JP4561297B2 - Hydraulic power steering device - Google Patents

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 the driver's labor burden required to operate 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 produced between the valve body and the valve spool as the torsion bar is twisted. It has a configuration.

  A plurality of oil grooves extending in the axial length direction are juxtaposed in the circumferential direction on the fitting circumference (the inner circumference of the former and the outer circumference of the latter) between the valve body and the valve spool. Each of the oil grooves is arranged in a staggered manner 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 positioned between an oil supply groove and an oil discharge groove respectively connected to a hydraulic power source and an oil discharge destination, and oil discharge grooves on both sides of the oil supply groove. A pair of oil feeding grooves are provided in the cylinder chamber.

  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 (assistance force characteristic) depends on the relative angular displacement between the valve spool and the valve body. Therefore, in the related art, the corner portion of the oil groove on the valve spool side facing each throttle portion has a predetermined inclination angle with respect to the circumferential surface. The chamfered portion (chamfer) for adjusting the aperture area is formed with a predetermined circumferential width, and a desired assisting force characteristic is obtained by the action of these chamfers.

  The chamfer generates a region in which each throttle area gradually decreases in accordance with the relative angular displacement between the valve spool and the valve body before each throttle part is closed. In the auxiliary force characteristics shown in FIG. Is provided so as to form a region where the steering assist force gradually increases in accordance with the increase, and a dead zone region where the steering assist force is maintained substantially constant at a smaller torque side than the start point and end point of the gradually increasing region. Are set according to the width of the chamfer, and the increase rate in the gradually increasing region is set according to the inclination of the chamfer, thereby realizing a desired assisting force characteristic.

  However, the width and inclination of the chamfer as described above are 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 been made to solve this problem.

As one proposal, the chamfers on both sides of the oil groove are formed with an inclination angle on one side with respect to the longitudinal direction of each oil groove, that is, the axial direction of the valve spool, and this inclination angle is newly designed. As a parameter, there is a hydraulic control valve for power steering configured to expand the selection range of auxiliary force characteristics (see, for example, Patent Document 1), and as another proposal, oil grooves on the valve spool side and the valve body side are provided, The groove has a trapezoidal shape that widens toward the opposite side in the axial direction, 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 power steering configured to realize a desired auxiliary force characteristic by this adjustment (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 is impossible to make adjustments in order to reduce 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. The force characteristics can be adjusted, and the desired characteristics can be obtained by eliminating the influence of the dimensional error of the chamfer. However, as described above, the trapezoidal oil groove is formed in the cylindrical valve body. There is a practical problem that it is difficult to form with high accuracy on the peripheral surface, which leads to 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 characteristic variation 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 on the fitting circumference of the valve spool and the 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 valve body and the valve spool can be moved relative to each other in the axial direction and positioned at an appropriate movement position. Yes assembled, the respective oil grooves, said a valve body and a rectangular groove that extends in the axial direction of the valve spool, said chamfer is directed to the other side from the one side of the axial direction Characterized in that is formed by increasing the respective circumferential width Te.

In the present invention, the oil grooves on both the inner peripheral surface of the valve body and the outer peripheral surface of the valve spool are formed into rectangular grooves that have a substantially constant width in the axial length direction and are easy to form. the corner portions on both sides of the oil groove to form a chamfer to increase the circumferential width toward the one side to the other side of the axial direction, by relatively moving the valve spool and the valve body in the axial direction in the assembly steps, as appropriate In this case, the aperture area of each aperture is adjusted by using the portions having different widths of the chamfer to realize a desired assisting force characteristic.

In the hydraulic power steering device according to the present invention, since the oil groove arranged on the fitting circumference of the valve body and the valve spool in the hydraulic control valve is a rectangular groove, it can be formed with high accuracy by simple processing. Since the circumferential width of the chamfers on both sides of the oil groove on the valve spool side is formed so as to increase from one side to the other side in the axial length direction, the throttle area of the throttle part controlled by these chamfers is a valve body and a valve spool are relatively moved in the axial direction, it can be freely changed at appropriate assembly stage by Rukoto be positioned at a position, adjustment for reducing variation in characteristics due to the influence of dimensional errors of the chamfer Thus, the present invention has excellent effects.

  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 15 that are arranged in a staggered 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 serving 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 15 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 evenly introduced into the oil supply grooves adjacent to each other on both sides, and further adjacent to these other sides. The oil is introduced into the oil draining groove and is discharged to the oil tank T through the hollow portion of the input shaft 2, the oil draining 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 slide in the axial direction, and the steering is performed. This slide is a reaction force from the road surface that acts on a steering wheel (not shown). In response to the steering torque applied to the steering wheel with torsion of the torsion bar 4 between the input shaft 2 and the output shaft 3, that is, between the valve spool 11 and the valve body 10. A relative angular displacement occurs, and the throttle area of the throttle part 15 arranged on the fitting periphery of the valve body 10 and the valve spool 11 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 15 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 15 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 hydraulic power steering apparatus according to the present invention is characterized by the formation of these oil grooves 12.12... More specifically, the chamfers 13 and 13 for adjusting the throttle area provided at the corners on both sides of each oil groove 12 are as follows. It is in the formation aspect.

  As shown in FIG. 2, the oil grooves 12, 12... Formed in the outer peripheral surface of the valve spool 11 are rectangular grooves extending with a substantially constant width in the axial direction of the valve spool 11 and the input shaft 2. is there. A pair of chamfers 13 and 13 are formed at the corners on both sides of the oil grooves 12 and 12... So that the corners are notched obliquely. In the longitudinal direction of the valve spool 11, that is, from one side to the other side in the axial length direction of the valve spool 11 and the input shaft 2, the width on the outer peripheral surface of the valve spool 11 is increased. In the figure, the lower end side of the input shaft 2 is narrow and is formed to increase in width toward the upper end side. On the contrary, the upper end side is made narrower and the width toward the lower end side. It may be formed so as to increase.

  FIG. 3 is an explanatory diagram showing an example of a processing method for the chamfers 13 and 13. The chamfers 13 and 13 on both sides of the oil groove 12 use a disk-shaped rotating grindstone R that rotates about an axis parallel to the longitudinal direction of the oil groove 12 and is positioned at the center of the oil groove 12 as shown in the figure. The width of the chamfers 13 and 13 can be increased in the longitudinal direction by applying a feed in the longitudinal direction of the oil groove 12 while pressing the outer peripheral grinding surface to the corners on both sides of the oil groove 12. This can be easily realized by a procedure of adding a feed that continuously increases in the depth direction of the oil groove 12 along with the feed in the direction. In the figure, the feed in the longitudinal direction is indicated by a long white arrow, and the feed in the depth direction is indicated by a short white arrow. The chamfers 13 and 13 perform these feeds simultaneously. Formed.

  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 are interposed in the communication portion. To do. Here, the widths of the chamfers 13 and 13 are continuously increased from one side in the axial length direction to the other side, and the valve body 10 and the valve spool 11 are arranged in the axial length direction (indicated by white arrows in the figure). The average width of the chamfers 13 and 13 interposed in the communicating portion between the oil groove 12 and the oil groove 14 can be increased or decreased. In the lower half of FIG. 4, the state where the average width of the chamfers 13 and 13 is increased is shown on the left side, and the state where the average width is reduced is shown on the right side.

  A torsion bar 4 for connecting the input shaft 2 and the output shaft 3 is a round bar having an outer diameter and a length determined to obtain a desired torsion characteristic, and is large for connecting the input shaft 2 and the output shaft 3. The connecting portions 40 and 41 having a diameter 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. The rotation of the shaft is restricted by the engagement of the serrations, and the connection pin 42 placed on the fitting portion restricts the movement in the axial length direction to connect, and then the diameter is reduced in the vicinity of the upper end of the input shaft 2. The other connecting portion 40 is fitted into the hollow portion, centering adjustment and characteristic adjustment are performed according to the following procedure, a stop pin 5 is driven in the radial direction from the outside of the input shaft 2, and rotation around the shaft and shaft This is done by constraining and fixing the movement in the long 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 part 15 between the oil grooves 12, 14 arranged on the fitting circumference of both of them changes, and these throttle parts 15 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 performed by a procedure of relatively moving the valve spool 11 in the axial length direction inside the valve body 10. When such relative movement occurs, as described above, on both sides of the oil groove 12 on the valve spool 11 side, the average of the chamfers 13 and 13 interposed in the throttle portion 15 between the oil groove 14 on the valve body 10 side. Since the width is increased or decreased, the internal pressures P ₁ and P _{2 of the} oil feed groove 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, a region where the chamfers 13 and 13 have an appropriate width can be used. In the auxiliary force characteristics shown in FIG. It is possible to achieve a desired assist force characteristic by appropriately adjusting the gradually increasing region in which the steering assist force gradually increases as the steering torque increases, including the dead zone where the steering assist force is maintained substantially constant. Become.

  After 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 portion thereof. A pin hole 50 that penetrates together 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 3 is completed. By incorporating the coupling body of the input shaft 2 and the output shaft 3 obtained in this way into 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 the steering wheel.

  In the hydraulic power steering apparatus according to the present invention, the valve body 10 includes a plurality of oil grooves 14, 14... Arranged on the inner periphery of the valve body 10 and a plurality of oil grooves 12, 12. The rectangular groove extending in the axial length direction of the valve spool 11 can be formed with high accuracy by simple processing using a general-purpose machine tool, and the oil groove 12 of the valve spool 11 facing the throttle portion 15 can be formed. Since the chamfers 13 and 13 whose width increases from one side to the other side in the axial direction are formed at the corners on both sides, the change mode of the aperture area of each aperture 15 controlled by these chamfers 13 and 13 The change characteristic of the steering assist force generated in response to this change can be adjusted at the assembly stage by relatively moving the valve body 10 and the valve spool 11 in the axial direction, and the dimensions of the chamfers 13 and 13 can be adjusted. Due to error Therefore, adjustments for reducing variations in characteristics can be made, so that labor and time required for processing and assembly can be reduced, and the occurrence rate of defective assembly can be reduced.

  In the above embodiment, the valve spool 11 is formed integrally with the input shaft 2 and the tubular valve body 10 that fits externally is coupled to the output shaft 3. 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 a chamfer. 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
10 Valve body
11 Valve spool
12 Oil groove (on valve spool side)
13 Chanfa
14 Oil groove (on the valve body side)
15 Aperture

Claims (1)

The valve spool is fitted inside the cylindrical valve body so as to be capable of relative angular displacement on the same axis, and a plurality of oil grooves arranged side by side 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 valve body and the valve spool are relatively moved in the axial length direction and assembled so as to be positioned at an appropriate moving position. Each of the oil grooves extends in the axial length direction of the valve body and the valve spool. The hydraulic power steering device according to claim 1, wherein the chamfer is formed by increasing a circumferential width from one side to the other side in the axial direction.

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