JPH09221049A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower the pumping work promptly while a steering device is kept in neutral position and to avoid fluid shortage during a rapid steering operation. SOLUTION: On each of the first branch passage 3 and the second passage 4 communicating with a pair of oil chambers of a power cylinder 5, a first control valve 7 is provided by disposing in series two throttle valves operable in response to steering torque. An orifice 9 is provided on a passage 8 which, between two throttle valves disposed in series, connects the branch passages 3, 4. A second control valve 14 is provided by disposing the throttle valves on each of the first exhaust passage 10 and the second exhaust passage 11 which connect a pair of oil chambers of the power cylinder 5 to a drain passage 12, as the throttle valves changes in throttled amount in response to steering torque. On a hydraulic fluid pressure passage 2, a flow rate control valve 15 is provided which controls hydraulic fluid flow rate in response to load pressure. The second control valve 14 is fully closed after the first control valve 7 is fully closed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering apparatus which is suitable for use in automobiles and the like.

[0002]

2. Description of the Related Art A power steering device for supplying steering oil to an actuator provided in a steering mechanism to obtain a steering assisting force is used in automobiles and the like in order to make steering operation lighter. A proposed power steering device has been proposed.

For example, in Japanese Unexamined Patent Publication No. 6-127398, there are four passages branched from an operating hydraulic passage into which operating oil from a hydraulic pump is branched, the throttle amount of which changes according to the steering torque of a steering shaft. A first control valve and a second control valve arranged so that the throttle valve constitutes a four-sided bridge type circuit are provided, and each throttle valve of the first control valve is a center open type valve, and Of the throttle valves of the second control valve communicating with the oil chamber, the throttle valve arranged on the branch passage side is a center close type valve, and the throttle valve arranged on the drain passage side is a center open type valve. On the other hand, a flow control valve for controlling the amount of hydraulic oil supplied to the first control valve and the second control valve to increase / decrease according to increase / decrease in load pressure is provided in the control hydraulic passage, Each throttle valve Power steering system branch passage side of the throttle valve of the second control valve is set in a relationship begins to close substantially at the same time begin to opening are disclosed.

In this improved power steering system, in the neutral region where the steering torque of the steering shaft is small, the throttle valve on the branch passage side of the second control valve is maintained in the closed state, and the hydraulic oil is supplied to the power cylinder. Is prevented, the rigidity in the neutral range is increased and the feeling of manual steering is improved.

[0005]

However, in the above-mentioned conventional example, when the power cylinder is operated when a rapid steering operation is performed, hydraulic oil is consumed for the movement of the power cylinder, There is a possibility that the pressure on the control valve side, that is, the load pressure may be delayed. That is, if the load pressure does not rise, the flow control valve does not perform control in the direction of increasing the hydraulic oil flow rate, so the flow rate of hydraulic oil supplied to the power cylinder becomes insufficient, and the assisting force obtained by this power steering device is insufficient. Is small and the steering feeling may be deteriorated.

In order to prevent this, it is necessary to supply a sufficient amount of hydraulic oil even when a rapid steering operation is performed. Therefore, at the neutral time when steering assist force is unnecessary. It is necessary to increase the flow rate (lower limit flow rate of the system) supplied to the control valve. Then, the amount of work of the hydraulic pump increases correspondingly, and energy saving cannot be sufficiently achieved.

The present invention has been devised in view of the above-mentioned conventional circumstances, and it is possible to reduce the work of the hydraulic pump as much as possible at the time of neutral steering operation that does not require a steering assist force, thus saving energy. An object of the present invention is to provide a power steering device that can contribute to a stable steering assist force without causing a shortage of the flow rate of hydraulic oil even when a sudden steering operation is performed.

[0008]

SUMMARY OF THE INVENTION Therefore, according to the first aspect of the present invention, in a power steering system for supplying and discharging hydraulic oil to and from a power cylinder connected to a steering mechanism to obtain a steering assisting force, hydraulic oil from a hydraulic pump is used. And a first branch passage and a second branch passage that branch from the operation hydraulic passage and communicate with the pair of oil chambers of the power cylinder, respectively, in the first branch passage and the second branch passage. 2 throttle valves whose throttle amount changes according to the steering torque of the steering shaft are arranged in series, and these 4 throttle valves are 4
Between a first control valve arranged to form a side-bridge circuit and a throttle valve arranged in series with the first control valve,
A connection passage communicating between the first branch passage and the second branch passage, a flow resistance means provided in the connection passage, and a first passage communicating each of a pair of oil chambers of the power cylinder with a drain passage. Discharge passages and second discharge passages, and throttle valves whose throttle amount changes according to the steering torque of the steering shaft are arranged in the first discharge passage and the second discharge passage, respectively.
A second control valve composed of these two throttle valves is provided in the working hydraulic passage so that the working oil amount supplied to the first control valve and the second control valve increases or decreases in accordance with increase or decrease of the load pressure. And a flow control valve for controlling the flow rate of the first control valve, and the throttle valve of the second control valve is fully closed after one of the throttle valves of the first control valve is fully closed.

According to a second aspect of the invention, the flow resistance means of the first aspect is an orifice.

According to the third aspect of the present invention, the flow resistance means of the first aspect is a check valve.

Here, since the flow resistance means provided in the connection passage is to generate a differential pressure before and after the flow resistance means, a check provided with various throttle valves and a check spring having a predetermined spring force. A valve or the like can be adopted, and the check valve in this case functions as a so-called pressure regulating valve.

The first control valve and the second control valve are center open type valves, and in the neutral position of the steering wheel, the first control valve and the second control valve are in the neutral position and are open. . In this case, since the load pressure is zero or extremely small, the flow rate control valve that is sensitive to the load pressure and controls the flow rate controls the working oil flow rate introduced into the working hydraulic passage to the minimum flow rate. The controlled hydraulic oil is returned to the drain passage via the first control valve and the second control valve.

When the steering operation is started from the neutral position of the steering wheel, the first control valve and the second control valve move to the first control valve.
After one of the throttle valves of the control valves is fully closed, the throttle valve of the second control valve is fully closed. That is, either one of the two throttle valves provided in the first branch passage of the first control valve is closed and the other is opened, and either one of the two throttle valves similarly provided in the second branch passage is opened. Either one closes. That is, the first
Of the throttle valves provided in the branch passage and the second branch passage, one of the throttle valves provided on the working hydraulic passage side is closed and the other is opened, and one of the throttle valves provided on the power cylinder side is opened. Close to open the other. Further, one of the throttle valves of the second control valve is closed and the other is opened, and this second control valve operates later than the first control valve. Therefore, at the neutral position of the steering wheel, the working oil that has been returned to the drain passage via the first control valve and the second control valve is throttled on the working hydraulic passage side of the first branch passage or the second branch passage. Flowing through an open throttle valve of the valves, for example, a throttle valve provided in the second branch passage, and flowing into the power cylinder and the second control valve through the flow resistance means and the other throttle valve provided in the first branch passage. become.

When the hydraulic oil passes through the flow resistance means, a pressure difference is generated before and after the flow resistance means, and the pressure on the upstream side of the flow resistance means increases. by this,
A flow rate control valve, which controls the flow rate in response to the load pressure, immediately controls so that the flow rate of the working oil guided to the working hydraulic passage and the second control valve increases.

As a result, a stable steering assist force can be obtained without causing a shortage of the flow rate of the hydraulic oil even when a rapid steering operation is performed.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an explanatory view of a power steering device showing an embodiment of the present invention. In the figure, 1 is a hydraulic pump which is rotationally driven by an internal combustion engine (not shown), 2 is an operating hydraulic passage through which the working fluid from the hydraulic pump 1 is introduced, and this operating hydraulic passage 2 is a first branch passage in the middle thereof. Three
To the second branch passage 4. The first branch passage 3 communicates with one oil chamber 5a of the power cylinder 5, and the second branch passage 4 communicates with the other oil chamber 5b of the power cylinder 5.

In the first branch passage 3, there are two throttle valves 6 whose throttle amount changes according to the steering torque of a steering shaft (not shown).
a and 6b are arranged in series, and in the second branch passage 4, two throttle valves 6c and 6d whose throttle amount changes similarly according to the steering torque of the steering shaft are arranged in series. The throttle valves 6a, 6b, 6c, 6d are arranged so as to form a four-sided bridge type circuit, and form a first control valve 7. In addition, these throttle valves 6a, 6b, 6c, 6d
Consists of a center-open type valve.

Reference numeral 8 denotes the first branch passage 3 and the second branch passage 4
Is a connection passage that communicates with
The first branch passage 3 is provided at an intermediate position between the throttle valve 6a and the throttle valve 6b arranged in series in the branch passage 3 and an intermediate position between the throttle valve 6c and the throttle valve 6d arranged in series in the second branch passage 4.
And the second branch passage 4 are communicated with each other.

The connection passage 8 is provided with an orifice 9 as a flow resistance means for giving a flow resistance to the working oil flowing through the connection passage 8.

Reference numeral 10 is a first discharge passage, 11 is a second discharge passage, and the first discharge passage 10 connects one oil chamber 5a of the power cylinder 5 and a drain passage 12 to each other, and
The discharge passage 11 communicates the other oil chamber 5b of the power cylinder 5 with the drain passage 12.

The first discharge passage 10 is provided with a throttle valve 13a whose throttle amount changes according to the steering torque of the steering shaft (not shown), and the second discharge passage 11 has the same steering torque of the steering shaft. A throttle valve 13b having a throttle amount that changes in accordance with the throttle valve 13b is provided.
The control valve 14 is formed.

Reference numeral 15 is a flow control valve provided in the working hydraulic passage 2, and the flow control valve 15 supplies working oil to the first control valve 7 and the second control valve 14 according to increase and decrease of load pressure. The amount is controlled to increase or decrease.

The flow control valve 15 slidably accommodates the spool valve 17 in a spool valve accommodating hole 16, and the spool valve accommodating hole 16 has a first pressure chamber 18 and a second pressure chamber 1 therein.
9 and the control orifice 2 is provided in the first pressure chamber 18.
The discharge passage 21, the introduction passage 22 and the drain passage 23, which communicate with the working hydraulic passage 2 via 0, are opened, and the pressure of the control hydraulic passage 2 is introduced into the second pressure chamber 19 and the spool valve 17 is provided in the second pressure chamber 19. A control spring 24 that is biased to the side of the first pressure chamber 18 is housed, and a necessary flow rate of hydraulic oil is introduced from the introduction passage 22 to the hydraulic pressure passage 2 via the control orifice 20 while excess oil is supplied to the required flow rate. Drain passage 23 controlled to open and close by movement of the spool valve 17
It is made to reflux.

The spool valve 17 has a bottomed cylindrical outer spool 25 having a through hole at the bottom, a large diameter portion fitted into the inner circumference of the cylindrical portion of the outer spool 25, and a small diameter portion fitted into the through hole. And a bottom portion of the outer spool 25 facing the second pressure chamber 19, and a low pressure is applied between the inner circumference of the cylindrical portion of the outer spool 25 and the outer circumference of the small diameter portion of the inner spool 26. A chamber 27 is formed. Further, the control spring 24 acts on the inner spool 26, and further, the inner spool 26
The inner spool 26 between the outer spool 25 and the outer spool 25.
A spring member 28 that urges the pressure chamber 18 side and urges the outer spool 25 toward the second pressure chamber 19 side is attached. Reference numeral 29 is a pressure guiding passage for guiding the pressure in the working hydraulic passage 2 into the second pressure chamber 19, and 30 is a pressure sensitive orifice provided in the pressure guiding passage 29.

A throttle valve 6a constituting the first control valve 7,
As shown in FIG. 2, 6b, 6c, and 6d are projections 36 formed on the outer periphery of a valve shaft 35 that is integrally rotatable with a steering shaft (not shown) and extending outward in the radial direction, and with respect to the valve shaft 35. A projection 3 formed on the inner circumference of an annular valve body 37 connected to the wheel side so as to be relatively rotatable via a torsion bar (not shown) and extending inward in the radial direction.
It is formed by 8 and. That is, the throttle valve 6a, the circumferential end of the projection 36 and the circumferential end of the projection 38,
6b, 6c and 6d are formed. The throttle valves 13a and 13b constituting the second throttle valve 14 are also formed by a protrusion 39 formed on the outer periphery of the valve shaft 35 and a protrusion 38 formed on the inner periphery of the valve body 37. That is, the throttle valves 13a and 13b are formed by the circumferential end portion of the protrusion 39 and the circumferential end portion of the protrusion 38. Here, the protrusion 3 formed on the valve shaft 35
Of the six and 39, the circumferential dimension of the projection 36 is larger than the circumferential dimension of the projection 39. Therefore,
The protrusions 36 and 39 form respective throttle valves with the circumferential end of the protrusion 38 formed on the inner circumference of the valve body 37, and the valve shaft 35 rotates relative to the valve body 37. At times, the throttle valves 6a, 6d or the throttle valves 6b, 6c constituting the first control valve 7 are fully closed earlier,
After that, the throttle valve 13a or the throttle valve 13b forming the second control valve 9 is fully closed (see FIG. 6).

Further, in the central passage 42 formed in the valve shaft 35, the drain passages 12 opening into the recesses 43 formed between the projections 39 are gathered and communicated with the oil storage tank 44. In FIG. 2, the three first control valves 7
The hydraulic pump 1 and the power cylinder 10 are connected to each of the
Is a single one. Further, FIG. 2 shows a neutral state of the steering wheel, that is, a neutral state of the first control valve 7 and the second control valve 14.

Next, the operation of the power steering device having such a structure will be described.

The hydraulic pump 1 is rotationally driven by an internal combustion engine (not shown) or the like, and the working oil discharged from the hydraulic pump 1 is introduced into the first pressure chamber 18 of the flow control valve 15 via the introduction passage 22. Be led to. The hydraulic oil introduced into the first pressure chamber 18 is generated only when the drainage passage 23 is released by the restricted flow passing through the control orifice 20 and the movement of the spool valve 17 based on the differential pressure across the control orifice 20. However, from the inside of the first pressure chamber 18 to the drain passage 2
It is divided into an excess oil flow that escapes to the suction side of the hydraulic pump 1 and the oil storage tank 44 through the oil flow path 3. As a result, the required amount of hydraulic oil is guided from the discharge passage 21 to the hydraulic pressure passage 2 and the branch passages 3 and 4 under the restriction of the control orifice 20.

Here, in the flow control valve 15, the spool valve 17 is composed of an outer spool 25 and an inner spool 26, and the inner spool 26 is provided between the outer spool 25 and the inner spool 26. Urged to 18,
A spring member 28 for urging the outer spool 26 toward the second pressure chamber 19 is attached, and the control spring 24 acts on the inner spool 26. Therefore, the first pressure chamber 1
8 and the second pressure chamber 19 are low in pressure, the outer spool 25 is moved to the second position by the spring member 28 attached thereto.
It is in a position biased to the pressure chamber 19 side, and the spool valve 17
Compresses the control spring 24 to a predetermined length and controls the flow rate by the differential pressure across the control orifice 20 and the spring force of the control spring 24 (see FIG. 1). Also, the first
When the pressures in the pressure chamber 18 and the second pressure chamber 19 are high, the outer spool 25 moves toward the first pressure chamber 18 side against the spring force of the spring member 28 due to the pressure in the second pressure chamber 19. Reach a predetermined position. This allows the outer spool 25
Moves, the relative position between the spool valve 17 and the drain passage 23 changes, so that the spool valve 17 further compresses the control spring 24, and the control spring 2
It moves by the balance with the spring force of No. 4 plus the spring force of the spring member 28, and the spool valve 17 controls the flow rate at that position (see FIG. 3).

That is, when the pressure in the first pressure chamber 18 is low (that is, when the internal pressure of the hydraulic pump 1 is low), the outer spool 25 is moved by the spring member 28 into the second pressure chamber 19.
It is in the position biased to the side, and in this state the inner spool 2
The spool valve 17 is configured integrally with the valve 6. Therefore, the spool valve 17 moves based on the spring force of the control spring 24 and the differential pressure across the control orifice 20,
The flow rate passing through the control orifice 20 is the flow rate indicated by AB in FIG.

Next, when the pressure in the first pressure chamber 18 rises, the flow rate passing through the control orifice 20 also increases and the pressure in the working hydraulic passage 2 also increases. Therefore, the pressure in the second pressure chamber 19 to which the pressure in the working hydraulic passage 2 is guided increases. When the pressure in the second pressure chamber 19 increases and exceeds the spring force of the spring member 28, the outer spool 25 moves to the first pressure until the spring force of the spring member 28 balances the pressure in the second pressure chamber 19. By moving to the chamber 18 side, the opening area of the drain passage 23 is reduced. If the opening area of the drain passage 23 becomes smaller, the differential pressure across the control orifice 20 becomes larger accordingly, so that the spool valve 17 resists the spring force of the control spring 24 in order to keep this differential pressure constant. It moves to the pressure chamber 19 side, and the flow rate is controlled at a position where the differential pressure across the control orifice 20 and the spring force of the spring member 28 and the control spring 24 are balanced. As a result, the flow rate passing through the control orifice 20 becomes the flow rate indicated by B-C in FIG.

When the pressures in the first pressure chamber 18 and the second pressure chamber 19 reach a predetermined pressure, the outer spool 25 compresses the spring member 28 most and comes closest to the first pressure chamber 18 side. In this state, the spool valve 17 has the control spring 24
Also, the flow rate is controlled in response to the differential pressure across the control orifice 20, and the flow rate passing through the control orifice 20 is controlled to the flow rate indicated by CD in FIG. This flow rate is the maximum flow rate supplied to the hydraulic pressure passage 2, and is normally controlled to this flow rate when the load pressure is high, that is, when the first control valve 7 and the second control valve 14 are in the operating state. become.

On the other hand, the neutral position of the steering wheel, that is, the first position
When the control valve 7 and the second control valve 14 are in the neutral position, the operation for guiding to the first control valve 7 and the second control valve 14 is performed by the center open type throttle valve 6 that constitutes the first control valve 7.
a, 6b, 6c, 6d and the second control valves 13a, 13b flow back to the drain passage 12, and the working pressure of the working hydraulic passage 2 drops, so the pressure of the second pressure chamber 19 also drops. Therefore, the spool valve 17 moves toward the second pressure chamber 19 side against the spring force of the control spring 24 in the second pressure chamber 19 in order to keep the differential pressure across the control orifice 20 constant, and the drain passage 23 Increase the opening area. As a result, most of the hydraulic oil introduced into the first pressure chamber 18 from the introduction passage 22 flows into the drain passage 23, the internal pressure (discharge pressure) of the hydraulic pump 1 decreases, and the work of the pump is reduced. Reduced.

At the same time, the first control valve 7 and the second control valve
When the pressure in the working hydraulic passage 2 decreases and the pressure in the second pressure chamber 19 decreases when the control valve 9 is in the non-operating state, the outer spool 25 that receives the pressure in the second pressure chamber 19 is the outer spool. The spring force of the spring member 28 attached to 25 moves to the second pressure chamber 19 side.

Therefore, the inner and outer double spools 25, 2
The spool valve 17 composed of
When the differential pressure between 0 and 0, that is, the pressure in the first pressure chamber 18 and the pressure in the second pressure chamber 19 are in a position where the force obtained by adding the spring force of the control spring 24 is balanced, the outer spool 25 is set to the second pressure. The opening area of the drain passage 23 opened by the spool valve 17 is further increased by the amount moved to the chamber 19 side.

As a result, the hydraulic oil supplied to the first pressure chamber 18 flows through the drain passage 23 having an increased opening area when the first control valve 7 and the second control valve 14 are inactive. Will be returned to the suction side and the oil storage tank 44. Therefore, in the hydraulic pump 1 that discharges the hydraulic oil to the first pressure chamber 18 through the introduction passage 22, the discharge pressure is reduced, the work amount is reduced, and energy saving is advantageously achieved.

Next, when the steering operation is started from the neutral position of the steering wheel, if the ground resistance of the wheel (not shown) is large,
Between the valve shaft 35, which is integrally rotatable with the steering shaft to which steering force is input from a steering wheel (not shown), and the valve body 37, which receives the ground resistance of the wheels, a relative rotation is provided via a torsion bar (not shown). Movement occurs. At this time, the first control valve 7 and the second control valve 9 are the throttle valves 13a of the second control valve 14 after the throttle valves 6a, 6d of the first control valve 7 or the throttle valves 6b, 6c are fully closed. , Or 13b is fully closed. That is, one of the two throttle valves 6a and 6b provided in the first branch passage 3 of the first control valve 7 is closed and the other is opened, and the two throttle valves 6c similarly provided in the second branch passage 4 are provided. , 6d is opened and the other is closed. That is, of the throttle valves 6a, 6b, 6c, 6d provided in the first branch passage 3 and the second branch passage 4,
One of the throttle valves 6a and 6c provided on the operating hydraulic passage 2 side is closed and the other is opened, and one of the throttle valves 6b and 6d provided on the power cylinder 5 side is closed and the other is opened. . Further, the throttle valves 13a, 13b of the second control valve 14
One of the two is closed and the other is opened, and the second control valve 14 operates later than the first control valve 7. Therefore, in the neutral position of the steering wheel,
Drain passage 1 via first control valve 7 and second control valve 14
The hydraulic oil that has been recirculated to the second branch passage 2 is the throttle valve 6a provided on the working hydraulic passage side 2 of the first branch passage 3 or the second branch passage 4,
6c flows through an open throttle valve, for example, a throttle valve 6c provided in the second branch passage 4, and through the orifice 9 and the other throttle valve 6b provided in the first branch passage 3, the power cylinder 5 and the second control valve. It will flow into 14.

When the working oil passes through the orifice 9 serving as the flow resistance means, a pressure difference is generated before and after the orifice 9, and the pressure on the upstream side of the orifice 9 becomes high (see FIG. 7). As a result, the flow rate control valve 15, which controls the flow rate in response to the load pressure, immediately controls so that the flow rate of the hydraulic oil guided to the hydraulic pressure passage 2 and the first control valve 7 increases.

That is, as shown in FIG. 5, when the valve shaft 35 rotates relative to the valve body 37 in the clockwise direction shown by the arrow N from the neutral position of the steering wheel shown in FIG. Throttle valves 6b and 6c of the control valve 7
Enlarges the opening and closes the throttle valves 6a and 6d.
The flow to the drain passage 12 via d is blocked. Further, the throttle valve 8a of the second control valve 14 starts to close, and the throttle valve 8b enlarges the opening. As a result, the hydraulic oil introduced from the hydraulic oil pressure passage 2 is introduced into the oil chamber 5a of the power cylinder 5 via the throttle valve 6c and the orifice 9, while the hydraulic oil in the oil chamber 5b of the power cylinder 10 is discharged. It will be discharged to the drain passage 12 via the throttle valve 13b. As a result, the power cylinder 5 operates in a predetermined direction, and a steering link connected to the power cylinder 5 is given a supporting force in a predetermined direction.

On the other hand, when the steering wheel (not shown) is steered in the opposite direction from the neutral position and the valve shaft 35 rotates relative to the valve body 37 counterclockwise, first, The throttle valves 6a and 6d of the first control valve 7 have large openings, the throttle valves 6b and 6c are closed, and the flow to the drain passage 12 via the throttle valve 6b is blocked. Further, the throttle valve 13b of the second control valve 14 starts to close, and the throttle valve 13a enlarges the opening. As a result, the hydraulic oil introduced from the hydraulic oil pressure passage 2 is introduced into the oil chamber 5b of the power cylinder 5 via the throttle valve 6a and the orifice 9 while the oil chamber 5a of the power cylinder 5 is introduced.
The hydraulic oil therein is discharged to the drain passage 12 via the throttle 13a. As a result, the power cylinder 10 operates in a predetermined direction, and a steering link connected to the power cylinder 10 is given a supporting force in a predetermined direction.

As a result, even when a rapid steering operation is performed, the flow control valve 15 immediately increases the flow rate of the hydraulic oil, and the increased hydraulic oil causes the throttle valves 6a, 6 of the first control valve 7 to increase.
Since the oil flows into the oil chamber 5a or the oil chamber 5b of the power cylinder 5 through d or the throttle valves 6b and 6c, the flow rate of the hydraulic oil does not become insufficient, and a stable steering assisting force can be obtained.

FIG. 8 is a drawing showing another embodiment of the present invention. The difference from this embodiment is that instead of the orifice 9 provided in the connection passage 8 in the embodiment as the flow resistance means, a check valve 45 having a bidirectional check function is provided in the connection passage 8. That is the point. As shown in FIG. 9, the check valve 45 has a valve hole 4 through which the connection passage 8 extends axially in the valve housing 46.
7, a spool valve 48 is slidably inserted into the valve hole 47, and the valve hole 47 is inserted into the first valve chamber 49 and the second valve chamber 5.
A check spring 51 for urging the spool valve 48 is housed in the first valve chamber 49 and the second valve chamber 50 while being divided into 0. An appropriate spring force is selected as the spring force of the check spring 51 in order to set the differential pressure across the check valve 45 to a desired value.

Further, the valve hole 4 is provided in the valve housing 46.
Detour passages 52, 53 are formed across the substantially central portion of 7, and connect both ends of the connection passage 8 with each other. These bypass passages 5
At the neutral position of the spool valve 48, the reference numerals 2 and 53 are closed by the body of the spool valve 48 to prevent mutual communication. Furthermore,
Circumferential grooves 54 and 55 are formed at predetermined positions on the outer circumference of the body on both ends of the spool valve 48. Since the other configurations are substantially the same as those in the above-mentioned embodiment, the same reference numerals are given to the substantially same components as those in the above-mentioned embodiment, and the duplicated description will be omitted.

According to this structure, when the throttle valves 6b and 6c of the throttle valves of the first control valve 7 have large openings and the throttle valves 6a and 6d are closed, they are introduced from the working hydraulic passage 2. The hydraulic oil that flows into the check valve 45 is introduced from the throttle valve 6c. Check valve 4 from the connection passage 8
The pressure of the hydraulic oil introduced into the second valve chamber 50 of No. 5 is increased, and this pressure causes the spool valve 48 to move to the first valve chamber 49.
It moves toward the first valve chamber 49 side against the spring force of the inner check spring 51, and reaches the position shown in FIG. As a result, the bypass passages 52 and 53, which are blocked from communicating with each other at the body of the spool valve 48, communicate with each other via the circumferential groove 55. As a result, the hydraulic oil introduced from the hydraulic oil pressure passage 2 is introduced into the oil chamber 5a of the power cylinder 5 via the throttle valve 6c and the check valve 45, while the hydraulic oil in the oil chamber 5b of the power cylinder 5 is introduced. Is discharged to the drain passage 12 through the throttle 13b. As a result, the power cylinder 10 operates in a predetermined direction, and a steering link connected to the power cylinder 10 is given a supporting force in a predetermined direction. When the steering operation is performed in the opposite direction, the oil chamber 5 of the power cylinder 5
The pressure of b is increased, and the assisting force in the opposite direction is given.

Therefore, in addition to the effect similar to that described in the above-mentioned embodiment, the check valve 45 not only provides a flow resistance to the working fluid flowing through the connection passage 8 but also functions as a so-called pressure regulating valve. As a result, it is possible to suppress the pressure increase of the working oil pressure in the working oil pressure passage 2. That is, when the hydraulic oil flows through the check valve 45 as the flow resistance means, the differential pressure generated before and after the check valve 45 can be set to a predetermined value by the spring force of the check spring 51, so that the hydraulic oil passes through the check valve 45. Even if the flow rate to be increased increases, the differential pressure is not increased more than necessary, and it is possible to advantageously prevent the temperature rise of the hydraulic oil and the accompanying deterioration thereof.

Although the embodiment has been described with reference to the drawings, the specific configuration is not limited to this embodiment, and can be changed without departing from the spirit of the invention.
For example, the connection passage 8 may be configured by two parallel passages, and each of the two passages may be provided with a check valve that allows only one-way flow.

[0048]

As described above in detail, according to the present invention, the work load of the hydraulic pump can be reduced as much as possible at the time of neutral operation of the steering operation where the steering assisting force is unnecessary, thus saving energy. It is possible to obtain a power steering device that can contribute to an advantage and that can provide a stable steering assist force without causing a shortage of the flow rate of hydraulic fluid even when a sudden steering operation is performed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a power steering device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a first control valve and a second control valve.

FIG. 3 is an explanatory diagram showing an operating state of the flow rate control valve when the load pressure is high.

FIG. 4 is a flow rate control characteristic diagram of a flow rate control valve.

FIG. 5 is an explanatory diagram showing a state in which the first control valve and the second control valve have transitioned from a neutral state to an operating state.

FIG. 6 is a diagram showing a relationship between an operating angle of a control valve and an opening area of a throttle valve.

FIG. 7 is a diagram showing a relationship between an operating angle of a control valve and pressures before and after an orifice provided in a connection passage.

FIG. 8 is an explanatory diagram showing another embodiment of the present invention.

9 is an explanatory diagram showing the configuration of the check valve shown in FIG.

FIG. 10 is an explanatory diagram showing an operating state of the check valve shown in FIG. 9.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 Operating hydraulic passage 3 1st branch passage 4 2nd branch passage 5 Power cylinder 7 1st control valve 8 Connection passage 9 Orifice (flow resistance means) 10 1st discharge passage 11 2nd discharge passage 14 2nd control valve 15 Flow control valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadaharu Yokota 1370 Onna, Atsugi City, Kanagawa Prefecture Unisia Jecs Co., Ltd.

Claims (3)

[Claims] 1. A power steering device for supplying and discharging hydraulic oil to and from a power cylinder connected to a steering mechanism to obtain a steering assisting force, and an operating hydraulic passage to which hydraulic oil from a hydraulic pump is introduced and an operating hydraulic passage. A first branch passage and a second branch passage that branch and communicate with the pair of oil chambers of the power cylinder, respectively, and throttle in each of the first branch passage and the second branch passage according to the steering torque of the steering shaft. A first control valve in which two throttle valves of varying amounts are arranged in series, and these four throttle valves are arranged so as to form a four-sided bridge type circuit, and a throttle in which the first control valve is arranged in series. A connection passage communicating between the valves and between the first branch passage and the second branch passage, and a flow resistance means provided in the connection passage,
A first discharge passage and a second discharge passage communicating with each of the pair of oil chambers of the power cylinder to a drain passage, and in each of the first discharge passage and the second discharge passage, depending on a steering torque of a steering shaft. A throttle valve having a variable throttle amount is arranged, and a second control valve constituted by these two throttle valves is provided in the working hydraulic passage, and the first control valve and the second control valve are provided in accordance with increase and decrease of load pressure. A flow rate control valve for controlling the amount of hydraulic oil supplied to the control valve to increase or decrease, and after any throttle valve of the first control valve is fully closed, the throttle valve of the second control valve is fully closed. Power steering device characterized by being closed 2. The power steering device according to claim 1, wherein the flow resistance means provided in the connection passage is an orifice. 3. The power steering device according to claim 1, wherein the flow resistance means provided in the connection passage is a check valve.