JPH0542882A - Power steering - Google Patents

Abstract

PURPOSE:To eliminate influence caused by the ascent of original pressure accompanying the action of an oil pressure control valve with a simple constitution, in a constitution that obtains the introduction oil pressure of an oil pressure reaction portion limiting the action of the oil pressure control valve, from feed oil pressure to the oil pressure control valve. CONSTITUTION:An oil pressure reaction portion 5 is provided at an oil pressure control valve 4 controlling feed oil pressure to a power cylinder 6 that generates steering auxiliary power. A solenoid valve 7 equipped with a pair of variable throttles S1, S2 that change throttling areas according to the detection vehicle speed of a vehicle speed sensor 8, is arranged at a branching off oil passage 15 that is made to diverge from a feed oil passage 14 to the oil pressure control valve 4 and connected to an oil tank T, and oil pressure that has been depressurized between both variable throttles S1, S2 in response to the retardation of a vehicle speed, is introduced into the portion 5. At the portion 5, an open oil passage 16 to open introduction oil pressure to the portion 5, to the oil tank T is provided, and at the middle of this oil passages 16, a throttling portion S3 to increase throttling areas by means of the movement of a plunger following the action of the valve 4 is constituted.

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 including 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 apparatus includes a hydraulic pump serving as a hydraulic source and an oil tank (low pressure portion) for storing hydraulic oil for the hydraulic pump, and a hydraulic actuator for assisting steering between the hydraulic actuator. It has a configuration in which a hydraulic control valve for controlling the supplied hydraulic pressure according to the steering wheel operation is arranged. As this hydraulic control valve, an input shaft connected to a steering wheel (steering wheel) and an output shaft operatively connected to a steering wheel (generally the front wheel) are coaxially connected via a torsion bar, When a steering torque is applied to the steered wheels by coaxially inserting a valve body that rotates in conjunction with one of the two shafts into a tubular valve body that rotates in conjunction with one of the two shafts, the torsion is provided between the valve body and the valve body. A rotary type is often used in which relative movement (relative angular displacement) is generated according to the twist of the bar, and the relative movement is utilized to control the hydraulic pressure.

Steering of a vehicle is performed against a road surface reaction force acting on steering wheels. The magnitude of the road surface reaction force corresponds to a slow vehicle speed and a steering angle. Therefore, a large amount of force is required for steering operation at the time of stopping and low speed traveling, so-called stationary steering, while steering during high speed traveling can be performed with a relatively small force.

However, in the power steering apparatus having the above-described structure, the only correspondence between the steering torque applied to the steering wheel and the steering assist force generated by the hydraulic actuator is the torsion characteristic of the torsion bar. Depends on
If the torsion bar is selected with reference to the large road surface reaction force at the time of stopping and low speed running, there is a problem that straight running stability is deteriorated due to insufficient rigidity of the steering wheel at high speed running, and conversely a small road surface at high speed running. If the reaction force is selected as a reference, there is a problem that a sufficient steering assist force cannot be obtained when the vehicle is stopped or traveling at low speed.

In order to solve these problems, therefore, a power steering system having a hydraulic reaction force section for limiting the control operation of the hydraulic control valve by generating a hydraulic reaction force that becomes large or small depending on the vehicle speed. Has been put to practical use. The hydraulic reaction force portion extends, for example, the valve body and the valve body of the hydraulic control valve to the same side, and forms a plurality of cylinder holes radially extending through the extension portion of the valve body. A plunger is inserted in the radial direction so that it can slide in the radial direction, and a reaction force chamber that collectively communicates with the cylinder holes is provided outside the extension of the valve body, and this reaction force chamber corresponds to the vehicle speed. Is applied to actuate one side of the plungers, and the other side of these plungers is pressed against a recess formed in an extension portion of the valve body, and the relative angular displacement between the valve body and the valve body, That is, the control operation of the hydraulic control valve is limited.

FIG. 5 is a graph showing an increase characteristic of the steering assist force obtained by the power steering apparatus having the hydraulic reaction force portion. As shown in this figure, in the power steering apparatus including the hydraulic reaction force portion having the above-described configuration, the steering torque applied to the steering wheel reaches a predetermined magnitude, and the valve body and the valve body are resisted against the pressing of the plunger. The steering assist force is maintained at a substantially constant value close to zero until the relative angular displacement with and begins to occur, and then a characteristic that it rapidly rises is obtained, and the pressing force of the plunger corresponds to the magnitude of the vehicle speed. Therefore, the rising position (rising point) shifts to the side where the steering torque increases as the vehicle speed increases.

That is, when the vehicle is stopped or traveling at a low speed, a small steering torque is required to reach the rising point, and thereafter, a large steering assist force is generated to reduce the force required to operate the steering wheel as much as possible. At high speeds, the steering assist force is within a certain range until a considerable amount of steering torque is applied to the steered wheels, so that the steered wheels are provided with appropriate rigidity and straight running stability is improved.

[0008]

Now, in the power steering apparatus having the hydraulic reaction force portion, it is necessary to obtain the hydraulic pressure corresponding to the vehicle speed to be introduced into the reaction force chamber. It is rational to obtain this hydraulic pressure from the hydraulic pressure supplied to the hydraulic control valve. This means that the oil pressure is connected to the low pressure part through the variable throttle and the fixed throttle, or a pair of throttle openings that change the throttle opening in different directions. An oil passage connected to the low pressure part via the variable throttle is provided on the supply side to the hydraulic control valve, and the throttle opening of the variable throttle on the upstream side is changed to decrease in accordance with the decrease in vehicle speed. It is realized by the configuration that obtains the introduced hydraulic pressure to the force section. That is, in this case, the introduced hydraulic pressure to the hydraulic reaction force section is the hydraulic pressure supplied to the hydraulic control valve which is reduced according to the slow speed of the vehicle.

However, since the hydraulic pressure on the supply side of the hydraulic control valve, which is the source pressure of the hydraulic pressure introduced into the hydraulic reaction force section, rises in accordance with the operation of the hydraulic control valve, the hydraulic reaction force section has the above-mentioned construction. When the hydraulic control valve starts to operate against the reaction force generated by, that is, the relative angular displacement between the valve body and the valve body begins to occur, the hydraulic reaction force further increases, and the normal operation of the hydraulic control valve is Inconvenience will occur.

As a means for solving this inconvenience, JP-A-61
The power steering apparatus disclosed in Japanese Patent Publication No. 105273 is known. This is because a cylindrical spool called a cut-off spool is slidably fitted onto a main spool that is moved according to the detection result of the vehicle speed, and the introduced hydraulic pressure to the hydraulic reaction force portion is determined. The variable diaphragm is configured between both spools. The cut-off spool receives the hydraulic pressure supplied to the hydraulic control valve to move relative to the main spool, and increases the throttle area of the variable throttle that is determined according to the vehicle speed in accordance with the increase in the hydraulic pressure supplied. This action eliminates the above-mentioned inconvenience.

However, in this structure, a variable throttle having a complicated structure having two kinds of spools, that is, a main spool and a cutoff spool is required, and when processing and assembling both spools which require high precision. There has been a problem that a lot of man-hours are required to adjust the positions of both spools.

The present invention has been made in view of the above circumstances, and does not complicate the configuration of the variable throttle for obtaining the introduced hydraulic pressure of the hydraulic reaction force portion, and the hydraulic pressure to be fed to the hydraulic control valve. An object of the present invention is to provide a power steering apparatus that can obtain appropriate steering characteristics according to the vehicle speed regardless of changes.

[0013]

A power steering apparatus according to the present invention includes a hydraulic control valve for controlling hydraulic pressure supplied to a hydraulic actuator for generating steering assist force in accordance with steering wheel operation, and a hydraulic pressure control valve for controlling vehicle speed. And a hydraulic reaction force portion that restricts the operation of the hydraulic control valve by pressing a plunger that receives the pressure, and the supply hydraulic pressure to the hydraulic control valve is used as the introduction hydraulic pressure to the hydraulic reaction force portion. In a power steering apparatus that uses a hydraulic pressure that is reduced according to the slow speed of the vehicle, an oil passage that opens the hydraulic reaction force portion to a low pressure portion and an oil passage that is arranged in the oil passage, and that resists the pressing. And a throttling portion that increases the throttling area by the movement of the plunger.

[0014]

In the present invention, the oil passage for releasing the introduced hydraulic pressure to the hydraulic reaction force portion to the low pressure portion and the throttle portion in the middle of this oil passage are provided, and the plunger is pressed by the hydraulic reaction force portion. When the hydraulic control valve starts operating against this, and the plunger moves in response to this operation, the throttle area of the throttle portion increases and the action of releasing the increase in the introduced hydraulic pressure to the hydraulic reaction force portion to the low pressure portion is exerted. None, which maintains the normal operating condition of the hydraulic control valve.

[0015]

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 an overall configuration of a power steering apparatus according to the present invention (hereinafter referred to as the present invention apparatus) equipped in a vehicle equipped with a rack and pinion type steering mechanism.

In the figure, 1 is a rack shaft extending in the left-right direction at the front of the vehicle body, and 10 is a steering wheel arranged inside the vehicle compartment. The rack and pinion type steering mechanism includes a pinion 12 fixedly mounted on the lower end of a steering wheel shaft 11 coaxially connected to the lower side of the steering wheel 10.
The rack shaft 1 is engaged with the rack shaft 1 by converting the rotation of the steering wheel 10 for steering into sliding in the extending direction of the rack shaft 1.
A pair of left and right steering wheels (generally the front wheels) 13, 13 connected to both ends of the steering wheel via separate knuckle arms are turned to make steering.

In the device of the present invention which assists the above steering operation in the rack and pinion type steering mechanism with hydraulic pressure, the hydraulic pressure generated by the hydraulic pump P, which is a hydraulic pressure source, is applied to the rack shaft 1.
In the double-acting power cylinder 6 that is configured midway,
The hydraulic control valve 4 formed in the middle of the steering wheel shaft 11 that connects the rack shaft 1 and the rack shaft 1 supplies the oil according to the operation of the steering wheel 10 by the operation described later, and the power cylinder 6 is generated by the supplied oil pressure. The hydraulic pressure is applied to the rack shaft 1 to assist the sliding of the rack shaft 1 and the steering operation of the steering wheels 13 and 13 associated therewith.

The operation of the hydraulic control valve 4 is limited to one side by a force corresponding to the vehicle speed, so that the straight running stability is deteriorated during high speed running and the steering assist force is stopped during stop or low speed running. A hydraulic reaction force portion 5 that operates to eliminate the shortage is configured. In the middle of the oil supply passage 14 from the hydraulic pump P to the hydraulic control valve 4, there is provided a branched oil passage 15 communicating with the oil tank T maintained at a low pressure state. The solenoid valve 7 is provided with a pair of variable throttles S ₁ and S ₂ that change the area in different directions by controlling the energization of the solenoid 70 (see FIG. 2) based on the detected vehicle speed of 8. In the hydraulic reaction portion 5, the hydraulic pressure between the variable throttles S ₁ and S ₂ of the solenoid valve 7, that is, the hydraulic pressure to be fed to the hydraulic control valve 4 is reduced by the pressure reduction amount of the variable throttle S _1. Has been introduced.

The variable throttle S _{1 on one} side (upstream side) of the solenoid valve 7 increases the throttle area in accordance with the increase in the vehicle speed detected by the vehicle speed sensor 8, and the other variable throttle S ₂ in accordance with the increase in the detected vehicle speed. The throttle area is reduced so that the hydraulic reaction force portion 5 obtained between both variable throttles S ₁ and S ₂ can be obtained.
The introduced hydraulic pressure is a hydraulic pressure obtained by increasing the depressurization level according to the slow speed of the vehicle. Further, the hydraulic reaction force portion 5 is provided with an open oil passage 16 for releasing the introduced hydraulic pressure to the oil tank T, and a throttle portion S ₃ which causes an area change in the middle of the oil passage 16 as described later. ..

FIG. 2 is a longitudinal sectional view showing the actual structure of the hydraulic control valve 4, the hydraulic reaction force portion 5, and the solenoid valve 7. In the figure, 2 is a hollow input shaft, 3 is a pinion shaft in which the pinion 12 is integrally formed in the lower half part thereof, and these shafts are provided in a common housing 20 having a tubular shape. It is rotatably supported around the center and is coaxially connected via a torsion bar 20 inserted in the hollow portion of the input shaft 2 located on the upper side.

The rack shaft 1 is supported on the lower part of the housing 20 in such a manner that the shaft center of the housing 20 intersects with the housing 20 and is engaged with the pinion 12 in the lower half of the pinion shaft 3. The protruding end of the input shaft 2 to the upper part of the housing 20 is connected to the rudder wheel shaft 11 continuously provided on the lower side of the rudder wheel 10 via a connecting member (not shown). The steering torque applied to 10 acts. That is, the input shaft 2 and the pinion shaft 3 are the steering wheel shafts that connect the steering wheel 10 and the rack shaft 1.
The rotation of the steering wheel 10 forms a part of 11 and is transmitted to the pinion shaft 3 via the input shaft 2 and the torsion bar 4, and the shaft length of the rack shaft 1 that meshes with the pinion 12 in the lower half of the shaft. The steering is converted into sliding in the direction.

A hydraulic control valve 4 for controlling the hydraulic pressure supplied to the power cylinder 6 formed in the middle of the rack shaft 1 has a short cylindrical valve body 40 rotatably fitted in a housing 20. A valve body (41) is coaxially and rotatably fitted therein. The pinion shaft 3 includes a cylindrical portion 30 that is coaxially connected to the coupling side with the input shaft 2, and the valve body 40 is coupled by restraining the rotation of the upper end of the cylindrical portion 30. I am doing it. Further, the valve body 41 is the cylindrical portion.
Valve body on the outer circumference of the input shaft 2 loosely fitted inside 30
It is integrally formed at a position matching with 40.

As described above, the input shaft 2 and the pinion shaft 3 are connected via the torsion bar 21, and when the steering wheel 10 is rotated, the torsion bar 21 is twisted due to the action of the steering torque. The relative angle between the input shaft 2 and the pinion 3 and between the valve body 41 and the valve body 40, which are respectively integrated with the input shaft 2 and the pinion 3, depend on the direction and magnitude of the steering torque applied to the steering wheel. Displacement occurs. In the hydraulic pressure control valve 4, the hydraulic pressure supply / discharge operation is performed by utilizing this relative angular displacement.

The oil supply passage 14 to the hydraulic control valve 4 is connected to a pump port 22 opening to the outside of the housing 20,
The oil pressure introduced into the oil pressure control valve 4 via the pump port 22 is distributed according to the relative angular displacement between the valve body 40 and the valve body 41, and both oil pressures of the oil pressure control valve 4 and the power cylinder 6 are distributed. The oil is fed to one oil chamber via one of the pair of oil feed passages 17a and 17b (see FIG. 1) connecting to the chamber, for example, oil feed passage 17a, and at this time, the pressure between the other oil chamber The hydraulic pressure generated by the power cylinder 6 due to the difference serves as a steering assist force that assists steering.

At the upper part of the valve body 40 inside the housing 20, there is a return chamber 23 which communicates with the hollow portion inside the input shaft 2 and which is connected to the oil tank T through a tank port 24 opening to the outside of the housing 20. The return oil that has been formed and flows back to the hydraulic control valve 4 through the oil supply passage 17b by the above-described operation of the power cylinder 6 passes through a through hole that radially penetrates the valve body 41 and is a hollow portion inside the input shaft 2. Is introduced into the oil tank T through the recirculation chamber 23 and the tank port 24.

The hydraulic reaction force portion 5 for limiting the control operation of the hydraulic control valve 4 with a force corresponding to the vehicle speed is formed in the cylindrical portion 30 at the upper end of the pinion shaft 3. 3 is an enlarged view of an essential part of FIG. 2 showing the structure of the hydraulic reaction force portion 5, and FIG. 4 is a transverse sectional view taken along line IV-IV of FIG.

As shown in FIG. 3, the cylindrical portion 30 is formed with a plurality of (four in this embodiment) cylinder holes 50, 50 ... Yes,
Plunger 51, 51 ... Of short cylinder shape is slidably fitted in each of these. A hemispherical convex portion is formed on the inner end portion of the plungers 51, 51 ... And the outer periphery of the input shaft 2 loosely fitted inside the cylindrical portion 30 is provided with the input shaft 2 and the pinion shaft 3. When there is no relative angular displacement between them, as shown in FIG. 4, recesses are formed which engage with the projections of the plungers 51, 51.

The cylinder hole is provided on the outer periphery of the cylindrical portion 30.
An annular groove for communicating the 50, 50 ... with each other is provided around, and between the annular groove and the outer circumference of the housing 20, a reaction force chamber liquid-tightly sealed by O-rings wound on both sides. 52 is formed, and this reaction force chamber 52 is connected via a pressure guide hole 26 to a throttle chamber 25 having a circular cross section arranged in parallel on one side of the housing 20.

The plungers 51, 51 ... Inserted in the cylinder holes 50, 50 ... Receive the hydraulic pressure introduced into the reaction force chamber 52 through the pressure guiding holes 26 at their outer end surfaces, respectively. 4, the projections of the plungers 51, 51 ... Tip are engaged with the recesses of the outer periphery of the input shaft 2, respectively, and the input shaft 2 with respect to the pinion shaft 3 having the cylindrical portion 30 is pressed as shown in FIG. Relative angular displacement, that is, the valve body of the hydraulic control valve 4 with respect to the valve body 40
The relative angular displacement of 41 is restricted by the force corresponding to the hydraulic pressure inside the reaction force chamber 52.

This restraint increases the steering torque applied to the steered wheels, and the radial outward force acting on each of the plungers 51, 51 ... via the concave portion on the side of the input shaft 2 exceeds these pressing forces and is released. At this time, since the relative angular displacement between the valve body 40 and the valve body 41 of the hydraulic control valve 4 can occur, the control operation of the hydraulic pressure fed to the power cylinder 6 is performed. As the relative angular displacement between the valve body 40 and the valve body 41 progresses after the restraint is released, the plungers 51, 51 ... Are pressed by the inclination of the concave portion on the outer periphery of the input shaft 2, Separate cylinder holes 5
Slide outward along 0, 50 ....

Now, the upper end of the cylindrical portion 30 has a hydraulic control valve 4
3 is fitted to the lower end of the valve body 40 for connection therewith, and as shown in FIG. 3, this fitting portion is a single cylinder hole 50 or a corresponding portion of a plurality of cylinder holes 50, 50 ... At the notch, an oil chamber 53 that is liquid-tightly sealed with the lower end of the valve body 40 is formed in this notch. The oil chamber 53 communicates with the inside of the corresponding cylinder hole 50 through a communication hole 54 having a small diameter, and also through a communication hole 27 penetrating the peripheral wall of the input shaft 2, a hollow portion inside the input shaft 2. Is further communicated with the oil tank T maintained at a low pressure via the reflux chamber 23 and the tank port 24.

The plunger 51 in the cylinder hole 50 which communicates with the oil chamber 53 has a drill hole of a predetermined depth which is opened at the outer end surface thereof.
A perforation 55 is formed, and in the vicinity of the bottom of the perforation hole 55, a small-diameter throttle hole 56 penetrating the sidewall in the radial direction is formed. As shown in FIG. 3, the throttle hole 56 is formed when the convex portion inside the plunger 51 is fitted in the concave portion on the outer periphery of the input shaft 2, that is, when the operation of the hydraulic control valve 4 is restricted. ,
It is located inside the opening end of the communication hole 54 to the inside of the cylinder chamber 50, and in response to the outward sliding of the plunger 51 which occurs as described above when the restraint of the hydraulic control valve 4 is released, the communication hole 54 is opened. It acts to increase the opening area.

As described above, in the device of the present invention, the drill hole
An open oil passage 16 (see FIG. 1) that releases the introduced hydraulic pressure of the hydraulic reaction force portion 5 to the reaction force chamber 52 to the oil tank T by the 55, the throttle hole 56, the communication hole 54, the oil chamber 53, and the communication hole 27 is formed. In addition, this open oil passage 16
The narrowed portion S ₃ is constituted by the narrowed hole 56 and the communication hole 54 midway. Since the throttle area of the throttle portion S ₃ increases as the plunger 51 moves, the reaction force chamber
The internal pressure of 52 is reduced according to the movement of the plunger 51 caused by the operation of the hydraulic control valve 4.

As shown in FIG. 2, the solenoid valve 7 for adjusting the introduced hydraulic pressure to the hydraulic reaction force portion 5 thus constructed is arranged substantially parallel to one side of the input shaft 2 and the pinion shaft 3 as shown in FIG. Are arranged side by side, and are formed in the throttle chamber 25 that communicates with the reaction force chamber 52 of the hydraulic reaction force portion 5 via the pressure guide hole 26 as described above. On the inner circumference of the throttle chamber 25, a pair of annular grooves are formed on both sides of the opening position of the pressure guiding hole 26, one of these is
The supply side of the hydraulic control valve 4 is communicated through the communication hole 27, and the other side is communicated with the oil chamber 53 formed as described above between the hydraulic reaction force portion 5 and the hydraulic control valve 4 through the communication hole 28. There is.

The solenoid valve 7 has a spool 71 slidably fitted in the throttle chamber 25 slidably in the axial direction, and an output end of a solenoid 70 screwed and fixed to one opening end of the throttle chamber 25. The spool 71 is slid according to the forward / backward movement of the solenoid 70. The spool 71 is provided with an annular groove 72 having a width that allows the pair of annular grooves on the inner circumference of the throttle chamber 25 to communicate with each other.
Reference numeral 72 constitutes a pair of variable diaphragms S ₁ and S ₂ between the pair of annular grooves on the side of the diaphragm chamber 25, which change the diaphragm opening in different directions according to the operation of the solenoid 70.

As described above, the solenoid valve 7 has a communication hole.
27, a throttle chamber 25, and a communication hole 28, and a pair of variable throttles is provided in the middle of a branch oil passage 15 (see FIG. 1) that branches to the oil chamber 53 whose supply side to the hydraulic control valve 4 is maintained at a low pressure state. S ₁ , S
₂ is arranged in series, and the hydraulic pressure between the variable throttles S ₁ and S ₂ is introduced into the reaction force chamber 52 of the hydraulic reaction force portion 5. When the solenoid 70 of the solenoid valve 7 is made to advance with the increase of the vehicle speed by the energization control based on the vehicle speed detected by the vehicle speed sensor 8, the throttle area of the variable throttle S ₁ is increased with the increase of the vehicle speed. And, conversely, the throttle area of the variable throttle S ₂ decreases, so that the hydraulic pressure introduced into the reaction force chamber 52 becomes higher as the vehicle speed increases, and the operation of the hydraulic reaction force portion 5 by this introduced hydraulic pressure causes high-speed traveling. It is possible to improve the deterioration of straight running stability when the vehicle is running, and to solve the shortage of the steering assist force when the vehicle is stopped or running at low speed.

When the operation of the hydraulic control valve 4, that is, when the relative angular displacement between the valve body 40 and the valve body 41 occurs, the hydraulic pressure on the upstream side, that is, on the supply side to the hydraulic control valve 4, rises. Therefore, the hydraulic pressure introduced into the hydraulic reaction force portion 5 which is determined by the pressure reduction caused by the passage of the variable throttle S ₁ using this hydraulic pressure as the original pressure also rises. The throttle area of the throttle portion S ₃ is increased with the movement of the valve, and a part of the introduced hydraulic pressure is released to the low pressure oil chamber 53 via the throttle portion S _3, and as a result, the plunger 51 of the hydraulic reaction force portion 5 is released. The pressure received by is kept substantially constant, the operation of the hydraulic control valve 4 is not impeded, and the desired characteristics as shown in FIG. 5 are stably obtained.

[0038] In this way, the device of the present invention, although the diaphragm portion S ₃ to increase the aperture area by the plunger 51, 51 ... movement forms a function similar to that of a cut-off spool in the conventional configuration, the throttle portion S ₃ is As described above, the simple structure including the drill hole 55 and the throttle hole 56 formed in the plunger 51 and the communication hole 54 formed in the side wall of the cylinder hole 50 is used to obtain the introduced hydraulic pressure of the hydraulic reaction force portion 5. As a result, appropriate steering characteristics according to the vehicle speed can be obtained without complicating the structure of the solenoid valve 7.

In this embodiment, an example of application to a vehicle equipped with a rack and pinion type steering mechanism has been described, but the device of the present invention is applied to a vehicle equipped with another steering mechanism such as a ball screw type. It goes without saying that is also applicable.

[0040]

As described above in detail, in the power steering apparatus according to the present invention, the throttle portion for increasing the throttle area in accordance with the movement of the plunger is formed inside the hydraulic reaction portion, so that the hydraulic control valve can be controlled. The introduced hydraulic pressure to the hydraulic reaction force section can be obtained by the variable throttle having a simple structure which is arranged on the supply side and has a function of only increasing the decompression degree according to the slow speed of the vehicle. The present invention has excellent effects such as obtaining appropriate steering characteristics according to the vehicle speed regardless of whether steering is performed or not.

[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 transverse sectional view taken along line IV-IV in FIG.

FIG. 5 is a graph showing a desirable steering assist force increasing characteristic obtained by a power steering apparatus including a hydraulic reaction force portion.

[Explanation of symbols]

 1 Rack Shaft 2 Input Shaft 3 Pinion Shaft 4 Hydraulic Control Valve 5 Hydraulic Reaction Force Section 6 Power Cylinder 7 Solenoid Valve 8 Vehicle Speed Sensor 10 Steering Wheel 14 Supply Oil Path 15 Branch Oil Path 16 Open Oil Path 20 Housing 21 Torsion Bar 40 Valve Body 41 Valve body 50 Cylinder hole 51 Plunger 52 Reaction force chamber 53 Oil chamber 54 Communication hole 55 Drill hole 56 Throttle hole P Hydraulic pump T Oil tank

Claims (1)

[Claims] 1. A hydraulic control valve for controlling a hydraulic pressure to be fed to a hydraulic actuator for generating a steering assist force according to a steering wheel operation, and a hydraulic pressure valve for introducing a hydraulic pressure according to a vehicle speed, and pressing a plunger for receiving the hydraulic pressure controls the hydraulic pressure. A hydraulic reaction force portion for limiting the operation of the hydraulic control valve is provided, and the hydraulic pressure supplied to the hydraulic control valve is reduced as the introduction hydraulic pressure to the hydraulic reaction force portion is used according to the slow speed of the vehicle. In a power steering apparatus, an oil passage that opens the hydraulic reaction force portion to a low pressure portion, and a throttle portion that is arranged in the oil passage and that increases the throttle area by movement of the plunger that occurs against the pressing. A power steering apparatus comprising: