JP7464456B2 - Rotating shaft bearing fixing structure - Google Patents

Description

The present invention relates to a bearing fixing structure for a rotating shaft.

Conventionally, a commonly used bearing fixing structure for this type of rotating shaft is as shown in FIG.
When mounting ball bearing 104 on rotating shaft 101 of a motor, step 102a is formed in advance in bearing mounting portion 102 of rotating shaft 101, which is then polished to an appropriate fit tolerance, and ball bearing 104 is press-fitted into bearing mounting portion 102 of rotating shaft 101, thereby fixing ball bearing 104 to rotating shaft 101. The outer ring of ball bearing 104 is fixed to bracket 103 of the motor.
Patent Document 1 lists drawbacks such as a long polishing time required for polishing to improve the finishing precision, the need for polishing equipment, and high costs due to poor workability, etc. However, in recent years, with improvements in the precision of polishing equipment, no particular adhesive is required, and the ball bearing can be fixed to the rotating shaft simply by pressing, with good circularity precision, and so this is commonly used in the case of rotating shafts with diameters larger than φ5 mm.

However, in the case of rotating shafts with a diameter of φ5 mm or less, small-diameter ball bearings are used, so the strength of the inner ring of the ball bearing is weak and it is necessary to pre-process a step in the bearing mounting portion of the rotating shaft and polish it to a highly accurate fitting tolerance. This requires a long polishing time and is difficult to work with, resulting in high costs, and these drawbacks have not been resolved.

As shown in FIG. 1 of Patent Document 1, the rotating shaft is a round bar, and a ball bearing mounting portion is knurled in advance to form an engagement portion with multiple projections and recesses along the axial direction, and the projections and recesses increase the apparent outer diameter of the rotating shaft, making it easy to press-fit the ball bearing. However, when the projections and recesses increase the apparent outer diameter of the rotating shaft, this is the case of knurling by rolling. When knurling by rolling, it is difficult to achieve precision on the order of μ in the projections and recesses. Before rolling, the rotating shaft needs to be measured and processed, and as rolling is performed, tools such as dies also wear out. In this way, maintaining and managing the precision is complicated and unrealistic, and the precision of the projections and recesses deteriorates, and when the ball bearing is pressed in, the inner ring of the ball bearing is deformed, the axis of the rotating shaft is tilted, or the position is shifted, which may result in poor precision of the shaft runout when the rotating shaft is assembled into the motor. In addition, rolling is not suitable for hard materials, so there is a restriction that it cannot be performed after hardening.

Therefore, when fixing a ball bearing to a rotating shaft with a diameter of φ5 mm or less, a fixing structure is implemented in which the rotating shaft and the inner diameter of the ball bearing are bonded with an appropriate gap of about 5 μm between them, and as described in Patent Document 2, a fixing structure is also implemented in which multiple holding grooves are provided on the outer peripheral surface of the rotating shaft to bond the inner diameter of the ball bearing. In the case of Patent Document 2, too, the holding grooves are recessed so that the circumferential surface of the rotating shaft remains, and adhesive is held in the holding grooves, and this adhesive bonds the circumferential surface of the rotating shaft and the inner peripheral surface of the inner ring of the ball bearing, so in Patent Document 2 too, it is necessary to bond the rotating shaft and the inner diameter of the ball bearing with an appropriate gap of about 5 μm between them.

Japanese Utility Model Application Publication No. 60-147971 JP 2000-346085 A

However, in such a conventional rotating shaft bearing fixing structure, even if the retaining grooves are provided uniformly at regular intervals on the circumferential surface of the rotating shaft as described in Patent Document 2, when bonding is performed with an appropriate gap of about 5 μm between the inner diameter of the ball bearing and the rotating shaft, it is difficult to bond the ball bearing to the rotating shaft so that the adhesive is of a uniform thickness (2.5 μm) around the circumferential surface, and the ball bearing ends up being bonded unevenly (in the worst case scenario, a deviation of 5 μm occurs).
This can cause the shaft center of the rotating shaft to tilt or become misaligned, which can lead to poor precision in shaft runout when the rotating shaft is installed in a motor. In addition, due to the tolerance of the inner diameter of the bearing and the machining tolerance of the rotating shaft, it is difficult to make the gap between the rotating shaft and the bearing smaller than 5 μm.
There was a problem:

The present invention was made with a focus on these conventional problems (disadvantages), and aims to provide a bearing fixing structure for a rotating shaft that can solve the above problems by irradiating the bearing mounting portion of the rotating shaft with three or more laser beams at equal intervals in the axial direction, aligning the rotating shaft and the bearing, and gluing and fixing the rotating shaft and the inner ring of the bearing together at both the laser irradiated and non-laser irradiated portions.

In order to solve the above-mentioned problems, the present invention provides a bearing mounting portion having three or more laser irradiation portions extending in the axial direction on the outer peripheral surface of a rotating shaft, the laser irradiation portions and non-laser irradiated portions are alternately provided on the outer peripheral surface of the bearing mounting portion, the rotating shaft is inserted into the inner ring of a ball bearing fixed to the mounting body via an outer ring, the rotating shaft and the inner ring are aligned by the laser irradiation portions , and the bearing mounting portion is joined to the inner ring by an adhesive interposed between the bearing mounting portion and the inner ring , so that the rotating shaft is rotatably supported relative to the mounting body.

According to claim 1, by forming a laser irradiated portion on the outer peripheral surface of the rotating shaft, the convex portion of the laser irradiated portion is aligned, so that misalignment can be prevented. Furthermore, adhesive can be applied to the uneven surface of the laser irradiated portion and the non-laser irradiated portion, so that the laser irradiated portion can be more firmly bonded and fixed.

FIG. 1 is an exploded perspective view of a rotating shaft before it is inserted into and fixed to a ball bearing. FIG. 2 is a cross-sectional view of a fixing portion in which a rotating shaft is inserted into and fixed to a ball bearing. FIG. 3 is an enlarged view of the laser irradiated portion of FIG. FIG. 4 is a partial enlarged view of the laser irradiation portion of FIG. FIG. 5 is a conceptual diagram showing a conventional fixing structure between a rotating shaft and a ball bearing.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows the rotating shaft 1 of a motor irradiated with a laser, and shows a fixed structure with a ball bearing 5 supporting the rotating shaft 1. The rotating shaft 1 is made of a round bar with a constant outer diameter. The rotating shaft 1 is provided with a bearing mounting portion 2 on the peripheral surface, and the laser irradiation portions 3 extending in the axial direction on the outer circumferential surface are provided at regular intervals along the circumferential direction of the peripheral surface on the bearing mounting portion 2. In the illustrated example, three laser irradiation portions 3 are provided in the circumferential direction. These laser irradiation portions 3 are provided at three or more locations at equal intervals in the circumferential direction of the rotating shaft 1, and the number of laser irradiation portions 3 can be increased to four, five, six or more as necessary. In addition, the axial length l of the laser irradiation portion 3 can be set arbitrarily, and the circumferential width m can also be set arbitrarily. The width m of the laser irradiation portion 3 can be set to a constant ratio, m:n=x, in relation to the width n of the non-laser irradiation portion 4 of the bearing mounting portion 2 that is not irradiated with a laser. This ratio x can also be set arbitrarily.

The ball bearing 5 has a large number of balls (not shown) loaded between the inner ring 6 and the outer ring 7 of the ball bearing 5, and the rotating shaft 1 is inserted inside the inner ring 6 of the ball bearing 5. The gap 8 between the bearing mounting portion 2 of the rotating shaft 1 and the inner ring 6 of the ball bearing 5 is filled with adhesive 9. The thickness p of this adhesive 9 can also be set as desired.

Next, the operation of the above embodiment will be described.
1, a certain length of laser is irradiated in the axial direction to a bearing mounting portion 2 of a rotating shaft 1 of a motor or the like, and these laser irradiated portions 3 are formed at three equally spaced locations along the circumferential direction on the peripheral surface of the bearing mounting portion 2 of the rotating shaft 1. On the outer peripheral surface of the bearing mounting portion 2, the portion not irradiated with the laser becomes a non-laser irradiated portion 4.
The rotating shaft 1 is a stainless steel round bar with a fixed outer diameter. The fit tolerance between the inner diameter of the inner ring 6 of the ball bearing 5, which is inserted and fixed into the bearing installation portion 2 of the rotating shaft 1, and the outer diameter of the rotating shaft 1 is a clearance fit of about 5 μm with a gap 8, and the rotating shaft 1 is fixed by bonding with an adhesive 9. A cross-sectional view of the rotating shaft 1 when inserted into the inner ring 6 of the ball bearing 5 and bonded to the bearing installation portion 2 of the rotating shaft is shown in Figure 2.

In the case of adhesively fixing metal members, a base treatment is performed in which projections and recesses are formed on the surface by laser irradiation, and then the members are adhesively fixed (Patent Literature: JP 2014-114327 A).
In the present application, as shown in Fig. 1, a laser is irradiated in the axial direction of the bearing mounting portion 2 of the rotating shaft 1, and three laser irradiated portions 3 are formed at equal intervals in the circumferential direction of the bearing mounting portion 2, so that the surface 30 of the laser irradiated portion 3 becomes an unevenly rough surface 30a as shown in Figs. 3 and 4. The size of the unevenness of the surface 30 of the laser irradiated portion 3 can be adjusted by the output, scan speed, and pulse period of the laser processing machine, and as shown in Fig. 3, the convex portion 31 is made to rise about 2 μm from the surface 1a of the rotating shaft 1. Fig. 4 shows an enlarged view of the laser irradiated surface 30a. The convex portion 31 is formed as a protrusion in which the periphery of the hole portion protrudes in an annular shape from the surface 1a.

The fit tolerance between the inner diameter of the inner ring 6 of the ball bearing 5 and the outer diameter of the rotating shaft 1 is a clearance fit of about 5 μm, but because a protrusion of about 2 μm is formed in the laser irradiated portion 3, as shown in FIG. 2, the protrusions 31 of the laser irradiated portion 3 at three locations are aligned to fill the gap between the inner diameter of the inner ring 6 of the ball bearing 5 and the outer diameter of the rotating shaft 1 and fit together. Furthermore, both the laser irradiated portion 3 and the non-laser irradiated portion 4 are bonded and fixed with adhesive 9 (see FIG. 2). An anaerobic adhesive is used as the adhesive 9.

As explained above, if the bonding is performed with a gap fit of 5 μm, there is a risk of misalignment, but by forming the laser irradiated portion 3, the convex portion 31 of the laser irradiated portion 3 is aligned, preventing misalignment. Furthermore, adhesive 9 can be interposed between the uneven surface between the convex portion 31 and the concave portion 32 of the laser irradiated portion 3 and the non-laser irradiated portion 4, allowing for more solid bonding and fixation.

Next, another embodiment of the present invention will be described.
In the above embodiment, the laser irradiation units 3 provided on the bearing mounting portion 2 of the rotating shaft 1 are described as being located at three positions in the circumferential direction, but the number of positions may be three or more, such as four, five, six, seven, eight or more. If there are no problems with strength or workability, the laser may be irradiated all around the circumference.
In addition, the rotating shaft 1 of the motor of the present invention is more effective when the outer diameter is 5 mm or less, but it may also be applied to a fixing structure of a rotating shaft 1 and a bearing having an outer diameter larger than 5 mm.

In this way, by irradiating the rotating shaft 1 of a motor or the like with a laser at equal intervals to create unevenness on the surface of the bearing mounting portion 2, the adhesive 9 penetrates into the uneven surface between the convex portion 31 and the concave portion 32 of the laser irradiated portion 3 and is more likely to remain on the unevenness, thereby stabilizing the adhesive strength.
Since the rotating shaft 1 of the motor and the ball bearing are aligned at the laser-irradiated convex portion 31 of the rotating shaft 1, it is possible to prevent the axis of the rotating shaft 1 from being tilted or displaced, which would result in poor precision of shaft runout when the rotating shaft 1 is assembled into the motor.

As described above, according to the above embodiment, the following effects can be obtained.
The rotating shaft 1 is configured such that the laser irradiation portion 3 extending in the axial direction is provided on the outer peripheral surface of the rotating shaft 1, and the bearing mounting portion 2 is provided at three or more locations at equal intervals in the circumferential direction, the rotating shaft 1 is inserted into the inner ring 6 of the bearing 5 fixed to the mounting body via the outer ring 7, and the bearing mounting portion 2 of the rotating shaft 1 is bonded to the inner ring 6 by an adhesive 9 interposed in the bearing mounting portion 2, and the rotating shaft 1 is rotatably supported with respect to the mounting body, so that by forming the laser irradiation portion 3 on the outer peripheral surface of the rotating shaft 1, the center is aligned with the convex portion of the laser irradiation portion 3, and thus misalignment can be prevented. Furthermore, the adhesive 9 can be interposed between the uneven surface of the laser irradiation portion and the non-laser irradiated portion 4, and the adhesive can be more firmly bonded and fixed.
The laser irradiation sections 3 and non-laser irradiated sections 4 are alternately provided on the peripheral surface of the bearing mounting section 2 of the rotating shaft 1, and an adhesive 9 is interposed between the bearing mounting section 2, in which the laser irradiation sections 3 and non-laser irradiated sections 4 are provided, and the inner ring 6 of the bearing 5. Therefore, the adhesive 9 penetrates into the uneven surface between the convex portions 31 and concave portions 32 of the laser irradiation section 3 and is more likely to remain on the unevenness, stabilizing the adhesive strength.
The laser irradiation section 3 provided on the bearing mounting section 2 of the rotating shaft 1 aligns the rotating shaft 1 of the motor and the inner ring 6 of the ball bearing 5 at the laser-irradiated convex portion 31 of the rotating shaft 1, thereby preventing the axis of the rotating shaft 1 from tilting or shifting in position, which would result in a decrease in the accuracy of axial runout when the rotating shaft 1 is installed in the motor.

The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the present invention is applied to the rotating shaft of a motor. However, the present invention is not limited to motors, and can be applied to other rotating electric machines such as generators, as long as the rotating shaft is not limited to motors. It goes without saying that the present invention can be modified and implemented as appropriate without changing the technical scope of the present invention.

REFERENCE SIGNS LIST 1 Rotating shaft 2 Bearing mounting portion 3 Laser irradiated portion 4 Non-laser irradiated portion 5 Ball bearing 6 Inner ring 7 Outer ring 8 Gap 9 Adhesive 30 Surface 31 Convex portion 32 Concave portion

Claims (5)

a bearing mounting portion is provided on an outer peripheral surface of a rotating shaft, and three or more laser irradiation portions extending in an axial direction are provided at equal intervals in a circumferential direction , and the laser irradiation portions and non-laser irradiation portions are alternately provided on the outer peripheral surface of the bearing mounting portion;
a rotating shaft inserted into the inner ring of a ball bearing fixed to the body to be mounted via an outer ring , the rotating shaft and the inner ring are aligned by the laser irradiation unit , and the bearing mounting portion is joined to the inner ring by an adhesive interposed between the bearing mounting portion and the inner ring , thereby supporting the rotating shaft rotatably relative to the body to be mounted. 2. The bearing fixing structure for a rotating shaft according to claim 1, wherein a surface of said laser irradiated portion has a convex portion and a concave portion, and said alignment is performed by said convex portion. 3. The bearing fixing structure for a rotating shaft according to claim 2, wherein the convex portion is raised higher than a surface of the non-laser irradiated portion, and the concave portion is recessed lower than a surface of the non-laser irradiated portion. 4. The rotating shaft bearing fixing structure according to claim 1, wherein the rotating shaft is a round bar having a constant outer diameter except for the bearing mounting portion . 5. The rotating shaft bearing fixing structure according to claim 1, wherein the rotating shaft has an outer diameter of 5 mm or less excluding the bearing mounting portion .