VANE PUMP

Abstract

A vane pump is used as a fluid pressure supply source and includes a rotor which is driven and rotated, a plurality of slits which are radially formed in the rotor, a plurality of vanes which slidably project from the slits, a cam ring with which tip parts of the vanes slide in contact as the rotor rotates, a pump chamber which is defined between the cam ring and adjacent ones of the vanes, a plurality of discharge ports which introduce working fluid discharged from the pump chamber contracting as the rotor rotates, a discharge passage which causes the working fluid introduced from the discharge ports to join, and a check valve which is opened for a flow of the working fluid discharged from one discharge port to the discharge passage.

Description

TECHNICAL FIELD

The present invention relates to a vane pump used as a fluid pressure supply source.

BACKGROUND ART

A vane pump includes a plurality of vanes housed in radial slits of a rotor. Each vane is biased in a direction to project from the slit by a hydraulic force of a vane back pressure chamber pressing a base end part of the vane and a centrifugal force acting on the vane with the rotation of the rotor and a tip part thereof slides in contact with an inner peripheral cam surface of a cam ring. The vanes sliding in contact with the inner peripheral cam surface reciprocate along the slits as the rotor rotates, whereby pump chambers expand and contract. Hydraulic oil pressurized in the pump chambers is discharged from discharge ports open on a side plate to a discharge pressure chamber in the vane pump and supplied from the discharge pressure chamber to a hydraulic device.

In such a vane pump, when the rotation of the rotor is stopped, the vanes located above the rotor fall toward the bottoms of the slits by gravity. Thus, there is a possibility that projecting movements of the vanes from the slits are delayed and a pump discharge pressure rises at a delayed timing at the start-up when the rotor is rotated again.

JP9-119383A discloses a vane pump provided with two grooves allowing communication between carrier holes and lower blade regions in slits and a cold start plate defining a fluidity communicating portion between these two grooves.

In this vane pump, since hydraulic oil discharged from the carrier holes is supplied to the lower blade regions through the fluidity communicating portion when the pump is started, vanes fallen into the slits by gravity when the pump is stopped are urged to project.

When the biased cold start plate is separated from the grooves as pressures in the carrier holes increase after the pump is started, the hydraulic oil discharged from the carrier holes is supplied from the grooves to a hydraulic device.

SUMMARY OF INVENTION

However, since the cold start plate is provided to face the grooves communicating with the two carrier holes in the above vane pump, there is a possibility that a pump discharge pressure escapes to a suction side when the pump is started.

This is described below. If a stopped state of the vane pump continues, the vanes located above a rotor fall into the slits and a clearance (pressure escape path) is defined between the vanes and a cam ring (see FIG. 1). This pressure escape path is defined from a first discharge region to a first suction region.

If the vane pump is started in this state and the biased cold start plate is separated from the grooves as the pressure in one carrier hole (discharge pressure in a second discharge region) increases, there is a possibility that the two grooves communicate with each other, the pressure in the one carrier hole escapes to the suction side (first suction region) through the other carrier hole and the pressure escape path and the pump discharge pressure rises at a delayed timing.

It is an object of the present invention to provide a vane pump capable of suppressing the escape of a pump discharge pressure to a suction side when the pump is started.

According to one aspect of the present invention, a vane pump used as a fluid pressure supply source is provided. The vane pump includes a rotor which is driven and rotated, a plurality of slits which are radially formed in the rotor, a plurality of vanes which slidably project from the slits, a cam ring with which tip parts of the vanes slide in contact as the rotor rotates, a pump chamber which is defined between the cam ring and adjacent ones of the vanes, a plurality of discharge ports which introduce working fluid discharged from the pump chamber contracting as the rotor rotates, a discharge passage which causes the working fluid introduced from the discharge ports to join, and a check valve which is opened for a flow of the working fluid discharged from one discharge port to the discharge passage.

Embodiments of the present invention and advantages thereof are described in detail below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of a vane pump according to an embodiment of the present invention,

FIG. 2 is a front view of a side plate,

FIG. 3A is a circuit diagram showing a path configuration when the vane pump is actuated, and

FIG. 3B is a circuit diagram showing a path configuration when the vane pump is started.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention are described with reference to the accompanying drawings.

FIG. 1 is a front view of a vane pump according to the embodiment of the present invention. FIG. 2 is a front view of a side plate. A vane pump 1 is used as a hydraulic pressure supply source for a hydraulic device mounted in a vehicle such as a transmission or a power steering device.

Although the vane pump 1 uses hydraulic oil (oil) as working fluid, working liquid such as water-soluble alternative liquid may be used instead of the hydraulic oil.

The vane pump 1 includes a drive shaft 9 to which power of an unillustrated engine or electric motor is transmitted on an end part, and a rotor 2 coupled to the drive shaft 9. The rotor 2 rotates in a direction shown by an arrow of each figure with the rotation of the drive shaft 9.

A pump body 10 is formed with a pump housing recess 10A for housing the rotor 2, a cam ring 4, a side plate 30 and the like. A pump cover (not shown) is fastened to the pump body 10 and the pump housing recess 10A is sealed by this pump cover. The drive shaft 9 is rotatably supported in the pump body 10 and the pump cover.

It should be noted that, without limitation to this, the cam ring 4 and the side plate 30 may be integrally formed to the pump body 10.

A discharge passage (high pressure chamber) 35 is defined between a bottom part of the pump housing recess 10A of the pump body 10 and the side plate 30. The side plate 30 is pressed against an end surface (end surface on a back side of the plane of FIG. 1) of the cam ring 4 by a pump discharge pressure introduced into the discharge passage 35.

A plurality of vanes 3 are interposed between the cam ring 4 and the rotor 2. The rotor 2 is formed with slits 5 in a radial shape and arranged at predetermined intervals. The vanes 3 are in the form of rectangular plates and slidably inserted into the slits 5.

A vane back pressure chamber 6 is defined between a back side of the slit 5 (radially inner side of the rotor 2) and a base end part of the vane 3, and the pump discharge pressure is introduced into the back pressure chamber 6. The vanes 3 are biased in directions to project from the slits 5 by pressures in the back pressure chambers 6 pressing the base end parts of the vanes 3 and a centrifugal force acting on the vanes 3 with the rotation of the rotor 2, and tip parts thereof slide in contact with an inner peripheral cam surface 4A of the cam ring 4.

The cam ring 4 is an annular member including the substantially elliptical inner peripheral cam surface 4A. Accordingly, as the rotor 2 rotates one turn, each vane 3 whose tip follows the inner peripheral cam surface 4A reciprocates twice.

Inside the cam ring 4, a plurality of pump chambers 7 are defined by the inner peripheral cam surface 4A of the cam ring 4, the outer periphery of the rotor 2 and adjacent ones of the vanes 3.

The vane pump 1 has a first suction region and a first discharge region where the vanes 3 make the first reciprocal movement and a second suction region and a second discharge region where the vanes 3 make the second reciprocal movement. A volume of the pump chamber 7 increases with the rotation of the rotor 2 in the first and second suction regions. The volume of the pump chamber 7 decreases with the rotation of the rotor 2 in the first and second discharge regions.

It should be noted, without limitation to this, the vane pump 1 may have three or more suction regions and three or more discharge regions.

The rotor 2 has two end surfaces perpendicular to a rotation center axis of the rotor 2. An end surface 21 on a front side (front side with respect to the plane of FIG. 1) of the rotor 2 shown in FIG. 1 slides in contact with an end surface of the pump cover. An end surface on a rear side (back side with respect to the plane of FIG. 1) of the rotor 2 slides in contact with an end surface 38 of the side plate 30.

As shown in FIG. 2, on the end surface 38 of the side plate 30, a first suction port 31 is open in the first suction region, a first discharge port 32 is open in the first discharge region, a second suction port 33 is open in the second suction region and a second discharge port 34 is open in the second discharge region.

As shown in FIG. 3A, the first and second suction ports 31, 33 communicate with a tank 26 via a suction passage 25 and hydraulic oil is introduced thereto from the tank 26.

The first and second discharge ports 32, 34 communicate with the unillustrated hydraulic device via a discharge passage 35. The pressurized hydraulic oil discharged from the first and second discharge ports 32, 34 is supplied to the hydraulic device through the discharge passage 35.

The end surface 38 of the side plate 30 with which the rotor 2 slides in contact is formed with four back pressure ports 41 to 44. The respective back pressure ports 41 to 44 extend along an arc centered on an axis of rotation of the rotor 2 and communicate with the vane back pressure chambers 6 in the first suction region, the first discharge region, the second suction region and the second discharge region.

The side plate 30 is formed with a discharge pressure introduction passage 51 allowing communication between the discharge passage 35 and the back pressure port 41 in the first suction region. Further, the side plate 30 is formed with a discharge pressure introduction passage 53 allowing communication between the discharge passage 35 and the back pressure port 43 in the second suction region.

When the vane pump 1 is actuated, the vanes 3 are biased in the directions to project from the slits 5 by the hydraulic oil pressures in the vane back pressure chambers 6 pressing the base end parts of the vanes 3 and the centrifugal force acting on the vanes 3 with the rotation of the rotor 2, and the tip parts thereof slide in contact with the inner peripheral cam surface 4A of the cam ring 4. The vanes 3 sliding in contact with the inner peripheral cam surface 4A reciprocate with the rotation of the rotor 2, whereby the pump chambers 7 expand and contract and the hydraulic oil pressurized in the pump chambers 7 is discharged to the discharge passage 35 from the first and second discharge ports 32, 34.

The vane pump 1 is so mounted that the first suction region is arranged on an upper side (see arrows of FIGS. 1 and 2) and the second suction region is arranged on a lower side.

When a stopped state of the vane pump 1 continues, the vanes 3 in the first suction region located on the upper side of the vane pump 1 fall into the slits 5 by gravity and a clearance is formed between the vanes 3 and the cam ring 4 as shown in FIG. 1. This clearance defines a pressure escape path 39 allowing communication between the first discharge port 32 and the first suction port 31. On the other hand, since the vanes 3 in the second suction region located on the lower side of the vane pump 1 project from the vanes 5 by gravity, the vanes 3 and the inner peripheral cam surface 4A are kept in a contact state.

If the pump chambers 7 contract in the second discharge region when the vane pump 1 is actuated, the pump discharge pressure is introduced into the discharge passage 35 from the second discharge port 34. At this time, if the pump discharge pressure in the discharge passage 35 escapes from the first discharge port 32 to the first suction port 31 and the suction passage 25 through the pressure escape path 39 as shown by an arrow A of FIG. 1, it takes time for the pump discharge pressure in the discharge passage 35 to increase.

Accordingly, a check valve 60 is provided in the first discharge port 32 in the vane pump 1 of the present embodiment. The check valve 60 is opened when the hydraulic oil flows from the first discharge port 32 to the discharge passage 35 and closed when the hydraulic oil flows from the discharge passage 35 to the first discharge port 32.

The check valve 60 is composed of a valve body (not shown) for closing an opening end of the first discharge port 32 to the discharge passage 35 and a biasing means (not shown) for biasing this valve body in a valve closing direction.

FIG. 3A shows a flow of the hydraulic oil when the vane pump 1 is actuated by arrows. When the vane pump 1 is actuated, the rotor 2 rotates in an arrow direction. The vanes 3 enter the slits 5, following the cam ring 4, in the first and second discharge regions and project from the slits 5, following the cam ring 4, in the first and second suction regions. The pump chambers 7 expand and contact by repeating such movements of the vanes 3. Associated with this, the hydraulic oil in the tank 26 is supplied to the pump chambers 7 successively through the suction passage 25, the first suction port 31 and the second suction port 33. The pressurized hydraulic oil discharged from the pump chambers 7 is supplied to the hydraulic device (working fluid supply destination) through the first discharge port 32, the second discharge port 34 and the discharge passage 35. At this time, the check valve 60 is opened for a flow of the hydraulic oil from the first discharge port 32 to the discharge passage 35. The hydraulic oil discharged from the hydraulic device is returned to the tank 26 through a return passage (not shown).

When the vane pump 1 is actuated, the pump discharge pressure in the discharge passage 35 is introduced to the vane back pressure chambers 6 from the discharge pressure introduction passages 51, 53 via the back pressure ports 41, 43 and the vanes 3 are biased in the directions to project from the slits 5 by this pressure.

As described above, if the stopped state of the vane pump 1 continues, the vanes 3 located on the upper side of the vane pump 1 fall into the slits 5 by gravity to define the pressure escape path 39 allowing communication between the first discharge port 32 and the first suction port 31. If the vane pump 1 is actuated in this state, the vanes 3 are fallen into the slits 5 and the pump chambers 7 are not defined in the first discharge region, wherefore the pressurized hydraulic oil is not introduced to the first discharge port 32. Thus, the check valve 60 is held closed. On the other hand, in the second discharge region, the vanes 3 enter the slits 5, following the cam ring 4, and the pump chambers 7 contract. The pressurized hydraulic oil discharged from the pump chambers 7 is introduced into the discharge passage 35 through the second discharge port 34. At this time, since the check valve 60 is closed, the escape of the pump discharge pressure introduced into the discharge passage 35 from the first discharge port 32 to the first suction port 31 and the section passage 25 through the pressure escape path 39 can be prevented. Thus, the pump discharge pressure in the discharge passage 35 quickly increases.

FIG. 3B shows a flow of the hydraulic oil when the vane pump 1, in which the pressure escape path 39 is defined, is actuated by arrows. The hydraulic oil in the tank 26 is supplied to the pump chambers 7 in the second suction region through the suction passage 25 and the second suction port 33. The pressurized hydraulic oil discharged from the pump chambers 7 in the second discharge region is supplied to the hydraulic device successively through the second discharge port 34 and the discharge passage 35. Further, since a reverse flow of the pressurized hydraulic oil in the discharge passage 35 to the first discharge port 32 is suppressed by the check valve 60, a reverse flow of the pressurized hydraulic oil to the first suction port 31 and the suction passage 25 through the pressure escape path 39 is suppressed.

When the vane pump 1 is actuated, the pump discharge pressure in the discharge passage 35 is introduced into the vane back pressure chambers 6 from the discharge pressure introduction passages 51, 53 via the back pressure ports 41, 43. The vanes 3 fallen into the slits 5 in the first suction region are urged to project from the slits 5 by the pressure introduced to the back pressure port 41, and the pump discharge pressure quickly increases by the pressure escape path 39 being blocked.

Functions and effects of the present embodiment are described below.

The vane pump 1 of the present embodiment is used as a fluid pressure supply source and includes the rotor 2 which is driven and rotated, a plurality of slits 5 which are radially formed in this rotor 2, a plurality of vanes 3 which slidably project from the slits 5, the cam ring 4 with which the tip parts of the vanes 3 slide in contact with the rotation of the rotor 2, the pump chambers 7 which are defined between the cam ring 4 and adjacent ones of the vanes 3, a plurality of discharge ports 32, 34 which introduce the working fluid discharged from the pump chambers 7 contracting with the rotation of the rotor 2, the discharge passage 35 which causes the working fluid introduced from the discharge ports 32, 34 to join, and the check valve 60 which is opened for the flow of the working fluid discharged from one discharge port 32 to the discharge passage 35.

This causes the check valve 60 to be closed to block the communication between the discharge passage 35 and the discharge port 32 when the pump is actuated to cause the upper vanes 3 to fall into the slits 5 and define the pressure escape path 39 between the vanes 3 and the cam ring 4, the escape of the working fluid pressures generated in the pump chambers 7 from the discharge passage 35 to the suction side (suction passage 25) through the discharge port 32 and the pressure escape path 39 can be suppressed.

Since the check valve 60 is opened for the flow of the working fluid discharged from the one discharge port 32 to the discharge passage 35, it is not opened by the pump discharge pressure introduced from the other discharge port 34 and the communication of the plurality of discharge ports 32, 34 can be avoided when the pump is actuated.

This can suppress the escape of the pump discharge pressure to the suction side (suction passage 25) when the pump is actuated, speed up an increase in the pump discharge pressure and improve the starting performance of the vane pump 1.

Further, the check valve 60 is provided in the region (first discharge region) where the pump chambers 7 are allowed to communicate with the suction side (suction passage 25) by the vanes 3 fallen into the slits 5.

This causes the check valve 60 to be closed when the pump is actuated, thereby being able to suppress the escape of the working fluid pressures generated in the pump chambers 7 to the suction side (suction passage 25) through the pressure escape path 39 defined by the vanes 3 fallen into the slits 5.

Further, the check valve 60 is not provided in the discharge port 34 in the region (second discharge region) where the pump chambers 7 do not communicate with the suction side (suction passage 25) since the vanes 3 do not fall into the slits 5.

This can prevent the check valve 60 from applying resistance to the flow of the working fluid from the one discharge port 34 into the discharge passage 35 and avoid a reduction in pump performance.

It should be noted that the check valve 60 may be provided in both of the first and second discharge ports 32, 34. This enables the above functions and effects to be obtained regardless of a mounting direction of the vane pump 1.

Further, the vane pump 1 has the first suction port and the first discharge port where the vanes 3 make the first reciprocal movement and the second suction region and the second discharge region where the vanes 3 make the second reciprocal movement, the first suction region is arranged to be higher than the second suction region and the check valve 60 is provided in the discharge port 32 disposed in the first discharge region.

This enables the check valve 60 to suppress the escape of the pump discharge pressure to the first suction region even if the vane pump 1 is actuated with the vanes 3 in the first suction region arranged on the upper side held in a state fallen into the slits 5 when the pump was stopped. This can quickly increase the pump discharge pressure of the vane pump 1 and improve starting performance.

The embodiments of the present invention described above are merely illustration of some application examples of the present invention and not of the nature to limit the technical scope of the present invention to the specific constructions of the above embodiments.

The present application claims a priority based on Japanese Patent Application No. 2011-231861 filed with the Japan Patent Office on Oct. 21, 2011, all the contents of which are hereby incorporated by reference.

Claims

1. A vane pump used as a fluid pressure supply source, comprising:

a rotor which is driven and rotated;

a plurality of slits which are radially formed in the rotor;

a plurality of vanes which slidably project from the slits;

a cam ring with which tip parts of the vanes slide in contact as the rotor rotates;

a pump chamber which is defined between the cam ring and adjacent ones of the vanes;

a plurality of discharge ports which introduce working fluid discharged from the pump chamber contracting as the rotor rotates;

a discharge passage which causes the working fluid introduced from the discharge ports to join; and

a check valve which is opened for a flow of the working fluid discharged from one discharge port to the discharge passage.

2. The vane pump according to claim 1, wherein:

the check valve is provided in a region where the pump chamber is caused to communicate with a suction side by the vanes fallen into the slits.

3. The vane pump according to claim 1, further comprising:

a first suction region and a first discharge region where the vanes make the first reciprocal movement and;

a second suction region and a second discharge region where the vanes make the second reciprocal movement, wherein:

the first suction region is arranged to be higher than the second suction region; and

the check valve is provided in the first discharge region.