POSITIVE DISPLACEMENT PUMP

Abstract

A positive displacement pump for pumping oil in a motor vehicle transmission comprises a pump stage that has a central kidney-shaped suction cavity and two kidney-shaped pressure cavities. Oil is selectively pumped via one kidney-shaped pressure cavity or the other kidney-shaped pressure cavity in accordance with the direction of rotation of the pump stage. This makes it possible to create, with little complexity, two operating stages for the positive displacement pump.

Claims

1. A positive displacement pump, for conveying oil in a gearbox or a combustion engine of a motor vehicle, comprising: a pump stage; a drive unit, the pump stage driven by the drive unit; a suction port in fluid communication with the pump stage, such that oil is drawn into the suction port by the pump stage; a pressure port which receives pressured oil from the pump stage; a switchover device operable for placing the pump stage in one of a plurality of modes of operation; a central kidney-shaped suction cavity in fluid communication with the suction port; and a plurality of kidney-shaped pressure cavities; wherein the pressure port receives pressurized fluid from one of the plurality of kidney-shaped pressure cavities when the positive displacement pump is placed in one of the plurality of modes of operation.

2. The positive displacement pump of claim 1, wherein the switchover device is connected to the drive unit such that the switchover device selectively controls the drive direction of the pump stage.

3. The positive displacement pump of claim 1, further comprising: a first plurality of check valves; wherein one of the first plurality of check valves places one of the two kidney-shaped pressure cavities in fluid communication with the single pressure port, and another of the first plurality of check valves places the other of the two kidney-shaped pressure cavities in fluid communication with the single pressure port.

4. The positive displacement pump of claim 1, further comprising: a second plurality of check valves; wherein one of the second plurality of check valves places one of the two kidney-shaped pressure cavities in fluid communication with suction port, and another of the second plurality of check valves places the other of the two kidney-shaped pressure cavities in fluid communication with the suction port.

5. The positive displacement pump of claim 1, wherein the switchover device places the pressure port in fluid communication with one of the plurality of kidney-shaped pressure cavities.

6. The positive displacement pump of claim 1, further comprising a multi-directional valve in fluid communication with the pump stage, wherein the switchover device places the multi-directional valve, in fluid communication with one of the two kidney-shaped pressure cavities, such that one of the two kidney-shaped pressure cavities is in fluid communication with the pressure port.

7. The positive displacement pump as claimed in claim 6, the multi-directional valve further comprising a plurality of switching stages, wherein during each of the switching stages, one of the two kidney-shaped pressure cavities is in fluid communication with the pressure port, and the other of the two kidney-shaped pressure cavities is placed in fluid communication with the suction port.

8. The positive displacement pump of claim 7, wherein the pressure port is deactivated during one of the plurality of switching stages of the multi-directional valve.

9. The positive displacement pump as claimed of claim 1, the pump stage further comprising an internal gear pump.

10. The positive displacement pump as claimed in claim 9, further comprising: an inner rotor; an outer rotor, the outer rotor surrounding the inner rotor; and a region of maximum eccentricity between the inner rotor and the outer rotor; wherein as the inner rotor and outer rotor are rotated in a counter-clockwise direction, oil is transferred from the suction port, through the kidney-shaped suction cavity, to one of the kidney-shaped pressure cavities, and flows through the pressure port, and when the inner rotor and outer rotor are rotated in a counter-clockwise direction, oil is transferred from the suction port, through the kidney-shaped suction cavity, to the other of the kidney-shaped pressure cavities, and flows through the pressure port.

11. The positive displacement pump as claimed in claim 10, further comprising: a first separation region located between the kidney-shaped suction cavity and one of the plurality of kidney-shaped pressure cavities, such that the first separation region is located within the region of maximum eccentricity between the inner rotor and the outer rotor; and a second separation region located between the kidney-shaped suction cavity and another of the plurality of kidney-shaped pressure cavities such that the second separation region is located outside the region of maximum eccentricity between the inner rotor and the outer rotor.

12. The positive displacement pump as claimed of claim 1, the pump stage further comprising a G-rotor pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention permits numerous embodiments. For the purpose of further clarifying its basic principle, several of the embodiments are illustrated in the drawing and are described below. The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0019] FIG. 1 is a diagrammatic illustration of a positive displacement pump, according to embodiments of the present invention;

[0020] FIG. 2 is a sectional view of a pump stage with adjacent regions of a positive displacement pump, according to embodiments of the present invention;

[0021] FIG. 3 is a sectional view of an alternate embodiment of a pump stage with adjacent regions of a positive displacement pump, according to embodiments of the present invention; and

[0022] FIGS. 4a-4c are sectional views of various switching positions of a multi-directional valve used as part of a pump stage of a positive displacement pump, according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

[0024] FIG. 1 diagrammatically shows a positive displacement pump 1 having a motorized drive unit 2 and a pump stage 3. The motorized drive unit 2 is connected to a switchover device 4 and selectively drives the pump stage 3 in one or the other direction of rotation. The positive displacement pump 1 has a suction port 5, via which oil is sucked in from a tank 6 or an oil pan, and a pressure port 7, via which oil is conveyed to a consumer (not shown), such as lubrication points of a combustion engine or of a gearbox of a motor vehicle. The pump stage 3 is connected to the pressure port 7 and to the suction port 5 via a total of four check valves 8-11.

[0025] As FIG. 2 diagrammatically shows in a sectional illustration, the pump stage 3 from FIG. 1 has two kidney-shaped pressure cavities 12, 13 and one central kidney-shaped suction cavity 14. Oil is sucked in via the kidney-shaped suction cavity 14 in both directions of rotation of the pump stage 3. The kidney-shaped pressure cavities 12, 13 are connected to the pressure port 7 via two of the check valves 8, 9. Furthermore, the kidney-shaped pressure cavities 12, 13 are connected to the suction port 5 via the further check valves 10, 11. The pump stage 3 is designed as an internal gear pump and has an inner rotor 15 and an outer rotor 16. The kidney-shaped suction cavity 14 and the kidney-shaped pressure cavities 12, 13 are arranged in a housing 17 that seals off the front faces of the rotors.

[0026] In the case of a rotation of the inner rotor 15, as a result of a corresponding current feed to the drive unit 2, in the anticlockwise direction, oil is sucked in from the tank 6 or the oil pan via the central kidney-shaped suction cavity 14 and conveyed to the pressure port 7 via the kidney-shaped pressure cavity 12 illustrated on the left in the diagram.

[0027] In case of negative pressure, the kidney-shaped pressure cavity 13 illustrated on the right in the diagram also sucks in oil from the suction port 5 and thus complements the function of the kidney-shaped suction cavity 14. The connection of the kidney-shaped pressure cavities 12, 13 to the suction port 5 or the pressure port 7 is realized via the check valves 8-11. In case of the inner rotor 15 being driven in the clockwise direction, the oil is conveyed to the pressure port 7 via the kidney-shaped pressure cavity 13 illustrated on the right in the diagram. FIG. 2 furthermore shows that the pump stage 3 has separation regions t1, t2 of differing sizes between the common kidney-shaped suction cavity 14 and the kidney-shaped pressure cavities 12, 13 that are used, according to the selected direction of rotation. The kidney-shaped suction cavity 14 is arranged outside the region of maximum eccentricity of the pump stage 3. Consequently, one of the separation regions t1 is arranged in the region of maximum eccentricity and the other of the separation regions t2 is arranged outside the maximum eccentricity. Additionally, the kidney-shaped pressure cavities 12, 13 have differing dimensions, so that the pump stage 3 has differing conveying pressures and conveying volumes according to the kidney-shaped pressure cavity 12, 13 that is used for conveying.

[0028] FIG. 3 diagrammatically shows a further embodiment of a pump stage 18, which differs from the embodiment of FIG. 2 only in that a multi-directional valve 19 is provided for controlling two kidney-shaped pressure cavities 20, 21 with the suction port 23 and with the pressure port 24. One kidney-shaped suction cavity 22 is, as in the case of the embodiment according to FIG. 2, connected to the suction port 23 without control. Control lines for controlling the multi-directional valve are illustrated in dotted form in the drawing, via which lines the position of the multi-directional valve 19 is controlled according to the direction of rotation of the pump stage 18. Alternatively, the multi-directional valve 19 may be connected to the switchover device 4 illustrated in FIG. 1 and is activated at the same time as the switchover of the direction of rotation of the pump stage 18.

[0029] The multi-directional valve 19 has three switching positions, wherein one of the switching positions shuts off the kidney-shaped pressure cavities 20, 21 and the pressure port 24.

[0030] FIGS. 4a to 4c show a multi-directional valve 25 which, for example, is used in the embodiment according to FIG. 3 and has a valve body 26 and a valve housing 27. The multi-directional valve 25 respectively has a port 28, 29 which is led to a kidney-shaped pressure cavity, a suction port 30 and two pressure ports 31. In the middle position illustrated in FIG. 4a, all ports 28-31 are closed. In FIGS. 4b and 4c, one or the other of the ports 28, 29 that is led to the kidney-shaped pressure cavities is selectively connected to the pressure port 31. At the same time, the port 29, 28 not used for conveying oil in each case is connected to the suction port 30. Spring elements 32, 33 preload the multi-directional valve 25 into the middle position illustrated in FIG. 4a. The position of the valve body 26 may, for example, be controlled by the switchover device 4 by means of an electromagnet (not shown). Control lines 34, 35 are provided for controlling the multi-directional valve 25, via which lines the position of the multi-directional valve 19 is controlled according to the direction of rotation of the pump stage 18.

[0031] The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.