Bearing holding structure and motor

Abstract

A bearing holding structure (1) for holding a bearing (2) in a resin-made cylindrical part (4) via an O-ring (5) disposed in contact with an inner cylindrical surface (4f) of the cylindrical part (4) is provided with a pair of protruding part groups (6G, 7G) that protrude radially inward from the inner cylindrical surface (4f) of the cylindrical part (4) and are disposed so as to sandwich the O-ring (5) in the axial direction. Each of the protruding part groups (6G, 7G) has a plurality of protrusions (6, 7) extending away from each other in the circumferential direction, and in the plurality of protrusions (6, 7), protrusions (6, 7) adjacent to each other in the circumferential direction have different circumferential lengths.

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 bearing itself can vibrate due to the rotation of the shaft it supports. When multiple raised portions arranged in an annular array have substantially the same shape, as in the bearing retention structure disclosed in Patent Document 1, these multiple raised portions may resonate with or sympathize 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 8 are all embodiments that can be selected as appropriate and are all embodiments that can be omitted. None of Embodiments 2 to 8 discloses an embodiment or configuration that is essential to the present invention.

[0007] Aspect 1. The disclosed bearing retention structure includes 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. The structure also includes a pair of protrusion groups that protrude radially inward from the inner cylindrical surface of the cylindrical portion and are arranged axially across the O-ring. Each of the protrusion groups has a plurality of protrusions that extend circumferentially and are spaced apart from each other. The plurality of protrusions have different circumferential lengths between adjacent protrusions in the circumferential direction.

[0008] Aspect 2. In aspects including the above-mentioned Aspect 1, it is preferable that the plurality of protrusions are asymmetrically arranged so as to be rotationally asymmetrical with respect to the axis of the cylindrical portion and line-symmetrical with respect to a diameter line intersecting the axis. Aspect 3. In aspects including the above-mentioned Aspect 2, it is preferable that the plurality of asymmetrically arranged protrusions all have different circumferential lengths.

[0009] Aspect 4. In an aspect including Aspect 3 above, it is preferable that the pair of convex portion groups comprises a first convex portion group located on the front side as viewed from the direction of inserting the bearing into the cylindrical portion, and a second convex portion group located on the rear side as viewed from the direction of insertion, and that the second convex portion group has the asymmetrically arranged convex portions. In this case, it is preferable that the bearing holding structure further comprises a restricting portion that connects each of the asymmetrically arranged convex portions and extends radially inward from the plurality of second convex portion groups to restrict movement of the bearing to the rear side.

[0010] Aspect 5. In an aspect including the above-mentioned Aspect 4, it is preferable that a through hole penetrating in the axial direction is arranged between adjacent convex portions in the circumferential direction. Aspect 6. In an aspect including the above-mentioned Aspect 5, it is preferable that the plurality of convex portions of the first convex portion group are arranged within an area overlapping with the through hole when viewed from the axial direction, and all have the same circumferential length. Aspect 7. In an aspect including the above-mentioned Aspect 6, it is preferable that the plurality of convex portions of the first convex portion group are arranged asymmetrically.

[0011] Aspect 8. 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 protrusions of one of the pair of protrusion groups.

[0012] Aspect 9. 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 8 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 has a cylindrical shape with a bottom, including 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, into which a bearing 2 that supports the shaft 21 is fitted. The cylindrical portion 3 has, for example, a cylindrical shape with a through-hole that penetrates in the axial direction. When assembling the motor 10, the bearing 2 is inserted into the cylindrical portion 3 from one axial direction to the other axial direction. An annular flange 43 extending radially outward from the side wall 41 may be provided on the open 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. A cylindrical portion 4, into which the bearing 2 is fitted, is disposed radially inward of the surface portion 51. The cylindrical portion 4 is, for example, cylindrical with a through-hole that penetrates in the axial direction. When assembling the motor 10, the bearing 2 is inserted into the cylindrical portion 4 from one axial direction to the other. 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, the retaining structure 1 applied to the tubular portion 4 of the end bell 50 is illustrated; however, when the retaining structure 1 is applied to the tubular portion 3 of the housing 40, a configuration similar to that described below can be applied to the tubular portion 3 side of the housing 40. As described above, the bearing 2 is inserted radially inside the tubular portion 4 from one axial direction to the other. Hereinafter, the front direction (here, one axial direction, downward in FIG. 1 ) as viewed from the direction in which the bearing 2 is inserted into the tubular portion 4 (i.e., one axial direction) will be referred to as the "first direction." Furthermore, the rear direction (here, the other axial direction, upward in FIG. 1 ) as viewed from the direction in which the bearing 2 is inserted into the tubular portion 4 will be referred to as the "second direction." The front side can be referred to as the side on which the bearing 2 is disposed with respect to the tubular portion 4 when the bearing 2 is inserted into the tubular portion 4, and the rear side can be referred to as the other side opposite the front side.

[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 shown in Fig. 2, the inner cylindrical surface 4f of the cylindrical tube portion 4 is disposed radially outwardly of and spaced apart from the outer peripheral surface 2g of the bearing 2. In this embodiment, the inner cylindrical surface 4f has a uniform diameter in the axial direction. The outer cylindrical surface 4g of the tube 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 extends in 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] Furthermore, as shown in FIGS. 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. As shown in FIG. 3 , the plurality of ribs 53 are provided in the same number as the plurality of second convex portions 7 of a second convex portion group 7G (described later) 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, a pair of convex portion groups 6G, 7G arranged axially on either side of the O-ring 5. 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 arranged 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 inserted from the first direction toward the second direction so as to be positioned between the pair of protrusion groups 6G, 7G. 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 pair of protrusion groups 6G, 7G are each a portion that protrudes radially inward from the inner cylindrical surface 4f of the cylindrical portion 4, and each protrusion group 6G, 7G has a plurality of protrusions 6, 7 that extend circumferentially and are spaced apart from each other. The plurality of protrusions 6, 7 are integrally molded with the cylindrical portion 4 from resin.

[0031] In this embodiment, a pair of convex portion groups 6G, 7G are provided, including a first convex portion group 6G located on the first direction side of the O-ring 5 in the held state, and a second convex portion group 7G located on the second direction side of the O-ring 5. As shown in FIG. 3 , the first convex portion group 6G has a plurality of first convex portions 6, and the second convex portion group 7G has a plurality of second convex portions 7. Note that in FIGS. 2 to 6, only one of the multiple first convex portions 6 is labeled with a reference numeral. Similarly, in FIGS. 2 to 6, only one of the multiple second convex portions 7 is labeled with a reference numeral.

[0032] In this embodiment, as shown in Fig. 3, each of the convex portion groups 6G, 7G has the same number of convex portions 6, 7. The multiple first convex portions 6 and the multiple second convex portions 7 are arranged alternately without overlapping in the circumferential direction. In other words, as viewed in the axial direction, for example, one convex portion 7 of the second convex portion group 7G is located between two convex portions 6 adjacent in the circumferential direction of the first convex portion group 6G. Here, an example is shown in which each of the pair of convex portion groups 6G, 7G has six convex portions 6, 7, and the other convex portion 7, 6 is provided between the convex portions 6, 7 adjacent in the circumferential direction with no gap in the circumferential direction as viewed in the axial direction.

[0033] Incidentally, bearing 2 may vibrate in conjunction with rotation of shaft 21. Here, when multiple protrusions 6, 7 protruding from tubular portion 4 are provided 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.

[0034] 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.

[0035] The first resonance suppression structure is that the circumferential lengths (hereinafter simply referred to as "circumferential lengths") of the protrusions 6, 7 of each of the pair of protrusion groups 6G, 7G are different from each other. That is, the circumferential lengths of the first protrusions 6 provided in the first protrusion group 6G and the circumferential lengths of the second protrusions 7 provided in the second protrusion group 7G are different from each other.

[0036] The second resonance suppression structure is that the multiple protrusions 6, 7 of the protrusion groups 6G, 7G are provided with non-uniform dimensions so that adjacent protrusions 6, 7 in the circumferential direction have different circumferential lengths. More specifically, when focusing on one first protrusion 6 among the multiple first protrusions 6 that make up the first protrusion group 6G, the circumferential length of this first protrusion 6 is set to be different from the circumferential length of another first protrusion 6 that is located circumferentially adjacent to this first protrusion 6. The same is true for the multiple second protrusions 7 that make up the second protrusion group 7G.

[0037] The plurality of protrusions 6, 7 provided with non-uniform dimensions may be at least the plurality of protrusions 6, 7 of one of the pair of protrusion groups 6G, 7G (i.e., the plurality of first protrusions 6 or the plurality of second protrusions 7), or may be the plurality of protrusions 6, 7 of both of the pair of protrusion groups 6G, 7G. In other words, in the holding structure 1, it is sufficient that the plurality of protrusions 6, 7 of at least one of the pair of protrusion groups 6G, 7G are provided with non-uniform dimensions as the second resonance suppression structure.

[0038] Furthermore, in this embodiment, as a second resonance suppression structure, multiple protrusions 6, 7 having non-uniform dimensions are arranged asymmetrically with respect to the axis C of the tubular portion 4. Here, the asymmetric arrangement means that the multiple protrusions 6, 7 having non-uniform dimensions are arranged so that they are non-rotationally symmetric with respect to the axis C (so that they do not overlap with each other even when rotated), and are arranged so that they are non-axially symmetric with respect to a diameter line (a line that coincides with the radial direction) that intersects with the axis C.

[0039] Below, the configuration of each of the first convex portion 6 and the second convex portion 7 will be described, and then the two resonance suppression structures will be described in detail. The first convex portion 6 is a part that constitutes the first convex portion group 6G, and is provided to protrude radially inward from the inner cylindrical surface 4f of the cylindrical portion 4. The protruding length of the first convex portion 6 from 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 held state, as shown in Figure 2. The first convex portion 6 in this embodiment is provided at the tip portion of the cylindrical portion 4 on the first direction side.

[0040] 4, the first convex portion 6 of this embodiment 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.

[0041] 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.

[0042] 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.

[0043] The peripheral surface 6c forms a curved surface extending in both the axial and circumferential directions. The edge of the peripheral 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 peripheral 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 that connects the outer end surface 6b and the peripheral surface 6c. Providing the tapered surface 6d makes it possible to easily insert the O-ring 5 between the two types of convex portions 6, 7 and also prevents the O-ring 5 from being damaged during insertion.

[0044] The second convex portions 7 are parts that constitute the second convex portion group 7G, and are provided to protrude radially inward from the inner cylindrical surface 4f of the cylindrical portion 4. The second convex portions 7 are positioned further in the second direction than the first convex portions 6, and are arranged with a gap between them. The distance between the first convex portions 6 and the second convex portions 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, this distance is more preferably set to be greater than the thickness of the O-ring 5. The protruding length of the second convex portions 7 from 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 held state, similar to the first convex portions 6.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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 as a gear) 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 multiple 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, when viewed in the axial direction, each first protrusion 6 is located within the area of ​​the through hole h.

[0049] As described above, in the holding structure 1, as a first resonance suppression structure, the circumferential lengths of the protrusions 6, 7 of each of the pair of protrusion groups 6G, 7G are different from each other. 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 of 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.

[0050] 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 convex portion 7. In this embodiment, the circumferential length of the second convex portion 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 convex portion 6. This makes the rigidity of the second convex portion 7 greater than the rigidity of the first convex portion 6, thereby suppressing bending or deformation of the second convex portion 7 when the bearing 2 is inserted. Furthermore, when the bearing 2 is inserted, the second convex portion 7, which has a circumferential length longer than the circumferential length of the first convex portion 6, restricts movement of the O-ring 5 in the second direction, and therefore suppresses slippage of the O-ring 5 in the second direction. This improves stability during assembly.

[0051] Furthermore, in the retaining structure 1, the multiple protrusions 6, 7 of the protrusion groups 6G, 7G are provided with unequal dimensions as a second resonance suppression structure. In this embodiment, the multiple second protrusions 7 of the second protrusion group 7G of the pair of protrusion groups 6G, 7G have the second resonance suppression structure. That is, the multiple second protrusions 7 are provided with unequal dimensions. As a result, the natural frequency of each of the multiple second protrusions 7 differs from the second protrusion 7 arranged adjacent to that second protrusion 7 in the circumferential direction, thereby suppressing resonance associated with vibration of the bearing 2.

[0052] Furthermore, in this embodiment, as a second resonance structure, the multiple second protrusions 7 are asymmetrically arranged. In other words, in this embodiment, the second protrusion group 7G has multiple second protrusions 7 that are asymmetrically arranged. By asymmetrically arranging the multiple second protrusions 7, resonance of the entire multiple second protrusions 7 (i.e., the second protrusion group 7G) ​​connected via the cylindrical portion 4, which is caused by vibration of the bearing 2, is suppressed.

[0053] In 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, which further suppresses resonance associated with vibration of the bearing 2. Furthermore, by setting the circumferential lengths in this manner, the multiple second protrusions 7 are inevitably arranged asymmetrically. 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.

[0054] On the other hand, all of the multiple first protrusions 6 are 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 arranged asymmetrically.

[0055] In this way, by making the circumferential lengths of the plurality of protrusions 6, 7 (here, the plurality of first protrusions 6) of one of the pair of protrusion groups 6G, 7G 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 with resin uniform, thereby improving productivity. Furthermore, by asymmetrically arranging the gaps between the plurality of second protrusions 7, i.e., the plurality of first protrusions 6, resonance of the entire plurality of first protrusions 6 (i.e., the first protrusion group 6G) connected via the tubular portion 4, which is caused by vibration of the bearing 2, is suppressed.

[0056] 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.

[0057] 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 .

[0058] 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.

[0059] 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.

[0060] 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).

[0061] 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 is provided to extend radially inward from the multiple second protrusions 7 (second protrusion group 7G) ​​and forms a surface portion that is disposed facing the end face of the bearing 2 in a held state. The restricting portion 8 restricts movement of the bearing 2 in the second direction by using this surface portion. Note that the restricting portion 8 may restrict movement of the bearing 2 in the second direction by directly abutting the surface portion 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 portion and the end face of the bearing 2, as shown in FIG. 2 .

[0062] [3. Actions and Effects] (1) In the above-described holding structure 1 and motor 10, a pair of protrusion groups 6G, 7G protruding radially inward from the inner cylindrical surface 4f of the cylindrical portion 4 are arranged with the O-ring 5 sandwiched between them in the axial direction. Each of the protrusion groups 6G, 7G has a plurality of protrusions 6, 7. Furthermore, among the pair of protrusion groups 6G, 7G, the plurality of second protrusions 7 of the second protrusion group 7G are provided with non-uniform dimensions. This allows the natural frequencies of adjacent second protrusions 7 to differ, thereby suppressing resonance associated with vibration of the bearing 2. This therefore enables vibration suppression associated with vibration of the bearing 2, thereby providing a quieter device (particularly the motor 10).

[0063] (2) Furthermore, by arranging the multiple second convex portions 7 asymmetrically, it is possible to further suppress resonance of the multiple second convex portions 7 as a whole that is caused by vibration of the bearing 2. (3) When the circumferential lengths of all of the multiple second convex portions 7 are different, it is possible to make the natural frequencies of all of the second convex portions 7 different, which makes it possible to further suppress resonance that is caused by vibration of the bearing 2.

[0064] (4) According to the above-described holding structure 1, the restricting portion 8 can restrict movement of the bearing 2 in the second direction. Therefore, the bearing 2 can be more stably held. Furthermore, by providing multiple second protrusions 7 that are susceptible to vibration of the bearing 2 via the restricting portion 8 with unequal dimensions and in an asymmetrical arrangement, resonance due to vibration of the bearing 2 can be more effectively suppressed.

[0065] (5) 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.

[0066] (6) In the above-described holding structure 1, the first convex portion 6 is disposed 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 disposed 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 during molding of 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.

[0067] Furthermore, the circumferential lengths of the plurality of first convex portions 6 are all the same. This allows the size of the punch of the mold used when integrally molding the tubular portion 4, the first convex portions 6, and the second convex portions 7 with resin to be uniform, thereby improving productivity.

[0068] (7) Furthermore, in the above-described holding structure 1, the multiple first protrusions 6 are arranged asymmetrically. This makes it possible to suppress resonance of the multiple first protrusions 6 connected via the cylindrical portion 4 as a whole, which is caused by vibration of the bearing 2.

[0069] (8) 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 of the second protrusion group 7G of the pair of protrusion groups 6G, 7G. This makes it possible to increase the rigidity of the component (here, end bell 50) on which the cylindrical portion 4 is provided and the rigidity of the second protrusions 7.

[0070] [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.

[0071] In the above-described holding structure 1, the multiple second protrusions 7 provided with non-uniform dimensions are all set to have different circumferential lengths, but the multiple second protrusions 7 may have different circumferential lengths at least between adjacent second protrusions 7. Regarding the multiple second protrusions 7, for example, some second protrusions 7 may be set to have the same circumferential length. The multiple second protrusions 7 do not need to be arranged asymmetrically.

[0072] Furthermore, in the above-described holding structure 1, the circumferential lengths of the multiple first protrusions 6 are all set to be the same, but the circumferential lengths of all the first protrusions 6 may be different, or some of the first protrusions 6 may have the same circumferential length and the remaining first protrusions 6 may have different circumferential lengths. The multiple first protrusions 6 do not have to be arranged asymmetrically.

[0073] Instead of the multiple second protrusions 7 of the second protrusion group 7G, multiple first protrusions 6 of the first protrusion group 6G may be provided with non-uniform dimensions. In this case, it is preferable that the multiple first protrusions 6 are arranged asymmetrically. Also, both the multiple first protrusions 6 and the multiple second protrusions 7 may be provided with non-uniform dimensions. The holding structure 1 does not need to include the first resonance suppression structure. In other words, the relationship in circumferential length between the first protrusions 6 and the second protrusions 7 is not limited to the above.

[0074] 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 arranged 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 arranged to overlap as viewed in the axial direction.

[0075] The first protrusions 6 and the second protrusions 7 are not limited to the above-described shapes as long as they are at least provided to protrude radially inward from the inner cylindrical surface 4 f and extend apart from each other in the circumferential direction. The cylindrical portion 4 is not limited to the above-described shapes as long as it is cylindrical and allows the bearing 2 and the O-ring 5 to be inserted at least radially inside thereof.

[0076] When the bearing 2 is inserted into the cylindrical portion 4 from the second direction toward the first direction, i.e., when the front side is the second direction side and the rear side is the first direction side, the first convex portion group 6G of the holding structure 1 described above may be defined as the "second convex portion group" described in the claims. In this case, the restricting portion 8 may be provided as a portion connecting the multiple first convex portions 6. When axial positioning of the bearing 2 is not necessary, the restricting portion 8 may be omitted. Furthermore, the restricting portion 8 need not have the above-described shape as long as it at least restricts movement of the bearing 2 toward the rear side.

[0077] The surface portion 51 and the rib 53 of 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 that is in phase with the plurality of first protrusions 6.

[0078] 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 end toward the other end in the axial direction. Therefore, the other end in the axial direction (upper side in FIG. 1 ) is the near side (first direction side) when viewed from the direction of inserting the bearing 2 into the tubular portion 3, and the one end in the axial direction (lower side in FIG. 1 ) is the far side (second direction side) when viewed from the direction of inserting the bearing 2 into the tubular portion 3. By providing the tubular portion 3 with a pair of protrusion groups similar to the pair of protrusion groups 6G, 7G of the above-described embodiment, the bearing 2 can be appropriately held while suppressing vibration (resonance) associated with 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 of the above-described embodiment may also be provided. For example, when the holding structure 1 is applied to the cylindrical portion 3 of the housing 40 , a rib similar to the rib 53 may be provided protruding from the bottom portion 42 .

[0079] DESCRIPTION OF SYMBOLS 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 (convex portion) 6G First convex portion group (convex portion group) 7 Second convex portion (convex portion) 7G Second convex portion group (convex portion group) 8 Restricting portion 10 Motor 20 Rotor 21 Shaft 30 Stator 40 Housing 50 End bell 51 Surface portion 53 Rib C Axis 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, wherein the bearing is held by the cylinder portion via the O-ring, the bearing holding structure comprising a pair of convex portion groups protruding radially inward from the inner cylindrical surface of the cylinder portion and sandwiching the O-ring in the axial direction, each of the convex portion groups having a plurality of convex portions extending circumferentially spaced apart from each other, and the plurality of convex portions having different circumferential lengths of adjacent convex portions in the circumferential direction.

2. The bearing holding structure according to claim 1, wherein the plurality of convex portions are asymmetrically arranged so as to be non-rotationally symmetric with respect to the axis of the cylinder portion and non-linearly symmetric with respect to a diameter line intersecting the axis.

3. The bearing holding structure according to claim 2, wherein all of the asymmetrically arranged plurality of convex portions have different circumferential lengths.

4. The pair of convex portion groups are a first convex portion group located on the front side when viewed from the direction of inserting the bearing into the cylinder portion and a second convex portion group located on the back side when viewed from the inserting direction, the second convex portion group having the asymmetrically arranged convex portions, and the bearing holding structure further comprising a restricting portion that connects each of the asymmetrically arranged convex portions and extends radially inward of the plurality of second convex portion groups to restrict movement of the bearing toward the back side.

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

6. The plurality of convex portions of the first convex portion group are arranged within a region overlapping the through hole when viewed from the axial direction and all have the same circumferential length.

7. The plurality of convex portions of the first convex portion group are asymmetrically arranged.

8. The cylinder portion has a surface portion extending radially outward from the outer cylindrical surface of the cylinder portion and a plurality of ribs protruding axially from the surface portion and extending radially outward from the outer cylindrical surface, and the plurality of ribs are arranged at positions in phase with the plurality of convex portions of one of the pair of convex portion groups.

9. A motor comprising: a bottomed cylindrical housing; an end bell closing the opening of the housing; a rotor and a stator housed 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 8.

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