JP4736025B2 - Direct drive motor - Google Patents

Description

  The present invention relates to a direct drive motor used in an atmosphere outside the atmosphere, for example, in a vacuum.

  For example, in a semiconductor manufacturing apparatus or the like, a workpiece is processed in an ultra-high vacuum atmosphere in a vacuum chamber in order to eliminate impurities as much as possible. As an actuator used in that case, for example, in a drive motor of a workpiece positioning device, a lubricant containing a volatile component such as general grease cannot be used for a drive shaft bearing. Lubrication is enhanced by plating soft metals such as gold and silver on the inner and outer rings of the bearing. In addition, there is a fact that a stable material with excellent heat resistance and low emission gas is selected for the coil insulating material of the drive motor, the wiring coating material, and the adhesive of the laminated magnetic pole.

  In particular, in recent years, the degree of integration of semiconductors has increased, and at the same time, higher density has been promoted by reducing the pattern width of the IC. In order to manufacture a wafer that can cope with this miniaturization, a high degree of uniformity in wafer quality is required. In order to meet the demand, it is important to further reduce the impurity gas concentration in the low-pressure gas processing chamber of the wafer. Further, in order to perform microfabrication as required, an extremely high precision positioning device is required. From the above viewpoint, the following problems are pointed out when the conventional actuator is examined.

  That is, in the case of a drive motor used in a vacuum chamber equipped with an ultra-vacuum atmosphere, even if a stable material with excellent heat resistance and low emission gas is selected for the coil insulation material or wiring coating of the drive motor, As long as it is an organic insulating material, it is microscopically porous and has numerous holes on its surface. Once this is exposed to the atmosphere, gas, water molecules, etc. are taken in and occluded in the holes on the surface. A long time is required for degassing to remove these occluded impure molecules by vacuum evacuation, and a reduction in production efficiency is unavoidable. Furthermore, since heat cannot be released due to air convection in a vacuum, when the coil temperature rises locally, the resistance of that portion increases, heat generation is accelerated, and the coil insulation film is burned out. Easy to invite. On the other hand, while using an inorganic material for the coil insulating material, it is conceivable to reduce adsorbed impure molecules by using a stainless steel sheath wire for the wiring. However, in that case, not only the cost becomes very high, but also the ratio of conductors such as copper in the coil winding space decreases, resulting in an increase in electrical resistance, resulting in a decrease in motor capacity. There is.

In order to solve such a problem, Patent Document 1 discloses a direct drive motor in which a stator is arranged inside a vacuum sealing body, an output member is arranged outside thereof, and a frog leg arm is driven using an output member, that is, a rotor. Are listed. According to the direct drive motor of Patent Document 1, coil insulators and wiring coverings attached to the stator are arranged inside a vacuum seal body maintained at atmospheric pressure, and therefore when they are arranged in a vacuum chamber It is possible to avoid the problem of the storage of impure molecules and the problem of heat generation.
JP 2000-69741 A

  However, in direct drive motors that are scattered even in a vacuum atmosphere, so-called baking out may be performed to heat the entire motor in order to forcibly release the outgas such as adhesive before the surroundings are made into a vacuum environment. If the temperature is too high, the coil coating may be damaged. Therefore, there is a problem that the temperature of baking out cannot be raised above a certain temperature, and it takes time to forcibly release outgas. In addition, when the direct drive motor is used, if the temperature rises due to the heat generated by the motor, the components may compete with each other due to the difference in thermal expansion.

  The present invention has been made in view of the problems of the prior art, and an object thereof is to provide a direct drive motor capable of effectively suppressing a temperature rise.

The direct drive motor of the present invention includes a hollow body and a housing made of a disc ,
A partition wall extending from the housing and isolating the atmosphere side from the atmosphere outside;
An outer rotor disposed outside the atmosphere with respect to the partition;
An inner rotor that is disposed on the atmosphere side with respect to the partition wall and is rotated together with the outer rotor;
A stator disposed on the atmosphere side with respect to the partition wall and driving the outer rotor ;
Is disposed on the atmosphere side with respect to the partition wall to have a detector for detecting a rotational position of the inner rotor, in a direct drive motor for use in an atmosphere of outside air,
The inner rotor is formed with a radially extending thin plate-like fin that rotates with the inner rotor,
A plurality of radially extending grooves are formed at the end of the main body where the bottom of the partition wall is disposed,
A plurality of openings penetrating in the axial direction are formed in the disk in which the mouth portion of the partition wall is disposed,
By driving the inner rotor that is rotated together with the outer rotor by the stator, the hollow structure main body, the plurality of grooves at the end of the main body, and the plurality of openings of the disc are communicated, The air in the vicinity of the fin is discharged .

  According to the direct drive motor of the present invention, since the cooling means for cooling the stator is provided, damage to the stator coil can be suppressed even if the entire motor is maintained at a high temperature during the bakeout. Further, although the coil generates heat during the operation of the motor, by cooling the periphery of the stator, it is possible to suppress thermal expansion and suppress competition between components.

  Further, when the cooling means includes fins that rotate together with the inner rotor, the periphery of the stator can be cooled by so-called air cooling as the rotor rotates.

  Furthermore, when a passage through which gas passes is formed in the housing, the heat-exchanged gas can be discharged to the outside through the passage, thereby enhancing the cooling effect.

  Furthermore, it is preferable that the cooling means is composed of a cooling blower or a cooling fan for cooling the direct drive motor, since it can efficiently cool the air.

  Further, when the cooling means includes a liquid passage formed in the housing and connected to an external liquid source, the periphery of the stator can be cooled by so-called liquid cooling.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a frog-leg-arm type transport device using a direct drive motor according to the present embodiment. In FIG. 1, two direct drive motors D1 and D2 are connected in series. A first arm A1 is connected to the rotor of the lower direct drive motor D1, and a first link L1 is pivotally connected to the tip of the first arm A1. On the other hand, the second arm A2 is connected to the rotor of the upper direct drive motor D2, and the second link L2 is pivotally connected to the tip of the second arm A2. The links L1 and L2 are pivotally connected to a table T on which the wafer W is placed.

  As is clear from FIG. 1, if the rotors of the direct drive motors D1 and D2 rotate in the same direction, the table T also rotates in the same direction. If the rotor rotates in the opposite direction, the table T The motors D1 and D2 are approached or separated from each other. Therefore, if the direct drive motors D1 and D2 are rotated at an arbitrary angle, the wafer W can be transferred to an arbitrary two-dimensional position within a range where the table T can reach.

  Thus, for example, in a wafer transfer arm disposed in a vacuum chamber in a semiconductor manufacturing apparatus, for example, an apparatus having a plurality of arms such as a scalar type or a frog-leg type shown in the figure, a plurality of rotary motors are required. . In a vacuum environment, it is necessary to reduce the surface area of contact with the outside as much as possible, and at the same time to reduce the number of mounting holes for a motor or the like as much as possible in order to effectively use the space. In addition, in order to transport the wafer W horizontally and with minimal vibration, it is necessary to firmly hold the moment acting on the tip of the arm with the rotor support. Therefore, a plurality of direct drive motors D1 and D2 are connected coaxially at the housing part, and the connecting part is tightly joined with a seal (tightly joined by welding, O-ring, metal gasket, etc.), and the motor rotor is disposed. It is also necessary to separate the open space and the housing external space.

  Further, in order to convey the wafer W horizontally and with less vibration, it is necessary to firmly hold the moment acting on the tips of the arms A1 and A2 by the rotor support portion. Furthermore, when driving multiple axes in a vacuum environment, if the current rotation position of the arm is not recognized when the power is turned on, the arm A1, A2, etc. are hit against the wall of the vacuum chamber or the shutter of the vacuum chamber. There is a possibility. A motor system in which direct drive motors that can meet such demands are connected coaxially will be described.

In this embodiment, a surface magnet type 32-pole 36-slot outer rotor brushless type direct drive motor is used. The slot combination of 32 poles and 36 slots has a configuration four times that of the slot combination of 8 poles and 9 slots, which is generally known to have a small cogging force but a large magnetic attraction force in the radial direction and a large vibration during rotation. It is. Since the magnetic attractive force in the radial direction is canceled by increasing ²ⁿ times (n is an integer), vibration during rotation without increasing the roundness and coaxiality of the stator and rotor and the rigidity of the mechanical parts Can be made small and cogging is inherently small, so that a very smooth rotation can be obtained. On the other hand, by using such a very multipolar motor, the electrical angle cycle is greater than the mechanical angle cycle, so that the positioning controllability is good. Therefore, as in the present invention, it is suitable for a direct drive motor that drives a robot apparatus without using a speed reducer. Further, since the thickness and salient pole width of the stator connecting portion and the yoke thickness of the rotor can be reduced without reducing the total magnetic flux amount, a direct drive motor having a thin and large diameter and narrow width as in the present invention is used. Is preferred.

  FIG. 2 is a view of the configuration of FIG. 1 taken along the line II-II and viewed in the direction of the arrow. The internal structure of the two-axis motor system will be described in detail with reference to FIG. First, the direct drive motor D1 will be described. A hollow cylindrical main body 12 fitted into the central opening 10a of the disk 10 installed on the surface plate G and fixed to each other by bolts 11 has a cup-shaped partition wall 13 attached to the upper end thereof. The center of the main body 12 can be used for passing wiring to the stator. The main body 12 and the disk 10 constitute a housing.

  The partition wall 13 is made of stainless steel, which is a non-magnetic material, and has a thick bottom portion 13a fitted to the main body 12 and a thin wall portion extending from the periphery thereof so as to penetrate the direct drive motors D1 and D2 in the axial direction. It consists of a cylindrical portion 13 b and a holder 15. Therefore, the partition wall 13 is commonly used for the direct drive motors D1 and D2. The lower end of the cylindrical portion 13b is joined to the holder 15 so as to be sealed by TIG welding, and the holder 15 is fixed to the disk 10 with bolts 16. Here, by setting the welded portions of the cylindrical portion 13b and the holder 15 to substantially the same thickness, it is possible to suppress heat from escaping only to the components on one side and to weld the fitting portions uniformly. The contact surface between the holder 15 and the disc 10 is provided with a groove processing for fitting the seal member. After the seal member OR is fitted into the groove, the holder 15 and the disc 10 are fastened by the bolts 16. The part is separated from the atmosphere side. The partition wall 13 is made of SUS316 made of austenitic stainless steel, which has high corrosion resistance and is less magnetic, and the holder 15 is also made of SUS316 because of its weldability with the partition wall 13.

  Further, the partition wall 13 and the holder 15 are airtightly joined, and the holder 15 and the disk 10 and the disk 10 and the surface plate G are hermetically sealed by O-rings OR, respectively. Therefore, the internal space surrounded by the disk 10 and the partition wall 13 is airtight from the outside. In addition, the partition 13 does not necessarily need to be a nonmagnetic material. Further, instead of using the O-ring OR, the members may be hermetically sealed by electron beam welding or laser beam welding.

  A bearing holder 17 is fixed by bolts 18 on the outer peripheral upper surface of the disk 10. An outer ring of a four-point contact ball bearing 19 used in a vacuum is fitted on the bearing holder 17 and fixed with bolts 20. On the other hand, the inner ring of the bearing 19 is fitted to the outer periphery of the first outer rotor 21 and is fixed by bolts 22. That is, the first outer rotor 21 is rotatably supported with respect to the partition wall 13, and a cylindrical member 23 that supports the arm A <b> 1 (FIG. 1) is fixed by the bolt 24. Here, the bolt 24 fastens the magnetic shield plate 25 extending inward in the radial direction together with the cylindrical member 23.

  The disc 10 and the bearing holder 17 are made of austenitic stainless steel having high corrosion resistance. The disc 10 also serves as a fitting and fixing device with the surface plate G serving as a chamber and a sealing device. A groove 10b for fitting the ring OR is provided.

  The magnetic shield plate 25 is subjected to nickel plating in order to improve rust prevention and corrosion resistance after press molding the SPCC steel plate, which is a magnetic material. The effect will be described later.

  The bearing 19 is a four-point contact ball bearing that can load radial, axial, and moment loads with a single bearing. By using this type of bearing, only one bearing of the direct drive motor D1 is required, so that the two-axis coaxial motor system of the present invention can be thinned. The bearing 19 is made of martensitic stainless steel, which has high corrosion resistance for both the inner and outer rings and can be hardened by quenching. The rolling elements are ceramic balls, and the lubricant is vacuum grease that does not solidify even in vacuum.

  The bearing 19 may be a metal lubrication that is plated with a soft metal such as gold or silver on the inner ring and the outer ring and does not emit outgas even in a vacuum, and is a four-point contact ball bearing. The first outer rotor 21 from the arm A1 can receive a moment in the tilting direction, but is not limited to a four-point contact type, and a cross roller, a cross ball, and a cross taper bearing can also be used. Alternatively, fluorine-based coating treatment (DFO) may be performed to improve lubricity.

  The first outer rotor 21 includes a permanent magnet 21a, an annular yoke 21b made of a magnetic material for forming a magnetic path, and a wedge made of a non-magnetic material for mechanically fastening the permanent magnet 21a and the yoke 21b ( (Not shown). The permanent magnet 21a is a segment type in which each of the N pole and S pole magnets is made of a magnetic metal and is divided into 16 poles in a 32 pole configuration, and each of the permanent magnets 21a has a sector shape. The arc centers of the inner diameter and the outer diameter are the same, but the tangential intersection of the circumferential end face is closer to the permanent magnet 21a, so that the wedge is tightened with a screw from the outer diameter side of the yoke 21b, thereby fixing the permanent magnet 21a to the yoke 21b. It is concluded to. By setting it as such a structure, a permanent magnet can be fastened without using the fixing member which generate | occur | produces outgas, such as an adhesive agent. The permanent magnet 21a is a neodymium (Nd—Fe—B) based magnet having a high energy product, and is coated with nickel in order to improve corrosion resistance. The yoke 21b is made of low carbon steel having high magnetism and is plated with nickel in order to improve rust prevention and corrosion resistance and prevent wear during bearing replacement after processing and molding.

  The first outer rotor 21 has a surface for fitting and fixing the inner ring of the bearing 19 and the cylindrical member 23. The four-point contact ball bearing 19 is a very thin bearing, and rotational accuracy and friction torque are greatly affected by differences in accuracy of members to be assembled and linear expansion coefficients. Therefore, in the case of the present embodiment, the inner ring of the bearing 19 that is a rotating ring is fixed to the yoke 21b that is easy to obtain machining accuracy and whose linear expansion coefficient is substantially the same as the bearing ring material of the bearing. The outer ring of the bearing 19, which is a ring, is fitted with a clearance holder made of austenitic stainless steel or an aluminum boss to prevent a decrease in rotational accuracy of the bearing 19 and an increase in friction torque due to a temperature rise. Yes.

  A first stator 29 is arranged on the inner side in the radial direction of the partition wall 13 so as to face the inner peripheral surface of the first outer rotor 21. The first stator 29 is attached to a cylindrically deformed lower portion of the flange portion 12a extending in the radial direction at the center of the main body 12, and is formed of a laminated material of electromagnetic steel plates. The motor coil is concentratedly wound after the bobbin is fitted. The outer diameter of the first stator 29 is approximately the same as or smaller than the inner diameter of the partition wall 13.

  A first inner rotor 30 is disposed on the inner side in the radial direction of the first stator 29. The first inner rotor 30 is rotatably supported by ball bearings 33 with respect to a resolver holder 32 that is bolted to the outer peripheral surface of the main body 12. A permanent magnet 30a is attached to the outer peripheral surface of the first inner rotor 30 via a back yoke 30b. A plurality of fins 30c are formed on the lower surface of the back yoke 30b at equal intervals in the circumferential direction. The thin plate-like fins 30c extend straight in the radial direction, but may be bent according to the rotational direction in order to enhance the blowing effect. The permanent magnet 30a has a configuration of 32 poles as in the case of the permanent magnet 21a of the first outer rotor 21, and each of 16 magnets of N poles and S poles is made of a magnetic metal alternately. Accordingly, the first inner rotor 30 is rotated along with the first outer rotor 21 driven by the first stator 29.

  The bearing 33 that rotatably supports the first inner rotor 30 is a four-point contact ball bearing that can apply radial, axial, and moment loads with a single bearing. By using this type of bearing, since only one bearing is required, the direct drive motor D1 can be thinned. Since the inside of the partition wall 13 is an atmospheric environment, a bearing using grease lubrication based on general bearing steel and mineral oil can be applied.

  Since the inside of the partition wall 13 is an atmospheric environment, the permanent magnet 30a is bonded and fixed to the back yoke 30b. The permanent magnet 30a is a neodymium (Nd—Fe—B) based magnet having a high energy product, and has a nickel coating to prevent demagnetization due to rust. The yoke 30b is made of low carbon steel having high magnetism, and is chromate plated for rust prevention after processing and forming.

  Resolver rotors 34 a and 34 b are assembled as detectors for measuring the rotation angle on the inner periphery of the first inner rotor 30, and resolver stators 35 and 36 are disposed on the outer periphery of the resolver holder 32 so as to face it. Although attached, in this embodiment, the high-resolution incremental resolver stator 35 and the absolute resolver stator 36 capable of detecting which position of the rotor is located in one rotation are arranged in two layers. Therefore, even when the power is turned on, the rotation angle of the absolute resolver rotor 34b is known, no return to origin is required, and the electrical phase angle of the magnet with respect to the coil is known. Therefore, the rotation used for driving current control of the direct drive motor D1 Angle detection is possible without using a pole detection sensor.

  The resolver holder 32 and the first inner rotor 30 are made of carbon steel, which is a magnetic material, so that electromagnetic noise from the motor field and the motor coil is not transmitted to the resolver stators 35, 36 that are angle detectors. Chromate plating is applied after molding to prevent rust.

  In the high-resolution variable reluctance resolver used in the present embodiment, the incremental resolver rotor 34a has a plurality of slot teeth having a constant pitch, and an outer peripheral surface of the incremental resolver stator 35 has a rotation shaft and a rotating shaft. In parallel with each magnetic pole, teeth whose phases are shifted with respect to the incremental resolver rotor 34a are provided, and a coil is wound around each magnetic pole. When the incremental resolver rotor 34a rotates integrally with the first inner rotor 30, the reluctance with the magnetic pole of the incremental resolver stator 35 changes, and the fundamental wave component of the change in reluctance becomes n cycles with one rotation of the incremental resolver rotor 34a. In this way, the change in reluctance is detected, digitized by the resolver control circuit shown in FIG. 3 and used as a position signal, whereby the rotational angle (or rotational speed) of the incremental resolver rotor 34a, that is, the first inner rotor 30 is used. Is supposed to be detected. The resolver rotors 34a and 34b and the resolver stators 35 and 36 constitute a detector.

  According to this embodiment, the first inner rotor 30 rotates at the same speed by the magnetic coupling action with respect to the first outer rotor 21, that is, rotates around, so that the rotation angle of the first outer rotor 21 is set to the partition wall 13. It can be detected over. Further, in the present embodiment, the resolver alone has the bearing 33 without using the motor forming parts and the housing. Therefore, the eccentricity adjustment by the resolver alone and the position adjustment of the resolver coil are performed before being incorporated in the housing. Therefore, there is no need to provide adjustment holes and notches in the housing and both flanges. Further, the rotating wheel of the bearing 19 that is rotatably supported by the first outer rotor 21 is fitted into a rotor yoke 21b that is easy to obtain machining accuracy and has substantially the same linear expansion coefficient as that of the driving wheel of the bearing 19, thereby rotating. It is possible to improve accuracy and prevent fluctuations in friction torque due to temperature changes.

  Next, although the direct drive motor D2 is demonstrated, the main body 12 comprises a housing here. The cylindrical member 23 of the direct drive motor D1 described above extends upward to a position where it overlaps with the direct drive motor D2, and the inner peripheral surface of the four-point contact ball bearing 19 ′ used in vacuum An outer ring is fitted in a fitting manner and is fixed by a bolt 20 '. On the other hand, the inner ring of the bearing 19 ′ is fitted to the outer periphery of the second outer rotor 21 ′ and is fixed by bolts 22 ′. Here, the bolt 22 'and the magnetic shield plate 41 extending inward in the radial direction are fastened together. The second outer rotor 21 ′ is rotatably supported with respect to the partition wall 13, and a ring-shaped member 23 ′ that supports the arm A <b> 2 (FIG. 1) is fixed by a bolt 24 ′. Further, the bolt 24 ′ fastens the magnetic shield plate 25 ′ extending inward in the radial direction together with the ring-shaped member 23 ′.

  The magnetic shield plates 41 and 25 ′ are subjected to nickel plating in order to improve rust prevention and corrosion resistance after press molding the SPCC steel plate, which is a magnetic material. The magnetic shield plates 41 and 25 ′ are interposed between the first outer rotor 21 and the second outer rotor 21 ′ to form a magnetic shield and prevent mutual rotation due to magnetic flux leakage from them. That is, the magnetic shield plate 25 ′ is fastened to the yoke 21 b ′ with the ring-shaped member 23 ′ that is a nonmagnetic material interposed therebetween, thereby preventing unnecessary magnetic circuits from being generated. Since the magnetic shield plates 41 and 25 ′ can prevent magnetic interference between the rotors, it is possible to achieve a configuration in which the overall axial length is suppressed despite being a two-axis coaxial motor system. The magnetic shield plate 41 prevents foreign matter from being attracted from the outside.

  The bearing 19 ′ is a four-point contact ball bearing that can load radial, axial, and moment loads with a single bearing. By using this type of bearing, only one bearing of the direct drive motor D2 is required, so that the biaxial coaxial motor of the present invention can be thinned. The inner and outer rings are made of martensitic stainless steel, which has high corrosion resistance and can be hardened by quenching. The rolling elements are ceramic balls, and the lubricant is vacuum grease that does not solidify even in vacuum.

  The bearing 19 'may be made of a metal lubrication in which a soft metal such as gold or silver is plated on the inner ring and the outer ring to prevent outgassing even in a vacuum, and is a four-point contact ball bearing. The first outer rotor 21 'from the arm A1 can receive a moment in the tilting direction, but is not limited to the four-point contact type, and a cross roller, a cross ball, and a cross taper bearing can also be used. You may use, and you may perform a fluorine-type film processing (DFO) for lubricity improvement.

  The second outer rotor 21 ′ is composed of a permanent magnet 21a ′, an annular yoke 21b ′ made of a magnetic material to form a magnetic path, and a nonmagnetic material for mechanically fastening the permanent magnet 21a ′ and the yoke 21b ′. It is composed of a body wedge (not shown). The permanent magnet 21a 'is a segment type in which each of the N poles and the S poles is made of a magnetic metal and is divided into 16 poles, and each of the permanent magnets 21a' has a sector shape. The arc centers of the inner diameter and the outer diameter are the same, but the tangent intersection of the circumferential end surface is closer to the permanent magnet 21a ′, so that the wedge is tightened with a screw from the outer diameter side of the yoke 21b ′, thereby permanent magnet 21a ′. Is fastened to the yoke 21b '. By setting it as such a structure, a permanent magnet can be fastened without using the fixing member which generate | occur | produces outgas, such as an adhesive agent. The permanent magnet 21a 'is a neodymium (Nd-Fe-B) magnet having a high energy product, and is coated with nickel in order to improve corrosion resistance. The yoke 21b 'is made of low carbon steel having high magnetism and is plated with nickel in order to improve rust prevention and corrosion resistance and prevent wear during bearing replacement after processing and molding.

  The second outer rotor 21 ′ has a surface for fitting and fixing the inner ring of the bearing 19 ′ and the ring-shaped member 23 ′. The four-point contact ball bearing 19 'is a very thin bearing, and rotational accuracy and friction torque are greatly affected by differences in accuracy of members to be assembled and linear expansion coefficients. Therefore, in the case of the present embodiment, the inner ring of the bearing 19 ′ has an interference fit or an intermediate fit on a yoke 21b that is easy to obtain machining accuracy and whose linear expansion coefficient is substantially the same as the bearing ring material of the bearing. The outer ring is configured to have a clearance fit with a bearing holder made of austenitic stainless steel or an aluminum boss, thereby preventing a decrease in rotational accuracy of the bearing 19 ′ and an increase in friction torque due to a temperature rise.

  A second stator 29 ′ is disposed on the inner side in the radial direction of the partition wall 13 so as to face the inner peripheral surface of the second outer rotor 21 ′. The second stator 29 ′ is attached to the upper part of the flange 12 a that extends in the radial direction in the center of the main body 12, is formed of a laminated material of electromagnetic steel plates, and each salient pole is insulated. After the bobbin is fitted, the motor coil is concentratedly wound. The outer diameter of the second stator 29 ′ is approximately the same as or smaller than the inner diameter of the partition wall 13.

  A second inner rotor 30 ′ is disposed on the inner side in the radial direction of the second stator 29 ′. The second inner rotor 30 ′ is rotatably supported by a ball bearing 33 ′ with respect to a resolver holder 32 ′ that is bolted to the outer peripheral surface of the main body 12. A permanent magnet 30a 'is attached to the outer peripheral surface of the second inner rotor 30' via a back yoke 30b '. A plurality of fins may be formed at equal intervals in the circumferential direction on the lower surface of the back yoke 30b '. The permanent magnet 30a 'has a configuration of 32 poles, like the permanent magnet 21a' of the second outer rotor 21 ', and is composed of 16 magnetic poles each having 16 N poles and S poles. Accordingly, the second inner rotor 30 ′ is rotationally driven by the second stator 29 ′ in synchronization with the second outer rotor 21 ′.

  The bearing 33 ′ that rotatably supports the first inner rotor 30 ′ is a four-point contact ball bearing that can load radial, axial, and moment loads with a single bearing. By using this type of bearing, since only one bearing is required, the direct drive motor D2 can be thinned. Since the inside of the partition wall 13 is an atmospheric environment, a bearing using grease lubrication based on general bearing steel and mineral oil can be applied.

  Since the inside of the partition wall 13 is an atmospheric environment, the permanent magnet 30a 'is fixedly bonded to the back yoke 30b'. The permanent magnet 30a 'is a neodymium (Nd-Fe-B) based magnet having a high energy product, and is coated with nickel to prevent demagnetization due to rust. The yoke 30b 'is made of a low-carbon steel having high magnetism, and is chromated for rust prevention after work forming.

  Resolver rotors 34 a ′ and 34 b ′ are assembled as detectors for measuring the rotation angle on the inner periphery of the second inner rotor 30 ′, and the resolver stator 32 ′ is disposed on the outer periphery of the resolver holder 32 ′ so as to face it. Although 35 'and 36' are attached, in this embodiment, a high resolution incremental resolver stator 35 'and two layers of an absolute resolver stator 36' capable of detecting which position of the rotor is in one rotation. Is arranged. Therefore, even when the power is turned on, the rotational angle of the absolute resolver rotor 34b 'is known, no return to origin is required, and the electrical phase angle of the magnet with respect to the coil is known. Therefore, the relative rotational angle of the direct drive motor D2 is This is possible without using a detection sensor.

  The resolver holder 32 ′ and the second inner rotor 30 ′ are made of carbon steel, which is a magnetic body, so that electromagnetic noise from the motor field and the motor coil is not transmitted to the resolver stators 35 ′, 36 ′, which are angle detectors. The material is chromate plated for rust prevention after processing and molding.

  According to the present embodiment, the second inner rotor 30 ′ rotates at the same speed by the magnetic coupling action with respect to the second outer rotor 21 ′. Can be detected through the partition wall 13. Further, in the present embodiment, the resolver alone has the bearing 33 without using the motor forming parts and the housing. Therefore, the eccentricity adjustment by the resolver alone and the position adjustment of the resolver coil are performed before being incorporated in the housing. Therefore, there is no need to provide adjustment holes and notches in the housing and both flanges. In addition, the rotating wheel of the bearing 19 ′ that is rotatably supported by the second outer rotor 21 ′ is fitted to a rotor yoke 21 b ′ that is easy to obtain machining accuracy and whose linear expansion coefficient is substantially the same as the driving wheel of the bearing 19 ′. Thus, it is possible to improve the rotation accuracy and prevent the fluctuation of the friction torque due to the temperature change.

  In the high-resolution variable reluctance resolver used in the present embodiment, the incremental resolver rotor 34a ′ has a plurality of slot teeth having a constant pitch, and the outer peripheral surface of the incremental resolver stator 35 ′ is rotated. Teeth whose magnetic poles are shifted in phase with respect to the incremental resolver rotor 34a ′ at each magnetic pole in parallel with the axis are provided, and a coil is wound around each magnetic pole. When the incremental resolver rotor 34a ′ rotates integrally with the second inner rotor 30 ′, the reluctance with the magnetic pole of the incremental resolver stator 35 ′ changes, and the fundamental wave component of the reluctance change is changed by one rotation of the incremental resolver rotor 34a ′. The change in reluctance is detected so as to be n cycles, digitized by a resolver control circuit shown in FIG. 3 as an example, and used as a position signal to rotate the incremental resolver rotor 34a ′, that is, the second inner rotor 30 ′. An angle (or rotational speed) is detected. The resolver rotors 34a 'and 34b' and the resolver stators 35 'and 36' constitute a detector.

  According to the present embodiment, since the magnetic shield plates 25 and 41 are arranged between the first outer rotor 21 and the second outer rotor 21 ′, mutual magnetic interference is suppressed, We avoid troubles such as companions. Further, the outer peripheral edge 12b of the flange portion 12a extending between the direct drive motors D1 and D2 in the main body 12 is made of carbon steel, which is a magnetic material, between the first stator 29 and the second stator 29 ′. It functions as a magnetic shield that shields each other's magnetic field so as to prevent the first outer rotor 21 or the second outer rotor 21 ′ from generating thrust in the wrong rotation direction due to the influence of leakage magnetic flux.

  The first stator 29 and the second stator 29 'are arranged vertically with the flange portion 12a as the center, and the resolver is arranged on the inner side in the radial direction. The main body 12 has a hollow structure, and the flange portion 12a has at least one radial through hole 12d communicating with the center, through which the motor wiring is drawn out to the center of the main body 12. It has become. On the other hand, both ends of the main body 12 are provided with at least one notch 12e and 12e, respectively, through which the resolver wiring is drawn out to the center of the main body 12. With this structure, it is possible to arrange the resolver of the direct motor D1, the stator 29, the stator 29 ′ of the direct motor D2, and the resolver in this order from the housing side. The angle of the stator and resolver can be adjusted. Therefore, if a facility for rotationally driving the reference outer rotor is prepared separately, the angle of the resolver relative to the stator can be adjusted with high accuracy by setting the main body 12 incorporating the stator and resolver in the facility. It is possible to prevent the angle positioning accuracy from being lowered due to the deviation of the commutation, and to improve the compatibility of the drive control circuit with the biaxial coaxial motor of the present invention.

  Further, a plurality of radially extending grooves 12g are formed at the upper end of the main body 12, and the inside and the outside of the main body 12 are connected via the grooves 12g even when the upper portion is covered with the partition wall 13. A communicating gas passage is formed. The disk 10 is formed with a plurality of openings 10c penetrating in the axial direction. According to the present embodiment, when the first inner rotor 30 rotates at the same speed by the magnetic coupling action with respect to the first outer rotor 21, the fin 30 c rotates and moves together therewith, so that the air blowing effect is exhibited. The Rukoto. In such a case, the air around the fin 30c is discharged to the outside outside through the opening (gas passage) 10c of the disk 10 due to the air blowing effect of the fin 30c. Then, as shown by arrows in FIG. 2, the air heated by the heated coils around the stators 29 and 29 ′ moves downward in the partition wall 13 and instead passes through the inside of the main body 12 and the groove 12g. Air at room temperature reaches the stators 29 and 29 ', and heat exchange, that is, forced air cooling, can be performed between the heated coils. Thereby, the competition between components by the difference in thermal expansion can be avoided. In such a case, the fin 20c constitutes a cooling means. At this time, a filter may be attached to the inside of the main body 12 into which air is introduced from the outside to prevent dust from entering.

  In addition, as shown by a dotted line in FIG. 2, the forced air cooling can be similarly performed by providing a fan F at the lower portion of the main body 12 and blowing air into the main body 12. For example, even when the first outer rotor 21 cannot be rotated such as during bakeout, the periphery of the coils of the stators 29 and 29 ′ can be cooled, thereby increasing the bakeout temperature without causing damage to the coils. The processing efficiency can be increased by increasing the efficiency. In such a case, the fan F constitutes a cooling means. In this case, the air is blown into the main body. However, a structure in which the temperature inside the main body is high (the partition wall portion is baked out from the outside) is sucked from here through the pipe and then discharged to the outside.

  FIG. 4 is a block diagram showing a drive circuit for the direct drive motors D1 and D2. When a motor rotation command is input from an external computer, the motor control circuit DMC1 for the direct drive motor D1 and the motor control circuit DMC2 for the direct drive motor D2 respectively drive signals from the CPU to the three-phase amplifier (AMP). And a drive current is supplied from the three-phase amplifier (AMP) to the direct drive motors D1 and D2. As a result, the outer rotors 21 and 21 'of the direct drive motors D1 and D1 rotate independently to move the arms A1 and A2 (FIG. 1). When the outer rotors 21, 21 ′ rotate, resolver signals are output from the resolver stators 35, 36, 35 ′, 36 ′ whose rotation angles have been detected as described above, and these are output by a resolver digital converter (RDC). The CPU input after the digital conversion determines whether or not the outer rotors 21 and 21 ′ have reached the command position, and when the command position is reached, stops the drive signal to the three-phase amplifier (AMP). The rotation of the outer rotors 21 and 21 ′ is stopped. This enables servo control of the outer rotors 21 and 21 '.

  When driving a multi-axis arm in a vacuum environment, the arm A1 or the like may hit the wall of the vacuum chamber or the shutter of the vacuum chamber unless the current rotational position of the arms A1 and A2 is recognized when the power is turned on. However, in the present embodiment, the variable reluctance comprising the absolute resolver stators 36 and 36 ′ for detecting the absolute position of one rotation of the rotating shaft and the incremental resolver stators 35 and 35 ′ for detecting the rotational position with finer resolution. Since the mold resolver is employed, the rotational position control of the outer rotors 21, 21 ', that is, the arms A1, A2, can be performed with high accuracy.

  Here, the resolver is adopted for detecting the rotation of the inner rotor 30. However, since the detector can be arranged on the atmosphere side inside the partition wall 13, a servo motor generally used for high-precision positioning is driven with high precision and smoothness. For example, an optical encoder that is employed as a position detecting means, a magnetic encoder using a magnetoresistive element, or the like can be used.

  FIG. 5 is a cross-sectional view showing a biaxial coaxial motor system according to another embodiment. Since the modification shown in FIG. 5 is the same as the structure shown in FIG. 2 except for the cooling means, the same reference numerals are assigned to the main components, and the description thereof is omitted.

  In this embodiment, in this embodiment, a plurality of cooling passages (liquid passages) 12h extending in the axial direction in the cylindrical wall of the main body 12 and extending radially in the flange portion 12a are provided. Forming. The bent cooling passage 12h as shown in FIG. 5 can be formed by connecting a plurality of parts having grooves formed on the surface thereof by welding or the like to form a single main body 12, but with respect to the integrally formed main body 12 The cooling passage 12h can also be formed by drilling a hole in the intersecting direction and closing the end with a plug or the like. An annular groove 12j is formed at the upper end of the main body 12, and a plurality of cooling passages 12h are connected to an annular space formed by closing the upper portion with an annular plate 12k. In the present embodiment, a through hole 12e is formed in place of the notch at the upper end of the main body 12 so as not to interfere with the annular groove 12g.

  A connector C1 is connected to the lower end of one cooling passage 12h. The connector C1 is connected to an external water pump (not shown). On the other hand, a connector C2 is connected to the lower end of the remaining cooling passage 12h. The connector C2 is connected to an external tank (not shown). When the cooling water is pumped from the water pump during the operation of the direct drive motors D1 and D2, the cooling water that has entered the cooling passage 12h passes through the flange portion 12a as shown by the arrows in FIG. Heat exchange with the stators 29 and 29 ′, that is, liquid cooling, is performed, and the heated cooling water is discharged through the connector C2 and reaches an external tank. By such liquid cooling, competing between parts due to a difference in thermal expansion can be avoided during operation of the direct drive motors D1 and D2, and around the coils of the stators 29 and 29 ′ can be cooled at the time of baking out, thereby It is possible to increase the bakeout temperature without causing damage to the substrate, thereby improving the processing efficiency. In such a case, the water pump and the cooling passage 12h constitute a cooling means.

  The cooling means is not limited to the above. For example, when a current is passed through a joint between two types of metal, heat is transferred from one metal to the other, and an element using the “Peltier effect” or a heat A pipe or the like may be provided on the flange portion 12 a of the main body 12.

  Furthermore, in the above embodiment, the example using the surface magnet type 32-pole 36-slot outer rotor type brushless motor has been described. However, the present invention is not limited to this type of motor, and any motor can be used. Other magnetic pole types, for example, a permanent magnet embedded type, other slot combinations, or an inner rotor type may be used.

  Further, as a countermeasure against interference of each axis, a configuration may be adopted in which the number of poles and the number of slots of the rotors adjacent to each other in the axial direction are different. For example, in the case of 2-axis coaxial, the first axis is 32 poles and 36 slots, the second axis is 24 poles and 27 slots, and in the case of 4-axis coaxial, the first axis and the third axis are 32 poles and 36 slots, and the second axis If the fourth axis has a configuration of 24 poles and 27 slots, it is possible to prevent mutual interference such as generation of thrust in the rotating direction on the rotor and the magnetic coupling device due to the magnetic field of each axis.

  The rotor permanent magnet is a neodymium (Nd-Fe-B) -based magnet and has been described using a nickel coating as an example of a coating for enhancing corrosion resistance. However, the material is limited to this material and surface treatment. However, it should be changed as appropriate depending on the environment in which it is used. For example, a samarium-cobalt (Sm · Co) -based magnet that is difficult to demagnetize at high temperatures should be used depending on the temperature conditions during baking. If used in ultra-vacuum, a titanium nitride coating with a high outgas barrier should be applied.

  In addition, the yoke has been described using an example in which nickel is plated with low carbon steel as a material. However, the yoke is not limited to this material and surface treatment, and may be appropriately changed depending on the environment used. In particular, regarding surface treatment, if it is used in ultra-vacuum, it should be subjected to Kanigen plating, clean s plating, titanium nitride coating, etc. with few pinholes.

  The method of fastening the permanent magnet to the yoke has been described using an example in which a non-magnetic wedge is tightened with a screw from the outer diameter side of the yoke, but it is appropriately changed depending on the environment in which it is used. May be bonded or other fastening methods.

  In addition, the bearings 19 and 19 ′ have been described using an example of a grease grease four-point contact ball bearing for vacuum. However, the bearings 19 and 19 ′ are not limited to this type, material, and lubrication method. It can be changed as appropriate according to the rotational speed, etc., and may be a cross roller bearing. In the case of a 4-axis coaxial motor, it may be structured to be supported by another bearing in order to further increase mechanical rigidity. When multi-point contact bearings cannot be used, such as when rotating at high speeds, bearings that support the rotor of each axis and other bearings may be structured to apply preload as deep groove ball bearings or angular bearings, When used in, a metal lubrication that does not release gas, such as plating of a soft metal such as gold or silver on the raceway, may be used.

  In addition, the inner rotor functioning as a magnetic coupling has been described as using a permanent magnet and a back yoke. However, the material and shape of the permanent magnet and the back yoke are not limited thereto. For example, depending on the mass of the resolver and the friction torque of the bearing, the number of poles may not be the same as that of the outer rotor, or the width may not be the same. A salient pole that does not use a permanent magnet may be used.

  Further, although an example in which a resolver is used as an angle detector has been described, it can be appropriately changed depending on manufacturing cost and resolution, and for example, an optical rotary encoder may be used.

  Moreover, although the example which used the grease lubrication 4-point contact ball bearing was demonstrated as bearings 33 and 33 'which rotatably support the rotation side of an angle detector, it is not limited to this form and a lubrication method. If the multi-point contact bearing cannot be used, such as high-speed rotation or reduction of friction torque, the angular bearing and deep groove ball bearing must be It is good also as a structure which arranges two for every axis | shaft and applies preload.

  In addition to the other partition walls, the structural parts and the material, shape, and manufacturing method of the partition parts and the partition walls are appropriately changed depending on the manufacturing cost, the environment used, the load conditions, the configuration, and the like.

  In the motor system described above, magnetic flux leaking from the magnetic couplings used in the rotors, stators, and resolvers of each axis does not generate thrust in the rotational direction in the magnetic couplings used in the rotors and rotation detectors. In addition, a magnetic shield for shielding each other's magnetic field is arranged between the rotors of each shaft, and the electromagnetic waves generated from the rotor, stator, and resolver of each shaft are not interfered with each other's resolver. Magnetic interference generated between each axis can be prevented by arranging a magnetic shield to shield the field, or changing the number of rotor poles and the number of stator slots between adjacent axes in the axial direction. Thus, the axial length of each axis and the axial distance of each axis can be shortened. Therefore, although it is a multi-axis coaxial motor system such as a 2-axis coaxial system and a 4-axis coaxial system, a configuration in which the entire axial length is suppressed is possible. In particular, in a system using a multi-axis direct drive motor such as a 4-axis coaxial system, two frog-leg-arm robots that can perform high-precision positioning without greatly changing the chamber structure can be installed. The operating rate can be increased.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. For example, the direct drive motor of the present embodiment can be used not only in a vacuum atmosphere but also in an atmosphere outside the atmosphere. For example, in the case of a semiconductor manufacturing process, a reactive gas for etching may be introduced into the vacuum chamber after evacuation, but in the direct drive motor of the present embodiment, the inside and the outside are shielded by the partition wall. Therefore, there is no possibility that the motor coil, the insulating material, and the like are etched.

It is a perspective view of the frog leg arm type conveying device using the direct drive motor concerning this embodiment. It is the figure which cut | disconnected the structure of FIG. 1 by the II-II line | wire, and looked at the arrow direction. It is a figure which shows the example of a resolver control circuit. It is a figure which shows the example of a motor control circuit. It is sectional drawing which shows another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Disc 11 Bolt 12 Main body 12a Flange part 12b Outer peripheral edge 12d Hole 12e Notch 12g Groove 12h Cooling passage 12j Annular groove 12k Annular plate 13 Bulkhead 13a Disc part 13b Cylindrical part 15 Holder 16 Bolts 17, 17 'Bearing holder 18, 18 'Bolt 19, 19' Four-point contact ball bearing 20, 20 'Bolt 21, 21' Outer rotor 21a, 21a 'Permanent magnet 21b, 21b' Yoke 22, 22 'Bolt 23' Ring-shaped member 23 Cylindrical member 24, 24 'Bolt 25, 25' Magnetic shield plate 29, 29 'Stator 30, 30' Inner rotor 30a, 30a 'Permanent magnet 30b, 30b' Back yoke 30c Fin 32, 32 'Resolver holder 33, 33' Bearing 34a, 34a 'Incremental Resolver rotor 34b, 34b 'Absolute training Luba rotor 35, 35 'Incremental resolver stator 36, 36' Absolute resolver stator 41 Magnetic shield plate 101 Lid member 107 Bearing holder 110 Upper disk portion 113a Bulkhead holder 113b Thin-walled cylinder 125 Magnetic shield plates A1, A2 Arm D1, D2 Direct drive motor DMC1 Motor control circuit DMC2 Motor control circuit G Surface plate L1, L2 Link OR O-ring T Table

Claims (2)

A hollow body and a housing made of a disc ;
A partition wall extending from the housing and isolating the atmosphere side from the atmosphere outside;
An outer rotor disposed outside the atmosphere with respect to the partition;
An inner rotor that is disposed on the atmosphere side with respect to the partition wall and is rotated together with the outer rotor;
A stator disposed on the atmosphere side with respect to the partition wall and driving the outer rotor ;
Is disposed on the atmosphere side with respect to the partition wall to have a detector for detecting a rotational position of the inner rotor, in a direct drive motor for use in an atmosphere of outside air,
The inner rotor is formed with a radially extending thin plate-like fin that rotates with the inner rotor,
A plurality of radially extending grooves are formed at the end of the main body where the bottom of the partition wall is disposed,
A plurality of openings penetrating in the axial direction are formed in the disk in which the mouth portion of the partition wall is disposed,
By driving the inner rotor that is rotated together with the outer rotor by the stator, the hollow structure main body, the plurality of grooves at the end of the main body, and the plurality of openings of the disc are communicated, A direct drive motor that discharges air near the fins . The direct drive motor according to claim 1, wherein the inner rotor is rotated together with the outer rotor with only the partition wall interposed therebetween .

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