JP2009038911A - Brushless motor - Google Patents

Abstract

Provided is a brushless motor that is used in an atmosphere outside the atmosphere with high motor performance and high reliability while avoiding atmospheric contamination caused by fixing of magnetic poles.
When a small piece is peeled off from a permanent magnet 30a due to inadequate handling or the like and a small piece is generated due to a chip or the like, the small piece is attracted to a rotor magnet on the other side. Even if the first inner rotor 30 is separated from the inner rotor 30, it is not sandwiched between the first inner rotor 30 and the first inner rotor 30 can be secured with high accuracy, and the detection accuracy of the detector can be maintained.
[Selection] Figure 4

Description

  The present invention relates to a surface magnet type brushless motor, and more particularly to a brushless motor suitable for a transfer robot used in an atmosphere outside the atmosphere such as 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.

  On the other hand, conventionally, as means for driving a frog-leg-arm robot in a vacuum chamber separated and isolated from the atmosphere side, cups such as a bellows drive system, a magnetic coupling drive system, and a magnetic fluid seal drive system are used. A method has been used in which the outputs of multiple motors arranged in the atmosphere are combined into a multi-structure shaft through a ring mechanism and a seal mechanism, and the multi-structure shaft is introduced into a vacuum chamber. However, when a coupling mechanism such as the bellows drive system or magnetic coupling drive system described above is used, the backlash is large and the torsional rigidity in the rotational direction is low, so that high positioning accuracy cannot be obtained. There was a problem. In addition, in the case of a method in which a rotational force is introduced through a sealing mechanism, outgas is generated due to volatile components contained in the sealing material, and it is difficult to apply it to an ultra-high vacuum chamber.

To solve this problem, a vacuum seal is provided in the air gap, bearings, rotors, and speed detector rotating members are arranged on the vacuum side, and the stator and speed detector fixing sides are placed on the atmosphere side. A frog-leg-arm robot that has a motor structure in which members are arranged, is stacked in multiple stages so that the motor protrudes outside the vacuum chamber, and the output of each motor is introduced into the vacuum chamber via a multi-structure shaft. Patent Documents 1 to 3 describe motor systems for driving the motor. According to the direct drive motors of Patent Documents 1 to 3, since the coil insulating material and the wiring coating attached to the stator are disposed on the atmosphere side of the vacuum sealing body and do not require a rotating vacuum seal, The problem of exhausting can be avoided.
Japanese National Patent Publication No. 08-506771 US Pat. No. 5,720,590 US Pat. No. 5,899,658 JP 2006-109656 A

  However, when using a coupling mechanism that employs the bellows drive system or magnetic coupling drive system described above, high backlash and low torsional rigidity in the rotational direction can be obtained, resulting in high positioning accuracy. There was a problem that it was not possible. On the other hand, in the case of a method in which a rotational force is introduced through a sealing mechanism, outgassing due to volatile components contained in the sealing material is generated, and it is difficult to apply it to an ultrahigh vacuum chamber.

  On the other hand, in the case of a two-shaft motor in which a cup-type partition wall is provided between the rotor and the stator for separation from the atmosphere side, when the bearing is arranged on each rotor, the bearing fixed ring is on the chamber side. This shaft can be fixed to a highly rigid member such as a motor base, but the other shaft must be fixed to a thin tubular bulkhead with low rigidity. When applied to a transfer robot such as a frog-leg arm type, Therefore, it was difficult to increase mechanical rigidity and load capacity.

  Also, bearings placed in an environment separated from the atmosphere side often use solid lubrication or special lubricants, and such bearings are frequently replaced because they have a shorter life than general bearings. There is a need. However, when a fixed ring of a bearing is arranged on a cup-shaped partition wall, it is necessary to remove the motor from the chamber when replacing one of the bearings, and the seal member is disassembled each time. A leak test was required to confirm the sealing performance, and the operating rate of the entire system was lowered.

  On the other hand, as shown in Patent Document 4, a magnetic coupling is configured by introducing magnetic poles facing the outer rotor and the inner rotor, and the outer rotor and the inner rotor are rotated by the magnetic attractive force of both magnetic poles. A motor system has also been developed that detects the rotational position of the outer rotor. Thereby, a motor system with high rigidity and easy bearing replacement can be configured. However, when a problem such as peeling or chipping occurs on the inner magnet of the inner rotor, the peeled magnet or the like may be sandwiched between the inner rotor and the partition wall, and the angle detector may be locked.

  The present invention has been made in view of the problems in the prior art, and is used in an atmosphere outside the atmosphere where the motor performance is high and the reliability is high while avoiding atmospheric contamination caused by fixing of the magnetic poles. An object of the present invention is to provide a brushless motor.

The brushless motor of the present invention is a surface magnet type brushless 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 wall and provided with an outer magnet;
A first bearing device that rotatably supports the outer rotor with respect to the housing;
A stator disposed on the atmosphere side 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 second bearing device that rotatably supports the inner rotor with respect to the housing;
A detector for detecting the rotational position of the inner rotor,
The inner rotor has inner magnets arranged side by side in the circumferential direction so as to face the outer magnet of the outer rotor with the partition wall in between, and is established between the inner magnet and the outer rotor. Due to the action, the inner rotor and the outer rotor are magnetically coupled,
The inner magnet is covered with a cover member interposed between the inner magnet and the partition wall.

  According to the brushless motor of the present invention, the inner magnet is covered with a cover member interposed between the inner magnet and the partition wall, so that when the small pieces are separated due to peeling or chipping of the inner magnet. Thus, the small piece is not sandwiched between the partition walls, and it is possible to ensure the precise rotation of the inner rotor and maintain the detection accuracy of the detector.

  The cover member includes a cylindrical portion that contacts a surface of the inner magnet that faces the partition, and a flange that extends radially inward from the cylindrical portion and contacts the inner rotor. Even when the parts are rubbed by mistake, the cover member can be prevented from falling off, and a structure that can be easily assembled can be provided.

  If the cover member has a belt shape that contacts the surface of the inner magnet that faces the partition wall, the shape of the cover member is simple and the manufacturing cost can be kept low.

The overall length of the belt-shaped cover member is longer than the inner peripheral length of a virtual cylindrical surface that is in contact with the surface of the inner magnet facing the partition, and the inner magnets are spaced apart in the circumferential direction.
A tension member is provided to increase the tension of the belt-shaped cover member by entering between the adjacent inner magnets in a state where the belt-shaped cover member surrounds the inner magnet around the entire circumference. And it is preferable because the belt-like cover member can be prevented from falling off.

  It is preferable that the assembly position of the tension member with respect to the inner rotor can be adjusted.

  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 transfer robot using a direct drive motor which is a surface magnet type brushless 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 40-pole 36-slot outer rotor brushless type direct drive motor is used. The slot combination of 40 poles and 36 slots has a configuration four times as large as the slot combination of 10 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 is coaxially joined to a central opening 10a of the disk 10 and fixed to each other by bolts 11 with respect to the upper surface of the disk 10 installed on a surface plate (not shown). A cup-shaped partition wall 13 is attached to the upper surface of the disk 10. The central space 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 13b and a thick annular mounting portion 13c formed at the lower edge of the cylindrical portion 13b. Therefore, the partition wall 13 is commonly used for the direct drive motors D1 and D2. The mounting portion 13c of the cylindrical portion 13b is bolted to the disc 10. The contact surface between the mounting portion 13c and the disk 10 is subjected to groove processing for fitting the seal member, and after the sealing member OR is fitted into the groove, the mounting portion 13c and the disk 10 are fastened with bolts. The fastening part is separated from the atmosphere side. The partition wall 13 is made of austenitic stainless steel SUS316, which has high corrosion resistance and is particularly low in magnetism.

  Further, since the disk 10 and the surface plate are hermetically sealed, the internal space surrounded by the disk 10 and the partition wall 13 is hermetically sealed 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 to the upper surface of the outer periphery of the disc 10 with bolts 16. An outer ring of a double row angular contact ball bearing 19 used in vacuum is fitted to the bearing holder 17 in a fitting manner. On the other hand, the inner ring of the angular contact ball bearing 19 is fixed by a bolt (not shown) that fits to the outer periphery of the first outer rotor member 21 and fastens the cylindrical member 23 together. That is, the first outer rotor member 21 is rotatably supported with respect to the disk 10 and the partition wall 13 integrally with the cylindrical member 23 that supports the arm A1 (FIG. 1). The first outer rotor member 21 and the cylindrical member 23 constitute an outer rotor.

  The disc 10 (including the bearing holder 17) is made of austenitic stainless steel having high corrosion resistance, and the disc 10 also serves as a fitting and fixing device with a surface plate as a chamber and a sealing device.

  The angular contact ball bearing 19 (first bearing) can carry 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 angular contact ball 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. ing.

  Note that the angular contact ball 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 so as not to release outgas even in a vacuum, or the first outer side from the arm A1. Although the rotor member 21 can receive a moment in the tilting direction, the present invention is not limited to this, and cross rollers, cross balls, and cross taper bearings can be used. Fluorine-based coating treatment (DFO) may be performed.

  The first outer rotor member 21 includes a permanent magnet (outer magnet) 21a, an annular yoke 21b made of a magnetic material to form a magnetic path, and a non-magnetic member for mechanically fastening the permanent magnet 21a and the yoke 21b. It is composed of a body wedge (not shown). The permanent magnet 21a has a configuration of 40 poles, and each of the N poles and the S poles is made of a magnetic metal, and each segment 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.

  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 member 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 adjacent to and parallel to the first stator 29. The first inner rotor 30 is bolted to the rotor holder 31 and is rotatably supported via a ball bearing 33 with respect to the flange portion 12 a of the main body 12.

  FIG. 3 is a cross-sectional view showing the first inner rotor 30 and the cover member 32 assembled, and FIG. 4 is a perspective view showing the first inner rotor 30 and the cover member 32 in an exploded state. As shown in FIG. 4, the first inner rotor 30 is composed of an annular (thick outer peripheral side) back yoke 30b made of a magnetic material for forming a magnetic path, and a plurality of permanent magnets (inner magnets) are formed on the outer periphery thereof. ) 30a is attached with an adhesive or the like at equal intervals in the circumferential direction. The permanent magnet 30a has a 40-pole configuration like the permanent magnet 21a of the first outer rotor member 21, and 20 magnets of N and S poles are alternately made of magnetic metal. Accordingly, the first inner rotor 30 is rotated along with the first outer rotor member 21 driven by the first stator 29 by a magnetic coupling action. The back yoke 30b is made of a low-carbon steel having high magnetism, and is chromate plated for rust prevention after work forming.

  The ring dish-shaped cover member 32 that covers the permanent magnet 30a includes a cylindrical portion 32a that contacts the outer surface facing the partition wall 13 of the permanent magnet 30a, and extends radially inward from the cylindrical portion 32a to extend the back yoke 30b. The flange portion 32b is in contact with the surface of the inner rotor 30 and is fixed with an adhesive so as to cover the inner rotor 30. The cover member 32 is made of a nonmagnetic material in consideration of the influence on the magnetic circuit causing the magnetic coupling, and is formed by sheet metal processing of a thin plate.

  A bearing (second 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 back yoke 30b is made of low carbon steel having high magnetism, and is chromate-plated for rust prevention after work forming.

  In FIG. 2, resolver rotors 34 a and 34 b are assembled as detectors for measuring the rotation angle on the inner periphery of the rotor holder 31 to which the first inner rotor 30 is attached. In this embodiment, the resolver stators 35 and 36 are attached. In this embodiment, the high-resolution incremental resolver stator 35 and the absolute resolver stator 36 that can detect the position of the rotor in one rotation are divided into two layers. Is arranged. In this way, based on the absolute angle information from the absolute resolver, the rotor machine angle is recognized immediately after the power is turned on and the motor coil is commutated. On the other hand, high-resolution angle positioning is performed based on relative angle information from the incremental resolver. 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. For this reason, it is suitable for a direct drive motor that drives the robot apparatus as in this embodiment.

  An outer boss that connects the rotation side of the detector and the rotation side of the bearing 19 and the detector coupling, and an inner boss that connects the stationary side of the angle detector and the stationary side of the bearing device are separated from the motor field and the motor coil. Carbon steel, which is a magnetic material, is used as a material to prevent electromagnetic noise from being transmitted to the resolver, which is a detector, and chromate plating is applied to prevent rust after processing.

  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 supported by the bearing 33, the reluctance with the magnetic pole of the incremental resolver stator 35 changes, and the fundamental wave of the reluctance change with one revolution of the incremental resolver rotor 34a. The reluctance change is detected so that the component has n cycles, and is digitized by the resolver control circuit shown in FIG. 5 and used as a position signal to rotate the incremental resolver rotor 34a, that is, the first 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, the first inner rotor 30 rotates at the same speed by the magnetic coupling action with respect to the first outer rotor member 21, that is, rotates around, so that the rotation angle of the first outer rotor member 21 is increased. It 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.

  According to the present embodiment, when a small piece is peeled off due to inadequate handling or the like and a small piece is generated due to a chip or the like, the small piece is attracted to the rotor magnet on the other side. For this reason, even if the first inner rotor 30 is separated from the first inner rotor 30, it is not sandwiched between the first inner rotor 30 and the first inner rotor 30 can be secured with high accuracy, and the detection accuracy of the detector can be maintained.

  Next, although the direct drive motor D2 is demonstrated, the main body 12 comprises a housing here. The above-described cylindrical member 23 of the direct drive motor D1 extends upward to a position where it is overlapped with the direct drive motor D2, and a double row angular contact ball bearing 19 ′ used in vacuum on the inner peripheral surface thereof. The outer ring is fitted and fixed in a mating manner. On the other hand, the inner ring of the angular contact ball bearing 19 'is fixed by a bolt (not shown) that fits to the outer periphery of the second outer rotor member 21' and fastens the cylindrical member 23 'together. In other words, the second outer rotor member 21 ′ is rotatably supported with respect to the partition wall 13 integrally with the cylindrical member 23 ′ that supports the arm A <b> 2 (FIG. 1). The second outer rotor member 21 'and the cylindrical member 23' constitute an outer rotor.

  The angular contact ball bearing 19 'can carry 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. Both 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 under vacuum.

  The angular contact ball bearing (first 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. The first outer rotor member 21 ′ from the arm A1 can receive a moment in the tilting direction, but not limited to this, a cross roller, a cross ball, and a cross taper bearing can also be used. Alternatively, fluorine film treatment (DFO) may be performed to improve lubricity.

  The second outer rotor member 21 ′ mechanically fastens a permanent magnet (outer magnet) 21a ′, an annular yoke 21b ′ made of a magnetic material to form a magnetic path, and the permanent magnet 21a ′ and yoke 21b ′. It is comprised by the wedge (not shown) which consists of a nonmagnetic material for doing. 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.

  A second 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 second outer rotor member 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 adjacent to and parallel to the second stator 29'. The second inner rotor 30 ′ is bolted to the rotor holder 31 ′ and is rotatably supported on the flange portion 12 a of the main body 12 via a ball bearing 33 ′.

  The second inner rotor 30 ′ has the same configuration as the first inner rotor 30, and the cover member 32 ′ has the same configuration as the cover member 32. Therefore, referring to FIG. 4, the second inner rotor 30 ′ is composed of an annular (thick outer peripheral side) back yoke 30b ′ made of a magnetic material for forming a magnetic path, and a plurality of permanent magnets on the outer periphery thereof. (Inner magnet) 30a 'is attached with an adhesive or the like at equal intervals in the circumferential direction. The permanent magnet 30a 'has a 40-pole configuration, like the permanent magnet 21a' of the second outer rotor member 21 ', and is composed of a magnetic metal with 20 N-pole and 20 S-pole magnets alternately. Therefore, the second inner rotor 30 'is rotated in synchronism with the second outer rotor member 21' driven by the second stator 29 'by a magnetic coupling action. The back yoke 30b 'is made of low carbon steel having high magnetism, and is chromate plated for rust prevention after work forming.

  A ring dish-shaped cover member 32 ′ covering the permanent magnet 30 a extends inward in the radial direction from the cylindrical portion 32 a ′ that contacts the outer surface facing the partition wall 13 of the permanent magnet 30 a ′ and the cylindrical portion 32 a ′. And a flange portion 32b 'that contacts the surface of the back yoke 30b', and is fixed with an adhesive so as to cover the inner rotor 30 '. The cover member 32 ′ is made of a non-magnetic material in consideration of the influence on the magnetic circuit causing the magnetic coupling, and is formed by thin sheet metal processing.

  A bearing (second bearing) 33 ′ that rotatably supports the second 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 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 back yoke 30b 'is made of low carbon steel having high magnetism, and is chromate plated 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. In this way, based on the absolute angle information from the absolute resolver, the rotor machine angle is recognized immediately after the power is turned on and the motor coil is commutated. On the other hand, high-resolution angle positioning is performed based on relative angle information from the incremental resolver. 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, so it is used for driving current control of the direct drive motor D2. The rotation angle can be detected without using a pole detection sensor. For this reason, it is suitable for a direct drive motor that drives the robot apparatus as in this embodiment.

  The outer boss that connects the rotation side of the detector and the rotation side of the bearing 19 'and the detector coupling, and the inner boss that connects the stationary side of the angle detector and the stationary side of the bearing device are derived from the motor field and the motor coil. In order to prevent electromagnetic noise from being transmitted to the resolver, which is a detector, carbon steel, which is a magnetic material, is used as a material, and chromate plating is applied to prevent rust after processing.

  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 member 21 ′. The rotation angle 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, before being incorporated in the housing, the eccentricity adjustment and the position of the resolver coil by the resolver alone are provided. Since adjustments such as adjustment can be performed, there is no need to provide adjustment holes or notches in the housing and both flanges.

  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 ′ supported by the bearing 33 ′, the reluctance with the magnetic pole of the incremental resolver stator 35 ′ changes, and one revolution of the incremental resolver rotor 34a ′. The reluctance change is detected so that the fundamental wave component of the reluctance change is n periods, digitized by the resolver control circuit shown in FIG. 5 as an example, and used as a position signal, so that the incremental resolver rotor 34a ′, 2 The rotation angle (or rotation speed) of the inner rotor 30 ′ is detected. The resolver rotors 34a 'and 34b and the resolver stators 35' and 36 'constitute a detector.

  Here, in the case where the permanent magnet 30a ′ is peeled off due to inadequate handling or the like and a small piece is generated due to chipping or the like, the small piece is attracted to the rotor magnet on the other side, but according to the present embodiment, the partition wall 13, the cover member 32 ′ is present between the first inner rotor 30 ′ and the second inner rotor 30 ′. Good swirl is ensured and the detection accuracy of the detector can be maintained.

  According to the present embodiment, the outer rotor (second outer rotor 21 ′ and cylindrical member 23 ′) of the direct drive motor D2 is replaced with the outer rotor (first outer rotor 21 and cylindrical member of the other direct drive motor D1. 23) is supported by the angular contact ball bearing 19 ', so that if the outer rotor of the direct drive motor D2 is removed, the angular contact ball bearing 19' supporting the outer rotor can be exposed, and then directly If the outer rotor of the drive motor D1 is removed, the angular contact ball bearings 19 supporting the outer rotor can be exposed, and their inspection and removal can be easily performed, so that maintainability is also improved. Furthermore, since it is only necessary to remove the outer rotor outside the partition wall 13, it is not necessary to remove the partition wall structure, and a leak check or the like is not required at the time of reassembly, thereby improving assemblability.

  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. 6 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 rotor members 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 rotor members 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 are output to the resolver digital converter (RDC). The CPU input after the digital conversion in step 1 determines whether or not the outer rotor members 21 and 21 'have reached the command position, and stops the drive signal to the three-layer amplifier (AMP) if the command position is reached. Thus, the rotation of the outer rotor members 21 and 21 ′ is stopped. This enables servo control of the outer rotor members 21 and 21 '.

  When driving multiple axes in a vacuum environment, there is a possibility that the arm A1 or the like may hit the wall of the vacuum chamber or the shutter of the vacuum chamber if the current rotational positions of the arms A1 and A2 are not 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 rotor members 21, 21 ′, that is, the arms A1 and 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. 7 is a cross-sectional view showing a state where the first inner rotor 30 and the cover member 132 according to the second embodiment are assembled, and FIG. 8 is an exploded view of the first inner rotor 30 and the cover member 132. It is a perspective view shown in a state. The present embodiment is the same as the above-described embodiment except for the cover member 132.

  In the present embodiment, an endless belt-like cover member 132 is used. The total length of the thin belt-shaped cover member 132 made of a nonmagnetic material such as SUS is longer than the inner peripheral length of the virtual cylindrical surface that is in contact with the outer surface facing the partition wall 13 of the permanent magnet 30a. When the member 132 is wound so as to surround the outer periphery of the permanent magnet 30a on the entire circumference, a slight gap is formed between them.

  In this state, when a “U” -shaped clip 100 made of a non-magnetic material is inserted between the circumferentially adjacent permanent magnets 30a as shown in FIG. 8, both ends sandwich the back yoke 30b. It enters a position facing the lighter weight hole 30c formed in the back yoke 30b. Here, the pair of legs 101a of the special nut 101 disposed in the lightening hole 30c is fitted into the holes formed at both ends of the clip 100, and the bolt 102 is attached to the special nut 101 from the inner peripheral side of the back yoke 30b. Screwed on. Then, the tip of the bolt 102 comes into contact with the inner periphery of the back yoke 30b, and acts to push the nut 101 radially inward by the reaction force. As a result, the clip 100 is displaced inward in the radial direction of the back yoke 30b, so that the belt-like cover member 132 is pulled in between the permanent magnets 30a and the tension increases, so that the surface of the permanent magnets 30a is increased. The slack is eliminated. The clip 100, the special nut 101, and the bolt 102 constitute a tension member.

  According to the present embodiment, since the belt-shaped cover member 132 is in close contact with the surface of the permanent magnet 30a, the belt-shaped cover member 132 moves outward from the cover member 132 even when the small pieces are separated due to peeling or chipping of the magnet. Can be effectively prevented.

  In the above embodiment, the example using the surface magnet type 40 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 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 differ. For example, in the case of 2-axis coaxial, the first axis is 40 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 40 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 angular contact ball bearings 19 and 19 'have been described using an example of grease lubrication for vacuum. However, the present invention is not limited to this type, material, and lubrication method, and the environment used, load conditions, rotational speed, etc. It may be changed as appropriate, and may be a cross roller bearing. In the case of a four-axis coaxial motor, it may be supported by another bearing in order to further increase mechanical rigidity. When multipoint contact bearings cannot be used, such as bearings that support the rotor of each shaft and other bearings may be preloaded as deep groove ball bearings or angular bearings, or used in ultra-vacuum In such a case, a metal lubrication that does not emit gas, such as plating of a soft metal such as gold or silver, 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 rotor, and 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.

  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 motor system according to 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 motor system 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.

1 is a perspective view of a frog-leg-arm type transfer robot using a motor system including a direct drive motor according to the present 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. FIG. 3 is a cross-sectional view showing a state in which a first inner rotor 30 and a cover member 32 are assembled. FIG. 3 is a perspective view showing the first inner rotor 30 and a cover member 32 in an exploded state. 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 shown in the state which assembled | attached the 1st inner side rotor 30 and the cover member 132 concerning 2nd Embodiment. FIG. 3 is a perspective view showing the first inner rotor 30 and a cover member 132 in an exploded state.

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, 113 Partition 16 Bolt 17, 17 'Bearing holder 18, 18' Bolt 19, 19 'Angular contact ball bearing 20, 20' Bolt 21, 21 'Outer rotor member 21a, 21a' Permanent magnet 21b, 21b 'Yoke 23, 23' Cylindrical member 29, 29 'Stator 30, 30' Inner rotor 30a, 30a 'Permanent magnet 30b, 30b' Back yoke 32, 32 ', 132, 132 'Cover member 33, 33' Bearing 34, 34 'Detection rotor 34a, 34a' Incremental resolver rotor 34b, 34b 'Absolute resolver rotor 35, 35' Incremental resolver stator 36, 36 'Absolute resolver stator 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 (5)

In a surface magnet type brushless 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 wall and provided with an outer magnet;
A first bearing device that rotatably supports the outer rotor with respect to the housing;
A stator disposed on the atmosphere side 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 second bearing device that rotatably supports the inner rotor with respect to the housing;
A detector for detecting the rotational position of the inner rotor,
The inner rotor has inner magnets arranged side by side in the circumferential direction so as to face the outer magnet of the outer rotor with the partition wall in between, and is established between the inner magnet and the outer rotor. Due to the action, the inner rotor and the outer rotor are magnetically coupled,
The brushless motor, wherein the inner magnet is covered with a cover member interposed between the inner magnet and the partition wall.   The said cover member has a cylindrical part contact | abutted to the surface facing the said partition of the said inner magnet, and a flange part extended inward in a radial direction from the said cylindrical part, and contact | abutted to the said inner rotor. Item 10. A brushless motor according to item 1.   The brushless motor according to claim 1, wherein the cover member has a belt shape that abuts against a surface of the inner magnet facing the partition wall. The overall length of the belt-shaped cover member is longer than the inner peripheral length of a virtual cylindrical surface that is in contact with the surface of the inner magnet facing the partition, and the inner magnets are spaced apart in the circumferential direction.
A tension member is provided to increase the tension of the belt-shaped cover member by entering between the adjacent inner magnets in a state where the belt-shaped cover member surrounds the inner magnet around the entire circumference. The brushless motor according to claim 3.   The brushless motor according to claim 4, wherein an assembly position of the tension member with respect to the inner rotor is adjustable.