Direct drive motor

Abstract

A direct drive motor includes a fixed shaft, a bearing portion in which an inner ring is fitted, an output shaft in which an outer ring of the bearing portion is fitted, a first restriction member arranged in a first direction of the inner ring, a second restriction member arranged in a first direction of the outer ring, and a motor portion. The fixed shaft has a first main body portion in which the inner ring is fitted, a first abutting portion abutting an end surface of the inner ring in a second direction, a base abutting portion abutting a base, and a first internal thread hole in which a first fastener is threadedly engaged. The output shaft has a second main body portion in which the outer ring is fitted, a second abutting portion abutting an end surface of the outer ring in a second direction, a mounting portion of a cylindrical shape in which an end surface in the first direction protrudes in the first direction than the second restriction member, and a second internal thread hole in which a second fastener is threadedly engaged. The first restriction member is fastened to the first main body portion and abuts an end surface of the inner ring in the first direction, and the second restriction member is fastened to the second main body portion and abuts an end surface of the outer ring in the first direction.

Description

Technical Field

[0001] This disclosure relates to direct drive motors. Background Technology

[0002] A direct drive motor is an electric motor that transmits generated power directly to an object without a reduction gear. Examples of objects include worktables for holding workpieces and arms for gripping workpieces. The direct drive motor in Patent Document 1 includes: a ring-shaped base fastened to a base by fasteners; a fixed shaft fitted into the inner circumferential surface of the base; a bearing fitted into the outer circumferential side of the fixed shaft; a connecting member fitted into the outer circumferential side of the bearing; an output shaft fitted into the connecting member; and a motor section that applies torque to the output shaft.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2002-233100 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In the direct drive motor of Patent Document 1, the fixed shaft is fixed to the base by means of a base. Furthermore, the output shaft is supported on the fixed shaft by means of a connecting member. This configuration sometimes results in reduced rigidity of the supporting fixed shaft and the output shaft. Moreover, when the output shaft rotates, it is prone to radial vibration, a phenomenon known as jitter.

[0008] This disclosure is made in view of the foregoing, and its purpose is to provide a direct drive motor capable of suppressing output shaft jitter.

[0009] Solution for solving the problem

[0010] To achieve the above objectives, a direct drive motor of the present disclosure comprises: a fixed shaft, which is cylindrical; a bearing portion, the inner ring of which is fitted onto the outer circumferential surface of the fixed shaft; an output shaft, which is cylindrical, the outer ring of which is fitted onto the inner circumferential surface of the output shaft; a first limiting member, which is disposed relative to the inner ring in a first direction in an axial direction parallel to the axis of the output shaft; a second limiting member, which is disposed relative to the outer ring in the first direction; and a motor portion that applies torque to the output shaft. The fixed shaft has: a first main body portion, which is cylindrical, for fitting the inner ring; a first abutting portion, which is cylindrical, extending from the first main body portion in a second direction opposite to the first direction, and abutting against the end face of the inner ring in the second direction; a base abutting portion, which extends from the first abutting portion in the second direction, the end face of the second direction abutting against the base; and a first internal threaded hole, which is provided on the end face of the base abutting portion in the second direction, for fastening the base abutting portion and the first fastener of the base to be threadedly engaged with the first internal threaded hole. The output shaft has: a second main body portion, which is cylindrical, for fitting the outer ring; a second abutment portion, which is cylindrical, located in a second direction position relative to the second main body portion, abutting against the end face of the outer ring in the second direction; a mounting portion, which is cylindrical, extending from the outer periphery of the second main body portion in a first direction, the end face in the first direction protruding in the first direction from the second limiting member; and a second internal threaded hole, which is provided on the end face of the mounting portion in the first direction, for a second fastener used to fasten the mounting portion and an object to be threaded into the second internal threaded hole. The first limiting member is fastened to the end face of the first main body portion in the first direction and abuts against the end face of the inner ring in the first direction. The second limiting member is fastened to the end face of the second main body portion in the first direction and abuts against the end face of the outer ring in the first direction.

[0011] According to the direct drive motor of this disclosure, there are no components between the base and the fixed shaft, no components between the fixed shaft and the bearing portion, and no components between the bearing portion and the output shaft. In other words, the fixed shaft is fastened by a first fastener threaded into a first internal threaded hole. Thus, the fixed shaft is directly supported by the base. The inner ring of the bearing portion is fitted into the first main body portion of the fixed shaft. Thus, the bearing portion is directly supported by the fixed shaft. The second main body portion of the output shaft is fitted into the outer ring of the bearing portion. Thus, the output shaft is directly supported by the bearing portion. As described above, the rigidity of the output shaft support is high. Therefore, the vibration of the output shaft is suppressed when the output shaft rotates. Furthermore, if the number of components between the fixed shaft and the output shaft increases, there is a possibility that the output shaft may be eccentric relative to the fixed shaft due to the influence of assembly tolerances; in other words, there is a possibility that the workpiece cannot be transported with high precision. However, according to the direct drive motor of this disclosure, the only component between the fixed shaft and the output shaft is the bearing portion. Therefore, the influence of assembly tolerances is less, and the concentricity of the output shaft relative to the fixed shaft is higher. Thus, workpieces can be transported with high precision. Furthermore, the bearing portion abuts against the first abutment portion of the fixed shaft and is positioned axially. The second abutment portion of the output shaft abuts against the bearing portion and is positioned axially. Therefore, regarding the axial positioning of the output shaft relative to the fixed shaft, the only component between the fixed shaft and the output shaft is the bearing portion. This minimizes the influence of assembly tolerances, allowing the position (height) of the object fixed to the output shaft to be set to the desired position (height). For this reason, workpieces can be transported with high precision. In addition, the first and second limiting members abut against the inner or outer ring. This suppresses axial movement of the output shaft and changes in the position of the object.

[0012] As a desired technical solution for a direct drive motor, the motor portion includes: a rotor fitted onto the outer peripheral surface of the output shaft; and a stator surrounding the outer peripheral side of the rotor. A stator support portion is fastened to the outer peripheral side of the base abutment portion, the stator support portion extending radially outward from the base abutment portion and supporting the stator.

[0013] The stator sometimes vibrates due to the magnetic attraction and repulsion forces generated between it and the rotor. Furthermore, if the stator is supported by a fixed shaft, the stator's vibration is transmitted to the fixed shaft, potentially causing vibration on the output shaft. In the direct drive motor of this disclosure, the stator is supported by a stator support portion fastened to a fixed shaft. Therefore, if the stator vibrates, the vibration is absorbed by the stator support portion and is difficult to transmit to the fixed shaft. Thus, vibration on the output shaft due to stator vibration is avoided.

[0014] As a technical solution for a direct drive motor, the inner and outer shapes of the second main body are circular with the axis as the center.

[0015] Conventionally, to fix other components to the outer circumferential surface of the output shaft, the outer circumferential surface of the output shaft is sometimes milled. During such machining, internal stress is generated in the rotating shaft, causing deformation of the inner circumferential surface. Furthermore, if the inner circumferential surface of the rotating shaft is not circular, the clamping force acting on the outer ring due to the fit is uneven in the circumferential direction of the outer ring, becoming a cause of vibration in the output shaft. On the other hand, in the output shaft of this disclosure, the inner and outer shapes of the second main body are circular. Therefore, the clamping force acting on the outer ring due to the fit acts evenly along the circumferential direction of the outer ring. Thus, when the output shaft rotates, vibration of the output shaft is suppressed.

[0016] As a technical solution for a direct drive motor, the inner and outer shapes of the first main body are circular with the axis as the center.

[0017] The tightening force exerted on the inner ring by the first main body due to the fitting acts uniformly along the circumference of the inner ring. Therefore, the vibration of the bearing portion relative to the fixed shaft is suppressed. Furthermore, the vibration of the output shaft supported by the bearing portion is also suppressed.

[0018] As a desired technical solution for a direct drive motor, the first internal threaded hole is positioned radially inward from the rolling surface of the inner ring. The second internal threaded hole is positioned radially outward from the rolling surface of the outer ring.

[0019] If the first fastener is threaded into the first internal threaded hole, the fixed shaft deforms by increasing the diameter of the first internal threaded hole. Assuming the first internal threaded hole overlaps axially with the rolling surface of the inner ring, the rolling surface of the inner ring deforms, and the rolling elements do not rotate smoothly. However, in this disclosure, the first internal threaded hole is located radially inward of the rolling surface of the inner ring and is separated from it. Therefore, the rolling surface of the inner ring is less prone to deformation. Similarly, the second internal threaded hole is separated from the rolling surface of the outer ring. Therefore, the rolling surface of the outer ring is less prone to deformation. As described above, the rolling elements roll smoothly on the rolling surfaces, and the output shaft rotates smoothly.

[0020] The effects of the invention

[0021] According to the direct drive motor disclosed herein, the vibration of the output shaft is suppressed when the output shaft rotates, enabling stable conveying of the workpiece. Attached Figure Description

[0022] Figure 1 This is a cross-sectional view that schematically illustrates an example of the overall structure of the direct drive motor of Embodiment 1.

[0023] Figure 2 It is magnification Figure 1 A cross-sectional view of a portion of a direct-drive motor.

[0024] Figure 3This is a bottom view obtained from observing the direct drive motor of Embodiment 1 from the second direction.

[0025] Figure 4 This is a top view obtained by observing the direct drive motor of Embodiment 1 from the first direction. Detailed Implementation

[0026] The embodiments for carrying out the invention are described in detail with reference to the accompanying drawings. The invention is not limited to the contents described below. Furthermore, the constituent elements described below include elements readily conceived by those skilled in the art, as well as substantially the same elements. Moreover, the constituent elements described below can be appropriately combined.

[0027] Figure 1 This is a cross-sectional view that schematically illustrates an example of the overall structure of the direct drive motor of Embodiment 1. Figure 2 It's enlarged. Figure 1 A cross-sectional view of a portion of a direct-drive motor. Figure 3 This is a bottom view obtained from observing the direct drive motor of Embodiment 1 from the second direction. Figure 4 This is a top view obtained by observing the direct drive motor of Embodiment 1 from the first direction.

[0028] like Figure 1 As shown, the direct drive motor 100 of Embodiment 1 is an electric motor that generates power to transport a workpiece (not shown). The direct drive motor 100 of Embodiment 1 has a base 110 disposed on one side of the axis AX of the output shaft 3. The direct drive motor 100 is fixed to the base 110. Furthermore, a worktable 120 is disposed on the other side of the axis AX of the output shaft 3. The worktable 120 is mounted on the direct drive motor 100. The direct drive motor 100 causes the worktable 120 to rotate about the axis AX, thereby transporting the workpiece (not shown) placed on the worktable 120.

[0029] Furthermore, while the direct drive motor 100 of this embodiment uses a mounting table 120 as an example, the direct drive motor of this disclosure is not limited to this. For example, the direct drive motor of this disclosure can also be used as a servo motor, which serves as a drive source for driving an arm. In addition, the direct drive motor of this disclosure can also be used in inspection devices, machine tools, and semiconductor manufacturing apparatuses, etc.

[0030] The direct drive motor 100 includes a fixed shaft 1, a bearing section 2, an output shaft 3, a first limiting member 4, a second limiting member 5, a first cover member 6, a stator support member 7, a motor section 8, and a second cover member 9. In the following description, the direction parallel to the axis AX is referred to as the axial direction. Furthermore, the direction in the axial direction from the direct drive motor 100 where the worktable 120 is positioned is referred to as the first direction A1. The direction from the direct drive motor 100 where the base 110 is positioned is referred to as the second direction A2.

[0031] Fixed shaft 1 is a cylindrical component extending axially from its center. For example... Figure 2 As shown, the fixed shaft 1 includes: a first main body portion 10, on which the inner rings 25 and 26 of the bearing portion 2 are fitted on its outer peripheral surface; a first abutting portion 11 extending from the first main body portion 10 in a second direction A2; a base abutting portion 12 extending from the first abutting portion 11 in a second direction A2; and a protrusion 13 protruding from the first main body portion 10 in a first direction. In other words, the fixed shaft 1 is a component integrally formed from the first main body portion 10, the first abutting portion 11, the base abutting portion 12, and the protrusion 13. Furthermore, in Figure 2 In order to clearly identify the various parts of the first main body 10, the first abutting part 11, the base abutting part 12, and the protrusion 13, auxiliary lines (dash lines) are drawn.

[0032] The first main body 10 is cylindrical with the axis AX as its center. That is, when viewed from the axis AX direction, the outer peripheral surface 10a and inner peripheral surface 10b of the first main body 10 are circular with the axis AX as their center (see reference). Figure 3 The axial length of the first main body 10 is the same as the axial length of the bearing part 2. A plurality of internally threaded holes 10d are provided on the end face 10c of the first direction A1 of the first main body 10, arranged at equal intervals in the circumferential direction. Furthermore, the thickness from the outer circumferential surface 10a to the inner circumferential surface 10b of the first main body 10 is T1 (see reference). Figure 1 ).

[0033] The outer diameter of the first abutting portion 11 is larger than the outer diameter of the first main body portion 10. That is, the first abutting portion 11 protrudes radially outward from the outer peripheral surface 10a of the first main body portion 10. Furthermore, the end face 11a of the first abutting portion 11 in the first direction A1 abuts against the end face 26a of the inner ring 26 of the bearing portion 2 in the second direction A2.

[0034] The base abutment portion 12 includes: a large-diameter portion 14, the outer diameter of which is larger than the outer diameter of the first abutment portion 11; and a protrusion portion 15, which protrudes from the end face 14a of the large-diameter portion 14 in the second direction A2 toward the second direction A2.

[0035] The end face 14a of the large diameter portion 14 in the second direction A2 is provided with a plurality of externally threaded holes 14b and a plurality of internally threaded holes 14c. The plurality of externally threaded holes 14b are located on the outer peripheral side of the protrusion 15, and the plurality of internally threaded holes 14c are located on the inner peripheral side of the protrusion 15. Figure 3 As shown, multiple outer circumferential internal threaded holes 14b and inner circumferential internal threaded holes 14c are provided at equal intervals in the circumferential direction.

[0036] like Figure 3 As shown, the protrusion 15 is annular when viewed from the axial direction. Figure 2 As shown, the end face 15a of the protrusion 15 in the second direction A2 is a flat surface. The end face 15a of the protrusion 15 in the second direction A2 abuts against the surface (placement surface) of the base 110 facing the first direction A1.

[0037] A first internal threaded hole 15b is provided on the end face 15a in the second direction A2 of the protrusion 15. Multiple first internal threaded holes 15b are provided at equal intervals in the circumferential direction (see reference). Figure 3 Furthermore, a first fastener 201, which penetrates the base 110, is threaded into the first internal threaded hole 15b. Thus, the protrusion 15 (base abutment 12) is fastened to the base 110, and the fixing shaft 1 is fixed to the base 110.

[0038] Furthermore, the end face 15a of the protrusion 15 in the second direction A2 is located closer to the second direction A2 than the first cover member 6 and the stator support member 7. That is, the first cover member 6 and the stator support member 7 do not abut against the base 110.

[0039] like Figure 2 As shown, the protrusion 13 protrudes from the inner circumference of the end face 10c of the first main body portion 10 in the first direction A1 toward the first direction A1. The outer circumferential surface of the protrusion 13 is circular when viewed from the axial direction.

[0040] Bearing section 2 includes a first bearing 21 and a second bearing 22 disposed in a second direction A2 relative to the first bearing 21. The first bearing 21 and the second bearing 22 are back-mounted angular contact ball bearings. 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 internal threaded hole 15b of the fixed shaft 1 (see reference). Figure 2 The virtual line L). In other words, the first internal threaded hole 15b of the fixed shaft 1 is located radially inward than the rolling surfaces of the inner rings 25 and 26. That is to say, the first internal threaded hole 15b and the rolling surfaces of the inner rings 25 and 26 do not overlap axially.

[0041] The output shaft 3 is a cylindrical component. The output shaft 3 includes: a second main body 30, which is cylindrical and fits into the outer rings 23 and 24; a second abutment portion 31 extending from the second main body 30 in a second direction A2; and a mounting portion 32, which is cylindrical and extends from the outer periphery of the second main body 30 in a first direction A1. In other words, the output shaft 3 is a cylindrical component. The output shaft 3 is a component integrally formed from the second main body 30, the second abutment portion 31, and the cylindrical mounting portion 32.

[0042] The second main body 30 is cylindrical with the axis AX as its center. That is, when viewed from the axial direction, the outer peripheral surface 30a and the inner peripheral surface 30b of the second main body 30 are circular with the axis AX as their center (see reference). Figure 4 ).like Figure 2 As shown, the axial length of the second main body 30 is the same as the axial length of the bearing part 2. A plurality of internally threaded holes 30d are provided on the end face 30c in the first direction A1 of the second main body 30, arranged at equal intervals in the circumferential direction. An annular protrusion 30e protrudes radially outward from the end in the first direction A1 on the outer circumferential surface 30a of the second main body 30. This protrusion 30e serves as an axial positioning part for the rotor 81. Furthermore, the thickness from the outer circumferential surface 30a to the inner circumferential surface 30b of the second main body 30 is T2 (refer to...). Figure 1 ).

[0043] The inner diameter of the second abutment portion 31 is smaller than the inner diameter of the second main body portion 30. That is, the second abutment portion 31 protrudes radially inward from the inner circumferential surface 30b of the second main body portion 30. The end face 31a of the second abutment portion 31 in the first direction A1 abuts against the end face 24a of the outer ring 24 in the second direction A2.

[0044] like Figure 4 As shown, the mounting portion 32 is annular when viewed from the axial direction. Figure 2 As shown, the end face 32a of the mounting portion 32 in the first direction A1 is the contact surface that abuts against the worktable 120. The mounting portion 32 protrudes in the first direction A1 compared to the second limiting member 5. That is, the end face 32a of the mounting portion 32 in the first direction A1 is located closer to the second limiting member 5 in the first direction A1. The end face 32a of the mounting portion 32 is a flat surface. A second internal threaded hole 32b for threaded engagement of the second fastener 202 is provided on the end face 32a of the mounting portion 32. A plurality of second internal threaded holes 32b are provided at equal intervals in the circumferential direction. Furthermore, the second internal threaded holes 32b are arranged radially outward from the rolling surfaces of the outer rings 23 and 24, and do not overlap with the outer rings 23 and 24 in the axial direction.

[0045] For the installation of workbench 120, such as Figure 1As shown, the worktable 120 abuts against the end face 32a of the mounting portion 32 from the first direction A1. The second fastener 202 passing through the worktable 120 is threaded into the second internal threaded hole 32b. Thus, the worktable 120 is fixed to the output shaft 3.

[0046] like Figure 2 As shown, the first limiting member 4 is an annular component. The first limiting member 4 is disposed between the inner ring 25 and the first main body portion 10 in the first direction A1. The first limiting member 4 is fastened by a fastener 203. The first limiting member 4 abuts against the end face 25a of the inner ring 25 in the first direction A1. Therefore, the bearing portion 2 is restricted from moving relative to the fixed shaft 1 in the first direction A1.

[0047] Furthermore, the inner diameter of the first restricting member 4 is the same as the outer diameter of the protrusion 13. That is, the entire circumference of the inner peripheral surface 4a of the first restricting member 4 abuts against the outer peripheral surface of the protrusion 13. This prevents the first restricting member 4 from moving radially and coming into contact with the second restricting member 5.

[0048] like Figure 1 As shown, the second limiting member 5 includes: a fastened portion 50, which is fastened by a fastener 204; a covering portion 51, which extends radially inward from the fastened portion 50; and a cylindrical portion 53, which extends from the inner peripheral end of the covering portion 51 in the second direction A2.

[0049] like Figure 2 As shown, the fastened part 50 is disposed in the first direction A1 between the outer ring 23 and the second main body part 30. The fastened part 50 is fastened by the fastener 204. The fastened part 50 abuts against the end face 23a of the outer ring 23 in the first direction A1. As a result, the output shaft 3 is restricted from moving relative to the bearing part 2 in the first direction A1.

[0050] Furthermore, the outer diameter of the fastened portion 50 is the same as the inner diameter of the mounting portion 32. That is, the entire circumference of the outer peripheral surface 50a of the fastened portion 50 abuts against the inner peripheral surface of the mounting portion 32. This prevents the fastened portion 50 from contacting the first restricting member 4 due to radial movement of the second restricting member 5.

[0051] like Figure 1 As shown, the cover portion 51 extends radially inward from the fastened portion 50. The radially inner end of the cover portion 51 is located radially inward from the inner circumferential surface 10b of the first main body portion 10. The cover portion 51 covers the space between the fastened portion 50 and the first restricting member 4, the first restricting member 4, and the protrusion 13 in the first direction A1. Therefore, even if lubricating oil leaks from the bearing portion 2 into the space between the fastened portion 50 and the first restricting member 4, it will not flow out beyond the cover portion 51 in the first direction A1.

[0052] The outer peripheral surface 52a of the cylindrical portion 52 faces the 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 separated radially. As a result, an annular space S capable of accommodating sensors and the like is provided between the cylindrical portion 52 and the fixed shaft 1.

[0053] The first cover member 6 is a component disposed on the inner circumference of the protrusion 15 and closing the annular space S in the second direction A2. Specifically, the first cover member 6 is a flat plate-shaped component that is annular around the axis AX and has a thinner thickness in the axial direction. The outer circumference of the first cover member 6 overlaps with the end face 14a of the large-diameter portion 14. The outer circumference of the first cover member 6 is fastened by a fastener 205 that is threaded into the outer circumferential internal threaded hole 14b. Thus, the first cover member 6 is supported on the fixed shaft 1.

[0054] The stator support member 7 is a component disposed on the outer periphery of the protrusion 15. The stator support member 7 has an annular portion 70 and a cylindrical stator mounting portion 71 protruding from the outer periphery of the annular portion 70 in a first direction A1. The inner periphery of the annular portion 70 overlaps with the end face 14a of the large-diameter portion 14. The inner periphery of the annular portion 70 is fastened by a fastener 206 threaded into an inner threaded hole 14c. Thus, the stator support member 7 is supported on the fixed shaft 1. The stator mounting portion 71 has a plurality of internally threaded holes 72 in the circumferential direction on its end face in the first direction A1. Furthermore, the thickness from the outer periphery to the inner periphery of the stator mounting portion 71 is T3 (see reference). Figure 1 Furthermore, the axial thickness of the ring 70 is T4 (refer to...). Figure 1 ).

[0055] The motor section 8 has a stator 80 and a rotor 81. The rotor 81 has an annular core embedded in the outer peripheral surface of the second main body section 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 has a cylindrical retainer 82, a plurality of cores 83 arranged at equal intervals in the circumferential direction along the inner peripheral surface of the retainer 82, a bobbin 84 supported on each core 83, and a coil 85 formed by winding multiple layers of wire on the bobbin 84.

[0056] The retainer 82 is disposed on the stator mounting portion 71 in the first direction A1. The retainer 82 has a plurality of holes 82a extending axially. Furthermore, the shaft portion of the fastener 207 passes through the holes 82a of the retainer 82 and is threaded into the internal threaded hole 72 of the stator mounting portion 71 (see reference). Figure 1 (See the diagram on the left side of the axis AX). Thus, the stator 80 is supported on the stator support member 7. Furthermore, a portion of the internal threaded hole 72 of the stator mounting portion 71 and a portion of the plurality of holes 82a of the retaining member 82 are used to fasten the second cover member 9 with fasteners 208 (see reference). Figure 1 (The diagram is on the right side of the midline AX).

[0057] The second cover member 9 is an annular component. The cross-sectional shape obtained by cutting the second cover member 9 radially outward from the axis AX is approximately L-shaped, covering the first direction A1 of the stator 80 and the outer periphery of the stator 80. The second cover member 9 is fastened by fasteners 208 and supported by the stator support member 7. Furthermore, a spacer 90 is sandwiched between the second cover member 9 and the retainer 82.

[0058] Next, the effects of the direct drive motor 100 of Embodiment 1 will be explained. In the direct drive motor 100 of Embodiment 1, there are no components between the base 110 and the fixed shaft 1, between the fixed shaft 1 and the bearing portion 2, or between the bearing portion 2 and the output shaft 3. That is, the protrusion 15 (base abutment portion 12) of the fixed shaft 1 and the base 110 are fastened by the first fastener 201. 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 on the base 110. Furthermore, the inner rings 25 and 26 of the bearing portion 2 are fitted into the first main body portion 10 of the fixed shaft 1. Thus, the bearing portion 2 is directly supported on the fixed shaft 1. Furthermore, the second main body portion 30 of the output shaft 3 is fitted into the outer rings 23 and 24 of the bearing portion 2. Thus, the output shaft 3 is directly supported on the bearing portion 2. As described above, the rigidity of the output shaft 3 is high. Therefore, when the output shaft 3 rotates, the vibration of the output shaft 3 is suppressed. Furthermore, the worktable 120 is fastened to the output shaft 3 by the second fastener 202. Thus, the output shaft 3 directly supports the worktable 120. As described above, the rigidity of the support for the worktable 120 is high. Therefore, when driven by the direct drive motor 100, the vibration of the worktable 120 is suppressed.

[0059] Furthermore, the stator 80 may vibrate due to the magnetic attraction and repulsion forces generated between it and the rotor 81. If the fixed shaft 1 directly supports the stator 80, the vibration of the stator 80 would be transmitted to the fixed shaft 1, potentially causing vibration on the output shaft 3. However, in Embodiment 1, the stator 80 is indirectly supported on the fixed shaft 1 by means of the stator support member 7. Therefore, the vibration of the stator 80 is absorbed by the stator support member 7 and is less likely to be transmitted to the fixed shaft 1. As described above, vibration on the output shaft 3 due to the vibration of the stator 80 can be suppressed.

[0060] Conventionally, in order to fix other components to the outer peripheral surface of the output shaft 3, machining such as milling is sometimes performed to cut the outer peripheral surface of the output shaft 3 into a D-shape. During such machining, internal stress is generated in the output shaft 3, causing deformation of the inner peripheral surface. If the inner peripheral surface of the output shaft 3 is not circular, the clamping force of the output shaft 3 is uneven in the circumferential direction, causing vibration. On the other hand, in Embodiment 1, the outer peripheral surface 30a and the inner peripheral surface 30b of the second main body 30 are circular when viewed from the axial direction. That is, the outer peripheral surface 30a of the second main body 30 is not machined, and the clamping force of the inner peripheral surface 30b of the second main body 30 acts uniformly in the circumferential direction. Therefore, when the output shaft 3 rotates, vibration of the output shaft 3 is suppressed.

[0061] Furthermore, the outer peripheral surface 10a and inner peripheral surface 10b of the first main body 10 in Embodiment 1 are circular when viewed from the axial direction. Therefore, no milling or other machining is performed on the first main body 10, and there is no internal stress. The fastening force on the outer peripheral surface 10a of the first main body 10 acts uniformly in the circumferential direction. As a result, the vibration of the bearing portion 2 relative to the fixed shaft 1 is suppressed, and consequently, the vibration of the output shaft 3 supported by the bearing portion 2 is suppressed.

[0062] Furthermore, the only component between the fixed shaft 1 and the output shaft 3 is the bearing section 2. If the number of components between the fixed shaft 1 and the output shaft 3 increases, the output shaft 3 may sometimes be eccentric relative to the fixed shaft 1 due to assembly tolerances. In other words, according to the direct drive motor 100 of Embodiment 1, the influence of assembly tolerances is less, and the concentricity of the output shaft 3 relative to the fixed shaft 1 is higher. Therefore, workpieces can be transported with high precision.

[0063] Furthermore, the bearing portion 2 abuts against the end face 11a of the first abutment portion 11 of the fixed shaft 1, thereby positioning the bearing portion 2 axially. The end face 31a of the second abutment portion 31 of the output shaft 3 abuts against the bearing portion 2, thereby positioning the output shaft 3 axially. Thus, the only component related to the axial positioning of the output shaft 3 relative to the fixed shaft 1 and located between the fixed shaft 1 and the output shaft 3 is the bearing portion 2. Therefore, the influence of assembly tolerances is minimal. Consequently, the end face 32a of the mounting portion 32 of the output shaft 3 is positioned at the desired height, enabling high-precision workpiece transport. Furthermore, no other components are clamped between the base 110 and the fixed shaft 1, nor between the output shaft 3 and the worktable 120. For this reason, the influence of assembly tolerances is minimal, enabling high-precision workpiece transport.

[0064] Furthermore, if the fastener is threaded into the internal threaded hole, the hole will deform by increasing its diameter. Assuming the first internal threaded hole 15b overlaps axially with the rolling surfaces of the inner rings 25 and 26, the first internal threaded hole 15b and the inner rings 25 and 26 will become closer together. Consequently, by threading the first fastener 201 into the first internal threaded hole 15b, the rolling surfaces of the inner rings 25 and 26 deform, potentially causing the rolling elements 27 and 28 to rotate unevenly. However, in Embodiment 1, the first internal threaded hole 15b of the fixed shaft 1 is positioned radially inward of the rolling surfaces of the inner rings 25 and 26, and is separated from them. Therefore, the rolling surfaces of the inner rings 25 and 26 do not deform. Similarly, the second internal threaded hole 32b is positioned radially outward from the rolling surfaces of the outer rings 23 and 24, and is separated from the rolling surfaces of the inner rings 25 and 26. Therefore, the rolling surfaces of the inner rings 25 and 26 do not deform. As described above, the rolling elements 27 and 28 roll smoothly, and the output shaft 3 rotates smoothly.

[0065] The radial thickness T1 of the first main body 10, the radial thickness T2 of the second main body 20, the axial thickness T3 of the ring 70, and the radial thickness T4 of the stator mounting portion 71 are in the order of T1 > T2 > T4 > T3. Furthermore, the radial thickness T1 of the first main body 10 is greater than the radial length (thickness) of the bearing portion 2. Therefore, the rigidity of the first main body 10 is increased. As a result, the rigidity of the output shaft 3 is higher, and vibration of the output shaft 3 is suppressed. Furthermore, although the first fastener 201 and the like are threaded into the fixed shaft 1 having the first main body 10, deformation of the fixed shaft 1 is suppressed. Similarly, the radial thickness T2 of the second main body 20 is greater than the radial length (thickness) of the bearing portion 2. Therefore, although the fastener 204 and the like are threaded into the output shaft 3 having the second main body 30, deformation of the output shaft 3 is suppressed. Furthermore, the thickness T3 of the second main body 30 is greater than that of the ring portion 70 and the thickness T4 of the stator mounting portion 71. Therefore, when the direct drive motor 100 is in operation, although there are magnetic attraction and repulsion forces acting between the stator 80 and the rotor 81, the second main body 20 is less prone to deformation, and the output shaft 3 rotates smoothly. Alternatively, in this disclosure, T2 ≥ T4. This also prevents the ring portion 70 from flexing and the second main body 20 from deforming under the influence of the magnetic force acting between the stator 80 and the rotor 81.

[0066] The direct drive motor 100 of Embodiment 1 includes: a fixed shaft 1, which is cylindrical; a bearing portion 2, whose inner rings 25 and 26 are fitted onto the outer peripheral surface of the fixed shaft 1; an output shaft 3, which is cylindrical, and the outer rings 23 and 24 of the bearing portion 2 are fitted onto the inner peripheral surface of the output shaft 3; a first limiting member 4, which is disposed relative to the inner rings 25 and 26 in a first direction A1 in an axial direction parallel to the axis AX of the output shaft 3; a second limiting member 5, which is disposed relative to the outer rings 23 and 24 in the first direction A1; and a motor portion 8, which applies torque to the output shaft 3. The fixed shaft 1 has: a first main body 10, which is cylindrical and fits into the inner rings 25 and 26; a first abutting part 11, which is cylindrical and extends from the first main body 10 toward a second direction A2 opposite to the first direction A1, and abuts against the end face 26a of the inner ring 26 in the second direction A2; a base abutting part 12, which extends from the first abutting part 11 toward the second direction A2, and the end face 15a of the second direction A2 abuts against the base 110; and a first internal threaded hole 15b, which is provided on the end face 15a of the base abutting part 12 in the second direction A2, for fastening the base abutting part 12 and the base 110 with a first fastener 201 threadedly engaged with the first internal threaded hole 15b. The output shaft 3 includes: a second main body 30, which is cylindrical and fits into the outer rings 23 and 24; a second abutting part 31, which is cylindrical and located further in the second direction A2 than the second main body 30, abutting against the end face 24a of the outer ring 24 in the second direction A2; a mounting part 32, which is cylindrical and extends from the outer periphery of the second main body 30 in the first direction A1, with the end face 32a in the first direction A1 protruding beyond the second limiting member 5 in the first direction A1; and a second internal threaded hole 32b, which is provided on the end face 32a of the mounting part 32 in the first direction A1, and a second fastener 202 for fastening the mounting part 32 and the object (worktable 120) is threaded into the second internal threaded hole 32b. The first limiting member 4 is fastened to the end face 10c of the first main body 10 in the first direction A1 and abuts against the end face 25a of the inner ring 25 in the first direction A1. The second limiting member 5 is fastened to the end face 30c of the second main body 30 in the first direction A1 and abuts against the end face 23a of the outer ring 23 in the first direction A1.

[0067] According to this direct drive motor 100, the rigidity of the output shaft 3 is high, which can suppress the vibration of the output shaft 3. The only component between the fixed shaft 1 and the output shaft 3 is the bearing part 2, so the influence of assembly tolerances is minimal. As a result, the concentricity of the output shaft 3 with respect to the fixed shaft 1 is high. Moreover, the end face 32a of the mounting part 32 of the output shaft 3 is at the desired position (height). As a result, the workpiece can be transported with high precision.

[0068] Furthermore, the motor section 8 of the direct drive motor 100 in Embodiment 1 has a rotor 81 that fits into 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, which 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.

[0069] With this direct drive motor 100, vibrations of the stator 80 are difficult to transmit to the fixed shaft 1. As a result, vibrations of the output shaft 3 can be suppressed.

[0070] Furthermore, in the direct drive motor 100 of Embodiment 1, the inner and outer shapes of the second main body 30 are circular with the axis AX as the center.

[0071] According to this direct drive motor 100, the clamping force of the inner circumferential surface 30b of the second main body 30 relative to the bearing 2 acts uniformly in the circumferential direction. As a result, the vibration of the output shaft 3 can be suppressed.

[0072] Furthermore, in the direct drive motor 100 of Embodiment 1, the inner and outer shapes of the first main body 10 are circular with the axis AX as the center.

[0073] According to this direct drive motor 100, the clamping force of the outer peripheral surface 10a of the first main body 10 relative to the bearing 2 acts uniformly in the circumferential direction. As a result, the vibration of the output shaft 3 can be suppressed.

[0074] Furthermore, in the direct drive motor 100 of Embodiment 1, the first internal threaded hole 15b is positioned radially inward from the rolling surfaces of the inner rings 25 and 26. The second internal threaded hole 32b is positioned radially outward from the rolling surfaces of the outer rings 23 and 24.

[0075] According to this direct drive motor 100, deformation of the rolling surfaces of the inner rings 25 and 26 and the outer rings 23 and 24 is suppressed. As a result, the rolling elements 27 and 28 rotate smoothly, and the output shaft 3 also rotates smoothly.

[0076] The direct drive motor 100 of Embodiment 1 has been described above, but the direct drive motor disclosed herein is not limited to this. For example, although the bearing section 2 has two bearings, it may also be composed of one or more bearings.

[0077] Explanation of reference numerals in the attached figures

[0078] 100. Direct drive motor; 1. Fixed shaft; 2. Bearing part; 3. Output shaft; 4. First limiting member; 5. Second limiting member; 6. First cover member; 7. Stator support member; 8. Motor part; 9. Second cover member; 10. First main body part; 11. First abutting part; 12. Base abutting part; 13. Protrusion; 14. Large diameter part; 15. Protrusion; 15b. First internal threaded hole; 30. Second main body part; 31. Second abutting part; 32. Mounting part; 32b. Second internal threaded hole; 110. Base; 120. Worktable.

Claims

1. A direct drive motor, wherein, This direct drive motor has the following features: A fixed shaft, which is cylindrical; The bearing portion has its inner ring fitted onto the outer circumferential surface of the fixed shaft; The output shaft is cylindrical, and the outer ring of the bearing portion is fitted into the inner circumferential surface of the output shaft; The first limiting member is disposed relative to the inner ring in a first direction in an axial direction parallel to the axis of the output shaft; A second limiting member, which is disposed relative to the outer ring in the first direction; and The motor section applies torque to the output shaft. The fixed shaft has: The first main body is cylindrical and is fitted into the inner ring; The first abutting part is cylindrical and extends from the first main body part in a second direction opposite to the first direction, and abuts against the end face of the inner ring in the second direction; A base abutment portion extends from the first abutment portion in the second direction, and the end face in the second direction abuts against the base; as well as A first internal threaded hole is provided on the end face of the base abutment portion in the second direction, for fastening the base abutment portion and the first fastener of the base to be threadedly engaged with the first internal threaded hole. The output shaft has: The second main body is cylindrical and is fitted into the outer ring; The second abutting part is cylindrical and located in the second direction, closer to the second main body part, and abuts against the end face of the outer ring in the second direction. The mounting part is cylindrical and extends from the outer periphery of the second main body in the first direction, and the end face in the first direction protrudes in the first direction more than the second limiting member; as well as A second internal threaded hole is provided on the end face of the mounting part in the first direction, and a second fastener for fastening the mounting part and the object is threaded into the second internal threaded hole. The first limiting member is fastened to the end face of the first main body in the first direction and abuts against the end face of the inner ring in the first direction. The second limiting member is fastened to the end face of the second main body in the first direction and abuts against the end face of the outer ring in the first direction.

2. The direct drive motor according to claim 1, wherein, The motor unit has: A rotor, which fits into the outer circumferential surface of the output shaft; and The stator, which surrounds the outer periphery of the rotor, A stator support portion is fastened to the outer periphery of the base abutment portion, the stator support portion extending radially outward from the base abutment portion and supporting the stator.

3. The direct drive motor according to claim 1 or 2, wherein, The inner and outer shapes of the output shaft are circular with the axis as the center.

4. The direct drive motor according to claim 1 or 2, wherein, The inner and outer shapes of the fixed shaft are circular with the axis as the center.

5. The direct drive motor according to claim 3, wherein, The inner and outer shapes of the fixed shaft are circular with the axis as the center.

6. The direct drive motor according to claim 1 or 2, wherein, The first internal threaded hole is located radially inward from the rolling surface of the inner ring. The second internal threaded hole is located radially outward from the rolling surface of the outer ring.

7. The direct drive motor according to claim 3, wherein, The first internal threaded hole is located radially inward from the rolling surface of the inner ring. The second internal threaded hole is located radially outward from the rolling surface of the outer ring.

8. The direct drive motor according to claim 4, wherein, The first internal threaded hole is located radially inward from the rolling surface of the inner ring. The second internal threaded hole is located radially outward from the rolling surface of the outer ring.

9. The direct drive motor according to claim 5, wherein, The first internal threaded hole is located radially inward from the rolling surface of the inner ring. The second internal threaded hole is located radially outward from the rolling surface of the outer ring.

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