JPH06185528A - Bearing device for rotary shaft - Google Patents

Abstract

PURPOSE:To improve reliability equivalent to a ball bearing by fitting an assist sintered metal plate, without containing lubricating oil, to a part where an exposed surface of a sintered oil-retaining bearing, so that a loss of lubricating oil is prevented to effectively hold it and to maintain a function of the lubricating oil till its own life expires. CONSTITUTION:An opening surface of a sintered oil-retaining bearing 18 is coated with a non-oil-retaining sintered metal plate 26, and a fine hole diameter of the non-oil-retaining sintered metal plate 26, closely attached to the bearing 18, is set larger than that of the bearing 18. Consequently, by a difference of capillary force in a boundary surface, a retaining amount of lubricating oil can be maintained at a fixed value by retaining lubricating oil in the bearing 18. Even in the case that lubricating oil, whose viscosity is decreased due to temperature rise by rotating a shaft 12, seeps from a surface of the oil-retaining bearing 18, the lubricating oil is moved, absorbed by capillary force by the non-oil-retaining sintered metal plate 26, restricted by capillary force by a fine hole of this metal plate and prevented from flowing out and vaporizing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating shaft bearing device, and more particularly to improvement of a bearing device utilizing an oil-impregnated bearing member.

[0002]

2. Description of the Related Art Generally, most applications of fan motors are cooling of heat generated from electronic parts, and the life of the fan is required to be equal to the life of the equipment to which it is attached, so that the bearing has high reliability. Is required. Especially, when long life is required, at present, a fan with a bearing structure using a ball bearing is often used, but it is expensive because it is a precision part, it is weak against impact, and it is enclosed in the bearing. There is a drawback that the noise level gradually increases as the grease deteriorates.

On the other hand, a sintered oil-impregnated bearing is known as a bearing member, which is manufactured by sintering a metal powder into the bearing member.
Lubricant oil is permeated and held in the voids. Such a sintered oil-impregnated bearing is inexpensive and widely used for a rotating body having a relatively small load. Especially, in a small fan motor, since the load on the bearing is small, this type of bearing is often used. .

FIG. 2 shows an example of a bearing device for a fan shaft using a conventional sintered oil-impregnated bearing. As shown, the small fan motor 1 has a casing 3 that houses the impeller 2.
The rotary shaft 4 mounted on the central portion of the housed impeller 2 is projected toward the central substrate surface of the casing 3. A boss portion 5 for supporting the rotation of the shaft 4 is formed in the casing 3, and a mounting hole 7 for mounting a sintered oil-impregnated bearing 6 as a shaft mounting member is formed in the boss portion 5.
A storage space 9 for the retaining ring 8 attached to the tip of the shaft that penetrates the bearing 6 is formed continuously with this. Lubricating oil in the sintered oil-impregnated bearing 6 exudes to the friction surface by the pumping action and thermal expansion accompanying the rotation of the shaft 4 to perform a lubricating action, and at the same time returns to the pores in the sintered metal by the hydraulic pressure generated in the lubricating film. Shows the behavior. When such a sintered oil-impregnated bearing is used, the noise level does not change and wear can be ignored as long as the lubricating oil is held in the pores in the sintered metal at a constant rate, so there is no change in bearing performance. Small and very stable.

[0005]

However, when continuous operation is carried out in a device using a conventional sintered oil-impregnated bearing, the bearing becomes hot due to friction with the rotating shaft, and the lubricating oil contained in the sintered metal becomes hot. Therefore, there is a problem that the viscosity is lowered, the outflow from the bearing is likely to occur, and the loss particularly from evaporation from the bearing open surface occurs, and the loss cannot be ignored. That is, if the lubricating oil in the bearing becomes insufficient,
The oil film formed on the sliding surface becomes incomplete, the lubrication performance deteriorates, and vibration, abnormal noise, and wear occur, leading to the life of the bearing.

That is, the lubricating oil contained in the sintered oil-impregnated bearing is impregnated into the pores, and the lubricating oil is retained by the capillary force of the pores. Therefore, in the state where the shaft does not rotate, the lubricating oil hardly exists on the surface but exists in the pores of the bearing and in the sliding portion. Since the clearance between the shaft and the bearing inner diameter is usually as small as a few microns in the sliding portion, the lubricating oil moves from the bearing due to the difference in capillary force, and a slight amount of lubricating oil exists on the sliding surface.

When the shaft starts to rotate, an oil film is formed on the sliding surface, but excess lubricating oil is pushed into the bearing, and the lubricating oil expands due to the temperature rise. Comes out. Since the lubricating oil that has floated on the surface has a weak binding force and is unstable, it is easy for the lubricating oil to flow out of the bearing due to a slight external force such as vibration, resulting in a loss of the lubricating oil. In particular, since the viscosity of the lubricating oil decreases in a high temperature range, the lubricating oil that has floated on the surface becomes even more likely to flow out. In this way, the lubricating oil once flowing out of the bearing diffuses to the outside and does not return to the inside of the bearing.

Further, although small, the lubricating oil has a constant vapor pressure, and since the vapor pressure rises especially at high temperatures, the loss of the lubricating oil due to evaporation cannot be ignored. In the case of a fan motor, the rotor (impeller) should be placed close to the bearing.
Since, is rotating, there is a considerable air flow near the bearing surface, which promotes evaporation of the lubricating oil. Therefore, even if only the outflow of the lubricating oil can be prevented, the loss of the lubricating oil proceeds due to evaporation, so that it is difficult to achieve a long life especially in a high temperature range.

If a resin washer is attached to the surface of the bearing in order to retain the lubricating oil floating on the surface, a certain holding effect can be obtained, but if it is completely adhered, the amount of oil held is limited and a gap is created. Therefore, it is difficult to obtain a stable effect for preventing the outflow of the lubricating oil and the evaporation loss.

The present invention focuses on the above-mentioned conventional problems, and in a bearing device using a sintered oil-impregnated bearing, the loss of the lubricating oil is prevented, and the lubricating oil is effectively retained so that the life of the lubricating oil itself is increased. It is an object of the present invention to provide a bearing device for a rotating shaft, which can maintain its function up to and has reliability comparable to that of a ball bearing and long life.

[0011]

In order to achieve the above object, a bearing device for a rotary shaft according to the present invention is a bearing device having a sintered oil-impregnated bearing for rotatably supporting the shaft. An open surface portion of the sintered oil-impregnated bearing was joined and covered with an oil-free sintered metal plate.

In this case, it is desirable that the oil-free sintered metal plate has a structure having pores larger than those of the sintered oil-impregnated bearing. Further, the oil-free sintered metal plate may be joined to the shaft penetrating surface of the sintered oil-impregnated bearing and attached in a sandwich shape, and the shaft may be penetrated therethrough.

[0013]

According to the above structure, the auxiliary sintered metal plate containing no lubricating oil is attached to the exposed surface of the sintered oil-impregnated bearing, so that the lubricating oil floating from the bearing is absorbed during rotation. The extra lubricating oil can be retained in the auxiliary sintered metal plate by its capillary force. This can prevent the lubricating oil from flowing out from the surface portion of the sintered oil-impregnated bearing.

Further, by using an auxiliary sintered metal plate structure having pores having a diameter larger than that of the sintered metal used for the sintered oil-impregnated bearing, the capillary force due to the difference in pore diameter at the joint surface is Depending on the difference, the lubricating oil will be absorbed by the oil-impregnated bearing side. Further, by forming the shaft penetrating portion on the auxiliary sintered metal plate, the lubricating oil flowing on the shaft surface portion is absorbed by the capillary force of the sintered metal plate, and at the same time, the lubricating oil that tries to flow out through the gap with the shaft. Can also be absorbed by an auxiliary sintered metal plate.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of a bearing device for a rotary shaft according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an enlarged sectional view of a bearing device portion of a rotary shaft according to an embodiment, which is an example applied to a small fan motor 10. In order to configure a bearing portion of the fan rotation shaft 12 of the small fan motor 10, a boss portion 16 for supporting rotation of the shaft 12 is formed in the fan casing 14, and a sintered oil-impregnated bearing serving as a shaft rotation support member is formed on the boss portion 16. A mounting hole 20 for fixing 18 is formed, and a receiving space 22 for a retaining ring 21 attached to the tip of the shaft penetrating from the bearing 18 is formed continuously from the mounting hole 20. The sintered oil-impregnated bearing 18 attached to the boss portion 16 has a shaft insertion hole 18C formed at the center thereof, and the outer peripheral surface portion thereof is attached to the attachment hole 20 by an interference fit. Therefore, the upper end surface 18A of the sintered oil-impregnated bearing 18 facing the impeller 24 and the lower end surface 18B facing the ring housing space 22 in FIG. 1 are open surfaces.

In such a structure, in the embodiment, pores having a diameter larger than that of the sintered metal used in the bearing 18 are formed in the open end surface portion of the sintered oil-impregnated bearing 18. It is a sintered metal plate obtained by sintering metal powder, and is an oil-free sintered metal plate 26 that is not impregnated with lubricating oil and is closely bonded. That is, the sintered oil-impregnated bearing 1
8 of the upper end surface 18A facing the impeller 24 and the lower end surface 18B facing the ring housing space 22 are attached by thinly adhering the oilless sintered metal plates 26 so as to be laminated. It is shaped like a sandwich. Since the mounting surface of the oilless sintered metal plate 26 is the shaft penetrating surface, the shaft insertion holes 22A and 22B are also formed in each of the oilless sintered metal plate 26. Between the shaft insertion holes 22A and 22B and the shaft 12, a minimum necessary minimum gap is provided.

Also, the equivalent diameter of the pores forming the voids inside the oil-free sintered metal plate 26 is made larger than that of the sintered oil-impregnated bearing 18, which differs in the capillary force against the lubricating oil at the boundary surface. Occurs, and a difference in diameter is given so that the lubricating oil that has floated to the boundary surface is sucked toward the sintered oil-impregnated bearing 18 side. In general, the pore size of the sintered metal is often about 18% of the metal particle size used industrially, and therefore, in order to increase the pore size on the oil-free sintered metal plate 26 side, firing It can be easily manufactured by using a binder metal powder having a particle size larger than that of the sintered oil-impregnated bearing 18. Furthermore, since the oil-free sintered metal plate 26 has a minimum void volume capable of absorbing the evaporated lubricating oil from the sintered oil-impregnated bearing 18 or the lubricating oil flowing out along the insertion hole, the plate thickness is thin. You may Of course, it is needless to say that the void volume needs to be set to a thickness such that the lubricating oil absorbed in the oil-free sintered metal plate 26 does not evaporate from its own outer surface.

In the above embodiment, the oil-free sintered metal plate 26 is the end surfaces 18A, 18B of the sintered oil-impregnated bearing 18.
However, if one end surface is in a sealed state, it may be attached only to the other open side.

According to the bearing device for a rotary shaft having such a structure, the open surface of the sintered oil-impregnated bearing 18 is covered with the oil-free sintered metal plate 26, and the oil-free sintered metal plate 26 adhered to the bearing 18 is adhered. Since the pore diameter is set to be larger than that of the bearing 18, the difference in capillary force at the boundary surface causes
The lubricating oil is held on the bearing 18 side, and the amount of lubricating oil held can be kept constant. Then, even when the lubricating oil whose temperature has risen due to the rotation of the shaft 12 and whose viscosity has decreased exudes from the surface of the oil-impregnated bearing 18, as shown in FIG.
The oil-free sintered metal plate 26 is moved and absorbed by the capillary force, and is restrained by the capillary force due to the pores thereof to be prevented from flowing out or evaporating. Shaft 1
When the rotation of No. 2 is stopped and the temperature drops, the lubricating oil that has moved to the oil-free sintered metal plate 26 re-migrates to the bearing 18 side because the capillary force on the bearing 18 side is set to a large value. Then, the lubricating oil holding amount is kept constant.

Furthermore, since the pore volume of the oil-free sintered metal plate 26 can be set to be sufficiently large with respect to the amount of the lubricating oil floating from the bearing 18, the lubricating oil transferred to the oil-free sintered metal plate 26 is Evaporation of the lubricating oil on the surface of the bearing 18 occurs through the pores of the bearing 18 without reaching the outer surface, and even if the airflow is generated by the rotation of the impeller 24 around the bearing, the evaporation rate is significantly suppressed. be able to.

Further, the oil-free sintered metal plate 26 is attached to the shaft 1.
Since the bearing 18 is sandwiched by being joined to the through surface of No. 2, the lubricating oil that is about to flow out through the sliding surface between the shaft 12 and the bearing 18 does not contain the oil-free sintered metal plate 26.
It is possible to suppress the outflow of the lubricating oil, which is moved and absorbed by the capillary force in the shaft insertion holes 22A and 22B, and tends to flow out to the outside along the shaft 12.

[0023]

As described above, according to the present invention,
In a bearing device provided with a sintered oil-impregnated bearing in which the shaft is inserted to rotatably support the shaft, since the open surface portion of the sintered oil-impregnated bearing is covered with an oil-free sintered metal plate that is bonded to the shaft, In bearing devices that use oil-impregnated bearings, the loss of lubricating oil due to outflow and evaporation can be prevented, and by effectively retaining the lubricating oil, its function is maintained for the life of the lubricating oil itself, and it is used as a ball bearing. The excellent effect that the reliability is comparable and the life can be extended can be obtained.

[Brief description of drawings]

FIG. 1 is a main-part sectional view and a schematic enlarged sectional view of a bearing device for a rotary shaft according to an embodiment.

FIG. 2 is a cross-sectional view including a bearing portion of a conventional small motor fan.

[Explanation of symbols]

 10 Small Fan Motor 12 Rotating Shaft 14 Fan Casing 16 Boss 18 Sintered Oil-impregnated Bearing 18C Shaft Insertion Hole 20 Bearing Mounting Hole 24 Impeller 26 Oil-free Sintered Metal Plate

Claims (1)

[Claims] 1. A bearing device comprising a sintered oil-impregnated bearing in which a shaft is inserted to rotatably support the shaft, wherein an open surface portion of the sintered oil-impregnated bearing is covered with an oil-free sintered metal plate. A bearing device for a rotating shaft.