electric motor

Abstract

A motor includes a housing including a housing base and a housing shaft portion provided to the housing base and extending in a direction along a rotation center axis, a motor stator arranged radially outward of the housing shaft portion, a motor rotor provided between the motor stator and the housing shaft portion, a bearing provided radially inward of the motor rotor and rotatably supporting the motor rotor to the housing shaft portion, a seal structure provided in an axial direction of the motor rotor on an opposite side to the housing base and sealing between the motor rotor and the housing shaft portion, and a resolver detecting rotation of the motor rotor, the resolver being arranged in the axial direction on the opposite side to the housing base with respect to the motor stator radially outward of the bearing and in the direction along the rotation center axis.

Description

Technical Field

[0001] This invention relates to an electric motor. Background Technology

[0002] Patent Documents 1 to 3 describe electric motors used in vacuum environments, etc. In the electric motors described in Patent Documents 1 to 3, a partition wall is provided between the motor rotor and the motor stator. This partition wall separates the space where the motor rotor is located from the space where the motor stator is located.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2006-311649

[0004] Patent Document 2: Japanese Patent No. 4445075

[0005] Patent Document 3: Japanese Patent Application Publication No. 2001-339920 Summary of the Invention

[0006] For example, in semiconductor manufacturing processes, where electric motors are used in vacuum and high-temperature environments, it is necessary to suppress the generation of dust or the release of gases from the motor. The electric motor described in Patent Document 1 is a so-called external rotor type, with the motor rotor located on the vacuum environment side (within the chamber). Therefore, dust or gases generated from the motor rotor may flow out towards the vacuum environment side.

[0007] In the electric motors described in Patent Documents 2 and 3, a bearing is provided on the outer periphery of the motor rotor or the output shaft connected to the motor rotor. Therefore, the bearing is exposed to the vacuum environment side, and dust generated from the bearing may flow out to the vacuum side.

[0008] The present invention was made in view of the above-mentioned problems, and its object is to provide an electric motor capable of suppressing the outflow of generated dust to the outside.

[0009] To achieve the above objectives, one aspect of the present invention relates to an electric motor comprising: a housing including a housing base and a housing shaft portion disposed on the housing base and extending in a direction along a rotational central axis; an electric motor stator disposed radially outward of the housing shaft portion; an electric motor rotor disposed between the electric motor stator and the housing shaft portion; a bearing disposed radially inward of the electric motor rotor and rotatably supporting the electric motor rotor on the housing shaft portion; a sealing structure disposed axially on the side opposite to the housing base (e.g., the output shaft 17 side in the embodiment) of the electric motor rotor and sealing the electric motor rotor and the housing shaft portion; and a rotary transformer that detects the rotation of the electric motor rotor, the rotary transformer being disposed radially outward of the bearing and axially opposite to the housing base (e.g., the output shaft 17 side in the embodiment) relative to the electric motor stator in a direction along the rotational central axis.

[0010] Based on the above configuration, the bearing is located radially inside the motor rotor. Because the output shaft side of the motor rotor is sealed by a cover or similar device during use, the outflow of dust generated at the bearing to the outside, such as a vacuum environment, can be prevented. Furthermore, even if metal dust generated due to bearing wear enters the motor, the metal dust is adsorbed onto the motor stator. Therefore, the motor can prevent internally generated dust from flowing out. Moreover, the outflow of metal dust towards the rotary transformer can be prevented, thus suppressing a decrease in the detection accuracy of the rotary transformer.

[0011] A preferred embodiment of the electric motor includes an electric motor partition wall disposed between the electric motor stator and the electric motor rotor, dividing the space where the electric motor stator is disposed and the space where the electric motor rotor is disposed. According to this embodiment, the electric motor partition wall can suppress the outflow of gas from the atmospheric environment side where the electric motor stator is disposed to the vacuum environment side where the electric motor rotor is disposed.

[0012] In a preferred embodiment of the electric motor, the rotary transformer described above has a rotary transformer rotor connected to the electric motor rotor, and a rotary transformer stator located radially outside the rotary transformer rotor and having an excitation coil. A rotary transformer partition wall is provided between the rotary transformer rotor and the rotary transformer stator. According to this embodiment, the partition wall divides the space where the rotary transformer rotor is located into a space where the rotary transformer stator is located and the space where the rotary transformer stator is located, thus preventing gas from flowing from the atmospheric side (where the stator is located) to the vacuum environment side (where the rotor is located). Furthermore, since the rotary transformer is used as an angle detector, no electronic components are installed within the electric motor. Therefore, even when the electric motor is used in a high-temperature environment, the angle can be detected effectively.

[0013] In a preferred configuration of the electric motor, the outer diameter of the motor rotor is smaller than that of the rotary transformer rotor. According to this configuration, the rotating structure, including both the motor rotor and the rotary transformer rotor, can be integrally pulled out from the output shaft side, thus facilitating bearing replacement or maintenance.

[0014] As a preferred embodiment of the electric motor, the aforementioned bearing is a non-lubricated bearing, comprising an inner ring disposed on the shaft portion of the housing, an outer ring disposed on the rotor of the electric motor, and rolling elements disposed between the inner ring and the outer ring. At least one of the inner ring, the outer ring, and the rolling elements is made of ceramic. According to this embodiment, dust generated due to wear from the rolling elements of the bearing, or gases released under high-temperature conditions, can be suppressed.

[0015] As a preferred embodiment of the electric motor, the aforementioned bearing is an unlubricated bearing, comprising an inner ring disposed on the shaft portion of the housing, an outer ring disposed on the rotor of the electric motor, and rolling elements disposed between the inner and outer rings. The inner and outer rings are made of magnetic ferrous components. According to this embodiment, even if dust generated due to bearing wear enters the interior of the electric motor, the metal powder is effectively adsorbed onto the permanent magnets of the electric motor stator or rotor.

[0016] In a preferred configuration of the electric motor, a connecting portion made of a magnetic material is arranged between the motor stator and the rotary transformer along the aforementioned rotational central axis. According to this configuration, the connecting portion can shield the magnetic force (magnetic field) generated from the motor stator, thus improving the detection accuracy of the rotary transformer. Furthermore, the connecting portion can absorb metal powder generated due to wear.

[0017] As a preferred embodiment of the electric motor, an outer ring pressing portion is disposed on the side opposite to the housing (e.g., the output shaft 17 side in the embodiment) in the axial direction of the motor rotor and fixed to the outer ring of the bearing; and an inner ring pressing portion is disposed on the side opposite to the housing (e.g., the output shaft 17 side in the embodiment) in the axial direction of the housing shaft portion and fixed to the inner ring of the bearing. The sealing structure has a labyrinthine structure formed by the outer ring pressing portion and the inner ring pressing portion. According to the above embodiment, dust from the electric motor generated due to bearing wear, etc., is shielded by the sealing structure, and its leakage to the outside can be suppressed.

[0018] In a preferred configuration of the electric motor, the stator is positioned in a space closer to the atmosphere than the space where the rotor is located. This configuration improves the cooling efficiency of the stator compared to a configuration where the stator is positioned in the same space as the rotor, for example, in a vacuum environment.

[0019] As a preferred embodiment of the electric motor, the rotor of the aforementioned motor comprises samarium cobalt permanent magnets. According to this embodiment, the motor will not demagnetize even when used in high-temperature environments, thus enabling efficient rotational drive of the motor rotor.

[0020] A preferred embodiment of the electric motor includes an electric motor control circuit that provides drive current to the excitation coil of the motor stator based on the detection signal from the aforementioned rotary transformer. According to this embodiment, the electric motor control circuit can continuously monitor rotational torque or speed fluctuations based on the detection signal from the rotary transformer. Therefore, for example, it can detect bearing malfunctions at an early stage, or determine the appropriate time to replace the bearings.

[0021] According to the present invention, it is possible to provide an electric motor that can suppress the outflow of generated dust to the outside. Attached Figure Description

[0022] Figure 1 This is an explanatory diagram illustrating the usage state of the electric motor involved in the implementation method.

[0023] Figure 2 It is a schematic cross-sectional view of the electric motor involved in the embodiment.

[0024] Figure 3 yes Figure 2 Section III-III' view.

[0025] Figure 4 This is an enlarged cross-sectional view showing the first bearing of the electric motor involved in the embodiment.

[0026] Figure 5 It is an enlarged cross-sectional view showing the motor stator, motor rotor and motor partition wall of the motor according to the embodiment.

[0027] Figure 6 This is an enlarged cross-sectional view showing the rotary transformer and the rotary transformer partition wall of the electric motor involved in the embodiment.

[0028] Figure 7 This is a cross-sectional view schematically illustrating the structure of the incremental rotary transformer of the electric motor according to the embodiment.

[0029] Figure 8 This is a block diagram illustrating an example of the structure of a signal processing circuit in a motor control circuit.

[0030] Figure 9 This is a flowchart illustrating the driving methods for incremental and absolute rotary transformers.

[0031] Figure 10 This is a schematic cross-sectional view of the electric motor involved in Variation Example 1.

[0032] Figure 11 This is a top view schematically representing a portion of the electric motor involved in Variation Example 2.

[0033] Figure 12 It is a schematic top view showing a portion of an electric motor with motor windings.

[0034] Figure 13 This is an enlarged cross-sectional view of the first bearing of the electric motor involved in Variation Example 3.

[0035] Figure 14 This is an enlarged cross-sectional view of the first bearing of the electric motor involved in variation example 4. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below. Furthermore, the structural elements of the embodiments described below include structural elements readily conceived by those skilled in the art, substantially identical structural elements, and structural elements of equivalent scope. Additionally, the structural elements disclosed in the embodiments described below can be appropriately combined.

[0037] Figure 1 This is an explanatory diagram illustrating the operating state of the electric motor involved in the implementation method. For example... Figure 1 As shown, an example of a manufacturing apparatus using an electric motor 1, such as a semiconductor manufacturing apparatus 100, will be described. The semiconductor manufacturing apparatus 100 includes: a chamber 101, an electric motor 1, an electric motor control circuit 90, a control device 99, and a conveying device 110. The electric motor 1 rotates around a central axis AX, with its output shaft 17 (see reference AX). Figure 2 The semiconductor manufacturing apparatus 100 rotates the transport tray 111 by driving it with the electric motor 1. The transport device 110, including the transport tray 111, is disposed inside the chamber 101 and connected to the electric motor 1 through the opening 102. The semiconductor manufacturing apparatus 100 carries a workpiece (transported part) 120, which exists in a vacuum environment Va, on the transport tray 111 and moves it. The workpiece 120 may be, for example, a semiconductor substrate, an artifact, or a tool.

[0038] The electric motor 1 can directly transmit rotational force to the transport tray 111 and the workpiece 120 without transmission mechanisms such as gears, conveyor belts, or rollers, causing the workpiece 120 to rotate. The electric motor 1 is a so-called direct drive motor. In this embodiment, the axial direction refers to the direction along the rotation center axis AX.

[0039] The control device 99 includes: an input circuit, a CPU (Central Processing Unit) as a central processing unit, a memory as a storage device, and an output circuit (none of which are shown). The control device 99 generates a motor rotation command i for controlling the motor 1 based on a program stored in the memory, and outputs it to the motor control circuit 90.

[0040] When a motor rotation command i is input from the control device 99, the motor control circuit 90 outputs a drive signal from the CPU (Central Processing Unit) 91 to a three-phase amplifier (hereinafter referred to as AMP (Amplifier) ​​92), and supplies a drive current Mi to the motor 1 from the AMP 92. The motor 1 is driven to rotate by the drive current Mi, causing the transport tray 111 to rotate. This moves the workpiece 120 mounted on the transport tray 111. In addition to the transport tray 111, the transport device 110 may also have other components such as a robotic arm for wafer transport, and can be appropriately structured to correspond to the workpiece 120.

[0041] As the transport tray 111 rotates, the rotary transformer 60 (reference) detects the rotation angle. Figure 2 An angle detector, such as an angle detector, outputs a detection signal (resolver signal) Sr. The motor control circuit 90 uses a resolver-to-digital converter (hereinafter referred to as RDC 93) to digitally convert the detection signal Sr. Based on the digital information of the detection signal Sr from the RDC 93, the CPU 91 determines whether the workpiece 120 has reached the commanded position. If the commanded position has been reached, the drive signal to the AMP 92 is stopped.

[0042] Furthermore, the motor control circuit 90 can always monitor rotational torque or speed fluctuations based on the detection signal Sr from the rotary transformer 60. Therefore, the motor control circuit 90 can detect early abnormalities such as those in the first bearing 21A and the second bearing 21B as shown in Figure 2, or determine the replacement period for the first bearing 21A and the second bearing 21B.

[0043] Typically, for semiconductor manufacturing apparatus 100, as the integration density of semiconductors increases, the pattern width of ICs gradually becomes smaller and higher. In order to manufacture wafers (semiconductor devices) that correspond to this miniaturization, a high degree of uniformity in wafer quality is required. To meet this requirement, it is important to further reduce the concentration of impurity gases in the vacuum environment Va. Therefore, in the motor 1 located in the mounting hole (opening 102) of the chamber 101, it is also necessary to separate the space of the vacuum environment Va from the external atmospheric environment At.

[0044] In this embodiment, the chamber 101 is a vacuum environment Va. However, the chamber 101 is not limited to a vacuum environment; it can also be an environment different from the atmospheric environment At, such as a depressurized environment or an environment filled with process gases such as nitrogen or inert gases. Furthermore, the chamber 101 can also employ a vacuum and high-temperature environment, such as a diffusion furnace used in semiconductor manufacturing. In this embodiment, "atmospheric side" refers to a space with a higher gas pressure than "vacuum side" (vacuum environment Va). Alternatively, "atmospheric side" can also be a space with a lower ratio of process gases than "vacuum side" (vacuum environment Va).

[0045] Figure 2 It is a schematic cross-sectional view of the electric motor involved in the embodiment. Figure 3 yes Figure 2 Section III-III' view. Additionally... Figure 2 This is a cross-sectional view of the motor 1 cut off by a virtual plane including the rotation center axis AX. In the following description, the direction toward the output shaft 17 side (vacuum environment Va side) along the rotation center axis AX is sometimes referred to as "upper side" or simply "upper". In addition, the direction toward the housing 11 side (atmospheric environment At side) along the rotation center axis AX is sometimes referred to as "lower side" or simply "lower".

[0046] For ease of understanding, the symbol is emphasized schematically. Figures 2 to 14 The dimensions of each structural element are shown. For example, the thickness of the motor partition wall 50 is illustrated as being thicker than its actual size. Furthermore, the sizes of gap G0 and gaps G1 through G4 are shown as being larger than their actual sizes, but gaps G0 and G1 through G4 are all formed as minute gaps.

[0047] like Figure 2 As shown, the electric motor 1 includes: a housing 10, a motor stator 30, a motor rotor 40, a first bearing 21A, a second bearing 21B, a rotary transformer 60, a motor partition 50, a rotary transformer partition 70, a connecting part 15, and an output shaft 17. Additionally, in Figure 2 and Figure 3 The first part explains the overall configuration relationship of each structural element, while the detailed connection or sealing structure between each structural element will be described later.

[0048] The housing 10 includes a housing base 11, a housing shaft portion 12, an outer shell 13, and a cover portion 14. The housing base 11 is a flat plate extending in a direction intersecting the rotation center axis AX, and is formed in an annular shape, with an opening at a position coinciding with the rotation center axis AX. The housing shaft portion 12 and the outer shell 13 are both cylindrical portions extending in the direction along the rotation center axis AX (hereinafter referred to as the axial direction). The lower end of the housing shaft portion 12 is connected to the inner peripheral edge of the housing base 11, and the lower end of the outer shell 13 is connected to the outer peripheral edge of the housing base 11. That is, the outer shell 13 is configured to be radially opposite to the radially outer side of the housing shaft portion 12.

[0049] The cover 14 is configured to cover the opening of the housing 11. The cover 14 separates the internal space SP of the housing shaft portion 12 from the atmospheric environment At, thus suppressing the inflow of foreign objects into the internal space SP.

[0050] Because the housing 11, housing shaft 12, and part of the cover 14 are exposed to a vacuum, austenitic stainless steel, aluminum alloy, and other vacuum materials that release little gas in a vacuum and whose released gas composition is known can be used. Furthermore, more preferably, depending on the vacuum level employed, surface treatments such as electropolishing, smoothing, and oxide film formation are performed to reduce the surface area and the release of dissolved gases. In this embodiment, the outer casing 13 is exposed to the atmospheric environment At, but not to a vacuum, so general structural materials such as cast iron and low-carbon steel can be used, and stainless steel can also be used. With this construction, the motor 1 can increase the proportion of structural materials used and reduce the amount of vacuum materials, which are more expensive than structural materials.

[0051] The motor stator 30, motor rotor 40, first bearing 21A, second bearing 21B, motor partition 50, and connecting part 15 are assembled between housing shaft part 12 and housing 13.

[0052] The motor stator 30 is disposed radially outside the housing shaft 12 and the motor rotor 40, and remains stationary. Specifically, the connecting portion 15 is provided to cover the upper side of the motor stator 30 (the rotary transformer 60 side), and the motor stator 30 is fixed to the housing 13 via the connecting portion 15. As a method of fixing the motor stator 30, for example, the stator core 31 of the motor stator 30 is fastened to the housing 10 (housing 13) by bolts. Thus, the motor stator 30, as a non-rotating part, is positioned and fixed to the housing 11. Furthermore, the motor rotor 40 is disposed between the motor stator 30 and the housing shaft 12. The first bearing 21A and the second bearing 21B support the motor rotor 40 so that it can rotate relative to the housing shaft 12. That is, the motor rotor 40 is configured to rotate relative to the motor stator 30.

[0053] like Figure 3 As shown, the motor stator 30, the motor rotor 40, and the first bearing 21A (in) Figure 3 (Not shown in the diagram) and the second bearing 21B are both annular structures, arranged concentrically around the rotation center axis AX. From the housing shaft portion 12, the bearings (first bearing 21A and second bearing 21B), the motor rotor 40, the motor partition wall 50, the motor stator 30, and the housing 13 are arranged radially outward in sequence. That is, the motor 1 is a so-called inner rotor type, with the motor rotor 40 located on the rotation center axis AX side compared to the motor stator 30. In other words, the motor rotor 40 is positioned on the vacuum environment Va side, and the motor stator 30 is positioned on the atmospheric environment At side.

[0054] The motor stator 30 is formed by stacking electromagnetic steel plates and includes: stator core 31 and insulator 34 (see reference). Figure 2 ) and excitation coil 35 (refer to Figure 2 The motor stator 30 is formed, for example, by bonding steel plates or in-mold riveting. This facilitates the machining of the stator core 31 and enables the motor stator 30 to achieve good magnetism. The stator core 31 has a back yoke 32 and teeth 33. The back yoke 32 is an annular component, positioned opposite to the inner circumferential surface of the housing 13 with a space between it and the back yoke 32. Multiple teeth 33 are arranged circumferentially on the back yoke 32 at equal intervals. The teeth 33 protrude radially inward from the back yoke 32. The motor stator 30 is not limited to such a monolithic core; it can be a segmented core with multiple segmented stator cores 31. Excitation coils 35 are wound around the teeth 33 of the stator core 31, separated by insulators 34. Wiring for supplying power from a power source is connected to the motor stator 30, and through this wiring, a drive current Mi is supplied from the motor control circuit 90 to the excitation coils 35.

[0055] Figure 2 The motor windings constituting the excitation coil 35 and the insulators 34 (insulating material) shown are both made of heat-resistant materials. For example, the motor windings and the insulators 34 (insulating material) have a heat resistance of 200°C or higher. Therefore, the motor 1 can operate well in high-temperature environments. A plating layer, for example made of polyimide, is applied to the motor windings. Furthermore, the insulators 34 are made of, for example, insulating paper, resin material, or a combination of insulating paper and resin material.

[0056] The motor rotor 40 includes a rotor yoke 41, a magnet 42, and a space 43 (see reference). Figure 2The rotor yoke 41 is a cylindrical component, and its outer diameter is smaller than that of the stator core 31. The motor rotor 40 is configured to have an annular shape with a gap serving as the magnetic gap MG on the radially inner side of the motor stator 30. Preferably, the rotor yoke 41 is formed of low-carbon steel with a strong magnetic material and has nickel plating applied to its surface. By applying nickel plating, rust can be prevented from forming on the rotor yoke 41, and gas release can be reduced.

[0057] like Figure 3 As shown, multiple magnets 42 are attached along the outer periphery of the rotor yoke 41. That is, the motor stator 30 (stator core 31) is disposed radially outside the magnets 42, separated by the motor partition wall 50. The rotating motor rotor 40 and the non-rotating motor stator 30 are arranged in a non-contact manner, thus suppressing the generation of foreign objects. In the magnets 42, the S poles and N poles are arranged at equal intervals in an alternating manner along the circumference of the rotor yoke 41. The number of poles of the motor rotor 40 is, for example, 20 poles. Furthermore, the number of poles of the motor rotor 40 and the number of slots of the motor stator 30 are not limited to a 20-pole, 18-slot structure and can be appropriately changed as needed.

[0058] In this embodiment, it is preferable that the magnet 42 is a samarium cobalt permanent magnet. Therefore, even when the motor 1 is used in a high-temperature environment, it will not demagnetize, thus enabling efficient rotational drive of the motor rotor 40. However, this is not a limitation; the magnet 42 may also be made of other materials such as neodymium magnets.

[0059] Figure 2 The space 43 shown is a space to prevent magnetic entanglement at the end face of the magnet 42. Ideally, the step size Y of the rotor yoke 41 forming the space 43 (refer to...) Figure 4 ) represents the thickness dimension X of magnet 42 (refer to...) Figure 4 The value should be between 1 / 3 and 1 / 2. If it exceeds this range, a magnetic field will form around the upper part of the magnet 42 of the motor rotor 40, and the magnet will not circulate towards the stator core 31, resulting in a decrease in output torque.

[0060] The motor partition 50 is located in the magnetic gap MG between the motor stator 30 and the motor rotor 40, dividing the space into the space where the motor rotor 40 is located (vacuum environment Va side) and the space where the motor stator 30 is located (atmospheric environment At side). The detailed structure of the motor partition 50 will be described later.

[0061] An output shaft 17 is connected to the upper end of the rotor yoke 41. The output shaft 17 rotates together with the rotor yoke 41 to transmit the rotational force of the motor 1 to an external source (e.g., a transport disk 111).

[0062] Bearing 21A and bearing 21B are disposed between the outer periphery of the housing shaft portion 12 and the inner periphery of the rotor yoke 41. Bearing 21A and bearing 21B are unlubricated bearings without any lubricant such as grease. Bearing 21A and bearing 21B are angular contact ball bearings arranged back-to-back. Bearing 21A and bearing 21B are rotary bearings having an inner ring 22, an outer ring 23, and rolling elements 24. The rolling elements 24 are disposed between the inner ring 22 and the outer ring 23. In the direction along the rotation center axis AX, bearing 21A is disposed on the output shaft 17 side, and bearing 21B is disposed on the housing 11 side. The inner ring 22 of bearing 21A and bearing 21B is fixed to the housing shaft portion 12. The outer ring 23 of bearing 21A and bearing 21B is fixed to the rotor yoke 41 of the motor rotor 40.

[0063] An inner ring spacer 25 is provided between the inner ring 22 of the first bearing 21A and the inner ring 22 of the second bearing 21B. An outer ring spacer 26 is provided between the outer ring 23 of the first bearing 21A and the outer ring 23 of the second bearing 21B. This defines the axial positions of the first bearing 21A and the second bearing 21B. An inner ring pressing part 16 is connected to the upper end of the housing shaft portion 12 (the end opposite to the housing seat 11 in the axial direction), and the position of the upper end of the inner ring 22 of the first bearing 21A is fixed by the inner ring pressing part 16. The output shaft 17 also serves as the outer ring pressing part, and the position of the upper end of the outer ring 23 of the first bearing 21A is fixed by the output shaft 17.

[0064] The lower end of the inner ring 22 of the second bearing 21B is fixed to the housing 11. Furthermore, the lower end of the outer ring 23 of the second bearing 21B is fixed to the rotor yoke 41. With this structure, the first bearing 21A, the spacers (inner ring spacer 25 and outer ring spacer 26), and the second bearing 21B are positioned axially without clearance (an undesirable situation), forming a rotating support structure with a positioning preload. A positioning preload is applied to the first bearing 21A and the second bearing 21B by the inner ring spacer 25 and the outer ring spacer 26, thus improving their stiffness compared to a constant pressure preload described later. Furthermore, the first bearing 21A and the second bearing 21B are arranged back-to-back, thereby improving their stiffness relative to torque loads.

[0065] A first sealing structure LS1 is provided on the output shaft 17 side of the motor rotor 40 (opposite to the housing 11 in the axial direction) to seal the motor rotor 40 and the housing shaft portion 12 in a non-contact manner. More specifically, the first sealing structure LS1 on the output shaft 17 side of the first bearing 21A is formed by a small gap between the output shaft 17 and the inner ring pressing portion 16. Furthermore, a second sealing structure LS2 is provided on the housing 11 side of the second bearing 21B to seal the motor rotor 40 and the housing shaft portion 12 in a non-contact manner. Thus, the output shaft 17 side and the housing 11 side of the first bearing 21A and the second bearing 21B are sealed by the first sealing structure LS1 and the second sealing structure LS2, respectively. The motor 1, through the first sealing structure LS1 and the second sealing structure LS2, can suppress the leakage of dust generated due to wear of the first bearing 21A and the second bearing 21B into the vacuum environment Va side.

[0066] In the inner ring 22, outer ring 23, and rolling element 24 of the first bearing 21A and the second bearing 21B, at least the rolling element 24 is made of ceramic. For example, the material of the rolling element 24 may be silicon nitride, zirconium oxide, aluminum oxide, etc. In this way, dust generated by wear or gases released from the rolling element 24 of the first bearing 21A and the second bearing 21B under high temperature conditions can be suppressed.

[0067] Furthermore, the inner ring 22 and outer ring 23 of the first bearing 21A and the second bearing 21B are made of magnetic ferrous components. For example, the magnetic ferrous components are martensitic stainless steel. Thus, even if dust (metal powder) generated by the wear of the bearings (first bearing 21A and second bearing 21B) gets inside the motor 1, it is attracted to the magnet 42 of the motor rotor 40 or (the magnetic force (magnetic field) of the motor stator 30) through the wall portion 51 (see below) Figure 5 The motor partition wall is 50 mm thick.

[0068] The rotary transformer 60 is located radially outward and axially in relation to the first bearing 21A and the second bearing 21B, closer to the output shaft 17 than the motor stator 30. The rotary transformer 60 is an angle detector that detects the rotation of the motor rotor 40.

[0069] The rotary transformer 60 includes an incremental rotary transformer 60A and an absolute rotary transformer 60B. The incremental rotary transformer 60A is differential and is a detector that detects relative angles with high resolution. The absolute rotary transformer 60B is a detector that detects absolute angles within one revolution of the output shaft 17. The motor stator 30, the absolute rotary transformer 60B, and the incremental rotary transformer 60A are arranged sequentially along the rotation center axis. Through this arrangement, the absolute rotary transformer 60B functions as a magnetic shield for the incremental rotary transformer 60A, suppressing the magnetic force (magnetic field) generated from the motor stator 30 from reaching the incremental rotary transformer 60A.

[0070] The incremental rotary transformer 60A has a rotary transformer stator 61A and a rotary transformer rotor 62A. The absolute rotary transformer 60B has a rotary transformer stator 61B and a rotary transformer rotor 62B. The rotary transformer rotors 62A and 62B are formed, for example, from low-carbon steel. The rotary transformer rotors 62A and 62B are arranged opposite to the rotary transformer stators 61A and 61B with a predetermined gap, and are rotatable relative to the rotary transformer stators 61A and 61B. Specifically, the rotary transformer stators 61A and 61B are fixed to the housing 13. In this way, the rotary transformer stators 61A and 61B are positioned and fixed relative to the motor stator 30 and the housing 11, maintaining a stationary state. Furthermore, the rotary transformer rotors 62A and 62B are fixed to the outer periphery of the output shaft 17. The rotary transformer rotors 62A and 62B rotate together with the motor rotor 40.

[0071] A rotary transformer partition 70 is provided between the rotary transformer rotors 62A and 62B and the rotary transformer stators 61A and 61B. The rotary transformer partition 70 is configured to cover the rotary transformer stators 61A and 61B. Furthermore, the rotary transformer partition 70 also serves as a cavity 101 (see reference). Figure 1 The mounting structure between the housing 13 and the chamber 101 is fixed by a portion extending radially outward from the housing 13. A groove 70b is provided on the upper surface 70a of the rotary transformer wall 70. The groove 70b is formed in an annular shape centered on the rotation center axis AX. The upper surface 70a of the wall and the chamber 101 are sealed by sealing components (not shown) such as O-rings embedded in the groove 70b.

[0072] With the above structure, the motor stator 30 is positioned closer to the atmospheric environment At side than the motor rotor 40. Furthermore, bearings (first bearing 21A and second bearing 21B) are located radially inside the motor rotor 40. More specifically, the rotor yoke 41 is positioned radially inside the magnet 42, and the bearings (first bearing 21A and second bearing 21B) are positioned radially inside the rotor yoke 41. Additionally, the rotary transformer 60 is axially positioned closer to the output shaft 17 side than the motor stator 30. During use, the output shaft 17 side of the motor rotor 40 is axially sealed by a cover or the like, thus preventing dust generated in the bearings from flowing out to the outside (vacuum environment Va side). Furthermore, even if metal dust generated due to bearing wear enters the motor 1, the metal dust is adsorbed onto the magnet 42 or the motor partition wall 50 (where the magnetic force (magnetic field) of the motor stator 30 operates through the wall portion 51). Therefore, the motor 1 can prevent dust generated internally from flowing out to the outside.

[0073] Furthermore, an exhaust port 80 communicating with the outside is provided in the housing 10. This allows gas in the space containing the motor stator 30 to be exhausted to the outside, improving the cooling efficiency of the motor stator 30. Furthermore, as... Figure 2 As shown, the outer diameter of the motor rotor 40 is smaller than the outer diameter of the rotary transformer rotors 62A and 62B. Therefore, by simply removing the inner ring pressing part 16 from the housing shaft part 12, the rotating structure including the motor rotor 40 and the rotary transformer rotors 62A and 62B can be integrally pulled out from the output shaft 17 side. Therefore, the bearings (first bearing 21A and second bearing 21B) can be easily replaced or maintained.

[0074] More specifically, the inner diameter r2 of the rotary transformer partition 70 is larger than the outer diameter r1 of the magnet 42. Furthermore, the inner diameter r3 of the connecting portion 15 is larger than the outer diameter r1 of the magnet 42. Additionally, the outer diameter r1 of the magnet 42 represents the diameter of the virtual circle formed by connecting the outer peripheries of multiple circumferentially arranged magnets 42. Moreover, the inner diameter r2 of the rotary transformer partition 70 refers to the inner wall portion 71 (see reference 1) radially disposed between the rotary transformer stators 61A, 61B and the rotary transformer rotors 62A, 62B. Figure 6 The inner diameter r2 of the connecting part 15 is the inner circumferential surface 15c of the connecting top plate part 15a (refer to...). Figure 5The inner diameter r3 of the rotor rotor 40 is also specified. Furthermore, the rotor yoke 41 is positioned radially inside the magnet 42, and the bearings (first bearing 21A and second bearing 21B) are positioned radially inside the rotor yoke 41. With this structure, the rotating structure, including the bearings (first bearing 21A and second bearing 21B), the motor rotor 40, and the rotary transformer rotors 62A and 62B, can be integrally pulled out from the output shaft 17 side without disassembling the non-rotating parts such as the rotary transformer partition 70, the motor partition 50, the connecting part 15, and the rotary transformer stators 61A and 61B.

[0075] Next, the detailed construction of each structural element of the electric motor 1 will be described. Figure 4 This is an enlarged cross-sectional view showing the first bearing of the electric motor according to the embodiment. (Example) Figure 4 As shown, the inner ring pressing part 16 is fixed to the upper end of the housing shaft part 12 by bolt BT1. The inner ring pressing part 16 is an annular component with an opening communicating with the internal space SP. The inner ring pressing part 16 may be a flat plate covering the internal space SP. A stepped part 16a is formed on the outer periphery of the inner ring pressing part 16, extending radially outward from the housing shaft part 12. The upper end of the inner ring 22 of the first bearing 21A abuts against the stepped part 16a. The lower end of the inner ring 22 of the first bearing 21A abuts against the inner ring spacer 25. The inner ring 22 of the first bearing 21A is positioned axially by being clamped by the stepped part 16a and the inner ring spacer 25.

[0076] Here, radially, a fourth clearance G4 is formed between the inner ring 22 of the first bearing 21A and the housing shaft portion 12. Furthermore, the inner ring spacer 25 and the inner ring 22 of the second bearing 21B (see reference) Figure 5 A fourth gap G4 is also formed between the bearing (bearing 21A and bearing 21B) and the housing shaft 12. The fourth gap G4 is, for example, about 0.10 mm or more and 0.15 mm or less. In this way, even when the motor 1 is used in a high-temperature environment, shaft misalignment caused by the difference in the coefficients of thermal expansion between the bearing (bearing 21A and bearing 21B) and the housing shaft 12 can be suppressed.

[0077] The output shaft 17 is fixed to the upper end of the rotor yoke 41 of the motor rotor 40 by bolts BT2. At the upper end of the rotor yoke 41 (the end opposite the housing 11 in the axial direction), a protruding portion 41d is provided. The protruding portion 41d is an annular member provided along the outer periphery of the rotor yoke 41, and is formed to have a width smaller than the radial width of the rotor yoke 41. The output shaft 17 is fixed to the radially inner side of the protruding portion 41d. That is, the output shaft 17 and the rotor yoke 41 are fixed by a so-called interlocking connection. Therefore, the positioning of the output shaft 17 can be easily performed when replacing or maintaining the bearings (first bearing 21A and second bearing 21B). Furthermore, it is preferable that the output shaft 17 is made of a material with a larger coefficient of thermal expansion than the rotor yoke 41 and the protruding portion 41d. This suppresses misalignment of the output shaft 17 when the motor 1 is used in a high-temperature environment.

[0078] The output shaft 17 has a stepped portion 17b extending radially inward from the inner circumferential surface of the rotor yoke 41. The upper end of the outer ring 23 of the first bearing 21A abuts against the stepped portion 17b. The lower end of the outer ring 23 of the first bearing 21A abuts against the outer ring spacer 26. The outer ring 23 of the first bearing 21A is positioned axially by being clamped between the stepped portion 17b and the outer ring spacer 26.

[0079] The output shaft 17 also has a flange portion 17a. The flange portion 17a is an annular member extending radially inward from the inner circumferential surface of the output shaft 17. The flange portion 17a is configured to cover the space between the inner ring 22 and the outer ring 23 of the first bearing 21A. Furthermore, the inner circumferential surface of the flange portion 17a and the outer circumferential surface of the inner ring pressing portion 16 are arranged opposite each other with a gap G0, thereby forming a first sealing structure LS1. The gap G0 constituting the first sealing structure LS1 is, for example, formed to be about 0.05 mm or more and 0.15 mm or less. Preferably, the first sealing structure LS1 adopts a labyrinth structure. The labyrinth structure can be any structure, for example, a groove can be formed at a position opposite to the flange portion 17a of the inner ring pressing portion 16, and the gap G0 is approximately C-shaped in cross-section.

[0080] Furthermore, the output shaft 17 also serves as a support structure for the rotary transformer rotors 62A and 62B. Specifically, the output shaft 17 has a protrusion 17d that extends radially outward from the motor rotor 40, and a stepped portion 17c is formed by the portion fixed to the motor rotor 40 and the protrusion 17d. The rotary transformer rotors 62A and 62B are assembled into the stepped portion 17c and secured by bolts BT3. With this structure, the rotary transformer rotors 62A and 62B rotate integrally with the output shaft 17 and the motor rotor 40.

[0081] Figure 5This is an enlarged cross-sectional view showing the motor stator, motor rotor, and motor partition wall of the motor according to the embodiment. The cover 14 of the housing 10 is fixed to the housing base 11 by bolts BT4. The cover 14 has a protrusion that protrudes into the internal space SP of the housing shaft portion 12, and the outer periphery of the protrusion is sealed with the inner periphery of the housing shaft portion 12 by a sealing member SL1 such as an O-ring.

[0082] The outer casing 13 is fixed to the outer edge of the housing base 11 by bolts BT5. On the upper surface of the housing base 11, a plurality of stepped portions 11a, 11b, 11c, 11d, and 11e are formed between the housing shaft portion 12 and the outer casing 13. The stepped portions 11a, 11b, 11c, 11d, and 11e are arranged in sequence radially outward from the housing shaft portion 12, and the height of the upper surface gradually decreases according to the order of the stepped portions 11a, 11b, 11c, 11d, and 11e.

[0083] The upper surface of the stepped portion 11a abuts against the lower end of the inner ring 22 of the second bearing 21B. The upper end of the inner ring 22 of the second bearing 21B abuts against the inner ring spacer 25. The inner ring 22 of the second bearing 21B is fixed in an axial position by being held between the stepped portion 11a and the inner ring spacer 25. A flange portion 41a is formed on the lower end side of the rotor yoke 41, protruding radially inward from the inner circumferential surface. The upper surface of the flange portion 41a abuts against the lower end of the outer ring 23 of the second bearing 21B. The upper end of the outer ring 23 of the second bearing 21B abuts against the outer ring spacer 26. The outer ring 23 of the second bearing 21B is fixed in an axial position by being held between the flange portion 41a and the outer ring spacer 26. Furthermore, because the stepped portions 11b and 11c are formed in the housing 11, the outer ring 23 of the second bearing 21B and the lower end side of the rotor yoke 41 are arranged in a manner that does not contact the housing 11. The second sealing structure LS2 is formed by a minute gap between the stepped portions 11b and 11c of the housing 11 and the lower end side of the rotor yoke 41. The minute gap constituting the second sealing structure LS2 is, for example, formed to be between 0.05 mm and 0.15 mm. Preferably, the second sealing structure LS2 adopts a labyrinthine structure. Furthermore, the stepped portion 41b formed on the outer periphery of the rotor yoke 41 is positioned by abutting against the upper end of the magnet 42.

[0084] Next, the detailed structure of the motor partition 50 will be described. For example... Figure 5 As shown, the motor partition 50 has a wall portion 51, a top plate portion 52, and a flange portion 53. The motor partition 50 is a partition that is designed to prevent gas in the space where the motor stator 30 is disposed (atmospheric environment At side) from flowing into the space where the motor rotor 40 is disposed (vacuum environment Va side).

[0085] Specifically, the wall portion 51 of the motor partition 50 is an axially extending cylindrical component disposed between the stator core 31 and the magnet 42 fixed to the rotor yoke 41. The wall portion 51 and the outer periphery of the magnet 42 are opposite each other with a first gap G1. In other words, the first gap G1 is a radially formed gap between the motor partition 50 and the motor rotor 40. The radial thickness of the wall portion 51 is more than 40% and less than 80% of the length of the gap between the stator core 31 and the magnet 42 fixed to the rotor yoke 41. This improves the strength of the motor partition 50 and suppresses deformation of the motor partition 50. Furthermore, it suppresses contact between the motor partition 50 and the motor rotor 40, which is a rotating component.

[0086] The top plate portion 52 is connected to the upper end of the wall portion 51 and extends radially outward. The top plate portion 52 is configured to cover at least a portion of the motor stator 30. That is, the top plate portion 52 is axially positioned closer to the output shaft 17 than the stator core 31, insulator 34, and excitation coil 35.

[0087] The connecting portion 15 is configured to cover the upper surface and radially outward of the top plate portion 52. Specifically, the connecting portion 15 has a connecting top plate portion 15a and a connecting wall portion 15b. The connecting wall portion 15b is a cylindrical component that extends axially and is disposed between the inner peripheral surface of the housing 13 and the outer peripheral surface of the insulator 34 and the top plate portion 52. The connecting top plate portion 15a is connected to the upper end of the connecting wall portion 15b and extends radially inward. The connecting top plate portion 15a coincides with the top plate portion 52 of the motor partition wall 50.

[0088] A flange portion 13a extending radially inward is provided on the inner circumferential surface of the outer casing 13. The upper end of the connecting wall portion 15b is fixed to the lower surface of the flange portion 13a by bolt BT6. Furthermore, the stator core 31 of the motor stator 30 is fixed to the lower end of the connecting wall portion 15b by bolt BT7. With the above structure, the motor stator 30 is fixed to the outer casing 13 of the housing 10 via the connecting portion 15.

[0089] A portion of the inner circumferential surface 15c of the connecting top plate portion 15a overlaps with the top plate portion 52. The top plate portion 52 is fixed to the connecting top plate portion 15a by bolts BT8. Thus, the top plate portion 52 is fixed to the outer casing 13 via the connecting portion 15. Furthermore, the lower surface of the connecting top plate portion 15a and the upper surface of the top plate portion 52 are sealed by a sealing member SL3 such as an O-ring.

[0090] Furthermore, the inner peripheral surface 15c of the connecting top plate portion 15a and the outer peripheral surface 41c of the rotor yoke 41 are disposed opposite each other with a third gap G3. The size of the third gap G3 is smaller than the size of the first gap G1. As a result, dust generated by the wear of the first bearing 21A and the second bearing 21B can be prevented from flowing out to the rotary transformer 60 side through the third gap G3. In addition, as described above, the connecting portion 15 is fixed to the housing 13 and positioned, thereby ensuring that the distance between the rotor yoke 41 of the motor rotor 40 and the connecting portion 15 (the third gap G3) is within a specified range.

[0091] The flange 53 of the motor partition 50 is configured to connect to the lower end of the wall portion 51 and extend radially inward. The flange 53 is fixed to the upper surface of the stepped portion 11d of the housing 11 by bolts BT9. The lower surface of the flange 53 and the upper surface of the stepped portion 11d are sealed by a sealing member SL2 such as an O-ring. With the above structure, the space enclosed by the motor partition 50, housing 11, housing 13 and connecting portion 15 is enclosed. The motor stator 30 is disposed in the space enclosed by the motor partition 50, housing 11, housing 13 and connecting portion 15. The motor rotor 40 and bearings (first bearing 21A and second bearing 21B) are disposed in the space enclosed by the motor partition 50, housing 11, housing shaft portion 12 and output shaft 17. Therefore, the positioning accuracy of each structural component and the rigidity of the motor 1 can be improved.

[0092] The motor partition 50 is made of a non-magnetic material. Suitable materials for the motor partition 50 include, for example, austenitic stainless steel. This helps to suppress the reduction of magnetic force (magnetic field) when driving the motor rotor 40 through the partition 51. The motor partition 50 can be formed into a cylindrical, integrally molded product, for example, by deep drawing a non-magnetic stainless steel. The partition 51 is formed to be thinner than the top plate 52 and the flange 53. Specifically, the thickness of the top plate 52 and the flange 53 is several millimeters, while the thickness of the partition 51 is stretched to 0.2 mm or more and 0.5 mm or less. This ensures the rigidity and airtightness of the motor partition 50 and suppresses magnetic losses when driving the motor rotor 40. Furthermore, because the first gap G1 is small, the magnetic connection between the motor stator 30 and the motor rotor 40 can be improved, and the motor rotor 40 can be rotated effectively.

[0093] Furthermore, the connecting portion 15 is made of a magnetic material. The connecting portion 15 is a soft magnetic material, for example, formed of low-carbon steel with a carbon concentration of 0.48% or less. Examples of low-carbon steel include S45C as specified in JIS standards. Therefore, the connecting portion 15 functions as a cover, suppressing the magnetic force (magnetic field) generated from the motor stator 30 from reaching the rotary transformer 60 side. Additionally, a portion of the connecting portion 15 (the inner peripheral surface 15c of the connecting top plate portion 15a) is exposed to the vacuum environment Va side, so it is preferable to use the same material as the rotor yoke 41 of the motor rotor 40.

[0094] More specifically, in the radial direction, the third gap G3 between the inner circumferential surface 15c of the connecting portion 15 and the outer circumferential surface 41c of the rotor yoke 41 is approximately 0.1 mm or more and 0.4 mm or less. Furthermore, the length of the third gap G3 between the inner circumferential surface 15c of the connecting portion 15 and the outer circumferential surface 41c of the rotor yoke 41, along the direction of the rotation center axis, is approximately 1 mm or more and 4 mm or less. Further, the thickness t of the portion of the connecting portion 15 opposite to the rotor yoke 41 is 1 mm or more. Here, the thickness t is the thickness of the connecting portion 15 compared to the bolt BT10 (see reference). Figure 6 The thickness at the radially inner side (rotor yoke 41 side).

[0095] With the above structure, a magnetic circuit is formed in which the magnetic force (magnetic field) generated from the motor stator 30 passes through the rotor yoke 41, the third gap G3, and the connecting part 15 and returns to the motor stator 30 side. This prevents the magnetic force (magnetic field) generated by the drive current Mi flowing through the excitation coil 35 from being transmitted to the motor rotor 40 and reaching the rotary transformer 60 side. As a result, the motor 1 can suppress erroneous detection of the position information of the rotary transformer 60.

[0096] With the above structure, even if metal powder is generated due to wear of the first bearing 21A and the second bearing 21B, the first sealing structure LS1 (refer to) provided on the output shaft side of the first bearing 21A can prevent metal powder from being generated. Figure 4 ) and the second sealing structure LS2 located on the housing 11 side of the second bearing 21B (refer to Figure 5 This can suppress the outflow of metal powder into the vacuum environment Va side. Furthermore, even if metal powder enters the interior of the motor 1 from the lower side (housing housing 11 side) of the second bearing 21B, it is adsorbed by the magnetic force (magnetic field) generated from the motor stator 30 through the wall portion 51 (see reference). Figure 5 The motor partition 50, which plays a role, or the connecting part 15, which is attracted to the magnetic force (magnetic field) generated from the motor stator 30, can suppress its outflow to the outside.

[0097] Next, the structure of the rotary transformer 60 will be explained. Figure 6This is an enlarged cross-sectional view showing the rotary transformer and the wall between the rotary transformers in the electric motor according to the embodiment. For example... Figure 6 As shown, the stators 61A and 61B of the rotary transformer are fixed to the upper surface of the flange portion 13a of the housing 13 by bolts BT12.

[0098] The stators 61A and 61B of the rotary transformer have a ring-shaped stacked iron core with multiple stator poles evenly spaced in the circumferential direction, and a rotary transformer coil is wound around each stator pole. Each rotary transformer coil is connected to the wiring of the output detection signal (rotary transformer signal) Sr.

[0099] The rotary transformer rotors 62A and 62B are composed of hollow annular laminated iron cores and are fixed to the stepped portion 17c on the outside of the output shaft 17. The rotary transformer 60 can be positioned axially closer to the output shaft 17 than the motor stator 30, and there are no particular restrictions as long as the rotation of the motor rotor 40 (output shaft 17) can be detected.

[0100] Motor control circuit 90 for controlling motor 1 (refer to) Figure 1 Based on the detection signal Sr from the rotary transformer 60, a drive current Mi is provided to the excitation coil 35 of the motor stator 30. Specifically, when the motor rotor 40 rotates, the output shaft 17 rotates together with the motor rotor 40, and the rotary transformer rotors 62A and 62B also rotate in conjunction with it. As a result, the magnetic reluctance between the rotary transformer rotors 62A and 62B and the rotary transformer stators 61A and 61B continuously changes. The rotary transformer stators 61A and 61B detect the change in magnetic reluctance and convert the detection signal Sr into a digital signal via RDC 93. The CPU 91 of the motor control circuit 90 controlling the motor 1 can calculate the position or rotation angle of the output shaft 17 and the motor rotor 40, which are linked to the rotary transformer rotors 62A and 62B, per unit time based on the electrical signal from RDC 93. As a result, the motor control circuit 90 can measure the rotational state of the output shaft 17 (e.g., rotational speed, rotational direction, or rotational angle).

[0101] The rotary transformer partition 70 has an inner wall portion 71, a rotary transformer top plate portion 72, a mounting portion 73, and a flange portion 74. The inner wall portion 71 is a cylindrical component extending axially and is disposed radially between the rotary transformer stators 61A and 61B and the rotary transformer rotors 62A and 62B.

[0102] The top plate portion 72 of the rotary transformer is connected to the upper end of the inner wall portion 71 and extends radially outward. The top plate portion 72 of the rotary transformer is configured to cover the stators 61A and 61B of the rotary transformer. Furthermore, the upper surface of the top plate portion 72 of the rotary transformer is the aforementioned partition wall upper surface 70a. The mounting portion 73 is located radially outward from the top plate portion 72 of the rotary transformer and is formed to be thicker than the top plate portion 72 of the rotary transformer. The mounting portion 73 is fixed to the upper end of the housing 13 by bolts BT11. Furthermore, as described above, the mounting portion 73 is fixed to the outer wall of the chamber 101 by fixing members such as bolts.

[0103] The flange portion 74 is connected to the lower end of the inner sidewall portion 71 and extends radially inward. The flange portion 74 is overlapped on the upper surface of the connecting portion 15 and is fixed to the connecting portion 15 by bolts BT10. The lower surface of the flange portion 74 and the upper surface of the connecting portion 15 are sealed by a sealing member SL4 such as an O-ring.

[0104] With the above structure, the rotary transformer partition 70 can be sealed to prevent gas from flowing from the space (atmospheric environment At side) where the rotary transformer stators 61A and 61B are located to the space (vacuum environment Va side) where the rotary transformer rotors 62A and 62B are located. In other words, the rotary transformer stators 61A and 61B are disposed in the space enclosed by the rotary transformer partition 70, the housing 13, and the connecting portion 15. The rotary transformer rotors 62A and 62B are disposed in the space between the rotary transformer partition 70 and the output shaft 17.

[0105] The outer peripheral surface 71a of the inner wall portion 71 and the outer peripheral surface of the protrusion 17d of the output shaft 17 are disposed opposite each other with a second gap G2. In other words, the second gap G2 is a gap formed radially between the rotary transformer partition 70 and the rotary transformer rotors 62A and 62B. The second gap G2 is larger than the first gap G1 and larger than the third gap G3.

[0106] Therefore, even if metal powder is generated due to wear of the first bearing 21A and the second bearing 21B, the metal powder is attracted to the connecting part 15 (where the magnetic force (magnetic field) generated from the motor stator 30 plays a role) when passing through the third gap G3, thus preventing it from flowing out to the rotary transformer 60 side. In addition, the second gap G2 is formed to be relatively large, so that the rotating parts (motor rotor 40, rotary transformer rotors 62A and 62B, output shaft 17, first bearing 21A and second bearing 21B) can be easily disassembled from the output shaft 17 side during maintenance, etc.

[0107] Next, the detailed structure of the differential incremental rotary transformer 60A will be explained. Figure 7 This is a cross-sectional view schematically illustrating the structure of the incremental rotary transformer of the electric motor according to the embodiment. Figure 8This is a block diagram illustrating an example of the structure of a signal processing circuit in a motor control circuit.

[0108] like Figure 7 As shown, the rotary transformer stator 61A of the incremental rotary transformer 60A has N-phase, for example, 3-phase 18-pole salient poles A11-A16, B11-B16, C11-C16 (first magnetic poles) protruding radially inward at predetermined intervals. At the midpoint of each of the salient poles A11-A16, B11-B16, C11-C16, are 3-phase 18-pole salient poles A21-A26, B21-B26, C21-C26 (second magnetic poles). These salient poles are arranged circumferentially in the order A11, C21, B11, A21, C11, B21, A12, C22… In each salient pole A11-C26, three teeth TS1, TS2, TS3 are provided on the inner circumferential end face, and an excitation winding LA11-LC26 is wound in the center. Therefore, salient poles at a 180-degree angle are in phase with each other.

[0109] Multiple slot teeth TR are formed on the outer peripheral surface of the rotary transformer rotor 62A. Here, the spacing of the slot teeth TR of the rotary transformer rotor 62A is formed such that, for example, if three adjacent teeth TR of the rotary transformer rotor 62A coincide with the teeth TS1, TS2, and TS3 of the salient pole A11 of the rotary transformer stator 61A, the teeth TS1, TS2, and TS3 of the adjacent salient pole C21 are mechanically offset by a 1 / 36 pitch phase relative to the slot teeth TR of the rotary transformer rotor 62A.

[0110] In the excitation windings LA11-LC26 of each salient pole A11-C26 (although the diagram is omitted), excitation windings LA11-LA16 are connected in series, excitation windings LB11-LB16 are connected in series, and excitation windings LC11-LC16 are connected in series. Furthermore, excitation windings LA21-LA26 are connected in series, excitation windings LB21-LB26 are connected in series, and excitation windings LC21-LC26 are connected in series.

[0111] like Figure 8 As shown, the incremental rotary transformer 60A outputs rotary transformer signals fa1, fa2, fb1, fb2, fc1, and fc2 to the differential amplifier circuit 95. These rotary transformer signals fa1, fa2, fb1, fb2, fc1, and fc2 are the output signals from the series-connected excitation windings LA11-LA16, LA21-LA26, LB11-LB16, LB21-LB26, LC11-LC16, and LC21-LC26, respectively.

[0112] More specifically, the rotary transformer signals fa1, fa2, fb1, fb2, fc1, and fc2 are represented by the following equations (1) to (6).

[0113] fa1=A0+A1cosθ+A2cos2θ+A3cos3θ+A4cos4θ…(1)

[0114] fb1=A0+A1cos(θ-120°)+A2cos2(θ-120°)+A3cos3(θ-120°)+A4cos4(θ-120°)…(2)

[0115] fc1=A0+A1cos(θ+120°)+A2cos2(θ+120°)+A3cos3(θ+120°)+A4cos4(θ+120°)…(3)

[0116] fa2=A0+A1cos(θ+180°)+A2cos2(θ+180°)+A3cos3(θ+180°)+A4cos4(θ+180°)…(4)

[0117] fb2=A0+A1cos(θ-300°)+A2cos2(θ-300°)+A3cos3(θ-300°)+A4cos4(θ-300°)…(5)

[0118] fc2=A0+A1cos(θ+300°)+A2cos2(θ+300°)+A3cos3(θ+300°)+A4cos4(θ+300°)…(6)

[0119] The rotary transformer signals fa1, fa2, fb1, fb2, fc1, and fc2 are provided to the differential amplifier circuit 95. Therefore, the output signals da, db, and dc of the differential amplifier circuit 95 are represented by the following equations (7), (8), and (9). Wherein, the output signal da is the differential output signal of rotary transformer signals fa1 and fa2. The output signal db is the differential output signal of rotary transformer signals fb1 and fb2. The output signal dc is the differential output signal of rotary transformer signals fc1 and fc2.

[0120] da=2A1cosθ+2A3cos3θ…(7)

[0121] db=2A1cos(θ-120°)+2A3cos3(θ-120°)…(8)

[0122] dc=2A1cos(θ+120°)+2A3cos3(θ+120°)…(9)

[0123] The three-phase output signals da, db, and dc of the differential amplifier circuit 95 are provided to the phase conversion circuit 96. The phase conversion circuit 96 converts the output signals da, db, and dc into two-phase AC signals fc(θ) and fs(θ) that cancel out third harmonic distortion, as expressed by the following equations (10) and (11).

[0124] fc(θ)=3A1cosθ / 2=sinωt×cosθ…(10)

[0125] fs(θ)=3A1sinθ / 2=sinωt×sinθ…(11)

[0126] These two-phase AC signals, fc(θ) and fs(θ), are provided to the signal processing circuit (RDC93). In the RDC93, in the initial state, the counter 93f is reset to zero, thereby digitally rotating the angle. Set to "0".

[0127] Therefore, the multiplication output of multiplier 93a is sinωt × sinθ, and the multiplication output of multiplier 93b is "0". The subtraction output of subtractor 93c is... Vsinωt × sinθ is provided to the synchronous rectifier 93d. The output Vsinθ, after the excitation voltage component is removed from the synchronous rectifier 93d, is output as a speed detection signal to the CPU 91 (see reference). Figure 1 Furthermore, the output Vsinθ of the synchronous rectifier 93d is provided to the voltage-controlled oscillator 93e and converted into a pulse signal corresponding to the voltage, which is then provided to the counter 93f. Thus, the count value of the counter 93f (digital rotation angle) is... It becomes a value equal to the phase angle θ.

[0128] In this state, if the rotary transformer rotor 62A continues to rotate in the same direction, the output of the subtractor 93c will increase the phase angle θ relative to the digital rotation angle. As the phase angle θ increases, the output of the synchronous rectifier 93d also increases accordingly. Therefore, the count value of the counter 93f increases by the phase angle θ and outputs the current digital rotation angle corresponding to the rotation of the rotary transformer rotor 62A.

[0129] Then, the CPU91 controls the rotational speed and positioning based on the speed detection signal from the incremental rotary transformer 60A. By using a differential rotary transformer as the incremental rotary transformer 60A, erroneous detections caused by the magnetic force (magnetic field) generated from the motor stator 30 can be suppressed.

[0130] Next, an example of the operating sequence of the rotary transformers 60 (incremental rotary transformer 60A and absolute rotary transformer 60B) of the CPU 91 of the motor 1 will be described. Figure 9 This is a flowchart illustrating the driving methods for incremental and absolute rotary transformers.

[0131] like Figure 9 As shown, when the power to the motor 1 is turned on, the CPU 91 first energizes the absolute rotary transformer 60B (step ST1). Therefore, based on the absolute angle information from the absolute rotary transformer 60B, the CPU 91 can determine the angle (position) of the motor rotor 40 when the power is on.

[0132] Next, CPU91 stops energizing the absolute rotary transformer 60B (step ST2) and energizes the incremental rotary transformer 60A (step ST3). Thus, as described above, CPU91 is able to detect precise position based on the rotary transformer signals fa1, fa2, fb1, fb2, fc1, and fc2 from the incremental rotary transformer 60A.

[0133] Based on position information and speed detection signals from the incremental rotary transformer 60A, the CPU91 drives the motor 1 (step ST4) and performs speed or positioning control. The absolute rotary transformer 60B functions as a shield to block the magnetic force (magnetic field) generated from the motor stator 30 when driving the motor 1, and can suppress the magnetic force (magnetic field) generated from the motor stator 30 from reaching the incremental rotary transformer 60A side.

[0134] Furthermore, the shape or structure of each structural element of the motor 1 described above is merely an example and can be appropriately modified. For instance, the rotary transformer partition 70 is not limited to being integrally formed, but can also be divided into multiple parts. In addition, the fixing or sealing structure of each structural element can also be appropriately modified.

[0135] As described above, the electric motor 1 of this embodiment includes a housing 10, a motor stator 30, a motor rotor 40, bearings (first bearing 21A and second bearing 21B), a sealing structure LS, and a rotary transformer 60. The housing 10 includes a housing base 11 and a housing shaft portion 12 disposed on the housing base 11 and extending in the direction along the rotation center axis AX. The motor stator 30 is disposed radially outward of the housing shaft portion 12. The motor rotor 40 is disposed between the motor stator 30 and the housing shaft portion 12. The bearings are disposed radially inward of the motor rotor 40 and support the motor rotor 40 rotatably on the housing shaft portion 12. The sealing structure LS seals the space between the motor rotor 40 and the housing shaft portion 12 on the output shaft 17 side of the motor rotor 40. The rotary transformer 60 detects the rotation of the motor rotor 40. The rotary transformer 60 is disposed radially outward of the bearings and in the direction along the rotation center axis AX, closer to the output shaft 17 than the motor stator 30.

[0136] Thus, the bearing is located radially inside the motor rotor 40. Because the output shaft 17 side of the motor rotor 40 is sealed by a cover or similar device during operation, the outflow of dust generated in the bearing to the external environment, such as a vacuum environment Va, is suppressed. Furthermore, even if dust (metal powder) generated by bearing wear enters the motor 1, the metal powder is attracted to the motor interlayer wall 50 (due to the magnetic force (magnetic field) of the motor stator 30). Therefore, the motor 1 can suppress the outflow of dust generated internally. Moreover, the outflow of metal powder to the rotary transformer 60 side can be suppressed, thus preventing a decrease in the detection accuracy of the rotary transformer 60.

[0137] Furthermore, the motor 1 is disposed between the motor stator 30 and the motor rotor 40, and has a motor partition 50 that divides the space where the motor stator 30 is disposed and the space where the motor rotor 40 is disposed. In this way, the motor partition 50 can suppress the outflow of gas from the atmospheric environment side where the motor stator 30 is disposed to the vacuum environment side where the motor rotor 40 is disposed.

[0138] Furthermore, in the electric motor 1, the rotary transformer 60 has rotary transformer rotors 62A and 62B connected to the motor rotor 40, and rotary transformer stators 61A and 61B located radially outside the rotary transformer rotors 62A and 62B and having excitation coils. A rotary transformer partition 70 is provided between the rotary transformer rotors 62A and 62B and the rotary transformer stators 61A and 61B. This partition 70 divides the space containing the rotary transformer rotors 62A and 62B into a space containing the rotary transformer stators 61A and 61B, thus preventing gas from flowing from the atmospheric side containing the rotary transformer stators 61A and 61B to the vacuum environment side containing the rotary transformer rotors 62A and 62B. Furthermore, since the rotary transformer 60 is used as an angle detector, no electronic components are placed inside the electric motor 1. Therefore, when the electric motor 1 is used in a high-temperature environment, angle detection is reliable.

[0139] Furthermore, in the electric motor 1, the outer diameter of the motor rotor 40 is smaller than the outer diameter of the rotary transformer rotors 62A and 62B. This allows the rotating structure, including the motor rotor 40 and the rotary transformer rotors 62A and 62B, to be integrally pulled out from the output shaft 17 side, thereby facilitating the replacement or maintenance of the bearings (first bearing 21A and second bearing 21B).

[0140] Furthermore, in the electric motor 1, the bearings (first bearing 21A and second bearing 21B) are unlubricated bearings, having an inner ring 22 disposed in the housing shaft portion 12, an outer ring 23 disposed in the motor rotor 40, and rolling elements 24 disposed between the inner ring 22 and the outer ring 23. At least the rolling elements 24 are made of ceramic. This suppresses dust generated by wear or gases released at high temperatures from the rolling elements 24 of the bearing.

[0141] Furthermore, in the electric motor 1, the bearings (first bearing 21A and second bearing 21B) are unlubricated bearings, having an inner ring 22 disposed in the housing shaft portion 12, an outer ring 23 disposed in the motor rotor 40, and rolling elements 24 disposed between the inner ring 22 and the outer ring 23. The inner ring 22 and the outer ring 23 are made of ferrous components. In this way, even if dust generated due to bearing wear enters the interior of the electric motor 1, the metal powder can be well adsorbed onto the permanent magnets of the motor stator 30 or the motor rotor 40.

[0142] Furthermore, in the electric motor 1, a connecting portion 15 made of a magnetic material is arranged between the motor stator 30 and the rotary transformer 60 in the direction along the rotation center axis AX. In this way, the connecting portion 15 can shield the magnetic force (magnetic field) generated from the motor stator 30, thereby improving the detection accuracy of the rotary transformer 60. In addition, the connecting portion 15 can adsorb metal powder generated due to wear.

[0143] Furthermore, the motor 1 has an outer ring pressing portion (stepped portion 17b) located on the output shaft 17 side of the motor rotor 40 and fixed to the outer ring 23 of the bearing, and an inner ring pressing portion 16 located on the output shaft 17 side of the housing shaft portion 12 and fixed to the inner ring 22 of the bearing. The sealing structure LS has a labyrinth structure formed by the outer ring pressing portion and the inner ring pressing portion 16. In this way, dust from the motor 1 generated due to bearing wear, etc., is shielded by the sealing structure LS, which can prevent it from flowing out to the outside.

[0144] Furthermore, in the electric motor 1, the motor stator 30 is disposed in a space closer to the atmosphere than the space where the motor rotor 40 is disposed. This improves the cooling efficiency of the motor stator 30 compared to a situation where the motor stator 30 is disposed in the same space as the motor rotor 40, such as a vacuum environment Va.

[0145] Furthermore, in the electric motor 1, the motor rotor 40 includes a samarium cobalt permanent magnet. Thus, even when the electric motor 1 is used in a high-temperature environment, the magnet 42 will not demagnetize, thereby enabling efficient rotational drive of the motor rotor 40.

[0146] Furthermore, the electric motor 1 includes a motor control circuit 90 that provides a drive current Mi to the excitation coil 35 of the motor stator 30 based on the detection signal Sr from the rotary transformer 60. Thus, the motor control circuit 90, based on the detection signal Sr from the rotary transformer 60, can always monitor rotational torque or speed fluctuations. This allows for early detection of bearing malfunctions, for example, or for determining the optimal time to replace the bearings.

[0147] Variation Example 1

[0148] Figure 10 This is a schematic cross-sectional view of the electric motor involved in Variation Example 1. For example... Figure 10 As shown, the motor 1A according to Modification 1 differs from the embodiment described above in that the housing shaft portion 12A of the housing 10 has a solid cylindrical structure. That is, no internal space SP is formed inside the housing shaft portion 12A. Therefore, the motor 1A according to Modification 1 simplifies the structure of the housing 10. Furthermore, the inner ring pressing portion 16A can be made into a disc shape without an opening. Moreover, in this modification, it is unnecessary to provide a cover portion 14 for sealing the internal space SP (see [reference]). Figure 2Therefore, the sealing structure between the internal space SP and the atmospheric environment At can also be omitted (see reference). Figure 5 (Sealing component SL1).

[0149] Variation Example 2

[0150] Figure 11 This is a top view schematically representing a portion of the electric motor involved in Variation Example 2. Figure 12 It is a schematic top view showing a portion of an electric motor with motor windings. Figure 11 This is a schematic representation of a portion of the electric motor 1B, specifically a schematic top view of the motor stator 30A and the motor rotor 40.

[0151] like Figure 11 As shown, the motor stator 30A includes a stator core 31A and an insulator 34 (see reference). Figure 12 ) and motor winding 35a (excitation coil 35) (refer to Figure 12 The stator core 31A has a back yoke 32A and teeth 33A (salient poles). The back yoke 32A is an annular component, and multiple teeth 33A are arranged circumferentially on the back yoke 32A at equal intervals. The teeth 33A protrude radially inward from the inner circumferential surface of the back yoke 32A and are formed in a straight line. That is, the ends of the teeth 33A in the extending direction do not have circumferentially protruding portions, and are formed to have a fixed amplitude in the extending direction.

[0152] The excitation coil 35 is wound around the teeth 33A of the stator core 31A, with the insulator 34 in between. In Modification 2, the teeth 33A are formed in a straight line, so the motor winding 35a is inserted into the teeth 33A in a state where it is pre-wound externally to form the excitation coil 35. As a result, compared with the case where the motor winding 35a is wound around the teeth 33A to form the excitation coil 35, the number of turns (duty cycle) of the motor winding 35a can be increased, and as a result, the temperature rise of the motor 1B caused by the drive current Mi flowing through the motor winding 35a can be suppressed.

[0153] Variation Example 3

[0154] Figure 13 This is an enlarged cross-sectional view of the first bearing of the electric motor involved in Variation Example 3. (As shown...) Figure 13 As shown, in the motor 1C involved in Modification 3, the difference in structure compared with the above-described embodiment, Modification 1 and Modification 2 is that the first bearing 21A is formed as a rotating support structure with constant pressure preload applied by the preload spring 18.

[0155] The outer ring 23 of the first bearing 21A is positioned by the outer ring spacer 26, and the inner ring 22 is preloaded by the preload spring 18. That is, in modified example 3, the inner ring spacer 25 is not provided (see reference). Figure 4 More specifically, the inner ring pressing portion 16A is configured to cover the inner circumferential side and the upper side of the inner ring 22 of the first bearing 21A. The flange portion 16Aa of the inner ring pressing portion 16A is provided to protrude radially inward and is fixed to the housing shaft portion 12 by bolt BT1.

[0156] An overlapping portion 16Ac is provided on the side opposite to the housing 11 of the inner ring 22 of the first bearing 21A. The overlapping portion 16Ac is configured to cover the upper side of the inner ring 22 of the first bearing 21A and the gap between the inner ring 22 and the outer ring 23. A groove 16Ab with a downward opening (inner ring 22 side) is provided in the overlapping portion 16Ac. A preload spring 18 is disposed in the groove 16Ab. The groove 16Ab is formed in a ring shape in the circumferential direction, and multiple preload springs 18 are arranged in the circumferential direction along the inner ring 22. In addition, a plate 19 is provided between the preload spring 18 and the inner ring 22. The plate 19 is a ring-shaped member opposite to the overlapping portion 16Ac (groove 16Ab), and the upper surface of the plate 19 is disposed in a non-contact manner with the lower surface of the overlapping portion 16Ac.

[0157] With the above structure, the preload spring 18 can apply a constant preload to the first bearing 21A. Therefore, even when the motor 1C is used in a high-temperature environment, changes in preload can be suppressed compared to a fixed preload.

[0158] Furthermore, in modified example 3, the first sealing structure LS1 is formed by the minute gap between the upper surface and outer peripheral surface of the overlapping portion 16Ac and the inner peripheral surface and flange portion 17a of the output shaft 17. Additionally, Figure 13 The preload spring 18 shown is a compression spring. However, it is not limited to this; the preload spring 18 can be any type of spring as long as it is capable of applying a constant preload. Furthermore, the structure that holds the inner ring pressing part 16A of the preload spring 18 is only an example and can be modified appropriately.

[0159] Variation Example 4

[0160] Figure 14 This is an enlarged cross-sectional view of the first bearing of the electric motor involved in variation example 4. For example... Figure 14As shown, the motor 1D involved in Modification 4 is similar to that in Modification 3 described above, forming a rotary bearing structure with constant preload applied by a preload spring 18. In Modification 4, the difference in structure compared to Modification 3 is that the outer ring spacer 26 has a bearing portion 26a. The bearing portion 26a is configured to protrude radially inward from the inner circumferential surface of the outer ring spacer 26 and cover the gap between the outer ring 23 and the inner ring 22. A groove 26b is formed on the surface of the bearing portion 26a opposite to the first bearing 21A. The bearing portion 26a and the groove 26b are overlapped with the first bearing 21A to form a ring.

[0161] Therefore, since the dust generated by the wear of the first bearing 21A is retained in the bearing portion 26a, the motor 1D of Modified Example 4 can suppress the outflow of dust to the outside of the first sealing structure LS1 and the second sealing structure LS2.

[0162] Furthermore, the electric motor 1 of this embodiment can take the following form.

[0163] (1-1) The stator of the motor is formed by overlapping electromagnetic steel plates. It includes a stator core with a back yoke and salient poles, and a heat-resistant motor winding disposed on the salient poles. The motor rotor includes a rotor yoke formed of magnetic material and a plurality of magnets disposed on the rotor yoke. The motor partition is made of non-magnetic material.

[0164] (1-2) The stator core is arranged radially outside the plurality of magnets, separated by the motor partition.

[0165] (1-3) The above stator core is formed by pasting steel plates or riveting in the mold.

[0166] (1-4) The above-mentioned convex pole protrudes radially inward from the inner circumference of the above-mentioned back yoke and forms a straight line.

[0167] (1-5) The stator core is fastened to the housing by bolts.

[0168] (1-6) The housing has a cylindrical outer shell disposed on the radially outer side of the housing shaft, and the motor stator and the inner circumferential surface of the outer shell are arranged opposite each other with a space between them.

[0169] (1-7) It has an insulating material that insulates the stator core from the motor winding, and the motor winding and the insulating material have a heat resistance of 200°C or higher.

[0170] (1-8) The thickness of the motor partition wall is more than 40% and less than 80% of the gap between the magnet and the stator core.

[0171] (1-9) The spacer wall of the above motor is made of austenitic stainless steel.

[0172] (1-10) The above magnet is a samarium cobalt permanent magnet.

[0173] (2-1) In the direction along the rotation center axis, a connecting part made of a magnetic body is provided between the motor stator and the rotary transformer. The connecting part is located on the radial outside of the motor rotor and is configured to cover the rotary transformer side of the motor stator and is fixed to the motor stator.

[0174] (2-2) The above-mentioned connecting part is formed of low carbon steel with a carbon concentration of less than 0.45%.

[0175] (2-3) The distance between the motor rotor and the connecting part in the radial direction is 0.1 mm or more and 0.4 mm or less, and the distance between the motor rotor and the connecting part in the direction along the rotation center axis is 1 mm or more and 4 mm or less.

[0176] (2-4) The housing has a cylindrical outer shell located radially outside the shaft portion of the housing, the motor stator and the inner circumferential surface of the outer shell are arranged opposite each other with a space between them, the outer shell is formed of a non-magnetic material, and the connecting portion is fixed to the outer shell.

[0177] (3-1) The above-mentioned rotary transformers include differential incremental rotary transformers.

[0178] (3-2) The above-mentioned rotary transformer also includes an absolute rotary transformer, and the above-mentioned motor stator, the above-mentioned absolute rotary transformer and the above-mentioned incremental rotary transformer are arranged sequentially along the direction of the above-mentioned rotation center axis.

[0179] (3-3) The absolute rotary transformer and the incremental rotary transformer mentioned above each include a rotary transformer stator with an excitation coil and a rotary transformer rotor disposed on the radial inner side of the rotary transformer stator. The rotary transformer rotor of the absolute rotary transformer is formed of low carbon steel.

[0180] (3-4) The absolute rotary transformer and the incremental rotary transformer mentioned above each include a rotary transformer stator with an excitation coil and a rotary transformer rotor disposed on the radial inner side of the rotary transformer stator. The rotary transformer rotor of the incremental rotary transformer is formed of low carbon steel and has multiple salient poles.

[0181] (3-5) The rotary transformer includes a rotary transformer stator with an excitation coil and a rotary transformer rotor disposed radially inside the rotary transformer stator. A rotary transformer partition wall formed of a non-magnetic body is disposed between the rotary transformer rotor and the rotary transformer stator.

[0182] (4-1) Includes an outer ring pressing part, which is provided axially on the side opposite to the housing on the motor rotor and fixed to the outer ring of the bearing; and an inner ring pressing part, which is provided axially on the side opposite to the housing on the shaft and fixed to the inner ring of the bearing. The rotary transformer has a rotary transformer rotor connected to the motor rotor and a rotary transformer stator provided radially outward of the rotary transformer rotor and having an excitation coil. The rotary transformer is provided radially outward of the bearing and along the rotation center axis, and is axially provided on the side opposite to the housing relative to the motor stator. The outer diameter of the motor rotor is smaller than the outer diameter of the rotary transformer rotor.

[0183] (4-2) The rotor of the electric motor has a rotor yoke and a plurality of magnets arranged along the outer periphery of the rotor yoke, and the inner diameter of the wall of the rotary transformer is larger than the outer diameter of the magnets.

[0184] (4-3) It has a connection part made of magnetic material, which is provided between the stator of the motor and the rotary transformer in the direction along the rotation center axis. The motor rotor has a rotor yoke and a plurality of magnets provided along the outer periphery of the rotor yoke. The inner diameter of the connection part is larger than the outer diameter of the magnets.

[0185] (4-4) The bearing described above is located on the radial inner side of the rotor yoke described above.

[0186] (4-5) A gap is formed in the radial direction between the bearing and the housing shaft.

[0187] (4-6) It has an output shaft disposed on the side opposite to the housing in the axial direction of the motor rotor, and a protrusion protruding in the axial direction is provided at the end of the motor rotor on the side opposite to the housing in the axial direction, and the output shaft is fixed to the radial inner side of the protrusion.

[0188] (4-7) The connecting part is disposed on the radial outside of the rotor of the motor and is configured to cover the rotary transformer side of the stator of the motor and is fixed to the stator of the motor.

[0189] (5-1) includes: a first sealing structure disposed on the side of the bearing opposite to the housing in the axial direction of the motor rotor, and sealing between the motor rotor and the housing shaft; a second sealing structure disposed on the housing side of the bearing in the axial direction of the motor rotor, and sealing between the motor rotor and the housing; and a rotary transformer that detects the rotation of the motor rotor, the rotary transformer being disposed on the side of the housing in the axial direction relative to the motor stator in the direction along the rotation center axis, the bearing being an unlubricated bearing, and having an inner ring disposed on the housing shaft, an outer ring disposed on the motor rotor, and rolling elements disposed between the inner ring and the outer ring.

[0190] (5-2) Of the inner ring, outer ring and rolling element of the bearing, at least the rolling element is made of ceramic.

[0191] (5-3) The inner ring and outer ring of the bearing are made of magnetic stainless steel.

[0192] (5-4) The motor rotor has a rotor yoke and a plurality of magnets arranged along the outer periphery of the rotor yoke, the rotor yoke being arranged radially inside the plurality of magnets, and the bearing being arranged radially inside the rotor yoke.

[0193] (5-5) The above bearing has multiple angular contact ball bearings arranged back to back.

[0194] (5-6) At least one of the first sealing structure and the second sealing structure described above has a labyrinthine structure formed with a gap of more than 0.05 mm and less than 0.15 mm.

[0195] (5-7) The bearing has a first bearing and a second bearing arranged along the axial direction, and has an inner ring spacer disposed between the inner ring of the first bearing and the inner ring of the second bearing, and an outer ring spacer disposed between the outer ring of the first bearing and the outer ring of the second bearing.

[0196] (5-8) includes: an inner ring pressing part disposed on the inner ring of the bearing, on the side opposite to the housing, and fixed to the housing shaft; and a preload spring disposed between the inner ring pressing part and the bearing, and applying a constant pressure preload to the bearing.

[0197] (5-9) The bearing has a first bearing and a second bearing arranged along the axial direction, and has an outer ring spacer disposed between the outer ring of the first bearing and the outer ring of the second bearing, and a bearing portion disposed thereon, which is configured to protrude radially inward from the inner circumferential surface of the outer ring spacer and cover the gap between the outer ring and the inner ring.

[0198] Symbol Explanation

[0199] 1. Electric motors: 1A, 1B, 1C, 1D

[0200] 10. Shell

[0201] 11. Shell

[0202] 12. Housing shaft portion

[0203] 15 Connecting parts

[0204] 17 Output shaft

[0205] 21A Bearing No. 1

[0206] 21B Bearing No. 2

[0207] 22 Inner Circle

[0208] 23 Outer ring

[0209] 24 Rolling elements

[0210] 30 Motor stator

[0211] 40 Electric motor rotor

[0212] 41 Rotor yoke

[0213] 50 Motor partition

[0214] 60 Rotary Transformer

[0215] 60A Incremental Rotary Transformer

[0216] 60B Absolute Rotary Transformer

[0217] 61A and 61B rotary transformer stators

[0218] Rotors of 62A and 62B rotary transformers

[0219] 70 Rotary Transformer Chamber

[0220] 90 Motor control circuit

[0221] 100 Semiconductor Manufacturing Equipment

[0222] 101 chambers

[0223] 111 Transfer Disk

[0224] At atmospheric environment

[0225] Vacuum environment

Claims

1. An electric motor, characterized in that, include: A housing, comprising a housing base and a housing shaft portion disposed on the housing base and extending in a direction along a rotational central axis; The motor stator is disposed radially outside the shaft portion of the housing; The motor rotor is disposed between the motor stator and the housing shaft portion; A bearing is disposed radially inside the motor rotor and supports the motor rotor rotatably on the housing shaft portion; A sealing structure is provided on the opposite side of the housing in the axial direction of the motor rotor, and seals the space between the motor rotor and the housing shaft. as well as A rotary transformer that detects the rotation of the motor rotor. The rotary transformer is axially positioned on the opposite side of the housing, relative to the motor stator, in a direction radially outward from the bearing and along the axis of rotation. A partition wall is provided between the motor stator and the motor rotor, dividing the space into a space for the motor stator and a space for the motor rotor. The rotary transformer has a rotary transformer rotor connected to the motor rotor, and a rotary transformer stator disposed radially outside the rotary transformer rotor and having an excitation coil. A rotary transformer partition wall is provided between the rotor and the stator of the rotary transformer.

2. The electric motor according to claim 1, wherein, The outer diameter of the motor rotor is smaller than the outer diameter of the rotary transformer rotor.

3. The electric motor according to claim 1 or 2, wherein, The bearing is an unlubricated bearing and has an inner ring disposed on the shaft portion of the housing, an outer ring disposed on the motor rotor, and rolling elements disposed between the inner ring and the outer ring. Of the inner ring, the outer ring, and the rolling element, at least the rolling element is made of ceramic.

4. The electric motor according to claim 1 or 2, wherein, The bearing is an unlubricated bearing and has an inner ring disposed on the shaft portion of the housing, an outer ring disposed on the motor rotor, and rolling elements disposed between the inner ring and the outer ring. The inner and outer rings are made of magnetic ferrous components.

5. The electric motor according to claim 1 or 2, wherein, Along the direction of the rotation center axis, a connection portion made of magnetic material is arranged between the motor stator and the rotary transformer.

6. The electric motor according to claim 1 or 2, wherein, include: An outer ring pressing portion, which is axially disposed on the side opposite to the housing of the motor rotor and fixed to the outer ring of the bearing; and An inner ring pressing portion is disposed axially on the side opposite to the housing seat of the housing shaft portion and is fixed to the inner ring of the bearing. The sealing structure has a labyrinthine structure formed by the outer ring pressing portion and the inner ring pressing portion.

7. The electric motor according to claim 1 or 2, wherein, The stator of the motor is located in a space closer to the atmosphere than the space where the rotor of the motor is located.

8. The electric motor according to claim 1 or 2, wherein, The motor rotor includes a samarium cobalt permanent magnet.

9. The electric motor according to claim 1 or 2, wherein, include: The motor control circuit provides drive current to the excitation coil of the motor stator based on the detection signal from the rotary transformer.

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