Gas pump with pressure relief for reducing the starting torque

Abstract

A gas pump including a delivery chamber with an inlet and an outlet for a gas. The delivery chamber is at least partially enclosed by a first housing part with a first sealing surface and a second housing part with a second sealing surface. A delivery device is moveable within the delivery chamber for delivering the gas. A pressing device presses one of the housing parts against the other with a pressing force such that the sealing surfaces abut each other and together form a sealing join which at least partially surrounds the delivery chamber in order to seal off the delivery chamber. The second housing part can be moved relative to the first housing part, against the pressing force, in order to be able to widen the sealing join to form a relieving gap through which liquid situated in the delivery chamber can escape.

Claims

1. A vacuum vane cell pump, comprising: a delivery chamber comprising an inlet and an outlet for a gas; at least one delivery rotor comprising one or more vanes arranged in the delivery chamber, and which is moveable within the delivery chamber, for delivering the gas; a first housing part comprising a first sealing surface which at least partially surrounds the delivery chamber; a second housing part comprising a second sealing surface which at least partially surrounds the delivery chamber, wherein the second housing part together with the first housing part at least partially enclose the delivery chamber; and a pressing device comprising a leaf spring which presses one of the first or second housing parts against the other with a pressing force, such that the first and second sealing surfaces abut each other and together form a sealing join which at least partially surrounds the delivery chamber, in order to seal off the delivery chamber; wherein the second housing part is moveable relative to the first housing part, against the pressing force, in order to be able to widen the sealing join to form a relieving gap through which lubricating liquid situated in the delivery chamber can escape into the environment, the lubricating liquid serving to lubricate and seal off the vacuum vane cell pump is, and wherein the pressing device is configured such that widening of the sealing join begins automatically when a predetermined maximum pressure in the delivery chamber is exceeded when the vacuum vane cell pump is started and during a first revolution of the vacuum vane cell pump and the sealing join is closed automatically by the pressing device when the pressure inside the delivery chamber is reduced to or below said maximum pressure and a negative pressure which prevails in the delivery chamber relative to the environment of the vacuum vane cell pump during pump operations assists the pressing force; wherein the outlet for the gas of the delivery chamber is connected to the environment and wherein the gas is air; wherein the relieving gap connects the delivery chamber to the environment of the vacuum vane cell pump; and wherein the vacuum vane cell pump is a negative pressure pump for supplying a brake servo of a vehicle with negative pressure, the brake servo being connected to the inlet of the vacuum vane cell pump, and suctioned gas is expelled into the environment via the outlet of the vacuum vane cell pump, the environment being a crankcase of an internal combustion engine of the vehicle.

2. The vacuum vane cell pump according to claim 1, wherein the pressing device comprises a first spring member which generates a first spring force which forms at least a part of the pressing force.

3. The vacuum vane cell pump according to claim 2, wherein the first spring member is a flexurally stressed spring.

4. The vacuum vane cell pump according to claim 2, wherein the first spring member is supported in a spring support region and coupled to the second housing part in a spring coupling region.

5. The vacuum vane cell pump according to claim 4, wherein the first spring member acts in its spring coupling region on the second housing part in the direction of the pressing force.

6. The vacuum vane cell pump according to claim 4, wherein the first spring member is also supported in an additional spring support region and in that the spring coupling region extends between the spring support regions.

7. The vacuum vane cell pump according to claim 4, wherein the spring coupling region of the first spring member is convex in relation to the second housing part and exhibits a spring bias which acts on the second housing part in the direction of the pressing force.

8. The vacuum vane cell pump according to claim 2, wherein the second housing part comprises a housing part base structure which comprises the second sealing surface, and the first spring member projects from the housing part base structure and is fixedly connected to the housing part base structure.

9. The vacuum vane cell pump according to claim 8, wherein the first spring member and the housing part base structure are formed in one piece together.

10. The vacuum vane cell pump according to claim 2, wherein the pressing device comprises a second spring member for generating an additional spring force, wherein the sum of the first spring force and the additional spring force form at least a part of the pressing force, and in that the first and second spring members are supported on mutually spaced points of the first housing structure or are coupled to the second housing structure at mutually spaced points of the second housing structure.

11. The vacuum cell pump according to claim 10, wherein the second housing part comprises a housing part base structure which comprises the second sealing surface, and in that the first spring member and the second spring member project from the housing part base structure and are fixedly connected to the housing part base structure.

12. The vacuum vane cell pump according to claim 10, wherein the second housing part is fastened on the first housing part by the first spring member or the second spring member.

13. The vacuum vane cell pump according to claim 2, wherein a guide is provided which extends in the direction in which the second housing part can be moved, and the second housing part is guided along the guide when it is moved, wherein a portion of the first spring member forms the guide.

14. The vacuum vane cell pump according to claim 1, wherein a sealing recess extends around the delivery chamber in at least one of the sealing surfaces which form the sealing join, wherein the sealing recess is filled with a sealing fluid at least while the vacuum vane cell pump is in operation, in order to seal off the delivery chamber on the outside, such that a seal by means of an additional sealing ring can be omitted.

15. The vacuum vane cell pump according to claim 1, wherein a movement of the second housing part in a direction which widens the sealing join is limited by a fixed abutment.

16. The vacuum vane cell pump according to claim 15, wherein the pressing device comprises a spring member and the spring member forms the fixed abutment.

17. The vacuum vane cell pump according to claim 1, wherein the pressing device is supported on the first housing part or on a third housing part of the vacuum vane cell pump or on a mounting unit which comprises the vacuum vane cell pump, and acts on the second housing part such that the pressing force is completely absorbed by the first or third housing parts or the mounting unit.

18. The vacuum vane cell pump according to claim 1, wherein the vacuum vane cell pump is connected to a lubricant circuit for lubricating one or more assemblies of a vehicle, and wherein the liquid is the lubricant for lubricating the one or more assemblies.

19. The vacuum vane cell pump according to claim 1, wherein the pressing device is elastically flexible over a spring path which is at least as large as a maximum gap width of the relieving gap.

20. A pump unit comprising the vacuum vane cell pump according to claim 1 and a lubricant pump which serves to supply a combustion engine with a liquid lubricant, the liquid lubricant forming the sealing fluid for the vacuum vane cell pump, wherein the lubricant pump comprises a delivery chamber with an inlet on a low-pressure side of the lubricant pump and an outlet on a high-pressure side of the lubricant pump for the liquid lubricant, and a delivery device which can be driven and which can perform a delivery movement in the delivery chamber when driven, which delivers the liquid lubricant from the inlet to the outlet of the delivery chamber of the lubricant pump; the lubricant pump furthermore comprises a housing part which forms one or more chamber walls of the delivery chamber of the lubricant pump; and the first housing part of the vacuum vane cell pump simultaneously also forms the housing part of the lubricant pump.

21. The pump unit according to claim 20 comprising a housing which is common to the vacuum vane cell pump and the lubricant pump, this common housing comprising: the first housing part which mounts moving components of the pump unit, including the delivery rotor of the vacuum vane cell pump and the delivery device of the lubricant pump, such that they can be moved; the second housing part which forms a cover of the vacuum vane cell pump; and a third housing part which forms a cover of the lubricant pump.

22. The pump unit according to claim 20, wherein the pump unit is partially immersed in a sump of the liquid lubricant.

23. The pump unit according to claim 20, wherein the pump unit is arranged on a lower side of a combustion engine and partially immersed in a sump of the liquid lubricant, the sump being the lubricant sump of the combustion engine.

24. A negative pressure system of a vehicle, comprising: a brake servo to be supplied with a negative pressure a pump comprising a delivery chamber comprising an inlet and an outlet for a gas, wherein the inlet of the pump is connected to the brake servo in order to supply it with a negative pressure; a first housing part comprising a first sealing surface which at least partially surrounds the delivery chamber; a second housing part comprising a second sealing surface which at least partially surrounds the delivery chamber, wherein the second housing part together with the first housing part at least partially encloses the delivery chamber; a delivery device, which can be moved within the delivery chamber, for delivering the negative pressure for the brake servo; and a pressing device comprising a leaf spring which presses one of the housing parts against the other with a pressing force, such that the first and the second sealing surfaces abut each other and together form a sealing join which at least partially surrounds the delivery chamber, in order to seal off the delivery chamber; wherein the second housing part is moveable relative to the first housing part, against the pressing force, in order to be able to widen the sealing join to form a relieving gap through which lubricating liquid situated in the delivery chamber can escape into the environment, the lubricating liquid serving to lubricate and seal off the pump; wherein the pressing device is configured to allow for discharge of excess fluid inside the pump by the delivery device when the pump is started and during a first revolution of the pump; wherein the negative pressure which prevails in the delivery chamber relative to the environment of the pump during pump operations assists the pressing force; wherein the outlet for gas of the delivery chamber is connected to the environment and wherein the gas is air; wherein the relieving gap connects the delivery chamber to the environment of the pump; and wherein suctioned gas is expelled via the outlet of the pump into a crankcase of an internal combustion engine of the vehicle.

25. The system according to claim 24, wherein the pump is a vane cell pump comprising a rotor with at least one vane.

26. A pump unit comprising a vacuum vane cell pump and a lubricant pump, the vacuum vane cell pump comprising: a delivery chamber comprising an inlet and an outlet for a gas; at least one delivery rotor comprising one or more vanes arranged in the delivery chamber, and which is moveable within the delivery chamber, for delivering the gas; a first housing part comprising a first sealing surface which at least partially surrounds the delivery chamber; a second housing part comprising a second sealing surface which at least partially surrounds the delivery chamber, wherein the second housing part together with the first housing part at least partially enclose the delivery chamber; and a pressing device comprising a leaf spring which presses one of the first or second housing parts against the other with a pressing force, such that the first and second sealing surfaces abut each other and together form a sealing join which at least partially surrounds the delivery chamber, in order to seal off the delivery chamber; wherein the second housing part is moveable relative to the first housing part, against the pressing force, in order to be able to widen the sealing join to form a relieving gap through which lubricating liquid situated in the delivery chamber can escape into the environment, the lubricating liquid serving to lubricate and seal off the vacuum vane cell pump, and wherein the pressing device is configured such that widening of the sealing join begins automatically when a predetermined maximum pressure in the delivery chamber is exceeded when the vacuum vane cell pump is started and during a first revolution of the vacuum vane cell pump and the sealing join is closed automatically by the pressing device when the pressure inside the delivery chamber is reduced to or below said maximum pressure and a negative pressure which prevails in the delivery chamber relative to the environment of the vacuum vane cell pump during pump operations assists the pressing force; wherein the outlet for the gas of the delivery chamber is connected to the environment and wherein the gas is air; wherein the relieving gap connects the delivery chamber to the environment of the vacuum vane cell pump; wherein the vacuum vane cell pump is a negative pressure pump for supplying a brake servo of a vehicle with negative pressure; the lubricant pump serving to supply a combustion engine with a liquid lubricant, the liquid lubricant forming the sealing fluid for the vacuum vane cell pump, wherein the lubricant pump comprises a delivery chamber with an inlet on a low-pressure side of the liquid pump and an outlet on a high-pressure side of the lubricant pump for the liquid lubricant, and a delivery device which can be driven and which can perform a delivery movement in the delivery chamber when driven, which delivers the liquid lubricant from the inlet to the outlet of the delivery chamber of the lubricant pump; the pump unit comprising a housing which is common to the vacuum vane cell pump and the lubricant pump, this common housing comprising: the first housing part which simultaneously also forms one or more chamber walls of the delivery chamber of the lubricant pump and mounts the delivery rotor of the vacuum vane cell pump and the delivery device of the lubricant pump such that they can be moved; the second housing part which forms a cover of the vacuum vane cell pump; and a third housing part which forms a cover of the lubricant pump; wherein the second housing part and the third housing part are each joined to the first housing part.

27. A vacuum vane cell pump, comprising: a delivery chamber comprising an inlet and an outlet for a gas; at least one delivery rotor comprising one or more vanes arranged in the delivery chamber, and which is moveable within the delivery chamber, for delivering the gas; a first housing part comprising a first sealing surface which at least partially surrounds the delivery chamber; a second housing part comprising a second sealing surface which at least partially surrounds the delivery chamber, wherein the second housing part together with the first housing part at least partially enclose the delivery chamber; and a pressing device which presses one of the first or second housing parts against the other with a pressing force, such that the first and second sealing surfaces abut each other and together form a sealing join which at least partially surrounds the delivery chamber, in order to seal off the delivery chamber; wherein the second housing part is moveable relative to the first housing part, against the pressing force, in order to be able to widen the sealing join to form a relieving gap through which lubricating liquid situated in the delivery chamber can escape into the environment, the lubricating liquid serving to lubricate and seal off the vacuum vane cell pump, and wherein the pressing device is configured such that widening of the sealing join begins automatically when a predetermined maximum pressure in the delivery chamber is exceeded when the vacuum vane cell pump is started and during a first revolution of the vacuum vane cell pump and the sealing join is closed automatically by the pressing device when the pressure inside the delivery chamber is reduced to or below said maximum pressure and a negative pressure which prevails in the delivery chamber relative to the environment of the vacuum vane cell pump during pump operations assists the pressing force; wherein the outlet for the gas of the delivery chamber is connected to the environment and wherein the gas is air; wherein the relieving gap connects the delivery chamber to the environment of the vacuum vane cell pump; wherein the vacuum vane cell pump is a negative pressure pump for supplying a brake servo of a vehicle with negative pressure; wherein the pressing device comprises a flexurally stressed spring member which generates a spring force which forms the pressing force; wherein the spring member is supported in a spring support region and acts in a spring coupling region on the second housing part in the direction of the pressing force; wherein the spring member is also supported in an additional spring support region and the spring coupling region extends between the spring support regions; and wherein the spring coupling region of the spring member is convex in relation to the second housing part and exhibits a spring bias which acts on the second housing part in the direction of the pressing force.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described below on the basis of example embodiments. Features disclosed by the example embodiments, each individually and in any combination of features, advantageously develop the subject-matter of the invention and also the embodiments discussed above. There is shown:

(2) FIG. 1 illustrates a pump unit comprising a gas pump of a first example embodiment, in an isometric view onto the gas pump;

(3) FIG. 2 illustrates the pump unit of the first example embodiment, in an isometric view onto a liquid pump of the arrangement;

(4) FIG. 3 illustrates the pump unit of the first example embodiment, in a longitudinal section;

(5) FIG. 4 illustrates a detail of FIG. 3 in an enlarged representation;

(6) FIG. 5 illustrates the pump unit of the first example embodiment, in an axial view onto the gas pump;

(7) FIG. 6 illustrates a pump unit comprising a gas pump of a second example embodiment, in a longitudinal section;

(8) FIG. 7 illustrates a detail of FIG. 6 in an enlarged representation;

(9) FIG. 8 illustrates the pump unit of the second example embodiment, in an axial view onto the gas pump;

(10) FIG. 9 illustrates a pump unit comprising a gas pump of a third example embodiment, in a longitudinal section;

(11) FIG. 10 illustrates a detail of FIG. 9 in an enlarged representation;

(12) FIG. 11 illustrates the pump unit of the third example embodiment, in an axial view onto the gas pump;

(13) FIG. 12 illustrates a pump unit comprising a gas pump of a fourth example embodiment, in a longitudinal section;

(14) FIG. 13 illustrates the pump unit of the fourth example embodiment, in an axial view onto the gas pump;

(15) FIG. 14 illustrates a detail of FIG. 13 in an enlarged, detailed representation;

(16) FIG. 15 illustrates a pump unit comprising a gas pump of a fifth example embodiment, in a longitudinal section;

(17) FIG. 16 illustrates a detail of FIG. 15 in an enlarged representation; and

(18) FIG. 17 illustrates the pump unit of the fifth example embodiment, in an axial view onto the gas pump.

DETAILED DESCRIPTION OF THE INVENTION

(19) FIG. 1 shows a pump unit comprising a gas pump 10 of a first example embodiment and a liquid pump 20, in an isometric view onto the gas pump 10. The pump unit comprises a housing which is common to both pumps 10 and 20. Such arrangements of pumps are also referred to as a tandem arrangement. The common housing comprises: a housing part 1 which mounts moving components of the pump unit, in particular a delivery device of the gas pump 10 and a delivery device of the liquid pump 20, such that they can be moved; a housing part 2 which forms a cover of the gas pump 10; and a housing part 27 which forms a cover of the liquid pump 20. The housing part 1 is formed—expediently, cast—in one piece. In principle, however, it can instead also be joined from a plurality of pieces. The housing parts 2 and 27 are each formed from metal in one piece and joined to the housing part 1, for example by means of a screw connection in each case, as shown.

(20) The gas pump 10 and the liquid pump 20 are embodied as rotary pumps. The rotary pumps 10 and 20 are arranged coaxially, one axially behind the other, along a common rotational axis. The housing part 1 is axially arranged centrally. The housing part 2 is arranged on one axial front face of the housing part 1, and the housing part 27 is arranged on the other axial front face of the housing part 1.

(21) The delivery device of the gas pump 10 comprises a delivery rotor 11, which can be rotated about the rotational axis, and a single vane 12 which is coupled to the delivery rotor 11 in a way which transmits torque. The delivery device is correspondingly single-vaned. The delivery rotor 11 radially guides the vane 12, such that it can be shifted. In the region of the gas pump 10, the housing part 1 forms a housing cup which limits a delivery chamber 3, on a front face of the chamber which axially faces the liquid pump 20, and surrounds the delivery chamber 3 over the circumference of the chamber. When the delivery rotor 11 is rotary-driven, the vane 12 revolves in the delivery chamber 3 and divides the delivery chamber 3 into a delivery cell which increases in size on a low-pressure side of the gas pump 10 and another delivery cell which decreases in size on a high-pressure side of the gas pump 10. The increase in the size of the delivery cell causes gas to be suctioned on the low-pressure side through an inlet 4 into the enlarging delivery cell and then expelled through an outlet 5 on the high-pressure side when the delivery cell decreases in size. The gas pump 10 can in particular be operated as a negative pressure pump or vacuum pump in order for example to supply a brake servo of a vehicle with negative pressure. In such an application, the brake servo or another or an additional assembly of the vehicle which is to be supplied with negative pressure is connected to the inlet 4, and the suctioned gas—preferably, air—is expelled into the environment via the outlet 5, for example into a crankcase of an internal combustion engine, wherein a lubricant which serves to lubricate the delivery device 10 is simultaneously also expelled through the outlet 5.

(22) The housing part 2 seals the delivery chamber 3 on one front face. FIG. 1 shows the housing part 2 before it is mounted, in a position in which the housing part 2 lies axially opposite the facing open front face of the housing part 1 and then has only to be axially pressed against and fixedly connected to the housing part 1 in order to seal the delivery chamber 3. Once they have been joined, a sealing surface 6 of the housing part 1 which axially faces the housing part 2 and a sealing surface 7 of the housing part 2 which axially faces the housing part 1 abut each other axially and form a sealing join which extends around the delivery chamber 3, in order to seal off the delivery chamber 3 over its circumference. In the sealing surface 6, a groove-shaped sealing recess 9 is formed over the entire circumference of the delivery chamber 3. A sealing element 19, for example a sealing ring, is arranged in the sealing recess 9 and elastically pressed when the housing parts 1 and 2 are joined, thus ensuring that the sealing join is sealed off as is required. Alternatively, the sealing join between the sealing surfaces 6 and 7 can however also be ensured by a sealing liquid situated in the sealing recess 9. In such embodiments, the sealing recess 9 is filled with the sealing liquid at least during pump operations. An elastic sealing ring or other sealing element is not then required in order to seal off the sealing join.

(23) FIG. 2 shows the pump unit of the first example embodiment, in an isometric view onto the liquid pump 20. The liquid pump 20, like the gas pump 10, is a vane cell pump. Unlike the gas pump 10, the liquid pump 20 comprises a multi-vaned delivery device featuring a delivery rotor 21, which can be rotated about the rotational axis which it has in common with the gas pump 10, and a plurality of vanes 22 which are arranged in a distribution over the circumference of the delivery rotor 21. The liquid pump 20 can be adjusted in terms of its specific delivery volume. It comprises a setting ring 23 which is mounted such that it can be pivoted relative to the housing part 1, in order to be able to adjust an eccentricity of the delivery device 21, 22 and therefore the specific delivery volume of the liquid pump 20. A restoring spring 26 exerts a restoring force, which acts in the direction of a maximum delivery volume, on the setting ring 23. The pressure liquid delivered by the liquid pump 20 is applied to the setting ring 23 in the direction of reducing the specific delivery volume, i.e. acting counter to said restoring force. The vanes 22 sub-divide a delivery chamber of the liquid pump 20 into delivery cells which increase in size on a low-pressure side of the delivery chamber when the delivery device 21, 22 is rotary-driven and the setting ring 23 is positioned eccentrically relative to the rotational axis, thus suctioning fluid into the delivery chamber, and which decrease in size again on a high-pressure side of the delivery chamber, such that the liquid is expelled at an increased pressure through an outlet 25 on the high-pressure side. In FIG. 2, the entire inlet region on the low-pressure side of the liquid pump 20 is indicated by 24, and the entire outlet region on the high-pressure side is indicated by 25. The inlet region comprises an inlet 24 of the housing part 1, which can be seen in FIG. 1, and an inlet portion 24 which is located in the housing part 1 upstream of the delivery chamber and in which the restoring spring 26 is for example arranged and from which a chamber inlet leads directly into the delivery chamber. The outlet region comprises: the chamber outlet, which leads directly out of the delivery chamber; an outlet portion 25 which is formed in the housing part 1; and, downstream of the outlet portion 25, an outlet 25 of the housing part 1.

(24) The liquid pump 20 can in particular be a lubricant pump for supplying an assembly with a liquid lubricant. In preferred applications, the liquid pump 20 is a lubricant pump for supplying a combustion engine, preferably a drive motor of a vehicle, with liquid lubricant.

(25) The pump unit is rotary-driven via a drive wheel 13. If the pump unit is assigned to a combustion engine, it can for example be driven by a crankshaft of the combustion engine via the drive wheel 13. The drive wheel 13 can be a component of a traction means gear system or also a component of a toothed wheel gear system or in principle also a component of a friction wheel gear system. The drive wheel 13 is mechanically coupled to both the delivery device 11, 12 and the delivery device 21, 22 and can in particular be non-rotationally connected to both delivery rotors 11 and 21.

(26) The pump unit can be partially or completely immersed in a sump or other type of reservoir of a liquid fluid, in particular a reservoir of the fluid which is delivered by the liquid pump 20. The pump unit can then be arranged in a lower region of a combustion engine, for example on a lower side of the combustion engine, such that it is partially or completely immersed in the lubricant sump of the combustion engine. Arranging it in a liquid reservoir, preferably a lubricant reservoir, is advantageous for sealing off the gas pump. Due to the negative pressure prevailing in the delivery chamber 3 during pump operations, lubricant is able and allowed to be suctioned, up to a certain extent, from the environment—the reservoir—via the sealing join 6, 7 into the sealing recess 9 and from there into the delivery chamber 3. The lubricant which surrounds the gas pump on the outside and which can optionally also simultaneously serve as a sealing fluid, effectively prevents ambient air from being suctioned via the sealing join 6, 7 in the region surrounded by the lubricant, thus enabling the strength of seal on the gas pump and therefore its effectiveness and delivery rate to be improved.

(27) FIG. 3 shows the pump unit of the first example embodiment, in a longitudinal section.

(28) FIGS. 3 to 5 show the pump unit of the first example embodiment in a longitudinal section (FIG. 3), a detail (FIG. 4) and an axial view onto the gas pump 10 (FIG. 5). The housing part 2 is joined to the housing part 1, such that the delivery chamber 3 is closed in a seal and the sealing surfaces 6 and 7 together form the sealing join 8 which surrounds the delivery chamber 3 over its circumference by extending around a central longitudinal axis of the delivery chamber 3. The sealing join 8 is located at an axial end of the delivery chamber 3; in the example embodiment, the sealing surface 6 is a front-facing surface at the open axial end of the housing part 2. The housing part 2 is planar over its front-facing surface which includes the sealing surface 7 and is turned towards the delivery chamber 3. In modifications, the sealing join 8 can for example also be formed at an axially recessed point—a collar surface—of the housing part 1 or in principle also of the housing part 2. Forming the sealing surface 6 at the axial front-facing end of the housing part 1, in combination with the housing part 2 which is planar at least on its side facing the housing part 1, does however facilitate production and thus reduce costs. It should also be noted that the sealing join 8 extends over the entire circumference, i.e. over 360°.

(29) The housing part 2 is pressed against the housing part 1 by means of a pressing device 30, such that the sealing surfaces 6 and 7 abut each other in a seal, forming the sealing join 8. The pressing device 30 is designed such that it allows a movement of the housing part 2 relative to the housing part 1 in a direction pointing axially away from the housing part 1, when an opening force which acts on the housing part 2 in said direction is greater than the pressing force. The opening force can in particular be generated by a positive pressure which prevails in the delivery chamber 3. The pressing device 30 can in particular be configured such that, while the pressing force which it exerts ensures a sufficient seal over the sealing join 8 when the pump is at a stop and during normal delivery operations of the pump, a widening movement is however generated by a positive pressure which arises in the delivery chamber 3 when the pump is started due to the lubricating fluid situated in the delivery chamber 3 and the delivery movement of the delivery device 11, 12. This positive pressure lifts the housing part 2 off the housing part 1, against the restoring pressing force of the pressing device 30, in the region of the sealing join 8, such that the sealing join 8 is widened to form a relieving gap through which excess lubricating liquid situated in the delivery chamber 3 can pass out of the delivery chamber 3 and thus be displaced by the delivery device 11, 12. This reduces the displacement work to be performed and therefore the forces and torques acting on the delivery device 11, 12. Consequently, the circumferential inner contour of the delivery chamber 3 and the vane 12 can be better adapted to each other, in order to enable a gap between the circumferential inner contour and the ends of the vane 12 which is narrower than in the prior art. A reverse rotary valve for relief during reverse rotation can be omitted. Venting provisions, which would reduce the effective delivery rate during normal pump operations, are also unnecessary.

(30) The pressing device 30 is formed entirely as a spring device. It comprises a single, uniform spring member 31 only, which is embodied and arranged as a flexurally stressed spring in order to generate the pressing force. In the example embodiment, the spring member 31 is a leaf spring. It consists of a left-hand and a right-hand spring support region 32 and a spring coupling region 33 which extends from the left-hand to the right-hand spring support region 32. All the spring regions 32 and 33 are formed in one piece from spring steel—in the example, a metal spring sheet. The spring support regions 32 and the spring coupling region 33 together form a spring clip, for example a sheet metal spring clip, such as is known in principle for sealing preserving jars.

(31) The spring member 31 straddles the housing part 2. The spring support regions 32 of the spring member 31 encompass an outer circumference of the housing part 2 and a shoulder of the housing part 1 which protrudes radially outwards. In a central region of the housing part 2, the spring member 31 is coupled to the housing part 2 in order to exert the pressing force, which is generated as a spring force, on the housing part 2 in this central region. In one modification, the spring member 31 can comprise a plurality of spring arms, for example three or four spring arms, which protrude outwards from a central region of the spring member in the direction of the sealing join 8 and in the direction of the housing part 2, in order to apply the spring force to the housing part 2 in a more uniform distribution and closer to the sealing join 8.

(32) The spring coupling region 33 of the spring member 31 is formed so as to be convex in relation to the housing part 2. In the example, it is a metal spring sheet which exhibits a convex profile. The coupling region 33 is shaped as a flat trough. In modifications, the spring coupling region 33 can for example exhibit a contour which is roundly convex throughout or can exhibit the shape of a flat “V”. In other words, it bulges out in the direction of the housing part 2 between the spring support regions 32. A region of the spring coupling region 33 which is a front region in the direction of the pressing force presses against the housing part 2. The spring member 31 is mounted with a bias.

(33) In its two spring support regions 32, the spring member 31 bends off from the spring coupling region 33, forming an enclosed acute angle in each case. At the free end of the respective spring support region 32, it bends off again, forming a holding element 34, as can best be seen in FIG. 4. In each of its spring support regions 32, the spring member 31 forms a flat “U”, the short end limb of which forms the holding element 34. The holding element 34 of the spring member 31 grips behind the housing part 1 which comprises a holding counter element 35 for the purpose of additional security. Respective pairs of the holding elements 34 and holding counter elements 35 can together form a locking connection. The sharp angular bends can be replaced with more gentle rounded bends. Sharply curved transitions, however, reduce the design space necessary for the pressing device 30 and thus enable a more compact design.

(34) As can be seen in FIG. 4, the sealing element 19 can exhibit a diamond profile, in order for it to be able to be axially expanded over a greater spring path in the course of the widening movement of the housing part 2, but nonetheless does not prevent fluid which is to be displaced from exiting through the sealing join 8. In principle, the sealing element 19 can also have a circular or square profile; it is however preferably elongated orthogonally with respect to the sealing surfaces 6 and 7 and can for example also be oval. This applies to all the embodiments of a gas pump in accordance with the invention which comprises an elastic sealing element such as for example the sealing element 19. In such embodiments, the respective sealing element is also preferably arranged in the sealing recess over the majority of its length, as measured in profile, or is secured in the sealing recess by some other provision, in order to prevent the respective sealing element from being swept along by fluid flowing off from the delivery chamber when the sealing join 8 is widened.

(35) If the pressing force which is predefined by the spring member 31 is exceeded, the housing part 2 can be moved away from the housing part 1, against the restoring pressing force of the spring member 31, as far as an end position which is predefined either by said pressing force or by a mechanical abutment. The spring member 31 can itself form such a mechanical abutment for the housing part 2, if the housing part 2 has not already been held or moved back in the direction of the housing part 1 by the restoring pressing force which increases as the housing part 2 is lifted off. The spring member 31 can in particular form a mechanical abutment in the region of the transition between the spring coupling region 33 and the respective spring support region 32.

(36) During the widening movement, the housing part 2 is guided relative to the housing part 1. This can be performed by the pressing device 30, for example directly by the spring member 31 as in the example embodiment. The spring member 31 fulfils the guiding function by means of its spring support regions 32. The guide can in particular be seen in an overview of FIGS. 4 and 5. The housing parts 1 and 2 form lateral guiding elements 36 and 37 for the spring support regions 32, by each comprising a flat cavity. The spring support regions 32 respectively engage with the assigned cavities, which mutually overlap, in a guiding engagement. The spring support regions 32 are trapped between the guides 36 and 37. The guiding elements 36 of the housing part 1 hold the spring member 31 in position, and the second housing part 2 is axially guided in the region of the side walls of its guiding elements 37 by the spring member 31. In this way, the pressing device 30 fulfils the functions of pressing and guiding the housing part 2 and, in an advantageous development, also the function of an abutment for limiting the widening movement of the housing part 2.

(37) FIGS. 6 to 8 show a pump unit comprising a gas pump 10 of a second example embodiment. The pump unit differs from the first example embodiment in that it has a modified pressing device 40. It otherwise corresponds to the first example embodiment. Aside from the differences described below, reference is therefore made to the statements made with respect to the first example embodiment.

(38) The pressing device 40 comprises one spring member 41 only, as in the first example embodiment, which is likewise formed and arranged as a flexurally stressed spring. Unlike the first example embodiment, however, it is not only the spring member 41 which ensures that the housing part 2 is arranged such that it is sufficiently fixed but flexible for the widening movement. In addition to the spring member 41, the pressing device 40 comprises a fastening device featuring fastening elements 44. The coupling region 43 of the spring member 41 corresponds to that of the spring member 31. The spring support regions 42 connected on the left and right to the outside of the spring coupling region 43 are however shorter and no longer encompass the housing parts 1 and 2. The spring support regions 42 of the spring member 41 are instead supported and also fastened on the housing part 1 by means of the fastening elements 44. As far as the spring action and/or generating and applying the pressing force is concerned, the spring member 41 corresponds to the spring member 31.

(39) One of the two spring support regions 42 is shown in an enlarged representation in FIG. 7. The spring support region 42 of the spring member 41 comprises a passage for the fastening element 44 which can for example be formed as a screw element or extrusion bolt. The fastening element 44 protrudes through first the spring member 41 and then the housing part 2 and into a bore of the housing part 1. It can for example be screwed or pressed in the bore. In a shaft region between the sealing surface 6 and the spring support region 42, the fastening element 44 is also surrounded by a sleeve-shaped guiding element 45 which also protrudes into the passage formed in the housing part 2 for the fastening element 44 and exhibits a certain clearance with respect to the housing part 2 in the region of the passage. The clearance is dimensioned such that the housing part 2 is guided by the guiding engagement 45 during a widening movement, but the guiding engagement 45 does not obstruct the widening movement. Instead of an additional guiding element 45, the fastening element 44 could also guide the housing part 2 directly in the corresponding shaft region. Tribologically, however, the use of an additional guiding element 45 is advantageous.

(40) As can also be directly seen in FIG. 8, the housing part 2 is held in its mounted position relative to the housing part 1 by the plurality of mutually spaced fastening and guiding points—in the example embodiment, two fastening and guiding points—such that it can only perform the widening movement and the corresponding closing movement.

(41) FIGS. 9 to 11 show a pump unit comprising a gas pump 10 and a liquid pump 20 in a third example embodiment which is derived from the second example embodiment and differs from the latter only in its pressing device 50, such that in order to describe the pressing device 50, reference is also made to the second example embodiment, and such that reference is also otherwise again made to the first example embodiment, in particular to the descriptions given with respect to the pressing device 30.

(42) The pressing device 50 comprises a plurality of separate spring members 51; four spring members 51 have been chosen by way of example. The spring members 51 each comprise a spring support region 52 and a spring coupling region 53 which is connected to the spring support region 52, wherein the spring support region 52 of each of the spring members 51 respectively presses against the housing part 2, in order to press the housing part 2, in the region of its sealing surface 7, against the sealing surface 6 of the housing part 1, as can be seen in particular in the detail in FIG. 10.

(43) The spring support regions 52 of the spring members 51 are respectively supported and fastened on the housing part 1 by means of a fastening element 54. Sleeve-shaped guiding elements 55 again ensure that the housing part 2 is axially guided and also positioned. The fastening elements 54 and the guiding elements 55 correspond at least substantially to the fastening elements 44 and the guiding elements 45, such that reference is made to the second example embodiment with regard to supporting and fastening the spring members 51 and guiding the housing part 2.

(44) In order to more reliably ensure that the spring members 51 retain their intended position during pump operations, the fastening elements 54 and the passages which protrude through them can be formed so to as conform to each other in the spring support regions 52, such that they co-operate to form a rotational block for the respective spring member 51. This is shown in FIG. 11 for the lower spring member 51 only, by way of example for the other spring members 51 also.

(45) FIGS. 12 to 14 show a pump unit of a fourth example embodiment, featuring a modified pressing device 60. One characteristic feature of the fourth example embodiment is that the spring members 61 of the pressing device 60 are a fixed component of the housing part 2. In this sense, they are integrated spring members 61.

(46) In the fourth example embodiment, the housing part 2 comprises a central housing part base structure 2c which is rigid in its own right, and the spring members 61 which project outwards from the housing part base structure 2c over its periphery. The spring members 61 are each formed in the shape of a spring arm. The spring arms first project slightly outwards from the housing part base structure 2c. Each of the short spring arm portions is connected to a comparatively longer spring arm portion which transitions into a spring support region 62 of the respective spring member 61 at an end facing away from the short spring arm portion. In this way, each of the spring members 61 comprises a spring coupling region 63 which projects freely from the central housing part base structure 2c and extends at least substantially in a circumferential direction over the majority of its length. As mentioned, the spring support regions 62 are arranged at the ends of the spring coupling regions 63. In the spring support regions 62, the spring members 61 are each fixed, such that they cannot be moved, relative to the housing part 1. In the top view of FIGS. 13 and 14, the spring members 61 are at least substantially C-shaped and each comprise an at least substantially L-shaped spring coupling region 63.

(47) The housing part base structure 2c comprises the sealing surface 7 on its inner or lower side facing the housing part 1, in order to form the sealing join 8 of the fourth example embodiment with the axially facing sealing surface 6. The sealing join 8 extends along the periphery of the housing part base structure 2c and—in the top view of FIG. 13—radially within the spring members 61.

(48) The housing part base structure 2c and the spring members 61 are formed in one piece, for example cast from a metallic material, and as applicable machine-finished, or preferably punched from a sheet of metal, in particular steel, or formed by means of another separating process. As can be seen in the top view of FIG. 13, the housing part 2 and the integrated spring members 61 together form a sinuous spring, the sinuous arms of which are the spring members 61. The spring members 61 are flexurally stressed springs in the form of sinuous arms.

(49) The housing part base structure 2c can be axially biased against the sealing surface 6 of the housing part 1 by the spring members 61. To this end, the lower side of the spring members 61 can comprise a clear distance from the facing front face of the housing part 1, by being slightly recessed there relative to the sealing surface 7 of the housing part 2 (FIG. 12). This enables the housing part 2 to be fastened on the housing part 1 with a bias.

(50) In the fourth example embodiment, an elastic sealing element such as for example the sealing element 19 (FIG. 4) has been omitted. Instead, the sealing recess 9 is filled with a sealing fluid, which can in particular be formed by the lubricating fluid for the gas pump 10, at least during pump operations. The lubricating fluid can be the fluid which is delivered by the liquid pump 20. Accordingly, a feed channel 14 can be seen in FIG. 12, through which the sealing recess 9 is supplied with the sealing fluid, preferably the lubricating fluid. It is also possible for the respective sealing recess 9 in the other example embodiments to be filled with sealing fluid and for an elastic sealing element to be omitted. Conversely, it is also possible for the fluid seal in the fourth example embodiment to be replaced with an elastic sealing element arranged in the sealing recess 9. With regard to sealing off using a sealing fluid and to supplying the sealing recess 9 with a sealing fluid, reference is made to German patent application No. 10 2012 222 753.9 which is also incorporated by reference in this respect.

(51) The gas pump of the fourth example embodiment and indeed the entire pump unit otherwise corresponds to that of the first example embodiment.

(52) FIGS. 15 to 17 show a pump unit of a fifth example embodiment. In this pump unit, a gas pump 10 and a liquid pump 20 are again combined to form a mounting unit. Aside from a pressing device 70 which has again been modified, the pump unit corresponds to the previous example embodiments, such that reference is again made to the statements made with respect to the first example embodiment.

(53) As in the third example embodiment (FIGS. 9 to 11), the pressing device 70 comprises a plurality of spring members 71. The spring members 71 are not however flexurally stressed spring members as in the other example embodiments, but rather a torsionally stressed spring member 71 in each case, for example a helical pressure spring in each case. The spring members 71 are each fixedly connected to the housing part 1 by means of a fastening element 74 which respectively protrudes through them. They each comprise a spring support region 72 at their ends facing away from the housing parts 1 and 2, and a spring coupling region 73 facing the housing part 2, as can best be seen in FIG. 16. They are each biased, such that when the pump is at a stop, they exert a biasing force—and correspondingly, in total, the pressing force—on the housing part 2. As in the third example embodiment, the spring members 71 are arranged in a distribution along the sealing join 8, such that aside from the opening and closing movement, they position and fix the housing part 2 relative to the housing part 1 and co-operate to apply the pressing force, necessary for sealing the delivery chamber 3, to the housing part 2.

(54) Aside from the differences described, reference is made to the statements made with respect to the other example embodiments.

(55) In the example embodiments, an axial block on the delivery rotor 11 and also the vane 12 is omitted. In one modification, the respective delivery rotor 11 and/or the respective vane 12 can be axially secured in order to prevent the delivery rotor or the vane from being axially moved, which can cause a clanging noise, during a widening movement of the housing part 2.

REFERENCE SIGNS

(56) 1 housing part 2 housing part 2a guiding element 2b holding element 2c housing part base structure 3 delivery chamber 4 inlet 5 outlet 6 sealing surface 7 sealing surface 8 sealing join 9 sealing recess 10 gas pump 11 delivery rotor 12 vane 13 drive wheel 14 feed channel 15 - 16 - 17 - 18 - 19 sealing element 20 liquid pump 21 delivery rotor 22 vane 23 setting ring 24 inlet, inlet region 25 outlet, outlet portion, outlet region 26 restoring spring 27 - 28 - 29 - 30 pressing device 31 spring member 32 spring support region 33 spring coupling region 34 holding element 35 holding counter element 36 guiding element 37 guiding element 38 - 39 - 40 pressing device 41 spring member 42 spring support region 43 spring coupling region 44 fastening element 45 guiding element 46 - 47 - 48 - 49 - 50 pressing device 51 spring member 52 spring support region 53 spring coupling region 54 fastening element 55 guiding element 56 - 57 - 58 - 59 - 60 pressing device 61 spring member 62 spring support region 63 spring coupling region 64 fastening element 65 - 66 - 67 - 68 - 69 - 70 pressing device 71 spring member 72 spring support region 73 spring coupling region 74 fastening element 75 guiding element