JPH0999850A - Pressure control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the change characteristic of the pressure of a hydraulic fluid equal when the steering torque is increased and when it is decreased by operating the second spool and the first spool for communicating a liquid feed discharge chamber and a liquid discharge chamber and for communicating a liquid feed chamber and the liquid feed/discharge chamber. SOLUTION: As the steering torque is decreased, a liquid feed/discharge chamber 48 and a liquid feed chamber 51 are kept in a noncommunicative state, and a liquid discharge port 56 and a liquid discharge chamber 54 are opened or closed in response to the balance of the steering torque applied to the second spool 45 against the hydraulic reaction of the hydraulic liquid in a pressure regulating chamber 70 and the pressing force of a pressing pin. The liquid discharge port 56 and the liquid discharge chamber 54 are kept at the communicative state until the pressure of the hydraulic liquid in a reaction chamber 46 becomes the set pressure or below, and the pressure of the hydraulic liquid in a cylinder chamber is quickly decreased. When the pressure of the hydraulic liquid in the reaction chamber 46 becomes the set pressure or below, the hydraulic reaction corresponding to the steering torque is generated in the pressure regulating chamber 70, the liquid discharge port 56 and the liquid discharge chamber 54 are made in a communicative state, and the decreasing rate of the pressure of the hydraulic liquid in the cylinder chamber is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure control device for supplying a hydraulic fluid having a desired characteristic to an actuator with respect to an operating force, and is particularly suitable for application to a vehicle power steering device. .

[0002]

2. Description of the Related Art In a power steering device using hydraulic pressure, a pressure control device for supplying a hydraulic pressure corresponding to a steering force to a power cylinder is incorporated, and the hydraulic pressure supplied to the power cylinder by this pressure control device is assisted. It is used as a typical steering force.

[0003] Conventionally, as such a power steering device, one disclosed in, for example, JP-A-61-85272 is known.

In this power steering apparatus, a pressure control valve driven according to a steering force is provided in a hydraulic fluid passage communicating between a hydraulic fluid pump driven by an electric motor and a power cylinder. A check valve that allows only the flow to the pressure control valve is provided in the working fluid supply passage between the working fluid pump and the accumulator is provided between the check valve and the pressure control valve to accumulate the working fluid, The stored hydraulic fluid is supplied to a power cylinder via a pressure control valve to generate a steering assist force. Then, the hydraulic pressure of the hydraulic fluid accumulated in the accumulator is detected by the pressure sensor, the electric motor is operated when the pressure drops to a predetermined pressure, and conversely, the electric motor is stopped when the pressure rises to the predetermined pressure. ing.

As a pressure control device used in such a power steering device, for example, there is a pressure control device described in Japanese Patent Application No. 6-30685 filed by the applicant of the present application. In this pressure control device, a spool opens according to a steering torque, and hydraulic fluid accumulated in an accumulator is supplied to a power cylinder. Furthermore, the pressure in the power cylinder is applied to the feedback chamber provided at the back of the spool to push back the valve spool.However, since the feedback chamber is equipped with a relief valve, the hydraulic fluid in the feedback chamber When the hydraulic pressure of is higher than a predetermined value, the rate of increase of the supply pressure of the hydraulic fluid to the power cylinder relative to the rate of increase of the steering torque up to that point is further increased, that is, steering can be performed more easily than before. Has become.

[0006]

[Patent Document 1] Japanese Patent Application No. 6-30685
In the pressure control device disclosed in Japanese Patent Publication No. JP-A-2003-279, although the supply pressure of the hydraulic fluid to the power cylinder with respect to the rate of increase in the steering torque can be made non-linear, the steering wheel from the turning state of the vehicle to the straight traveling state When the steering torque is changed from the increasing tendency to the decreasing tendency, as in the case of returning, the pressure drop of the hydraulic fluid in the power cylinder decreases in proportion to the decrease rate of the steering torque. It is not possible to obtain nonlinear characteristics such as when the steering torque increases. Therefore, there is room for improvement in order to improve the steering feeling.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to obtain a good steering feeling by matching the characteristics of change in hydraulic pressure of hydraulic fluid when the steering torque rises and falls to reduce the hysteresis width. It is to provide a pressure control device that can realize a possible power steering device.

[0008]

According to a first aspect of the pressure control device of the present invention, there is provided a liquid supply chamber connected to a supply source of hydraulic fluid to supply the hydraulic fluid, and a liquid supply / discharge fluid connected to an actuator. A chamber, a first spool that can be reciprocally moved to switch the communication state between the liquid supply / drainage chamber and the liquid supply chamber, and the first spool so that the liquid supply chamber and the liquid supply / drainage chamber do not communicate with each other. Spool urging means for urging the spool, and a working fluid that resists movement of the first spool in the direction in which the liquid supply chamber and the liquid supply / drainage chamber communicate with the spool urging means are filled. Reaction chamber, a pressure adjusting means for maintaining the hydraulic pressure of the working fluid in the reaction chamber below a predetermined pressure, a drainage chamber connected to the drainage passage of the working fluid, the drainage chamber and the supply / drainage chamber. A reciprocating second spool that switches the communication state with the liquid chamber, and the hydraulic pressure of the hydraulic fluid in the supply / drain chamber. Accordingly, the reaction force generating means for pressing the second spool so that the supply / drainage chamber and the drainage chamber communicate with each other, and the supply / drainage chamber and the drainage chamber are in a non-communication state, and The liquid supply chamber and the liquid supply / drainage chamber are provided with a spool operating means capable of operating the second spool and the first spool so as to communicate with each other.

Further, in the pressure control device of the present invention according to claim 2, there is further provided a pressure regulation chamber formed between the second spool and the first spool, into which the hydraulic fluid in the reaction force chamber is introduced. It is characterized by having.

Further, the pressure control device of the present invention according to claim 3 is characterized in that the pressure adjusting means has a relief valve.

On the other hand, the pressure control device of the present invention according to claim 4 is characterized in that the actuator is a power cylinder of a vehicle power steering device.

According to the first aspect of the present invention, when the spool operating means is not operated, the liquid supply chamber and the liquid supply / discharge chamber are shut off by the spool urging means, and the working fluid is supplied to the actuator side. Not done. At this time, the hydraulic pressure of the hydraulic fluid in the supply / drainage chamber presses the second spool via the reaction force generating means so that the supply / drainage chamber and the drainage chamber communicate with each other, and the hydraulic fluid in the actuator is drained. The liquid is discharged from the liquid chamber through the discharge passage, and the actuator is deactivated.

When the spool operating means is operated against the hydraulic pressure of the working fluid in the reaction force chamber and the spool urging means, the drain chamber and the supply / drain chamber are shut off by the second spool, and the spool urging means is further operated. Due to the balance between the urging force of the hydraulic fluid and the hydraulic pressure of the hydraulic fluid in the supply / drainage chamber and the reaction force chamber and the operating force of the second spool, the liquid supply chamber and the supply / drainage chamber communicate with each other intermittently. The hydraulic pressure of the hydraulic fluid gradually rises. When the hydraulic pressure of the hydraulic fluid in the reaction force chamber exceeds a predetermined value, the hydraulic pressure of the hydraulic fluid in the reaction force chamber becomes constant, and the urging force of the spool urging means and the hydraulic pressure of the hydraulic fluid in the supply / discharge fluid chamber are increased. And the operating force of the second spool, the liquid supply chamber and the liquid supply and discharge chamber communicate intermittently, the hydraulic pressure of the hydraulic fluid in the actuator gradually increases, and The rate of increase of the hydraulic pressure of the hydraulic fluid in the actuator becomes larger than before.

When the operating force of the spool operating means is reduced from such a state, the liquid supply chamber and the liquid supply / drainage chamber are held in a non-communication state by the spool urging means, and the hydraulic fluid in the reaction force chamber is maintained. Until the hydraulic pressure reaches a predetermined value, the drainage chamber and the drainage chamber are balanced by the balance between the pressing force of the reaction force generating means corresponding to the hydraulic pressure of the hydraulic fluid in the supply / drainage chamber and the operating force of the second spool. The fluid supply / drainage chamber communicates intermittently, and the hydraulic pressure of the hydraulic fluid in the actuator decreases. However, when the hydraulic pressure of the hydraulic fluid in the reaction force chamber falls below a predetermined value, the pressing force of the reaction force generating means,
Due to the balance with the operation force of the second spool, the drainage chamber and the supply / drainage chamber communicate with each other intermittently, and the hydraulic pressure of the hydraulic fluid in the actuator decreases, resulting in a decrease rate of the operating force. The rate of decrease of the hydraulic pressure of the hydraulic fluid in the actuator is smaller than that before.

According to the second aspect of the present invention, when the hydraulic pressure of the hydraulic fluid in the reaction force chamber falls below a predetermined value, the hydraulic fluid in the pressure regulating chamber is added to the pressing force of the reaction force generating means. Due to the balance between the pressure and the operating force of the second spool, the drainage chamber and the supply / drainage chamber communicate with each other intermittently, and the hydraulic pressure of the hydraulic fluid in the actuator gradually decreases. The rate of decrease of the hydraulic pressure of the hydraulic fluid in the actuator relative to the rate of decrease of is smaller than before.

Further, according to the present invention corresponding to claim 3, when the hydraulic pressure of the working fluid in the reaction force chamber reaches a predetermined value, the relief valve is opened and the working fluid in the reaction force chamber is discharged. The reaction force chamber is maintained at a predetermined pressure or less.

On the other hand, according to the present invention corresponding to claim 4, in a region where the hydraulic pressure of the hydraulic fluid in the reaction force chamber is less than a predetermined value,
A relatively small steering assist force is generated, and when this reaches a predetermined value, a relatively large steering assist force is generated. That is, the steering assist force is small in a region where the steering torque is small, and conversely, the steering assist force is large in a region where the steering torque is large.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which a pressure control device according to the present invention is applied to a power steering device for an automobile will be described in detail with reference to FIGS.

FIG. 1 showing the schematic structure of this embodiment and its structure.
As shown in FIG. 2 showing a sectional structure taken along the line II-II, a rack bar 12 having tie rods (not shown) connected to both ends thereof is provided in a gear housing 11 extending in the width direction of the vehicle body (not shown) (left-right direction in the figure). In the figure, it penetrates slidably in the left-right direction. One end of the gear housing 11 (see FIG.
A cylinder portion 13 that surrounds the rack rod 12 in a sealed state is integrally formed on the left side). On the outer periphery of the rack rod 12 located in the cylinder portion 13, a piston 15 for partitioning the inside of the cylinder portion 13 into two left and right cylinder chambers 14L and 14R is integrally provided, and in the present embodiment, the cylinder portion described above is provided. 13, a piston 15 slidably fitted to the cylinder portion 13 to partition the inside of the cylinder portion 13 into two cylinder chambers 14L and 14R, a rack rod 12 integrated with the piston 15 and the like of the present invention. It constitutes an actuator.

The other end of the gear housing 11 (FIG. 1)
The pinion shaft 1 that intersects with the rack rod 12 is on the inside and the right side).
6 is rotatably held via a pair of upper and lower bearings 17, 18. A rack 20 formed on the rack rod 12 meshes with a pinion 19 formed on a pinion shaft 16 having an upper tubular shape. That is, by driving and rotating the pinion shaft 16, the tie rods change the direction of the steered wheels (not shown) via the rack rods 12.

A lower end portion of a torsion bar spring 21 is fitted to the center of the pinion shaft 16 by serration, and a cylindrical input shaft 22 coaxially surrounding the torsion bar spring 21 has a pair of upper and lower bearings 23, It is held rotatably relative to a cylindrical shaft holder 25 integrally fixed to the pinion shaft 16 and the gear housing 11 via 24. A connecting pin 26 for integrally connecting the torsion bar spring 21 and the input shaft 22 is mounted on the upper end of the input shaft 22, and a steering handle (not shown) is attached to the upper end of the input shaft 22. The lower end of the steering shaft 27 is serrated. That is, the rotational force of the steering shaft 27 by operating the steering handle is transmitted to the pinion shaft 16 only through the torsion bar spring 21.

Between the input shaft 22 and the shaft holder 25, a lifting sleeve 28 is slidable with respect to the input shaft 22.
And a swivel sleeve 29 rotatably connected to the elevating sleeve 28. The elevating sleeve 28 is attached to the shaft holder 25 via a rotation stopping mechanism (not shown).
The shaft holder 25 can be moved up and down along the input shaft 22. A swivel sleeve 29 that can be moved up and down integrally with the elevating sleeve 28 is rotatably held by the input shaft 22 and the shaft holder 25, and a spiral elevating guide groove formed in the swivel sleeve 29. Three
0 is a lift drive pin 31 protruding from the outer circumference of the input shaft 22.
Are slidably engaged. Further, a connecting pin 33 integrally attached to the upper end of the pinion shaft 16 is slidably engaged with a locking groove 32 formed at a lower portion of the revolving sleeve 29 along the longitudinal direction of the input shaft 22, As a result, the rotational force transmitted from the steering shaft 27 to the input shaft 22 is transmitted from the lifting drive pin 31 to the turning sleeve 29, but the locking groove 32 of the turning sleeve 29 is engaged with the connecting pin 33 of the pinion shaft 16. As a result, the input shaft 22 is converted into an elevating operation of the revolving sleeve 29 and the elevating sleeve 28 along the longitudinal direction thereof.

An oscillating ring 34 having an annular shape is slidably fitted between the elevating sleeve 28 and the shaft holder 25, and the oscillating ring 34 has an inner periphery of the elevating sleeve 28. A swivel guide pin 36, which slidably engages with a spiral swivel drive groove 35 formed in the upper part, is provided in a protruding manner. Further, a swing lever 37 is provided on the outer circumference of the swing ring 34, and a tip end portion of the swing lever 37 is orthogonal to the longitudinal direction of the input shaft 22 (left and right in FIG. 2). Direction), and is engaged with a lever receiving portion 39 at the center of a spool driver 38 slidably attached to the shaft holder 25. The swinging ring 37 restrains the swinging movement of the shaft holder 25 and the lifting sleeve 28 along the longitudinal direction of the swinging ring 34, so that the swinging ring 34 swings through the swivel guide pin 36 in conjunction with the lifting movement of the lifting sleeve 28. The ring 34 swings. That is, the swing lever 37 of the swing ring 34 drives the spool driver 38 left and right in FIG. 2 in accordance with the rotation operation of the steering shaft 27.

A pair of valve housings 40 facing each other in a direction orthogonal to the longitudinal direction of the input shaft 22 are fixed to the shaft holder 25 with a spool driver 38 serving as a spool operating means of the present invention interposed therebetween. These valve housings 40 are provided with stepped holes 41 extending in a direction parallel to the sliding direction of the spool driver 38.
A spool holder 43 fitted with a seal plug 42 is tightly fitted to the opening end of the large diameter portion on the opposite side of the spool driver 38.

The structure inside the stepped hole 41 is exactly the same for the pair of valve housings 40. As shown in FIG. 2 and FIG. 3 in which one valve housing 40 is extracted and enlarged, as shown in FIG. In the spool holder 43,
Both ends of the first spools 44L, 44R (may be simply referred to as 44) are slidably fitted, and further, both ends can contact the spool driver 38 and the first spool 44. Is slidably fitted in the small diameter portion of the stepped hole 41.

Then, by this first spool 44,
The reaction force chambers 46L and 46R (which may be simply referred to as 46) surrounded by the seal plug 42 and the spool holder 43 and the oil supply / discharge oil passages 47L and 47R (which may be simply referred to as 47) are provided. Through the cylinder chamber 13 of the cylinder portion 13
The oil supply / discharge chambers 48L, 48R (corresponding to the supply / drainage chamber of the present invention, which may be simply referred to as 48 hereinafter) communicating with the 4L, 14R, and the hydraulic oil from the oil pump 49 are the pressure oil supply paths. 5
The inside of the stepped hole 41 is partitioned into oil supply chambers 51L and 51R (corresponding to the liquid supply chamber of the present invention, which may be simply referred to as 51 hereinafter) supplied via 0. Further, on the outer periphery of the tip end portion of the second spool 45, annular oil drain chambers 54L, 54R (corresponding to the liquid drain chamber of the present invention, which communicates with the oil sump 53 through the oil drain passage 52 of the present invention. However, hereinafter, it may be simply referred to as 54) is formed, and the oil supply / discharge passage 47 is formed on the inner circumference of the stepped hole 41 via the branch oil passage 55 so as to communicate with the oil discharge chamber 54. The annular oil drain ports 56L, 56R (may be simply referred to as 56) are formed to be connected to.

In this embodiment, when the steering shaft 27 is in the neutral state and no steering torque is generated, the oil discharge chamber 54 and the oil discharge port 56 communicate with each other to supply the hydraulic oil in the cylinder chambers 14L, 14R. The oil drain passage 47 and the branch oil passage 55 are used to drain the oil drain passage
The oil is drained into the oil sump 53 from No. 2.

The reaction force chamber 46 and the oil supply / discharge passage 47 are connected to each other by a communication passage 57 and an annular groove 58 formed in the spool holder 43.
A throttle 60, which communicates with each other via a conduction path 59 connected to the oil supply port, and which allows the working oil from the oil supply / discharge passage 47 to be provided in the middle of the conduction path 59.
It is adapted to be supplied into the reaction force chamber 46 via.
Further, an oil drain passage 61 connected to the oil sump 53 is connected to the annular groove 58 communicating with the reaction force chamber 46.
In the middle of the operation, a check valve 62 for preventing the reverse flow of the hydraulic oil from the oil sump 53 side to the reaction force chamber 46, and a relief for keeping the hydraulic pressure of the hydraulic fluid in the reaction force chamber 46 below a predetermined pressure. The valve 63 is interposed in series. The oil discharge passage 61, the relief valve 63 and the like constitute the pressure adjusting means of the present invention.

At the central portion of the first spool 44, there is provided a conical valve body 65 which can be brought into contact with the step portion 64 of the stepped hole 41 to bring the oil supply / discharge chamber 48 and the oil supply chamber 51 into a non-communication state. The valve body 65 and the spool holder 43 are integrally formed.
A compression coil spring 66 serving as a spool urging means of the present invention for urging the oil supply / discharge chamber 48 and the oil supply chamber 51 to be in a non-communication state is interposed between and. Further, the first spool 44 has a pin fitting hole 67 whose one end side communicates with the oil supply / discharge chamber 48 and the other end side which opens to the end face facing the second spool 45, and one end side communicates with the reaction force chamber 46. In addition, a communication path 68 is formed, the other end of which is open to the end surface facing the second spool 45. The second spool 4 is attached to the end of the pin fitting hole 67 on the second spool 45 side.
5, a pressing pin 69 that comes into contact with the end face opposite to 5 is slidably fitted, and these pin fitting hole 67 and pressing pin 6 are provided.
9 corresponds to the reaction force generating means of the present invention.

In this embodiment, a circular pressure adjusting chamber 70 is provided on the tip surface of the second spool 45 facing the first spool 44.
By forming the reaction force chamber 46 in the pressure regulation chamber 70.
However, depending on the desired characteristics of the power steering device, no inconvenience will occur even if the pressure adjusting chamber 70 is not provided. .

In the pressure oil supply passage 50 between the oil pump 49 and the oil supply chamber 51, the accumulator 71 for accumulating pressure and the pressure of the hydraulic oil in the pressure oil supply passage 50 are sequentially arranged from the oil supply chamber 51 side. When the pressure is equal to or less than a predetermined value, the pressure switch 73 for operating the electric motor 72 for driving the oil pump 49 and the oil supply chamber 5
A check valve 74 for preventing the hydraulic fluid from flowing back from the first side to the oil pump 49 side is incorporated.

Therefore, in the neutral state of the steering wheel as shown in FIG. 2, such as when the vehicle is traveling straight, the valve element 65 of the first spool 44 is forced by the spring force of the compression coil spring 66 into the stepped hole 41. The oil supply chamber 51 and the oil supply / discharge chamber 48 are brought into non-communication with each other by being brought into contact with the stepped portion 64 of the oil supply chamber 51 and pressed by the hydraulic pressure of the hydraulic oil in the oil supply / discharge chamber 48 guided to the pin fitting hole 67. The pin 69 is pressed against the second spool 45,
The base end surface thereof contacts the spool driver 38, and the oil discharge port 56 and the oil discharge chamber 54 are in communication with each other. Therefore, the hydraulic oil pumped from the oil sump 53 to the pressure oil supply passage 50 by the oil pump 49 is accumulated in the accumulator 71 and is kept at a predetermined pressure by the pressure switch 73. In addition, the cylinder chambers 14L and 14R in the cylinder portion 13 and the oil sump 5
3 is a supply / discharge oil passage 47, a branch oil passage 55, an oil discharge port 56,
A communication state is established via the oil drain chamber 54 and the oil drain passage 52.

Next, when the steering shaft 27 is operated in the clockwise direction through the steering handle to turn the vehicle to the right, for example,
The steering force is applied to the pinion shaft 16 via the torsion bar spring 21.
Is transmitted from the pinion 19 to the rack 20 of the rack rod 12. When a steering reaction force larger than a predetermined value is generated in response to the operation of the steering wheel, the lifting sleeve 2 is moved along with the lowering operation of the turning sleeve 29 that rotates integrally with the torsion bar spring 21.
2, the swing ring 34 turns counterclockwise in FIG.
The tip end of the rocking lever 37 is displaced to the left side in the direction opposite to the steering direction, that is, from the neutral state shown in FIG. 2 to slide the spool driver 38 to the left side in FIG.

As a result, the second spool 45L on the left side moves to the first spool 44L side so that the oil discharge port 56L and the oil discharge chamber 54L are not in communication with each other, and then the second spool 4L.
After the front end surface of 5L contacts the first spool 44L, the first spool 44L is pushed out to the oil supply / discharge chamber 48L side against the spring force of the compression coil spring 66. As a result, the stepped hole 4
The contact state between the stepped portion 64 of No. 1 and the valve body 65 is released, the oil supply chamber 51L and the oil supply / discharge chamber 48L are brought into communication with each other, and the hydraulic oil from the pressure oil supply passage 50 flows through the supply / discharge oil passage 47L. It is supplied to the cylinder chamber 14L via the. Further, a part of this hydraulic oil is also supplied into the reaction force chamber 46L from the communication path 59, but the hydraulic pressure of the hydraulic oil in this reaction force chamber 46L tends to be delayed by the throttle 60. The hydraulic oil introduced into the reaction force chamber 46L is also supplied to the pressure regulation chamber 70 via the communication passage 68, and the pressure of both end faces of the first spool 44L facing the reaction force chamber 46L and the pressure regulation chamber 70 is received. According to the area difference, a hydraulic reaction force (a force that pushes back the first spool 44 to the spool driver 38 side) corresponding thereto is applied to the first spool 44L. In parallel with this, the second spool 45L has a pressing pin 6 connected to the oil supply / discharge chamber 48L via a pin fitting hole 67.
9, the steering reaction force is applied.

On the other hand, the valve body 65 of the first spool 44R on the opposite side (the right side in FIG. 2) contacts the step portion 64 of the stepped hole 41 by the spring force of the compression coil spring 66, and the oil supply chamber 5
The 1R and the oil supply / discharge chamber 48R remain in the non-communication state. Further, the first spool 44R is attached to the second spool 45R.
Since the pressing force to the side is not generated, the base end portion thereof continues to contact the spool driver 38, and the communication state between the oil discharge port 56R and the oil discharge chamber 54R is continuously maintained.

In this way, as the working oil is supplied into the cylinder chamber 14L of the cylinder portion 13, the cylinder chamber 14L
The hydraulic oil in R is returned from the supply / discharge oil passage 47R to the oil sump 53 through the branch oil passage 55, the oil discharge port 56R, the oil discharge chamber 54R, and the oil discharge passage 52, and the piston 15 together with the rack rod 12 is shown in FIG. The steering assist is generated by being urged to the right in the middle. And
Due to the generation of the steering assist force corresponding to the steering reaction force, the pinion shaft 16 also rotates clockwise in FIG. 2, the relative rotation of the torsion bar spring 21 with respect to the pinion shaft 16 is canceled, and the original neutral state shown in FIG. Return.

When the steering wheel is operated counterclockwise to turn the vehicle counterclockwise, the second spool 45 and the first spool 44 in the left and right valve housings 40 are operated.
However, as the working oil is supplied into the cylinder chamber 14R, the working oil in the cylinder chamber 14L is transferred from the supply / discharge oil passage 47L to the branch oil passage 55 and the discharge oil port 56.
L, the oil drain chamber 54L, and the oil drain passage 52 are returned to the oil sump 53, and the piston 15 together with the rack rod 12 is biased to the left in FIG. Then, due to the generation of the steering assist force corresponding to the steering reaction force, the pinion shaft 16 also rotates counterclockwise in FIG. 2, the relative rotation of the torsion bar spring 21 with respect to the pinion shaft 16 is canceled, and the original neutral position shown in FIG. Return to the state.

That is, the swing reaction ring 34 is generated by the steering reaction force.
When the tip portion of the swing lever 37 of FIG. 2 is displaced along the sliding direction of the spool driver 38, hydraulic oil is supplied to either one of the cylinder chambers 14L and 14R so as to eliminate this displacement, and the pressure of this hydraulic oil is increased. Since the rack rod 12 is forcibly pushed out in the steering direction by this, the steering operation can be performed with a slight steering force. In this case, when the first spool 44 is pushed toward the oil supply / discharge chamber 48 side with the movement of the spool driver 38 and the second spool 45, the reaction force chamber 46.
A hydraulic reaction force in the direction of pushing back the first spool 44 is generated on the second spool 45 side. And the first spool 44
When the sum of the hydraulic reaction force, the reaction force of the compression coil spring 66, and the reaction force of the pressing pin 69 becomes larger than the steering torque that presses, the first spool 44 is pushed back to the second spool 45 side again, and the oil supply is performed. The discharge chamber 48 and the oil supply chamber 51 will be returned to a non-communication state. That is, the pressure oil corresponding to the increase in the steering torque by the driver is supplied to the cylinder chambers 14L and 14R of the cylinder portion 13.

When the steering torque is increased in this way, the pressure of the working oil in the reaction force chamber 46 also rises. However, the pressure of the working oil in the reaction force chamber 46 is set by the relief valve 63. If it becomes above, the relief valve 63 will open at this time and the working oil in the reaction force chamber 46 will be discharged to the oil sump 53 from the oil discharge path 61. Along with this, the hydraulic reaction force of the reaction force chamber 46 that has been loaded on the first spool 44 also becomes constant. Therefore, when the steering torque is further increased, the first spool 44 is increased at a smaller increase rate of the steering torque than before. Can be pushed out to the oil supply / discharge chamber 48 side, and thereafter, the rate of increase in steering assist can be increased.

On the other hand, when the steering torque is reduced from such a state, the oil supply / discharge chamber 48 and the oil supply chamber 51 are kept in a non-communication state, and the hydraulic reaction force of the hydraulic fluid in the pressure adjusting chamber 70 is maintained. The oil drain port 56 is opened / closed with respect to the oil drain chamber 54 in accordance with the balance of the steering torque acting on the second spool 45 with respect to the pressing force of the pressing pin. Then, until the pressure of the hydraulic fluid in the reaction force chamber 46 becomes equal to or lower than the set pressure of the relief valve 63, the oil discharge port 5 is rotated by a slight relative rotation of the torsion bar spring 21.
6 and the oil discharge chamber 54 are in communication with each other, and as a result, the cylinder portion 1
The pressure of the hydraulic oil in the third cylinder chamber 14L, 14R sharply decreases. However, when the pressure of the hydraulic fluid in the reaction force chamber 46 becomes equal to or lower than the set pressure of the relief valve 63, the relief valve 63
Is closed and a hydraulic reaction force corresponding to the steering torque is generated in the pressure adjusting chamber 70. Therefore, after that, when the relative rotation amount of the torsion bar spring 21 becomes larger, the oil drain port 56 and the oil drain chamber 5
As a result of being in communication with No. 4, the reduction rate of the pressure of the hydraulic oil in the cylinder chambers 14L, 14R of the cylinder unit 13 decreases.

That is, as shown in FIG. 4 showing the relationship between the steering torque and the pressure of the hydraulic oil in the oil supply / exhaust passage 47 in the present embodiment, the steering torque is increased or decreased with the relief pressure set in the relief valve 63 as a boundary. It is possible to change the increase / decrease rate of the hydraulic oil pressure with respect to, and particularly to easily perform steering, so-called stationary steering, etc. in a stopped state.

Although the oil pump 49 is driven by the electric motor 72 in the above-described embodiment, a variable displacement pump is adopted as the driving oil pump, and it may be driven by the vehicle engine. good. As the variable displacement pump, a variable displacement vane pump or a plunger pump capable of changing the discharge amount of the hydraulic fluid from almost zero by changing the eccentricity of the cam ring can be used. It is also possible to employ a swash plate type in which the discharge amount of the hydraulic fluid can be changed from almost 0 by changing the angle.

[0043]

According to the pressure control device of the present invention corresponding to claim 1, the fluid supply chamber connected to the hydraulic fluid supply source and supplied with the hydraulic fluid communicates with the fluid supply / drainage chamber connected to the actuator. A reciprocating first spool for switching the state, a spool urging means for urging the first spool so that the liquid supply chamber and the liquid supply / drainage chamber are in a non-communication state, and the liquid supply together with the spool urging means. And a pressure adjusting means for maintaining the hydraulic pressure of the working fluid in the reaction force chamber filled with the working fluid, which resists the movement of the first spool in the direction in which the chamber and the liquid supply / drainage chamber communicate with each other, below a predetermined pressure. , A reciprocating second spool that switches the communication state between the drainage chamber connected to the working fluid discharge path and the supply / drainage chamber, and the supply / drainage chamber according to the hydraulic pressure of the working fluid in the supply / drainage chamber Reaction force generating means for pressing the second spool so as to communicate with the drainage chamber,
Since the supply / drainage chamber and the drainage chamber are in the non-communication state, and the spool operating means capable of operating the second spool and the first spool so that the liquid supply chamber and the supply / drainage chamber communicate with each other are provided.
It is possible to obtain a non-linear operation characteristic having a narrow hysteresis width with a cutoff point both when the operation force increases and when the operation force decreases.

Further, according to the pressure control device of the present invention corresponding to claim 2, since the pressure adjusting chamber for introducing the hydraulic fluid in the reaction force chamber is formed between the second spool and the first spool, the operating force is increased. It is possible to further reduce the rate of decrease of the hydraulic pressure of the hydraulic fluid in the actuator with respect to the rate of decrease of (1), and it is possible to obtain a non-linear operation characteristic with a narrow hysteresis width.

Further, according to the pressure control device of the present invention corresponding to claim 3, the relief valve is used to maintain the reaction force chamber at a predetermined pressure or less, so that the pressure adjusting means is simplified in construction. The cost can be suppressed.

On the other hand, according to the pressure control device of the present invention according to claim 4, the hydraulic pressure control means controls the hydraulic pressure of the hydraulic fluid in the pressure control chamber based on the operating state of the vehicle. It is possible to obtain a good steering feeling according to the traveling speed of the vehicle.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic structure of an embodiment in which a pressure control device according to the present invention is applied to a power steering device of an automobile.

FIG. 2 is a hydraulic circuit diagram in which a portion of the pressure control device in the embodiment shown in FIG. 1 is enlarged along a cross section taken along line II-II in FIG.

FIG. 3 is a hydraulic circuit diagram in which a part of the pressure control device in the embodiment shown in FIGS. 1 and 2 is extracted and enlarged.

FIG. 4 is a graph showing a relationship between a steering torque associated with a steering operation and a pressure of hydraulic oil supplied to a power cylinder.

[Explanation of symbols]

 13 Cylinder part (actuator) 14L, 14R Cylinder chamber 15 Piston 38 Spool driver (spool operating means) 39 Lever receiving part 40 Valve housing 41 Stepped hole 44, 44L, 44R First spool 45 Second spool 46, 46L, 46R Anti Power chamber 48, 48L, 48R Oil supply / discharge chamber (supply / discharge chamber) 49 Oil pump 51, 51L, 51R Oil supply chamber (supply chamber) 54, 54L, 54R Oil discharge chamber (discharge chamber) 63 Relief valve ( Pressure adjusting means) 66 Compression coil spring (spool biasing means) 67 Pin fitting hole 69 Pressing pin (reaction force generating means) 70 Pressure adjusting chamber

Claims (4)

[Claims] 1. A liquid supply chamber to which a hydraulic fluid is supplied by being connected to a hydraulic fluid supply source, a liquid supply / drainage chamber connected to an actuator, and a communication state between the liquid supply / drainage chamber and the liquid supply chamber. A reciprocating first spool that is switched, a spool urging unit that urges the first spool so that the liquid supply chamber and the liquid supply / drainage chamber are not in communication with each other, the liquid supply chamber and the liquid supply chamber A reaction force chamber filled with a working fluid that resists the movement of the first spool in a direction communicating with the drainage chamber, and the hydraulic pressure of the working fluid in the reaction force chamber is maintained below a predetermined pressure. A pressure adjusting means, a drainage chamber connected to the discharge passage of the hydraulic fluid, a reciprocating second spool that switches a communication state between the drainage chamber and the supply / drainage chamber, and an operation in the supply / drainage chamber. According to the liquid pressure of the liquid, the reaction force that presses the second spool so that the supply / drainage chamber and the drainage chamber communicate with each other. The generator and the liquid supply / drainage chamber and the liquid drainage chamber are in a non-communication state, and the second spool and the first spool are operated so that the liquid supply chamber and the liquid supply / drainage chamber communicate with each other. A pressure control device, comprising: 2. The pressure according to claim 1, further comprising a pressure adjusting chamber formed between the second spool and the first spool to guide the hydraulic fluid in the reaction force chamber. Control device. 3. The pressure control device according to claim 1, wherein the pressure adjusting means has a relief valve. 4. The pressure control device according to claim 1, wherein the actuator is a power cylinder of a vehicle power steering device.