Gear pump with variable throughput volume
In a gear pump with variable throughput volume, with two meshed gears with external toothing which are rotatably held in the working chamber of a pump housing, at least one of the two gears is driven from a drive shaft and one of the gears, preferably the driven gear, is shiftable in the direction of its axis. In order to realize a control mechanism in a simple manner a gap width defined as the distance measured in axial direction between an essentially plane first interior side wall of the working chamber of the pump housing and a first front face of the shiftable gear, is designed to be variable.
1. Gear pump with variable throughput volume which comprises a housing defining a working chamber, two meshing gears with external toothing rotatably mounted in the working chamber of the housing, at least one of the two gears being driven from a drive shaft and one of the two gears being shiftable in the direction of an axis thereof, wherein a gap-width, which defined as a free space between an essentially plane first interior side wall of the working chamber of the housing and a first front face of the shiftable gear, is variable.
2. Gear pump according to claim 1 , wherein a driven gear is shiftable in the direction of its axis.
3. Gear pump according to claim 1 , wherein the gap-width is variable in a range between 0 and d/5, d being an outer diameter of the shiftable gear.
4. Gear pump according to claim 3 , wherein the gap-width is variable in a range between 0 and d/50.
5. Gear pump according to claim 1 , wherein a second plane interior side wall of the working chamber parallel to and opposite of the first interior side wall is furnished with an essentially cylindrical recess concentric with the gear axis and situated in an area of a second front face of the shiftable gear facing away from the first front face, the diameter of said recess being larger that the outer diameter d of the gear, at least in an area of the shiftable gear.
6. Gear pump according to claim, 5 , wherein a sealing plate is placed in an area of the recess, which plate separates the working chamber of the pump housing from a dead space inside the recess.
7. Gear pump according to claim 6 , wherein the sealing plate is configured disk-shaped.
8. Gear pump according to claim 6 , wherein the sealing plate is being fixedly attached to the shiftable gear.
9. Gear pump according to claim 6 , wherein the sealing plate has radial relief grooves on the side facing the second front face of the shiftable gear, which are positioned such that each space between the teeth of the shiftable gear corresponds to at least one relief groove.
10. Gear pump according to claim 9 , wherein an outlet groove is located in the second interior side wall of the working chamber opposite the first interior side wall in the meshing area of the gears on the pressure side, i.e., on the side where the sealing plate is located, which outlet groove is positioned in such a way that each relief groove communicates at least once with the outlet groove during each revolution of the sealing plate.
11. Gear pump according to claim 6 , wherein the dead space is flow-connected via a relief passage with a pressure sink.
12. Gear pump according to claim 11 , wherein the dead center is flow-connected via the relief passage to a suction side of the pump.
13. Gear pump according to claim 11 , wherein the dead center is flow-connected via the relief passage to a pump environment.
14. Gear pump according to claim 11 , wherein the relief passage is furnished with a pressure relief valve opening in the direction of the pressure sink.
15. Gear pump according to claim 6 , wherein the sealing plate has at least one sealing groove in its side wall, which groove extends along an entire circumference.
16. Gear pump according to claim 1 , wherein a leakage channel departs from the dead space.
17. Gear pump according to claim 16 , wherein the leakage channel is configured as a groove in the pump housing adjacent to the control shaft.
18. Gear pump according to claim 17 , wherein the groove is shaped helically.
19. Gear pump according to claim 16 , wherein the control shaft is shifted, at least in one direction, by an electric motor.
20. Gear pump according to claim 1 , wherein the shiftable gear is rigidly mounted on a control shaft which rotates in the pump housing and can be shifted in the direction of axis.
21. Gear pump according to claim 20 , wherein the sealing plate is rigidly mounted on the control shaft.
22. Gear pump according to claim 20 , wherein the control shaft is furnished with at least one pressure plunger to effect the axial shift, which plunger cooperates with a pressure chamber containing a pressure medium.
23. Gear pump according to claim 22 , wherein the pressure medium is identical with the medium to be pumped and the pressure chamber is flow-connected to the pressure side of the gear pump.
24. Gear pump according to claim 22 , wherein the pressure chamber is connected with an external pressure source.
25. Gear pump according to claim 22 , wherein the pressure chamber is connected with a clean-oil control device.
26. Gear pump according to claim 22 , wherein a restoring spring acts on the control shaft thus counteracting displacement by the pressure plunger.