Vacuum pump with an inlet opening extending axially over a pump element

Abstract

A vacuum pump comprises a rotor with pump-active elements and an axis of rotation around which the pump-active elements rotate during operation of the vacuum pump and which defines an axial direction, as well as an inlet opening arranged in a housing of the vacuum pump. The inlet opening comprises an open region extending outside the pump-active elements of the rotor and adjacent to them in the axial direction, and an overlap region in which the inlet opening extends at least partially in the axial direction over one of the pump-active elements of the rotor.

Description

[0001] The invention relates to a vacuum pump, in particular a turbomolecular pump, which comprises a rotor with pump-active elements and an inlet opening arranged in a housing of the vacuum pump.

[0002] Vacuum pumps often require a special design of their inlet area to integrate the vacuum pump into a vacuum system as desired. However, a special design of the vacuum pump's inlet area can lead to limitations in the vacuum pump's suction capacity.

[0003] Furthermore, in so-called differential pumping, both a main inlet of the vacuum pump and a side inlet or port between pumping stages can be used. Such a side inlet, located, for example, in a housing wall of the vacuum pump, can limit the pumping capacity of the vacuum pump due to its limited opening area.

[0004] From JP H07 189984 A a vacuum pump with the features according to the preamble of claim 1 is known.

[0005] DE 601 01 898 T2 describes a vacuum pump with features according to a similar technology, in which, however, an axial length of an inlet opening or of its overlap region with a pump-active element of the vacuum pump on an outer side of a housing of the vacuum pump is greater than the corresponding axial length on an inner side of the housing.

[0006] US 2007 / 0031263 A1 describes a similar vacuum pump.

[0007] A similar vacuum pump is also described in DE 10 2008 013 142 A1.

[0008] US 9 309 892 B2 also describes a similar vacuum pump.

[0009] An object of the invention is to provide a vacuum pump which has a high suction capacity despite special requirements regarding its inlet area.

[0010] This object is achieved by a vacuum pump having the features of claim 1. Advantageous developments of the invention are specified in the subclaims, the description, and the drawings.

[0011] The vacuum pump, which is particularly designed as a turbomolecular pump, comprises a rotor having pumping elements and a rotational axis around which the pumping elements rotate during operation of the vacuum pump and which defines an axial direction, and an inlet opening arranged in a housing of the vacuum pump. The inlet opening comprises an open region extending outside the pumping elements of the rotor and adjacent to them in the axial direction, and an overlap region in which the inlet opening extends at least partially over one of the pumping elements of the rotor in the axial direction.

[0012] The pumping element of the rotor can, for example, be a rotor disk if the vacuum pump is designed as a turbomolecular pump. Furthermore, the axial direction can extend, for example, from a rough or medium vacuum side of the vacuum pump to a high vacuum side or inlet side of the vacuum pump.

[0013] The vacuum pump according to the invention is characterized in that the inlet opening comprises both the open area and the overlap area, which extends into the space of the active pumping elements. As a result, the inlet opening is larger than that of conventional vacuum pumps due to the overlap area. The larger size of the inlet opening compared to conventional vacuum pumps increases their pumping capacity.

[0014] The inlet opening further has, in the overlap region, an inner edge on an inner side of the vacuum pump housing and an outer edge on an outer side of the housing. The inner edge and the outer edge of the inlet opening are spaced apart in the axial direction in the overlap region. As a result, the overlap region has a greater axial length on the inner side of the housing than on the outer side of the housing. In other words, a boundary surface of the inlet opening in the overlap region runs obliquely from the outer edge to the inner edge of the overlap region, with the inner edge being further away from the open region than the outer edge. Such an arrangement allows the inlet opening to be extended into the overlap region even if, for example, dimensions on the outer edge of the inlet opening or of the vacuum pump housing are specified for the axial direction or must not be exceeded.

[0015] Furthermore, the inlet opening extends within the overlap region in the axial direction over at least half the axial length of one of the pumping elements of the rotor. Such an extension of the inlet opening, i.e., over half the axial length of the first pumping element of the rotor in the axial direction, represents a lower limit for the extension of the inlet opening in order to achieve a practically relevant increase in the pumping speed of the vacuum pump.

[0016] According to one embodiment, the inlet opening within the overlap region can extend in the axial direction completely over the axial length of one of the pump-active elements of the rotor. The inlet opening can thus be extended in the axial direction over the entire first pump-active element of the rotor or, in the case of a turbomolecular pump, over the first rotor disk. This allows a maximum increase in the pumping speed to be achieved without significantly reducing the compression of the rotor disk and without impairing the operation of the rotor or the vacuum pump. The extension of the inlet opening over the entire first pump-active element of the rotor in the axial direction thus represents an upper limit for the extension of the inlet opening in the axial direction.In such an embodiment, an edge of the inlet opening can be located in the axial direction near a first stator element of the vacuum pump, which is adjacent to the first pump-active element of the rotor.

[0017] In an alternative embodiment not claimed, however, the inlet opening can extend within the overlapping area in the axial direction over less than the full axial length of one of the pump-active elements of the rotor. The safety during operation of the vacuum pump can be improved by means of such an embodiment, in particular in the event of a malfunction in which one of the pump-active elements of the rotor, over which the inlet opening only partially extends, breaks away from the rotor. Since the inlet opening in the present embodiment does not extend over the full axial

[0018] There is a section of the vacuum pump housing over which the pumping element extends in the axial direction, but not the inlet opening. This section of the housing can form a barrier for the pumping element if it breaks off. This can at least partially prevent fragments of the pumping element from reaching an area outside the vacuum pump's inlet opening.

[0019] According to the invention, an axial length of the open region is greater than an axial length of the overlay region.

[0020] Furthermore, the open region of the inlet opening can have a length in the axial direction that is smaller than or equal to a diameter of the pump-active elements. If the pump-active elements are designed, for example, as rotor disks of a turbomolecular pump, they can have the same diameter. Thus, the axial length of the open region of the inlet opening can be smaller than the diameter of the pump-active element or the first rotor disk over which the inlet opening extends in the overlap region. By limiting the axial length of the overlap region relative to the open region of the inlet opening and limiting the axial length of the open region, the operational reliability of the vacuum pump can be improved.

[0021] According to an unclaimed example, the inner edge and the outer edge of the inlet opening can be arranged at the same height in the axial direction. In this embodiment, the inner edge and the outer edge of the inlet opening in the overlap region can thus be arranged at a nearly identical position in the axial direction. This can facilitate the manufacture of the inlet opening.

[0022] The outer edge of the inlet opening can be arranged in the overlap region at the same axial height as an axial end of the pump-active element adjacent to the open region of the inlet opening, over which the inlet opening extends in the overlap region. In other words, the outer edge of the inlet opening in the overlap region can be almost flush with the axial end of the first pump-active element, while the inner edge of the inlet opening in the overlap region is shifted in the axial direction into the region of the first pump-active element. As a result, the inlet opening can only overlap the pump-active element on the inside of the housing, so that the extension of the inlet opening into the overlap region is not visible from the outside of the pump.

[0023] The inner edge of the inlet opening in the overlap region can further be connected to the outer edge via one or more surfaces that have a rectilinear profile in an axial cross-section. Such rectilinear surfaces can facilitate the manufacture of the inlet opening. Alternatively, the inner edge can be connected to the outer edge via one or more surfaces, at least one of which is curved. Such a curved surface can, for example, have a predefined radius. By curving one or more surfaces between the inner and outer edges of the overlap region, the extent of the overlap region can be optimized.

[0024] Furthermore, a distance between the inner edge and the outer edge in the axial direction can be greater than half of an axial length over which the pump-active element extends. In this embodiment, the pump-active element is again the one of the pump-active elements over which the overlap region of the inlet opening extends at least partially. Half of the axial length of the pump-active element can thus again specify a lower limit for the expansion of the inlet opening, wherein this expansion is defined by the inner edge of the overlap region and its distance from the outer edge of the overlap region and optionally by a displacement of the outer edge relative to the open region in the axial direction.

[0025] The surface or surfaces between the inner and outer edges of the overlay region can thus comprise one or more flat surfaces, one or more chamfers or bevels, one or more radii, or a combination of these. This allows the extension of the inlet opening in the form of the overlay region to be adapted, for example, to specifications regarding the dimensions of the inlet opening.

[0026] According to a further embodiment, the inlet opening can be arranged laterally on the housing of the vacuum pump and extend parallel to the rotor's axis of rotation in the axial direction. In this embodiment, a gas flow through the inlet opening runs perpendicular to the axial direction defined by the rotor's axis of rotation. The inlet opening arranged laterally on the housing can enable special installation positions of the vacuum pump, in which, for example, the inlet opening of the vacuum pump is to be arranged in a predefined spatial area.

[0027] The vacuum pump may further include an additional inlet port at one axial end of the rotor on its low-pressure side. Such a vacuum pump is also referred to as a split-flow vacuum pump, which can accommodate an inlet flow at different positions on the housing, thus enabling differential pumping.

[0028] The inlet opening of the vacuum pump can also be arranged at an axial end of the rotor. This axial end of the rotor can, for example, be located on a low-pressure or high-vacuum side of the rotor and the vacuum pump. Alternatively or additionally, the inlet opening or a further inlet opening can be arranged in an axial region of the housing between axial ends of the rotor. Such an arrangement of an inlet opening is also referred to as an interstage port, in which the inlet opening is located between pumping stages, i.e., at a predetermined position between an axial end on the low-pressure or high-vacuum side of the rotor and an opposite axial end on a high-pressure side of the rotor.

[0029] The invention is described below by way of example using advantageous embodiments with reference to the accompanying figures. They show, schematically: Fig. 1 is a cross-sectional view of a portion of a vacuum pump according to the prior art, Fig. 2 is a cross-sectional view of a portion of a vacuum pump according to an example, Fig. 3 is a cross-sectional view of a portion of a vacuum pump according to an embodiment of the invention, Fig. 4 is a perspective view of a portion of a vacuum pump according to the prior art, and Fig. 5 is a perspective view of a portion of a vacuum pump.

[0030] Fig. 1 shows a cross-sectional view of a portion of a vacuum pump 100 configured as a turbomolecular pump. The vacuum pump 100 comprises a housing 110 having an inlet opening 112 for the vacuum pump 100, and a rotor 120 having a rotational axis 122 and a plurality of pumping elements 124 configured as rotor disks of the turbomolecular pump. The vacuum pump 100 further comprises a stator 130 having pumping elements 132 in the form of stator disks.

[0031] The inlet opening 112 extends in the axial direction, i.e., parallel to the axis of rotation 122 of the rotor 120, which defines the axial direction, over an open region 140 that is free of the pump-active elements 124, 132. The open region 140 of the inlet opening 112 thus extends outside the pump-active elements or rotor disks 124 of the rotor 120 and borders on them in the axial direction, i.e., on a first rotor disk 124-1 of the rotor disks or pump-active elements 124 of the rotor 120. The first pump-active element or the first rotor disk 124-1 of the rotor 120 further has an axial end or an axial edge 125 that borders the open region 140 of the inlet opening 112. A corresponding edge of the inlet opening 112 is aligned almost flush with the axial end 125 of the first pumping element 124-1.

[0032] The inlet opening 112 of the vacuum pump 100 according to the prior art thus ends almost flush with an edge of the first rotor disk 124-1 in the axial direction. In the axial direction, the inlet opening 112 therefore has an axial length or port height 142, which is predetermined according to the conditions and requirements when installing the vacuum pump 100 in a vacuum system. In an exemplary vacuum pump 100, the port height 142 or the axial length is 17.75 mm.

[0033] Fig. 2 shows a cross-sectional view of a portion of a vacuum pump 200 according to a non-claimed example. The vacuum pump 200 also includes a housing 110 and a rotor 120, as described above in connection with Fig. 1 All elements described in Fig. 2 with the same reference numerals as in Fig. 1 are identical or similar to the elements described therein and are not described again below.

[0034] From the Fig. 1 Vacuum pump 100 shown differs from vacuum pump 200 Fig. 2 in that it has an inlet opening 212 which, in addition to the above-described open region 140, comprises an overlay region 214 in which the inlet opening 212 extends in the axial direction over one of the pump-active elements 124 of the rotor 120, i.e., over the first rotor disk 124-1. Specifically, the overlay region 214 extends completely over an axial length of the pump-active element 124 of the rotor 120 or over a complete height of the first rotor disk 124-1 in the axial direction, so that an axial length 216 of the overlay region 214 corresponds to the height of the first rotor disk 124-1 or its axial length.

[0035] The inlet opening 212 has, in the overlay region 214, an inner edge 220 on an inner side of the housing 110 and an outer edge 230 on an outer side of the housing 110. The inner edge 220 and the outer edge 230 are in the embodiment of Fig. 2 arranged at the same height in the axial direction. In other words, the inner edge 220 and the outer edge 230 are in one plane or in the sectional view of Fig. 2 arranged on a straight line perpendicular to the rotational axis 122 of the rotor 120. This straight line, which extends over the inner edge 220 and the outer edge 230 of the overlay region 214, also runs along a rear end of the first rotor disk 124-1, which is opposite the front axial end 125, which in turn is adjacent to the open region 140.

[0036] As explained below in connection with Fig. 4 und 5 As will be explained in more detail, the enlargement of the inlet opening 212 from Fig. 2 due to the additional overlay area 214 compared to the inlet opening 112 of the vacuum pump 100 of Fig. 1 to an increased pumping speed of the vacuum pump 200. The enlargement of the inlet opening 212 does lead to a backflow of the gas that is to be conveyed by means of the rotor 120 via the inlet opening 212 and transported out of a recipient (not shown) connected to it. The backflow can cause a compression loss of the rotor 120, and the pumping speed may not be increased but reduced if the overlay region 214 is extended too far, for example, beyond the first rotor disk 124-1. However, it has been found that the expected backflow has almost no influence on the pumping speed and a tolerable compression loss occurs as long as the axial length 216 of the overlay region 214 is equal to or smaller than the height or axial length of the first rotor disk 124-1.

[0037] However, the axial length 142 of the open region 140 is greater than the axial length 216 of the overlay region 214. Furthermore, the axial length 142 of the open region 140 is smaller than a diameter D of the first pump-active element of the rotor or the first rotor disk 124-1. In Fig. 2 For better orientation, a radius R of the first rotor disk 124-1 is shown, which is known to be half the size of the diameter D. The above relationships between the axial lengths 142, 216 and between the axial length 142 and the diameter D can ensure the stability and operational reliability of the vacuum pump 200.

[0038] Fig. 3 shows a cross-sectional view of a portion of a vacuum pump 300 according to an embodiment of the invention. The embodiment of Fig. 3 differs from that in Fig. 2 shown vacuum pump 200 in that the vacuum pump 300 comprises an inlet opening 312 with the open area 140 as described above and with an overlay area 314 which, in contrast to the overlay area 214 of Fig. 2 a chamfer or an inclined surface 315. Due to the inclined surface 315, the overlay region 314 of the inlet opening 312 has an axial length 316 that is smaller than an axial length 318 of the pump-active element 124-1 of the rotor 120 or smaller than the height of the first rotor disk 124-1.

[0039] The inclined surface 315 has an inner edge 320 on the inside of the housing 110, which is spaced axially from an outer edge 330 of the overlay region 314 on the outside of the housing 110. The outer edge 330 is located at the same axial height or at the same axial position as the axial end 125 of the first pump-active element or the first rotor disk 124-1, which adjoins the open region 140. The embodiment of Fig. 3 allows an extension of the inlet opening 312 by the overlay area 314 even if a predetermined dimension, for example a specification for the axial length or height 142 of the inlet opening 312, has to be maintained on the outside of the housing 110.

[0040] To effectively increase the suction capacity of the vacuum pumps 200, 300, the axial length 216, 316 of the overlap region 214, 314 must be selected such that it is greater than half the axial length or height 318 of the first rotor disk 124-1. On the other hand, the axial length 216, 316 of the overlap region 214, 314 must not be greater than the axial length or height 318 of the first rotor disk 124-1 in order not to impair the operational reliability of the vacuum pump 200, 300.

[0041] For the execution of Fig. 3 This means that the axial length of the chamfer 315, ie the axial distance between the inner edge 320 and the outer edge 330, is greater than half the axial length or height of the first rotor disk 124-1. As in Fig. 3 As can be seen, the inner and outer axial edges 320, 330 are connected to one another on the one hand by the chamfer or inclined surface 315 and on the other hand by a further flat surface which runs perpendicular to the axis of rotation 122 of the rotor 120 and thus perpendicular to the axial direction.

[0042] Instead of the Fig. 3 However, in an alternative embodiment, the overlay region 314 may be defined by a curved surface (not shown) having a predefined radius. If the inner edge 320 and the outer edge 330 of the overlay region 314 are as shown in Fig. 3 are spaced apart from each other, any combination of flat and curved surfaces may be provided between the edges 320, 330 of the overlay region 314 to define the overlay region 314.

[0043] Fig. 4 shows a perspective view of a portion of the vacuum pump 100 of Fig. 1 according to the state of the art, while Fig. 5 a perspective view of a corresponding portion of the vacuum pump 200 of Fig. 2 shows. The respective inlet openings 112, 212, which are configured differently, can be seen in respective sections of the housing 110 of the vacuum pump 100, 200. Furthermore, a section of the rotor 120 is shown in each case, with a stator disk 132 depicted between the first rotor disk 124-1 and the next rotor disk 124.

[0044] In the vacuum pump 100 according to the prior art, the inlet opening 112 has a length 142 in the axial direction parallel to the axis of rotation 122 of the rotor 120 such that a rear edge 410 of the inlet opening 112 is arranged in the region of the axial end 125 of the first rotor disk 124-1 (cf. also Fig. 1 ). In the concrete example of Fig. 4 is an axial length 412 in the outer region of the inlet opening 112, which is approximately Fig. 2 illustrated axial length 142 of the inlet opening 112, 17.75 mm.

[0045] In the vacuum pump 200, whose inlet opening 212 is in Fig. 5 As shown in perspective, the inlet opening 212 is in contrast to the inlet opening 112 of the vacuum pump 100 of Fig. 4 in the axial direction by the length 216 of the overlay area 214 (cf. Fig. 2 ), so that the overlay region 214 overlies the first rotor disk 124-1 of the rotor 120 in the axial direction. Conversely, the first rotor disk 124-1 of the rotor 120 in the vacuum pump 200 protrudes from Fig. 5 in the axial direction into the area of ​​the inlet opening 212. In the embodiment of Fig. 5 the axial length 216 of the overlay area 214 is approximately 6.9 mm, so that in comparison to Fig. 4 a total axial length 516 in the outer region of the enlarged inlet opening 212 which is approximately 24.65 mm.

[0046] For the vacuum pumps 100, 200, for the respective sections in Fig. 4 As shown in Figures 1 and 5, respectively, simulation calculations were performed for the pumping speed of the respective vacuum pumps 100 and 200 using the dimensions mentioned above. For the simulation calculation, nitrogen was assumed to be the gas to be pumped at an ambient temperature of 20°C with a particle number of 20,000. Furthermore, a speed of 1100 Hz was used for the rotor 120 of the respective vacuum pumps 100 and 200.

[0047] Furthermore, it was assumed that the vacuum pumps 100, 200 are designed as split-flow turbomolecular pumps. This means that the vacuum pumps 100, 200 each have, in addition to the respective inlet opening 112, 212, further inlet openings (not shown), which, for example, like the inlet opening 112, 212, are arranged laterally on the housing 110 of the respective vacuum pump 100, 200. Between the inlet opening 112, 212 and the first rotor disk 124-1 there is also a protective grid (not shown), for which a permeability of 82.6% was assumed. The inlet opening 112 or 212 is thus arranged laterally in the respective housing 110 of the vacuum pump 100, 200 in the region of the axial end 125 of the first rotor disk 124-1. The inlet opening 112 or 212 can therefore also be referred to as a high vacuum port. Alternatively, the inlet opening 112 or212 may also be designed as an interstage port arranged between pumping stages of the vacuum pump 100, 200.

[0048] For the vacuum pump 100 from Fig. 4 With the inlet opening 112, the simulation calculation yielded an effective suction capacity of 106 liters per second, while the simulation calculation for the vacuum pump 200 of Fig. 5 with the enlarged inlet opening 212 resulted in an effective suction capacity of 136 liters per second. The enlargement of the inlet opening 212 by about 7 mm compared to the inlet opening 112 of Fig. 4 This led to a significant increase in the effective suction capacity of the vacuum pump 200. Bezugszeichenliste

[0049] 100Vacuum pump according to the prior art 110Housing 112Inlet opening 120Rotor 122Axis of rotation 124Pump-active element of the rotor, rotor disk 124-1First rotor disk 125Axial end of the first rotor disk 130Stator 132Pump-active element of the stator, stator disk 140Open area 142Axial length of the open area 200Vacuum pump according to an example 212Inlet opening 214Overlay area 216Axial length of the overlay area 220Inner edge of the overlay area 230Outer edge of the overlay area 300Vacuum pump according to an embodiment of the invention 312Inlet opening 314Overlay area 315Sloped surface 316Axial length of the overlay area 318Axial length or height of the first rotor disk 320Inner edge of the Overlay area 330Outer edge of the overlay area 410Rear edge of the inlet opening 412Axial length in the outer area of ​​the inlet opening 516Total axial length of the extended inlet opening DDiameter of the rotor RRadius of the rotor

Claims

1. A vacuum pump (300), in particular a turbomolecular pump, comprising a rotor (120) which has pump-active elements (124) and an axis of rotation (122) about which the pump-active elements (124) rotate during operation of the vacuum pump (300) and which defines an axial direction, and an inlet opening (312) which is arranged in a housing (110) of the vacuum pump (300), wherein the inlet opening (312) comprises an open region (140), which extends outside the pump-active elements (124) of the rotor (120) and adjoins them in the axial direction, and an overlap region (314) in which the inlet opening (312) extends at least partly over one of the pump-active elements (124) of the rotor (120) in the axial direction, the inlet opening (312) has, in the overlap region (314), an inner margin (320) at an inner side of the housing (110) and an outer margin (330) at an outer side of the housing (110), the overlap region (314) has an obliquely extending boundary surface (315) between the outer margin (330) and the inner margin (320), the inner margin (320) and the outer margin (330) are spaced apart in the axial direction such that the overlap region (314) has a greater axial length (316) at the inner side of the housing (110) than at the outer side of the housing (110), and the axial length (316) of the overlap region (314) is greater than half the axial length of the one of the pump-active elements (124) of the rotor (120) over which the inlet opening (312) extends in the overlap region (314), characterized in that an axial length (142) of the open region (140) is greater than the axial length (316) of the overlap region (314).

2. A vacuum pump (300) according to claim 1, wherein, within the overlap region (314), the inlet opening (312) extends completely over an axial length (318) of the one of the pump-active elements (124) of the rotor (120) in the axial direction.

3. A vacuum pump (300) according to claim 1 or 2, wherein the open region (140) of the inlet opening (312) has a length (142) in the axial direction that is smaller than or equal to a diameter (D) of the pump-active elements (124).

4. A vacuum pump (300) according to any one of the claims 1 to 3, wherein the outer margin (330) of the inlet opening (312) in the overlap region (314) is arranged at the same axial height as an axial end (125) of the pump-active element (124-1) which adjoins the open region (140) of the inlet opening (312) and over which the inlet opening (312) extends in the overlap region (314).

5. A vacuum pump (300) according to any one of the claims 1 to 4, wherein the inner margin (320) is connected to the outer margin (330) via one or more surfaces (315) which have a rectilinear course in an axial cross-section.

6. A vacuum pump (300) according to any one of the claims 1 to 5, wherein the inner margin (320) is connected to the outer margin (330) via one or more surfaces, of which at least one surface is curved.

7. A vacuum pump (300) according to any one of the claims 1 to 6, wherein a spacing (316) between the inner margin (320) and the outer margin (330) in the axial direction is greater than half an axial length (318) over which the pump-active element (124) extends.

8. A vacuum pump (300) according to any one of the claims 1 to 7, wherein the inlet opening (312) is laterally arranged at the housing (110) and extends parallel to the axis of rotation (122) of the rotor (120) in the axial direction.

9. A vacuum pump (300) according to any one of the claims 1 to 8, wherein the vacuum pump (300) has an additional inlet opening at an axial end of the rotor (120) at a low-pressure side of the rotor (120).

10. A vacuum pump (300) according to any one of the claims 1 to 9, wherein the inlet opening (312) is arranged at an axial end of the rotor (120).

11. A vacuum pump (300) according to any one of the claims 1 to 10, wherein the inlet opening (312) is arranged between axial ends of the rotor (120) in an axial region of the housing (110).

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