Variable displacement vane pump

Abstract

A sliding vane pump includes a passageway that fluidly connects one or more pumping chambers to a side chamber. The passageway pressurizes the side chamber. This fluid pressure exerts a force that counteracts the force caused by pressure differences between the outlet pumping chambers and the inlet pumping chambers. At high speed, part of the side chamber is pressurized by the smallest volume outlet pumping chamber while another portion of the side chamber is pressurized by the largest volume outlet chamber. This results in a force counteracting an uncommanded displacement decrease of the pump.

Claims

1. A sliding vane pump comprising: a fixed housing defining inlet and outlet ports; a sliding housing defining a cylindrical chamber and configured to slide within the fixed housing, the fixed housing and sliding housing defining a side chamber; a rotor configured to rotate within the cylindrical chamber and having a plurality of vanes configured to seal against a wall of the cylindrical chamber to define a plurality of pumping chambers; and a spring biasing the sliding housing to a position relative to the fixed housing in which a pump displacement is a maximum; wherein the side chamber is fluidly connected to a first pumping chamber of the plurality of pumping chambers by a first passageway such that fluid pressure in the side chamber exerts a first force on the sliding housing, the first force opposing a second force on the sliding housing due to differential fluid pressures amount the pumping chambers; and wherein the first pumping chamber is fluidly connected to the outlet.

2. The sliding vane pump of claim 1 wherein the first pumping chamber has a first volume less than a volume of any other of the plurality of pumping chambers.

3. The sliding vane pump of claim 1 wherein a second pumping chamber of the plurality of pumping chambers is fluidly connected to the side chamber by a second passageway separate from the first passageway and fluidly connected to the outlet port.

4. The sliding vane pump of claim 3 wherein the second pumping chamber has a second volume greater than a volume of any other of the plurality of pumping chambers.

5. A pump comprising: a slider defining a cylindrical chamber and configured to slide within a housing; a rotor configured to rotate within the cylindrical chamber and having a plurality of vanes configured to seal against a wall of the cylindrical chamber to define a plurality of pumping chambers; and a spring biasing the slider to a position relative to the housing in which a pump displacement is a maximum; wherein the slider and the housing define a side chamber fluidly connected to a subset of the pumping chambers, including a pumping chamber having a minimum volume among the plurality of pumping chambers, by passageways defined in the slider.

6. The pump of claim 5 wherein the side chamber is fluidly connected to a first pumping chamber of the plurality of pumping chambers by a first passageway defined in the slider and fluidly connected to a second pumping chamber of the plurality of pumping chambers by a second passageway defined in the slider.

7. The pump of claim 6 wherein the first pumping chamber has a volume less than volumes of all other pumping chambers in the plurality of the pumping chambers.

8. The pump of claim 7 wherein the second pumping chamber has a volume greater than volumes of all other pumping chambers in the plurality of the pumping chambers.

9. The pump of claim 6 wherein the first and second pumping chambers are fluidly connected to an outlet port defined in the housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is schematic diagram of a vehicle powertrain.

(2) FIG. 2 is a cross section of a sliding pocket vane pump in a full displacement position.

(3) FIG. 3 is a cross section of a sliding pocket vane pump in a partial displacement position.

(4) FIG. 4 is a cross section of a sliding pocket vane pump with compensation grooves.

DETAILED DESCRIPTION

(5) Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.

(6) A sliding pocket vane pump 28 is illustrated in FIG. 2. The pump includes a fixed outer housing 50 which may be integrated into a valve body housing. A sliding housing 52 fits within a chamber within outer housing 50. A spring 54 biases the sliding housing toward the full displacement position shown in FIG. 2. The sliding housing defines a circular interior chamber. A rotor 56 rotates within the circular chamber about an axis that is fixed with respect to the outer housing 50. A number of vanes 58 rotate with rotor 56 such that the tips of each rotor follow an inner surface 60 of the circular chamber of sliding housing 52. The rotor, vanes, and sliding housing collectively define a number of pumping chambers 62, 64, 66, 68, 70, and 72. The volumes of chambers 62, 64, and 66 increase as the rotor turns clockwise. An inlet port 74 is defined in the outer housing, extending above or below the plane of the cross section of FIG. 2, such that fluid is drawn from the inlet port into the expanding chambers. The volumes of chambers 68, 70, and 72, on the other hand, decrease as the rotor turns clockwise. An outlet port 76 is defined in the outer housing such that fluid is pushed into the outlet port as the chambers shrink. Fluid at controlled pressure is supplied to chambers 78, 80, 82, and 84. To command the pump to the full displacement position shown in FIG. 2, fluid at equal and low pressure is supplied to these chambers.

(7) When the demand for fluid is low and/or the engine speed is high, pump 28 is commanded to the low displacement condition illustrated in FIG. 3 by supplying high pressure fluid to chamber 84. Chambers 78, 80, and 82 continue to be supplied with low pressure fluid, so there is a net hydraulic force pushing against spring 54. In the condition shown in FIG. 3, the volumes of pumping chambers 62, 64, and 66 continues to increase as rotor 56 turns clockwise, but by substantially less than in FIG. 2. Similarly, the volumes of pumping chambers 68, 70, and 72 increases by substantially less than in FIG. 2. Consequently, the quantity of fluid draw from inlet 74 and pushed into outlet 76 per revolution of rotor 56 is substantially less.

(8) In addition to chambers 78, 80, 82, and 84, pumping chambers 62, 64, 66, 68, 70, and 72 also exert force on sliding housing 52. In order to push the fluid through downstream flow restrictions, the pressure in the outlet port 76 in higher than the pressure in inlet port 74. At relatively low speed, the pressure in pumping chambers 62, 64, and 66 is approximately equal to the pressure in inlet port 74 and the pressure in pumping chambers 68, 70, and 72 is approximately equal to the pressure in outlet port 76. These pressures produce a net force toward the left. This net force increases the frictional force between outer housing 50 and sliding housing 52. This frictional force tends to make the sliding housing stay in the same position when commanded to change position, making the pump unresponsive to small displacement change commands.

(9) When the pump is rotating quickly, the pressures in chambers 68, 70, and 72 are not equal. Due to entrained air in the fluid, the fluid has non-negligible compressibility. As the chamber moves through the position occupied by chamber 68 in FIGS. 2 and 3, the percentage change in volume per degree of rotation is small. Consequently, the pressure in the chamber in that position may be less than the pressure in outlet port 76. On the other hand, the chamber in the position of chamber 72 has a large percentage decrease in volume per degree of rotation. Therefore, the pressure in higher than the pressure in outlet port 76. This effect is particularly strong when the slider is in the full displacement position of FIG. 2 and the air content of the fluid is high. The differential pressure between the chambers in these positions results in a net force biasing the sliding housing toward the low displacement position of FIG. 3. At high rotor speeds, this effect may overcome the force of spring 54 causing the displacement to decrease despite a full displacement command. If the controller had commanded full displacement in response to a high flow demand, the flow rate produced may fail to satisfy that demand.

(10) FIG. 4 illustrates a sliding vane pump designed to avoid the high speed control issues discussed above. Two grooves 92 and 94 have been added to the sliding housing 52. Groove 92 connects the pumping chamber in the position of chamber 72 to the adjacent region of side chamber 82. A side chamber is a chamber in the same plane as the rotor but on the outside of the sliding housing. Groove 94 connects the pumping chamber in the position of chamber 68 to the adjacent region of side chamber 82. Unlike the pumps of FIGS. 2 and 3, side chamber 82 is not separately supplied with low pressure fluid from the valve body. Chambers 78 and 80 are continuously supplied with low pressure fluid. Chamber 84 is supplied with fluid at a pressure indicating the desired displacement.

(11) At all rotor speeds, the average pressure in side chamber 82 is approximately equal to the average pressure in chambers 68, 70, and 72 such that no net side force is generated. Furthermore, at high rotor speed, the upper portion of side chamber 82 is at substantially higher pressure than the lower portion. Although some fluid will flow from the high pressure region to the low pressure region, the passage connecting these regions has sufficiently high flow resistance to maintain substantial pressure difference. The pressure gradient within side chamber 82 causes a net force on sliding housing 52 biasing it toward the full displacement position. This force counteracts the force produced by the differential pressures between chambers 68 and 72. Consequently, the sliding housing stays in the full displacement position until commanded to move and then responds smoothly and proportionately to a command to decrease the displacement. In alternative embodiments, passageways 92 and/or 94 may be formed in outer housing 50 such that they pass under or over sliding housing 52.

(12) While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.