Rotor for high-speed electromachines

Abstract

A rotor (1) for a high-speed electric machine with gas bearings comprises at least one rotor-side radial bearing (21), a rotor-side axial bearing (31), a rotor body section (29) with the at least one rotor-side radial bearing (21), and a rotor end section (39) with the rotor-side axial bearing, where the radial bearing section (22) is defined as the section along which the radial bearing extends, as viewed along the rotor axis of rotation, in which an outer rotor part (27) extends along the rotor end section and the rotor body section, the outer rotor part (27) is shaped to form a hollow cylinder or bearing sleeve (28) within the rotor body section (29), and at least one rotor plug (5) is disposed inside the bearing sleeve (28), the material of the at least one rotor plug (5) having a CTE lower than 7E-6KA-1.

Description

Technical Field

[0001] The present invention relates to the field of electric machinery. The present invention relates to a rotor for a high-speed electric machine having a gas bearing as described in the preamble of the independent claim.

[0002] An electric motor generally comprises a rotor and a stator, the stator comprising an electric stator and a stator body for supporting and housing the bearing. The bearing comprises one or more radial (also called journal) and axial (also called thrust) bearings which are gas bearings. In many cases, there are two radial bearings. They can be arranged on opposite sides of the stator, i.e., the electromagnetic elements for driving the rotor are arranged between the two radial bearings or on the same side of the stator. The latter arrangement is often called an overhang motor design. With an overhang design, the two radial bearings can be integrated into a single component. However, as a result of this approach, the rotor generally becomes longer, thus resulting in more significant rotor dynamics behavior and an increase in the manufacturing effort of the rotor. For this reason, there are conflicting requirements due to the desire to keep the rotor short, simplify the manufacturing effort and thus the cost, and for example increase the performance limits caused by the rotor dynamics behavior.

[0003] In many cases, the manufacturing tolerances and material requirements are different for the rotor radial bearing and the rotor axial bearing, and it has become difficult to find a rotor structure with simple manufacturing, few different pieces, materials, and joint surfaces.

[0004] WO 2018 / 041938 discloses a turbo compressor shaft having a radial air bearing and an axial air bearing. A shaft for carrying an impeller and an axial bearing plate is inserted at one end of the tubular bearing portion, and a drive portion for carrying an element of an electric motor is inserted at the other end. The tubular bearing portion is made of a hard material, and the impeller portion and / or the drive portion are made of a relatively soft material compared to the hard material of the tubular bearing portion.

[0005] U.S. Patent No. 4,063,850 discloses a gas turbine rotor having a ceramic turbine wheel and rotor shaft formed in part from a ceramic material, wherein the wheel and part of the rotor are integrally formed. The ceramic shaft portion of the rotor extends into the engine's cooling zone, where it encloses a support tube and connects to a steel shaft portion that bridges the two shaft portions. The ceramic shaft portion is supported by radial air bearings. A ceramic axial bearing disc is integrally formed with the ceramic shaft portion.

[0006] U.S. Patent No. 4,585,396, U.S. Patent No. 4,854,025, and U.S. Patent No. 4,639,194 disclose ceramic turbine wheels or impellers connected to a steel rotor shaft.

[0007] International Publication Nos. 2014 / 175766 and International Publication Nos. 2017 / 200828 disclose a rotor shaft having a hollow cross-section, in which heat conduction elements are arranged to disperse heat within the hollow cross-section. The heat conduction elements are made from a material with a higher thermal conductivity than the material of the rotor shaft.

[0008] British Patent Application Publication No. 962277 discloses a similar configuration having cooling ribs inside the heat conduction element.

[0009] International Publication Nos. 2017202941 and 2020002509 disclose rotors having air bearings in which radial and axial bearings are made from a single piece and material.

[0010] U.S. Patent Application Publication No. 2004 / 0051416 describes a rotor having a reinforcing sleeve mounted around a permanent magnet, with the sleeve positioned around a turbine shaft on one side of the magnet and around a bearing member on the other side. The reinforcing sleeve does not include any bearing compartments.

[0011] Conventional rotors are all difficult to manufacture and / or cannot use materials that are optimal for the various parts and functions of the rotor.

[0012] Therefore, an object of the present invention is to create a rotor for a high-speed electric machine having a gas bearing that provides an improvement over the prior art.

[0013] These objectives are achieved by a rotor for a high-speed electric machine having a gas bearing as described in the claims.

[0014] The rotor is for high-speed electric machinery with gas bearings, and the rotor is, At least one rotor-side radial bearing, Rotor-side axial bearing and A rotor body section having at least one rotor-side radial bearing, A rotor end section equipped with a rotor-side axial bearing, When viewed along the rotor's axis of rotation, the radial bearing section is defined as the section along which the radial bearing extends.

[0015] Within that, the outer rotor portion extends along the rotor end section and the rotor body section, The outer rotor portion is molded to form a hollow cylindrical body that functions as a bearing sleeve within the rotor body section. At least one rotor plug is positioned inside the bearing sleeve, and the material of at least one rotor plug has a CTE lower than 7E-6K^-1, especially lower than 5E-6K^-1, and even more especially lower than 4E-6K^-1.

[0016] This allows the CTE of the rotor, particularly in the radial direction, to be controlled by the relatively low CTE of the rotor plug.

[0017] In this embodiment, the rotor plug does not extend to the axial bearing section when viewed along the rotor's axis of rotation.

[0018] In this embodiment, the rotor plug is a separate component and is not combined with the rotor end piece.

[0019] In this embodiment, the rotor plug does not contain any permanent magnetic material. In the embodiment, the rotor plug is intentionally constructed to deform the bearing sleeve when the rotor plug is assembled to the bearing sleeve, more specifically to apply pre-tension to the bearing sleeve. This is in contrast to the conventional technique in which the rotor plug is made from a soft material (meaning a material with low resistance to elastic or plastic deformation) used with the aim of not deforming the bearing sleeve.

[0020] In this embodiment, the material of the outer rotor portion is a metal or a metallic material, particularly steel. In this embodiment, the material of the outer rotor portion has a Rockwell hardness greater than 40 HRC, particularly greater than 50 HRC, and even more particularly greater than 55 HRC.

[0021] In the embodiment, the material of at least one rotor plug has a density of less than 4500 kg / m³, and in particular less than 3500 kg / m³.

[0022] In the embodiment, the material of at least one rotor plug has a CTE of less than 7E-6K^-1, particularly less than 5E-6K^-1, and even more particularly less than 4E-6K^-1.

[0023] In the embodiment, there exists a first set of material features, which includes the feature that the material of at least one rotor plug has a CTE of less than 7E-6K^-1, more particularly less than 5E-6K^-1, and even more particularly less than 4E-6K^-1, and the outer rotor portion material is a metal or metallic material, particularly steel.

[0024] In the embodiment, there is a second set of material features which includes a first set of material features, further including the feature that the material of the outer rotor portion has a Rockwell hardness greater than 40 HRC, particularly greater than 50 HRC, and even more particularly greater than 55 HRC.

[0025] In an embodiment, there is a third set of material characteristics that includes a second set of material characteristics and further includes the feature that the material of at least one rotor plug has a density of less than 4500 kg / m^3, particularly less than 3500 kg / m^3.

[0026] In an embodiment, there is a fourth set of material characteristics that includes a third set of material characteristics and further includes the feature that the material of at least one rotor plug has a Young's modulus to density ratio greater than 250 GPa / 3100 kg / m^3, particularly greater than 350 GPa / 3100 kg / m^3.

[0027] According to an embodiment, the order of priority of the above-described material property priorities that define the rotor plug and the outer rotor portion is as follows.

[0028] · First priority: CTE of the rotor plug, · Second priority: Material of the outer rotor portion, · Third priority: Rockwell hardness of the outer rotor portion, · Fourth priority: Density of the rotor plug, · Fifth priority: Young's modulus to density ratio of the rotor plug.

[0029] · Sixth priority: Tensile strength to density ratio of the outer rotor portion. As a result, it becomes possible to achieve one or more of the following advantages.

[0030] · One or more rotor plugs can be of a simple cylindrical shape, so having a first type of material, such as ceramic, for the rotor plug can simplify the process for manufacturing parts of the first type of material.

[0031] · Having a second type of material, such as high-performance steel, for the bearing sleeve makes machining easier than the first type of material. This is particularly advantageous when it is integrally formed with the rotor stub shaft.

[0032] Having a bearing sleeve made of a second type of material within a radial bearing compartment means it has a relatively high CTE, which is generally disadvantageous because it heats up during operation. However, by pushing a plug made of a first type of material into a rotor sleeve made of a second type of material, the CTE of this combination can be reduced to approach the CTE of the plug alone.

[0033] Similar to expansion under temperature, in press-fitting a plug with a relatively high modulus-to-density ratio and a sleeve with a potentially low modulus-to-density ratio, the expansion of this combination due to centrifugal force at high rotational speeds decreases toward the expansion of the plug. As the speed increases, the press-fit, which generates pre-tension within the bearing sleeve, initially loosens partially, and the tightness begins to decrease before the bearing sleeve begins to expand. The expansion of the sleeve corresponds more to the expansion of a solid than a hollow cylinder, and more to the plug material parameters than the sleeve material parameters. In the embodiment, the thickness of the sleeve is less than 20% of the radius of the plug; that is, the outer radius of the sleeve is less than 120% of the radius of the plug.

[0034] The axial bearing plate, which is part of the outer rotor, can be made from a second type of material. Therefore, it can have higher strength than the part made of the first type of material, which is advantageous in the axial bearing plate because it has the largest diameter and is subjected to the highest centrifugal force.

[0035] The outer rotor portion of the rotor end section can form a rotor stub shaft. The rotor stub shaft and bearing sleeve can be made from the same material as separate parts and then joined together, or they can be molded integrally, i.e., as a single part. The rotor plug can be a solid or hollow cylindrical body.

[0036] In some embodiments, the high-speed electromachine designed to use a rotor is a turbo compressor, in which case it can drive an impeller attached to the rotor end piece. In other embodiments, the high-speed electromachine drives a beam chopper or a rotating prism or mirror or any other load. In other embodiments, the high-speed electromachine is driven by a turbine, with or without a turbo compressor impeller.

[0037] In another embodiment, the rotor is not driven by an electromechanism or a part of an electromechanism.

[0038] Gas bearings are also called gas-lubricated bearings or fluid membrane bearings with a gaseous fluid. Gas bearings include air bearings.

[0039] In the embodiment, the rotor plug is made from a material that does not expand as much as possible under a) rotation and b) temperature, since both high speed rotation and high temperature are present within the high-speed rotor. Ideally, expansion should be minimized in order to maintain a small gas bearing clearance between the rotor and stator bearing bushings. Furthermore, the rotor plug should be lightweight and rigid in order to increase bearing performance (i.e., increase the maximum stable rotational speed).

[0040] While it is preferable for the rotor plug to be easy to machine, a decrease in machinability can be tolerated as a trade-off with the aforementioned characteristics. This can be mitigated by keeping the shape of the rotor plug simple, making it easier to manufacture than the outer rotor portion.

[0041] In the embodiment, the outer rotor portion is made from a material with high tensile strength and a high tensile strength-to-density ratio, particularly compared to the rotor plug, which allows for a relatively high peripheral speed for a given rotational speed, and therefore a larger axial bearing outer diameter. A larger axial bearing diameter allows for a larger maximum axial load, which is beneficial for withstanding vibrations and axial thrusts, for example, from an impeller mounted on the rotor. Furthermore, for the outer rotor portion, which has a more complex shape than the rotor plug, a material that is easier to machine than the rotor plug material can be used, thereby reducing machining costs. In addition, to minimize wear during the start-up and stop-down of gas bearings with dry friction between the rotor and stator bearings, the material of the outer rotor portion should ideally be hard.

[0042] The outer rotor portion preferably exhibits low expansion under a) rotation and b) temperature conditions, but higher expansion can be tolerated as a trade-off with the above characteristics and is mitigated by the rotor plug.

[0043] As a result, the outer rotor section and the rotor plug are made of different materials. This allows the rotor to be made from two different materials by separating it into two parts. • The outer rotor portion, in particular, the strength of the axial bearing, and the simple machining of the more complex shapes and tolerances of the outer rotor, • Rotor plugs, especially radial bearings, with low expansion under temperature and rotation. This makes it possible to meet different requirements. The expansion of radial bearings can be limited by press-fitting, which combines a thin bearing sleeve made of a material that can tolerate higher expansion with a thicker rotor plug that has lower expansion in the radial direction. Press-fitting results in lower overall expansion because the expansion is mainly determined by the rotor plug rather than the bearing sleeve. The axial bearing and / or rotor stub shaft can be manufactured as a separate part made of the same material as the bearing sleeve, or it can be molded integrally with the bearing sleeve, making it easier to machine than the material of the rotor plug.

[0044] In this embodiment, there is no press-fit between the rotor plug and the bearing sleeve, but the rotor plug and the bearing sleeve are rigidly connected by other means (such as welding, bonding, or soldering), and as a result, the rotor plug restricts the bearing sleeve from expanding due to temperature or centrifugal force, potentially without pre-tension.

[0045] In conventional technologies where combinations of different materials exist, materials with a high coefficient of thermal expansion (CTE) are arranged on the inside, and materials with a low CTE are arranged on the outside. However, according to the present invention, the opposite configuration can be achieved.

[0046] In summary, the rotor plug is made of a first type of material, which may also be called a ceramic material. In some embodiments, the first type of material has one or more of the following properties:

[0047] Low CTE: less than 7E-6K^-1, or less than 5E-6K^-1 or 4E-6K^-1. • Low density (independent of elastic modulus): less than 4500 kg / m³ or less than 3500 kg / m³.

[0048] • High elastic modulus-density ratio: 250 GPa / 3100 kg / m³ or greater than 350 GPa / 3100 kg / m³.

[0049] Typical materials of the first type: ceramic materials, more specifically SiN, SiC, AlO. Further alternatives: iron-nickel alloys (such as Invar), glass-ceramics, tungsten carbide, metal carbides.

[0050] In summary, a second type of material, which may also be called a metallic material, is used for the outer rotor portion 28. In embodiments, the second type of material has good machinability and possesses one or more of the following properties:

[0051] • High hardness (Rockwell hardness): 40 HRC or 50 HRC or above 55 HRC, • High strength-to-density ratio: exceeding 700 MPa / 7700 kg / m³ or 1500 MPa / 7700 kg / m³ or 2000 MPa / 7700 kg / m³.

[0052] Typical materials: metals, more specifically steel, and more specifically high-strength / high-strength steel, especially EN 10027-2 steel numbers 1.4108, 1.4125, and 1.4112.

[0053] In the embodiment, in at least one, and in all, of the one or more radial bearing compartments, the rotor plug extends along most, and in all, of the radial bearing compartments.

[0054] This allows the rotor plug to define and stabilize the diameter of the rotor body within the radial bearing compartment. A rotor plug extending along most of the radial bearing compartment means extending along at least 90%, and especially at least 100% or 105%, of the length of the radial bearing compartment.

[0055] In the embodiment, in at least one, and in particular all, of one or more radial bearing compartments, the rotor plug extends only along the radial bearing compartment and not beyond it when viewed in the axial direction, or extends only 30% or 40% further relative to the length of the radial bearing compartment.

[0056] A single rotor plug may exist extending along two or more radial bearing compartments, or separate rotor plugs may exist, each extending along corresponding radial bearing compartments, typically separated by gaps. A rotor plug made from separate plug elements, typically having the same radius, positioned opposite each other or very close to each other (viewed along the axial direction), may be functionally identical to a single rotor plug and can therefore be considered a single rotor plug.

[0057] In this embodiment, the rotor comprises first and second rotor-side radial bearings corresponding to first and second radial bearing sections, respectively, and the first and second rotor plugs are arranged to extend along the first and second radial bearing sections, respectively.

[0058] This allows for a relatively lightweight structure. The first and second rotor plugs can be assembled one after the other and are shorter than a single plug, simplifying the press-fit process.

[0059] In this embodiment, the rotor comprises first and second rotor-side radial bearings corresponding to first and second radial bearing compartments, respectively, and a single rotor plug is positioned to extend along both the first and second radial bearing compartments.

[0060] This allows for a relatively simple structure, a more rigid rotor body, and therefore better dynamic behavior. Furthermore, the bearing sleeve can be thinner than when two separate, spaced-out rotor plugs are present.

[0061] In this embodiment, the bearing sleeve is manufactured by coating the rotor plug, or a portion of the rotor plug. In this way, a very thin bearing sleeve can be manufactured. The coating may be a hard material with good tribological properties, such as hard chromium or tungsten carbide, or diamond-like carbon (DLC).

[0062] In the embodiment, the rotor plug is combined with the rotor end piece, i.e., the rotor plug and rotor end piece are manufactured as a single part from the same material. This can be a ceramic material. The bearing sleeve that is placed on such a rotor plug can be manufactured by coating the rotor plug, as described above.

[0063] In this embodiment, the bearing sleeve is a proximal sleeve that extends along the first radial bearing compartment rather than along the second radial bearing compartment, and a further or distal sleeve (28b) extends along the second radial bearing compartment rather than along the first radial bearing compartment.

[0064] This reduces the overall weight of the rotor body. The sleeve can be pressed from the opposite side on the rotor plug, making it easier to assemble the rotor body.

[0065] In this embodiment, the distal sleeve extends over the distal end of the rotor plug, and the permanent magnet is located within the distal sleeve.

[0066] This enables simple mounting and support of permanent magnets without additional parts, in embodiments having two separate sleeves.

[0067] In this embodiment, the bearing sleeve extends over the distal end of the rotor plug, and the permanent magnet is located within the bearing sleeve.

[0068] This enables simple mounting and support of a permanent magnet without additional parts, in embodiments having a single bearing sleeve.

[0069] In this embodiment, the permanent magnet is placed inside a magnet sleeve, which extends over the permanent magnet and forms a press-fit with the distal rotor plug end.

[0070] This implements simple mounting and support of permanent magnets using additional parts for both embodiments with a single rotor plug or embodiments with two or more separate rotor plugs. This allows the magnet sleeve to be manufactured from a different material than the bearing sleeve, and / or the magnet sleeve to be easily manufactured to have a different diameter and / or thickness than the bearing sleeve or distal sleeve. Furthermore, press-fitting within the radial bearing compartment is unaffected by the connection to the permanent magnet, and / or the bearing sleeve can be separated from the permanent magnet, reducing the impact on the magnetic field. In embodiments, the magnet sleeve is made from a non-magnetic material. In embodiments, the magnet sleeve is made from a magnetic material, i.e., with a permeability greater than 1, and is made relatively thin so as not to impair the magnetic field of the permanent magnet. For example, the thickness of the magnet sleeve is less than 5% of the diameter of the magnet.

[0071] In the embodiment, at least one rotor plug has at least one rotor plug end, particularly both ends, tapered. When viewed along the rotor's axis of rotation, the tapered section is defined as the section in which the plug becomes tapered along it. As a result, the pressing force between the rotor plug and the sleeve in the tapered section is gradually reduced. In particular, the tapered section does not overlap with the bearing section.

[0072] This makes it possible to avoid excessive stress on the bearing sleeve and the rotor plug at the end of the rotor plug that is press-fitted into the bearing sleeve.

[0073] In the embodiment, the tapered section is tapered only to a limited extent, and the press-fitting force is such that the press-fit between one or more rotor plugs and bearing sleeves is present along at least the entire axial length of the radial bearing.

[0074] In the embodiment, the tapered section has an axial length of less than one-tenth of the rotor plug length or less than 5 millimeters. The maximum reduction in plug radius at each end of the rotor plug may be less than one-thousandth of the plug diameter or less than 10 micrometers.

[0075] In this embodiment, the permanent magnet is positioned between the first rotor plug and the second rotor plug.

[0076] This allows the electromagnetic elements of the electromachine to be positioned between the radial bearing compartments when viewed in the axial direction, resulting in a shorter rotor and machine structure.

[0077] In this embodiment, the rotor is A rotor body having at least one rotor-side radial bearing, A rotor end piece equipped with a rotor-side axial bearing, The rotor end piece and the rotor body are parts that are manufactured separately and connected to each other. This is done by press-fitting, and more specifically, the rotor end piece radially surrounds the rotor body at the joint surface of these two parts.

[0078] Therefore, in this embodiment, the rotor body and rotor end pieces are separately manufactured parts and are assembled when the rotor is manufactured.

[0079] In this embodiment, the rotor end piece is connected to the rotor plug, and the bearing sleeve is connected to the rotor plug, and both connections are press-fitted in particular.

[0080] In this embodiment, the rotor end piece is connected to a single rotor plug, and the bearing sleeve is connected to that single plug, and both connections are press-fitted in particular.

[0081] In this embodiment, the rotor end piece includes a hollow compartment that acts as a press-fit compensation volume, capable of receiving displaced gas when establishing the press-fit. This eliminates the problem of compressed gas forcibly disengaging the press-fit. Furthermore, it can make the outer rotor portion more elastic and improve the press-fit between the outer rotor portion and the rotor plug. In addition, the hollow, protruding rotor end piece reduces its weight and improves the dynamic behavior of the rotor and the stability of the bearings.

[0082] In the embodiment, the rotor end piece comprises a hollow section, the hollow section extending axially along at least the axial bearing section, particularly along at least 50% or 70% of the length of the rotor end piece in the axial direction. especially, The hollow compartment comprises or comprises ventilation ducts that establish fluid connections to the rotor, and in particular, the ventilation ducts are through-holes that extend axially. Alternatively, the hollow compartment includes or constitutes a press-fit compensation volume section and is airtightly enclosed.

[0083] In the embodiment, the inner diameter of the hollow compartment is 10% to 60% of the diameter of the central plug of the axial stub or rotor stub shaft. The rotor stub shaft is typically designed to be driven by a rotor or to support components that drive the rotor.

[0084] In this embodiment, the wall thickness of the rotor end piece in the region other than the axial bearing section, where a hollow section exists, is at least 50% of the radius of the rotor end piece in the same axial location.

[0085] If the hollow compartment and / or pressurized compensation volume section is equipped with or constitutes a ventilation duct, in addition to eliminating the compression of the gas as described above, the presence of gas pockets that could leak process gases slowly and cause contamination is also eliminated.

[0086] When the press-fit compensation volume is airtight, this has the advantage of preventing solid materials such as particles or dust that may appear during manufacturing or in the process gas from entering the rotor, thus preventing undesirable wear or imbalance of the process gas or undesirable contamination during operation. In embodiments, the central hole constituting the hollow compartment and / or press-fit compensation volume is machined to close at the end opposite the press-fit with the rotor plug. In other embodiments, the central hole is manufactured as a through hole and closed with a cap or plug element. Such a plug can also be used to enlarge the central hole and compensate for deformation of the rotor end piece by the plug within the rotor body.

[0087] According to one aspect of the present invention, which can be implemented in combination with or independently of the above-described features, a rotor having the following features is provided.

[0088] A rotor for a high-speed electric machine having a gas bearing as described in any one of the preceding claims, • At least one rotor-side radial bearing, • Rotor-side axial bearing and • comprising at least one rotor-side radial bearing, When viewed along the rotor's axis of rotation, the radial bearing section is defined as the section along which the radial bearing extends. When viewed along the rotor's axis of rotation, the axial bearing compartment is the compartment that includes the rotor-side axial bearing. A rotor in which circumferential grooves are located between the axial bearing compartment and the nearest radial bearing compartment.

[0089] This creates a thermal barrier between the axial or thrust bearing, which is heated by windage losses, and the radial bearing, which is also sensitive to temperature changes. A further advantage is that the circumferential groove can reduce deformation of the thrust bearing area within the axial bearing compartment due to stress arising from press-fitting within the radial bearing compartment.

[0090] In the embodiment, the radial depth of the circumferential groove is at least 10%, particularly at least 20%, and particularly at least 30% of the radius of the bearing sleeve in the nearest radial bearing compartment.

[0091] According to one aspect of the present invention, a stator bushing is provided that forms a non-rotating portion of a gas bearing.

[0092] According to the first embodiment, the stator bushing is for use in the stator of a high-speed electromachine having an air bearing, and the stator bushing is, • At least one sleeve in the form of a hollow cylindrical body, comprising at least one stator-side radial bearing, • comprising a stator-side axial bearing plate in the form of an annular plate, A stator bushing having a flange attached to a sleeve, the flange having an alignment surface that extends radially, i.e., perpendicular to the axis of rotation, for aligning the stator-side axial bearing plate with the sleeve.

[0093] According to the second embodiment, in the stator bushing of the first embodiment, the flange is made from a metallic material.

[0094] According to the third embodiment, in the stator bushing of the first or second embodiment, the sleeve is made from a ceramic material.

[0095] According to the fourth embodiment, in the stator bushing of the first, second, or third embodiment, the stator-side axial bearing plate is made from a metal material.

[0096] According to the fifth embodiment, the stator bushing is for use in the stator of a high-speed electromachine having an air bearing, and the stator bushing is, • At least one sleeve in the form of a hollow cylindrical body, comprising at least one stator-side radial bearing, • comprising a stator-side axial bearing plate in the form of an annular plate, A stator bushing is a bearing where the stator-side axial bearing plate and sleeve are manufactured separately and joined together.

[0097] In some embodiments, the joining can be, for example, adhesive bonding, welding, or soldering.

[0098] According to the sixth embodiment, in the stator bushing of the fifth embodiment, the flange is made from a metallic material.

[0099] According to the seventh embodiment, in the stator bushing of the fifth or sixth embodiment, the stator-side axial bearing plate is made from a metal material.

[0100] According to the eighth embodiment, the stator bushing is for use in the stator of a high-speed electromachine having an air bearing, and the stator bushing is, • At least one sleeve in the form of a hollow cylindrical body, comprising at least one stator-side radial bearing, The stator bushing comprises an inner sleeve and an outer sleeve made from different materials, i.e., the inner sleeve is made from an inner sleeve-type material and an outer sleeve-type material.

[0101] In this embodiment, the inner sleeve material has the following characteristics. It is a metallic material or a second type of material as defined herein.

[0102] In this embodiment, the outer sleeve material has the following characteristics. Low CTE: less than 7E-6K^-1, especially less than 5E-6K^-1, and even more especially less than 4E-6K^-1.

[0103] Typical materials for outer sleeves: ceramic materials, more specifically SiN, SiC, AlO. Other alternatives: iron-nickel alloys (such as Invar), glass-ceramics, tungsten carbide, metal carbides.

[0104] According to the ninth embodiment, in the stator bushing of the eighth embodiment, the outer sleeve comprises a flange integrally formed with the outer sleeve.

[0105] In the embodiment, there is a fifth set of material features, which includes the feature that the sleeve material has a CTE lower than 7E-6K^-1, particularly lower than 5E-6K^-1, and even more particularly lower than 4E-6K^-1, and the flange is made of metal, particularly steel.

[0106] In the embodiment, there is a sixth set of material features, which further includes a fifth set of material features, wherein the sleeve has an HK5 or Vickers hardness greater than 10 GPa, particularly greater than 15 GPa, and even more particularly greater than 20 GPa.

[0107] In the embodiment, there is a seventh set of material features which includes a sixth set of material features, further including the feature that the stator-side axial bearing plate is made of metal, particularly steel.

[0108] According to the embodiment, the priority order of the above-mentioned material properties defining the sleeve, flange, and stator-side axial bearing plate is as follows:

[0109] • First priority: CTE of the sleeve and material of the flange, • Second priority: Vickers hardness of the sleeve, • Third priority: Material for the stator-side axial bearing plate.

[0110] Further embodiments are evident from the dependent claims. The subject matter of the present invention will be described in more detail below with reference to exemplary embodiments illustrated in the accompanying drawings, which are schematically shown below. [Brief explanation of the drawing]

[0111] [Figure 1] This diagram shows a rotor with two separate rotor plugs. [Figure 2] This diagram shows a rotor with two separate rotor plugs. [Figure 3] This figure shows a rotor with a single rotor plug. [Figure 4] This figure shows a rotor with a single rotor plug. [Figure 5] This diagram exaggerates the tapered end of the rotor plug. [Figure 6] This diagram shows a rotor with a permanent magnet between two rotor plugs. [Figure 7] This diagram shows a rotor having rotor end pieces joined to the rotor body. [Figure 8] This figure shows a further modification of the rotor. [Figure 9] This figure shows a further modification of the rotor. [Figure 10] This figure shows a further modification of the rotor. [Figure 11] This figure shows an embodiment of a stator bushing having a flange. [Figure 12] This figure shows an embodiment of a stator bushing having a flange. [Figure 13] This figure shows an embodiment of a stator bushing having a flange. [Figure 14] This figure shows an embodiment of a stator bushing having a flange. [Figure 15] This figure shows a stator bushing made from a concentric sleeve. [Modes for carrying out the invention]

[0112] In principle, identical parts in a drawing are assigned the same reference numeral. Figure 1 schematically shows a rotor 1 having a rotor body 2 and rotor end pieces 3. The rotor body 2 has two rotor-side radial bearings 21. The rotor end piece 3 comprises a rotor-side thrust bearing plate or a rotor-side axial bearing 31. When viewed along the rotation axis of the rotor, for each rotor-side radial bearing 21, the corresponding radial bearing compartment 22 is defined as the compartment along which the radial bearing 21 extends. This is the compartment where the gas bearing generates radial force. Typically, the radial bearing compartment has at least a substantially constant radial bearing clearance. Similarly, the axial bearing compartment 32 is defined as the portion along which the rotor-side axial bearing 31 extends. The rotor end piece 3 comprises an axial stub or rotor stub shaft 38 for supporting components driven by or driving the rotor 1, such as an impeller, turbine, beam chopper, rotating prism, etc.

[0113] The rotor end piece 3, which has a rotor stub shaft 38 and a rotor-side axial bearing 31, is located at the first end or proximal end of the rotor body 2. At the opposite, second end or distal end, the permanent magnet 4 is joined to the rotor body 2. When viewed along the rotor's axis of rotation, the rotor body section 29, the rotor end section 39, and the magnet section 42 are defined as the sections to which the rotor body 2, rotor end piece 3, and permanent magnet 4 extend, respectively.

[0114] A bearing sleeve 28 is integrally molded with the rotor end piece 3. Together, these form the outer rotor portion 27. The bearing sleeve 28 is a hollow cylindrical body, and one or more rotor plugs 5 are arranged inside the bearing sleeve 28 concentrically with the bearing sleeve 28. The rotor-side radial bearings 21 can be mounted by bearing sleeves 28 having a slightly larger diameter in the region of the rotor-side radial bearings 21, but in other embodiments, as shown in Figure 1, the bearing sleeves 28 can have the same diameter along the rotor-side radial bearings 21 and the sections between them.

[0115] The rotor plug 5 is seated within the bearing sleeve 28 by press-fitting. Press-fitting is also known as compression fitting or compression fitting. The bearing sleeve 28 is relatively thin and is held in place by pre-tensioning relative to the rotor plug 5, and the thermal expansion of the bearing sleeve 28 adapts to the expansion of the rotor plug 5. This makes machining easier and allows for the manufacture of a bearing sleeve 28 made of a metallic material with a relatively high CTE (coefficient of thermal expansion), which is suitable for the rotor-side radial bearing 21 but unsuitable for the rotor-side radial bearing 21 if this CTE is effective and does not decrease in combination with the plug(s) under pre-tensioning. The rotor plug 5 is manufactured from a ceramic material with a relatively low CTE, or even zero or negative CTE. As a result, the combination of the two materials results in the entire rotor body 2, particularly the radial bearing section 22, having a relatively low CTE in the radial direction.

[0116] The permanent magnet 4 is attached to the distal rotor plug end 51b of the rotor plug 5 by a concentric magnet sleeve 43 extending along the permanent magnet 4 and a connecting stub for the distal rotor plug end 51b. The rotor plug 5 has a proximal rotor plug end 51a. If there are two rotor plugs 5, each of them has a proximal rotor plug end 51a and a distal rotor plug end 51b.

[0117] For clarity, not all reference numbers shown in Figure 1 are repeated in the following figures.

[0118] To further distinguish the elements, two separate rotor plugs 5 are labeled as the first rotor plug 5a and the second rotor plug 5b. Each plug corresponds to one, two, or more rotor-side radial bearings 21, which correspond to radial bearing compartments 22 labeled as the first radial bearing compartment 22a and the second radial bearing compartment 22b, as shown in Figure 2.

[0119] Figure 2 shows a modification of the rotor design, in which the rotor end piece 3 is equipped with a central hole 33. This can function as a ventilation duct when the rotor plug 5 is pushed into the bearing sleeve 28. By reducing the weight of the protruding rotor end piece 3, the central hole 33 can also improve the dynamic characteristics of the rotor 1. A first centering sheet 25 can be placed at the outer end of the hole, and a second centering sheet 26 can be placed at the distal rotor plug end 51b of the second rotor plug. These centering sheets can be used to assemble the rotor stub shaft 38, rotor-side axial bearing 31, and rotor-side radial bearing 21 to form a partial assembly, which can all be machined together, which is advantageous for the machining quality of the rotor 1.

[0120] In other embodiments not shown, the central hole 33 may be closed by an end cap that is machined integrally with the outer rotor portion 27 and can airtightly cover the end of the central hole 33, or it may be another element driven by the impeller 7 or rotor 1, or a separate element. This prevents solid material or gas from entering or leaving the central hole 33. The diameter of the rotor stub shaft 38 varies when viewed along the axial direction, for example, by a stepwise change in the outer and inner diameters.

[0121] Figure 3 shows a rotor 1 in which a bearing sleeve 28 extends to support a permanent magnet 4, thereby replacing the magnet sleeve 43 of the previously described embodiment. Furthermore, there is a single rotor plug 5 that extends along both rotor-side radial bearings 21. Such a single rotor plug 5 can also be implemented in combination with the magnet sleeve 43.

[0122] Figure 4 shows a rotor 1 having a single rotor plug 5, in which the bearing sleeve 28 is divided into a proximal sleeve 28a and a distal sleeve 28b. These two sleeves are pressed against both ends of the rotor plug 5. The proximal sleeve 28a can be molded integrally with the rotor end piece 3. The distal sleeve 28b can be molded integrally with the sleeve supporting the permanent magnet 4, or, as shown, there may be a magnet sleeve 43 already installed.

[0123] Figure 5 shows a rotor plug 5 with tapered sections at each rotor plug end 51a, 51b. The tapered section in the upper figure has a continuously decreasing diameter, while the tapered section in the lower figure has a diameter that, when viewed in the direction of the rotation axis, first continuously decreases in the first section and then remains constant in the second section. The degree to which the rotor plug 5 is tapered is relatively small and is greatly exaggerated in the drawings. For example, the tapered section can extend along 2 millimeters in the direction of the rotation axis, resulting in a maximum reduction of 4 micrometers in the radius of the plug at each end of the rotor plug 5. The taper results in a gradual reduction of internal stress in the bearing sleeve 28, avoiding excessive stress near each end of the rotor plug 5.

[0124] Figure 6 shows the permanent magnet 4 positioned inside the bearing sleeve 28, between the two separate rotor plugs 5, and therefore also between the rotor-side radial bearings 21. This shortens the structure of the rotor 1.

[0125] Figure 7 shows an embodiment in which the outer rotor portion 27 is manufactured from separate parts, which are a bearing sleeve 28 and a rotor stub shaft 38 having a rotor-side axial bearing 31. The bearing sleeve 28 and one or more rotor plugs 5 constitute the rotor body 2, and the rotor stub shaft 38 and rotor-side axial bearing 31 constitute the rotor end piece 3. The rotor body 2 and the rotor end piece 3 are joined, in particular by press-fitting, by the rotor end piece 3 which radially surrounds the rotor body 2 at the joint surface of these two parts. Both the rotor end piece 3 and the bearing sleeve 28 can be made from metallic materials and are easier to machine than the rotor plugs 5. In an alternative embodiment not shown, the rotor body 2 radially surrounds the rotor end piece 3 at the joint surface of these two parts.

[0126] Figure 8 corresponds to the embodiment in Figure 2, but has a split bearing sleeve 28. The rotor end piece 3 is connected to the rotor plug 5a by the proximal section of the split bearing sleeve 28, and the distal section of the split bearing sleeve 28 is connected to the rotor plug 5a, and both connections are press-fit.

[0127] Figure 9 corresponds to the embodiment shown in Figure 8, but has one rotor plug instead of two.

[0128] Figure 10 shows an embodiment in which a circumferential groove 35 is provided between the rotor end piece 3 (which has a rotor stub shaft 38 and a rotor-side axial bearing 31) and the bearing sleeve 28. The circumferential groove 35 can thermally and / or mechanically separate the rotor end piece 3 and the bearing sleeve 28 from each other.

[0129] In the embodiment, at least a portion of the outer rotor portion 27, particularly the bearing sleeve 28, is manufactured by coating the rotor plug 5 or a portion of the rotor plug 5. The coating may be, for example, hard chromium, tungsten carbide, or diamond-like carbon (DLC). This makes it possible to create a very thin bearing sleeve 28. Its thermal expansion is controlled by the thermal expansion of the bearing plug 5.

[0130] Such coatings constituting the bearing sleeve can be present, for example, in the embodiment of Figure 4 (as distal sleeve 28b) or in the embodiment of Figure 9 (as bearing sleeve 28).

[0131] Figures 11 to 15 show embodiments of a stator bushing 100 that includes a sleeve 101 and a flange 102 for aligning the stator-side axial bearing plate 131 with the sleeve 101.

[0132] Figure 11 shows a stator bushing 100 comprising a substantially cylindrical sleeve 101 and an annular stator flange 102, the flange 102 having an alignment surface 103. The stator bushing 100 is designed to function as a bearing bushing for a rotor 1 having the type of journal bearings presented herein, but is not limited thereto. The sleeve 101 constitutes one or more stator-side radial bearings 121 on its inner cylindrical surface. The alignment surface 103 is perpendicular to the axis of rotation, which coincides with the longitudinal axis of the stator bushing 100. The alignment surface 103 serves to align a stator-side axial bearing plate 131 (not shown in Figure 10) with the sleeve 101. This stator-side axial bearing plate 131, together with a second stator-side axial bearing plate, constitutes a thrust bearing in which the rotor's axial bearing plate rotates. By manufacturing the flange 102 as a separate part from the stator bushing 100 and then joining them together, it is possible to manufacture each of them as simple parts by machining, and / or they can be made from different materials. The joining of the sleeve 101 and the flange 102 can be done by press-fitting, bonding, welding, or soldering.

[0133] The stator-side axial bearing plate 131, thus aligned with the sleeve 101, can be used in a bearing configuration such as that described in International Publication No. 2017 / 202941, which is incorporated herein by reference.

[0134] Figure 12 shows a substantially cylindrical flange 102 that is coaxially positioned and fixedly mounted to the sleeve 101. The flange 102 is pressed against the axial bearing plate 131 by an axial compensating element 132, as disclosed in International Publication No. 2017 / 202941. The axial compensating element 132 may be a leaf spring (conical spring washer), a spring washer, or an O-ring. It is configured to axially push the bushing sleeve 101 away from the stator body (not shown) relative to the axial bearing plate 131 or stator disc by applying an axial force to its flange 102. The axial bearing plate 131 or stator disc is then pressed and held against the stator body by fasteners (not shown).

[0135] Figure 13 shows an axial bearing plate 131 attached to the sleeve 101 so as to be fixed by, for example, adhesive, welding, or soldering.

[0136] Figure 14 shows an axial bearing plate 131 mounted to be fixed to the sleeve 101, with one or more ventilation openings 104 passing through the axial bearing plate 131 and / or the sleeve 101 in the area where they are joined to each other.

[0137] Figure 15 shows a sleeve 101 comprising a coaxially arranged inner sleeve 101a and outer sleeve 101b. They can be assembled by press-fitting or by other means of connection such as bonding, welding, or soldering. In their own way, they can be made from separate materials. Furthermore, the outer sleeve 101b is provided with an integrally molded flange 105. In this way, the outer sleeve 101b can be selected to be thicker than the inner sleeve 101a, thereby controlling the total CTE resulting from the combination of the two materials. This is the same principle as in rotor embodiments where the CTE of the rotor plug 5 combined with the bearing sleeve 28 controls the total CTE of the rotor body 2. The material of the inner sleeve 101a can be selected according to the requirements for one or more radial bearings 121.

[0138] Although the present invention has been described in this embodiment, it should be clearly understood that the present invention is not limited thereto and may be embodied and practiced in various other ways within the scope of the claims.

Claims

1. A rotor for a high-speed electric machine having a gas bearing, At least one rotor-side radial bearing (21) and Rotor-side axial bearing (31) and A rotor body section (29) having at least one rotor-side radial bearing (21), The rotor end section (39) includes the rotor-side axial bearing, When viewed along the rotation axis of the rotor, the radial bearing section (22) is defined as a section along which the radial bearing extends. The outer rotor portion (27) extends along the rotor end portion and the rotor body portion, The outer rotor portion (27) is formed to form a hollow cylindrical body that functions as a bearing sleeve (28) within the rotor body section (29), which includes at least one rotor-side radial bearing (21). The outer rotor portion (27) of the rotor end section (39) forms a rotor stub shaft (38). The rotor stub shaft (38) is driven by the rotor or carries a component that drives the rotor. A rotor (1) characterized in that at least one rotor plug (5) is disposed inside the bearing sleeve (28), and the material of the at least one rotor plug (5) has a coefficient of thermal expansion (CTE) lower than 7E-6K⁻¹.

2. The rotor (1) according to claim 1, wherein the material of the outer rotor portion (27) is at least one of metal, metallic material, or steel.

3. The rotor (1) according to claim 1, wherein the material of the outer rotor portion (27) has a Rockwell hardness greater than 40 HRC.

4. The rotor (1) according to claim 1, wherein the material of at least one rotor plug (5) has a density of less than 4500 kg / m³.

5. The rotor (1) according to claim 1, wherein in at least one of one or more radial bearing compartments (22), the at least one rotor plug (5) extends along the entire radial bearing compartment (22).

6. The rotor (1) according to any one of claims 1 to 5, comprising first and second rotor-side radial bearings (21) corresponding to first and second radial bearing sections (22a, 22b), respectively, and first and second rotor plugs (5a, 5b) respectively arranged to extend along the first and second radial bearing sections (22a, 22b).

7. The rotor (1) according to any one of claims 1 to 5, comprising first and second rotor-side radial bearings (21) corresponding to first and second radial bearing sections (22a, 22b), respectively, and a single rotor plug (5) arranged to extend along both of the first and second radial bearing sections (22).

8. The rotor (1) according to claim 7, wherein the bearing sleeve (28) is a proximal sleeve (28a) that extends along the first radial bearing section (22a) rather than along the second radial bearing section (22b), and a further or distal sleeve (28b) extends along the second radial bearing section (22b) rather than along the first radial bearing section (22a).

9. The rotor (1) according to claim 8, wherein the distal sleeve (28b) extends over the distal end of the rotor plug (5), and the permanent magnet (4) is disposed within the distal sleeve (28b).

10. The rotor (1) according to any one of claims 1 to 5, wherein the bearing sleeve (28) extends over the distal end (51b) of the rotor plug (5), and the permanent magnet is disposed within the bearing sleeve (28).

11. The rotor (1) according to any one of claims 1 to 5, wherein the permanent magnet is disposed within a magnet sleeve (43), the magnet sleeve (43) extends over the permanent magnet, and forms a press fit with the distal rotor plug end (51b).

12. The at least one rotor plug (5) has one rotor plug end (51) or both ends tapered, When viewed along the rotation axis of the rotor, the tapered section is defined as the section along which the rotor plug (5) becomes tapered. The rotor (1) according to any one of claims 1 to 5, wherein the pressing force between the rotor plug (5) and the bearing sleeve in the tapered section is gradually reduced.

13. The rotor (1) according to any one of claims 1 to 5, wherein the permanent magnet (4) is positioned between the first rotor plug (5a) and the second rotor plug (5b).

14. A rotor body (2) having at least one rotor-side radial bearing (21), The rotor end piece (3) includes the rotor side axial bearing, The rotor (1) according to any one of claims 1 to 5, wherein the rotor end piece (3) and the rotor body (2) are components that are manufactured separately and connected to each other.

15. The rotor (1) according to any one of claims 1 to 5, wherein the rotor end piece (3) comprises a hollow section, the hollow section extending axially along at least 50% of the axial length of the rotor end piece (3) along at least the axial bearing section (32).

16. A rotor (1) for a high-speed electric machine having a gas bearing according to any one of claims 1 to 5, - The at least one rotor-side radial bearing (21) and - comprising the rotor-side axial bearing (31), When viewed along the rotation axis of the rotor, the axial bearing section (32) is a section that includes the rotor-side axial bearing (31). - The circumferential groove (35) is located between the axial bearing section (32) and the nearest radial bearing section (22). Rotor (1).

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