Bearing holding structure and motor

Abstract

This bearing holding structure (1) for holding a bearing (2) in a cylindrical part (4) with an O-ring (5) interposed therebetween comprises: a plurality of first protruding parts (6) that protrude radially inward from an inner cylindrical surface (4f) of the cylindrical part (4) and are arranged so as to be separated from each other in the circumferential direction; and a plurality of second protruding parts (7) that protrude radially inward from the inner cylindrical surface (4f) of the cylindrical part (4) at the positions where the O-ring (5) is interposed between the plurality of second protruding parts (7) and the plurality of first protruding parts (6), and are arranged so as to be separated from each other in the circumferential direction. The circumferential length of the first protruding parts (6) is different from that of the second protruding parts (7).

Description

Bearing retention structure and motor

[0001] The present invention relates to a bearing holding structure for holding a bearing, and a motor to which the same is applied.

[0002] Conventionally, a structure has been known in which a bearing is held in place by an O-ring interposed between a cylindrical fixed portion and a bearing inserted radially inside the fixed portion. For example, Patent Document 1 (JP-A-2005-102623) discloses a structure in which a bearing is fixed to an end plate of a motor by a sealing member (O-ring) provided between the inner surface of a cylindrical receiving portion and the outer surface of the bearing. In Patent Document 1, the receiving portion is provided with a plurality of raised portions protruding from its inner surface. The O-ring is inserted into the clearance between a plurality of raised portions arranged in a first annular array and a plurality of raised portions arranged in a second annular array axially spaced from the first annular array. All of the raised portions have substantially the same shape and are arranged symmetrically.

[0003] European Patent Publication No. 4186148

[0004] However, bearings that rotatably support a shaft are required to support the shaft so that it can rotate stably, but the rotation of the shaft they support can cause the bearing itself to vibrate. When multiple protrusions protruding from a receiving portion have substantially the same shape, as in the bearing retention structure disclosed in Patent Document 1, these multiple protrusions may resonate with the vibrations of the bearing. In other words, the bearing retention structure disclosed in Patent Document 1 leaves room for improvement in terms of suppressing vibrations (resonance) associated with bearing vibrations.

[0005] The bearing retention structure and motor of the present invention were devised in consideration of these problems, and one of the objects thereof is to suppress vibration (resonance) caused by bearing vibration. However, this object is not limited to this. Another object of the present invention is to achieve effects that cannot be obtained by conventional techniques, which are derived from the configurations shown in the below-described detailed description of the invention.

[0006] The disclosed bearing retention structure and motor can be realized as the following disclosed embodiments (application examples), which solve at least part of the above-mentioned problems. Embodiments 2 to 7 are all embodiments that can be selected as appropriate additionally, and all embodiments can be omitted. None of Embodiments 2 to 7 discloses an embodiment or configuration that is essential to the present invention.

[0007] Aspect 1. The disclosed bearing retention structure comprises a resin cylindrical portion and an O-ring arranged in contact with the inner cylindrical surface of the cylindrical portion, and retains a bearing in the cylindrical portion via the O-ring, and further comprises a plurality of first protrusions that protrude radially inward from the inner cylindrical surface of the cylindrical portion and extend spaced apart in the circumferential direction, and a plurality of second protrusions that protrude radially inward from the inner cylindrical surface of the cylindrical portion at positions where the O-ring is interposed between the first protrusions and extend spaced apart in the circumferential direction, and the first protrusions and the second protrusions have different circumferential lengths.

[0008] Aspect 2. In aspects including the above-mentioned Aspect 1, it is preferable that the second convex portion is a portion against which the O-ring is pressed when the bearing is inserted into the cylindrical portion, and that the circumferential length of the second convex portion is longer than the circumferential length of the first convex portion. Aspect 3. In aspects including the above-mentioned Aspect 2, it is preferable that the bearing holding structure includes a restricting portion that connects each of the plurality of second convex portions and extends radially inward beyond the plurality of second convex portions to restrict movement of the bearing.

[0009] Aspect 4. In an aspect including the above-described aspect 3, it is preferable that a through hole penetrating in the axial direction is disposed between two of the second convex portions that are adjacent in the circumferential direction. Aspect 5. In an aspect including the above-described aspect 4, it is preferable that the first convex portion is disposed within a region that overlaps with the through hole when viewed in the axial direction.

[0010] Aspect 6. In any aspect including Aspect 1 described above, it is preferable that the first convex portion has an end surface extending radially inward from the inner cylindrical surface of the cylindrical portion, a circumferential surface facing radially inward at a position radially inward of the end surface, and a tapered surface connecting the end surface and the circumferential surface and guiding the insertion of the O-ring.

[0011] Aspect 7. In any aspect including Aspect 1 described above, the cylindrical portion preferably has a surface portion extending radially outward from an outer cylindrical surface of the cylindrical portion, and a plurality of ribs protruding in the axial direction from the surface portion and extending radially outward from the outer cylindrical surface. In this case, the plurality of ribs are preferably arranged in the same phase as the plurality of first convex portions or the plurality of second convex portions.

[0012] Aspect 8. The disclosed motor includes a cylindrical housing with a bottom, an end bell that closes an opening of the housing, a rotor and a stator built into the housing, a shaft that rotates integrally with the rotor, a bearing that rotatably supports the shaft, a cylindrical portion that is disposed on at least one of the housing and the end bell and into which the bearing is inserted, and an O-ring that is interposed between the inner cylindrical surface of the cylindrical portion and the outer peripheral surface of the bearing, and the bearing is held by the bearing holding structure described in any one of Aspects 1 to 7 above.

[0013] According to the disclosed bearing holding structure and motor, vibration (resonance) caused by vibration of the bearing can be suppressed.

[0014] Fig. 3 is an axial cross-sectional view of a motor to which a bearing retention structure of an embodiment is applied. Fig. 4 is an enlarged cross-sectional view of a portion X in Fig. 1. Fig. 5 is a plan view of an end bell provided in the motor of Fig. 1, seen from a first direction. Fig. 6 is a cross-sectional view taken along the arrows A-A in Fig. 3. Fig. 7 is a cross-sectional view taken along the arrows B-B in Fig. 3. Fig. 8 is a plan view of an end bell provided in the motor of Fig. 1, seen from a second direction. Fig. 9 is an enlarged view of a portion Y in Fig. 3.

[0015] A bearing holding structure and a motor according to an embodiment will be described with reference to the drawings. The embodiments described below are merely examples, and are not intended to exclude various modifications or applications of techniques not explicitly described in the following embodiments. The configurations of the present embodiment can be modified in various ways without departing from the spirit thereof. Furthermore, they can be selected or appropriately combined as needed. In the following description, the direction in which the axis of a shaft rotatably supported by a bearing extends is referred to as the "axial direction," the radial direction of the shaft centered on the axis is simply referred to as the "radial direction," and the direction circumferentially around the axis is referred to as the "circumferential direction."

[0016] [1. Overall Configuration] Figure 1 is an axial cross-sectional view of a motor 10 to which a bearing retention structure 1 of this embodiment (hereinafter simply referred to as "retention structure 1") is applied. As shown in Figure 1, the motor 10 is an inner rotor type brushless motor, and is configured by incorporating a rotor 20 that rotates integrally with a shaft 21 and a stator 30 located radially outward of the rotor 20 into a housing 40. The motor 10 functions as a drive source for a blower, for example, by fixing an impeller (not shown) to the shaft 21.

[0017] The rotor 20 has a magnet 22 fixed to the shaft 21 and two balancers 23 that axially sandwich the magnet 22, and is rotatably fixed to the housing 40 and the end bells 50 by bearings 2. The stator 30 has a stator core 31 fixed to the inner circumferential surface of the housing 40, and a coil 33 wound around the stator core 31 with an insulator 32 interposed therebetween.

[0018] The housing 40 is a resin member that forms a space to accommodate the rotor 20 and the stator 30. The housing 40 is cylindrical and has a cylindrical side wall 41 that forms the arrangement space for the rotor 20 and the stator 30, and a bottom 42 that closes the side wall 41 from one axial direction. A cylindrical portion 3 is disposed radially inside the bottom 42, forming a through hole through which the shaft 21 is inserted and into which the bearing 2 is fitted. An annular flange 43 extending radially outward from the side wall 41 may be provided on the opening side (the other axial side) of the housing 40. A flange 52 (described later) of the end bell 50 is placed on the flange 43. Note that the surface of the flange 43 facing the other axial side may be provided with irregularities as shown in the figure.

[0019] The end bell 50 is a resin cover member that closes the opening of the housing 40 and is assembled to the housing 40. The end bell 50 has a surface portion 51 that extends radially and an annular flange portion 52 that extends radially outward from the surface portion 51. The surface portion 51 is the portion that mainly closes the opening of the housing 40. The cylindrical portion 4 is disposed radially inward of the surface portion 51, and forms a through hole through which the shaft 21 is inserted and into which the bearing 2 is fitted. The flange portion 52 is placed on the flange portion 43 of the housing 40. In this state, the end bell 50 is fixed to the housing 40. Note that the surface of the flange portion 52 facing one axial side may be provided with irregularities that fit into the irregularities of the flange portion 43 of the housing 40.

[0020] The retaining structure 1 of this embodiment is for retaining the above-described bearing 2, and may be applied to each of the cylindrical portion 3 of the housing 40 and the cylindrical portion 4 of the end bell 50. The retaining structure 1 is provided with the cylindrical portions 3, 4 and an O-ring 5, and is a structure that retains the bearing 2 on the radially inner side of the cylindrical portions 3, 4 via the O-ring 5 that is arranged on the radially inner side of the cylindrical portions 3, 4.

[0021] The bearing 2 is a component that supports the shaft 21, and is cylindrical with a through hole in the center. The bearing 2 is disposed coaxially with the axis C of the shaft 21. Note that in this embodiment, a ball bearing is exemplified as the bearing 2, but the type of bearing 2 is not particularly limited. Also, in this embodiment, a bearing having a uniform outer diameter in the axial direction is exemplified as the bearing 2, but the outer diameter of the bearing 2 does not have to be uniform in the axial direction.

[0022] In the following description, a retaining structure 1 applied to the tubular portion 4 of end bell 50 is exemplified, but when the retaining structure 1 is applied to the tubular portion 3 of housing 40, a configuration similar to the configuration described below can be applied to the tubular portion 3 side of housing 40. Bearing 2 is inserted radially inside tubular portion 4 from one axial direction to the other. Hereinafter, the direction in which bearing 2 is positioned relative to tubular portion 4 before insertion (here, one axial direction, downward in FIG. 1 ) will be referred to as the "first direction," and the direction in which bearing 2 inserted into tubular portion 4 faces (here, the other axial direction, upward in FIG. 1 ) will be referred to as the "second direction."

[0023] Fig. 2 is an enlarged view of portion X in Fig. 1, Fig. 3 is a plan view of end bell 50 as viewed from a first direction (housing 40 side), and Fig. 4 is a cross-sectional view taken along the line A-A in Fig. 3. For convenience, Fig. 2 shows surface portion 51, a rib 53 (described later), tubular portion 4, a second convex portion 7 (described later), and a restricting portion 8 (described later) with different hatching, but these portions 4, 7, 8, 51, 53 and a first convex portion 6 (described later) may be integrally molded from resin as end bell 50. As shown in Figs. 2 to 4, end bell 50 can also be said to have a cylindrical tubular portion 4 that is disposed substantially coaxially with axis C of shaft 21, a surface portion 51 that extends radially outward from tubular portion 4, and a flange portion 52 that connects to the outer periphery of surface portion 51.

[0024] As described above, the cylindrical portion 4 is a portion that forms a through hole into which the bearing 2 is fitted. As shown in Fig. 2, the inner cylindrical surface 4f of the cylindrical portion 4 is disposed radially outwardly of and facing the outer peripheral surface 2g of the bearing 2 with a gap therebetween. In this embodiment, the inner cylindrical surface 4f has a uniform diameter in the axial direction. The outer cylindrical surface 4g of the cylindrical portion 4 may have a uniform outer diameter in the axial direction, or the diameter of the portion on the first direction side may decrease as it approaches the first direction, as shown in Figs. 2 and 4.

[0025] The surface portion 51 is a flat plate-shaped portion extending radially outward from a portion of the outer cylindrical surface 4g. In the present embodiment, the surface portion 51 extends radially outward from a portion of the outer cylindrical surface 4g on the second direction side, and is set to a shape and size sufficient to cover the entire opening of the housing 40. For example, as shown in FIG. 3 , the surface portion 51 has a circular outer shape when viewed in the axial direction. A plurality of through holes for positioning the stator 30 may be provided in the surface portion 51. As shown in FIG. 4 , the flange portion 52 is a portion that extends radially outward and in the first direction continuously from the outer circumferential edge of the surface portion 51, and then forms a surface portion that is placed on the flange portion 43 of the housing 40.

[0026] 3 and 4 , the end bell 50 may be provided with a plurality of ribs 53 for reinforcing the end bell 50. The ribs 53 protrude from the surface portion 51 in the axial direction (a direction perpendicular to the extending direction of the surface portion 51) and extend radially outward from the outer cylindrical surface 4g. In this embodiment, the ribs 53 protrude in a first direction from the surface portion 51 and extend radially outward from a portion of the outer cylindrical surface 4g on the first direction side. The radially outer ends of the ribs 53 may be connected to the flange portion 52. In this embodiment, as shown in FIG. 3 , the plurality of ribs 53 are provided in the same number as the plurality of second convex portions 7 described below and are arranged in the same phase as these second convex portions 7. This not only reinforces the end bell 50 but also reinforces the second convex portions 7.

[0027] 2. Bearing Retaining Structure The configuration of the retaining structure 1 will be described below with reference to Figures 2 to 7. Figure 5 is a cross-sectional view taken along the line B-B in Figure 3, and Figure 6 is a plan view of the end bell 50 as viewed from a second direction. Also, Figure 7 is an enlarged view of the Y portion in Figure 3.

[0028] 2 , the retaining structure 1 includes, in addition to the cylindrical portion 4 and the O-ring 5, two types of protrusions 6 and 7 that protrude radially inward from the inner cylindrical surface 4 f of the cylindrical portion 4. The retaining structure 1 of this embodiment further includes a restricting portion 8 as a portion that restricts movement of the bearing 2.

[0029] The O-ring 5 is an annular sealing component made of an elastic material (e.g., rubber) and is disposed in contact with the inner cylindrical surface 4f of the cylindrical portion 4. Before the bearing 2 is inserted into the cylindrical portion 4, the O-ring 5 is interposed (inserted) between the two types of protrusions 6, 7 from the first direction to the second direction. In a state in which the bearing 2 is held radially inside the cylindrical portion 4 (hereinafter referred to as the "held state"), the O-ring 5 is interposed between the inner cylindrical surface 4f of the cylindrical portion 4 and the outer peripheral surface 2g of the bearing 2, and is pressed against both the inner cylindrical surface 4f and the outer peripheral surface 2g.

[0030] The two types of protrusions 6, 7 are portions that protrude radially inward from the inner cylindrical surface 4f and are arranged to sandwich the O-ring 5 in the axial direction in the retained state. The protrusion length of each of the protrusions 6, 7 relative to the inner cylindrical surface 4f of the cylindrical portion 4 is set to a length that does not interfere with the bearing 2 in the retained state. The two types of protrusions 6, 7 are integrally molded with the cylindrical portion 4 from resin. Multiple protrusions 6, 7 are provided, extending circumferentially at a distance from each other. In this embodiment, as shown in FIG. 3 , the same number of protrusions 6, 7 are provided and are arranged alternately in the circumferential direction without overlapping. In other words, the other protrusion 7 is located between two circumferentially adjacent protrusions 6 as viewed in the axial direction. Here, a configuration is illustrated in which six of each of the two types of protrusions 6, 7 are provided, and the other protrusion 7 is arranged between two circumferentially adjacent protrusions 6 as viewed in the axial direction with no gap in the circumferential direction.

[0031] Incidentally, bearing 2 may vibrate in conjunction with rotation of shaft 21. Here, when two types of protrusions 6, 7 protruding from tubular portion 4 are provided in plural numbers as portions that restrict axial movement of O-ring 5, as in retaining structure 1 of the present embodiment, these protrusions 6, 7 may resonate (vibrate) in conjunction with the vibration of bearing 2. In particular, when these protrusions 6, 7 are molded integrally with tubular portion 4 (end bell 50) using a resin that is softer than metal, protrusions 6, 7 deform more flexibly, making them more likely to resonate with bearing 2.

[0032] Therefore, in the retaining structure 1 of this embodiment, the convex portions 6 and 7 are provided to suppress resonance with the bearing 2. In other words, the retaining structure 1 has a resonance suppression structure provided on the convex portions 6 and 7. In this embodiment, two resonance suppression structures will be described. The retaining structure 1 may have both of the two resonance suppression structures, or only one of them.

[0033] The first resonance suppression structure is that the circumferential lengths (hereinafter simply referred to as "circumferential lengths") of the two types of protrusions 6, 7 are different from each other. That is, the circumferential length of one of the multiple protrusions 6, 7 and the circumferential length of the other of the multiple protrusions 7, 6 are different from each other.

[0034] The second resonance suppression structure is such that at least one of the two types of protrusions 6, 7 is arranged asymmetrically with respect to the axis C of the cylindrical portion 4, and at least two circumferentially adjacent protrusions 6, 7 have different circumferential lengths. Here, the asymmetric arrangement means that at least one of the multiple protrusions 6, 7 is non-rotationally symmetrical about the axis C (a shape that does not overlap with itself even when rotated), and is arranged so as to be non-axially symmetrical with respect to a diameter line (a line that coincides with the radial direction) that intersects with the axis C.

[0035] Hereinafter, the convex portion 6 located in the first direction relative to the O-ring 5 in the held state will be referred to as the "first convex portion 6," and the convex portion 7 located in the second direction relative to the O-ring 5 in the held state will be referred to as the "second convex portion 7." After explaining the configurations of the first convex portion 6 and the second convex portion 7, the two resonance suppression structures will be described in detail.

[0036] 4 , the first convex portion 6 has an inner end surface 6a facing the second direction, an outer end surface 6b (end surface) facing the first direction, and a circumferential surface 6c facing radially inward and radially inward from the inner end surface 6a and the outer end surface 6b. These surfaces 6a, 6b, and 6c form a substantially rectangular axial cross section of the first convex portion 6. In this embodiment, the first convex portion 6 is provided at the tip end portion of the tubular portion 4 on the first direction side.

[0037] The outer end surface 6b is a surface extending radially inward from the inner cylindrical surface 4f, and forms a partially annular plane extending in the circumferential direction when viewed from the axial direction, as shown in Fig. 3. Note that, since the first convex portion 6 in this embodiment is located at the tip end of the cylindrical portion 4, the outer end surface 6b is provided so as to be continuous with and substantially flush with the end surface of the cylindrical portion 4 facing the first direction side.

[0038] The inner end surface 6a is a surface extending radially inward from the inner cylindrical surface 4f and forms a partially annular surface extending circumferentially as viewed from the axial direction. From the viewpoint of increasing the rigidity of the first convex portion 6, the inner end surface 6a may be inclined so that the radially outer portion faces radially inward, as shown in FIG. 4 . This increases the thickness (axial dimension) of the base end of the first convex portion 6, thereby improving rigidity. The O-ring 5 is restricted from moving in the first direction by abutting against the inner end surface 6a of the first convex portion 6 facing the O-ring 5 side.

[0039] The circumferential surface 6c is a curved surface extending in the axial and circumferential directions. The edge of the circumferential surface 6c on the second direction side is connected to the radially inner edge of the inner end surface 6a. Meanwhile, the edge of the circumferential surface 6c on the first direction side is connected to the radially inner edge of the outer end surface 6b via a tapered surface 6d. In other words, the first convex portion 6 is provided with a tapered surface 6d connecting the outer end surface 6b and the circumferential surface 6c. The tapered surface 6d is a surface that guides the insertion of the O-ring 5 when inserting it between the first convex portion 6 and the second convex portion 7. In this embodiment, as described above, the O-ring 5 is inserted from the first direction, and therefore the first convex portion 6 located on the first direction side of the tubular portion 4 has the guide surface 6d. Providing the tapered surface 6d allows the O-ring 5 to be easily inserted between the two types of convex portions 6, 7 and prevents the O-ring 5 from being damaged during insertion.

[0040] The second convex portion 7 is a portion that is disposed with a gap in the axial direction from the first convex portion 6 at a position where the O-ring 5 is interposed between the first convex portion 6 and the second convex portion 7. The distance between the first convex portion 6 and the second convex portion 7 is set to be at least equal to or greater than the axial thickness of the O-ring 5. From the viewpoint of allowing deformation of the O-ring 5 in the held state, the distance is more preferably set to be greater than the thickness of the O-ring 5.

[0041] The second convex portion 7 of this embodiment is provided at the tip end portion on the second direction side of the tubular portion 4, and is provided at an axial position that overlaps the axial position of the surface portion 51. As shown in Figures 2 and 5 , the second convex portion 7 of this embodiment has a substantially rectangular axial cross section, and has an inner end surface 7a that faces the first direction, and a circumferential surface 7c that is radially inward of the inner end surface 7a and faces radially inward.

[0042] The inner end surface 7a extends radially inward from the inner cylindrical surface 4f and forms a partially annular surface extending in the circumferential direction when viewed from the axial direction, as shown in FIG. 3 . From the perspective of increasing the rigidity of the second convex portion 7, the inner end surface 7a may be inclined so that the radially outer portion faces radially inward, as shown in FIG. 5 . This increases the thickness (axial dimension) of the base end of the second convex portion 7 and improves rigidity. The O-ring 5 is restricted from moving in the second direction by abutting against the inner end surface 7a of the second convex portion 7 facing the O-ring 5 side. The peripheral surface 7c forms a curved surface extending in the axial and circumferential directions, and its edge on the first direction side is connected to the radially inner edge of the inner end surface 7a.

[0043] In this embodiment, the restricting portion 8 is connected to the second direction side of the second protrusion 7. In other words, the second protrusion 7 also functions as a leg connecting the tubular portion 4 and the restricting portion 8. Note that, although the restricting portion 8 is also connected to the tubular portion 4 in this embodiment, the restricting portion 8 does not have to be connected to the tubular portion 4. For example, as shown in FIG. 6 , the restricting portion 8 has an outer shape like a gear arranged coaxially with the axis C when viewed from the second direction side.

[0044] The notches provided on the outer peripheral edge of the restricting portion 8 (the gaps between the teeth of the restricting portion 8 when viewed in a gear shape) coincide with the gaps between two circumferentially adjacent second protrusions 7. Between two circumferentially adjacent second protrusions 7, as shown in FIGS. 4 and 6 , a through hole h defined by the restricting portion 8 and the inner cylindrical surface 4 f of the cylindrical portion 4 is disposed. The through hole h penetrates in the axial direction between two circumferentially adjacent second protrusions 7. In this embodiment, the multiple first protrusions 6 and the multiple second protrusions 7 are alternately disposed without overlapping in the circumferential direction as described above. Therefore, the first protrusions 6 are disposed in an area that completely overlaps with the through hole h when viewed in the axial direction. In other words, the first protrusions 6 are located within the area of ​​the through hole h when viewed in the axial direction.

[0045] As described above, in the holding structure 1, as a first resonance suppression structure, the two types of protrusions 6, 7 are provided with different circumferential lengths. As a result, the natural frequencies of the first protrusions 6 and the second protrusions 7 are different, and therefore, resonance of both the first protrusions 6 and the second protrusions 7 due to vibration of the bearing 2 is suppressed. This suppresses vibration in the holding structure 1 and the motor 10 to which the holding structure 1 is applied. In this embodiment, the circumferential length of the second protrusions 7 is set longer than the circumferential length of the first protrusions 6. In other words, when comparing the second protrusions 7, which have the shortest circumferential length, with the first protrusions 6, which have the longest circumferential length, the circumferential length of the former is longer. This not only suppresses vibration as described above, but also improves stability during assembly work.

[0046] More specifically, when the bearing 2 is inserted, the O-ring 5 is attached to the cylindrical portion 4, and the O-ring 5 is pressed in the second direction, applying a load to the second protrusion 7. In this embodiment, the circumferential length of the second protrusion 7, which is located on the side against which the O-ring 5 is pressed when the bearing 2 is inserted into the cylindrical portion 4, is set to be longer than the circumferential length of the first protrusion 6. This makes the rigidity of the second protrusion 7 greater than the rigidity of the first protrusion 6, thereby suppressing bending or deformation of the second protrusion 7 when the bearing 2 is inserted. Furthermore, when the bearing 2 is inserted, the second protrusion 7, which has a circumferential length longer than the circumferential length of the first protrusion 6, restricts movement of the O-ring 5 in the second direction, thereby suppressing removal of the O-ring 5 in the second direction. This improves stability during assembly.

[0047] Furthermore, in the retention structure 1, as a second resonance suppression structure, at least one of the two types of protrusions 6, 7 is arranged asymmetrically and such that at least two circumferentially adjacent protrusions 6, 7 have different circumferential lengths. In this embodiment, the second protrusions 7 have the second resonance suppression structure. That is, the multiple second protrusions 7 are arranged asymmetrically and such that at least two circumferentially adjacent second protrusions 7 have different circumferential lengths. Because the circumferential lengths of two adjacent second protrusions 7 are different, the natural frequencies of the two adjacent second protrusions 7 are different, thereby suppressing resonance associated with vibration of the bearing 2. Furthermore, because the multiple second protrusions 7 are arranged asymmetrically, resonance associated with vibration of the bearing 2 is suppressed for all of the multiple second protrusions 7 connected via the cylindrical portion 4.

[0048] Furthermore, in the retention structure 1 of this embodiment, the multiple second protrusions 7 are all set to have different circumferential lengths. As a result, the natural frequencies of all the second protrusions 7 are different, further suppressing resonance associated with vibration of the bearing 2. Furthermore, setting the circumferential lengths in this manner inevitably results in an asymmetric arrangement of the multiple second protrusions 7. Note that it is preferable that the multiple second protrusions 7 are arranged randomly (in no particular order) rather than being arranged in order of shortest circumferential length in the clockwise or counterclockwise direction as viewed from the axial direction.

[0049] On the other hand, the multiple first protrusions 6 are all set to have the same circumferential length. In this embodiment, as described above, the first protrusions 6 are provided with no gaps in the circumferential direction between two adjacent second protrusions 7, and therefore, in other words, the gaps between the multiple second protrusions 7 are set to have the same circumferential length. The multiple second protrusions 7 are all set to have different circumferential lengths, and their arrangement and circumferential lengths are set so that these gaps are asymmetrically arranged.

[0050] In this way, by making the circumferential lengths of one of the two types of protrusions 6, 7 equal, it is possible to make the size of the punch of the mold used when integrally molding the tubular portion 4, the first protrusions 6, and the second protrusions 7 from resin uniform, thereby improving productivity. Furthermore, by asymmetrically arranging the gaps between the multiple second protrusions 7, i.e., the multiple first protrusions 6, resonance of the entire multiple first protrusions 6 connected via the tubular portion 4, which is caused by vibration of the bearing 2, is suppressed.

[0051] Here, the six second protrusions 7 of this embodiment are referred to as the first second protrusion 7-1, the second second protrusion 7-2, the third second protrusion 7-3, the fourth second protrusion 7-4, the fifth second protrusion 7-5, and the sixth second protrusion 7-6, in order of increasing circumferential length. The central angle of the arc corresponding to the circumferential length of the first protrusion 6 that forms a partial ring shape when viewed from the axial direction is designated as α. The central angles of the arc corresponding to the circumferential length of the second protrusions 7 that form a partial ring shape when viewed from the axial direction are designated as β1, β2, β3, β4, β5, and β6, in order of increasing circumferential length.

[0052] In this embodiment, the circumferential lengths of the six first protrusions 6 and the six second protrusions 7 are set so that α<β1<β2<β3<β4<β5<β6 is satisfied. The central angle α of the first protrusions 6 (i.e., the circumferential lengths of the first protrusions 6) is set to a size that allows at least all of the first protrusions 6 to prevent the O-ring 5 from coming off in the first direction. Furthermore, the six second protrusions 7 are arranged randomly (in no particular order) rather than being arranged in order of shortest circumferential length in the clockwise or counterclockwise direction as shown in FIG. 7 .

[0053] 7, in this embodiment, the first second convex portion 7-1 at the upper right in the drawing and the second second convex portion 7-2 at the lower left in the drawing are disposed on either side of the axis C. Furthermore, the third second convex portion 7-3 and the fourth second convex portion 7-4 are disposed adjacent to the second second convex portion 7-2, respectively, and the fifth second convex portion 7-5 and the sixth second convex portion 7-6 are disposed adjacent to the first second convex portion 7-1, respectively.

[0054] The second protrusions 7, excluding the first second protrusion 7-1 and the second second protrusion 7-2, are arranged so that the difference between the sum of the central angles of the two second protrusions 7 located on one side of the circumferential direction (for example, the clockwise direction) from the first second protrusion 7-1 and the sum of the central angles of the two second protrusions 7 located on the other side of the circumferential direction (for example, the counterclockwise direction) from the first second protrusion 7-1 is smallest. In this embodiment, the sixth second protrusion 7-6 and the third second protrusion 7-3 are arranged adjacent to each other in the clockwise direction from the first second protrusion 7-1, and the fifth second protrusion 7-5 and the fourth second protrusion 7-4 are arranged adjacent to each other in the counterclockwise direction from the first second protrusion 7-1.

[0055] To explain the arrangement of the multiple second protrusions 7 in this embodiment in another way, it can be said that the first second protrusion 7-1, which has the smallest central angle, is arranged so as not to be adjacent to either the second or third second protrusions 7-2, 7-3, which have the second and third smallest central angles. It can also be said that the sixth second protrusion 7-6, which has the largest central angle, is arranged so as not to be adjacent to either the fourth or fifth second protrusions 7-4, 7-5, which have the second and third largest central angles. This makes it possible to hold the O-ring 5 more reliably and to prevent bending of the second protrusions 7, which have a relatively short circumferential length (e.g., the first second protrusion 7-1).

[0056] As described above, the restricting portion 8 is a component that restricts movement of the bearing 2. The restricting portion 8 is connected to the second direction side of each of the multiple second protrusions 7 and connects the multiple second protrusions 7 together. As shown in FIG. 2 , the restricting portion 8 extends radially inward from the multiple second protrusions 7 and forms a surface that faces the end face of the bearing 2 in a retained state. The restricting portion 8 restricts movement of the bearing 2 in the second direction by using the surface. Note that the restricting portion 8 may restrict movement of the bearing 2 in the second direction by directly abutting the surface against the end face of the bearing 2, or may restrict movement of the bearing 2 in the second direction via a spring 9 interposed between the surface and the end face of the bearing 2, as shown in FIG. 2 .

[0057] [3. Functions and Effects] (1) The above-described holding structure 1 and motor 10 include a plurality of first protrusions 6 protruding radially inward from the inner cylindrical surface 4f of the cylindrical portion 4, and a plurality of second protrusions 7 protruding radially inward from the inner cylindrical surface 4f of the cylindrical portion 4 at positions where the O-ring 5 is interposed between the first protrusions 6. The first protrusions 6 and the second protrusions 7 have different circumferential lengths. In other words, the circumferential lengths of the first protrusions 6 are set so as not to match any of the second protrusions 7. This allows the natural frequencies of the first protrusions 6 and the second protrusions 7 to be different. Therefore, resonance between the first protrusions 6 and the second protrusions 7 due to vibration of the bearing 2 can be suppressed, thereby suppressing vibrations associated with the vibration of the bearing 2. This allows for a quieter device (particularly, the motor 10).

[0058] (2) In the above-described retaining structure 1, of the first convex portion 6 and the second convex portion 7, the second convex portion 7, which is the portion against which the O-ring 5 is pressed when the bearing 2 is inserted into the tubular portion 4, has a circumferential length set longer than the circumferential length of the first convex portion 6. This makes it possible to prevent the O-ring 5 from being pushed through in the second direction and the second convex portion 7 from being bent when the bearing 2 is inserted into the tubular portion 4, thereby improving stability (performance of the retaining structure 1) during assembly.

[0059] (3) In the above-described holding structure 1, a restricting portion 8 is provided that connects the plurality of second protrusions 7 and extends radially inward beyond the plurality of second protrusions 7. This restricts movement of the bearing 2 in the second direction, thereby enabling the bearing 2 to be held more stably. Furthermore, by setting the circumferential length of the second protrusions 7 to be longer than the circumferential length of the first protrusions 6, a large area can be secured for the connection portion between the second protrusions 7 and the restricting portion 8. This makes it possible to suppress vibrations of the bearing 2 transmitted via the restricting portion 8, as well as breakage of the second protrusions 7 and bottom-out (disappearance of the restricting portion 8) due to the load when inserting the bearing 2.

[0060] (4) Furthermore, when the restricting portion 8 is provided, if a through hole h penetrating in the axial direction is disposed between two circumferentially adjacent second protrusions 7, air can be taken in through the through hole h to cool the bearing 2. Therefore, the through hole h can be utilized to appropriately cool the bearing 2, thereby extending the life of the bearing 2.

[0061] (5) In the above-described holding structure 1, the first convex portion 6 is positioned within the area overlapping with the through hole h when viewed from the axial direction. In other words, the first convex portion 6 is positioned within the area of ​​the through hole h when viewed from the axial direction, and is arranged so as not to overlap with the second convex portion 7. This allows the tubular portion 4, the first convex portion 6, and the second convex portion 7 to be molded integrally without providing an undercut portion, thereby improving productivity. Furthermore, it is possible to avoid forceful removal when molding the tubular portion 4, the first convex portion 6, and the second convex portion 7, and it is possible to improve the precision of the convex portions 6, 7.

[0062] (6) In the above-described holding structure 1, the first convex portion 6 is provided with a tapered surface 6d that connects the outer end surface 6b and the circumferential surface 6c and guides the insertion of the O-ring 5. This prevents the O-ring 5 from being damaged when inserting it between the two types of convex portions 6, 7, and makes it easier to insert the O-ring 5 between the two types of convex portions 6, 7. This makes the assembly process easier.

[0063] (7) In the above-described retaining structure 1, the cylindrical portion 4 has a surface portion 51 extending radially outward from the outer cylindrical surface 4g, and a plurality of ribs 53 that protrude in the axial direction from the surface portion 51 and extend radially outward from the outer cylindrical surface 4g. The plurality of ribs 53 are also arranged in the same phase as the plurality of second protrusions 7. This increases the rigidity of the component (here, end bell 50) on which the cylindrical portion 4 is provided, and also increases the rigidity of the second protrusions 7.

[0064] [4. Other] The configurations of the holding structure 1 and motor 10 described above are merely examples, and are not limited to the above configurations. The device to which the holding structure 1 is applied may be any device that is provided with at least a bearing 2, and is not limited to the motor 10. The holding structure 1 of the present invention is particularly suitable for devices that require vibration suppression.

[0065] In the retention structure 1 described above, the multiple second protrusions 7 are all set to have different circumferential lengths, but the relationship between the circumferential lengths of the multiple second protrusions 7 is not limited to this. For example, the multiple second protrusions 7 may all be set to have the same circumferential length, or multiple second protrusions 7 may be provided with the same circumferential length. Similarly, the multiple first protrusions 6 are all set to have the same circumferential length, but the relationship between the circumferential lengths of the multiple first protrusions 6 is not limited to this. The multiple first protrusions 6 may all be set to have different circumferential lengths, or some of the multiple first protrusions 6 may be set to have the same circumferential length. The retention structure 1 does not need to include a second resonance suppression structure. The multiple first protrusions 6 and the multiple second protrusions 7 do not need to be asymmetrically arranged.

[0066] In the above-described holding structure 1, the multiple first convex portions 6 and the multiple second convex portions 7 are alternately arranged without any gaps in the circumferential direction as viewed in the axial direction, but gaps may be provided in the circumferential direction between the multiple first convex portions 6 and the multiple second convex portions 7. In other words, the first convex portions 6 may be provided in a part of the region that overlaps with the through hole h as viewed in the axial direction. Note that, when priority is given to holding force and resonance suppression effect rather than productivity of the tubular portion 4, the first convex portions 6, and the second convex portions 7, the first convex portions 6 and the second convex portions 7 may be provided so as to overlap as viewed in the axial direction.

[0067] The shapes of the plurality of first protrusions 6 and the plurality of second protrusions 7 are not limited to those described above, as long as they at least protrude radially inward from the inner cylindrical surface 4f and extend spaced apart from each other in the circumferential direction. The tapered surface 6d of the first protrusions 6 may be omitted. Furthermore, depending on the insertion direction of the O-ring 5, a tapered surface that guides the insertion of the O-ring 5 may be provided on the second protrusions 7. The shape of the cylindrical portion 4 is not limited to those described above, as long as it is cylindrical enough to allow the bearing 2 and O-ring 5 to be inserted at least radially inside it.

[0068] The plurality of first protrusions 6 and the plurality of second protrusions 7 need only differ in circumferential length from one another, and are not limited to the above-described length relationship. In other words, the circumferential length of each of the plurality of first protrusions 6 needs to be different from that of at least any of the plurality of second protrusions 7, and similarly, the circumferential length of each of the plurality of second protrusions 7 needs to be different from that of at least any of the plurality of first protrusions 6. For example, the circumferential length of the first protrusion 6 may be set longer than the circumferential length of the second protrusion 7. In this case, it is possible to prevent the O-ring 5 from coming off in the first direction when the shaft 21 rotates, thereby improving stability (performance of the holding structure 1) during rotation of the shaft 21.

[0069] Furthermore, when the bearing 2 is inserted into the cylindrical portion 4 from the second direction toward the first direction, the first convex portion 6 of the holding structure 1 described above may be defined as the "second convex portion" described in the claims. In this case, the restricting portion 8 may be provided as a portion connecting the multiple first convex portions 6. Note that when axial positioning of the bearing 2 is not required, the restricting portion 8 may be omitted. The restricting portion 8 need only at least restrict the movement of the bearing 2, and does not have to have the shape described above.

[0070] The surface portion 51 and the rib 53 extending from the cylindrical portion 4 may be omitted. In other words, the "cylindrical portion" described in the claims may be provided as a separate body from the end bell 50 and the housing 40. The rib 53 may be disposed in a position in phase with the plurality of first protrusions 6.

[0071] In the above-described embodiment, the retaining structure 1 is described as being applied to the tubular portion 4 of the end bell 50. However, the retaining structure 1 may also be applied to the tubular portion 3 of the housing 40. In this case, the bearing 2 is inserted radially inside the tubular portion 3 from the other axial direction toward the other axial direction. Therefore, when the retaining structure 1 is applied to the tubular portion 3, the other axial direction (upward in FIG. 1 ) corresponds to the first direction in the above-described embodiment, and the one axial direction (downward in FIG. 1 ) corresponds to the second direction in the above-described embodiment. By providing two types of protrusions similar to the first protrusion 6 and the second protrusion 7 in the above-described embodiment on the tubular portion 3, the bearing 2 can be appropriately held while suppressing vibration (resonance) associated with the vibration of the bearing 2. Furthermore, when the retaining structure 1 is applied to the tubular portion 3, a restricting portion, a through hole, a tapered surface, and a rib similar to the restricting portion 8, the through hole h, the tapered surface 6d, and the rib 53 in the above-described embodiment may be provided. For example, when the retaining structure 1 is applied to the tubular portion 3 of the housing 40, a rib similar to the rib 53 may be provided on the bottom portion 42.

[0072] REFERENCE SIGNS LIST 1 Retaining structure (bearing retaining structure) 2 Bearing 3 Cylindrical portion 4 Cylindrical portion 4f Inner cylindrical surface 4g Outer cylindrical surface 5 O-ring 6 First convex portion 6b Outer end surface (end surface) 6c Circumferential surface 6d Tapered surface 7 Second convex portion 8 Restricting portion 10 Motor 20 Rotor 21 Shaft 30 Stator 40 Housing 50 End bell 51 Surface portion 53 Rib h Through hole

Claims

1. A bearing holding structure comprising a resin cylinder portion and an O-ring disposed in contact with the inner cylindrical surface of the cylinder portion, and holding a bearing on the cylinder portion via the O-ring, the bearing holding structure comprising: a plurality of first convex portions protruding radially inward from the inner cylindrical surface of the cylinder portion and extending circumferentially spaced apart from each other; a plurality of second convex portions protruding radially inward from the inner cylindrical surface of the cylinder portion at a position where the O-ring is interposed between the plurality of first convex portions and extending circumferentially spaced apart from each other; and the circumferential lengths of the first convex portions and the second convex portions being different from each other.

2. The bearing holding structure according to claim 1, wherein the second convex portion is a portion where the O-ring is pressed when the bearing is inserted into the cylinder portion, and the circumferential length of the second convex portion is longer than the circumferential length of the first convex portion.

3. The bearing holding structure according to claim 2, further comprising a restricting portion that connects each of the plurality of second convex portions and extends radially inward of the plurality of second convex portions to restrict movement of the bearing.

4. The bearing holding structure according to claim 3, wherein a through hole penetrating in the axial direction is disposed between two adjacent second convex portions in the circumferential direction.

5. The bearing holding structure according to claim 4, wherein the first convex portion is disposed within a region overlapping the through hole when viewed in the axial direction.

6. The bearing holding structure according to claim 1, wherein the first convex portion has an end surface extending radially inward from the inner cylindrical surface of the cylinder portion, a circumferential surface facing radially inward at a position radially inward of the end surface, and a tapered surface connecting the end surface and the circumferential surface to guide insertion of the O-ring.

7. The bearing holding structure according to claim 1, wherein the cylinder portion has a face portion extending radially outward from the outer cylindrical surface of the cylinder portion, and a plurality of ribs protruding axially from the face portion and extending radially outward from the outer cylindrical surface, and the plurality of ribs are disposed at positions in the same phase as the plurality of first convex portions or the plurality of second convex portions.

8. A motor comprising: a bottomed cylindrical housing; an end bell closing the opening of the housing; a rotor and a stator built in the housing; a shaft that rotates integrally with the rotor; a bearing that rotatably supports the shaft; a cylindrical portion disposed on at least one of the housing and the end bell into which the bearing is inserted; and an O-ring interposed between the inner cylindrical surface of the cylindrical portion and the outer peripheral surface of the bearing, wherein the bearing is held by the bearing holding structure according to any one of claims 1 to 7.

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