CN114258623A

CN114258623A - Direct drive motor

Info

Publication number: CN114258623A
Application number: CN202080057916.4A
Authority: CN
Inventors: 丸山正幸; 田口俊文; 福山健一
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 2019-08-21
Filing date: 2020-08-06
Publication date: 2022-03-29
Anticipated expiration: 2040-08-06
Also published as: JPWO2021033557A1; CN114258623B; JP7533465B2; WO2021033557A1

Abstract

The direct drive motor includes a stator having a stator core and a rotor having a magnet. A1 st distance along the axial direction from an end in the 1 st direction to an end in the 2 nd direction of the magnet is smaller than a 2 nd distance along the axial direction from the end in the 1 st direction to the end in the 2 nd direction of the stator core. A1 st position of the magnet, which is apart by a half of a 1 st distance from the 1 st direction end toward the 2 nd direction, coincides with a 2 nd position of the stator core, which is apart by a half of a 2 nd distance from the 1 st direction end toward the 2 nd direction.

Description

Direct drive motor

Technical Field

The present disclosure relates to direct drive motors.

Background

A motor including a stator and a rotor having a magnet is known (see patent document 1). In the motor of patent document 1, the rotor is fixed to the load shaft, and the fan is attached to the load shaft, so that the rotor, the load shaft, and the fan rotate integrally.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 4-331438

Disclosure of Invention

Problems to be solved by the invention

In the motor described in patent document 1, one end portion of the magnet in the axial direction of the load shaft is positioned on one side in the axial direction than one end portion in the axial direction of the stator. Therefore, the stator is not disposed radially outward of the one end portion in the axial direction of the magnet, and therefore the magnetic flux (magnetic field) generated from the magnet may not be sufficiently transmitted to the stator.

The present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide a direct drive motor capable of reducing leakage of magnetic flux by transmitting more magnetic flux generated by a magnet to a stator core.

Means for solving the problems

In order to achieve the above object, with a direct drive motor according to an aspect, the direct drive motor includes: a stator having a stator core arranged along a circumferential direction around a central axis; and a rotor having a rotor core and a magnet, the rotor core being disposed outside or inside the stator core in a radial direction orthogonal to the central axis, the magnet is fixed to the rotor core and arranged to be opposed to the stator core in a radial direction, one of axial directions of the central axis is a 1 st direction, and a direction opposite to the 1 st direction is a 2 nd direction, a 1 st distance of the magnet from an end in a 1 st direction to an end in a 2 nd direction along an axial direction is smaller than a 2 nd distance of the stator core from the end in the 1 st direction to the end in the 2 nd direction along the axial direction, and a 1 st position that is apart from the 1 st direction end of the magnet by a half distance of the 1 st distance toward the 2 nd direction coincides with a 2 nd position that is apart from the 1 st direction end of the stator core by a half distance of the 2 nd distance toward the 2 nd direction.

Therefore, even when the axial positions of the magnet and the stator core are displaced due to the dimensional deviation in the axial direction that occurs when the components of the DD motor are assembled, the magnetic flux (magnetic field) generated by the magnet can be transmitted to the stator core to a greater extent, thereby reducing the leakage of the magnetic flux. Therefore, a larger output can be obtained, and even a smaller magnet can rotate the rotor. Further, since the 1 st position and the 2 nd position coincide with each other in the axial direction, the magnetic flux (magnetic field) generated by the magnet can be transmitted to the stator core more, regardless of whether the magnet is shifted to one side in the axial direction with respect to the stator core or the magnet is shifted to the other side in the axial direction with respect to the stator core.

Preferably, the stator core and the rotor core have a laminated steel plate in which a plurality of steel plates are laminated in an axial direction. When a metal material is cut by lathe machining to produce a stator core or a rotor core, it is difficult to form the outer peripheral surface into a complicated shape. However, in the case of a laminated steel sheet in which steel sheets after punching are laminated, it is easy to form the outer peripheral surface into a complicated shape.

Preferably, the laminated steel plates of the stator core and the laminated steel plates of the rotor core are formed by laminating the same number of steel plates having the same thickness. Thus, when the laminated steel sheets for the stator core and the rotor core are manufactured using the steel sheets of coil stock, the steel sheets of the laminated steel sheets for the stator core and the steel sheets of the laminated steel sheets for the rotor core can be manufactured from the same coil stock.

Preferably, the laminated steel plate of the rotor core is formed by stacking a predetermined number of 1 st units in an axial direction, 1 magnet is fixed to each of the 1 st units, and a 3 rd distance from an end in the 1 st direction to an end in a 2 nd direction along the axial direction of the magnet is smaller than a 4 th distance from the end in the 1 st direction to the end in the 2 nd direction along the axial direction of the 1 st unit. Thus, a plurality of changes of the rotor core having different lengths in the axial direction can be made in a state where the length of the stator core in the axial direction is larger than the length of the magnet in the axial direction.

Preferably, the difference between the 4 th distance and the 3 rd distance is equal to the thickness of 1 steel plate. Thus, a plurality of changes of the rotor core having different lengths in the axial direction can be made using the minimum number of steel plates in a state where the length of the stator core in the axial direction is larger than the length of the magnet in the axial direction.

Preferably, the laminated steel plate of the stator core is formed by stacking a plurality of 2 nd units of a predetermined number of laminated steel plates in an axial direction, and the 3 rd distance is smaller than a 5 th distance from a 1 st-direction end to a 2 nd-direction end of the 2 nd unit in the axial direction. Thus, a plurality of changes of the stator core having different lengths in the axial direction can be made in a state where the length of the stator core in the axial direction is larger than the length of the magnet in the axial direction.

Preferably, the difference between the 5 th distance and the 3 rd distance is equal to the thickness of 1 steel plate. Thus, a plurality of changes of the stator core having different lengths in the axial direction can be made using the minimum number of steel plates in a state where the length of the stator core in the axial direction is larger than the length of the magnet in the axial direction.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present disclosure, it is possible to provide a direct drive motor that can reduce magnetic flux leakage by transmitting more magnetic flux generated by a magnet to a stator core.

Drawings

Fig. 1 is a sectional view schematically showing the overall configuration of a direct drive motor according to an embodiment.

Fig. 2 is a perspective view schematically showing the entire structure of the motor unit according to the embodiment.

Fig. 3 is an enlarged perspective view of a part of fig. 2.

Fig. 4 is a schematic diagram showing a cross section of the motor unit.

Fig. 5 is a schematic view showing a vertical positional relationship between the stator core, the rotor core, and the permanent magnet.

Fig. 6 is a perspective view schematically showing the entire structure of a motor unit according to a modification.

Detailed Description

The mode (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. The components described below include those that can be easily conceived by those skilled in the art and those that are substantially the same. Further, the following constituent elements can be appropriately combined.

[ embodiment ]

First, the embodiment will be explained. Fig. 1 is a sectional view schematically showing the entire structure of a direct drive motor. The direct drive motor 1 according to the embodiment can directly transmit the rotational force to the rotor without interposing a speed reduction mechanism (e.g., a speed reduction gear, a transmission belt, or the like) to rotate the rotor.

As the direct drive motor 1 (hereinafter, also referred to as "DD motor 1"), there are an outer rotor type, an inner rotor type, and the like, but in the present embodiment, as an example, the inner rotor type DD motor 1 is shown in fig. 1.

The DD motor 1 includes a base 2, a rotating body 3 (also referred to as a motor output shaft), and a motor portion 4.

The base 2 has a bottom portion 21, an inclined portion 22, and a vertical wall portion 23. The susceptor 2 is an annular member centered on the central axis Ax. The bottom portion 21 is placed on the base 10 and fixed to the base 10. The inclined portion 22 extends obliquely upward from the radially inner end 21a of the bottom portion 21 toward the radially inner side. The vertical wall portion 23 extends upward from the upper end portion 22a of the inclined portion 22 along the axial direction of the central axis Ax.

The vertical wall portion 23 is a cylindrical member centered on the central axis Ax. The 1 st holding body 24 is disposed above the vertical wall portion 23. The 1 st retaining body 24 is a cylindrical member having a center axis Ax as a center. The 1 st holding body 24 is fastened to the vertical wall portion 23 by screws BL 1. Radially outward of the vertical wall portion 23, a 1 st step portion 23a and a 2 nd step portion 23b are provided. The inner peripheral portion of the bearing 100 is fitted to the 1 st step portion 23 a. The bearing 100 is an annular member centered on the central axis Ax. The 2 nd holding body 25 is placed on the 2 nd step portion 23 b. The 2 nd holding body 25 is an annular member having a center axis Ax as a center. The 2 nd holding body 25 is fastened to the 2 nd step portion 23b by a screw BL2, and the inner peripheral portion of the bearing 100 is sandwiched between the 2 nd holding body 25 and the 1 st step portion 23a from the vertical direction (the axial direction of the central axis Ax).

The rotor 3 has a 3 rd holder 26 and a 4 th holder 27. The rotating body 3 is supported to be rotatable with respect to the base 2. The rotating body 3 is disposed radially outward of the vertical wall portion 23 and the 1 st holding body 24 of the base 2. The rotary body 3 is an annular member centered on the central axis Ax. The 3 rd holding body 26 has a 3 rd step portion 26a at the lower end of the radially inner portion (inner peripheral portion). The 4 th holding body 27 has a 4 th stepped portion 27a at a radially inner side. The 4 th holding body 27 is fastened to the 3 rd holding body 26 by the screw BL3, and the outer peripheral portion of the bearing 100 is sandwiched by the 3 rd step portion 26a and the 4 th step portion 27a from the vertical direction (the axial direction of the central axis Ax). The rotating body 3 performs a rotational motion around the central axis Ax. Various workpieces (not shown) are attached to the rotary body 3, and the rotary body 3 is rotated by the motor portion 4, whereby the various workpieces can be rotated.

A rotation sensor 5 is provided between the 1 st holding body 24 and the 3 rd holding body 26. The rotation sensor 5 has a pair of members opposed in the radial direction. One of the pair of members is fixed to the 3 rd holding body 26 by a screw BL4, and the other is fixed to the 1 st holding body 24 by a screw BL 5. The rotation sensor 5 detects a rotation state (for example, a rotation angle) of the motor unit 4. The rotation sensor 5 can accurately rotate various workpieces attached to the rotary body 3 by a predetermined angle, and can accurately position the workpieces at a target position. As the rotation sensor 5, a detection element such as a commercially available resolver can be applied. The rotation sensor 5 is protected from the outside by the disc-shaped 1 st cover 101 provided on the upper portion of the 1 st holding body 24.

The motor unit 4 is provided between the bottom 21 of the base 2 and the rotating body 3, and rotates the rotating body 3. The motor unit 4 includes a stator 40(stator) and a rotor 42 (rotor). The stator 40 and the rotor 42 are annular members centered on the central axis Ax. The stator 40 is fixed to the bottom 21 of the base 2 by screws BL 6. The motor unit 4 of the embodiment has a so-called inner rotor type structure.

The stator 40 includes a stator core 41(stator core), an insulator 43, and a coil 44. The insulator 43 is provided on the stator core 41, and the coil 44 is wound around the insulator 43. The upper portion of the stator core 41 is covered with an annular 2 nd cover 102. The 2 nd cover 102 has an L-shaped cross section and includes a vertical portion 102a extending in the axial direction and a horizontal portion 102b extending radially inward. The 2 nd cover 102 is fixed to the base 2 by screws BL 7. The rotor 42(rotor) is disposed radially inward of the stator core 41 so as to face the stator core 41.

The rotor 42(rotor) includes a permanent magnet 421 (magnet in claims) and a rotor core 422(rotor core). The permanent magnet 421 is fixed to the radially outer side of the rotor core 422 by bonding. The rotor 42 is fixed to the 3 rd retaining body 26 by a screw BL 8.

When the coil 44 is energized, a rotational force can be applied to the rotary body 3 via the rotor 42 by the left-hand rule of fleming due to the magnetic interaction between the stator 40 and the rotor 42. This enables the rotary body 3 and the workpiece to rotate.

Fig. 2 is a perspective view schematically showing the entire structure of the motor unit according to the embodiment. Fig. 3 is an enlarged perspective view of a part of fig. 2.

As shown in fig. 2 and 3, in the embodiment, a rotor 42(rotor) including a permanent magnet 421 (magnet in claims) and a rotor core 422(rotor core) is disposed on the inner peripheral side of a stator 40(stator) including a stator core 41(stator core).

The stator core 41 has a back yoke 411 and teeth 412. The back yoke 411 and the teeth 412 are integral. The back yoke 411 is an annular member centered on the center axis Ax when viewed in the axial direction of the center axis Ax. The teeth 412 protrude from the inner circumferential surface of the back yoke 411 toward the central axis Ax toward the inner circumferential side (radially inward). The coil 44 (see fig. 1) is wound around the teeth 412 with the insulator 43 interposed therebetween.

A through hole 411a extending in the axial direction is provided in a portion of the back yoke 411 corresponding to the tooth 412. The through hole 411a extends in the axial direction of the central axis Ax. Here, the stator core 41 includes laminated steel plates. The laminated steel sheet is formed by stacking a plurality of 1 steel sheets formed by punching and having the back yoke 411, the teeth 412, and the through holes 411a in the axial direction.

The through hole 411a is used for caulking, for example. That is, for example, the 2

nd units

413 and 414 are produced by stacking a predetermined number of steel sheets, inserting a rivet into the through hole 411a, and then crushing the rivet in the axial direction. The plurality of 2

nd units

413 and 414 are stacked in the axial direction, thereby manufacturing the stator core 41. The 2 nd unit 413 is stacked on one side (upper side in fig. 2, 3) in the axial direction of the 2 nd unit 414.

In the present embodiment, the 2 nd unit 413 and the 2 nd unit 414 are formed of steel sheets having the same thickness and the same number. In fig. 2 and 3, the boundary S1 between the 2 nd cell 413 and the 2 nd cell 414 is easily visually recognized and is shown by a thick line for convenience, but actually, steel sheets having the same thickness are stacked without a gap in the axial direction. The stator core 41 may be manufactured by fixing all the steel plates without passing through the 2

nd units

413 and 414 by riveting with rivets (japanese patent No. かしめ), for example. The material of the steel sheet constituting the stator core 41 is not particularly limited, and various steel sheets can be used, and for example, a silicon steel sheet is preferable.

The rotor 42 includes a rotor core 422 and a permanent magnet 421 (magnet of the claims). The rotor core 422 is also formed of a laminated steel plate in which a plurality of 1 steel plate formed into a desired shape by punching is stacked in the axial direction. The rotor core 422 is provided with a through hole 422b extending in the axial direction.

The through hole 422b is used for caulking, for example. That is, for example, the 1

st units

425 and 426 are produced by stacking a plurality of steel plates of a predetermined number, inserting a rivet into the through hole 422b, and then crushing the rivet in the axial direction. The rotor core 422 is configured by stacking the 1 st unit 425 on one side (upper side in fig. 2 and 3) in the axial direction of the 1 st unit 426. In the present embodiment, the 1 st unit 425 and the 1 st unit 426 are made of steel plates having the same thickness and the same number. In fig. 2 and 3, for easy visual confirmation of boundary S2 between 1 st cell 425 and 1 st cell 426, the boundary is shown in bold line for convenience, but actually steel sheets of the same thickness are stacked without a gap in the axial direction.

The rotor core 422 may be manufactured by fixing all the steel plates without passing through the 1

st units

425 and 426 by riveting with rivets (japanese patent No. かしめ), for example. The material of the steel plate constituting the rotor core 422 is not particularly limited, and various steel plates can be used, and for example, a silicon steel plate is preferable.

The thickness of the 1 steel sheet constituting the rotor core 422 is the same as the thickness of the 1 steel sheet constituting the stator core 41. By making the number of the steel sheets of the laminated steel sheet constituting the rotor core 422 equal to the number of the steel sheets of the laminated steel sheet constituting the stator core 41, the height (thickness) of the laminated steel sheet of the rotor core 422 in the axial direction can be easily made equal to the height (thickness) of the laminated steel sheet of the stator core 41 in the axial direction.

Fig. 4 is a schematic diagram showing a cross section of the motor unit. Fig. 5 is a schematic view showing a vertical positional relationship between the stator core, the rotor core, and the permanent magnet. Hereinafter, one of the axial directions is referred to as the 1 st direction D1, and the other of the axial directions is referred to as the 2 nd direction D2. The 2 nd direction D2 is a direction opposite to the 1 st direction D1. The 1 st direction D1 is a direction toward the upper side in fig. 4 and 5, and the 2 nd direction D2 is a direction toward the lower side in fig. 4 and 5.

As shown in fig. 4, the stator core 41 includes the 2

nd cells

413 and 414. The 2 nd unit 413 has a lower surface 413b and an upper surface 413 a. The 2 nd cell 414 has a lower surface 414b and an upper surface 414 a. An end of the stator core 41 in the 1 st direction D1 is an upper surface 413a of the 2 nd cell 413. An end of the stator core 41 in the 2 nd direction D2 is a lower surface 414b of the 2 nd cell 414.

The 2 nd cell 413 and the 2 nd cell 414 have the same height in the axial direction as each other. Specifically, the height in the axial direction of each of the 2 nd cell 413 and the 2 nd cell 414 is B/2. The height of the entire stator core 41 in the axial direction, which is the sum of the 2 nd unit 413 and the 2 nd unit 414, is the 2 nd distance B. That is, the distance from the end of the stator core 41 in the 1 st direction D1 to the end in the 2 nd direction D2 along the axial direction is the 2 nd distance B. Further, the center of the stator core 41 in the axial direction between the end in the 1 st direction D1 and the end in the 2 nd direction D2 is the 2 nd center CL 2. The 2 nd center CL2 is located at the same height as the upper surface 414a of the 2 nd cell 414 and the lower surface 413b of the 2 nd cell 413. In other words, when the 2 nd position is a position separated from the end of the stator core 41 in the 1 st direction D1 by a distance B/2 half the 2 nd distance B in the 2 nd direction D2, the 2 nd center CL2 coincides with the 2 nd position.

As shown in fig. 4, rotor core 422 includes 1 st cell 425 and 1 st cell 426. The 1 st cell 425 has a lower surface 425b and an upper surface 425 a. The 1 st unit 426 has a lower surface 426b and an upper surface 426 a. The upper surface 425a of the 1 st cell 425 abuts against the lower surface 26b of the 3 rd holding body 26. In other words, the upper surface 425a of the 1 st unit 425 is supported by the lower surface 26b of the 3 rd holding body 26 in the vertical direction. Thereby, the upper surface 425a of the 1 st cell 425 is positioned in the axial direction. An end of the rotor core 422 in the 1 st direction D1 is an upper surface 425a of the 1 st cell 425. An end of the rotor core 422 in the 2 nd direction D2 is a lower surface 426b of the 1 st cell 426.

The 1 st cell 425 and the 1 st cell 426 have the same height in the axial direction as each other. Specifically, the height of each of the 1 st cell 425 and the 1 st cell 426 in the axial direction is F/2. The height in the axial direction of the entire rotor core 422 where the 1 st cell 426 and the 1 st cell 425 are combined is F. The lower surface 426b of the 1 st unit 426 is located below the lower surface 414b of the 2 nd unit 414.

In addition, the permanent magnet 421 (magnet of the claim) has a 1 st permanent magnet 423 (magnet of the claim) and a 2 nd permanent magnet 424 (magnet of the claim). The 1 st permanent magnet 423 is fixed to the outer circumferential surface of the 1 st cell 425. The 1 st permanent magnet 423 has a lower surface 423b and an upper surface 423 a. The upper surface 423a and the upper surface 425a are located at the same height. The

upper surfaces

423a and 425a are located below the upper surface 413a of the 2 nd cell 413. The 2 nd permanent magnet 424 is fixed to the 1 st unit 426 on the outer circumferential surface. The 2 nd permanent magnet 424 has a lower surface 424b and an upper surface 424 a. The upper surface 424a and the upper surface 426a are located at the same height.

An end of the permanent magnet 421 in the 1 st direction D1 is an upper surface 423a of the 1 st permanent magnet 423. The end of the permanent magnet 421 in the 2 nd direction D2 is the lower surface 424b of the 2 nd permanent magnet 424. The distance of the permanent magnet 421 in the axial direction from the end in the 1 st direction D1 to the end in the 2 nd direction D2 is the 1 st distance a. The 1 st distance a is smaller than the 2 nd distance B of the stator core 41. The center in the axial direction between the end in the 1 st direction D1 and the end in the 2 nd direction D2 of the permanent magnet 421 is a 1 st center CL 1. The 1 st center CL1 is located at the center in the axial direction between the upper surface 423a of the 1 st permanent magnet 423 and the lower surface 424b of the 2 nd permanent magnet 424. When the 1 st position is a position separated from the end of the permanent magnet 421 in the 1 st direction D1 by a distance a/2 half of the 1 st distance a in the 2 nd direction D2, the 1 st center CL1 coincides with the 1 st position. In addition, the 1 st center CL1 and the 2 nd center CL2 coincide in the axial direction, and the 1 st position and the 2 nd position also coincide in the axial direction.

Using fig. 5, the vertical positional relationships of the 2 nd unit 413, the 1 st unit 425, and the 1 st permanent magnet 423 are compared. The end of the 2 nd unit 413 in the 1 st direction D1 is an upper surface 413 a. The end of the 2 nd element 413 in the 2 nd direction D2 is the lower surface 413 b. The end of the 1 st cell 425 in the 1 st direction D1 is an upper surface 425 a. The end of the 1 st cell 425 in the 2 nd direction D2 is the lower surface 425 b. The end of the 1 st permanent magnet 423 in the 1 st direction D1 is an upper surface 423 a. An end of the 1 st permanent magnet 423 in the 2 nd direction D2 is a lower surface 423 b.

Here, the distance of the 1 st permanent magnet 423 from the end in the 1 st direction D1 to the end in the 2 nd direction D2 in the axial direction is the 3 rd distance C. The distance of the 1 st cell 425 from the end in the 1 st direction D1 to the end in the 2 nd direction D2 along the axial direction is the 4 th distance D. The distance of the 2 nd unit 413 from the end in the 1 st direction D1 to the end in the 2 nd direction D2 along the axial direction is a 5 th distance E. The 3 rd distance C is less than the 4 th distance D. The difference G between the 4 th distance D and the 3 rd distance C is an amount of 1 sheet thickness. The 3 rd distance C is less than the 5 th distance E. The difference G between the 5 th distance E and the 3 rd distance C is an amount of 1 sheet thickness.

The thickness of the 1 steel plate constituting the 2 nd unit 413 is the same as the thickness of the 1 steel plate constituting the 1 st unit 425, and the number of steel plates constituting the 2 nd unit 413 is the same as the number of steel plates constituting the 1 st unit 425. Thus, the 4 th distance D is the same as the 5 th distance E.

As shown in fig. 4, the thickness of the 1 st steel plate constituting the 2 nd unit 414 is the same as the thickness of the 1 st steel plate constituting the 1 st unit 426, and the number of steel plates constituting the 2 nd unit 414 is the same as the number of steel plates constituting the 1 st unit 426. Therefore, the 2 nd unit 414 and the 1 st unit 426 have the same height in the axial direction. As described above, the laminated steel plates of the stator core 41 and the rotor core 422 are formed by laminating the same number of steel plates having the same thickness.

As described above, the DD motor 1 of the embodiment includes: a stator 40 having a stator core 41; and a rotor 42 having a rotor core 422 disposed radially inward of the stator core 41 and a permanent magnet 421 (magnet of the claims) fixed to the rotor core 422.

A 1 st distance a of the permanent magnet 421 in the axial direction from the end in the 1 st direction D1 to the end in the 2 nd direction D2 is smaller than a 2 nd distance B of the stator core 41 in the axial direction from the end in the 1 st direction D1 to the end in the 2 nd direction D2. In addition, the 1 st position separated from the end of the permanent magnet 421 in the 1 st direction D1 by a half distance a/2 of the 1 st distance a toward the 2 nd direction D2 coincides with the 2 nd position separated from the end of the stator core 41 in the 1 st direction D1 by a half distance B/2 of the 2 nd distance B toward the 2 nd direction D2 in the axial direction.

Therefore, even when the permanent magnet 421 is displaced from the stator core 41 in the axial direction due to the dimensional deviation in the axial direction generated when the components of the DD motor 1 are assembled, the magnetic flux (magnetic field) generated by the permanent magnet 421 is transmitted to the stator core 41 to a greater extent, and the leakage of the magnetic flux can be reduced. Therefore, a larger output can be obtained, and even a smaller permanent magnet 421 can rotate the rotor 42.

Further, since the 1 st position and the 2 nd position coincide in the axial direction, the amount of magnetic flux (magnetic field) transmitted from the permanent magnet 421 to the stator core 41 can be made uniform regardless of whether the permanent magnet 421 is displaced upward in the axial direction with respect to the stator core 41 or the permanent magnet 421 is displaced downward in the axial direction with respect to the stator core 41.

The stator core 41 and the rotor core 422 have a laminated steel plate in which a plurality of steel plates are laminated in the axial direction. When a metal material is cut by lathe machining to produce a stator core or a rotor core, it is difficult to form the outer peripheral surface into a complicated shape. However, in the case of a laminated steel sheet in which steel sheets after punching are laminated, it is easy to form the outer peripheral surface into a complicated shape.

The laminated steel sheets of the stator core 41 and the laminated steel sheets of the rotor core 422 are formed by laminating the same number of steel sheets having the same thickness. Thus, when the laminated steel sheets for the stator core 41 and the rotor core 422 are manufactured using the steel sheets of coil stock, the steel sheets of the laminated steel sheets for the stator core and the steel sheets of the laminated steel sheets for the rotor core can be manufactured from the same coil stock.

Each of the 1 st units 425 has 1 st permanent magnet 423 (magnet of claim) fixed thereto. The 3 rd distance C is less than the 4 th distance D.

Thereby, a plurality of changes of the rotor core 422 having different lengths in the axial direction can be configured in a state where the length of the 1 st cell 425 in the axial direction is larger than the length of the 1 st permanent magnet 423 in the axial direction.

By setting the difference G between the 4 th distance D and the 3 rd distance C to the thickness of 1 steel plate, the length of the 1 st unit 425 can be made longer than the 1 st permanent magnet 423 while minimizing the steel plate material constituting the rotor core 422. Further, by setting the difference G between the 4 th distance D and the 3 rd distance C to the thickness of 1 steel plate, it is possible to use a plurality of changes in the number of steel plates of the minimum number to configure the rotor core 422 having different lengths in the axial direction in a state where the length of the stator core 41 in the axial direction is larger than the length of the 1 st permanent magnet 423 in the axial direction.

The 3 rd distance C is less than the 5 th distance E. Thereby, a plurality of changes of the stator core 41 having different lengths in the axial direction can be configured in a state where the length in the axial direction of the 2 nd unit 413 is larger than the length in the axial direction of the 1 st permanent magnet 423.

By setting the difference G between the 5 th distance E and the 3 rd distance C to the thickness of 1 steel plate, the length of the 1 st unit 425 can be made longer than the 1 st permanent magnet 423 while minimizing the steel plate material constituting the stator core 41. Further, by setting the difference G between the 5 th distance E and the 3 rd distance C to the thickness of 1 steel plate, it is possible to use a plurality of changes of the stator core 41 having different lengths in the axial direction in a state where the length of the 2 nd unit 413 in the axial direction is larger than the length of the 1 st permanent magnet 423 in the axial direction, with the minimum number of steel plates.

[ modified examples ]

Next, a modified example will be described. The same reference numerals are given to the same components as those in the embodiment, and the description thereof is omitted. Fig. 6 is a perspective view schematically showing the entire structure of a motor unit according to a modification.

As shown in fig. 6, in the modification, a rotor 42A (rotor) including a permanent magnet 421A (magnet of the claims) and a rotor core 422A (rotor core) is disposed on the outer peripheral side of a stator 40a (stator) including a stator core 41A (stator core). The modification has a so-called outer rotor type structure.

The stator core 41A has a back yoke 411A and teeth 412A. The back yoke 411A and the teeth 412A are integrated. The back yoke 411A is an annular member centered on the center axis Ax when viewed in the axial direction of the center axis Ax. The teeth 412A protrude from the outer circumferential surface of the back yoke 411A toward the outer circumferential side (radially outward). The coil is wound around the teeth 412A with an insulator not shown.

The back yoke 411A is provided with a through hole 411Aa extending in the axial direction. The through hole 411Aa extends in the axial direction of the central axis Ax. Here, the stator core 41A includes laminated steel plates. The laminated steel sheet is formed by stacking a plurality of 1 steel sheets formed by punching and having the back yoke 411A, the teeth 412A, and the through holes 411Aa in the axial direction.

The through hole 411Aa is used for caulking, for example. That is, for example, the 2

nd units

413A and 414A are produced by stacking a predetermined number of steel sheets, inserting a rivet into the through hole 411Aa, and then crushing the rivet in the axial direction. The stator core 41A is manufactured by laminating a plurality of 2

nd units

413A and 414A in the axial direction.

The 2 nd unit 413A is stacked on one side (upper side in fig. 6) of the 2 nd unit 414A in the axis direction. In the modification, the 2 nd unit 413A and the 2 nd unit 414A are formed of laminated steel sheets having the same thickness and the same number of steel sheets laminated thereon. In fig. 6, the boundary S3 between the 2 nd cell 413A and the 2 nd cell 414A is easily visually recognized and is shown by a thick line for convenience, but actually, steel sheets having the same thickness are stacked without a gap in the axial direction.

The stator core 41A may be manufactured by fixing all the steel plates without passing through the 2

nd units

413A and 414A by, for example, riveting with rivets (japanese patent No. かしめ). The material of the steel plate constituting the stator core 41A is not particularly limited, and various steel plates can be used, and for example, a silicon steel plate is preferable.

The rotor 42A includes a rotor core 422A and a permanent magnet 421A (magnet of the claims). The rotor core 422A is also formed of a laminated steel plate in which a plurality of 1 steel plate formed into a desired shape by punching is stacked in the axial direction. The rotor core 422A is provided with a through hole 422Ab extending in the axial direction.

The through hole 422Ab is used for caulking, for example. That is, for example, the 1

st units

425A and 426A are produced by stacking a plurality of steel plates of a predetermined number, inserting a rivet into the through hole 422Ab, and then crushing the rivet in the axial direction. The rotor core 422A is configured by stacking the 1 st unit 425A on one side (upper side in fig. 6) in the axial direction of the 1 st unit 426A. In the modification, the 1 st unit 425A and the 1 st unit 426A are made of steel plates having the same thickness and the same number.

In fig. 6, for easy visual confirmation of boundary S4 between 1 st cell 425A and 1 st cell 426A, the boundary is shown in bold line for convenience, but actually steel sheets of the same thickness are stacked without a gap in the axial direction. The rotor core 422A may be manufactured by fixing all the steel plates without passing through the 1

st cells

425A and 426A by riveting with rivets (japanese patent No. かしめ), for example. The material of the steel plate constituting rotor core 422A is not particularly limited, and various steel plates can be used, and for example, a silicon steel plate is preferable.

The thickness of 1 steel sheet constituting rotor core 422A is the same as the thickness of 1 steel sheet constituting stator core 41A. By making the number of steel sheets of the laminated steel sheets constituting the rotor core 422A equal to the number of steel sheets of the laminated steel sheets constituting the stator core 41A, the height of the laminated steel sheets of the rotor core 422A in the axial direction can be easily made equal to the height of the laminated steel sheets of the stator core 41A in the axial direction.

As described above, the DD motor of the modified example has a so-called outer rotor type structure. Specifically, the rotor 42A is disposed on the outer peripheral side of the stator 40A. Since the basic structure of the DD motor of the modification is the same as that of the DD motor 1 of the embodiment, the operational effects that can be obtained in the embodiment can also be obtained in the modification. For example, even when the permanent magnet 421A (a magnet in the claims) is displaced from the axial position of the stator core 41A due to the dimensional variation in the axial direction generated when the components of the DD motor are assembled, the magnetic flux (magnetic field) generated by the permanent magnet 421A can be transmitted to the stator core 41A to a greater extent, thereby reducing the leakage of the magnetic flux. Therefore, a larger output can be obtained, and even a smaller permanent magnet 421A can rotate the rotor 42A.

Description of the reference numerals

1. DD motors (direct drive motors); 40. 40A, a stator; 41. 41A, a stator core; 42. 42A, a rotor; 413. 413A, 414A, Unit 2; 421. 421A, permanent magnet (magnet); 422. 422A, a rotor core; 423. 1 st permanent magnet (magnet); 424. 2 nd permanent magnet (magnet); 425. 425A, 426A, unit 1; A. a 1 st distance; B. a 2 nd distance; C. a 3 rd distance; D. a 4 th distance; E. the 5 th distance.

Claims

1. A direct drive motor, wherein,

the direct drive motor includes:

a stator having a stator core arranged along a circumferential direction around a central axis; and

a rotor including a rotor core disposed on an outer side or an inner side in a radial direction orthogonal to the central axis with respect to the stator core, and a magnet fixed to the rotor core and disposed to face the stator core in the radial direction,

one of the axial directions of the central axis is set as a 1 st direction, and the direction opposite to the 1 st direction is set as a 2 nd direction,

a 1 st distance of the magnet from an end in a 1 st direction to an end in a 2 nd direction along an axial direction is smaller than a 2 nd distance of the stator core from the end in the 1 st direction to the end in the 2 nd direction along the axial direction,

a1 st position separated from the end of the magnet in the 1 st direction by a half distance of the 1 st distance in the 2 nd direction coincides with a 2 nd position separated from the end of the stator core in the 1 st direction by a half distance of the 2 nd distance in the 2 nd direction in the axial direction.

2. The direct drive motor of claim 1,

the stator core and the rotor core have a laminated steel plate formed by laminating a plurality of steel plates in an axial direction.

3. The direct drive motor of claim 2,

the laminated steel plates of the stator core and the laminated steel plates of the rotor core are formed by laminating the same number of steel plates having the same thickness.

4. The direct drive motor according to claim 2 or 3,

the laminated steel plate of the rotor core is formed by stacking a predetermined number of 1 st units in an axial direction, and 1 magnet is fixed to each of the 1 st units,

a3 rd distance of the magnet from an end in a 1 st direction to an end in a 2 nd direction along the axial direction is smaller than a 4 th distance of the 1 st unit from the end in the 1 st direction to the end in the 2 nd direction along the axial direction.

5. The direct drive motor of claim 4,

the difference between the 4 th distance and the 3 rd distance is an amount of 1 sheet of the steel plate.

6. The direct drive motor according to claim 4 or 5,

the laminated steel plate of the stator core is obtained by stacking a plurality of No. 2 units of laminated steel plates with a predetermined number in the axial direction,

the 3 rd distance is smaller than a 5 th distance of the 2 nd unit from an end in the 1 st direction to an end in the 2 nd direction along the axis direction.

7. The direct drive motor of claim 6,

the difference between the 5 th distance and the 3 rd distance is an amount of 1 sheet of the steel plate.