Method for manufacturing a permanent magnet bearing insert for a vacuum pump, permanent magnet bearing insert, and temporary masking shroud

Abstract

A method for manufacturing a permanent magnet bearing insert for a vacuum pump, the vacuum pump comprising a rotor shaft defining a cavity configured to house a permanent magnet bearing insert in a press-fit configuration, the method comprising: a) preparing one or more permanent magnet alloy rings for the rotor bearing half of a permanent magnet bearing; b) masking the surface of the or one or more permanent magnet alloy rings, wherein the or each permanent magnet alloy ring is configured to substantially interface with another surface of the permanent magnet bearing insert and / or the rotor shaft cavity when the permanent magnet bearing insert is housed in the rotor shaft cavity; and c) coating the or each permanent magnet alloy ring, wherein step b) substantially prevents the masked surface from being coated during step c), and steps b) and c) are performed substantially outside the vacuum pump.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a permanent magnet bearing insert for a vacuum pump and a method for manufacturing a vacuum pump. Further, the present invention relates to a permanent magnet bearing insert and a vacuum pump provided with the same.

Background Art

[0002] A vacuum pump generally includes a housing having an inlet and an outlet, and a stator is coupled to the housing. A rotor is disposed within the housing and is rotatably supported by bearings. The rotor includes at least one rotor element that interacts with the stator to convey a gaseous medium from the inlet to the outlet. In the case of a turbomolecular vacuum pump, the stator generally includes a plurality of vanes that interact with a plurality of rotor vanes.

[0003] Generally, a vacuum pump uses a permanent magnet bearing to support the rotor.

[0004] A permanent magnet bearing generally includes a rotor-side and a stator-side bearing half each including one or more permanent magnets. Generally, the permanent magnets on each bearing half are arranged as one or more permanent magnet alloy rings. The bearing halves are arranged close to each other and are generally configured to repel each other during use. Thereby, the rotor is supported without contact, avoiding the need to use lubricants or greases.

[0005] However, there still remains a continuing need to maintain accurate tolerances between the permanent magnets and the cavities of the rotor and stator configured to house them while coating the permanent magnet bearings with a protective coating to protect them from corrosive components in the vacuum pump process.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention aims to solve these problems and other problems in the prior art. [Means for solving the problem]

[0007] Accordingly, in a first aspect, the present invention provides a method for manufacturing a permanent magnet bearing insert for a vacuum pump, comprising a rotor shaft defining a cavity configured to house a magnet bearing insert in a tight-fit configuration.

[0008] This delicious, a) The step of preparing one or more permanent magnet alloy rings for the rotor bearing half of a permanent magnet bearing, b) A step of masking one or more surfaces of the above-mentioned permanent magnet alloy ring or each permanent magnet alloy ring, wherein the above-mentioned permanent magnet bearing insert or each permanent magnet alloy ring is configured to substantially interface with another surface of the permanent magnet bearing insert or with the rotor shaft cavity when the permanent magnet bearing insert is housed in the rotor shaft cavity, C) The step of applying a coating to the above or each permanent magnet alloy ring, Includes.

[0009] Step b) is performed such that, while the mask is in place, the masking is substantially prevented from being coated by the coating.

[0010] Furthermore, steps b) and c) are performed substantially outside the vacuum pump.

[0011] Generally, the coating is a substantially corrosion-resistant coating, for example, a coating that prevents or reduces corrosion of a permanent magnet alloy ring. In embodiments, the coating may be a coating other than a substantially corrosion-resistant coating, or a combination of coatings or coating layers.

[0012] The process components of vacuum pumps are often known to be highly corrosive to permanent magnet bearings. Therefore, known protective coatings and coating methods have been developed, for example, to minimize or avoid corrosion caused by hydrogen (H2) induced degradation, where hydrogen molecules come into contact with a magnet (e.g., a neodymium or samarium-cobalt magnet), and a chemical reaction occurs between them, resulting in hydrogen degradation on the magnet. When a corresponding vacuum pump is not used, protective coatings can also be provided to protect permanent magnet bearings from corrosion caused by the environment (i.e., air).

[0013] However, known coating methods often hinder the need for precise tolerances between the permanent magnet and the corresponding cavity on the rotor shaft configured to house it. Specifically, the permanent magnet alloy ring is typically press-fitted into the rotor shaft cavity. Therefore, precise tolerances are required to minimize the risk of damage to the magnetic element, which is generally brittle and can fracture under tensile stress, while ensuring a proper interference fit between the permanent magnet bearing insert and the rotor shaft cavity. A proper interference fit means minimizing the movement of the permanent magnet bearing insert relative to the rotor shaft cavity as the components of the vacuum pump undergo thermal expansion and contraction during use.

[0014] Traditionally, magnetic elements have been coated with a protective coating before vacuum pump assembly, generally before magnetization, to facilitate handling and minimize the risk of demagnetization (coating processes often require high temperatures, which can cause demagnetization). However, these existing methods increase the press-fit tolerance between the ring and the rotor shaft cavity. It is generally important that the magnetic alloy ring is substantially coated over its entire surface. Larger fitting tolerances increase the risk of the magnet being subjected to stress exceeding its limits during use and / or losing contact with the vacuum pump.

[0015] Other known coating methods, such as those described in European Patent Application Publication No. 2759726, describe coating a permanent magnet alloy ring in place, for example, after it has been inserted into the rotor shaft cavity, selectively coating only the surface of the magnetic alloy ring that may come into contact with corrosive process gases during use. However, access to the permanent magnet bearing is limited when it is placed inside a vacuum pump. This limits the available coating processes and the accuracy of the coating on the magnetic alloy ring, due to the mechanical constraints when coating a permanent magnet alloy ring placed inside a vacuum pump. Processes such as immersion or bath methods become difficult to implement.

[0016] The present invention is particularly advantageous in that it provides a method for selectively coating only surfaces that may be potentially exposed to corrosive process gases during use, while not coating surfaces that are not configured to be exposed (e.g., surfaces that would not be well coated). This is achieved while addressing existing mechanical constraints when coating permanent magnets in place. More specifically, since the permanent magnet bearing insert is coated outside the vacuum pump, a wider range of coating processes can be used with high precision. Furthermore, since the permanent magnet bearing insert can be inspected directly after coating, it is ensured that all surfaces to be coated are coated and surfaces that should not be coated are not coated. Thus, precise tolerances can be achieved between the permanent magnet bearing insert and the rotor shaft cavity that houses it.

[0017] As used herein, the term “interference fit” means a fit between parts in which the external dimensions of a first part are at least substantially the same as (or better than) the internal dimensions of a second part into which the first part fits.

[0018] In embodiments, the permanent magnet bearing insert may include a sleeve configured to bond to the circumferential surface of the rings or each permanent magnet alloy ring. Typically, the rings or each permanent magnet alloy ring are bonded to the sleeve outside the vacuum pump, and then the permanent magnet bearing insert (including the sleeve and each permanent magnet alloy ring) is inserted into the rotor shaft cavity. The sleeve is generally a radially outward-extending sleeve configured to bond to the outer circumferential surface of the rings or each permanent magnet alloy ring. In embodiments, the sleeve may be a radially inward-extending sleeve configured to bond to the inner circumferential surface of the rings or each permanent magnet alloy ring.

[0019] Generally, when the above-mentioned permanent magnet alloy rings or each of them are coupled to a sleeve, a first compressive force is applied to the permanent magnet alloy rings, and then, when the permanent magnet bearing insert (including the permanent magnet alloy rings and sleeves) is inserted into the rotor shaft cavity, a further compressive force is applied to the permanent magnet bearing insert.

[0020] The present invention is particularly advantageous when at least one of the permanent magnet alloy rings is a neodymium magnet or neodymium magnet alloy, because such magnets or magnet alloys typically have a low coefficient of thermal expansion. Therefore, cooling of the magnetic elements during the assembly process typically has only a negligible thermal expansion effect, and depending on the rotor shaft material, the maximum temperature to which the magnetic elements can be exposed before demagnetization occurs is relatively low, making it desirable to apply a stepwise compressive force to the permanent magnet alloy rings. Alternatively or additionally, the interference fit to which the maximum heating temperature of the rotor can be achieved may be limited. Therefore, this configuration is advantageous in that it reduces the risk of demagnetization or damage to at least one permanent magnet alloy ring and makes it easier to install the permanent magnet alloy rings into the rotor shaft cavity with sufficient interference fit.

[0021] Typically, the sleeve of a permanent magnet bearing insert is nearly tubular. The sleeve can extend from the proximal end to the distal end. When in its original position within a vacuum pump, the proximal end is typically located towards the low-pressure, inlet end of the rotor, while the distal end is typically located towards the relatively high-pressure, outlet section of the rotor.

[0022] In embodiments, the sleeve may include one or more radially inwardly extending annular flanges for holding a plurality of permanent magnet alloy rings. During use, the permanent magnet alloy rings can be in direct contact with the radially inwardly extending annular flanges. For example, the flanges may be positioned towards the proximal, low-pressure end of the sleeve. Such radially inwardly extending annular flanges may be integral to the sleeve or may be separate, typically annular units. In embodiments, the sleeve may include a plurality of radially inwardly extending annular flanges. In embodiments, one or more surfaces of the flanges may be coated during step c).

[0023] In some embodiments, one end of the sleeve may include a substantially funnel-shaped opening. This helps to form an interlocking fit between the sleeve and the permanent magnet alloy rings. Typically, before inserting the permanent magnet alloy rings, the funnel-shaped opening reduces the inner diameter of the sleeve from a diameter larger than the diameter of the permanent magnet alloy rings to a diameter smaller than the diameter of the permanent magnet alloy rings. When placed in its intended position, the rings typically form an interlocking fit.

[0024] In an embodiment, one end of the sleeve can include a tapered and / or stepped outer surface. The stepped outer surface can include one or more steps. This can assist in pushing the bearing insert into the rotor shaft cavity. Typically, before the bearing insert is inserted into the rotor shaft cavity, the tapered outer surface is such that the outer diameter of the sleeve increases from a diameter smaller than the inner diameter of the rotor shaft cavity to a diameter larger than the diameter of the rotor shaft cavity. This can assist in pushing the bearing insert into the rotor shaft cavity and / or forming an interference fit.

[0025] Typically, the rotor shaft cavity is positioned at the end of the rotor shaft, or towards the distal end, or towards the low-pressure end. However, in an embodiment, the rotor shaft cavity can be present at the end of the rotor shaft, or towards the proximal end, towards the relatively high-pressure end, or at both ends of the rotor shaft, or towards both ends. The rotor shaft cavity can be configured to slidably accommodate the bearing insert to achieve a close fit around the outer periphery of the bearing insert. Typically, the rotor shaft cavity has a generally circular cross-section. The fit between the rotor shaft cavity and the bearing insert can be permanent or semi-permanent.

[0026] Typically, the bearing insert can comprise from about 1 to about 10 permanent magnet alloy rings, more preferably from about 2 to about 6 permanent magnet alloy rings, and particularly preferably 2 to 4 permanent magnet alloy rings.

[0027] In an embodiment, step b) can include coupling the above or each permanent magnet alloy ring to the sleeve to form an interference fit therebetween. Thus, the coupling between the sleeve and the above or each permanent magnet alloy ring may occur before step c), and the sleeve can function to mask one or more surfaces of the above or each permanent magnet alloy ring and / or assist in the step of installing the permanent magnet alloy ring into the rotor shaft cavity. In an embodiment, in step c), when a coating is applied to the sleeve, this method can include the step of removing at least a portion of the coating applied to the sleeve. For example, in an embodiment, the coating is applied to the surface of the sleeve and then (partially or completely) removed by machining from those surfaces of the sleeve configured to interface with the rotor cavity. Thus, the permanent magnet bearing insert can be properly coated while ensuring that a proper interference fit is achieved and maintained between the insert and the rotor cavity.

[0028] Prior to step c), coupling the above or each permanent magnet alloy ring to the sleeve masks the surface of the permanent magnet alloy ring that will not be coated.

[0029] In use, the sleeve generally engages in contact with the rotor shaft cavity of the vacuum pump, and the above or each permanent magnet alloy ring is coupled to the sleeve. Thus, the sleeve can function as a buffer between the rotor shaft cavity and the above or each permanent magnet alloy ring. This is particularly advantageous since the sleeve can also function to strengthen the required interference fit configuration between the rotor shaft cavity and the permanent magnet bearing insert.

[0030] Therefore, it is important that the sleeve can function to mask the surface that is not configured to be coated while applying a compressive force to the above or each permanent magnet alloy ring outside of the vacuum pump and simultaneously coating it.

[0031] In the embodiment, step b) may substantially consist only of coupling the sleeve to the above or each permanent magnet alloy ring. In other words, the sleeve may only provide masking of the surface of the above or each permanent magnet alloy ring.

[0032] In embodiments, step b) may include the steps of applying a temporary masking shroud to the permanent magnet bearing insert and removing the temporary masking shroud after step c). For example, step b) may include applying a separate masking shroud or similar to the permanent magnet bearing insert in conjunction with coupling the sleeve to the above or each permanent magnet alloy ring. For example, a temporary non-stick masking agent can be applied to the surface of one or more permanent magnet alloy rings and / or one or more surfaces of the sleeve to substantially prevent those surfaces from being coated during step c).

[0033] In embodiments, a temporary masking shroud can be applied to one or more surfaces of the sleeve configured not to be coated during step c). In other words, step b) may include masking one or more surfaces of the permanent magnet bearing insert, including another surface of the permanent magnet bearing insert or a sleeve configured to substantially interface with the rotor shaft cavity, when the permanent magnet bearing insert is housed in the rotor shaft cavity. Thus, in embodiments, the masking in step b) may include a combination of the steps of the sleeve masking one or more surfaces of each permanent magnet alloy ring and the temporary shroud masking one or more surfaces of the sleeve and / or one or more permanent magnet alloy rings.

[0034] In embodiments, the temporary masking shroud may include a non-adhesive agent. For example, the temporary masking shroud may include a gel or similar substance that can be applied to one or more surfaces of the above or each permanent magnet alloy ring during step b).

[0035] In embodiments, the temporary masking shroud may include a casing. For example, the casing may take the form of a shell having one or more parts provided for temporary coupling to the permanent magnet bearing insert before step c). In another example, the casing may include a substantially cylindrical tube configured to be positioned around the outer circumferential surface of the permanent magnet alloy ring or each permanent magnet alloy ring before step c). Thus, when the permanent magnet bearing insert is housed in the rotor shaft cavity during use, other surfaces of the permanent magnet bearing insert (permanent magnet alloy ring or sleeve, if present) or those surfaces of the permanent magnet alloy ring configured to interface with the rotor shaft cavity are not coated during step c).

[0036] In embodiments, step b) may include arranging two or more permanent magnet alloy rings together to substantially prevent coating of one or more surfaces of at least one permanent magnet alloy ring. For example, step b) may include stacking a plurality of permanent magnet alloy rings to mask one or more surfaces of those rings before coating.

[0037] Typically, the permanent magnet alloy ring has a substantially continuous annular configuration. However, in embodiments, the permanent magnet alloy ring may have a substantially discontinuous structure. For example, in embodiments, the permanent magnet alloy ring may take the form of a plurality of permanent magnet alloy blocks arranged substantially circumferentially, for example, within a substantially annular unit.

[0038] In the embodiments, the coating may be a thermosetting electrical insulating coating or conformal coating, and / or a UV-curable and / or visible light-curable and / or moisture-curable electrical insulating coating or conformal coating. In the embodiments, the coating may be based on a synthetic resin such as epoxy, acrylic, acrylic urethane, polyurethane, or silicone.

[0039] In the embodiment, the permanent magnet bearing insert may become substantially demagnetized during step c). For example, if the bearing insert comprises a single permanent magnet alloy ring, the bearing insert may become substantially demagnetized during step c) and then be magnetized. This is advantageous because it makes handling and coating the bearing insert easier.

[0040] In embodiments, the method may further include a step of magnetizing the above or each permanent magnet alloy ring before step c). In embodiments, the method may include a step of magnetizing the above or each permanent magnet alloy ring before step b).

[0041] Typically, if the permanent magnet bearing insert includes a sleeve, the above or each permanent magnet alloy ring is magnetized before being coupled to the sleeve and before step c). Advantageously, the sleeve can facilitate handling of the permanent magnet bearing insert during the coating process.

[0042] In embodiments, for example, if the permanent bearing insert includes a sleeve, the coating process can typically be performed at a temperature below the demagnetization threshold of the permanent magnet alloy rings, at which demagnetization and / or thermal degradation of the permanent magnet alloy rings may occur. For example, if the permanent magnet alloy rings include neodymium (NdFeB), demagnetization may begin at temperatures above 120°C for commonly used grades.

[0043] In this embodiment, the coating can be a varnish, and the varnish can be curable at a temperature below the demagnetization threshold.

[0044] In this embodiment, the coating may be a two-component coating. For example, the first and / or second component may include a nickel-copper-nickel coating (NiCuNi).

[0045] In embodiments, the coating can be applied to result in a coating thickness between approximately 0.008 mm and approximately 0.5 mm, preferably between approximately 0.02 mm and approximately 0.2 mm, more preferably between approximately 0.05 mm and approximately 0.2 mm, for example, 0.1 mm. For example, certain epoxy coatings can result in thicknesses between approximately 0.02 mm and approximately 0.03 mm. Thus, the permanent magnet bearing insert can be provided with improved protection, for example, impact resistance to minimize the risk of damage to the permanent magnet bearing insert during vacuum pump assembly. For example, the coating thickness can be increased to provide additional protection and / or encapsulation effect to the above or each permanent magnet alloy ring, enabling enhanced protection. In embodiments, different coating types can be provided as separate coating layers with different intended effects, at least one of the layers can be configured to provide impact resistance to the coating surface(s), and another layer can be configured to provide protection to the coating surface(s) against corrosion by air and / or process gases.

[0046] In embodiments, coating can be applied by brushing, dipping, painting, bath treatment, spraying, curing, vacuum impregnation (VPI), chemical vapor deposition, physical vapor deposition, electrodeposition, or a combination thereof. For example, a permanent magnet bearing insert can be dipped in a varnish bath during step c). Alternatively or additionally, the coating can be sprayed or brushed. In embodiments, the coating can be applied by a combination of coating processes.

[0047] In embodiments, the above-mentioned or each permanent magnet alloy ring may include a neodymium magnet or neodymium magnet alloy, such as NdFeB. The NdFeB magnet may contain other elements besides Nd, Fe, and B. For example, praseodymium may be added in a variable amount as a substitute for neodymium. Other elements may include one or more of Dy, Ga, Co, Al, and Cu. In other embodiments, the magnet may include a PrFeB magnet.

[0048] In the embodiment, the permanent magnet alloy ring may contain samarium cobalt.

[0049] In a further embodiment, the present invention provides a permanent magnet bearing insert for a rotor bearing half of a permanent magnet bearing, manufactured according to any of the above embodiments.

[0050] In a further embodiment, the present invention provides a method for manufacturing a permanent magnet bearing insert for a vacuum pump, comprising a stator defining a base configured to interface with a permanent magnet bearing insert. a) The step of preparing one or more permanent magnet alloy rings for the stator bearing half of a permanent magnet bearing, b) When the permanent magnet bearing insert interfaces with the stator base, the step of masking the surface of the permanent magnet alloy ring or each permanent magnet ring configured to substantially interface with another surface of the permanent magnet bearing insert or stator base, c) The step of applying a coating to the above or each permanent magnet alloy ring, Includes.

[0051] Therefore, the above coating method can be applied to the stator bearing half of a permanent magnet bearing, in addition to or instead of the rotor bearing half. For example, each of the two permanent magnet bearing inserts of a permanent magnet bearing (one rotor half and one stator half) can be coated according to the above method.

[0052] Typically, if a vacuum pump includes two permanent magnet bearing inserts, a rotor half and a stator half, both inserts can be housed in the rotor cavity, and the rotor half insert is housed in the rotor cavity in an interference fit configuration.

[0053] In embodiments, the stator base may include a stator surface to which the inner circumferential surfaces of the permanent magnet alloy rings abut when the permanent magnet bearing insert is in its original position. For example, typically substantially annular permanent magnet bearing inserts can engage with the stator in a sliding fit configuration and / or an interlocking fit configuration. Typically, the permanent magnet bearing insert is configured to form a sliding fit with the stator, and the axial position of the permanent magnet bearing insert can be adjusted relative to the rotor bearing half of the permanent magnet bearing. Selective coating of the permanent magnet bearing insert on the stator half of the permanent magnet bearing allows for improved radial positioning of the bearing insert on the stator.

[0054] In the embodiment, the permanent magnet bearing insert may include a sleeve configured to bond with the circumferential surface of the permanent magnet alloy ring or each permanent magnet alloy ring. Generally, the sleeve may be a radially inward-extending sleeve configured to bond with the inner circumferential surface of the permanent magnet alloy ring or each permanent magnet alloy ring.

[0055] In embodiments, the stator half is housed substantially slidably on the stator, allowing the axial position of the stator bearing half to be changed. For example, in embodiments where the insert includes a sleeve, the sleeve can slidably engage with the stator. Alternatively, the stator may include a stator support to which the stator bearing half is attached, and the stator support itself may be adjustable to change the axial position of the stator bearing half.

[0056] Typically, the permanent magnet bearing described above includes a rotor bearing half located outside its stator bearing half during use. In other words, the stator bearing half has an outer diameter smaller than the inner diameter of the rotor bearing half, and the stator bearing half lies within a boundary defined by the inner diameter of the rotor bearing half, with a gap between them. However, this is not always the case in embodiments, for example, the rotor half of a permanent magnet bearing may constitute its innermost circumference, while the stator half constitutes its outermost circumference. In such cases, the sleeve in the stator insert may be located outside the permanent magnet alloy ring, and the sleeve in the rotor insert may be located inside the permanent magnet alloy ring.

[0057] In a further embodiment, the present invention provides a permanent magnet bearing insert for a stator bearing half of a permanent magnet bearing manufactured according to the above embodiment.

[0058] In a further embodiment, the present invention provides a method for manufacturing a vacuum pump, preferably a turbomolecular pump. The vacuum pump comprises a rotor shaft configured such that one or more rotor blades are coupled to the rotor shaft, and a stator defining a cavity for housing a magnetic bearing insert for the rotor half of a permanent magnet bearing and / or defining a base for mounting a magnetic bearing insert for the stator half of a permanent magnet bearing. This method, i. A step of performing any of the above embodiments ii. The steps of inserting the permanent magnet bearing insert for the rotor half into the rotor shaft cavity of the vacuum pump in an interlocking configuration and / or inserting it onto the stator base of the vacuum pump, Includes.

[0059] By selectively coating the permanent magnet bearing inserts before inserting them into the rotor shaft cavity or stator cavity of a vacuum pump, a wider range of coating processes become available, as described above, and the coating quality of the permanent magnet bearing inserts can be improved.

[0060] Typically, the above or each permanent magnet alloy ring is magnetized before step ii, usually during step i. However, in embodiments, this method may include a step of magnetizing the above or each permanent magnet alloy ring of the insert after step ii.

[0061] In a further embodiment, the present invention provides a vacuum pump manufactured according to any of the above embodiments.

[0062] In a further embodiment, the present invention provides a permanent magnet bearing insert for a vacuum pump, the vacuum pump comprising a rotor shaft to which one or more rotor blades are coupled, the rotor shaft defining a cavity configured to accommodate the magnet bearing insert in an interference fit configuration.

[0063] A permanent magnet bearing insert comprises one or more permanent magnet alloy rings in the rotor bearing half of a permanent magnet bearing.

[0064] The permanent magnet bearing insert includes a coating. The coating is arranged such that, when the permanent magnet bearing insert is housed in the rotor shaft cavity, one or more surfaces of another surface of the permanent magnet bearing insert or of a permanent magnet alloy ring configured to substantially interface with the rotor shaft cavity are substantially uncoated.

[0065] Advantageously, the permanent magnet bearing inserts are coated before being inserted into the rotor shaft cavity.

[0066] Generally, the coating is essentially a corrosion-resistant coating, i.e., a coating that prevents or reduces corrosion of the permanent magnet alloy ring.

[0067] In embodiments, the permanent magnet bearing insert may include a sleeve coupled to the permanent magnet alloy ring, substantially around the circumferential surface of the ring or each permanent magnet alloy ring, for example, around the outer circumferential surface of the ring or each permanent magnet alloy ring. The sleeve protects the ring or each permanent magnet alloy ring and increases the compressive force to improve the interference fit between the permanent magnet bearing insert and the rotor cavity of the vacuum pump. The sleeve is generally a sleeve that extends radially outward, but in embodiments, the sleeve may be a sleeve that extends radially inward.

[0068] In the embodiment, the rings described above or each permanent magnet alloy ring can be coupled to a sleeve before the permanent magnet bearing insert is coated. Thus, the sleeve can serve to mask the surface of the rings described above or each permanent magnet alloy ring, which will be substantially uncoated after the permanent magnet bearing insert is coated.

[0069] In the embodiment, the above or each permanent magnet alloy ring is a neodymium magnet or neodymium magnet alloy, preferably Nd2Fe 14 B may be included. In the embodiment, the above or each permanent magnet alloy ring is made of samarium cobalt, preferably SmCo5 or Sm2Co 17 This may include neodymium magnets (plural) which are particularly preferred. Typically, if multiple magnet alloy rings are present, each contains substantially the same material.

[0070] In the embodiment, the coating may be a thermosetting electrical insulating coating or conformal coating, and / or UV curable, and / or visible light curable, and / or moisture curable electrical insulating coating or conformal coating. In the embodiment, the coating may be based on synthetic resins such as epoxy, acrylic, acrylic or acrylated urethane, polyurethane, or silicone.

[0071] In embodiments, the coating may have a thickness between approximately 0.005 mm and approximately 0.20 mm, preferably between approximately 0.01 mm and approximately 0.15 mm, for example, 0.05 mm, approximately 0.05 mm, or approximately 0.13 mm. For example, certain epoxy coatings can provide thicknesses between approximately 0.02 mm and approximately 0.03 mm.

[0072] In the embodiments, the coating can be applied by dipping, painting, bath treatment, spraying, UV curing, moisture curing, vacuum impregnation (VPI), chemical vapor deposition, physical vapor deposition, electrodeposition, or a combination thereof.

[0073] In a further embodiment, the present invention provides a vacuum pump, preferably a turbomolecular pump, the vacuum pump comprising a rotor shaft configured such that one or more rotor blades are coupled to the rotor shaft, the rotor shaft defining a cavity for housing a permanent magnet bearing insert according to any of the above embodiments, typically in an interference fit configuration.

[0074] In a further embodiment, the present invention provides a permanent magnetic bearing insert for a vacuum pump, the vacuum pump including a stator defining a base configured to interface with the magnetic bearing insert in an interlocking fit configuration.

[0075] A permanent magnet bearing insert includes one or more permanent magnet alloy rings in the stator bearing half of a permanent magnet bearing.

[0076] The permanent magnet bearing insert includes a coating. Generally, the coating is a substantially corrosion-resistant coating, i.e., a coating that prevents or reduces corrosion of the permanent magnet alloy ring. The coating is arranged such that, when the permanent magnet bearing insert is housed in the stator base, one or more surfaces of the permanent magnet bearing insert that are configured to substantially interface with the stator base are substantially uncoated.

[0077] Advantageously, the permanent magnet bearing insert is coated before it interfaces with the stator base.

[0078] In the embodiment, the permanent magnet bearing insert may include a sleeve configured to bond with the circumferential surface of the permanent magnet alloy ring. Generally, the sleeve may be a radially inwardly extending sleeve configured to bond with the inner circumferential surface of the ring or each permanent magnet alloy ring.

[0079] In embodiments, the stator half can be substantially slidably housed on the stator so as to change the axial position of the stator bearing half. For example, in embodiments where the insert includes a sleeve, the sleeve can be slidably engaged with the stator. Alternatively, the stator may include a stator support to which the stator bearing half is mounted, and the stator support itself may be adjustable so as to change the axial position of the stator bearing half.

[0080] In a further embodiment, the present invention provides a vacuum pump, preferably a turbomolecular pump, comprising a stator defining a base that interfaces with a permanent magnet bearing insert according to any of the above embodiments. In the embodiment, the stator base and the permanent magnet bearing insert may be substantially in a pressure-fit configuration.

[0081] In a further embodiment, the present invention provides a temporary masking shroud for a permanent magnet bearing insert for a rotor or stator bearing half of a permanent magnet bearing of a vacuum pump, wherein the permanent magnet bearing insert comprises one or more permanent magnet alloy rings that are partially, for example, selectively coated.

[0082] The temporary masking shroud comprises one or more compartments for housing permanent magnet bearing inserts. The compartments are configured such that, when the permanent magnet bearing inserts are housed therein, one or more surfaces of the permanent magnet alloy rings are substantially exposed for coating, but one or more other surfaces of the permanent magnet alloy rings are substantially prevented from being coated.

[0083] For example, when a permanent magnet bearing insert is housed in a temporary masking shroud, the surface that is substantially prevented from being coated may be another surface of the permanent magnet bearing insert or a surface configured to interface with the rotor shaft cavity or stator base of the vacuum pump when the permanent magnet bearing insert is housed therein. The surface substantially exposed for coating may be the surface of a permanent magnet alloy ring configured to be exposed to process gases in the vacuum pump when the permanent magnet bearing insert is housed therein during use.

[0084] In the embodiment, one or more compartments of the temporary masking shroud can be configured to accommodate permanent magnet bearing inserts in a substantially interlocking fit configuration.

[0085] In the embodiment, the permanent magnet bearing insert may include a sleeve configured to bond to the circumferential surface of the permanent magnet alloy ring or each permanent magnet alloy ring, and the temporary masking shroud may be configured to mask one or more surfaces of the sleeve. Generally, the sleeve is a radially outward-extending sleeve configured to bond to the outer circumferential surface of the permanent magnet alloy ring or each permanent magnet alloy ring. In the embodiment, the sleeve may be a radially inward-extending sleeve configured to bond to the inner circumferential surface of the permanent magnet alloy ring or each permanent magnet alloy ring.

[0086] In embodiments, the temporary masking shroud may include non-adhesive materials, such as fluid agents and / or casings. For example, the temporary masking shroud may include removable gels or the like.

[0087] To avoid misunderstanding, the features of the embodiments and models described herein can be combined but remain within the scope of the present invention.

[0088] Preferred features of the present invention will be described below with reference to the accompanying drawings. [Brief explanation of the drawing]

[0089] [Figure 1] This shows a cross-sectional view of a permanent magnet bearing insert according to the present invention, which is placed inside a turbomolecular vacuum pump.

[0090] [Figure 2] This shows a cross-sectional view of a permanent magnet bearing insert according to the present invention, which is placed inside a turbomolecular vacuum pump.

[0091] [Figure 3] This shows a cross-sectional view of a permanent magnet bearing insert according to the present invention, which is placed inside a turbomolecular vacuum pump.

[0092] [Figure 4] Figure 3 shows a cross-sectional view of a permanent magnet bearing insert.

[0093] [Figure 5] A cross-sectional view of another permanent magnet bearing insert according to the present invention is shown. [Modes for carrying out the invention]

[0094] Figure 1 shows the permanent magnet bearing insert 10 of the rotor bearing half 12 of the permanent magnet bearing 16 in the turbomolecular vacuum pump 100.

[0095] The vacuum pump 100 comprises a housing having an inlet and an outlet. The stator 103 forms part of the housing or is coupled to the housing, and the rotor 104 is positioned on it and rotatably supported by bearings. The rotor comprises a plurality of rotor vanes (shown in Figure 3) configured to interact with a plurality of stator vanes during use to transport a gaseous medium from the inlet to the outlet.

[0096] At least one of the bearings is a permanent magnet bearing 16 having a rotor bearing half 12 and a stator bearing half 14. The other bearing can be an additional permanent magnet bearing or a mechanical bearing, such as a rolling bearing.

[0097] Each of the rotor and stator bearing halves 12 and 14 comprises one or more permanent magnets in the form of a permanent magnet alloy ring 18. In Figure 1, each of the rotor and stator bearing halves 12 and 14 includes three permanent magnet alloy rings 18 arranged adjacent to each other in the vertical direction. During use, the bearing halves 12 and 14 are positioned close to each other and are configured to repel each other so that the rotor is supported by the permanent magnet bearing 16 in a substantially non-contact manner.

[0098] In Figure 1, the rotor bearing half 12 is in the form of a permanent magnet bearing insert 12. The rotor shaft defines a cavity 28 configured to house the permanent magnet bearing insert in an interference fit configuration.

[0099] The permanent magnet bearing insert 12 comprises three permanent magnet alloy rings 18. Generally, the permanent magnet alloy rings 18 have a substantially continuous annular configuration.

[0100] The permanent magnet bearing insert 12 is fitted with a substantially corrosion-resistant coating. This substantially corrosion-resistant coating is configured to prevent, or at least reduce, corrosion of the permanent magnet alloy ring 18.

[0101] The material of the substantially corrosion-resistant coating may depend on the material of the permanent magnet alloy ring 18 and / or one or more process gases of the vacuum pump 100. This coating can be selected to protect the magnet alloy ring from process gases and / or chemicals that may impair the integrity or performance of the permanent magnet bearing insert. For example, as described above, a coating can be selected to protect the permanent magnet alloy ring from hydrogen (or other) degradation. For example, the substantially corrosion-resistant coating can be a chemical or galvanic metal deposition.

[0102] More specifically, the coating is arranged such that one or more surfaces of the permanent magnet bearing insert 12 are substantially uncoated, when the permanent magnet bearing insert 12 is housed in the rotor shaft cavity, and these surfaces substantially interface with other surfaces of the permanent magnet bearing insert or the surface of the rotor shaft cavity. In the embodiment of Figure 1, the outer circumferential surfaces of each permanent magnet alloy ring are primarily uncoated. Thus, when the permanent magnet bearing insert is housed therein, the surfaces that would normally be fully exposed to the process gas in the vacuum pump are coated with a substantially corrosion-resistant coating. In the embodiment of Figure 1, the inner circumferential surfaces, preferably the radial surfaces, of each permanent magnet alloy ring are also coated.

[0103] It is important that the permanent magnet bearing insert 12 is coated before being inserted into the rotor shaft cavity. The permanent magnet bearing insert is coated on the outside of the vacuum pump, and surfaces that are not selectively coated are masked by permanent or temporary masking components. Individual permanent magnet alloy rings can be individually masked and selectively coated (in which case a single magnet may become substantially demagnetized upon coating), or multiple permanent magnet alloy rings can be masked and coated simultaneously.

[0104] The permanent magnet bearing insert 12 is coated by a) preparing each of the permanent magnet alloy rings 18; b) masking another surface of the permanent magnet bearing insert 12 and / or a surface configured to substantially interface with the rotor shaft cavity when the permanent magnet bearing insert 12 is housed inside; and c) applying a substantially corrosion-resistant coating to the permanent magnet alloy ring so that the unmasked surfaces are substantially coated.

[0105] By selectively coating the surface of the permanent magnet alloy ring 18, the interference fit configuration of the permanent bearing insert 12 in the rotor shaft cavity 28 is improved. Specifically, since other surfaces of the permanent bearing insert 12 or surfaces configured to interface with the rotor shaft cavity 28 are not coated, the tolerance of the radial outer diameter of the permanent magnet alloy ring is not unnecessarily increased. Therefore, the tolerance between the permanent magnet bearing insert 12 and the rotor shaft cavity becomes more precise, minimizing the risk of damage to or detachment of the permanent magnet alloy ring 18.

[0106] In Figures 2 and 3, the permanent magnet bearing insert 12 further comprises a sleeve 20 extending radially outward. The sleeve 20 is coupled to the outer circumferential surface of the permanent magnet alloy ring 18 and is in contact with the radially outward-facing wall of the rotor shaft cavity when the permanent magnet bearing insert 12 is housed in the rotor shaft cavity.

[0107] If the permanent magnet bearing insert 12 includes a sleeve 20, masking of the selectively uncoated surface may occur by attaching the permanent magnet alloy ring 18 to the sleeve 20. Therefore, the surface of the permanent magnet alloy ring 18 interfaced with the sleeve 20 will remain uncoated. The stator bearing half 14 is also assumed to include a sleeve (not shown in Figures 2 and 3).

[0108] A first compressive force is applied to the permanent magnet alloy ring 18 when it is coupled to the sleeve 20. Subsequently, a second compressive force is applied to the permanent magnet bearing insert 12, and therefore to the permanent magnet alloy ring 18, when the permanent magnet bearing insert 12 (including the permanent magnet alloy ring 18 and the sleeve 20) is inserted into the rotor shaft cavity 28.

[0109] The outer surface of the permanent magnet bearing insert 12 engages with the inward wall of the rotor cavity, resulting in an interlocking fit.

[0110] Referring to Figures 4 and 5, before inserting the bearing insert 12 into the rotor cavity 28, the surfaces of the permanent magnet alloy rings 18, including the surface 24 configured to be exposed to the vacuum pump process gas, are coated with unmasked surfaces. If those surfaces are masked in step b), those surfaces are not coated. For example, the axial surface of each permanent magnet alloy ring 18 is unmasked and therefore coated, while the masked radial surface is not coated.

[0111] In the embodiments of Figures 4 and 5, each of the permanent magnet alloy rings 18 has a substantially chamfered outer surface; however, in the embodiments, each of the permanent magnet alloy rings 18 may not be substantially chamfered. Therefore, when the permanent magnet alloy rings 18 are coupled to the sleeve 20 at their outer surfaces, a pocket such as 26 may exist between the chamfered portion of an adjacent permanent magnet alloy ring 18 and the sleeve 20. The chamfered portion may be coated because it may come into contact with the process gas of the vacuum pump 100. For example, the openings between adjacent surfaces of the permanent magnet bearing insert 12 may, in practice, allow the coating to reach the chamfered portion of the permanent magnet alloy ring 18, for example, by capillary action, or the openings themselves may be coated and sealed to prevent the process gas from reaching the coated or uncoated chamfered surface. The degree of opening between adjacent permanent magnet alloy rings will depend at least in part on the assembly process and the forces between the permanent magnet alloy rings. Alternatively, when the permanent magnet alloy ring 18 is coupled with the sleeve 20, the chamfered portions and the pockets 26 they define are substantially sealed from the external environment, so these chamfered portions can be left uncoated when the permanent magnet bearing insert 18 is coated before being inserted into the vacuum pump 100.

[0112] Preferably, if the permanent magnet bearing insert 12 includes a sleeve 20, the permanent magnet alloy ring 18 is coupled to the sleeve 20 during masking step b), i.e., before coating step c). In this way, the sleeve 20 can function as a masking material for masking the surface of the permanent magnet alloy ring 18 that is left uncoated.

[0113] Furthermore, referring to Figure 5, the permanent magnet bearing insert 12 includes three permanent magnet alloy rings 18a-18c and a sleeve 20. The coating is arranged so that the inner circumferential surface of each permanent magnet alloy ring 18 is coated. The radial surface of one of the permanent magnet alloy rings, ring 18c, is also coated as it is exposed during use. The surface of the sleeve 20 that is adjacent to but does not interface with the permanent magnet alloy rings 18 is also coated, and the coating is configured to substantially prevent process gases and chemicals from penetrating towards or into the pocket 26 between the sleeve 20 and the alloy rings 18, where damage, such as hydrogen degradation, could normally occur. If, during the coating step, the coating coats the circumferential surface of the sleeve 20 opposite to the permanent magnet alloy ring, this coated surface can then be machined to remove any excess coating so that a proper interlocking fit is achieved and maintained between the insert 12 and the rotor cavity 28. The coating can also be removed from one or more radial surfaces of the sleeve.

[0114] The sleeve 20 of the permanent magnet bearing insert 12 in Figures 4 and 5 is generally tubular. In both cases, the sleeve 20 has an annular flange extending radially inward for holding the permanent magnet alloy ring. The sleeve 20 in Figure 5 further includes a tapered portion 30 at the end opposite the generally tubular structure.

[0115] Alternatively or additionally, one or more surfaces left uncoated are subjected to a temporary masking shroud, for example, in the form of a casing or a removable chemical agent. If a temporary masking shroud is applied, it is removed before inserting the permanent magnet bearing insert 12 into the rotor shaft cavity.

[0116] During coating step c), a substantially corrosion-resistant coating is applied via one or more of several coating processes. Since the permanent magnet bearing insert 12 is coated outside the vacuum pump and before being inserted into the vacuum pump, there are fewer mechanical and spatial constraints on the coating process, allowing for a wider range of coating processes to be used. For example, a substantially corrosion-resistant coating can be provided by a vacuum pressure impregnation (VPI) process or electrodeposition.

[0117] The coating method can be part of the manufacturing method of the vacuum pump 100, and the method for manufacturing the vacuum pump includes the steps of manufacturing the permanent magnet bearing insert 12 as described above, and the subsequent step of inserting the permanent magnet bearing insert 12 into the rotor shaft cavity of the vacuum pump 100 in an interlocking configuration.

[0118] Generally, each of the permanent magnet alloy rings 18 contains a neodymium magnet or a neodymium magnet alloy.

[0119] Generally, the sleeve 20 is formed from a metal, such as a stainless steel alloy or an aluminum alloy. However, the sleeve 20 can also be formed from a composite material. [Explanation of symbols]

[0120] 10 Permanent magnet bearing inserts 12 Rotor bearing half 14 Stator bearing half 16 permanent magnet bearings 18(ac) permanent magnet alloy ring 20 sleeves 24 Radial plane 26 pockets 28 Rotor cavities 30 Tapered section 100 Vacuum pump 103 stata 104 Rotor

Claims

1. A method for manufacturing a permanent magnet bearing insert for a vacuum pump, wherein the vacuum pump comprises a rotor shaft defining a cavity configured to house the permanent magnet bearing insert in a press-fit configuration, and the method is a) A step of preparing one or more permanent magnet alloy rings for the rotor bearing half of a permanent magnet bearing, b) A step of masking one or more surfaces of the or each permanent magnet alloy ring, wherein the or each permanent magnet alloy ring is configured to substantially interface with another surface of the permanent magnet bearing insert and / or the rotor shaft cavity when the permanent magnet bearing insert is housed in the rotor shaft cavity, c) The step of applying a coating to the above or each permanent magnet alloy ring, Includes, Step b) substantially prevents the masked surface from being coated during step c), Steps b) and c) are performed substantially outside the vacuum pump. method.

2. The permanent magnet bearing insert includes a sleeve configured to bond to the circumferential surface of the or each permanent magnet alloy ring, and step b) includes bonding the or each permanent magnet alloy ring to the sleeve to form an interference fit between them, Optionally, step c) includes the step of applying a coating to one or more surfaces of the sleeve. The method according to claim 1.

3. The method according to claim 1 or 2, wherein step b) comprises applying a temporary masking shroud to the permanent magnet bearing insert, the method further comprises removing the temporary masking shroud after step c), optionally the temporary masking shroud comprising an anti-adhesion agent and / or casing.

4. A method for manufacturing a permanent magnet bearing insert for a vacuum pump, comprising a stator defining a base configured to interface with a magnetic bearing insert, a) A step of preparing one or more permanent magnet alloy rings for the stator bearing half of a permanent magnet bearing, b) When the permanent magnet bearing insert interfaces with the stator base, the step of masking another surface of the permanent magnet bearing insert and / or one or more surfaces of the or each permanent magnet alloy ring configured to substantially interface with the stator base, c) The step of applying a coating to the above or each permanent magnet alloy ring, Includes, Step b) substantially prevents the masked surface from being coated during step c), Steps b) and c) are performed substantially outside the vacuum pump. method.

5. The method according to any one of claims 1 to 4, wherein the coating is applied to result in a coating thickness of between approximately 0.008 mm and approximately 0.5 mm, optionally between approximately 0.02 mm and approximately 0.2 mm.

6. The method according to any one of claims 1 to 5, wherein the coating is a thermosetting and / or UV-curing and / or visible light-curing and / or moisture-curing coating, and optionally the coating is applied by brushing, dipping, painting, bath treatment, spraying, UV curing, moisture curing, vacuum pressure impregnation, chemical vapor deposition, physical vapor deposition, electrodeposition, or a combination thereof.

7. A method for manufacturing a vacuum pump, preferably a turbomolecular pump, the vacuum pump comprising a rotor shaft configured to which one or more rotor blades are coupled, the rotor shaft defining a cavity for housing a magnetic bearing insert for the rotor half of a permanent magnet bearing, and a stator defining a base for mounting a magnetic bearing insert for the stator half of the permanent magnet bearing, i. The step of performing the method according to any one of claims 1 to 6, ii. The steps of inserting the permanent magnet bearing insert for the rotor half into the rotor shaft cavity of the vacuum pump in a press-fit configuration and / or installing the permanent magnet bearing insert for the stator half on the stator base, A method that includes this.

8. A permanent magnet bearing insert manufactured according to any one of claims 1 to 6, or a vacuum pump, preferably a turbomolecular pump, manufactured according to claim 7.

9. A permanent magnet bearing insert for a vacuum pump, wherein the vacuum pump includes a rotor shaft to which one or more rotor blades are coupled, and the rotor shaft defines a cavity configured to accommodate the permanent magnet bearing insert in an interference fit configuration. The permanent magnet bearing insert comprises one or more permanent magnet alloy rings in the rotor bearing half of the permanent magnet bearing, The permanent magnet bearing insert includes a coating, The coating is arranged such that, when the permanent magnet bearing insert is housed in the rotor shaft cavity, one or more surfaces of the permanent magnet alloy ring that are configured to substantially interface with the rotor shaft cavity are not substantially coated. The permanent magnet bearing insert is coated before being inserted into the rotor shaft cavity.

10. The permanent magnet bearing insert according to claim 9, comprising a sleeve coupled substantially around a circumferential surface to the above or each permanent magnet alloy ring, wherein the above or each permanent magnet alloy ring is coupled to the sleeve before the permanent magnet bearing insert is coated.

11. A permanent magnet bearing insert for a vacuum pump, wherein the vacuum pump includes a stator defining a base configured to interface with the magnet bearing insert, The permanent magnet bearing insert comprises one or more permanent magnet alloy rings in the stator bearing half of the permanent magnet bearing, The permanent magnet bearing insert includes a coating, The coating is arranged such that, when the permanent magnet bearing insert interfaces with the stator base, another surface of the permanent magnet bearing insert or one or more surfaces of the permanent magnet alloy ring configured to substantially interface with the stator base are substantially uncoated. The permanent magnet bearing insert for a vacuum pump is coated before interfacing with the stator base.

12. A vacuum pump, preferably a turbomolecular pump, the vacuum pump comprising a rotor shaft defining a cavity and a stator defining a base, wherein one or more rotor blades are coupled to the rotor shaft, the cavity of the rotor shaft includes, in an interference fit configuration, a permanent magnet bearing insert according to claim 9 or 10, and / or the stator base interfaces with a permanent magnet bearing insert according to claim 11.

13. A permanent magnet bearing insert according to any one of claims 9 to 11, or a vacuum pump according to claim 12, wherein the aforementioned or each permanent magnet alloy ring includes a neodymium magnet or a neodymium magnet alloy.

14. The coating is a thermosetting and / or UV-curable and / or visible light-curable and / or moisture-curable coating, optionally having a coating thickness between approximately 0.008 mm and approximately 0.5 mm, optionally between approximately 0.02 mm and approximately 0.2 mm, and optionally being a multi-component coating, the permanent magnet bearing insert according to any one of claims 9 to 11 or 13, or the vacuum pump according to claim 12 or 13.

15. A temporary masking shroud for a permanent magnet bearing insert for the rotor bearing half of a permanent magnet bearing of a vacuum pump, wherein the permanent magnet bearing insert comprises one or more partially coated permanent magnet alloy rings, The temporary masking shroud comprises one or more compartments for housing the permanent magnet bearing insert inside, A temporary masking shroud, wherein, when the permanent magnet bearing insert is housed, one or more surfaces of the one or more permanent magnet alloy rings are substantially exposed for coating, but one or more other surfaces of the one or more permanent magnet alloy rings are substantially prevented from being coated.

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