JPH09226609A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power loss of a pump in case that the discharge amount of a variable capacity pump is changed by preventing operating oil from passing through a specific throttle and decreasing the discharge amount of the pump when steering is not operated. 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 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 room the downstream side of the control orifice 5 is increased so that the cam ring 8 is oscillated to the left side around a pivotally supporting pin 11 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 which are arranged to face each other on both sides of the piston are provided, and the first control oil chamber accommodates a first control spring and a control orifice. Hydraulic oil is introduced downstream of the first control oil chamber, a second control spring is housed in the second control oil chamber, and hydraulic oil upstream of the control orifice is introduced to the first control oil chamber. The increased hydraulic pressure led to the Goyu chamber, and a control device for the discharge of the variable displacement pump to urge the changing means in the direction of increasing, provided in the control device,
A control pressure chamber to which the pressure of the first control oil chamber is guided, and a first control spring which is provided between the control pressure chamber and the first control oil chamber and has one end surface facing the first control oil chamber. A movable spring receiving member facing the control pressure chamber with the other end surface having an area larger than that of the one end surface, and a spring member applying a biasing force to the control pressure chamber side to the movable spring receiving member. It has a different structure.

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.

Here, the variable displacement pump includes 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 with respect to the rotor. 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.

Further, the spring force of the first control spring and the second control spring provided in each of the first control oil chamber and the second control oil chamber of the control device for urging the piston is equal to that of the first control spring. The spring force is slightly higher, and the changing means is biased via 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. The control device is guided to the first control oil chamber of the control device, and the control device changes the discharge amount of the variable displacement pump in the direction in which the discharge amount of the variable displacement pump increases due to the increase of the working oil pressure (pressure P2) guided to the first control oil chamber. Is designed to be urged.

Therefore, when the steering is not operated, the pressure P1 upstream of the control orifice is set.
Is also higher than the pressure P2 on the downstream side, the control device controls the control oil pressure (pressure P) to be guided to the second control oil chamber.
According to 1), the changing means is moved in the direction in which the discharge amount of the variable displacement pump decreases. As a result, the control device gradually reduces the discharge amount of the variable displacement pump. After that, 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 working hydraulic pressure (pressure P2) guided to the first control oil chamber, and FIG. The discharge amount is controlled to a constant low discharge amount indicated by Q1.

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, since 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, the control hydraulic passage downstream of the control orifice has a pressure equal to the load pressure of the actuator. Will be given.

Here, the hydraulic oil in the control hydraulic passage on the downstream side of the control orifice is guided to the first control oil chamber of the control device. That is, the load pressure of the actuator is guided to the first control oil chamber, and the control device biases and moves the changing means in the direction in which the discharge amount of the variable displacement pump increases in accordance with the load pressure of the actuator. As a result, the discharge flow rate from the variable displacement pump increases from the flow rate Q1 to the flow rate Q2, as shown in FIG. This flow rate Q
2 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 P2) guided to the first control oil chamber.

The hydraulic fluid discharged from the variable displacement pump is supplied to the actuator and appropriately controls the steering assisting operation.

As a result, when the discharge amount of the variable displacement pump is changed in response to the increase of the load pressure of the actuator, the hydraulic oil does not pass through the special throttle, so that the energy loss of the hydraulic 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 required, 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, the movable spring receiving member is moved by the pressure of the control pressure chamber in which the same pressure as the load pressure introduced in the first control oil chamber is introduced, and the spring force of the first control spring and the second control spring is changed. Therefore, the cam ring can be quickly moved and controlled according to the load pressure.

Furthermore, by operating the changing means with a 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 feel can be obtained. .

[0026]

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 apparatus 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 this 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 hydraulic oil supply / discharge passage 15 is opened at the bottom of each of the plunger accommodating holes 13, and these supply / discharge passages 15 are integrally formed on 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.

A valve plate 17 is provided inside the pump housing 9 so as to face one end surface of the drive shaft 16, and a pair of ports 18 and 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 is formed in the pump housing 9 and is slidably inserted into a cylinder 26 having one end sealed by a plug 25, and a substantially central portion thereof is connected to the cam ring 8. The piston 22 is provided, and the inside of the cylinder 26 is defined by the piston 22 into a first control oil chamber 23 and a second control oil chamber 24. In addition, in the first control oil chamber 23 and the second control oil chamber 24, respectively, a first control spring 27 and a second control spring 27 for biasing the piston 22 are provided.
A control spring 28 is housed.

29 is the first control oil chamber 23 and the plug 2
The control pressure chamber formed between the control pressure chamber 2 and the control pressure chamber 2
9 is formed at the axial position of the cylinder 26. Reference numeral 30 denotes a movable spring receiving member arranged between the control pressure chamber 29 and the first control oil chamber 23. This movable spring receiving member 3
0 is a cylindrical portion 31 and a collar portion 32 having a diameter larger than that of the cylindrical portion 31.
And the cylindrical portion 31 is inserted into the first control oil chamber 23, and the one end surface 33 on the side of the cylindrical portion 31 has the first control oil chamber 2
3 is in contact with the first control spring 27, while the collar portion 32 is inserted into the control pressure chamber 29, and the one end surface 33
The other end surface 34 on the side of the collar portion 32 having a larger area faces the control pressure chamber 29. A passage 35 penetrates the movable spring receiving member 30. The passage 35 guides the pressure in the first control oil chamber 23 into the control pressure chamber 29.

Reference numeral 36 is a spring member attached to the movable spring receiving member 30, and this spring member 36 is the control pressure chamber 29.
Inside the spring member accommodating chamber 37 formed between the bottom surface of the first control oil chamber 23 side and the flange 32, the movable spring receiving member 30 is urged toward the control pressure chamber 29 side.

The inside of the spring member accommodating chamber 37 communicates with the tank T via a drain passage 38.

Reference numeral 39 is a plug which closes the opening end on the other end side of the cylinder 26 and also serves as a spring bearing for the second control spring 28. The plug 39 is screwed and fixed to the opening end on the other end side of the cylinder 26, and cooperates with the nut 40 to adjust the spring force (set load) of the first control spring 27 and the second control spring 28. It constitutes the device 41.

The piston 22 is connected to the other end side of the cam ring 8 (a 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 42. is there. As a result, the piston 2
As the 2 moves in the cylinder 26, the cam ring 8 swings about 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 43 is provided between the piston 22 and the connecting pin 42.
Is provided.

The first control oil chamber 2 of the control device 21
The hydraulic oil on the downstream side of the control orifice 5 is led to the third passage 3 via the first passage 44, 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 passage 45. This control device 21 is
The cam ring 8 can be urged in the direction in which the discharge amount of the variable displacement pump 1 increases by increasing the operating oil pressure introduced to the control oil chamber 23.

46 and 47 are radial bearings for supporting the drive shaft 16 on the pump housing 9, and 48 is a radial bearing.
The thrust bearing is arranged between the rotor 7 and the pump housing 9. Reference numeral 49 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 guided to the first control oil chamber 23 of the control device 21, and the control device 21 increases the operating oil pressure (pressure P2) guided to the first control oil chamber 23 to increase the pressure of the variable displacement pump 1. The cam ring (changing means) 8 is biased in the direction in which the discharge amount increases.

Therefore, when the steering is not operated, the pressure P1 upstream of the control orifice 5 is set.
However, since it is also higher than the pressure P2 on the downstream side, the control device 21 controls the cam ring (in the direction in which the discharge amount of the variable displacement pump 1 is reduced by the control oil pressure (pressure P1) guided to the second control oil chamber 24 thereof. Change means) 8 will be moved. That is, the second control oil chamber 2 of the first control device 21
As the pressure in 4 increases, the control piston 22
Of the control oil pressure acting on the first control oil chamber 23 (and the first control oil chamber 23).
As a result of moving to the right in FIG. 1 against the spring force of the control spring 27), the cam ring 8 swings to the right in FIG. 1 with the pivot pin 11 as the pivot point.

As a result, the rotor 7 and the cam ring 8 are
The eccentricity of the variable displacement pump 1 and the discharge amount of the variable displacement pump 1 are reduced. After that, the control device 21 moves the cam ring 8 at a balance position between the working oil pressure (pressure P1) guided to the second control oil chamber 24 and the working oil pressure (pressure P2) guided to the first control oil chamber 23. (Oscillation) 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, the reciprocating motion of the plunger 15 is the smallest, and the variable displacement pump 1
Will be operating near an unloaded state.

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 27 and the second control spring 28 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 27 and the second control spring 28. 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 controlled to be opened / closed in accordance with the steering operation, and the actuator 4 exerts a steering assisting force. As a result, a pressure equal to the load pressure of the actuator 4 is applied to the control hydraulic passage 3 on the downstream side of the control orifice 5.

The hydraulic oil in the control hydraulic passage 3 downstream of the control orifice 5 is supplied to the first control oil chamber 2 of the control device 21.
It is led to 3. That is, the load pressure of the actuator 4 is introduced into the first control oil chamber 23, and the control device 21 causes the discharge pressure of the variable displacement pump 4 to increase in accordance with the load pressure of the actuator 4 (left in FIG. 1). The cam ring 8 is urged in the direction) to move (see FIG. 3). That is, as the pressure in the first control oil chamber 23 of the control device 21 increases, the control oil pressure at which the piston 22 acts on the second control oil chamber 24 (and the second control spring 28).
1), the cam ring 8 is swung leftward in FIG. 1 with the pivot pin 11 as a pivot point.

Therefore, the eccentricity between the rotor 7 and the cam ring 8 is gradually increased, and the flow rate discharged from the variable displacement pump 1 is from the flow rate Q1 to the flow rate Q as shown in FIG.
It will be increased to 2. This flow rate Q2 is the operating hydraulic pressure (pressure P) guided to the second control oil chamber 24 of the control device 21.
1) and the operating hydraulic pressure (pressure P) guided to the first control oil chamber 23.
It is determined by controlling the cam ring 8 in balance with 2).

At this time, since the first control oil chamber 23 and the control pressure chamber 29 communicate with each other through the passage 35,
At the same time that the pressure in the control oil chamber 23 rises, the control pressure chamber 29
The pressure of the movable spring receiving member 30 also increases.
Moves to the left in FIG. 1 against the spring force of the spring member 36. As a result, the first control spring 27 that abuts on the movable spring receiving member 36 is compressed and contracted, and the spring force of the first control spring 27 increases, so that the cam ring 8 swivels quickly and the variable capacity changes. The discharge amount of the pump 1 rapidly increases (see FIG. 3).

When the load pressure on the actuator 4 side is reduced, the pressures of the second control oil chamber 23 and the control pressure chamber 29 are also reduced, so that the spring force of the spring member 36 is predominant to move. The spring receiving member 30 is the control pressure chamber 29.
It moves to the side and the spring force of the first control spring 27 decreases.
Therefore, the cam ring 8 swivels rapidly, and the discharge amount of the variable displacement pump 1 is rapidly reduced.

The hydraulic fluid discharged from the variable displacement pump 1 is supplied to the actuator 4 and appropriately controls the steering assisting operation.

As a result, when the discharge amount of the variable displacement pump 1 is changed in accordance with 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 is operated to change the displacement.
In addition to reducing the discharge amount of the steering wheel, the cam ring 8 as a changing means is controlled in association with the load pressure of the actuator 4 when the steering assisting force is required, so that the steering assisting force to be exerted by the actuator 4 can be adjusted. Since the discharge amount can be gradually increased or decreased, the variable displacement pump 1 consumes the 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 movable spring receiving member 30 is moved by the pressure of the control pressure chamber 29, which is the same pressure as the load pressure introduced to the first control oil chamber 23, and the first control spring 27 is moved.
Since the spring force of the second control spring 28 is changed, the movement of the cam ring 8 can be quickly controlled according to the load pressure.

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

[0059]

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 has increased.

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 (change means) 21 Control device 22 Piston 23 First control oil chamber 24 Second control oil chamber 27 First control spring 28 Second control spring 29 Control pressure chamber 30 Movable spring receiving member 36 Spring member

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

Claims (4)

[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 that are provided, a first control spring is housed in the first control oil chamber, and hydraulic oil downstream of a control orifice is introduced to the second control oil chamber; A second control spring is accommodated in the control oil chamber, and the working oil upstream of the control orifice is introduced to increase the working oil pressure introduced to the first control oil chamber. A control device for urging the changing means in the direction in which the discharge amount of the pump increases, and the control device,
A control pressure chamber to which the pressure of the first control oil chamber is introduced, and a first control spring that is provided between the control pressure chamber and the first control oil chamber and has one end surface facing the first control oil chamber. A movable spring receiving member that contacts the control pressure chamber with an area of which the other end surface is larger than the area of the one end surface, and a spring member that gives the movable spring receiving member a biasing force to the control pressure chamber side. A power steering device characterized by the following. 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.