JPH0769227A - Power steering device - Google Patents

Abstract

PURPOSE:To stably provide a desirable auxiliary power characteristic in a device wherein operation of an oil pressure control valve for controlling feed oil pressure to a power cylinder is restricted in accordance with car speed, by conducting the restriction by utilizing relative angular displacement between a valve spool and a valve body. CONSTITUTION:An extension part 43 of a valve spool integrated with an input shaft is fitted inside of an extension part 42 of a valve body continuously equipped on an output shaft joined to a steering mechanism. In this fitting part, an O-ring 52 retained by a seal presser 51 projectingly provided on the extension part 42 is made to abut on bottom surfaces of recessed grooves 55, 55 in the outer periphery of the extension part 42, and reaction force chambers A1, A2 are defined on both the sides of the abutting position. Oil pressure corresponding to a car speed and introduced to a hydraulic reaction force part 5 via a lead hole 26 is introduced onto a fitting periphery of the extension part 43 of the valve spool via a lead hole 53, and introduced to a reaction force chamber A1 or A2 via a communication hole 56 or 57 in accordance with relative angular displacement between both the extension parts 42, 43, thereby applying angular moment in the direction restricting the relative angular displacement to the extension part 43.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic power steering apparatus using a hydraulic actuator such as a power cylinder arranged in a steering mechanism as a source of a steering assist force. The present invention relates to a hydraulic power steering apparatus that includes a hydraulic reaction force section that limits the operation of a hydraulic control valve that controls the hydraulic pressure supplied to an actuator with a force that corresponds to the vehicle speed.

[0002]

2. Description of the Related Art A hydraulic power steering system is provided between a hydraulic actuator such as a power cylinder arranged in a steering mechanism of an automobile and an oil tank for accommodating a hydraulic pump and hydraulic oil as a hydraulic source. A hydraulic control valve for supplying / discharging hydraulic pressure according to the operation of the steering wheel is arranged, and the hydraulic pressure (steering assist force) generated by the hydraulic actuator is steered by the hydraulic pressure fed from the hydraulic control valve. In addition to the mechanism,
It is intended to reduce the labor load required for steering.

As the hydraulic control valve, a rotary type is generally used, which is formed in the middle of a steering wheel shaft (steering column) connecting a steering wheel and a steering mechanism. In this, the input shaft on the side of the steering wheel and the output shaft on the side of the steering mechanism are coaxially connected via a connecting member such as a torsion bar, and is integrally formed with one of the two shafts at this connecting portion. The valve spool is internally fitted into a tubular valve body that is continuous with the other, and a plurality of throttle portions are arranged in parallel on the fitting circumference. Thus, when a steering torque is applied to the steered wheels, a relative angular displacement occurs between the valve spool and the valve body due to the torsion of the torsion bar, and the throttle area of the throttle portion changes, and this area The hydraulic pressure supplied to the hydraulic actuator is controlled according to the change.

However, in the power steering apparatus having only this type of hydraulic control valve, there is a corresponding relationship (assist force characteristic) between the steering torque applied to the steering wheel and the steering assist force generated by the hydraulic actuator. , Is uniquely determined by the torsional characteristics of the torsion bar that connects the input shaft and the output shaft, while steering the vehicle is performed against the road surface reaction force that acts on the steering wheels. The magnitude of the variable corresponds to the slow speed of the vehicle and the magnitude of the steering angle. Therefore, when the torsional characteristics of the torsion bar are selected with reference to the large road surface reaction force at the time of stopping and low speed traveling, steering is performed with a slight force applied to the steering wheel at high speed traveling, and straight running stability is impaired. On the other hand, when the torsion bar is selected on the basis of a small road surface reaction force during high-speed traveling, there is a drawback that a sufficient steering assist force cannot be obtained when steering while stopping, which requires a large amount of force, so-called stationary steering. .

Therefore, conventionally, a hydraulic reaction force portion that generates a hydraulic reaction force that becomes large or small depending on the vehicle speed is provided in parallel with the hydraulic control valve, and the control operation of the hydraulic control valve, specifically, the torsion is performed. A power steering apparatus has been put into practical use in which the relative angular displacement between the valve spool and the valve body due to the twist of the bar is limited by the hydraulic reaction force.

FIG. 7 is a cross-sectional view showing a general structure of a conventional hydraulic reaction force portion disclosed in Japanese Patent Laid-Open No. 61-200063. As shown in the figure, the hydraulic reaction force portion 7 has an input shaft 2 integrally forming the valve spool inside a cylindrical extension portion of the output shaft 3 that connects the valve body.
The extension portion of the output shaft 3 is loosely fitted coaxially, and the extension portion of the output shaft 3 has a plurality of cylinder holes 70 radially extending therethrough.
70 are formed, and plungers 71, 71 ... Are inserted into these so as to be slidable in the radial direction, and the cylinder holes 70, 70 are provided between the output shaft 3 and the housing 20 outside thereof.
The pressure guiding chamber 72 that collectively communicates with ... Is provided around.

In the pressure guiding chamber 72, as indicated by an arrow in the figure,
The hydraulic pressure corresponding to the vehicle speed is introduced. This hydraulic pressure passes through the cylinder holes 70, 70 ... And the plungers 71, 71.
Acting on the outer end surfaces of the output shaft 3 and pressing these inner ends against the outer periphery of the input shaft 2.
Relative to the input shaft 2, that is, the relative angular displacement between the valve spool and the valve body in the hydraulic control valve is limited.

Then, the steering torque applied to the steered wheels reaches a predetermined magnitude, and after the relative angular displacement between the valve spool and the valve body begins to occur against the pressing of the plungers 71, 71 ... A force characteristic is obtained, and the magnitude of the pressing force corresponds to the level of the introduced hydraulic pressure to the pressure guiding chamber 72, that is, the level of the vehicle speed. Therefore, when the vehicle is stopped or traveling at low speed, the vehicle reaches the rising point with a relatively small steering torque, and thereafter, a large steering assist force is generated to reduce the force required for steering wheel operation. As long as the steering torque is not applied, steering assist is not performed, appropriate rigidity is imparted to the steered wheels, and straight running stability is ensured, so that the above-mentioned difficulties can be solved.

[0009]

However, in the power steering apparatus having the hydraulic reaction force portion 7 as described above, after the relative angular displacement starts to occur between the valve spool and the valve body of the hydraulic control valve. Also, the pressing state of the plungers 71, 71 ... Continues, and the friction between the plungers 71, 71 ... And the input shaft 2 acts as resistance against the relative angular displacement, so that the smooth operation of the hydraulic control valve is achieved. In addition to being hindered
Hysteresis occurs between the increasing direction and the decreasing direction of the relative angular displacement, and there is a problem that a desired assisting force characteristic cannot be stably obtained.

The present invention has been made in view of the above circumstances, and realizes a hydraulic reaction force portion that limits the operation of the hydraulic control valve regardless of friction, and stabilizes a desired assist force characteristic according to the vehicle speed. It is an object of the present invention to provide a power steering device that can be obtained.

[0011]

A power steering apparatus according to the present invention coaxially connects an input shaft connected to a steering wheel and an output shaft connected to a steering mechanism, and is integrally formed on one of both shafts. The valve spool is fitted inside a cylindrical valve body connected to the other, and the relative angular displacement that occurs between the two when the steering wheel is operated is used to supply hydraulic pressure to the hydraulic actuator for steering assistance. In a power steering apparatus including a hydraulic control valve to be controlled and a hydraulic reaction force portion that is provided in parallel with the hydraulic control valve and limits the relative angular displacement by the action of an introduced hydraulic pressure corresponding to a vehicle speed, The reaction force portion includes a pressure chamber formed on a fitting circumference of the valve body and the valve spool,
A pair of reaction chambers projectingly provided on one of the valve body and the valve spool and abutting against the other on an appropriate radial line of the pressure chamber, and dividing the pressure chamber into two in the circumferential direction to be liquid-tight to each other. A seal means for forming a force chamber, and a pressure guide path that selectively guides the introduced hydraulic pressure to one of the reaction force chambers in accordance with the direction of the relative angular displacement, and in addition, The pressure guiding path is configured to guide the introduced hydraulic pressure to both of the pair of reaction force chambers in a neutral state in which the relative angular displacement has not occurred.

[0012]

According to the present invention, when a relative angular displacement occurs between the valve spool and the valve body of the hydraulic control valve,
The hydraulic pressure according to the vehicle speed is introduced into one of a pair of reaction force chambers formed by dividing the pressure chambers formed on the fitting circumference in the circumferential direction by the sealing means through the pressure guiding path, and the other reaction force chamber is reacted. A rotational moment is generated due to the pressure difference between the force chamber and the pressure sensor, which directly limits the relative angular displacement between the valve spool and the valve body, that is, the control operation of the hydraulic control valve.

The pressure chambers are connected to each other via a connecting member such as a torsion bar, and the fitting state may change due to the connection, not on the fitting circumference of the input shaft and the output shaft. It is formed on the fitting circumference of a valve spool integrally formed with one side and a valve body separately provided from the other side, and the valve spool is prevented from interfering with a relative angular displacement between the valve spool and the valve body. Liquid tightness can be maintained on both sides of the reaction chamber. In addition, in the neutral state where relative angular displacement does not occur between the valve spool and the valve body, the oil pressure is introduced into both reaction force chambers via the pressure guiding path, so that the valve spool in the neutral state and Ensure the rigidity of the valve body.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a block diagram showing the overall configuration of a power steering apparatus according to the present invention (hereinafter referred to as the present invention apparatus) mounted on a vehicle equipped with a rack and pinion type steering mechanism.

The rack and pinion type steering mechanism includes a steering wheel 1
Pinion is attached to the lower end of the steering wheel axle 10 that is coaxially connected to the lower side of
11 is fixed, the pinion 11 is meshed with a middle portion of a rack shaft 12 extending in the left-right direction at the front part of the vehicle body, and rotation of the steering wheel 1 for steering is slid in the extending direction of the rack shaft 12. A pair of left and right steering wheels (generally front wheels) that are converted into motion and are connected to both ends of the rack shaft 12 via separate knuckle arms.
It is configured to change the direction of 13, 13 and steer.

The device of the present invention assists the steering operation in the rack and pinion type steering mechanism as described above by hydraulic pressure, and connects the steering wheel 1 and the rack shaft 12 to the steering wheel shaft.
The hydraulic control valve 4 configured in the middle of 10 is interposed in the middle of a circulating oil passage that connects the hydraulic pump P serving as a hydraulic pressure source and the oil tank T that stores hydraulic oil, and the hydraulic control according to the operation of the steering wheel 1 is performed. By the operation of the valve 4 which will be described later, the hydraulic pressure generated by the hydraulic pump P is fed to the power cylinder S for steering assistance which is arranged in the middle of the rack shaft 12, and the hydraulic pressure generated by the power cylinder S by this fed hydraulic pressure ( The steering assist force) is directly applied to the rack shaft 12.

On one side of the hydraulic control valve 4, a hydraulic reaction force portion 5 for limiting the operation of the hydraulic control valve 4 with a force corresponding to the vehicle speed is provided in parallel. In the middle of the supply oil passage 14 from the hydraulic pump P to the hydraulic control valve 4, a branch oil passage 15 that branches and communicates with the oil tank T is provided.
The branch oil passage 15 is provided with a pressure regulating valve 6 having a pair of variable throttles S ₁ and S ₂ that change the area in different directions based on the detection result of the vehicle speed. The reaction force section 5 includes two variable throttles S ₁ and S ₂ in the pressure regulating valve 6.
A hydraulic pressure between the two, that is, a hydraulic pressure in which the hydraulic pressure to be fed to the hydraulic control valve 4 is reduced by the reduced pressure at the variable throttle S ₁ is introduced.

As will be described later, the variable throttle S _{1 on one} side (upstream side) of the pressure regulating valve 6 increases the throttle area as the vehicle speed increases, and the other variable throttle S ₂ changes the throttle area as the vehicle speed increases. The introduced hydraulic pressure to the hydraulic reaction force portion 5 obtained between the variable throttles S ₁ and S ₂ is the hydraulic pressure obtained by reducing the hydraulic pressure supplied to the hydraulic control valve 4 according to the slow speed of the vehicle, That is, the hydraulic pressure corresponds to high and low vehicle speeds.

FIG. 2 is a vertical cross-sectional view showing a structural example of the hydraulic control valve 4, the hydraulic reaction force portion 5 and the pressure regulating valve 6. In the figure, 2 is a hollow input shaft, and 3 is a pinion shaft (output shaft). These are rotatably supported around an axis in a common housing 20 having a cylindrical shape, and the tip of a small-diameter torsion bar 21 inserted in the hollow portion of the input shaft 2 is attached to the upper end of the pinion shaft 3. They are coaxially connected by being press-fitted into the shaft center position of the portion and spline-coupled. The pinion 11 is formed in the lower half portion of the pinion shaft 3, and the pinion 11 is
It is meshed with the rack shaft 12 supported on the lower part of the housing 20. The input shaft 2 is made to project above the housing 20 by an appropriate length, and the projecting end is connected to the steering wheel shaft 10 that is continuously provided below the steering wheel 1.

When the steering wheel 1 is rotated, the rotation of the steering wheel shaft 10 is accompanied by the rotation of the input shaft 2 and the torsion bar.
It is transmitted to the pinion shaft 3 via 21 and is converted into sliding in the axial direction of the rack shaft 12 that meshes with the pinion 11 in the lower half of the pinion shaft 11, and steering is performed. A relative angular displacement corresponding to the steering torque applied to the steered wheels 1 is generated between the shaft 3 and the torsion bar 21 while being twisted.

The hydraulic control valve 4 is a well-known type which controls the hydraulic pressure fed to the power cylinder S by utilizing the relative angular displacement thus generated, and is coaxially rotatable inside the housing 20. With the cylindrical valve body 40 fitted,
It is provided with a valve spool 41 fitted inside thereof. The valve body 40 is connected to the upper end of the pinion shaft 3 via a dowel pin 30 that is formed on the outer periphery of the pinion shaft 3.
It is adapted to rotate together with the pinion shaft 3. The valve spool 41 is integrally formed on the outer circumference of the middle of the input shaft 2 fitted inside the valve body 40. Thereby, between the valve body 40 of the hydraulic control valve 4 and the valve spool 41, the relative angular displacement between the input shaft 2 and the pinion shaft 3 caused by the operation of the steering wheel 1, that is, the steering wheel 1 is added. Relative angular displacement occurs depending on the direction and magnitude of the steering torque.

The feed hydraulic pressure from the hydraulic pump P is introduced into the hydraulic control valve 4 through a pump port 22 opening to the outside of the housing 20, and this hydraulic pressure is transmitted to the valve body 40 and the valve spool 41. Between the oil chambers of the power cylinder S and the oil chambers 16a and 16b (see FIG. 1), which are distributed according to the relative angular displacement occurring as described above, for example, the oil channel 16a. Is sent to one of the oil chambers. With this hydraulic pressure supply, the power cylinder S generates an oil pressure according to the pressure difference between the power cylinder S and the other oil chamber,
As described above, this hydraulic pressure is applied to the rack shaft 12 as a steering assist force.

At the upper part of the valve body 40 inside the housing 20, a reflux chamber 23 communicating with the hollow portion inside the input shaft 2 is formed, and the reflux chamber 23 passes through a tank port 24 opening to the outside of the housing 20. The return oil, which is connected to the oil tank T, is pushed out from the other oil chamber in accordance with the above-described operation of the power cylinder S, and is returned to the hydraulic control valve 4 via the other oil feed passage 16b, is returned to the valve spool 41. Is introduced into a hollow portion inside the input shaft 2 through a through hole that radially penetrates the oil tank T through the reflux chamber 23 and the tank port 24.
It is designed to recirculate to.

The device of the present invention limits the control operation of the hydraulic control valve 4 by a force corresponding to the vehicle speed.
It has a feature in the configuration. 3 is an enlarged cross-sectional view around the hydraulic reaction force portion 5, and FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG.

The hydraulic reaction force portion 5 utilizes an extension portion 42 of the valve body 40 on the side connected to the pinion shaft 3 and an extension portion 43 on the same side of the valve spool 41 (input shaft 2). It is configured. Extension of valve body 40 as shown in FIG.
Reference numeral 42 denotes a cylindrical shape which is thinned from the inner diameter side, the lower end of which is loosely fitted to the upper end of the pinion shaft 3 and a part of which is engaged with the dowel pin 30. On the other hand, the extension portion 43 of the valve spool 41 has a larger diameter than the other portions, and is tightly fitted inside the extension portion 42 on the valve body 40 side.

In the extension portion 42 of the valve body 40, as shown in FIG. 4, a pair of through holes 5 are formed at positions facing each other in the radial direction.
0 and 50 are formed, and a seal retainer 5 is attached to each of these.
1, 51 are fitted inside. As shown in FIG. 4, the seal retainer 51
Is provided with a disk-shaped collar portion in a manner of projecting outward, on the base end side of the cylindrical main body portion fitted in the through hole 50. The tip portion of the seal retainer 51 is formed so that only one cross section shown in FIG. 3 has a semicircular shape, and at this tip portion, a seal groove that is orthogonal to the one cross section and extends along the side surface to the collar portion. Is formed in the seal groove.
A ring 52 (sealing means) is fitted and held.

Further, in the extension portion 42 of the valve body 40, there are formed pressure guiding holes 53, 53 having small diameters at two positions substantially orthogonal to the positions where the through holes 50, 50 are formed. Pressure holes 53, 53
Also, the through holes 50, 50 are provided around the outside of the extension portion 42, and as shown in FIG. 3, by the pressure guiding chamber 54 which is liquid-tightly sealed on the upper and lower sides at the fitting portion with the housing 20. They are in communication with each other.

On the other hand, the extension portion 43 on the valve spool 41 side is
A pair of recessed grooves 5 are provided on the outer side of this in positions facing each other in the radial direction.
Equipped with 5, 55. These have a semi-circular bottom surface corresponding to the shape of the tip of the seal retainer 51, and extend in the direction orthogonal to the axis of the valve spool 41, and between the valve body 40 and the valve spool 41. In a neutral state in which no relative angular displacement is generated in the pair, a pair of arcuate cross-sectional shapes as shown in FIG. 4 are formed inside the fitting positions of the seal retainers 51, 51 on the fitting circumferences of the extension parts 42, 43 of both. Forming a pressure chamber. Seal retainer 51, O-ring 52 held by 51,
52 is abutted on the bottom surface and the side surface of the corresponding recessed grooves 55, 55 on an appropriate radius line.
Each of the pressure chambers formed by is divided into two in the circumferential direction, and as shown in FIG. 4, a pair of reaction force chambers A ₁ and A ₂ that are liquid-tight in a clockwise direction are formed. .

On the other hand, in the neutral state, the inside of the pressure guiding holes 53 formed in the extension portion 42 of the valve body 40 is
As shown in FIG. 4, the extended portion 43 of the valve spool 41 has an opening at substantially the center of a portion where the concave grooves 55, 55 are not formed,
The reaction chamber A on one side of the concave groove 55 is formed by the pair of communication holes 56 and 57 formed in the extension portion 43 on both sides of the opening end.
₁ and the reaction force chamber A ₂ on the other side of the groove 55 are communicated with each other.

FIG. 5 is an enlarged view of the vicinity of the inner open ends of the pressure guiding holes 53, 53 in a neutral state where no relative angular displacement occurs between the valve body 40 and the valve spool 41. As shown in the figure, the communication holes 56, 57 are formed with a slight communication portion on both sides of the open ends of the pressure guiding holes 53, 53, and will be described later in a pressure guiding chamber 54 outside the valve body 40. In the neutral state, the hydraulic pressure thus introduced is evenly introduced into both the reaction force chambers A ₁ and A ₂ through the communication holes 56 and 57, while it is applied between the valve body 40 and the valve spool 41. Due to the slight relative angular displacement that occurs, one of the communication holes 56, 57 and the pressure guiding holes 53, 53
The communication with the pressure guiding chamber 54 is cut off, and the hydraulic pressure introduced into the pressure guiding chamber 54 passes through the communicating hole 56 or 57 for maintaining the communicating state, and then the reaction force chamber A ₁ or A.
It is designed so that only one of the _two can be assigned.

In order to distribute the introduced hydraulic pressure as described above, in the portion where the recessed grooves 55, 55 are not formed, a liquid-tight seal is formed at the fitting portion between the extension portion 42 of the valve body 40 and the extension portion 43 of the valve spool 41. It needs to be maintained,
As is apparent from FIG. 3, the valve body 40 is loosely fitted to the output shaft 3 whose diameter is affected by the press-fitting of the torsion bar 21, and is restrained from rotating only by the engagement with the dowel pin 30. Liquid tightness at the joint is
Strict control can be performed by appropriately setting the processing tolerance of the inner peripheral surface of and the outer peripheral surface of the extension 43. Therefore, the distribution of the hydraulic pressure to the reaction force chambers A ₁ and A ₂ is surely performed without the risk of mutual leakage, and the relative angular displacement between the valve body 40 and the valve spool 41 due to the influence of the fitting portion. There is no risk of being hindered.

As shown in FIG. 2, the pressure regulating valve 6 for generating the introduced hydraulic pressure into the hydraulic reaction force portion 5 configured as described above is circularly arranged on one side of the housing 20 in parallel with the pressure regulating valve 6. A hollow cylindrical throttle spool 61 is slidably inserted in a spool chamber 60 having a cross section in the axial direction. The rotation of a stepping motor (not shown) driven based on the detection result of the vehicle speed is transmitted to the throttle spool 61 via an engagement pin 62 that engages with the outer periphery of one side, and the spool chamber 60
Inside, the throttle spool 61 is adapted to change its sliding position according to the level of the vehicle speed. The driving means for the aperture spool 61 is not limited to the stepping motor, and any driving means that operates by energization control based on the vehicle speed detection result may be used, such as a solenoid.

The throttle spool 61 is provided with annular grooves 63, 64 at two locations on the outer periphery which are spaced apart by an appropriate length. As shown in the drawing, a portion closer to the end than one annular groove 63 and the other annular groove. 64 is communicated with a hollow portion inside the throttle spool 61. The spool chamber 60 has a pressure guide hole that is always open between the annular grooves 63 and 64.
The feed hydraulic pressure to the hydraulic control valve 4 is introduced via 25.
Further, the spool chamber 60 is communicated with the hydraulic reaction force portion 5 through a pressure guide hole 26 formed so as to be always opened in the one annular groove 63 regardless of the sliding position of the throttle spool 61. Further, it is communicated with the reflux chamber 23 inside the housing 20 through a reflux hole 27 formed so as to be always opened in the other annular groove 64.

Then, the spool chamber 60 is passed through the pressure guiding hole 25.
The hydraulic pressure introduced into the oil reaches the other annular groove 64 through the gaps on both sides of the one annular groove 63, the hollow portion of the throttle spool 61, and further returns to the oil tank T via the return hole 27 and the return chamber 23.
That is, the oil passage from the pressure guiding hole 25 to the reflux chamber 23 is
Corresponding to the branch oil passage 15 in FIG. 1, the gaps on both sides of the annular groove 63 function as variable throttles S ₁ and S ₂ that change the throttle area in different directions according to the sliding of the throttle spool 61. At this time, the hydraulic reaction force portion 5 is provided with the variable throttles S ₁ , S.
_The hydraulic pressure regulated between the _two is introduced through the pressure guiding hole 26 opening in the annular groove 63.

FIG. 2 shows the sliding position of the throttle spool 61 at the time of stopping and running at a low speed. The sliding of the throttle spool 61 by the operation of the driving means corresponds to the annular groove 64 side as the vehicle speed increases. It is designed to occur toward (the upper side of the figure). Thus, the upstream variable diaphragm S ₁ increases the diaphragm area as the vehicle speed increases, and the downstream variable diaphragm S ₂ conversely decreases the diaphragm area. Therefore, both variable diaphragms S ₁ , S _The hydraulic pressure introduced into the hydraulic reaction force section 5 obtained between the _two is a hydraulic pressure obtained by reducing the hydraulic pressure supplied to the hydraulic control valve 4 according to the slow speed of the vehicle, that is, a hydraulic pressure corresponding to the high or low of the vehicle speed.

The introduced hydraulic pressure to the hydraulic reaction force portion 5 obtained as described above is provided around the outside of the extension portion 42 of the valve body 40 through the pressure guiding hole 26 as shown by the arrow in FIG. It is introduced into the pressure guiding chamber 54. This introduced hydraulic pressure is introduced into the pressure guiding holes 53, 53 communicated with each other by the pressure guiding chamber 54, and as described above, the reaction force chambers A ₁ and A ₁ according to the relative angular displacement between the valve body 40 and the valve spool 41. Assigned to A ₂ . On the other hand, this introduced hydraulic pressure is applied to the through hole 50, which is communicated by the pressure guiding chamber 54,
The seal retainers 51, 51 fitted in the 50 are pressed inward, and the O-rings 52, 52 on the tip side of these are pressed against the recessed grooves 55, 55. By this action, the reaction force chamber A ₁ , The liquid tightness between A ₂ is maintained well.

As shown in FIG. 4, when the valve body 40 and the valve spool 41 are in the neutral state, the reaction force chambers A ₁ , A
The hydraulic pressure is equally distributed to the _two , and this hydraulic pressure acts to keep the internal pressures of the reaction force chambers A ₁ and A ₂ equal and maintain the neutral state. On the other hand, when a steering torque is applied to the steering wheel 1 and a relative angular displacement occurs between the valve body 40 and the valve spool 41, the communication holes 56, 56 or 57,
The communication between either one of the pressure guiding holes 53 and 53 is cut off, and the hydraulic pressure introduced into the hydraulic reaction force portion 5 which has reached the inside of the pressure guiding holes 53 and 53 is the reaction chamber A. It is introduced into either ₁ , A ₁ or A ₂ , A ₂ .

In FIG. 6, the extension portion 43 of the valve spool 41 is
The figure shows a state in which the valve body 40 is angularly displaced relative to the extension portion 42 in the clockwise direction. In this case, of the reaction force chambers A ₁ and A ₂ formed on both sides of the seal retainer 51, the volume of _one reaction force chamber A ₁ decreases, and at the same time, the communication that communicates with the other reaction force chamber A ₂ The communication between the hole 57 and the pressure guiding hole 53 is blocked. Therefore, the introduced hydraulic pressure to the hydraulic reaction force portion 5 is introduced only into the reaction force chamber A ₁ through the communication hole 56 that maintains the communication state with the pressure guiding hole 53, as indicated by the arrow in the figure. This hydraulic pressure acts in a direction to prevent the volume reduction of the reaction force chamber A ₁ as shown by the white arrow in the figure.

That is, in the hydraulic reaction force portion 5, when a relative angular displacement is about to occur between the valve body 40 of the hydraulic control valve 4 and the valve spool 41 in accordance with the steering torque applied to the steering wheel 1, one of The hydraulic pressure corresponding to the vehicle speed is introduced into the reaction force chamber (reaction force chamber A _{1 in} FIG. 6), and the rotational moment due to the differential pressure between the other reaction force chamber (reaction force chamber A ₂ in FIG. 6) is generated. It acts on the valve spool 41 and directly limits the relative angular displacement with respect to the valve body 40, that is, the control operation of the hydraulic control valve 4.

At this time, the O-ring 52 held by the seal retainer 51 is in a state of being pressed against the concave groove 55 formed in the extension portion 43 of the valve spool 41. It is on the radius line, and there is almost no change in the pressing position due to the relative angular displacement between the valve body 40 and the valve spool 41, and the control operation of the hydraulic control valve 4 due to the relative angular displacement is obstructed by friction. There is no risk of hysteresis occurring due to the difference in steering direction.

In this embodiment, the application example in the rack and pinion type steering mechanism has been described, but the scope of application of the present invention is not limited to this, and in other types of steering mechanisms such as a ball screw type steering mechanism. It goes without saying that is also applicable.

[0042]

As described above in detail, in the power steering system according to the present invention, the valve body connected to one of the input shaft and the output shaft and the valve spool integrally formed with the other are fitted together. A pair of reaction chambers, which are divided into two, are formed on the circumference by sealing means protruding from one of the two and abutting the other on an appropriate radial line, and a relative angle formed between the valve body and the valve spool. Since the hydraulic pressure corresponding to the vehicle speed is introduced into one of the two reaction force chambers according to the displacement, the control action of the hydraulic control valve can be limited by the direct action of the introduced hydraulic pressure, which is caused by the frictional intervention. The present invention has excellent effects such that the obstruction of the operation of the hydraulic control valve is eliminated and a desired assist force characteristic corresponding to the vehicle speed can be stably obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a device of the present invention.

FIG. 2 is a vertical sectional view showing a main part of the device of the present invention.

FIG. 3 is an enlarged sectional view of a hydraulic reaction force portion.

4 is a cross-sectional view taken along the line IV-IV in FIG.

FIG. 5 is an enlarged view of a pressure guiding path that guides an introduced hydraulic pressure to a hydraulic reaction force section to a reaction force chamber.

FIG. 6 is a diagram for explaining the operation of the hydraulic reaction force section.

FIG. 7 is a cross-sectional view of a conventional hydraulic reaction force portion.

[Explanation of symbols]

1 Steering wheel 2 Input shaft 3 Pinion shaft 4 Hydraulic control valve 5 Hydraulic reaction force part 6 Pressure regulating valve 11 Pinion 12 Rack shaft 20 Housing 21 Torsion bar 40 Valve body 41 Valve spool 50 Through hole 51 Seal retainer 52 O ring 53 Conducting hole 55 Groove 56 Communication hole 57 Communication hole 61 Throttle spool A ₁ Reaction chamber A ₂ Reaction chamber P Hydraulic pump S Power cylinder S ₁ Variable throttle S ₂ Variable throttle T Oil tank

Claims (2)

[Claims] 1. A tubular valve in which an input shaft connected to a steering wheel and an output shaft connected to a steering mechanism are coaxially connected, and a valve spool integrally formed on one of both shafts is connected to the other. A hydraulic control valve that is fitted inside the body and that controls the hydraulic pressure supplied to the hydraulic actuator for steering assistance by using the relative angular displacement that occurs between the steering wheel and the hydraulic control valve In the power steering apparatus including a hydraulic reaction force portion that limits the relative angular displacement by the action of the introduced hydraulic pressure corresponding to the vehicle speed, the hydraulic reaction force portion includes the valve body and the valve spool. The pressure chamber formed on the fitting circumference and one of the valve body and the valve spool are projected and abut on the other on an appropriate radial line inside the pressure chamber, and the pressure chamber is circumferentially divided into two. A pair of halves that are liquid-tight to each other A power steering apparatus comprising: a sealing means that forms a force chamber; and a pressure guiding path that selectively guides the introduced hydraulic pressure to one of the reaction force chambers according to the direction of the relative angular displacement. . 2. The power steering apparatus according to claim 1, wherein the pressure guiding path is configured to guide the introduced hydraulic pressure to both of the pair of reaction force chambers in a neutral state in which the relative angular displacement has not occurred.