Ball bearing holding structure, fan motor, and method for manufacturing ball bearing holding structure

Abstract

To suppress deformation of a ball bearing caused when press-fitting and fixing a bearing holder.SOLUTION: A holding structure of a ball bearing 2 supporting a shaft freely rotatably comprises: a bearing holder 4 including a cylindrical holder part 40 inside which the ball bearing 2 is fitted from one side in an axial direction of the shaft and a positioning part 45 which is arranged on the other side in an axial direction of the holder part 40 and abuts, from the other side, against the ball bearing 2; and a mounting plate 3 including a cylindrical mounting part 31 into which a part 41 of the holder part 40 is press-fitted from the other side. An inner surface of the holder part 40 is arranged with: an adhesive surface 42 to be caused to adhere to an outer peripheral surface 2f of the ball bearing 2 with an adhesive; a relief surface 43 having an inner diameter D3 larger than an inner diameter D2 of the adhesive surface 42 on the one side of the adhesive surface 42; and a step surface 44 for connecting the adhesive surface 42 and the relief surface 43. A position of the step surface 44 in the axial direction is overlapped with a position of the ball bearing 2 in a state that the ball bearing 2 is fitted into the bearing holder 4.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a ball bearing holding structure that rotatably supports a shaft, and a fan motor to which the ball bearing holding structure is applied. [Background technology]

[0002] Conventionally, ball bearings that rotatably support a shaft are held in the outer casing or base of a device such as a motor or a reducer that is provided with a shaft as a rotating shaft. For example, Patent Document 1 discloses a structure in which a ball bearing is fitted and held in a bearing holder that is press-fitted and fixed to the base of a spindle motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-228453 Summary of the Invention [Problem to be solved by the invention]

[0004] In the ball bearing holding structure disclosed in Patent Document 1, the bearing holder is press-fitted into the base, which causes the press-fit portion to deform radially inward, narrowing the space for holding the ball bearing. As a result, when the ball bearing is fitted into the bearing holder, the outer ring of the ball bearing is compressed, which can deform the ball passage space inside the ball bearing. Deformation of the ball passage space causes uneven ball passage speeds during shaft rotation, which ultimately leads to the generation of abnormal noise.

[0005] The present invention has been devised in view of these problems, and one of its objects is to provide a ball bearing holding structure that can suppress deformation of the ball bearing that can occur when the bearing holder is press-fitted, and a fan motor to which said holding structure is applied. However, this object is not limited to this object, and 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 embodiments. [Means for solving the problem]

[0006] Disclosed ball bearing holding structure and fan motor and a method for manufacturing a ball bearing holding structure The above can be realized as the embodiments or application examples disclosed below, which solve at least some of the above problems. (1) The ball bearing holding structure disclosed herein is a ball bearing holding structure that rotatably supports a shaft, and comprises a cylindrical holder portion into which the ball bearing is fitted from one axial side of the shaft, a bearing holder having a positioning portion provided on the other axial side of the holder portion that abuts against the ball bearing from the other side, and a mounting plate having a cylindrical mounting portion into which a part of the holder portion is press-fitted from the other side. The inner surface of the holder portion has an adhesive surface that is bonded to the outer circumferential surface of the ball bearing with an adhesive, a relief surface on the one side of the adhesive surface that has an inner diameter larger than the inner diameter of the adhesive surface, and a connecting portion between the adhesive surface and the relief surface. The adhesive is applied when the ball bearing is fitted into the bearing holder. a stepped surface is provided, and the stepped surface is axially positioned so as to overlap with the ball bearing when the ball bearing is fitted into the bearing holder.

[0007] (2) When the bearing holder and the mounting plate are combined, the axial position of the other end surface of the mounting portion is preferably a position overlapping the ball bearing. In this case, the axial position of the stepped surface is preferably a position overlapping both the mounting portion and the ball bearing.

[0008] (3) The inner diameter of the relief surface is preferably larger than the sum of the outer diameter of the ball bearing and the interference for press-fitting the holder portion. (4) Preferably, the ball bearing has an outer diameter of 12 mm, the adhesive has a viscosity of 2000 mPa·s or more and 3000 mPa·s or less, and the difference between the outer diameter of the ball bearing and the inner diameter of the relief surface is 150 μm or more and 255 μm or less.

[0009] The fan motor disclosed herein comprises a motor section having a rotor that rotates integrally with the fan section via a shaft and a stator that is arranged opposite the rotor, and the ball bearing holding structure described in any one of (1) to (4) above is applied to a ball bearing that rotatably supports the shaft. The presently disclosed method for manufacturing a ball bearing holding structure is a method for manufacturing a ball bearing holding structure that rotatably supports a shaft, and the holding structure includes a bearing holder having a cylindrical holder portion and a positioning portion provided on the other axial side of the holder portion of the shaft, and a mounting plate having a cylindrical mounting portion, and the inner surface of the holder portion is provided with an adhesive surface that is bonded to the outer circumferential surface of the ball bearing, a relief surface that is located on one axial side of the adhesive surface and has an inner diameter larger than the inner diameter of the adhesive surface, and a step surface connecting the adhesive surface and the relief surface. The manufacturing method includes the steps of fitting the ball bearing into the holder portion from the one side and abutting the positioning portion against the ball bearing from the other side to determine the axial position of the ball bearing, and fitting the ball bearing into the bearing holder, and press-fitting a part of the holder portion into the attachment portion from the other side. The fitting step includes the steps of applying the adhesive to the stepped surface, and fitting the ball bearing into the bearing holder so that the adhesive applied to the stepped surface is spread between the outer peripheral surface and the adhesive surface, thereby bonding the outer peripheral surface and the adhesive surface. The axial position of the stepped surface is a position that overlaps the ball bearing when the ball bearing is fitted into the bearing holder. [Effects of the Invention]

[0010] According to the disclosed ball bearing holding structure and fan motor, deformation of the ball bearing that may occur when the bearing holder is press-fitted and fixed can be suppressed. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an axial cross-sectional view showing a holding structure for a ball bearing according to an embodiment. [Figure 2] FIG. 2 is an enlarged view of the X portion of FIG. [Figure 3] 2] FIG. 2 is an axial cross-sectional view showing a part of a bearing holder (the part shown in FIG. 2) included in the ball bearing holding structure of FIG. 1 before the bearing holder is press-fitted into a mounting plate. [Figure 4] 1 is an axial cross-sectional view showing a motor portion of a fan motor to which a ball bearing holding structure according to an embodiment is applied; DETAILED DESCRIPTION OF THE INVENTION

[0012] A ball bearing holding structure and a fan motor according to an embodiment will be described with reference to the drawings. The following embodiment is merely an example, and is not intended to exclude various modifications and applications of techniques not explicitly described in the following embodiment. The configurations of the present embodiment can be modified in various ways without departing from the spirit of the invention. Furthermore, they can be selected or combined as needed.

[0013] [1. Ball bearing holding structure] A ball bearing holding structure (hereinafter simply referred to as "holding structure") of this embodiment will be described with reference to Figures 1 to 3. As shown in Figure 1, the holding structure of this embodiment holds a ball bearing 2 (hereinafter simply referred to as "bearing 2") that rotatably supports a shaft 1. Here, the example shows a bearing 2 that supports an end 1a on one end side (the lower side in Figure 1) of the shaft 1. The end 1a on one end side of the shaft 1 is press-fitted into the inner ring of the bearing 2, whereby the shaft 1 is fixed and supported by the bearing 2. The size of the bearing 2 is not particularly limited, but a relatively small one with an outer diameter of 12 mm, for example, is used.

[0014] Hereinafter, the direction in which the center line C of the shaft 1 extends will be referred to as the axial direction, the direction perpendicular to the center line C will be referred to as the radial direction, and the direction going around the center line C will be referred to as the circumferential direction. In the axial direction, one end side of the shaft 1 (the lower side in FIG. 1 where the end 1a is located) will be referred to as the "one side," and the opposite side (the upper side in the figure) will be referred to as the "other side." In addition, in the radial direction, the side of the center line C will be referred to as the "inner side," and the opposite side (the side away from the center line C) will be referred to as the "outer side."

[0015] The holding structure includes a mounting plate 3 and a bearing holder 4. The mounting plate 3 is a member fixed to the outer casing or base (base) of a device (not shown) on which the shaft 1 is mounted. Examples of such a device include a motor and a reducer. The mounting plate 3 does not have to be separate from the outer casing or base of the device, but may be configured as part of the outer casing or base. The bearing holder 4 is a member that holds the bearing 2 by having the bearing 2 adhered to its inside, and is press-fitted and fixed into the mounting plate 3. The bearing holder 4 and bearing 2 are bonded with an adhesive. Unless otherwise specified, the following explanation of the components 3 and 4 will be given assuming the state shown in FIG. 1 , i.e., the state in which the bearing 2 that supports the shaft 1 is fitted into the bearing holder 4, and the bearing holder 4 is press-fitted and fixed into the mounting plate 3.

[0016] As described above, the mounting plate 3 is a member that is fixed to the outer casing or base of the device in which the shaft 1 is provided. The mounting plate 3 is formed, for example, from an iron-based steel plate such as a galvanized steel plate. However, the mounting plate 3 is not limited to the above material as long as it is formed from a material that is stronger than the material from which the bearing holder 4 is formed. The mounting plate 3 is provided with a cylindrical mounting portion 31 inside which the bearing holder 4 can be press-fitted. The mounting plate 3 of this embodiment includes the mounting portion 31 and a base portion 32 connected to one side of the mounting portion 31. The base portion 32 is a plate-shaped portion that extends outward from one side of the mounting portion 31, and is attached to the outer casing or base of the above-mentioned device.

[0017] The mounting portion 31 is a cylindrical portion extending in the axial direction. Here, a cylindrical mounting portion 31 is shown, in which the inner and outer circumferential surfaces each have a uniform diameter in the axial direction. The center line of the mounting portion 31 coincides with the center line C of the shaft 1. One end 46 of the bearing holder 4 (hereinafter referred to as "one side end 46") is press-fitted and fixed into the mounting portion 31 from the other side. Therefore, before the mounting plate 3 and the bearing holder 4 are combined, the inner diameter of the mounting portion 31 is set to be smaller than the outer diameter of the one side end 46 of the bearing holder 4.

[0018] The axial position of the other end face 31f of the mounting portion 31 (hereinafter referred to as the "other-side end face 31f") is a position overlapping with the ball bearing 2 in the axial direction. In other words, the mounting portion 31 can be said to extend axially from the position overlapping with the ball bearing 2 in the axial direction toward one side. In this embodiment, the other-side end face 31f is disposed on the other side of the axial center position E of the bearing 2 and at a position overlapping with the bearing 2 in the axial direction (a position that does not protrude from the other-side end face of the bearing 2 to the other side), as shown in FIG. 2 . The mounting portion 31 extends axially from the position of the other-side end face 31f to, for example, a position approximately coincident with the end face of one end 46 of the bearing holder 4. However, the axial position and length of the mounting portion 31 are not limited thereto as long as the bearing holder 4 can be press-fitted and fixed to the mounting portion 31.

[0019] As described above, the bearing holder 4 is a component that is press-fitted into the mounting plate 3 and into which the bearing 2 is fitted. The bearing holder 4 is made of an aluminum-based material such as duralumin so that the bearing 2 can be accurately fitted inside. However, the material from which the bearing holder 4 is made is not limited to this and may be, for example, brass.

[0020] The bearing holder 4 comprises a cylindrical holder portion 40 into which the bearing 2 is fitted, and a positioning portion 45 that determines the axial position of the bearing 2. A portion (one side portion) of the holder portion 40 is a press-fit portion 41 that is press-fitted into the mounting portion 31, and this press-fit portion 41 includes one side end 46 of the bearing holder 4 described above. Here, a cylindrical holder portion 40 that extends in the axial direction and has a center line that coincides with the center line C of the shaft 1 is shown as an example, corresponding to the shape of the mounting portion 31 described above. The outer peripheral surface of the holder portion 40 has a uniform outer diameter in the axial direction. When the press-fit portion 41 including the one side end 46 is press-fitted into the mounting portion 31, the outer peripheral surface of the press-fit portion 41 is pressed against the inner peripheral surface of the mounting portion 31.

[0021] The positioning portion 45 is provided on the other side of the holder portion 40, for example, as a portion that protrudes inward from the inner circumferential surface of the holder portion 40. The bearing 2 is fitted into the holder portion 40 from one side, and when the bearing 2 abuts against the positioning portion 45, displacement to the other side is restricted and its axial position is determined.

[0022] Before the mounting plate 3 and the bearing holder 4 are combined, the outer diameter of one side end 46 of the bearing holder 4, i.e., the outer diameter of the holder portion 40, is set larger than the inner diameter of the mounting portion 31 so as to satisfy the set interference range. For example, if the interference (press-fit interference) of the holder portion 40 relative to the mounting portion 31 is set in the range of 35 μm or more and 45 μm or less, the outer diameter of the holder portion 40 is set larger than the inner diameter of the mounting portion 31 so as to satisfy this range. Note that the press-fit interference is not limited to the above range. However, from the perspective of preventing the bearing holder 4 from coming loose from the mounting plate 3, it is preferable that the press-fit interference be set within a range that prevents this from happening.

[0023] When the bearing holder 4 is press-fitted into the mounting plate 3, the holder portion 40 undergoes an internal deformation equivalent to the interference caused by the press-fit. This deformation narrows the space inside the holder portion 40, compressing the outer ring of the bearing 2 and causing a problem of deformation of the ball passage space provided inside the bearing 2. Deformation of the ball passage space causes uneven ball passage speeds when the shaft 1 rotates, which ultimately leads to the generation of abnormal noise. The deformation of the bearing holder 4 increases the more firmly the bearing holder 4 is fixed to the mounting plate 3, in other words, the greater the interference caused by the press-fit.

[0024] Therefore, the holder part 40 of this embodiment is provided on its inner surface with a structure that suppresses compression of the outer ring of the bearing 2 due to press-fitting. Specifically, as shown in Figures 2 and 3, the inner circumferential surface of the holder part 40 is provided with an adhesive surface 42 that is bonded to the bearing 2 with an adhesive, and a relief surface 43 on one side of the adhesive surface 42 and having an inner diameter larger than the inner diameter of the adhesive surface 42. Furthermore, the inner surface of the holder part 40 is provided with a stepped surface 44 that connects the adhesive surface 42 and the relief surface 43. In other words, the holder part 40 has a stepped shape with two inner circumferential surfaces 42, 43 that have different inner diameters as its inner surface.

[0025] The boundary position between the adhesive surface 42 and the relief surface 43, i.e., the axial position of the stepped surface 44, is a position that overlaps with the bearing 2. In this embodiment, the axial position of the stepped surface 44 is a position that overlaps with both the bearing 2 and the mounting portion 31. The deformation of the holder portion 40 due to press-fitting is greater toward one side from the portion where the outer peripheral surface of the holder portion 40 and the inner peripheral surface of the mounting portion 31 are in pressure contact (close contact), i.e., the axial position of the other end face 31f of the mounting portion 31. For this reason, by positioning the stepped surface 44 in the axial position that overlaps with both the bearing 2 and the mounting portion 31, in other words, by providing the relief surface 43 in a range to one side from that position, it is possible to suppress compression of the outer ring of the bearing 2 due to deformation of the holder portion 40.

[0026] Here, the example shows a stepped surface 44 provided on one side of the axial center position E of the bearing 2. By providing the stepped surface 44 on one side of the axial center position E of the bearing 2 in this way, a wide area can be secured for the bonding surface 42. This allows the bearing 2 to be bonded to the holder part 40 more firmly.

[0027] The axial position of the stepped surface 44 is not limited to the position described above. For example, if the stepped surface 44 is provided on the other side of the axial center position E of the bearing 2, compression of the outer ring of the bearing 2 at the axial center position E can be further suppressed. This can further suppress deformation of the ball passage space provided inside the bearing 2. The axial position of the stepped surface 44 may be set based on the results of experiments or simulations conducted during the design of the holder part 40 to determine, for example, from what position and to what extent the holder part 40 will deform due to press-fitting. In this embodiment, the stepped surface 44 is provided as a flat surface extending in the radial direction; however, the stepped surface 44 may be, for example, inclined relative to the radial direction, or may not be a flat surface.

[0028] When the bearing 2 is fitted into the bearing holder 4, the adhesive is applied to the stepped surface 44 (or to the periphery of the stepped surface 44), and when the bearing 2 is fitted, the adhesive wears away and spreads between the outer peripheral surface 2f of the bearing 2 and the adhesive surface 42, forming a predetermined adhesive film. In other words, the stepped surface 44 in this embodiment not only connects the adhesive surface 42 and the relief surface 43, but also functions as a marker for applying the adhesive. The inner diameter D2 of the adhesive surface 42 (see FIG. 3) is set larger than the outer diameter D1 of the bearing 2 to such an extent that an adhesive film of an appropriate thickness can be formed between the adhesive surface 42 and the outer peripheral surface 2f of the bearing 2.

[0029] The appropriate thickness varies depending on, for example, the adhesive material (viscosity) and the outer diameter D1 of the bearing 2. For example, suppose a relatively small bearing 2 with an outer diameter of 12 mm is used, and the viscosity of the adhesive used is the recommended viscosity for bonding the bearing 2 to the bearing holder 4 (for example, a range of 2000 mPa·s or more and 3000 mPa·s or less at room temperature (approximately 25°C)). In this case, the difference (adhesion margin) between the outer diameter D1 of the bearing 2 and the inner diameter D2 of the bonding surface 42 is preferably in the range of 1 μm or more and 16 μm or less. Therefore, the inner diameter D2 of the bonding surface 42 is set larger than the outer diameter D1 of the bearing 2 so as to satisfy the above-mentioned range of adhesion margin (1 μm to 16 μm).

[0030] The inner diameter D3 of the relief surface 43 is set to be at least larger than the inner diameter D2 of the adhesive surface 42 before the mounting plate 3 and the bearing holder 4 are combined. The inner diameter D3 of the relief surface 43 is preferably set to be larger than the value obtained by adding the interference (interference for press-fitting) of the bearing holder 4 to the mounting plate 3 to the outer diameter D1 of the bearing 2 (D3 > D1 + interference).

[0031] As described above, when the bearing 2 is fitted into the bearing holder 4, the adhesive is applied to the stepped surface 44. For this reason, the inner diameter D3 of the relief surface 43 is more preferably set to a value that allows an appropriate amount of adhesive to be applied to the stepped surface 44. This value varies mainly depending on the material (viscosity) of the adhesive, and more specifically, on the outer diameter D1 of the bearing 2. For example, suppose the viscosity of the adhesive is in the range of 2000 mPa·s to 3000 mPa·s at room temperature (approximately 25°C) as mentioned above, and the outer diameter D1 of the bearing 2 is 12 mm. In this case, the difference between the outer diameter D1 of the bearing 2 and the inner diameter D3 of the relief surface 43 is preferably set to be 150 μm or more and 255 μm or less. Here, the reason why the inner diameter D3 of the relief surface 43 is determined by the difference with the outer diameter D1 of the bearing 2, rather than the inner diameter D2 of the adhesive surface 42, is that the inner diameter D2 of the adhesive surface 42 and the inner diameter D3 of the relief surface 43 are set based on the dimensions and tolerances of the bearing 2, and also because the above-mentioned adhesive allowance is minute compared to this difference.

[0032] The procedure for assembling the shaft 1, bearing 2, mounting plate 3, and bearing holder 4 may be, for example, to press-fit and fix the bearing holder 4 into the mounting plate 3, and then fit the bearing 2 with the shaft 1 pressed-fitted and fixed into the bearing holder 4. Alternatively, the bearing holder 4 may be press-fit and fixed into the mounting plate 3, and then fit the bearing 2 into the bearing holder 4, and then the shaft 1 may be press-fit and fixed into the bearing 2. Note that the mounting plate 3 may be assembled to the outer casing or base of the device, and then the bearing holder 4 may be press-fit and fixed into the mounting plate 3.

[0033] [2. Application example of ball bearing retention structure] FIG. 4 is an axial cross-sectional view of a motor section 10 of a fan motor to which the retaining structure of this embodiment is applied. The fan motor corresponds to the above-mentioned "device in which the shaft 1 is provided." As shown in FIG. 4, the fan motor is provided with two ball bearings 2, 12 spaced apart from each other in the axial direction of the shaft 1. The retaining structure of this embodiment is applied to retain the ball bearing 2, which is provided on one axial side (the lower side in the figure) of the two ball bearings 2, 12. Hereinafter, the one provided on one side of the two ball bearings 2, 12 will be referred to as the first bearing 2, and the one provided on the other axial side (the upper side in the figure) will be referred to as the second bearing 12. The center line C of the shaft 1 coincides with the center line of the fan motor.

[0034] The bearing holder 4 of this embodiment holds both ball bearings 2, 12. To this end, the bearing holder 4 is provided with a cylindrical second holder portion 48 for holding the second bearing 12, in addition to the holder portion 40 and positioning portion 45 described above. The second holder portion 48 extends axially from the positioning portion 45 toward the other side. The outer diameter of the other end portion 47 of the bearing holder 4, including the second holder portion 48, is smaller than the outer diameter of the one end portion 46. Furthermore, a mounting surface 49 is provided on the outer peripheral surface of the bearing holder 4 in a portion that overlaps with the positioning portion 45 in the axial direction, connecting the outer peripheral surface of the one end portion 46 and the outer peripheral surface of the other end portion 47. A stator core 14a, which will be described later, is mounted on the mounting surface 49.

[0035] The fan motor is, for example, a centrifugal fan that draws in air and sends it outward in the radial direction. A fan unit (not shown) equipped with multiple blades is connected to the other end 1b of the shaft 1. The fan motor includes a motor unit 10 having a rotor 13 that rotates integrally with the fan unit via the shaft 1 and a stator 14 arranged inside the rotor 13. In other words, the fan motor is an outer rotor type brushless motor. Two ball bearings 2 and 12 are arranged inside the stator 14 via a bearing holder 4. The shaft 1 is rotatably supported at one end 1a and an axial middle portion by the two ball bearings 2 and 12.

[0036] The rotor 13 includes a cup-shaped rotor yoke 13a and a magnet 13b fixed to the inner peripheral surface of the rotor yoke 13a. A shaft hole 13h is formed inside the rotor yoke 13a, penetrating the rotor 13 in the axial direction. The rotor 13 is fixed to the shaft 1, for example, by press-fitting the shaft 1 into the shaft hole 13h, preventing the rotor 13 from rotating relative to the shaft 1. The magnet 13b is, for example, a long, rectangular rubber magnet. The magnet 13b is formed by joining both ends of the rubber magnet to form a ring having an outer diameter equal to or smaller than the inner diameter of the inner peripheral surface of the rotor yoke 13a. Note that multiple magnets 13b may be provided circumferentially spaced apart along the inner peripheral surface of the rotor yoke 13a. When the stator 14 is assembled inside the rotor 13, the magnet 13b is positioned to surround the stator core 14a of the stator 14, facing the stator core 14a with a gap between them.

[0037] The stator 14 includes an annular stator core 14a and a coil 14c wound around the stator core 14a via an insulator 14b. The stator core 14a is an annular laminated core formed by laminating multiple steel plates of the same shape. The stator core 14a is fitted and fixed to the other end 47 of the bearing holder 4 with the lamination direction of the steel plates aligned with the axial direction at its center. For example, the fixing method may be a method of bonding the outer circumferential surface of the other end 47 to the inner circumferential surface of the stator core 14a with an adhesive. The stator core 14a may be fixed to the bearing holder 4 by press-fitting the other end 47 into an inner hole of the stator core 14a. The stator 14 is thereby fixed to the outer casing or base (not shown) of the fan motor via the bearing holder 4 and the mounting plate 3.

[0038] [3. Actions and Effects] (1) In the above-described holding structure, the inner surface of the holder portion 40 is provided with an adhesive surface 42, a relief surface 43 with a larger diameter than the adhesive surface 42, and a stepped surface 44 connecting these surfaces 42, 43. The stepped surface 44 is positioned axially so as to overlap with the bearing 2. In other words, the relief surface 43 is positioned axially to one side of the position where it overlaps with the bearing 2 in the axial direction. This prevents one side of the outer peripheral surface 2f of the bearing 2 from being compressed by the inner surface of the holder portion 40, which would be caused by deformation of the holder portion 40 when a part of the holder portion 40 (the press-fit portion 41) is press-fitted and fixed into the mounting portion 31. This prevents deformation of the bearing 2 that could occur due to deformation of the holder portion 40. This in turn keeps the passing speed of the balls of the bearing 2 constant, thereby reducing the generation of abnormal noise.

[0039] Additionally, in the holder part 40, the adhesive can be applied using the stepped surface 44 as a guide, allowing the adhesive to be applied in the appropriate position. When the bearing 2 is inserted, the adhesive wears away and spreads to the other side. Therefore, by applying the adhesive to the stepped surface 44, which is the base point on one side of the adhesive surface 42, it is possible to prevent the adhesive from spreading to the other side beyond the bearing 2, while ensuring a wide adhesive area.

[0040] (2) In the above-described holding structure, the axial position of the stepped surface 44 is set at a position overlapping both the mounting portion 31 and the bearing 2. As described above, the deformation of the holder portion 40 due to press-fitting is greater toward one side from the portion where the outer peripheral surface of the holder portion 40 and the inner peripheral surface of the mounting portion 31 are in pressure contact, i.e., the position of the other side end face 31f of the mounting portion 31. For this reason, by setting the axial position of the stepped surface 44, which is the base point on the other side of the relief surface 43, to a position that is toward the other side of the other side end face 31f and overlaps with the bearing 2, i.e., a position that overlaps with both the bearing 2 and the mounting portion 31, the amount of deformation (amount of compression) of the holder portion 40 can be suppressed, and compression of the outer ring of the bearing 2 due to this deformation can be further suppressed.

[0041] (3) In the above-described holding structure, the inner diameter D3 of the relief surface 43 is set to be larger than the outer diameter D1 of the bearing 2 plus the interference for press-fitting. The holder portion 40 is compressed and deformed when the holder portion 40 is press-fitted and fixed into the attachment portion 31, but the amount of deformation (amount of compression) does not exceed the interference for press-fitting. In other words, even if the holder portion 40 deforms, the amount of deformation is smaller than the interference for press-fitting. Therefore, by setting the inner diameter D3 of the relief surface 43 to be larger than the outer diameter D1 of the bearing 2 plus the interference for press-fitting, deformation of the bearing 2 fitted inside the holder portion 40 can be more reliably suppressed.

[0042] (4) In the above-described retention structure, when the outer diameter D1 of the bearing 2 is 12 mm and the viscosity of the adhesive is 2000 mPa·s or more and 3000 mPa·s or less, the difference between the outer diameter D1 of the bearing 2 and the inner diameter D3 of the relief surface 43 is set to 150 μm or more and 255 μm or less. This makes it possible to apply an appropriate amount of adhesive to the stepped surface 43 and form an appropriate adhesive film in a retention structure that uses a relatively small bearing 2 with an outer diameter of 12 mm. This makes it possible to more reliably achieve adhesion between the bearing 2 and the bonding surface 42.

[0043] (5) In the above-described holding structure, the bearing holder 4 is firmly fixed to the mounting plate 3 by press-fitting, and the inner surface of the bearing holder 4 is provided with a structure that suppresses deformation of the bearing 2 that may occur when the bearing holder 4 is press-fitted. Therefore, by applying the above-described holding structure to a fan motor, it is possible to prevent the shaft 1, which is fixed to the mounting plate 3 via the bearing holder 4, the rotor 13 that rotates integrally with the shaft 1, and the fan unit from coming loose, while suppressing the generation of abnormal noise from the fan motor. Note that in the above-described fan motor, not only the shaft 1, the fan unit, and the rotor 13, but also the stator 14 is fixed to the mounting plate 3 via the bearing holder 4. Therefore, a fan motor to which the above-described holding structure is applied can also prevent the stator 14 from coming loose.

[0044] [4. Other] The ball bearing holding structure and fan motor configurations described in the above embodiments are merely examples and are not limited to those described above. The fan motor does not have to be a centrifugal fan or an outer rotor brushless motor. The fan motor may be, for example, an axial fan that flows fluid in the axial direction of the shaft 1. The device to which the ball bearing holding structure is applied may be any device that is provided with a shaft 1, and is not limited to a fan motor.

[0045] The adhesion margin between the bearing 2 and the bonding surface 42 is not limited to the above-mentioned range (1 μm to 16 μm) and may be set appropriately depending on the viscosity of the adhesive and the outer diameter D1 of the bearing 2. For example, suppose the adhesive used is of medium or high viscosity, with the lower limit being greater than the above-mentioned upper viscosity limit (3000 mPa·s). In this case, the range of the adhesion margin may be set within a predetermined range of values ​​greater than the above-mentioned range (1 μm to 16 μm) (a range with a lower limit greater than 1 μm and an upper limit greater than 16 μm). Furthermore, for example, if a bearing with an outer diameter greater than the above-mentioned bearing 2 is used in this retention structure, the range of the adhesion margin may be set within a predetermined range of values ​​greater than the above-mentioned range (1 μm to 16 μm) (a range with a lower limit greater than 1 μm and an upper limit greater than 16 μm).

[0046] Similarly, the difference between the outer diameter D1 of the bearing 2 and the inner diameter D3 of the relief surface 43 is not limited to the above-mentioned range of values ​​(150 μm to 255 μm) and may be set appropriately depending on, for example, the viscosity of the adhesive and the outer diameter D1 of the bearing 2. The inner diameter D3 of the relief surface 43 is not limited to the above-mentioned set value as long as it is at least larger than the inner diameter D2 of the bonding surface 42.

[0047] The interference for press-fitting between the mounting plate 3 and the bearing holder 4 is not limited to the above range. For example, the interference for press-fitting may be set appropriately depending on the outer diameter D1 of the bearing 2. For example, suppose that a bearing with an outer diameter larger than that of the above-mentioned bearing 2 is applied to this holding structure. In this case, the interference for press-fitting may be set within a predetermined range (a range with a lower limit greater than 35 μm and an upper limit greater than 45 μm) that is larger than the above-mentioned range (35 μm to 45 μm). Furthermore, the interference may be set appropriately depending on the weight of the component held by the mounting plate 3 via the bearing holder 4. Examples of the component to be held include the bearing 2, the shaft 1, a component supported by the shaft 1 (e.g., the rotor 13), and another component (e.g., the stator 14) fixed to the mounting plate 3 via the bearing holder 4. The interference may be set appropriately to satisfy the required fastening force depending on the usage conditions (external forces such as external vibrations depending on the usage location) of the device to which this holding structure is applied.

[0048] The shape of the mounting plate 3 is not limited to the above-described shape as long as it has a mounting portion 31. For example, the base portion 32 may be provided so as to close the inner hole of the mounting portion 31 from one side of the mounting portion 31. The base portion 32 may extend outward from the other side of the mounting portion 31, or may extend outward from the entire outer circumferential surface of the mounting portion 31. Furthermore, for example, if the base portion 32 has a large plate thickness, a hole formed penetrating the base portion 32 in the plate thickness direction can itself serve as the mounting portion 31. The base portion 32 may be omitted.

[0049] The shape of the mounting portion 31 is not limited to a cylindrical shape, and may be any shape that allows the holder portion 40 to be press-fitted into the inside. Similarly, the shape of the holder portion 40 is not limited to a cylindrical shape. The holder portion 40 may be any shape that allows it to be press-fitted into the mounting portion 31 and that allows the bearing 2 to be fitted inside. In the holding structure shown in FIG. 1 , the base portion 32 (one end portion of the mounting portion 31) of the mounting plate 3 and the end face of one end portion 46 of the holder portion 40 are flush with each other, but the one end portion 46 may protrude to one side from the base portion 32, or may be located on the other side from the base portion 32.

[0050] The positioning portion 45 of the holder portion 40 is not limited to the above, as long as it abuts against the bearing 2 from the other side and restricts displacement of the bearing 2 to the other side. For example, the positioning portion 45 may be configured as a bottom portion that closes the inner hole of the holder portion 40 from the other side of the holder portion 40. In this case, the bearing 2 may rotatably support the other end of the shaft 1. Furthermore, the positioning portion 45 may be configured as a separate member from the holder portion 40. [Explanation of symbols]

[0051] 1 shaft 2 Bearings (first bearing, ball bearing) 2f Outer surface 3 Mounting plate 4 Bearing holder 10 Motor section 13 rotor 14 Stator 31 Mounting part 31f Other end face (other end face of mounting part) 40 Holder part 41 Press-fit part (part of the holder) 42 Adhesive surface 43 Relief surface 44 Step surface 45 Positioning part D1 Bearing outer diameter D2 Inner diameter of adhesive surface D3 Inner diameter of relief surface

Claims

1. A ball bearing holding structure that rotatably supports a shaft, a bearing holder including a cylindrical holder portion into which the ball bearing is fitted from one axial side of the shaft, and a positioning portion provided on the other axial side of the holder portion and abutting against the ball bearing from the other side; a mounting plate having a cylindrical mounting portion into which a part of the holder portion is press-fitted from the other side, an inner surface of the holder portion is provided with an adhesive surface that is bonded to an outer circumferential surface of the ball bearing with an adhesive; a relief surface that is on the one side of the adhesive surface and has an inner diameter that is larger than the inner diameter of the adhesive surface; and a stepped surface that connects the adhesive surface and the relief surface and onto which the adhesive is applied when the ball bearing is fitted into the bearing holder, The axial position of the step surface is a position that overlaps with the ball bearing when the ball bearing is fitted into the bearing holder. A ball bearing holding structure characterized by:

2. With the bearing holder and the mounting plate combined, an axial position of the other end surface of the mounting portion overlaps with the ball bearing; The step surface is positioned in the axial direction so as to overlap both the mounting portion and the ball bearing.

2. The ball bearing holding structure according to claim 1, wherein:

3. The inner diameter of the relief surface is larger than the outer diameter of the ball bearing plus the interference for press-fitting the holder portion.

2. The ball bearing holding structure according to claim 1, wherein:

4. The inner diameter of the relief surface is larger than the outer diameter of the ball bearing plus the interference for press-fitting the holder portion.

3. The ball bearing holding structure according to claim 2, wherein:

5. The outer diameter of the ball bearing is 12 mm, The viscosity of the adhesive is 2000 mPa·s or more and 3000 mPa·s or less, The difference between the outer diameter of the ball bearing and the inner diameter of the relief surface is 150 μm or more and 255 μm or less.

5. The ball bearing holding structure according to claim 1, wherein the ball bearing holding structure is a ball bearing holding structure.

6. a motor unit having a rotor that rotates integrally with the fan unit via a shaft and a stator that is disposed opposite the rotor; The ball bearing holding structure according to any one of claims 1 to 4 is applied to the ball bearing that rotatably supports the shaft. A fan motor characterized by:

7. a motor unit having a rotor that rotates integrally with the fan unit via a shaft and a stator that is disposed opposite the rotor; The ball bearing holding structure according to claim 5 is applied to the ball bearing that rotatably supports the shaft. A fan motor characterized by:

8. A method for manufacturing a holding structure for a ball bearing that rotatably supports a shaft, comprising: The holding structure includes a bearing holder having a cylindrical holder portion and a positioning portion provided on the other side of the holder portion in the axial direction of the shaft, and a mounting plate having a cylindrical mounting portion, an inner surface of the holder portion is provided with an adhesive surface that is bonded to an outer circumferential surface of the ball bearing with an adhesive; a relief surface that is located on one side of the adhesive surface in the axial direction and has an inner diameter that is larger than the inner diameter of the adhesive surface; and a step surface that connects the adhesive surface and the relief surface, The manufacturing method includes: a step of fitting the ball bearing into the holder portion from the one side and abutting the positioning portion against the ball bearing from the other side to determine the axial position of the ball bearing, and fitting the ball bearing into the bearing holder; and a step of press-fitting a part of the holder portion into the attachment portion from the other side, The fitting step includes: applying the adhesive to the step surface; a step of fitting the ball bearing into the bearing holder, causing the adhesive applied to the stepped surface to be scraped and spread between the outer circumferential surface and the adhesive surface, thereby adhering the outer circumferential surface and the adhesive surface, The axial position of the step surface is a position that overlaps with the ball bearing when the ball bearing is fitted into the bearing holder. A method for manufacturing a ball bearing holding structure, comprising:

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