JPH1193941A - Dynamic pressure bearing device - Google Patents

Abstract

(57) [Problem] To provide a dynamic pressure bearing device used for various rotating parts, which can be used in a rotational speed range from about several hundred revolutions per minute to about 10,000 revolutions per minute. SOLUTION: By providing metal films 107 and 108 at the valleys of the herringbone grooves 105 and 106 on the inner periphery of the porous members 102 and 103, respectively, adverse effects due to pores of the porous member during high-speed rotation are provided. In addition, sufficient fluid lubrication by dynamic pressure is performed to prevent reduction in load-bearing rigidity, and during low-speed rotation, sufficient boundary lubrication by a sliding bearing is performed to improve wear resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing device used for a recording device in the OA and AV fields.

[0002]

2. Description of the Related Art In recent years, an optical media recording apparatus as a recording medium has a function of a CD-ROM, which is required to rotate the medium at a high speed in order to reduce an access speed, as typified by a digital video disk, and a conventional type. The role of a multifunction device incorporating the function of a CD for music in the low-speed rotation region is increasing. Needless to say, the spindle motor used for the spindle motor is required to be usable in a wide range of rotation speeds. The lower side is from a region of several hundred rotations per minute of a CD, and the upper side is a region corresponding to a CD-ROM. It is necessary to cover an area up to around 10,000 rotations per minute. Conventionally, the bearing portion of this type of spindle motor is generally made of an oil-impregnated porous material such as a sintered oil-impregnated bearing, but as the speed increases, the rotation accuracy is maintained and the rotation speed is proportional to the square of the rotation speed. Inferior in vibration resistance due to load imbalance and the like, for example, a tracking error, a focus error, and the like are increased, thereby causing a trouble in setting.
Therefore, even in the high-speed rotation range, low noise, low vibration, high accuracy,
Dynamic pressure bearings that can withstand increased load loads are attracting attention, but in general, the generated dynamic pressure is proportional to the number of revolutions.
When a dynamic pressure type bearing used in an extremely high speed range such as a CD-ROM is used in an extremely low speed range such as a CD, the generated dynamic pressure is extremely reduced, metal wear occurs and the life is shortened. cause. Conversely, if the design is such that the generated dynamic pressure equivalent to the CD-ROM specification at high speed is secured in an extremely low speed rotation region such as a CD, the bearing loss torque increases in the low speed rotation region, and the current only increases significantly. In the high-speed rotation region, the loss is further increased, and it becomes difficult to start the motor. Therefore, a method has been devised in which a bearing made of the oil-containing porous material is provided with a dynamic pressure function to prevent wear at low speed rotation. This type of dynamic pressure bearing device is disclosed in Japanese Utility Model Laid-Open Publication No. Sho 59-188322 and Japanese Patent Laid-Open Publication No. Sho 58-1721.
No. 9 is known.

FIG. 2 shows the structure of a conventional hydrodynamic bearing device. In FIG. 2, reference numeral 1 denotes a shaft, and herringbone grooves 9 and 10 are engraved on an outer peripheral portion thereof. Further, porous members 2 and 8 are arranged at positions facing the herringbone grooves 9 and 10, and the shaft 1 is suspended. The porous members 2 and 8 are fixed to the bracket 3. Further, a thrust plate 5 is disposed on the cover 4 disposed below the bracket 3,
The lower end of the shaft 1 forms a thrust bearing. Further, a coil 7 is provided on the cover 4,
An electromagnetic driving force is generated by the magnet 6 disposed at a position facing the coil 7 to rotate the shaft 1.
At this time, the shaft 1 is centered by the dynamic pressure generated in the herringbone grooves 9 and 10, and is rotated without contact. At the time of low-speed rotation, boundary lubrication as a sliding bearing is performed to prevent wear of the bearing.

[0004]

In the hydrodynamic bearing device having the above structure, stable lubrication in the bearing can be obtained in a low-speed rotation region where the boundary lubrication effect is emphasized, but the pores of the porous member are reduced to zero. The lubricant that should be collected at the center of the porous member in the herringbone groove by the rotation of the shaft due to the rotation of the shaft is drawn in or discharged by the holes, causing a reduction in the generated dynamic pressure, and Even if the rigidity is reduced and designed for use in the fluid lubrication region, it is actually used in the boundary lubrication region. Then, as the motor vibration increases at the time of high-speed rotation, the noise also increases, the rotation accuracy also deteriorates, the load-bearing load decreases, and a tracking error and a focus error increase in the set are caused. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dynamic pressure bearing device which has low noise, low vibration, high accuracy, and can withstand an increase in load.

[0006]

According to the present invention, there is provided a sleeve comprising an oil-containing porous member and a metal film provided on a valley of a shallow groove on an inner peripheral surface of the sleeve. .

[0007]

DETAILED DESCRIPTION OF THE INVENTION The invention according to claim 1 of the present invention comprises a shaft, a sleeve surrounding the shaft, having a cylindrical hole, and further having a shallow groove on the inner peripheral portion of the cylindrical hole. A dynamic pressure-type radial bearing portion between the shaft outer peripheral surface and the sleeve inner peripheral surface, and wherein the bearing portion is lubricated with a lubricant, wherein the sleeve is made of an oil-containing porous member. In addition to the structure, a metal film is provided on the valley of the shallow groove on the inner peripheral surface of the sleeve, and the hole area on the inner peripheral surface of the sleeve is reduced by the area of the groove. The amount of agent that is drawn in or discharged by the holes decreases, suppressing the decrease in the generated dynamic pressure, preventing the decrease in bearing stiffness, and performing sufficient fluid lubrication to increase the load load such as unbalance. Withstands low noise and vibration Precision can be achieved. Also,
On the other hand, at the time of low-speed rotation, sufficient boundary lubrication as a sliding bearing can be performed, and there is an effect that wear between metals does not occur and reliability is improved.

[0008]

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

FIG. 1 is a longitudinal sectional view of a hydrodynamic bearing device according to a first embodiment of the present invention.
4, porous members 102 and 103 are arranged on the inner periphery, and the shaft 101 is rotatably mounted on the shaft. Herringbone grooves 105 and 106 are engraved in the inner peripheral portions of the porous members 102 and 103, and a lubricant (not shown) is interposed between the shaft 101 and the porous members 102 and 103 so that a hydrodynamic bearing device is provided. Is composed. Further, the metal members 107 and 108 are provided in the valleys of the herringbone grooves 105 and 106, respectively.
And 103 have herringbone grooves 105 and 1
Since the surface is coated by the area of the metal films 107 and 108 provided in the valleys of 06, the pore area on the inner peripheral surface of the sleeve is reduced, and at the time of high-speed rotation, the lubricant is drawn in by the pores. It reduces the amount of exhaust, reduces the generated dynamic pressure, prevents the rigidity of the bearing from lowering, and performs sufficient fluid lubrication, so it can withstand increased load loads such as unbalance, and has low noise and low vibration. , High accuracy can be realized. Conversely, during low-speed rotation, sufficient boundary lubrication as a sliding bearing can be performed, and there is such an effect that wear between metals does not occur and reliability is improved.

In the above embodiment, as a method of forming the metal film material, a metal material such as electroless nickel may be provided by a method such as plating. Alternatively, after plating, the inner peripheral surface of the sleeve may be processed by polishing or the like to remove an excess metal coating layer on the inner peripheral portion of the sleeve except for the valley of the herringbone groove. Alternatively, the inner peripheral portion of the sleeve except for the valley portion of the herringbone groove may be masked and subjected to a method such as plating.

Although the example of the system in which the shaft rotates is shown, a shaft fixing system in which the shaft is fixed and the sleeve side rotates may be used.

Further, a dynamic pressure groove shape forming a bearing portion,
The type and the like of the lubricant used are appropriately changed within the scope of the claims.

[0013]

As described above, according to the present invention, the hole area of the inner peripheral surface of the sleeve is reduced by the area of the groove, so that the lubricant is drawn in or discharged by the holes during high-speed rotation. The reduction in the amount of friction generated, the reduction in dynamic pressure generated, the reduction in bearing stiffness can be prevented, and sufficient fluid lubrication can be performed.
Low noise, low vibration, and high accuracy can be realized. At the time of low-speed rotation, sufficient boundary lubrication as a sliding bearing can be performed, and there is obtained an advantageous effect that metal-to-metal wear does not occur, reliability is improved, and life is extended.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a hydrodynamic bearing device according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a conventional hydrodynamic bearing device.

[Explanation of symbols]

 101 Shaft 102, 103 Porous member 104 Bracket 105, 106 Herringbone groove 107, 108 Metal film

Claims (1)

[Claims] 1. A shaft comprising: a shaft; a sleeve surrounding the shaft and having a cylindrical hole; and a sleeve having a shallow groove in an inner peripheral portion of the cylindrical hole, and between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve. Constitutes a dynamic pressure type radial bearing, and
In the hydrodynamic bearing device in which the bearing portion is lubricated with a lubricant, the sleeve is formed of an oil-containing porous member, and a metal film is provided on a valley of a shallow groove on an inner peripheral surface of the sleeve. Dynamic pressure bearing device.