EP4538532A2 - Scroll vacuum pump - Google Patents

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

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 therewith 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.

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 .

A scroll pump, particularly 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 chamber connected to a gas inlet of the scroll vacuum pump.

Scroll vacuum pumps are also known as spiral vacuum pumps or spiral conveying devices. The pumping principle underlying a scroll vacuum pump is generally known from the prior art. A stationary spiral component has a spiral groove in a support, into which a spiral wall engages. This spiral wall is arranged on a corresponding support of the movable spiral component. Optionally, circular grooves can also be provided in the stationary spiral component and correspondingly circular walls in the movable spiral component to improve the pumping effect. The spiral components are inserted into one another in such a way that crescent-shaped volumes, also known as pockets, are formed by the wall of the movable spiral component in the groove of the fixed 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 carrier, is also referred to as an orbiter. This movable spiral component thus performs a so-called centrally symmetric oscillation relative to the fixed spiral component, which is also referred to as "orbiting" or "wobbling." The fixed spiral component, together with its carrier, is accordingly also referred to as a stator. A crescent-shaped volume enclosed between a wall in the corresponding groove migrates increasingly inward within the groove as the movable spiral component orbits. By means of the migrat-ing volume, the process gas to be pumped is conveyed from a radially outer gas inlet of the pumping system radially inward to a gas outlet of the pumping system, particularly one located in a center.

The eccentric drive, i.e. the drive shaft with the eccentric section, is located within the housing of the scroll vacuum pump on the side of the carrier facing away from the volumes moving there. In practice, it is usually surrounded by a deformable sleeve, for example a corrugated bellows, which serves on the one hand to seal the drive from the intake area and on the other hand to prevent the orbiter from rotating, as it could otherwise rotate around itself without a rotation lock. To ensure this rotation lock, for example, the deformable sleeve can be connected to the carrier at a first end, whereas the second end of the deformable sleeve, opposite the first end, can be screwed to the housing base by means of several fastening means inside the housing. Common scroll vacuum pumps are usually designed for continuous operation. It should be noted that, especially at the beginning of the scroll vacuum pump's operation, the thermal load changes, especially on the components of the scroll vacuum pump's pumping system, as these components heat up, and a stable temperature distribution in the pumping system only becomes established after a certain period of time.

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

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 emerge from the subclaims, the description, and the drawings.

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-effective 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 circular part and a spiral 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 The spiral component has a stator carrier, the spiral part being formed by engagement of a spiral spiral wall extending from the orbiter carrier into a spiral spiral groove arranged in the stator carrier, and the circular part being formed by 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 inside 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 outside of the circular wall and a radially outer outer wall of the circular groove.

The scroll vacuum pump according to the invention represents 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 in the pumping system; in other words, it remains stationary relative to the rest of the scroll vacuum pump during operation of the scroll vacuum pump. The other spiral component, however, is movable. In particular, the movable spiral component is mechanically operatively connected to an eccentric section of the drive shaft, so that this movable spiral component, driven by the drive motor, executes the movement associated with the orbiting or wobbling described above.

The pumping system of the scroll vacuum pump according to the invention comprises a circular part and a spiral part, with the spiral part being arranged radially within the circular part. Both the circular part and the spiral part extend from an inlet end to an outlet end, with 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 part is connected to the inlet end of the spiral part, so that an effective pumping distance extends from the inlet end of the circular part to to the outlet end of the spiral part. Preferably, the outlet end of the spiral part is arranged radially centrally in the pump system, whereby the inlet end of the spiral part is automatically arranged radially further outward than the outlet end of the spiral part.

In both the circular part and the spiral part, the sickle-shaped volumes described above are formed by a wall element that engages in a groove. A circular circular wall is provided for the circular part, and a spiral spiral wall is provided for the spiral part, both of which extend from an orbiter carrier which, as part of the movable spiral component, interacts with the drive shaft, in particular 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. Adapted to the designs of the circular wall and the spiral wall, a circular groove and a spiral groove are provided in the stator carrier of the stationary spiral component.

When the pump system is assembled, the circular wall engages the circular groove, and the spiral wall engages the spiral groove in such a way that crescent-shaped volumes form 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 displaced radially further 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.

The dimensioning and in particular the arrangement of the circular wall and the spiral wall relative to the circular groove or the spiral groove is selected in such a way that during operation, in particular during continuous operation, the Good pumping performance can be achieved. This can be achieved, among other things, by keeping the distance between the respective wall and the walls of the groove, i.e., between the spiral wall and the two walls of the spiral groove, and between the circular wall and the two walls of the circular groove, as small as possible. This allows for good sealing of the correspondingly formed crescent-shaped volumes at their two tapered ends, thus minimizing pumping losses.

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 in both the spiral path and the circular path from the respective inlet end toward the outlet end. A "minimum 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 "minimum 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 "minimum distance" explicitly refers to the smallest acceptable value at this position.

mit einer materialabhängigen Konstante α, der radialen Position r und der Temperaturänderung dT. As already explained above, the pumping system is in a thermally stable state during continuous operation, with the pumping system components heating 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, a change in the radial position (dr) of a particular wall follows the following formula: $$\mathit{dr}\sim \alpha \cdot r\cdot \mathit{dT}$$

with a material-dependent constant α , the radial position r and the temperature change dT.

It should be noted that this formula describes the simple case where the orbiter carrier and the stator carrier, 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. When different materials are used for these components, which usually also exhibit different expansion behaviors, the above formula becomes more complex to account for this circumstance.

According to the invention, it has been found to be particularly advantageous if, in a thermally cold state of the pump system, a minimum radial distance between a radially inner inner side 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 outside of the circular wall and a radially outer outer wall of the circular groove. A thermally cold state within the meaning of the invention is, in particular, an assembled state or cold state of the scroll vacuum pump. In its 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 completely cooled down again. In other words, in the switched-off and cooled-down state of the scroll vacuum pump according to the invention, the minimum gap that can be set between the circular wall and a corresponding wall of the circular groove in the circular part varies depending on whether the circular wall forms the radially outer or the radially inner boundary of the gap. The minimum distance is smaller if the circular wall is located radially outward and larger if the circular wall forms the radially inner boundary of the gap.

According to the above formula, the radial position of the circular wall will change until a constant operating temperature is reached, with the radial position shifting radially outwards in particular. This radial position change also occurs relative to the circular groove, since the arrangement of the circular groove on the movable spiral component means that it heats up more than the circular groove on the stationary spiral component. The difference in the minimum distances radially inward and radially outward between the circular wall and the corresponding wall of the circular groove provided according to the invention makes it possible for the minimum distances that occur during continuous operation to be equalized 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 good sealing of the correspondingly formed crescent-shaped volumes at their tapered ends and thus minimize pumping losses.

According to a further development, it can be provided in the scroll vacuum pump according to the invention that, in a thermally cold state of the pump system, a minimum radial distance between the inner side 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 inner side of the circular wall and the inner wall of the circular groove at the outlet end of the circular part.

As already explained above, when the pump system, and in particular the movable spiral component, heats up, a radial positional shift of the spiral wall and the circular wall is to be expected. According to the formula given above, this shift is particularly greater the further radially outward a section of the respective wall is located. Based on this, it would be assumed that the minimum radial distance between the inner side of the spiral wall and the inner wall of the spiral groove at the inlet end of the spiral section should be set larger. as 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 part. However, it has surprisingly 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 start of operation. Such contact is also referred to as start-up or start-up. By providing a minimum distance between the inside of the spiral wall and the radially inner inner wall of the spiral groove in this embodiment, with a smaller value than the minimum distance between the circular wall and the radially inner inner wall of the circular groove, this so-called start-up of the circular wall on the inner wall of the circular groove can be avoided. Overall, the cold start behavior of the scroll vacuum pump according to the invention can be improved in this way.

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 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.

Furthermore, the scroll vacuum pump according to the invention can also be characterized in that, in a thermally cold state of the pumping system, the minimum radial distance between the inner side of the spiral wall and the inner wall of the spiral groove in the spiral part 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 is spirally from the inlet end of the spiral part, which is arranged radially further outwards, to the outlet end of the spiral part, which is positioned radially further inwards, preferably radially centrally, the spiral wall has different radii depending on the section under consideration, which in turn means that changes of different sizes in the respective radial position of the spiral wall are to be expected. In particular, it is to be expected that the changes decrease from the inlet end to the outlet end. This can be compensated for by the intended increase in the minimum radial distance between the inside of the spiral wall and the inner wall of the spiral groove in the spiral part from the inlet end to the outlet end, preferably in such a way that a constant minimum distance is established over the entire extent of the spiral wall during continuous operation. This makes it possible, in particular, to minimize pumping losses.

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

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 and connected thereto, 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. Circular parts, however, 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 grooves that require complex milling. By providing an additional circular section, the pumping effect of the scroll vacuum pump according to the invention can be improved without excessively increasing the manufacturing effort.

In a further embodiment of the scroll vacuum pump according to the invention, it can further be provided that the inlet ends and the outlet ends of the circular part and of the further circular part are each connected, thereby connecting the circular part and the further circular part in parallel, or wherein the outlet end of the further circular part is connected to the inlet end of the circular part, thereby connecting the circular part and the further circular part in series. By connecting the circular parts in parallel, the overall pumping volume can be increased. By connecting them in series, the compression achievable by the entire pumping system can be increased. Depending on requirements, the scroll vacuum pump according to the invention can thus be designed accordingly.

It should be noted that if there are several additional circuit sections, combinations of parallel connection and series connection of individual circuit sections are also possible.

Furthermore, the scroll vacuum pump according to the invention can be designed such that, in a thermally cold state of the pump system in the further circular part, a minimum radial distance between a radial inner side of the further circular wall and a radially inner inner wall of the further circular groove is smaller than a minimum radial distance between a radial outer side of the further circular wall and a radially outer wall of the further circular groove. The circular wall of the further circular part also experiences heating at the beginning of operation, and consequently, until temperature-stable continuous operation is reached, the radial position of this circular wall will also change radially outward. In this embodiment, the relative minimum distances in the wider circular section between the circular wall and the inner or outer wall of the circular groove are designed analogously to the circular section already described above. All of the advantages described above with regard to this design of the circular section can also be achieved for this further circular section by a corresponding design of the further circular section. In particular, pumping losses can be minimized.

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 side of the circular wall and the inner wall of the circular groove and the minimum radial distance between the inner side 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 part arranged radially adjacent to the spiral part can be selected such that contact of the circular wall with the inner wall of the circular groove can be avoided. The minimum distance set for this circular part is thus precisely sufficient to prevent this contact. It can therefore be advantageous to also set the minimum distance between the inner side of the circular wall and the inner wall of the circular groove in the further circular part accordingly, in particular to the same value. Complex test series to determine the minimum distance to be set for the further circular part to prevent contact can thus be avoided.

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

In the previously described embodiment of the scroll vacuum pump according to the invention, the respective radially inner distances between the respective inner sides of the circular walls and the respective inner walls of the circular grooves are of the same design. Since the circular parts, the at least one circular part and the further circular part, are located at different radial positions and thus have a different radii, it can be advantageous, however, to take into account the different changes in the radial position of the respective circular wall upon heating, which can be expected according to the above formula, in order, for example, to achieve the already described equalization of the minimum distances between the respective circular wall and the inner or outer wall of the respective circular groove. The design proposed in this embodiment with different minimum radial distances between the outer side of the respective circular wall and the outer wall of the respective circular groove can make this possible, as an alternative to or in addition to identical minimum distances on the radially inner side of the respective circular wall.

According to a further development of the scroll vacuum pump according to the invention, it can further be provided that, in a thermally cold state of the pump system, the minimum radial distance between the outer side of the circular wall and the outer wall of the circular groove is smaller than the minimum radial distance between the outer side of the further circular wall and the outer wall of the further circular groove. The further circular part is arranged radially outside the already existing circular part, thus in particular has a larger radius. According to the formula given above, this leads to a larger expected change in the radius during a cold start until continuous operation is reached. This can be compensated 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 outside of the circular wall and the radially outer wall of the circular groove, in order to nevertheless achieve an adjustment of the minimum distances in the to obtain a further circular part radially inside and radially outside between the circular wall and the inner or outer wall of the circular groove.

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

As circular elements, circular segments each have a constant radius. Therefore, according to the formula given above, and assuming a uniform temperature, a constant change in the radial position can be expected across the entire respective circular segment. This can be taken into account by maintaining a constant minimum distance between an inner side of the circular wall and the inner wall of the corresponding circular groove over the entire extent of the respective circular wall, since a constant radial position change across the entire circular wall will result in a constant value for the respective minimum distance.

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.

The considerations previously outlined for the radially inner minimum distances in the circular sections also apply to the respective outer minimum distances, i.e., between a radial outer side of the respective circular wall and a radial outer wall of the corresponding circular groove, and are applicable analogously. For these radially outer minimum distances, a constant minimum distance can be achieved across the entire extent of the respective circular wall, so that the expected radial position change across the entire circular wall will result in a constant value for the respective minimum distance.

Furthermore, in the scroll vacuum pump according to the invention, it can be provided that a radial wall thickness of the spiral wall and/or the circular wall and/or the further circular wall is constant. Constant wall thicknesses are mechanically particularly simple to construct. Circular walls in particular, but also spiral walls, with constant radial wall thicknesses are also particularly easy to manufacture. Furthermore, such a constant radial wall thickness is particularly advantageous for circular walls which, in the thermally cold state, have constant minimum distances to the respective inner and outer walls of the corresponding circular grooves, since this does not, or only insignificantly, influence the change in the radial position of the circular wall when heated to a continuous operating temperature. With regard to the spiral wall, reference is made to the embodiment already described above, in which an inner radial minimum distance between the inner side 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 design the radial position changes to be expected along the extension of the spiral wall are already compensated by this change in the minimum distances, the mechanically simple design with constant radial wall thickness can also be selected for the spiral wall.

According to a further embodiment, the scroll vacuum pump according to the invention can also be characterized in that the inside and/or the outside 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, for example between a spiral wall and an associated spiral groove. The surface hardness of a component can also be changed, in particular increased, by a corresponding coating. Overall, a coating can increase the resistance of surfaces to reactive elements, which can, for example, enable the use of a scroll vacuum pump according to the invention with a reactive fluid to be pumped.

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

According to a first further development, the scroll vacuum pump according to the invention can further be provided with a coating thickness that is constant along a circumferential extension 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 in terms of production technology. The coating can be applied, for example, by uniformly spraying the coating onto the inside and/or outside of the spiral wall or the circular wall.

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 options in particular for influencing such a minimum distance. Firstly, the variable thickness of the coating can be used to compensate for inaccuracies when setting the minimum distances, which may have arisen, for example, during the mechanical production of the components, in particular, for example, the spiral wall or one of the circular walls. Secondly, the variable thickness of the coating can also be used to set this minimum distance for the first time. Various methods can be used to generate such a variable thickness. Without restriction, for example, an area of a spiral wall in which a thicker coating is desired can be coated several times, or, for example, in the case of spray coating, the feed speed of a spray head can be reduced for these areas.

Fig. 1

ein Ausführungsbeispiel einer erfindungsgemäßen Scrollvakuumpumpe in einer Schnittansicht,

Fig. 2

eine Schnittansicht eines Pumpsystems einer erfindungsgemäßen Scrollvakuumpumpe, und

Fig. 3

eine schematische Darstellung zur Erläuterung minimalen Abstände im Spiralteil und in zwei Kreisteilen.

The invention is described below by way of example with reference to the drawings, each of which shows schematically:

Fig. 1

an embodiment of a scroll vacuum pump according to the invention in a sectional view,

Fig. 2

a sectional view of a pumping system of a scroll vacuum pump according to the invention, and

Fig. 3

a schematic representation to explain minimum distances in the spiral part and in two circular parts.

Fig. 1 , 2 show schematically the structure of a scroll vacuum pump 10 according to the invention. In Fig. 1 a sectional view of an entire scroll vacuum pump 10 is shown, in Fig. 2 a sectional view of a pumping system 20 of the scroll vacuum pump 10 according to the invention from Fig. 1 . In the following, both Fig. 1 , 2 described together, with the different representations being discussed separately.

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 in a pumping manner 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.

At the front end of a pump housing 28 of the scroll vacuum pump 10 is the pump system 20 with the fixed spiral component 30 and the movable spiral component 40. The fixed 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 hood that is also attached to the pump housing 28.

The movable scroll component 40 comprises an orbiter carrier 42, the fixed scroll 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, 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.

This forms a radially central spiral part 100 and two radially outwardly adjoining circular parts 200, 300, see in particular Fig. 2 The two circular parts 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 parts are connected to the inlet end 102 of the spiral part 100 (not shown).

Between the respective walls 110, 210, 310 and walls 122, 124, 222, 224, 322, 324 of the grooves 120, 220, 320 (cf. Fig. 3 ) crescent-shaped volumes or pockets form. Due to the wobbling movement 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 parts 200, 300 and in the spiral part 100, as a result of which a fluid to be conveyed, usually a gas, is conveyed from the inlet end 202, 302 of the circular parts 200, 300 to their outlet end 204, 304, further to the inlet end 102 of the spiral part 100 and finally to its outlet end 104.

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 ). By means of such a coating 50, for example, friction in the pump system 20 can be reduced and/or the resistance, in particular of the walls 110, 210, 310, to reactive or aggressive gases can be increased. 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, wherein the latter also for a setting of minimum distances 130, 132, 134, 136, 230, 323, 330, 332 (cf. Fig. 3 ) can be used.

In Fig. 3 are for the Fig. 1 , 2 The scroll vacuum pump 10 shown comprises the spiral part 100 (Figure A), the circular part 200 (Figure B) and the further circular part 300 (Figure C), each along its extension between the inlet ends 102, 202, 302 (on the right in the figures) and their outlet ends 104, 204, 304 (on the left in the figures). The selected illustration shows, for each position along this extension, the minimum possible distances 130, 132, 134, 136, 230, 232, 330, 323, which are achieved with a corresponding relative positioning of the orbiter carrier 42 to the stator carrier 32 (cf. 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 between the circular wall 210 and the walls 222, 224 of the circular groove 220, whereby the previously described pockets are formed.

The distances 130, 132, 134, 136, 230, 232, 330, 332 shown are for a thermally cold state of the scroll vacuum pump 10. 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 occurring during operation, the respective walls 110, 210, 310 are displaced radially outward, the further they are from a center.

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 a Outer side 116 of the spiral wall 110 and a radially outer wall 124 of the spiral groove 120, 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 outward (cf. Fig. 2 ). During continuous operation of the scroll vacuum pump 10, i.e. after the temperature rise at a then constant temperature, constant inner minimum distances 130, 134 and outer minimum distances 132, 136 preferably result.

Figures B and C show the situation for the circular parts 200 and 300, respectively. In contrast to the spiral part 100 (Figure A), the circular walls 210 and 310 are essentially located at a constant radius. For this reason, the values of the minimum inner distances 230 and 330, each determined analogously to the spiral part 100, between an inner side 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, are identical at the respective inlet end 202 and 302 and at the respective outlet end 204 and 304. 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 outer wall 224, 324 of the respective circular groove 220, 320.

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 circle part 300 assume the same value.

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.

In order 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.

In summary, the values of the minimum distances 130, 132, 134, 136, 230, 232, 330, 332 are selected such that they compensate for a relative change in temperature of the respective walls 110, 210, 310. At the same time, they are not selected too small to prevent the walls 110, 210, 310 from sticking in the corresponding grooves 120, 220, 320 during a cold start.

List of reference symbols

10

Scroll vacuum pump

20

Pump system

22

drive shaft

24

Eccentric section

26

drive motor

28

Pump housing

30

fixed spiral component

32

Stator carrier

40

movable spiral component

42

Orbiter carrier

50

Coating

100

Spiral part

102

Admitting

104

Omitting

110

Spiral wall

112

Wall thickness

114

inside

116

outside

120

spiral groove

122

inner wall

124

exterior wall

130

radial inner minimum distance (inlet end)

132

radial outer minimum distance (inlet end

134

radial inner minimum distance (outlet end)

136

radial outer minimum distance (outlet end)

200

part of a circle

202

Admitting

204

Omitting

210

circular wall

212

Wall thickness

214

inside

216

outside

220

circular groove

222

inner wall

224

exterior wall

230

radial inner minimum distance

232

radial outer minimum distance

300

further part of the district

302

Admitting

304

Omitting

310

further circular wall

312

Wall thickness

314

inside

316

outside

320

further circular groove

322

inner wall

324

exterior wall

330

radial inner minimum distance

332

radial outer minimum distance

Claims (15)

Scroll vacuum pump (10) with - a pumping system (20) comprising a fixed spiral component (30) and a movable spiral component (40) cooperating with the latter for pumping purposes, - a drive shaft (22) rotating about an axis of rotation during operation, with 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 fixed spiral component (30) forms a circular circular part (200) and a spiral spiral part (100) radially inwardly adjoining the circular part (200), 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 connected to 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 pumping system (20) a minimum radial distance (230) between a radially inner inside (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 outside (214) of the circular wall (210) and a radially outer outside wall (224) of the circular groove (220). 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). 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). 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). Scroll vacuum pump (10) according to claim 4, wherein the inlet ends (202, 302) and the outlet ends (204, 304) of the circuit part (200) and the further circuit part (300) are each connected and thereby the circuit part (200) and the further circuit part (300) are connected in parallel, or wherein the outlet end (304) of the further circuit part (300) is connected to the inlet end (202) of the circuit part (200) and thereby the circuit part (200) and the further circuit part (300) are connected in series. 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). 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. 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. Scroll vacuum pump (10) according to claim 8,
wherein in a thermally cold state of the pump 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). Scroll vacuum pump (10) according to one of the preceding claims, wherein in a thermally cold state of the pump 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 pump 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. 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 pump 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. 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. 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). 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). 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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