GB2106986A - Rotary positive-displacement fluid-machines - Google Patents

Abstract

In a sliding-vane type liquid pump, which may be double-acting (as shown), vanes 37 carried by the rotor 34 are biassed towards a cam ring 27 by pins 38 and pressure transmitted thereto from e.g. outlet ports 47', by way of an annular groove 41 and a set of lateral bores 43 in the rotor. Communication between the ports 47' and the bores 43 may be effected through ports 52 in a cheek plate 24. Additional ports 53 communicating with another set of lateral bores 43 in the rotor may be incorporated in a further cheek plate 23. The working fluid in the bores 43 and ports 52, 53 lubricates the side surfaces of the rotor and the adjacent surfaces of the cheek plates. <IMAGE>

Description

SPECIFICATION Side feed vane pump rotor Background of the Invention The instant invention relates to an improvement in a vane-type hydraulic pump which utilizes a hydraulically actuated pin beneath each vane to bias the vanes into engagement with the cam ring, and has a pressure loaded port plate.

More specifically, the invention relates to means for supplying pressure fluid to actuate each pin, which supply means also lubricates the area of minimum clearance between the port plates and the rotor.

A typical vane pump includes a rotor, a stator or cam ring which surrounds the rotor, a plurality of vane slots formed in the rotor and a vane positioned in each slot. One end of each vane engages the inner surface of the cam ring. The sides of the rotor and the side edges of each vane are in sliding, sealing engagement with a pair of port or side plates positioned one on each side of the rotor. A fluid pumping or intervane space is defined by the rotor periphery, the inner surface of the cam ring, the port plates and pairs of adjacent vanes. The inner surface of the cam ring is contoured so that the distance between it and the periphery of the rotor varies. This causes the volume of the intervane space to change. As the rotor is turned, the vanes sequentially traverse an intake or suction zone, a transfer zone, a discharge or pressure zone and a sealing zone.

It is important for the efficient operation of the pump to have each vane remain in positive contact with the inner surface of the cam ring. A preferred means for assuring that each vane maintains contact with the cam ring is disclosed in USPN 2,832,293 to Adams et al. In that patent, a vane pump is shown in which each vane is biased outwardly of its slot and into engagement with a cam ring by means of a hydraulically actuated pin.

The pin is positioned in a bore in the vane slot beneath the vane. Pressure fluid is supplied to the inner end of the pin to bias it radially outward of its bore and into engagement with the vane. This is known as a pin vane pump.

It has been found that a vane pump can be operated more efficiently at higher pressures by changing the design of the port plate which contains the inlet and exhaust fluid ports from that of a fixed port plate to that of a pressure loaded port plate, as shown in USPN 3,223,044 to Adams et al. In a fixed port plate pump, as shown in '293 Adams et al. patent, one half of the port plate contains a suction or inlet port and the other half of the port plate contains a pressure or exhaust port. A problem with a pump which has a fixed port plate is that as the pressure in the intervane space increases, the fluid acts to bias the port plates outwardly, away from the rotor.

This causes the clearance between the rotor and port plates to increase, which causes increased fluid leakage and loss of efficiency. As the fluid pressure in the intervane space increases, the fluid leakage increases which limits the maximum pressure at which a fixed port plate pump can operate efficiently.

In a pump which has a pressure loaded port plate, such as shown in the '044 Adams et al.

patent, a pair of pressure ports are formed in a port plate 1800 apart and the back of the port plate is connected to the working or pressure fluid outlet. The port plate is formed in such a way that the area of the plate exposed to pressure fluid acting to bias the plate towards the rotor and cam ring is greater than the area of the plate exposed to pressure fluid acting to bias the plate away from the rotor and cam ring. Consequently, the port plate is hydraulically unbalanced and the working pressure fluid clamps the port plate towards the cam ring and rotor. The portion of the port plate which engages the cam ring remains stationary after it engages the cam ring. However, the portion of the port plate radially inward of the inner surface of the cam ring can deflect or move axially inward towards the rotor as the pressure of the working fluid increases.The port plate deflection is greatest near its center. As the pressure loaded port plate moves towards the rotor, clearance, which is the total distance between the pressure loaded port plate and the rotor and between the rear port plate and the rotor, is decreased. Since deflection of the pressure loaded port plate is greatest at the center, the area of least clearance between the rotor and port plates is radially just beyond the rotor port plate drive shaft bores.

Clearance between the rotor and port plates is inversely proportional to working fluid pressure.

Thus at pump startup, this clearance is greatest.

As the pressure of the working fluid increases, clearance between the rotor and the port plates decreases. This decreasing clearance as working fluid pressure increases has several advantages.

When a pump is initially started the pressure fluid is usually cold and lubrication between the rotor and port plates is minimal. Since a pump is normally run at low speeds and pressures when it is first started, the large clearance between the port plates and the rotor prevents friction damage, or galling, of the rotor and port plates caused by inadequate lubrication. As the pressure of the working fluid increases, and the clearance between the central portion of the port plates and the central portion of the rotor decreases, the likelihood of galling of the port plates or rotor increases. Thus, lubrication in the area of minimum clearance is extremely important.

Galling of the rotor and port plates can be eliminated by simply increasing the clearance between the rotor and port plates or by improving lubrication in the area of minimum clearance. A disadvantage of increasing clearance is that, as the clearance is increased, leakage of the working fluid also increases and the efficiency of the pump is reduced.

It is desirable to have a pin vane pump having a pressure loaded port plate in which pressure fluid is provided to actuate the pins and to provide lubrication in the area of least clearance between the rotor and port plates to permit reduced clearance therebetween without galling.

Summary of the Invention The instant invention provides a pin vane pump which includes a pressure loaded port plate. A feed groove, which opens into the bottom of each pin, is formed in the rotor. An equal number of lateral bores are formed in each side of the rotor radially inward of the bottom of the vane slots in the area of least clearance between the rotor and port plates. All of the lateral bores open into the feed groove and are interconnected through the groove. A pair of pressure fluid feed ports which extend angularly a short arc are formed in each port plate, which ports are aligned with the lateral bores and supply pressure fluid thereto to actuate the pins and to lubricate the rotor and port plates in the area of least clearance therebetween.

Description of the Drawings Fig. 1 is an axial cross-section of a pump according to the instant invention; Fig. 2 is a view of the inner face of the pressure loaded port plate of the pump; and Fig. 3 is a side view of the pump rotor.

Description of the Preferred Embodiment Referring to Figs. 1-3, the vane pump 10 of the instant invention includes a housing formed by a main body casting 11 and an end cap 12. End cap 12 has an annular projection 13 which is received in a mating bore 14 in one end of body 11 and is sealed with respect to body 11 by an O-ring 15. End cap 12 is conventionally secured to body 11 by bolts, not shown.

End cap 12 has a central opening 1 6 which receives a drive shaft 1 7. Drive shaft 1 7 is supported for rotation in end cap 1 2 by a bearing 18 which is secured against axial movement by a snap ring 19. A seal 20 prevents fluid leakage along shaft 1 7. Drive shaft 1 7 projects through the main portion of body 11 and is supported at its outer end by a bearing 21 which is mounted in an annular bore 22, formed in a rear port or side plate 23. A pressure loaded front port or side plate 24 is supported in end cap 12. Port plate 24 has a smooth, flat, inner surface 25 which bears against one side 26 of an annular cam ring 27, which is supported in a rib 28 in body 11.The opposite side 29 of cam ring 27 bears against a smooth, flat surface 30 on the front of rear port plate 23, and holds the latter against a shoulder 31 in body 11. Cam ring 27 and front and rear port plates 24, 23 are clamped together by bolts, not shown.

The vane pump 10 has a fluid inlet passage 32 which extends into body 11 and communicates with a pair of passageways 33, 33' located on each side of cam ring 27. Inside of cam ring 27 is a rotor 34 which is driven by drive shaft 1 7 through a splined connection 35. The rotor 34 has a plurality of slots 36, each of which receives a vane 37.

In the instant invention each van 37 is biased radially outward of its slot 36 by a hydraulically operated piston or pin 38 which slides in a bore 39 in rotor 34. Bore 39 is centered laterally in slot 36, projects radially inward from the bottom edge 40 of slot 36 and opens into an annular feed groove 41. Annular groove 41 is sealed from the splined connection 35 in rotor 34 by a sleeve 42.

Referring to Figs. 1 and 3, a plurality of lateral feed bores 43 are formed in rotor 34, which bores 43 project laterally inward from one side 44 or the other side 45 of rotor 34 and open into annular groove 41. The feed bores 43 supply working or exhaust pressure fluid from the front and rear port plates 23, 23, respectively, as explained hereinafter, to the annular groove 41 to bias the pins 38 against the vanes 37 to maintain the latter in contact with a contoured inner surface 46 formed on cam ring 27.

The minimum number of feed bores 43 required, which in the instant pump is six, is determined by several factors. One factor is that there must be a sufficient number of feed bores 43 to insure that at least one bore 43 is in communication with the pressure fluid feed means at all times. Another factor is that an equal number of feed bores 43 must open into each side 44, 45 of the rotor 34 so that it is hydraulically balanced between the port plates 23, 24 during operation. The number of positioning of feed bores 43 is also dependent upon the number of vane slots 36, since it is necessary to position the feed bores 43 between two adjacent vane slots 36 to preserve the strength of the rotor 34.

As shown in Figs. 1 and 3, the rotor 34 has three lateral bores 43 which open into one side 44 of the rotor 34 and three lateral bores 43 which open into the other side 45 of rotor 34. As shown in Fig. 2, the length of each pressure fluid feed means formed in the port plates 23, 24 covers an arc of 360. Actually only five equally spaced feed bores 43, one between every other vane slot 36, would be sufficient to ensure that one bore 43 is always in alignment with the pressure fluid feed means, since 720, which is the arc covered by two of the fluid feed means, divides into 3600 five times. However, the sixth bore is necessary so that an equal number of bores 43 open into each side 44, 45 of the rotor 34.It would also be acceptable to put ten equally spaced feed bores in rotor 34, five of the bores opening into each side of the rotor and reduce the length of each of the two pressure fluid feed means in each of the port plates 23, 24 so that the length of one fluid feed means covers an arc of 180 or the two fluid feed means together cover an arc of 360. Adjacent feed bores would open into opposite sides of the rotor.

In a pump having twelve vanes and a total of six equally spaced feed bores 43, one between every other vane slot, the length of each of the pressure fluid feed means would only have to cover an arc of 300. If the twelve vane pump had twelve equally spaced feed bores 43, the length of each pressure fluid feed means would only have to cover an arc of 1 50. With either six or twelve feed bores, adjacent feed bores would open into opposite sides of the rotor.

Referring to Fig. 2, two diametrically opposed exhaust pressure ports 47, 47' are formed in front port plate 24. The pressure ports 47, 47' are connected through internal passages, not shown, to a fluid outlet 48 in end cap 12 which delivers the high pressure working or exhaust fluid to an external hydraulic circuit. A pair of suction ports 49, 49' are spaced 900 from the pressure ports 47, 47' and receive low pressure suction fluid from an external source through the passages 33, 33'. Two diametrically opposed pressure ports 50 are formed in rear port plate 23. These ports 50 are the same size and shape as those 47, 47' in the front port plate 24. Rear port plate 23 also has a pair of suction ports 51, which are offset 900 from the pressure ports 50 and are the same size and shape as those 49, 49' in the front port plate 24.The reason for having identical fluid ports in the front and rear port plates 24, 23, respectively, is to ensure that the lateral forces exerted on the rotor 34 by the working fluid in the exhaust pressure ports 47, 47', 50 are equal.

Referring to Figs. 1 and 2, high pressure fluid is fed to the lateral feed bores 43 in rotor 34 from a pair of feed ports 52, 52' formed in front port plate 24. Feed ports 52, 52' open into the pressure ports 47, 47', respectively. Two feed ports 43, one of which is shown in Fig. 1, are also formed in rear port plate 23 and open into the pressure ports 50.

The feed ports 52, 52', 53 project radially inward from the pressure ports 47, 47', 50 towards the center of the port plates 24, 23 and are radially aligned with the lateral feed bores 43 during operation of the pump 1 0. As previously mentioned, each of the feed ports 52, 52", 53 have an arc of about 36 . It has been found that if each feed port 52, 52', 53 extends from an arc 360 and six feed bores 43 are formed in rotor 34, sufficient fluid pressure is maintained in feed groove 41 to permit the pins 38 to keep the vanes 37 in contact with the inner surface 46 of cam ring 27 and, at the same time, minimize fluid leakage during operation of the pump 10 at high pressure.

The low fluid leakage is attributed to the short flow path for the working pressure fluid as a result of the relative short arcuate length of the feed ports 52,52,53.

When the vane pump 10 is operating, high pressure fluid biases front port plate 24 against cam ring 27 and rotor 34. Since port plate 24 cannot deflect further once it engages the side 26 of cam ring 27, only that portion of the port plate 24 which is radially inward of cam ring 27 can deflect further inward towards rotor 34 as the pressure of the working fluid increases. The center of the front port plate 24 can deflect the farthest inward towards rotor 34. Therefore, clearance between the rotor port plates 24, 23 is at a minimum in the annular space between the bottom of the vane slots 36 and the splined connection 35.

During operation of pump 10 each lateral feed bore 43 communicates with the two feed ports 52, 52' in front port plate 24 or the two feed ports 53 in rear port plate 23, once for each rotation of rotor 34, and at least one feed bore 43 is always in fluid communication with a feed port 52, 52', 53. In this manner working pressure fluid is supplied through each feed bore 43 to lubricate the sides 44, 45 of the rotor 34 and the front surfaces 30, 25 of the port plates 23, 24 in the area of least clearance. Since feed bores 43 are all interconnected via annular groove 41 , the pressure in each of feed bores 43 is equal.

In the instant pump, it has been found that with the lubrication from the feed bores 43, clearance between the port slates 23, 24 and the rotor 34 could be reduced from .0023" to .0014" without causing galling of the rotor 34 or port plates 23, 24 during operation of the pump 10 at its maximum psi rating. Since the clearance between the rotor 34 and the port plates 23, 24 is reduced, fluid leakage is reduced at all pressures. In an experimental pump incorporating the instant invention, the reduced leakage resulted in an overall increase in pump efficiency of 6% at 3000 psi.

Claims (10)

1. A vane pump for pumping pressure fluid having a rotor, a pair of sidewalls formed on the rotor, a cam ring, a pair of sidewalls formed on the cam ring, a contoured inner cam surface formed on the cam ring, a plurality of vane slots each defined by a pair of sidewalls and a bottom surface formed in the rotor, a vane in each slot for movement relative thereto, wherein each vane engages the inner cam surface, a pin bore in each slot which extends radially inward from the bottom surface of the slot, a hydraulically actuated pin in each pin bore, a central feed groove connected to the bottom of each pin; a drive shaft for driving the rotor, a front port plate clamped against one sidewall of the cam ring by pressure fluid, a rear port plate clamped against the other sidewall of the cam ring, a first pair of pressure ports formed in the front port plate, a second pair of pressure ports formed in the rear port plate; and characterised by a plurality of feed bores formed in the rotor, each extending laterally inward from one of the rotor sidewalls and opening into the central feed groove, wherein each feed bore is positioned radially inward of the bottoms of the vane slots, and means for supplying pressure fluid to the feed bores to bias the pins outwardly of their slots and to lubricate the rotor sidewalls and the adjacent front and rear port plates respectively radially inward of the bottom of the vane slots.

2. The vane pump of claim 1, characterized by the number of feed bores which extend inward from the one rotor sidewall being equal to the number of feed bores which extend inward from the other rotor sidewall.

3. The vane pump of claim 1, characterized by the means for supplying pressure fluid to the feed bores including a first pair of feed ports formed in the front port plate which are each connected to one of the first pair of pressure ports, the first pair of feed ports being positioned radially such that they are connected with the rotor feed bores in one of the rotor sidewalls, and s second pair of feed ports formed in the rear port plate which are each connected to one of the second pair of pressure ports, the second pair of feed ports being positioned radially such that they are connected with rotor feed bores in the other of the rotor sidewalls.

4. The vane pump of claim 3, characterized by the number of rotor feed bores being such that at least one feed bore is always connected with one of the first or second pair of feed ports.

5. The vane pump of claim 3, characterized by having ten vane slots formed in the rotor, three feed bores opening into each rotor sidewall and each feed port covering an arc equal to approximately 360.

6. The vane pump of claim 3, characterized by having ten vane slots formed in the rotor, five equally spaced feed bores opening into each rotor sidewall and each feed port covering an arc equal to approximately 180.

7. The vane pump of claim 3, characterized by having twelve vane slots formed in the rotor, three equally spaced feed bores opening into each rotor sidewall and each feed port covering an arc equal to approximately 300.

8. The vane pump of claim 3, characterized by having twelve vane slots formed in the rotor, six equally spaced feed bores opening into each rotor sidewall and each feed port covering an arc equal to approximately 150.

9. The vane pump of claim 1, characterized by having each feed bore angularly centered between two adjacent vanes to retain the strength of the rotor.

10. A vane pump substantially as hereinbefore described with reference to the accompanying drawings.