JP2006111172A - Hydraulic power steering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic power steering apparatus enabling adjustment for reducing dispersion of the characteristics by the influence of the dimensional errors of an oil groove and a chamfer by adjusting the auxiliary force characteristics in the assembly stage of a hydraulic control valve, and does not need time and effort for the processing therefor. <P>SOLUTION: An oil groove 12 on a valve spool 11 side facing each throttle part juxtaposed on a circumference to be fitted to a valve body is a trapezoidal groove with the width thereof being reduced from one side to the other in the axial direction, and chamfers 13, 13 for adjusting the throttling area are formed in corner parts 9 on both sides of the oil groove 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydraulic power steering apparatus configured to assist a steering operation of a steering mechanism with a generated force of a hydraulic cylinder disposed in the steering mechanism.

  The hydraulic power steering system assists the steering operation with the hydraulic pressure generated by a double-acting hydraulic cylinder (power cylinder) arranged in the steering mechanism, and burdens the driver on the operation of the steering wheel for steering. Steering force applied to the steering wheel between the cylinder chambers of the power cylinder and the hydraulic pump as the hydraulic source and the oil tank as the oil discharge destination. A hydraulic control valve that controls hydraulic supply / discharge according to the direction and magnitude of torque is provided.

  As this hydraulic control valve, a rotary hydraulic control valve that directly uses the rotation of the steering wheel is generally used. This is because the input shaft connected to the steering wheel and the output shaft connected to the steering mechanism are connected coaxially via a torsion bar, and the other connection is made inside the cylindrical valve body engaged with one connection end. A valve spool formed integrally with the end is fitted so as to be relatively rotatable, and when a steering torque is applied to the steering wheel, a relative angular displacement is generated between the valve body and the valve spool as the torsion bar is twisted. It has a configuration.

  On the fitting circumference (the inner circumference of the former and the outer circumference of the latter) of the valve body and the valve spool, a plurality of oil grooves extending in the axial length direction are arranged in parallel in the circumferential direction. The valve body and the valve spool are assembled such that respective oil grooves are staggered in the circumferential direction, and a plurality of throttle portions that change the throttle area according to the relative angular displacement are formed between adjacent oil grooves. Each of the oil grooves is located between an oil supply groove and an oil discharge groove that are respectively connected to a hydraulic pressure source and an oil discharge destination, and oil discharge grooves on both sides of the oil supply groove, and is a power cylinder that serves as an oil supply destination. A pair of oil feeding grooves that are respectively connected to both cylinder chambers are configured.

  The valve body and valve spool are centered and adjusted so that the plurality of throttle parts arranged on the fitting circumference have the same throttle area in the neutral state where the torsion bar is not twisted. The supplied pressure oil is evenly distributed and introduced into the oil feeding grooves adjacent to each other on both sides, and further introduced into the oil draining grooves adjacent to these other sides and discharged to the oil discharge destination. At this time, no pressure difference is generated between the cylinder chambers respectively connected to the oil feeding groove, and the power cylinder does not generate any force.

  On the other hand, when a rotational torque (steering torque) for steering is applied to the steering wheel and a relative angular displacement occurs due to torsion of the torsion bar between the input shaft and the output shaft, the valve spool and the valve body The pressure area supplied to the oil supply groove is introduced into one oil supply groove through the throttle part on the side where the throttle area is increased, and the oil supply groove A pressure difference is generated between one cylinder chamber communicated with the groove and the other cylinder chamber communicated with the other oil feed groove, and the oil pressure generated by the power cylinder in response to this pressure difference is applied to the steering mechanism. In addition, the steering operation of the steering mechanism is assisted. In addition, the hydraulic oil pushed out from the other cylinder chamber by this operation returns to the other oil feeding groove, and is introduced into the oil draining groove through a throttle portion having an increased throttle area on one side of the oil feeding groove. It is discharged to the oil drain destination.

  In the hydraulic power steering apparatus configured as described above, the relationship between the steering torque applied to the steering wheel and the steering assist force generated by the power cylinder (auxiliary force characteristics) depends on the relative angular displacement between the valve spool and the valve body. Thus, it depends on the change mode of the stop area generated in the stop portion described above. Therefore, conventionally, the corner portion of the oil groove on the valve spool side facing each throttle portion is inclined at a predetermined inclination angle with respect to the peripheral surface, and is used as a chamfered portion having a predetermined circumferential width for adjusting the throttle area. These chamfers are formed so that desired assisting force characteristics can be obtained by the action of these chamfers.

  The chamfer generates a region in which each throttle area gradually decreases according to the relative angular displacement before each throttle part is closed, and in the auxiliary force characteristics shown in FIG. It is provided to form a region where the assist force gradually increases, and the start point and end point of this gradually increase region and the dead zone region where the steering assist force is maintained substantially constant on the smaller torque side than the start point are defined as the width of the chamfer. The desired auxiliary force characteristic is realized by setting the groove width on the circumference of the valve spool and setting the increasing rate in the gradually increasing region by the inclination of the chamfer.

  However, the width and inclination of the chamfer as described above are both very small values, and it is difficult to form the chamfer with high precision in each of the plurality of throttle portions in the circumferential direction, and it is difficult to obtain a desired auxiliary force characteristic. Various proposals have conventionally been made to solve this problem.

As one proposal, the chamfers on both sides of the oil groove are formed to be inclined to one side with respect to the longitudinal direction of each oil groove, that is, the axial direction of the valve spool. There is a hydraulic control valve for a power steering device configured to expand the selection range of force characteristics (see, for example, Patent Document 1). As another proposal, oil grooves on the valve spool side and the valve body side are arranged in the axial direction. The groove has a trapezoidal shape that widens toward the opposite side, and the throttle area of the throttle part between them can be adjusted by moving the valve spool and valve body relative to each other in the axial direction. There is a hydraulic control valve for a power steering apparatus configured to realize a desired assisting force characteristic (see, for example, Patent Document 2).
Japanese Utility Model Publication No. 5-92051 Japanese National Patent Publication No. 4-500644

  However, the configuration disclosed in Patent Document 1 has the advantage that the degree of design freedom is increased and the desired assisting force characteristic can be easily realized. However, the actual assisting force characteristic is influenced by the dimensional error of the chamfer. Inevitably, it cannot be adjusted in order to reduce the variation in characteristics in the assembly stage, and there is a problem that high machining accuracy is still required for chamfer machining.

  On the other hand, in the configuration disclosed in Patent Document 2, the valve spool and the valve body are moved in the axial direction, and the throttle area of the throttle portion arranged on the fitting circumference of both is changed, thereby assisting in the assembly stage. It is possible to adjust the force characteristics and obtain the desired characteristics. However, as described above, the oil groove having a trapezoidal shape can be formed on the inner peripheral surface of the cylindrical valve body with high accuracy. There is a practical problem that it is difficult and causes an increase in the number of processing steps.

  The present invention has been made in view of such circumstances, and by adjusting the assisting force characteristic at the assembly stage of the hydraulic control valve, it is possible to adjust to reduce the variation in characteristics due to the influence of the dimensional error of the chamfer. Another object of the present invention is to provide a hydraulic power steering apparatus that does not require labor for machining the oil groove and chamfer on the fitting circumference of the valve spool and valve body.

  A hydraulic power steering apparatus according to the present invention includes a plurality of oil grooves arranged in parallel on the fitting circumference of a valve spool that is fitted inside a cylindrical valve body so as to be capable of relative angular displacement coaxially. Are arranged in a zigzag manner in the circumferential direction to form a throttle part that changes the throttle area according to the relative angular displacement between the oil grooves adjacent to each other, and corners on both sides of the oil groove of the valve spool facing each throttle part In the hydraulic power steering apparatus having a hydraulic control valve in which a chamfer for adjusting the throttle area is formed, the oil groove of the valve body extends with a substantially constant width in the axial direction of the valve body. The oil groove of the valve spool is a trapezoidal groove extending in the axial length direction of the valve spool from the one side toward the other side.

  In the present invention, the oil groove on the inner periphery of the valve body, which is difficult to perform complicated processing, is a rectangular groove having a substantially constant width in the axial length direction, while the outer periphery of the valve spool that can easily cope with complicated processing. Only the oil groove is a trapezoidal groove whose width is changed in the axial direction, and chamfers are formed on both sides of the oil groove, and the valve spool and valve body are moved relative to each other in the axial direction at the assembly stage. By using the portions having different widths of the groove and the chamfer, the throttle area of each throttle portion is adjusted to achieve a desired assisting force characteristic.

  In the hydraulic power steering device according to the present invention, only the oil groove on the outer periphery of the valve spool is a trapezoidal groove, and chamfers that are parallel to the axial direction of the valve spool are formed at the corners on both sides of the oil groove. By moving the valve spool and the valve spool relative to each other in the axial length direction, the throttle area of the throttle parts arranged on the fitting circumference of both can be changed at the assembly stage, and the variation in characteristics due to the influence of the dimensional error of the chamfer is reduced. The present invention has an excellent effect that adjustment is possible and the processing for this is not time-consuming.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a longitudinal sectional view showing a configuration of a main part of a hydraulic power steering apparatus according to the present invention.

  In the figure, reference numeral 2 denotes an input shaft, and 3 denotes an output shaft, which are supported so as to be rotatable about the same axis with the respective ends thereof being brought into contact with each other inside a cylindrical housing H. The butt end (lower end) of the input shaft 2 configured as a hollow shaft is fitted into a cylindrical portion 30 connected to the butt end (upper end) of the output shaft 3 to an appropriate length, and is supported so as to be relatively rotatable. The input shaft 2 and the output shaft 3 are coaxially connected through a torsion bar 4 inserted through the hollow portion of the input shaft 2 as will be described later.

  The upper part of the input shaft 2 protrudes outside the housing H, and the protruding end is connected to a steering wheel (not shown). A pinion 31 is formed in the lower half of the output shaft 3, and the pinion 31 is engaged with a rack shaft 32 supported in a manner crossing the output shaft 3 at the lower part of the housing H. A rack and pinion type steering mechanism is configured to convert the rotation into movement in the axial direction of the rack shaft 32 to perform steering.

  A hydraulic control valve 1 including a valve body 10 and a valve spool 11 is configured at the connecting portion between the input shaft 2 and the output shaft 3. The valve body 10 is a cylindrical member rotatably held coaxially at a corresponding portion of the housing H, and the output shaft 3 is formed by a dowel pin 33 placed on the outer periphery of the cylindrical portion 30 of the output shaft 3. Are connected together. The valve spool 11 is integrally formed on the outer periphery of the connection side of the input shaft 2 that is fitted inside the valve body 10 so as to be relatively rotatable.

  As is well known, a plurality of oil grooves extending in the axial length direction are arranged in parallel on the inner peripheral surface of the valve body 10 and the outer peripheral surface of the valve spool 11 in the circumferential direction. A plurality of throttle portions 8 that are arranged in a zigzag manner in the circumferential direction on the fitting circumference and change the throttle area according to the relative angular displacement are formed between adjacent oil grooves.

The hydraulic pump P serving as an oil supply source is communicated with one of the oil grooves (oil supply groove) via a pump port 20 penetrating the housing H in and out. Further, adjacent oil grooves (oil feed grooves) on both sides of these oil supply grooves penetrate through the housing H into both cylinder chambers S _L and S _R of a power cylinder (not shown) formed in the middle of the rack shaft 33. The cylinder ports 21 and 22 are connected to each other. Furthermore, the oil groove (oil drain groove) adjacent to the other side of these oil feed grooves communicates with the oil drain chamber 23 formed on one side of the valve body 10 through the hollow portion of the input shaft 2. The oil tank 23 is communicated with an oil tank T as an oil discharge destination through a tank port 24 penetrating the housing H in and out at a corresponding position of the oil discharge chamber 23.

The valve body 10 and the valve spool 11 are positioned in the circumferential direction so that in the neutral state where the torsion bar 4 is not twisted, the throttle portions 8 between the oil grooves on the fitting circumference have substantially the same throttle area. Adjusted (centering adjustment), the pressure oil supplied from the hydraulic pump P through the pump port 20 to the oil supply groove is introduced evenly distributed to the oil supply grooves adjacent to each other on both sides, and further to these other sides The oil is introduced into the oil drain grooves adjacent to each other and discharged to the oil tank T through the hollow portion of the input shaft 2, the oil drain chamber 23 and the tank port 24. At this time, no pressure difference is generated between the cylinder chambers S _L and S _R communicated with the oil feeding groove, and the power cylinder does not generate any force.

  On the other hand, when a rotational torque (steering torque) for steering is applied to a steering wheel (not shown), this steering torque is transmitted to the input shaft 2 and further transmitted to the output shaft 3 via the torsion bar 4. The rack shaft 32 that meshes with the pinion 31 in the lower half is converted into a movement in the axial direction, and steering is performed. At this time, the rack shaft 32 is moved against the reaction force from the road surface acting on the steering wheel (not shown), and therefore, between the input shaft 2 and the output shaft 3, that is, the valve spool 11 and the valve. A relative angular displacement is generated between the body 10 and the torsion bar 4 in accordance with the steering torque applied to the steering wheel as the torsion bar 4 is twisted. The area changes.

This change in the throttle area occurs on both sides of each oil groove to reduce the throttle area on one side and increase the throttle area on the other side, and the pressure oil supplied to the oil supply groove is on the side where the throttle area is increased. One cylinder chamber S _L (or S _R ) that passes through the throttle portion 8 and is mainly introduced into one oil feeding groove and communicated with the oil feeding groove via a cylinder port 21 (or 22). And the other cylinder chamber S _R (or S _L ) communicated with the other oil feeding groove via the cylinder port 22 (or 21), and the power cylinder responds to this pressure difference. The oil pressure is generated and this oil pressure is applied to the rack shaft 32 in the steering mechanism as a steering assist force.

Further, at this time, the hydraulic oil is pushed out from the other cylinder chamber S _R (or S _L ), returns to the other oil feed groove through the corresponding cylinder port 22 (or 21), and enters one side of this oil feed groove. Then, the oil is introduced into the oil drain groove through the throttle portion 8 having an increased throttle area, and is discharged to the oil tank T through the hollow portion of the input shaft 2, the oil drain chamber 23 and the tank port 24.

  FIG. 2 is a perspective view showing an oil groove formation mode on the outer peripheral surface of the valve spool 11. The features of the hydraulic power steering device according to the present invention are the mode of formation of these oil grooves 12, 12..., And further, for adjusting the throttle area provided at the corners 9 on both sides of these oil grooves 12, 12. It is in the formation mode of chamfers 13 and 13.

As shown in FIG. 2, the oil grooves 12, 12... Formed on the outer peripheral surface of the valve spool 11 are extended to have a predetermined length in the axial length direction of the valve spool 11. These oil grooves 12, 12... Have a circumferential width W ₁ at one end portion in the extending direction, that is, in the axial direction of the valve spool 11, and are also larger than a circumferential width W ₂ at the other end portion. The groove is formed as a concave groove having a trapezoidal cross section that is wide and continuously decreases in width from one side to the other side in the axial direction. The oil grooves 12, 12... Shown in the figure are wide at the upper end side of the input shaft 2 and have a trapezoidal shape that decreases in width toward the lower end side. On the contrary, the lower end side is wide. A trapezoidal shape that reduces the width toward the upper end side may be used.

FIG. 3 is an explanatory view showing an example of a method for processing the oil groove 12 on the outer periphery of the valve spool 11. As shown in this figure, the oil groove 12 is processed by a disk-shaped rotary grindstone R (other rotations) having a grinding surface width larger than the half width of the maximum width W ₁ of the oil groove 12 and smaller than the minimum width W _2. First, the rotational axis of the rotating grindstone R is inclined at a predetermined angle α to one side with respect to the circumferential direction of the valve spool 11, that is, the width direction of the oil groove 12. One side which is inclined with respect to the axial length direction by applying a feed in a direction orthogonal to the rotation axis as shown by white arrows in the figure while pressing the outer peripheral grinding surface against the circumferential surface of the valve spool 11 Next, the same procedure can be performed in a state where the rotation axis of the rotating grindstone R is inclined to the opposite side by the same angle, and the other side is formed by the processing procedure. . Such processing can be performed easily and with high accuracy by two-step grinding (or cutting) performed by changing the inclination angle of the valve spool 11 with respect to a single rotating grindstone R.

  A pair of chamfers 13 and 13 are formed at the corners 9 on both sides of the oil grooves 12, 12. These chamfers 13 and 13 use a large-diameter disk-shaped rotary grindstone R having a rotation axis parallel to the axial direction of the valve spool 11, and this is used as a predetermined chamfer at all corners 9 on both sides of the oil groove 12. It can be formed by a known procedure in which it is positioned so as to have a corner and is processed by feeding in a direction perpendicular to the axial direction of the valve spool 11. Here, since the oil groove 12 has a trapezoidal shape, the circumferential width of the chamfers 13 and 13 on both sides is narrow on the wide side of the oil groove 12 and wide on the narrow side, and the axial length of the valve spool 11 The width is continuously increased from one side of the direction to the other side.

  On the other hand, the oil groove 14 arranged in parallel on the inner peripheral surface of the valve body 10 is a simple rectangular groove extending with a substantially constant width in the axial length direction of the valve body 10 and the output shaft 3. FIG. 4 is an explanatory view showing the relative positional relationship between the oil groove 12 and the oil groove 14 arranged on the fitting circumference of the valve body 10 and the valve spool 11, and the fitting between the valve body 10 and the valve spool 11. The circumferential surface is developed in a plane, the oil groove 12 is indicated by a solid line, and the oil groove 14 is indicated by a two-dot chain line.

  As described above, the oil groove 12 communicates with the oil grooves 14 and 14 on both sides with a substantially equal throttle area, and the chamfers 13 and 13 formed on both sides of the oil groove 12 in this communication part. 13 intervenes. Here, the oil groove 12 is formed as a trapezoidal groove, and the chamfers 13 and 13 on both sides of the oil groove 12 have a width that continuously increases from one side to the other side in the axial direction. By moving the valve body 10 and the valve spool 11 relative to each other in the axial length direction (the direction indicated by the white arrow in the figure), the average communication width of the oil groove 12 with respect to the oil groove 14 and the chamfer interposed in the communication portion The average width of 13 and 13 can be increased or decreased. In the lower half of FIG. 4, a state in which the average communication width of the oil groove 12 is reduced is shown on the left side, and a state in which it is increased is shown on the right side.

  As shown in FIG. 1, the torsion bar 4 that connects the input shaft 2 and the output shaft 3 is a round bar having an outer diameter and a length determined to obtain desired torsional characteristics. The connecting portions 40 and 41 having large diameters are provided at both ends. The connection between the input shaft 2 and the output shaft 3 by such a torsion bar 4 is formed on one of the connecting portions 41 in a connecting hole formed in the upper end surface of the output shaft 3 and on the periphery of the two. After the coupling of the serrations, the rotation around the axis is constrained and connected, and the other connecting part 40 is fitted into the hollow part reduced in diameter in the vicinity of the upper end of the input shaft 2. This is done by adjusting the characteristics, driving a stop pin 5 in the radial direction from the outside of the input shaft 2, and constraining and fixing the rotation around the axis and the movement in the axial length direction.

FIG. 5 is an explanatory diagram of a procedure for performing centering adjustment and characteristic adjustment. As shown in the figure, the centering adjustment is performed by temporarily assembling the input shaft 2, the output shaft 3, the torsion bar 4 and the valve body 10 in a state where the connection between the connecting portion 40 of the torsion bar 4 and the input shaft 2 by the retaining pin 5 is omitted. , It is supported inside the test jig 6 corresponding to the housing H, the oil drain hole 64 corresponding to the tank port 24 is connected to the oil drain destination, and the oil supply groove is passed through the pressure guiding hole 60 corresponding to the pump port 20. While introducing the test hydraulic pressure P _0, as indicated by the arrows in the figure, a rotational force is applied to the shaft end of the input shaft 2 and detected by the pressure detection holes 61 and 62 corresponding to the cylinder ports 21 and 22. This is performed by comparing the internal pressures P ₁ and P ₂ of the oil feeding groove.

The connecting portion 40 of the torsion bar 4 has an extended portion protruding from the shaft end of the input shaft 2, and the aforementioned application of the rotational force to the input shaft 2 grips the extended portion, and the output shaft 3 and This is performed with the rotation of the valve body 10 constrained. As a result, the valve spool 11 rotates inside the valve body 10, and the throttle area of the throttle portion 8 between the oil grooves 12 and 14 aligned on the fitting circumference of both of them changes, so that these throttle portions 8 have the same throttle area. As described above, the internal pressures P ₁ and P ₂ of the oil supply grooves on both sides of the oil supply groove are equal. Accordingly, the centering adjustment is completed by rotating the input shaft 2 while monitoring the difference between the pressures P ₁ and P ₂ detected in the pressure detection holes 61 and 62 and obtaining the rotational position where the differential pressure between the two is zero. To do.

Next, the characteristic adjustment was performed by applying a force in the axial direction to the shaft end of the input shaft 2 while continuing the introduction of the test hydraulic pressure P ₀ as indicated by white arrows in the figure. This is carried out by a procedure for moving the valve spool 11 in the axial direction relative to the inside of the valve body 10. When such relative movement occurs, the average communication width in the throttle portion 8 between the oil groove 14 on the valve body 10 side increases or decreases on both sides of the oil groove 12 on the valve spool 11 side, as described above, The average widths of the chamfers 13 and 13 interposed in the throttle portion 8 increase or decrease, and the internal pressures P ₁ and P _{2 of the} oil feeding grooves detected by the pressure detection holes 61 and 62 change. Therefore, by obtaining the axial length direction position at which the predetermined internal pressures P ₁ and P ₂ are detected, the communication width with the oil grooves 14 and 14 on both sides of the oil groove 12 and the width of the chamfers 13 and 13 are appropriate. In the assist force characteristics shown in FIG. 6, the gradually increasing region where the steering assist force gradually increases with the increase of the steering torque is included, including the dead zone region where the steering assist force is maintained substantially constant. Thus, it is possible to realize a desired assisting force characteristic by adjusting.

  FIG. 6 shows the characteristic management width realized in the hydraulic power steering apparatus of the present invention and the characteristic management width in the conventional hydraulic power steering apparatus. By implementing the present invention, the characteristic management width is narrowed. You can see that

  After completing the centering adjustment and the characteristic adjustment as described above, as shown by the broken line in the figure, the adjusted rotational position and axial length direction position are maintained, and the input shaft 2 is fitted in the vicinity of the shaft end thereof. A pin hole 50 penetrating with the connecting portion 40 of the torsion bar 4 is formed, and a stop pin 5 is driven into the pin hole 50 to connect the connecting portion 40 and the input shaft 2, whereby the input shaft 2 and the output shaft are connected. 3 is completed. By incorporating the connection body of the input shaft 2 and the output shaft 3 thus obtained in the housing H, the hydraulic power steering apparatus according to the present invention is configured as shown in FIG. At this time, the extended portion of the connecting portion 40 protruding from the shaft end of the input shaft 2 is cut so as not to hinder the connection of the input shaft 2 to an intermediate shaft (not shown) connected to the steering wheel.

  In the hydraulic power steering apparatus according to the present invention, the plurality of oil grooves 14, 14 ... arranged on the inner periphery of the valve body 10 are rectangular grooves, and the plurality of oil grooves 12, 12 ... arranged on the outer periphery of the valve spool 11 are trapezoidal grooves. Therefore, these can be formed with high accuracy by simple processing using a conventional processing machine that is not particularly required, and the chamfers 13 and 13 are formed at the corner portions 9 on both sides of the oil groove 12. Since the valve body 10 and the valve spool 11 are axially lengthened according to the change mode of the throttle area of each throttle portion 8 governed by these chamfers 13 and 13 and the change characteristic of the steering assist force generated according to this change. Relative movement in the direction allows adjustment at the assembly stage, and adjustment to reduce the variation in characteristics due to the influence of dimensional errors of the chamfers 13 and 13 is possible. Reduction, and also can maintain the quality variation of less stable with respect to the target characteristic, it can be supplied to the hydraulic power steering system with little performance hidden between vehicles.

  In the above embodiment, the case where the valve spool 11 is formed integrally with the input shaft 2 and the cylindrical valve body 10 that fits externally is coupled to the output shaft 3 has been described. Needless to say, a configuration in which the valve spool 11 is formed integrally with the output shaft 3 and the valve body 10 is coupled to the input shaft 2 is also possible.

  Moreover, in the above embodiment, although the application example to the hydraulic power steering apparatus provided with the rack and pinion type steering mechanism has been described, the present invention is a hydraulic system including other types of steering mechanisms such as a ball screw type. The present invention can be applied to the power steering apparatus in exactly the same manner.

It is a longitudinal cross-sectional view which shows the structure of the principal part of the hydraulic power steering apparatus which concerns on this invention. It is a perspective view which shows the formation aspect of the oil groove in the outer peripheral surface of a valve spool. It is explanatory drawing which shows an example of the processing method of the oil groove of a valve spool outer periphery. It is explanatory drawing which shows the relative positional relationship of the oil groove lined up on the fitting periphery of a valve body and a valve spool. It is explanatory drawing of the implementation procedure of centering adjustment and characteristic adjustment. It is explanatory drawing of the auxiliary force characteristic in a hydraulic power steering apparatus.

Explanation of symbols

1 Hydraulic control valve 8 Throttle part 9 Corner part
10 Valve body
11 Valve spool
12 Oil groove (on valve spool side)
13 Chanfa
14 Oil groove (on the valve body side)

Claims (1)

The valve spools are fitted inside the cylindrical valve body so that they can be displaced relative to each other on the same axis, and a plurality of oil grooves arranged in parallel on both fitting circumferences are arranged in a staggered manner in the circumferential direction. A throttle part that changes the throttle area according to the relative angular displacement is formed between the adjacent oil grooves, and chamfers for adjusting the throttle area are formed at the corners on both sides of the oil groove of the valve spool facing each throttle part. In a hydraulic power steering apparatus provided with a hydraulic control valve,
The oil groove of the valve body is a rectangular groove extending with a substantially constant width in the axial direction of the valve body, and the oil groove of the valve spool is in the axial direction of the valve spool. The hydraulic power steering device is characterized by a trapezoidal groove extending from one side to the other side with a reduced width.

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