JPH1142514A - Manufacture of bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a bearing which can high accurately obtain a coaxial degree of a plurality of bearing main units without being influenced by dimensional accuracy of a housing. SOLUTION: In both ends of a press fit hole 2a of a resin-made housing 2, a metal-made bearing main unit 3 inserted to a guide pin 12 is press fitted by an upper/lower punch 10, 11. Here in the upper/lower punch 10, 11, ultrasonic vibration is given from a horn 13, 14. The ultrasonic vibration is transmitted to the housing 2 and the bearing main unit 3, between both thereof, friction heat is generated. By this friction heat, an internal peripheral surface of the housing 2 is fused, as a result, the bearing main unit 3, while fusing the housing 2, is press fitted. After press fitting, the ultrasonic vibration is stopped, the bearing main unit 3 is fused in the housing. An internal peripheral surface of the housing 2 into contact with the bearing main unit 3 is fused, so that a residual degree of elastic stress is small, even when the guide pin 12 is extracted, by preventing the bearing main unit 3 from moving, a coaxial degree of a bearing hole 3a of the bearing main unit 3 is well held.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a bearing in which a plurality of bearing bodies are press-fitted inside a cylindrical housing.

[0002]

2. Description of the Related Art As bearings for various motors, two or more bearing bodies are press-fitted into a sleeve-shaped housing. For example, there is a structure in which a bearing main body is incorporated one by one at both ends inside a housing while being separated from each other. In such a bearing, since a plurality of bearing bodies substantially support the rotating shaft, high precision is required for the coaxiality of the bearing holes in the bearing bodies. The reason is that if the coaxiality is low, uneven wear due to one-sided contact and accompanying increase in frictional resistance are caused, and especially the bearing performance for motors is inferior. Conventionally, in order to increase the coaxiality, correction processing such as reamer processing has been performed. However, for example, when the bearing body is made of a sintered metal, the reaming process deteriorates the pore distribution state of the inner peripheral surface, and may cause the loss of the properties of the sintered metal. Further, since the correction processing itself increases the number of steps and devices, it is not preferable. Therefore, it is most desirable that a high-precision coaxiality be obtained when the bearing body is pressed into the interior of the housing. For this purpose, the following manufacturing method is employed.

That is, a guide pin which can be slidably inserted into a bearing hole of a bearing body is inserted into the housing, and the guide pin is inserted into a bearing hole of the bearing body on both sides of the housing. The main body is pressed into the housing along the guide pins. Thereafter, the guide pins are removed. According to this method, the bearing hole of each bearing body is previously determined coaxially by the guide pin, and the state is maintained even after the guide pin is pulled out, so that the above-described correction processing is not required.

[0004]

The material of the housing includes metal and resin. Since a resin housing is usually manufactured by injection molding, it can be obtained at a lower price than a metal housing which requires processing, but has a disadvantage in that dimensional accuracy is inferior to a metal housing. For this reason, the inner wall portion reduced by press-fitting the bearing main body, that is, the press-fitting margin may become non-uniform. When the above method is applied to such a housing, the resin is elastically restored and the bearing body is displaced in the radial direction after the guide pin is pulled out,
As a result, there has been a problem that high-precision coaxiality is impaired. To solve this problem, it is conceivable to solve the problem by setting the press-fitting margin large enough to ignore the degree of non-uniformity, but in this case, cracks occur in the resin housing which is inferior to metal in strength. There is a possibility that it is difficult to realize. Therefore, an object of the present invention is to provide a method of manufacturing a bearing in which the coaxiality of a plurality of bearing bodies can be obtained with high accuracy without being affected by the dimensional accuracy of the housing.

[0005]

SUMMARY OF THE INVENTION The present invention is a method for manufacturing a bearing in which a plurality of bearing bodies are press-fitted into a cylindrical housing with their respective bearing holes coaxial with each other. The housing is made of a material having a melting point lower than that of the bearing body, and a guide pin that can be slidably inserted into a bearing hole of the bearing body is inserted into the housing, and a guide is inserted into the bearing hole of each bearing body. By inserting the pin, each bearing main body is supported by the guide pin, and then, while applying high-frequency vibration to at least one of the bearing main body or the housing, each bearing main body is pressed into the housing along the guide pin. It is characterized by: According to the above manufacturing method, when the bearing body is press-fitted into the housing, frictional heat is generated between the two due to high-frequency vibration. The frictional heat causes the lower melting point, that is, the inner peripheral surface of the housing in contact with the bearing body to melt. That is, the bearing body is press-fitted while melting the inner peripheral surface of the housing. After the press-fitting, the bearing body is welded to the housing.
Thereafter, the guide pin is removed to obtain a bearing. Since the plurality of bearing bodies are press-fitted into the housing along the guide pins, the coaxiality is high at the time of press-fitting. Even if the guide pins are removed after the bearing main body is welded to the housing, the inner peripheral surface of the housing around the bearing main body is melted, so that the residual elastic stress is small, and the movement of the bearing main body due to the elastic stress is suppressed. As a result, high coaxiality is maintained in the bearing holes of the plurality of bearing bodies while the guide pins are inserted.

For example, if the bearing body is made of a metal such as a bronze bearing material and the housing is made of a resin, the housing can have a lower melting point than the bearing body. In addition, when the housing is made of resin, the dimensional accuracy tends to vary, so that the press-fit allowance of the bearing body may increase. small. Therefore, while maintaining coaxiality,
Cracking of the housing due to press-fitting of the bearing body is prevented. In addition, when the outer peripheral surface of the bearing main body is subjected to knurling, steps, grooves and the like, unevenness processing such as a knurl, a step, a groove, and the like, an increase in frictional force due to an increase in the contact area with the inner peripheral surface of the housing and mechanical fixation are achieved. Increases the binding power of

The high frequency may be about several hundred KHz as long as the inner peripheral surface of the housing in contact with the bearing body is melted by frictional heat. According to the study of the present inventors, for example, when the housing is made of resin, it is effective that the frequency of the high frequency is 1 KHz or more, and it is more effective if the frequency is 1.4 KHz or more in the ultrasonic range. It is known. A frequency of 20 KHz is sufficient, and even if it exceeds 20 KHz, no further improvement in the effect can be expected. Therefore, the high frequency is desirably a frequency of 1 to 20 KHz, and more preferably an ultrasonic wave.
When a high frequency is obtained by ultrasonic waves having a frequency of 20 KHz, 20,000 vibrations / second can be given to the bearing body or the housing, and the amplitude is also 0.1%.
mm or less. Therefore, as many as 2,000 vibrations can be applied to the bearing body or the housing in 0.1 second, so that the press-fitting of the bearing body into the housing and the welding to the housing are completed in a very short time.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a mold apparatus suitable for carrying out the method for manufacturing a bearing according to one embodiment, and the bearing 1 shown in FIG. 2 is manufactured by this mold apparatus. The bearing 1 is formed by press-fitting a ring-shaped bearing body 3 having a smooth inner and outer peripheral surfaces into both ends of a press-fit hole 2a formed at the center of a sleeve-like housing 2.
Each bearing main body 3 is formed to have the same dimensions by, for example, a bronze bearing material, and rotatably supports the rotating shaft 4 inserted into the bearing hole 3a of the bearing main body 3. The diameter of the press-fit hole 2 a of the housing 2 is slightly smaller than the outer diameter of the bearing body 3, and the difference is set as the press-fit allowance of the bearing body 3.

The mold device shown in FIG.
And a lower punch 11 disposed below the upper punch 10.
And a round bar-shaped guide pin 12 inserted into the upper and lower punches 10 and 11, and upper and lower horns 13 and 14 abutted on the upper and lower punches 10 and 11. The diameter of the guide pin 12 is set to a size that can be slidably inserted into the bearing hole 3 a of the bearing body 3. Therefore, when the guide pin 12 is inserted into the bearing hole 3a of the bearing main body 3, the bearing main body 3 is supported so as not to be displaced in the radial direction and to be slidable along the guide pin 12.
Pin insertion holes 10a and 11a into which the guide pins 12 are inserted are formed coaxially with each other at the centers of the upper and lower punches 10 and 11, respectively. These pin insertion holes 1
The diameters of 0a and 11a are set to the same diameter as the bearing hole 3a of the bearing body 3. Thereby, the pin insertion holes 10a,
When the guide pin 12 is inserted into the 11a, both slide relatively in the axial direction without being displaced in the radial direction. The upper and lower horns 13 and 14 apply ultrasonic vibration of a predetermined frequency to the upper and lower punches 10 and 11, respectively.

Next, a method of manufacturing the bearing 1 shown in FIG. 2 using the above-described mold apparatus will be described. First, the guide pin 12 is inserted into the pin insertion hole 11a from below the lower punch 11,
When the upper end of the guide pin 12 projects upward from the pin insertion hole 11a, the upper end of the guide pin 12 is inserted into the bearing hole 3 of the lower bearing body 3.
Insert into a. Next, the housing 2 is arranged between the upper and lower punches 10 and 11, and the guide pin 12 is held while the bearing body 3 fitted to the guide pin 12 is held substantially at that position.
To be inserted into the press-fit hole 2a of the housing 2. When the upper end of the guide pin 12 projects from the press-fit hole 2a, the upper end is inserted into the bearing hole 3a of the upper bearing body 3, and the guide pin 12 is further pushed up to be inserted into the pin insertion hole 10a of the upper punch 10. After this, the upper and lower horns 1
The upper and lower punches 3, 11 are brought into contact with the upper and lower punches 10, 11, respectively. Further, the housing 2 is moved by a die (not shown) or the like.
The press-fit hole 2a is arranged so as to be coaxial with the guide pin 12.

As described above, the housing 2 is inserted into the mold apparatus.
After setting the two bearing bodies 3, the upper and lower horns 13, 14 are moved in the direction of the housing 2 while the upper and lower horns 13, 14 are brought into contact with the upper and lower punches 10, 11, respectively. The bearing body 3 is press-fitted into the press-fitting hole 2a of the housing 2. In this press-in process,
The ultrasonic vibrations emitted from the horns 13 and 14 are transmitted from the upper and lower punches 10 and 11 to the respective bearing bodies 3 and further transmitted from the bearing bodies 3 to the housing 2. Then, friction occurs between the outer peripheral surface of the bearing main body 3 and the inner peripheral surface of the housing 2, and the inner peripheral surface of the housing 2 having a lower melting point than the bearing main body 3 is melted by the frictional heat. That is, the bearing body 3 is pressed into the press-fitting hole 2a while melting the inner peripheral surface of the housing 2 and without itself melting. When the upper and lower punches 10 and 11 abut against the end surfaces of the housing 2 respectively, the press-fitting of the upper and lower bearing main bodies 3 is completed, and thereafter, the operations of the horns 13 and 14 are stopped. Subsequently, after allowing time for the inner peripheral surface of the melted housing 2 to fuse to the outer peripheral surface of the bearing main body 3, the upper and lower punches 10 and 11 are opened, and the guide pin 12 is pulled out from the upper and lower bearing main bodies 3, and FIG. 2 is obtained.

According to the above manufacturing method, each bearing body 3 is
Since it is press-fitted into the press-fitting hole 2a of the housing 2 along the guide pin 12 inserted into the bearing hole 3a, first, the coaxiality of the bearing hole 3a at the time of press-fitting is high. The inner peripheral surface of the housing 2 is melted by ultrasonic vibration when the bearing main body 3 is press-fitted, and then welded to the outer peripheral surface of the bearing main body 3. That is, the bearing body 3 is ultrasonically welded to the housing 2. Therefore, the elastic stress remaining on the inner peripheral surface of the housing 2 is small. Therefore, even if the press-fit hole 2a of the housing 2 is inferior in dimensional accuracy and the press-fit allowance is not uniform, the bearing body 3 is returned by the elastic return of the housing 2 after the guide pins 12 are removed from the upper and lower bearing bodies 3. It does not move radially.
As a result, the bearing hole 3a of each bearing body 3 is
A high coaxiality is maintained with the state of 2 being inserted.

In the above embodiment, each bearing body 3
Are simultaneously pressed into the housing 2 while applying ultrasonic vibrations by the upper and lower horns 13 and 14, but the press-fitting may be performed sequentially instead of simultaneously. When press-fitting is performed simultaneously as described above, ultrasonic vibration may be applied to only one of the bearing bodies 3. Furthermore, one of the bearing bodies 3 may be press-fitted into the housing 2 as usual without applying ultrasonic vibration, and then the other bearing body 3 may be press-fitted into the housing 2 while applying ultrasonic vibration. . In either case, as a result, ultrasonic vibration is transmitted to both bearing bodies 3, and these bearing bodies 3 are ultrasonically welded to the housing 2.

FIGS. 3 and 4 show a modification of the bearing body. In the bearing main body 3 of the above-described embodiment, the outer peripheral surface is smooth. However, a knurl 6 is formed on the outer peripheral surface of the bearing main body 3A shown in FIG. 3 by a plurality of grooves 5 along the axial direction. I have. As a result, the area of welding to the inner peripheral surface of the housing 2 is increased, and a retaining action is exhibited. In addition, a circumferential groove 7 is formed on the outer peripheral surface of the bearing main body 3B shown in FIG. The resin melted when the bearing main body 3B is pressed into the housing 2 flows into the circumferential groove 7, and the bearing main body 3B is mechanically fixed to the housing 2 as well. Since the circumferential groove 7 is orthogonal to the direction in which the circumferential groove 7 comes off from the housing 2, the resin that has flowed into the circumferential groove 7 and has been solidified significantly improves the retaining function, and increases the bonding force to the housing 2. In this manner, by performing unevenness processing such as knurls, circumferential grooves, or steps on the outer peripheral surface of the bearing main body, the bearing main body is less likely to come off from the housing 2 and the coupling force is improved.

[0015]

Next, specific examples 1 and 2 in which a bearing is manufactured based on the above embodiment will be described. [Example 1] Inside a resin housing having a roundness of a press-in hole of 50 µm, an inner diameter of 5 mm, an outer diameter of 10 mm, and a shaft length of 6 mm.
The two bearing bodies were press-fitted by applying the ultrasonic vibration to the upper and lower punches by the method shown in FIG. The same bearing body was press-fitted into a resin housing having a press-fitting hole having a roundness of 100 μm while applying ultrasonic vibration to produce Sample 2. The material of the housing was a resin in which 30% of glass reinforced fiber was mixed with polycarbonate. The press-fitting allowance of the press-fitting hole in the housing was set to 20 μm based on the minimum value of the inner diameter. Therefore, the press-in allowance for the housing of sample 1 is in the range of 20 to 70 μm, and the press-in allowance for sample 2 is in the range of 20 to 120 μm. The bearing body used was made of a bronze bearing material. The ultrasonic vibration applied to the upper and lower punches when these bearing bodies are pressed into the housing has a frequency of 20 kHz and an amplitude of 20 μm.
m, the vibration direction was the axial direction, and the vibration time was 0.1 second. Further, the dimensions of the housing and the bearing main body and the used mold apparatus were the same, and the bearing main body was pressed into the housing without applying ultrasonic vibration to prepare Samples 3 and 4, which were used as comparative examples. For the above samples 1 to 4, the inner diameters of the upper and lower bearing bodies and the penetration dimensions of the upper and lower bearing bodies were measured.
It is shown in Table 1.

[0016]

[Table 1]

As can be seen from Table 1, the coaxiality of the samples 1 and 2 obtained by press-fitting the bearing body into the housing while applying ultrasonic vibration showed a small value of 2 μm in coaxiality. In particular, in the case of sample 2, the roundness of the housing is 100 μm, twice that of the housing of sample 1,
Despite the large press-in allowance, it showed the same concentricity as Sample 1. On the other hand, among the samples 3 and 4 to which no ultrasonic vibration is applied, the coaxiality of the sample 3 is 4 to 5 μm.
And a value twice or more than that of the example. Sample 4 was not measured because a crack occurred in the housing. This is presumably because the housing press-fitting margin is large and an excessive load is applied to the housing during press-fitting of the bearing body. As described above, by applying the bearing main body into the housing along the guide pins while applying ultrasonic vibration, it was possible to obtain a good coaxiality even if there was a dimensional error in the press-fitting hole of the housing.

Second Embodiment Next, a description will be given of a second embodiment in which the relationship between the shape of the outer peripheral surface of the bearing body and the coupling force to the housing is evaluated. The type of the outer peripheral surface is three types: one in which the knurl shown in FIG. 3 is formed and the one in which the peripheral groove shown in FIG.
Type. These bearing bodies were press-fitted into the housing under two conditions, with and without ultrasonic vibration, to produce a sample. Then, the bearing bodies of these samples were removed from the housing, and the removal force required at that time is shown in Table 2.
The roundness of the housing is 50 μm.

[0019]

[Table 2]

According to Table 2, first, when the outer peripheral surface is smooth,
It can be seen that the bonding force is lower when there is ultrasonic vibration. This is presumably because the inner peripheral surface of the housing, which is melted by the ultrasonic vibration, comes into contact with the bearing main body, so that the elastic stress acting on the bearing main body from the housing is smaller than that without ultrasonic vibration. If it is evaluated only from the viewpoint of the bonding force, it is better to press-fit without ultrasonic vibration, but in that case, the coaxiality is inferior as is clear in the first embodiment. When the outer peripheral surface is knurled and has ultrasonic vibration, it is considered that the frictional force increases as the molten resin flows into the groove and the contact area increases. For this reason, although the direction in which the irregularities extend is the detaching direction, the coupling force is not significantly reduced as compared with the case without ultrasonic vibration coupled by elastic stress. When the outer peripheral surface is a circumferential groove and there is ultrasonic vibration, it is considered that the molten resin flows into the circumferential groove orthogonal to the pull-out direction, so that the bearing body is mechanically fixed to the housing. For this reason, the coupling force is higher than in the case without ultrasonic vibration.

[0021]

As described above, according to the present invention, a plurality of bearing bodies are pressed into the housing along the guide pins while applying high-frequency vibration, so that the inner peripheral surface of the housing around the bearing bodies is melted by frictional heat. As a result, the residual degree of elastic stress is reduced, and as a result, the movement of the bearing main body is suppressed even after the guide pin is pulled out, and high coaxiality is maintained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a mold device suitable for carrying out a method for manufacturing a bearing according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an example of a bearing according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a modification of the bearing according to the embodiment of the present invention.

FIG. 4 is a perspective view showing another modified example of the bearing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Bearing, 2 ... Housing, 3 ... Bearing main body, 3a ... Bearing hole, 6 ... Knurl, 7 ... Peripheral groove, 12 ... Guide pin.

Claims (5)

[Claims] 1. A method of manufacturing a bearing in which a plurality of bearing bodies are press-fitted into a cylindrical housing in a state where respective bearing holes are coaxial with each other. Manufactured with a material having a melting point lower than that of the bearing body, and a guide pin which can be slidably inserted into a bearing hole of the bearing body is inserted into the housing, and a guide pin is inserted into a bearing hole of each bearing body. By
A bearing, wherein each guide body is supported by the guide pin, and then each bearing body is press-fitted into the housing along the guide pin while applying high-frequency vibration to at least one of the bearing body or the housing. Manufacturing method. 2. The method according to claim 1, wherein the bearing body is made of metal, and the housing is made of a resin having a lower melting point than the bearing body. 3. A knurl, on an outer peripheral surface of the bearing body,
3. The method for manufacturing a bearing according to claim 1, wherein unevenness processing such as steps and grooves is performed. 4. The method for producing a bearing according to claim 1, wherein the high frequency is 1 to 20 KHz. 5. The method according to claim 1, wherein the high frequency is an ultrasonic wave.