JPH04118370A - Hydraulic driver for rear-wheel steering system - Google Patents

Abstract

PURPOSE:To control operation of a steering shaft without enlarging the rating of a solenoid by installing two pilot pressure generators, exciting each of their solenoids and generating each pressure (pilot pressure) in a fixed throttle, through which selecting a spool valve. CONSTITUTION:A rear-wheel steering system is provided with a steering shaft 80 being shifted by hydraulic pressure being added to either of cylinder chambers 94, 95 and steering rear wheels, and pressure oil to be fed to these cylinder chamber 94, 95 is selected by a spool valve mechanism inclusive of a spool 60. In this case, there are provided a first pilot pressure generator comprising a first solenoid 20 driving a first rod member 23 in the axial direction, and a second pilot pressure generator comprising a second solenoid 30 driving a second rod member 23 in the axial direction, respectively. One side of these solenoids 20, 30 is excited, driving these rod members 23, 33, and two fixed throttles 42, 52 is made to generate pressure, thereby adding pilot pressure to both third and fourth cylinder chambers 72, 82, thus the spool 60 is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a hydraulic drive device that supplies pressure oil to a rear wheel steering device for steering rear wheels in a four-wheel steering device to drive the same.

(Prior Art and Its Issues) When a Φhydraulic drive device supplies pressure oil to a rear wheel steering device to drive it, there is a system in which the movement of the steering shaft is controlled by a spool valve built into the hydraulic drive device. There is something.

This spool valve moves in a predetermined manner based on the balance between the suction force of a solenoid installed in the hydraulic drive device and the biasing force of a centering spring that keeps the spool in a neutral position. Controls the movement of the steered shaft by controlling the supply of pressure oil.

However, this type of hydraulic drive device has the following problems.

First, it is not possible to increase the rating of a solenoid due to reasons such as the limited space available for arranging it and the fact that it generates a considerable amount of heat during operation. Therefore, the operating force of the spool is small and the operation of the spool valve becomes unstable.

Second, a characteristic adjustment mechanism is required to adjust the variations in the suction force of the solenoid and the biasing force of the centering spring, which increases the number of parts and complicates the overall structure.

The present invention solves the above problems in the conventional example, namely, provides a hydraulic drive device for a rear wheel steering device that can control the operation of a steered shaft by a solenoid without increasing the rating of the solenoid. It was made for the purpose of providing.

(Means and effects for solving the problem) In order to achieve the above object, in the present invention, (1) the first and second cylinder chambers 94,95 and the liquid added to either of the two cylinder chambers a rear wheel steering device having a steering shaft 80 that is moved in the axial direction by pressure to steer the rear wheels; and (2) a first cylinder chamber that communicates with the hydraulic pressure supply path 152 or recovery path 154 and the first cylinder chamber. passage 97 and hydraulic supply passage 1
52 or the recovery path 154 and a second passage 98 that communicates with the second cylinder chamber, and a third cylinder chamber 72 and a fourth cylinder chamber.
a cylinder chamber 82, a spool 60 that moves in the axial direction by hydraulic pressure applied to the third or fourth cylinder chamber to close or open the first or second passage, and the spool is attached in one direction. (3) a spool valve mechanism including a first biasing member 73 that biases the body and a second biasing member 83 that biases in the other direction; (3) a fifth cylinder 24 connected to a hydraulic power source and the third A sixth cylinder chamber 25 communicated with the cylinder chamber, and a first cylinder chamber 25 provided between the sixth cylinder chamber and the hydraulic pressure source.
A first rod member 23 that moves in the axial direction within the fifth or sixth cylinder chamber, and a first solenoid 20 that drives the first rod member in the axial direction. (4) a seventh cylinder 34 (not shown) communicated with a hydraulic power source and an eighth cylinder chamber 35 communicated with the fourth cylinder chamber; a second fixed throttle 52 provided between the cylinder chamber and the hydraulic pressure source; a second rod member 33 that moves in the axial direction within the seventh or eighth cylinder chamber; and a second pilot pressure generating device including a second solenoid 30 driven in the axial direction.

Therefore, one of the second solenoids is energized to drive the first or second rod member to generate pressure in the first or second fixed throttle, and The spool valve is switched by applying pilot pressure from the eighth cylinder chamber to the third or fourth cylinder chamber.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In the accompanying drawing showing the hydraulic drive device 10, a spool 60 and a steering shaft 80 are arranged parallel to each other in the middle part in the height direction of the housing 12, and a pair of mutually parallel solenoids 20 and 30 are arranged above the spool. A solenoid 100 is arranged in a direction perpendicular to the steering shaft 8.
It is placed parallel to 0. The steering shaft 80 is connected to steering rods (not shown) at both ends thereof, and its axial movement steers the rear wheels to the left or right. The solenoids 20, 30 are for controlling the operation of the spool 60, the spool 60 is for controlling the operation of the steered shaft 80, and the solenoid 100 is for so-called fail-safe purposes. These will be explained in detail later.

First, the pressure oil supply device 150 that supplies pressure oil to the hydraulic drive device 10 will be described. This pressure oil supply device includes a pressure oil supply path 152 and a recovery path 154, a pump 156 disposed on the supply path, a check valve 158, and an accumulator 160.
, an oil pressure sensor 162, an unload valve 164 disposed between the supply path and the recovery path, and the like.

A bin rod 23.33 is located within a chamber 21.31 formed above the housing 12 and adjacent to the solenoid 20.30.
is arranged to be movable up and down, and is always kept at a neutral position by springs 22, 32 (32 not shown), but is drawn upward when the solenoid is energized. Bin rod 23.
Chambers 24, 34 (34 is not shown) and 25, 35 are formed on both sides of the upper and lower sides of 33. Passages 41 and 51 branched from the passage 14 formed in the housing 12 and communicating with the supply pipe 152 communicate with the chamber 25.35, respectively, and a fixed throttle 42.52 is formed at the connection between the passage and the chamber. There is. Channels 43.53, which also branch off from the channel 14, each communicate with the chambers 21.31. Solenoid 20.
30, chamber 24.34, chamber 25.35, bin rod 23.
33, variable throttle 28, 38, etc., constitute a first or second pilot pressure generating device.

Further, a passage 44.54 branched from the passage 16 formed in the housing 12 and communicating with the recovery pipe 154 is connected to the chamber 27.3.
7 and communicates with the chamber 25.3 through a variable throttle 28.38.
5 can be communicated with.

A chamber 61 formed in the left-right direction in the middle part of the housing 12
Inside, the spool 60 is arranged so as to be movable in the left and right direction. Chambers 72 and 82 on each side of the spool 60
is formed, with which the chamber 25.35 communicates.

The spool 60 has three large diameter sections 63.64 and 65 and is biased inwardly from both sides by springs 73.83. The amount of movement of the spool 60 is measured by a stroke sensor 69 connected thereto. The spool 60 including the large diameter portion 63 and the entrances of the passages 97 and the like constitute a sprue valve.

The passage 14 communicates with the longitudinally intermediate portion of the chamber 61 in the annular boat 66, and the passage 16 communicates with both sides of the boat 67, 68, respectively.

Further below the housing 12, a large hollow portion extending in the left-right direction is formed, and the steering shaft 80 is inserted into this hollow portion. The hollow part has two chambers 91 and 92 having different inner diameters, and the left end part 77 and the middle part 78 of the steering shaft are opposed to these.

A rack portion 87 that meshes with the output shaft 130 of a steering shaft position sensor (not shown) is formed at the right end of the steered shaft 80, and a flange portion 84 with a seal is formed at the intermediate portion 78 to close the intermediate chamber. 92 is divided into two cylinder chambers 94 and 95. Passages 97,98 extending from chamber 61 communicate with chambers 94,95, respectively. A holder 101 is placed in the chamber 92.
is fitted and fixed, and the chamber 6 is inserted into the chamber 102 formed therein.
A passage 103 extending from 6 is in communication.

An inner cylinder 116 is fitted inside the chamber 91 in contact with the holder 101, and a pair of annular portions 122 are provided at the left end 77 of the steering shaft.
．． 123 are formed at a certain distance. A pair of spring retainers 124 and 125 are movably attached to the left end portion 77 between both annular portions, and are biased in directions away from each other by a compression spring 126 interposed between both spring retainers. These annular portions, spring holders, springs, etc. constitute a centering mechanism that maintains the steered shaft at a neutral position. An outer cover 127 of one of the spring holders 124 is screwed onto the left end of the housing 12 . Steering shaft 80, cylinder chamber 94
．． 95, the centering mechanism and the like constitute a rear wheel steering device.

A passage 111 extending from the boat 63 communicates with an annular space 112 between both spring holders. In addition, the above chamber 10
2 communicates with a chamber 115 outside the other spring retainer 124 via a passage 114 formed in the center of the steered shaft 80.

A fail-safe control member 135 is disposed in a hollow portion formed at the bottom of the housing 12 and coupled to the output shaft of the solenoid 100. The control member 135 has a generally cylindrical shape and includes three holes 136 extending in the circumferential direction.
．． 137 and 138 are axially spaced apart so that two seals 139, 140 and 141 remain. Passages 107, 108 extend downwardly from said chambers 94, 95 and open into the hollows in the boats 141, 142, and passages 106 extending from the chambers 102 open into the boats 143. A passage 145 extending from the annular space 112 communicates with the hole 144 at the left end. The control member 135 is moved to the right by the solenoid 100 which is in an energized state when the device is normal, and is moved to the left by the biasing force of the spring 146 when the solenoid is turned off when an abnormality occurs.

Next, the operation of this embodiment will be explained.

When the solenoids 2o and 30 are not energized, the bin rods 23 and 33 are moved downward by the biasing force of the spring 22, etc., and this movement causes the variable aperture 28. 38 are closed. In this state, the pressure oil of the supply device 150 is supplied from the supply path 152 into the drive device 10, but does not flow, and the rod bin 23.
The upper and lower chambers 21.25 of the spool 33, the chamber 31.35, and the chambers 72.82 at both ends of the spool 60 are all at the same pressure. Therefore, the spool 60 is in a neutral position where the biasing forces of the pair of springs 73.83 are balanced, and the large diameter portions 63.64 and 65 are opposed to the boats 66.67 and 68, respectively.

Next, when only one solenoid 2o is energized, the rod pin 23 moves upward, the variable throttle 28 opens, and the chamber 25
The high pressure oil inside flows into the chamber 27. Due to this flow, a pressure P1 smaller than the pressure P is generated in the fixed throttle 4I, and the same pressure (P2) is generated in the variable throttle 28.

Here, there is no throttle in the chamber 24 (the high pressure P is applied as it is, so the rod bin 23 has a pressure P of the fixed throttle 41).
1 and the cross-sectional area Sl of the rod pin 23 (PlxSl)
, the sum of the suction force F of the solenoid 20 (7), the product of the high pressure P in the chamber 24 and the cross-sectional area S1 of the rod bin 23 (PxSl
) maintain a state of equilibrium.

Here, since the pressure P and the cross-sectional area S1 are constants, the pilot pressure P1 is determined by the suction force F of the rod bin 23 generated by the current of the solenoid 20.

The pressure P1 of the fixed throttle 42 is applied to the chamber 72, but since the chamber 82 on the opposite side is at a high pressure P, the spool is at a high pressure P1.
The pressure difference between and the pilot pressure P1 and the cross-sectional area s of the spool
2 (P-PL) x S2, and stops at a position where the driving force due to the pressure difference balances the biasing force of the spring 73. As a result, the spool valve 148 formed by the large diameter portion 64 and the like and the boat 66 is switched, and the steered shaft 8o can be driven. That is, spool 6
When the large diameter portion 64 of 0 is removed from the boat 66 and comes to a position where it closes the entrance of the passage 97, pressure oil is supplied from the passage 14 to the chamber 95 through the passage 98, and the steering shaft 80 is moved to the left.

Even in this state, pressure oil is supplied from the passage 14 to the chamber 102 via the passage 103 and further to the chamber 115 via the passage 114. In this way, a high pressure is supplied to the annular spaces 102, 115 on both sides of the spring holders 124, 125. Since the driving force based on this pressure difference is greater than the biasing force of the spring 126, the spring 116 is compressed and both spring retainers 124.
125 move toward each other, and the annular portion 122.1
Stay away from 23. Therefore, the spring presser does not hinder the movement of the steered shaft 80.

On the other hand, when only the other solenoid 30 is energized, the variable throttle 38 opens, the spool 60 moves to the right, pressure oil is supplied to the cylinder chamber 94, and the steered shaft 80
moves to the right. At this time, the spring 126 does not hinder the movement of the steered shaft, as in the case described above.

The above is a case where the hydraulic oil drive device is operating normally. Next, a case where an abnormality occurs in the pressure oil drive device will be described. The abnormality is a drop in pressure of pressure oil, spool 6
These abnormalities are detected by a sensor (not shown) having the sensor 162, the sensor 69, or the output shaft 130, respectively.

The pressure in the cylinder chambers 94,95 is guided through passages 107, 108 to the hollow space in which the control member 135 connected to the solenoid 100 is accommodated, and the pressure in the cylinder chambers 94, 95 on both sides of the centering mechanism is conducted through the passages 106. High pressure within 115 is being channeled. In the normal state of the device, the control member 135 of the solenoid 100 is in the advanced position to the right, and the boats 141, 142 and 143 are in the closed part 139.
．． 140 and 14]. Therefore,
The pressure oil in each passage 106, 107 and 108 is separated from each other, and the steering shaft 80 is moved to the left or right by the pressure applied to the chamber 94 or 95.

However, when an abnormality occurs, the solenoid 100 is demagnetized,
The control member 135 moves to the left by the biasing force of the spring 146,
As a result, the boats 141, 142 and 143 open simultaneously, and the pressure becomes the same momentarily. As a result, the chambers 94 and 95 have the same pressure, so the steering shaft 80 does not move in the axial direction.At the same time, the chambers 102 and 115 and the annular space 112 have the same pressure, and the spring Presser foot 124.125
are moved away from each other by the spring 126 and come into contact with the annular portions 122 and 123, thereby centering the steered shaft 80.

(Effects of the Invention) As described above, according to the present invention, a pilot pressure proportional to the magnitude of the current value of the solenoid can be generated in the hydraulic oil drive device that drives the rear wheel steering device. I can do it. This pilot pressure is determined by the cross-sectional area and suction force of the solenoid's rod bin, and is not affected by the biasing force of the centering spring that keeps the spool in the neutral position, so that even if the biasing force varies, the drive device has stable characteristics. can get.

In addition, since the operating force of the spool is large, it is possible to stably switch the spool valve and increase the driving force of the steered shaft without increasing the rating of the solenoid. The effect is that it can effectively deal with the situation.

[Brief explanation of drawings]

The accompanying drawing is a front sectional view showing one embodiment of the present invention. [Explanation of symbols of main parts] 20.30.100: Solenoid 23.33: Rod bin 24.25.34.35: Chamber 28.38: Variable throttle 60 Nisbourg 63.64.65: Large diameter section 69: Stroke sensor 97.98: Passage 80: Steering shaft 94.95 Niji cylinder chamber 122.123: Annular portion 124.125: Spring retainer 126: Spring 135: Control member 162: Oil pressure sensor

Claims (1)

[Scope of Claims] A rear wheel steering device having first and second cylinder chambers and a steering shaft that is moved in the axial direction by hydraulic pressure applied to either of the cylinder chambers and steers the rear wheels. A first passage that communicates between the hydraulic pressure supply passage or recovery passage and the first cylinder chamber; a second passage that communicates the hydraulic pressure supply passage or recovery passage and the second cylinder chamber; and a third passage. a cylinder chamber, a fourth cylinder chamber, a spool that moves in the axial direction by hydraulic pressure applied to the third or fourth cylinder chamber to close or open the first or second passage; a spool valve mechanism including a first biasing member that biases in one direction and a second biasing member that biases in the other direction; a fifth cylinder that communicates with a hydraulic power source and the third cylinder chamber; a first fixed throttle provided between the sixth cylinder chamber and the hydraulic power source;
A first pilot pressure generating device including a first rod member that moves in the axial direction within the fifth or sixth cylinder chamber, and a first solenoid that drives the first rod member in the axial direction. , a seventh cylinder communicating with a hydraulic power source, an eighth cylinder chamber communicating with the fourth cylinder chamber, and a second fixed throttle provided between the eighth cylinder chamber and the hydraulic power source. and,
a second pilot pressure generator including a second rod member that moves in the seventh or eighth cylinder chamber in the axial direction; and a second solenoid that drives the second rod member in the axial direction; , energizing one of the first or second solenoid and energizing the first solenoid.
or driving a second rod member to generate pressure in the first or second fixed throttle to apply pilot pressure from the sixth or eighth cylinder chamber to the third or fourth cylinder chamber; A hydraulic drive device for a rear wheel steering device, characterized in that the spool valve is switched.