vacuum pump

Abstract

A vacuum pump (10) with a housing (12) that defines a working chamber (14) and with a rotor (24) rotatably mounted in the housing (12) about a rotor axis (22) and carrying at least one vane (26) that is movably mounted in the radial direction, wherein the vane (26) has a transverse extension (d1) and divides the working chamber (14) into a suction side (34) with a suction inlet (32) and a pressure side (28) with a pressure outlet (33), characterized in that the housing (12) has at least one oil outlet (36, 52) opening into the working chamber (14), which is separate from the pressure outlet (33) and is closed by a pressure relief valve (38, 46), wherein the pressure relief valve (38, 46) assumes an open position when a limit pressure prevailing in the working chamber (14) above a nominal pressure is exceeded, and that the transverse extension (d1) of the wing (26) is so large that when the wing passes the oil outlet (36, 52), the oil outlet is closed by the wing (26),so that there is no fluid connection between the suction side (34) and the pressure side (28) via the oil outlet (36, 52).

Description

[0001] The invention relates to a vacuum pump with a housing that defines a working space and with a rotor rotatably mounted in the housing about a rotor axis, the rotor having at least one vane that is movable in a radial direction, wherein the vane has a transverse extension and divides the working space into a suction side with a suction inlet and a pressure side with a pressure outlet.

[0002] Vacuum pumps typically have a crescent-shaped pump chamber, which is divided into pressure chambers by at least one impeller. By rotating the rotor, which is eccentric to the surrounding wall, a pressure differential can be created between the suction side with a suction inlet and a pressure side with a pressure outlet.

[0003] Vacuum pumps are used in many applications, particularly in motor vehicles. During operation, vacuum pumps are regularly lubricated with oil from the combustion engine. When the combustion engine is switched off, the vacuum pump fills with oil because it is usually located low on the engine, allowing excess oil to flow from the engine into the working chamber. When the combustion engine is then restarted, this excess oil must be expelled. This is particularly critical if the combustion engine has cooled down in the meantime, making the oil viscous and difficult to expel. Such problems also occur in hybrid vehicles because they require a high number of starts.

[0004] During a cold start of the vacuum pump, high accelerations result in comparatively high torques acting on the impeller. However, this leads to significant problems during a cold start because the cooled oil in the working chamber has a higher viscosity. Therefore, during a cold start, the impeller works against the resistance of the cold, especially highly viscous, oil to expel the accumulated oil from the working chamber. Under this stress, an impeller can, in the worst case, break. To counteract this, it is known in the art to use the largest possible leaf springs at the pressure outlet, which provide a large cross-section and thus reduce the starting torque and the stress on the impeller(s). Additionally, it is known to use ventilation holes. These allow air to flow into the pump chamber after the engine is switched off. This quickly reduces the vacuum in the pump chamber and less oil is drawn into it.However, both of these solutions have significant drawbacks. Large leaf springs lead to unwanted leakage and thus increased power consumption, because the incoming air has to be constantly expelled. The ventilation holes also result in permanently increased power consumption.

[0005] From DE 20 28 602 A a mechanical vacuum pump with oil sealing is known, in which oil is fed into an oil reservoir via a pump main outlet valve.

[0006] The invention is based on the objective of remedying the aforementioned problems of the prior art.

[0007] This problem is solved by a vacuum pump with the features of claim 1. Accordingly, the housing has an oil outlet, separate from the pressure outlet and closed by a pressure relief valve. The pressure relief valve opens when a limit pressure prevailing in the working chamber, which is above a nominal pressure, is exceeded. Furthermore, the transverse extent of the impeller is such that the oil outlet is closed by the impeller when it passes through it, so that there is no fluid connection between the suction side and the pressure side via the oil outlet.

[0008] The nominal pressure is the operating pressure during normal operation of the vacuum pump. The transverse extent of the impeller is its extent perpendicular to the plane of displacement. Due to the presence of oil in the working chamber, this nominal pressure is regularly exceeded during a cold start of the vacuum pump. As soon as the pressure becomes so high that the limit pressure is also exceeded, the pressure relief valve opens, allowing oil to flow out of the oil outlet. A particularly small and fast-acting pressure relief valve allows the highly viscous oil to be quickly discharged from the working chamber, thus advantageously reducing the resistance forces on the impeller. However, when the impeller passes the oil outlet, it covers the outlet to prevent a short circuit. Consequently, the suction side cannot communicate with the pressure side via the oil outlet; rather, they are fluid-tightly separated.Of course, multiple oil outlets can also be provided.

[0009] Pressures of 10 to 15 bar can regularly occur during a cold start, while the limiting pressure can be between 0.3 and 0.7 bar, and especially around 0.5 bar. This is significantly higher than the nominal pressure.

[0010] Overall, the cold-start torque acting on the impeller during a cold start can therefore be limited without reducing performance during normal operation. Consequently, the pump's function and power consumption are not negatively affected.

[0011] In particular, the impeller, together with the rotor, can be designed to divide the working chamber, at least in the so-called neutral position, into a suction side with a suction inlet, a pressure side with a pressure outlet, and a pump side. The volume of the pump side defines the pump's displacement. The oil outlet can be located on the pump side and thus open into the pump side of the working chamber. This design prevents a reduction in pump performance while still allowing for efficient oil removal from the pump during cold starts.

[0012] Advantageously, the pressure relief valve is relatively small and, in particular, relatively responsive. This allows for high efficiency in the vacuum pump despite the inclusion of an additional oil outlet alongside the pressure outlet.

[0013] An advantageous embodiment of the invention provides that an outlet valve is provided at the outlet for opening and closing the outlet, wherein the outlet valve assumes an open position when the nominal pressure in the working chamber is exceeded, and wherein the nominal pressure is lower than the limit pressure. Thus, the pressure relief valve remains closed during normal operation. Such an outlet valve therefore regulates normal operation.

[0014] A further advantageous embodiment of the invention provides that the oil outlet on the housing is arranged in the axial direction. Thus, the wing tip does not pass over the oil outlet. Instead, the oil outlet is covered by the transverse extension of the wing as it passes over it.

[0015] It is also advantageous if the housing has a cover extending transversely to the rotor axis, with the oil outlet located in the cover. This allows the oil outlet to be easily covered by the transverse extension of the blade as it passes over the blade.

[0016] It is particularly preferred if the housing has a cup-shaped housing section with a housing base, wherein the oil outlet is provided in the housing base. The circular cylindrical section of the cup-shaped housing section is therefore advantageously designed to be completely fluid-tight, so that the wing tip can slide along it and a comparatively high efficiency is enabled.

[0017] It would also be conceivable to have an oil outlet in both the housing cover and the housing base to allow for particularly rapid emptying of the working space.

[0018] It is particularly preferred if the oil outlet extends radially in a direction transverse to the rotor axis.

[0019] In this way, it is particularly easy to cover the oil outlet when the wing passes through it, in order to prevent a short circuit.

[0020] It is particularly preferred if several oil outlets are provided, wherein the oil outlets can be arranged rotationally symmetrically around the rotor axis. An n-fold rotational symmetry is possible, depending on the number of oil outlets provided. These oil outlets can, in particular, open sequentially in a cascade-like manner, since the pressure is regularly highest before the blade reaches the respective oil outlet, and thus the limit pressure may be exceeded in this area.

[0021] Advantageously, the oil outlet is slot-shaped, with the slot width being smaller than the wing width. If the slot extends radially, the slot width is the extent of the slot perpendicular to the radial direction.

[0022] On the other hand, the oil outlet can be circular, with the opening diameter being smaller than the blade width. Such outlet geometries are particularly easy to create in the housing and can be opened and closed very quickly using a valve.

[0023] The wing's transverse extent can be, for example, nine millimeters. The slot width can be 7 mm, or, in the case of a circular oil outlet, the diameter can be 7 mm. Consequently, the wing can seal the oil outlet as it passes through.

[0024] A particularly preferred embodiment of the invention is that the pressure relief valve comprises a closing element and a return element, wherein the return element forces the closing element into a closed position in which the oil outlet is closed.

[0025] Such a pressure relief valve closes and opens particularly quickly and can be made comparatively small in order to quickly and efficiently remove oil from the working chamber without significantly impairing efficiency.

[0026] A particularly preferred embodiment of the invention provides that the closing element comprises an elastically compliant closing tongue. The closing tongue can be made, for example, of steel, in particular spring steel, or plastic, and enables quick and precise opening and closing of the pressure relief valve in a simple manner.

[0027] It is particularly preferred if the return element comprises a leaf spring. The leaf spring can be designed as a spring-elastic valve and can comprise several leaves. The return element can be attached to the pump housing at one end, particularly by means of a fastening device such as a screw. Such a return element is particularly easy to manufacture and allows the pressure relief valve to open quickly when the limit pressure is exceeded.

[0028] Advantageously, the closing tongue is formed by the leaf spring. Such a pressure relief valve is particularly easy to manufacture, thus providing a cost-effective and still effective pressure relief valve.

[0029] The outlet valve may also incorporate leaf springs. However, these leaf springs are significantly weaker than those of the pressure relief valve, so that during normal operation the pressure relief valve is closed while the outlet valve is open to release pumped medium.

[0030] Preferably, a stop is provided that limits the movement of the closing tongue from a closed position to the open position. This enables precise and efficient opening and closing of the pressure relief valve.

[0031] On the other hand, it is conceivable that the closing element includes a closing ball. Additionally or alternatively, the return element can include a spring, particularly a coil spring. Such a pressure relief valve is particularly easy and compact to manufacture. Furthermore, the coil spring allows the oil outlet to be efficiently closed even in a vacuum pump position where gravity does not act towards the closed position of the pressure relief valve. In contrast, a leaf spring can be used particularly where gravity acts on the leaf spring towards the closed position, so that the leaf spring is subjected to gravity against the valve seat.

[0032] Further details and advantageous embodiments of the invention can be found in the following description, which further describes and explains the embodiment of the invention shown in the figures. The figures show: Fig. 1 Rear view of a vacuum pump according to a first embodiment; Fig. 2 Front view of the vacuum pump after Fig. 1 with the housing cover removed in a first vane position, which defines the neutral position of the pump; Fig. 3 Front view of the vacuum pump after Fig. 2 in a second wing position; Fig. 4 Perspective view of the vacuum pump after Fig. 1; Fig. 5 Side view of the vacuum pump according to Fig. 1; Fig. 6. Perspective view of a vacuum pump according to a second embodiment; Fig. 7 Rear view of the vacuum pump after Fig. 6; Fig. 8 Front view of the vacuum pump after Fig. 6 in a first wing position; Fig. 9 Front view of the vacuum pump after Fig. 6 in a second wing position; and Fig. 10 Front view of the vacuum pump after Fig. 6 in a third wing position.

[0033] Fig. Figure 1 shows a vacuum pump 10 with a housing 12 that includes one in the Fig. 2 and Fig. The working space 14 shown in Figure 3 is limited. The vacuum pump 10 can be used in particular in a motor vehicle and can be lubricated with oil from the internal combustion engine. The housing 12 is constructed in two parts and comprises a pot-shaped housing section 16 with a housing base 18, which is inserted into the Fig. 2 and Fig. 3 is clearly visible. Furthermore, the housing 12 includes a housing cover 20, which is located in the Fig. 1 and Fig. As can be seen in Figure 4, a rotor 24 is provided in the working chamber 14, rotatably arranged about a rotor axis 22. The rotor 24 is arranged eccentrically in the working chamber 14 and rests against the circular cylindrical section of the cup-shaped housing section 16. The rotor 24 thus occupies an eccentric position in the working chamber 14. For rotation, the rotor 24 is rotaryally coupled by means of a rotor shaft. The rotor 24 serves to drive a vane 26, which is mounted to be displaceable in the radial direction in a guide 25. In the axial direction, i.e., in the direction of the rotor axis 22, the working chamber 14 is bounded by a first upper contact surface and a second lower contact surface parallel to it. The upper contact surface is formed by the housing cover 20, while the lower contact surface is formed by the housing base 18.

[0034] In Fig. Figure 2 shows the so-called neutral position in the vacuum pump 10. Here, the rotor 24 and the vane 26 divide the working chamber 14 into three sides: The pump 10 comprises a pressure side 28 and a suction side 34. Furthermore, a pump side 29 is present as a third side. The volume of the pump side 29 defines the displacement of the vacuum pump 10. A similar configuration is shown. Fig. 8 for the second embodiment. When the rotor 24 rotates, a pressure gradient is created in the working chamber 14.

[0035] In Fig. Figure 1 shows a laterally arranged suction inlet 32. This opens into the working chamber 14 via the suction side 34. Furthermore, a [missing information] is visible in the Fig. 1 and Fig. A pressure outlet 33 is provided in the housing base 18 as shown in Figure 4. The pressure outlet 33 extends axially through the housing base 18 into the working chamber 14 in the area of ​​the pressure side 28. Consequently, when the rotor 24 rotates, fluid is drawn in from the suction inlet 32 ​​and discharged via the pressure outlet 33 (see Figure 4). Fig. 4) is pumped from pump 10. In the housing base 18, in the pump area 29, a different outlet is provided next to the pressure outlet 33. This outlet is the oil outlet 36 (see figure). Fig. 2) The oil outlet 36 thus opens into the pump section 29 of the vacuum pump 10. This section is slot-shaped and extends radially with respect to the rotor axis 22. As in Fig. As shown in Figure 1, the oil outlet 36 is closed by a pressure relief valve 38. The pressure relief valve 38 includes a closing tongue 40, which is designed as a leaf spring. This leaf spring is attached at one end to the housing 12 by means of a fastening element 42 designed as a screw. The closing tongue 40 can, in particular, comprise several leaves and can be made of steel. This leaf spring also acts as a return element 44, so that the closing tongue 40 tightly closes the oil outlet 36 in its resting position.

[0036] A stop may be provided to limit the movement of the closing tongue 40. An outlet valve 35 is provided to close the pressure outlet 33, and this outlet valve 35 is open during normal operation of the vacuum pump 10. The outlet valve 35 is also attached to the housing 12 by a fastening element 37 designed as a screw. This valve 35 comprises two elastically compliant closing sections 39, 41, which may be designed as leaf springs. During normal operation, a nominal pressure prevails in the working chamber 14. This nominal pressure is below a limit pressure, so that the pressure relief valve 38 is closed and no oil can escape from the oil outlet 36. If the closing sections 39, 41 are designed as leaf springs, they are significantly weaker than the leaf springs of the closing tongue 40, so that the outlet valve 35 regulates normal operation in which the pressure relief valve 38 is closed.

[0037] In contrast, the situation is completely different during a cold start of pump 10. Pump 10 is lubricated with oil. Residual oil may be present in working chamber 14 during a cold start. Furthermore, oil may be present in the supply lines and in the combustion engine. Since pump 10 is typically located very low in a motor vehicle, it fills completely within a few seconds after the engine is switched off. However, the oil has a high viscosity during a cold start. Therefore, very high accelerations occur at impeller 26 during a cold start of pump 10. Consequently, a high torque acts on impeller 26, as it works against the force of the oil. This results in a pressure in pump 10 that exceeds a limit pressure.If the limit pressure in working chamber 14 is exceeded, such a high pressure force acts against the restoring force of the pressure relief valve 38 that the closing tongue 40 lifts off the valve seat, thus opening the oil outlet 36. Oil can then be discharged from working chamber 14. This can occur very quickly. Nevertheless, the pressure relief valve 38 can be kept relatively small, so that the efficiency of the vacuum pump remains comparatively high despite the provision of a second outlet. Overall, rapid and efficient pressure reduction during cold starts can therefore be achieved via the oil outlet 36 without negatively affecting the function of the pump 10 or its power consumption.

[0038] Wing 26 has a transverse extension d1 (cf. Fig. 2) This transverse dimension can, for example, be 9 mm. In contrast, the slot-shaped oil outlet 36 has a transverse dimension d2 that is smaller than the transverse dimension d1 and can, for example, be 7 mm. Consequently, if the vane 26 is moved over the oil outlet 36, as in Fig. As shown in Figure 3, this completely covers the oil outlet 36 at this moment, effectively preventing a so-called "short circuit". This means that the pressure chamber 28 and the suction chamber 34 are at all times completely sealed against each other at the oil outlet 36, preventing oil from flowing from the pressure side 28 to the suction side 34 and vice versa.

[0039] In summary, a vacuum pump 10 can therefore be provided which limits the cold start torque acting on the wing 26 during cold start without reducing the performance in normal operation.

[0040] The Fig. Figures 6-10 show a second embodiment of the vacuum pump 10. In this embodiment, a second pressure relief valve 46 is provided next to the first pressure relief valve 38. For this purpose, the housing 12 of the vacuum pump 10 has a projection 48 to which the pressure relief valve 46 is attached by means of a screw 50. The pressure relief valve 46 is identical in construction to the pressure relief valve 38. The second pressure relief valve 38 covers a second oil outlet 52 (see Figure 6-10). Fig. 9 and Fig. 10). This oil outlet 52 is also slot-shaped and extends radially with respect to the rotor axis 22. As shown from Fig. As can be seen in Figure 8, the wing 26 also completely covers the oil outlet 52 at the moment it is moved over the oil outlet 52. If the wing is moved as shown in Figure 8, the wing 26 also completely covers the oil outlet 52 at the moment it is moved over the oil outlet 52. Fig.As shown in Figure 9, the movement continues, sweeping over the area between oil outlets 36 and 52. The distance between the oil outlets is greater than the blade width, thus preventing a "short circuit" between pressure chamber 28 and suction chamber 34. By providing a second oil outlet or even several oil outlets, efficient pressure reduction in the working chamber during a cold start can be achieved.

Claims

[1] Vacuum pump (10) with a housing (12) that defines a working chamber (14) and with a rotor (24) rotatably mounted in the housing (12) about a rotor axis (22) and carrying at least one vane (26) that is movably mounted in the radial direction, wherein the vane (26) has a transverse extension (d1) and divides the working chamber (14) into a suction side (34) with a suction inlet (32) and a pressure side (28) with a pressure outlet (33), characterized by, that the housing (12) has at least one oil outlet (36, 52) open into the working chamber (14) and closed by a pressure relief valve (38, 46), the pressure relief valve (38, 46) being open when a limit pressure prevailing in the working chamber (14) above a nominal pressure is exceeded, and that the transverse extent (d1) of the vane (26) is such that when the vane passes the oil outlet (36, 52), the oil outlet (36, 52) is closed by the vane (26), so that there is no fluid connection between the suction side (34) and the pressure side (28) via the oil outlet (36, 52). [2] Vacuum pump (10) according to claim 1, characterized by, that the rotor (24) and the vane (26) divide the working chamber (14) in the neutral pump position into the suction side (34) with the suction inlet (32), the pressure side (28) with the pressure outlet (33) and a pump side (29), wherein the volume of the pump side (29) defines the displacement of the vacuum pump (10), and wherein the oil outlet (36, 52) is provided in the area of ​​the pump side (29) and / or opens into the working chamber (14) in the area of ​​the pump side (29). [3] Vacuum pump (10) according to claim 1 or 2, characterized by , that an outlet valve (35) is provided at the pressure outlet (33) for opening or closing the pressure outlet (33), wherein the outlet valve (35) assumes an open position when the nominal pressure in the working chamber (14) is exceeded, and wherein the nominal pressure is lower than the limit pressure. [4] Vacuum pump (10) according to claim 1 or 2 or 3, characterized by , the oil outlet (36, 52) is provided on the housing (12) in the axial direction. [5] Vacuum pump (10) according to one of the preceding claims, characterized by , that the housing (12) has a housing cover (20) extending transversely to the rotor axis (22), wherein the oil outlet (36, 52) is provided in the housing cover (20). [6] Vacuum pump (10) according to one of claims 1 to 4, characterized by , that the housing (12) has a pot-shaped housing section (16) with a housing bottom (18), wherein the oil outlet (36, 52) is provided in the housing bottom (18). [7] Vacuum pump (10) according to claim 5 or 6, characterized by , that the oil outlet (36, 52) extends transversely to the rotor axis (22) in a radial direction. [8] Vacuum pump (10) according to claim 7, characterized by , that several oil outlets (36, 52) are provided, wherein the oil outlets (36, 52) are arranged rotationally symmetrically around the rotor axis (22). [9] Vacuum pump (10) according to any one of the preceding claims, characterized by, that the oil outlet (36, 52) is slot-shaped, wherein a slot width (d2) is smaller than the transverse extent (d1) of the wing (26). [10] Vacuum pump (10) according to any one of claims 1 to 8, characterized by , that the oil outlet (36, 52) is circular, with its opening diameter being smaller than the transverse extent (d1) of the wing (26). [11] Vacuum pump (10) according to any of the preceding claims, characterized by , that the pressure relief valve (38, 46) comprises a closing element (40) and a return element (44), wherein the return element (44) forces the closing element (40) into a closed position in which the oil outlet (36, 52) is closed. [12] Vacuum pump (10) according to claim 11, characterized by , that the closing element (40) comprises an elastically compliant closing tongue. [13] Vacuum pump (10) according to claim 11 or 12, characterized by , that the return element (44) comprises a leaf spring. [14] Vacuum pump (10) according to claims 12 and 13, characterized by , that the locking tongue is formed by the leaf spring and / or that a stop is provided which limits the movement of the locking element (40) away from a closed position to the open position. [15] Vacuum pump (10) according to claim 11, characterized by , that the locking element (40) comprises a locking ball, and / or that the return element (44) comprises a spring, in particular a coil spring.

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