VANE PUMP

Abstract

A vane pump having a pump containing a rotor driven via a drive shaft with the rotor having a number of generally radially extending grooves distributed over its circumference each of which grooves support a vane shaped delivery element in sliding fashion. The rotor is encompassed by an eccentric circumferential wall, against which the radially outer ends of the vanes rest. Housing end walls are situated adjacent to the rotor in the direction of its rotation axis. When the rotor turns, the vanes deliver medium from a suction region to a pressure region offset in the rotation direction. An annular groove is provided in at least one of the housing end walls which annular groove encompasses the rotation axis of the rotor, is situated opposite the inner regions delimited in the grooves of the rotor by the vanes, and is connected to the pressure region via a connecting groove in the housing end wall. The annular groove extends in eccentric fashion in relation to the rotation axis of the rotor.

Description

PRIOR ART

The invention relates to a vane pump as generically defined by the preamble to claim 1.

A vane pump of this kind is known from DE 199 52 167 A1. This vane pump has a pump housing that contains a rotor, which is driven to rotate via a drive shaft. The rotor has a number of grooves distributed over its circumference that extend in an at least essentially radial direction in relation to the rotation axis of the rotor, each of which has a respective vane-shaped delivery element guided in it in sliding fashion. The pump housing has a circumference wall encompassing the rotor and extending eccentrically in relation to its rotation axis, against which the radially outer ends of the vanes rest. The pump housing has housing end walls situated adjacent to the rotor in the direction of the rotation axis of the rotor. Because of the eccentric arrangement of the circumference wall, the vanes form chambers, which expand and contract during rotation of the rotor and between which the medium to be supplied is conveyed with an increase in pressure from a suction region to a pressure region that is offset from it in the circumference direction. Centrifugal forces when the rotor is turning hold the vanes in contact with the circumference wall, but at low speeds, particularly when vane pump rotation is just starting, only slight centrifugal forces are exerted so that the vane pump only delivers a small amount. In the known vane pump, another delivery pump that forms a combined pump unit with the vane pump supplies the inner regions, which are delimited in the grooves by the vanes, with compressed medium, which presses the vanes outward toward the circumference wall in addition to the centrifugal force. In this case, at least one housing end wall is provided with an annular groove extending over part of the circumference of the rotor, which is supplied with compressed medium by the additional delivery pump. The annular groove is separated from the drive shaft by a sealing region in which the rotor and the adjoining housing end wall are situated spaced slightly apart from each other in the axial direction. The annular groove is situated concentric to the rotation axis of the rotor so that the sealing region has a constant radial span. The disadvantage in this known vane pump is that the annular groove extending over only part of the circumference of the rotor only exerts pressure on the inner regions of the grooves of the rotor over a corresponding part of a rotation of the rotor, as a result of which under some circumstances, there is only a slight pressing force of the vane against the circumference wall. Moreover, the sealing region can permit leakage of pressurized medium from the annular groove toward the drive shaft.

ADVANTAGES OF THE INVENTION

The vane pump according to the invention, with the characteristics according to claim 1, has the advantage of the prior art that the exertion of pressure on the inner regions of the grooves of the rotor is intensified by means of the annular groove extending over the entire circumference of the rotor. In addition, by means of the eccentricity of the annular groove in relation to the rotation axis of the rotor the sealing region between the annular groove and the drive shaft, it is possible to intentionally enlarge the radial span of the sealing region in a circumference region of the rotor, which can be used to reduce the leakage from the annular groove.

Advantageous embodiments and modifications of the vane pump according to the invention are disclosed in the dependent claims.

DRAWINGS

An exemplary embodiment of the invention is shown in the drawings and will be explained in detail in the subsequent description.

FIG. 1 shows a simplified view of a vane pump in a cross section along the line I-I in FIG. 3,

FIG. 2 shows the vane pump in a cross section along the line II-II in FIG. 3, and

FIG. 3 shows the vane pump in a longitudinal section along the line III-III in FIG. 1.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

FIGS. 1 through 3 show a vane pump that is preferably provided for delivery of fuel, in particular diesel fuel. In this instance, the vane pump delivers fuel from a tank to a high-pressure pump. The vane pump can be separate from the high-pressure pump, built onto the high-pressure pump, or integrated into the high-pressure pump. The vane pump has a pump housing 10 that is comprised of multiple parts and a drive shaft 12 that protrudes into the pump housing 10. The pump housing 10 has two housing end walls 14, 16 that delimit a pump chamber in the axial direction, i.e. in the direction of the rotation axis 13 of the drive shaft 12. In the circumference direction, the pump chamber is delimited by a circumference wall 18 that is integrally joined to the housing end walls 14, 16 or can be embodied as a component separate from them.

As shown in FIGS. 1 and 3, the pump chamber contains a rotor 20 that is attached in a torsionally fixed manner to the drive shaft 12, for example by means of a groove/spring connection 22. The rotor 20 has a plurality of grooves 24 distributed over its circumference, extending at least essentially radially to the rotation axis 13 of the rotor 20. The grooves 24 extend into the rotor 20 from the outer circumference of the rotor 20 toward the rotation axis 13. For example, four grooves 24 are provided; it is also possible for fewer or more than four grooves 44 to be provided. In each groove 24, a plate-shaped delivery element 26 is situated in sliding fashion, which will be referred to below as a vane and whose radially outer end region protrudes out from the groove 24. Each vane 26 delimits an inner region 25 situated toward the radial inside in the respective groove 24.

The inside of the circumference wall 18 of the pump housing 10 is situated eccentrically to the rotation axis 13 of the rotor 20, for example in the form of a circle or some other shape. In at least one housing end wall 14, 16, as shown in FIG. 2, a suction region is provided, which communicates with at least one suction opening 28. The suction opening 28 connects to the suction groove 30, preferably in its end region oriented opposite the rotation direction 21 of the rotor 20. The suction opening 28 is connected to an inlet leading from the tank. At least one housing end wall 14, 16 is also provided with high-pressure region, which communicates with at least one pressure opening 32. In the pressure region, preferably in at least one housing end wall 14, 16, an elongated pressure groove 34 is provided, which is curved in an approximately kidney-shaped fashion, extends in the circumference direction of the rotor 20, and communicates with the pressure opening 32. The pressure opening 32 connects to the pressure groove 34, preferably in its end region oriented in the rotation direction 21 of the rotor 20. The pressure opening 32 is connected to an outlet that leads to the high-pressure pump. The suction opening 28, the suction groove 30, the pressure opening 32, and the pressure groove 34 are situated spaced radially apart from the rotation axis 13 of the rotor 20, close to the inside of circumference wall 18. The radially outer ends of the vanes 26 rest against the inside of the circumference wall 18 and slide along it in the rotation direction 21 as the rotor 20 turns. Because of the eccentric design of the inside of the circumference wall 18 in relation to the rotation axis 13 of the rotor 20, the vanes 26 form chambers 36 with changing volumes. The suction groove 30 and the suction opening are situated in a circumference region in which the rotating motion of the rotor 20 in the rotation direction 21 causes the volume of the chambers 36 to increase so that they are filled with fuel. The compression groove 34 and the pressure opening 32 are situated in a circumference region in which the rotating motion of the rotor 20 in the rotation direction 21 causes the volume of the chambers 36 to decrease so that fuel is displaced from them into the pressure groove 34 and from there into the pressure opening 32.

In at least one housing end wall 14, 16, as shown in FIG. 2, an annular groove 38 is provided, which extends over the entire circumference of the rotor 20 and communicates with the pressure groove 34 via a connecting groove 40. In lieu of the connecting groove 40, it is also possible for a connecting bore to be provided. Between the annular groove 38 and the drive shaft 12, a sealing region 39 is formed in which there is only a slight axial distance between the rotor 20 and the adjoining housing end wall 14, 16. In the region around the drive shaft 12, there is only a slight amount of pressure so that between the annular groove 38 and the region around the drive shaft 12, there is a pressure difference. The annular groove 38 extends eccentrically in relation to the rotation axis 13 of the rotor 20 so that the radial span s of the sealing region 39 is different over the circumference of the annular groove 38. The annular groove 38 can, for example, be at least approximately circular, having a center point M, which is situated offset from the rotation axis 13 of the rotor 20 by a distance e that constitutes the eccentricity. Preferably, the eccentricity e of the annular groove 38 is at least approximately of the same magnitude and oriented in the same direction as the eccentricity of the inside of the circumference wall 18 of the pump housing 10. Preferably, the center point M of the annular groove 138 is situated offset from the rotation axis 13 in a direction toward a region of the circumference wall 18 situated between the suction groove 30 and the pressure groove 34 in the rotation direction 21 of the rotor 20. This eccentric arrangement of the annular groove 38 increases the radial span s1 of the sealing region 39 inside the annular groove 38 in relation to the drive shaft 12 on the side toward which the center point M is offset in relation to the rotation axis 13 while decreasing the radial span s2 of the sealing region 39 on the opposite side. It is also possible for the annular groove 38 to not be circular, but to have an eccentric course in relation to the rotation axis 13, in which case the radial span s1 of the sealing region 39 in a region between the suction groove 30 and the pressure groove 34 in the rotation direction 21 of the rotor 20 is greater than the radial span s2 of the sealing region 39 in the opposite region.

The connecting groove 40 can, for example, extend inward from the pressure groove 34 in a radial direction or at an angle to a radius with regard to the rotation axis 13. The connecting groove 40 can, in particular, extend in such a way that it approaches the annular groove 38 in the rotation direction 21 of the rotor 20. In addition, the connecting groove 40 can extend in a spiral curve. The connecting groove 40 is preferably connected at one end at least approximately tangentially to the pressure groove 34 and/or at the other end, at least approximately tangentially to the annular groove 38. Preferably, the connecting groove 40 connects to the end region of the pressure groove 34 oriented opposite from the rotation direction 21 of the rotor 20. As a result of the connection of the annular groove 38 to the pressure groove 34, an increased pressure prevails in the annular groove 38 and therefore in the inner end regions of the grooves 24 of the rotor 20 with which it communicates, which increases the contact force with which the vanes 26 rest against the inside of the circumference wall 18, thus improving the delivery capacity of the vane pump. The curved course of the connecting groove 40 also generates a drag flow in it as the rotor 20 turns, resulting in a further pressure increase in the annular groove 38 and therefore in the grooves 24, thus further increasing the contact force of the vanes 26 against the circumference wall 18. In particular, this drag flow achieves a pressure increase in the annular groove 38 even when the vane pump rotation is just starting so that the vane pump delivers a sufficient quantity of fuel even as it is starting to turn. The curved course of the connecting groove 40 also assures that when the rotor 20 is turning, the vanes 26 move across the connecting groove 40 in an approximately tangential fashion, which minimizes the wear on the vanes 26 and the housing end wall 14, 16.

It is possible for the annular groove 38 and the connecting groove 40 that connects it to the pressure groove 34 to be provided in only one housing end wall 14 or 16 or for an annular groove 38 and a connecting groove 40 to be provided in both housing end walls 14 and 16, which grooves are then preferably situated in mirror-image fashion in relation to each other in the housing end walls 14 and 16. It is also possible for a respective annular groove 38 to be provided in each of the two housing end walls 14 and 16, but for a connecting groove 40 to be provided in only one housing part 14 or 16. It is also possible for the suction groove 30 and/or the pressure groove 34 to be provided in only one housing end wall 14 or 16, in which case the other housing end wall 16 or 14 is embodied as smooth or for a respective suction groove 30 and/or pressure groove 34 to be provided in each of the two housing end walls 14 and 16, which grooves are then preferably situated in mirror-image fashion in relation to each other in the housing end walls 14 and 16. In this case, however, the suction opening 28 and the pressure opening 32 are each provided in only one respective housing end wall 14 or 16, with the suction opening 28 provided in one housing end wall 14 and the pressure opening 32 provided in the other housing wall 16. With the mirror-image arrangement of the suction grooves 30 and pressure grooves 34 and of the annular grooves 38 and connecting grooves 40 in the two housing walls 14 and 16, the rotor 20 and the vanes 26 are loaded in at least approximately equal fashion at both ends in the axial direction so that little or no resulting force is exerted on the rotor 20 and the vanes 26 in the direction of the rotation axis 13. For example, the depth of the annular groove 38 and connecting groove 40 in the housing end wall 14, 16 is between 0.1 and 2 mm and the width of the grooves 38, 40 is preferably greater than their depth.

Claims

1-5. (canceled)

6. In a vane pump having a pump housing that contains a rotor driven to rotate via a drive shaft and which has a number of grooves distributed over its circumference that extend at least essentially in a radial direction in relation to the rotation axis of the rotor, each of which grooves has a respective vane-shaped delivery element guided in it in sliding fashion; having a circumferential wall of the pump housing encompassing the rotor and extending eccentrically in relation to its rotation axis, against which circumferential wall the radially outer ends of the delivery elements rest; having housing end walls of the pump housing that are situated adjacent to the rotor in the direction of its rotation axis, in which, when the rotor turns, the delivery elements deliver medium from a suction region to a pressure region offset from the suction region in the rotation direction of the rotor and an annular groove in at least one of the housing end walls in the suction region which annular groove extends over at least part of the circumference of the rotor and is situated opposite the inner regions delimited in the grooves of the rotor by the delivery elements, and a sealing region formed between the annular groove and the drive shaft, the improvement wherein the annular groove extends over the entire circumference of the rotor, is connected to the pressure region via a connecting groove in the housing end wall, and is embodied as eccentric in relation to the rotation axis of the rotor.

7. The vane pump according to claim 6, wherein the annular groove extends in an at least approximately circular fashion and its center point (M) is offset in relation to the rotation axis of the rotor toward a region of the circumferential wall of the pump housing situated between the suction region and the pressure region in the rotation direction of the rotor.

8. The vane pump according to claim 6, wherein in a circumferential region situated between the suction region and the pressure region in the rotation direction of the rotor, the annular groove is spaced a greater radial distance apart from the rotation axis of the rotor than in the opposite circumference region.

9. The vane pump according to claim 6, wherein the annular groove extends in such a way that it at least approximately follows the stroke of the vanes in the grooves of the rotor as the latter turns.

10. The vane pump according to claim 6, wherein the eccentricity of the annular groove is at least approximately of the same magnitude and oriented in the same direction as the eccentricity of the circumferential wall of the pump housing.

11. The vane pump according to claim 7, wherein the eccentricity of the annular groove is at least approximately of the same magnitude and oriented in the same direction as the eccentricity of the circumferential wall of the pump housing.

12. The vane pump according to claim 8, wherein the eccentricity of the annular groove is at least approximately of the same magnitude and oriented in the same direction as the eccentricity of the circumferential wall of the pump housing.

13. The vane pump according to claim 9, wherein the eccentricity of the annular groove is at least approximately of the same magnitude and oriented in the same direction as the eccentricity of the circumferential wall of the pump housing.