Motor frame and motor device

Abstract

For the motor frame, the motor frame can be easily installed on an external component, and the influence caused by non-uniformity in the circumferential direction can be restrained. The motor frame (3) is provided with a cylindrical body (30) penetrating in the direction in which the axis of the rotating shaft of the motor embedded therein extends. The cylindrical body (30) has four outer wall surfaces (4), an inner wall surface (5), and four connection parts (6). The inner wall surface (5) surrounds the rotating shaft and has a cylindrical inner surface shape along the rotating shaft. The four connecting parts (6) are respectively located at four boundaries formed by adjacent outer wall surfaces (4) among the four outer wall surfaces (4). Each of the four connecting parts (6) has a stress relaxation groove (7) recessed toward the axis at the boundary between two adjacent outer wall surfaces (4). At least one of the connecting sections (6) has a stress relaxation groove (7) in a portion in the direction in which the axial center extends, and has a wall section (8) not having the stress relaxation groove (7) in another portion in the direction in which the axial center extends.

Description

Technical Field

[0001] The present invention relates to a motor frame and a motor device. More specifically, the present invention relates to a motor frame having a cylindrical body having four planar outer wall surfaces and an inner wall surface in the shape of a cylindrical inner surface, and a motor device having the motor frame. Background Art

[0002] Patent Document 1 discloses a permanent magnet motor including a stator core, a cylindrical frame, a plurality of spacers, and a rotor core.

[0003] The stator core is composed of a magnetic body formed into a cylindrical shape, windings are implemented in a plurality of slots, and a plurality of first axial slots are formed at equal intervals in the circumferential direction on the outer periphery. A circular hole is formed in the cylindrical frame, the inner diameter of the circular hole is larger than the outer diameter of the stator core, the circular hole is provided for the stator core, and a plurality of second axial slots are formed at positions of the circular hole opposite to the first axial slots. A plurality of spacers are interference-fitted with the plurality of first and second axial slots, and the stator core is fixed to the frame in a manner that there is a gap between the frame and the stator core. The rotor core is rotatably supported on the frame and arranged in the stator core, and a plurality of permanent magnets are provided on the outer periphery of the rotor core. The rotor core is composed of a magnetic body formed into a cylindrical shape.

[0004] The stator core is not fixed to a frame having a wall thickness greatly fluctuating in the circumferential direction by shrink fitting, but is fixed to the frame with a gap between the inner periphery of the frame and the outer periphery of the stator core and via a plurality of spacers of the same shape arranged at equal intervals in the circumferential direction.

[0005] According to the permanent magnet motor described in Patent Document 1, even if the circumferential wall thickness of the frame fluctuates greatly, the stator core is subjected to uniform pressing pressure from multiple spacers of the same shape arranged at equal intervals in the circumferential direction. Therefore, the stress generated in the stator core will not be different, the magnetic circuit of the stator core will not be distorted, and the tooth torque will not be deteriorated.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2005-269803 Summary of the invention

[0009] However, the frame described in Patent Document 1 is difficult to attach to an external member because its outer shape is formed in a rectangular shape.

[0010] An object of the present invention is to provide a motor frame that is easily mounted on an external member and that is easy to suppress the influence of uneven thickness in the circumferential direction, and a motor device including the motor frame.

[0011] A motor frame of one form of the present invention has a cylindrical body that passes through in the direction in which the axis of the rotating shaft of the motor embedded inside extends. The cylindrical body has four outer wall surfaces, an inner wall surface, and four connecting parts. The four outer wall surfaces are arranged in a manner to surround the rotating shaft and each has a planar shape along the rotating shaft. The inner wall surface surrounds the rotating shaft and has a cylindrical inner surface shape along the rotating shaft. The four connecting parts are respectively located at each of the four boundaries formed by adjacent outer wall surfaces among the four outer wall surfaces. The four connecting parts respectively have stress relief grooves that are recessed toward the axis at the boundaries of the outer wall surfaces on two adjacent sides. At least one of the connecting parts has the stress relief groove in a portion of the direction extending along the axis, and has a wall portion in the other portion of the direction extending along the axis, and the stress relief groove is not formed on the wall portion.

[0012] A motor device according to one aspect of the present invention includes: the motor frame; and the motor embedded in the cylindrical body of the motor frame.

[0013] The motor frame and the motor device of the present invention are easy to attach to the external member, and the influence of the uneven thickness of the motor frame in the circumferential direction can be easily suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is an exploded perspective view of the motor device according to the first embodiment of the present invention.

[0015] Figure 2 It is a front view of the motor device according to the first embodiment of the present invention.

[0016] Figure 3 It is a perspective view of a motor frame included in the motor device according to the first embodiment of the present invention.

[0017] Figure 4 It is a side view of the motor frame according to the first embodiment of the present invention.

[0018] Figure 5 It is a plan view of the motor frame according to the first embodiment of the present invention.

[0019] Figure 6 1 is a graph showing the relationship between the angle θ and the thickness t of the motor frame according to the first embodiment of the present invention.

[0020] Figure 7 This is a graph showing the shape of the inner diameter of the stator core of the motor according to the first embodiment of the present invention.

[0021] Figure 8 This is a graph showing the shape of the inner diameter of the stator core when the motor of the comparative example is inserted into the motor frame.

[0022] Fig. 9 This is a graph showing the relationship between each order when Fourier series expansion is performed on the thickness function of the motor frame according to the first embodiment of the present invention and the amplitude at the order.

[0023] Fig.10 It is an exploded perspective view of a motor device according to a second embodiment of the present invention.

[0024] Fig.11 It is a front view of a motor device according to a second embodiment of the present invention.

[0025] Fig.12 It is a perspective view of a motor frame included in a motor device according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0026] (1) Summary

[0027] The motor frame and the motor device of the present invention are described below. The embodiments described below are only a part of various embodiments of the present invention, and various changes can be made to the following embodiments according to design etc. as long as the purpose of the present invention can be achieved.

[0028] Figure 1 It is an exploded perspective view of the motor device 1 according to the first embodiment of the present invention. Figure 2 It is a front view of the motor device 1. Figure 3 FIG. 1 is a perspective view of a motor frame 3 included in the motor device 1. Figure 1 As shown in FIG. 2 , the motor frame 3 of the present invention includes a cylindrical body 30 that penetrates in the direction in which the axis 20 of the rotating shaft 23 of the motor 2 embedded therein extends. Figure 2 , Figure 3 As shown, the cylindrical body 30 has four outer wall surfaces 4, an inner wall surface 5, and four connecting portions 6. The four outer wall surfaces 4 are arranged in a manner to surround the rotation axis 23 and are respectively in a planar shape along the rotation axis 23. The inner wall surface 5 surrounds the rotation axis 23 and is in the shape of a cylindrical inner surface along the rotation axis 23. The four connecting portions 6 are respectively located between adjacent outer wall surfaces 4 among the four outer wall surfaces 4. The four connecting portions 6 respectively have a stress relief groove 7 that is recessed toward the axis 20 at the boundary between the two adjacent outer wall surfaces 4. At least one connecting portion 6 has a stress relief groove 7 in a portion in the direction in which the axis 20 extends and has a wall portion 8 in which the stress relief groove 7 is not formed in the other portion in the direction in which the axis 20 extends.

[0029] The motor device 1 of the present invention includes: a motor frame 3 ; and a motor 2 embedded in a cylindrical body 30 of the motor frame 3 .

[0030] The motor frame 3 and the motor device 1 of the present invention can make the stress distribution applied to the stator 21 uniform by alleviating the unevenness of the wall thickness distribution of the cylindrical body 30, so that the shape of the stator 21 is close to a perfect circle, and the cogging torque generated in the motor 2 can be easily reduced. In addition, since the wall portion 8 is formed, it is easy to install the cylindrical body 30 on an external component.

[0031] (2) First Embodiment

[0032] The following is based on Figures 1 to 9 The motor frame 3 and the motor device 1 according to the first embodiment will be described.

[0033] (2.1) Overview of motor device

[0034] Figure 1 1 is an exploded perspective view of the motor device 1 according to the first embodiment of the present invention. Figure 2 FIG. 1 is a front view of a motor device 1 according to a first embodiment of the present invention. Figure 1 As shown, the motor device 1 includes a motor (electric motor) 2 and a motor frame 3 in which the motor 2 is embedded. The motor 2 is a so-called servo motor. The motor device 1 also includes a position detector 121, a bracket 12, a detector cover 13, and a seal 122. The position detector 121 is a so-called rotary encoder. The position detector 121 converts the displacement of the rotor of the motor 2 rotating around the axis into a digital quantity.

[0035] The bracket 12 is a member for mounting the position detector 121 on the motor frame 3. The bracket 12 is a plate-shaped member having an opening inside. The position detector 121 is mounted on the bracket 12 by an appropriate mounting method such as screwing. The bracket 12 with the position detector 121 mounted thereon is mounted on the motor frame 3 by an appropriate mounting method such as screwing. The seal 122 is interposed between the bracket 12 and the motor frame 3. That is, the bracket 12 is mounted on the motor frame 3 via the seal 122.

[0036] The detector cover 13 includes a frame portion 131 and a lid portion 132. The lid portion 132 is attached to the frame portion 131 by an appropriate attachment method such as screwing. The frame portion 131 is attached to the motor frame 3 by an appropriate attachment method such as screwing.

[0037] (2.2) Motor

[0038] The motor 2 has a stator 21, a rotor 22, and a rotating shaft 23. The stator 21 is inserted into the motor frame 3 by shrink fitting. The stator 21 generates a magnetic force for rotating the rotor 22. The stator 21 has a stator core and a winding coil.

[0039] The rotor 22 is arranged in the motor frame 3 (stator 21) so as to be rotatable relative to the stator 21. The motor 2 is an inner rotor type motor in which the rotor 22 is arranged inside the stator 21. The rotor 22 is surrounded by the stator core and rotates under the action of the magnetic force generated by the stator core. The rotor 22 is repeatedly arranged with a plurality of N poles and S poles of magnets along the rotation direction. The rotor 22 is a surface magnet type rotor in which a permanent magnet is mounted on the surface of the rotor core.

[0040] The rotating shaft 23 is a shaft fixed to the center of the rotor 22. The rotor 22 and the rotating shaft 23 rotate with the axis 20 of the rotating shaft 23 as the rotation center. The rotating shaft 23 is formed of metal and extends in two directions along the direction of the axis 20 of the rotor 22. The rotating shaft 23 is fixed to the rotor 22 by being fitted into an opening formed in the center of the rotor 22 by shrink fitting.

[0041] The rotating shaft 23 is rotatably supported by the first bearing and the second bearing on the stator 21. The motor 2 also has a first bearing and a second bearing. The first bearing and the second bearing are rolling bearings that rotatably support the rotating shaft 23. The first bearing is embedded in the motor frame 3 and mounted on the motor frame 3. The second bearing is mounted on the bracket 12 by an appropriate mounting method such as screw fixing.

[0042] (2.3) Motor frame

[0043] (2.3.1)Tubular body

[0044] Figure 3 It is a perspective view of the motor frame 3 included in the motor device according to the first embodiment of the present invention.

[0045] Figure 4 It is a side view of the motor frame 3 according to the first embodiment of the present invention. Figure 5 It is a plan view of the motor frame 3 according to the first embodiment of the present invention.

[0046] like Figure 1 to Figure 5 As shown, the motor frame 3 is mounted with the motor 2 and holds the motor 2. The motor frame 3 includes a cylindrical body 30. The cylindrical body 30 has the motor 2 embedded therein. The cylindrical body 30 is in the shape of a cylinder that penetrates in the direction in which the axis 20 of the rotating shaft 23 of the motor 2 extends.

[0047] (2.3.2) End face

[0048] The cylindrical body 30 has two end faces (a first end face 31 and a second end face 32), four outer wall faces 4 (a first outer wall face 41, a second outer wall face 42, a third outer wall face 43, and a fourth outer wall face 44), an inner wall face 5, and four connecting portions 6 (a first connecting portion 61, a second connecting portion 62, a third connecting portion 63, and a fourth connecting portion 64). Figure 1As shown in the figure, the front-back direction and the left-right direction are defined for convenience of explanation. The direction in which the axis 20 of the rotating shaft 23 extends is set as the front-back direction, one of which is set as the front, and the other is set as the rear. In addition, the left and right when viewing the rear from the front are respectively set as the left and right.

[0049] like Figure 1 and Figure 2 As shown, the cylindrical body 30 has a first end face 31 at the front and a second end face 32 at the rear. The outer periphery of the first end face 31 is roughly quadrilateral, more specifically rectangular, and more specifically square. The inner periphery of the first end face 31 is circular. The normal line of the first end face 31 faces forward.

[0050] The outer periphery of the second end surface 32 is substantially quadrilateral, more specifically rectangular, and more specifically square. The inner periphery of the second end surface 32 is circular. The normal line of the second end surface 32 faces rearward.

[0051] The outer periphery of the first end surface 31 and the outer periphery of the second end surface 32 are substantially the same size when viewed in the direction in which the axis 20 extends. The cylindrical body 30 is square in shape when viewed in the direction in which the axis 20 extends.

[0052] The inner circumference of the first end face 31 is larger than the inner circumference of the second end face 32 when viewed in the direction extending along the axis 20. The inner circumference of the first end face 31 is substantially the same size as the outer circumference of the stator 21 of the motor 2, but the inner circumference of the second end face 32 is smaller than the outer circumference of the stator 21 of the motor 2. The stator 21 can be inserted into the interior of the cylindrical body 30 from the first end face 31, but cannot be inserted from the second end face 32.

[0053] (2.3.3)Outer wall surface

[0054] like Figure 2 As shown, the four outer wall surfaces 4 are arranged in a manner to surround the rotation axis 23 and are respectively in a planar shape along the rotation axis 23. For the sake of convenience, among the four outer wall surfaces 4, the outer wall surface 4 with a normal line facing the right is set as the first outer wall surface 41, the outer wall surface 4 with a normal line facing upward is set as the second outer wall surface 42, the outer wall surface 4 with a normal line facing the left is set as the third outer wall surface 43, and the outer wall surface 4 with a normal line facing downward is set as the fourth outer wall surface 44. The first outer wall surface 41 to the fourth outer wall surface 44 are respectively composed of planes. In addition, the first outer wall surface 41 to the fourth outer wall surface 44 may also have a portion that does not constitute a plane.

[0055] The first to fourth outer wall surfaces 41 to 44 are generally rectangular in shape when viewed from the front. That is, the first outer wall surface 41 is generally rectangular in shape when viewed from the right, the second outer wall surface 42 is generally rectangular in shape when viewed from the top, the third outer wall surface 43 is generally rectangular in shape when viewed from the left, and the fourth outer wall surface 44 is generally rectangular in shape when viewed from the bottom. The cylindrical body 30 is generally rectangular in shape when viewed from the left, the top, the left, and the bottom.

[0056] In the cylindrical body 30, a through hole 33 is formed on one outer wall surface 4 (for example, the second outer wall surface 42) and penetrates in the inner and outer directions orthogonal to the front-back direction. The wiring connected to the motor 2 embedded in the cylindrical body 30 can be passed through the through hole 33 from the outside of the cylindrical body 30.

[0057] (2.3.4)Inner wall surface

[0058] like Figure 2 and Figure 3 As shown, the inner wall surface 5 surrounds the rotation axis 23 and is in the shape of a cylindrical inner surface along the rotation axis 23. In addition, Figure 3 Only the motor frame 3 is shown. The stator 21 of the motor 2 is embedded in the inner wall surface 5 .

[0059] (2.3.5) Connection

[0060] like Figure 2 As shown, the four connection parts 6 are respectively located between adjacent outer wall surfaces among the four outer wall surfaces 4. For the convenience of explanation, among the four connection parts 6, the connection part 6 between the first outer wall surface 41 and the second outer wall surface 42 is set as the first connection part 61, the connection part 6 between the second outer wall surface 42 and the third outer wall surface 43 is set as the second connection part 62, the connection part 6 between the third outer wall surface 43 and the fourth outer wall surface 44 is set as the third connection part 63, and the connection part 6 between the fourth outer wall surface 44 and the first outer wall surface 41 is set as the fourth connection part 64.

[0061] (2.3.6) Stress relief groove

[0062] Each of the four connecting portions 6 has a stress relief groove 7 that is recessed toward the axis 20 at the boundary between the two adjacent outer wall surfaces 4. To further explain, in each connecting portion 6, a stress relief groove 7 is formed that is recessed inward (toward the axis 20) relative to an imaginary extension of a plane constituting the outer wall surface 4, and the outer wall surface 4 is the outer wall surface 4 that is adjacent in both directions of the connecting portion 6. The stress relief groove 7 is a groove that extends in the direction in which the axis 20 extends, and is open at least in the normal direction of the adjacent outer wall surface 4. In addition, the stress relief groove 7 may also be open in the direction in which the axis 20 extends.

[0063] Each of the four connection portions 6 has a stress relief groove 7 over the entire length of the portion where the contact portion is located in the front-rear direction. In the first embodiment, the embedded stator 21 contacts the portion of the inner wall surface 5 where the step portion 51 is formed over the entire length in the front-rear direction.

[0064] (2.3.7) Wall

[0065] like Figure 3 As shown, at least one connection portion 6 has a wall portion 8. The wall portion 8 is a portion of the connection portion 6 where the stress relief groove 7 is not formed. One connection portion 6 having the wall portion 8 has the stress relief groove 7 in a portion in the direction in which the axis 20 extends, and the wall portion 8 is formed in the other portion in the direction in which the axis 20 extends. In the first embodiment, the stress relief groove 7 and the wall portion 8 are formed in all of the first connection portion 61 to the fourth connection portion 64.

[0066] As the wall portion 8, a first wall portion 81 is formed at the front end portion of the connection portion 6 (cylindrical body 30), and a second wall portion 82 is formed at the rear end portion of the connection portion 6. The first wall portion 81 is not formed in the first connection portion 61 and the third connection portion 63, and only the second wall portion 82 is formed. Therefore, the stress relief groove 7 formed in the first connection portion 61 and the third connection portion 63 is not open to the rear but is open to the front. In addition, both the first wall portion 81 and the second wall portion 82 are formed in the second connection portion 62 and the fourth connection portion 64. Therefore, the stress relief groove 7 formed in the second connection portion 62 and the fourth connection portion 64 is not open to the front and rear.

[0067] (3) Thickness of the cylindrical body

[0068] The thickness of the cylindrical body 30 will be described. First, the thickness of the cylindrical body 30 in the inner and outer directions perpendicular to the front-back direction is defined as the wall thickness t (mm). Figure 2 In the embodiment, the angle of any point of the cylindrical body 30 around the axis 20 relative to the reference line 10 when viewed from the front-back direction is set to angle θ (rad). In addition, the units of thickness t and angle θ are for convenience of description, and the unit of thickness t may not be (mm), and the unit of angle θ may not be (rad).

[0069] Next, let the thickness function be t=f(θ). The t-θ relationship diagram in the first embodiment is shown in Figure 6 In addition, Figure 6 In the figure, the thickness t is the thickness of the portion in contact with the stator 21 embedded inside, at the center portion in the direction in which the axis 20 extends. The angle θ is represented by (°). The cylindrical body 30 has stress relief grooves 7 formed in all of the first connecting portion 61 to the fourth connecting portion 64, so that Figure 6The change in the shape of the inner diameter of the stator core 21 when the motor 2 is embedded in the cylindrical body 30 is shown in FIG. Figure 7 In other words, Figure 7 : is a diagram showing the shape of the inner diameter of the stator core 21 of the motor 2 according to the first embodiment of the present invention. Figure 7 The graph shown shows the angle θ of any point of the cylindrical body 30 relative to the reference line 10 around the axis 20 and the change in the inner diameter of the stator core 21 before and after the motor 2 is embedded at the position of the angle θ. Figure 7 The range indicated by the dot pattern in is the range within which the shape formed by the relationship line between the change in the inner diameter of the stator core 21 and θ can be allowed to be a circle. Figure 7 The circle C indicating 0 located in the center of the dot pattern in FIG. 1 represents the shape of the inner diameter of the stator core 21 before the motor 2 is inserted into the cylindrical body 30. Figure 7 In the graph shown, the closer the shape formed by the line representing the inner diameter of the stator core 21 after the motor 2 is embedded is to a perfect circle, the more the cogging torque generated in the motor 2 can be suppressed. Figure 7 As can be seen from the graph shown, the line indicating the inner diameter of the stator core 21 after the motor 2 is fitted is close to a circle, and the non-uniformity of the inner diameter of the stator core 21 is alleviated.

[0070] Next, the cylindrical body 30 of the comparative example is described. In the cylindrical body 30 of the comparative example, the stress relief groove 7 is not formed in the second connection part 62 and the fourth connection part 64, and the stress relief groove 7 is formed only in the first connection part 61 and the third connection part 63. The change in the inner diameter of the stator core 21 when the motor 2 is embedded in the cylindrical body 30 is shown in FIG. Figure 8 In other words, Figure 8 Graph showing the angle θ of any point of the cylindrical body 30 around the axis 20 relative to the reference line 10 and the change in the inner diameter of the stator core 21 before and after the motor 2 is inserted into the motor frame when the motor 2 of the comparative example is inserted into the motor frame. Figure 8 The range indicated by the dot pattern in is the range that the inner diameter of the stator core 21 can be allowed as a circle. Figure 8 The circle C indicating 0 located in the center of the dot pattern in FIG. 1 represents the shape of the inner diameter of the stator core 21 before the motor 2 is embedded. Figure 8 In the graph shown, when θ is 135 (°) and 315 (°), the change in the positive direction, that is, the direction of increasing radius, is greater when observed relative to the circumference C of the stator core 21. When θ is 45 (°) and 225 (°), the change in the negative direction, that is, the direction of decreasing radius, is greater when observed relative to the circumference C of the stator core 21. Figure 8As can be seen from the graph shown, the shape of the inner diameter of the stator core 21 is elliptical, and the non-uniformity of the inner diameter of the stator core 21 is not alleviated. In the cylindrical body 30 of the comparative example, in the motor device 1, the non-uniformity of the stress distribution applied to the stator 21 increases, and the cogging torque generated in the motor 2 increases. In contrast, for the cylindrical body 30 of the first embodiment, by having the stress relieving groove 7, as shown in FIG. Figure 7 As shown, the non-uniformity of the inner diameter shape of the stator core 21 is alleviated. Therefore, the stress distribution applied to the stator 21 can be made uniform, and the shape of the stator 21 can be made close to a perfect circle, so that the cogging torque generated in the motor 2 can be easily reduced.

[0071] In the first embodiment, the minimum wall thickness t of the portion having the stress relief groove 7 is the same as the minimum wall thickness t of the portion not having the stress relief groove 7. The minimum wall thickness t of the portion having the stress relief groove 7 is the wall thickness t at the position where the angle θ is (1 / 4)×π, (3 / 4)×π, (5 / 4)×π, (7 / 4)×π (rad). In addition, the minimum wall thickness t of the portion not having the stress relief groove 7 is the wall thickness t at the position where the angle θ is (1 / 2)×π, π, (3 / 2)×π, 2×π (rad). As a result, it is easier to alleviate the unevenness of the inner diameter of the stator core 21.

[0072] In addition, the four connection parts 6 have the stress relief grooves 7 over the entire length of the portion where the contact portion is located in the front-rear direction. This makes it easier to relieve the unevenness of the inner diameter of the stator core 21.

[0073] Next, a description will be given of the conditions under which the thickness t and the angle θ satisfy a t-θ relationship that makes it easy to reduce the cogging torque generated in the motor 2 .

[0074] The average value of the thickness function value t for the angle θ is defined as Tave (mm). Next, the thickness function is subjected to Fourier series expansion. Fig. 9 , a graph showing the result of Fourier series expansion of the thickness function for the motor frame 3 in the first embodiment is shown. That is, Fig. 9 1 is a graph showing the relationship between the order of Fourier series expansion of the thickness function of the motor frame 3 according to the first embodiment of the present invention and the amplitude at that order. Fig. 9 In the graph of , the horizontal axis represents each order, and the vertical axis represents the amplitude (mm). In addition, the phase of the result of Fourier series expansion is omitted.

[0075] T2(mm), which is the coefficient of the second-order term resulting from Fourier series expansion, preferably satisfies T2≤Tave×0.25. Fig. 9 In the graph of , T2≤Tave×0.25 is satisfied.

[0076] The larger the coefficient T2 (mm) of the quadratic term as a result of Fourier series expansion, the stronger the following tendency: in a pair of angles θ constituting the relative angle, the change in the positive direction, that is, the direction of increasing radius when observed relative to the circumference C of the stator core 21, becomes larger, and in another pair of angles θ orthogonal to the pair of angles θ, the change in the negative direction, that is, the direction of decreasing radius when observed relative to the circumference C of the stator core 21, becomes larger. That is, there is the following tendency, Figure 8 The ratio of the major diameter to the minor diameter of the ellipse formed by the shape of the inner diameter of the stator core 21 shown becomes larger, the non-uniformity of the stress distribution applied to the stator 21 increases, and the cogging torque generated in the motor 2 increases.

[0077] By making T2 (mm), which is the coefficient of the quadratic term resulting from Fourier series expansion, satisfy T2≤Tave×0.25, the stress distribution applied to the stator 21 is made uniform, and the shape of the stator 21 is made close to a perfect circle, thereby facilitating the suppression of the cogging torque generated in the motor 2.

[0078] (4) Second Embodiment

[0079] The following is based on Figure 10 to Figure 12 A motor device 1 and a motor frame 3 according to a second embodiment will be described. Fig.10 It is an exploded perspective view of a motor device 1 according to a second embodiment of the present invention. Fig.11 It is a front view of a motor device 1 according to a second embodiment of the present invention. Fig.10 : is a perspective view of a motor frame 3 according to a second embodiment of the present invention. The motor frame 3 shown in the first embodiment differs from the motor frame 3 shown in the second embodiment in that the motor frame 3 shown in the second embodiment has a step portion 51, a protrusion 811, and a resin injection port 91. Fig.10 The other structures of the motor frame 3 shown are Figure 3 The motor frame 3 is shown similarly.

[0080] The stator 21 of the motor 2 is embedded in the inner wall surface 5 of the motor frame 3. In the second embodiment, the inner wall surface 5 itself serves as a contact portion with the motor 2 embedded inside.

[0081] The first wall portion 81 constitutes a mounting portion for mounting a specific component. The first wall portion 81 serving as the mounting portion has a protrusion 83. A fixing hole 811 into which a bolt is screwed is formed in the protrusion 83. The protrusion 83 is a wall portion for providing a space required for arranging a component above the through-hole 33. When mounting a specific component on the first wall portion 81, the bolt is rotated using a tool such as a screwdriver. The component is, for example, a waterproof or dustproof component of the motor device 1, but is not particularly limited. In addition, a fixing hole 311 into which a bolt is screwed is formed in the first end face 31, and the bracket 12 is mounted using the bolt screwed into the fixing hole 311.

[0082] The second wall portion 82 of the first connection portion 61 and the third connection portion 63 constitutes a mounting portion for mounting the motor frame 3 on an external device. In addition, a through hole 821 penetrating in the front-to-back direction is formed in the second wall portion 82 of the first connection portion 61 and the third connection portion 63, and the cylindrical body 30 is mounted on an external device using a fixing device consisting of a bolt and a nut. When the cylindrical body 30 is mounted on an external device, the fixing device is rotated using a tool such as a wrench or a screwdriver. At this time, the operator can insert the tool into the stress relief groove 7, and the tightening operation of the fixing device is easy.

[0083] In the second embodiment, a step portion 51 having a slightly smaller diameter than the front and rear portions is formed in a portion of the inner wall surface 5 in the direction in which the axis extends (ie, the front-rear direction). The step portion 51 is a contact portion with the motor 2 embedded therein.

[0084] (5) Modification

[0085] The position detector 121 , the bracket 12 , the detector cover 13 , and the seal 122 are arbitrary structures, and the motor device 1 may not have the above structures.

[0086] The position detector 121 may be, for example, a slip ring or the like, and is not limited to a rotary encoder.

[0087] The motor 2 is not limited to a servo motor.

[0088] The rotor 22 is not limited to a surface magnet type rotor.

[0089] The through-hole 33 is an arbitrary structure, and may not be formed in the cylindrical body 30 .

[0090] The inner wall surface 5 may also have a portion that does not constitute the inner surface of the cylinder. In addition, the inner wall surface 5 may have a contact portion that contacts the stator 21 of the motor 2 embedded inside the inner wall surface 5 over the entire length of the direction in which the axis extends (i.e., the front-to-back direction). In addition, the contact portion of the inner wall surface 5 that contacts the stator 21 of the motor 2 embedded inside the inner wall surface 5 may be formed by the step portion 51 or may not be formed by the step portion 51. That is, the front and rear portions of the contact portion and the contact portion may also be located on the same surface extending in the front-to-back direction.

[0091] The range in which the stress relief groove 7 is formed does not necessarily have to be the entire length in the front-rear direction of the portion where the contact portion is located.

[0092] The specific member mounted on the mounting portion formed by the wall portion 8 is not limited to the detector cover 13 .

[0093] The protrusion 83 is an arbitrary structure, and may not be provided on the motor frame 3 .

[0094] In the above-mentioned embodiment, the thickness t at the center of the portion in contact with the stator 21 embedded inside in the direction in which the axis 20 extends satisfies T2≤Tave×0.25. In contrast, the thickness t at any portion in the direction in which the axis 20 extends may also satisfy T2≤Tave×0.25. In addition, it is more preferable if the thickness t at all locations along the entire length of the portion in contact with the stator 21 embedded inside in the direction in which the axis 20 extends satisfies T2≤Tave×0.25.

[0095] In addition, the range that satisfies T2 ≤ Tave×0.25 does not necessarily need to be the thickness t of all the parts in the direction in which the axis 20 extends.

[0096] (6) Summary

[0097] As described above, the motor frame 3 of the first form has a cylindrical body 30 that penetrates in the direction in which the axis 20 of the rotating shaft 23 of the motor 2 embedded inside extends. The cylindrical body 30 has four outer wall surfaces 4, an inner wall surface 5, and four connecting portions 6. The four outer wall surfaces 4 are arranged in a manner to surround the rotating shaft 23 and each has a planar shape along the rotating shaft 23. The inner wall surface 5 surrounds the rotating shaft 23 and has a cylindrical inner surface shape along the rotating shaft 23. The four connecting portions 6 are respectively located at each of the four boundaries formed by the adjacent outer wall surfaces 4 among the four outer wall surfaces 4. The four connecting portions 6 each have a stress relief groove 7 that is recessed toward the axis 20 at the boundary between the outer wall surfaces 4 on both sides that are adjacent. At least one connecting portion 6 has a stress relief groove 7 in a portion of the direction extending along the axis 20, and has a wall portion 8 in the other portion of the direction extending along the axis 20, and the wall portion 8 does not have a stress relief groove 7.

[0098] In the first embodiment, the unevenness of the inner diameter of the stator core 21 is alleviated, thereby seeking to make the stress distribution applied to the stator 21 uniform, making the shape of the stator 21 close to a perfect circle, and facilitating the reduction of the cogging torque generated in the motor 2. In addition, since the wall portion 8 is formed, it is easy to mount the cylindrical body 30 on an external member.

[0099] The second aspect can be realized by combining with the first aspect. In the second aspect, at least one connecting portion 6 has a mounting portion at one end in the direction in which the axis 20 extends. The mounting portion is constituted by a wall portion 8 and is used to mount a specific member.

[0100] In the second embodiment, it is easy to attach a specific member to the cylindrical body 30 .

[0101] The third aspect can be realized by combining with the second aspect. In the third aspect, at least one connecting portion 6 further includes a protrusion 83 extending from the other end portion in the direction extending from the mounting portion toward the axial center 20 .

[0102] In the third embodiment, the protrusion 83 can be used to provide a space required for arranging a component above the through-hole 33 .

[0103] The fourth form can be realized by combining with any one of the first to third forms. In the fourth form, when the thickness of the cylindrical body 30 in the inner and outer directions perpendicular to the direction in which the axis 20 extends is set as the wall thickness, the minimum wall thickness of the portion having the stress relief groove 7 is the same as the minimum wall thickness of the portion not having the stress relief groove 7.

[0104] In the fourth embodiment, it is easier to alleviate the unevenness of the inner diameter of the stator core 21 .

[0105] The fifth form can be realized by combining with any one of the first to fourth forms. In the fifth form, the inner wall surface 5 has a contact portion that contacts the stator 21 of the motor 2 embedded inside in a part or all of the direction in which the axis 20 extends. The four connecting portions 6 have stress relief grooves 7 over the entire length of the portion where the contact portion is located in the direction in which the axis 20 extends.

[0106] In the fifth embodiment, it is easier to alleviate the unevenness of the inner diameter of the stator 21 .

[0107] The sixth form can be realized by combining with any one of the first to fifth forms. In the sixth form, the thickness of the cylindrical body 30 in the inner and outer directions perpendicular to the direction in which the axis 20 extends is set to the wall thickness t (mm) for the entire length or a portion of the portion in contact with the stator 21 of the motor 2 embedded inside in the direction in which the axis 20 extends. The angle of the cylindrical body 30 relative to the reference line at any point around the axis 20 when observed from the direction in which the axis 20 extends is set to the angle θ (rad). The thickness function is set to t=f(θ). When the average value of the thickness function t for the angle θ is set to Tave(mm), T2(mm), which is the coefficient of the second-order term when the thickness function is expanded in the Fourier series, satisfies T2≤Tave×0.25.

[0108] In the sixth embodiment, the stress applied to the stator 21 is made uniform, and the shape of the stator 21 is made close to a perfect circle, so that the cogging torque generated in the motor 2 can be easily reduced.

[0109] The seventh embodiment can be realized by combining with any one of the first to sixth embodiments. In the seventh embodiment, the cylindrical body 30 has a through hole 33 formed in a portion corresponding to the outer wall surface 4 so as to penetrate in the inner and outer directions perpendicular to the direction in which the axis 20 extends.

[0110] In the seventh embodiment, the wiring connected to the motor 2 embedded in the cylindrical body 30 can be passed from the outside of the cylindrical body 30 .

[0111] The eighth aspect can be realized by combining with any one of the first to seventh aspects. In the eighth aspect, the motor device 1 includes: the motor frame 3 of any one of the first to seventh aspects; and the motor 2 embedded in the cylindrical body 30 of the motor frame 3 .

[0112] In the eighth embodiment, the stress applied to the stator 21 is made uniform by alleviating the unevenness of the inner diameter of the stator core 21, so that the shape of the stator 21 is close to a perfect circle, and the cogging torque generated in the motor 2 is easily reduced. In addition, since the wall portion 8 is formed, it is easy to mount the cylindrical body 30 on an external component.

[0113] Industrial Applicability

[0114] The motor frame and the motor device of the present invention are easy to be installed on external components, and are easy to suppress the influence caused by circumferential unevenness. Therefore, the performance of the motor frame and the motor device can be improved. As such, the motor frame and the motor device of the present invention are useful in industry.

[0115] Description of Reference Numerals

[0116] 1. Motor device; 10. Base line; 2. Motor; 20. Axis; 23. Rotating shaft; 3. Motor frame; 30. Cylindrical body; 33. Through-hole; 4. Outer wall surface; 41. First outer wall surface; 42. Second outer wall surface; 43. Third outer wall surface; 44. Fourth outer wall surface; 5. Inner wall surface; 6. Connecting part; 61. First connecting part; 62. Second connecting part; 63. Third connecting part; 64. Fourth connecting part; 7. Stress relief groove; 8. Wall part; 81. First wall part; 82. Second wall part; 83. Protrusion; 121. Position detector; 122. Seal.

Claims

1. A motor frame, wherein: The motor frame includes a cylindrical body that penetrates in a direction in which the axis of a rotating shaft of a motor embedded inside extends. The cylindrical body has: four outer wall surfaces arranged in a manner of surrounding the rotation axis and each having a planar shape along the rotation axis; an inner wall surface surrounding the rotation axis and having a cylindrical inner surface shape along the rotation axis; as well as four connecting portions, the four connecting portions are respectively located at each of four boundaries formed by adjacent outer wall surfaces among the four outer wall surfaces, The four connecting parts each have a stress relief groove recessed toward the axis at the boundary between the two adjacent outer wall surfaces. At least one of the connection portions has the stress relief groove in a portion along a direction in which the axis extends, and has a wall portion in another portion along the direction in which the axis extends, the wall portion not having the stress relief groove.

2. The motor frame according to claim 1, wherein: At least one of the connection parts has a mounting portion at one end portion in the direction in which the axis extends, and the mounting portion is formed by the wall portion and is used for mounting a specific component.

3. The motor frame according to claim 2, wherein: The at least one connecting portion further includes a protrusion extending from the other end of the mounting portion in a direction in which the axial center extends.

4. The motor frame according to any one of claims 1 to 3, wherein: When the thickness of the cylindrical body in the inner and outer directions perpendicular to the direction in which the axis extends is defined as the wall thickness, the minimum wall thickness of the portion having the stress relief groove is the same as the minimum wall thickness of the portion not having the stress relief groove.

5. The motor frame according to any one of claims 1 to 3, wherein: The inner wall surface has a contact portion that contacts a stator of the motor embedded inside in a part or all of the direction in which the axis extends. Each of the four connection portions has the stress relief groove over the entire length of a portion where the contact portion is located in the direction in which the axial center extends.

6. The motor frame according to any one of claims 1 to 3, wherein: The thickness of the cylindrical body in the inner and outer directions perpendicular to the direction in which the axis extends is set as the wall thickness t, over the entire length or a portion of the portion in contact with the stator of the motor embedded inside in the direction in which the axis extends. The angle of any point of the cylindrical body around the axis relative to the reference line when viewed from the direction in which the axis extends is defined as angle θ. Let the thickness function be t = f(θ), When the average value of the thickness function t with respect to the angle θ is set to Tave, T2, which is the coefficient of the second-order term when the thickness function is expanded by Fourier series, satisfies T2≤Tave×0.25, Among them, the unit of wall thickness t is mm, the unit of angle θ is rad, the unit of Tave is mm, and the unit of T2 is mm.

7. The motor frame according to any one of claims 1 to 3, wherein: The cylindrical body has a through-hole formed at a portion corresponding to the outer wall surface, the through-hole penetrating in an inner-outer direction perpendicular to a direction in which the axis extends.

8. A motor device, wherein: The motor device has: The motor frame according to any one of claims 1 to 7; and The motor is embedded in the cylindrical body of the motor frame.

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