This disclosure relates to vane pumps. Vane pumps include different varieties such as single acting or double acting and can be fixed or variable displacement. This disclosure is applicable to all types of vane pumps.
A typical double-acting vane pump 10 is depicted in
As the vanes move through the inlet regions 24, a quantity of fluid is trapped within a fluid flow chamber defined between the vanes 12 in the direction of rotation and between rotor 14 and the cam block inner surface 22 in the direction the radial direction. The volume of this chamber begins at an initial size that is progressively increased as the vane transitions from inlet region 24 to pump arc 26. In the pump arc 26 the vane 12 extends a constant amount from the rotor 14. As the vane 12 transitions from the pump arc 26 to the discharge region 30, the radial distance between the rotor 14 and the cam block inner surface 22 is gradually decreased. The decrease in volume of the fluid flow chamber coincides with removal of fluid from the flow chamber through the pump discharge. The discharge pressure is dependent upon the resistance of the downstream system
The vanes rotate through pump arcs 26 where high pressure is exerted on the leading surface of the vane and low pressure is exerted on the trailing surface, and through seal arcs 28 where low pressure is exerted on the leading surface of the vane and high pressure is exerted on the trailing surface of the vane. In the inlet regions 24, inlet fluid pressure is provided to support the vanes so that the vanes are radially pressure balanced. In the discharge regions 30, discharge fluid pressure is provided to support the vanes so that the vanes are also radially pressure balanced in the discharge regions.
In the pump arc and the seal arc, pressure has often been required under the vanes to maintain a seal between the vane tip and the cam block inner surface. Such under-vane pressure can combine with pressure in the fluid flow chamber to result in excess radial pressure load and outward centrifugal force pushing the vane against the cam inner surface. This can result in high adhesive wear stresses between the vane tips and the inner surface of the cam block resulting in damage to the vane and to the cam block. However, prior attempts to remove or reduce under-vane pressurization have often resulted in inadequate outward radial load during low speed operation such as at startup, when centrifugal forces are insufficient to drive the vanes radially outward into engagement with the cam block surface.
U.S. Pat. No. 7,637,724 discloses a vane pump where a vane tip 31 has a radius centered on a centerline offset relative to a leading surface of the vane. This offset provides an imbalance of the fluid pressure forces acting radially on the vane tip to generate a positive contact force that in the pump arc that can supplement the centrifugal force at low operating speeds to reduce or eliminate the need for under-vane pressurization in the pump arc. This is depicted in
In some aspects of the disclosure, a vane pump comprises a housing including an inlet and an outlet. A cam block is disposed in the housing, and has a continuous inner surface including a pump arc and a seal arc. A rotor is configured to rotate within the cam block, and includes a plurality of radial slots. A plurality of radially-extendable vanes are disposed in the slots and configured to radially extend from the slots as they rotate past the cam block pump arc. The vanes retract as they rotate past the cam block seal arc. Each of the vanes comprises a radial portion in one of the radial slots and a tip portion extending transverse to the radial portion in a direction of rotation of the rotor. The tip portion has an arcuate surface that engages with the cam block inner surface to provide a fluid seal point along the arcuate surface. Each of the plurality of vanes and radial slots are configured to provide a gap between the vane and the radial slot such that the vane has a different angular position relative to the direction of rotation in a radially extended position compared to an angular position in a radially-retracted position. The different angular positions provide different orientation of the arcuate surface of the vane tip portion with respect to the cam body inner surface, thus providing different fluid stop points on the vane tip portion arcuate surface.
The subject matter which is regarded as the present disclosure is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Referring to
As shown in
The gap between the radial portion of the vane 15 and the slot in
The shape and configuration of the arcuate surface of vane tip 17 can be designed based on parameters such as the radius of cam surfaces, length of the radial vane portion 15, length of extension of the vane out of the slot, and angle of rotation of the van within the slot, to control the location of the fluid stop position along the arcuate surface of the vane tip 17 and to provide desired levels of radial load urging the vane 12 into engagement with the cam block inner surface 22. The arcuate surface of the vane tip 17 should be configured to have a greater angle of curvature (e.g., smaller radius of curvature) at the point of engagement with the cam block inner surface, and to provide the desired re-positioning of the point of engagement along the arcuate surface of the vane tip 17 in response to tipping of the vane. The vane and slot can be configured to provide an angular rotational range of the vane of 0.1° to 2.0° in the slot in the extended position, more specifically from 0.3° to 1.5°. The vane and slot can be configured to provide an angular rotational range of 0.1° to 2.0° in the extended position, more specifically from 0.0° to 1.5°.
The capability of angularly re-positioning the vanes of a vane pump at different cycles of the pump's rotation allows for an offset in the direction of rotation between a fluid stop point where the vane engages the cam block inner surface in the pump arc compared to a leading surface of the vane's radial portion, while also allowing for a zero or negative offset in the seal arc, so that a desired level of radial load can be maintained on the vanes throughout the pump's rotational cycle to maintain a desired level of engagement of the vane with the cam block inner surface. This can avoid the need for complex under-vane pressurization schemes to supplement outward centrifugal force that can be insufficient at low pump speeds such as during startup.
As mentioned above, under-vane pressurization can contribute to under-vane pressure pulsations, which can cause vane tip wear quickly, cavitation, control valve pressure droop, and the avoidance of such under-vane pressurization can help avoid pressure pulsations. Pressure pulsations can be further reduced by a channel to equalize pressure under the vane and the fluid flow chamber area trailing the vane. As shown in
While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Number | Name | Date | Kind |
---|---|---|---|
3221665 | Hartmann | Dec 1965 | A |
3869231 | Adams | Mar 1975 | A |
3981647 | Schoeps | Sep 1976 | A |
3981648 | Jordan | Sep 1976 | A |
4274816 | Kobayashi et al. | Jun 1981 | A |
5163825 | Oetting | Nov 1992 | A |
5733109 | Sundberg | Mar 1998 | A |
7637724 | Cygnor | Dec 2009 | B2 |
7707987 | Guthrie | May 2010 | B2 |
8360759 | Pekrul | Jan 2013 | B2 |
20140271310 | Whitesel | Sep 2014 | A1 |
Entry |
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Search Report regarding related EP App. No. 16180630.2; dated Sep. 13, 2016; 7 pgs. |
Number | Date | Country | |
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20170022813 A1 | Jan 2017 | US |