JPH0821375A - Variable-displacement pump - Google Patents

Abstract

PURPOSE:To prevent the vibration phenomenon of a cam ring by eliminating the unbalanced force generated on the inner diameter side of the cam ring to prevent the large fluctuation of the flow rate on the pump discharge side. CONSTITUTION:A cam ring 17 to form a pump chamber 18 on an outer circumferential part of a rotor which is rotatable in a body 11 is movably arranged, and energized in the direction where the volume of the pump chamber is maximized. Sealing means 21, 45 are interposed in the annular space between the outer circumferential part of the cam ring and the body to form first and second hydraulic chambers 34, 35 to move and displace the cam ring. Pistons 50, 51 capable of pressing in the centrifugal direction are provided on the outer circumferential surface of the cam ring corresponding to intermediate ranges 48, 49 between the respective ranges by openings 25a, 24a on the suction and discharge sides. The inner pressure of the pump chamber at each intermediate range is introduced to the back surface side of the piston, and the piston is pressed and kept at the prescribed position with the balanced pressing force of the cam ring at the respective pistons.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement vane pump used in a pressure fluid utilizing device such as a power steering device for reducing steering force of an automobile.

[0002]

2. Description of the Related Art As a pump for a power steering apparatus, a displacement vane pump which is directly driven by an automobile engine has been generally used. However, in such a displacement pump, since the discharge flow rate is increased / decreased according to the engine speed that is the drive source, a large steering assist force is generated when the vehicle is stopped or traveling at low speed, and the steering assist force is generated at high speed traveling. It has a characteristic that is contrary to the power steering device of making it smaller.

Therefore, as such a pump,
A flow rate control is used to control the discharge flow rate when the number of rotations is high, and a discharge flow rate that ensures the required steering assist force is used even when the vehicle is traveling at low speeds. A valve is required. Therefore, in such a pump, the number of constituent components is increased, the structure is complicated, and the passage structure is also complicated, so that the overall size and cost are inevitable.

Further, when the flow rate control valve is used, the discharge flow rate is returned to the tank side, so that there is a problem that driving horsepower increases, energy loss increases, and the oil temperature rises.

As a means for solving such a problem in the displacement type, there is, for example, a variable displacement vane pump capable of proportionally decreasing the discharge flow rate per revolution (cc / rev) as the number of revolutions increases. JP-A-53-130505, JP-A-56-143383, JP-A-58-
Various proposals have been made in Japanese Patent No. 93978, Japanese Utility Model Publication No. 63-14078, and the like.

In such a variable displacement type pump, a flow rate control valve like that of a displacement type is not required, useless increase of driving horsepower is prevented, energy efficiency is excellent, and the return flow rate to the tank side is further improved. Therefore, the problem of oil temperature rise can be reduced, and problems such as leakage inside the pump and volumetric efficiency decrease can be prevented.

Here, for example, Japanese Patent Laid-Open No. 56-14338.
The variable displacement pump disclosed in Japanese Patent No. 3 or the like has a cam ring configured to be movable within a pump casing, and
Fluid pressure chambers that form a pair of control chambers are formed in the gap formed between the cam ring and the pump casing, and pressures before and after the orifice provided in the middle of the discharge passage are introduced to the respective chambers, and the pressure difference is applied to the cam ring. By directly acting and moving this cam ring appropriately against the urging force of the spring, the volume of the pump chamber is changed and the appropriate discharge flow rate control is performed.

However, in such a conventional pump, the cam ring is held so as to be linearly movable within the pump housing, and the cam ring is moved and displaced by the pressure difference on the downstream side on the orifice provided directly or indirectly in the discharge passage. However, there are many constituent parts and fluid passages etc. of each part of the pump, and there are problems in terms of workability and assembly, reliability in operation, and durability, and it is not feasible. there were.

An example of the variable displacement vane pump as described above will be briefly described with reference to FIG. 7. In the figure, 1 is a pump body, 1 a is an adapter ring, and 2 is formed in the adapter ring 1 a of the body 1. Oval space part 1
The cam ring is provided so as to be capable of swinging displacement via the support shaft portion 2a in b and is biased by the pressing means in the direction indicated by the white arrow F in the figure. In the cam ring 2, a rotor 3 is housed eccentrically toward the other side so as to form a pump chamber 4 on one side, and is driven to rotate by an external drive source so that the vanes 3a held in the radial direction can be moved in and out. Is.

In the figure, 3b is a drive shaft of the rotor 3, and the rotor 3 is rotationally driven in the direction shown by the arrow in the figure. Also,
In the figure, 5a and 6a are formed in the body space 1b by opening to both side chambers 5 and 6 of the cam ring 2, and are provided in the chambers 5 and 6 for control pressure for oscillating displacement of the cam ring 2, for example, in the pump discharge side passage. In the passage for guiding fluid pressure before and after the variable orifice, the cam ring 2 is oscillated and displaced according to the flow rate on the pump discharge side, and the flow rate on the discharge side is decreased as the pump speed increases. It is configured to control the flow rate.

Reference numeral 7 denotes a pump suction side opening of the pump chamber 4 which faces the pump suction side area 4A, and 8 denotes a pump discharge side opening of the pump chamber 4 which faces the pump discharge side area 4B. Openings 7 and 8 are formed in either a pressure plate or a side plate (not shown) which is a fixed wall portion for holding the pump constituent element including the rotor 3 and the cam ring 2 by sandwiching it from both sides. .

Reference numerals 5 and 6 are a pair of high pressure side and low pressure side fluid pressure chambers formed on both sides of the outer peripheral portion of the cam ring 2 in the elliptical space portion 1b of the adapter ring 1a of the body 1 as described above. , These chambers 5 and 6 have the above-mentioned passage 5
a, 6a on the variable orifice of the pump discharge side passage,
The fluid pressure on the downstream side is introduced, the cam ring 2 is oscillated and displaced in a desired direction, the volume in the pump chamber 4 is varied, and the discharge flow rate is variably controlled according to the flow rate on the pump discharge side. is there. Here, the cam ring 2 is given an urging force from the fluid pressure chamber 6 side as indicated by F in the figure, and is normally pump chamber 4
The inner volume can be maintained at the maximum. Also,
In the figure, 2b is a shaft supporting portion 2a provided on the outer peripheral portion of the cam ring 2.
Together with this, it is a sealing material for defining the fluid pressure chambers 5 and 6 on both the left and right sides.

Reference numeral 8a is a whisker-shaped notch formed continuously at the end of the pump discharge side opening 8 in the pump rotation direction. This notch 8a is the tip of each vane 3a as the rotor 3 rotates. Between the vanes approaching the ends of the openings 7 and 8 and the space between the vanes adjacent to the vanes in the case where the sliding contact with the inner periphery of the cam ring 2 is performed to perform the pumping action. The purpose is to gradually release the fluid pressure from the high pressure side to the low pressure side. According to such a notch 8a, the space between the vanes 3a is formed by the openings 7, 8
By directly reaching the end of the, it is effective in preventing a sudden pressure fluctuation and a surge pressure, resulting in a pulsation problem in the fluid pressure on the pump discharge side.

[0014]

By the way, according to the conventional variable displacement vane pump structure as described above, the pump cartridge (pump action portion) formed by the pump components such as the rotor 3 and the cam ring 2 is provided in the pump chamber 4. An intermediate region corresponding to a region from the end point of the suction side opening 4A to the start point of the discharge side opening 4B and a region from the end point of the discharge side opening 4B to the start point of the suction side opening 4A (reference numeral 9A in FIG. 7, The pump chamber (the chamber partitioned by the vane 3a) located at the portion 9B) changes alternately between the pump discharge pressure and the pump suction pressure.

This is because when the vane 3a preceding the rotor 3 in the rotation direction reaches the opening 4B or 4A on the tip side in the rotation direction, it becomes a port pressure on the pump discharge side or suction side at the opening 4B or 4A. This is also because when the subsequent vane 3a is in the opening 4A or 4B on the rear end side in the rotational direction, the port pressure is generated by the subsequent opening.

In particular, this type of variable displacement vane pump generally employs an odd number of vanes 3a,
Opposing intermediate regions 9 centered on the rotation axis 3b of the rotor 3
Since A and 9B rotate while causing an angular deviation of 360 ° / 2n, the intermediate regions 9A and 9A facing each other also from this point.
There was a situation where the pressure balance at 9B was easily broken.

Due to such pressure fluctuations and pressure imbalances, thrust due to the mutual difference between the pump chambers in the intermediate regions 9A and 9B facing each other is applied to the inner surface of the cam ring 2, and the cam ring 2 vibrates, resulting in the pump. There is a problem that a large flow rate fluctuation and a large hydraulic pressure pulsation phenomenon occur on the discharge side, which causes a noise problem.

In this type of variable displacement pump, a relief valve for relieving excessive fluid pressure on the discharge side of the pump is generally attached, but the location and the construction of the relief valve are also incorporated. Depending on the operation, there may be a problem in reliability and embeddability in operation, and it is desired to take some measures to eliminate such a problem.

The present invention has been made in view of such circumstances, and the pressure in the intermediate region between the pump suction side region and the pump discharge side region in the pump chamber alternates between the suction side and the discharge side. A variable displacement pump that eliminates the imbalance of the cam ring due to the change in the output, prevents the cam ring from oscillating, reduces large flow fluctuations and pulsations on the pump discharge side, and eliminates noise problems. The purpose is to get.

[0020]

In order to meet such demands, a variable displacement pump according to the present invention has a rotor having a vane and rotatably arranged in a pump body, and a rotor fitted around the rotor. Are formed to form a pump chamber, and first and second fluid pressure chambers are formed in the outer peripheral portion between the pump body and the pump body to which a fluid pressure corresponding to the flow rate on the pump discharge side is introduced and swing in the pump body. The displaceable cam ring and the side wall portion provided in contact with the side surface portion of the cam ring, which correspond to the pump chamber, are opened at predetermined intervals in the rotational direction of the rotor, and the fluid pressure on the pump suction side and the discharge side is maintained. A pump suction side opening and a pump discharge side opening to be introduced, and an intermediate portion formed on the outer peripheral surface of the cam ring between the suction side area of the suction side opening of the pump chamber and the discharge side area of the discharge side opening. A pair of pistons capable of pressing the cam ring in the centripetal direction are provided in a region corresponding to the region, and on the back side of each of the pistons, a pump chamber formed between the vanes in each intermediate region of the pump chamber is provided. It is configured to introduce internal pressure.

The variable displacement pump according to the present invention is
The first and second fluid pressure chambers are fitted so as to form a pump chamber with the outer peripheral portion of the rotor and are movably arranged in the pump body, and in the outer peripheral clearance space between the rotor and the pump body. On the metering orifice provided in the pump discharge side passage and the cam ring in which the pressure is formed, and the first and second fluid pressures are operated according to the discharge flow rate of the pressure fluid discharged from the pump chamber by the pressure difference on the downstream side. A direct-acting relief valve that is equipped with a spool-type switching valve that controls the fluid pressure supplied to the chamber and that relieves excessive fluid pressure on the pump discharge side is provided in the pump discharge side passage or in the pump discharge side passage. It is provided directly on a part of the pump body so as to face the low pressure side chamber of the switching valve that communicates via the.

Further, the variable displacement pump according to the present invention is fitted so as to form a pump chamber with the outer peripheral portion of the rotor, is movably arranged in the pump body, and is disposed between the pump body and the pump body. Of the cam ring in which the first and second fluid pressure chambers are formed in the clearance space of the outer peripheral portion of the pump, and the pressure fluid from the pump chamber which is operated by the pressure difference on the downstream side on the metering orifice provided in the pump discharge side passage. A spool-type switching valve that controls the fluid pressure supplied to the first and second fluid pressure chambers in accordance with the discharge flow rate of
It is equipped with a relief valve that relieves excessive fluid pressure on the pump discharge side.The relief valve is inserted into a large-diameter hole that is recessed in the joint surface of the body that constitutes the pump body and the pump body The valve body is held in a hole portion having a diameter smaller than that of the large diameter hole that is open in the joining surface of the other body.

[0023]

According to the present invention, by the pair of pistons,
Since the pressing force corresponding to the fluid pressure in the intermediate region in the pump chamber is constantly applied to the outer peripheral surface of the cam ring and the cam ring can be pressed and held at a required position, the unbalanced force in the cam ring that is likely to occur in the conventional pump is reduced. Opposing and erasing this, it is possible to suppress or prevent the oscillation phenomenon of the cam ring,
As a result, a large flow rate fluctuation and pulsation that occur on the pump discharge side can be reduced, and a quiet variable displacement pump can be obtained.

That is, the internal pressure in the intermediate region of the pump chamber described above alternately changes to the pump discharge pressure and the pump suction pressure. As a result, the pressing force by each piston alternately becomes large and small, the position of the cam ring is pressed and held at the required position, and the force of pressing the piston is just balanced with the unbalanced force generated on the inner surface of the cam ring. It is possible to prevent the cam ring from vibrating due to the unbalanced force, and to prevent the flow rate fluctuation and the pulsation phenomenon on the pump discharge side due to this vibration.

Further, according to the present invention, the relief valve for relieving excessive fluid pressure on the pump discharge side can be easily incorporated in a desired portion such as a portion facing the pump discharge side passage of the pump body. Therefore, the function as a relief valve can be exerted, and the assembling property can be improved.

[0026]

1 to 3 (a) and 3 (b) show an embodiment of a variable displacement pump according to the present invention. In these drawings, in this embodiment, hydraulic pressure generation of a power steering apparatus is shown. The case of a vane type oil pump as a source will be described.

First, as is apparent from FIGS. 1 and 2, a vane type variable displacement pump, generally designated by reference numeral 10, is provided with a front body 11 and a rear body 12 which constitute a pump body. This front body 1
As is clear from FIG. 2, 1 has a cup-like shape as a whole, in which a storage space 14 for storing and arranging a pump component 13 as a pump cartridge is formed, and an opening end of the storage space 14 is formed. The rear body 12 is combined and integrated so as to be closed. In addition,
The front body 11 includes the pump component 13
Bearings 16 in a state where a drive shaft 16 for rotationally driving the rotor 15, which is the rotor of the
a, 16b, 16c (16b is the rear body 12 side, 16b
c is disposed on the pressure plate 20 side described later)
It is rotatably supported by.

Reference numeral 17 has an inner cam surface 17a fitted and arranged on the outer peripheral portion of the rotor 15 having a vane 15a,
A cam ring that forms a pump chamber 18 between the inner cam surface 17a and the rotor 15
As will be described later, is arranged so as to be movable and displaceable 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. The adapter ring 19 is for holding the cam ring 17 in the housing space 14 of the body 11 so that the cam ring 17 can be displaced.

Reference numeral 20 denotes the rotor 15 and the cam ring 1 described above.
7 and the adapter ring 19 is a pressure plate that is laminated in pressure contact with the front body 11 side of the pump cartridge (pump component 13), and the end face of the rear body 12 is on the opposite side of this pump cartridge. The side plates are pressed against each other, and the front body 11 and the rear body 12 are integrally assembled into a desired assembled state. The pump constituent element 13 is constituted by these members.

Here, these pressure plates 20
The rear body 12 serving as a side plate laminated on the cam ring 17 via the cam ring 17 includes a seal pin 21, which will be described later, which also functions as a shaft support portion and a positioning pin for swinging displacement of the cam ring 17, and an appropriate anti-rotation means (Fig. (Not shown), they are 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 opening formed in a pressure plate 20 that 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 aisle, this aisle 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 the pump chamber 18, the pump discharge side passage 24, the pump discharge side pressure chamber 23, and the pressure chamber 2
3 extending upward from the front body 11 to the passage hole 23a
The pump discharge side passage connected via
A metering orifice 29 is provided in the middle of the flow path, and a discharge port 28a for feeding the pump discharge side fluid pressure to a hydraulic device such as a power steering device (not shown in the figure) (PS) is provided on the outer end side. It is provided.

Reference numeral 30 is a switching valve which is disposed substantially orthogonally above the storage space 14 in the front body 11 and which displaces the cam ring 17 described above with respect to the rotor 15 in the pump body 11 (adapter ring 19). The switching valve 30 is a relief valve that slides on a metering orifice 29 of the pump discharge side passage 28 in a valve hole 30a formed in the body 11 by a pressure difference on the downstream side and a biasing force of a spring 31. It is equipped with an attached spool 32.

In the figure, 29a and 29b are orifices 2.
9 is a passage for introducing pressure on the upstream side into the valve hole 30a. Further, a low pressure side passage 25b is formed in the central portion of the valve hole 30a so as to branch from a part of the pump suction side passage 25 to guide the fluid pressure to the tank side, which is selected as the spool 32 moves. Is controlled to be opened / closed, and a fluid pressure is introduced into first and second fluid pressure chambers (34 and 35 described later) on both sides of a cam ring 17 described later.

That is, in such a switching valve 30, the pressure chamber 2 on the pump discharge side is provided in the one chamber (first chamber on the left side in FIG. 1, which is the high pressure side) 32a of the spool 32.
3, the fluid pressure on the upstream side of the metering orifice 29 is introduced through the pump discharge side passage 28 and the passage 29a. In the figure, 33 is the spool 32 in the valve hole 30a.
Is a plug for closing the valve hole 30a, which has a rod 33a that locks the leftward moving position of the valve at a position that does not close the opening end of the passage 29a. Further, reference numeral 32c in the drawing denotes a relief valve provided in the valve spool 32.

A spring 31 is arranged in the other chamber (second chamber on the right side of FIG. 1 on the low pressure side) 32b of the spool 32, and the fluid pressure on the downstream side of the metering orifice 29 is discharged. It is guided from the middle of the passage 28 reaching the port 28a through the passage 29b. In addition, this passage 2
The small diameter part in the middle of 9b is a damper orifice part.

Further, in the substantially central portion of the valve hole 30a,
In the first fluid pressure chamber 34 formed between the outer peripheral portion of the cam ring 19 and the adapter ring 19 on the body 11 side, a pressure guide passage 36 formed through the body 11 and the adapter ring 19 (of the adapter ring 19). (Including passage hole 36a)
Is opened. It should be noted that the outer peripheral portion of the cam ring 17 is preferably formed with a groove or the like having a substantially half circumference so that the first fluid pressure chamber 34 can be secured even when the first fluid pressure chamber 34 contacts the adapter ring 19 along the circumferential direction. .

From the downstream side of the metering orifice 29 of the pump discharge side passage 28, the cam ring 19
In the second fluid pressure chamber 35 formed between the outer periphery of the body 11 and the adapter ring 19 on the body 11 side, a pressure guide passage 37 (a passage hole of the adapter ring 19 is formed through the body 11 and the adapter ring 19. (Including 37a) is opened. Here, 37b in the figure is a throttle formed in a part of the pressure guiding passage 37, and the cam ring 17 is formed by the throttle 37b.
The vibration control effect of is obtained. In addition, such a pressure guide passage 37 on the downstream side of the metering orifice 29.
Alternatively, instead of the above-described embodiment, the valve hole 30a may be configured to be guided through the low pressure side chamber 32b at the right end portion.

These passages 36 and 37 are used for the pressure difference before and after the metering orifice 29 and the spool 32.
As is apparent from FIG. 1 and the like, by means of the movement of FIG. 1 or the like, it is selectively connected to the pump discharge side passage 28 via the passage 29b or to the pump suction opening 25b side via the passage 25b. There is.

That is, when the pump is operating, the flow rate fluctuation on the discharge side is sensed by the switching valve 30 operated by the pressure difference on the downstream side on the metering orifice 29, and the fluid pressure controlled by this valve 30 is First and second fluid pressure chambers 34, 35 on both sides of the cam ring 17
Is supplied to the cam ring 17, the cam ring 17 is oscillated and displaced in a desired state to change the volume in the pump chamber 18,
The pump discharge flow rate can be controlled as desired.

Reference numeral 40 in FIG. 1 denotes the pump body 11,
The cam ring 17 arranged so as to be movable and displaceable in 12
The coil spring 41 is a pressing member that urges the pump chamber 18 formed on the outer peripheral portion of the rotor 15 to have the maximum volume.
And a tubular presser plug 42.

Reference numeral 45 in the drawing is provided in a part of the outer peripheral portion of the cam ring 17 and cooperates with the seal pin 21 in a clearance space between the cam ring 17 and the adapter ring 19 to cooperate with the first and second fluid pressure chambers 34. , 35 for forming a seal. Further, reference numeral 24c in the drawing denotes a whisker-shaped notch formed to extend to the pump suction side region side in the pump discharge side opening 24 that opens to the pump discharge side region in the pump chamber 18.

In the vane type variable displacement pump 10 described above, the configuration other than that described above is well known in the art, and a detailed description thereof will be omitted.

Here, according to the variable displacement pump 10 according to the present embodiment having the above-mentioned structure, the variable displacement pump 10 is fitted so as to form the pump chamber 18 between the rotor 15 and the outer peripheral portion thereof, and inside the pump bodies 11 and 12. Movable displacement possible (oscillation displacement possible)
Cam ring 17 which is disposed at the first and second fluid pressure chambers 34 and 35 in the outer peripheral clearance space between the pump bodies 11 and 12 via sealing means 21 and 45. The coil spring 41 as a biasing means for biasing the pump 15 in the direction to maximize the volume of the pump chamber 18 with the outer peripheral portion of the rotor 15, and the pump discharge side passage 28.
The first and second fluid pressure chambers 3 are operated on the metering orifice 29 provided in the first and second fluid pressure chambers according to the discharge flow rate Q of the pressure fluid discharged from the pump chamber 18 depending on the pressure difference on the downstream side.
A spool type switching valve 30 for controlling the pressure of the fluid supplied to 4, 35 is provided.

In such a structure, the cam ring 17
Of the fluid pressure chambers 34, 35 at the outer peripheral portion, the metering orifice 29 is provided in the second fluid pressure chamber 35 that gives the displacement in the direction in which the volume of the pump chamber 18 is maximized (left side in FIG. 1).
The fluid pressure on the downstream side of is introduced through the pressure guiding passage 37.

Further, according to this structure, the flow rate Q on the pump discharge side is set by the spool type switching valve 30 in the high pressure side fluid pressure chamber 34 formed outside the cam ring 17.
By introducing the fluid pressure according to the magnitude of the above, and by introducing the fluid pressure downstream of the metering orifice 29 in the pump discharge passage 28 into the fluid pressure chamber 35 on the low pressure side,
In the initial stage of the operation of the pump 10, not only the required discharge flow rate control is performed to obtain a predetermined flow rate, but also when there is a pump load such as the operation of the equipment to be used, etc. Unbalanced fluid pressure exerts an unbalanced force to prevent the cam ring 17 from oscillating and displacing carelessly. As a result, flow rate fluctuation and flow rate decrease on the pump discharge side are eliminated, and stable flow rate control is achieved. Can be done.

That is, in such a configuration, the downstream pressure after the metering orifice 29, which is close to the discharge pressure close to the extent that the increase in the internal pressure of the cam ring 17 due to the fluid pressure change can be counteracted, is set to the low pressure side outside the cam ring 17. Fluid pressure chamber 3
5, the flow rate fluctuation and the flow rate decrease are prevented even when the discharge side pressure P is increased by the pump load or the like, as is clear from the characteristic diagram of FIG. 3A or 3B. be able to. In particular, even when the pump discharge side fluid pressure P rises when the pump load is caused by the operation of the equipment to be used to which the fluid pressure from the pump 10 is supplied, it is possible to prevent a problem such as a decrease in the flow rate.

This will be briefly described with reference to FIGS. 3A and 3B. In order to eliminate the movement of the cam ring 17 in the discharge amount decreasing direction due to the unbalanced force as described above, the low pressure is eliminated. The fluid pressure PB in the fluid pressure chamber 35 on the side is introduced to the fluid pressure on the downstream side of the metering orifice 29, which is close to the discharge pressure. Then, by doing so, a pressure (PB) substantially equal to the pump discharge side pressure P
Can be introduced into the fluid pressure chamber 35 on the low pressure side, and as a result, the pressure difference (P-PB) inside and outside the cam ring 17 can be reduced, for example, by the operation of the power steering, which is the equipment to be used. Even when the discharge side fluid pressure P rises as in the case of pump load, the flow rate Q does not decrease, and the flow rate control of the pump can be performed stably.

Further, according to such a construction, in the conventional pump structure, the pump suction side is communicated with while controlling in the flow rate adjusting region, or the upstream pressure of the metering orifice 29 is introduced immediately after the pump is operated. No need for passages,
As a result, the structure of each part can be simplified and the workability of each part can be improved.

Here, when the fluid pressure on the pump discharge side is increased, the fluid pressure to the left and right fluid pressure chambers 34 and 35 for controlling the swing displacement of the cam ring 17 is set to a differential pressure by the switching valve 30. Is being controlled. In this embodiment, the unbalanced force on the cam ring 17 is eliminated so that only the adjusted flow rate is controlled under such a situation. This is because in FIG. 3A, the flow characteristic when no load is applied, the flow characteristic when loaded is b, and the flow characteristic when loaded c in the conventional structure are shown in FIG.
As described above, the rapid decrease in the flow rate in the adjusted flow rate range does not occur.

Further, the pressure condition in this embodiment is as shown in FIG. 3 (b). In the device of this embodiment, the fluid pressure PB in the second fluid pressure chamber 34 in the flow rate adjusting region is The pressure difference in the discharge pressure P is small.

In the above-described structure, when the pump 10 is started, the cam ring 17 has a maximum inner volume of the pump chamber 18 between the rotor 15 and one side of the housing space 14 of the body 11, as is apparent from FIG. As described above, the coil spring 41 of the pressing member 40 is urged. At this time, the switching valve 30 is different from FIG. 1 in that the first fluid pressure chamber 34 is connected to the pump suction side and the second fluid pressure chamber 35 is connected to the downstream side of the metering office 29 on the pump discharge side. Is in a state.

When the pump rotational speed is gradually increased, the switching valve 30 is driven by the differential pressure due to the fluid pressure on the orifice 29 on the pump discharge side and on the downstream side, which is obtained in proportion to the pump rotational speed. In the adjusted flow rate region, the first fluid pressure chamber 34 outside the cam ring 17 is on the pump discharge side upstream of the metering orifice 29, and the second fluid pressure chamber 35 is on the meter side. The cam ring 17 which is connected to the downstream side of the ring orifice 29 and is eccentric with respect to the rotor 15
Is displaced in the direction in which the inner volume of the pump chamber 18 decreases (see FIG. 1) against the coil spring 41.

At this time, by the switching operation by the spool 32 of the switching valve 30 according to the magnitude of the fluid flow rate on the pump discharge side, the pump discharge side is positioned opposite to the first fluid pressure chamber 34. Since the downstream side of the orifice 29, which has a lower pressure than the second fluid pressure chamber 35, is appropriately connected to the second fluid pressure chamber 35, the cam ring 17 includes the switching valve 30.
The flow rate of the fluid discharged from the pump chamber 18 whose displacement is appropriately changed depending on the operating state of (1) and the internal volume of which is changed as a result can be controlled in a required state, and a predetermined flow rate to the power steering apparatus PS can be fed.

Further, according to the above-mentioned configuration, the switching valve 30 is switched and controlled according to the differential pressure generated at the metering orifice 29 by the pump discharge amount which increases and decreases with the pump rotation speed, whereby the cam ring 17 is driven. It can be displaced to the right side in the figure against the urging force of the coil spring 41, or to the left side in the figure by this urging force.
As a result, the internal volume of the pump chamber 18 is variably controlled, and the discharge amount from the pump is balanced in accordance with the pump rotation speed as shown in, for example, FIGS. Can be controlled to obtain

Now, the variable displacement pump 10 according to the present invention.
According to the above, the rotor 15 and the cam ring 1 which constitute the pump component 13 which is the pump cartridge as described above.
In the pump chamber 18 between the pump suction side opening 7 and the pump suction side opening 2
5a and the pump discharge side opening 24 form a pair as a pressing means capable of pressing the cam ring 17 in the centripetal direction on the outer peripheral surface portion of the cam ring 17 corresponding to the intermediate areas 48, 49 between the suction side area and the discharge side area. Pistons 50, 51 are provided, and vanes 15a, in intermediate regions 48, 49 in the pump chamber 18 are provided on the back side of the pistons 50, 51.
Introducing the internal pressure of the pump chamber formed between 15a,
The cam ring 17 is configured to be pressed and held at a desired position by the balance of the pressing force of the cam ring 17 by the pistons 50 and 51.

Here, the pistons 50 and 51 described above are
Rods 50a and 51a, which are slidably arranged in holes 52 and 53 formed in the body 11 and extend toward the cam ring 17, are pressed against the outer peripheral surface of the cam ring 17. Touching. Also, the pistons 50, 51
In the chambers 54a, 55a on the rod portions 50a, 51a side of
Tank pressure or pressure from the drain portion is introduced through the passages 54 and 55 in the figure.

Further, springs 56 and 57 are provided in the back side chambers 50b and 51b into which the pump chamber internal pressure in the above-mentioned intermediate region is introduced, and function to press the rod portions 50a and 51a against the cam ring 17 side. There is.

In the figure, 58 and 59 are intermediate regions 48 and 4.
9 is a passage for guiding the internal pressure of the pump chamber at 9 to the rear side chambers 58a and 59a of the pistons 50 and 51. Also,
The pressure receiving area of the pistons 50 and 51 and the pressing area of the rod tip portion, particularly the pressure receiving area of the piston diameter, are appropriate conditions, that is, the output that balances the unbalanced force acting on the cam ring 17 can be obtained. It may be appropriately selected and determined according to Further, reference numerals 60 and 61 in the figure are plugs that close the open ends of the hole portions 52 and 53 of the pistons 50 and 51.

According to this structure, the pair of pistons 50 and 51 constantly exerts a pressing force on the outer peripheral surface of the cam ring 17 in accordance with the fluid pressure in the intermediate region of the pump chamber 18, thereby allowing the cam ring to move. Since 17 can be pressed and held at a required position, the unbalanced force in the cam ring 17 which is apt to occur in the conventional variable displacement pump 10 is eliminated so as to suppress the oscillation phenomenon of the cam ring 17. It is possible to prevent, and as a result, it is possible to obtain a quiet variable displacement pump 10 by reducing large flow rate fluctuations and pulsations that have occurred on the pump discharge side.

In other words, the internal pressure in the intermediate region of the pump chamber 18 described above alternately changes to the pump discharge pressure and the pump suction pressure. As a result, the pressing force exerted by the pistons 50 and 51 is alternately increased and decreased, and the position of the cam ring 17 is pressed and held at a desired position. Especially the piston 5
The force that pushes 0 or 51 comes to just balance the unbalanced force generated on the inner surface of the cam ring 17, thereby preventing the cam ring 17 from vibrating due to the unbalanced force, and as a result, at the pump discharge side due to the vibration. It is possible to prevent the flow rate fluctuation and the pulsation phenomenon.

Here, in the above-described embodiment, the pump chamber 1
A piston, which is a pressing unit that applies a pressing force in the centripetal direction to the outer peripheral surface of the cam ring 17, corresponding to two intermediate regions 48 and 49 formed between the pump suction side region and the pump side region in the pump 8. Although the case where 50 and 51 are provided as a pair is shown, the present invention is not limited to this, and the piston 50 or 51 may be provided corresponding to only one of the intermediate regions 48 or 49. In addition, in such one piston, two pistons 50 and 5 like the above-mentioned embodiment are used.
Although the effect is a little inferior to the case where 1 is provided, the effect of preventing the flow rate fluctuation and the pulsation phenomenon on the pump discharge side due to the above-described vibration can be exhibited to some extent.

FIG. 4 shows another embodiment of the present invention. In this embodiment, the first and second fluid pressure chambers 34 and 35 arranged in the pump body 11 in the above-mentioned embodiment are shown.
The spool 3 of the spool-type switching valve 30 for swinging the cam ring 17 by controlling the fluid pressure supplied to the spool 3.
The relief valve 32c provided in the pump body 11 or 12 so as to face a part of the pump discharge side passage 28 or the valve hole 30a of the valve 30.
It was installed in.

That is, in the variable displacement pump 10 as described above, when the relief valve 32c is incorporated in the spool 32 of the switching valve 30, the valve spool 32 is affected at the time of relief and an oscillation phenomenon occurs. There is a possibility that it may lead to an oscillation phenomenon in the cam ring 17. In addition, the relief valve 3 built in the valve spool 32
In 2c, there is also a problem that it is difficult to relieve all discharge flow rates at the time of relief.

In this embodiment, in view of such a point, the direct-acting relief valve 32c is provided in the front body 11 or the rear body 12 on the pump discharge side passage 28 downstream of the metering orifice 29 or in the passage 28b. It is provided so as to face the low pressure side chamber 32b of the valve 30 which communicates with each other via the.

According to such a structure, there is an advantage that at the time of relief, the function as the relief valve 32c can be exerted and all the discharge flow rate can be relieved.

FIGS. 5 and 6 show still another embodiment of the present invention. In this embodiment, the structure for assembling the relief valve 32c into the pump body in the above-described embodiment is improved to improve the assemblability. It was done like this.

Here, in the variable displacement pump 10 of this embodiment, the relief valve 32c for relieving excessive fluid pressure on the pump discharge side is provided on the joint surface of one body (front body 11) constituting the pump body. Recessed passage hole 6
A valve seat 6 which is fitted into the large-diameter hole 60 at one opening end by light press-fitting or the like and has its end face flush with the joining face.
2 and a needle pin 64 as a valve body held in a hole portion 63 having a diameter smaller than that of the large diameter hole 60 opening at the joint surface of the other body (rear body 12) constituting the pump body. .

Incidentally, 65 is a passage hole communicating with the hole 63,
Reference numeral 66 is a valve element urging spring provided in the hole 63, and 67 is an O-ring groove. Further, it goes without saying that the valve element described above may be a steel ball or the like.

According to this structure, the relief valve 32c for relieving excessive fluid pressure on the pump discharge side.
Is configured so that it can be easily incorporated in a required portion such as a portion facing the pump discharge side passage 28 of the pump bodies 11 and 12, so that the function as the relief valve 32c can be exerted and the assembling property is further improved. Can be made.

Particularly, in the above-mentioned configuration, the valve seat 6
Since the hole portion 63 on the rear body 12 side has a smaller diameter than the large diameter hole 60 on the front body 11 side into which the two are fitted, the valve seat 62 can be prevented from being pulled out from the body 11 side. 62 does not move when the fluid pressure rises, a reliable assembled state is secured, and the valve seat 62 and the needle pin 64 can function as the relief valve 32c.

Further, in such a structure, since the valve seat 62 is not strongly press-fitted, the press-fitting hole is distorted, causing deformation or the like on the front body 11 side and assembling with the rear body 12. Can not be attached,
The relief valve 32c has an advantage that fluctuations in the relief pressure can be prevented and the relief pressure can be stabilized.

The present invention is not limited to the structure of the embodiment described above, and the shape and structure of each part can be freely modified and changed, and various modifications can be considered. For example, in the above-described embodiment, the case where the annular gap space that holds the cam ring 17 so as to be movable and displaced is formed between the annular space and the adapter ring 19 is shown, but the present invention is not limited to this, and is provided in the pump body 11. The cam ring 17 may be configured so as to be movable and displaceable.

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.

[0076]

As described above, according to the variable displacement pump according to the present invention, the rotor rotatably arranged in the pump body and the pump chamber fitted to the outer periphery of the rotor are formed. A cam ring having first and second fluid pressure chambers for guiding fluid pressure according to a flow rate on the pump discharge side is formed in an outer peripheral portion between the cam ring and the pump body, the cam ring being capable of oscillating displacement in the pump body, and a side surface of the cam ring. The pump suction side and the discharge side into which the fluid pressures of the pump suction side and the discharge side are introduced and which are opened at a predetermined interval in the rotation direction of the rotor in the portion corresponding to the pump chamber in the side wall portion arranged in contact with the section Centering the cam ring on the outer peripheral surface of the cam ring corresponding to an intermediate region formed between the suction side region of the pump chamber by the suction side opening and the discharge side region of the discharge side opening. Since a pair of pistons that can be pressed toward each other are provided, and the back side of each piston is configured to introduce the internal pressure of the pump chamber formed between the vanes in each intermediate region of the pump chamber, Despite the simple structure, the following various excellent effects are achieved.

That is, according to the present invention, the pair of pistons always exerts a pressing force on the outer peripheral surface of the cam ring in accordance with the fluid pressure in the intermediate region of the pump chamber, and the cam ring is pressed and held at a predetermined position. Therefore, the unbalanced force on the cam ring, which is likely to occur in conventional pumps, is countered and eliminated, and the oscillation phenomenon of the cam ring can be suppressed or prevented, and as a result, the large flow rate fluctuation that has occurred on the pump discharge side. It is possible to obtain a quiet variable displacement pump with reduced pulsation.

Particularly, according to the present invention, the internal pressure in the intermediate region of the pump chamber is alternately changed to the pump discharge pressure and the pump suction pressure, whereby the pressing force by each piston is alternately increased and decreased, and the cam ring Holding the position at the required position and pushing the piston forces the force that just balances the unbalanced force generated on the inner surface of the cam ring, thus preventing the cam ring from vibrating due to the unbalanced force. It is possible to prevent flow rate fluctuations and pulsation phenomena on the pump discharge side.

Further, according to the variable displacement pump of the present invention, the metering orifice provided in the pump discharge side passage is actuated by the pressure difference on the downstream side, and is controlled according to the discharge flow rate of the pressure fluid from the pump chamber. The relief valve includes a spool-type switching valve that controls the fluid pressure supplied to the first and second fluid pressure chambers, and a direct-acting relief valve that relieves excessive fluid pressure on the pump discharge side. , The pump discharge side passage, or provided directly on a part of the pump body so as to face the low pressure side chamber of the switching valve communicating with the pump discharge side passage through the passage, or on the joint surface of one body forming the pump body. It is composed of a valve seat fitted in a large-diameter hole that is recessed, and a valve body that is held in a hole that is smaller than the large-diameter hole that opens in the joint surface of the other body that constitutes the pump body. Since interest exhibits the following excellent effects.

According to the present invention, the relief valve can be easily incorporated in a required portion such as a portion facing the pump discharge side passage of the pump body, and can function as a relief valve.
Furthermore, there is an advantage that the assembling property can be improved.

[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.

3A is a characteristic diagram showing a relationship between a pump rotation speed N and a discharge flow rate Q according to the present invention, and FIG. 3B is a characteristic diagram showing a relationship between a pump rotation speed N and a pump discharge side pressure P according to the present invention. It is a figure.

FIG. 4 is a schematic cross-sectional view of the structure of a pump main part showing another embodiment of the variable displacement pump according to the present invention.

FIG. 5 is a schematic cross-sectional view of the main structure of a pump showing still another embodiment of the variable displacement pump according to the present invention.

6 is a sectional view taken along line VI-VI in FIG.

FIG. 7 is a schematic diagram for explaining a structure of a main part of a conventional variable displacement pump.

[Explanation of symbols]

10 ... Vane type variable displacement pump, 11 ... Front body (pump body), 12 ... Rear body, 13 ...
Pump component, 14 ... Storage space, 15 ... Rotor, 15
a ... vane, 16 ... drive shaft (rotating shaft), 17
... cam ring, 17a ... cam surface, 18 ... pump chamber, 19
… Adapter ring, 20… Pressure plate, 21…
Seal pin (cam ring shaft support), 23 ... Pump discharge side pressure chamber, 23a ... Pump discharge side passage, 24 ... Pump discharge side opening, 25 ... Pump suction side passage, 25a ... Pump suction side opening, 25b ... Low pressure side passage, 26 … Suction port, 28
... pump discharge side passage, 28b ... high pressure side passage, 29 ... metering orifice, 29a ... passage, 29b ... passage, 3
0 ... Spool type switching valve, 31 ... Spring, 32 ... Spool, 32b ... Low pressure side second chamber, 34 ... First (high pressure side) fluid pressure chamber, 35 ... Second (low pressure side) fluid pressure chamber Three
6 ... Pressure guide passage, 37 ... Pressure guide passage (for introducing fluid pressure downstream of metering orifice), 37b ... Throttling portion, 40 ... Pressing member, 48, 49 ... Intermediate region, 50, 51 ... Piston,
52, 53 ... Hole portion, 54, 55 ... Passage, 56, 57 ... Spring, 58, 59 ... Pressure passage, 60 ... Large diameter hole, 61 ... Passage, 62 ... Valve seat, 63 ... Hole portion, 64 ... Needle Pin (valve body), 65 ... passage hole, 66 ... Spring.

Claims (4)

[Claims] 1. A rotor, which has a vane and is rotatably disposed in a pump body, and a rotor which is fitted around the rotor to form a pump chamber and which is located at an outer peripheral portion between the pump body and a pump discharge side. A cam ring which is formed with first and second fluid pressure chambers through which a fluid pressure corresponding to a flow rate is guided and which can be oscillated and displaced in a pump body, and the side wall portion arranged in contact with a side surface portion of the cam ring. The portion corresponding to the pump chamber is provided at predetermined intervals in the rotation direction of the rotor, and is provided with a pump suction side opening and a pump discharge side opening through which the fluid pressure on the pump suction side and the discharge side is introduced, and the cam ring The cam ring is pressed toward the centripetal direction on a portion of the outer peripheral surface corresponding to an intermediate region formed between the suction side region of the suction side opening of the pump chamber and the discharge side region of the discharge side opening. A variable capacity characterized in that a pair of possible pistons are provided, and the internal pressure of the pump chamber formed between the vanes in each intermediate region of the pump chamber is introduced to the back side of each piston. Shaped pump. 2. The variable displacement pump according to claim 1, wherein the pair of pistons for pressing a portion corresponding to an intermediate region of the cam ring are slidably held in a hole portion in the pump body, and the pump chamber. A variable displacement pump characterized in that an urging means is provided in a rear side chamber into which the internal pressure in the intermediate region of the above is introduced, and a tank pressure or a drain pressure is introduced into the front side chamber of the piston. 3. A rotor, which has a vane and is rotatably disposed in the 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 cam ring in which the first and second fluid pressure chambers are formed in the outer peripheral clearance space between the pump body and the pump body, and on a metering orifice provided in the pump discharge side passage. A spool-type switching valve that is operated by a pressure difference on the downstream side and controls the fluid pressure supplied to the first and second fluid pressure chambers in accordance with the discharge flow rate of the pressure fluid from the pump chamber. And a low pressure of the switching valve that connects a direct-acting relief valve that relieves excessive fluid pressure on the pump discharge side to the pump discharge side passage or via the passage to the pump discharge side passage. A variable displacement pump characterized by being provided directly on a part of the pump body so as to face the side chamber. 4. A rotor, which has a vane and is rotatably disposed in the 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 cam ring in which the first and second fluid pressure chambers are formed in the outer peripheral clearance space between the pump body and the pump body, and on a metering orifice provided in the pump discharge side passage. A spool type switching valve which is operated by a pressure difference on the downstream side and controls the fluid pressure supplied to the first and second fluid pressure chambers in accordance with the discharge flow rate of the pressure fluid from the pump chamber; It is equipped with a relief valve that relieves excessive fluid pressure on the discharge side, and this relief valve is inserted into a large-diameter hole that is recessed in the joint surface of the body that constitutes the pump body. And,
A variable displacement pump, comprising: a valve body held in a hole having a diameter smaller than that of the large diameter hole, which is opened in a joint surface of the other body constituting the pump body.