Motor

Abstract

To provide a motor for suppressing an increase in labor and costs even when used in applications such as a drone or other floating type mobile body that receives a large impact.SOLUTION: A motor 1 includes: a shaft 41; a plurality of bearings 42 supporting the shaft 41; a cartridge 4 having a sleeve 43 surrounding the bearings 42; a bottom part 51 that receives an impact from the outside; and a housing 5 having a mounting part 54 provided on the bottom part 51. The bottom part 51 of the housing 5 extends in a direction intersecting a longitudinal direction of the shaft 41. The cartridge 4 is detachably attached to the mounting part 54.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a brushless motor that can be mounted on a floating mobile object such as a drone. [Prior art documents] [Patent documents]

[0002] [Patent Document 1] Japanese Patent Application Publication No. 2018-117429 Summary of the Invention

[0003] The motor of the present invention comprises a housing having a shaft having one end and the other end, a plurality of ball bearings supporting a portion of the shaft on the one end side, a sleeve surrounding the plurality of ball bearings, a rotor fixed to a portion of the shaft between the other end of the shaft and the plurality of ball bearings, a stator surrounded by the rotor, a bottom, and a stator fixing portion provided on the rotor side of the bottom, wherein the inner surface of the sleeve has a plurality of recesses in the radial direction of the shaft, and the plurality of ball bearings are fixed to the plurality of recesses, the bottom of the housing extends in a direction intersecting the longitudinal direction of the shaft, the stator is fixed to the stator fixing portion, the rotor comprises a magnet, a cylindrical portion supporting the magnet, and a disk portion connecting the cylindrical portion to the shaft, and the cylindrical portion of the rotor is formed of a magnetic material. [Brief explanation of the drawings]

[0004] [Figure 1] 1 is a cross-sectional view of an outer rotor type motor according to an embodiment that is an example of the present invention. [Figure 2] 1 is a cross-sectional perspective view of a motor according to an embodiment of the present invention; [Figure 3] FIG. 3 is a cross-sectional perspective view of only the cartridge extracted from FIG. 2. [Figure 4] FIG. 2 is an exploded view illustrating a state in which the cartridge is attached to the housing. [Figure 5] FIG. 2 is a cross-sectional view of only the cartridge and the housing extracted from FIG. 1. [Figure 6] FIG. 4 is an exploded view illustrating a state in which the rotor is attached to the shaft. [Figure 7] FIG. 10 is a cross-sectional view of an inner rotor type motor according to a modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0005] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view of a motor 1 according to an embodiment of the present invention, and Fig. 2 is a cross-sectional perspective view of the same cross section as Fig. 1, viewed obliquely from above. In the description of this embodiment, when referring to "upper" or "lower," it means the up-down relationship in Figs. 1 and 2, and does not necessarily coincide with the up-down relationship in the direction of gravity.

[0006] The motor 1 comprises a stator 2 including teeth 23 extending radially outward and coils 22 wound around the teeth 23, a rotor 3 including magnets 31 facing the teeth 23 on the radially outer side of the stator 2, a cartridge 4 to which a shaft 41 fixed to the center of the rotor 3 as a rotating shaft is attached, and a housing 5 to which the stator 2 is fixed and which accommodates it, thereby constituting an outer rotor type brushless motor. The rotor 3 is rotatable relative to the stator 2.

[0007] The stator 2 surrounded by the rotor 3 includes a stator core 21 including teeth 23 and a coil 22 . The stator core 21 is a laminate of silicon steel plates or the like, and consists of a circular ring portion (core) 24 arranged coaxially with the shaft 41, and a plurality of teeth portions (magnetic pole portions) 23 formed to extend radially from the circular ring portion 24 toward the outer diameter side. The coils 22 are wound around each of the plurality of teeth 23. The stator core 21 and the coils 22 are insulated by an insulator (not shown) made of an insulating material. Instead of an insulator, an insulating film may be painted on the surface of the stator core to insulate it from the coils.

[0008] The rotor 3 is made up of a magnet 31 and a rotor yoke 32, and the rotor yoke 32 is made up of a cylindrical portion 33 on the outer edge and a disk portion 34 that connects the shaft 41 and the cylindrical portion 33. The cylindrical portion 33 rises vertically (downward in FIGS. 1 and 2) from the outer edge of the disk portion 34, has a cylindrical shape centered on the axis of the shaft 41, and surrounds the stator 2.

[0009] Rotor yoke (iron core) 32 is made of a magnetic material and has the function of preventing leakage of a magnetic field from inside rotor yoke 32. Although cylindrical portion 33 and disk portion 34 of rotor yoke 32 are made of a magnetic material, they may be made of a non-magnetic material if there is no problem in terms of characteristics. For example, the cylindrical portion 33 and the disk portion 34 may both be formed integrally from aluminum, or one of the cylindrical portion 33 and the disk portion 34 may be formed from a magnetic material and the other from a non-magnetic material. The magnet 31 is attached to the inner peripheral surface of the cylindrical portion 33 so as to face the stator 2. The magnet 31 has an annular shape, and regions magnetized to the north pole and regions magnetized to the south pole are provided alternately at a constant interval along the circumferential direction.

[0010] In this embodiment, the cartridge 4 is made up of a shaft 41, two bearings 42, 42', and a sleeve 43. Only the cartridge 4 is extracted from FIG. 2 and shown in a cross-sectional perspective view in FIG. The shaft 41 is made of, for example, aluminum to reduce weight, and is hollow (more specifically, cylindrical) as shown in FIG. The shaft 41 is provided with a step 41c at approximately the center in the axial direction, and the outer shape (diameter) of the upper side of the step 41c is smaller than the outer shape (diameter) of the lower side.

[0011] The two bearings 42, 42' are mounted side by side with a fixed distance between them on the lower side of the shaft 41. In the following description, when the term "bearing 42" is simply used, unless otherwise specified, the description applies to the two bearings 42, 42' (including the outer ring 42a, inner ring 42b, and bearing balls 42c, which are components of the bearing 42, as described below).

[0012] The bearing 42 is a so-called ball bearing consisting of outer rings 42a, 42a', inner rings 42b, 42b', and bearing balls 42c, 42c' interposed between the outer ring 42a and the inner ring 42b. The bearing balls 42c roll between the outer ring 42a and the inner ring 42b, significantly reducing the rotational resistance of the inner ring 42b relative to the outer ring 42a. Due to its function, the bearing 42 is made of, for example, a hard metal such as iron or a ceramic member.

[0013] The sleeve 43 is a cylindrical member made of, for example, plastic or metal. The outer peripheral surface of the sleeve 43 is smooth, but the inner peripheral surface of the sleeve 43 has a protruding portion (small-diameter inner peripheral portion) 43a that protrudes toward the central axis in the axial direction at the center, and a recessed portion (large-diameter inner peripheral portion) 43b that is recessed on both sides in the axial direction. Hereinafter, the protruding portion will be referred to as the small-diameter portion, and the recessed portion will be referred to as the large-diameter portion.

[0014] The sleeve 43 may be integrally molded by known means to have a shape having a small inner diameter portion 43a and a large inner diameter portion 43b. Alternatively, the sleeve 43 may be formed from two or more members, for example, by inserting a small diameter circular tube having an inner diameter of the small inner diameter portion 43a and an outer diameter equal to the inner diameter of the large inner diameter portion 43b into the inside of a large diameter circular tube having the inner diameter of the large inner diameter portion 43b, so that the small diameter circular tube is positioned approximately in the center of the large diameter circular tube in the axial direction. The small diameter circular tube may be made of a different material from that of the large diameter circular tube, for example, an elastic material such as a spiral spring.

[0015] The shaft 41 has, in the longitudinal direction (axial direction), one end 41a located on the bottom 51 side of the housing 5 (described later) and the other end 41b on the opposite side. Two bearings 42, 42' are positioned side by side near the one end 41a of the shaft 41. The shaft 41 is fitted into and fixed to the inner peripheral rings 42b of the two bearings 42, 42', and is supported by the two bearings 42, 42'. Thus, the shaft 41 is rotatably supported in the housing 5. A snap ring 44 is attached to the shaft 41 closer to the one end 41a than the bearing 42, preventing the shaft 41 from moving upward in FIG. 1 (removal of the shaft 41). If necessary, a metal washer may be used instead of the snap ring 44 to more firmly prevent the shaft 41 from coming off.

[0016] On the other hand, the outer rings 42a, 42a' of the two bearings 42, 42' are fitted into, fixed to, and supported by the two large inner diameter portions 43b of the sleeve 43. Therefore, in the cartridge 4, the shaft 41 is supported so as to be rotatable relative to the sleeve 43.

[0017] The housing 5 has a substantially flat bottom 51, an attachment portion 54 to which the cartridge 4 is detachably attached, and a stator fixing portion 55 to which the stator 2 is fixed. Of these, the bottom 51 forms a surface that receives external impacts. The bottom 51 also extends in a direction that intersects with the longitudinal direction (axial direction) of the shaft. Fig. 4 is an exploded view for explaining the state in which the cartridge 4 is attached to the housing 5. Also, Fig. 5 is a cross-sectional view of only the cartridge 4 and the housing 5 extracted from Fig. 1.

[0018] The bottom 51 has a circular opening 51a around a position (the center of the bottom 51) that intersects with the longitudinal direction of the shaft 41, an annular flat region (flat portion) 51b around the opening 51a, and an annular inclined region (inclined portion) 51c that is connected to the outer edge and inclined upward (toward the stator 2) toward the outer periphery. The shaft 41 can be seen from below the motor 1 through the opening 51a.

[0019] A cylindrical portion 52 that houses a part or all of the cartridge 4 is provided in the bottom portion 51, and in addition to an opening 51a, a protruding portion 51d that protrudes in an annular shape from the inner peripheral surface of the cylindrical portion 52 toward the central axis is formed in the inner (center) region of the cylindrical portion 52. A ring-shaped elastic member 56a is attached to the upper surface of the protruding portion 51d (the inner surface of the housing 5).

[0020] The stator fixing portion 55 has a flat cylindrical shape extending from the bottom portion 51 toward the stator 2 (upward in the axial direction of the shaft 41), and a stepped portion 55a where the wall thickness becomes thinner and the outer diameter becomes smaller is formed on the outer periphery of the stator fixing portion 55. The inner periphery of the annular portion 24 fits into this stepped portion 55a, and the stator 2 is fixed by known means such as adhesive. The stator 2 surrounds the cartridge 4. The mounting portion 54 is composed of a cylindrical portion 52 extending from the bottom portion 51 toward the stator 2 (upward in the axial direction of the shaft 41), and a ring-shaped fixing member 53 that is separate from the cylindrical portion 52. The cylindrical portion 52 has one end portion on the bottom portion 51 side and the other end portion on the opposite side of the bottom portion 51, and the fixing member 53 is provided at the other end portion of the cylindrical portion 52.

[0021] The fixing member 53 has a cylindrical portion (hereinafter referred to as the "cylindrical portion") 53a and an annular portion (hereinafter referred to as the "holding piece portion") 53b that projects in an annular shape from one end of the cylindrical portion 53a toward the central axis. A spiral groove (not shown) is provided on the inner peripheral surface of the cylindrical portion 53a so that it can be threaded into a spiral groove (not shown) provided on the upper outer peripheral surface of the cylindrical portion 52.

[0022] Additionally, a ring-shaped elastic member 56b is attached to the lower surface (the surface facing the bottom 51) of the pressing piece 53b. The lower surface of this pressing piece 53b faces the upper end of the sleeve 43. The elastic members 56a and 56b are made of an elastic material such as natural rubber, synthetic rubber, silicone rubber, or elastomer. In this embodiment, the elastic members 56a and 56b are made of the same material and have the same shape, but they may be made of different materials or may have different shapes, such as different thicknesses or diameters.

[0023] The cartridge 4 (sleeve 43) is attached to the housing 5 by being housed in the cylindrical portion 52. Then, the fixing member 53 is screwed and fixed to the upper part of the cylindrical portion 52 (the end opposite to the bottom portion 51), thereby sandwiching and fixing the cartridge 4 (sleeve 43) between the bottom portion 51. In other words, the cartridge 4 is sandwiched and fixed between the fixing member 53 and the bottom portion 51. In this way, the cartridge 4, together with the shaft 41, is detachably attached to the attachment portion 54.

[0024] At this time, in the longitudinal direction (axial direction) of the shaft 41, the elastic member 56a is interposed between the lower end of the sleeve 43 and the bottom portion 51 (projecting portion 51d), and the elastic member 56b is interposed between the upper end of the sleeve 43 and the fixed member 53. These elastic members 56a and 56b can suppress the transmission of external impacts to the cartridge 4.

[0025] When the cartridge 4 is attached to the housing 5, one end 41a of the shaft 41 is located inside the housing 5 (upper side in FIG. 1) of the bottom 51. That is, one end 41a of the shaft 41 is floating above the bottom 51. Therefore, for example, an impact from below is prevented from being directly transmitted to the shaft 41.

[0026] The rotor 3 is detachably fixed to the shaft 41 of the cartridge 4 attached to the housing 5 between the bearing 42' and the other end 41b of the shaft 41 opposite the bottom 51. Fig. 6 is an exploded view illustrating the state in which the rotor 3 is attached to the shaft 41. Note that the stator 2 and the housing 5 are not shown in Fig. 6.

[0027] When the shaft 41 is inserted from the other end 41b side into a hole (hereinafter referred to as the axial hole 35) provided in the central axis of the rotor 3, the inner periphery of the axial hole 35 abuts against the stepped portion 41c of the shaft 41. Next, the shaft 41 is inserted into the axial hole 36a of the mounting fixture 36, and the threaded holes 37 of the rotor 3 and the threaded holes 36b of the mounting fixture 36 are screwed in four places, thereby fixing the rotor 3 to the shaft 41. The rotor 3 or the mounting fixture 36 and the shaft 41 are fixed with a fixing means (not shown), so that movement in the rotational direction is restricted and the shaft 41 rotates along with the rotation of the rotor 3.

[0028] By assembling in the above manner, the motor 1 of this embodiment having the structure shown in FIGS. 1 and 2 is completed. According to the motor of this embodiment, the cartridge 4 can be removed from the mounting portion 54 of the housing 5 simply by removing the rotor 3 from the shaft 41 and removing the fixing member 53 from the upper end of the cylindrical portion 52. As described above, the mounting of the cartridge 4 is also easy; that is, according to the motor of this embodiment, the cartridge 4 can be easily attached and detached.

[0029] It is known that the impact on the drone body when landing can damage the bearings in the motors that drive the blades. For this reason, the motors must be replaced every time a large impact landing occurs, which requires time and effort and increases costs.

[0030] Therefore, the present invention has been made in consideration of the above background, and aims to provide a motor that minimizes increases in effort and cost even when used in applications that are subject to large impacts, such as floating mobile objects such as drones. The above-mentioned problems are solved by the present invention, which provides a motor comprising: a cartridge having a shaft, a plurality of bearings supporting the shaft, and a sleeve surrounding the bearings; and a housing having a bottom that receives external impacts and a mounting portion provided on the bottom, the bottom of the housing extending in a direction intersecting the longitudinal direction of the shaft, and the cartridge being detachably mounted to the mounting portion.

[0031] In the motor of the present invention, it is preferable that the cartridge is detachably attached to the attachment portion together with the shaft. In the motor of the present invention, it is preferable that the material forming the shaft has a smaller specific gravity than the material forming the bearing, and that the shaft is hollow. In the motor of the present invention, it is preferable that one of the two end portions of the shaft, which is located on the bottom side, is located more inward of the housing than the bottom.

[0032] In the motor of the present invention, the mounting portion may have a cylindrical portion that accommodates the cartridge, and in this case, in the longitudinal direction of the shaft, the cylindrical portion has one end on the bottom side and the other end on the opposite side from the bottom, and it is preferable that the cartridge is fixed by being sandwiched between the fixing member and the bottom.

[0033] In addition, in the motor of the present invention, it is preferable that there is an elastic member at least in a portion between the cartridge and the housing, and in this case, it is preferable that the elastic member is interposed between a portion of the cartridge and a portion of the housing that face each other in the longitudinal direction of the shaft, or it is preferable that the elastic member is interposed between the cartridge and the bottom, or between the cartridge and the fixed member, or both, in the longitudinal direction of the shaft.

[0034] The motor of the present invention may include a rotor detachably fixed to the shaft. In this case, the motor may include a stator surrounded by the rotor, and the rotor may have a disk portion detachably fixed to the shaft.

[0035] For example, when used in a floating mobile object such as a drone, bearings, which are precision components, are susceptible to damage when subjected to a large impact upon landing. Conventionally, when such damage occurs, the entire motor must be replaced. However, with the motor of this embodiment, the cartridge 4 is detachably attached to the mounting portion 54 while supporting the shaft 41. Therefore, only the cartridge 4 supporting the shaft 41 is prepared as a replacement part, and by simply replacing this, the damaged bearings can be restored and the motor can be revived. Therefore, motor replacement can be accomplished simply and inexpensively by replacing the cartridge 4, significantly reducing the effort and cost involved.

[0036] When assembling an entire motor, there are many parts and many factors that affect performance and tolerances, which makes it easy for individual differences in performance to occur between motors. Replacing the entire motor likely requires a review of the drive adjustment, which also requires time and cost. However, with the cartridge 4, which has a small number of parts and is easy to manufacture with high precision and uniform quality, individual differences are unlikely to occur. Therefore, in this embodiment, in which only the cartridge 4 is replaced, not only is there no need to review the drive adjustment before and after replacement, but added value in terms of performance can be expected, such as a longer motor life, improved performance due to reduced mechanical load, and reduced vibration and noise caused by rotational irregularities.

[0037] Furthermore, in contrast to conventional structures in which bearings are attached directly to the outer peripheral member, impact loads to the outer peripheral surface of the motor can damage the bearings, and because bearing 42 is attached via sleeve 43, which is a separate component, in motor 1 of this embodiment, impact is less likely to be transmitted directly to bearing 42. As a result, this embodiment can improve strength against external impacts.

[0038] Furthermore, in the motor 1 of this embodiment, elastic members 56a, 56b are interposed at least partially between the cartridge 4 and the housing 5. Because the cartridge 4 and the housing 5 are separate members in this manner, the elastic members 56a, 56b are interposed therebetween as shock absorbers, thereby protecting the bearing 42.

[0039] In particular, when used for drone applications, the cartridge 4 is susceptible to axial impact loads when landing. However, in this embodiment, at the point where the cartridge 4 and the housing 5 face each other in the axial direction of the shaft 41, i.e., in the longitudinal direction (axial direction) of the shaft 41, an elastic member 56a is interposed between a portion of the cartridge 4 (sleeve 43) and the bottom 51, and an elastic member 56b is interposed between a portion of the cartridge 4 (sleeve 43) and the fixing member 53, thereby further improving impact resistance to axial impact loads.

[0040] In the motor 1 of this embodiment, elastic members 56a, 56b are provided between the sleeve 43 and the bottom 51 or fixed member 53, but the elastic members may be provided with the outer ring 42a instead of the sleeve 43, or between the sleeve 43 and the outer ring 42a and the bottom 51 or fixed member 53, or even an elastic member may be provided to cover the entire cartridge 4.As long as an elastic member is interposed at least partially between the cartridge 4 and the housing 5, it is possible to expect improved impact resistance against external impacts.

[0041] Furthermore, in the motor of this embodiment, one end 41a of the shaft 41 is located closer to the interior of the housing 5 (upper side in Figure 1) than the bottom 51, and is floating above the bottom 51, which prevents impacts from below from being directly transmitted to the shaft 41, further improving impact resistance against axial impact loads.

[0042] In the motor 1 of this embodiment, the area inside (the central axis side of) the cylindrical portion 52 of the bottom 51 is open, making the shaft 41 visible from below the motor 1, but if there is no opening or the opening is narrow and the bottom is located opposite one end 41a of the shaft 41, the same effect as this embodiment can be achieved as long as the bottom and one end of the shaft are spaced apart. This state in which the bottom and one end of the shaft are spaced apart is included in the concept of "one end on the bottom side is located inside the housing with respect to the bottom" according to the present invention.

[0043] Furthermore, in motor 1 of the present embodiment, shaft 41 is made of, for example, aluminum to reduce weight, and has a smaller specific gravity than the material (iron) that forms bearing 42. By reducing the weight of shaft 41, damage to bearing 42 when subjected to external impact can be reduced.

[0044] Furthermore, in this embodiment, shaft 41 is hollow (more preferably cylindrical), which further reduces damage. Even if the same material as bearing 42 or a material with the same specific gravity is used, making shaft 41 hollow can reduce the weight of shaft 41 and reduce damage to bearing 42 when it receives an external impact.

[0045] Although the motor of this embodiment is configured as an outer rotor brushless motor, the present invention is also applicable to motors other than brushless motors. The present invention is also applicable to inner rotor motors. Fig. 7 is a cross-sectional view of a modified motor in which the configuration of the present invention is applied to an inner rotor motor. In Fig. 7, components that have the same function, configuration, and shape as those in the embodiment shown in Fig. 1 are assigned the same reference numerals as in Fig. 1 (embodiment), and detailed descriptions thereof will be omitted.

[0046] 7, in an inner rotor type motor 101, a rotor 103 is disposed inside a stator 102. This rotor 103 has a rotor yoke 132 and an annular magnet 131 attached to the outer peripheral surface of the rotor yoke 132. Furthermore, because the rotor yoke 132 is located inside the stator 102, the outer diameter of the cylindrical portion 133 is smaller than that of the annular portion 124 of the stator 102, and the outer diameter of the disk portion 134 is sized accordingly.

[0047] The stator 102, which is arranged to surround the rotor 3, comprises a stator core 121 including a circular ring portion (core) 124 arranged coaxially with the shaft 41 and a plurality of teeth portions (magnetic pole portions) 123 formed to extend from the circular ring portion 124 toward (the center of) the shaft 41, and a coil 122 wound around each of the plurality of teeth portions 123.

[0048] The housing 105 has the same structure as the housing 5 of the embodiment in the vicinity of the mounting portion 54 to which the cartridge 4 is detachably attached, but differs in that the stator fixing portion 155 to which the stator 102 is fixed is located on the outer edge of the inclined region 151c, and the step portion 155a is formed on the inner circumferential side of the stator fixing portion 155. In accordance with these differences in configuration, the sizes and shapes of the flat region 151b and the inclined region 151c also differ.

[0049] As shown as a modified example in Figure 7, the configuration of the present invention can be applied without any problems to an inner rotor type motor 101, and this modified example not only has the effect of making it easy to attach and detach the cartridge 4, but also provides the various other accompanying effects of the present invention described in the embodiment section.

[0050] Although the motor of the present invention has been described above with reference to preferred embodiments, the motor of the present invention is not limited to the configuration of the above embodiments. For example, although the above embodiments have been described with reference to an example in which two bearings, 42 and 42', the number of bearings included in the cartridge may be three or more.

[0051] In the above embodiment, an example is given in which the cartridge 4 is configured as one cartridge including the shaft 41, but in the present invention, the cartridge may be configured to have a plurality of bearings and sleeves without including a shaft. Even in a configuration without a shaft, if it is necessary to replace a bearing due to damage, etc., the bearing can be easily replaced along with the cartridge.

[0052] Furthermore, by separating the shaft from the cartridge, for example, it is possible to replace only the cartridge containing the damaged bearing, and the shaft in usable condition can be reused.If you also want to replace the shaft, you can prepare a replacement shaft along with the cartridge, press it into the bearing in advance, and then replace the entire cartridge that supports the shaft.

[0053] Even for cartridges that do not include a shaft, the bearings can be assembled to the sleeve with high precision, making it easy to produce a homogeneous product with high precision. As a result, when replacing only the cartridge 4, not only is there no need to review the drive adjustment before and after replacement, but it is also possible to expect added value improvements in terms of performance, such as a longer motor life, improved performance due to reduced mechanical load, and reduced vibration and noise caused by uneven rotation.

[0054] Of course, the configuration exemplified in the above embodiment, in which one cartridge is configured including the shaft, is preferable in terms of work efficiency, as the entire cartridge supporting the shaft can be easily replaced.

[0055] Furthermore, in the above embodiment, an example is given in which the elastic members 56a, 56b are attached (adhered) to the components on the housing 5 side (the protruding portion 51d on the bottom 51 and the pressing piece portion 53b on the fixing member 53), but the elastic members do not necessarily have to be attached to the components on the housing 5 side, and may be attached to the components on the cartridge 4 side (for example, the sleeve 43, etc.), or may be independent parts that are simply sandwiched in place without being attached to either.

[0056] In order to achieve the effects of the present invention based on the detachable cartridge, it is not necessary to interpose an elastic member between the cartridge and the housing, but it is of course preferable that an elastic member be interposed.

[0057] Furthermore, although the example of the housing 5 has been given in which the bottom 51 includes a flat region (flat region 51b), the bottom of the housing may be flat as a whole, or may not have a flat region and may be formed, for example, in a gentle dome shape or with only an inclined surface. Regardless of whether or not there is a flat region, as long as there is a surface that can constitute the bottom of the housing as a whole, the surface is considered to be included in the concept of a "flat or approximately flat bottom."

[0058] Furthermore, in this embodiment, the sleeve 43 has been described as having a small inner diameter portion 43a and a large inner diameter portion 43b, and the outer diameter is of a uniform shape, but in the present invention, there are no restrictions on the shape of the sleeve, and any sleeve can be used without problem as long as it can support the outer rings of multiple bearings and is configured to be detachable from the mounting portion of the housing.

[0059] In addition, those skilled in the art can appropriately modify the motor of the present invention in accordance with conventionally known knowledge. As long as such modifications still comprise the configuration of the present invention, they are of course included in the scope of the present invention. [Explanation of symbols]

[0060] 1,101...motor, 2,102...stator, 21,121...stator core, 22,122...coil, 23,123...teeth portion, 24,124...annular portion, 3,103...rotor, 31,131...magnet, 32,132...rotor yoke, 33,133...tubular portion, 34,134...disk portion, 35...shaft hole, 36...mounting fixture, 36a...shaft hole, 4...cartridge, 41...shaft, 41a...one end, 41b...other end, 41c...step portion, 42,42'...bearing, 42 a, 42a'...outer ring, 42b, 42b'...inner ring, 42c, 42c'...bearing ball, 43...sleeve, 43a...small inner diameter portion, 43b...large inner diameter portion, 44...snap ring, 5,105...housing, 51, 151...bottom, 51a...opening, 51b, 151b...flat region, 51c, 151c...inclined region, 51d...projecting portion, 52...cylindrical portion, 53...fixing member, 54...mounting portion, 55, 155...stator fixing portion, 55a, 155a...step portion, 56a, 56b...elastic member

Claims

1. a shaft having one end and an opposite end; a plurality of ball bearings supporting a portion of one end side of the shaft; and a sleeve surrounding the plurality of ball bearings; a rotor fixed to a portion of the shaft between the other end of the shaft and the plurality of ball bearings; a stator surrounded by the rotor; a housing having a bottom; In a radial direction of the shaft, the bottom of the housing includes a rotor side portion and a shaft side portion, The inner circumferential surface of the sleeve has a plurality of recesses in the radial direction of the shaft, the plurality of ball bearings are fixed to the plurality of recesses, a stator fixing portion provided on a rotor side portion of a bottom of the housing, the sleeve is provided on a portion of the bottom of the housing on the shaft side, a portion of the bottom of the housing between the sleeve and the stator fixing portion extends in a direction intersecting with a longitudinal direction of the shaft; the stator is fixed to the stator fixing portion, the rotor includes a magnet, a cylindrical portion supporting the magnet, and a disk portion connecting the cylindrical portion to the shaft, The motor, wherein the cylindrical portion of the rotor is formed of a magnetic material.

2. The motor according to claim 1 , wherein a space is enclosed by the sleeve, the stator fixing portion, and a portion of the bottom of the housing between the sleeve and the stator fixing portion.

3. The motor of claim 1 or 2, further comprising a mounting fixture fixed to the rotor.

4. the bottom of the housing includes a mounting portion provided on the shaft side; 4. The motor according to claim 1, wherein a cartridge having the plurality of ball bearings and the sleeve is detachably attached to the attachment portion together with the shaft.

5. 5. The motor according to claim 1, wherein a member forming said shaft has a specific gravity smaller than that of a member forming said ball bearing.

6. The motor according to any one of claims 1 to 5, wherein the shaft is hollow.

7. 7. The motor according to claim 1, wherein one end of the shaft that is closer to the bottom is located more inward of the housing than the bottom.

8. The motor according to claim 4 , wherein the mounting portion has a cylindrical portion that houses the cartridge.

9. A floating mobile body comprising the motor according to any one of claims 1 to 8.

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