first oil chamber 6d (or the second oil chamber 6e) of the hydraulic cylinder 6 is formed. The periphery of the second port P2 is welded to the cylinder tube 6a of the hydraulic cylinder 6.
[0022]
The spool 22 has a step having a small-diameter portion 22a and a large-diameter portion 22b having an inner diameter and an outer diameter larger than the small-diameter portion 22a. The small-diameter portion 22a is located on the first chamber C1 side of the valve sleeve 23. It is inserted so as to be movable in the axial direction with respect to the inner periphery. A predetermined gap S1 is provided between the outer periphery of the large-diameter portion 22b and the inner periphery of the first chamber C1, and the right end surface of the large-diameter portion 22b and the left end surface of the second connector 21c in FIG. Is provided with a clearance S <b> 2 that allows the hydraulic oil to flow therethrough. The compression spring 26 is introduced into the large diameter portion 22b.
[0023]
The valve sleeve 23 is formed continuously with one end portion of the first connector 21b, and a communication passage 23a having one end opened to the first chamber C1 and the other end opened to the second chamber C2 on the peripheral wall portion. Is formed. A plurality of communication passages 23a are formed at equal circumferences (see FIG. 3).
On the end surface of the valve sleeve 23 facing the first chamber C1, annular grooves 23b communicating with the communication passages 23a are formed. The annular groove 23b is provided concentrically with the valve plate 25 in a state of being opposed to one side surface of the valve plate 25, and the downstream end of the communication passage 23a is opened at the bottom thereof. The groove width of the annular groove 23b is wider than the opening width (opening diameter) of the communication passage 23a, and the whole is covered with the valve plate 25.
[0024]
The inside of the valve sleeve 23 and the spool 22 constitutes an oil supply path F1 for supplying hydraulic oil supplied from the hydraulic control valve 8 through the first port P1 to the second chamber C2. Further, the communication passage 23a, the gap S1 between the spool 22 and the first chamber C1, and the gap S2 between the spool 22 and the second connector 21c return to the first chamber C1 side from the second chamber C2. The recirculation path F2 which guides the hydraulic oil to be performed to the first port P1 is configured.
[0025]
The check valve 24 is a cylindrical case 24a provided in the valve sleeve 23, a movable valve body 24b disposed in the case 24a, and housed in the case 24a to urge the movable valve body 24b. And a ring-shaped valve seat member 24d attached to the case 24a and on which the movable valve body 24b is seated. The check valve 24 is a unit obtained by integrally assembling these components, and is press-fitted and fixed to the inner periphery of the valve sleeve 23.
[0026]
The movable valve body 24b is disposed so as to be movable along the oil passage, and is usually an opening provided in the central portion of the valve seat member 24d in close contact with the valve seat member 24d by the urging force of the coil spring 24c. Is blocking. As a result, the check valve 24 blocks the inside of the valve sleeve 23 and prevents the flow of hydraulic oil from the hydraulic cylinder 6 toward the hydraulic control valve 8. Further, the movable valve body 24b moves away from the valve seat member 24d against the urging force of the coil spring 24c due to the pressure of the hydraulic oil that tends to flow from the hydraulic control valve 8 to the hydraulic cylinder 6 side. Thereby, the inside of the valve sleeve 23 is opened, and the hydraulic oil sequentially passes through the oil supply path F1 and the second port P2 from the first port P1. As a result, the hydraulic oil from the hydraulic control valve 8 is supplied to the oil chamber on the side corresponding to the steering direction of the steering wheel, and the steering wheel rotation operation can be assisted.
[0027]
Referring also to FIG. 4, the valve plate 25 is formed of a flat annular body made of a thin metal plate, and the inner periphery thereof is fitted to the outer periphery of the small diameter portion 22 a of the spool 22. The annular groove 23 b is covered by a predetermined range on the outer peripheral side of the valve plate 25. The thickness of the valve plate 25 is set to such a value that the outer peripheral side thereof can be elastically deformed by the low flow rate hydraulic oil that is recirculated through the communication passage 23a. This elastic deformation gradually increases as the flow rate of hydraulic oil increases. Thereby, the communication path 23a can be opened and closed delicately according to the flow rate of the hydraulic oil.
The valve sleeve 23 is formed with an annular relief portion 22c for allowing elastic deformation of the valve plate 25.
[0028]
The compression spring 26 urges the spool 22 to the second port P2 side with a predetermined pressure, and the left end surface of the large diameter portion 22b of the spool 22 passes through the valve plate 25 to the first chamber C1 of the valve sleeve 23. It faces the surface that faces. The compression spring 26 is interposed in a state of being elastically contracted between the spool 22 and the second connector 21c so as to expand and contract in accordance with the flow rate of the hydraulic oil to be returned from the hydraulic cylinder 6 to the hydraulic control valve 8 side. It is. The urging force of the compression spring 26 is such that when the valve plate 25 is elastically deformed by a predetermined amount or more, that is, when the flow rate of the circulating hydraulic oil reaches the high flow rate region from the low flow rate region, the valve plate 25 and the spool 22 The value is set to be separated from the valve sleeve 23.
[0029]
In the damper valve 20 configured as described above, when the piston rod 6b of the hydraulic cylinder 6 vibrates left and right with the slight vibration of the steered wheels, a small amount of hydraulic oil returns from the hydraulic cylinder 6 to the second port P2 and the communication path 23a. Then, when the valve member 25 is elastically deformed according to the flow rate, the hydraulic oil is returned to the hydraulic control valve 8 side through the first chamber C1 and the first port P1. At this time, since the return path F <b> 2 is throttled by the valve member 25, a damper effect is exhibited, and transmission of vibration from the steered wheels to the steering wheel via the piston rod 6 b of the hydraulic cylinder 6 is suppressed. Further, since the opening degree of the communication passage 23a is automatically adjusted by the valve plate 25 in accordance with the flow rate of the hydraulic oil, good steering characteristics can be easily obtained. In addition, since the hydraulic oil in the communication passage 23a can be guided to the annular groove 23b to prevent the oil film from being cut over the entire circumference of one side of the valve member 25, the valve plate 25 is in close contact with the valve sleeve 23. Thus, it is possible to effectively prevent the so-called sticking phenomenon that is difficult to separate. Further, since the valve plate 25 can be pressed over the entire circumference by the hydraulic oil, the operation of the valve plate 25 can be stabilized as compared with the conventional example in which the valve plate 25 is partially pressed. In particular, since the groove width of the annular groove 23b is wider than the opening width of the communication passage 23a and the contact area between the hydraulic oil and the valve member 25 is increased, the sticking phenomenon is more effectively prevented. In addition to being able to prevent, the entire circumference of one side surface of the valve plate can be pressed over a wide range by the hydraulic oil, so that the operation of the valve plate 25 can be more effectively stabilized. Therefore, a better steering feeling can be obtained.
[0030]
On the other hand, when the hydraulic oil to be returned to the hydraulic control valve 8 side is in a high flow rate region, such as when the steering wheel is steered suddenly, the valve plate 25 is moved when the valve plate 25 is elastically deformed by a predetermined amount. A wide gap S3 is formed between the spool 22 and the valve sleeve 23 (see FIG. 5). As a result, the hydraulic oil from the hydraulic cylinder 6 is smoothly returned to the hydraulic control valve 8 through the second port P2 and the return path F2. As a result, it is possible to prevent the occurrence of problems such as an abnormally heavy steering wheel by preventing a reduction in steering assist force.
Further, in the case of the high flow rate region, the valve plate 25 is greatly elastically deformed, and is largely separated from the valve sleeve 23 together with the spool 22, so that a large differential pressure is generated between the left end surface and the right end surface of the valve sleeve 23. It is suppressed from occurring. For this reason, it is possible to satisfactorily ensure followability to sudden steering.
Note that the predetermined range on the outer peripheral edge side of the annular groove 23b may be exposed without being covered by the valve plate 25 (see FIG. 6), and in this case, the hydraulic fluid recirculated to the first chamber C1 side. However, even if the pressure is below a certain pressure and the valve plate 25 cannot be elastically deformed, the hydraulic oil can be recirculated to the first chamber C1 through the gap S4 between the valve plate 25 and the annular groove 23b. . For this reason, when the flow rate of the hydraulic oil increases and the valve plate 25 is elastically deformed, the driver feels a so-called ON / OFF feeling due to the sudden return of the hydraulic oil to the first chamber C1. Can be suppressed.
The damper valve 20 may be any of a hydraulic circuit between the output ports 8d and 8e of the hydraulic control valve 8 and the hydraulic cylinder 6, such as the inside of the first output port 8d and the second output port 8e of the hydraulic control valve 8. It should be provided at that position.
[0032]
As described above, according to the oil pressure power steering apparatus of the present invention, the hydraulic fluid is returned to the first chamber side through the communicating path from the second chamber, the entire periphery of one side of the valve plate is guided to the annular groove As a result, it is possible to prevent the oil film from being cut over, so that the valve plate can be effectively prevented from sticking to the valve sleeve. Further, since the valve plate can be pressed over the entire circumference by the hydraulic oil, it is possible to effectively prevent the valve plate from sticking to the valve sleeve, and to obtain a better steering feeling. it can.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a hydraulic power steering apparatus according to an embodiment of the present invention.
2 is a sectional view showing a damper valve in the present invention.
3 is a cross-sectional view taken along line III-III in FIG.
4 is an enlarged cross-sectional view of a main part of FIG.
FIG. 5 is a cross-sectional view showing the operation of the damper valve.
FIG. 6 is a cross-sectional view of a main part showing another embodiment.
FIG. 7 is a cross-sectional view showing a conventional example of a damper valve.

Claims (1)

A hydraulic pump, a hydraulic actuator that outputs a steering assist force by the hydraulic oil supplied from the hydraulic pump, and a hydraulic actuator that is interposed between the hydraulic actuator and the hydraulic pump, and supply and discharge of the hydraulic oil to and from the hydraulic actuator according to steering A hydraulic power steering device comprising a hydraulic control valve for controlling
A damper valve is provided in a predetermined portion of the hydraulic circuit between the output port of the hydraulic control valve and the hydraulic actuator;
This damper valve
A hollow casing having a first port connected to the hydraulic pump side and a second port connected to the hydraulic actuator side;
A valve sleeve that divides the inside of the casing into a first chamber that communicates with the first port and a second chamber that communicates with the second port, and has a plurality of communication passages that communicate the first chamber and the second chamber. When,
A spool provided on the first chamber side and movable relative to the valve sleeve in the axial direction;
A spring for urging the spool toward the second chamber;
An oil supply passage for supplying hydraulic oil supplied to the first chamber through the first port to the second chamber through the inside of the spool and the valve sleeve;
A check valve that is provided in an oil supply passage in the valve sleeve, allows hydraulic oil to flow from the first port to the second port, and restricts flow in the opposite direction;
A reflux path that guides the hydraulic oil that is refluxed from the second chamber to the first chamber through the communication path to the first port;
In close contact with the opening facing the first chamber of the communication path, the opening is opened by elastic deformation caused by the working oil recirculated from the second chamber to the first chamber, and the working oil is recirculated at a predetermined flow rate or more. and the move with the spool against the biasing force of the spring, and an annular valve plate to open further increase the aperture,
An annular groove communicating with each communication path is provided on an end surface of the valve sleeve facing the valve plate, and the groove width of the annular groove is wider than the opening width of the communication path. Hydraulic power steering device .

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