JP2004353871A - Hydrodynamic type porous oil-impregnated bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a high rotational precision by reducing running-out of a shaft through suppressing unstable vibrations. <P>SOLUTION: A hydrodynamic type porous oil-impregnated bearing has been configured such that a bearing body made of a porous material has a bearing surface formed so as to face, through a bearing clearance, the sliding surface of a shaft to be supported, and is impregnated with lubricating oil or lubricating grease. The bearing body is mainly made of copper or iron or both of them, and is formed with sintered metal containing 20 to 95 wt.% copper, and has hydrodynamic grooves formed on the bearing surface of the bearing body, and has opening portions distributed thereon including the hydrodynamic grooves. The sliding surface of the shaft is floatingly supported by a hydrodynamic oil film located in the bearing clearance. At the same time, the lubricating oil is circulated through the bearing clearance inside the bearing body via the opening portions including the hydrodynamic grooves. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides a self-lubricating function by impregnating a porous body with a lubricating oil or a lubricating grease, and a hydrodynamic porous oil-impregnating device that floats and supports a sliding surface of a shaft by a hydrodynamic oil film of oil interposed in a bearing gap. The bearing 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.

  Generally, porous oil-impregnated bearings are widely used as self-lubricating bearings.However, since they are a type of perfect circular bearing, unstable vibration is likely to occur where the eccentricity of the shaft is small, and the rotational speed is reduced. There is a disadvantage that so-called whirling at half the 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. Conventional examples of forming a dynamic pressure groove in a porous oil-impregnated bearing, supporting the shaft by the dynamic pressure effect, and suppressing unstable vibration are described in Patent Documents 1 and 2 below.

Patent Document 1 discloses a bearing device in which a porous oil-impregnated member having a herringbone groove is fitted to a rotating shaft and combined with a sleeve having a cylindrical radial inner peripheral surface. On the other hand, Patent Literature 2 discloses that a bearing surface of a porous oil-impregnated bearing is provided with a groove for generating a dynamic pressure that has been subjected to surface blanking.
Japanese Patent Publication No. 64-11844 Japanese Utility Model Publication No. 63-19627

  Patent Literature 1 discloses a method in which a porous oil-impregnated member having a herringbone groove is fitted to a rotating shaft, and the centrifugal force accompanying rotation of the shaft causes oil to seep into a bearing gap. Such a structure has the following disadvantages.

  (1) The number of parts of the bearing device is changed from two points of a normal rotating shaft and a bearing to three points of a rotating shaft, a porous oil-impregnated member, and a sleeve (bearing), which complicates assembly and increases costs.

  (2) In the case of a dynamic pressure type bearing device, high dimensional accuracy is required, but there are three parts, and each accuracy affects the accuracy after combination. It is difficult to obtain accuracy.

  (3) During rotation, the centrifugal force continues to be applied to the porous oil-impregnated member. Therefore, the oil continues to seep out, the bearing gap eventually becomes saturated with oil, and if the rotation continues, the oil will have to leak out of the bearing gap. Therefore, oil spills are inevitable.

  Next, Patent Literature 2 discloses that a groove for dynamic pressure generation is provided on a bearing surface of a porous oil-impregnated bearing, the surface of which is subjected to a blanking process. Such a structure has the following disadvantages.

  (1) Since the groove is completely sealed, circulation of oil, which is the greatest feature of the porous oil-impregnated bearing, is impeded in the groove. Therefore, the oil that has once oozed into the bearing gap is pushed into the bent portion of the groove by the action of the herringbone groove and stays there. Since a large shearing action is exerted in the bearing gap, the oil remaining in the groove tends to be denatured by the shearing force and the frictional heat, and the oxidative deterioration tends to be accelerated by the temperature rise. Therefore, the bearing life is shortened. In contrast, 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.

  (2) It is extremely difficult to seal the groove. Although the publication states that the hole can be sealed by plastic working, the depth of the dynamic pressure groove is usually on the order of μm, and the opening on the surface is not sealed by compression molding of this degree. In addition, although coating is mentioned as another means of plastic working, it is necessary to make the thickness of the coating film 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, problems to be solved by the present invention are as follows.

  The number of parts of the bearing portion is set to two, so that the cost is low, the accuracy is easily obtained, and the bearing is suitable for mass production.

  As in a normal porous oil-impregnated bearing, the impregnated oil is circulated between the bearing gap and the inside of the bearing, so that the oil is hardly deteriorated.

  Suppresses unstable vibration such as whirl and reduces shaft runout to achieve high rotational accuracy.

  In order to solve the above problems, the present invention provides a bearing body made of a porous body, in which a bearing surface opposed to a sliding surface of a shaft to be supported via a bearing gap is impregnated with lubricating oil or lubricating grease. In the hydrodynamic porous oil-impregnated bearing, the bearing body is formed of a sintered metal containing copper or iron or both as a main component and having a copper content of 20 to 95 wt%. A dynamic pressure groove is formed on the surface, and apertures are distributed including the dynamic pressure groove. The sliding surface of the shaft is floated and supported by a dynamic pressure oil film of oil interposed in the bearing gap. The present invention provides a configuration in which oil is circulated between the inside of a bearing main body and a bearing gap through an opening in a bearing surface including a dynamic pressure groove.

  According to the present invention, the following effects can be obtained.

  Surrounding pollution due to oil spillage, scattering, evaporation and the like can be significantly reduced.

  Unstable vibrations such as whirl can be suppressed, and shaft rotation can be reduced to achieve high rotational accuracy.

  A good dynamic pressure oil film can always be maintained.

  Durability can be greatly improved.

  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), an oil flow in an axial cross section is as shown in FIG. 2, for example. Oil flows into and out of the bearing gap (4) between the rotary 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 arrows. 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 apertures on the surface is small, and when the ratio is large, the oil is easy to move. In addition, the viscosity of the impregnated oil is also related to the ease of movement of the oil. In addition, in this specification, the "opening portion" refers to a portion in which 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 seeps into the bearing gap (4) by the action of the dynamic pressure groove (5) is easily removed from the inside of the bearing body (1). , The dynamic pressure effect is reduced and high rotational accuracy cannot be maintained. In addition, when the shaft (2) and the bearing body (1) come into contact with each other, the bearing body (1) is worn and the bearing function is reduced. It may be damaged. 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 increases. Degradation is promoted.

  Therefore, there is an optimum range of the porosity and the viscosity of the oil in which the formation of a dynamic pressure oil film of the oil necessary for supporting and supporting the shaft is secured, and at the same time, the proper circulation of the oil is secured.

  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, and (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. 5, “示 す” indicates that there was no problem in the durability test after continuous operation for 1000 hours. "△" indicates troubles such as shaft run-out rise (5 μm or more), torque rise = rotation speed decrease (rotation speed does not increase up to 10,000 rpm), abnormal noise, etc. during 500 to 1000 hours, and abnormal operation Indicates that it is possible. “X” indicates that the above-mentioned trouble occurred by 500 hours.

From the above evaluation experiments, it can be understood that the optimum range of the porosity and the viscosity of the oil (the range in which “x” does not exist) is a region defined by the solid line in FIG. 5, that is, a case where the following conditions are satisfied. .
a: The surface area ratio of the opening portion on the bearing surface including the dynamic pressure groove is 2% or more and 20% or less,
b: the kinematic viscosity at 40 ° C. of the impregnated oil is 2 cSt or more;
c: The kinematic viscosity at 40 ° C. of the surface area ratio of the opening portion on the bearing surface and the oil is (3/5) A−1 ≦ η ≦ (40/6) A + (20/3).
Here, A: surface area ratio [%] of the hole, η: kinematic viscosity of oil at 40 ° C. [cSt]

  By selecting the porosity and the viscosity of the oil in such a range, a dynamic 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 optimal 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), and a sufficient dynamic pressure effect cannot be obtained outside this range. it is conceivable that. 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 rotation speed was 10000 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, the values of the shaft runout with respect to c / h (c: radial gap, h: groove depth) were plotted, and the results shown in FIG. 8 were obtained. According to FIG. 8, if c / h is in the range of 0.5 to 4.0, the shaft runout becomes 5 μm or less, but if it is less than 0.5 or larger 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.

  The porous oil-impregnated bearing is usually used without lubrication, but it is inevitable that the oil is gradually consumed and flows out due to scattering and evaporation of the oil. In this case, since the oil film formation range is contracted, the rotation accuracy such as shaft runout is deteriorated. In particular, the shaft attitude is often used in a vertical type, and a motor for a laser beam printer (LBP) or a motor for a magnetic disk drive (HDD) used at a high speed of 10,000 rotations or more per minute is shown in FIG. As shown, the oil easily leaked out due to the effect of the centrifugal force, and it was difficult to maintain lubricating performance such as oil film forming properties.

  In an LBP or HDD, the occurrence of oil film breakage is fatal in maintaining high-precision rotation. In particular, when the bearing body is used alone, when rotating at a high speed, the oil engulfs the surrounding air and circulates inside the bearing, so that 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.

  In this embodiment, as shown in FIG. 1, a synthetic resin is used as such a base material, and a lubricating oil or lubricating grease is blended or impregnated with the base material at a temperature of at least 20 ° C. The solid lubricating composition (3) in which the oil contained therein oozes out to the surface even when it is placed 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, the solid lubricating composition (3) is prepared by adding lubricating oil contained in the bearing body or lubricating grease using the lubricating oil as a base oil to 5 to 99 wt% and an average molecular weight of 1 × 10 ^{6 to} 5 ×. 95 to 1 wt% of the ultrahigh molecular weight polyolefin powder of 10 ⁶ is mixed and dispersed and maintained at a temperature not lower than the gel point of the ultrahigh molecular weight polyolefin powder and not higher than the drop point of the grease when lubricating grease is used. Thereby, it is molded.

  As described above, when the lubricating composition is composed of a mixture of lubricating oil or lubricating grease and ultra-high molecular weight polyolefin powder to be solid, the lubricating composition is low in cost, rich in mass productivity, easy to handle, and easy to incorporate. Become. Further, since the solid lubricating composition oozes out the oil contained therein at a temperature not lower than room 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) of the present invention to stand still and examining the standing time and oil separation rate. It can be seen that the oil continues to be separated little by little over 1000 hours even 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 was brought into close contact with the bearing and the case where no such bunkering member was provided. Approximately 30% of the oil contained was washed away after 2,000 hours of operation. However, if there was a bunkering member (shown by a black circle), even if the oil flowed out of the bearing body, it was replaced with oil. It can be seen that the loss is reduced to only about 5%.

  When used in a high-temperature atmosphere or when used at high rotation speeds and generates 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 a bleeding inhibitor.

  As shown in FIG. 1, a cylindrical oil leak having an inner diameter equal to or slightly larger than that of the bearing body (1) is provided on one or both sides in the axial direction of the bearing body (1) (porous oil-impregnated bearing A). An airflow that flows toward the bearing body side through a gap between the shaft and the shaft during relative rotation with the shaft on the inner peripheral surface of the oil leakage prevention member. 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 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 also possible to arrange an oil leakage prevention member (11) on the inside of the bearing, and it is also possible to arrange the oil leakage prevention member (11) on one or both sides of the lower bearing body (1).

  With this configuration, as shown in FIG. 11, a bearing (13) is provided in the gap (13) between the rotating shaft (2) and the inner peripheral surface of the oil leakage preventing member (12) with the rotation of the shaft (2). Since an air current flows in the direction of the main body (1) (downward in the drawing), even if oil leaks from the bearing portion, the gap (13) between the shaft (2) and the oil leak prevention member (11) is removed. I can't 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 the rotation stops.

  In this case, the oil leakage prevention member (11) is preferably made of a porous material, and a space (14) is preferably provided between the oil leakage prevention member (11) and the adjacent bearing body (1). With this configuration, the leaked oil can be absorbed by the oil leakage prevention member (11) made of a porous body. In addition, since the oil between the oil leakage prevention member (11) and the shaft (2) can be absorbed at rest, 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, the end face (11a) and the chamfer portion (11b) of the oil leak prevention member (11) on the side opposite to the bearing body (1) are crushed, and the surface porosity of this portion is reduced by the area. If the ratio is 5% or less, desirably completely sealed, the 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 is brought into contact with the bearing body (1). The solid lubricating composition (3) is housed, and the oil leakage preventing 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, the oil is constantly replenished from the lubricating composition (3). Therefore, it is possible to always maintain a good dynamic pressure oil film formation, and to maintain the high dynamic pressure oil film for a long time. Rotational accuracy can be maintained. Further, oil leakage from the bearing portion is captured 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). If the air flow path (16) is provided so as to communicate at a location other than 4), the air flow path (16) functions as an air vent. This facilitates insertion of the shaft (2) during assembly. Further, during rotation, the internal pressure may increase due to heat generation, and the shaft (rotor) may be pushed up to make 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 surface of the bearing body (1) opposed to the rotor. If the thrust load is supported by the dynamic pressure generated in this dynamic pressure groove during the rotation of ()), not only the radial load but also the thrust load can be supported, and the thrust receiver (9) becomes unnecessary.

  In this case, it is preferable that the surface area ratio of the opening on the end face of the bearing body (1) provided with the dynamic pressure groove is 2% or more and 20% or less.

  Hereinafter, one embodiment of the present invention will be described in more detail.

  FIG. 1 shows an example of a hydrodynamic porous oil-impregnated bearing device according to the present invention, in which a housing (7) having one end open and the other end closed is provided with two bearing surfaces (17). The bearing body (1) is press-fitted and fixed, and a shaft (2) (rotating shaft) is inserted into the inner peripheral portion of the bearing body (1) to form two porous oil-impregnated bearings (A) which are separated in the axial direction. Things. The material of the bearing body (1) is not particularly limited, and is formed into a well-known porous body having a large number of pores by powder metallurgy or by sintering or foaming cast iron, ceramic, or the like. Preferably, it is formed of a sintered metal containing copper or iron or both of them as a main component, more preferably a sintered metal containing 20 to 95 wt% of copper.

  Between the two bearing bodies (1), a solid lubricating composition (3) comprising a synthetic resin as a base material and a lubricating oil or lubricating grease is arranged, and the open-side (upper-stage) bearing is provided. An oil leakage prevention member (11) is disposed above the main body (1) and closes an 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. A space (15) is provided between the end surface (1a) of the bearing body (1) on the closing side (lower stage) and the bottom surface (7a) of the housing (7). An air flow passage (16) is provided for communication. The air flow passage (16) is formed by, for example, providing an axial cutout in 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 grooves 5 and airflow generating grooves 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 a 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, by providing a herringbone type dynamic pressure groove (5) on the bearing surface (17) of the bearing body (1), the bearing gap (4) can be formed during relative rotation with the rotating shaft (2). ), A dynamic oil film is formed, and unstable vibration such as whirl can be effectively suppressed. 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 set to 0.5 to 4.0, and more preferably, c / h is set to 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. If it is less than 2%, the circulation of oil is hindered, and if it is more than 20%, 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, but may be a solid material. It is preferable to use a solid lubricating composition that continuously oozes the oil contained at a temperature of at least 20 ° C. or more to the surface. This 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 ultrahigh molecular weight olefin powder are uniformly mixed and poured into a mold having a predetermined shape, and at a temperature equal to or higher than the gel point of the ultrahigh molecular weight polyolefin powder, When a lubricating grease is used, it is obtained by dispersing and maintaining the lubricating grease at a temperature equal to or lower than its dropping point and cooling it at room temperature. The ultra-high molecular weight polyolefin powder in the present invention is a powder composed of polyethylene, polypropylene, polybutene or a copolymer thereof, or a mixed powder containing a single powder, and the molecular weight of each powder is measured by a viscosity method. The average molecular weight is selected to be 1 × 10 ^{6 to} 5 × 10 ⁶ . Polyolefins having such an average molecular weight range are superior in rigidity and oil retaining property to low molecular weight polyolefins, and hardly flow even when heated to a high temperature. The blending 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 not particularly limited, and as a lubricating grease added with soap or non-soap, lithium soap-diester type, lithium soap-mineral oil type, sodium soap-mineral oil type, aluminum soap, aluminum soap -Mineral oil type, lithium soap diester mineral oil type, non-soap-diester type, non-soap-mineral oil type, non-soap-polyol ester type, lithium soap-polyol ester type grease, and the like. Similarly, the lubricating oil is not particularly limited, and examples thereof include diester-based, mineral oil-based, diester mineral oil-based, and polyol ester-based lubricating oils. 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 ultrahigh molecular weight polyolefin is not constant because it varies according to the average molecular weight. For example, the melting point of 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 is at a temperature higher than the temperature at which the polyolefin gels and the lubricating grease is used, the droplets are dropped. Heat to a temperature below the point, for example 150-200 ° C.

  Such bearing devices are widely used in various motors, such as polygon mirror motors for laser beam printers, spindle motors for magnetic disk drives, electric products such as axial fans, ventilation fans, and electric fans, and electrical components for automobiles. It can be used, and the durability of the bearing can be significantly improved without contaminating the periphery of the bearing 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 due to the oil leakage prevention member (11). Since oil is supplied from the object (3), the oil film is always maintained, and high rotational accuracy can be always maintained by the dynamic pressure effect of the dynamic pressure groove (5) provided on the bearing surface of the bearing body (1). . Further, wear due to running out of oil at the time of starting 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.

  In addition, since the structure is not sealed with a magnetic fluid seal, the oil leakage prevention member (11), the bearing body (1), and the oil replenishment member (lubricating composition 3) are respectively press-fitted into the housing (7) by means such as press fitting. Since it is only necessary to fix, there is an advantage that the efficiency at the time of assembly is good and the cost is low.

It is an axial sectional view showing one embodiment of the present invention. It is an axial 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 partial cross-sectional view conceptually showing an LBP spindle motor. It is an axial sectional view of the porous oil-impregnated bearing for evaluation tests. It is a figure showing a result of an evaluation test. FIG. 3 is an axial partial cross-sectional view conceptually showing an LBP spindle motor. It is a radial cross section of a porous oil-impregnated bearing. It is a figure showing the result of an evaluation test which asks for relation between c / h and axis run-out. It is a figure which shows the time-dependent change of the oil separation rate of a solid lubricating composition. It is a figure which shows the result of the comparative test by the presence or absence of a solid lubricating composition. It is an axial sectional view showing movement of oil in a porous oil-impregnated bearing which has an oil leak prevention member. It is an axial sectional view of a general porous oil-impregnated bearing.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Bearing main body 2 Rotating shaft 4 Bearing clearance 5 Dynamic pressure groove 8 Rotor (hub)
17 Bearing surface A Porous oil-impregnated bearing

Claims (1)

In a bearing body made of a porous body, a bearing surface opposed to a sliding surface of a shaft to be supported via a bearing gap is formed, and in a dynamic pressure type porous oil-impregnated bearing impregnated with lubricating oil or lubricating grease,
The bearing body is formed of a sintered metal having copper or iron, or both as main components, and a copper content of 20 to 95 wt%.
A dynamic pressure groove is formed on the bearing surface of the bearing body, and apertures are distributed including the dynamic pressure groove,
The sliding surface of the shaft is floated and supported by a dynamic pressure oil film of oil interposed in the bearing gap, and oil is transferred between the inside of the bearing main body and the bearing gap through an opening in the bearing surface including the dynamic pressure groove. A dynamic pressure-type porous oil-impregnated bearing characterized by being circulated between the bearing.

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