VACUUM PUMP

Abstract

A vacuum pump having a housing which limits a working space and having a rotor, rotatably mounted in the housing about a rotor axis, the rotor guides a vane being movably mounted in the radial direction, the vane has a transverse extent, and the vane divides the working space into a suction side having a suction inlet and a pressure side having a pressure outlet, the housing has at least one oil outlet, the oil outlet is closed by a relief valve, the relief valve assumes an open position, when a limit pressure lying above a nominal pressure is exceeded in the working space, and the transverse extent of the vane is large enough that when the vane passes the oil outlet, the oil outlet is closed by the vane, so that there is no fluid connection between the suction side and the pressure side over the oil outlet.

Claims

1. A vacuum pump, comprising: a housing which limits a working space, and a rotor, which is rotatably mounted in the housing about a rotor axis, wherein the rotor guides at least one vane being movably mounted in a radial direction, wherein the vane has a transverse extent, and wherein the vane divides the working space into a suction side having a suction inlet and a pressure side having a pressure outlet, the housing further comprising at least one oil outlet different from the pressure outlet, wherein the oil outlet is closed by a relief valve, wherein the relief valve assumes an open position when a limit pressure lying above a nominal pressure is exceeded in the working space, and wherein the transverse extent of the vane is large enough that when the vane passes the oil outlet, the oil outlet is closed by the vane, so that there is no fluid connection between the suction side and the pressure side over the oil outlet.

2. The vacuum pump according to claim 1, wherein the rotor and the vane divide the working space in the neutral pump position into a suction side having a suction inlet, a pressure side with a pressure outlet, and a pump side, wherein the volume of the pump side defines the cubic capacity of the pump, and wherein the oil outlet is provided in the region of the pump side, and/or wherein the oil outlet terminates in the working space in the region of the pump side.

3. The vacuum pump according to claim 1, wherein at the outlet, an outlet valve is provided for opening or closing the outlet, wherein the outlet valve assumes an open position when the nominal pressure in the working space is exceeded, and wherein the nominal pressure is lower than the limit pressure.

4. The vacuum pump according to claim 1, wherein the oil outlet is provided at the housing in an axial direction.

5. The vacuum pump according to claim 1, wherein the housing has a housing cover extending transversely to the rotor axis, and wherein the oil outlet is provided in the housing cover.

6. The vacuum pump according to claim 1, wherein the housing has a pot-shaped housing section with a housing bottom, and wherein the oil outlet is provided in the housing bottom.

7. The vacuum pump according to claim 5, wherein the oil outlet extends transversely to the rotor axis in the radial direction.

8. The vacuum pump according to claim 7, wherein a plurality of several oil outlets are provided, and wherein the oil outlets are arranged rotationally symmetrically about the rotor axis.

9. The vacuum pump according to claim 1, wherein the oil outlet is configured in a slotted shape, and wherein the slot width is smaller than the vane width.

10. The vacuum pump according to claim 1, wherein the oil outlet is circular, and wherein the opening diameter is smaller than the van width.

11. The vacuum pump according to claim 1, wherein the relief valve comprises a closing body and a return element, and wherein the return element pushes the closing body into a closed position in which the oil outlet is closed.

12. The vacuum pump according to claim 11, wherein the closing body comprises an elastically pliant closing tongue.

13. The vacuum pump according to claim 11, wherein the return element comprises a leaf spring.

14. The vacuum pump according to claim 13, wherein the closing tongue is formed by the leaf spring, and/or a stop is provided which limits the movement of the closing body from a closed position to the opening position.

15. The vacuum pump according to claim 10, wherein the closing body comprises a closing ball, and/or the return element comprises a spring, in particular a screw spring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Further details and advantageous configurations of the invention may be found in the following description, with reference to which the embodiments of the invention shown in the figures are described and explained in more detail:

[0031] FIG. 1 shows a rear view of a vacuum pump according to a first embodiment;

[0032] FIG. 2 shows a front view of the vacuum pump according to FIG. 1 with the housing covering removed, in a first vane position which defines the neutral position of the pump;

[0033] FIG. 3 shows a front view of the vacuum pump according to figure in a second vane position;

[0034] FIG. 4 shows a perspective view of the vacuum pump according to FIG. 1;

[0035] FIG. 5 shows a side view of the vacuum pump at FIG. 1;

[0036] FIG. 6 shows a perspective view of a vacuum pump according to a second embodiment;

[0037] FIG. 7 shows a rear view of the vacuum pump according to FIG. 6:

[0038] FIG. 8 shows a front view of the vacuum pump according to FIG. 6 in a first vane position;

[0039] FIG. 9 shows a front view of the vacuum pump according to FIG. 6 in a second vane position; and

[0040] FIG. 10 shows a front view of the vacuum pump according to FIG. 6 in a third vane position.

DETAILED DESCRIPTION

[0041] FIG. 1 shows a vacuum pump 10 having a housing 12 which limits a working space 14 shown in FIGS. 2 and 3. The vacuum pump 10 can in particular be used in a motor vehicle and in particular can be lubricated with oil from the internal combustion engine. The housing 12 is designed in two parts and comprises a pot-shaped housing section 16 with a housing bottom 18, which can be clearly discerned in the FIGS. 2 and 3. Furthermore the housing 12 comprises a housing cover 20, which is visible in FIGS. 1 and 4. In the working space 14, a rotor 24 is provided which is rotatably arranged about a rotor axis 22. The rotor 24 is eccentrically arranged in the working space 14 and lies against the cylindrical section of the pot-shaped housing section 16. The rotor 24 thus assumes an eccentric position in the working space 14. For rotating the rotor 24, it is rotationally coupled by a rotor shaft. The rotor 24 serves for transporting a vane 26 displaceably mounted in the radial direction in a guide 25. In the axial direction, thus in the direction of the rotor axis 22, the working space 14 is limited by a first upper contact surface and a second lower contact surface formed parallel thereto. The upper contact surface is here formed by a housing cover 20, while the lower contact surface is formed by the housing bottom 18.

[0042] FIG. 2 shows the so-called neutral position in the vacuum pump 10. The rotor 24 and the vane 26 divide the working space 14 into three sides: The pump 10 comprises first a pressure side 28 and a suction side 34. Further, a pump side 29 is present as the third side. The volume of the pump side 29 defines the cubic capacity of the vacuum pump 10. FIG. 8 shows a similar configuration for the second exemplary embodiment. On rotation of the rotor 24, a pressure gradient arises in the working space 14.

[0043] FIG. 1 shows a laterally arranged suction inlet 32. This terminates via the suction side 34 into the working space 14. Furthermore, pressure outlet 33 (cf. FIG. 4) is provided in the housing bottom 18. The pressure outlet 33 extends in the direction of the pressure side 28 in the axial direction through the housing bottom 18 into the working space 14. Thus, on rotation of the rotor 24, fluid is suctioned from the suction inlet 32 and conveyed via the pressure outlet 33 (cf. FIG. 4) out of the pump 10. An outlet is provided in the housing bottom 18 in the pump region 29 additionally to the pressure outlet 33. This outlet is the oil outlet 36 (cf. FIG. 2). The oil outlet 36 thus terminates in the pump region 29 of the vacuum pump 10. This has a slotted design and extends in the radial direction with respect to the rotor axis 22. As shown in FIG. 1, the oil outlet 36 is closed by a relief valve 38. The relief valve 38 here comprises a locking tongue 40, which is configured as a leaf spring. This leaf spring is secured by fastening means 42 configured as a screw to the housing 12. The locking tongue 40 can in particular comprise several leaves and can be made of steel. This leaf spring acts simultaneously as a return element 44, so that in the basic position the locking tongue 40 tightly closes the oil outlet 36. A stop can be provided for limiting the motion of the locking tongue 40. For locking the pressure outlet 33, an outlet valve 35 is provided, wherein this outlet valve 35 is opened in normal operation of the vacuum pump 10. The outlet valve 35 is likewise secured by a fastening means 37 configured as a screw to the housing 12. This valve 35 comprises two elastically pliant closing section 39, 41, which can be configured as leaf springs. During operation a nominal pressure predominates in the working space. This nominal pressure is below a limit pressure so that the relief valve 38 is closed and no oil can exit the oil outlet 36. If the closing sections 39, 41 are configured as leaf springs, they are markedly weaker than the leaf springs of the locking tongue 40, so that the outlet valve 35 controls the normal operation, in which the relief valve 40 is closed.

[0044] In a cold start of the pump 10, the situation is entirely different from the above. Actually, the pump 10 is lubricated with oil. Residual oil in the working space 14 can be present in the working space 14 during a cold start. Furthermore, oil can be located in the lines and in the internal combustion engine. Since the pump is regularly arranged very far down in a motor vehicle, the pump 10 runs completely full a few seconds after engine cutoff. In a cold start the oil has a high viscosity. Thus, during a cold start of the pump, very high accelerations occur in the vane 26. Thus, a high torque acts on the pump vane, since it works against the force of the oil. Consequently, a pressure arises in the pump 10 which exceeds a limit value. If the limit value is exceeded in the working space, such a high pressure force acts against the return force of the relief valve that the locking tongue 40 lifts off from the valve seat, so that the oil outlet 36 opens. In this way the oil can be discharged from the working space 14. This can occur very quickly. Nonetheless the relief valve 38 can be kept comparatively small, so that the effectiveness of the vacuum pump is comparatively high despite the provision of a second outlet. All in all, therefore, a quick and efficient pressure reduction can occur during a cold start via the oil outlet 36, without negatively impairing the function of the pump 10 and its power consumption.

[0045] The vane 26 has a transverse extent d1 (cf. FIG. 2). This transverse extent can be 9 mm, for example. In comparison, the slot-shaped oil outlet 36 has a transverse extent d2 which is smaller than the transverse extent d1, and can be 7 mm, for example. Consequently, if the vane 26 moves via the oil outlet 36, as shown in FIG. 3, at this moment it completely covers the oil outlet 36, and a so-called short circuit can be effectively prevented. This means that the pressure space 28 and the suction space 34 are sealed liquid-tight against one another at the oil outlet 36, and no oil can flow via the oil outlet 36 from the pressure side 28 to the suction side 34 and vice versa.

[0046] Consequently, all in all a vacuum pump 10 can be provided that limits the cold start torque action on the vane 26 without reducing the performance in normal operation.

[0047] FIGS. 6-10 show a second embodiment of the vacuum pump 10. Here a second relief valve 46 is provided next to the first relief valve 38. The housing 12 of the vacuum pump 10 has a protrusion 48, to which the relief valve 46 is secured by means of a screw 50. The relief valve 46 here is identical in construction to the relief valve 38. The second relief valve 38 covers a second oil outlet 52 (cf. FIGS. 9 and 10). This oil outlet 52 likewise has a slotted design and extends in the radial direction with respect to the rotor axis 22. As is clear from FIG. 8, the vane 26 likewise completely covers the oil outlet 52 at the moment when it moves over the oil outlet 52. If the vane, as is visible in FIG. 9, moves further, it passes the region between the oil outlets 36 and 52. The distance between the oil outlets here is greater than the vane width, so that here as well a short circuit between the pressure space 28 and the suction space 34 is prevented. By providing a second oil outlet or even several oil outlets, an efficient pressure reduction can be achieved in the working space during a cold start.