JP2002168239A - Oil containing porous bearing of dynamic-pressure type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve the high accuracy of rotation by controlling an instable vibration like a whirl and the like, and also by suppressing a shaft dislocation. SOLUTION: A bearing face opposing a sliding face of a shaft to be held via the gap of a bearing is formed at a bearing body made of a porous material, and an inclining dynamic-pressure groove is formed at the bearing face. Openings including the dynamic-pressure groove are distributed at the bearing face, and the ratio of a surface area of the openings is 2 to 20 percent. The sliding face of the shaft is floated and held by a dynamic-pressure oil film of oil lying in the gap of the bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a self-lubricating function by impregnating a porous body with a lubricating oil or a lubricating grease, and floats a sliding surface of a shaft by a hydrodynamic oil film of oil interposed in a bearing gap. The present invention relates to a hydrodynamic porous oil-impregnated bearing and a bearing device to be supported, and is particularly suitable as a bearing for equipment requiring high rotational accuracy at high speed, such as a polygon mirror of a laser beam printer and a spindle motor for a magnetic disk drive.

[0002]

2. Description of the Related Art Porous oil-impregnated bearings are widely used as self-lubricating bearings. However, since they are a kind of perfect circular bearing, unstable vibration is likely to occur where the eccentricity of the shaft is small. There is a drawback that so-called whirling, which swings at half the rotation speed, is likely to occur. As a countermeasure, a dynamic pressure groove such as a herringbone type or a spiral type may be provided on the bearing surface. A conventional example of forming a dynamic pressure groove in a porous oil-impregnated bearing and supporting the shaft by the dynamic pressure action to suppress unstable vibration is described in Japanese Utility Model Publication No. 63-196.
There is one described in No. 27 gazette.

[0003] Japanese Utility Model No. 63-19627 is the bearing surface of the porous oil-impregnated bearing, is provided with a groove for dynamic pressure generating subjected to surface blinding machining.

[0004]

[Problems to be solved by the invention]

The structure of Japanese Utility Model Publication No. 63-19627 has the following problems.

[0006] Since the groove is completely sealed, oil circulation, which is the most characteristic feature of the porous oil-impregnated bearing, is hindered in the groove. Therefore, the oil that has once leaked into the bearing gap is pushed into the bent portion of the groove by the action of the herringbone groove,
You will stay there. Since a large shearing action is acting in the bearing gap, the oil remaining in the groove due to the shearing force and frictional heat tends to be denatured, and oxidative deterioration tends to be accelerated due to a rise in temperature. Therefore, the bearing life is shortened. On the other hand, in a normal porous oil-impregnated bearing, the impregnated oil always circulates in the bearing gap and inside the bearing with the rotation of the shaft, so that it does not receive a continuous shearing force in the bearing gap, Once heated, it is cooled inside the bearing, so it is less susceptible to oxidative degradation due to temperature rise.

[0007] It is extremely difficult to seal the groove. Although the publication states that the hole can be sealed by plastic working, the groove depth of the dynamic pressure groove is usually on the order of μm, and the opening on the surface is not sealed by this degree of compression molding. In addition, coating is mentioned as another means of plastic working, but the thickness of the coating film needs to be thinner than the groove depth, and it is extremely difficult to apply a coating film of several μm only to the inclined groove portion. is there.

In view of such circumstances, the problem to be solved by the present invention is to allow impregnated oil to circulate through the bearing gap and the inside of the bearing as in a normal porous oil-impregnated bearing, thereby deteriorating the oil. The purpose is to find a bearing specification that can exert a dynamic pressure effect even if there is a hole in the dynamic pressure groove so that the structure can be made industrially feasible.

[0009]

When a dynamic pressure groove (a plurality of inclined grooves such as a herringbone type or a spiral type) is provided on the bearing surface of the bearing body (1), the oil flow in the axial cross section becomes
For example, as shown in FIG. Oil flows in and out of the bearing gap (4) between the rotating shaft (2) and the opening through the opening in the bearing surface 17 (inner peripheral surface) of the bearing body (1) as shown by the arrow. In order to maintain the appropriateness, it is desirable that the apertures be distributed almost uniformly in the dynamic pressure groove (5) and the “back” portion (6) other than the groove (see FIG. 7). The oil becomes difficult to move when the ratio of the openings on the surface is small, and the oil is easy to move when the ratio is large. The viscosity of the impregnated oil also relates to the ease of movement of the oil. The lower the viscosity, the easier it is to move, and the higher the viscosity, the harder it is to move. In the present specification, the "opening portion" refers to a portion where pores forming a porous structure of a bearing body, which is a porous body, are opened on the outer surface.

When the porosity is large and the viscosity is low, the oil becomes extremely easy to move, but the oil that has oozed into the bearing gap (4) by the action of the dynamic pressure groove (5) is easily removed from the bearing body (1). ), The dynamic pressure effect is reduced,
Not only cannot high rotation accuracy be maintained, but also the bearing body (1) is worn by contact between the shaft (2) and the bearing body (1), and the bearing function may be impaired. Conversely, when the porosity is small and the viscosity is high, the oil becomes extremely difficult to move, so the generated pressure increases, but proper circulation is hindered and the torque also increases. Degradation is promoted.

Therefore, there is an optimum range of the porosity and the viscosity of the oil that can secure the formation of a dynamic pressure oil film of the oil necessary for floatingly supporting the shaft, and at the same time, ensure the proper circulation of the oil. I do.

In order to clarify this optimum range, an evaluation test was performed using the actual LBP motor shown in FIGS. In both figures, (7) is a housing, (8)
Is a hub (rotor) fixed to the shaft (2). Further, (9) is a thrust receiver for supporting the thrust load by contacting the tip of the shaft (2). The actual motor used in the evaluation test had a shaft diameter of φ4, was in a state where a mirror was mounted, and had a rotation speed of 10,000 rpm and an ambient temperature of 40 ° C.

FIG. 5 shows the results of the evaluation test. In FIG.
"O" indicates that there was no problem in the durability test after continuous operation for 1000 hours. “Δ” indicates a problem such as an increase in shaft runout (5 μm or more), an increase in torque = a decrease in the number of revolutions (the number of revolutions does not increase until 10,000 rpm), abnormal noise, etc. Indicates that it is possible. “X” indicates that the above-mentioned trouble occurred by 500 hours.

From the above evaluation experiments, the optimum range of the porosity and the viscosity of the oil (the range in which “x” does not exist) is the area defined by the solid line in FIG. 5, that is, the following conditions: The surface area ratio of the opening in the surface is 2% or more and 20% or less, the kinematic viscosity of the impregnated oil at 40 ° C. is 2 cSt or more, and the surface area ratio of the opening in the bearing surface and the oil at 40 ° C. Has a kinematic viscosity of (3/5) A-1 ≦ η ≦ (40/6) A + (2
0/3) Here, it can be understood that the case where A; the surface area ratio [%] of the opening portion; and the kinematic viscosity [cSt] of the oil at 40 ° C. is satisfied. By selecting the porosity and the viscosity of the oil in such a range, a dynamic pressure oil film sufficient to support and float the shaft is formed, and at the same time, appropriate circulation of the oil is ensured. Accuracy and long life can be achieved.

The surface area ratio of the opening on the bearing surface is desirably 2% or more and 15% or less.

There is an optimum range for the ratio between the groove depth (h: see FIG. 7) of the dynamic pressure groove (5) and the bearing clearance (radial clearance: c). Outside this range, a sufficient dynamic pressure effect is obtained. Probably not. In order to clarify this optimum range, as shown in FIG. 6, an evaluation test was performed by replacing the shaft (2) of the actual LBP motor shown in FIG. 3 with a longer one so that the shaft runout could be measured. The number of revolutions was 10,000 rpm, the test atmosphere was room temperature and normal humidity, and the LBP actual motor was φ4 and no mirror was mounted. (10) is a non-contact type displacement meter.

Under the above conditions, c / h (c; radius gap,
h; groove depth) was plotted, and the results shown in FIG. 8 were obtained. According to FIG. 8, when c / h is in the range of 0.5 to 4.0, the shaft runout becomes 5 μm or less, but when it is less than 0.5 or more than 4.0, it becomes 5 μm or more. Therefore, in order to maintain high accuracy, it is desirable that c / h be in the range of 0.5 to 4.0.

A porous oil-impregnated bearing is usually used without lubrication. However, it is inevitable that the oil is gradually consumed and flows out due to scattering and evaporation of the oil. In this case, the oil film formation range shrinks, which causes deterioration of rotation accuracy such as shaft runout.
In particular, a shaft attitude is often used in a vertical type, and a laser beam printer (LB) used at a high speed of 10,000 rpm or more is used.
P) motor or magnetic disk drive (HD
In the motor for D), as shown in FIG. 12, the oil easily leaked out due to the action of the centrifugal force, and it was difficult to maintain the lubricating performance such as the oil film forming property.

In an LBP or HDD, the occurrence of oil film shortage is fatal in maintaining high-precision rotation. Especially when the bearing body is used alone, when rotating at high speed,
Oil circulates inside the bearing by entraining the surrounding air,
Air may enter the bearing gap. In order to prevent air from being mixed in, an effective measure is to arrange a member (oil replenishing member) for replenishing oil when a small amount of holes are formed inside the bearing body.

As such a bunkering member, in the present invention,
As shown in FIG. 1, a synthetic resin is used as a base material, and lubricating oil or lubricating grease is blended or impregnated with the synthetic resin as a base material. The solid lubricating composition (3) is placed in contact with the bearing body (1). With this configuration, even if the oil in the bearing body (1) runs off, new oil is generated from the lubricating composition (3) disposed in contact with the bearing body (1) by the capillary phenomenon inside the bearing body (1). , It is possible to always form a good dynamic pressure oil film with the rotating shaft (2).

Specifically, a solid lubricating composition (3)
Is obtained by adding lubricating oil contained in a bearing main body or lubricating grease having the lubricating oil as a base oil to 5-99 wt% and an average molecular weight of 1 ×
95 to 1 wt% of ultra high molecular weight polyolefin powder of 10 6 to 5 × 10 6 is mixed, and at a temperature higher than the gel point of the ultra high molecular weight polyolefin powder and below the drop point of the grease when lubricating grease is used. It is molded by dispersing and holding.

As described above, when the lubricating composition is composed of a mixture of lubricating oil or lubricating grease and ultrahigh molecular weight polyolefin powder and is solid, the lubricating composition is low in cost, has high mass productivity, is easy to handle, and is easy to assemble. It becomes something. Further, since the solid lubricating composition oozes out the oil contained therein at a temperature not lower than the normal temperature (about 20 ° C.), the oil can be continuously supplied to the bearing continuously. FIG. 9 shows the results obtained by allowing the solid lubricating composition (3) according to the present invention to stand still and examining the standing time and the oil separation rate. It can be understood that the oil continues to be separated little by little over 1000 hours even when the atmosphere is at 20 ° C. As the ambient temperature increases, the amount of separation increases.

FIG. 10 shows a comparison between the case where the solid lubricating composition is brought into close contact with the bearing and the case where no such bunkering member is provided. ), The oil initially contained was about 3 hours after 2000 hours of operation.
Although 0% is lost, if there is a refueling member (indicated by "black circles"), the oil is replenished even if the oil flows from the bearing body, so that the loss amount is suppressed to only about 5%. I can understand.

When used in a high-temperature atmosphere or when used at high speed rotation and generating a large amount of heat due to friction, oil may ooze out of the solid lubricating composition too much. It is preferable to add and mix one or more of solid wax, low molecular weight polyethylene and polyamide resin at a ratio of 1 to 50 wt% as an oil oozing inhibitor of the product.

As shown in FIG. 1, on one or both sides in the axial direction of the bearing body (1) (porous oil-impregnated bearing A), a cylindrical body having an inner diameter equal to or slightly larger than the bearing body (1) is provided. The oil leakage prevention member (11) is disposed on the inner peripheral surface of the oil leakage prevention member (11). Airflow generating groove (12) for generating an airflow flowing through the airflow may be provided.
The airflow generating groove (12) can be formed by, for example, providing a plurality of inclined grooves. In the drawings, a case is shown in which the bearing main body (1) is arranged in the upper and lower stages and the oil leakage prevention member (11) is arranged outside the upper stage bearing body (1). It is possible to arrange an oil leakage prevention member (11) inside the bearing, and further, the lower bearing body (1)
It is also possible to arrange an oil leakage prevention member (11) on one side or both sides of the oil leakage prevention member.

With this configuration, as shown in FIG. 11, a gap (13) between the rotating shaft (2) and the inner peripheral surface of the oil leakage preventing member (12) is provided for rotation of the shaft (2). As a result, an airflow that flows in the direction of the bearing body (1) (downward in the drawing) is generated, so that even if oil leaks from the bearing portion, the gap between the shaft (2) and the oil leakage prevention member (11) ( 13) can not pass. This action prevents oil leakage. In addition, at rest, the oil is held by the capillary force of the gap (13), so that the oil does not leak even if rotation stops.

In this case, the oil leakage preventing member (11) is made of a porous material, and the space (1) is formed between the oil leak preventing member (11) and the adjacent bearing body (1).
4) should be provided. With this configuration, the leaked oil can be absorbed by the oil leakage prevention member (11) made of a porous body. When stationary, oil leakage prevention member (11)
The oil between the shaft and the shaft (2) can also be absorbed, so that the portion exposed to the atmosphere is reduced, and the evaporation and dust generation of the oil can be reduced. The oil absorbed by the oil leakage prevention member (11) is drawn into the gap (13) with the rotation, and is caused to flow through the space (14) by the airflow generated by the action of the airflow generation groove (12). 1) Returned to the side.

As shown in FIG. 1, an oil leakage prevention member (11)
If the end face (11a) and the chamfer part (11b) on the opposite side of the bearing body (1) are crushed, the surface porosity of this part is 5% or less in area ratio, preferably if it is completely sealed. Further, evaporation and dust generation of the oil absorbed by the oil leakage prevention member (11) can be further reduced.

As shown in FIG. 1, a bearing body (1) is press-fitted and fixed in a cylindrical housing (7) having one end opened and the other end closed, and the bearing body (1) is fixed.
The lubricating composition (3) in a solid state is accommodated by contacting the oil-injection member, and an oil leakage prevention member (11) is arranged outside the bearing body (1) to close the opening of the housing (7). In this case, as described above, the bearing has a dynamic pressure effect, and further, oil is constantly replenished from the lubricating composition (3). Therefore, it is possible to always maintain good dynamic pressure oil film formation, and to maintain a high oil pressure for a long period of time. Rotational accuracy can be maintained. Oil leakage from the bearing portion is supplemented by the oil leakage prevention member (11) and does not flow out.

A space (15) is provided between the bottom surface (7a) of the housing (7) and the inner end surface (1a) of the bearing body (1) facing the housing (7). When the air flow passage (16) is provided so as to communicate at a location other than the bearing gap (4), the air flow passage (16) functions as an air vent. This makes it easier to insert the shaft (2) during assembly. Also, when rotating, the internal pressure increases due to heat generation,
The shaft (rotor) may be pushed up to make the rotation unstable, but such a situation can be prevented.

A rotating member, for example, a rotor (8) is attached to the rotating shaft (2), and a dynamic pressure groove of a herringbone type or a spiral type is provided on an end face of the bearing body (1) opposed to the rotor. If the thrust load is supported by the dynamic pressure generated in the dynamic pressure groove when the shaft (2) rotates, not only the radial load but also the thrust load can be supported, and the thrust receiver (9) becomes unnecessary.

In this case, the bearing body (1) provided with the dynamic pressure groove
The surface area ratio of the opening at the end face of
% Is preferable.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below.

FIG. 1 shows an example of a hydrodynamic porous oil-impregnated bearing device according to the present invention. A bearing surface (17) is provided in a housing (7) having one end opened and the other end closed. Two bearing bodies (1) are press-fitted and fixed, and two porous oil-impregnated bearings (A) are axially separated by inserting a shaft (2) (rotary shaft) into the inner peripheral portion of the bearing body (1). It is what constituted. The material of the bearing body (1) is not particularly limited, and is formed into a well-known porous body having many pores by powder metallurgy or by sintering or foaming cast iron, ceramic, or the like. Preferably, copper or iron, or a sintered metal containing both as a main component, more preferably copper is 20 to 95 watts.
It is preferable to use a sintered metal containing t%.

Between the two bearing bodies (1), there is disposed a solid lubricating composition (3) composed of a synthetic resin as a base material and mixed with lubricating oil or lubricating grease. Above the bearing body (1), an oil leakage prevention member (11)
Are disposed to close the upper end opening of the housing (7). The upper end surface (11a) and the upper chamfer portion (11b) of the oil leakage prevention member (11) are sealed. Further, a space (15) is provided between the end surface (1a) of the bearing body (1) on the closed side (lower stage) and the bottom surface (7a) of the housing (7). An air flow passage (16) is provided so as to be in communication. The air flow passage (16) is formed, for example, by providing a notch in the axial direction on a part of the outer surface of the bearing body (1), the lubricating composition (3), and the oil leakage preventing member (11). . A plurality of inclined grooves (dynamic pressure groove 5 and airflow generation groove 12) are provided on the inner peripheral surfaces of the bearing body (1) and the oil leakage prevention member (11). The oil leakage prevention member (11) is formed of a porous body, and is not impregnated with lubricating oil or the like. The material of the oil leakage prevention member (11) is not particularly limited, and is a well-known porous material having a large number of pores by powder metallurgy or by sintering or foaming cast iron, synthetic resin, ceramic, or the like. It is formed into a solid body.

As shown in FIG. 1, for example, a herringbone type dynamic pressure groove (5) is provided on the bearing surface (17) of the bearing body (1) so that the bearing can be rotated relative to the rotating shaft (2). dynamic pressure oil film is formed in the gap (4), it is possible to effectively suppress the unstable vibration such whirl. In the bearing surface (17) shown in FIG. 1 (the same applies to the bearing surface shown in FIG. 4), the groove region 5 (the black portion) is inclined in opposite directions toward both sides in the axial direction. An annular back 6 (white portion) is provided between the groove regions 5 inclined in the inclined direction (in the figure, the annular back 6 is located at the axial center of the bearing surface). The width (c) of the bearing gap (4) is desirably c / R = 1/2000 to 1/400, where R is the radius of the shaft (2). When the groove depth is h, c / h is preferably 0.5 to 4.0, and more preferably, c / h is 0.5 to 3.0.

The porosity of the bearing surface of the bearing body (1) is desirably 2 to 20% in terms of surface area ratio. 2
% Or less, the oil circulation is inhibited, and if it is 20% or more, the dynamic pressure effect is not exhibited, and a satisfactory dynamic pressure oil film is not formed. The viscosity of the oil is selected according to the surface porosity.

The refueling member (3) arranged in contact with the bearing body (1) may be a porous material such as metal or resin, or a known material in which oil is contained in a fibrous material such as felt. It is preferable to use a solid lubricating composition that is solid and that continues to ooze oil containing oil at a temperature of at least 20 ° C. to the surface. The lubricating composition can be manufactured in a very simple way. For example, a predetermined amount of lubricating grease or lubricating oil and a predetermined amount of ultra-high molecular weight olefin powder are uniformly mixed and poured into a mold having a predetermined shape,
When lubricating grease is used at a temperature higher than the gel point of the ultrahigh molecular weight polyolefin powder, and further when the lubricating grease is used, the dispersion is maintained at a temperature lower than the drop point, and the resultant is cooled at room temperature. The ultra-high molecular weight polyolefin powder in the present invention is a powder made of polyethylene, polypropylene, polybutene or a copolymer thereof, or a mixed powder in which a single powder is blended, and the molecular weight of each powder is
The average molecular weight measured by the viscosity method is 1 × 10 6 to 5 ×
It is chosen to be 106. Polyolefins having such an average molecular weight range are superior in rigidity and oil retention to low molecular weight polyolefins, and hardly flow even when heated to a high temperature. The compounding ratio of such an ultrahigh molecular weight polyolefin in the lubricating composition is 95 to
1 wt%. The amount depends on the degree of oil release, toughness and hardness required for the composition. The greater the amount of ultrahigh molecular weight polyolefin, the greater the hardness of the gel after being dispersed and maintained at a predetermined temperature.

The lubricating grease used in the present invention is:
It is not particularly limited, and as a lubricating grease thickened with soap or non-soap, lithium soap-diester system, lithium soap-mineral oil system, sodium soap-mineral oil system, aluminum soap-mineral oil system, lithium soap diester mineral oil system, Non-soap-diester, non-soap-mineral oil,
Greases such as non-soap-polyol ester type and lithium soap-polyol ester type are exemplified. Similarly, the lubricating oil is not particularly limited, and examples thereof include luster oils such as diester, mineral oil, diester mineral oil, and polyol ester. The base oil or lubricating oil of the lubricating grease is preferably the same as the lubricating oil initially impregnated in the bearing body (1), but may be slightly different as long as the lubricating characteristics are not impaired.

The melting point of the above-mentioned ultrahigh molecular weight polyolefin varies depending on its average molecular weight, but is not constant. For example, the melting point of a substance having an average molecular weight of 2 × 10 6 determined by a viscosity method is 136 ° C. Commercial products having the same average molecular weight include "Miperon (registered trademark) XM-220" manufactured by Mitsui Petrochemical Industries, Ltd. Therefore, in order to disperse and maintain the ultra-high molecular weight polyolefin in the lubricating grease or lubricating oil, after mixing the above-mentioned materials, if the ultra-high-molecular-weight polyolefin gels or exceeds the temperature, and if lubricating grease is used, a drop of the lubricating grease is used. Heat to a temperature below the point, e.g.

Such bearing devices include various types of motors such as polygon mirror motors for laser beam printers and spindle motors for magnetic disk drives, as well as electric products such as axial fans, ventilating fans and electric fans, and electrical components for automobiles. The bearing portion can be used in a wide range, and the durability around the bearing portion can be significantly improved without contaminating the periphery of the bearing portion with oil. In other words, even if the oil initially held in the porous oil-impregnated bearing spills out, it does not flow out of the bearing because of the oil leakage prevention member (11). Since oil is supplied from the object (3), an oil film is always maintained, and high rotational accuracy can always be maintained by the dynamic pressure effect of the dynamic pressure groove (5) provided on the bearing surface of the bearing body (1). . Further, wear and the like due to running out of oil at the time of startup can be prevented, and the durable life can be greatly improved. Since this solid lubricating composition does not contain a fibrous material unlike felt, dust such as fibers does not enter the bearing gap. Furthermore, unlike grease, since it is solid, it does not cling to the rotating shaft (2) and does not cause rotation fluctuation. And since it is solid, it is very easy to handle and the efficiency at the time of assembly is good.

Since the structure is not sealed with a magnetic fluid seal, the oil leakage preventing member (11), the bearing body (1), and the oil replenishing member (lubricating composition 3) are each press-fitted into the housing (7). Therefore, there is an advantage that the efficiency at the time of assembly is high and the cost is low.

[0043]

As is apparent from the foregoing description, according to the present invention, it is possible to suppress unstable vibrations such as whirl,
High rotational accuracy can be achieved by reducing shaft runout. A good dynamic pressure oil film can always be maintained. It can be significantly improved durability. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is an axial sectional view showing one embodiment of the present invention.

FIG. 2 is an axial cross-sectional view showing movement of oil in a porous oil-impregnated bearing provided with a herringbone type dynamic pressure groove.

FIG. 3 is an axial sectional view of a porous oil-impregnated bearing for an evaluation test.

FIG. 4 is an axial sectional view of a porous oil-impregnated bearing for an evaluation test.

FIG. 5 is a diagram showing the results of an evaluation test.

FIG. 6 is an axial sectional view of a porous oil-impregnated bearing for an evaluation test.

FIG. 7 is a radial cross-sectional view of a porous oil-impregnated bearing.

FIG. 8 is a diagram showing the results of an evaluation test for determining the relationship between c / h and shaft runout.

FIG. 9 is a graph showing the change over time in the oil separation rate of the solid lubricating composition according to the present invention.

FIG. 10 is a graph showing the results of a comparative test depending on the presence or absence of a solid lubricating composition.

FIG. 11 is an axial sectional view showing movement of oil in a porous oil-impregnated bearing having an oil leakage prevention member.

FIG. 12 is an axial sectional view of a general porous oil-impregnated bearing.

[Explanation of symbols]

 1 the bearing body 2 rotates shaft 3 lubricating composition 4 bearing gap 5 hydrodynamic grooves 7 housing 8 rotor (hub) 11 oil leak preventing member 12 airflow generating grooves 16 air duct 17 bearing surface A porous oil-impregnated bearing

Claims (4)

[Claims] 1. A porous body in which a bearing body made of a porous body is provided with a bearing surface opposed to a sliding surface of a shaft to be supported via a bearing gap and an inclined dynamic pressure groove is formed in the bearing surface. In the high quality oil-impregnated bearing, the sliding surface of the shaft is floated and supported by a dynamic pressure oil film of the oil interposed in the bearing gap, and the bearing surface is provided with apertures including the dynamic pressure groove, A hydrodynamic porous oil-impregnated bearing, wherein the surface area ratio of the opening is 2 to 20%. 2. A porous body in which a bearing body made of a porous body is provided with a bearing surface opposed to a sliding surface of a shaft to be supported via a bearing gap, and an inclined dynamic pressure groove is formed in the bearing surface. In a high quality oil-impregnated bearing, the sliding surface of the shaft is levitated and supported by a dynamic pressure oil film of oil interposed in the bearing gap, and the ratio between the groove depth (h) of the dynamic pressure groove and the bearing gap (c) is adjusted. A dynamic pressure type porous oil-impregnated bearing, wherein c / h is 0.5 to 4.0. 3. The hydrodynamic porous oil-impregnated bearing according to claim 1, wherein the bearing body is formed of a sintered metal. 4. The hydrodynamic porous oil-impregnated bearing according to claim 3, wherein the sintered metal contains copper or iron, or both of them as main components.