JP7818145B2 - Bearing retention structure and motor - Google Patents

Description

This case relates to a bearing holding structure that holds a bearing, and a motor to which this is applied.

Conventionally, a structure is known in which a bearing is held in place by an O-ring interposed between a cylindrical fixed portion and a bearing inserted radially inward of the fixed portion. For example, Patent Document 1 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 multiple protrusions protruding from its inner surface. The O-ring is inserted into the clearance between multiple protrusions arranged in a first annular array and multiple protrusions arranged in a second annular array at a position axially spaced from the first annular array. All of the multiple protrusions have substantially the same shape and are arranged symmetrically.

European Patent Publication No. 4186148

However, bearings that support a rotatable 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 the 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.

The present bearing retention structure and motor were devised in light of these issues, and one of their objectives is to suppress vibrations (resonance) associated with bearing vibrations. However, this objective is not the only objective. Another objective of the present invention is to achieve effects that cannot be obtained with conventional technology, which are derived from the various configurations shown in the detailed description of the invention below.

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

Aspect 1. The disclosed bearing retention structure comprises a resin cylindrical portion and an O-ring disposed 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 comprises a plurality of first protrusions that protrude radially inward from the inner cylindrical surface of the cylindrical portion and extend circumferentially at a distance from one another, 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 circumferentially at a distance from one another, and the first protrusions and the second protrusions have different circumferential lengths.

Aspect 2. In any aspect including Aspect 1 described above, 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 any aspect including Aspect 2 described above, it is preferable that the bearing holding structure includes a restricting portion that connects each of the plurality of second protrusions and extends radially inward from the plurality of second protrusions to restrict movement of the bearing.

Aspect 4. In any aspect including the aspect 3 described above, it is preferable that a through hole penetrating in the axial direction is disposed between two of the second protrusions that are adjacent to each other in the circumferential direction.
Aspect 5. In any aspect including Aspect 4 above, the first convex portion is preferably disposed within a region overlapping with the through hole when viewed in the axial direction.

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

Aspect 7. In aspects including Aspect 1 above, the cylindrical portion preferably has a surface portion extending radially outward from the outer cylindrical surface of the cylindrical portion, and a plurality of ribs that protrude axially from the surface portion and extend 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.

Aspect 8. The disclosed motor comprises a cylindrical housing with a bottom, an end bell that closes the 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 disposed on at least one of the housing and the end bell and 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, and the bearing is held by a bearing holding structure described in any one of Aspects 1 to 7 above.

The disclosed bearing retention structure and motor can suppress vibration (resonance) associated with bearing vibration.

1 is an axial cross-sectional view of a motor to which a bearing holding structure according to an embodiment is applied; FIG. 2 is an enlarged cross-sectional view of a portion X in FIG. 1 . 2 is a plan view of an end bell provided in the motor of FIG. 1 as viewed from a first direction. FIG. FIG. 4 is a cross-sectional view taken along the line AA in FIG. 3. 4 is a cross-sectional view taken along the line BB in FIG. 3. 2 is a plan view of an end bell provided in the motor of FIG. 1 as viewed from a second direction. FIG. FIG. 4 is an enlarged view of a portion Y in FIG. 3 .

With reference to the drawings, a bearing holding structure and a motor will be described as embodiments. The embodiments shown below are merely examples, and are not intended to exclude various modifications or applications of techniques not explicitly stated in the following embodiments. Each configuration of this embodiment can be implemented with various modifications within the scope of their spirit. Furthermore, they can be selected or combined as needed. In the following description, the direction in which the axis of the shaft rotatably supported by the bearing extends will be referred to as the "axial direction," the radial direction of the shaft centered on the axis will be referred to simply as the "radial direction," and the direction circumferential around the axis will be referred to as the "circumferential direction."

[1. Overall structure]
Fig. 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 Fig. 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.

The rotor 20 has a magnet 22 fixed to the shaft 21 and two balancers 23 that sandwich the magnet 22 in the axial direction, and is rotatably fixed to the housing 40 and end bell 50 by bearings 2. The stator 30 has a stator core 31 fixed to the inner surface of the housing 40 and a coil 33 wound around the stator core 31 via an insulator 32.

The housing 40 is a resin component that forms a space to accommodate the rotor 20 and stator 30. The housing 40 is cylindrical and has a cylindrical side wall 41 that forms the arrangement space for the rotor 20 and stator 30, and a bottom 42 that closes the side wall 41 from one axial direction. A cylindrical portion 3 is located radially inward of 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. The surface of the flange 43 facing the other axial side may be provided with irregularities, as shown.

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 primarily closes the opening of the housing 40. The cylindrical portion 4 is located radially inward of the surface portion 51, forming 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.

The retaining structure 1 of this embodiment is for retaining the above-mentioned bearing 2, and may be applied to both the cylindrical portion 3 of the housing 40 and the cylindrical portion 4 of the end bell 50. The retaining structure 1 includes cylindrical portions 3, 4 and an O-ring 5, and is a structure that retains the bearing 2 radially inside the cylindrical portions 3, 4 via the O-ring 5 arranged radially inside the cylindrical portions 3, 4.

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 arranged 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 2 having a uniform outer diameter in the axial direction is exemplified, but the outer diameter of the bearing 2 does not have to be uniform in the axial direction.

The following description illustrates the retaining structure 1 applied to the tubular portion 4 of the end bell 50, but 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. The bearing 2 is inserted radially inside the tubular portion 4 from one axial direction to the other. Hereinafter, the direction in which the bearing 2 is positioned relative to the tubular portion 4 before insertion (here, one axial direction, downward in Figure 1) will be referred to as the "first direction," and the direction in which the bearing 2 inserted into the tubular portion 4 faces (here, the other axial direction, upward in Figure 1) will be referred to as the "second direction."

Figure 2 is an enlarged view of portion X in Figure 1, Figure 3 is a plan view of end bell 50 as viewed from the first direction (housing 40 side), and Figure 4 is a cross-sectional view taken along the line A-A in Figure 3. For convenience, Figure 2 shows different hatching for surface portion 51, rib 53 (described later), tubular portion 4, second convex portion 7 (described later), and restricting portion 8 (described later). However, these portions 4, 7, 8, 51, 53, and first convex portion 6 (described later) may be integrally molded from resin as end bell 50. As shown in Figures 2 to 4, end bell 50 can also be said to have a cylindrical tubular portion 4 that is disposed approximately 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.

As described above, the cylindrical portion 4 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 cylindrical 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 portion on the first direction side may have a smaller diameter as it approaches the first direction, as shown in FIGS. 2 and 4.

The surface portion 51 is a flat portion extending radially outward from a portion of the outer cylindrical surface 4g. In this embodiment, the surface portion 51 extends radially outward from the portion of the outer cylindrical surface 4g on the second direction side, and is sized and shaped to cover the entire opening of the housing 40. The surface portion 51 has a circular outer shape when viewed in the axial direction, as shown in FIG. 3, for example. The surface portion 51 may be provided with a plurality of through holes for positioning the stator 30. As shown in FIG. 4, the flange portion 52 extends radially outward and in the first direction, continuing from the outer peripheral edge of the surface portion 51, and then forms the surface portion that rests on the flange portion 43 of the housing 40.

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 extension 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 the 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 positioned 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.

[2. Bearing retention 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.

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

The O-ring 5 is an annular sealing component made of an elastic material (e.g., rubber) and is placed 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. When 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.

The two types of protrusions 6, 7 protrude radially inward from the inner cylindrical surface 4f and are positioned so as to sandwich the O-ring 5 in the axial direction when in a held state. The protrusion length of each protrusion 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 when in a held state. The two types of protrusions 6, 7 are integrally molded from resin with the cylindrical portion 4. Multiple protrusions 6, 7 are provided, extending circumferentially at a distance from each other. In this embodiment, as shown in Figure 3, the same number of protrusions 6, 7 are provided and are staggered circumferentially without overlapping. In other words, when viewed axially, a different protrusion 7 is located between two adjacent protrusions 6. Here, a configuration is illustrated in which six of each type of protrusion 6, 7 are provided, and the different protrusions 7 are located between two adjacent protrusions 6 in the circumferential direction with no gaps in the circumferential direction when viewed axially.

However, the bearing 2 may vibrate as the shaft 21 rotates. When, as in the retaining structure 1 of this embodiment, multiple of each of the two types of protrusions 6, 7 protruding from the tubular portion 4 are provided as portions that restrict axial movement of the O-ring 5, these protrusions 6, 7 may resonate (vibrate) as the bearing 2 vibrates. In particular, when these protrusions 6, 7 are molded integrally with the tubular portion 4 (end bell 50) using a resin that is softer than metal, the protrusions 6, 7 deform more flexibly, making them more likely to resonate with the bearing 2.

Therefore, in the retaining structure 1 of this embodiment, 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 are described. The retaining structure 1 may have both of the two resonance suppression structures, or only one of them.

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. In other words, 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.

The second resonance suppression structure is one in which at least one of the two types of protrusions 6, 7 is arranged asymmetrically with respect to the axis C of the tubular portion 4, and at least two circumferentially adjacent protrusions 6, 7 have different circumferential lengths. "Asymmetric arrangement" here 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.

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

As shown in Figure 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 peripheral 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 give the first convex portion 6 a generally rectangular axial cross section. In this embodiment, the first convex portion 6 is provided at the tip of the tubular portion 4 on the first direction side.

The outer end surface 6b is a surface extending radially inward from the inner cylindrical surface 4f, and as shown in Figure 3, forms a partially annular plane extending circumferentially when viewed from the axial direction. 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 approximately flush with the end surface of the cylindrical portion 4 facing the first direction.

The inner end surface 6a extends radially inward from the inner cylindrical surface 4f and forms a partially annular surface extending circumferentially when viewed axially. To increase 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 Figure 4. This increases the thickness (axial dimension) of the base end of the first convex portion 6, 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.

The peripheral surface 6c is 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 the 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 peripheral 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 a guide surface 6d. 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.

The second convex portion 7 is a portion that is positioned with an axial gap from the first convex portion 6 at a position where the O-ring 5 is interposed between the first convex portion 7 and the first convex portion 6. 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 perspective of allowing deformation of the O-ring 5 in the held state, this distance is preferably set to be greater than the thickness of the O-ring 5.

In this embodiment, the second convex portion 7 is provided at the tip end of the tubular portion 4 on the second direction side, and is provided at an axial position that overlaps the axial position of the surface portion 51. Furthermore, as shown in Figures 2 and 5, the second convex portion 7 in this embodiment has a substantially rectangular axial cross section, an inner end surface 7a facing the first direction, and a peripheral surface 7c facing radially inward and radially inward from the inner end surface 7a.

The inner end surface 7a extends radially inward from the inner cylindrical surface 4f and, as shown in FIG. 3, forms a partially annular surface extending circumferentially when viewed from the axial direction. To enhance 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 its 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. The peripheral surface 7c forms a curved surface extending axially and circumferentially, and its edge on the first direction side is connected to the radially inner edge of the inner end surface 7a.

In this embodiment, the regulating portion 8 is connected to the second direction side of the second convex portion 7. In other words, the second convex portion 7 also functions as a leg connecting the tubular portion 4 and the regulating portion 8. Note that in this embodiment, the regulating portion 8 is also connected to the tubular portion 4, but the regulating portion 8 and the tubular portion 4 do not have to be connected. For example, as shown in Figure 6, when viewed from the second direction side, the regulating portion 8 has an outer shape like a gear arranged coaxially with the axis C.

The notch provided on the outer peripheral edge of the restricting portion 8 (the gap between the teeth of the restricting portion 8 when viewed as a gear) coincides with the gap between two circumferentially adjacent second protrusions 7. Between two circumferentially adjacent second protrusions 7, as shown in Figures 4 and 6, a through hole h defined by the restricting portion 8 and the inner cylindrical surface 4f of the tubular portion 4 is located. The through hole h passes axially between two circumferentially adjacent second protrusions 7. In this embodiment, the multiple first protrusions 6 and the multiple second protrusions 7 are alternately arranged without overlapping in the circumferential direction, as described above. Therefore, the first protrusions 6 are located in an area that completely overlaps with the through hole h when viewed axially. In other words, the first protrusions 6 are located within the area of the through hole h when viewed axially.

As described above, the retention structure 1 has a first resonance suppression structure in which the two types of protrusions 6, 7 are configured with different circumferential lengths. This results in different natural frequencies for the first protrusions 6 and the second protrusions 7, thereby suppressing resonance of both the first protrusions 6 and the second protrusions 7 due to vibrations of the bearing 2. This suppresses vibrations in the retention structure 1 and the motor 10 to which the retention 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 vibrations as described above, but also improves stability during assembly.

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 increases the rigidity of the second protrusion 7 relative to the rigidity of the first protrusion 6, thereby preventing 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, preventing the O-ring 5 from coming loose in the second direction. This improves stability during assembly.

Furthermore, in the retaining structure 1, as a second resonance suppression structure, at least one of the two types of protrusions 6, 7 is arranged asymmetrically and so 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 so 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.

In addition, in the retaining structure 1 of this embodiment, the multiple second convex portions 7 are all set to have different circumferential lengths. As a result, the natural frequencies of all second convex portions 7 are different, further suppressing resonance associated with vibration of the bearing 2. Furthermore, by setting the circumferential lengths in this manner, the multiple second convex portions 7 are inevitably arranged asymmetrically. Note that it is preferable that the multiple second convex portions 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.

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 arranged with no circumferential gap between two adjacent second protrusions 7. 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.

By making the circumferential length of one of the two types of protrusions 6, 7 equal in this way, it is possible to standardize the size of the punch used in the mold used to integrally mold the tubular portion 4, first protrusions 6, and second protrusions 7 from resin, 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 due to vibration of the bearing 2 is suppressed.

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

In this embodiment, the circumferential lengths of the six first convex portions 6 and the six second convex portions 7 are set so that α < β1 < β2 < β3 < β4 < β5 < β6 is satisfied. The central angle α of the first convex portions 6 (i.e., the circumferential length of the first convex portions 6) is set to a size that allows at least all of the first convex portions 6 to prevent the O-ring 5 from slipping out in the first direction. Furthermore, the six second convex portions 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 Figure 7 .

As an example, in this embodiment, as shown in FIG. 7, the first second convex portion 7-1 at the top right of the figure and the second second convex portion 7-2 at the bottom left of the figure are arranged on either side of the axis C. In addition, the third second convex portion 7-3 and the fourth second convex portion 7-4 are arranged 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 arranged adjacent to the first second convex portion 7-1, respectively.

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 two second protrusions 7 located on one side of the circumferential direction (e.g., clockwise) from the first second protrusion 7-1 is smallest, and the sum of the central angles of two second protrusions 7 located on the other side of the circumferential direction (e.g., counterclockwise) 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.

Another way of explaining the arrangement of the multiple second protrusions 7 in this embodiment is to say that the first second protrusion 7-1, which has the smallest central angle, is arranged so that it is not adjacent to either the second or third second protrusions 7-2, 7-3, which have the second and third smallest central angles. Furthermore, it can also be said that the sixth second protrusion 7-6, which has the largest central angle, is arranged so that it is not 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 second protrusions 7 with a relatively short circumferential length (e.g., the first second protrusion 7-1).

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, connecting 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 retaining state. The restricting portion 8 restricts movement of the bearing 2 in the second direction by directly abutting the surface against the end face of the bearing 2. Alternatively, as shown in FIG. 2, the restricting portion 8 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.

[3. Actions 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).

(2) In the above-described retaining structure 1, of the first convex portion 6 and the second convex portion 7, the circumferential length of 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, is set to be longer than the circumferential length of the first convex portion 6. This prevents 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.

(3) The above-described holding structure 1 is provided with a restricting portion 8 that connects the multiple second protrusions 7 and extends radially inward beyond the multiple second protrusions 7. This restricts movement of the bearing 2 in the second direction, thereby more stably holding the bearing 2. Furthermore, by setting the circumferential length of the second protrusions 7 longer than the circumferential length of the first protrusions 6, a large area can be secured for the connection between the second protrusions 7 and the restricting portion 8. This prevents vibrations of the bearing 2 transmitted via the restricting portion 8, as well as breakage of the second protrusions 7 and bottom-out (detachment of the restricting portion 8) due to the load applied when inserting the bearing 2.

(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 for cooling the bearing 2 can be taken in through the through hole h. Therefore, the bearing 2 can be appropriately cooled by utilizing the through hole h, thereby extending the life of the bearing 2.

(5) In the above-described holding structure 1, the first convex portion 6 is positioned within the area that overlaps 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, first convex portion 6, and second convex portion 7 to be molded integrally without creating an undercut portion, thereby improving productivity. Furthermore, it is possible to avoid forceful removal when molding the tubular portion 4, first convex portion 6, and second convex portion 7, thereby improving the precision of the convex portions 6 and 7.

(6) In the above-described holding structure 1, a tapered surface 6d is provided on the first convex portion 6, connecting the outer end surface 6b and the peripheral surface 6c and guiding 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 assembly easier.

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

[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.

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

In the above-described holding structure 1, the multiple first convex portions 6 and the multiple second convex portions 7 are arranged alternately without any gaps in the circumferential direction when viewed from the axial direction, but gaps in the circumferential direction may be provided 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 portion of the area that overlaps with the through hole h when viewed from the axial direction. Note that if priority is given to holding force and resonance suppression effect over the 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 so that they overlap when viewed from the axial direction.

The multiple first protrusions 6 and multiple second protrusions 7 need only protrude radially inward from the inner cylindrical surface 4f and extend circumferentially at a distance from each other, and are not limited to the shapes described above. The tapered surface 6d of the first protrusion 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 protrusion 7. The cylindrical portion 4 need only be cylindrical enough to allow the bearing 2 and O-ring 5 to be inserted at least radially inside it, and is not limited to the shapes described above.

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

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 retaining 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 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.

The surface portion 51 and rib 53 extending from the tubular portion 4 may be omitted. In other words, the "tubular portion" described in the claims may be provided separately from the end bell 50 and the housing 40. The rib 53 may be positioned in the same phase as the multiple first protrusions 6.

In the above-described embodiment, the retaining structure 1 is 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 inward of 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 embodiment, and the one axial direction (downward in FIG. 1) corresponds to the second direction in the above embodiment. By providing two types of protrusions similar to the first protrusion 6 and second protrusion 7 in the above embodiment on the tubular portion 3, the bearing 2 can be properly 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 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.

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 (8)

A bearing holding structure comprising a resin cylindrical portion and an O-ring arranged in contact with an inner cylindrical surface of the cylindrical portion, the bearing holding structure holding a bearing in the cylindrical portion via the O-ring,
a plurality of first protrusions projecting radially inward from the inner cylindrical surface of the cylindrical portion and extending apart from each other in the circumferential direction;
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 the second protrusions, and that extend apart from each other in the circumferential direction,
A bearing holding structure, characterized in that the first convex portion and the second convex portion have different circumferential lengths. the second protrusion is a portion against which the O-ring is pressed when the bearing is inserted into the cylindrical portion,
2. The bearing retaining structure according to claim 1, wherein a circumferential length of the second protrusion is longer than a circumferential length of the first protrusion. 3. The bearing holding structure according to claim 2, further comprising a restricting portion that connects each of the plurality of second protrusions and extends radially inward from the plurality of second protrusions to restrict movement of the bearing. The bearing retaining structure according to claim 3 , wherein a through hole penetrating in the axial direction is disposed between two of the second protrusions that are adjacent in the circumferential direction. The bearing retaining structure according to claim 4 , wherein the first protrusion is disposed within a region overlapping with the through hole when viewed in the axial direction. 2. The bearing retaining structure of claim 1, wherein the first convex portion has an end face 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 face, and a tapered surface connecting the end face and the circumferential surface and guiding the insertion of the O-ring. the cylindrical portion 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,
2. The bearing holding structure according to claim 1, wherein the plurality of ribs are arranged at positions in phase with the plurality of first protrusions or the plurality of second protrusions. a cylindrical housing with a bottom;
an end bell that closes 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;
an O-ring interposed between an inner cylindrical surface of the cylindrical portion and an outer peripheral surface of the bearing,
A motor, characterized in that the bearing is held by a bearing holding structure according to any one of claims 1 to 7.