Scroll vacuum pump

Abstract

A scroll vacuum pump (10) comprising a pumping system (20) comprising a stationary spiral component (30) and a movable spiral component (40) cooperating therewith for pumping, a drive shaft (22) rotating about a rotational axis during operation, said drive shaft having an eccentric section (24) for driving the movable spiral component (40), and an electric drive motor (24) for the drive shaft (22). In a thermally cold state of the pumping system (20), a minimum radial distance (230) between a radially inner inner side (214) of a circular wall (210) and a radially inner inner wall (222) of a circular groove (220) is smaller than a minimum radial distance (232) between a radially outer outer side (214) of the circular wall (210) and a radially outer outer wall (224) of the circular groove (220).

Description

[0001] The present disclosure relates to the improvement of scroll vacuum pumps. Scroll vacuum pumps according to the invention comprise a pumping system including a stationary scroll member and a movable scroll member cooperating with the scroll member for pumping purposes, a drive shaft rotating about a rotational axis during operation, having an eccentric portion for driving the movable scroll member, and an electric drive motor for the drive shaft.

[0002] Scroll vacuum pumps are generally known, e.g. from EP 3 153 708 A2, EP 3 617 511 A2 and EP 3 647 599 A2.

[0003] A scroll pump, especially a scroll vacuum pump, is a positive displacement pump that compresses against atmospheric pressure and can be used, among other things, as a compressor. A scroll vacuum pump can be used to create a vacuum in a container connected to a gas inlet of the scroll vacuum pump.

[0004] Scroll vacuum pumps are also known as spiral vacuum pumps or spiral conveying devices. The pumping principle underlying a scroll vacuum pump is fundamentally known from the prior art. A stationary spiral component has a spiral groove in a support, into which a spiral wall engages. This wall is arranged on a corresponding support of the movable spiral component. Optionally, circular grooves in the stationary spiral component and correspondingly circular walls in the movable spiral component can also be provided to improve pumping action. The spiral components are nested in such a way that crescent-shaped volumes, also referred to as pockets, are formed by the wall of the movable spiral component in the groove of the stationary spiral component.The movable spiral component can be moved along a circular path via the eccentric section of the drive shaft, which is why this movable spiral component, together with its support, is also referred to as an orbiter. This movable spiral component thus performs a so-called centrally symmetrical oscillation relative to the stationary spiral component, which is also known as "orbiting" or "wobbling." The stationary spiral component, accordingly, together with its support, is also referred to as a stator. A crescent-shaped volume enclosed between a wall in the corresponding groove moves progressively inwards within the groove during the orbiting of the movable spiral component. This moving volume conveys the process gas to be pumped from a radially outer gas inlet of the pumping system to a radially inner gas outlet of the pumping system, which is located, in particular, at its center.

[0005] The eccentric drive, i.e., the drive shaft with the eccentric section, is located inside the scroll vacuum pump housing on the side of the carrier facing away from the moving volumes and is usually surrounded by a deformable sleeve, such as a bellows. This sleeve serves both to seal the drive against the intake area and to prevent the orbiter from rotating, as it could otherwise spin freely without this anti-rotation device. To ensure this anti-rotation, the deformable sleeve can, for example, be connected to the carrier at one end, while the other end of the deformable sleeve, opposite the first end, can be screwed to the base of the housing inside using several fasteners. Most scroll vacuum pumps are designed for continuous operation.It should be taken into account that, especially at the beginning of operation of the scroll vacuum pump, the thermal load on the components of the pump system of the scroll vacuum pump changes, as these components heat up and a stable temperature distribution in the pump system is only established after a certain time.

[0006] Based on the previously described known scroll vacuum pumps, the object of the invention is therefore to improve these scroll vacuum pumps. In particular, the object of the invention is to enable high pumping performance of the scroll vacuum pump in continuous operation and / or improved cold-start performance of such scroll vacuum pumps.

[0007] The object of the invention is achieved by the patent claims. In particular, the object is achieved by a scroll vacuum pump according to claim 1. Further developments of the scroll vacuum pump according to the invention are evident from the dependent claims, the description, and the drawings.

[0008] According to one aspect of the invention, the object is achieved by a scroll vacuum pump with a pumping system comprising a stationary spiral component and a movable spiral component cooperating therewith in a pumping manner, a drive shaft rotating about a rotational axis during operation and having an eccentric section for driving the movable spiral component, and an electric drive motor for the drive shaft, wherein the movable spiral component, together with the stationary spiral component, forms a circular part and a spiral part adjoining the circular part radially inward, wherein the circular part and the spiral part each extend from an inlet end to an outlet end, and wherein the outlet end of the circular part is connected to the inlet end of the spiral part, wherein the movable spiral component has an orbiter carrier cooperating with the drive shaft, and the stationary spiral component has a stator carrier,wherein the spiral part is formed by an engagement of a spiral spiral wall extending from the orbiter carrier into a spiral spiral groove arranged in the stator carrier, and furthermore the circular part is formed by an engagement of a circular circular wall extending from the orbiter carrier into a circular circular groove arranged in the stator carrier. The scroll vacuum pump according to the invention is characterized in that, in a thermally cold state of the pump system, a minimum radial distance between a radially inner inner surface of the circular wall and a radially inner inner wall of the circular groove is smaller than a minimum radial distance between a radially outer outer surface of the circular wall and a radially outer outer wall of the circular groove.

[0009] The scroll vacuum pump according to the invention is a scroll vacuum pump with a pumping system as described above. The pumping system has, in particular, two spiral components, one of which is fixedly arranged within the pumping system; in other words, it remains stationary relative to the rest of the scroll vacuum pump during operation. The other spiral component, however, is movable. Specifically, the movable spiral component is mechanically connected to an eccentric section of the drive shaft, so that this movable spiral component, driven by the drive motor, performs the movement associated with the orbiting or wobbling described above.

[0010] The pumping system of the scroll vacuum pump according to the invention comprises a circular section and a spiral section, the spiral section being arranged radially within the circular section. Both the circular section and the spiral section extend from an inlet end to an outlet end, the terms "inlet" and "outlet" being chosen with reference to the pumping direction of the fluid to be pumped. The outlet end of the circular section is connected to the inlet end of the spiral section, resulting in an overall effective pumping path from the inlet end of the circular section to the outlet end of the spiral section. Preferably, the outlet end of the spiral section is arranged radially centrally within the pumping system, which automatically places the inlet end of the spiral section radially further outward than the outlet end of the spiral section.

[0011] In both the circular and spiral sections, the crescent-shaped volumes described above are formed by a wall element that engages in a groove. For the circular section, a circular wall is provided, and for the spiral section, a spiral wall. Both extend from an orbiter carrier, which, as part of the movable spiral section, interacts with the drive shaft, particularly with the eccentric section. It should be noted that the circular wall usually does not describe a full circle of 360°, but only a partial circle, for example, encompassing between 300° and 345°. The spiral wall, in turn, can often be mathematically described as an involute. Corresponding to the designs of the circular and spiral walls, a circular groove and a spiral groove are provided in the stator carrier of the stationary spiral section.

[0012] When the pump system is assembled, the circular wall engages the circular groove, and the spiral wall engages the spiral groove, forming crescent-shaped volumes between these components. As the movable spiral component orbits, and thus the circular wall in the circular groove and the spiral wall in the spiral groove, these volumes are shifted radially inward, resulting in the fluid being pumped from the inlet end of the circular part to its outlet end, then to the inlet end of the spiral part, and through the spiral part to its outlet end, preferably radially centered in the pump system.

[0013] The dimensions and, in particular, the arrangement of the circular and spiral walls relative to the circular groove and spiral groove, respectively, are selected to achieve the best possible pumping performance during operation, especially continuous operation. This can be achieved, among other things, by minimizing the distance between each wall and the groove walls—that is, between the spiral wall and each of the two walls of the spiral groove, and between the circular wall and each of the two walls of the circular groove. This ensures a good seal at the two tapered ends of the resulting crescent-shaped volumes, thereby minimizing pumping losses.

[0014] In this context, it should be noted that the minimum distances introduced above are not fixed in place due to the orbiting of the movable spiral component with respect to the stationary spiral component, but rather move from the respective inlet end toward the outlet end in both the spiral path and the circular path. A "minimal distance" within the meaning of the present invention thus represents a distance between a wall and a wall of a groove, the value of which is minimized by a corresponding relative positioning of the wall to the wall. This can generally be done without specifying a specific position, so that the minimum distance is then described over the entire extent of the respective wall in the groove. Alternatively, the specification of a "minimal distance" can also be made with such a position specification, for example, "at the inlet end" or "at the outlet end."In this case, the "minimal distance" explicitly refers to the smallest acceptable value at that position.

[0015] As previously explained, the pump system operates continuously in a thermally stable state, during which the components of the pump system heat up until this state is reached. This heating causes a change in the relative position of the spiral wall in the spiral groove and the circular wall in the circular groove. This change is greater the further radially outward a section of the respective wall is located and the greater the temperature change. Essentially, the change in the radial position (dr) of a given wall follows the following formula: dr ∼ α ⋅ r ⋅ dT with a material-dependent constant α , the radial position r and the temperature change dT.

[0016] It should be noted that this formula describes the simple case where the orbiter support and the stator support, and in particular at least the spiral wall and the circular wall, as well as the spiral groove and the circular groove, are made of the same material. If different materials are used for these components, which usually also exhibit different expansion behavior, the above formula becomes more complex to account for this.

[0017] According to the invention, it has proven particularly advantageous if, in a thermally cold state of the pump system, the minimum radial distance between a radially inner inner surface of the circular wall and a radially inner inner surface of the circular groove is smaller than the minimum radial distance between a radially outer outer surface of the circular wall and a radially outer outer surface of the circular groove. A thermally cold state within the meaning of the invention is, in particular, an assembled or cold state of the scroll vacuum pump. In this thermally cold state, the scroll vacuum pump is not yet in operation, and, in particular, has not been in operation for such a long time beforehand that the components of the pump system have cooled down completely.In other words, when the scroll vacuum pump according to the invention is switched off and cooled down, the minimum gap that can be established between the circular wall and a corresponding wall of the circular groove differs depending on whether the circular wall forms the radially outer or the radially inner boundary of the gap. The minimum distance is smaller when the circular wall is located radially outside, and larger when the circular wall forms the radially inner boundary of the gap.

[0018] According to the formula above, the radial position of the circular wall will change until a constant operating temperature is reached, with a particular shift of the radial position towards the radial outside. This radial position change also occurs relative to the circular groove, since the arrangement of the circular groove on the movable spiral component causes it to heat up more compared to the circular groove on the stationary spiral component. The differences in the minimum distances radially inside and radially outside between the circular wall and the corresponding wall of the circular groove, as provided for in the invention, allow the minimum distances that develop during continuous operation to equalize on both sides of the circular wall.This makes it possible to set the smallest possible minimum distance on both sides of the circular wall in order to achieve a good seal of the correspondingly formed crescent-shaped volumes at their converging ends and thereby minimize pumping losses.

[0019] According to a further development, in the scroll vacuum pump according to the invention it can be provided that in a thermally cold state of the pump system a minimum radial distance between the inside of the spiral wall and the inner wall of the spiral groove at the inlet end of the spiral part is smaller than a minimum radial distance between the inside of the circular wall and the inner wall of the circular groove at the outlet end of the circular part.

[0020] As already explained above, when the pump system heats up, and in particular the moving spiral component, a radial position shift of the spiral wall and the circular wall is to be expected, according to the formula given above, the further radially outward a section of the respective wall is located, the greater the shift. Based on this, it would be assumed that the minimum radial distance between the inside of the spiral wall and the inner wall of the spiral groove at the inlet end of the spiral section should be set greater than the minimum radial distance between the inside of the circular wall and the inner wall of the circular groove at the outlet end of the circular section. Surprisingly, however, it has been found that this leads or can lead to contact between the circular wall and the inner wall of the circular groove during a cold start of the pump system, i.e. at the beginning of operation. Such contact is also referred to as start-up or startup.By ensuring that the minimum distance between the inner surface of the spiral wall and the radially inside inner wall of the spiral groove is smaller than the minimum distance between the circular wall and the radially inside inner wall of the circular groove, this so-called contact of the circular wall with the inner wall of the circular groove can be avoided. Overall, this improves the cold-start performance of the scroll vacuum pump according to the invention.

[0021] It should be noted that in the exemplary embodiment described above, the minimum distance between the inner side of the spiral wall and the radially inner wall of the spiral groove in the thermally cold state of the pump system can preferably be optimized for the achievable pumping performance in continuous operation. In other words, the radial position of the spiral wall is determined, particularly taking into account these specifications regarding the pumping performance to be achieved, and based on this, the radial position of the circular wall is then adjusted accordingly.

[0022] Furthermore, the scroll vacuum pump according to the invention can also be characterized in that, in a thermally cold state of the pump system, the minimum radial distance between the inner surface of the spiral wall and the inner wall of the spiral groove in the spiral section increases from the inlet end to the outlet end. According to the formula given above, the expected change in the radial position of the spiral wall is particularly greater the further radially outward a section of the spiral wall is located. Since the spiral wall extends spirally from the radially outer inlet end of the spiral section to the radially inner, preferably radially central, outlet end of the spiral section, the spiral wall has different radii depending on the section under consideration, which in turn leads to different changes in the respective radial position of the spiral wall. In particular, it is expected that the changes will decrease from the inlet end to the outlet end.This can be compensated for by increasing the minimum radial distance between the inner side of the spiral wall and the inner wall of the spiral groove in the spiral section from the inlet end to the outlet end, preferably in such a way that a constant minimum distance is established over the entire extension of the spiral wall during continuous operation. This makes it possible, in particular, to minimize pumping losses.

[0023] In a preferred embodiment of the scroll vacuum pump according to the invention, for example, the minimum radial distance between the inside of the spiral wall and the inner wall of the spiral groove in the spiral part can increase steadily from the inlet end towards the outlet end, preferably linearly.

[0024] In the scroll vacuum pump according to the invention, it can also be further provided that the movable spiral component, together with the stationary spiral component, form at least one further circular circular part radially adjoining the circular part on the outside and connected to it, wherein the further circular part extends from an inlet end to an outlet end and is formed by the engagement of a further circular circular wall extending from the orbiter carrier into a further circular circular groove arranged in the stator carrier. The essential pumping action of the scroll vacuum pump is provided by the spiral part, with the existing one circular part having a supporting effect. However, circular parts are significantly less complex to manufacture, since the elements of a circular part, in particular the circular wall and / or the circular groove, can be manufactured as turned parts, in contrast to the spiral wall and / or spiral groove, which must be laboriously milled.By providing a further circular part, the pumping effect of the scroll vacuum pump according to the invention equipped therewith can be improved without excessively increasing the manufacturing costs.

[0025] In a further embodiment of the scroll vacuum pump according to the invention, the inlet and outlet ends of the circuit section and the further circuit section can each be connected, thereby connecting the circuit section and the further circuit section in parallel, or the outlet end of the further circuit section can be connected to the inlet end of the circuit section, thereby connecting the circuit section and the further circuit section in series. Connecting the circuit sections in parallel increases the overall pumping volume. Conversely, connecting them in series increases the compression achievable by the entire pumping system. Depending on the requirements, the scroll vacuum pump according to the invention can thus be configured accordingly.

[0026] It should be noted that if several other circuit sections are present, combinations of parallel and series connection of individual circuit sections are also possible.

[0027] Furthermore, the scroll vacuum pump according to the invention can be designed such that, in a thermally cold state of the pump system, the minimum radial distance in the further circular section between a radial inner surface of the further circular wall and a radially inner inner wall of the further circular groove is smaller than the minimum radial distance between a radial outer surface of the further circular wall and a radially outer outer wall of the further circular groove. The circular wall of the further circular section also heats up at the beginning of operation, and consequently, until a temperature-stable continuous operating temperature is reached, the radial position of this circular wall will also shift radially outwards. In this embodiment, the relative minimum distances in the further circular section between the circular wall and the inner and outer walls of the circular groove are designed analogously to the circular section already described above.All the advantages described above with regard to this design of the circuit section can also be achieved by a corresponding design of the additional circuit section. In particular, pumping losses can be minimized.

[0028] Furthermore, the scroll vacuum pump according to the invention can also be characterized in that, in a thermally cold state of the pump system, the minimum radial distance between the inner surface of the circular wall and the inner wall of the circular groove and the minimum radial distance between the inner surface of the further circular wall and the inner wall of the further circular groove are the same. As explained above, the minimum distance between the circular wall and the inner wall of the circular groove in the circular section that is radially adjacent to the spiral section can be selected such that contact between the circular wall and the inner wall of the circular groove can be avoided. The minimum distance set for this circular section is thus precisely sufficient to prevent this contact. Therefore, it can be advantageous to adjust the minimum distance between the inner surface of the circular wall and the inner wall of the circular groove in the further circular section accordingly, in particular to the same value.This avoids the need for costly test series to determine the minimum distance to be set for the further part of the circle to prevent it from starting up.

[0029] The scroll vacuum pump according to the invention can also be further developed in such a way that, in a thermally cold state of the pump system, the minimum radial distance between the outside of the circular wall and the outer wall of the circular groove and the minimum radial distance between the outside of the further circular wall and the outer wall of the further circular groove are different.

[0030] In the previously described embodiment of the scroll vacuum pump according to the invention, the radial inner distances between the respective inner surfaces of the circular walls and the respective inner walls of the circular grooves are identical. However, since the circular segments—at least one circular segment and the other circular segment—are located at different radial positions and thus have different radii, it can be advantageous to take into account the different changes in the radial position of the respective circular wall expected upon heating, as described above. This allows, for example, the previously described equalization of the minimum distances between the respective circular wall and the inner or outer wall of the respective circular groove.The proposed design with different minimum radial distances between the outside of the respective circular wall and the outer wall of the respective circular groove makes this possible, alternatively or additionally to equal minimum distances on the radial inside of the respective circular wall.

[0031] According to a further development of the scroll vacuum pump according to the invention, it can also be provided that, in a thermally cold state of the pump system, the minimum radial distance between the outer surface of the circular wall and the outer wall of the circular groove is smaller than the minimum radial distance between the outer surface of the further circular wall and the outer wall of the further circular groove. The further circular section is arranged radially outside the existing circular section and thus has a larger radius. According to the formula given above, this leads to a greater expected change in the radius during a cold start until continuous operation is reached.This can be compensated for by a larger minimum distance in the further circular part on the radially outer side of the circular wall, i.e. between the radially outer outer side of the circular wall and the radially outer outer wall of the circular groove, in order to still obtain an alignment of the minimum distances in the further circular part radially inside and radially outside between the circular wall and the inner and outer walls of the circular groove, respectively.

[0032] Furthermore, in the scroll vacuum pump according to the invention, it can also be provided that in a thermally cold state of the pump system, the minimum radial distance between the inside of the circular wall and the inner wall of the circular groove is constant in the circular section between the inlet end and the outlet end, and / or that in a thermally cold state of the pump system, the minimum radial distance between the inside of the further circular wall and the inner wall of the further circular groove is constant in the further circular section between the inlet end and the outlet end.

[0033] Circular segments, being circular elements, each have a constant radius. Therefore, according to the formula above, assuming a uniform temperature, a constant change in radial position is to be expected across the entire respective circular segment. This can be accounted for by maintaining a constant minimum distance between the inner surface of the circular wall and the inner surface of the corresponding circular groove across the entire length of the respective circular wall, since a uniform change in radial position across the entire circular wall will ultimately result in a constant value for the respective minimum distance.

[0034] Alternatively or additionally, the scroll vacuum pump according to the invention can also be designed such that in a thermally cold state of the pump system in the circular part between the inlet end and the outlet end, the minimum radial distance between the outside of the circular wall and the outer wall of the circular groove is constant, and / or in a thermally cold state of the pump system in the further circular part between the inlet end and the outlet end, the minimum radial distance between the outside of the further circular wall and the outer wall of the further circular groove is constant.

[0035] The considerations previously outlined for the radially inner minimum distances within the circular segments also apply to the respective outer minimum distances, i.e., between a radial outer surface of the respective circular wall and a radial outer wall of the corresponding circular groove, and can be applied analogously. For these radially outer minimum distances, a constant minimum distance across the entire extent of the respective circular wall ensures that the expected uniform radial position change across the entire circular wall will ultimately result in a constant value for the respective minimum distance.

[0036] Furthermore, the scroll vacuum pump according to the invention can be designed with a constant radial wall thickness of the spiral wall and / or the circular wall and / or the further circular wall. Constant wall thicknesses are mechanically particularly simple. In particular, circular walls, but also spiral walls, with constant radial wall thicknesses are also particularly easy to manufacture. Moreover, such a constant radial wall thickness is particularly advantageous for circular walls that, in their thermally cold state, have constant minimal distances to the respective inner and outer walls of the corresponding circular grooves, since this means that the change in the radial position of the circular wall when heated to a continuous operating temperature is not affected, or only minimally so.With regard to the spiral wall, reference is made to the embodiment already described above, in which an inner radial minimum distance between the inside of the spiral wall and an inner wall of the spiral groove increases from the inlet end of the spiral part towards the outlet end of the spiral part. Since, in this embodiment, the radial position changes expected to vary along the length of the spiral wall are already compensated for by this change in minimum distances, the mechanically simple design with a constant radial wall thickness can also be chosen for the spiral wall.

[0037] According to a further embodiment, the scroll vacuum pump according to the invention can also be characterized in that the inner and / or outer surface of the spiral wall and / or the circular wall and / or the further circular wall are provided with at least one coating. Coatings can have many different properties. For example, a coating can reduce friction between components, such as between a spiral wall and an associated spiral groove. The surface hardness of a component can also be modified, and in particular increased, by a suitable coating. Overall, a coating can increase the resistance of surfaces to reactive elements, which, for example, enables the use of a scroll vacuum pump according to the invention with a reactive fluid to be pumped.

[0038] The coating can be single-layered or multi-layered. In other words, the entire coating can also consist of several individual layers. In multi-layered coatings, the individual layers can be made of the same coating material. Alternatively, at least two of the coating layers can be made of different materials.

[0039] According to a first further development, the scroll vacuum pump according to the invention can also be provided with a coating thickness that is constant along a circumferential extent of the spiral wall and / or the circular wall and / or the further circular wall. A coating with a constant thickness represents a particularly simple type of coating from a manufacturing perspective. The coating can be applied, for example, by uniformly spraying the coating onto the inside and / or the outside of the spiral wall or the circular wall.

[0040] Alternatively or additionally, the scroll vacuum pump according to the invention can also be further developed such that a thickness of the coating is variable along a circumferential extension of the spiral wall and / or the circular wall and / or the further circular wall. As already explained several times above, it may be useful and / or necessary to set an inner or outer minimum distance between the spiral wall and the corresponding wall of the spiral groove or between the circular wall and the corresponding wall of the circular groove. A coating with a variable thickness offers two possibilities for influencing such a minimum distance.Firstly, the variable thickness of the coating can be used to compensate for inaccuracies in setting the minimum distances, which may have arisen, for example, during the mechanical manufacturing of the components, particularly the spiral wall or one of the circular walls. Secondly, the variable thickness of the coating can also be used to establish this minimum distance setting for the first time. Various methods can be used to create such a variable thickness. For example, an area of ​​a spiral wall where a thicker coating is desired can be coated multiple times, or, in the case of spray coating, the feed rate of the spray head can be reduced for these areas.

[0041] The invention is described below by way of example with reference to the drawings. The drawings schematically depict: Fig. 1 shows an embodiment of a scroll vacuum pump according to the invention in a sectional view, Fig. 2 shows a sectional view of a pump system of a scroll vacuum pump according to the invention, and Fig. 3 shows a schematic representation to illustrate the minimum distances in the spiral part and in two circular parts.

[0042] Fig. 1 , 2 The diagram schematically shows the structure of a scroll vacuum pump 10 according to the invention. Fig. 1 A cross-sectional view of an entire scroll vacuum pump 10 is shown, in Fig. 2 a sectional view of a pump system 20 of the scroll vacuum pump 10 according to the invention Fig. 1 . In the following, both Fig. 1 , 2 jointly described, with separate discussion of the different representations.

[0043] The Fig. 1 The scroll vacuum pump 10 shown comprises, like essentially all scroll vacuum pumps 10, a pumping system 20 with a stationary spiral component 30 and a movable spiral component 40, which cooperate to provide pumping power during operation. Furthermore, the scroll vacuum pump 10 comprises a drive shaft 22 that rotates about an axis of rotation during operation and has an eccentric section 24 for driving the movable spiral component 40. Furthermore, the scroll vacuum pump 10 shown is provided with an electric drive motor 26, which serves to set the drive shaft 22 in rotation about the axis of rotation.

[0044] At the front end of a pump housing 28 of the scroll vacuum pump 10 is the pump system 20 with the stationary spiral component 30 and the movable spiral component 40. The stationary spiral component 30, also referred to as the spiral housing, is screwed onto the front end of the pump housing 28 and surrounded by a cover also attached to the pump housing 28.

[0045] The movable spiral component 40 comprises an orbiter carrier 42, the stationary spiral component 30 a stator carrier 32. In the illustrated embodiment of the scroll vacuum pump 10 according to the invention, a spiral wall 110, a circular wall 210 and a further circular wall 310 extend from the orbiter carrier 42, which engage in corresponding grooves, in particular a spiral groove 120, a circular groove 220 and a further circular groove 320, which are arranged in the stator carrier 32.

[0046] This forms a radially central spiral part 100 and two radially outer circular parts 200, 300, see in particular Fig. 2 The two circular sections 200, 300 are connected in parallel by connecting their inlet ends 202, 302 and their outlet ends 204, 304. Furthermore, the outlet ends 204, 304 of the circular sections are connected to the inlet end 102 of the spiral section 100 (not shown).

[0047] Between the respective walls 110, 210, 310 and walls 122, 124, 222, 224, 322, 324 of the grooves 120, 220, 320 (see Fig. 3 Crescent-shaped volumes or pockets are formed. Due to the wobbling motion of the orbiter carrier 42 relative to the stator carrier 32 caused by the eccentric section 24, these volumes or pockets move in the circular sections 200, 300 and in the spiral section 100, resulting in the conveying of a fluid to be pumped, usually a gas, from the inlet end 202, 302 of the circular sections 200, 300 to their outlet end 204, 304, then to the inlet end 102 of the spiral section 100 and finally to its outlet end 104.

[0048] Furthermore, the spiral wall 110, the circular wall 210 and / or the further circular wall 310 can have a coating 50, in particular on the respective inner side 114, 214, 314 or outer side 116, 216, 316 (cf. Fig. 3 ). Such a coating 50 can, for example, reduce friction in the pump system 20 and / or increase the resistance, in particular of the walls 110, 210, 310, to reactive or aggressive gases. The coating 50 can be designed in one or more layers, made of one or more materials. The thickness of the coating can be homogeneous or variable, the latter also being suitable for setting minimum distances 130, 132, 134, 136, 230, 323, 330, 332 (cf. Fig. 3 ) can be used.

[0049] In Fig. 3 are for the in Fig. 1 , 2The scroll vacuum pump 10 shown comprises the spiral section 100 (Figure A), the circular section 200 (Figure B), and the further circular section 300 (Figure C), each along its extent between the inlet ends 102, 202, 302 (right in each figure) and its outlet ends 104, 204, 304 (left in the figures). The chosen representation shows, for each position along this extent, the minimum possible distances 130, 132, 134, 136, 230, 232, 330, 323 that result from a corresponding relative positioning of the orbiter carrier 42 to the stator carrier 32 (see Figure 1). Fig. 1 , 2 ) can be assumed. Therefore, a development of a specific positioning, for example of the circular wall 210 in the circular groove 220, is not shown, since this representation would show an oscillation of the distances of the circular wall 210 to the walls 222, 224 of the circular groove 220, thereby forming the pockets described above.

[0050] The distances shown, 130, 132, 134, 136, 230, 232, 330, 332, are for the scroll vacuum pump 10 in a thermally cold state. In other words, these are the values ​​present at the beginning of a cold start of the scroll vacuum pump 10. Due to the heating that occurs during operation, the respective walls 110, 210, 310 are displaced radially outwards, the further they are from a center.

[0051] Figure A clearly shows that in the spiral part 100, the radially inner minimum distance 130 at the inlet end 102 has a smaller value than the radially inner minimum distance 134 at the outlet end 102. Both distances 130, 134 are defined between an inner side 114 of the spiral wall 110 and a radially inner inner wall 122 of the spiral groove 120. Conversely, at the same time, a radially outer minimum distance 132, 136, defined between an outer side 116 of the spiral wall 110 and a radially outer outer wall 124 of the spiral groove 120, decreases from the inlet end 102 towards the outlet end 104. Both changes take into account that the outlet end 104 of the spiral part 100 is preferably arranged centrally in the pump system 20, and the inlet end 102 is correspondingly arranged radially further out (cf. Fig. 2 ). In continuous operation of the scroll vacuum pump 10, i.e. after the temperature increase at a then constant temperature, preferably constant inner minimum distances 130, 134 and outer minimum distances 132, 136 result.

[0052] Figures B and C show the situation for circular segments 200 and 300, respectively. In contrast to spiral segment 100 (Figure A), the circular walls 210 and 310 are essentially on a constant radius. For this reason, the values ​​of the minimum inner distances 230 and 330, determined analogously to spiral segment 100, between an inner surface 214 and 314 of the respective circular wall 210 and 310 and a radially inner inner wall 222 and 322 of the respective circular groove 220 and 320, at the respective inlet end 202 and 302 and at the respective outlet end 204 and 304, are identical. The same applies to the values ​​of the minimum outer distances 232, 332. These are also defined, again analogously to the spiral part, between an outer side 216, 316 of the respective circular wall 210, 310 and a radially outer wall 224, 324 of the respective circular groove 220, 320.

[0053] Preferably, the radially inner minimum distance 230 of the radially inner circular part 200 (cf. Fig. 2 ) and the radially inner minimum distance 330 of the further circular part 300 assumes the same value.

[0054] In particular, it can be provided that the radially inner minimum distance 230 of the radially inner circular part 200 at its outlet end 204 is greater than a radially inner minimum distance 130 of the spiral part 100.

[0055] To take into account the radial position of the further circular part 300 outside the radially inner circular part 200, the radially outer minimum distance 232 of the circular part 200 can be smaller than the radially outer minimum distance 332 of the further circular part 300.

[0056] In summary, the minimum distance values ​​130, 132, 134, 136, 230, 232, 330, 332 are chosen to compensate for relative changes due to temperature increases in the respective walls 110, 210, 310. At the same time, they are not chosen to be too small, so as not to prevent condensation from forming on the walls 110, 210, 310 in the corresponding grooves 120, 220, 320 during a cold start. Bezugszeichenliste

[0057] 10Scroll vacuum pump 20 Pump system 22 Drive shaft 24 Eccentric section 26 Drive motor 28 Pump housing 30 fixed spiral component 32 stator carrier 40Movable spiral component 42Orbiter carrier 50 coating 100 Spiral part 102 Inlet end 104 Outlet end 110 Spiral wall 112 Wall thickness 114 Inside 116 Outside 120 Spiral groove 122 Inner wall 124 Outer wall 130radial inner minimum distance (inlet end) 132radial outer minimum distance (inlet end) 134radial inner minimum distance (outlet end) 136radial outer minimum distance (outlet end) 200 Circular section 202 Incoming end 204 Outgoing end 210 Circular wall 212 Wall thickness 214 Inside 216 Outside 220 Circular groove 222 Inner wall 224 Outer wall 230 radial inner minimum distance 232 radial outer minimum distance 300 further circle section 302 incoming end 304 outgoing end 310 further circular wall 312 wall thickness 314 inside 316 outside 320 further circular groove 322 inner wall 324 outer wall 330 radial inner minimum distance 332 radial outer minimum distance

Claims

1. Scroll vacuum pump (10) with - a pumping system (20) comprising a stationary spiral component (30) and a movable spiral component (40) cooperating therewith in a pumping manner, - a drive shaft (22) rotating about an axis of rotation during operation, said drive shaft having an eccentric section (24) for driving the movable spiral component (40), and - an electric drive motor (24) for the drive shaft (22), wherein the movable spiral component (40) together with the stationary spiral component (30) forms a circular part (200) and a spiral part (100) adjoining the circular part (200) radially inwardly, wherein the circular part (200) and the spiral part (100) each extend from an inlet end (202, 102) to an outlet end (204, 104), and wherein the outlet end (204) of the circular part (200) is provided with the inlet end (102) of the spiral part (100),wherein the movable spiral component (40) has an orbiter carrier (42) cooperating with the drive shaft (22) and the fixed spiral component (30) has a stator carrier (32), wherein the spiral part (100) is formed by an engagement of a spiral spiral wall (110) extending from the orbiter carrier (42) in a spiral spiral groove (120) arranged in the stator carrier (32), and furthermore the circular part (200) is formed by an engagement of a circular circular wall (210) extending from the orbiter carrier (42) in a circular circular groove (220) arranged in the stator carrier (32),and wherein, in a thermally cold state of the pump system (20), a minimum radial distance (230) between a radially inner inner side (214) of the circular wall (210) and a radially inner inner wall (222) of the circular groove (220) is smaller than a minimum radial distance (232) between a radially outer outer side (214) of the circular wall (210) and a radially outer outer wall (224) of the circular groove (220).

2. Scroll vacuum pump (10) according to claim 1, wherein in a thermally cold state of the pumping system (20) a minimum radial distance (130) between the inner side (114) of the spiral wall (110) and the inner wall (122) of the spiral groove (120) at the inlet end (102) of the spiral part (100) is smaller than a minimum radial distance (230) between the inner side (214) of the circular wall (210) and the inner wall (222) of the circular groove (220) at the outlet end (204) of the circular part (200).

3. Scroll vacuum pump (10) according to one of the preceding claims, wherein in a thermally cold state of the pumping system (20) the minimum radial distance (130, 134) between the inner side (114) of the spiral wall (110) and the inner wall (122) of the spiral groove (120) in the spiral part (100) increases from the inlet end (102) towards the outlet end (104).

4. Scroll vacuum pump (10) according to one of the preceding claims, wherein the movable spiral component (40) together with the fixed spiral component (30) form at least one further circular circular part (300) which adjoins the circular part (200) radially on the outside and is connected to the latter, wherein the further circular part (300) extends from an inlet end (302) to an outlet end (304) and is formed by an engagement of a further circular circular wall (310) extending from the orbiter carrier (42) into a further circular circular groove (320) arranged in the stator carrier (32).

5. Scroll vacuum pump (10) according to claim 4, wherein the inlet ends (202, 302) and the outlet ends (204, 304) of the circular part (200) and the further circular part (300) are each connected and thereby the circular part (200) and the further circular part (300) are connected in parallel, or wherein the outlet end (304) of the further circular part (300) is connected to the inlet end (202) of the circular part (200) and thereby the circular part (200) and the further circular part (300) are connected in series.

6. Scroll vacuum pump (10) according to claim 4 or 5, wherein in a thermally cold state of the pump system (20) in the further circular part (300) a minimum radial distance (330) between a radial inner side (314) of the further circular wall (310) and a radially inner inner wall (322) of the further circular groove (320) is smaller than a minimum radial distance (332) between a radial outer side (314) of the further circular wall (310) and a radially outer outer wall (324) of the further circular groove (320).

7. Scroll vacuum pump (10) according to one of the preceding claims 4 to 6, wherein in a thermally cold state of the pumping system (20) the minimum radial distance (230) between the inner side (214) of the circular wall (210) and the inner wall (222) of the circular groove (220) and the minimum radial distance (330) between the inner side (314) of the further circular wall (310) and the inner wall (322) of the further circular groove (320) are the same.

8. Scroll vacuum pump (10) according to one of the preceding claims 4 to 6, wherein in a thermally cold state of the pumping system (20) the minimum radial distance (232) between the outer side (214) of the circular wall (210) and the outer wall (224) of the circular groove (220) and the minimum radial distance (332) between the outer side (314) of the further circular wall (310) and the outer wall (324) of the further circular groove (320) are different.

9. Scroll vacuum pump (10) according to claim 8, wherein in a thermally cold state of the pumping system (20) the minimum radial distance (232) between the outer side (214) of the circular wall (210) and the outer wall (224) of the circular groove (220) is smaller than the minimum radial distance (332) between the outer side (314) of the further circular wall (310) and the outer wall (324) of the further circular groove (320).

10. Scroll vacuum pump (10) according to one of the preceding claims, wherein in a thermally cold state of the pumping system (20) in the circular part (200) between the inlet end (202) and the outlet end (204) the minimum radial distance (230) between the inner side (214) of the circular wall (210) and the inner wall (222) of the circular groove (220) is constant, and / or that in a thermally cold state of the pumping system (20) in the further circular part (300) between the inlet end (302) and the outlet end (304) the minimum radial distance (330) between the inner side (314) of the further circular wall (310) and the inner wall (322) of the further circular groove (320) is constant.

11. Scroll vacuum pump (10) according to one of the preceding claims, wherein in a thermally cold state of the pumping system (20) in the circular part (200) between the inlet end (202) and the outlet end (204) the minimum radial distance (232) between the outer side (214) of the circular wall (210) and the outer wall (224) of the circular groove (220) is constant, and / or in a thermally cold state of the pumping system (20) in the further circular part (300) between the inlet end (302) and the outlet end (304) the minimum radial distance (332) between the outer side (314) of the further circular wall (310) and the outer wall (324) of the further circular groove (320) is constant.

12. Scroll vacuum pump (10) according to one of the preceding claims, wherein a radial wall thickness (112, 212, 312) of the spiral wall (110) and / or the circular wall (210) and / or the further circular wall (310) is constant.

13. Scroll vacuum pump (10) according to one of the preceding claims, wherein the inner side (114, 214, 314) and / or the outer side (114, 214, 314) of the spiral wall (110) and / or the circular wall (210) and / or the further circular wall (310) are provided with at least one coating (50).

14. Scroll vacuum pump (10) according to claim 13, wherein a thickness of the coating (50) is constant along a circumferential extension of the spiral wall (110) and / or the circular wall (210) and / or the further circular wall (310).

15. Scroll vacuum pump (10) according to claim 13 or 14, wherein a thickness of the coating (50) is variable along a circumferential extension of the spiral wall (110) and / or the circular wall (210) and / or the further circular wall (310).

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