JP2000035041A - Dynamic pressure type sintered and oil retaining bearing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent the outflow and splash of oil. SOLUTION: A seal 13, equipped with an oil absorbing member 13a for absorbing and catching oil leaked from a dynamic pressure type sintered and oil retaining bearing 1a, is provided on the opening part of a housing 1b; and is composed of a seal main body 13b fixed to the housing 1b, and an oil absorbing member 13a composed of a fiber material or a porous body. The oil absorving member 13a is arranged in a space between the seal main body 13b fixed to the housing 1b and the opening side end surface of the bearing 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic sintered oil-impregnated bearing unit having features such as high rotational accuracy, high-speed stability and high durability, and more particularly to a spindle motor for information equipment, for example, a DVD-ROM, It is suitable for supporting a spindle of an optical disk such as a DVD-RAM, a magneto-optical disk such as an MO, a magnetic disk such as an HDD, or a polygon scanner motor of a laser beam printer (LBP).

[0002]

2. Description of the Related Art In addition to high rotational accuracy, higher speed, lower cost, lower noise, and the like are required for spindle motors of the above information devices. One of the components that determine these required performances is as follows. One type is a bearing that supports a motor spindle. Conventionally, a ball bearing or a general round-shaped sintered oil-impregnated bearing is used as this bearing.

However, this kind of spindle motor is often used at a high speed of about 8,000 to 10,000 rpm, especially a polygon scanner motor used for LBP at tens of thousands of rpm, and has a shaft runout, NRRO (non-repetitive rotation). It is necessary to consider rotational accuracy such as accuracy) and jitter, so that it is difficult to satisfy the required performance in ball bearings and sintered oil-impregnated bearings.

In view of the above, the use of a dynamic pressure type sintered oil-impregnated bearing has been studied in recent years as this type of bearing. This bearing impregnates a sintered metal bearing body with lubricating oil or lubricating grease, forms a lubricating oil film in the bearing gap by the dynamic pressure effect of the dynamic pressure groove provided on the bearing surface, and supports the spindle in a non-contact manner. Therefore, the above-mentioned required performance can be sufficiently satisfied at a low cost.

[0005]

Generally, when a dynamic pressure bearing is used, it is important to fill the gap in the bearing with oil.
The above-described sintered oil-impregnated bearing contains oil inside the bearing body, but when inserting the rotating shaft into the bearing body, it is desirable to lubricate the bearing gap separately from this. . This means that if oil is filled in the bearing gap from the initial stage of assembly, it becomes difficult for air to be entrained during driving, so that stable bearing performance can be exhibited from the beginning of operation. This is because the sliding portion (the contact portion between the spherical shaft end and the thrust washer) is in an oil-free state.

However, when the shaft is used in a horizontal orientation, or when the rotation speed is 2 m / or more at the peripheral speed of the shaft surface even in the vertical orientation, oil spills or scatters. If the lubricated oil leaks out or scatters, eventually it becomes easier for air to be trapped in the bearing gap, so that the function as a dynamic pressure bearing cannot be maintained.

In view of the above, an object of the present invention is to make it possible to reliably prevent oil that has been infused, in particular, from being washed away or scattered.

[0008]

In order to achieve the above object, according to the present invention, a lubricating oil is applied to a bearing body formed of a sintered metal and having a bearing surface opposed to an outer peripheral surface of a shaft via a bearing gap. Alternatively, a hydrodynamic sintered oil-impregnated bearing which is impregnated with lubricating grease and supports the shaft in a non-contact manner by a dynamic pressure effect generated by the relative rotation of the shaft and the bearing body, and one end of which is opened and the above-mentioned hydrodynamic sintered A housing containing an oil-impregnated bearing;
A thrust bearing for supporting the shaft in the thrust direction at the other end of the housing, wherein a seal having an oil absorbing member for absorbing oil leaked from the bearing is provided at the opening of the housing. .

As the dynamic pressure-type sintered oil-impregnated bearing, for example, a bearing in which an inclined dynamic pressure groove is provided on the bearing surface can be used.

[0010] The oil absorbing member can be made of a fibrous material or a porous body.

The seal comprises a seal body fixed to the housing and the oil absorbing member arranged at least partially so as to face a space on the other end side of the housing with respect to the seal body. In this case, the oil absorbing member can be provided in a space between the seal main body and the opening-side end face of the hydrodynamic sintered oil-impregnated bearing, or can be provided on the outer peripheral portion of the shaft facing the seal main body.

The thrust bearing can be constituted by a dynamic pressure groove provided on an end face of the shaft or an opposing portion thereof. Alternatively, the bearing surface at the other end of the housing is constituted by an inclined dynamic pressure groove formed asymmetrically on both sides in the axial direction, and the dynamic pressure groove is formed on the other end of the housing with relative rotation between the shaft and the shaft. The oil may be supplied to the hopper.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view showing one embodiment of a hydrodynamic sintered oil-impregnated bearing unit 1 according to the present invention.

As shown in the figure, the bearing unit 1 comprises a dynamic pressure type sintered oil-impregnated bearing 1a, a housing 1b in which the sintered oil-impregnated bearing 1a is fixed to the inner diameter, and a thrust bearing 12 provided at the bottom of the housing 1b. It consists of. The housing 1b has a substantially cylindrical shape with one end (upper side in the drawing) opened, and the other end side is sealed by a thrust bearing 12. The thrust bearing 12 is formed by laminating, for example, a resin-made thrust washer 12a formed in a disc shape and a back metal 12b that supports the thrust washer 12a. The rotating shaft 2 inserted into the inner diameter portion of the bearing 1a has a spherical surface. The lower end of the shape is pivotally contacted with a thrust washer 12a of the thrust bearing 12 and is rotatably supported.

As shown in FIG. 2, the sintered oil-impregnated bearing 1a has a bearing surface 10b opposed to the outer peripheral surface of the rotating shaft 2 via a bearing gap.
The bearing body 10 is formed by impregnating a lubricating oil or lubricating grease into a cylindrical bearing body 10 made of a sintered metal having The bearing body 10 made of a sintered metal is formed of a sintered metal containing copper or iron, or both as a main component, and is desirably formed using 20 to 95% of copper. On the inner periphery of the bearing body 10, two bearing surfaces 10b are formed, which are separated in the axial direction,
On both of the two bearing surfaces 10b, a plurality of dynamic pressure grooves 10c (herringbone type) each inclined with respect to the axial direction are arranged in the circumferential direction. It is sufficient that the dynamic pressure groove 10c is formed to be inclined with respect to the axial direction. As long as this condition is satisfied, a shape other than the herringbone type, for example, a spiral type may be used. On the outer periphery of the sintered oil-impregnated bearing 1a, one or more grooves 10g for venting air when inserting the shaft 2 into the inner diameter of the bearing 1a.
Are formed along the axial direction. In addition, both bearing surfaces 10b
The inner diameter of the region 10f between them is set to be larger than the inner diameter of the convex portion (back portion 10e) excluding the dynamic pressure groove portion on the bearing surface 10b.

In this embodiment, a single bearing body 10 is provided, and a plurality of bearings 1 are provided at a plurality of locations (two locations in the present embodiment) on the inner diameter surface of the bearing body 10 so that a plurality of bearings 1 are separately provided. The disadvantages such as poor accuracy which may be a problem in the arrangement are avoided.

In the sintered oil-impregnated bearing 1a, a lubricant (lubricating oil or a base oil of lubricating grease) inside the bearing body 10 is generated by pressure generation due to rotation of the rotary shaft 2 and thermal expansion of the oil due to temperature rise. It oozes out from the surface of 10 and is drawn into the bearing gap by the action of the dynamic pressure groove. The oil drawn into the bearing gap forms a lubricating oil film and supports the rotating shaft in a non-contact manner.
That is, when the above-mentioned inclined dynamic pressure groove 10c is provided on the bearing surface 10b, the bearing body 10 which is oozed by the dynamic pressure action is provided.
The internal lubricant is drawn into the bearing gap and the bearing surface
As the lubricant continues to be pushed into 10b, the oil film strength increases, and the rigidity of the bearing can be improved.

When a positive pressure is generated in the bearing gap, the bearing surface 10b
There is a hole on the surface (opening part: the part where the pores of the porous body structure are open on the outer surface), so the lubricant flows back into the bearing body, but new lubricants are successively added to the bearing. The oil film force and the rigidity are maintained in a high state because the oil film force and the rigidity continue to be pushed into the gap. In this case, since a continuous and stable oil film is formed, high rotation accuracy is obtained, and shaft runout, NRRO, jitter and the like are reduced. Further, since the rotating shaft 2 and the bearing main body 10 rotate in a non-contact manner, the noise is low and the cost is low.

The two bearing surfaces 10b are provided with a dynamic pressure groove 10 inclined to one side.
c, a second groove region m2 in which a dynamic pressure groove 10c that is axially spaced from the first groove region m1 and is inclined to the other groove region, and two groove regions an annular smooth portion n located between m1 and m2, and two groove regions m1 and m2.
The dynamic pressure groove 10c is partitioned by a smooth portion n and is discontinuous. The back portion 10e between the smooth portion n and the dynamic pressure groove 10c is at the same level. This type of non-continuous type dynamic pressure groove 10c is a continuous type,
That is, the smooth portion n is omitted, and the dynamic pressure groove 10c is formed in both groove regions m1,
Compared to the case of forming a continuous V-shape between m2, the oil film pressure is high because oil is collected around the smooth portion n, and the advantage that the bearing rigidity is high because the smooth portion n without grooves is provided. Have.

In the present invention, a seal 13 for sealing the opening is provided near the opening of the housing 1b. The seal 13 includes a thin ring-shaped oil absorbing member 13a made of a fiber material (felt or the like) or a porous body (formed of sintered metal or resin), and a thin ring-shaped seal body made of a resin or metal. 13b (for example, a washer), and the seal body 13b is disposed on the opening end side of the housing 1b and is incorporated in the inner diameter portion of the housing 1b.
Of the seal 13, the oil absorbing member 13a may be fixed to the housing 1b, or may be placed on the opening-side end face of the bearing body 10 without being particularly fixed. It is preferable to leave a slight gap on the inner diameter side of the oil absorbing member 13a with respect to the outer peripheral surface 2a of the shaft 2. However, when a fibrous oil absorbing member 13a such as a felt is used, a torque increase or torque increase is required. The shaft 2 may be brought into contact with the shaft 2 within a range that does not change. On the other hand, the seal body 13b is fixed to the inner peripheral surface of the housing 1b with a small gap (0.3 mm or less in diameter, preferably 0.2 mm or less in diameter) from the outer peripheral surface 2a of the shaft 2.

The seal having the oil absorbing member 13a as described above
13 allows the bearing 1a to have an opening-side end face (inside and outside diameter chamfer portions) regardless of whether the shaft attitude is vertical or horizontal.
(Including 10h and 10i), the oil O which is about to leak out can be absorbed and captured and held inside. Therefore, it is possible to prevent a situation in which oil flows out and scatters around due to centrifugal force.

Further, if the oil retaining force due to the capillary force of the bearing 1a is set to be stronger than that of the oil absorbing member 13a, even if an oil-free hole is formed inside the bearing, the oil absorbing member 13
Since the oil absorbed and captured by a flows back to the bearing 1a, oil shortage hardly occurs, and the life of the bearing is extended. From this viewpoint, it is preferable that the oil absorbing member 13a be in contact with the end face of the bearing 1a (if the recirculating property does not matter, the oil absorbing member 13a may be separated).

The oil absorbing member 13a may be impregnated with oil in advance and then incorporated in the housing 1b. Alternatively, the oil absorbing member 13a may be incorporated without impregnating the oil, and the injected oil may be injected into the bearing 1a of the shaft 2.
When it is pushed up through the air vent groove 10g at the time of insertion into the inner peripheral portion, it may be absorbed and captured and impregnated. In the latter case, there is an advantage that the air that has been pushed out together with the oil easily escapes, so that the air hardly remains in the bearing gap.

FIG. 3 shows another embodiment of the bearing unit according to the present invention, in which a cylindrical oil absorbing member 13a is attached to a seal body.
13b is fixed to the outer peripheral portion of the shaft 2 so as to face the inner diameter end of the shaft 13b. The oil absorbing member 13a is, for example, as shown in FIG.
It is fixed by being fitted into a circumferential groove 2b provided on the shaft 2. According to this configuration, oil that is likely to flow out of the bearings together with the rotating shaft 2 can be absorbed and captured, and the scattering of the oil can be further suppressed. in this case,
It is desirable to leave a slight gap between the oil absorbing member 13a and the seal body 13b, but they may be in contact with each other as long as the torque does not increase or the torque fluctuates.

The oil absorbing member 13a only needs to be at a position where it can absorb and leak oil leaking from the bearing 1a, that is, at a position where at least a part thereof faces the space on the bottom side of the housing 1b with respect to the seal body 13b. It is not limited to the structure shown in FIG.

FIGS. 5 and 6 show another embodiment of the thrust bearing 12, in which the end surface 2c of the shaft 2 is formed flat and the surface 12a1 of the thrust washer 12a facing the shaft end surface 2c.
A spiral dynamic pressure groove 12c is formed in the groove. This dynamic pressure groove 12c can be formed by pressing a thrust washer 12a made of, for example, a soft metal material. The dynamic pressure groove 12c may be formed on the flat end face 2c of the shaft 2.

FIG. 7 shows another embodiment of the thrust bearing 12, in which the bearing surface on the other end side (the thrust bearing side) of the housing 1b is shown.
Inclined hydrodynamic grooves formed asymmetrically on both sides in the axial direction in 10b
The thrust bearing 12 is constituted by 10c1 and 10c2. In this case, the oil is pushed downward along with the rotation of the shaft 2, so that the shaft 2 can be floated and supported. In order to obtain a sufficient dynamic pressure effect, the end face of the sintered oil-impregnated bearing 1a and the thrust washer
It is good to make contact with 12a.

In the above description, a type having an inclined hydrodynamic groove has been exemplified as a hydrodynamic sintered oil-impregnated bearing. However, the present invention is not limited to this, and other hydrodynamic bearings such as a step bearing, The present invention is similarly applicable to arc bearings, tapered bearings, and tapered land bearings.

[0030]

EXAMPLES The outline of tests performed to confirm the effects of the present invention and the test results will be described below.

Oil splash test by polygon scanner motor As shown in FIG. 8, the polygon scanner motor has a bearing unit 1 for supporting the rotating shaft 2, a polygon mirror 11, a stator 5, and a rotor 6 attached to the upper end of the rotating shaft 2.
The motor section M is composed of a polygon mirror 11 and a rotor hub 18.
The preload spring 17 presses the polygon mirror 11 with the rotation of the rotor 6 by energizing the stator 5. Laser light that has entered the polygon mirror 11 from a laser light source via a predetermined optical system is reflected by the polygon mirror 11 and scans the photosensitive drum surface.

A cylindrical piece of paper is arranged so as to surround this motor, and the first embodiment (the bearing unit in FIG. 1), the second embodiment (the bearing unit in FIG. 3), the first comparative example (without the seal 13), and For Example 2 (seal with only the washer 13b), the state of oil scattering was examined. The atmosphere is room temperature and normal humidity, the shaft diameter is φ3, the shaft posture is vertical, and the rotation speed is 10,000 to 3000.
0 rpm, test time is 20 hours.

As shown in FIG. 9, in the case of no seal (Comparative Example 1), oil scattering was observed at 10,000 rpm (peripheral speed of 1.57 m / s), and in the case of a seal having only a washer (Comparative Example 2). Is 15,000 rpm (peripheral speed 2.36 m / s
The above high speed rotation was found to be unsuitable for practical use. On the other hand, in the case of the structures of Examples 1 and 2, the oil scattering prevention effect was recognized even at a high rotation speed of 30,000 rpm (peripheral speed of 4.71 m / s).

Endurance Test Using Optical Disk Motor As shown in FIG. 10, the optical disk motor includes a bearing unit 1 for supporting the rotating shaft 2, a turntable 4 attached to the upper end of the rotating shaft 2 and supporting and fixing the optical disk 3. The motor unit M includes a clamper 8, a stator 5, and a rotor 6. A rotor case 7 integrated with the rotor 6 by energizing the stator 5, a turntable 4,
The optical disc 3 and the clamper 8 are integrally rotated.

This motor was fixed so that the shaft attitude was horizontal, and a continuous operation test was carried out. For each of Examples 1 and 2 and Comparative Examples 1 and 2 (the structure of each bearing unit was the same), An operation test was performed and the durability was compared. In the evaluation, the motor was taken out of the thermostat every 200 hours, the shaft runout and the current value were measured, and the shaft runout was 1.5 times or more of the initial value, or the current value exceeded the range of ± 20% of the initial value. The life was judged at the next point. In the table of FIG. 11 showing the test results, the test time at the time when the life was determined is written. The test was performed for up to 2000 hours, and when the life was not reached at that time, "2000 °" was recorded. The atmosphere is 50 ° C., the shaft diameter is φ3, the shaft posture is horizontal, the rotation speed is 7000 rpm, the continuous operation is performed, and the unbalance load is ^0.501 cm.

In both Comparative Examples 1 and 2, the shaft runout was increased and the life was extended. In each case, the oil leakage to the surroundings was remarkably observed especially in the case without the seal. The increase in shaft runout due to lack of oil film seems to be the cause of the service life. In both Examples 1 and 2, the shaft oscillated, the current value did not change even at the time of 2,000 hours, the state where continuous use was possible, and no oil leakage was observed.

[0037]

According to the present invention, it is possible to prevent oil from flowing out of the hydrodynamic sintered oil-impregnated bearing, so that a good oil film can be maintained over a long period of time, and the durability is dramatically improved. Further, the surroundings are not polluted by the oil leak.

[Brief description of the drawings]

FIG. 1 is a sectional view of a hydrodynamic sintered oil-impregnated bearing unit according to the present invention.

FIG. 2 is a sectional view of a hydrodynamic sintered oil-impregnated bearing used in the bearing unit.

FIG. 3 is a longitudinal sectional view showing another embodiment.

FIG. 4 is an enlarged sectional view of a main part of FIG.

FIG. 5 is a sectional view showing another embodiment of the thrust bearing.

FIG. 6 is a plan view of a thrust washer.

FIG. 7 is a plan view of a thrust washer.

FIG. 8 is a sectional view of a polygon scanner motor.

FIG. 9 is a diagram showing the results of an oil splash test.

FIG. 10 is a sectional view of an optical disk motor.

FIG. 11 is a diagram showing the results of a durability test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dynamic-pressure-type sintered oil-impregnated bearing unit 1a Dynamic-pressure-type sintered oil-impregnated bearing 1b Housing 2 Shaft 2a Outer peripheral surface 10 Bearing body 10b Bearing surface 10c Dynamic-pressure groove 12 Thrust bearing 12a Thrust washer 13 Seal 13a Oil absorbing member 13b Seal body O Oil

Claims (8)

[Claims] A bearing body formed of a sintered metal and having a bearing surface opposed to an outer peripheral surface of a shaft via a bearing gap is impregnated with lubricating oil or lubricating grease. A dynamic pressure type oil-impregnated bearing that supports the shaft in a non-contact manner by a dynamic pressure action generated by the relative rotation, a housing having one end opened and the above-mentioned dynamic pressure type oil-impregnated bearing mounted inside the inner diameter portion, and a housing on the other end side. A thrust bearing for supporting a shaft in a thrust direction, wherein a seal having an oil absorbing member for absorbing oil leaked from the bearing is provided at an opening of the housing. Oil-impregnated bearing unit. 2. The hydrodynamic sintered oil-impregnated bearing unit according to claim 1, wherein an inclined hydrodynamic groove is provided on the bearing surface of the hydrodynamic sintered oil-impregnated bearing. 3. The hydrodynamic sintered oil-impregnated bearing unit according to claim 1, wherein the oil absorbing member is made of a fiber material or a porous body. 4. The seal according to claim 1, wherein the seal includes a seal main body fixed to the housing, and the oil absorbing member disposed at least partially so as to face a space on the other end side of the housing with respect to the seal main body. 3. The hydrodynamic sintered oil-impregnated bearing unit according to any one of 3). 5. The hydrodynamic sintered oil-impregnated bearing unit according to claim 4, wherein the oil-absorbing member is provided in a space between the seal body and the open end surface of the hydrodynamic sintered oil-impregnated bearing. 6. The hydrodynamic sintered oil-impregnated bearing unit according to claim 4, wherein the oil absorbing member is provided on an outer peripheral portion of the shaft facing the seal body. 7. The hydrodynamic sintered oil-impregnated bearing unit according to claim 1, wherein the thrust bearing is constituted by a hydrodynamic groove provided on an end face of the shaft or an opposing portion thereof. 8. The thrust bearing is constituted by an inclined dynamic pressure groove formed asymmetrically on both sides in the axial direction on the bearing surface on the other end side of the housing, and the dynamic pressure groove is rotated relative to the shaft. 7. The dynamic pressure type sintered oil-impregnated bearing unit according to claim 1, wherein oil is fed to the other end of the housing in accordance with the above.