KR100210886B1 - Power-assist steering system with control valve - Google Patents

Abstract

The hydraulic control valve of the power steering system is equipped with a flow resistor to suppress high frequency noise due to the flow of the fluid. This flow resistor is disposed between the inlet port connected to the pump and the inlet hole of the supply passage opening to the outer circumferential groove of the outer valve body communicating with the inlet port. According to this embodiment, the flow resistor includes a plurality of parallel rods fixed to each inlet hole of the supply passage.

Description

Power Steering System with Control Valve

The present invention relates to a hydraulic control valve and a power steering system for a power steering system.

Among various hydraulic control valves used in power steering systems, rotary hydraulic control valves are known as disclosed in Japanese Patent Application No. Hei 3-79473. According to this type of control valve, the torsion bar connects the input shaft connected to the steering column and the output shaft supporting the pinion coupled to the rack shaft of the steering gear. The rackshaft is slidably arranged in the tubular housing section of the steering gear housing. In addition, a tubular housing section is arranged with a power assisted power piston fixedly connected to the rack shaft. This piston forms two chambers on opposite sides of the tubular housing section. The control valve includes a coaxial inner valve body and an outer valve body in a valve housing fixed to the steering gear housing. The inner valve body takes the form of a spool integral with the input shaft. The outer valve element is connected thereto for rotation with the output shaft. The valve housing forms an inlet port connected to an external pump. The inner valve body takes the form of a spool forming an axial hole through which the torsion bar passes. The space in the through hole around the torsion bar is set separately as a drainage space. The inner valve body is radially disposed in the axially extending drain groove at an outer circumference formed between two first and second axially extending outer lands spaced at an angle with a radially inner end or aperture opening in the drainage space. At least one radial or drainage passage having an outer end or a hole is formed. The outer valve body takes the form of a sleeve, the cylindrical outer peripheral surface of which has a first peripheral groove which is always in communication with the inlet port and a second peripheral groove for connection to one of two chambers on opposite sides of the piston And a third peripheral groove for connecting to the other two chamber chambers. These peripheral grooves are axially spaced apart from each other along the axis of rotation of the outer valve body. The outer valve body is disposed on the bottom wall of the first peripheral groove and forms two supply passages having radially outer ends or inlet holes spaced apart from each other in the peripheral direction. These two feed passages have radially inner ends or holes respectively formed on the inner circumferential surface of the outer valve body and disposed at two angularly spaced first and second axially extending inner lands. The nearest edges of the first and second axial lands of the outer valve body are angularly spaced apart from the furthest edges of the first and second axial lands of the inner valve body. Further, a third axially extending inner land is formed on the inner circumferential surface of the outer valve body so as to be angularly spaced therebetween between the first axially inner land and the second axially inner land. The angularly spaced edges of the third axial inner land of the outer valve body are angularly less spaced apart than the nearest edges of the first and second axial outer lands of the inner valve body. Between the first and third axial inner lands of the outer valve body a first axially extending inner groove connected to the second peripheral groove via a passage is disposed, and the second and third axial inner lands of the outer valve body. Between the passage a second axially extending inner groove is arranged, connected to the third peripheral groove. If the torsion bar is not twisted while adjusting the steering column to rotate the outer valve body of the valve housing, all fluids are first, second and third axial inner lands of the outer valve body and the first of the inner valve body. And through the non-limiting passageway formed between the second and third axial outer lands is allowed to pass into the axial drainage groove and drainage space. Under this condition, the supply of fluid to one of the chambers on opposite sides of the piston and the discharge of fluid from the other chamber are performed without substantially resisting the movement of the piston. When the torsion bar is twisted during the rotational movement of the outer valve body, the inner valve body is angularly displaced in its rotational direction with respect to the outer valve body to limit the discharge flow of fluid from the first axial inner groove to the drain groove and Limiting the supply flow of fluid to the axial inner groove causes pressure to be generated in one of the chambers and a drop in pressure in the other chamber. In this case, if the direction of rotation of the outer valve body is reversed, the supply flow of fluid to the first axial inner groove is restricted and the discharge flow of fluid from the second axial inner groove is restricted so that the pressure in one of the chambers is reduced. And pressure in other chambers. In this way, the piston helps the rack shaft move.

According to the known control valve, high frequency noise is generated during rotation of the outer valve body in the valve housing due to the concentration of fluid flow into one of the feed passages when the inlet hole of the feed passage is moved to or overlapped with the inlet port. .

This problem is described in U.S. Patent Nos. 4,860,635 (August 29, 1989), 4,771, 841 (September 20, 1988), 4,862,985 (September 9, 1989), and 4,865,147 (September 1989). 4,884,648 (December 5, 1989), 4,860,846 (August 29, 1989), 4,958,695 (September 25, 1990), 4,875,542 (October 24, 1989), 4,846,296 (1989) 7. 11), 4,852,462 (August 1, 1989), 4,844,126 (July 4, 1989) and 4,830,131 (May 16, 1989).

It is an object of the present invention to solve the problems in the prior art described above.

1 is a fragmentary cross sectional view of a power steering system;

FIG. 2 is an enlarged sectional view taken along line 2-2 of FIG.

3 is a diagram showing a relationship between the coaxial outer valve body and the inner valve body in the valve housing.

4 is a plan view of an outer valve body;

5 is a diagram illustrating the flow of a fluid.

6 is a plan view similar to FIG. 4, showing a modification of the external valve element.

FIG. 7 is a plan view similar to FIG. 6, showing yet another modification of the outer valve body; FIG.

8A is a side view of the plug used in FIG.

Fig. 8B is an end view of the plug shown in Fig. 8A.

* Explanation of symbols for the main parts of the drawings

10 gear housing 12 housing section

14: rack shaft 16: piston

18, 20, 22: seal 24, 26: annular groove

28: output shaft 30: bearing

40: valve housing 46: torsion bar

56: internal valve body 58: external valve body

60: through hole 86, 88: seal groove

92a, 92b, 92c, 92d: Drainage passage 100, 102, 104, 106: Supply groove

166, 168: side walls 172, 174, 176: rod

According to one aspect of the present invention, an input shaft, an output shaft, a torsion bar connecting the input shaft and the output shaft to each other, a housing having an inlet port formed therein, and a rotationally disposed in the housing and connected thereto to rotate together with the output shaft and fluid through the inlet port. An outer valve body having a plurality of supply passages having a peripheral groove which is always in communication with the inlet port and an inlet hole opening in the peripheral groove for accommodating the valve, and which is rotationally disposed on the external valve body and which rotates together with the input shaft. There is provided a hydraulic control valve for a power steering system, comprising a connected internal valve body and a fluid flow resistor disposed in fluid communication between the inlet port and the inlet hole of the plurality of supply passages.

According to another aspect of the invention there is provided a gear housing having a tubular housing section, a rack shaft slidably disposed in the gear housing and extending into the tubular housing section, and slidably disposed in the tubular housing section and fixedly connected to the rack shaft. An output shaft having a piston having a first chamber and a second chamber in a tubular housing section, a pinion rotationally disposed in the gear housing and coupled to the rack shaft, a valve housing fixed to the gear housing, and connected to a steering column The inner shaft and the inner valve body disposed in the second housing and integral to the input shaft and the torsion bar connecting the input shaft and the output shaft to each other, the input shaft surrounding the torsion bar, and the inner valve body An outer valve body enclosed and rotatably disposed in the second housing and connected thereto for rotation with the output shaft, A pump as a sieve source and a fluid flow resistor disposed fluidically between the inlet port and the inlet hole of the plurality of supply passages, the valve housing defining an inlet port connected to the pump for receiving fluid, The outer valve body forms a first peripheral groove which is always in communication with the inlet port, the outer valve body having a second peripheral groove for connection with the first chamber of the cylindrical housing section and the second chamber of the tubular housing section. An inlet hole for forming a third peripheral groove for connection, wherein the first, second and third peripheral grooves are spaced apart from each other along a rotation axis of the external valve body, and the external valve body is opened in the first peripheral groove. A power steering system is provided, which forms a plurality of supply passages having a plurality of supply passages.

1 shows a power steering gear of a power steering system. Reference numeral 10 denotes a gear housing comprising a tubular housing section or cylinder 12. The rack shaft 14 is slidably disposed in the gear housing 10 and extends into the tubular housing section 12. The piston 16 is fixedly connected to the rack shaft 14 for sliding movement within the tubular housing section 12. The piston 16 has a seal 18 on its periphery for sealingly sealing to the inner wall of the tubular housing section 12. In addition, a tubular housing section 12 is arranged with a first annular seal 20 and a second annular seal 22. The first and second annular seals 20, 22 seal the annular space between the rack shaft 14 and the inner wall of the tubular housing section 12 at two longitudinally spaced portions of the rack shaft 14. It has an inner periphery which forms the sliding engagement with the rack shaft 14. As shown in FIG. The piston 16 includes a first annular groove or chamber 24 cooperating with the first annular seal 20 and a second annular groove or chamber 26 cooperating with the second annular seal 22. To form).

In FIG. 2, the pinion shaft or output shaft 28 is rotationally disposed in the gear housing 10 by the ball bearing 30 and the needle bearing 32 to rotate about the shaft 34. The output shaft 28 has or forms a pinion 36 coupled to the teeth of the rack shaft 14. Between the teeth of the pinion 36 and the ball bearing 30, a seal 38 for preventing the leakage of fluid toward the ball bearing 30 is provided. The valve housing 40 is fixed to the gear housing 10. The valve housing 40 is rotatably arranged with an input shaft 42 for connection with the steering column 44 shown in dashed lines. The torsion bar 46 connects the input shaft 42 and the output shaft 28 to each other, and is connected to the input shaft 42 by the one end portion 48 and the dowel pins 52 splined to the output shaft 28. The other end 50 is buried.

The rotary hydraulic control valve is shown generally at 54. The control valve 54 includes a coaxial inner valve body 56 and an outer valve body 58 in the valve housing 40. The inner valve body 56 takes the form of a spool which is integral with the input shaft 42 and forms an axial through hole 60 through which the torsion bar 46 passes. As described later, the space in the through hole 60 surrounding the torsion bar 46 is set separately as a drainage space. The outer valve body 58 takes the form of a sleeve connected to it by a dowel pin 62 to surround the inner valve body 56 and rotate with the output shaft 28. The outer valve body 58 is rotationally disposed in the valve housing 40 to rotate about the rotation shaft 34. As shown in FIG. 2, the valve housing 40 forms an inlet port 64 connected to the external pump 66 through a line schematically shown at 68. As shown in FIG. 1, the valve housing 40 forms a left port connected to a left inlet 70 that opens in the first chamber 24 through a line schematically shown at 72. The valve housing 40 also forms a rightward port connected to the rightward inlet 74 opening in the second chamber 26. As shown in FIG. 4, the cylindrical outer peripheral surface of the outer valve body 58 has a first or supply peripheral groove 78 and a second or left peripheral groove 80 and a third or right peripheral groove 82. Formed. These peripheral grooves 78, 80, 82 are axially spaced apart from each other along the axis of rotation 34 of the outer valve body 58. Four seal grooves 84, 86, 88, and 90 are formed in the peripheral wall of the outer valve body 58. The first peripheral groove 78 is formed between the seals disposed in the seal grooves 86 and 88, the second peripheral groove 80 is formed by the seal of the seal grooves 84 and 86, the third peripheral edge The groove 82 is formed by the seal of the seal grooves 88 and 90. As can be seen from FIGS. 1 and 2, the first peripheral groove 78 is connected to the pump 66, and the second peripheral groove 80 communicates with the first chamber 24 of the tubular housing section 12. To the left inlet 70, and the third peripheral groove 82 is connected to the right inlet 74 for communication with the second chamber 26 of the tubular housing section 12.

In FIG. 3, the inner valve body 56 forms four radial or drain passages 92a, 92b, 92c, 92d having radially inner ends or holes opening in the drainage space around the torsion bar 46 and have. The radially outer ends or holes of the drain passages 92a, 92b, 92c and 92d are disposed in four axially extending drain grooves 94a, 94b, 94c and 94d respectively formed in the outer circumferential surface of the inner valve body 56. do. The drain grooves 94a, 94b, 94c, and 94d are spaced at equal intervals. The drain groove 94a is formed between two first sets of angularly spaced first and second axially extending outer lands 96a and 98a. A drain groove 94b is formed between two first and second axially extending outer lands 96b and 98b of the second set that are angularly spaced apart. A drain groove 94c is formed between two first sets of angularly spaced two first and second axially extending outer lands 96c and 98c. The drain groove 94d is formed between two first sets of angularly spaced two first and second axially extending outer lands 96d and 98d. The first, second, third and fourth sets of first and second axially extending outer lands 96a, 98a, 96b, 98b, 96c, 98c, 96d and 98d are two adjacent sets of four axial directions It is angularly spaced from each other so as to be formed between the extension supply grooves 100, 102, 104, 106, ie the first, second, third and fourth supply grooves. In particular, the first supply groove 100 is formed between the first set of first axially extending lands 96a and the fourth set of second axially extending lands 98d. The second supply groove 102 is formed between the first set of second axially extending lands 98a and the second set of first axially extending lands 96b. The third supply groove 104 is formed between the second set of second axially extending lands 98b and the third set of first axially extending lands 96c. The fourth supply groove 106 is formed between the third set of second axially extending lands 98c and the fourth set of first axially extending lands 96d. The outer valve body 58 has a plurality of supply passages 108, 110, 112, 114 (four in this embodiment) coupled to the supply grooves 100, 102, 104, 106 of the inner valve body 56, respectively. Forming. The feed passages 108, 110, 112, 114 are disposed in the bottom wall of the first peripheral groove 78 and have radially outer ends or holes spaced apart from each other. The radially inner ends or holes of the feed passages 108, 110, 112, 114 are formed in the inner circumferential surface of the outer valve body 58, respectively, and the feed grooves 100, 102, 104, 106 of the inner valve body 56 are provided. Axially spaced inner lands 116, 118, 120, 122 opposing each other).

The angularly closest edges of the axially extending inner lands 116, 118 are more than the angularly spaced edges of the first set of first and second axially extending outer lands 96a, 98a. More angularly spaced apart. The angularly closest edges of the axially extending inner lands 118, 120 are greater than the angularly spaced edges of the second set of first and second axially extending outer lands 96b, 98b. More angularly spaced apart. The angularly closest edges of the axially extending inner lands 120, 122 are greater than the angularly spaced edges of the third set of first and second axially extending outer lands 96c, 98c. More angularly spaced apart. The angularly spaced edges of the axially extending inner lands 122, 116 are greater than the angularly spaced edges of the fourth set of first and second axially extending outer lands 96d, 98d. More angularly spaced apart.

On the inner circumferential surface of the outer valve body 58, third axially extending inner lands 126, 128, 130, 132 are formed. An axially extending inner land 126 is disposed between the axially extending inner lands 116, 118. The angularly spaced edges of this land 126 are angularly less spaced apart than the angularly closest spaced edges of the first set of first and second axially extending outer lands 96a and 98a. It is. An axially extending inner land 128 is disposed between the axially extending inner lands 118, 120. The angularly spaced edges of this inner land 128 are angularly less than the angularly closest spaced edges of the second set of first and second axially extending outer lands 96b and 98b. Are spaced apart. An axially extending inner land 130 is disposed between the axially extending inner lands 120, 122. The angularly spaced edges of this inner land 130 are angularly less than the angularly closest spaced edges of the third set of first and second axially extending outer lands 96c and 98c. Are spaced apart. An axially extending inner land 132 is disposed between the axially extending inner lands 122, 116. The angularly spaced edges of this inner land 132 are angularly less than the angularly spaced edges of the fourth set of first and second axially extending outer lands 96d and 98d. Are spaced apart. The axially extending inner lands 126, 128, 130, and 132 are disposed opposite the drainage grooves 94a, 94b, 94c, 94d of the inner valve body 56, respectively.

An axially extending inner groove 134 is formed between the axially extending inner lands 116 and 126. An axially extending inner groove 136 is formed between the axially extending inner lands 118 and 128. An axially extending inner groove 138 is formed between the axially extending inner lands 120 and 130. An axially extending inner groove 140 is formed between the axially extending inner lands 122 and 132. These axially extending inner grooves 134, 136, 138, 140 are disposed opposite the first, second, third and fourth sets of first axially extending outer lands 96a, 96b, 96c, 96d, respectively. And a third peripheral groove 82 connected to a rightward inlet 74 opening in the chamber 26 via corresponding passages 142, 144, 146, 148. These passages 142, 144, 146, 148 are shown in dashed lines.

An axially extending inner groove 150 is formed between the axially extending inner lands 126 and 118. An axially extending inner groove 152 is formed between the axially extending inner lands 128 and 120. An axially extending inner groove 154 is formed between the axially extending inner lands 130 and 122. An axially extending inner groove 156 is formed between the axially extending inner lands 132 and 116. These axially extending inner grooves 150, 152, 154, 156 are disposed opposite the first, second, third and fourth sets of second axially extending outer lands 98a, 98b, 98c and 98d, respectively. And a second peripheral groove 80 connected to a left inlet 70 opening in the chamber 26 via corresponding passages 158, 160, 162, 164. These passages 158, 160, 162 and 164 are shown in dashed line in FIG.

The angularly spaced edges of the first set of first axially extending outer lands 96a are less angularly spaced than the angularly most closely spaced edges of the axially extending inner lands 116, 126. It is. The angularly spaced edges of the first set of second axially extending outer lands 98a are less angularly spaced than the angularly closest edges of the axially extending inner lands 126, 118. It is. The angularly spaced edges of the second set of first axially extending outer lands 96b are less angularly spaced than the angularly closest edges of the axially extending inner lands 118, 128. It is. The angularly spaced edges of the second set of second axially extending outer lands 98b are angularly less spaced than the angularly closest edges of the axially extending inner lands 128 and 120. It is. The angularly spaced edges of the third set of first axially extending outer lands 96c are less angularly spaced than the angularly closest edges of the axially extending inner lands 120 and 130. It is. The angularly spaced edges of the third set of second axially extending outer lands 98c are angularly less spaced than the angularly closest edges of the axially extending inner lands 130 and 122. It is. Angularly spaced edges of the fourth set of first axially extending outer lands 96d are less angularly spaced than angularly closest edges of the axially extending inner lands 122 and 132. It is. The angularly spaced edges of the fourth set of second axially extending outer lands 98d are less angularly spaced than the angularly most closely spaced edges of the axially extending inner lands 132, 116. It is.

As shown in FIG. 4, the first peripheral groove 78 has two spaced apart sidewalls 166, 168 and a bottom wall 170 connecting the sidewalls 166, 168 with each other. Bottom wall 170 and two spaced apart sidewalls 166, 168 cooperate to form first peripheral groove 78. Inlet holes of the feed passages 108, 110, 112, 114 are disposed in the bottom wall 170 of the peripheral groove 78. In this embodiment a plurality of three generally parallel rods 172, 174, 176 are secured to each inlet hole of the feed passage 108, 110, 112, 114. These rods 172, 174, 176 are formed by a plurality of wires (three in this embodiment) wound around the outer valve body 58 at the bottom wall 170 of the first peripheral groove 78. These rods 172, 174, 176 may be formed of one or less than three wires wound from the bottom wall 170 of the first peripheral groove 78 to the outer valve body 58.

5 illustrates the interaction of the flow of fluid with the rods 172, 174, 176. It can be seen that the rods 172, 174, 176 function as fluid flow resistors disposed between the inlet port 64 and the inlet holes of the feed passages 108, 110, 112, 114. By this arrangement, the flow of fluid diverges before being introduced into the feed passages 108, 110, 112, 114 to effectively suppress high frequency noise.

In operation, when the torsion bar 46 is not twisted during steering of the steering column 44 to rotate the outer valve body 58 of the valve housing 40, all fluid is transferred to the shaft of the outer valve body 58. Axial extending outer lands 96a, 98a, 96b, 98b, 96c, 98c, 96d, 98d of the directionally extending inner lands 116, 118, 120, 122, 126, 128, 130, 132 and the inner valve body 56. Pass through the non-limiting passageway formed between the axially extending drainage grooves 94a, 94b, 94c, 94d and into the drainage space around the torsion bar 46. Under this condition, the supply of fluid to one of the chambers 24 and 26 and the discharge of fluid from the other on the opposite sides of the piston 16 are performed without any resistance to the movement of the piston 16. When the torsion bar 46 is twisted during the rotational movement of the outer valve body 58, the inner valve body 56 is angularly displaced with respect to the outer valve body 58, thereby extending the axially extending inner grooves 134, 136, 138. Limiting the discharge flow of fluid from one group of the group consisting of 140 to the drainage groove and the axially extending inner grooves 150, 152, 154 and 156. Restricting the feed flow causes pressure to be generated in one of the chambers 24 and 26 and a pressure drop in the other. In this case, if the direction of rotation of the outer valve body 58 is reversed, the supply flow of fluid to one group of the axially extending inner grooves is restricted and the discharge flow of fluid from the other group is restricted to the chambers 24 and 26. One causes the pressure to drop and the other causes pressure to be generated. In this way the piston 16 assists in the movement of the rack shaft 14.

By providing fluid flow resistors in the form of rods 172, 174, 176 fixed to respective inlet holes of the feed passages 108, 110, 112, 114, 116, the inlet of the feed passages 108, 110, 112, 114. Even if one of the holes moves or overlaps the inlet port 64, the fluid flow branches, thereby suppressing or preventing the generation of high frequency noise.

The fluid flow resistor may take the form of a body 180 forming a mesh covering the bottom wall 170 of the first peripheral groove 78, as shown in FIG. 6. In Fig. 6, the body 180 forming the mesh covers the inlet holes of the supply passages 108, 110, 112, 114. Alternatively, the fluid flow resistor, as shown in Figures 7, 8A and 8B, may in this case take the form of a plurality of plugs 182 forming a four mesh. These plugs 182 are fixed to the inlet holes of the supply passages 108, 110, 112, 114, respectively.

Those skilled in the art may modify the embodiments of the present invention in various forms, and control valves including such modifications also fall within the scope of the invention described in the claims.

Claims (23)

In a hydraulic control valve for a power steering system, Input shaft, With output shaft, A torsion bar connecting the input shaft and the axial shaft to each other, A housing having an inlet port, A plurality of feed passages formed in the housing and connected to rotate with the output shaft and having a peripheral groove always in communication with the inlet port for receiving fluid through the inlet port and an inlet hole opening in the peripheral groove. With an external valve body, An inner valve body rotatably disposed on the outer valve body and connected thereto for rotation with the input shaft, And a fluid flow resistor disposed in fluid communication between the inlet port and the inlet apertures of the plurality of supply passages. The hydraulic control valve according to claim 1, wherein the fluid flow resistor is disposed in the peripheral groove. 3. The hydraulic control valve of claim 2, wherein the peripheral groove has two spaced apart opposing side walls and a bottom wall connecting the side walls to each other, wherein the bottom wall and the two side walls cooperate to form a peripheral groove. 4. The hydraulic control valve according to claim 3, wherein the inlet holes of the plurality of supply passages are disposed in the bottom wall of the peripheral groove. 5. The hydraulic control valve according to claim 4, wherein the fluid flow resistor is wound around the outer valve body at the bottom wall of the peripheral groove. 6. The hydraulic control valve according to claim 5, wherein the fluid flow resistor includes a plurality of parallel rods fixed to each inlet hole of the plurality of supply passages. 7. The fluid flow resistor of claim 6, wherein the fluid flow resistor comprises at least one wire wound around the outer valve body at the bottom wall of the peripheral groove to form a plurality of rods fixed to each inlet hole of the plurality of supply passages. Hydraulic control valve. 7. A hydraulic system according to claim 6, wherein the fluid flow resistor comprises a plurality of wires wound on the outer valve body at the bottom wall of the peripheral groove to form a plurality of rods fixed to each inlet hole of the plurality of fluid passages. Control valve. 6. The hydraulic control valve according to claim 5, wherein the fluid flow resistor comprises a body forming a mesh covering the inlet holes of the plurality of supply passages. 5. The hydraulic control valve according to claim 4, wherein the fluid flow resistor comprises a plurality of plugs forming a mesh fixed to each of the plurality of inlet holes of the supply passage. In the power steering system, Gear housing with tubular housing section, A rack shaft slidably disposed in the tubular housing section, A piston slidably disposed in the gear housing and extending into the tubular housing section and fixedly connected to the rack shaft and forming a first chamber and a second chamber in the tubular housing section; An output shaft rotatably disposed in the gear housing and having a pinion coupled to the rack shaft, A valve housing fixed to the gear housing, An input shaft rotatably disposed in the second housing for connecting to the steering column; A torsion bar connecting the input shaft and the output shaft to each other, An internal valve body integral with the input shaft surrounding the torsion bar and disposed in the second housing; An outer valve body surrounding the inner valve body and rotatably disposed in the second housing and connected thereto to rotate with the output shaft, A pump as a fluid source, A fluid flow resistor disposed in fluid flow between the inlet port and the inlet hole of the plurality of supply passages, The valve housing defines an inlet port connected to the pump for receiving fluid, The outer valve body forms a first peripheral groove that is always in communication with the inlet port, The outer valve body defines a second peripheral groove for connection with the first chamber of the cylindrical housing section and a third peripheral groove for connection with the second chamber of the tubular housing section, The first, second and third peripheral grooves are spaced apart from each other along the rotation axis of the outer valve body, And the outer valve body forms a plurality of supply passages having an inlet hole opened in the first peripheral groove. 12. The method of claim 11, wherein the first peripheral groove has two spaced sidewalls and a bottom wall connecting the sidewalls to each other, wherein the bottom wall and the two spaced sidewalls cooperate to form a first peripheral groove. Power steering system. 13. The power steering system according to claim 12, wherein the inlet holes of the plurality of supply passages are disposed in the bottom wall of the first peripheral groove. 14. The power steering system of claim 13, wherein the fluid flow resistor is wound around the outer valve body at the bottom wall of the first peripheral groove. 15. The power steering system of Claim 14, wherein the fluid flow resistor includes a plurality of parallel rods fixed to each inlet hole of the plurality of supply passages. The fluid flow resistor of claim 15 wherein the fluid flow resistor comprises at least one wire wound around the outer valve body at the bottom wall of the first peripheral groove to form a plurality of rods fixed to each inlet hole of the plurality of supply passages. Power steering system. The fluid flow resistor of claim 15, wherein the fluid flow resistor comprises a plurality of wires wound around the outer valve body at the bottom wall of the first peripheral groove to form a plurality of rods respectively secured to respective inlet holes of the plurality of supply passages. Power steering system. 15. The power steering system of Claim 14, wherein the fluid flow resistor comprises a body forming a mesh covering the inlet openings of the plurality of supply passages. 14. The power steering system of claim 13, wherein the fluid flow resistor comprises a plurality of plugs forming meshes that are each secured to a plurality of holes in the supply passage. A plurality of input shafts, an output shaft driven to the steering mechanism, a torsion bar connecting the input shaft and the output shaft to each other, a power assisted hydraulic cylinder, and a plurality of positions configured to oppose the inlet port and arranged at a position in which the input shaft and the output shaft are driven to each other. 10. A power steering system comprising: a hydraulic control valve forming two supply passageways and operative to control fluid supply to and from a fluid assisted hydraulic cylinder; The hydraulic control valve includes means for fluidly connecting the inlet port to the plurality of supply passages, and means for restricting fluid flow from the inlet port to the plurality of supply passages to suppress high frequency noise due to the flow of the fluid. Power steering system, characterized in that. 21. The power steering system according to claim 20, wherein the flow resistance means comprises at least one wire. 21. The power steering system according to claim 20, wherein the flow resistance means comprises a body forming a mesh. 21. The power steering system according to claim 20, wherein the flow resistance means comprises a plurality of plugs forming a mesh and fitted in each of the inlet holes of the plurality of supply passages.