JPH09226610A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power loss of a pump by controlling a cam ring in relation to the negative pressure of an actuator when steering assisting force is required so that the discharge amount is increased or decreased, depending on the steering assisting force. SOLUTION: When steering is not operated, a variable capacity pump 1 remains stopped. When the rotating number of the pump 1 is increased in such a stopped state, operating oil passes through a control orifice 5 to cause differential pressure between the time before and the time after. The operating oil on the upper stream side of the control orifice 5 is guided to the second control oil room 24 in a control device 21 and the operating oil on the downstream side is guided to the first control oil room 23 via the first orifice 35 to energize a cam ring 8 to the direction of increasing the discharge amount of the pump. In such a state, when steering is operated and an actuator 4 shows steering assisting force, the pressure of the operating oil on the downstream side of the control orifice 5 is increased so that the cam ring 8 is oscillated around a pivotally supporting pin 11 with the pressure of the operating oil reduced by the first orifice 35 to increase the discharge amount of the pump 1.

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, Japanese Patent Application Laid-Open No. 59-58186 discloses a power steering device equipped with a variable displacement pump whose discharge flow rate can be changed according to load pressure.
That is, the first working chamber and the second working chamber are arranged to face each other on both sides of the cam ring that accommodates the rotor in which the plurality of vanes are mounted so as to be retractable in the substantially radial direction, and the first working chamber and the second working chamber are opposed to each other. Communicate with each other through a fixed throttle and a variable throttle that is arranged in parallel with the fixed throttle and that responds to the load pressure, and guides the discharge oil of the pump to the first working chamber while the fixed throttle is provided to the second working chamber. Disclosed is a power steering device in which the hydraulic oil after passing through the valve is guided to communicate with the actuator of the power steering device, and further a spring for urging the cam ring toward the first operation chamber is provided in the second operation chamber. .

In this improved power steering device, when the steering operation is not performed, the cam ring is moved to the second working chamber side against the spring due to the pressure in the first working chamber which increases with the increase of the pump rotation speed. Thus, the amount of eccentricity with respect to the rotor is reduced, and the discharge amount with respect to the pump rotation speed is controlled to a constant small value. On the other hand, as the load pressure increases with the steering operation, the opening area of the variable throttle is increased and the pressure in the first working chamber is reduced. As a result, the spring provided in the second working chamber moves the cam ring toward the first working chamber to increase the amount of eccentricity with the rotor and increase the discharge amount of the pump.

Therefore, this power steering system reduces the discharge amount of the pump to reduce power consumption when steering operation is not performed, and supplies a sufficient amount of hydraulic oil to the actuator during steering operation.

[0006]

However, in the above-mentioned conventional example, the variable aperture is opened and the cam ring is moved at the time of steering operation. Therefore, the hydraulic fluid discharged from the pump is subject to the resistances of both the fixed throttle and the variable throttle. That is, since the discharge oil passes through the variable throttle to control the discharge flow rate, the energy loss of the hydraulic oil, that is, the power loss of the pump may increase correspondingly. If the power loss increases, the fuel consumption of an automobile or the like will deteriorate.

The present invention has been devised in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide a power steering device in which power loss of a pump is small.

[0008]

In view of the above, the invention according to claim 1 is a power steering device for supplying and discharging hydraulic oil to and from an actuator of a steering mechanism to obtain a steering assisting force, which is constantly driven to rotate by a driving means and discharges. A variable displacement pump having changing means for changing the amount, an operating hydraulic passage for guiding the operating oil discharged from the variable displacement pump to an actuator, a control orifice provided in the middle of the operating hydraulic passage, and the changing means. A piston connected to the piston and a first control oil chamber and a second control oil chamber that are arranged to face each other on both sides of the piston are provided, and the first control oil chamber is provided with a control orifice through a first control hydraulic passage. Also the hydraulic oil on the downstream side is introduced, and the hydraulic oil on the upstream side of the control orifice is introduced into the second control oil chamber via the second control hydraulic passage.
By increasing the working hydraulic pressure introduced to the first control oil chamber,
A control device for urging the changing means in a direction in which the discharge amount of the variable displacement pump increases, a first orifice provided in the middle of the first control hydraulic passage, and the first orifice and the first control oil chamber. Is connected to a first control hydraulic passage between
A pressure reducing valve for releasing the hydraulic pressure downstream of the first orifice to the drain passage in accordance with the hydraulic pressure upstream of the orifice, and a second orifice provided in the drain passage downstream of the pressure reducing valve. It is equipped with it.

According to a second aspect of the present invention, in the configuration of the first aspect of the invention, the variable displacement pump has a plurality of sliding members mounted so as to be retractable in a substantially radial direction, and the rotor. A configuration is provided in which the cam ring is rotatably accommodated and is eccentric to the rotor, and the cam ring is configured to be eccentric to the rotor to change the discharge amount.

According to a third aspect of the present invention, the sliding member having the second aspect is a plunger.

According to the invention of claim 4, the sliding member having the structure of claim 2 is a vane.

According to a fifth aspect of the present invention, the first control oil chamber and the second control oil chamber of the control device according to the first aspect of the present invention respectively urge the piston to urge the first control spring and the second control spring. It has a structure with attached.

Here, as the variable displacement pump, a rotor having a plurality of sliding members attached to and retractable in a substantially radial direction, and a cam ring that rotatably accommodates the rotor and is eccentric to the rotor are provided. It is possible to employ a plunger pump in which the sliding member attached to the rotor is a plunger, or a vane in which the sliding member is a vane, and a swash plate that is connected to the piston and whose inclination angle changes Various variable displacement pumps such as a swash plate type piston pump can be adopted. These variable displacement pumps are rotationally driven by driving means such as an internal combustion engine, and the cam ring and the swash plate serve as changing means to change the discharge amount of the pump.

Preferably, the first control oil chamber and the second control oil chamber of the control device are respectively provided with a first control spring and a second control spring for urging the piston, and these control springs are attached. Urges the changing means through the piston in the direction in which the discharge amount of the variable displacement pump increases as a whole. Therefore, when the variable displacement pump is in a stopped state, the changing means is in a position where the variable displacement pump can discharge the most amount of hydraulic oil.

The variable displacement pump can be constantly driven to rotate by a driving means such as an internal combustion engine. The hydraulic oil discharged from the variable displacement pump is guided to the actuator via the hydraulic pressure passage and the control orifice. The hydraulic oil guided to the actuator is consumed to appropriately exert the steering assisting force when the actuator requiring the steering assisting force is operated.

First, when the steering is not operated,
When the rotational speed of the variable displacement pump is increased from the stopped state, the discharge flow rate gradually increases from zero (see FIG. 4). At this time, the hydraulic oil discharged from the variable displacement pump to the hydraulic oil passage passes through the control orifice to generate a differential pressure before and after the control orifice, and the pressure P2 of the hydraulic oil after passing the control orifice. The pressure is lower than the pressure P1 of the hydraulic oil before passing.

Here, the hydraulic oil (pressure P1) upstream of the control orifice is guided to the second control oil chamber of the control device, while the hydraulic oil (pressure P2) downstream of the control orifice is supplied. First control device via first orifice
Guided to the control oil chamber. That is, the working oil (pressure P2) on the downstream side of the control orifice is introduced into the first control pressure chamber of the control device after being reduced to a predetermined pressure (P3) by the first orifice, This control device energizes the changing means in a direction in which the discharge amount of the variable displacement pump increases as the hydraulic pressure (P3) introduced into the first control oil chamber increases.

Therefore, when the steering is not operated, the pressure P1 upstream of the control orifice is set.
Is also higher than the pressure P2 (and P3) on the downstream side, so that the control device is superior in the control oil pressure (pressure P1) guided to the second control oil chamber, which causes the discharge amount of the variable displacement pump to rise. The changing means will be moved in the decreasing direction.

As a result, the control device controls the discharge amount of the variable displacement pump to a predetermined amount. afterwards,
The movement of the changing means is stopped at a balance position between the working hydraulic pressure (pressure P1) guided to the second control oil chamber of the control device and the pressure (P3) related to the working hydraulic pressure guided to the first control oil chamber. The discharge amount is controlled to a constant low discharge amount indicated by Q1 of No. 4. At this time, since the load pressure of the actuator is zero, the pressure reducing valve sensitive to this load pressure is open. However, since the second orifice is provided in the drain passage, the pressure (P3) introduced into the first control hydraulic chamber is maintained at a pressure higher than the atmospheric pressure (P0).

The constant discharge amount Q1 can be set to an arbitrary value by selecting the throttle amount of the control orifice and the spring force of the control spring for urging the control piston of the control device.

Next, when the steering is operated and the actuator is in an operating state in which the steering assisting force is exerted while the discharge amount of the variable displacement pump is controlled to a constant low discharge amount by the control of the control device, The pressure (P2) of the working oil in the working hydraulic passage downstream of the control orifice increases. That is, the control valve of the actuator is controlled to be opened / closed in accordance with the steering operation, and the actuator exerts a steering assisting force. Therefore, the load pressure (P2) of the actuator is provided in the control hydraulic passage downstream of the control orifice. Will be given a pressure equal to.

Here, the hydraulic oil in the control hydraulic passage downstream of the control orifice is introduced into the first control oil chamber of the control device via the first orifice. That is, the load pressure (P2) of the actuator is reduced (P3) at the first orifice and then introduced into the first control oil chamber, and the control device controls the pressure (P2) related to the load pressure (P2) of the actuator. Therefore, the changing means is biased and moved in the direction in which the discharge amount of the variable displacement pump increases.

At this time, the pressure (P3) downstream of the first orifice increases as the pressure (P2) in the first control hydraulic passage upstream of the first orifice increases. ) Gradually starts to close, the flow rate passing through the first orifice also gradually decreases, and finally the pressure reducing valve is fully closed to substantially equalize the pressure (P2) before passing through the first orifice. Become. As a result, the discharge flow rate from the variable displacement pump gradually increases from the flow rate Q1 to the flow rate Q2, as shown in FIG. This flow rate Q2 is
It is determined by controlling the changing means by the balance between the working hydraulic pressure (pressure P1) guided to the second control oil chamber of the control device and the working hydraulic pressure (pressure P3 substantially equal to the pressure P2) guided to the first control oil chamber. It

A predetermined flow rate of hydraulic fluid discharged from the variable displacement pump is supplied to the actuator to appropriately control the steering assisting operation.

As a result, when the discharge amount of the variable displacement pump is changed according to the increase of the load pressure of the actuator, the working oil does not pass through the special throttle, so that the energy loss of the working oil, that is, the pump. It is possible to obtain the power steering device which can suppress the power loss of the power steering device and which has good operation efficiency.

Further, the driving force consumed by the variable displacement pump is related to the discharge amount. In the present invention, when the steering assisting force is unnecessary, the changing means is operated to minimize the discharge amount of the variable displacement pump. When the steering assisting force is needed, the discharge amount can be gradually increased or decreased according to the steering assisting force to be exerted by the actuator by controlling the changing means in association with the load pressure of the actuator when the steering assisting force is required. Therefore, the variable displacement pump consumes driving force as needed. Therefore, it is possible to obtain a power steering device capable of preventing unnecessary power consumption in the variable displacement pump and advantageously avoiding power loss.

Further, by operating the changing means with the load pressure related to the steering assisting force, the discharge characteristic of the variable displacement pump can be minutely changed, so that a power steering device having a smooth steering feeling can be obtained.

[0028]

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, and is a drawing including a sectional view taken along the line AA of FIG. 2, and FIG. 2 is a sectional view taken along the line BB of FIG. is there.

In the figure, reference numeral 1 is a variable displacement pump, which has a changing means 2 for changing the discharge amount, and is constantly driven to rotate by an internal combustion engine (not shown) as a driving means. It is possible. Reference numeral 3 designates an actuator 4 for operating oil discharged from the variable displacement pump 1.
A control orifice 5 is provided in the middle of the operating hydraulic passage 3 leading to the control hydraulic passage 3.

In the present embodiment, the variable displacement pump 1 has a rotor 7 in which a plurality of plungers 6 are mounted so as to be retractable in a substantially radial direction, and the rotor 7 is rotatably housed therein. A plunger pump with an eccentric cam ring 8 is shown. A pump housing 9 houses the rotor 7 and the cam ring 8.

The cam ring 8 has an outer ring 8a and an inner ring 8b, and a bearing 10 is provided between the outer ring 8a and the inner ring 8b. One end side (the upper side in FIG. 1) of the outer ring 8a is rotatably supported by the pump housing 9 via a pivot pin 11, whereby the cam ring 8 swings with respect to the rotor 7. The center of the rotor 7 and the center of the cam ring 8 can be eccentric. Therefore, the cam ring 8 serves as a changing means to change the discharge amount of the variable displacement pump 1. A bearing 12 is provided between the outer ring 8a and a pivot pin 11 that rotatably supports the outer ring 8a.

The plunger 6 has a cylindrical shape with a bottom, and the plunger 6 is attached in a retractable manner in a plurality of substantially radial-direction plunger accommodating holes 13 provided in the rotor 7 which are open to the outer periphery. Has been. This plunger 6
Is the inside of the plunger 6 and the plunger receiving hole 1
Spring 14 is elastically urged in a substantially radial direction by a spring 14 that is contracted between the inner peripheral surface of the cam ring 8 and the inner peripheral cam surface 8c of the cam ring 8.

A supply / discharge passage 15 for hydraulic oil is opened at the bottom of each of the plunger accommodating holes 13, and these supply / discharge passages 15 are integrally formed with the drive shaft 1 of the rotor 7.
The drive shaft 16 is formed in the axial direction of 6 and opens at one end surface (left side in FIG. 2) of the drive shaft 16. The openings of the supply / discharge passages 15 are arranged on the one end surface of the drive shaft 16 at substantially equal intervals on the circumference.

Inside the pump housing 9, a valve plate 17 is provided facing one end face of the drive shaft 16, and a pair of ports 18, 18 are formed in the valve plate 17. . These ports 18,1
8 are arranged on opposite sides of the center of the rotor 7 in the direction of a line segment connecting the center of the pivot pin 11 and the center of the rotor 7. Also, each of these ports 18, 18
The drive shaft 1 has an arc shape substantially concentric with the rotor 7.
It is possible to communicate with some of the supply / discharge passages 15 that open at the end face of 6 at the same time. In addition, the valve plate 17 includes the spring 1
It is urged by 9 so as to contact one end surface of the drive shaft 16.

Further, in this embodiment, of the pair of ports 18, 18 provided on the valve plate 17, the port 18 located on the upper side in FIG. 1 communicates with the working hydraulic passage 3 as a discharge port, and also the lower port. The port 18 located on the side communicates with the oil storage tank T via an intake passage 20 as an intake port.

Reference numeral 21 is a control device, and this control device 21
Piston 2 linked to the cam ring (changing means) 8
2 and a first control oil chamber 23 and a second control oil chamber 24, which are arranged facing each other on both sides of the piston 22. That is, the control device 21 has a piston 22 slidably inserted in a cylinder 25 with one end sealed formed in the pump housing 9, and a substantially central portion thereof is connected to the cam ring 8. The piston 22 defines the inside of the cylinder 25 into a first control oil chamber 23 and a second control oil chamber 24. A first control spring 26 and a second control spring 27 that bias the piston 22 are housed in the first control oil chamber 23 and the second control oil chamber 24, respectively.

Reference numeral 28 denotes a plug which closes the opening end on the other end side of the cylinder 25 and also serves as a spring bearing for the first control spring 26. The plug 28 is screwed and fixed to the opening end on the other end side of the cylinder 25, and cooperates with the nut 29 to adjust the spring force (set load) of the first control spring 26 and the second control spring 27. The device 30 is configured.

The piston 22 is connected to the other end side of the cam ring 8 (lower side in FIG. 1, more specifically, a position substantially symmetrical to the pivot pin 11 with the center of the cam ring 8 interposed therebetween) via a connecting pin 31. is there. As a result, the piston 2
As 2 moves in the cylinder 25, the cam ring 8 swings around the pivot pin 11 as a fulcrum, and the eccentric amount of the cam ring 8 with respect to the rotor 7 can be controlled. In addition,
A bearing 32 is provided between the piston 22 and the connecting pin 31.
Is provided.

Further, the first control oil chamber 2 of the control device 21
3 to the control orifice 5 via the first control hydraulic passage 33.
The hydraulic oil on the downstream side of the control oil is introduced, and the hydraulic oil on the upstream side of the control orifice 5 is introduced into the second control oil chamber 24 via the second control hydraulic passage 34. 21 is capable of urging the cam ring 8 in a direction in which the discharge amount of the variable displacement pump 1 increases due to an increase in operating hydraulic pressure introduced to the first control oil chamber 23.

Reference numeral 35 is a first orifice provided in the middle of the first control hydraulic passage 33. The first control hydraulic passage 33 between the first orifice 35 and the first control oil chamber 23.
A pressure reducing valve 37 is provided to allow the hydraulic pressure on the downstream side of the first orifice 35 to escape to the drain passage 36 in accordance with the hydraulic pressure on the upstream side of the first orifice 35. A second orifice 38 is provided in the drain passage 36 downstream of the pressure reducing valve 37.

Reference numerals 39 and 40 denote radial bearings for supporting the drive shaft 16 on the pump housing 9, and 41 denotes the rotary bearing.
The thrust bearing is arranged between the rotor 7 and the pump housing 9. Reference numeral 42 is a seal member that seals the drive shaft 16.

In such a structure, the variable displacement pump 1 is always rotationally driven in the clockwise direction (arrow N direction) by an internal combustion engine (not shown) as a driving means,
This variable displacement pump 1 is provided with a suction passage 20 from an oil storage tank T.
The hydraulic oil is sucked in through and discharged into the hydraulic pressure passage 3.
The hydraulic oil discharged to the hydraulic oil pressure passage 3 is guided to the actuator 4 through the control orifice 5 and is consumed in order to exert the steering assisting force when the actuator 4 requiring the steering assisting force is operated. .

First, the operation when the steering wheel is not operated will be described. That is, in the state where the variable displacement pump 1 is stopped by stopping the driving means (not shown),
The controller 21 biases the cam ring (changing means) 8 to a position where the discharge flow rate of the variable displacement pump 1 can be maximized. If the rotation speed of the pump is increased from this stopped state,
The discharge flow rate gradually increases from zero (see FIG. 4). At this time, the working oil discharged from the variable displacement pump 1 to the working hydraulic passage 3 passes through the control orifice 5 to generate a differential pressure before and after the control orifice 5. As a result, the pressure P2 of the hydraulic oil after passing through the control orifice 5
Is the pressure P1 of the hydraulic oil before passing through the control orifice 5.
The pressure is lower than that of.

Here, the hydraulic oil (pressure P1) on the upstream side of the control orifice 5 is guided to the second control oil chamber 24 of the control device 21, while the hydraulic oil on the downstream side of the control orifice 5 ( The pressure P2) is introduced into the first control oil chamber 23 of the control device 21 via the first orifice 35. That is, the working oil (pressure P2) downstream of the control orifice 5 is introduced into the first control oil chamber 23 of the control device 21 after being depressurized to the predetermined pressure (P3) by the first orifice 35. The control device 21 biases the cam ring (changing means) 8 in the direction in which the discharge amount of the variable displacement pump 1 increases due to the increase of the operating oil pressure (pressure P3) introduced to the first control oil chamber 23. It is supposed to do.

Therefore, when the steering is not operated, the pressure P1 upstream of the control orifice 5 is set.
Is also higher than the pressure P2 (and P3) on the downstream side, so that the control device 21 has a higher control hydraulic pressure (pressure P1) guided to the second control oil chamber 24 of the control device 21. The cam ring (changing means) 8 is moved in the direction in which the discharge amount decreases. That is, as the pressure in the second control oil chamber 24 of the control device 21 increases, the control piston 22 becomes the control oil pressure acting on the first control oil chamber 23 (and the spring force of the first control spring 26). As a result, the cam ring 8 is swung to the right in FIG. 1 with the pivot pin 11 as a pivot point as a result of moving to the right in FIG.

As a result, the rotor 7 and the cam ring 8 are
The eccentricity between and will gradually decrease, and the discharge amount of the variable displacement pump 1 will be controlled to a predetermined amount. After that, the control device 21 moves the cam ring at a balance position between the working hydraulic pressure (pressure P1) guided to the second control oil chamber 24 and the pressure (P3) related to the working hydraulic pressure guided to the first control oil chamber 23. 8
The movement (oscillation) of (1) is stopped, and the discharge amount is controlled to a constant low discharge amount indicated by Q1 in FIG. In this state, the displacement of the variable displacement pump 1 is at the minimum position, and the reciprocating motion of the plunger 15 is the smallest, so that the variable displacement pump 1 is operated in a nearly unloaded state. At this time, since the load pressure of the actuator 4 is zero, the pressure reducing valve 37 sensitive to this load pressure is open. However, the drain passage 36 has a second
Since the orifice 38 is provided, the pressure (P3) introduced into the first control oil chamber 23 is kept higher than the atmospheric pressure (P0).

Here, the constant discharge amount Q1 is determined by the throttle amount of the control orifice 5, and the spring force of the first control spring 26 and the second control spring 27 for urging the piston 22 of the control device 21. Determined by That is, by loosening the nut 40 of the adjusting device 41 of the control device 21, adjusting the screwing amount of the plug 39, and changing the spring force (set load) of the first control spring 26 and the second control spring 27. Adjusted and determined.

Next, the operation when the steering wheel is operated will be described. That is, when the steering is operated and the actuator 4 is in an operating state in which the actuator 4 exerts a steering assisting force while the discharge amount of the variable displacement pump 1 is controlled to a constant low discharge amount by the control of the control device 21,
The pressure (P2) of the working oil in the working hydraulic passage 3 downstream of the control orifice 5 increases. That is, the control valve (not shown) of the actuator 4 is associated with the steering operation.
Is controlled to be opened and closed, and the actuator 4 exerts a steering assisting force. Thereby, the control orifice 5
An actuator 4 is provided in the control hydraulic passage 3 downstream of the actuator 4.
A pressure equal to the load pressure will be applied.

Here, the hydraulic oil in the control hydraulic passage 3 on the downstream side of the control orifice 5 is introduced into the first control oil chamber 23 of the control device 21 via the first orifice 35. That is, after the load pressure (P2) of the actuator 4 is reduced by the first orifice 35 (pressure is P3), it is guided to the first control oil chamber 23.
1 indicates the pressure (P3) related to the load pressure (P2) of the actuator 4 to urge and move the cam ring 8 in the direction in which the discharge amount of the variable displacement pump 4 increases (left in FIG. 1) (FIG. 3). reference). That is, the control device 2
By increasing the pressure in the first control oil chamber 23 of No. 1,
The piston 22 moves to the left in FIG. 1 against the control oil pressure (and the spring force of the second control spring 27) acting on the second control oil chamber 24, and the cam ring 8 pivots the pivot pin 11 to the pivot point. 1 is swung to the left in FIG.

At this time, the pressure (P3) on the downstream side of the first orifice 35 increases as the pressure (P2) on the first control hydraulic passage upstream of the first orifice 35 increases. Since the pressure reducing valve 37 that responds to (P2) begins to gradually close, the flow rate passing through the first orifice 35 also gradually decreases, and finally the pressure reducing valve 37 is fully closed.
It becomes substantially equal to the pressure (P2) before passing through the orifice 35. As a result, the discharge flow rate from the variable displacement pump 1 gradually increases from the flow rate Q1 to the flow rate Q2, as shown in FIG. This flow rate Q2 is equal to the second flow rate of the control device 21.
Determined by controlling the cam ring 8 (changing means) by the balance between the hydraulic pressure (pressure P1) guided to the control oil chamber 24 and the hydraulic pressure (pressure P3 substantially equal to the pressure P2) guided to the first control oil chamber 23. To be done.

A predetermined flow rate of hydraulic oil discharged from the variable displacement pump 1 is supplied to the actuator 4 and appropriately controls the steering assisting operation.

When the load pressure on the actuator 4 side is reduced, the pressure in the second control oil chamber 23 is reduced and the pressure reducing valve 37 is opened according to the load pressure. 1 The pressure in the control oil chamber 23 is quickly reduced. Therefore, the spring force of the second control spring 27 is superior,
The piston 22 quickly moves to the first control pressure chamber 23 side. As a result, the cam ring 8 rapidly swings,
The discharge amount of the variable displacement pump 1 is rapidly reduced.

As a result, when the discharge amount of the variable displacement pump 1 is changed according to the increase of the load pressure of the actuator 4, the hydraulic oil does not pass through a special throttle, so that the energy loss of the hydraulic oil, That is, loss of power of the pump can be suppressed, and a power steering device with high operating efficiency can be obtained.

Further, the driving force consumed by the variable displacement pump 1 is related to the discharge amount. In the present invention, when the steering assisting force is unnecessary, the changing means 2 is operated to discharge the variable displacement pump 1. When the steering assisting force is required, the cam ring 8 as the changing means is controlled in relation to the load pressure of the actuator 4 to reduce the discharge amount according to the steering assisting force to be exerted by the actuator 4. The variable displacement pump 1 can be increased or decreased.
Will consume driving force as needed. Therefore, it is possible to obtain a power steering device capable of preventing unnecessary power consumption in the variable displacement pump 1 and advantageously avoiding power loss.

Further, the discharge characteristic of the variable displacement pump 1 can be minutely changed by operating the cam ring 8 with a load pressure related to the steering assisting force, so that a power steering device having a smooth steering feeling can be obtained. .

[0057]

As described above in detail, according to the present invention, when the discharge amount of the variable displacement pump is changed according to the increase of the load pressure of the actuator, the hydraulic oil passes through the special throttle. Therefore, it is possible to suppress energy loss of hydraulic oil, that is, power loss of the pump, and to obtain a power steering device with high operating efficiency.

[Brief description of drawings]

1 is an explanatory view of a power steering device showing an embodiment of the present invention, and is a drawing including a cross-sectional view taken along the line AA of FIG.

FIG. 2 is a cross-sectional view of the variable displacement pump, taken along line BB in FIG.

FIG. 3 is a drawing similar to FIG. 1, showing a state in which the discharge amount of the variable displacement pump is increased and the pressure reducing valve is closed.

FIG. 4 is a diagram showing a relationship between a pump rotation speed and a discharge flow rate.

FIG. 5 is a diagram showing a relationship between load pressure and discharge flow rate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable displacement pump 2 Change means 3 Actuating hydraulic passage 4 Actuator 5 Control orifice 8 Cam ring (changing means) 21 Control device 22 Piston 23 First control oil chamber 24 Second control oil chamber 33 First control hydraulic passage 34 Second control hydraulic pressure Passage 35 First orifice 36 Drain passage 37 Pressure reducing valve 38 Second orifice

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshinori Aihara 1370 Onna, Atsugi-shi, Kanagawa Prefecture

Claims (5)

[Claims] 1. A variable displacement pump having a changing means for changing a discharge amount, which is constantly driven by a driving means to change a discharge amount, in a power steering device for supplying and discharging hydraulic oil to an actuator of a steering mechanism to obtain a steering assisting force. A working hydraulic passage for guiding the working oil discharged from the variable displacement pump to the actuator, a control orifice provided in the middle of the working hydraulic passage, a piston connected to the changing means, and a piston connected to both sides of the piston. A first control oil chamber and a second control oil chamber are provided, and the working oil downstream of the control orifice is guided to the first control oil chamber via a first control hydraulic passage, and the second control oil chamber is introduced. The hydraulic oil upstream of the control orifice is introduced into the oil chamber via the second control hydraulic passage, and the hydraulic oil introduced into the first control oil chamber is increased to increase the operating pressure of the variable displacement pump. A control device for urging the changing means in the direction in which the discharge amount increases, a first orifice provided in the middle of the first control hydraulic passage, the first orifice and the first orifice.
A pressure reducing valve connected to a first control hydraulic pressure passage between the control oil chamber and the pressure reducing valve for releasing the working hydraulic pressure downstream of the first orifice to the drain passage in accordance with the operating hydraulic pressure upstream of the first orifice; A power steering device comprising: a second orifice provided in a drain passage downstream of the pressure reducing valve. 2. The variable displacement pump has a rotor having a plurality of sliding members attached to and retractable from each other in a substantially radial direction, and a cam ring that rotatably accommodates the rotor and is eccentric to the rotor. The power steering device according to claim 1, wherein the cam ring is a changing unit that is eccentric to the rotor to change the discharge amount. 3. The power steering device according to claim 2, wherein the sliding member is a plunger. 4. The sliding member is a vane.
A power steering device as described. 5. The first control oil chamber and the second control oil chamber of the control device are respectively attached with a first control spring and a second control spring for urging a piston. Power steering device.