JPH06167281A - Variable displacement pump - Google Patents

Abstract

PURPOSE:To simplify a structure of a variable orifice which displaces a cam ring in respect to a rotor in a variable volume pump, and improve reliability in operation. CONSTITUTION:A cam ring 17 which forms a pump chamber in a body 11 and between it and a rotator 15 is displaceably arranged, and energized so as to obtain a maximum volume of the pump chamber. Seal means 21, 47, 48 are arranged in a circular space between the cam ring and the body, for determining first, second and third fluid chambers 44, 45. A changeover valve 30 is provided for switching introduction passages of a fluid pressure across a variable metering orifice 40 and a pump suction side fluid pressure in respect to the respective fluid chambers. The variable orifice is composed of a port 29 which is formed on a plate as a side wall arranged on the side surface of the cam ring displaceably arranged in the body for communicating the pump discharge side with a circular space between the cam ring 17 and the rotor 15, and the side surface of the cam ring 17 which opens and closes an opening end of the port.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vane type variable displacement pump suitable for use in, for example, a power steering device for reducing the steering force of an automobile.

[0002]

2. Description of the Related Art A displacement vane pump, which is generally used as a pump for a power steering apparatus, is directly driven by an automobile engine to rotate. The higher the engine speed, the larger the discharge flow rate. On the other hand, the power steering device requires a higher steering assist force when the vehicle is stopped or traveling at a low speed, while reducing the steering assist force when traveling at a high speed, in contrast to the traveling stability and steering. It is desired from the viewpoint of feeling.

For this reason, in the conventional displacement pump, a pump capable of ensuring a discharge flow rate so as to obtain a required steering assist force when the rotation speed is in a low rotation range is used, and the rotation speed is a high rotation type. In some cases, a flow rate control valve is provided for returning a part of the discharge flow rate to the tank side. Then, the flow rate supplied to the power steering apparatus is controlled to be constant regardless of the number of revolutions of the engine, or the flow rate is controlled to be smaller in the high rotation range than in the low rotation range.

However, in such a conventional pump, it is necessary to attach a flow rate control valve, the structure of the entire pump is complicated, and not only the size is increased, but also the cost is increased. Further, in such a conventional displacement pump, the flow rate to be recirculated to the tank side becomes larger in the high engine speed region, which is a problem in terms of energy loss.

Therefore, as a pump used for this type of power steering apparatus, for example, Japanese Patent Laid-Open No. 53-130.
Japanese Patent Laid-Open No. 505 and JP-A-56-143383 have already proposed a variable displacement pump configured so that the discharge flow rate of the pump can be decreased stepwise as the rotation speed increases. In such a variable displacement pump, it is not necessary to use the above-mentioned flow rate control valve.

Here, in the former variable displacement pump, the eccentric amount between the rotor center of the vane pump and the center of the cylindrical cam surface on which the vane slides is variable, and the communication area of the variable orifice provided in the pump discharge passage is cylindrical. The cam ring having the cam surface is configured to be reduced in size in response to the displacement in the direction of reducing the eccentric amount. Then, by controlling the movement of the cam ring by utilizing the differential pressure before and after the variable orifice, the discharge flow rate can be reduced as the rotation speed of the rotor increases.

Further, in the latter variable displacement pump, the cam ring is configured to be movable, and a pair of control chambers are formed in a gap portion formed between the cam ring and the pump casing, each of which has a discharge passage. The pressure before and after the orifice is guided, and the differential pressure is directly applied to the cam ring to appropriately move against the urging force of the spring, so that an appropriate discharge flow rate control can be performed.

However, according to the above-mentioned conventional variable displacement pump, the cam ring is held in the pump housing so as to be linearly movable, and the cam ring is movable by the differential pressure before and after the variable orifice provided directly or indirectly in the discharge passage. However, it was a problem in terms of workability, reliability in operation, and durability, and was unrealizable.

Further, in Japanese Patent Laid-Open No. 58-93978 and Japanese Utility Model Publication No. 63-14078, a cam ring is arranged in a pump housing so as to be linearly displaceable in the radial direction, and a pump chamber is provided in the cam ring. The rotor for forming the rotor is rotatably accommodated, and the cam ring is moved and displaced with respect to the rotor by the pressure difference before and after the orifice provided in the pump discharge passage, and the orifice is moved in response to the eccentricity of the cam ring with respect to the rotor. There is disclosed a variable displacement pump capable of varying the flow passage area and varying the discharge flow rate to obtain a desired flow rate.

Particularly, in the latter conventional example, a control pin having a small diameter portion is interposed between the inner wall portion of the pump housing and the outer peripheral portion of the cam ring which can be displaced inside the pump housing. A variable orifice is formed with the control surface of the outer peripheral portion. The pressure before and after this orifice is applied to the cam ring to displace it, while forming an orifice whose opening area decreases as the eccentric amount of this cam ring decreases, thereby obtaining a desired discharge flow rate. It was something that

[0011]

However, in such a conventional structure, the structure of the variable orifice portion for moving and displacing the cam ring is complicated, it is difficult to obtain the processing accuracy of each portion, and in terms of processing and assemblability. This causes a problem and is unfavorable in terms of the reliability of the operation of the variable orifice section.

In particular, according to the above-mentioned conventional structure, the cam ring is required by the pressure before and after the orifice at the time of deformation such that dust or the like is mixed in the hydraulic fluid as the control fluid or the pump housing is distorted at high pressure. The operation performance of displacing in that state was likely to become unstable. In other words, as is well known, the cam ring has only a small gap on the side surface to prevent internal leakage, and smooth movement displacement can be obtained by clogging dust and increasing contact resistance on the side surface. Could not be achieved, and there was a risk of causing a problem that a desired adjusted flow rate could not be obtained.

If the pressure difference before and after the orifice is increased in order to overcome these resistances, the characteristic of the low displacement type power steering device, which is the original purpose of the variable displacement pump, is lost. Therefore, it is necessary to take some measures to solve these problems.

The present invention has been made in view of the above circumstances. For example, in a vane type oil pump, the cam ring is configured so that the discharge flow rate per one rotation is variable in accordance with the change in the pump rotation speed. With a simple structure, it is possible to obtain a desired discharge flow rate according to the pump rotation speed by increasing or decreasing the flow passage area of the flow rate adjusting metering orifice by means of the cam ring that moves and displaces. The purpose is to obtain a variable displacement pump that is highly reliable in operation.

[0015]

In order to meet such demands, a variable displacement pump according to the present invention is a cam ring which is movably arranged in a pump body and which forms a pump chamber with an outer peripheral portion of a rotor. An urging means for urging the cam ring so as to maximize the volume of the pump chamber, a variable metering orifice provided in the middle of the pump discharge side passage, and an annular clearance space between the cam ring and the pump body. The first, second and third fluids that are formed by being divided by the sealing means interposed at predetermined positions to move and displace the cam ring by selectively introducing the fluid pressure before and after the orifice and the fluid pressure on the pump suction side. A variable chamber, and a switching valve that controls switching between the fluid pressure before and after the orifice for each fluid chamber and the introduction path of the fluid pressure on the suction side of the pump. And a cam ring side surface portion that controls opening and closing of the opening end of the opening portion, which is formed in a side wall portion of the cam ring side surface portion and connects the pump discharge side and the annular gap space. To the fluid chamber of the pump, the fluid pressure on the upstream side of the orifice or the fluid pressure on the suction side of the pump is selectively introduced on the discharge side of the pump, and the fluid pressure on the suction side of the pump or the fluid pressure on the downstream side of the orifice is selectively introduced to the second fluid chamber. In addition, the fluid pressure on the downstream side of the orifice is introduced into the third fluid chamber.

[0016]

According to the present invention, when the pump is started, the cam ring is urged to one side in the pump body by the urging means so as to maximize the volume of the pump chamber between the cam ring and the rotor. The switching valve is in a state in which the first fluid chamber is connected to the pump suction side and the second and third fluid chambers are connected to the variable metering orifice downstream side on the pump discharge side.

When the pump speed is gradually increased and driven, the switching valve is operated by the differential pressure between the fluid pressure on the upstream side of the orifice on the pump discharge side and the fluid pressure on the downstream side, whereby the cam ring is driven. The fluid pressure before and after the orifice is introduced into the first fluid chamber and the third fluid chamber on both sides and the second fluid chamber is connected to the pump suction side, whereby the cam ring resists the biasing means. Is moved and displaced in the direction in which the pump chamber volume decreases.

At this time, the second fluid chamber positioned opposite to the first fluid chamber is connected to the pump suction side by the switching operation of the switching valve. The cam ring is moved and displaced in a desired state by the fluid pressure before and after the orifice introduced into the third fluid chamber and the difference in the pressure receiving area of each chamber, whereby the side face of the cam ring opens and closes the opening end of the hole. By changing the amount and changing the variable metering orifice, it is possible to obtain a stable movement displacement of the cam ring and obtain a predetermined flow rate.

[0019]

1 to 5 show an embodiment of a variable displacement pump according to the present invention. In these drawings, in this embodiment, a vane type oil pump serving as a hydraulic pressure generation source of a power steering apparatus is shown. Will be described.

First, a vane type variable displacement pump, generally designated by reference numeral 10, is provided with a front body 11 and a rear body 12 constituting a pump body, as is apparent from FIGS. 1 and 2. This front body 1
1 has a substantially cup shape as a whole, and a storage space 14 for storing and arranging the pump component 13 therein is formed therein, and a rear body 12 is combined so as to close an open end of the storage space 14. It is integrated. It should be noted that the front body 11 has a drive shaft 16 for rotatably driving the rotor 15 as a rotor of the pump component 13 from the outside, and the bearing 1
6a, 16b, 16c (16b is the rear body 12 side, 1
6c is rotatably supported by a pressure plate 20 described later).

Reference numeral 17 denotes an inner cam surface 17a fitted and arranged on the outer peripheral portion of the rotor 15 having a vane 15a. A pump chamber 18 is provided between the inner cam surface 17a and the rotor 15.
The cam ring 17 forms a cam ring 17 that can be moved and displaced in an adapter ring 19 provided in a fitted state on the inner wall portion of the storage space 14 so as to change the volume of the pump chamber 18, as described later. It is located in. The adapter ring 19 holds the cam ring 17 in the housing space 14 of the body 11 so that the cam ring 17 can move and displace, and forms a fluid passage 19a described later with the inner wall portion of the body.

Reference numeral 20 denotes the rotor 15 and the cam ring 1 described above.
7 and an adapter ring 19 are pressure plates that are stacked in pressure contact with the front body 11 side of the pump cartridge, and the end surface of the rear body 12 is pressed against the opposite side surface of the pump cartridge as a side plate. The bodies 11 and 12 are integrally assembled into a required assembled state. Then, by these members, the pump component 13
Is configured. The pressure plate 20 and the rear body 12 serving as a side plate laminated on the pressure plate 20 via the cam ring 17 are formed by a seal pin 21 (which will be described later) that also functions as a positioning pin and an appropriate detent means (not shown). It is integrally assembled and fixed while being positioned in the rotational direction.

Reference numeral 23 denotes a pump discharge side pressure chamber formed on the bottom side of the storage space 14 of the front body 11 so that the pump discharge side pressure is applied to the pressure plate 20. Reference numeral 24 denotes a pump discharge side passage which is formed in a pressure plate 20 which guides the pressure oil from the pump chamber 18 to the pump discharge side pressure chamber 23.

Reference numeral 25 denotes a pump suction side formed in the rear body 12 so as to guide the pump suction side fluid from a suction port 26 (detailed illustration is omitted) provided in a part of the rear body 12 to the pump chamber 18. In the passage, this passage 25
Is a pump suction opening 2 that opens at the end surface of the rear body 12.
It is connected to the pump chamber 18 via 5a.

Reference numeral 28 denotes a fluid passage 20 formed at different positions from the pump chamber 18 to the pump discharge side passage 24, the pump discharge side pressure chamber 23, and the pressure plate 20.
a and a pump discharge side fluid pressure sent through the small diameter hole 29, a power steering device (P in the figure)
(Shown by S), and a variable metering orifice 40 is provided at a side portion of the front body 11 at a connecting portion to the storage space 14. It is provided as it is formed.

Numeral 30 is disposed substantially orthogonal to the side of the storage space 14 in the front body 11, and fluid pressure control for moving and displacing the cam ring 17 with respect to the rotor 15 is performed by a variable metering orifice 40 which will be described later. The switching valve 30 is a spool 3 that is slidably operated by a fluid pressure difference and a biasing force of a spring 31 in a valve hole 30a formed in the body 11 from the side.
Equipped with 2.

In this switching valve 30, the spool 3
The fluid pressure on the upstream side of the variable metering orifice 40, which will be described later, is introduced from the pressure chamber 23 on the pump discharge side to the one chamber 32a (the left chamber in FIG. 2) 2 via the fluid passage 23a. Reference numeral 33 in the figure is a plug for closing the valve hole 30a, which has a rod 33a for locking the leftward movement position of the spool 32 in the valve hole 30a at a position that does not close the opening end of the fluid passage 23a.

A spring 31 is provided in the other chamber (right chamber in FIG. 2) 32b of the spool 32, and the fluid pressure on the downstream side of the variable metering orifice 40 described above is connected to the discharge port 28. From the middle of the body 11,
It is guided through a fluid passage 19 a formed between the adapter rings 19 and a fluid passage 34 formed in the body 11.

Further, in the substantially central portion of the valve hole 30a,
Suction side passage 2 branched from the pump suction side passage 25
7 is open, and fluid passages 35, 3 from the chambers divided into a plurality of annular gap spaces formed between the adapter ring 19 and the cam ring 17 are provided on both sides in the axial direction thereof.
6 (including the passage holes 35a and 36a of the adapter ring 19) are opened, and these passages 35 and 36 are selectively provided to the pump suction side passage 27, the left chamber 32a or the right chamber 32b by the movement of the spool 32. Is configured to be connected to.

In the vane type variable displacement pump 10 described above, most of its construction is well known in the art, and its detailed description is omitted.

According to the present invention, in the variable displacement pump 10 having the above-described structure, the cam ring 17 which is arranged in the bodies 11 and 12 so as to be movable and displaceable and which forms the pump chamber 18 between the outer periphery of the rotor 15 and the cam ring 17. Is provided in the middle of the pump discharge side passage (24, 23, 20a, 29, 28) and a coil spring 42 which is a means for urging the pump chamber 18 through the cylindrical pressing member 41 so as to maximize the volume of the pump chamber 18. Fluid pressure before and after the orifice 40, pump suction by the sealing means interposed in a predetermined position of the annular gap space between the variable metering orifice 40 and the body 11 (adapter ring 19) on the outer peripheral portion of the cam ring 17. The first, second, and third fluid chambers 43, 44, 4 that move and displace the cam ring 17 by selectively introducing the fluid pressure in the side passage 27 If, each of these fluid chambers 43, 44,
A switching valve 3 for controlling the switching of the introduction paths of the fluid pressure before and after the orifice 40 with respect to 45 and the fluid pressure on the pump suction side.
It has 0 and.

The variable metering orifice 40 is formed in the pressure plate 20, which is a side wall portion arranged on the side surface of the cam ring 17, to form a hole 29 for connecting the pump discharge side and the annular gap space. And a side surface portion of the cam ring 17 for controlling the opening and closing of the opening end, and selectively introduces the fluid pressure of the orifice 40 upstream side or the fluid pressure of the pump suction side into the first fluid chamber 43 on the pump discharge side,
The pump suction side fluid pressure or the orifice 40 downstream side fluid pressure is selectively introduced into the second fluid chamber 44, and the orifice 40 downstream side fluid pressure is introduced into the third fluid chamber 45. It has a feature.

Here, in order to divide the above-mentioned annular clearance space between the cam ring 17 and the adapter ring 19, in this embodiment, as apparent from FIG. 1, the annular clearance space is divided into left and right. The second seal pin 21 that is positioned above and below the first seal pin 21 that also functions as the above-described positioning pin and the groove that is recessed in the sliding contact surface of the cam ring 17 are incorporated through the resin sheet into the second groove. A seal pin 47 is provided, and the left space is used as a first fluid chamber 43, and this chamber 43 can be connected to the left chamber 32a of the switching valve 30 or the pump suction side via the fluid passages 35a, 35. There is.

Further, in the space on the left side in FIG. 1, a third seal pin 48 is arranged so as to be movable back and forth toward the outer peripheral portion of the cam ring 17 above the variable metering orifice 40 portion reaching the discharge port 28. The upper right space partitioned by this is the second fluid chamber 44, which can be connected to the pump suction side of the switching valve 30 or the right chamber 32b via the fluid passages 36a, 36.

Further, the lower right space partitioned by the third seal pin 48 is a third fluid chamber 45, which is a variable metering orifice 40 in the pump discharge side passage.
It is configured as a chamber on which the fluid pressure on the downstream side of is acting.
The chamber 45 is provided with a switching valve 30 via a passage 19a and a passage 34 formed outside the adapter ring 19.
Is connected to the right chamber 32b.

Here, the third seal pin 48 described above is used.
As is clear from the relationship between FIG. 1 and FIG. 3, the upper and lower chambers 44, irrespective of the amount of displacement of the cam ring 17,
It is configured to be held with a biasing force and a guide amount in a direction capable of appropriately partitioning 45, and for example, fluid pressure or the like may be used as the above-mentioned biasing force. However, the present invention is not limited to this, and for example, a spring 48a or the like may be used as shown in FIG. The point is that the seal pin 48 moves in accordance with the movement of the cam ring 17 and the sealing property at that portion can be secured.

On the other hand, the pressing member 41 having the above-mentioned cylindrical shape.
As is clear from FIGS. 1, 2 and 4, the guide hole 19 is formed in a part of the outer peripheral portion of the adapter ring 19.
The coil spring 42 is arranged so as to be movable back and forth in the centripetal direction with respect to the cam ring 17 in b, and is constantly pressed to the left side in FIG. 1 by a coil spring 42 interposed between the cam ring 17 and the discharge port 28. . The pressing member 41
As the pressure of the cam ring 17, the fluid flow to the discharge port 28 and the variable metering orifice 4
If the shape does not interfere with the hole 29 that constitutes 0,
It may have any shape.

According to the above-described structure, when the pump 10 is started, the cam ring 17 has a maximum volume of the pump chamber 18 between the cam ring 17 and the rotor 15 on one side in the storage space 14 of the body 11, as shown in FIG. The coil spring 42 and the pressing member 41 are urged so that At this time, as is clear from FIG. 1, the switching valve 30 has the first fluid chamber 43 on the pump suction side and the second and third fluid chambers 44,
45 is a variable metering orifice 40 on the pump discharge side
Is connected to the downstream side of.

When the pump rotational speed is gradually increased and driven, the spool 32 of the switching valve 30 is switched by the pressure difference between the fluid pressure on the upstream side of the orifice 40 on the pump discharge side and the fluid pressure on the downstream side. The cam ring 17
The fluid pressure before and after the orifice 40 is introduced into the first fluid chamber 43 and the third fluid chamber 45 on both sides, and the second fluid chamber 44 is connected to the pump suction side. As a result, the cam ring 1
7 moves and displaces in the direction in which the volume of the pump chamber 18 decreases (right side in FIGS. 1 and 3) against the coil spring 42.

At this time, the switching operation of the switching valve 30 causes the second fluid chamber 44, which is positioned to face the first fluid chamber 43, together with the third fluid chamber 45.
Is connected to the suction side of the pump, the orifice 40 introduced into the first fluid chamber 43 and the third fluid chamber 45.
The cam ring 17 is moved and displaced in a required state by the difference between the front and rear fluid pressures and the pressure receiving areas of the respective chambers 43, 44, 45, whereby the opening and closing amount of the side surface of the cam ring 17 with the opening end of the hole 29 is opened. By making the change as apparent from FIG. 5 and changing the variable metering orifice 40, it is possible to obtain a stable movement displacement of the cam ring 17 and obtain a predetermined flow rate to reach the power steering apparatus PS.

In particular, according to the above-mentioned structure, the switching valve 30 is switched and controlled by the differential pressure generated in the variable metering orifice 40 by the pump discharge amount which increases and decreases with the pump rotation speed, whereby the cam ring 17 is coiled. Against the biasing force of the spring 42, or in response to this biasing force,
It can be moved and displaced, resulting in a pump chamber 18
Is variably controlled, and the discharge amount from the pump can be controlled so as to obtain a desired characteristic by balancing the discharge amount from the pump in accordance with the pump rotation speed as shown in FIG. 5, for example.

That is, the variable metering orifice 4
Due to the opening area that changes when the cam ring 17 closes the hole 29 that forms 0, as shown in FIG. 5, the hole 29 is set up so that a predetermined flow rate is obtained when the rotation speed is small, and is larger than a certain value. It is preferable that the flow rate is reduced when it reaches a predetermined value, and that the flow rate is about half of the initial flow rate at a predetermined number of revolutions or more. Here, such discharge amount control is obtained by the variable metering orifice 40 including the hole 29 and the cam ring 17 that controls the opening amount, and for example, the hole 29.
The characteristics can be changed by arbitrarily changing the shape of or by adjusting the opening / closing control amount by the cam ring 17.

Further, according to the present invention, the fluid pressure on the upstream side of the orifice 40 guides the displacement of the cam ring 17 for controlling the flow rate by the variable metering orifice 40 as described above due to the rotation around the seal pin 21. The fluid pressure on the downstream side is introduced into the chamber 43 of about half the circumference of the cam ring 17 and a part of the chamber 45 facing the chamber 43, and the remaining part (second fluid chamber 44) is connected to the pump suction side. Thus, the cam ring 17 is made easy to move.

Therefore, for example, even if the pump discharge pressure becomes high and the bodies 11 and 12 are distorted or deformed, or dust or the like is mixed in the fluid and intervenes at a position where the movement of the cam ring 17 is hindered. The force for moving the cam ring 17 can be obtained by comparing the pump discharge pressure with a sufficiently small pump suction pressure, and the cam ring 17 can be moved and displaced lightly with a strong force. In this case, a predetermined flow rate can be stably obtained, and the differential pressure before and after the orifice may be small, so that power consumption can be saved.

The present invention is not limited to the structure of the embodiment described above, and the shape and structure of each portion can be freely modified or changed. For example, the cam ring 17 constituting the variable metering orifice 40 can be opened and closed. Of the hole 29 to be formed, the structure of the switching valve 30, the seal pins 21, 47,
Needless to say, various modifications may be adopted for the parts such as 48. Further, in the above-described embodiment, the case where the hole 29 that is opened and closed by the cam ring 17 that constitutes the variable metering orifice 40 is formed in the pressure plate 20 that is arranged on the side surface of the cam ring 17 is illustrated.
The present invention is not limited to this, and any hole may be used as long as it is a hole formed in the side wall portion facing the side surface of the cam ring 17.

Further, the vane type variable displacement pump 10 having the above-mentioned structure is not limited to the structure of the above-mentioned embodiment, and of course, various devices other than the power steering device described in the above-mentioned embodiment, It goes without saying that it may be applied to a device.

[0047]

As described above, according to the variable displacement pump according to the present invention, the cam ring which is arranged in the pump body so as to be movable and displaceable and which forms the pump chamber with the rotor, and the pump chamber volume. The biasing means for maximizing the pressure, the variable metering orifice provided in the middle of the pump discharge side passage, and the sealing means interposed at a predetermined position in the annular clearance space between the cam ring outer periphery and the body. First, second, and third fluid chambers that are dividedly formed and that move and displace the cam ring by selectively introducing fluid pressures before and after the orifice and fluid pressure on the pump suction side, and orifices for these fluid chambers It is equipped with a switching valve that controls switching between the front and rear fluid pressure and pump suction side fluid pressure introduction paths, and a variable metering orifice is formed in the side wall of the cam ring. A hole connecting the pump discharge side and the annular gap space, and a cam ring side surface controlling the opening and closing of the opening, and in the first fluid chamber, on the pump discharge side, the orifice upstream side fluid pressure or the pump suction side. A fluid pressure is selectively introduced, and a pump suction side fluid pressure or an orifice downstream side fluid pressure is selectively introduced into the second fluid chamber;
Since the fluid pressure on the downstream side of the orifice is introduced into the fluid chamber, the various excellent effects listed below are exhibited despite the simple structure.

The pump discharge flow rate is made variable in accordance with the change of the pump rotation speed so that the cam ring can be moved and displaced easily and appropriately in a required state, and the flow of the flow rate adjusting metering orifice can be made by the moving and displacing cam ring. It is possible to increase or decrease the passage area to a required state to obtain a desired discharge flow rate according to the pump rotation speed.

For example, even if the pump discharge pressure becomes high and the body is distorted or deformed, or dust or the like is mixed in the fluid and the body is placed at a position that hinders the movement of the cam ring, the force for moving the cam ring. Can be obtained by comparing the pump discharge pressure with a sufficiently small pump suction pressure, and the cam ring can be moved and displaced lightly with a strong force. Then, a predetermined flow rate can be stably obtained,
Further, since the pressure difference before and after the orifice may be small, the power consumption can be saved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a variable displacement pump according to the present invention and showing a main structure of the pump.

FIG. 2 is a longitudinal sectional view of an essential part shown in section for explaining the structure of the essential part of FIG.

FIG. 3 is a schematic cross-sectional view for explaining a state when driving the pump from FIG.

FIG. 4 is a schematic perspective view showing an example of a pressing member for pressing and urging the cam ring.

FIG. 5 is a characteristic diagram for explaining the relationship between the rotation speed and the flow rate in the pump according to the present invention.

FIG. 6 is an enlarged view of a main part showing a modified example of the present invention.

[Explanation of symbols]

 10 vane type variable displacement pump 11 front body 12 rear body 13 pump component 14 storage space 15 rotor 15a vane 16 drive shaft 17 cam ring 17a cam surface 18 pump chamber 19 adapter ring 20 pressure plate 21 seal pin 23 pump discharge side pressure chamber 23a pump Discharge side passage 25 Pump suction side passage 28 Discharge port 29 Hole portion constituting variable metering orifice 30 Switching valve 32 Spool 34 Fluid passage 35 Passage hole 36 Passage hole 40 Variable metering orifice 42 Coil spring (biasing means) 43th 1st fluid chamber 44 2nd fluid chamber 45 3rd fluid chamber 47 2nd seal pin 48 3rd seal pin

Claims (1)

[Claims] 1. A rotor, which has a vane and is rotatably disposed in a pump body, and is fitted so as to form a pump chamber between the rotor outer peripheral portion and is movable and displaceable in the pump body. And a biasing means for biasing the cam ring so as to maximize the volume of the pump chamber between the cam ring and the outer peripheral portion of the rotor, and a midway on the discharge side passage of the pressure fluid discharged from the pump chamber. Fluid pressure before and after the variable metering orifice and the suction side of the pump, which are divided and formed by sealing means interposed at a predetermined location of an annular clearance space between the variable metering orifice provided and the pump body at the outer peripheral portion of the cam ring. First, second and third fluid chambers for moving and displacing the cam ring by selectively introducing the fluid pressure of the fluid chambers and the variable mechanisms for the respective fluid chambers. And a switching valve for switching and controlling the introduction path of the fluid pressure before and after the turbineing orifice and the fluid pressure on the suction side of the pump, and the variable metering orifice is bored in the side wall portion arranged on the side surface portion of the cam ring. The pump discharge side is connected to the cam ring and the annular gap space between the rotor and the cam ring side surface part that controls opening and closing of the opening end of the hole portion. Side, the variable metering orifice upstream fluid pressure and the pump suction side fluid pressure are selectively introduced, and the pump suction side fluid pressure and the variable metering orifice downstream fluid pressure are selectively introduced into the second fluid chamber. And a variable pressure pump downstream side fluid pressure is introduced into the third fluid chamber.