JPS63270918A - Oil impregnated sintered bearing - Google Patents

Abstract

PURPOSE:To prevent galling of a shaft and drying up of oil film by making up the inside diameter of a bearing of a small diameter part and a circular-arc shaped large diameter part, so that the part changing from the small diameter part to the large diameter part makes an obtuse angle. CONSTITUTION:The inside diameter d1 at each of both ends of respective oil impregnated sintered bearings 71, 72 is made to be smaller than the inside diameter d2 at the axial central part. Since each of recesses 81a, 82a is formed in a circular-arc shape in its axial cross section, the part X (not shown) changing from the inner circumferential surface of the small diameter part d1 to the respective recessed parts 81a, 82a of the large diameter part d2 makes an obtuse angle. Thus, the damage of a shaft due to galling at the part X caused by the deflection of the shaft or the like can be prevented, and also the breakage of oil film at the part X on the inner circumferential surface from the small diameter part d1 to the large diameter part d2 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sintered oil-impregnated bearing in which the inner diameter of the bearing is small at both end portions of the bearing and large at the central portion in the axial direction.

[Conventional technology]

There are various applications and usage methods for this type of oil-impregnated bearing manufactured by powder metallurgy, but two of the same bearing may be used in parallel.

An example is the coreless morph shown in FIG. .2 should be attached to the resin the boat 5, and the resin support 5 should be attached to the iron core 6.

By the way, conventionally, as the oil-impregnated bearing 1.2, a simple cylindrical bearing with a uniform cross-sectional shape in the axial direction has been used.

However, it goes without saying that there will be variations in their positioning, and there will also be variations in the size of the individual bearings 1.2, so it is important to install the two oil-impregnated bearings 1.2 without eccentricity to the motor shaft 4. This made it difficult to avoid problems such as noise and shaft galling.

As a way of thinking to solve such problems,
A sintered oil-impregnated bearing described in Japanese Patent No. 8842 is known.

[Problem that the invention seeks to solve]

However, in the technology described in the above publication, since the portion of the inner circumferential surface of the bearing from the small diameter portion to the large diameter portion is at right angles, not only does the problem of shaft galling still remain due to shaft deflection, but also If the part leading to the large diameter part is at a right angle, there is a problem in that the oil film tends to run out at that part, and it is impossible to achieve a long life due to seizing or the like.

The present invention was made against the background as described above.
The purpose of the present invention is to provide a sintered oil-impregnated bearing that is free from soybean galling and oil film depletion.

[Means for solving problems]

This invention is constructed entirely of sintered material, has a small inner diameter at both end portions in the axial direction, is formed in an arcuate cross section in the axial direction, and has a diameter difference of 2 μm or more between the small diameter portion and the large diameter portion. be.

〔Example〕

Hereinafter, the content of the present invention will be explained in detail with reference to the attached FIGS. 2 to 5.

The sintered oil-impregnated bearing 71.72 of the present invention is entirely made of sintered material, and as shown in FIG.
An arc-shaped relief 81a in the axial cross section is provided at the center of the axial center of the
, 82a are provided. Therefore, in the oil-impregnated bearings 7I and 72 of the present invention, the inner diameter d1 (small diameter portion) at both end portions of the bearing is equal to the inner diameter dt at the central portion in the axial direction.
(large diameter part).

Each of these oil-impregnated bearings 71, 72 is used in place of bearings 1 and 2 in a planar coreless morph, for example (Fig. 3), but each of these oil-impregnated bearings 71, 72 is integral as a whole. Despite this, the two end portions 81b, 81c; 82b, 82c, which are separated from each other, perform the same functions as independent conventional bearings 1.2. In this case, in order to effectively perform such functions, da-d.

It is necessary to set the thickness to ≧2 μm.

On the other hand, when dtd+<2μm, the difference in radius is only 1μm, and it is not possible to secure a sufficient amount of lubricating oil in these reliefs 81a and 82a, which causes them to lose their function as oil reservoirs, and It is no different from a simple cylindrical bearing with a uniform cross section.

Therefore, when dt d1≧2 μm, the relief portions 81a and 82a function as oil reservoirs, making it possible to extend the life of the bearing.

In addition, since the reliefs 81a and 82a are formed in an arc shape in the axial cross section, the small diameter part d and the large diameter part d from the inner peripheral surface.
, since the portions X leading to the reliefs 81a and 82a are obtuse angles, there is no possibility that the shaft will be damaged by hitting the X portion due to deflection of the shaft, and it is possible to move from the small diameter portion d to the large diameter portion d. The oil film does not break in the X portion of the inner circumferential surface, preventing seizure etc. over a long period of time, resulting in stable quality and extended service life. Furthermore, when inserting the shaft into the bearing, the arcuate surface smoothly guides the tip of the shaft, which is preferable in that it does not damage the inner circumferential surface of the bearing or the shaft. In addition, the size of each oil-impregnated bearing 71.72 is as follows.
For example, outer diameter 3~5 mm, length 4~7 mm, inner diameter 1~
2+nm.

Incidentally, the reliefs 81a and 82a can be formed by selective etching or electric discharge machining after sintering, but it is best to use the following manufacturing method that takes advantage of the characteristics of powder metallurgy.

Sintered parts are usually manufactured through a powder compaction process, a sintering process, and a repressing process after sintering, but here, as shown in FIG. A ring-shaped groove 10a is provided on the outer circumferential surface of the central portion in the axial direction (corresponding to the location where the reliefs 81a and 82a are provided).

10b, one having loc is formed in advance. These grooves 10a, IOb, and 10c can be formed by cutting or by changing the shape of the die used during powder compaction. Note that the sizes, shapes, etc. of these grooves 10a, 10b, and 10C are as per the bearing hole 8! .

It can be selected as appropriate depending on the size of the reliefs 81a, 82a of 82, etc.

Then, such a sintered body 9 is re-pressed in the usual manner, that is, as shown in FIG. Upper bunch 12, lower punch 13 and core rod! 4, it is compressed from both ends in the axial direction. Then, the outer diameter portion of the sintered body 9 and the grooves IOa, IOb, IOc portions are connected to the die 1.
The meat moves outward following the shape of 1. On the other hand, the bearing hole portion swells outward at the grooves 10a, 1Ob, and 1Oc, creating areas where it hits the core rod I4, which has a uniform cross-sectional shape in the axial direction, and areas where it does not. The shapes of the bearings 71 and 72 as shown in FIG.

In the bearings 71 and 72 of the present invention manufactured in this manner, there are reliefs 81a in the bearing holes 81 and 82.

82a is formed, and both end portions 81b, 82c; 82b, 82c without reliefs 81a, 82a are simultaneously compressed, so that eccentricity and dimensional variations are considerably reduced.

Next, the effects of the present invention will be made clearer by giving an example of a test actually conducted on an example of application to a coreless motor.

The outer diameter is 4φ, the inner diameter of the bearing hole is 1.2φ, and the length is 611I.
The sintered oil-impregnated bearing of the present invention made of In and having a diameter of 2.5φ in the relief part at the center of the bearing hole was tested at a rotational speed of 510 rpm, and the results shown in the following table were obtained.

(Note) These current values (X) become larger as eccentricity and galling become larger.

〔Effect of the invention〕

In this invention, the entire bearing is made of sintered material, and the inner diameter of the bearing is made up of a small diameter part and an arc-shaped large diameter part, so the part from the small diameter part to the large diameter part forms an obtuse angle, and as a result, the bearing is bent in a straight line. Not only does it not cause galling of the soyaft, but it also prevents oil film from breaking, resulting in a longer service life.

In addition, since the diameter difference between the small diameter part and the large diameter part is set to 2 μm or more, a sufficient oil reservoir can be secured, and lubricating oil can be stably supplied to the inner peripheral surface of the small diameter part over a long period of time. In this respect as well, the life of the product can be extended.

[Brief explanation of drawings]

Figure 1 shows an application example of a conventional bearing of this type, and Figure 2 (
a) and (b) are cross-sectional views showing examples of the sintered oil-impregnated bearing according to the present invention, FIG. 3 is a view showing an application example of the bearing of the present invention, and FIGS. FIG. 5 is a sectional view showing each side of the sintered body used in the manufacturing method of the invention, and FIG. 5 is a sectional view of the main part showing the pressurized and compressed state in the repressing step in the invention. 71.72... Sintered oil-impregnated bearing according to this invention,
81.82...Bearing hole, 81a, 82a...
...Escape (center in axial direction), 8 lb, 81c; 8
2b, 82c... Both ends of the bearing, 9...
...Sintered body, 10a, lOb, 10C...Ring-shaped groove, 11...Gui, 14...Core rod.

Claims (1)

[Claims] The entire bearing is made of sintered material, and the axial cross section is formed in an arc shape so that the inner diameter of the bearing is smaller at both ends in the axial direction and larger at the center, and the difference in diameter between the small diameter part and the large diameter part is set to 2 μm or more. A sintered oil-impregnated bearing characterized by: