JP2000170666A - Variable delivery pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably vary the volume of a pump chamber while simplifying the structure of a pump. SOLUTION: In a variable delivery pump 10, an orifice 46 is fixed to the discharge passage 28 of the pump 10, and a part of the fluid before passing the fixed orifice 46 is introduced to a first fluid pressure chamber 44A through a first throttle 48A, and a part of the fluid after passing the fixed orifice 46 is introduced to a second fluid pressure chamber 44B through a second throttle 48B, and the first fluid pressure chamber 44A is communicated with the suction side of the pump 10 through a variable orifice 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement pump used for a power steering device of an automobile.

[0002]

2. Description of the Related Art Conventionally, a variable displacement pump as disclosed in Japanese Patent Application Laid-Open No. 8-200239 has been proposed in order to assist a steering force in a hydraulic power steering device of an automobile. This conventional variable displacement pump is directly driven to rotate by an automobile engine. As shown in FIG. 6, a rotor 3 is provided in a cam ring 2 which is fitted to a pump casing 1 so as to be movable and displaceable. A pump chamber 4 is formed between the rotor 2 and the outer periphery of the rotor 3.

In this prior art, the cam ring 2
Is applied to the cam ring 2 by the spring 5 so that the volume of the pump chamber 4 is maximized, and a first and a second force are applied between the cam ring 2 and the pump casing 1. 2 fluid pressure chambers 6A, 6
B is divided and the cam ring 2 is moved against the urging force by the differential pressure of the pressures acting on the two fluid pressure chambers 6A and 6B, and the discharge flow rate can be controlled by changing the volume of the pump chamber 4. It has a discharge flow control device. Thus, in this variable displacement pump, the discharge flow rate is increased so that a large steering assist force is obtained when the vehicle having a low rotation speed is stopped or running at a low speed, and the steering assist force is reduced when the rotation speed is high at a high speed. As described above, the discharge flow rate is controlled to be equal to or less than the predetermined amount, and the steering assist force required for the power steering device can be generated.

In this prior art discharge flow control device, a variable orifice 7 is provided in a discharge passage of a pump, and a part of the fluid before passing through the variable orifice 7 is transferred to a first fluid pressure chamber 6A via a switching valve 8. All the fluid after passing through the variable orifice 7 can be supplied to the power cylinder via the second fluid pressure chamber 6B. The variable orifice 7 is set so that the degree of restriction increases as the rotational speed of the pump increases. The switching valve 8 is closed at the beginning of the rotation of the pump,
Then it is set to open.

[0005]

However, the prior art has the following problems. The device configuration is complicated, such as using a plunger that can be moved by the discharge pressure of the pump as the switching valve that guides the fluid to the first fluid pressure chamber 6A.

Since the entire discharge flow rate supplied from the pump to the power cylinder side passes through the second fluid pressure chamber 6B, an unexpected steering reaction such as kickback in which the wheel receives a lateral force from the curb of the road is performed. When the force acts on the power cylinder, all of the oil flowing backward from the power cylinder side directly flows into the second fluid pressure chamber 6B. As a result, an unexpected displacement of the cam ring and an unexpected change in volume of the pump chamber are caused, and steering stability is impaired.

[0007] Since the entire discharge flow rate supplied from the pump to the power cylinder side is supplied to the second fluid pressure chamber 6B through the variable orifice 7, fluctuations in the discharge flow rate due to rotation of the pump are provided. All act on the second fluid pressure chamber 6B, and when the variable orifice 7 has a low degree of throttle, the fluctuation directly acts on the second fluid pressure chamber 6B. As a result, vibrations due to fluctuations (pulsations) in the discharge flow rate of the pump are generated in the cam ring, and as a result, the control of the change in the volume of the pump chamber becomes unstable, and the steering stability is impaired.

It is an object of the present invention to stably change the volume of a pump chamber while simplifying the device configuration in a variable displacement pump.

[0009]

According to the first aspect of the present invention, a pump is fixedly mounted on a pump shaft inserted into a pump casing, is driven to rotate, and moves in a radial direction while accommodating a large number of vanes in a groove. A possible rotor, a cam ring fitted to the pump casing and forming a pump chamber between the outer periphery of the rotor, and a cam ring that can be displaced within the pump casing and maximizes the volume of the pump chamber. And the first and second fluid pressure chambers are divided between the cam ring and the pump casing, and the differential pressure between the pressures acting on the two fluid pressure chambers causes the cam ring to act on the biasing force. And a discharge flow control device that controls the discharge flow rate by changing the volume of the pump chamber. Is a fixed orifice in the discharge passage of the pump is provided, a portion of the fluid before passing through the fixed orifice first
A part of the fluid after passing through the fixed orifice is guided to the second fluid pressure chamber through the second orifice via the throttle and the first fluid pressure chamber through the variable orifice. The variable orifice has a greater degree of throttling as the rotational speed of the pump increases.

According to a second aspect of the present invention, in the first aspect of the present invention, the variable orifice further includes a communication passage with a first fluid pressure chamber provided on a cam ring side and a suction passage provided on a pump casing side. It is provided in the connection area of the communication path with the side, and the degree of throttle is changed according to the displacement of the cam ring.

According to a third aspect of the present invention, in the second aspect of the present invention, the variable orifice has a notch shape having a sharp tip.

[0012]

According to the first aspect of the present invention, the following effects are obtained. A fixed orifice provided in a discharge passage of the pump, a first throttle and a second throttle for guiding a part of fluid before and after the fixed orifice to each of the first fluid pressure chamber and the second fluid pressure chamber, and a first fluid pressure chamber. A variable orifice communicating with the suction side makes it possible to control the discharge flow rate by changing the volume of the pump chamber according to the pump speed. Therefore, the device configuration can be simplified.

[0013] Only a part of the discharge flow rate supplied from the pump is guided to the first fluid pressure chamber and the second fluid pressure chamber via the first restrictor and the second restrictor. For example, a hydraulic power steering device In the above, when an unexpected steering reaction force such as kickback in which the wheels receive a lateral force from the curb of the road acts on the power cylinder, all of the oil flowing backward from the power cylinder remains in the first fluid pressure chamber or the second fluid pressure chamber. Does not flow into As a result, unexpected movement displacement of the cam ring and, consequently, unexpected volume change of the pump chamber are not caused.

[0014] Only a part of the discharge flow rate supplied from the pump is guided to the first fluid pressure chamber and the second fluid pressure chamber via the first restrictor and the second restrictor. Fluctuations (pulsations) of the discharge flow rate do not directly act on the first fluid pressure chamber or the second fluid pressure chamber. This allows
Vibration resulting from fluctuations in the discharge flow rate of the pump is not caused in the cam ring, and control of the change in volume of the pump chamber can be stabilized.

The first fluid pressure chamber on the high pressure side is depressurized by a variable orifice, and the discharge flow rate can be controlled by changing the degree of throttle of the variable orifice according to the pump speed. Therefore, the flow rate characteristics of the pump can be easily changed by changing the change in the degree of restriction of the variable orifice with respect to the rotation speed of the pump.

According to the second aspect of the present invention, the following operations are provided. Since the variable orifice is provided in the connection area between the communication path with the first fluid pressure chamber provided on the cam ring side and the communication path with the suction side provided on the pump casing side, the degree of throttle of the orifice is set to the cam ring. It can be easily changed by moving.

According to the third aspect of the present invention, the following operations are provided. Since the variable orifice has a notch shape with a sharp tip, the opening of the orifice can be reduced only to the sharp tip side of the notch as the pump rotation speed increases. Can be easily varied.

[0018]

1 is a schematic view showing a variable displacement pump, FIG. 2 is a sectional view showing a variable displacement pump, FIG. 3 is a circuit diagram showing a variable displacement pump, and FIG. 4 shows a variable orifice. FIG. 5 is an enlarged view, FIG. 5 is a characteristic diagram showing a relationship between a pump rotation speed and a discharge flow rate of the variable displacement pump, and FIG. 6 is a schematic diagram showing a conventional example.

The variable displacement pump 10 is a vane pump serving as a hydraulic pressure source of a hydraulic power steering device of an automobile, and sucks and discharges a working fluid of a reservoir 101 as shown in FIG. The working fluid discharged from the pump 10 is supplied to the power cylinder side.

At this time, the pump 10 is, as shown in FIGS. 1 and 2, a pump shaft 1 inserted into a pump casing 11.
2 has a rotor 13 fixed by serration and driven to rotate. The pump casing 11 is configured by integrating a front casing 11A and a rear casing 11B with bolts, and supports the pump shaft 12 via bearings 15A and 15B. The pump shaft 12 can be directly driven to rotate by an automobile engine.

The rotor 13 accommodates vanes 17 in grooves 16 provided at a plurality of positions in the circumferential direction, and allows each vane 17 to move in the radial direction along the grooves 16.

A pressure plate 18 and an adapter ring 19 are fitted on the front casing 11A of the pump casing 11 in a stacked state, and these are positioned in the circumferential direction by fulcrum pins 21 in the rear casing 1A.
1B is fixedly held from the side. Fulcrum pin 21
Is mounted and fixed to the rear casing 11B.

A cam ring 22 is fitted on the adapter ring 19 fixed to the pump casing 11. The cam ring 22 surrounds the rotor 13 with a certain amount of eccentricity with the rotor 13 and forms a pump chamber 23 between the cam ring 22 and the outer peripheral portion of the rotor 13. A suction port 24 provided in the rear casing 11B is opened on the upstream side in the rotor rotation direction of the pump chamber 23. The suction port 24 of the pump 9 is connected to the suction port 24 via a suction passage 25 provided in the casing 11B. Are communicated. On the other hand, pump room 2
3, a pressure plate 1 is provided on the downstream side in the rotor rotation direction.
The discharge port 27 provided in the discharge port 2 is opened.
A discharge port 29 of the pump 10 is communicated with 7 via a discharge passage 28 provided in the casing 11A.

Thus, in the variable displacement pump 10, the rotor 13 is driven to rotate by the pump shaft 12,
The vane 17 of the rotor 13 has a centrifugal force and the back pressure groove 16 of the vane.
When rotating by being pressed against the cam ring 22 at the pressure of the pump chamber 23, the volume surrounded by the adjacent vanes 17 and the cam ring 22 is enlarged along with the rotation on the upstream side in the rotor rotation direction of the pump chamber 23 to suck the working fluid from the suction port 24, On the downstream side of the pump chamber 23 in the rotor rotation direction, the volume enclosed between the adjacent gates 17 and the cam ring 22 is reduced with rotation and the working fluid is discharged from the discharge port 27.

The variable displacement pump 10 has a discharge flow control device 40 as described below.

The discharge flow control device 40 mounts the above-mentioned fulcrum pin 21 on the vertically lower part of the above-mentioned adapter ring 19 fixed to the pump casing 11 and
2 is supported by the fulcrum pin 21, and the cam ring 22 is swingably displaceable within the adapter ring 19. The discharge flow control device 40 can apply an urging force to the cam ring 22 so that the volume of the pump chamber 23 is maximized by the spring 42 backed up by the cap 41 screwed to the front casing 11A.

The discharge flow control device 40 has first and second fluid pressure chambers 44A and 44B divided between the cam ring 22 and the adapter ring 19. That is, the first fluid pressure chamber 44A and the second fluid pressure chamber 44B
And the adapter ring 19 are divided by the fulcrum pin 21 and the sealing material 45 provided at the axially symmetric position.

The discharge flow control device 40 is provided with a fixed orifice 46 (metering orifice) at an intermediate portion of the discharge passage 28 of the front casing 11A, and a part of the fluid before passing through the fixed orifice 46 is branched into a branch passage 47A. A part of the fluid after passing through the fixed orifice 46 is supplied to the first fluid pressure chamber 44A through the first throttle 48A from the branch passage 47.
B is guided to the second fluid pressure chamber 44B via the second throttle 48B.

Further, the discharge flow control device 40 controls the first fluid pressure chamber 44A through the cover 11 through the variable orifice 51.
B communicates with the suction passage 25 from the communication passage 52 provided in
The degree of restriction of the variable orifice 51 is set to increase as the rotation speed of the pump 10 increases. At this time, the variable orifice 51 connects the communication passage 53 (having the throttle 53A) with the first fluid pressure chamber 44A provided on the cam ring 22 and the communication passage 52 with the above-described suction passage 25 provided on the cover 11B side. Provided in the area. Variable orifice 5
A pump 1 has a notch shape with a sharp tip (FIG. 4).
As the rotation speed of 0 increases, the cam ring 22 moves so as to reduce the volume of the pump chamber 23,
The area of communication with the communication passage 52 is reduced, in other words, the degree of restriction is increased.

Accordingly, the discharge flow characteristics of the pump 10 provided with the discharge flow control device 40 are as follows (FIG. 5).

(1) AB In the region from the start of the engine where the rotation speed of the pump 10 is low to the idling state, the pressure loss at the fixed orifice 46 of the discharge fluid discharged from the pump chamber 23 is still small. The differential pressure between the pressure applied from the throttle 48A to the first fluid pressure chamber 44A and the pressure applied from the second throttle 48B to the second fluid pressure chamber 44B is small.
Maintain the original state of being energized. Therefore, the pump 10
Discharge flow rate increases in proportion to the rotation speed.

(2) BC If the discharge flow rate from the pump chamber 23 increases due to an increase in the rotation speed of the pump 10, the pressure loss in the fixed orifice 46 increases, and the first throttle 48A moves to the first fluid pressure chamber 44A. From the second throttle 48B to the second fluid pressure chamber 4
The differential pressure of the pressure reaching 4B increases, and the cam ring 22 moves due to this differential pressure, and the volume of the pump chamber 23 is gradually reduced. Therefore, the discharge flow rate of the pump 10 can maintain a constant large flow rate by offsetting the increase in the flow rate due to the increase in the number of revolutions and the decrease in the flow rate due to the volume reduction of the pump chamber 23 with respect to the increase in the number of revolutions. it can.

At this stage, the degree of restriction of the variable orifice 51 for reducing the pressure in the first fluid pressure chamber 44A is low, and the variable orifice 51 is divided into the first fluid pressure chamber 44A and the second fluid pressure chamber 44B.
Is reduced, and the degree of decrease in the flow rate due to the reduction in the volume of the pump chamber 23 is made relatively small.

(3) C-D When the number of revolutions of the pump 10 continuously increases and the cam ring 22 further moves, the degree of restriction of the variable orifice 51 for reducing the pressure in the first fluid pressure chamber 44A increases, and the variable orifice 51 Reference numeral 51 further increases the pressure difference between the first fluid pressure chamber 44A and the second fluid pressure chamber 44B, increases the flow rate decrease due to the volume reduction of the pump chamber 23, and reduces the discharge flow rate of the pump 10.

(4) D-E When the rotational speed of the pump 10 reaches a high-speed operation range of the automobile exceeding a certain value, the cam ring 22 reaches the limit of movement, and the volume of the pump chamber 23 becomes minimum. The discharge flow rate of the pump 10 is
The presence of the fixed orifice 46 maintains a constant small flow rate.

Therefore, according to the present embodiment, the following operations are provided. A fixed orifice 46 provided in the discharge passage 28 of the pump 10 and a part of the fluid around the fixed orifice 46
A first throttle 48A and a second throttle 48B leading to the fluid pressure chamber 44A and the second fluid pressure chamber 44B, respectively;
The discharge flow rate can be controlled by changing the volume of the pump chamber 23 according to the pump rotation speed by the variable orifice 51 that communicates A with the suction side. Therefore, the device configuration can be simplified.

Only a part of the discharge flow supplied from the pump 10 to the power cylinder side is guided to the first fluid pressure chamber 44A and the second fluid pressure chamber 44B via the first throttle 48A and the second throttle 48B. When an unexpected steering reaction force such as kickback, in which the wheels receive a lateral force from the curb of the road, acts on the power cylinder, all of the oil flowing backward from the power cylinder remains in the first fluid pressure chamber 44A or the second fluid pressure chamber 44A. It does not flow into the fluid pressure chamber 44B. As a result, unexpected movement displacement of the cam ring 22 and, consequently, unexpected volume change of the pump chamber 23 are not caused, and steering stability can be improved.

Only a part of the discharge flow rate supplied from the pump 10 is guided to the first fluid pressure chamber 44A and the second fluid pressure chamber 44B via the first throttle 48A and the second throttle 48B. Fluctuations (pulsations) in the discharge flow rate due to the rotation of the pump 10 do not directly act on the first fluid pressure chamber 44A or the second fluid pressure chamber 44B. As a result, vibrations caused by fluctuations in the discharge flow rate of the pump 10 are reduced.
2, the control of the volume change of the pump chamber 23 is stabilized, and the steering stability can be improved.

The first fluid pressure chamber 44A on the high pressure side is depressurized by the variable orifice 51, and the variable orifice 51
The discharge flow rate can be controlled by changing the throttling degree according to the pump rotation speed. Therefore, by changing the change in the degree of throttle of the variable orifice 51 with respect to the rotation speed of the pump 10, the flow characteristics of the pump 10 can be easily changed.

The variable orifice 51 is provided on the cam ring 22
The orifice 5 is provided in the connection area of the communication passage 53 with the first fluid pressure chamber 44A provided on the side of the pump casing 11A and the communication passage 52 with the suction side provided on the side of the pump casing 11A.
The aperture of 1 can be easily changed by moving the cam ring 22.

By making the variable orifice 51 have a notch shape with a sharp tip, the opening of the orifice 51 is reduced only to the sharp tip side of the notch as the pump rotation speed increases. The aperture of the orifice 51 can be easily changed.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and the design may be changed without departing from the scope of the present invention. The present invention is also included in the present invention. For example, in the embodiment of the present invention, the configuration of the discharge flow control device 40 provided in the pump 10 can be variously modified. The variable orifice 51 is not limited to the notch shape, and can adopt various forms, and as a result, the flow characteristics of the pump 10 can be variously modified.

The present invention can be applied to various devices other than the hydraulic power steering device.

[0044]

As described above, according to the present invention, in the variable displacement pump, the volume of the pump chamber can be stably changed while simplifying the device configuration.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a variable displacement pump.

FIG. 2 is a sectional view showing a variable displacement pump.

FIG. 3 is a circuit diagram showing a variable displacement pump.

FIG. 4 is an enlarged view showing a variable orifice.

FIG. 5 is a characteristic diagram showing a relationship between a pump speed and a discharge flow rate of the variable displacement pump.

FIG. 6 is a schematic diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 10 variable displacement pump 11 pump casing 12 pump shaft 13 rotor 16 groove 17 vane 21 fulcrum pin 22 cam ring 23 pump chamber 24 suction port 25 suction passage 27 discharge port 28 discharge passage 40 discharge flow control device 44A first fluid pressure chamber 44B first 2 fluid pressure chamber 46 fixed orifice 48A first restrictor 48B second restrictor 51 variable orifice 52, 53 communication passage

Claims (3)

[Claims] A rotor fixed to a pump shaft inserted into a pump casing, driven to rotate, and accommodates a large number of vanes in a groove so as to be movable in a radial direction. A cam ring forming a pump chamber between the cam ring and the outer circumference of the cam ring;
In addition, a biasing force for maximizing the volume of the pump chamber is applied to the cam ring, and first and second fluid pressure chambers are divided between the cam ring and the pump casing, and the pressure acting on both fluid pressure chambers is formed. A variable displacement pump having a discharge flow control device capable of controlling a discharge flow rate by changing a volume of a pump chamber by moving a cam ring against the urging force by a differential pressure of the discharge flow rate. The control device is provided with a fixed orifice in the discharge passage of the pump, a part of the fluid before passing through the fixed orifice is passed through the first throttle to the first fluid pressure chamber, and a part of the fluid after passing through the fixed orifice is passed through the second throttle. And the first fluid pressure chamber communicates with the suction side of the pump via a variable orifice, and the degree of throttle of the variable orifice is increased as the rotational speed of the pump increases. Variable displacement pump, wherein the door. 2. The variable orifice is provided in a connection area of a communication passage with a first fluid pressure chamber provided on a cam ring side and a communication passage with a suction side provided on a pump casing side, so that the variable displacement orifice is provided for the displacement of the cam ring. 2. The variable displacement pump according to claim 1, wherein the degree of restriction is changed according to the degree of restriction. 3. The variable displacement pump according to claim 2, wherein the variable orifice has a notch shape with a sharp tip.