JPH10196657A - Oil retaining bearing unit and motor provided with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain fluid lubrication so as to attain required a high speed characteristic and rotational precision and to accomplish improvement in productivity and reduction in a cost at the same time by using a high density sintered oil retaining bearing provided with a specific effective porosity and density. SOLUTION: A slinger 8 is arranged on an opened end side of a bearing housing 7, an oil retaining bearing 2a is arranged at an interval from the slinger 8, an oil retaining member 3 and an oil retaining bearing 2b are arranged so as to be brought into tight contact with the oil retaining bearing 2a, and a thrust bearing 5 and a lid 6 are arranged at certain intervals from the oil retaining member 3 and the oil retaining bearing 2b, while lubrication oil 4a is injected to the position (e) in which a part of the oil retaining member 3 is impregnated. For preventing deterioration of an oil film pressure due to rotation of a shaft, a high density sintered oil retaining bearing, in which an effective porosity is less than 18vol.% while density is 6.8 or more, is used for each of the bearings 2a, 2b. As the bearings 5, 2b are always impregnated with the lubrication oil 4a, no shortage of oil is caused. According to a capillary phenomenon, the lubrication oil 4a is fed from the porous member 3, which is provided with a pore diameter larger than those for the bearings 2a, 2b, to the bearing 2a. In this way, compliance with high speed rotation is accomplished, and rotational precision can be improved, and reduction in a cost and improvement in productivity can be accomplished at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact motor and its bearing unit, and more particularly, to a CD-ROM device, a magnetic disk device, a DVD device, a laser beam printer,
The present invention relates to a bearing and a motor suitable for a TR or the like.

[0002]

2. Description of the Related Art CD-ROM devices, magnetic disk devices,
DVD device or laser beam printer, audio equipment,
Ball bearings and sintered oil-impregnated bearings are used as bearing units used in precision rotating small motors used in video equipment and the like. In addition, with high performance, miniaturization, and multifunctionality of devices, motors used in these devices have been required to rotate at high speed and with high accuracy. With respect to the high speed, for example, a VTR cylinder motor is used in a CD-ROM device at a rotational speed of 1800 to 9000 revolutions per minute, and a laser scanning polygon mirror motor is used in a thousands to tens of thousands revolutions per minute. The speed of disk drive motors is increasing from several hundred rotations to 10,000 rotations per minute, and all motors are required to rotate with high precision. At such a high speed rotation, it is difficult to cope with the ball bearing from the viewpoint of rotation accuracy, and a sliding bearing using oil as a lubricant has been adopted. In particular, recent CD-R
A sintered oil-impregnated bearing is used for a disk drive motor used in an OM device in terms of mass productivity and cost.

[0003]

The precision rotary motor used in the above-mentioned conventional apparatus is required to have high speed, high shaft runout accuracy, mass productivity and low cost.

For high-speed operation, a groove bearing having a shaft provided with a shallow groove for generating a dynamic pressure has been proposed and partially used as a bearing. This groove bearing is excellent in characteristics such as high-speed performance and shaft runout accuracy, but has a problem of high production cost and mass productivity. Sintered oil-impregnated bearings are low-cost slide bearings that are excellent in mass productivity, but cannot be expected to provide fluid lubrication only with oil impregnated in the bearings, and therefore are not used for motors that require high-speed rotation and high rotational accuracy. In the case of a sintered oil-impregnated bearing which has begun to be applied to a disk drive motor used in a recent CD-ROM device, the bearing gap is reduced to accurately support the disk with respect to the unbalance amount of the disk. And the shape of the bearings. However, in order to achieve high-speed and high-precision rotation using a plain bearing, it is necessary to consider that it can be used for fluid lubrication. However, a sintered oil-impregnated bearing basically has an effective porosity of 18 vol%. Due to the above-mentioned porous material, the oil film pressure generated on the sliding surface due to the rotation of the shaft is released from the pores, the load supporting capacity is reduced, and the wear and the life are increased due to wear. That is, the conventional sintered oil-impregnated bearing is a self-lubricating type bearing which is made by impregnating a porous bearing with a large amount of lubricating oil and lubricating the lubricating oil for a long time with this amount of lubricating oil. 30vol%, density 6.0 to 6.
However, conventional sintered oil-impregnated bearings with a density of about 6.7 or less are difficult to compensate for fluid lubrication only by devising the bearing dimensions and shape described above. Even if pressure occurs, if it exceeds a certain pressure,
Since the pressure does not rise due to the presence of the pores, the load bearing capacity is reduced, and high-precision rotation cannot be expected. Further, it is often difficult to retain the lubricating oil impregnated in the bearing depending on the configuration of the bearing unit, and it is difficult to maintain sufficient lubrication of the bearing for a long period by simply increasing the oil content, and wear of the bearing cannot be avoided.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described drawbacks of the prior art, and has as its object to provide a bearing having excellent high-speed performance and mass productivity and a motor for precision rotation using the bearing with high life and reliability. To provide.

[0006]

According to the present invention, unlike conventional sintered oil-impregnated bearings, fluid lubrication is achieved by using high-density sintered oil-impregnated bearings having an effective porosity of less than 18 vol% and a density of 6.8 or more. To achieve the required high speed and rotational accuracy, and at the same time to achieve mass productivity and lower costs. Further, when a high-density sintered oil-impregnated bearing having a density of 6.8 or more is used, the oil content is smaller than that of a conventional sintered oil-impregnated bearing. It is in close contact with the sintered oil-impregnated bearing to achieve fluid lubrication compensation, high speed, and rotational accuracy.

That is, according to the present invention, as a first means, the above-described high-density oil-impregnated bearing which rotatably supports a shaft in a bottomed bearing housing having one end opened and the other end closed is provided at intervals. A plurality of oil-impregnated bearings are provided, and a porous oil-impregnated member for supplying lubricating oil is adhered between the oil-impregnated bearings, and a thrust bearing is arranged at the bottom of the bearing housing. For lubrication of the bearing, lubricate the lubricating oil in advance to such an extent that a part of the porous spacer is immersed in the lubricating oil. Means for supplying lubricating oil to the oil-impregnated bearing on the open end side of the bearing housing by capillary action using a porous oil-impregnated member having a large diameter.

Further, according to the present invention, as a second means, a magnetic fluid is used as a lubricating oil in the above-described configuration, and a shaft and a magnetic fluid are magnetized by arranging a permanent magnet in a bearing housing, thereby forming a first means. As a result, higher sealing performance and fluid lubrication are ensured than the bearing unit configuration described above. In addition, the oil-impregnated bearing generates dynamic pressure on the sliding surface of the bearing by using the wedge shape of the oil film by making the inner diameter of the bearing a non-circular bearing, such as a three-arc bearing, by using a wedge-shaped oil film. In this way, the shaft can be supported with high precision.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a compact disk (CD) drive motor used for a CD-ROM device and a DVD device, showing one embodiment of the present invention. In FIG. 1, a bearing unit has a bottomed bearing housing 7 having one end opened and the other end closed by a lid 6, and an oil drain 8 and an effective porosity of 18 vo
Two high-density sintered oil-impregnated bearings (hereinafter referred to as oil-impregnated bearings) having a density of less than 1% and a density of 6.8 or more, a thrust bearing 5 and a porous oil-impregnated member 3 are arranged, and a suitable lubricating oil 4a is filled therein. ing. The bearing housing 7 includes a motor stator 12, a magnetic field generating coil 13, and a motor substrate 14.
Is arranged. The rotating member includes a multi-pole magnetized motor rotor 11, a rotor case 10, a CD holder 9, and a shaft 1, which are arranged to face a stator 12 of the motor. The shaft 1 has two oil-impregnated bearings 2a, 2b. It is rotatably supported by.

Here, the bearing unit will be described in more detail. FIG. 2 is a longitudinal sectional view of the bearing unit. The bearing housing 7 is provided with an oil drain 8 on the open end side, and is closely spaced from the first oil-impregnated bearing 2a. A porous oil-impregnated member 3 having a larger pore diameter than the oil-impregnated bearing, the second oil-impregnated bearing 2b, and a thrust bearing 5 and a lid 6 are arranged at an interval. And
The lubricating oil 4a is sealed from the thrust bearing 5 to a position indicated by e in the drawing to such an extent that a part of the oil-containing member 3 is immersed.

On the other hand, in a conventional bearing unit having an oil-impregnated bearing, smooth rotation is attempted only by lubricating oil impregnated in the oil-impregnated bearing. With only the lubricating oil impregnated in the bearing, the oil may run out, smooth rotation may not be performed, and the bearing may be worn. For this reason, in the present invention, in order to prevent such a shortage of oil, the lubricating oil 4a is sealed in advance from the thrust bearing 5 to the position of e in the drawing to such an extent that a part of the oil-containing member 3 is immersed as shown in the drawing. I have. Also, in order to prevent the oil film pressure from dropping due to the rotation of the shaft,
A high density sintered oil-impregnated bearing having an effective porosity of less than 18 vol% and a density of 6.8 or more is used. Specifically, copper is 90
In the case of a copper-based oil-impregnated bearing having a component of wt% or more, the effective porosity is 15 vol% or less, the density is 7.2 or more, and copper is 50% or less.
In an iron-copper-based oil-impregnated bearing containing 50% by weight of iron and 50% by weight of iron, the effective pore size is 15% or less and the density is 7.0 or more.
Next, the bearing unit will be described in more detail.

In the bearing unit of the present invention, since the thrust bearing 5 and the lower oil-impregnated bearing 2b are always immersed in the lubricating oil 4a, no oil shortage occurs. Also, the higher the speed of the oil-impregnated bearing 2a, the higher the oil-impregnated rate compared with the conventional oil-impregnated bearing. The porous oil-impregnated member 3 is provided with a large lubricating oil 4 from the oil-impregnated member 3 to the upper oil-impregnated bearing 2a by capillary action.
a is supplied. Therefore, in the bearing unit of the present invention, the shaft can be supported by smooth rotation by fluid lubrication even during high-speed rotation. This lubrication mechanism utilizes the so-called capillary phenomenon, in which a fluid moves from a larger pore size to a smaller pore size between porous materials. Further, in this configuration, as shown in FIGS. 2 and 3, a passage s is provided in the outer peripheral portions of the oil-impregnated bearings 2a and 2b in order to easily supply the lubricating oil 4a to the oil-impregnated member 3. This passage s is effective for increasing the suction of the lubricating oil 4a to the oil-impregnated member 3 on the lower bearing side, and is a path necessary for returning the lubricating oil 4a overflowing from the oil-impregnated bearing 2a to the oil-impregnated member 3 on the upper bearing side. It has become. Therefore, in the configuration of the bearing unit according to the present invention, even if the lubricating oil expands in volume due to a temperature rise during high-speed rotation, an appropriate amount of lubricating oil 4a is sealed so as to absorb the volume expansion. Even if the lubricating oil 4a overflows from the lubricating oil 2a, the passage s is formed between the oil-impregnated bearing and the bearing housing as described above.
Is provided, the lubricating oil 4a is collected on the spacer side,
Lubricating oil does not leak out of the bearing unit. Also,
The thrust receiver 5 is also always immersed in the lubricating oil 4a and is reliably lubricated. The novel structure of such a bearing unit and the effect of improving the density of the oil-impregnated bearing were confirmed using a CD-ROM, a disk drive motor for a magnetic disk device, and a polygon mirror motor. In particular, the oil-impregnated members sandwiched between oil-impregnated bearings are effective in compensating for fluid lubrication and prolonging life.
Experiments have confirmed that increasing the density of oil-impregnated bearings is effective in improving shaft runout, that is, improving rotational accuracy.

Further, in the present invention, in addition to increasing the density of the oil-impregnated bearings, the inner diameters of the oil-impregnated bearings 2a and 2b are formed as non-circular dynamic pressure bearings in order to increase the rotational accuracy. That is, as a non-circular type dynamic pressure bearing, specifically, a three-arc bearing as shown in FIG. 3 is used to generate a high dynamic pressure on the bearing sliding surface by utilizing a wedge effect of an oil film. 1 is accurately supported. In particular, even if the illustrated three-circle arc bearing having a large dynamic pressure effect is used for the high-density oil-impregnated bearing which is one of the features of the present invention, the decrease in the oil film pressure which has been a problem in the conventional low-density oil-impregnated bearing has almost been reduced. Therefore, the original performance of the dynamic pressure bearing can be exhibited.

Further, the thrust bearing 5 constitutes a pivot bearing in which the tip of the shaft 1 is spherical for the purpose of reducing friction torque, and the thrust bearing 5 is made of a resin having a low friction coefficient (for example, polyethylene, polytetrafluoroethylene). ,
Sliding materials such as polycarbonate and polyimide) are used. Therefore, the motor using the bearing unit according to the present invention has a good startability, can smoothly rotate even at a high speed, and has no oil leakage and no risk of bearing wear. Motor can be provided.

As a result of confirming the above-mentioned effects by experiments using a motor equipped with a bearing unit having a bearing diameter of 3 mm, a conventional lubricating oil was impregnated only in an oil-impregnated bearing without enclosing lubricating oil in the bearing unit. Immediately after starting, the motor using the bearing unit generates abnormal noise due to running out of oil.
It was found that if the rotation was maintained for a while, the lubricating oil would seep out due to the rise in the temperature of the bearing, and the rotation would shift to smooth. On the other hand, the motor using the bearing unit according to the present invention was operated with smooth rotation immediately after the start, and the effect of sealing the lubricating oil and the operation of the oil-containing member 3 were confirmed. Also, C
D is mounted on the CD holder 9 with a gap of about 0.1 mm, and the end user may attach a label to the CD, which may increase the amount of imbalance during rotation. For this reason, the load due to the centrifugal force increases as the rotation speed increases, and the oil-containing bearing may be worn. As described above, the oil-impregnated bearing according to the present invention hardly reduces the oil film pressure due to the high density of the oil-impregnated bearing. Therefore, it is confirmed that the shaft 1 is smoothly supported by the fluid lubrication, the rotation accuracy is maintained, and the bearing is not worn. did.

FIG. 4 is a CD-ROM showing another embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of a disk drive motor used for a ROM device and a DVD device. The embodiment shown in FIG. 4 has basically the same configuration as the embodiment shown in FIG. 1, and therefore the description of the configuration of the motor is omitted. And a magnetic fluid 4b is sealed as lubricating oil. FIG. 5 shows a longitudinal sectional view of the bearing unit. Here, a functional difference from the bearing unit shown in FIG. 2 will be described. In this configuration, the shaft 1 uses a magnetically permeable material such as SUS420J2, uses a material magnetized by the ring-shaped permanent magnet 15, and uses the non-magnetic material that is not magnetized by the ring-shaped permanent magnet 15 as the bearing housing 7. ing. In this configuration, the shaft and the magnetic fluid 4b are magnetized by disposing the ring-shaped permanent magnet 15 on the oil-impregnated bearing 2a. In the configuration of FIG. 2 described above, the lubricating oil 4a is supplied to the upper oil-impregnated bearing 2a by capillary action. However, in the bearing unit shown in FIG.
Is the upper oil-impregnated bearing 2a due to the magnetic attraction force of the permanent magnet 15.
As a result, the upper oil-impregnated bearing 2a can be more reliably lubricated. Further, since the shaft 1 is magnetized, the magnetic fluid 4b always adheres to the surface of the shaft 1, so that the oil film is surely formed even at the time of starting and stopping, and can be used with smooth rotation. Further, since the magnetic fluid has a lower surface tension than general lubricating oils, when it is used for a sintered oil-impregnated bearing having good impregnation and high density, there is an advantage that the oil-impregnated bearing is easily supplied.

The motor may be used vertically as shown in the figure, or horizontally (not shown). 5, the ring-shaped permanent magnet 15
This magnetizes the magnetic fluid 4b. Therefore,
Since the ring-shaped permanent magnet 15 not only supplies the magnetic fluid to the oil-impregnated bearing 2a but also has a function of sealing the shaft, it does not leak out of the bearing unit even when the motor is used horizontally. The material of the oil-impregnated bearing of the present invention may be selected according to the conditions of use of the motor, etc. In the configuration of FIG. 5, when the material of the oil-impregnated bearing is an iron-based oil-impregnated bearing, particularly, the upper oil-impregnated bearing 2a has a ring shape. Since it is directly magnetized by the permanent magnet 15,
The holding of the magnetic fluid 4b and the lubrication of the bearing sliding surface become more reliable. Specifically, in the bearing unit according to the present invention, as the material of the oil-impregnated bearing, in addition to the iron-based bearing, copper having good conformability of the bearing is 30 wt% to 60 wt%, and iron is 40 wt% to 70 wt%.
An iron-copper-based oil-impregnated bearing containing wt% as a component has the same effect.

[0018]

According to the present invention, a high-density oil-impregnated bearing is used, and lubricating oil can be supplied to the bearing by utilizing the capillary phenomenon of a porous material. Therefore, reliable lubrication can be performed and high-speed rotation can be accommodated. . In addition, since a decrease in the oil film pressure caused by the rotation of the shaft can be prevented, more reliable fluid lubrication is maintained, and rotation accuracy can be improved and bearing wear can be prevented. In addition to using a magnetic fluid as the lubricating oil and using the magnetizing action of the permanent magnet to ensure reliable lubrication and sealing by combining with a magnetically permeable shaft, there is no leakage of lubricating oil and a clean environment. Can be provided as a bearing unit for a motor suitable for use in a vehicle. In particular, in an oil-impregnated bearing unit using the above-described magnetic fluid as lubricating oil, a non-magnetic bearing housing, a permeable rotating shaft and the ring-shaped permanent magnet are combined to hold a magnetic fluid sealed in the bearing unit. With the seal function, the motor can be used both vertically and horizontally. further,
Since an oil-impregnated bearing that is low in cost and excellent in mass productivity is used, the production cost is low and it can be provided as a motor bearing suitable for mass production.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a compact disk (CD) drive motor used for a CD-ROM device using an oil-impregnated bearing unit according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a bearing unit showing one embodiment of the present invention.

FIG. 3 is a sectional view taken along line II of the bearing unit shown in FIG. 2;

FIG. 4 is a longitudinal sectional view of a compact disk (CD) drive motor used for a CD-ROM device according to another embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a bearing unit showing another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Shaft, 2a, 2b ... Oil-impregnated bearing, 3 ... Oil-impregnated member, 4a ...
Lubricating oil, 4b: magnetic fluid, 5: thrust bearing, 7: bearing housing, 15: permanent magnet.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Yoshihiro Sato 502, Kandachi-cho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratory, Hitachi, Ltd. (72) Inventor Seiichiro Terashima 1410 Inada, Inada, Hitachinaka City, Ibaraki Prefecture Visual Information Media Division (72) Inventor Makoto Kondo 520 Minorudai, Matsudo-shi, Chiba Hitachi Powder Metallurgy Co., Ltd. (72) Inventor Hidekazu Tokushima 520 Minordai, Matsudo-shi, Chiba Hitachi Powdered Metals Co., Ltd.

Claims (10)

[Claims] 1. An oil-impregnated bearing unit in which two oil-impregnated bearings for rotatably supporting a shaft are arranged in a bearing housing at an interval, the effective porosity of the oil-impregnated bearing is set to 18 vo.
An oil-impregnated bearing unit characterized by being less than l%. 2. An oil-impregnated bearing unit having two oil-impregnated bearings for rotatably supporting a shaft in a bearing housing, wherein copper is used as a main component of the oil-impregnated bearing.
0 to 60 wt%, iron is 40 to 70 wt%,
An oil-impregnated bearing unit, wherein the density of the oil-impregnated bearing is 6.8 or more. 3. An oil-impregnated bearing for rotatably supporting a shaft is disposed in a bottomed bearing housing having one end opened and the other end closed at intervals, and lubricating between the oil-impregnated bearings. A porous oil-impregnated member for oil supply is brought into close contact with the thrust bearing, and a thrust bearing is arranged at the bottom of the bearing housing. The open end of the bearing housing is set to the upper part, and the other end is set to the lower part. An oil-impregnated bearing unit in which the amount of lubricating oil in which the oil-impregnated member is immersed is sealed, wherein the effective porosity of the oil-impregnated bearing is less than 18 vol%. 4. The oil-impregnated bearing according to claim 3, wherein copper is 30 to 60 wt% and iron is 40 to 70 watts as main components.
An oil-impregnated bearing unit characterized in that the oil-impregnated bearing unit has a density of at least 6.8 and a density of 6.8 or more. 5. An oil-impregnated bearing for rotatably supporting a shaft in a bottomed bearing housing having one end opened and the other end closed has an effective porosity of less than 18 vol%, and the oil-impregnated bearings are spaced apart from each other. In the oil-impregnated bearing, a porous oil-impregnated member for supplying lubricating oil is tightly sandwiched between the oil-impregnated bearings, and a ring-shaped permanent magnet is arranged on the oil-impregnated bearing on the open end side of the bearing housing. A thrust bearing is arranged at the bottom of the bearing housing, and the opening end of the bearing housing is set at the upper part, and the other end is set at the lower part, and the amount of the magnetic fluid in which the porous oil-impregnated member is immersed is sealed to constitute a bearing unit. An oil-impregnated bearing unit characterized in that: 6. The oil-impregnated bearing according to claim 5, wherein copper is 30 to 60 wt% and iron is 40 to 70 watts as main components.
An oil-impregnated bearing unit characterized in that the oil-impregnated bearing unit has a density of at least 6.8 and a density of 6.8 or more. 7. A lubricating oil passage is provided at a part of a fitting portion between an outer peripheral portion of the oil-impregnated bearing and an inner peripheral portion of a bearing housing according to any one of claims 3 to 6. Oil-impregnated bearing unit. 8. An oil-impregnated bearing unit comprising a porous oil-impregnated member having a pore diameter larger than that of the oil-impregnated bearing according to any one of claims 3 to 6. 9. An oil-impregnated bearing unit according to claim 1, wherein said oil-impregnated bearing has a non-circular inner diameter. 10. A motor comprising the oil-impregnated bearing unit according to claim 1.