JPH1182479A - Supporting device for information equipment spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-noise and highly precise bearing while reducing the cost. SOLUTION: Lubricating oil is supplied to a porous bearing main body 1 having bearing surfaces 17 opposing each other via the outer peripheral surface of a rotary shaft 2 and a bearing gap, and dynamic pressure grooves 5 are formed in the bearing surfaces 17. By the dynamic pressure oil film of lubricating oil formed in the bearing gap, the outer peripheral surface of the rotary shaft 2 for a spindle motor mounted in an information equipment is supported to be floated, and oil is circulated between the inside of the bearing main body 1 and the bearing gap via the open hole parts of the bearing surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for supporting a spindle motor mounted on information equipment. The information equipment here includes a magnetic disk device (HDD / FD)
D), an optical disk device (CD / DVD), a magneto-optical disk device (ODD), a digital audio tape recorder (DAT) and other information storage devices using information recording carriers (disks and tapes), as well as laser beam printers ( L
(BP), digital facsimile, digital PPC and the like.

[0002]

2. Description of the Related Art FIG. 16 shows a polygon mirror motor (scanner motor) of a laser beam printer which is a kind of the above information equipment. The motor includes a rotating shaft (22) inserted and accommodated in a housing (21), a rotor (23) formed on an outer peripheral surface of the rotating shaft (22), and a stator (24) opposed to the rotor (23). , A bearing (25) rotatably supporting the rotating shaft (22), and a polygon mirror (26) (polyhedral mirror) coupled to the rotating shaft (22). Stator (24)
When the current flows through the rotor, the rotor (23) rotates by the exciting force of the stator coil, and the polygon mirror (26) connected to the rotating shaft (22) rotates with this rotation. Laser light incident on the polygon mirror (26) from the laser light source via a predetermined optical system is reflected by the polygon mirror (26) and scans the photosensitive drum surface.

In recent years, spindle motors for various information devices have been required to be further reduced in cost, noise, and performance. One of the components determining these required performances is the support of the motor. There is a bearing (25) that is a device.
Conventionally, ball bearings, fluid dynamic pressure bearings (for example, JP-A-8-247139), or sintered oil-impregnated bearings have been used as this type of bearing.

[0004]

However, the use of ball bearings has the following disadvantages.

[0005] This type of spindle motor is 8000
In many cases, a laser beam printer is used at a high speed of about tens of thousands of rpm. Ball bearings have a unique race sound (sound of the ball rolling on the raceway) and noise generated by the self-excited vibration of the cage. When used at high speed, the noise level is large, and noise reduction has reached its limit.

The spindle motor has a shaft runout,
High rotational accuracy is required to deal with NRRO, jitter, and the like. Ball bearings are often composed of outer rings, inner rings, balls, cages, seals, and grease, and factors that affect rotational accuracy, such as the mechanical accuracy of each one, the accuracy of assembly to the motor, and the pressurization method. Many are intricately related. Therefore, precision control is difficult, and even if control is possible, the cost is high.

[0007] Due to the large number of components, the manufacturing costs are necessarily high.

On the other hand, fluid dynamic pressure bearings are superior to ball bearings in terms of performance, such as low noise, high rotational accuracy, small number of parts and easy management. There are drawbacks such as:

When a dynamic pressure groove is formed on a shaft by etching, the groove processing can be performed with high precision, but the processing cost becomes extremely high.

As disclosed in JP-A-8-232958, there is a method in which a bearing is made of a soft metal or the like and a dynamic pressure groove is formed on the inner peripheral surface of the bearing using plastic working. Since the material is raised in the adjacent portion, it is necessary to perform reaming or the like to remove the material. For this reason, it can be cheaper than the etching process, but the cost is still high.

It is necessary to fill the lubricating oil without mixing air into the bearing gap of only a few microns. For this purpose, it is necessary to prepare a special process and a special jig, so that the process is complicated and the manufacturing cost is increased.

Since the operation is performed using only the lubricating oil initially injected into the bearing gap of only a few microns, when the oil evaporates or the oil is scattered due to centrifugal force, poor lubrication due to insufficient oil is likely to occur, resulting in poor durability. It is stable.

In the case of a sintered oil-impregnated bearing, there are the following disadvantages.

In a disk drive motor such as a CD-ROM or a DVD-ROM, a whirling load is applied to a bearing due to an unbalanced load of a disk. If the rotation speed is high and the whirling is large, the load area moves in the circumferential direction with the rotation, so that the oil film cannot follow this.
Further, in the sintered oil-impregnated bearing, air is also entrained with the rotation, but under high-speed rotation, the entrained amount increases, and the formation of an oil film is hindered. If the oil film formation is insufficient,
Abrasion proceeds due to metal contact, and whirling increases due to the abrasion. This causes a vicious cycle in which formation of an oil film becomes more difficult.

Further, since the sintered oil-impregnated bearing is a kind of perfect circular bearing, when it is used for HDD, LBP, etc., unstable vibration such as whirl occurs.

Accordingly, an object of the present invention is to solve the above-mentioned problems of a ball bearing, a fluid dynamic bearing, or a sintered oil-impregnated bearing.

[0017]

[Means for Solving the Problems]

1. In order to solve the above problems, a supporting device for a spindle motor of an information device according to the present invention includes a rotating shaft on which a rotating element of the information device is mounted and which is rotationally driven by an exciting force generated between a rotor and a stator. And a bearing that rotatably supports the rotating shaft, wherein the bearing is impregnated with a porous bearing body having a bearing surface facing an outer peripheral surface of the rotating shaft via a bearing gap, and a bearing body. A lubricating oil or lubricating grease, and a hydrodynamic groove provided on the bearing surface of the bearing body at an angle, and the rotating shaft is non-contact supported by a hydrodynamic oil film of lubricating oil formed in the bearing gap,
Oil is circulated between the inside of the bearing main body and the bearing gap through an opening in the bearing surface (claim 1).

If the information device is a laser beam printer and the rotating element is a polygon mirror, the information device is a spindle motor for the polygon mirror, and the information device is a disk device (magnetic disk device, optical disk device, magneto-optical disk device, etc.). If the rotary element is a turntable for supporting a disk as an information recording carrier, it can be used as a spindle motor for a disk drive (claims 2 and 3).

In this type of porous oil-impregnated bearing, the lubricant (lubricating oil or lubricating grease) inside the bearing body is drawn into the bearing gap as the shaft rotates. The oil drawn into the bearing gap forms a lubricating oil film and supports the rotating shaft in a non-contact manner. At this time, if a plurality of dynamic pressure grooves are provided on the bearing surface, the lubricant inside the bearing body is further drawn into the bearing gap by the dynamic pressure action, and the lubricant is continuously pushed into the bearing surface. Rigidity can be improved. Of course, when a positive pressure is generated, the lubricant flows back into the bearing body because there are holes (openings) in the surface of the bearing surface, but the lubricant continues to be pushed in one after another, so the oil film force and rigidity are high. Is maintained in. Therefore, high rotational accuracy is achieved, and shaft runout, NRRO, and jitter are reduced. Further, since the shaft and the bearing main body rotate in a non-contact manner, low noise and low cost are obtained. Furthermore, even when bubbles are generated or entrained in the oil film, the oil is circulated so that the bubbles are absorbed into the inside of the bearing body and the bearing function is not destabilized.

The dynamic pressure groove is formed on the outer peripheral surface of the core rod with a groove shape (consisting of unevenness inclined in the axial direction) corresponding to the shape of the dynamic pressure groove. It can be formed by supplying a material, applying a compressive force to the porous material, and pressing the inner diameter portion of the porous material against the groove of the core rod. Even if the porous material is compression-molded, no bulging occurs at the adjacent portion of the groove, so that the reamer processing as in JP-A-8-232958 is unnecessary, and the processing can be performed at low cost.

2. A first dynamic pressure generation region in which a plurality of dynamic pressure grooves inclined to one side with respect to the axial direction are arranged in the circumferential direction on the bearing surface, and are separated in the axial direction from the first dynamic pressure generation region, A second dynamic pressure generating region in which a plurality of dynamic pressure grooves inclined in the other direction are arranged in the circumferential direction, and a smooth portion located between the first and second dynamic pressure generating regions. 6).

With such a structure, when relative rotation occurs between the shaft and the bearing main body, the oil is collected in the smooth portion by the dynamic pressure grooves formed in opposite regions on both sides in the axial direction. The oil film pressure in this part increases. Since the smooth portion has no dynamic pressure grooves, the bearing rigidity is higher than when the dynamic pressure grooves are continuous in the axial direction. Therefore, shaft runout can be suppressed to a small value. The nonuniformity of the dynamic pressure generation due to the variation of the opening can be avoided. In addition, in this specification, the "opening portion" refers to a portion where pores of a porous body structure are opened on the outer surface.

As shown in FIG. 1, a dynamic pressure groove (5: a herringbone type dynamic pressure groove is illustrated in the drawing) continuous with the inner diameter surface of a cylindrical bearing body (1) made of an oil-containing porous body.
Is provided, the oil flow in the axial cross section is as shown in FIG. That is, with the rotation of the shaft (2), the oil (O) exudes from both sides in the axial direction of the bearing body (1), and the exuded oil (O) is pushed into the axial center of the bearing gap (4). Pressure (dynamic pressure), which causes the shaft (2) to be supported in a non-contact manner.

However, when such a pressure is generated,
Oil returns to the inside of the bearing from the opening on the surface. In addition, since it is generally difficult to make the distribution of apertures on the bearing surface uniform, large and small holes are mixed on the bearing surface. This tendency becomes more remarkable when unevenness is provided on the bearing surface as in the case of providing a dynamic pressure groove. For example, if there is a large hole in the middle of the dynamic pressure groove, the oil flows from that part back into the bearing, so that the dynamic pressure effect is greatly reduced. Therefore, the degree of recirculation of oil into the bearing must be non-uniform at each part.
In this case, it is difficult to form an oil film in the area where oil escapes easily,
The oil film tends to be formed in the hard to escape area.
As shown in the figure (showing a development of the bearing surface in the circumferential direction), the distribution of the oil film (S) on the bearing surface (1a) becomes uneven in the axial direction. In this state, although it has a certain effect in suppressing unstable vibration (such as whirl) as compared with a perfect circular bearing, it cannot exert a sufficient dynamic pressure effect.

The back portion (6) between the dynamic pressure grooves (5) serves as a support surface for supporting the shaft. However, since the cross-sectional shape of the bearing surface is uneven, the back portion (6) serves as the support surface. 6) The area is reduced, and the bearing rigidity is reduced.

On the other hand, as shown in FIG. 4, when an annular smooth portion (n) is provided between the first and second dynamic pressure generating regions (m1) and (m2), the smooth portion (n) is reduced. Makes it easier to control the degree of aperture. In both regions (m1) and (m2), oil flow in the groove direction is dominant, but in the smooth portion (n), oil flow in the circumferential direction also exists. As the oil is replenished one after another, the dynamic pressure effect is far less reduced. FIG. 5 shows a developed view of the bearing surface (1a) in this case in the circumferential direction. As shown in the drawing, the difference between the wide portion and the narrow portion of the oil film (S) is reduced, and the oil film distribution is made uniform, so that a stable dynamic pressure effect can be obtained. Further, not only the back portion (6) between the dynamic pressure grooves (5) but also the smooth portion (n) is a support surface for supporting the shaft, so that the area of the support surface is enlarged and the rigidity of the bearing can be increased. it can.

In this case, the surface porosity is determined by the first and second porosity.
The dynamic pressure generation region (m1) (m2) is set in the range of 3 to 40%, preferably 3 to 20%, and the smooth portion (n) is set in the range of 2 to 3%.
It is good to set it in the range of 0%, preferably in the range of 2 to 20%. If the surface porosity in both regions is less than 3%, the amount of oil supplied from inside the bearing to the bearing clearance may decrease, resulting in insufficient oil and poor lubrication. If it exceeds 40%, the amount of oil escaping into the bearing And the oil is not supplied to the smooth portion, which may result in insufficient oil and poor lubrication. If the surface porosity of the smooth portion is less than 2%, the production becomes extremely difficult and the cost increases. If it exceeds 30%, the amount of oil escaping into the bearing increases and lubrication failure may occur. There is.

The ratio r of the smooth portion (n) in the bearing width direction
When the bearing width is 1, r is preferably set in a range of r = 0.1 to 0.6, and more preferably, in a range of r = 0.2 to 0.4. If the width is less than 0.1 with respect to the bearing width 1, the effects (increase in dynamic pressure and increase in bearing rigidity) provided by the smooth portion (n) do not appear remarkably, and are the same as in the case of continuous grooves. Further, when r is larger than 0.6 with respect to the bearing width 1, the dynamic pressure groove is reduced, the force for pushing the oil into the central portion in the axial direction is weakened, and the dynamic pressure effect is not effectively exhibited.

The surface porosity in the smooth portion (n) is preferably smaller than the surface porosity in the first and second regions (m1) and (m2). This makes it difficult for the oil collected in the smooth portion (n) by the dynamic pressure grooves to escape from the opening on the surface into the inside of the bearing, thereby increasing the pressure generated. Also,
Since the area of the support surface for supporting the shaft is sufficiently ensured, the rigidity of the bearing can be increased.

3. By the way, when two bearings (porous oil-impregnated bearings) are press-fitted into the housing, accuracy of the two bearings such as coaxiality and cylindricity becomes a problem. If the accuracy is poor,
In some cases, the shaft and the bearing make line contact, or in the worst case, the shaft does not pass through the two bearings.

In this case, as shown in FIG. 6, a bearing surface (1a) having the shape shown in FIG. 4 is preferably provided at two or more locations in the axial direction of the bearing body (1). . This bearing has a single bearing body (1) and a hydrodynamic bearing surface (1a) at a plurality of locations (two locations in the drawing) of the inner diameter surface. It is possible to avoid the above-mentioned adverse effects such as poor accuracy due to the arrangement.

In this case, if the precision of the sizing pin for transferring the dynamic pressure groove is finished well, the precision of the bearing is also improved. It is not so difficult to finish the sizing pin with required precision, for example, within a circularity of 1 μm or less and a cylindricity of 2 μm or less, and it can be easily achieved. Therefore, assembling can be performed easily, and the number of bearings is one, so that the bearing can be manufactured at low cost.

4. Since the polygon mirror motor is used at a high speed as described above, if the viscosity of the lubricant such as lubricating oil or lubricating grease is too high, it does not increase to a predetermined rotational speed.
Problems such as large heat generation occur. Therefore, it is necessary to set the optimum viscosity. Kinematic viscosity at 40 ° C is 30 cS
If it is larger than t, it will hinder high-speed driving. Conversely, if it is smaller than 5 cSt, the kinematic viscosity is too small, and the oil is liable to be scattered, causing a problem in durability. Based on the above, the lubricating oil impregnated in the bearing body or 40 g
The kinematic viscosity at ° C is set to 5 cSt or more and 30 cSt or less (claim 4).

5. When lubricating grease is used as the lubricant, the apparent viscosity becomes significantly larger than that of the oil except for the bearing gap receiving the shearing force, so that the lubricant does not easily flow out to the surroundings. But,
If the amount of the thickener mixed and dispersed in the oil is larger than 5 wt%, the apparent viscosity is too high to impregnate the bearing body, and the work of removing excess grease adhering to the surface after the impregnation becomes complicated. . On the other hand, 0.5 wt
If it is less than%, the effect of grease is small, and the degree of outflow is not different from that in the case of using oil. From the above, the thickener concentration of the lubricating grease is 0.5 wt% or more,
wt% or less (claim 5).

6. There is an optimal range for the ratio between the groove depth (h: see FIG. 8) of the dynamic pressure groove (5) and the radial gap (c), and it is considered that a sufficient dynamic pressure effect cannot be obtained outside this range. . To clarify this optimum range, the LBP shown in FIG.
An evaluation test for measuring the run-out of the shaft (2) of the actual motor was performed. The number of revolutions was 10,000 rpm, and the test atmosphere was room temperature and normal humidity. In FIG. 7, (7) is a housing, (8) is a rotor, and (9) is a thrust receiver. Rotor (8)
Is arranged to face a stator (not shown), and the shaft (2) is rotationally driven by an exciting force generated between the rotor (8) and the stator.

Under the above conditions, the values of the shaft runout with respect to c / h were plotted, and the results shown in FIG. 9 were obtained. According to FIG. 9, 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 larger than 4.0, it becomes 5 μm or more. Therefore,
In order to maintain high accuracy, it is desirable that the ratio between the groove depth h of the dynamic pressure groove and the bearing gap c be in the range of c / h = 0.5 to 4.0 (claim 8). .

The same test was performed on the actual CD-ROM motor shown in FIG. The rotation speed is 8000 rpm,
The test atmosphere was room temperature and normal humidity, and an unbalance load of 500 mg · cm was applied to the shaft. In FIG. 11, (18) is a turntable, (19) is a disk, and (20) is a clamper. The test results are shown in FIG. From FIG. 12, c / h is 0.5
If it is within the range of ~ 4.0, the shaft runout will be 10m or less, but if it is less than 0.5 or larger than 4.0, it will be 10m.
m 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 as in the case of the LBP.

7. There is an optimal range for the ratio between the bearing clearance (radial clearance: c) and the radius (r) of the rotating shaft, and it is considered that a sufficient dynamic pressure effect cannot be obtained outside this range. To clarify this optimum range, the LBP shown in FIG.
An evaluation test for measuring the run-out of the shaft (2) of the actual motor was performed. The number of revolutions was 10,000 rpm, and the test atmosphere was room temperature and normal humidity.

Under the above conditions, the values of the shaft runout with respect to c / r were plotted, and the results shown in FIG. 10 were obtained. According to FIG. 10, when c / r is in the range of 0.0005 to 0.01, the shaft runout becomes 5 μm or less,
If it is less than 5, the torque is too large to increase the speed to a predetermined number of revolutions. On the other hand, when it is larger than 0.01, the shaft runout becomes 5 μm or more. Therefore, in order to maintain high accuracy, the ratio between the bearing clearance c and the radius r of the rotating shaft is determined by c / r =
It is desirable to be in the range of 0.0005 to 0.01 (claim 9).

The same test was performed on the actual CD-ROM motor shown in FIG. The rotation speed is 8000 rpm,
The test atmosphere was room temperature and normal humidity, and an unbalance load of 500 mg · cm was applied to the shaft. The test results are shown in FIG. As shown in FIG. 13, when c / r is in the range of 0.0005 to 0.003, the shaft runout becomes 10 μm or less.
If it is less than 005, the speed cannot be increased to a predetermined number of revolutions.
If it exceeds 0.003, the shaft runout will be 10 μm or more. Therefore, in order to maintain high accuracy, the ratio between the bearing clearance c and the radius r of the rotating shaft should be c as in the case of the LBP.
/R=0.005-0.01, and more preferably, c / r = 0.005-0.00.
It is preferably within the range of 3.

8. Porous oil-impregnated bearings are usually used without lubrication, but oil gradually depletes due to oil scattering and evaporation.
Outflow is inevitable. In this case, the oil film formation range shrinks, which causes deterioration of rotation accuracy such as shaft runout. In particular, the shaft attitude is often used in a vertical type,
In a motor for a laser beam printer (LBP) used at a high speed of 10,000 rotations or more, oil easily flows out due to the action of centrifugal force, and it is difficult to maintain lubrication performance such as oil film forming properties.

In the polygon mirror motor, the occurrence of oil film shortage is fatal in maintaining high-precision rotation. In particular, when the bearing body is used alone, when rotating at a high speed, the oil also entrains 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.

As such a refueling member, a solid resin lubricating composition in which a synthetic resin is used as a base material and a lubricating oil or lubricating grease is blended or impregnated therewith is considered. This resin lubricating composition can be obtained, for example, by mixing a synthetic resin powder and lubricating oil or lubricating grease, and baking the mixture, and bringing the mixture into contact with the bearing body (excluding the bearing surface) of the bearing. If it is arranged, even if oil from the bearing body flows out, new oil is replenished from the resin lubricating composition into the bearing body by capillary action, so that a good dynamic pressure oil film is always formed between the bearing and the rotating shaft. can do. It is desirable that the resin lubricating composition has such a property that at least at a temperature of 20 ° C. or more, the oil contained therein oozes out to the surface even in a stationary state.

Specifically, lubricating oil contained in the bearing body or lubricating grease containing the lubricating oil as a base oil is 5 to 99 wt%.
Is mixed with 95 to 1 wt% of an ultrahigh molecular weight polyolefin powder having an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶ , and a gel point of the ultrahigh molecular weight polyolefin powder or higher.
In addition, when lubricating grease is used, it can be dispersed and maintained at a temperature below the grease drop point, and can be molded by cooling at room temperature. A simple resin lubricating composition is provided. The ultra-high molecular weight polyolefin powder is a powder composed of polyethylene, polypropylene, polybutene or a copolymer thereof, or a mixed powder in which a single powder is blended.

In addition, a lubricating member made of either a lubricating resin composite in which the above-described resin lubricating composition and a felt material are integrally combined or a felt material impregnated with oil is brought into contact with the bearing body. The same bunkering effect can be obtained also by (claim 10). The lubricating resin composite can be formed, for example, by mixing a synthetic resin powder with lubricating oil or lubricating grease, impregnating the mixture with felt, and firing.

9. As shown in FIG. 14, an oil leakage prevention member (11) is arranged on one or both sides in the axial direction of the bearing body (1), and a rotating shaft (2) is provided on the inner peripheral surface of the oil leakage prevention member (11). ) May be provided with an airflow generating groove (12) for generating an airflow flowing toward the bearing main body in a gap between the rotary shaft (2) and the rotary shaft (2). The oil leakage prevention member (11) is, for example, cylindrical with an inner diameter equal to or slightly larger than the bearing body (1), and the airflow generation groove (12) is, for example, a plurality of inclined grooves.

In this configuration, as shown in FIG. 15, a gap (13) between the rotating shaft (2) and the inner peripheral surface of the oil leakage preventing member (12) is formed with the rotation of the shaft (2). Since an airflow is generated in the direction of the bearing body (1) (downward in the drawing), even if oil leaks from the bearing body (1), the gap between the shaft (2) and the oil leakage prevention member (11) (13) cannot pass. This action prevents oil leakage. Also, at rest,
Since the oil is held by the capillary force of the gap (13), the oil does not leak even if the rotation stops.

If the oil leakage prevention member (11) is made of a porous material and a space (14) is provided between the oil leakage prevention member (11) and the adjacent bearing body (1), the leaked oil can be leaked out of the porous material. The oil can be absorbed by the prevention member (11), and at rest, the oil between the oil leakage prevention member (11) and the shaft (2) can be absorbed. Dust generation 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.

Further, the end face (11a) of the oil leakage prevention member (11) on the opposite side to the bearing body (1) and the chamfer portion (11
If b) is subjected to crushing and the surface porosity of this portion is 5% or less in area ratio, desirably completely sealed, evaporation and dust generation of the oil absorbed by the oil leakage prevention member (11) can be prevented. It can be further reduced.

[0050]

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

FIG. 14 shows an example of a supporting device for a spindle motor (for a polygon mirror motor) according to the present invention, wherein a shaft (7) in which one end is open and the other end is closed is provided. Radial bearing surface (1
7) is press-fitted and fixed, and a rotating shaft (2) in which a rotor and a polygon mirror are assembled is inserted into the inner peripheral portion of the bearing body (1) to insert a porous oil-impregnated bearing ( A).

In a space (15) between the lower end surface of the bearing body (1) and the upper surface of the thrust plate (9), a refueling member (3) made of an oil-impregnated felt material is provided. ). Above the bearing body (1), a cylindrical oil leakage prevention member (11) is disposed via a small space (14), and the oil leakage prevention member (11) is used to open the upper end opening of the housing (7). Is closed. The oil leakage prevention member (11) is formed of a porous body, and is not impregnated with lubricating oil or the like.

The space (15) at the bottom of the housing (7) communicates with the outside of the housing via an air flow passage (16). The air flow passage (16) functions as an air vent, and is, for example, a bearing body (1) and an oil leakage prevention member (1).
It is formed by providing a notch in the axial direction on a part of the outer surface of 1). As a result, the shaft (2) can be easily inserted at the time of assembling, and the internal pressure increases due to heat generation at the time of rotation, and the shaft (rotor) may be pushed up to make the rotation unstable, but such a situation can be prevented. Become.

On the two bearing surfaces (17) of the bearing body (1) and the inner peripheral surface of the oil leakage preventing member (11), a plurality of inclined grooves (dynamic pressure grooves 5 and airflow generating grooves 12) are provided. . These grooves may have a spiral shape in addition to the herringbone shape illustrated. Two bearing surfaces (1
7) In the first dynamic pressure generation region (m1), a plurality of dynamic pressure grooves (5) inclined to one side with respect to the axial direction are arranged in the circumferential direction.
And a second dynamic pressure generation region (m2) in which a plurality of dynamic pressure grooves (5) that are axially separated from the first dynamic pressure generation region (m1) and are inclined in the other direction with respect to the axial direction are arranged in the circumferential direction. ) And both areas (m1)
(M2) and a smooth portion (n) located between them.

The molding material of the bearing body (1) and the oil leakage preventing member (11) is not particularly limited, and may be obtained by sintering or foaming powder metallurgy, cast iron, synthetic resin, ceramic, or the like. It is formed into a well-known porous body having vent holes.

The lubricating oil or lubricating grease to be impregnated into the bearing body (1) is not particularly limited. However, the lubricating oil has a small amount of evaporation, is excellent in oxidative stability, and has little foaming during stirring. It is desirable to use α-olefin or ester synthetic oils (diester, polyol ester synthetic oils). As a thickener for lubricating grease, it is desirable to use a lithium-based thickener which is easy to handle and has excellent productivity. The kinematic viscosity at 40 ° C. of the lubricating oil or the base oil of the lubricating grease is set to 5 cSt or more and 30 cSt or less. When using lubricating grease, the thickener concentration should be 0.5 wt% or more and 5 wt%
The following are selected:

The groove depth (h) of the dynamic pressure groove, the bearing gap (c),
Each ratio of the radius (r) of the rotation axis is c / h = 0.5
４4.0, c / r = 0.0005 to 0.01.

Such a bearing device is not only a polygon mirror motor of a laser beam printer, but also a rotary shaft (2).
Turntable (1) to support the disc (19)
The present invention can also be applied to a spindle motor (CD-ROM motor, DVDROM motor, etc.) for a disk drive equipped with 8). In addition, it can be used for a wide range of motors, such as electric products such as axial fans, ventilation fans, and electric fans, and electrical components for automobiles. Can be improved.

[0059]

As described above, according to the present invention, as a support device for a spindle motor of an information device, rigidity is increased by dynamic pressure action, and rotation accuracy such as shaft runout, NRRO, and jitter is improved. The shape and structure of the dynamic pressure groove, the kinematic viscosity of the lubricant, the amount of the thickener, the ratio of the groove depth to the bearing clearance, and the ratio of the bearing clearance to the radius of the rotating shaft have been optimized. Since the refueling member is arranged so as to be in contact with the bearing, a favorable oil film is always formed and the durability life is greatly improved.

[Brief description of the drawings]

FIG. 1 is an axial sectional view of a porous oil-impregnated bearing having a continuous herringbone groove.

FIG. 2 is an axial sectional view showing movement of oil in a porous oil-impregnated bearing having a herringbone groove.

FIG. 3 is a developed view of a bearing surface of the porous oil-impregnated bearing shown in FIG. 1 in a circumferential direction.

FIG. 4 is an axial sectional view of the porous oil-impregnated bearing according to the present invention.

FIG. 5 is a developed view of a bearing surface in a circumferential direction in the product of the present invention.

FIG. 6 is an axial sectional view of the porous oil-impregnated bearing according to the present invention.

FIG. 7 is an axial cross-sectional view of an evaluation tester using an actual LBP motor.

FIG. 8 is a radial cross-sectional view of a dynamic pressure type porous oil-impregnated bearing.

FIG. 9 is a diagram showing the results of an evaluation test (FIG. 7) for determining the relationship between c / h and shaft runout.

FIG. 10 is a diagram showing the results of an evaluation test (FIG. 7) for determining the relationship between c / r and shaft runout.

FIG. 11 is an axial sectional view of an evaluation tester using a CD-ROM actual motor.

FIG. 12 is an evaluation test for determining the relationship between c / h and shaft runout (FIG.
It is a figure which shows the result of 11).

FIG. 13 is an evaluation test for determining a relationship between c / r and shaft runout (FIG.
It is a figure which shows the result of 11).

FIG. 14 is an axial sectional view showing one embodiment of the bearing device according to the present invention.

FIG. 15 is an axial sectional view showing movement of oil in a porous oil-impregnated bearing having an oil leakage prevention member.

FIG. 16 is a sectional view of a polygon mirror motor.

[Description of Signs] 1 Bearing main body 2 Rotary shaft 3 Refueling member 4 Bearing gap 5 Dynamic pressure groove 7 Housing 8 Rotor 11 Oil leakage prevention member 12 Air flow generation groove 17 Bearing surface 18 Turntable 26 Polygon mirror A Porous oil-impregnated bearing m1 First dynamic pressure generation area m2 Second dynamic pressure generation area n Smoothing section

Claims (12)

[Claims] 1. A spindle motor, comprising: a rotating shaft on which a rotating element of an information device is mounted and driven to rotate by an exciting force generated between a rotor and a stator; and a bearing rotatably supporting the rotating shaft. In the supporting device, the bearing is a porous bearing body having a bearing surface opposed to an outer peripheral surface of a rotating shaft via a bearing gap, a lubricating oil or lubricating grease impregnated in the bearing body, and a bearing surface of the bearing body. A dynamic pressure groove provided in a slanted manner, the rotary shaft is supported in a non-contact manner by a dynamic pressure oil film of lubricating oil formed in the bearing gap, and oil is supplied to the bearing body through an opening in the bearing surface. A support device for a spindle motor of an information device that circulates between the inside and a bearing gap. 2. The apparatus according to claim 1, wherein the information device is a laser beam printer, and the rotating element is a polygon mirror. 3. A supporting device for a spindle motor of an information device according to claim 1, wherein said information device is a disk device, and said rotating element is a turntable for supporting a disk as an information recording carrier. 4. The kinematic viscosity at 40 ° C. of a lubricating oil or a lubricating grease base oil impregnated in a bearing body is 5 cSt or more.
The support device for a spindle motor of an information device according to claim 1 or 2, wherein the support speed is 30 cSt or less. 5. The lubricating grease having a thickener concentration of 0.5
5. The supporting device for a spindle motor of an information device according to claim 1, wherein the content is not less than 5 wt% and not more than 5 wt%. 6. A first dynamic pressure generating region in which a plurality of dynamic pressure grooves inclined in one direction with respect to the axial direction are arranged in a circumferential direction, and a bearing surface is axially separated from the first dynamic pressure generating region. A second dynamic pressure generating region in which a plurality of dynamic pressure grooves inclined in the other direction with respect to the axial direction are arranged in a circumferential direction, and a smooth portion located between the first and second dynamic pressure generating regions. Item 6. A support device for a spindle motor of an information device according to any one of Items 1 to 5. 7. The support device for a spindle motor of an information device according to claim 1, wherein the bearing surface is provided at two or more positions in the axial direction of the bearing body. 8. The information according to claim 1, wherein the ratio of the groove depth h of the dynamic pressure groove to the bearing gap c is c / h = 0.5 to 4.0. Support device for motor for spindle of equipment. 9. The spindle motor for information equipment according to claim 1, wherein the ratio of the bearing clearance c to the radius r of the rotating shaft is c / r = 0.0005 to 0.01. Support device. 10. A resin lubricating composition comprising a synthetic resin as a base material and blended or impregnated with lubricating oil or lubricating grease,
A lubricating resin composite in which the resin lubricating composition and a felt material are integrally composited, or an oil-impregnated oil-impregnated oil replenishing member is in contact with the bearing body according to any one of claims 1 to 9. Support device for spindle motor of information equipment. 11. An oil leakage prevention member is disposed on one or both sides in the axial direction of the bearing body according to claim 1,
A support device for a spindle motor of an information device, wherein an airflow generating groove for generating an airflow flowing toward a bearing body side in a gap between the rotary shaft and the rotary shaft when the rotary shaft rotates is provided on an inner peripheral surface of the oil leakage prevention member. 12. An oil leakage preventing member is disposed on one or both sides of the bearing body in the axial direction, and a bearing body is provided on an inner peripheral surface of the oil leakage preventing member in a gap between the rotating shaft and the rotating shaft. The support device for a spindle motor of an information device according to claim 10, further comprising an airflow generation groove for generating an airflow flowing to the side.