JPH07215230A - Control valve for power steering device - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the occurrence of abnormal noise in the control valve. [Structure] A tubular valve body 21 and a valve shaft 22 fitted to the inside of the valve body 21 so as to be movable relative to each other are provided, and one of the left and right hydraulic chambers of a power cylinder is provided depending on a steering direction. A control valve for a power steering device that distributes and supplies pressure oil, and as a high-speed oil flow separation promoting means, a sidewall 23a of a valve body groove 23 formed in the inner peripheral surface of the valve body 21 at predetermined intervals in parallel with the axial direction. In addition, by forming a concave groove 23c that is recessed in the circumferential direction, the speed of the jet flow a is reduced at an early stage to suppress the occurrence of cavitation and reduce the shoe noise generated in the control valve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control valve for controlling hydraulic pressure of a power steering device.

[0002]

2. Description of the Related Art For example, FIG.
FIG. 1 is a sectional plan view of a control valve used in a conventional power steering device described in Japanese Patent Publication No. 69, which is a cylindrical valve body 1.
And a cylindrical valve shaft 2 fitted inside the valve body 1 so as to be rotatable relative to each other. A valve body groove 3 having a rectangular cross section is formed in the inner circumference of the valve body 1 at a position that divides the inner circumference into eight equal parts and is formed between the two body grooves 3 and 3 in parallel with the axial direction. A supply passage 5 for pressure oil to be pressurized and supplied by a vane pump or the like is formed in every other four out of the eight outer land portions 4 formed, and the bottom portion of each valve body groove 3 is formed. , And pressure oil distribution holes 6 are formed respectively.

On the other hand, the valve shaft 2 fitted in the valve body 1 has an inner land portion 8 slightly narrower than the width of the valve body groove 3 at a position where the outer circumference of the valve shaft 2 is divided into eight equal parts.
Valve shaft grooves 9 having a rectangular cross section are formed on both sides of the inner land portion 8 in parallel with the axial direction, and the edge portion of the inner land portion 8 has a gentle inclination with respect to the inner land portion. The chamfered portion 8a is provided. A throttle gap 7 (see FIG. 14) is formed between the inner land portion 8 and the outer land portion 4 on the valve body 1 side.

The pressure oil supply passage 5 of the valve body 1
One of the pressure oil distribution holes 6 and 6 formed in the pair of valve body grooves 3 and 3 located on both sides of each outer land portion 4 in which the left hydraulic chamber 1 of the power cylinder 10 is formed.
0a, and the other pressure oil distribution hole 6 is connected to the right hydraulic chamber 10b by piping. A rack shaft 12 is connected to a piston 11 that defines the inside of the power cylinder 10 into two hydraulic chambers 10a and 10b. In FIG. 12, reference numeral 14 is a torsion bar, 12a is a rack tooth, and 13 is a pinion.

The control valve used in the conventional power steering system constructed as described above is
When a steering shaft (not shown) is rotated, the valve body 1 is rotated by a predetermined angle and the pressure oil supply passage 5 is rotated.
Of the gaps 7, 7 formed between the edges on both sides of the outer land portion 4 formed with the chamfered portions 8a, 8a of the inner land portions 8, 8 facing each other, pressure oil is applied to the side where the gap is expanded. Flows into the valve body groove 3 as it is, and the pressure oil is distributed from the pressure oil distribution hole 6 formed at the bottom of the valve body groove 3 to either the left hydraulic chamber 10a or the right hydraulic chamber 10b of the power cylinder 10. Is supplied to drive the piston 11, thereby assisting the steering force of the front wheels via the rack shaft 12.

In this conventional control valve for a power steering device, if the chamfer provided at the edge of the inner land portion 8 is steep with respect to the inner land portion 8, as shown in FIG. Becomes a turbulent flow c and flows into the low pressure valve body groove 3 to generate cavitation. Therefore, by making the chamfering inclination provided at the edge portion of the inner land portion 6 gentle with respect to the inner land portion 8, as shown in FIG. 14, turbulence is not generated and cavitation is prevented from occurring. Was.

[0007]

However, in the control valve for the power steering device as described above, as shown in FIG. 15, the outer land portion 4 and the inner land portion which are narrowed in the gap 7 where the gap is reduced. The pressure oil is passed through the gap between the inner surface 8 and the inner surface of the inner land portion 8 to form the jet a, which remains at the high pressure and flows into the low-pressure valve body groove 3. Then, the jet flow a flowing into the valve body groove 3 having a low pressure causes a swirl flow b having a gentle flow velocity.
Further, the generated vortex flow b is generated by the bottom portion 3 b of the valve body groove 3.
And the side wall 3a, and the jet flow a flows without being separated from the surface of the inner land portion 8 by the action of the vortex flow b.
The distance to the separation point becomes long, that is, the jet flow a flows at high speed without being damped, and therefore the pressure drop is large and cavitation is likely to occur. When this cavitation occurs, an abnormal noise of a shoe is generated in the valve, which gives a driver discomfort.

An object of the present invention is to prevent the generation of abnormal noise in the control valve for the power steering device by promoting the separation of the jet flow from the inner land portion.

[0009]

As a means for solving the above problems, the present invention is directed to a valve body groove having a pressure oil distribution hole communicating with a hydraulic chamber of a power cylinder and a pressure from a hydraulic pressure source. Power steering having a valve body having a supply passage to which oil is supplied and a valve shaft fitted in the valve body so as to be relatively movable, and having a land portion at a position substantially facing the valve body groove. The control valve for an apparatus is characterized by comprising high-speed oil flow separation promoting means for promoting separation of a high-speed oil flow flowing along the land portion from the supply passage into the valve body groove along the land portion. There is.

[0010]

According to the control valve for the power steering device having the above-described structure, the valve shaft relatively moves in the valve body by the driver's steering operation, and the power cylinder of the power cylinder on the side assisting the driver to steer in the steering direction. The gap between the edge portion of the valve body groove and the edge portion of the land portion, in which the pressure oil distribution hole communicating with the hydraulic chamber is formed, is expanded. The pressure oil from the pressure oil source, which is supplied through the supply passage, flows through the gap between the narrowed edge of the valve body groove and the edge of the land into the valve body groove along the land as a high-speed oil flow. It flows in, but
It is separated from the land portion by the high speed oil flow separation promoting means. The oil flow separated from the land portion becomes a low speed, and becomes a resistance of the oil flow not separated yet from the land portion. Therefore, the flow velocity of the oil flow flowing from the supply passage into the valve body groove along the land portion is reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control valve for a power steering system according to the present invention will be described below with reference to FIGS. 1 to 11.

FIGS. 1 and 5 show a first embodiment in which the control valve for a power steering device of the present invention is applied to a rotary control valve. The rotary control valve used in this power steering device is , Cylindrical valve body 22
And a cylindrical valve shaft 22 fitted inside the valve body 22 so as to be rotatable relative to each other. The inner circumference of the valve body 21 is
A valve body groove 23 having a rectangular cross-section is formed in parallel with the axial direction at two equally divided positions.
Eight outer land portions 2 formed between 3 and 23, respectively
Out of the four, every four are provided with a supply passage 25 for pressure oil that is pressurized and supplied by a vane pump or the like, and a pressure oil distribution hole 26 is provided at the bottom of each valve body groove 23. Has been formed.

On the other hand, the valve shaft 22 fitted inside the valve body 21 has an inner land portion 28 having a width slightly narrower than the width of the valve body groove 23 at a position where the outer circumference thereof is divided into eight equal parts. Valve shaft grooves 29, 29 having a rectangular cross section are formed on both sides of the land portion 28 in parallel with the axial direction. And each inner land portion 2
The edge portion of 8 is chamfered in a taper shape, and the outer land portion 2
The narrowed portion 27 is formed between the edge portion 4 and the edge portion 4.

Further, one side wall 23a of each valve body groove 23, which is also a side wall of the outer land portion 24 in which the pressure oil supply passage 25 of the valve body 21 is formed, is formed with the side wall 23a in the circumferential direction. In addition, a concave groove 23c having a U-shaped cross section is formed, and each valve body groove 23 is formed in a cross-sectional shape in which the depth of the groove is expanded.

Next, the operation of this embodiment configured as described above will be described. First, in the control valve used in this power steering apparatus, a steering shaft (not shown) is rotated. When,
The valve shaft 22 rotates by a predetermined angle. When the valve shaft 22 rotates, it is formed between the edges on both sides of the outer land portion 24 where the pressure oil supply passage 25 is formed and the chamfered portions 28a, 28a of the inner land portions 28, 28 facing each other. One of the narrowed portions 27, 27 is enlarged and changed, and the other gap is narrowed. As a result, the pressure oil flows toward the enlarged and changed throttle portion 27 side to supply the pressure oil from the pressure oil distribution hole 26 to one of the left and right hydraulic chambers of the power cylinder (not shown) to drive the piston, It is designed to assist the steering force of the front wheels.

In the control valve for the power steering device, as shown in FIG. 2, the throttle between the edge of the outer land portion 24 where the gap is narrower and the chamfered portion 28a of the inner land portion 28 is narrowed. The pressure oil that flows into the valve body groove 23 through the portion 27 becomes a high-speed oil flow (jet flow a) that flows along the surface of the inner land portion 28. This jet flow a is applied to the hydraulic oil in the valve body groove 23.
An eddy current b having a gentle flow velocity is generated. The vortex flow b flows along the bottom portion 23b and the side wall 23a of the valve body groove 23. At this time, since the concave groove 23c is formed on the one side wall 23a of the valve body groove 23, the vortex flow b generated in the valve body groove 23 flows along the concave groove 23c, and the vortex flow b is formed. The position is closer to the side wall 23a.

Therefore, in the jet flow a flowing along the surface of the inner land portion 28 of the valve shaft 22, the vortex flow b which is pressed against the valve shaft side is formed near the side wall 23a. The distance to the separation point is shortened, the resistance is increased due to the separation of the flow, and the flow velocity is decreased, so that the high-speed section of the jet flow is shortened and cavitation occurs as compared with the case where the concave groove 23c is not formed in the side wall. It is reduced and the generation of abnormal noise is suppressed.

As a result, it is possible to suppress the generation of shoe noise in the valve caused by cavitation without changing the valve characteristic of the control valve, and to reduce the discomfort felt by the driver.

In the present embodiment, the concave groove 23c is formed as a vortex flow transition means by making the vortex flow b transition toward the side wall of the valve body groove, thereby promoting the separation of the high speed oil flow (jet flow a) from the land portion. And corresponds to a means for promoting high-speed oil flow separation.

In the above embodiment, as the eddy current transition means, the case where the one side wall 23a of the valve body groove 23 on the inflow side of the jet a is formed with the U-shaped concave groove 23c is described. As shown in FIG. 3, even if the transition means is a concave groove 23d having a triangular cross section instead of the concave groove 23c having a U-shaped cross section, the same operation and effect as in the case of the above-described embodiment can be obtained. The shape of the concave groove may be an arbitrary polygonal concave groove 23e composed of linear elements as shown in FIG. 4, and the shape of the concave groove as eddy current transition means may be the concave groove 23f shown in FIG. , It is not necessary to be uniform in the axial direction.

A second embodiment of the present invention in which a convex portion is formed instead of the concave groove as a means for shifting the formation position of the vortex flow is shown in FIG.
It will be described based on. 6, the same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

In the present embodiment, the valve body groove 23
A convex portion 23g is provided on the bottom portion 23b. Since the vortex flow b is formed closer to the side wall 23a of the valve body groove 23 than the convex portion 23g by the convex portion 23g, the distance to the separation point where the jet flow a is separated from the surface of the inner land portion 28 is shortened, and cavitation occurs. Is reduced and the generation of abnormal noise is suppressed.

Further, the high-speed oil flow separation promoting means is not limited to the above-mentioned vortex flow transition means, and a case where a high-speed oil flow separation force applying means is provided instead of the vortex flow transition means will be described next. 7 to 10, the same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

FIGS. 7 and 8 show a third embodiment of the present invention equipped with a high-speed oil flow separation force imparting means. The inner land portion 28 of the valve shaft 22 has an edge portion of the inner land portion. The chamfered portion 28a formed in the above and a top portion of the inner land portion 28 are formed with a communication passage 28b. The communication passage 28b has a relative movement amount of the valve shaft 22 with respect to the valve body 21 of a predetermined value or more. In this case, it is formed at a position that connects the upstream side and the downstream side of the throttle portion 27.

In the above control valve for the power steering device, the steering operation by the driver causes
When the valve shaft 22 relatively moves in the valve body 21, as shown in FIG. 8, in a region where the relative movement amount of the valve body 21 and the valve shaft 22 is equal to or more than a predetermined amount, the outer land portion 24 with the narrower gap is formed. The pressure oil flows into the valve body groove 23 through the narrowed portion 27 and the communication passage 28b between the edge portion of the above and the chamfered portion 28a of the inner land portion 28. The pressure oil that flows into the valve body groove 23 via the throttle portion 27 becomes a jet flow a that flows along the surface of the inner land portion 28, but the pressure oil also flows into the valve body groove 23 through the communication passage 28b. (Oil flow d in FIG. 8), the jet land a is moved by the oil flow d to the inner land portion 28.
A force in the direction of separating from the jet a
Peels off from the inner land portion 28 and becomes slower. Since the jet flow a separated from the inner land portion 28 that has become low speed and the oil flow d flowing through the communication passage 28b become the resistance of the jet flow a not yet separated from the inner land portion 28, the flow velocity of the jet flow a decreases. The generation of cavitation is reduced and the generation of abnormal noise is suppressed.

As a result, the valve characteristic of the control valve is not changed during the initial steering until the relative movement amount between the valve body 21 and the valve shaft 22 becomes a predetermined amount or more,
The generation of shoe noise in the valve caused by cavitation can be suppressed, and the discomfort felt by the driver can be reduced.

In the present embodiment, the inner land portion of the high speed oil flow is imparted by applying a force to the high speed oil flow (jet a) so as to separate it from the inner land portion 28 as the high speed oil flow separation force imparting means for the communication passage 28b. It promotes the separation from 28 and corresponds to a high speed oil flow separation promoting means.

In the above-described embodiment, the valve body 21 of the valve shaft 22 is used as the high-speed oil flow separation force imparting means.
When the amount of relative movement with respect to
Although the case where the communication passage 28b is provided at a position that communicates the upstream side and the downstream side of 7 has been described, as shown in FIG. 9, the communication passage 2 is always provided at a position that communicates the upstream side and the downstream side of the throttle portion 27.
8c may be provided. In this case, although the valve characteristic of the control valve is changed at the initial stage of steering, the generation of shoe noise caused by cavitation is suppressed, and the discomfort felt by the driver can be reduced.

FIG. 10 shows a fourth embodiment of the present invention in which a means other than the communication passage is provided as a high-speed oil flow separation force applying means. The control valve for a power steering device of this embodiment is as follows: A convex portion 28 d is provided on the surface of the inner land portion 28 of the valve shaft 22.

In this embodiment, the convex portion 28d acts as an obstacle and a force is applied to the high-speed oil flow (jet flow a) to separate it from the inner land portion 28, and the jet flow a separated from the inner land portion 28 is applied. Becomes a low speed, and becomes a resistance of the jet flow a which is not separated from the inner land portion 28. Therefore, since the flow velocity of the jet flow a is reduced at an early stage, the occurrence of cavitation is reduced and the occurrence of abnormal noise is suppressed.

In the embodiments described above, the rotary type control valve has been described, but the spool type control valve can be similarly applied. A fifth embodiment in which the control valve for a power steering device of the present invention is applied to a spool type control valve will be described below with reference to FIG.

A spool type control valve used in a power steering system is a cylindrical valve body 31 and a cylindrical valve shaft fitted inside the valve body 31 so as to be slidable in the axial direction. (Spool) 32. A valve body groove 33 having a rectangular cross section is formed in an inner periphery of the valve body 31 in an annular shape at two positions orthogonal to the axial direction.
In the outer land portion 34 formed between these two valve body grooves 33, there is formed a pressure oil supply path 35 which is pressurized and supplied by a hydraulic pressure generation source such as a vane pump. A hydraulic distribution hole 36 is formed at the bottom of each.

On the other hand, the valve shaft 32 fitted inside the valve body 31 has an inner land having a width slightly narrower than the width of the valve body groove 33 at a position facing the valve body grooves 33, 33 on the outer periphery thereof. A portion 38 and valve shaft grooves 39, 39 having a rectangular cross section are formed on both sides of the inner land portion 38 so as to be orthogonal to the axial direction. The edge portion of each inner land portion 38 is tapered to form a chamfered portion 38 a, and the narrowed portion 37 is formed between the inner land portion 38 and the edge portion of the outer land portion 34.

The side wall 3 is formed on one side wall 33a of each valve body 33 which is also a side wall of the outer land portion 34 where the pressure oil supply passage 35 of the valve body 31 is formed.
3a is recessed in a direction parallel to the axis to form a groove 33 having a U-shaped cross section.
c is formed, and each valve body groove 33 is formed in a cross-sectional shape in which the inner part thereof is expanded.

Next, the operation of this embodiment configured as described above will be described. First, in the control valve provided in this power steering device, a steering shaft (not shown) is rotated. Then, the valve shaft 32 slides in the axial direction for a predetermined distance. When the valve shaft 32 slides, the pressure oil supply passage 3
5 on both sides of the outer land portion 34 and the chamfered portion 38 of the inner land portions 38, 38 facing each other.
The gap of one of the narrowed portions 37, 37 formed between a and 38a is expanded and changed, and the gap of the other is narrowed. As a result, the pressure oil separation hole 36
The hydraulic fluid is supplied to the left or right hydraulic chamber of a power cylinder (not shown) via the hydraulic fluid as it is, and the piston is driven, thereby assisting the steering force of the front wheels.

In this power steering device control valve, as shown in FIG. 11, the gap between the edge portion of the outer land portion 34 and the chamfered portion 38a of the inner land portion 48 is narrowed. The pressure oil flowing into the valve body groove 33 through the throttle portion 37 becomes a jet flow a flowing along the surface of the inner land portion 38. The jet flow a causes the working oil in the valve body groove 33 to generate a swirl flow b having a gentle flow velocity. The vortex flow b flows along the bottom portion 33b and the side wall 33a of the valve body groove 33. At this time, since the concave groove 33c is formed in the one side wall 33a of the valve body groove 33, the valve body groove 33 is formed.
The vortex flow b generated inside flows along the inside of the concave groove 33c, and the formation position of this vortex flow b is near the side wall 33a.

Therefore, in the jet a flowing along the surface of the inner land 38 of the valve shaft 32, the vortex b which presses the valve shaft 32 side is formed near the side wall 33a, so the jet a is on the surface of the inner land 38. Since the distance from the separation point to the separation point is shortened, the resistance increases due to the separation of the flow, and the flow velocity decreases.
Compared with the case where c is not formed, the high-speed section of the jet flow a is shortened, the occurrence of cavitation is reduced, and the occurrence of abnormal noise is suppressed.

As a result, generation of shoe noise in the valve caused by cavitation can be suppressed without changing the valve characteristics of the control valve, and the discomfort felt by the driver can be reduced.

In this embodiment, the concave groove 33c is used as the vortex flow transition means, and the vortex flow b is used as the side wall 33 of the valve body groove 33.
The high-speed oil flow (jet a) is promoted to be separated from the land portion by being formed by transitioning to the a side, and corresponds to the high-speed oil flow separation promoting means.

In the spool type control valve of the above embodiment, the case where a groove having a U-shaped cross section as vortex flow transition means is adopted as the high speed oil flow separation promoting means has been described, but like the rotary control valve, It is possible to employ various high speed oil flow separation promoting means such as high speed oil flow separation force applying means.

The present invention is not limited to the above-mentioned embodiments, but can be carried out in various modified and improved modes such as combined use of the vortex flow transition means and the high speed oil flow separation force imparting means. it can.

[0042]

As described above, in the control valve for a power steering device of the present invention, the flow velocity of the high-speed oil flow flowing from the supply passage along the land portion in the valve body groove is reduced by the high-speed oil flow separation promoting means. Because it is done
It is possible to reduce the occurrence of cavitation and suppress the generation of abnormal noise in the control valve.

[Brief description of drawings]

FIG. 1 is a cross-sectional plan view of a rotary control valve of a power steering device according to a first embodiment of the present invention.

FIG. 2 is an enlarged plan view of an essential part of FIG.

FIG. 3 is a cross-sectional plan view of relevant parts showing another mode of the groove shape of the first embodiment.

FIG. 4 is a cross-sectional plan view showing another mode of the groove shape of the first embodiment.

FIG. 5 is a cross-sectional plan view showing still another aspect of the groove shape of the first embodiment.

FIG. 6 is a sectional plan view of a control valve according to a second embodiment of the present invention.

FIG. 7 is a sectional plan view of a control valve according to a third embodiment of the present invention.

FIG. 8 is a cross-sectional plan view showing an operating state of the control valve of the third embodiment.

FIG. 9 is a cross-sectional plan view of a control valve showing another aspect of the communication passage of the third embodiment.

FIG. 10 is a sectional plan view of a control valve according to a fourth embodiment of the present invention.

FIG. 11 is a sectional plan view showing a fifth embodiment in which the control valve of the present invention is applied to a spool type control valve.

FIG. 12 is a cross-sectional plan view of a conventional control valve.

FIG. 13 is a cross-sectional plan view of relevant parts showing a turbulent flow generation state when the angle of the chamfered portion of the edge is steep in the conventional control valve.

FIG. 14 is a cross-sectional plan view of relevant parts showing the flow of a high-speed oil flow when the angle of the chamfered portion of the edge is gentle in the conventional control valve.

FIG. 15 is a sectional plan view of a conventional control valve showing the action of a vortex flow generated by a high-speed oil flow.

[Explanation of symbols]

 Reference Signs List 21 valve body 22 valve shaft 23 valve body groove 23a sidewall 23c U-shaped groove 23d as eddy current transition means 23d similarly triangular groove 23e similarly polygonal groove 23f similarly uneven groove 23g eddy current transition means 25 Supply path 26 Pressure oil distribution hole 28 Inner land 28a Chamfer 28b Communication passage as high-speed oil flow separation force imparting means 28c Another communication path 28d Convex portion as high-speed oil flow separation force imparting means 32 Valve shaft (spool) 33c U-shaped concave groove as vortex flow transition means a Jet flow b Vortex flow

Claims (1)

[Claims] 1. A valve body having a valve body groove, in which a pressure oil distribution hole communicating with a hydraulic chamber of a power cylinder is formed, and a supply passage to which pressure oil from a hydraulic pressure source is supplied, and the valve body. A control valve for a power steering device, which has a valve shaft having a land portion at a position substantially opposite to the valve body groove, and is fitted into the valve body groove from the supply passage into the valve body groove. A control valve for a power steering device, comprising: a high speed oil flow separation promoting means for promoting separation of a high speed oil flow flowing along the section from the land section.