Motor

Abstract

To provide a motor which can achieve a request of downsizing.SOLUTION: A motor 1 has a shaft member 5, a cylindrical rotor 3 rotatable relative to the shaft member 5, a bearing 4 supporting the rotor 3 relative to the shaft member 5, and a stator 2 positioned at an inner side of the rotor 3. Preferably, the rotor 3 has a cylindrical member 32 formed by a single member, and a magnet 31.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a motor.

Background Art

[0002] Conventionally, various motors have been developed, manufactured, and used according to various applications and required performances. However, there is a demand for further miniaturization. In addition, in various other applications, there are also demands for high torque and miniaturization. That is, a motor that can achieve high performance as a motor while being small is desired.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, an example of an object of the present invention is to provide a motor that can achieve the requirement of miniaturization.

Means for Solving the Problems

[0005] The above problems are solved by the following present invention. That is, the motor of the present invention includes a shaft member, a cylindrical rotating body rotatable with respect to the shaft member, a bearing that supports the rotating body with respect to the shaft member, a stator inside the rotating body, and.

[0006] In the motor of the present invention, the rotating body can be configured to include a cylindrical member formed of a single member and a magnet. Further, in the motor of the present invention, the stator can be fixed to the shaft member. As the radial dimension of the stator, it can be made smaller than or equal to the radial dimension of the bearing.

[0007] As the bearing, it can be provided with two bearings, a first bearing and a second bearing. At this time, the rotating body includes a cylindrical member formed of a single member and a magnet, In the axial direction of the shaft member, either one or both of the magnet and the stator can be provided between the first bearing and the second bearing.

[0008] Further, the rotating body has two end portions in the axial direction of the shaft member, and the first bearing is fixed to a part of the rotating body on one end portion side of the two end portions, The second bearing may be fixed to another part of the rotating body on the other end portion side of the two end portions.

[0009] Also, the first bearing and the second bearing may be fixed to the rotating body at both end portions of the rotating body or in the vicinity thereof in the axial direction of the shaft member. Also, the cylindrical member may be formed of a single member from a part of the cylindrical member to which the first bearing is fixed to another part of the cylindrical member to which the second bearing is fixed.

[0010] In the motor of the present invention, the first bearing and the second bearing can be members having the same configuration. Also, in the motor of the present invention, the radial dimension of the cylindrical member on one end portion side of the shaft member can be made larger than the radial dimension of the cylindrical member on the other end portion side of the shaft member.

[0011] Furthermore, in the motor of the present invention, it is preferable that the shaft member is coaxially fixed to the rotating body.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0013] Hereinafter, the motor according to the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional perspective view of the motor 1 according to an embodiment which is an example of the present invention, as viewed obliquely from above, and FIG. 2 is a longitudinal sectional view thereof.

[0014] In the description of the present embodiment, when referring to upward to downward, it means the vertical relationship in FIGS. 1 and 2, and does not necessarily coincide with the vertical relationship in the direction of gravity (the same applies to the modifications described later). Further, in the description of the present embodiment, the portion that rotates within the motor 1 may be referred to as the "rotating side", and the portion that supports the members on the rotating side and is fixed without rotating itself may be referred to as the "fixed side".

[0015] In the motor 1 of the present embodiment, a shaft member (column 5) described later is fixed to the member to be attached 7. The member to be attached 7 is an object to which the motor 1 is fixed, and examples thereof include the housing of the motor, and a device (electronic device, automobile as a moving body, frame or substrate of a rotating device, etc.) to which the motor is attached. The member to be attached 7, together with the shaft member, becomes a member on the fixed side.

[0016] The shaft member and the attached member 7 are members that are stationary relative to the rotating body described later. Therefore, these are collectively referred to as the stationary member (stationary part). Note that the stationary member (stationary part) only needs to be stationary relative to the rotating body, and it is not necessary for the stationary member (stationary part) itself to be completely stationary. It may be swayed by the rotation of the rotating body. That is, it only needs to be stationary relative to the rotating body. The attached member 7 uses the motor 1 as the attached member and serves as the mounting member to which the attached member is attached.

[0017] The motor 1 includes a rotor 3 that is a rotating body, a stator 2 surrounded by the rotor 3, a bearing 4, and a column 5 that is a shaft member. The stator 2 includes a stator core 21 fixed to the column 5 and having a magnetic pole portion 23 that radially extends outward from the column 5 as an axis, and a coil 22 wound around the magnetic pole portion 23.

[0018] The stator core 21 is a laminate such as a silicon steel sheet, and includes an annular portion 24 arranged coaxially with the column 5, and a plurality of magnetic pole portions 23 formed to radially extend outward from the annular portion 24. The coil 22 is wound around each of the plurality of stator cores 21. The stator core 21 and the coil 22 are insulated by an insulator (not shown) formed of an insulator. Note that instead of the insulator, an insulating film may be coated on the surface of the stator core to insulate from the coil.

[0019] The rotor 3 includes a magnet 31 that faces the magnetic pole portion 23 on the outer peripheral side of the stator 2, and a cylindrical tubular member 32 to which the magnet 31 is attached to the inner peripheral surface directly or via another member such as an adhesive. The tubular member 32 is cylindrical with the axis of the column 5 as the center and surrounds the stator 2. Also, the tubular member 32 is formed of a single member. The tubular member 32 also has a function of suppressing the leakage of the magnetic field from inside the tubular member 32 and is formed of a magnetic material. Note that if there are no problems in terms of characteristics, the tubular member 32 may be formed of a non-magnetic material such as aluminum or plastic.

[0020] The magnet 31 is attached to the inner peripheral surface of the cylindrical member 32 so as to face the stator 2. The magnet 31 has an annular shape, and regions magnetized to the N pole and regions magnetized to the S pole are alternately provided at regular intervals along the circumferential direction. The magnet 31 may be an annular integrally molded product, or a plurality of magnets may be arranged side by side on the inner peripheral surface of the cylindrical member 32 and arranged in a cylindrical shape. A predetermined magnetic gap G is provided between the magnet 31 and the stator 2. This magnetic gap G is arranged in a plurality or continuously in the circumferential direction. Also, a predetermined gap is provided between the magnet 31 and the stator 2 so that the magnetic gap G has at least a certain radial dimension.

[0021] The bearings 4 are arranged on both sides of the stator 2 in the axial direction of the column 5, and have two bearings, a first bearing 41 located above and a second bearing 42 located below. That is, the magnet 31 and the stator 2 are located between the first bearing 41 and the second bearing 42 in the axial direction of the column 5. The first bearing 41 and the second bearing 42 use members having the same configuration (same shape, structure, size, and material). Hereinafter, the first bearing 41 will be taken up for explanation, but the same applies to the second bearing 42.

[0022] The first bearing 41 is a so-called ball bearing having an outer peripheral ring 41a, an inner peripheral ring 41b, and bearing balls 41c interposed between the outer peripheral ring 41a and the inner peripheral ring 41b. By rolling the bearing balls 41c between the outer peripheral ring 41a and the inner peripheral ring 41b, the rotational resistance of the inner peripheral ring 41b with respect to the outer peripheral ring 41a is significantly reduced. The first bearing 41 is formed of a member such as a hard metal such as iron or ceramics due to its function.

[0023] The outer peripheral rings 41a of the first bearing 41 and the outer peripheral rings 42a of the second bearing 42 are fixed to the inner peripheral surfaces at both ends of the cylindrical member 32. Also, in the axial direction of the column 5 which is a shaft member, the outer peripheral ring 41a of the first bearing 41 and the outer peripheral ring 42a of the second bearing 42 face the stator 2. On the other hand, the inner peripheral rings 41b of the first bearing 41 and the inner peripheral rings 42b of the second bearing 42 are respectively fixed to the peripheral surface of the column 5. In the axial direction of the column 5 which is a shaft member, the inner peripheral ring 41b of the first bearing 41 and the inner peripheral ring 42b of the second bearing 42 face the magnet 31.

[0024] Thereby, the rotor 3 is rotatable with respect to the column 5. Also, the rotor 3 is configured to be rotatable about the axis of the column 5 as the central axis. As shown in FIG. 2, in the present embodiment, the radius dimension b which is the dimension in the radial direction of the bearing 4 (first bearing 41) is larger (b > a) than the radius dimension a which is the dimension in the radial direction of the stator 2.

[0025] The column 5 is formed of, for example, aluminum to be lightweight and is in a hollow state (more specifically, a cylindrical state). In the present embodiment, the column 5 is a member on the fixed side. Since it is a member having a function of fixing and supporting the entire motor 1, rigidity corresponding to the function is required.

[0026] An opening 51 is provided in the middle of the column 5, and the lead wire 25 connected to the coil 22 is drawn into the cavity 52 inside the column 5 from the opening 51 and is drawn out from the end opening 53 of the column 5 to the outside of the motor 1.

[0027] In the motor 1 according to the present embodiment, both ends of the cylindrical member 32 are closed by the first bearing 41 and the second bearing 42. Power is supplied from the outside to the coil 22 of the stator 2 in the closed space.

[0028] In the motor 1 according to the present embodiment, by passing the lead wire 25 through the cavity 52 inside the column 5, the space enclosed by the cylindrical member 32, the bearing 4, etc. is electrically connected to the outside thereof. Therefore, the lead wire 25 enables power supply to the coil 22 of the stator 2 in the enclosed space.

[0029] In the motor 1 configured as described above, the rotor 3 surrounding the stator 2 is rotatable with respect to the stator 2 fixed to the column 5, constituting a so-called outer rotor type brushless motor. However, in a general outer rotor type brushless motor, the shaft fixed to the rotor rotates, and the rotational force is extracted by the shaft. In the motor 1 according to the present embodiment, the column 5 whose axis coincides with the center axis of the rotation of the rotor 3 is a fixed-side member, and the rotational force is directly extracted from the rotor 3.

[0030] By forming the cylindrical member 32 as a single member, the central axes of the first bearing 41 and the second bearing 42 can be made coaxial with respect to the column 5. When the cylindrical member 32 is formed of a plurality of members, it may be necessary to consider a plurality of tolerances for the plurality of members constituting the cylindrical member 32 and the first bearing 41 and the second bearing 42. However, by forming the cylindrical member 32 as a single member, the number of tolerances to be considered can be reduced, and it becomes easy to align the central axes of the first bearing 41 and the second bearing 42 coaxially with respect to the column 5.

[0031] The member to be attached 7 is a member to which the motor 1 is fixed, and is formed of, for example, plastic or metal. The member to be attached 7 is depicted as a flat plate in the drawing, but this is only an example assuming that the periphery of the portion where the motor 1 is attached is flat. The member to be attached 7 can have various shapes depending on what the member to be attached 7 itself is. The periphery of the portion where the motor 1 is attached does not have to be flat.

[0032] In the motor 1 according to the present embodiment, the column (shaft member) 5 is coaxially fixed to the member 7 to be attached. Further, in the motor 1 according to the present embodiment, the column (shaft member) 5 is coaxially fixed to the rotor 3 which is a rotating body.

[0033] In the motor 1 according to the present embodiment, the column 5 is on the fixed side, and the rotor 3 which is a rotating body is rotated with respect to the column 5 via the bearing 4. Therefore, as shown in FIG. 2, the radial dimension a of the stator 2 can be made smaller than the radial dimension b of the bearing 4 (b > a). Therefore, the stator 2 can be made very small.

[0034] In a conventional outer-rotor type brushless motor in which a rotating body that contacts the rotor 3 and a shaft that contacts the column 5 are fixed and rotate together, a bearing must be arranged between the stator, which is the fixed side located inside the rotating body, and the shaft. Therefore, the radial dimension a of the stator is inevitably larger than the radial dimension b of the bearing 4 (b < a).

[0035] However, if the configuration of the present invention is provided, it is possible to make the radial dimension a of the stator smaller than the radial dimension b of the bearing (b > a), or to make the two the same (b = a), and miniaturization of the entire motor can be realized. Further, when it is not necessary to project a shaft member for extracting the rotational force from the motor, further miniaturization and space saving can be realized.

[0036] In a conventional motor in which a rotating shaft member projects from the motor, one side of the shaft member is supported and rotates, and the rotational force is extracted from the protruding other end side. Therefore, rotational vibration is likely to occur. However, in the motor 1 according to the present embodiment, since the rotor 3 supported by the bearing 4 itself rotates as a rotating body, the rotation of the rotor 3 is stabilized.

[0037] In addition, in the motor 1 according to the present embodiment, the first bearing 41 and the second bearing 42 are respectively fixed to both end portions of the rotor 3, and the rotor 3 serving as a rotating body is supported. Therefore, the rotation of the rotor 3 is stabilized with respect to the column 5. In particular, the magnet 31, which is a constituent member of the rotor 3 as a rotating body and has a predetermined weight, is located between the first bearing 41 and the second bearing 42 that rotatably support the rotor 3 in the axial direction of the column 5. Therefore, the rotation of the rotor 3 is stabilized.

[0038] Note that as the positions where the bearings are arranged, it is more desirable that they are both end portions of the rotating body as in the present embodiment. However, if they are in the vicinity of both end portions of the rotating body, the rotation of the rotating body with respect to the shaft member will be in a sufficiently stable state. The "vicinity" mentioned here means a position closer to both end portions of the rotating body, and although it cannot be clearly defined numerically, for example, a region with a length of 20% from both ends in the axial direction of the rotating body, preferably a region with a length of 10% from both ends, is included in the concept of "vicinity of both end portions".

[0039] Furthermore, in the motor 1 according to the present embodiment, since the first bearing 41 and the second bearing 42 are members having the same configuration, the rotation of the rotor 3 is stabilized. As described above, the motor 1 according to the present embodiment is less likely to cause vibration in the rotation of the rotor 3 and can achieve high-precision stabilization. The stabilization of the rotation of the rotor 3 means that it is less likely to cause rotational unevenness, so it is also possible to realize a higher torque of the motor 1. That is, the motor 1 according to the present embodiment can provide a motor with excellent basic characteristics while achieving miniaturization.

[0040] Next, the motor 1a according to the first modification of the present invention will be described with reference to the drawings. FIG. 3 is a longitudinal sectional view of a motor 1a according to a first modified example which is an example of the present invention. This FIG. 3 is a longitudinal sectional view of a cross section at substantially the same position as that in FIG. 2. In the description of this modified example, members or components having the same functions and structures as those in the above-described embodiment are given the same reference numerals as those in the above-described embodiment in FIG. 3, and detailed descriptions thereof are omitted (however, this is not the case when specific descriptions are added).

[0041] In this modified example, the configuration of the bearing 4a and the rotor 3a which is a rotating body is different from that of the bearing 4 and the rotor 3 in the above-described embodiment. As shown in FIG. 3, the bearing 4a in this modified example has the same second bearing 42 on the lower side as that in the above-described embodiment, but an antifriction bearing 44 is adopted on the upper side.

[0042] The antifriction bearing 44 is easier to be made smaller in size and diameter than a bearing which is a rolling bearing, and is suitable for high-speed rotation. Therefore, it can be said that it is suitable for adoption as a member of the motor of the present invention. As shown in FIG. 3, the antifriction bearing 44 is flat, and both the inner diameter and the outer diameter can be made smaller in diameter, so the outer diameter is smaller than that of the second bearing 42.

[0043] Also, in this modified example, the cylindrical member 32a in the rotor 3a has a stepped portion 33a near the upper end in the axial direction, and the outer diameter above the stepped portion 33a is reduced in diameter so as to be smaller than the outer diameter below, corresponding to the antifriction bearing 44 having a small outer diameter. And the outer diameter of the antifriction bearing 44 is fixed to the inner peripheral surface of the cylindrical member 32a where the diameter is reduced and the inner diameter is made smaller. That is, the radius dimension of the cylindrical member 32a on one end side of the column (shaft member) 5 is larger than the radius dimension of the cylindrical member 32a on the other end side of the column (shaft member) 5.

[0044] In this modification example, as shown in FIG. 3, the vertical direction (axial direction) is shortened, and at the upper part, the diameter of the rotor 3a is narrowed, so that further miniaturization is achieved compared with the above-described embodiment. Also, although the bearings 4a are different in the vertical direction, since the configuration of the motor 1a other than that is the same as that of the motor 1 in the above-described embodiment, the rotation can be stabilized.

[0045] As shown in FIG. 3, also in this modification example, the radius dimension b which is the dimension in the radial direction of the bearing 4a (second bearing 42) is larger (b > a) than the radius dimension a which is the dimension in the radial direction of the stator 2. Note that also on the lower side of the bearing 4a, the same bearing as the sliding bearing 44 is adopted instead of the second bearing 42, instead of the cylindrical member 32a whose diameter is reduced at the upper part, a cylindrical member with a smaller overall diameter is used, and instead of the stator 2, a stator with a smaller diameter than the inner diameter of the cylindrical member is used. In this case, the radius dimension b of the bearing is also larger (b > a) than the radius dimension a of the stator. In this case, the outer diameter of the rotor can be made even smaller, and further miniaturization can be achieved.

[0046] Next, the motor 1b according to the second modification example of the present invention will be described with reference to the drawings. FIG. 4 is a longitudinal sectional view of the motor 1b according to the second modification example which is an example of the present invention. The FIG. 4 is a longitudinal sectional view of a cross section at substantially the same position as FIGS. 2 and 3. In the description of this modification example, members or components having the same functions and structures as those in the above-described embodiment and the first modification example are given the same reference numerals as in the above-described embodiment and the first modification example in FIG. 4, and the detailed description thereof is omitted (however, this is not the case when particularly described).

[0047] In this modified example, similar to the first modified example, as the bearing 4a, the lower second bearing 42 is the same as that in the above embodiment, and a sliding bearing 44 is adopted on the upper side. However, the configuration of the rotor 3b, which is a rotating body, is different from that of the rotor 3a in the first modified example. In this modified example, the cylindrical member 32b in the rotor 3b has not only a stepped portion (first stepped portion 33b) near the upper end in the axial direction but also a stepped portion (second stepped portion 34b) near the lower end. That is, in this embodiment, the difference in the outer diameters between the second bearing 42 and the sliding bearing 44 is adjusted by the two-step diameter reduction of the first stepped portion 34a and the second stepped portion 33b.

[0048] In this embodiment, in the axial direction of the cylindrical member 32b, in the region near the lower end, the cylindrical member 32b has an inner diameter such that the second bearing 42 with a large outer diameter can be press-fitted and fitted. The diameter is reduced at the second stepped portion 34b, and the outer diameter becomes smaller above the second stepped portion 34b. Then, the diameter is further reduced at the first stepped portion 33b, which is in the same position as the stepped portion 33a in the first modified example, and the outer diameter becomes even smaller above the first stepped portion 33b, corresponding to the sliding bearing 44 with a small outer diameter. Since the difference in the outer diameter of the bearing 4a is adjusted by the two-step diameter reduction, although the first stepped portion 33b is in the same position as the stepped portion 33a in the first modified example, the degree of diameter reduction is gentler than that of the stepped portion 33a.

[0049] In this embodiment, by providing the first stepped portion 33b and the second stepped portion 34b, the central axes of the second bearing 42 and the sliding bearing 44 can be coaxially arranged with a small number of intersections with respect to the central axis (the dashed-dotted line in the figure) of the cylindrical member 32b. Further, when the second bearing 42 is press-fitted from the lower opening of the cylindrical member 32b, it is positioned by the second stepped portion 34b, which facilitates manufacturing and improves accuracy.

[0050] As shown in FIG. 4, also in this modified example, the radius dimension b, which is the dimension in the radial direction of the bearing 4a (second bearing 42), is larger (b > a) than the radius dimension a, which is the dimension in the radial direction of the stator 2.

[0051] Next, the motor 1c according to the third modification of the present invention will be described with reference to the drawings. FIG. 5 is a longitudinal sectional view of the motor 1c according to the third modification which is an example of the present invention. FIG. 5 is a longitudinal sectional view of a section at substantially the same position as FIGS. 2 to 4. In the description of this modification, members or parts having the same functions and structures as those in the above embodiment are denoted by the same reference numerals as in the above embodiment in FIG. 5, and detailed descriptions thereof are omitted (however, this is not the case when particularly described).

[0052] In this modification, unlike the first and second modifications, the bearing 4 has the same configuration as that in the above embodiment. In this modification, the configurations of the stator 2c and the rotor 3c which is a rotating body are different from those of the stator 2 and the rotor 3 in the above embodiment. In this modification, in the stator 2c, the radial length of the magnetic pole portion 23c is shorter than that of the magnetic pole portion 23 in the above embodiment, and accordingly, the width of the winding of the coil 22c is also shorter than that of the coil 22 in the above embodiment. Therefore, the radius dimension a which is the dimension in the radial direction of the stator 2c is shorter than that of the stator 2 in the above embodiment.

[0053] As described above, since the bearing 4 has the same configuration as that in the above embodiment, the inner diameter of the portion of the cylindrical member 32c corresponding to the bearing 4 is the same as that of the same portion of the cylindrical member 32 in the above embodiment, but the inner diameter of the portion of the cylindrical member 32c corresponding to the stator 2c is required to be smaller than that of the same portion of the cylindrical member 32 in the above embodiment.

[0054] In this modification, the difference between the inner diameter of the portion of the cylindrical member 32c corresponding to the bearing 4 and the inner diameter of the portion of the cylindrical member 32c corresponding to the stator 2c is adjusted by two stepped portions (the first stepped portion 33c and the second stepped portion 34c) at the upper and lower positions in the axial direction (the one-dot chain line in FIG. 5) of the cylindrical member 32c. In this modification, the cylindrical member 32c has an inner diameter such that the first bearing 41 and the second bearing 42 with large outer diameters can be press-fitted and fitted in the regions near the upper end and the lower end, and the inner diameter is smaller in the region therebetween corresponding to the stator 2c.

[0055] That is, the cylindrical member 32c has a large inner diameter in the region where the first bearing 41 is press-fitted, is reduced in diameter at the first stepped portion 33c, and has a small inner diameter in the region corresponding to the stator 2c. Then, the cylindrical member 32c is expanded in diameter again at the second stepped portion 34c and has a large inner diameter in the region where the second bearing 42 is press-fitted. At this time, the inner diameter of the cylindrical member 32c is equal in the region where the first bearing 41 is press-fitted and the region where the second bearing 42 is press-fitted.

[0056] In this modification, the first stepped portion 33c and the second stepped portion 34c can optimally adjust the inner diameter of the cylindrical member 32c in the axial direction between the portion corresponding to the bearing 4 and the portion corresponding to the stator 2c. Thereby, it is possible to reduce the diameter of the portion of the cylindrical member 32c corresponding to the stator 2c in the axial direction.

[0057] As shown in FIG. 5, also in this modification, the radius dimension b, which is the dimension of the bearing 4 (the first bearing 41 and the second bearing 42) in the radial direction, is larger (b > a) than the radius dimension a, which is the dimension of the stator 2c in the radial direction.

[0058] As described above, the preferred embodiments and modifications of the motor of the present invention have been described. However, the motor of the present invention is not limited to the configurations of the above embodiments and modifications. For example, in the above embodiments and the third modification, although the first bearing 41 and the second bearing 42 are assumed to be members having the same configuration, the present invention is not limited thereto, and members having different configurations (different shapes, different structures, different sizes, different materials) may be used.

[0059] In the motor according to the above embodiment, the first bearing 41 and the second bearing 42 are respectively fixed to both ends of the rotor, but the present invention is not limited thereto. The first bearing 41 may be fixed to a part of the rotor 3 on the magnet 31 side with respect to both ends of the rotor 3, and the second bearing 42 may be fixed to another part of the rotor 3. Even in such a mode, since the rotor 3 serving as a rotating body is supported, the rotation of the rotor 3 is stabilized with respect to the column 5.

[0060] Further, one end of the cylindrical members 32, 32a, 32b, 32c provided in the motor 1 according to the above embodiment or modification example may be made into a tub, and the first bearing 41 may be fixed to a part of the cylindrical members 32, 32a, 32b, 32c on the rotor 3 side from one end, and the second bearing 42 may be fixed to the other part of the cylindrical members 32, 32a, 32b, 32c on the other end or on the rotor 3 side from the other end.

[0061] Note that the arrangement of the first bearing 41 and the second bearing 42 is not limited to the mode of the above embodiment, and the order of the first bearing 41 and the second bearing 42 may be used, or the order of the second bearing 42 and the first bearing 41 may be used.

[0062] From the above, the rotating body includes two ends in the axial direction of the shaft member, the first bearing is fixed to a part of the rotating body on one end side of the two ends, and the second bearing may be fixed to another part of the rotating body on the other end side of the two ends.

[0063] In the motor according to the above embodiment or modification example, for the cylindrical members 32, 32a, 32b, 32c, at least from a part of the cylindrical members 32, 32a, 32b, 32c to which the first bearing 41 (or the sliding bearing 44) is fixed to the other part of the cylindrical members 32, 32a, 32b, 32c to which the second bearing 42 is fixed, the cylindrical members 32, 32a, 32b, 32c are formed of a single member.

[0064] In the motors according to the above-described embodiments and modifications, regarding the cylindrical members 32, 32a, 32b, 32c, at least from a part of the cylindrical members 32, 32a, 32b, 32c to which the first bearing 41 (or the sliding bearing 44) is fixed to the other part of the cylindrical members 32, 32a, 32b, 32c to which the second bearing 42 is fixed, the cylindrical members 32, 32a, 32b, 32c may have substantially the same radial dimension.

[0065] Also, in the above-described embodiments and modifications, the cylindrical members 32, 32a, 32b, 32c are formed of a single member, but are not limited thereto, and the cylindrical members may be formed of a plurality of members as necessary. In addition, those skilled in the art can appropriately modify the motor of the present invention according to conventionally known knowledge. As long as the configuration of the present invention is still provided by such modifications, of course, it is included in the scope of the present invention.

Explanation of Reference Numerals

[0066] 1, 1a, 1b, 1c... motors, 2, 2c... stators, 3, 3a, 3b, 3c... rotors (rotating bodies), 4, 4a... bearings, 5... columns (shaft members), 7... members to be attached, 21, 21c... stator cores, 22, 22c... coils, 23, 23c... magnetic pole portions, 24, 24c... annular portions, 25... lead wires, 31... magnets, 32, 32a, 32b, 32c... cylindrical members, 33a... stepped portions, 33b, 33c... first stepped portions, 34b, 34c... second stepped portions, 41... first bearing (bearing), 41a, 42a... outer peripheral rings, 41b, 42b... inner peripheral rings, 41c, 42c... bearing balls, 42... second bearing (bearing), 43... ring members, 44... sliding bearings, 51... openings, 52... cavities, 53... end openings

Claims

1. A shaft member, a cylindrical rotor rotatable with respect to the shaft member, a first bearing that supports a first portion of the rotor with respect to a first portion of the shaft member, a second bearing that supports a second portion of the rotor with respect to a second portion of the shaft member, a stator inside the rotor, and a magnet fixed to a third portion of the rotor, wherein the stator is fixed to a third portion of the shaft member, the radial dimension of the first bearing and the radial dimension of the second bearing are larger than the radial dimension of the magnet, the outer peripheral surface of the rotor is in the axial direction of the shaft member, a first step portion between the outer peripheral surface of the third portion of the rotor and the outer peripheral surface of the first portion of the rotor, and a second step portion between the outer peripheral surface of the third portion of the rotor and the outer peripheral surface of the second portion of the rotor, and the radial dimension of the outer peripheral surface of the third portion of the rotor is smaller than the radial dimension of the outer peripheral surface of the first portion of the rotor and the radial dimension of the outer peripheral surface of the second portion of the rotor, a motor.

2. A shaft member, a cylindrical rotor rotatable with respect to the shaft member, a first bearing that supports a first portion of the rotor with respect to the shaft member, a second bearing that supports a second portion of the rotor with respect to the shaft member, a stator inside the rotor, and a magnet fixed to a third portion of the rotor, wherein the stator is fixed to the shaft member, the radial dimension of the inner surface of the first portion of the rotor and the radial dimension of the inner surface of the second portion of the rotor are larger than the radial dimension of the inner surface of the third portion of the rotor, the outer peripheral surface of the rotor is in the axial direction of the shaft member, a first step portion between the outer peripheral surface of the third portion of the rotor and the outer peripheral surface of the first portion of the rotor, and a second step portion between the outer peripheral surface of the third portion of the rotor and the outer peripheral surface of the second portion of the rotor, and the radial dimension of the outer peripheral surface of the third portion of the rotor is smaller than the radial dimension of the outer peripheral surface of the first portion of the rotor and the radial dimension of the outer peripheral surface of the second portion of the rotor, a motor.

3. The motor according to claim 1 or 2, wherein the magnet and the stator are between the first bearing and the second bearing in the axial direction of the shaft member.

4. The rotor includes two end portions in the axial direction of the shaft member. The first bearing is fixed to a first portion of the rotating body on one end side of the two ends with respect to the stator. The second bearing is fixed to a second portion of the rotating body on the other end side of the two ends with respect to the stator. The motor according to any one of claims 1 to 3.

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