High-speed motor

Abstract

An electric machine comprises a stator (1) having a stator body (25) supporting an electric stator (3) and a rotor (5) supported by a bearing comprising a radial bearing portion (17) forming a radial gas bearing and an axial bearing portion (12) forming an axial gas bearing, the stator-side portion of these bearing portions comprising an axial bearing assembly (11) and a bushing (18). The bushing (18) is aligned with respect to the stator body (25) by aligning the bushing (18) with respect to a reference body (143) and by aligning the reference body (143) with respect to the stator body (25). The rotor (5) is removable from the stator body (25) while retaining the reference body (143) in situ.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of electric machines, in particular to high speed electric machines with gas bearings. BACKGROUND

[0002] Electric motors generally comprise a rotor and a stator, the stator comprising a stator body supporting and housing the electric stator and bearings. The position of the bearings relative to the stator body can be defined by bearing flanges of the stator body. Typically, there are two journal bearings, which are typically located on opposite sides of the stator. In this case, the alignment accuracy of the bearings is mainly defined by the machining accuracy of the bearing flanges and the stator body. For fluid film bearings, in particular gas bearings, accurate alignment is crucial and such an arrangement typically requires special measures, such as self-alignment or flexible bushing mounting, or machining of the bearing pairs after assembly (e.g. reaming). Alternatively, the journal bearings can be arranged on the same side of the stator. Such an arrangement is typically referred to as a suspended motor design. With a suspended design, the two journal bearings can be integrated into a single part, thus making it easier to achieve accurate bearing alignment. However, this approach typically results in a longer rotor and thus more critical rotor dynamics. Furthermore, the windage losses caused by air resistance increase, negatively impacting the overall motor efficiency.

[0003] WO 2017 / 202941 A1 and WO 2020 / 002509 A1 (equivalent to US 2021 / 242747 A1) show a bearing structure for a suspended high speed electric machine. According to WO 2020 / 002509 A1, the first stator disc (14c) and the second stator disc (14d) of the axial bearing assembly (11) hold the bushings in place and pressed against the alignment surfaces, and a spacer element (15) is arranged between the two stator discs (14c, 14d) pressed against each other by a disc spring (14b). The disc spring (14b) in turn is compressed in axial direction by a compressor housing (14a). The first stator disc (14c) serves as a reference body, which is aligned relative to the stator body by pressing against the stator body. When assembling the rotor, the bushings are aligned in the stator, deforming the elastic O-rings (21) between the bushings and the stator body. The axis of the bushings needs to be aligned in radial direction in order to be concentric with the electromagnetic components of the machine. An axial compression force is applied to the first stator disc, which keeps the bushings in an aligned state. If the rotor needs to be removed or replaced, the compressor housing and the second stator disc need to be removed. This removes the compression force on the first stator disc, in turn causing the bushings to become misaligned. Thus, removing the rotor causes the first stator disc, as the reference body, to change its position. When reassembling the rotor, the radial position of the bushings needs to be readjusted. This requires special mechanical equipment and can require removal of the entire machine from the factory where it is installed.

[0004] JPH066739U shows a journal bearing in which a radial journal bearing comprises two tubular sleeve cylinders, each of which is elastically suspended by an O-ring. One of the sleeve cylinders comprises a bearing plate for an axial bearing at one end thereof. The axial force acting on the axial bearing plate compresses the elastic ring at the opposite end of the sleeve cylinder. SUMMARY

[0005] One of the problems of prior art machines is the complexity of disassembly and reassembly.

[0006] There is a need for electric machines suitable for high speed applications and which simplify disassembly and reassembly.

[0007] It is therefore an object of the present invention to create a high speed electric machine of the type initially mentioned which overcomes the above mentioned drawbacks.

[0008] This object is achieved by a high speed electric machine according to a first aspect of the invention.

[0009] It is a further object of the present invention to create a bushing structure for such high speed electric machines which allows a rigid, high precision alignment of the bushing with a reference body.

[0010] This object is achieved by a bushing structure for a high speed electric machine according to a second aspect of the invention.

[0011] According to a first aspect, there is provided an electric machine having the following features.

[0012] The electric machine comprises a stator having a stator body supporting the electric stator and a rotor supported by bearings comprising radial bearing sites forming radial gas bearings and axial bearing sites forming axial gas bearings, the stator side parts of the bearing sites comprising an axial bearing assembly and a bushing. The bushing is aligned with respect to the stator body by aligning the bushing with respect to a reference body and by aligning the reference body with respect to the stator body. The reference body is aligned with respect to the stator body by pressing a first reference surface of the reference body against a stator body reference surface of the stator body. The rotor is removable from the stator body while leaving the reference body in place.

[0013] In other words, the reference body can remain attached to the stator body when the rotor is removed. Removing the rotor can require disassembly or removal of the axial bearing assembly. Therefore, in other words, it is the case in some embodiments that the reference body remains attached to the stator body when the axial bearing assembly is disassembled. In some embodiments it is the case that the reference body remains attached to the stator body when the axial bearing assembly is removed. Again in other words, the bushing remains in place in the stator body, independent of at least one outer stator disc of the axial bearing assembly.

[0014] Another advantage is that the force required to attach the reference body to the stator body is generally higher than the force required to compress the axial bearing assembly. By using separate fasteners, the requirements to attach and compress the axial bearing assembly are reduced and less space can be used.

[0015] In some embodiments, the sleeve is aligned relative to the reference body by pressing the alignment surface of the sleeve against the second reference surface of the reference body.

[0016] In some embodiments, the alignment surface is pressed against the second reference surface by a force exerted by an axial compensation element compressed between the sleeve structure and the stator body.

[0017] In some embodiments, the sleeve comprises a sleeve flange, and wherein the alignment surface is located at a front side of the sleeve flange, and the axial compensation element is compressed between a rear side of the sleeve flange and the stator body. Thus, the elements constituting the rigid attachment of the sleeve to the stator body, i.e. the first reference surface, the second reference surface, the alignment surface and the axial compensation element, are located at the same end of the sleeve. This end is the end where the axial bearing is located. At the opposite end, the sleeve is not rigidly attached and can move to some extent, so that the sleeve is not deformed by inaccuracies of the stator body.

[0018] In some embodiments, the first reference surface and the stator body reference surface are flat surfaces orthogonal to the axis of rotation of the machine.

[0019] In some embodiments, the alignment surface and the second reference surface are flat surfaces orthogonal to the axis of rotation of the machine.

[0020] In some embodiments, the first axial reference surface and the second reference surface are coplanar.

[0021] The reference body can be flat, delimited by two opposite parallel surfaces. In this case, it can be referred to as a reference plate. This simplifies the manufacturing of the reference body.

[0022] In some embodiments, the sleeve is aligned relative to the reference body by being rigidly attached to the reference body, the sleeve and the reference body together forming a sleeve structure. This allows the sleeve structure to be removed and handled as a whole, without affecting the alignment between the sleeve and the reference body.

[0023] In some embodiments, the reference body and the inner stator disc are the same part. This simplifies the structure of the machine. Thus, the axial bearing assembly comprises a reference body that serves as an inner stator disc and an outer stator disc.

[0024] In some embodiments, the reference body and the inner stator disc are separate parts.

[0025] An axial bearing assembly comprising an inner stator disc and an outer stator disc can be clamped and aligned to a reference body.

[0026] In both cases, where the inner stator disc and the reference body are one and the same part or separate parts, the axial bearing assembly can be held together or compressed by other means, independently of the attachment of the reference body to the stator body. This makes it possible to disassemble the axial bearing assembly without affecting the attachment of the reference body to the stator body. The axial bearing assembly can be removed while leaving the bushing in place and thus without affecting the alignment of the bushing in the stator body.

[0027] In some embodiments, the axial bearing assembly is held together by the impeller housing. This simplifies the structure of the axial bearing assembly, since no additional fastening elements are needed to attach the axial bearing assembly to the stator body.

[0028] In some embodiments, the reference body is pressed against the stator body by a screw.

[0029] In particular, the parts along the screw and / or the parts of the threaded hole in the stator body where the screw is arranged are adjacent to the stator body reference surface without threads.

[0030] This prevents a slight deformation of the stator body in the area of the drilled hole by the thread tension. Furthermore, the non-threaded parts of the screw are longer, so that the screw has a longer part that can elastically expand when the screw is tightened. The non-threaded parts usually have a length of about the nominal diameter of the thread. The diameter of the hole in the stator body in such parts is about 1.2 times the nominal diameter of the thread.

[0031] In some embodiments, deformation of the reference body is prevented by chamfering the side of the through hole in the reference body facing the stator body where the screw is arranged.

[0032] In some embodiments, the head of the screw is sunk into the reference body and a sealing ring, in particular an O-ring, is arranged around the head of the screw to seal the thread. This prevents contamination of the axial bearing by dirt and debris from the threaded area.

[0033] In some embodiments, the reference body is pressed against the stator body by one or more fasteners arranged in one or more radial slots at the outer circumference of the reference body. In particular, the fasteners are fixing rings, more particularly wedge-shaped fixing rings. This enables a space-saving attachment of the reference body and the bushing structure in the stator body, in particular shorter in length along the longitudinal axis when compared to a screw.

[0034] According to a second aspect, which relates to a rigid attachment between the bushing and the reference body, a bushing structure is provided having the following features. The second aspect can be implemented in combination with the first aspect or completely independently.

[0035] In embodiments according to the second aspect, the bushing is rigidly attached to the reference body by the bushing, which comprises a bushing flange, and the bushing flange is held against the reference body by a bushing screw being screwed into the reference body.

[0036] In some embodiments, at least one or more of the following applies:

[0037] • the bushing screw is arranged in an axial channel or groove in the bushing flange or in a connecting ring surrounding the bushing flange and holding the bushing flange,

[0038] • there is a clearance in radial direction between the bushing and the reference body, preferably, wherein the clearance is at least 0.1 mm or at least 0.2 mm or at least 0.4 mm.

[0039] This allows to attach a relatively thick reference body, optionally used as inner stator disc, to the bushing. Such a thick reference body can be required due to the force with which it is pressed against the stator body. The alignment is achieved by pressing the second reference surface of the reference body against the alignment surface of the bushing. The elastic element and / or the clearance in this connection allow to compensate for differences in thermal expansion. The connecting ring distributes the force applied by the bushing screw around the bushing flange. It is advantageous if the bushing and its flange are made of a ceramic material. The connecting ring is typically made of metal.

[0040] In some embodiments, one or more bushing springs are arranged between the bushing flange and the bushing screw and are compressed by the bushing screw.

[0041] The one or more bushing springs allow to compensate for differences in thermal expansion of the bushing flange and the bushing screw. Otherwise, repeated temperature changes can cause the bushing screw to loosen.

[0042] In some embodiments, the bushing is rigidly attached to the reference body by the bushing, which comprises a bushing flange, and the reference body comprises at least one attachment element, a holding site of which is curved to hold the bushing at the bushing flange,

[0043] In some embodiments, at least one or more of the following applies:

[0044] • the at least one attachment element forms part of the reference body or is rigidly attached to the reference body,

[0045] • the at least one attachment element is a cylindrical sleeve and the holding site is an axially extending finger structure.

[0046] The axial direction corresponds to the axis of rotation of the rotor, also referred to as longitudinal direction.

[0047] In some embodiments, the axial bearing assembly is rigidly mounted to the stator body. Optionally, the bushing is rigidly connected to the axial bearing assembly.

[0048] In some embodiments, the bushing is rigidly mounted to the stator body near one end of the bushing. Optionally, the bushing is elastically supported by the stator body near the opposite end of the bushing.

[0049] Thus, the bushing is rigidly attached at one end, e.g. by the axial bearing portion, while the rest of the bushing is elastically suspended - which eliminates or reduces mechanical stress - but can be thermally coupled to the cooling body.

[0050] The journal bearing can be integrated into a single part, thus allowing for easier precise alignment than on separate parts.

[0051] In some embodiments, the radial bearing portion of the bushing extends in the longitudinal direction of the rotational axis, and all bearing elements of the radial bearing portion and the mating rotor bearing surface are located outside the magnetic gap between the electrical stator and the rotor.

[0052] In other words, this means that the machine is suspended, i.e. when looking along the longitudinal axis of the machine, the journal bearing, or the bushing and the cooling body, respectively, are located at different positions than the electrical stator and the permanent magnets.

[0053] Here and throughout the document, the use of the terms "rigid" and "fixed" is opposite to "elastic". An elastic connection has a spring stiffness coefficient or Young's modulus that is at least, e.g. 100 times, 10,000 times or 1,000,000 times larger than a rigid connection.

[0054] A rigid connection is a connection that is designed such that the connected parts do not move relative to each other during normal operation of the machine. Thus, a rigid connection can be established by screwing the parts together or using springs to press them against each other. In this case, the springs are not part of the rigid connection, but provide the force that maintains the rigidity of the connection.

[0055] The elastic support can be an O-ring, typically made of (synthetic) rubber, or a metal spring.

[0056] The term "high speed electric machine" encompasses machines suitable for more than 100,000 revolutions per minute.

[0057] The gas of the gas bearing can be any gas in which the machine is operated, such as air, coolant, natural gas, etc. The gas bearing can be a passive gas bearing or an active gas bearing.

[0058] The bushings can be made of ceramic material or other materials that provide sufficient mechanical stiffness and do not influence the magnetic field in the magnetic air gap. The advantage of ceramic materials is that they are suitable both for gas bearings and can be placed in the magnetic air gap, where they are penetrated by the magnetic field that generates the torque. In general, electrically insulating or low- conductivity materials, such as ceramics, glass-ceramics or technical glasses, plastics, composite materials, mineral materials, etc., can be used to avoid excessive eddy current losses caused by the alternating magnetic air gap field.

[0059] In some embodiments, the electric machine is slotless. In other words, the electric stator comprises air gap windings instead of slot windings. In other embodiments, the electric machine is slotted.

[0060] Generally, the stator body accommodates the electric stator. The "substance-to-substance bond", also called "substance-to-substance joining", is generally realized by shrink fitting or by potting, welding or brazing.

[0061] In some embodiments, the stator flange forms at least a portion of the coolant channel wall. This allows the coolant to effectively cool both the stator body and the cooling body.

[0062] The terms "axially adjacent" and "radially adjacent" are understood to mean "adjacent when looking in the direction of the axis of rotation" and "adjacent when looking in the radial direction", respectively.

[0063] Further embodiments are apparent from the dependent patent claims. BRIEF DESCRIPTION OF DRAWINGS

[0064] The subject matter of the present application will be explained in more detail in the following text with reference to exemplary embodiments shown in the attached drawings, in which:

[0065] Figure 1 : longitudinal section of the bearing site of a machine for a turbocompressor;

[0066] Figure 2 : Figure 1 : subset of elements of the machine for a turbocompressor for aligning the bushings with the stator body;

[0067] Figure 3 : Figure 2 : exploded section of the machine for a turbocompressor;

[0068] Figures 4-5 : retaining ring holding the combined inner stator disc and reference body;

[0069] Figures 6-9 : detail of the attachment of the reference body by screws;

[0070] Figure 10 : bushing structure;

[0071] Figures 11-16 Details of different ways of attaching the bushing to the reference body. DETAILED DESCRIPTION

[0072] In principle, identical or functionally identical parts are provided with the same reference symbols in the Figures.

[0073] Figure 1 A longitudinal section of a bearing site of a machine for a turbo-compressor is shown. The machine comprises a stator 1 and a rotor 5. The stator 1 comprises a stator body 25 in which the rotor 5 is rotatably arranged in bearings comprising a radial bearing site 17 and an axial bearing site 12.

[0074] In the radial bearing site 17, there is a journal bearing with a bearing air gap 7 between the rotor 5 and a bushing 18. The bushing 18 is rigidly attached at one end, close to the axial bearing assembly 11. This proximal attachment also comprises an axial compensation element 20, which can act as a first radial elastic support 21. This proximal attachment defines the alignment of the bushing 18 with respect to the stator body 25. At the opposite distal end, the bushing 18 is elastically supported in the stator body 25 by a second radial elastic support 22. Since the bushing 18 is rigidly attached to the stator body 25 at only one side, the bushing 18 is not affected by deformations of the stator body 25, in particular deformations due to temperature variations.

[0075] In the axial bearing assembly 11, a rotor disc 54 of the rotor is arranged in rotation between an inner stator disc 141 and an outer stator disc 142, separated by a spacer element 15. The inner stator disc 141 acts as a reference body 143 for aligning the bushing 18 with the stator body 25, as described hereafter in Figure 2 and Figure 3 The inner stator disc 141 is attached to the stator body 25 by inner fasteners 161, which in this embodiment are in the form of screws. The axial bearing assembly 11 is attached to the stator body 25 by outer fasteners 162. In this embodiment, these are impeller housing fasteners 62, for holding the impeller housing 61 against the stator body 25, thereby pressing the axial bearing assembly 11 against the stator body 25. In other embodiments, the outer fasteners 162 press the outer stator disc 142 and the intermediate spacer element 15, and optionally the inner stator disc 141, against the stator body 25.

[0076] Since the inner stator disc 141, or more generally the reference body 143, for alignment of the bushing 18 is attached to the stator body 25 and aligned therewith, the rotor 5 can be removed by removing the outer stator disc 142, and the rotor 5 can be refitted without disturbing the alignment of the bushing 18 with respect to the stator body 25.

[0077] The rotor 5 has a shaft 51 driving an impeller 6 arranged inside an impeller housing 61. For the sake of clarity, the motor part to the right of the shown elements is omitted, having an electric stator comprising motor coils and a core, and permanent magnets inside the rotor. Of course, the shown bearing structure can also be implemented in other contexts, without turbo-compressor elements such as the impeller 6 and the impeller housing 61.

[0078] Figure 2 A subset of the elements of Figure 1 is shown, having a reference body 143 for aligning the bushing with the stator body 25. The electric stator 3 is only shown schematically. Figure 3 Elements of Figure 2 are shown in an exploded cross-section. The reference body 143 can serve as the inner stator disc 141, or it can be a separate element (not shown) from the inner stator disc 141. The reference body 143 comprises a first reference surface 144, which is pressed against a stator body reference surface 24 of the stator body 25. This defines an alignment between the reference body 143 and the stator body 25. The reference body 143 comprises a second reference surface 145, which is pressed against an alignment surface 184 of the bushing 18. This defines an alignment between the reference body 143 and the bushing 18. The pressure at both alignments is influenced by one or more fasteners (in this embodiment screws 163), pressing the reference body 143 against the stator body 25 in axial direction, and by one or more axial compensation elements 20 compressed between the bushing 18 and the stator body 25, and thus creating a counter force in opposite direction, pressing the bushing 18 against the reference body 143.

[0079] Figures 4-5 A fastener in the form of a retaining ring 164 is shown, instead of screws 163, for retaining the reference body 143 (in this embodiment also serving as the inner stator disc 141) against the stator body 25. The retaining ring 164 uses less space in axial direction, allowing for a shorter overall length of the machine. The retaining ring 164 can be wedge-shaped, allowing for a certain compliance in axial direction of the fixation.

[0080] Figures 6-9 Details of the attachment of the reference body by screws are shown. They have in common that they serve to avoid deformation of the high-precision stator body reference surface 24 due to forces exerted on the threads of the stator body 25. This can be achieved by providing an initial part of the drill hole into which the screw 163 is screwed, having a larger unthreaded hole, as shown in Figure 6 and Figure 7 Alternatively, this can be achieved by screws 163 having a shank diameter smaller than the thread diameter, as shown in Figure 8As shown. In both cases, the thread engages only at locations remote from the stator body reference surface 24. The unthreaded portion typically has a length of at least 50%, 80%, or 100% of the nominal thread diameter.

[0081] Figure 7 Also shown is an axial compensation element 20 having a washer 26 compressed between the bushing flange 182 of the bushing 18 and the radially inwardly protruding portion of the stator body 25.

[0082] Due to the slender, unthreaded shaft, Figure 8 The screw has a longer section that is elastically stretched when screw 163 is tightened. This increases the range of temperature variations the connector can absorb and prevents the screw from loosening.

[0083] Embodiments without threads along the drilled and / or screw locations also provide a volume for collecting debris generated from thread or threadlocker wear without contaminating the axial bearing. Figure 9 Screw 163 is shown, with an O-ring around its head and between the head and reference body 143. This prevents such contaminants from migrating or escaping from the borehole.

[0084] Figure 10 A bushing structure 181 is shown, including a reference body 143 attached to the bushing 18. They are aligned by a corresponding second reference surface 145 and an alignment surface 184, which are pressed against each other by bushing screws 185. Figure 11 It shows Figure 10 The cross-sectional view shows details of the bushing screw 185. The bushing screw 185 can be arranged in a radial groove in the bushing flange 182, simplifying its manufacture. The bushing screw 185 holds the bushing 18 against the reference body 143 via the bushing flange 182. A connecting ring 187, typically made of metal, is pressed against the bushing flange 182, typically made of ceramic, by the bushing screw 185, and is integral with the rest of the bushing 18. The connecting ring 187 distributes the force of the bushing screw 185 to potentially fragile surfaces of the bushing flange 182. The connecting ring 187 can introduce a degree of elasticity into the stack of components compressed by the bushing screw 185, thus preventing the bushing screw 185 from loosening. For example, the connecting ring 187 can be a leaf spring or a disc spring. In this case, the connecting ring 187 should be referred to as a bushing spring 186. Figure 12 It shows the relationship with Figure 10 and 11 The same basic structure, but more clearly shown, with the connecting ring 187 acting as a bushing spring 186. In all... Figures 10 to 12 In this process, the connecting ring 187 or the bushing spring 186 can be shaped into elastic parts that are compressed and bent by the bushing screw 185 when the bushing screw 185 is tightened.Figure 10 and 11 The bush spring 186 is shown fully compressed, and thus in a flattened state.

[0085] Figure 13 The separate connecting ring 187 and bush spring 186 are shown. The bush flange 182 is shorter in the radial direction, as shown in the previous figure, while the bush screw 185 presses the bush spring 186 against the bush flange 182 near its inner circumference, and against the connecting ring 187 near its outer circumference. The shorter bush makes it easier to manufacture.

[0086] Figure 14 The connecting ring 187 is again shown with the function of the bush spring 186. The inwardly projecting rim around the inner circumference of the connecting ring 187 engages with the bush flange 182. When the connecting ring 187 is screwed against the reference body 143, it can act as a leaf spring.

[0087] Figure 15 The arrangement is shown with a similar structure, but with a different proportion of connecting ring 187 or bush spring 186, in the form of a curved sheet metal in one piece. Figure 14

[0088] Figure 16 The attachment element 188 is shown with axially extending finger-like structures that are curved to hold the bush flange 182 against the reference body 143. The attachment element 188 is shaped as part of the reference body 143. Alternatively (not shown), it can be attached to the reference body 143 by other means. Typically, it is in the form of a ring or annular wall that supports multiple finger-like structures, or the finger-like structures extend independently of the reference body 143, without being connected by a ring.

[0089] While the application has been described in embodiments, it is clear that the application is not limited thereto, but can be embodied and practiced in other various ways within the scope of the claims.​

Claims

1. An electric machine comprising a stator (1) having a stator body (25) supporting an electric stator (3) and a rotor (5) supported by bearings comprising radial bearing portions (17) forming radial gas bearings and axial bearing portions (12) forming axial gas bearings, the stator side portions of these bearing portions comprising an axial bearing assembly (11) and a bushing (18), wherein the bushing (18) is aligned relative to the stator body (25) by aligning the bushing (18) relative to a reference body (143) and by aligning the reference body (143) relative to the stator body (25), wherein the reference body (143) is aligned relative to the stator body (25) by pressing a first reference surface (144) of the reference body (143) against a stator body reference surface (24) of the stator body (25), wherein the rotor (5) can be removed from the stator body (25) while the reference body (143) is left in place.

2. The electric machine according to claim 1, wherein the bushing (18) is aligned relative to the reference body (143) by pressing an alignment surface (184) of the bushing (18) against a second reference surface (145) of the reference body (143).

3. The electric machine according to claim 2, wherein the alignment surface (184) is pressed against the second reference surface (145) by a force exerted by an axial compensation element (20) compressed between the bushing structure (181) and the stator body (25).

4. The electric machine according to claim 3, wherein the bushing (18) comprises a bushing flange (182) and the alignment surface (184) is located at a front side of the bushing flange (182) and the axial compensation element (20) is compressed between a rear side of the bushing flange (182) and the stator body (25).

5. The electric machine according to claim 1, wherein the bushing (18) is aligned relative to the reference body (143) by being rigidly attached to the reference body (143), the bushing (18) and the reference body (143) together forming a bushing structure (181).

6. The electric machine according to any of the preceding claims, wherein the reference body (143) and an inner stator disc (141) are one and the same part.

7. The electric machine according to any of claims 1-5, wherein the reference body (143) and an inner stator disc (141) are separate parts.

8. The electric machine according to any of the preceding claims, wherein the axial bearing assembly (11) is held together by a impeller housing (61).

9. The electric machine according to any of the preceding claims, wherein the reference body (143) is pressed against the stator body (25) by a screw, and In particular, the parts along the screw and / or the parts in which the threaded holes of the screw are arranged in the stator body (25) are adjacent to the stator body reference surface (24) without threads present.

10. Electric machine according to claims 1-8, wherein the reference body (143) is pressed against the stator body (25) by one or more fasteners arranged in one or more radial slots at the outer circumference of the reference body (143), In particular by means of a fixing ring (164), In particular by means of a wedge-shaped fixing ring (164).

11. Electric machine according to claim 5, wherein The bushing (18) is rigidly attached to the reference body (143) by means of the bushing (18) comprising a bushing flange (182), and the bushing flange (182) is held against the reference body (143) by means of a bushing screw (185) screwed into the reference body (143).

12. Electric machine according to claim 11, wherein at least one or more of the following applies: • The bushing screw (185) is arranged in an axial channel or groove in the bushing flange (182), or in a connecting ring surrounding the bushing flange (182) and holding the bushing flange (182), • There is a gap in radial direction between the bushing (18) and the reference body (143), preferably wherein the gap is at least 0.1 mm or at least 0.2 mm or at least 0.4 mm.

13. Electric machine according to claim 11 or 12, wherein one or more bushing springs (186) are arranged between the bushing flange (182) and the bushing screw (185) and are compressed by the bushing screw (185).

14. Electric machine according to claim 5, wherein the bushing (18) is rigidly attached to the reference body (143) by means of the bushing (18) comprising a bushing flange (182), and the reference body (143) comprises at least one attachment element (188) whose holding site is curved to hold the bushing (18) at the bushing flange (182).

15. Electric machine according to claim 14, wherein at least one or more of the following applies: • The at least one attachment element (188) is formed as part of the reference body (143) or is rigidly attached to the reference body (143), • The at least one attachment element (188) is a cylindrical sleeve and the holding site is an axially extending finger structure.

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