Rotary vane pump

Abstract: A rotary vane pump comprising a stator (10) having a cylindrical surface; a rotor (2) which is positioned relative to the stator to define a fluid chamber between the rotor and the stator, the rotor being rotatable about a longitudinal axis (L) and having a number of radially extending slots therein; a vane (11) slidably mounted in each slot and biased towards the fluid chamber and into engagement with the surface of the stator, the vanes reciprocating in their respective slots as the rotor rotates about the stator; a first fluid passage (36) providing fluid at a first pressure from a fluid inlet to the fluid chamber; a second fluid passage taking fluid at a second pressure higher than the first pressure from the fluid chamber to a fluid outlet; and a electrically operated valve (15) positioned adjacent the fluid chamber and fluidly connecting the first and second fluid passages on detection of a predetermined condition. Energy saving design.

Description: This invention relates to a rotary vane pump, and in particular to a rotary vane pump which is usable in a power steering system of a motor vehicle. Designs of rotary vane pump are well known. These well known designs typically comprise a stator which has a cylindrical bore, and a rotor having a longitudinal axis about which the rotor rotates in the bore. Either the longitudinal axis of the bore is offset from the longitudinal axis of the rotor, or the bore has a contoured inner surface. The rotor has a number of circumferentially spaced, radially extending, slots therein. A vane is positioned in, and slidable in, each slot, with each vane being biased outwardly to engage the inner surface of the bore in the stator. A fluid inlet and a fluid outlet open into the bore. The arrangement is such that rotation of the rotor within the bore causes the vanes to reciprocate in their respective slots, and drives fluid from the inlet to the outlet. These designs, however, have a limitation in that they are continually driving fluid from the inlet to the outlet, which above certain vehicle speeds is unnecessary, and consequently wastes energy. DE-A-2362810 discloses a rotary vane pump in accordance with the preamble of Claim 1. US-A-5026263 discloses a rotary vane pump having a stator which surrounds the rotor, and an electrically operated valve to provide a fluid connection between the inlet and the outlet passages. It is an object of the present invention to provide an improved design of rotary vane pump. A rotary vane pump in accordance with the present invention is characterised over DE-A-2362810 by the features specified in the characterising portion of Claim 1. Where the rotary vane pump of the present invention is used in a power steering system of a motor vehicle, the predetermined condition is preferably a predetermined level of vehicle speed, with the first and second fluid passage being fluidly connected when the vehicle speed is above a predetermined level. The rotary vane pump is preferably as described and claimed in our patent application no. EP-A-0674104 (MJD/G-9795), filed the same day as the present application. The present invention will now be described, by way of example, with reference to the accompanying drawings, in which :- Figure 1 is a cross-sectional view of a rotary vane pump in accordance with the present invention, taken on the line A-A of Figure 2; Figure 2 is a cross-sectional view taken on the line B-B of Figure 1; Figure 3 is an inner end view of the cover plate of the rotary vane pump of Figure 1; Figure 4 is a cross-sectional view on the line C-C of Figure 3; Figure 5 is an inner end view of the rotor of the rotary vane pump of Figure 1; Figure 6 is a cross-sectional view on the line D-D of Figure 5; Figure 7 is an inner end view of the pressure plate and stator of the rotary vane pump of Figure 1; Figure 8 is a cross-sectional view on the line E-E of Figure 7; Figure 9 is a cross-sectional view of the line F-F of Figure 7; and Figure 10 is a cross-sectional view of the sleeve of the solenoid operated valve of Figure 1. Referring to Figures 1 and 2 of the drawings, the rotary vane pump comprises a housing 1 preferably of cast metallic material; a substantially annular rotor 2 positioned within the housing; a stator 10 formed on a pressure plate 3 and positioned within the rotor; and sixteen vanes 11 mounted in corresponding slots 12 in the rotor. The housing 1 is substantially cylindrical and defines a through bore 17 of stepped diameter. The larger open end 18 of the through bore 17 in the housing 1 is closed by a cover plate 6 which is secured to the housing by screws 19. An O-ring seal 16 forms a substantially fluid-tight seal between the housing 1 and the cover plate 6. A solenoid operated valve 15 is secured in the cover plate 6 and projects into the pressure plate 3. The rotor 2 is integrally formed with a back plate 20 and a drive shaft 21 which extends out of the smaller open end 22 of the through bore 17 in the housing 1. The drive shaft 21 is rotatably mounted in the through bore 17 by a bearing 4. A high pressure seal 5 acts between the through bore 17 and the drive shaft 21 to form a substantially fluid-tight seal at the smaller open end of the through bore. The rotor 2 is rotatably mounted in the through bore 17 by needle bearing 13 or a suitable bushing (such as a Babbitt bushing). Drive means (not shown) rotates the rotor 2 about its longitudinal axis L. The pressure plate 3 is located in a predetermined position relative to the cover plate 6 by locating pins 14 which locate the pressure plate within the housing 1 with the stator 10 positioned inside the rotor 2. A fluid chamber 24 is defined between the rotor 2 and the stator 10. The stator 10 has an outer surface 23 (Figure 2) which is contoured to form a cam surface, and a longitudinal axis which is aligned with the longitudinal axis L of the rotor 2. The slots 12 extend radially through the rotor 2. A circumferentially extending groove 25 is formed in the rotor 2 at the outer radial ends of the slots 12. Each vane 11 is slidably mounted in its respective slot and is capable of reciprocating movement therein. Each vane 11 protrudes out of its respective slot 12 and is biased by a garter spring 7 positioned in the groove 25 into engagement with the outer surface 23 of the stator 10. The positioning of the vanes 11 is symmetrical about the longitudinal axis L of the rotor 2, although the vanes are unequally spaced apart. Referring to Figures 3 and 4, the cover plate 6 comprises a fluid inlet 26 which is connected to a fluid reservoir (not shown) and a fluid outlet 27. A flow control valve (not shown) may be positioned in the fluid outlet 27. A supercharge fluid passage 28 may interconnect the inlet 26 and outlet 27. In the inner surface 29 of the cover plate 6 is formed an annular groove 30 which fluidly connects the inlet 26 to two low pressure depressed areas 31 in the inner surface, and a central depressed area 32 fluidly connected by channels 33 to two high pressure depressed areas 34 and the outlet 27. The central depressed area 32 is also connected with a through bore 46 within which the solenoid operated valve 15 is secured. Referring to Figure 8 and 9, the outer surface 35 of the pressure plate 3 has two low pressure through bores 36 and two high pressure through bores 37 which align with the corresponding depressed areas 31,34 in the inner surface 29 of the cover plate 6 on assembly of the rotary vane pump. The low pressure through bores 36 and depressed areas 31 define a first fluid passage, and the high pressure through bores 37 and depressed areas 34 defined a second fluid passage. Further, the outer surface 35 has a centrally positioned stepped through bore 38 which aligns with the central depressed area 32 in the cover plate 6, and which is fluidly connected with the high pressure through bores 37 by a channel 39 in the outer surface 35. On assembly, the solenoid operated valve 15 extends into the stepped bore 38. Referring to Figures 7 and 8, the inner surface 40 of the pressure plate 3 has the stator 10 integrally formed thereon, a channel 41 therein for fluidly connecting the low pressure through bores 36, and an annular channel 42 therein adjacent the outer edge 43 for the passage of high pressure fluid between the slots 12 in the rotor 2 adjacent the outer radial end of the slots. The high pressure fluid acts on the vanes 11 (along with the garter spring 7) to bias the vanes into engagement with the outer surface 23 of the stator 10. Referring to Figures 7 and 9, a bore 47 extends though the stator 10 from adjacent each low pressure through bore 36 to the stepped bore 38. The speed bore 38 also has an opening 48 through the stator 10 which is directed towards the back plate 20 on assembly of the rotary vane pump. Referring to Figures 5 and 6, the rotor 2 is shown with the back plate 20 and the drive shaft 21, radially extending slots 12, and circumferential groove 25. A pair of bores 44 extend through the back plate 20 and fluidly connect with radially extending channels 45 in the back plate to provide an additional passage for high pressure fluid from the fluid chamber 24 to the outer radial end of each slot 12 to provide bias on the vanes 11 and a hydraulic balance of the rotor 2 relative to the cover plate 6. A longitudinally extending bore 49 passes through the back plate 20 into the drive shaft 21, and a radially extending bore 50 extends from the bore 49 to the outer surface 51 of the drive shaft. On assembly of the rotary vane pump, the bore 49 aligns with the opening 48 in the stator 10 and is closed at the other end by a ball 52 or something similar, and the bore 50 opens adjacent the bearing 4. This arrangement allows fluid at low pressure to flow to the bearing 4 to lubricate the bearing. Referring to Figures 1, 2 and 10, the solenoid operated valve 15 comprises a valve member 53 having a frustoconical surface connected to a longitudinally extending stem 54, an electromagnetic coil 55, and a sleeve 56. The stem 54 is reciprocally mounted in the electromagnetic coil 55 which is secured in the through bore 46 in the cover plate 6. The stem 54 is also sealing mounted in the through bore 46 by an O-ring seal 57. The sleeve 56 is mounted in the stepped bore 38 in the pressure plate 3 and extends into the centrally depressed area 32 in the cover plate 6. The sleeve 56 has a through bore 58 comprising a large diameter portion 59, a small diameter portion 60, and a shoulder 61 therebetween. The small diameter portion 60 is directed towards, and opens to, the opening 48 in the stator 10. The valve member 53 is located within the large diameter portion 59 and the shoulder 61 defines a valve seat for the valve member. A diametrically extending bore 62 opens into the small diameter portion 60 and aligns with the bores 47 in the stator 10 on assembly of the rotary vane pump. A diametrically extending channel 63 opens into the large diameter portion 59 and aligns with the channels 39 in the pressure plate 3 and the channels 33 in the cover plate 6 on assembly of the rotary vane pump. A coil spring 64 extends through the small diameter portion 60 and acts on the valve member 53 to bias the valve member to a normally open position. The electromagnetic coil 55 is electrically connected to a control module 65 which monitors signals from a speed sensor 66 mounted in the motor vehicle. On detection of a vehicle speed below a predetermined level, the control module 65 energises the electromagnetic coil 55 to move the valve member 53 into engagement with the shoulder 61 to close the solenoid operated valve 15. In operation, the rotor 2 is driven by the drive means (not shown) to rotate about its longitudinal axis L relative to the housing 1 and stator 10. As the rotor 2 rotates with the vanes 11 in contact with the outer surface 23 of the stator 10, the vanes reciprocate within the slots 12, with the vanes being fully extended inwardly between the low pressure through bores 36 and the high pressure through bores 37 as the vanes move from the low pressure through bores 36 towards the high pressure through bores 37. Fluid at low pressure enters the fluid chamber 24 from the fluid reservoir (not shown) by way of fluid inlet 26 and the low pressure through bores 36. The vanes 11 drive the fluid towards and out through the high pressure through bores 37 to the fluid outlet 27, thereby increasing the pressure in the fluid. The pressurised fluid is used in a power steering system (not shown) of a motor vehicle. Excess fluid flow passes through the supercharge fluid passage 28 to the inlet 26 to help to pressurise the fluid entering the fluid chamber 24. When the valve member 53 is in its open position, the low pressure through bores 36 and the high pressure through bore 37 in the pressure plate 3 are fluidly connected by way of bores 47 and 62, channels 39 and 63, and through bore 58. In this situation, with the vehicle speed above the predetermined level, the rotary vane pump is effectively disconnected and only a minimal amount of energy is being consumed by the rotary vane pump, thereby saving energy. However, when the control module 65 detects a vehicle speed below the predetermined level, the valve member 53 is moved to its closed position to separate the low and high pressure fluid passages so that the rotary vane pump operates as described above to provide pressurised fluid to the power steering system of the motor vehicle. The above described embodiment of rotary vane pump can be modified within the scope of the present invention. For example, the stator could have a substantially circular cross-section, with the longitudinal axis of the stator offset from the longitudinal axis of the rotor to provide the required reciprocating movement of the vanes as the rotor rotates. Other forms of electrically operated valve could be used besides a solenoid operated valve. In either case, the arrangement may be that the valve member is biased to a normally closed positioned, and is moved to an open position on detection of a vehicle speed above the predetermined level.

Claims: A rotary vane pump comprising a stator (10) having a cylindrical outer surface (23); a rotor (2) is substantially annular and positioned around the stator to define a fluid chamber (24) between the rotor and the stator; the rotor being rotatable about a longitudinal axis (L) and having a number of radially extending slots (12) therein; a vane (11) slidably mounted in each slot and biased towards the fluid chamber and into engagement with the outer surface of the stator, the vanes reciprocating in their respective slots as the rotor rotates relative to the stator; a first fluid passage (36) providing fluid at a first pressure from a fluid inlet (26) to the fluid chamber; and a second fluid passage (37) taking fluid at a second pressure higher than the first pressure from the fluid chamber to a fluid outlet (27); characterised by an electrically operated valve (15) positioned adjacent the fluid chamber and fluidly connecting the first and second fluid passages on detection of a predetermined condition; and in that the slots are, circumferentially, unequally spaced apart. A rotary vane pump as claimed in Claim 1, wherein the predetermined condition is vehicle speed, the first and second fluid passages being fluidly connected when vehicle speed is above a predetermined level. A rotary vane pump as claimed in Claim 1 or Claim 2, wherein the stator (10) is integrally formed with a pressure plate (3) which comprises through bores (17) to allow fluid to flow from the fluid inlet (26) through the fluid chamber (24) to the fluid outlet (27) and which define the first and second fluid passages. A rotary vane pump as claimed in Claim 3, wherein the electrically operated valve (15) is situated at least in part in the pressure plate (3) and the stator (10). A rotary vane pump as claimed in any one of Claims 1 to 4, wherein the electrically operated valve (15) is normally open but is closed on detection of the predetermined condition. A rotary vane pump as claimed in any one of Claims 1 to 5, wherein the electrically operated valve is a solenoid operated valve (15).

Inventors: BOTTI JEAN JOSEPH, ROETHLISBERGER JERRY MYRON, BOTTI, JEAN JOSEPH, ROETHLISBERGER, JERRY MYRON
Applicants: DELPHI FRANCE AUTOMOTIVE SYS, GEN MOTORS CORP, DELPHI FRANCE AUTOMOTIVE SYSTEMS, GENERAL MOTORS CORPORATION
Application year: 1995
Main classification: F04C15
IPC codes: F04C14, F04C2