Claims:We Claim

1. A vane pump (10), said vane pump (10) comprising:
a rotor (12) that is adapted to rotate about a pump shaft (14);
a stator (16) that is held in a fixed position and eccentrically defined about the rotor (12), wherein a compression volume (18) is defined between the stator (16) and the rotor (12), the compression volume (18) having a first diameter at a first end (20) and a second diameter at an opposite second end (22), wherein the first diameter is greater than the second diameter;
a first vane (24) positioned in the rotor (12) at the first diameter and a second vane (26) positioned in the rotor (12) at the second diameter, said first vane (24) and said second vane (26) each adapted to press against a circumference of the stator (16) due to the centrifugal force caused due to the rotation of the rotor (12); characterized in that
a first spring member (28), a first end of said first spring member (28) positioned against said rotor (12), an opposite second end of said first spring member (28) positioned against said first vane (24).

2. The vane pump in accordance with Claim 1 further comprising a second spring member (30), a first end of said second spring member (30) positioned against said rotor (12), an opposite second end of said second spring member (30) positioned against said second vane (26).

3. The vane pump (10) in accordance with Claim 1 wherein four vanes are secured circumferentially about the rotor (12) and are each adapted to press against the stator (16) to prevent fuel from escaping from the compression volume (18) and out of the vane pump (10).
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to a vane pump, and more specifically to a spring member that is secured to a vane of the vane pump.

Background of the invention
[0002] US 2002172610 A describes a constant flow vane pump. A variable capacity pump includes a housing and a rotatable rotor within the housing. The rotor includes radial slots to accommodate slidable vanes or rotor blades, wherein the vanes are urged outwards by centrifugal force into contact with the inner surface of a surrounding cam ring. The cam ring is surrounded on one end by a pressure chamber including a piston under hydraulic pressure, and on the other end by a seated spring. By controlling the pressure distributed to the pressure chamber, the position of the cam ring with respect to the rotor may be changed to automatically vary the displacement of the pump in response to a pressure differential across a restriction orifice, thereby regulating the output flow to be constant over a defined speed range.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a schematic diagram of a vane pump in one embodiment of the invention.
[0004] Figure 2 illustrates an exploded view of the schematic diagram of the vane pump in one embodiment of the invention.

Detailed description of the embodiments
[0005] Figure 1 illustrates a vane pump 10. The vane pump 10 comprises a rotor 12 that is adapted to rotate about a pump shaft 14. A stator 16 is held in a fixed position and eccentrically defined about the rotor 12, wherein a compression volume 18 is defined between the stator 16 and the rotor 12, the compression volume 18 having a first diameter at a first end 20 and a second diameter at an opposite second end 22, wherein the first diameter is greater than the second diameter. A first vane 24 is positioned in the rotor 12 at the first diameter and a second vane 26 is positioned in the rotor 12 at the second diameter, the first vane 24 and the second vane 26 each adapted to press against the circumference of the stator 16 due to the centrifugal force caused due to the rotation of the rotor 12. The first vane 24 prevents fuel that is present in the compression volume 18 from escaping out of the vane pump 10 via the first end 20, the second vane 26 prevents fuel that is present in the compression volume 18 from escaping out of the vane pump 10 via the opposite second end 22. A first spring member 28, a first end of the first spring member 28 positioned against the rotor 12, an opposite second end of the first spring member 28 positioned against the first vane 24 to facilitate pressing the first vane 24 against the circumference of the stator 16 and preventing fuel from escaping out of the vane pump 10 via the first end 20. A second spring member 30, a first end of the second spring member 30 positioned against the rotor 12, an opposite second end of the second spring member 30 positioned against the second vane 26 to facilitate pressing the second vane 26 against the circumference of the stator 16 and preventing fuel from escaping out of the vane pump 10 via the opposite second end 22.

[0006] The vane pump 10 comprises a rotor 12 that is adapted to rotate about a pump shaft 14. A stator 16 is eccentrically positioned about the rotor 12 and is held fixed about the axis of the pump shaft 14. Therefore, a compression volume 18 is defined between the stator 16 and the rotor 12 that gradually decreases from a first larger diameter to a second smaller diameter. More specifically, the compression volume 18 has a first diameter at its first end and a second diameter at its opposite second end. In the exemplary embodiment, the first diameter of the compression volume 18 is greater than the second diameter of the compression volume 18. In an alternate exemplary embodiment, the first diameter of the compression volume 18 may be smaller than the second diameter of the compression volume 18.

[0007] A first vane 24 is positioned in the rotor 12 at the first diameter. More specifically, the first vane 24 is positioned within a groove that is defined between the rotor 12 and the stator 16, and is adapted to reciprocate within the groove. A second vane 26 is positioned in the rotor 12 at the second diameter. The second vane 26 is positioned within a groove that is defined between the rotor 12 and the stator 16, and is adapted to reciprocate within the groove. When the rotor 12 rotates, due to the centrifugal force caused by the rotor 12, the first vane 24 and the second vane 26 are each adapted to translate towards the periphery of the rotor 12 and press against the circumference of the stator 16. Therefore, the compression volume 18 that is defined between the rotor 12 and the stator 16 is closed at the first end and at the second end of the rotor 12 and the stator 16 respectively when the first vane 24 and the second vane 26 translate towards the periphery of the rotor 12 and press against the circumference of the stator 16.

[0008] The first vane 24 prevents fuel that is present in the compression volume 18 from escaping out of the vane pump 10 via the first end 20. More specifically, when the first vane 24 presses against the circumference of the stator 16, thereby closing the first end 20 of the rotor 12 and the stator 16, the fuel that is present in the compression volume 18 is prevented from escaping out of the vane pump 10 via the first end 20. The second vane 26 prevents fuel that is present in the compression volume 18 from escaping out of the vane pump 10 via the opposite second end 22. More specifically, when the second vane 26 presses against the circumference of the stator 16, thereby closing the opposite second end 22 of the rotor 12 and the stator 16, the fuel that is present in the compression volume 18 is prevented from escaping out of the vane pump 10 via the opposite second end 22.

[0009] When the rotor 12 rotates, the fuel that is present within the compression volume 18 gets compressed as the diameter of the compression volume 18 decreases from the first diameter to the second diameter. Due to the decrease in the compression volume 18 of the fuel, the fuel is compressed before it is delivered out of the vane pump 10 from the opposite second end 22. However, at low engine operating speeds the centrifugal force acting on the vane pump 10 is insufficient to cause the first vane 24 and the second vane 26 to translate outwardly within the first groove and the second groove respectively to completely close the gap between the rotor 12 and the stator 16. Hence, a small amount of fuel leakage occurs between the compression volume 18 and the first vane 24 as well as the second vane 26 respectively to cause a reduction in the volume of compressed fuel that is delivered from the compression volume 18 to the engine. Due to the reduction in the volume of compressed fuel that is delivered from the compression volume 18 to the engine, the efficiency of the engine decreases. It is therefore desirable to maintain the quantity of compressed fuel that is delivered from the compression volume 18 to the engine by ensuring that the compression volume between the rotor 12 and the stator 16 is completely sealed by the first vane 24 and the second vane 26 respectively.

[0010] A first spring member 28 is positioned between the first vane 24 and the rotor 12, and a second spring member 30 is positioned between the second vane 26 and the rotor 12. More specifically, a first end of the first spring member 28 is positioned against the rotor 12. An opposite second end of the first spring member 28 is positioned against the first vane 24 to facilitate pressing the first vane 24 against the circumference of the stator 16, and preventing fuel from escaping out of the vane pump 10 via the first end 20. More specifically, the pre-tension that is applied by the first spring member 28 on the first vane 24 causes the compression volume 18 between the rotor 12 and the stator 16 to be completely sealed at the first end 20. Even though the fuel is pressurized between the first vane 24 and the second vane 26, the pressure of the fuel is insufficient to cause the first spring member 28 to compress and allow the fuel to escape from the compression volume 18 of the vane pump 10.

[0011] A second spring member 30 is positioned between the second vane 26 and the rotor 12. More specifically, a first end of the second spring member 30 is positioned against the rotor 12. An opposite second end of the second spring member 30 is positioned against the second vane 26 to facilitate pressing the second vane 26 against the circumference of the stator 16, and preventing fuel from escaping out of the vane pump 10 via the second end 22. More specifically, the pre-tension that is applied by the second spring member 30 on the second vane 26 causes the compression volume 18 between the rotor 12 and the stator 16 to be completely sealed at the second end 22. Even though the fuel is pressurized between the first vane 24 and the second vane 26, the pressure of the fuel is insufficient to cause the second spring member 30 to compress and allow the fuel to escape from the compression volume 18 of the vane pump 10. Therefore, the fuel that is trapped in the compression volume 18 between the first vane 24 and the second vane 26 gets completely compressed without any leakage from the first end 20 or the second end 22 of the compression volume 18 of the vane pump 10.

[0012] A working of the springs that are secured to the vane pump 10 are described as an example. Fuel from a fuel tank enters into the compression volume 18 of the vane pump 10 via a fuel inlet and is stored between the first vane 24 and the second vane 26. The first spring member 28 that is secured between the first vane 24 and the rotor 12 applies a pre-tension on the first vane 24, thereby compressing the first vane 24 against the circumference of the stator 16, and closing the first end 20 of the compression volume 18. The second spring member 30 that is secured between the second vane 26 and the rotor 12 applies a pre-tension on the second vane 26, thereby compressing the second vane 26 against the circumference of the stator 16, and closing the second end 22 of the compression volume 18. Therefore, pressurized fuel is secured in the compression volume 18 between the first vane 24 and the second vane 26. As the rotor 12 rotates, the pressurized fuel that is present between the first vane 24 and the second vane 26 gets compressed due to the decrease in the compression volume 18. At the second end 22 of the compression volume 18, the pressurized fuel is delivered from the compression volume 18 and out of the vane pump 10. Due to the tension that is applied by the first spring 28 and the second spring 30 on the first vane 24 and the second vane 26 respectively, the pressurized fuel is contained within the compression volume 18 and is therefore prevented from escaping out of the vane pump 10. Therefore, the quantity of pressurized fuel that is delivered to the engine is exactly equal to the volume of the fuel that is contained within the compression volume 18 without any fuel leakage out of the compression volume 18 and the vane pump 10. Hence the combustion efficiency of the engine is enhanced due to positioning the first spring member 28 and the second spring member 30 within the grooves that are defined between the rotor 12 and the stator 16 respectively.

[0013] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to dimensions of various components are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.