Electrical machinery

Abstract

To provide an electrical machine having a gas bearing, capable of simplifying designing.SOLUTION: An electrical machine has a stator 1 having a stator body 25 supporting an electrical stator 3, and a rotor 5. The rotor is supported by a bearing including a radial bearing section 17 forming a radial gas bearing and an axial bearing section 12 forming an axial gas bearing, stator side parts of these bearing sections are a stator side radial bearing part and a stator side axial bearing part, the stator side radial bearing part and the stator side axial bearing part are rigidly connected to each other, and together form a stator bearing structure. The stator side radial bearing part is a bushing 18, the bushing is radially surrounded by a cooling body 71, and the bushing is connected to the cooling body by an elastic support body comprising a thermally conducting filler 23.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Electric motors typically include a rotor and a stator, with the stator comprising a stator body that supports and houses the electric stator and bearings. The bearing position relative to the stator body can be defined by the bearing flanges on the stator body. As shown in the arrangement of Figure 1a (stator body not shown), two journal bearings are often present, typically located on opposite sides of the stator. In this case, the precision of the bearing alignment is primarily determined by the precision with which the bearing flanges and stator body are machined. Accurate alignment is crucial for fluid film, especially gas, bearings, and this alignment typically requires special measures, such as self-aligning or standard bushing mounting of the pair of bearings after assembly, or machining, e.g., reaming. Alternatively, the journal bearings can be located on the same side of the stator. This arrangement is often referred to as a bulged motor design (Figure 1b). A bulged design facilitates accurate bearing alignment because the two journal bearings can be integrated into a single component. However, this approach typically results in a longer rotor, making rotor dynamic behavior more critical. Additionally, windage losses caused by air resistance increase, adversely affecting the overall efficiency of the motor. Summary of the Invention [Problem to be solved by the invention]

[0003] US Pat. No. 3,502,920 discloses a slotted electric machine with an air gap bearing, in which a bushing is located in the magnetic gap between the stator and rotor. The bushing can be resiliently suspended relative to the stator. It defines a radial bearing on the one hand and may have a central thrust bearing or thrust block as an axial bearing. To assemble the machine, the rotor must be axially separated. This design is not suitable for high-speed motors.

[0004] WO03 / 019753 A2 shows a spindle motor in which a rotor rotates within a stator within a thin layer of epoxy that forms a cylindrical through-hole in the stator and serves to define both radial and axial bearing surfaces. The thin layer of epoxy is bonded directly to the stator housing, so that any thermally induced deformation of the housing immediately affects the shape of the bearing.

[0005] US2006 / 0061222 A1 and US2006 / 0186750 A1 show conventional air bearings.

[0006] WO2017 / 202941 A1 discloses an electric machine and an associated rotor, which address the above problem by supporting the rotor with radial bearing sections forming radial gas bearings and axial bearing sections forming axial gas bearings, the stator-side portions of these bearing sections being stator-side radial bearing sections and stator-side axial bearing sections, which are rigidly connected to each other and together form a stator bearing structure. The stator-side radial bearing sections or stator-side axial bearing sections are rigidly attached to other parts of the stator, which are either elastically supported or not supported at all. All or part of the air bearing section is located in the magnetic gap between the electrical stator and rotor. It has been found necessary to conduct heat away from the rotor and bearing, for example from windage losses (caused by the relative movement of the rotor within the stator bore and the relative movement of the bearing surface and air within the air bearing) and electromagnetic losses.

[0007] SUMMARY OF THE INVENTION It is therefore a possible object of the present invention to create an electric machine of the type mentioned at the outset, which overcomes the above-mentioned disadvantages.

[0008] A further possible object of the present invention is to simplify the design of electric machines of the type mentioned at the outset, which can improve the mechanical stability, manufacturability and quality of the machines. [Means for solving the problem]

[0009] At least one of these objects is achieved by the electric machine according to the claims. According to a first aspect of the present invention, an electric machine includes a stator having a stator body supporting an electric stator, and a rotor. The rotor is supported by bearings including radial bearing sections forming radial gas bearings and axial bearing sections forming axial gas bearings, the stator-side portions of the bearing sections being stator-side radial and stator-side axial bearing sections, which are rigidly connected to each other and together form a stator bearing structure. The stator-side radial bearing section is a bushing, which is radially surrounded by a cooling body and which is connected to the cooling body by an elastic support comprising a thermally conductive filler.

[0010] Typically, the thermally conductive filler is in contact with both the bushing and the cooling body along a section of the axial length of the bushing where the radial bearing section resides.

[0011] This allows heat to be efficiently dissipated from the stator bearing structure, and in particular from the bushings. The elastic supports make it possible to compensate for possible deformations of the stator parts, for example due to thermal expansion, and to improve vibration characteristics.

[0012] The thermal coupling of the bushing to the stator can be achieved by using O-rings as flexible support elements and to seal in a thermally conductive filler material placed between these O-rings. Depending on its viscosity, the filler material can have a damping effect similar to a squeeze film damper.

[0013] Thermally conductive fillers are generally deformable materials, in particular: solids, such as silicone or silicone foams, or Fluid or flowable materials, such as pastes or gels, especially Liquids, for example oils with additives.

[0014] The thermally conductive filler can absorb relative movement between the bushing and the heat sink and / or compensate for possible deformation of these parts while maintaining physical contact between the bushing and the heat sink to provide a thermally conductive connection between the bushing and the heat sink.

[0015] Thermally conductive in this context means a thermal conductivity coefficient of at least 0.5 W / °K / m, or at least 1 W / °K / m, or at least 2 W / °K / m, or at least 4 W / °K / m.

[0016] In an embodiment, the bushing is radially surrounded by a cooling body, and the axial direction of the bushing is The heat sink is thermally coupled to the cooling body via the thermally conductive filler over at least 20%, 40%, 60%, or 80% of the length.

[0017] A thermally conductive filler is typically disposed in the gap between the cooling body and the bushing. In an embodiment, the stator bearing structure extends in the axial direction of the electric machine from a first end to a second end, and the stator bearing structure is rigidly supported by other parts of the stator near one of the two ends and is resiliently supported or not supported at all near the other end.

[0018] The "other part" mentioned above can therefore be the stator body itself or an assembly comprising the electric stator and the carrier, this assembly being resiliently supported by the stator body.

[0019] The axial direction corresponds to the axis of rotation of the rotor and is also called the longitudinal direction. In an embodiment, the stator bearing structure is attached to other parts of the stator by means of a stator-side axial bearing part, in particular an axial bearing assembly, which is rigidly attached to these other parts.

[0020] As a result, the stator bearing structure is suspended at one end by the axial bearing portion, and the remainder of the stator bearing structure is resiliently suspended, eliminating or reducing mechanical stress, but still thermally coupled to the cooling body.

[0021] Because the journal bearings can be integrated into a single part, it is easier to achieve accurate alignment than if the journal bearings were separate parts.

[0022] In an embodiment, the radial bearing section extends longitudinally of the rotating shaft, and the bearing elements and cooperating rotor bearing surfaces of the radial bearing section are all located outside the magnetic gap between the electrical stator and the rotor.

[0023] In other words, this means that the machine is of the overhang type, i.e., when viewed along the longitudinal axis of the machine, the journal bearings, or bushings and cooling bodies, are located at different positions from the electric stator and permanent magnets, respectively.

[0024] In an embodiment, the radial bearing section extends longitudinally of the rotating shaft, and at least 60%, 70%, 80% or 90% of the radial bearing section is located outside the magnetic gap between the electrical stator and the rotor.

[0025] Here, and throughout this document, the terms "rigidly" and "fixed" are used in contrast to "elastically." An elastic connection has a spring constant or Young's modulus that is at least, for example, 100 times or 10,000 times or 1,000,000 times greater than a rigid connection.

[0026] A rigid connection is one that is designed so that the connected parts do not move relative to one another during normal operation of the machine. Thus, a rigid connection can be established by screwing the parts together or by pressing them together with a spring. In this case, the spring is not part of the rigid connection, but provides the force that maintains the rigidity of the connection.

[0027] The elastic support may be an O-ring, typically made of (synthetic) rubber, or a metal spring.

[0028] The term "high speed electric machine" is to be construed to include machines suitable for speeds in excess of 100,000 revolutions per minute.

[0029] The gas in the gas bearing may be any gas in which the machine operates, such as air, refrigerant, natural gas, etc. The gas bearing may be a passive gas bearing or an active gas bearing.

[0030] The bushings may be made of ceramic or another material that provides sufficient mechanical rigidity and does not affect the magnetic field in the magnetic gap. The advantage of ceramic materials is that they are suitable for gas bearings and can be installed in magnetic gaps where the torque generating the magnetic field penetrates them. In general, to avoid excessive eddy current losses caused by the alternating magnetic gap field, electrical insulators or materials with low electrical conductivity can be used, such as ceramics, glass ceramics or technical glasses, plastics, composites, inorganic materials, etc.

[0031] In an embodiment, the electric machine is of the slotless type, in other words the electric stator comprises air-gap windings rather than slotted windings, while in another embodiment the electric machine is of the slotted type.

[0032] In an embodiment, the cooling body comprises coolant channels for carrying a cooling medium to remove heat from the cooling body. The cooling medium is typically a fluid such as a gas or a liquid.

[0033] According to a second aspect of the present invention, which can be implemented independently of or in combination with one or more of the other aspects, the cooling body is radially surrounded by a stator flange (which may also be referred to as a "stator cooling jacket"), and the stator body and the stator flange are manufactured as a single piece or are materially joined to each other, thereby thermally coupling the stator body and the cooling body and thereby cooling the stator body via the cooling body.

[0034] Generally, the stator body houses the electrical stator. "Materially joined" is also referred to as "substance to substance joining," and is typically achieved by welding or soldering.

[0035] In an embodiment, the stator flange forms at least part of the wall of the coolant channel, which allows the coolant to efficiently cool both the stator body and the cooling body.

[0036] In an embodiment, the stator body comprises a coolant channel, the coolant channel being arranged in a region radially surrounding the electric stator, which may be the case when the stator body comprises an outer stator body radially surrounding an inner stator body, the coolant channel being arranged between the outer and inner stator bodies.

[0037] According to a third aspect of the present invention, which may be implemented independently of or in combination with one or more of the other aspects, a heat transfer wall is disposed axially adjacent to an electrical stator, and an electrically non-electrically conductive but thermally conductive gap tube is attached to the stator radially adjacent to a rotor including permanent magnets, the rotor, and the heat transfer wall is thermally coupled to the gap tube, thereby enabling cooling of the motor air gap via the heat transfer wall and other portions of the stator body.

[0038] The expressions "axially adjacent" and "radially adjacent" are understood to mean "adjacent when viewed in the direction of the axis of rotation" and "adjacent when viewed radially", respectively.

[0039] In an embodiment, the heat transfer wall is arranged between the electrical stator and the cooling body, which may be the case when the electrical stator and the cooling body are located in different regions along the axis, separated by the heat transfer wall, as viewed in the axial direction.

[0040] In an embodiment, the cooling body is arranged radially around the electrical stator, and the heat transfer wall may be arranged on one side of the electrical stator and the cooling body to form a thermal bridge between the two for transferring heat from the electrical stator to the cooling body.

[0041] In an embodiment, instead of gap tubes there are gap bars, which are elongated elements or rods, which can be placed in the slots of a slotted electric machine.

[0042] In this way, the gap tube or gap bar is arranged axially along the longitudinal axis of rotation at a position where at least the permanent magnet is present.

[0043] Typically, the gap tube is positioned in the magnetic gap between the electrical stator and rotor.

[0044] The thermal bonding of the heat transfer wall to the gap tube or gap bar can be done by a pressure fit, for example a press fit, or by a material fit. In particular, an adhesive, for example a thermally conductive adhesive, can be used.

[0045] In order for the gap tubes or gap bars to be electrically non-electrically conductive but thermally conductive, they may be made of a ceramic material such as aluminum nitride or silicon carbide or certain grades of silicon nitride, which has a high thermal conductivity, for example higher than 20 W / °K / m or 40 W / °K / m or 60 W / °K / m or 100 W / °K / m or 140 W / °K / m.

[0046] In an embodiment, the heat transfer wall includes radial slits to reduce eddy currents in the heat transfer wall caused by permanent magnets near the rotor. In an embodiment, there are at least 6, 12, or 18 slits. The slits may be evenly spaced.

[0047] In an embodiment, the heat transfer wall and gap tube form part of the airtight separation between the electrical stator and the rotor, separating the air bearing, which is susceptible to contamination by small particles, from the space within the stator body, which is more prone to contamination in general.

[0048] In an embodiment, the electric machine includes a heat transfer flange thermally coupled to the gap tube at a distal end opposite the proximal end where the heat transfer wall is located, and the heat transfer flange may include coolant channels to allow for better cooling of the gap tube by removing heat at both ends of the gap tube.

[0049] According to a fourth aspect of the present invention, which can be implemented independently of or in combination with one or more of the other aspects, the axial bearing assembly is axially compressed by an elastic element that acts as a disk-shaped spring and also acts as a wall of a flow passage of a compressor driven by an electric machine, in particular a wall of a diffuser of a centrifugal compressor, thereby enabling a space-saving and simple construction of the motor-compressor combination.

[0050] Generally, disc springs or Belleville washers, also known as conical disc springs, conical spring washers, leaf springs, Belleville springs or cupped spring washers, are used for static or dynamic loads. The axial extension of the ...

[0051] In an embodiment, the disc spring is axially compressed by a compressor housing part, preferably by the spiral casing of the compressor, which allows for a further simplification of the construction of the motor and compressor combination.

[0052] The compressor housing generally includes a plenum and, optionally, at least one wall of a diffuser leading to the plenum, which may be molded as a single piece with the rest of the housing or may be molded as a separate piece.

[0053] In an embodiment, the first and second stator discs of the axial bearing assembly and the spacer element disposed between the two stator discs are pressed against each other by a disc spring.

[0054] In an embodiment, the first stator disk is integrally molded with the bushing, in other words, the first stator disk and the bushing of the axial bearing assembly are manufactured as a single part or component.

[0055] A thrust or axial bearing generally comprises a rotor disk within a rotor and an adjacent stator disk on the stator, on either side of the rotor disk as viewed axially. The two stator disks are separated by shims or spacer elements so that a well-defined gap is formed between the rotating and stationary parts of the thrust bearing. The stator disks, spacers, and connecting elements together form an axial bearing assembly.

[0056] In an embodiment, each of the stator disk and the bushing of the axial bearing assembly has an axially facing surface as an axial reference surface, and these two axial reference surfaces are installed against each other, thereby ensuring that the rotation axis is perpendicular to the bearing surface of the axial bearing assembly.

[0057] In an embodiment, the stator disc and the bushing, which are arranged against each other, are pressed against each other by elastic elements, in particular disc springs, if they are not integrally formed.

[0058] Further embodiments are evident from the dependent patent claims. The subject matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments that are illustrated in the accompanying drawings. [Brief explanation of the drawings]

[0059] [Figure 1a] 1 is a longitudinal section of a prior art machine having gas bearings; FIG. [Figure 1b] 1 is a longitudinal section of a prior art machine having gas bearings; FIG. [Figure 2]1 illustrates an embodiment of an electric machine. [Figure 3] FIG. 10 is an exploded view of the same embodiment. [Figure 4] FIG. 10 is a diagram showing the stator body showing the arrangement of slits. [Figure 5] FIG. 10 is a cross-sectional view with further embodiment details. DETAILED DESCRIPTION OF THE INVENTION

[0060] In the figures, parts that are essentially the same or have similar functions are provided with the same reference symbols.

[0061] Figure 1a shows a schematic diagram of a prior art electric machine with air or gas bearings, in which a stator body (not shown) carries an electric stator 3 with coils 31 and core 32, which in turn carries axial and radial bearing sections 12 and 17 around which a rotor 5 with a shaft 51 and permanent magnets 52 rotates. The individual bearing elements 19 that make up the radial bearing section 17 are located at opposite ends of the machine, with the electric stator 3 in between. Figure 1b shows the same elements in a prior art overhanging arrangement, with the individual bearing elements 19 located at the same end of the machine, i.e., both on the same side of the electric stator 3.

[0062] Here, and in other arrangements, a fan 6 or impeller driven by an electric machine acting as a motor is shown as one example of an application of this machine. It will be appreciated that any other end device, particularly one requiring high speed drive, may be arranged to be driven by an electric machine.

[0063] 2 shows a schematic representation of an embodiment having the above elements but arranged differently, and also shows the stator 1 with a stator body 25 which acts as a housing and support for the electromagnetic components of the stator 1, i.e., the coils 31 and the cores 32.

[0064] The portions of axial bearing section 12 and radial bearing section 17 that are attached to the stator, rather than the rotor, form a stator bearing structure that includes the stator-side bearing surfaces of axial bearing section 12 and radial bearing section 17 and defines the relative positions of these surfaces. The stator bearing structure is designed to be rigid and easy to assemble and align with high precision.

[0065] The axial or thrust bearing section of the rotor portion 12 comprises a generally disc-shaped thrust plate or rotor disk 54 extending outward from the outer circumferential surface of the shaft 51 near one end of the rotor 5. The rotor disk 54 has two opposite axially facing faces which cooperate with two stator disks 14c, 14d between which the rotor disk 54 rotates to form an axial bearing.

[0066] The axial bearing section 12 of the stator part comprises these stator discs 14c, 14d, i.e. the first stator disc 14c and the second stator disc 14d, which are part of the axial bearing assembly 11. The axial bearing assembly 11 further comprises spacer elements 15, typically washers, which define the distance between the axially facing faces of the stator discs 14c, 14d facing each other.

[0067] The radial bearing section 17 or journal bearing section of a portion of the rotor comprises at least a portion of the outer circumferential surface of the shaft 51. This portion serves as the rotor bearing surface 53, which cooperates with the bushing 18 to form a radial bearing having the bearing gap 7. The outer side of the rotor bearing surface 53 may have a radially outwardly projecting section 19a. In this case, the inner side of the bushing 18 may have a constant inner diameter. Alternatively or additionally, the bushing 18 may have bearing elements in the form of radially inwardly projecting sections located in discrete regions along the inside of the bushing 18.

[0068] A radial bearing section 17 in a portion of the stator includes this bushing 18. In this embodiment, the first stator disc 14c is integrally formed with the bushing 18.

[0069] The stator discs 14c, 14d and the spacer element 15 can be clamped together by the disc springs 14b, in particular by applying an axial force. The force applied by the disc springs 14b can also clamp the first stator disc 14c against the cooling body 71.

[0070] The disc spring 14b also serves as the wall of the diffuser of the compressor, which is driven by an electric machine. The compressor is a centrifugal compressor having a centrifugal impeller 6 with a set of rotating vanes (or blades) that gradually increase the energy of the working gas from the intake 76. Downstream of the impeller 6 in the flow path, a diffuser 77 converts the kinetic energy of the gas (high velocity) into pressure by gradually slowing (diffusing) the gas velocity. The gas is discharged from the diffuser into a plenum 78, also known as a volute or scroll.

[0071] The plenum 78 and one wall of the diffuser 77 are formed as part of the compressor housing 14a, which is rigidly attached to the cooling body 71 to clamp or compress the disc spring 14b against the first stator disk 14c.

[0072] At the first and second ends of the bushing 18, the bushing 18 is supported by the cooling body 71 using elastic supports 21, for example O-rings. This damps mechanical vibrations that may occur at the otherwise free end of the bushing 18. The elastic supports, together with the gap between the bushing 18 and the cooling body 71, make it possible to compensate for possible deformations of the stator parts due to, for example, thermal expansion. The gap between the bushing 18 and the cooling body 71 can be filled with a thermally conductive filler 23. This allows heat to be dissipated from the bushing 18 to the cooling body 71.

[0073] Generally, the bushing 18 is located completely or mostly outside the magnetic (air) gap separating the electrical stator 3 and rotor 5 and / or the volume through which the magnetic flux that drives the motor passes. This also typically applies to the outwardly projecting section 19a and / or bearing element 19 (if present), and the cooperating rotor and stator bearing surfaces of the radial bearing section 17.

[0074] It is also possible for the radial bearing section to be located in the same area as the electrical stator in the axial or longitudinal direction, in which case the thermally conductive filler is arranged between the bushing and the electrical stator.

[0075] The position of the bushing 18 relative to the axial bearing assembly 11 is tightly constrained by only one mechanical linkage, which is defined by the integrally molded bushing 18 and first stator disc 14c of the stator bearing structure 11, or otherwise by an axial reference surface on one of the bushing 18 and stator disc 14 where the bushing and stator disc are fastened together.

[0076] The other mechanical links between the bushing 18 and the axial bearing assembly 11 via the cooling body 71 are elastic or resilient because they extend through the elastic support 21 and the thermally conductive filler 23. In this way, the relative position of these parts, particularly the bushing 18, with respect to the stator disk 14 is not overly constrained. Therefore, by precise machining of the integral bushing 18 and first stator disk 14c or the axial reference surface, the precision of the alignment of the axial bearing section and the radial bearing section can be easily achieved and maintained even under thermal and mechanical stress.

[0077] In other words, the axial bearing assembly 11 and bushing 18, which together form the stator bearing structure, and the rotor 5 are part of one or more kinematic loops. Thus, each loop includes at least one resilient element. Conversely, the axial bearing assembly 11 and bushing 18 are not part of an overly constrained loop or arrangement.

[0078] Furthermore, the position of the bushing 18, and therefore the rotation axis, is constrained in a fixed manner by the position of the cooling body 71 by at most one mechanical link, namely: Mounting the axial bearing assembly 11 on the cooling body 71 · Mounting of bushing 18 to cooling body 71.

[0079] The stator flange 28 is molded integrally with the stator body 25. The stator flange 28 is a hollow cylinder that radially surrounds at least a portion of the cooling body 71, in particular the portion of the cooling body that is actively cooled. Coolant channels 75 are arranged between the cooling body 71 and the stator flange 28. Although Figures 2 and 3 show the coolant channels 75 molded in the cooling body 71, they may alternatively or additionally be molded in the stator flange 28.

[0080] The stator body 25 includes a heat transfer wall 27 disposed between the cooling body 71 and the electric stator 3. The heat transfer wall 27 extends radially from a peripheral section of the stator body 25, where it is joined to the stator flange 28, to an inner section, where it is joined to a gap tube 29. The gap tube 29 is a hollow cylinder disposed in the electric machine air gap 7a (motor air gap) and is made of a thermally conductive but electrically non-electrically conductive material. The heat transfer wall 27 is arranged to conduct heat away from the gap tube 29, and therefore from the electric machine air gap. The heat transfer wall 27 is thermally coupled to the gap tube 29 at a first end of the gap tube proximal to the bushing 18.

[0081] The heat transfer wall 27 includes radial slits 24 to reduce eddy currents generated in the heat transfer wall 27 by the alternating magnetic field of the permanent magnets 52 of the rotor 5. The radial slits 24 may extend from the beginning to the end of the heat transfer wall 27, in which case the slits may be filled with a non-conductive material to keep the heat transfer wall 27 airtight. Alternatively, the radial slits 24 may be made to leave a thin section of the heat transfer wall 27 to keep the heat transfer wall 27 airtight.

[0082] The main structural components, in particular the compressor housing 14a, the cooling body 71 and the stator body 25 including the stator flange 28, are generally made of a metal with good thermal conductivity, in particular aluminum or an aluminum alloy.

[0083] Figure 3 shows an exploded view of some of the elements of Figure 2. Figure 4 shows a view of the stator body 25 alone (with slightly different exterior features than in Figure 2) and shows the arrangement of the radial slits 24.

[0084] Figure 5 shows a cross-sectional view with further embodiment details, in which the stator body 25 includes coolant channels 75a. These coolant channels 75a may be formed by separate parts, namely the stator body 25 including an outer stator body 25a radially surrounding an inner stator body 25b. The coolant channels 75a are then molded on the outside of the inner stator body 25b and / or on the inside of the outer stator body 25a, with the insides and outsides in contact. The inner and outer stator bodies are rigidly attached to each other.

[0085] Alternatively, the coolant channels 75a may be formed by manufacturing the stator body 25 through an additional manufacturing process that forms the coolant channels 75a when the stator body 25 is made.

[0086] Gap tube 29 is shown thermally coupled at a second or distal end to heat transfer flange 27a.

[0087] The heat transfer wall 27 is joined to the gap tubes 29 at their outer periphery, while the heat transfer flange 27a can be joined to the gap tubes 29 at their inner and / or outer periphery. The heat transfer flange 27a comprises the coolant channels 75b. The heat transfer flange 27a may be rigidly attached to the stator body 25 or may be part of the stator body 25, in particular the inner stator body 25b.

[0088] Thermal coupling of the heat transfer wall 27 and / or heat transfer flange 27b to the gap tube 29 can be achieved, for example, by a thermally conductive filler placed between an O-ring, a thermally conductive adhesive, or a press fit.

[0089] Although reference is made to coolant channels 75, 75a, 75b, it is understood that there are additional conduits for supplying and removing coolant.

Claims

1. An electric machine comprising a stator (1) having a stator body (25) supporting an electric stator (3), and a rotor (5), said rotor (5) being supported by bearings; a heat transfer wall (27) disposed axially adjacent to the electric stator (3); an electrically non-electrically conductive but thermally conductive gap tube (29) attached to the stator (1) at a position radially adjacent to the rotor (5) having permanent magnets (52); the heat transfer wall (27) thermally coupled to the gap tube (29); and the heat transfer wall (27) having radial slits (24) for reducing eddy currents in the heat transfer wall (27) caused by the nearby permanent magnets (52).

2. An electric machine comprising a stator (1) having a stator body (25) supporting an electric stator (3), and a rotor (5), the rotor (5) being supported by bearings; a heat transfer wall (27) arranged axially adjacent to the electric stator (3); an electrically non-electrically conductive but thermally conductive gap tube (29) attached to the stator (1) at a position radially adjacent to the rotor (5) comprising permanent magnets (52), the heat transfer wall (27) being thermally coupled to the gap tube (29), the heat transfer wall (27) and the gap tube (29) forming part of the gas-tight separation between the electric stator (3) and the rotor (5).

3. An electric machine comprising a stator (1) having a stator body (25) supporting an electric stator (3), and a rotor (5), the rotor (5) being supported by bearings, a heat transfer wall (27) disposed axially adjacent to the electric stator (3); an electrically non-electrically conductive but thermally conductive gap tube (29) attached to the stator (1) at a position radially adjacent to the rotor (5) comprising permanent magnets (52); the heat transfer wall (27) thermally coupled to the gap tube (29); and a heat transfer flange (27b) thermally coupled to the gap tube (29) at a distal end opposite to a proximal end of the gap tube (29) at which the heat transfer wall (27) is disposed.

4. An electric machine as described in claim 3, wherein the heat transfer flange (27b) is provided with a coolant channel (75b).

5. 5. Electric machine according to any one of the preceding claims, wherein the heat transfer wall (27) is arranged between the electrical stator (3) and a cooling body (71).

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