JP4618422B2 - Direct drive motor - Google Patents

Description

The present invention relates to a plurality of direct drive motor for use in an atmosphere such as a vacuum outside atmosphere.

  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

  By the way, the magnetic coupling formed between the stator and the rotor can increase the amount of magnetic flux for each pole by narrowing the interval, that is, the air gap, and obtain a strong magnetic attractive force in the rotation direction. Therefore, the transmission torque can be increased. That is, it is desirable that the air gap of the magnetic coupling is narrow. Therefore, when the stator and the rotor are separated by the partition, it is preferable to make the partition very thin in order to ensure a narrow air gap.

  However, when the partition walls are made thin as described above, the rigidity of the partition walls decreases, and it becomes difficult to accurately process the coaxiality between both ends of the partition walls. In such a case, when the partition wall is attached to the housing, inclination or the like is likely to occur, and in order to prevent interference between the rotor and the partition wall, there is a problem that the air gap must be widened in consideration of the lower limit of the coaxiality. On the other hand, in order to increase the coaxiality, it is necessary to increase the rigidity of the partition wall, but there is a problem that the air gap is widened.

  Furthermore, in general, in order to increase the helical rigidity of the magnetic coupling, the magnetic attractive force with respect to the relative angle is abruptly changed by increasing the number of poles. In other words, it is preferable that the number of poles of the magnetic coupling is large as long as the magnetic flux density for each pole is not lowered.

  However, when the number of poles is increased as described above, the number of changes of the magnetic flux passing through the partition increases in accordance with the rotational speed of the magnetic coupling, so that eddy current loss generated in the partition increases and heat generation also increases. At this time, a difference in eddy current loss occurs due to the uneven thickness of the partition wall, so that a temperature distribution is generated in the circumferential direction of the partition wall, and there is a problem that the partition wall is inclined even if the coaxiality between both ends is high. Therefore, in order to prevent interference between the rotor and the partition wall, there is a problem that the air gap must be widened in consideration of the maximum temperature change.

  In order to avoid the above problems, it is possible to consider a method of fastening the bottom of the partition wall opposite to the housing mounting surface to the housing via some member so as not to tilt, but heat generated due to eddy current loss, It is difficult to prevent deformation in the normal direction based on the tensile and compressive stress in the axial direction of the partition wall due to temperature difference with the connecting member, dimensional error with the connecting member, etc. When a stress is repeatedly applied to the partition wall due to a heat cycle during operation, there is a risk of fatigue failure.

The present invention has been made in view between problems point of the prior art, while avoiding the atmosphere pollution, and to provide a direct drive motor capable of generating high torque.

The direct drive motor of the present invention is a direct drive motor used in an atmosphere outside the atmosphere.
A housing;
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;
A stator disposed on the atmosphere side with respect to the partition; an inner rotor disposed on the atmosphere side with respect to the partition;
A detector that is disposed on the atmosphere side with respect to the partition wall and detects a rotational position of the inner rotor,
The partition includes an attachment portion attached to the housing, a cylindrical portion extending from the attachment portion between the outer rotor, the stator, and the inner rotor, and a bottom portion connected to the cylindrical portion. Have
One of the bottom part and the housing is provided with a convex part, and the other part is provided with a concave part. By engaging the convex part and the concave part, the bottom part is positioned with respect to the housing. And
The bottom portion and the housing are engaged with each other so as to be relatively movable in the axial direction but immovable in the direction orthogonal to the axial line .

The direct drive motor of the present invention includes a housing, 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 wall, and an atmosphere with respect to the partition wall. A stator disposed on the side and an inner rotor disposed on the atmosphere side with respect to the partition, and a detector disposed on the atmosphere side with respect to the partition and detecting a rotational position of the inner rotor And the stator drives the outer rotor, and the inner rotor is rotated together with the outer rotor. The molecules are prevented from contaminating the atmosphere outside the partition wall. In addition, the partition wall includes a mounting portion attached to the housing, a cylindrical portion extending from the mounting portion between the outer rotor, the stator, and the inner rotor, and a bottom portion connected to the cylindrical portion. The bottom portion is positioned with respect to the housing, and therefore, even when the cylindrical portion is thinned to reduce rigidity, the partition can be accurately positioned by the bottom portion. Can be suppressed. Further, if the cylindrical portion is made thinner, the air gap between the outer rotor and the stator can be made smaller, so that the torque generated in the outer rotor can be increased without increasing the power supply.

  Further, a convex portion is provided on one of the bottom portion and the housing, and a concave portion is provided on the other side. By engaging the convex portion and the concave portion, the bottom portion is positioned with respect to the housing. If it is done, accurate positioning can be performed. In this case, if the convex portion is a column and the concave portion is a cylindrical hole, a highly accurate shape can be formed at low cost, and highly accurate positioning can be realized by fitting.

  The bottom portion and the housing are relatively movable in the axial direction but are engaged so as to be immovable in the direction orthogonal to the axial direction, causing a dimensional error between the housing and the partition wall, or Even when the cylindrical portion expands or contracts due to a temperature change, relative movement of the bottom portion with respect to the housing is allowed, and an increase in internal stress of the cylindrical portion can be suppressed and deformation can be suppressed, so that rotor interference can be avoided as much as possible. In addition, it is possible to suppress the repeated stress generated in the partition wall due to the heat cycle accompanying the operation / stop of the direct drive motor.

  When the rigidity of the cylindrical portion is lower than the rigidity of the bottom portion, it is preferable that even when the cylindrical portion is inclined, the cylindrical portion is easily deformed into an appropriate shape according to the positioned bottom portion.

  The motor system formed by coaxially connecting a plurality of direct drive motors according to any one of claims 1 to 4, wherein the housing and the partition wall are preferably used in common for each direct drive motor.

  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 the cogging is essentially 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 commonly used for the direct drive motors D1 and D2. 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 part 13b and a holder 15 as an attachment part. A cylindrical portion (convex portion) 13c is coaxially formed on the bottom surface of the bottom portion 13a. A cylindrical hole (concave portion) 12f is coaxially formed in the upper portion of the main body 12, and the bottom portion 13a is positioned with respect to the main body 12 by engaging the cylindrical portion 13c with the cylindrical hole 12f. At this time, if the fitting between the cylindrical portion 13c and the cylindrical hole 12f is a clearance fit, the cylindrical portion 13c can move in the axial direction with respect to the cylindrical hole 12f, but is restrained so as not to move in the radial direction. The Rukoto. On the other hand, the outer peripheral portion of the holder 15 is fitted and fitted to the disc 10 and fixed with bolts 16. Therefore, it is possible to assemble the partition wall 13 while maintaining good coaxiality with the cylindrical portion 13c fitted in the cylindrical hole 12f.

  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 to form 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. 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 is provided with a rotating shaft and 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. In addition, the rotating wheel of the bearing device 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 device 19. Thus, it is possible to improve the rotation accuracy and prevent the fluctuation of the friction torque due to the temperature change.

  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 '. 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 ′ can be known, no return to origin is required, and the electrical phase angle of the magnet with respect to the coil can be known. 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. Further, the rotating wheel of the bearing device 19 ′ that is rotatably supported by the second outer rotor 21 ′ is fitted into a rotor yoke 21b ′ that is easy to obtain machining accuracy and has the same linear expansion coefficient as the driving wheel of the bearing device 19 ′. By combining, it is possible to improve the rotational accuracy and prevent the friction torque from fluctuating due to temperature changes.

  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. 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.

  Furthermore, according to the present embodiment, the bottom portion 13a of the partition wall 13 is fitted to the main body 12 and restrained in the radial direction, and the rigidity of the bottom portion 13a is higher than the rigidity of the cylindrical portion 13b. Even if the coaxiality of 13b is poor, the coaxiality of the cylindrical portion 13b is secured by the bottom portion 13a and the holder 15 positioned with respect to the main body 12, and the rotating first outer rotor 21 and second outer rotor 21 ′ Interference is avoided. Further, since it is not necessary to ensure the rigidity of the cylindrical portion 13b, the thickness of the cylindrical portion 13b can be reduced, whereby the air gap between the first outer rotor 21 and the first stator 29, and the second outer rotor 21 ′ and the second stator. The air gap with 29 'can be kept small, the rated torque of the motor can be increased, and high-accuracy driving can be realized.

  Further, since the bottom portion 13a is supported so as to be movable in the axial direction with respect to the main body 12, the relative position can be changed by a dimensional error, or it is allowed to expand and contract in accordance with a temperature change of the cylindrical portion 13b. Thus, the generation of internal stress in the cylindrical portion 13b is suppressed and deformation is suppressed, and interference between the rotating first outer rotor 21 and second outer rotor 21 ′ and the first inner rotor 30 and second inner rotor 30 ′ is prevented. Avoid as much as possible. Further, since the repeated stress generated in the partition wall 13 due to the heat cycle accompanying the operation / stop of the direct drive motors D1 and D2 can be suppressed, the sealed state can be maintained for a long time.

  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.

  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-layer amplifier (AMP). Is output from the three-layer 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. When the CPU reaches the command position, the drive signal to the three-layer amplifier (AMP) is stopped. 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.

  In the above embodiment, the example using the surface magnet type 32-pole 36-slot outer rotor brushless motor has been described. However, the present invention is not limited to this type of motor, and any brushless motor can be applied. 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 rotor poles and the number of slots of adjacent axes 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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Disc 11 Bolt 12 Main body 12a Flange part 12b Outer peripheral edge 12d Hole 12e Notch 13 Bulkhead 13a Disc part 13b Cylindrical part 13c Cylindrical part (convex part)
15 Holder 16 Bolt 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-like 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 32, 32' Resolver Holder 33, 33 'Bearing 34a, 34a' Incremental resolver rotor 34b, 34b 'Absolute resolver rotor 35, 35' Incremental resolver stator 36, 36 'Absolute resolver stator 41 Magnetic shield plate 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 (1)

In direct drive motors used in atmospheres outside the atmosphere,
A housing;
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;
A stator disposed on the atmosphere side with respect to the partition; an inner rotor disposed on the atmosphere side with respect to the partition;
A detector that is disposed on the atmosphere side with respect to the partition wall and detects a rotational position of the inner rotor,
The partition includes an attachment portion attached to the housing, a cylindrical portion extending from the attachment portion between the outer rotor, the stator, and the inner rotor, and a bottom portion connected to the cylindrical portion. Have
One of the bottom part and the housing is provided with a convex part, and the other part is provided with a concave part. By engaging the convex part and the concave part, the bottom part is positioned with respect to the housing. And
The direct drive motor, wherein the bottom portion and the housing are engaged with each other so as to be relatively movable in the axial direction but immovable in the direction orthogonal to the axial line .

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