Direct drive motor

Abstract

This direct drive motor is provided with a fixed shaft, a bearing unit which comprises an inner ring which mates with the fixed shaft, an output shaft which mates with an outer ring of the bearing unit, a first restricting member which is arranged in a first direction of the inner ring, a second restricting member which is arranged in the first direction of the outer ring, and a motor unit. The fixed shaft comprises a first main body which mates with the inner ring, a first contact part which contacts the inner ring in a second direction, a base contact part which contacts a base, and a first female screw hole where a first fastening member is screwed in. The output shaft comprises a second main body which mates with the outer ring, a second contact part which contacts the end surface of the outer ring in the second direction, a cylindrical attachment unit which has a first-direction end surface that protrudes in the first direction beyond the second restricting member, and a second female screw hole where a second fastening member is screwed in. The first restricting member is fastened to the first main body and contacts the first-direction end surface of the inner ring, and the second restricting member is fastened to the second main body and contacts the first-direction end surface of the outer ring.

Description

[Technical field]

[0001] The present disclosure relates to direct drive motors. [Background technology]

[0002] A direct drive motor is an electric motor that directly transmits generated power to an object without going through a reduction mechanism. The object may be a table on which a workpiece is placed, an arm that grips the workpiece, etc. The direct drive motor of Patent Document 1 below includes an annular base that is fastened to a base by a fastener, a fixed shaft that fits on the inner peripheral surface of the base, a bearing that fits on the outer peripheral side of the fixed shaft, a connecting member that fits on the outer peripheral side of the bearing, an output shaft that fits on the connecting member, and a motor unit that applies torque to the output shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-233100 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the direct drive motor of Patent Document 1, the fixed shaft is fixed to a foundation via a base. The output shaft is supported by the fixed shaft via a connecting member. This structure can reduce the rigidity of the fixed shaft and the output shaft. As a result, the output shaft is prone to vibrate in the radial direction when it rotates, which is called runout.

[0005] The present disclosure has been made in consideration of the above, and has an object to provide a direct drive motor that can suppress runout of the output shaft. [Means for solving the problem]

[0006] In order to achieve the above object, a direct drive motor according to one aspect of the present disclosure includes a cylindrical fixed shaft, a bearing unit having an inner ring fitted to an outer peripheral surface of the fixed shaft, a cylindrical output shaft having an outer ring of the bearing unit fitted to an inner peripheral surface, a first restricting member arranged in a first direction of an axial direction parallel to an axis of the output shaft with respect to the inner ring, a second restricting member arranged in the first direction with respect to the outer ring, and a motor unit that applies torque to the output shaft. The fixed shaft has a cylindrical first main body portion with which the inner ring is fitted, a cylindrical first abutment portion extending from the first main body portion in a second direction opposite to the first direction and abutting an end face of the inner ring in the second direction, a base abutment portion extending from the first abutment portion in the second direction and having an end face in the second direction abutting a base, and a first female screw hole provided on the end face in the second direction of the base abutment portion and into which a first fastener for fastening the base abutment portion and the base is screwed. The output shaft has a cylindrical second body portion into which the outer ring is fitted, a cylindrical second abutment portion located in the second direction from the second body portion and abutting an end face of the outer ring in the second direction, a cylindrical mounting portion extending in the first direction from an outer periphery of the second body portion and having an end face in the first direction protruding in the first direction beyond the second regulating member, and a second female screw hole provided in the end face in the first direction of the mounting portion and into which a second fastener for fastening the mounting portion to an object is screwed. The first regulating member is fastened to the end face in the first direction of the first body portion and abuts the end face in the first direction of the inner ring. The second regulating member is fastened to the end face in the first direction of the second body portion and abuts the end face in the first direction of the outer ring.

[0007] According to the direct drive motor of the present disclosure, there is no part interposed between the base and the fixed shaft, no part interposed between the fixed shaft and the bearing, and no part interposed between the bearing and the output shaft. In other words, the fixed shaft is fastened to the first fastener that screws into the first female screw hole. Thus, the fixed shaft is directly supported by the base. The bearing is fitted at its inner ring to the first body of the fixed shaft. Thus, the bearing is directly supported by the fixed shaft. The output shaft is fitted at its second body to the outer ring of the bearing. Thus, the output shaft is directly supported by the bearing. From the above, the rigidity of the output shaft is high. Therefore, the runout of the output shaft is suppressed when the output shaft rotates. In addition, if the number of parts interposed between the fixed shaft and the output shaft increases, the output shaft may become eccentric with respect to the fixed shaft due to the influence of assembly tolerance, in other words, the workpiece may not be transported with high precision. However, according to the direct drive motor of the present disclosure, the only part interposed between the fixed shaft and the output shaft is the bearing. Therefore, the influence of assembly tolerance is small, and the concentricity of the output shaft with respect to the fixed shaft is high. Therefore, the workpiece can be transported with high precision. Furthermore, the bearing portion abuts against the first abutment portion of the fixed shaft, and is positioned in the axial direction. The output shaft is positioned in the axial direction with the second abutment portion abutting against the bearing portion. Therefore, regarding the axial positioning of the output shaft with respect to the fixed shaft, the only part interposed between the fixed shaft and the output shaft is the bearing portion. Therefore, the influence of assembly tolerance is small, and the position (height) of the object fixed to the output shaft can be set to the desired position (height). For these reasons, the workpiece can be transported with high precision. In addition, the first and second regulating members abut against the inner or outer ring. Therefore, the output shaft is prevented from moving in the axial direction, and the position of the object is prevented from changing.

[0008] In a preferred embodiment of the direct drive motor according to the present invention, the motor section includes a rotor that fits to an outer circumferential surface of the output shaft, and a stator that surrounds the outer circumferential side of the rotor. A stator support section that extends radially outward from the base contact section and supports the stator is fastened to the outer circumferential side of the base contact section.

[0009] The stator may vibrate due to magnetic attraction and repulsion generated between the stator and the rotor. Furthermore, if the stator is supported by a fixed shaft, the vibration of the stator may be transmitted to the fixed shaft, causing runout in the output shaft. In the direct drive motor disclosed herein, the stator is supported by a stator support portion fastened to the fixed shaft. Therefore, when the stator vibrates, the vibration is absorbed by the stator support portion, and the vibration is not easily transmitted to the fixed shaft. This prevents runout in the output shaft due to the vibration of the stator.

[0010] In a preferred embodiment of the direct drive motor according to the first aspect, the inner and outer shapes of the second main body portion form a circle centered on the axis.

[0011] Conventionally, in order to fix other components to the outer peripheral surface of the output shaft, the outer peripheral surface of the output shaft may be milled or the like. When such processing is performed, internal stress is generated in the rotating shaft, and the inner peripheral surface of the rotating shaft is distorted. When the inner peripheral surface of the rotating shaft becomes non-circular, the tightening force on the outer ring due to the fitting is not uniform in the circumferential direction of the outer ring, which causes runout of the output shaft. On the other hand, in the output shaft of the present disclosure, the inner and outer shapes of the second main body portion are circular. Therefore, the tightening force on the outer ring due to the fitting acts uniformly in the circumferential direction of the outer ring. Therefore, runout of the output shaft is suppressed when the output shaft rotates.

[0012] In a preferred embodiment of the direct drive motor according to the present invention, the inner and outer shapes of the first main body portion are circular with the axis as a center.

[0013] The fastening force applied to the inner ring by the fitting of the first main body portion acts uniformly in the circumferential direction of the inner ring, which suppresses runout of the bearing portion relative to the fixed shaft, and also suppresses runout of the output shaft supported by the bearing portion.

[0014] In a preferred embodiment of the direct drive motor according to the first aspect, the first female threaded hole is disposed radially inward from the rolling surface of the inner ring, and the second female threaded hole is disposed radially outward from the rolling surface of the outer ring.

[0015] When the first fastener is screwed into the first female threaded hole, the fixed shaft is deformed so that the diameter of the first female threaded hole becomes larger. If the first female threaded hole were to overlap with the rolling surface of the inner ring in the axial direction, the rolling surface of the inner ring would be distorted and the rolling elements would not rotate smoothly. However, the first female threaded hole of the present disclosure is disposed radially inward and separated from the rolling surface of the inner ring. Therefore, the rolling surface of the inner ring is less likely to deform. Similarly, the second female threaded hole is separated from the rolling surface of the outer ring. Therefore, the rolling surface of the outer ring is less likely to deform. From the above, the rolling elements roll smoothly on the rolling surface and the output shaft rotates smoothly. Effect of the Invention

[0016] According to the direct drive motor of the present disclosure, vibration of the output shaft is suppressed when the output shaft rotates, enabling the workpiece to be transported stably. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view illustrating an example of the overall configuration of a direct drive motor according to a first embodiment. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a portion of the direct drive motor of FIG. [Diagram 3] FIG. 3 is a bottom view of the direct drive motor of the first embodiment as viewed from a second direction. [Figure 4] FIG. 4 is a plan view of the direct drive motor of the first embodiment as viewed from a first direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The embodiment of the invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following description. The components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the components described below can be appropriately combined.

[0019] Fig. 1 is a cross-sectional view showing an example of the overall configuration of a direct drive motor of embodiment 1. Fig. 2 is a cross-sectional view showing an enlarged portion of the direct drive motor of Fig. 1. Fig. 3 is a bottom view of the direct drive motor of embodiment 1 as viewed from a second direction. Fig. 4 is a plan view of the direct drive motor of embodiment 1 as viewed from a first direction.

[0020] As shown in FIG. 1, the direct drive motor 100 of the first embodiment is an electric motor that generates power to transport a workpiece (not shown). In the direct drive motor 100 of the first embodiment, a base 110 is disposed on one side of the axis AX of the output shaft 3. The direct drive motor 100 is fixed to the base 110. In addition, in the direct drive motor 100, a table 120 is disposed on the other side of the axis AX of the output shaft 3. The table 120 is attached to the direct drive motor 100. Then, the direct drive motor 100 rotates the table 120 about the axis AX to transport a workpiece (not shown) placed on the table 120.

[0021] Although the direct drive motor 100 of the embodiment is exemplified by an example in which the table 120 is attached as an object, the direct drive motor of the present disclosure is not limited to this. For example, the direct drive motor of the present disclosure may be used as a servo motor used as a drive source for driving an arm. In addition, the direct drive motor of the present disclosure may be used in an inspection device, a machine tool, a semiconductor manufacturing device, etc.

[0022] The direct drive motor 100 includes a fixed shaft 1, a bearing unit 2, an output shaft 3, a first restricting member 4, a second restricting member 5, a first cover member 6, a stator support member 7, a motor unit 8, and a second cover member 9. In the following description, a direction parallel to the axis AX is referred to as the axial direction. In addition, within the axial direction, a direction in which the table 120 is disposed as viewed from the direct drive motor 100 is referred to as a first direction A1. A direction in which the base 110 is disposed as viewed from the direct drive motor 100 is referred to as a second direction A2.

[0023] The fixed shaft 1 is a cylindrical part whose center extends in the axial direction. As shown in FIG. 2, the fixed shaft 1 includes a first main body portion 10, the inner rings 25 and 26 of the bearing portion 2 being fitted to the outer circumferential surface thereof, a first abutment portion 11 extending from the first main body portion 10 in the second direction A2, a base abutment portion 12 extending from the first abutment portion 11 in the second direction A2, and a protruding portion 13 protruding from the first main body portion 10 in the first direction. In other words, the fixed shaft 1 is a part in which the first main body portion 10, the first abutment portion 11, the base abutment portion 12, and the protruding portion 13 are integrally formed. In FIG. 2, auxiliary lines (two-dot chain lines) are drawn to clarify the respective portions of the first main body portion 10, the first abutment portion 11, the base abutment portion 12, and the protruding portion 13.

[0024] The first body portion 10 has a cylindrical shape centered on the axis AX. That is, when viewed from the axis AX direction, the outer peripheral surface 10a and the inner peripheral surface 10b of the first body portion 10 have a circular shape centered on the axis AX (see FIG. 3). The axial length of the first body portion 10 is the same as the axial length of the bearing portion 2. The end face 10c of the first body portion 10 in the first direction A1 is provided with a plurality of female screw holes 10d arranged at equal intervals in the circumferential direction. The thickness of the first body portion 10 from the outer peripheral surface 10a to the inner peripheral surface 10b is T1 (see FIG. 1).

[0025] The outer diameter of the first contact portion 11 is larger than the outer diameter of the first main body portion 10. In other words, the first contact portion 11 protrudes radially outward from the outer circumferential surface 10a of the first main body portion 10. An end face 11a of the first contact portion 11 in the first direction A1 abuts against an end face 26a of the inner ring 26 of the bearing portion 2 in the second direction A2.

[0026] The base abutment portion 12 has a large diameter portion 14 whose outer diameter is larger than the outer diameter of the first abutment portion 11, and a protrusion portion 15 that protrudes in the second direction A2 from an end face 14a of the large diameter portion 14 in the second direction A2.

[0027] An end face 14a of the large diameter portion 14 in the second direction A2 is provided with a plurality of outer peripheral female threaded holes 14b located outer circumferentially further outward than the protrusion 15, and a plurality of inner peripheral female threaded holes 14c located inner circumferentially further outward than the protrusion 15. As shown in Fig. 3, the outer peripheral female threaded holes 14b and the inner peripheral female threaded holes 14c are provided at equal intervals in the circumferential direction.

[0028] As shown in Fig. 3, the protrusion 15 is annular when viewed from the axial direction. As shown in Fig. 2, the end surface 15a of the protrusion 15 in the second direction A2 is a flat surface. The end surface 15a of the protrusion 15 in the second direction A2 abuts against a surface (mounting surface) of the base 110 facing the first direction A1.

[0029] A first female screw hole 15b is provided in an end surface 15a of the protrusion 15 in the second direction A2. A plurality of first female screw holes 15b are provided at equal intervals in the circumferential direction (see FIG. 3). A first fastener 201 penetrating the base 110 is screwed into the first female screw hole 15b. As a result, the protrusion 15 (base abutment portion 12) is fastened to the base 110, and the fixed shaft 1 is fixed to the base 110.

[0030] Further, an end surface 15a of the protrusion 15 in the second direction A2 is located further in the second direction A2 than the first cover 6 and the stator support member 7. In other words, the first cover 6 and the stator support member 7 do not abut against the base 110.

[0031] 2, the protrusion 13 protrudes in the first direction A1 from the inner circumferential side of the end face 10c in the first direction A1 of the first main body portion 10. The outer circumferential surface of the protrusion 13 has a circular shape when viewed in the axial direction.

[0032] The bearing unit 2 includes a first bearing 21 and a second bearing 22 disposed in the second direction A2 relative to the first bearing 21. The first bearing 21 and the second bearing 22 are angular contact ball bearings in a back-to-back configuration. The first bearing includes an outer ring 23, an inner ring 25, and a plurality of rolling elements 27 disposed between the outer ring 23 and the inner ring 25. The second bearing includes an outer ring 24, an inner ring 26, and a plurality of rolling elements 28 disposed between the outer ring 24 and the inner ring 26. The rolling surfaces of the inner rings 25 and 26 are located radially outward from the first female threaded hole 15b of the fixed shaft 1 (see the imaginary line L in FIG. 2). In other words, the first female threaded hole 15b of the fixed shaft 1 is located radially inward from the rolling surfaces of the inner rings 25 and 26. That is, the first female threaded hole 15b and the rolling surfaces of the inner rings 25 and 26 do not overlap in the axial direction.

[0033] The output shaft 3 is a cylindrical part. The output shaft 3 includes a cylindrical second main body portion 30 that fits into the outer rings 23, 24, a second abutment portion 31 that extends from the second main body portion 30 in the second direction A2, and a cylindrical attachment portion 32 that extends from the outer periphery of the second main body portion 30 in the first direction A1. In other words, the output shaft 3 is a cylindrical part. The output shaft 3 is a part in which the second main body portion 30, the second abutment portion 31, and the cylindrical attachment portion 32 are integrally formed.

[0034] The second body portion 30 is cylindrical with the axis AX at the center. That is, when viewed from the axial direction, the outer peripheral surface 30a and the inner peripheral surface 30b of the second body portion 30 are circular with the axis AX at the center (see FIG. 4). As shown in FIG. 2, the axial length of the second body portion 30 is the same as the axial length of the bearing portion 2. The end face 30c of the second body portion 30 in the first direction A1 is provided with a plurality of female screw holes 30d arranged at equal intervals in the circumferential direction. The outer peripheral surface 30a of the second body portion 30 is provided with an annular protruding portion 30e that protrudes radially outward from the end in the first direction A1. This protruding portion 30e determines the axial position of the rotor 81. The thickness from the outer peripheral surface 30a to the inner peripheral surface 30b of the second body portion 30 is T2 (see FIG. 1).

[0035] The inner diameter of the second abutment portion 31 is smaller than the inner diameter of the second main body portion 30. In other words, the second abutment portion 31 protrudes radially inward from the inner circumferential surface 30b of the second main body portion 30. An end face 31a of the second abutment portion 31 in the first direction A1 abuts against an end face 24a of the outer ring 24 in the second direction A2.

[0036] As shown in FIG. 4, the mounting portion 32 is annular when viewed from the axial direction. As shown in FIG. 2, the end surface 32a of the mounting portion 32 in the first direction A1 is an abutment surface that abuts against the table 120. The mounting portion 32 protrudes in the first direction A1 further than the second regulating member 5. That is, the end surface 32a of the mounting portion 32 in the first direction A1 is located further in the first direction A1 than the second regulating member 5. The end surface 32a of the mounting portion 32 is a flat surface. The end surface 32a of the mounting portion 32 is provided with a second female screw hole 32b into which the second fastener 202 is screwed. A plurality of second female screw holes 32b are provided at equal intervals in the circumferential direction. The second female screw hole 32b is disposed radially outward of the rolling surfaces of the outer rings 23 and 24, and does not overlap with the outer rings 23 and 24 in the axial direction.

[0037] 1, the table 120 is attached by abutting the table 120 against the end surface 32a of the attachment portion 32 from the first direction A1. The second fastener 202 penetrating the table 120 is screwed into the second female screw hole 32b. In this way, the table 120 is fixed to the output shaft 3.

[0038] As shown in Fig. 2, the first restricting member 4 is an annular part. The first restricting member 4 is disposed in the first direction A1 of the inner ring 25 and the first main body portion 10. The first restricting member 4 is fastened to a fastener 203. The first restricting member 4 abuts against an end face 25a of the inner ring 25 in the first direction A1. This restricts the bearing portion 2 from moving in the first direction A1 relative to the fixed shaft 1.

[0039] Moreover, the inner diameter of the first restricting member 4 is the same as the outer diameter of the protruding portion 13. In other words, the entire circumference of the inner circumferential surface 4a of the first restricting member 4 abuts against the outer circumferential surface of the protruding portion 13. This prevents the first restricting member 4 from moving in the radial direction and coming into contact with the second restricting member 5.

[0040] As shown in FIG. 1, the second regulating member 5 comprises a fastened portion 50 fastened to the fastener 204, a covering portion 51 extending radially inward from the fastened portion 50, and a cylindrical portion 53 extending from the inner end of the covering portion 51 in the second direction A2.

[0041] 2, the fastened portion 50 is disposed in the first direction A1 of the outer ring 23 and the second main body portion 30. The fastened portion 50 is fastened to a fastener 204. The fastened portion 50 abuts against an end face 23a of the outer ring 23 in the first direction A1. This restricts the output shaft 3 from moving in the first direction A1 relative to the bearing portion 2.

[0042] In addition, the outer diameter of the fastened portion 50 is the same as the inner diameter of the mounting portion 32. In other words, the entire circumference of the outer circumferential surface 50a of the fastened portion 50 abuts against the inner circumferential surface of the mounting portion 32. This prevents the second restricting member 5 from moving in the radial direction and causing the fastened portion 50 to come into contact with the first restricting member 4.

[0043] 1, the covering portion 51 extends radially inward from the fastened portion 50. The radial inner end of the covering portion 51 is located radially inward from the inner circumferential surface 10b of the first main body portion 10. The covering portion 51 covers the space between the fastened portion 50 and the first restricting member 4, the first restricting member 4, and the protruding portion 13 in the first direction A1. As a result, even if lubricating oil leaks from the bearing portion 2 to the space between the fastened portion 50 and the first restricting member 4, it will not flow out beyond the covering portion 51 in the first direction A1.

[0044] An outer peripheral surface 52a of the cylindrical portion 52 faces an inner peripheral surface 1a of the fixed shaft 1. The outer peripheral surface 52a of the cylindrical portion 52 and the inner peripheral surface 1a of the fixed shaft 1 are spaced apart in the radial direction. Therefore, an annular space S capable of accommodating a sensor or the like is provided between the cylindrical portion 52 and the fixed shaft 1.

[0045] The first cover member 6 is disposed on the inner periphery side of the protrusion 15, and is a part that closes the second direction A2 of the annular space S. In detail, the first cover member 6 is a flat part that is annular about the axis AX and has a thin axial thickness. The outer periphery of the first cover member 6 is overlapped on the end face 14a of the large diameter portion 14. The outer periphery of the first cover member 6 is fastened to a fastener 205 that screws into the outer periphery female threaded hole 14b. In this way, the first cover member 6 is supported by the fixed shaft 1.

[0046] The stator support member 7 is a component disposed on the outer circumferential side of the protrusion 15. The stator support member 7 has a ring-shaped ring portion 70 and a cylindrical stator attachment portion 71 that protrudes from the outer circumferential portion of the ring portion 70 in the first direction A1. The inner circumferential portion of the ring portion 70 is overlapped on the end face 14a of the large diameter portion 14. The inner circumferential portion of the ring portion 70 is fastened to a fastener 206 that screws into the inner circumferential female screw hole 14c. In this way, the stator support member 7 is supported by the fixed shaft 1. The stator attachment portion 71 has a plurality of female screw holes 72 provided in the circumferential direction on the end face in the first direction A1. The thickness from the outer circumferential surface to the inner circumferential surface of the stator attachment portion 71 is T3 (see FIG. 1). The axial thickness of the ring portion 70 is T4 (see FIG. 1).

[0047] The motor unit 8 has a stator 80 and a rotor 81. The rotor 81 includes an annular core fitted onto the outer peripheral surface of the second main body portion 30 of the output shaft 3, and a plurality of permanent magnets (not shown) embedded in the core and arranged at equal intervals in the circumferential direction. The stator 80 includes a cylindrical holder 82, a plurality of cores 83 arranged at equal intervals in the circumferential direction along the inner peripheral surface of the holder 82, bobbins 84 supported by the cores 83, and coils 85 formed by multiple windings of a wire around the bobbin 84.

[0048] The holder 82 is disposed in the first direction A1 of the stator mounting portion 71. The holder 82 is provided with a plurality of holes 82a penetrating in the axial direction. The shaft of the fastener 207 penetrates the hole 82a of the holder 82 and is screwed into the female threaded hole 72 of the stator mounting portion 71 (see the view on the left side of the axis AX in FIG. 1). In this way, the stator 80 is supported by the stator support member 7. Note that some of the female threaded hole 72 of the stator mounting portion 71 and the plurality of holes 82a of the holder 82 are intended for the fastener 208 that fastens the second cover member 9 (see the view on the right side of the axis AX in FIG. 1).

[0049] The second cover member 9 is an annular part. A cross-sectional shape of the second cover member 9 cut radially outward from the axis AX forms a substantial L-shape that covers the first direction A1 of the stator 80 and the outer circumferential side of the stator 80. The second cover member 9 is fastened to a fastener 208 and supported by the stator support member 7. In addition, a spacer 90 is interposed between the second cover member 9 and the holder 82.

[0050] Next, the effect of the direct drive motor 100 of the first embodiment will be described. In the direct drive motor 100 of the first embodiment, there are no parts interposed between the base 110 and the fixed shaft 1, no parts interposed between the fixed shaft 1 and the bearing unit 2, and no parts interposed between the bearing unit 2 and the output shaft 3. That is, the first fastener 201 fastens the protrusion 15 (base abutment portion 12) of the fixed shaft 1 to the base 110. The protrusion 15 (base abutment portion 12) of the fixed shaft 1 abuts against the base 110. Thus, the fixed shaft 1 is directly supported by the base 110. Moreover, the inner rings 25 and 26 of the bearing unit 2 are fitted into the first main body portion 10 of the fixed shaft 1. Thus, the bearing unit 2 is directly supported by the fixed shaft 1. Moreover, the second main body portion 30 of the output shaft 3 is fitted into the outer rings 23 and 24 of the bearing unit 2. Thus, the output shaft 3 is directly supported by the bearing unit 2. For the above reasons, the rigidity of supporting the output shaft 3 is high. Therefore, when the output shaft 3 rotates, vibration of the output shaft 3 is suppressed. Furthermore, the table 120 is fastened to the output shaft 3 by the second fastener 202. Therefore, the output shaft 3 directly supports the table 120. For the above reasons, the rigidity of supporting the table 120 is high. Therefore, when the direct drive motor 100 is driven, vibration of the table 120 is suppressed.

[0051] Furthermore, the stator 80 may vibrate due to magnetic attractive and repulsive forces generated between the stator 80 and the rotor 81. If the fixed shaft 1 directly supported the stator 80, the vibration of the stator 80 would be transmitted to the fixed shaft 1, and vibration of the output shaft 3 may occur. However, the stator 80 of the first embodiment is indirectly supported by the fixed shaft 1 via the stator support member 7. Therefore, vibration of the stator 80 is absorbed by the stator support member 7 and is unlikely to be transmitted to the fixed shaft 1. From the above, vibration of the stator 80 is prevented from causing vibration of the output shaft 3.

[0052] Conventionally, in order to fix other parts to the outer peripheral surface of the output shaft 3, the outer peripheral surface of the output shaft 3 may be cut by milling or the like to have a D-shaped cross section. When such processing is performed, internal stress is generated in the output shaft 3, and the inner peripheral surface of the output shaft 3 is distorted. When the inner peripheral surface of the output shaft 3 becomes non-circular, the tightening force of the fitting of the output shaft 3 is not uniform in the circumferential direction, which causes runout. On the other hand, the outer peripheral surface 30a and the inner peripheral surface 30b of the second main body portion 30 of the first embodiment are circular when viewed from the axial direction. In other words, the outer peripheral surface 30a of the second main body portion 30 is not processed by milling or the like, and the tightening force of the inner peripheral surface 30b of the second main body portion 30 acts uniformly in the circumferential direction. Therefore, runout of the output shaft 3 is suppressed when the output shaft 3 rotates.

[0053] In addition, the outer peripheral surface 10a and the inner peripheral surface 10b of the first main body portion 10 in the first embodiment are circular when viewed from the axial direction. Therefore, the first main body portion 10 is not subjected to processing such as milling, and no internal stress acts on it. The tightening force of the outer peripheral surface 10a of the first main body portion 10 acts uniformly in the circumferential direction. Therefore, the runout of the bearing portion 2 relative to the fixed shaft 1 is suppressed, and thus the runout of the output shaft 3 supported by the bearing portion 2 is suppressed.

[0054] Furthermore, the only part interposed between the fixed shaft 1 and the output shaft 3 is the bearing portion 2. If the number of parts interposed between the fixed shaft 1 and the output shaft 3 were to increase, the output shaft 3 could become eccentric with respect to the fixed shaft 1 due to the influence of assembly tolerances. In other words, according to the direct drive motor 100 of the first embodiment, the influence of assembly tolerances is small, and the concentricity of the output shaft 3 with respect to the fixed shaft 1 is high. As a result, the workpiece can be transported with high precision.

[0055] Moreover, the bearing portion 2 abuts against the end face 11a of the first abutment portion 11 of the fixed shaft 1, and is positioned in the axial direction. The output shaft 3 is positioned in the axial direction by the end face 31a of the second abutment portion 31 abutting against the bearing portion 2. Therefore, with regard to the axial positioning of the output shaft 3 relative to the fixed shaft 1, the only part interposed between the fixed shaft 1 and the output shaft 3 is the bearing portion 2. Therefore, there is little effect of assembly tolerance. For this reason, the end face 32a of the mounting portion 32 of the output shaft 3 is at the desired position (height), and the workpiece can be transported with high precision. Furthermore, there are no other parts interposed between the base 110 and the fixed shaft 1, and between the output shaft 3 and the table 120. For these reasons, there is little effect of assembly tolerance, and the workpiece can be transported with high precision.

[0056] In addition, when a fastener is screwed into the female thread hole, the female thread hole is deformed so that the hole diameter of the female thread hole becomes larger. If the first female thread hole 15b overlaps with the rolling surfaces of the inner rings 25, 26 in the axial direction, the first female thread hole 15b and the inner rings 25, 26 become relatively close to each other. Therefore, when the first fastener 201 is screwed into the first female thread hole 15b, the rolling surfaces of the inner rings 25, 26 may be distorted, and the rolling elements 27, 28 may not rotate smoothly. However, the first female thread hole 15b of the fixed shaft 1 of the first embodiment is disposed radially inward and separated from the rolling surfaces of the inner rings 25, 26. Therefore, the rolling surfaces of the inner rings 25, 26 are not deformed. Similarly, the second female thread hole 32b is disposed radially outward from the rolling surfaces of the outer rings 23, 24 and separated from the rolling surfaces of the inner rings 25, 26. Therefore, there is no deformation of the rolling surfaces of the inner rings 25, 26. As a result, the rolling elements 27, 28 roll smoothly, and the output shaft 3 rotates smoothly.

[0057] The radial thickness T1 of the first body portion 10, the radial thickness T2 of the second body portion 20, the axial thickness T3 of the ring portion 70, and the radial thickness T4 of the stator mounting portion 71 are in the order of T1>T2>T4>T3. The radial thickness T1 of the first body portion 10 is greater than the radial length (thickness) of the bearing portion 2. This improves the rigidity of the first body portion 10. This increases the rigidity of the output shaft 3, and suppresses runout of the output shaft 3. Although the first fastener 201 and the like are screwed into the fixed shaft 1 having the first body portion 10, deformation of the fixed shaft 1 is suppressed. Similarly, the radial thickness T2 of the second body portion 20 is greater than the radial length (thickness) of the bearing portion 2. This suppresses deformation of the output shaft 3, although the fastener 204 and the like are screwed into the output shaft 3 having the second body portion 30. Also, the second body portion 30 is larger than both the thickness T3 of the ring portion 70 and the thickness T4 of the stator attachment portion 71. Therefore, when the direct drive motor 100 is driven, although a magnetic attraction force and a magnetic repulsion force act between the stator 80 and the rotor 81, the second body portion 20 is difficult to deform, and the output shaft 3 rotates smoothly. Note that in the present disclosure, T2≧T4 may also be satisfied. This also allows the ring portion 70 to bend due to the magnetic force acting between the stator 80 and the rotor 81, and deformation of the second body portion 20 is avoided.

[0058] As described above, the direct drive motor 100 of embodiment 1 comprises a cylindrical fixed shaft 1, a bearing unit 2 whose inner rings 25, 26 fit onto the outer peripheral surface of the fixed shaft 1, a cylindrical output shaft 3 whose inner peripheral surface is fitted onto the outer rings 23, 24 of the bearing unit 2, a first regulating member 4 arranged in a first direction A1 in the axial direction parallel to the axis AX of the output shaft 3 relative to the inner rings 25, 26, a second regulating member 5 arranged in the first direction A1 relative to the outer rings 23, 24, and a motor unit 8 that imparts torque to the output shaft 3. The fixed shaft 1 has a cylindrical first main body portion 10 that fits into the inner rings 25, 26, a cylindrical first abutment portion 11 that extends from the first main body portion 10 in a second direction A2 opposite to the first direction A1 and abuts against an end face 26a of the inner ring 26 in the second direction A2, a base abutment portion 12 that extends in the second direction A2 from the first abutment portion 11 and has an end face 15a in the second direction A2 abutting the base 110, and a first female threaded hole 15b provided on the end face 15a in the second direction A2 of the base abutment portion 12 and into which a first fastener 201 for fastening the base abutment portion 12 to the base 110 is screwed. The output shaft 3 has a cylindrical second main body portion 30 that fits into the outer rings 23 and 24, a cylindrical second abutment portion 31 that is located in the second direction A2 from the second main body portion 30 and abuts against an end face 24a of the outer ring 24 in the second direction A2, a cylindrical mounting portion 32 that extends in the first direction A1 from the outer periphery of the second main body portion 30 and has an end face 32a in the first direction A1 that protrudes in the first direction A1 further than the second regulating member 5, and a second female screw hole 32b that is provided in the end face 32a in the first direction A1 of the mounting portion 32 and into which a second fastener 202 for fastening the mounting portion 32 to an object (table 120) is screwed. The first regulating member 4 is fastened to the end face 10c in the first direction A1 of the first main body portion 10 and abuts against an end face 25a in the first direction A1 of the inner ring 25. The second restricting member 5 is fastened to an end face 30c of the second main body portion 30 in the first direction A1, and abuts against an end face 23a of the outer ring 23 in the first direction A1.

[0059] Such a direct drive motor 100 has high rigidity for supporting the output shaft 3, and can suppress runout of the output shaft 3. The only part between the fixed shaft 1 and the output shaft 3 is the bearing portion 2, and the influence of assembly tolerances is small. Therefore, the concentricity of the output shaft 3 with respect to the fixed shaft 1 is high. Furthermore, the end surface 32a of the mounting portion 32 of the output shaft 3 is at the desired position (height). Therefore, the workpiece can be transported with high precision.

[0060] Moreover, the motor section 8 of the direct drive motor 100 of the first embodiment has a rotor 81 that fits onto the outer peripheral surface of the output shaft 3, and a stator 80 that surrounds the outer peripheral side of the rotor 81. A stator support member 7 that extends radially outward from the base abutment portion 12 and supports the stator 80 is fastened to the outer peripheral side of the base abutment portion 12.

[0061] According to such a direct drive motor 100, vibrations of the stator 80 are unlikely to be transmitted to the fixed shaft 1. Therefore, vibrations of the output shaft 3 can be suppressed.

[0062] In the direct drive motor 100 of the first embodiment, the inner and outer shapes of the second main body portion 30 form a circle centered on the axis AX.

[0063] According to such a direct drive motor 100, the fastening force of the inner peripheral surface 30b of the second main body portion 30 against the bearing portion 2 acts uniformly in the circumferential direction. Therefore, the runout of the output shaft 3 can be suppressed.

[0064] In the direct drive motor 100 of the first embodiment, the inner and outer shapes of the first main body portion 10 form a circle centered on the axis AX.

[0065] According to such a direct drive motor 100, the fastening force of the outer circumferential surface 10a of the first main body portion 10 against the bearing portion 2 acts uniformly in the circumferential direction. Therefore, the runout of the output shaft 3 can be suppressed.

[0066] In the direct drive motor 100 of the first embodiment, the first female threaded hole 15b is disposed radially inward from the rolling surfaces of the inner rings 25 and 26. The second female threaded hole 32b is disposed radially outward from the rolling surfaces of the outer rings 23 and 24.

[0067] Such a direct drive motor 100 suppresses deformation of the rolling surfaces of the inner rings 25, 26 and the outer rings 23, 24. This allows the rolling elements 27, 28 to rotate smoothly, and the output shaft 3 to also rotate smoothly.

[0068] Although the direct drive motor 100 of the first embodiment has been described above, the direct drive motor of the present disclosure is not limited to this. For example, the bearing unit 2 includes two bearings, but may be configured with one bearing or three or more bearings. [Explanation of symbols]

[0069] 100 Direct Drive Motor 1 Fixed axis 2 Bearing section 3 Output shaft 4. First restricting member 5 Second restricting member 6 First cover member 7 Stator support member 8 Motor section 9 Second cover member 10 First body part 11 First contact part 12 Base contact part 13 Protrusion 14 Large diameter section 15 Protrusion 15b First female thread hole 30 Second main body part 31 Second contact part 32 Mounting part 32b 2nd female thread hole 110 Foundation 120 Table

Claims

1. A cylindrical fixed shaft, a bearing portion in which an inner ring fits onto the outer peripheral surface of the fixed shaft, a cylindrical output shaft in which the outer ring of the bearing portion fits onto the inner peripheral surface, a first restricting member that is arranged in a first direction in the axial direction parallel to the axis of the output shaft with respect to the inner ring, a second restricting member that is arranged in the first direction with respect to the outer ring, a motor portion that applies torque to the output shaft, and comprising, the fixed shaft has a cylindrical first main body portion onto which the inner ring fits, a cylindrical first abutting portion that extends from the first main body portion in a second direction opposite to the first direction and abuts against the end surface of the inner ring in the second direction, a base abutting portion that extends from the first abutting portion in the second direction and whose end surface in the second direction abuts against a base, a first female screw hole that is provided on the end surface of the base abutting portion in the second direction and into which a first fastener for fastening the base abutting portion and the base is screwed, and having, the output shaft has a cylindrical second main body portion onto which the outer ring fits, a cylindrical second abutting portion that is located in the second direction from the second main body portion and abuts against the end surface of the outer ring in the second direction, a cylindrical mounting portion that extends from the outer peripheral portion of the second main body portion in the first direction and whose end surface in the first direction protrudes in the first direction from the second restricting member, a second female screw hole that is provided on the end surface of the mounting portion in the first direction and into which a second fastener for fastening the mounting portion and an object is screwed, and having, the first restricting member is fastened to the end surface of the first main body portion in the first direction and abuts against the end surface of the inner ring in the first direction, the second restricting member is fastened to the end surface of the second main body portion in the first direction and abuts against the end surface of the outer ring in the first direction Direct drive motor.

2. The motor portion has a rotor that fits onto the outer peripheral surface of the output shaft, a stator that surrounds the outer peripheral side of the rotor, and having, on the outer peripheral side of the base abutting portion, a stator support portion that extends radially outward from the base abutting portion and supports the stator is fastened The direct drive motor according to claim 1.

3. The inner shape and the outer shape of the output shaft form a circular shape centered on the axis The direct drive motor according to claim 1 or claim 2.

4. The inner shape and the outer shape of the fixed shaft form a circular shape centered on the axis The direct drive motor according to any one of claims 1 to 3.

5. The first female screw hole is arranged radially inward of the rolling surface of the inner ring, The second female screw hole is arranged radially outside the rolling surface of the outer ring. The direct drive motor according to any one of claims 1 to 4.

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