JPH04248014A - Dynamic pressure fluid bearing device - Google Patents

Abstract

PURPOSE:To obtain a dynamic pressure fluid bearing device in such a structure that lubricant, gradually running through a bearing gap, can be automatically refilled. CONSTITUTION:A shaft 1 is fitted to a sleeve 2, when it is relatively rotatable via a radial bearing R which has grooves at two places apart in an axial direction to generate dynamic pressure. At a position in a bearing gap 6 between two places, a lubricant reservoir 10 which has a larger gap than the bearing gap is provided, and the vicinity 11 of the bearing gap of the lubricant reservoir is connected to the bearing gap in a taper shape with a taper angle of 2-8 deg., narrower toward the bearing gap 6. Lubricant in the lubricant reservoir 10 is automatically refilled into the radial bearing gap 6 via the taper portion with a capillary phenomenon.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device used in information equipment, office machines, measuring equipment, etc.

0002

2. Description of the Related Art This type of hydrodynamic bearing device includes one for magnetic disks, for example. In recent years, the density of magnetic disks has become higher and higher, and as a result, bearing devices for magnetic disks are required to reduce the fluctuation of the non-rotational speed synchronous component of the bearing in order to improve the linear recording density. is required. In order to meet this demand,
A hydrodynamic bearing device with low vibration is suitable as an alternative to conventional ball bearings.

[0003] In a conventional hydrodynamic bearing device, cylindrical radial bearing surfaces are provided at two locations spaced apart in the axial direction on the inner diameter surface of a housing (sleeve) into which the shaft is fitted. . On the other hand, the shaft that fits into the sleeve is provided with radial bearing surfaces at two locations spaced apart in the longitudinal direction.
The radial bearing surface and the radial bearing surface face each other with a bearing clearance interposed therebetween to form a radial bearing. A herringbone-shaped groove for generating dynamic pressure is provided on the radial bearing surface, and the pumping action of the herringbone-shaped groove for generating dynamic pressure affects the extremely small amount of lubricant held in the radial bearing clearance. Hydrodynamic lubrication is achieved by generating pressure. The area between the two bearing gaps is a lubricant reservoir that is larger than the bearing gap. The portion of the lubricant reservoir near the bearing clearance has a tapered shape with a large taper angle that narrows toward the bearing clearance. If the lubricant in the bearing gap is lost due to leakage or evaporation, the bearing will soon cease to function as a bearing.

0004

However, in the conventional hydrodynamic bearing device described above, the lubricant in the lubricant reservoir is insufficiently supplied to the radial bearing clearance. The present invention
The purpose of the present invention is to provide a hydrodynamic bearing device with a special fluid reservoir that can feed lubricant in the radial bearing gap into the radial bearing clearance with a simple structure, and to solve the above-mentioned conventional problems. There is.

[0005]

[Means for Solving the Problems] According to the present invention, the inner diameter surface of the sleeve has cylindrical radial bearing surfaces at two locations separated in the axial direction, and the shaft that fits into the sleeve has a bearing clearance on the radial bearing surface. At least one of the radial bearing surfaces is provided with a herringbone-shaped groove for generating dynamic pressure, and the portion between the two bearing gaps is a bearing clearance. In a hydrodynamic bearing device in which the lubricant reservoir has a larger clearance, the portion of the lubricant reservoir near the bearing clearance has a tapered shape with a taper angle of 2 to 8 degrees that narrows toward the bearing clearance. It is characterized by connecting.

[0006]

[Operation] Since a lubricant reservoir with a gentle taper connected to the radial bearing clearance is provided, lubricant is replenished toward the radial bearing clearance by capillary action. Therefore, a hydrodynamic bearing device with good durability can be obtained.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view of an embodiment of the present invention, in which a cylindrical radial bearing surface 4 is provided at two locations spaced apart in the axial direction on the inner diameter surface 3 of a sleeve 2 into which a shaft 1 is fitted. It is provided in On the other hand, the shaft 1 is provided with radial bearing surfaces 5 at two locations spaced apart in the longitudinal direction, and the radial bearing surfaces 4 and 5 face each other with a radial bearing clearance 6 in between. It constitutes R. The radial receiving surface 5 is provided with a herringbone-shaped groove 7 for generating dynamic pressure. The grooves 7 for generating dynamic pressure have an asymmetric herringbone groove pattern in which the groove length on the shaft end side of the bent portion 7a is longer than the groove length on the opposite shaft end side of the bent portion 7a. . This makes it difficult for the lubricant in the radial bearing clearance 6 to leak toward the shaft end.

[0008] The inner diameter surface 3 of the sleeve 2 has an inner diameter larger than the inner diameter of the portion of the radial bearing clearance 6 (that is, the inner diameter of the radial bearing surface 4) between the two radial bearing gaps 6, so that the radial A lubricant reservoir 10 having a clearance larger than the bearing clearance 6 is provided. Moreover, the inner surface of the lubricant reservoir 10 has a tapered shape with a taper angle θ = 2 to 8 degrees such that the radial bearing clearance vicinity portion 11 narrows toward the radial bearing clearance 6 and is connected to the radial bearing clearance 6. ing. The reason why both ends of the lubricant reservoir 10 are tapered is to make it easier for the lubricant in the lubricant reservoir 10 to be pulled toward the narrower gap with the shaft 1 due to capillary action. . If the taper angle θ is smaller than 2°, this tensile force is too weak. On the other hand, if the taper angle θ is greater than 8°, the lubricant retention force at the larger gap will be weaker, and the lubricant will flow out due to gravity or external impact. In addition, when there is no change in the clearance between the shaft 1 and the sleeve 2, that is, when the taper angle θ is 0° and when it is smaller than 2°,
The flow of the lubricant decreases, making it difficult to smoothly supply the lubricant to the radial bearing clearance 6.

Note that an air vent hole 13 is provided in the middle of the lubricant reservoir 10, passing through the sleeve 2 in the radial direction and communicating with the inside of the hub 12. This air vent hole 13
This makes the air pressure inside and outside the sleeve 2 the same even if there is a temperature change, and prevents the lubricant in the radial bearing clearance 6 from leaking to the outside. The lower end of the shaft 1 is a flat thrust bearing surface 15
The thrust bearing surface 15 faces a thrust bearing surface 17 provided on a thrust plate 16 fixed to the sleeve 2, and the thrust bearing surface 15 and the thrust bearing surface 17 constitute a thrust bearing S. There is. Thrust bearing surface 17
Although not shown, a groove for generating dynamic pressure is provided, and a relief portion 18 having a larger diameter than the lower radial bearing surface 4 is provided at the lower end of the inner diameter surface 3 of the sleeve 2. However,
The groove for generating dynamic pressure of the thrust bearing S is located on the thrust bearing surface 15.
Alternatively, it may be provided on both the thrust bearing surface 17 and the thrust bearing surface 15.

This hydrodynamic bearing device is lubricated with an extremely small amount of lubricant held in the radial bearing clearance 6 and the thrust bearing clearance between the thrust bearing surface 15 and the thrust bearing surface 17 by capillary action. A hub 12 is fitted to the upper end of the shaft 1 so as to be able to rotate integrally with the shaft 1, and a magnetic disk (not shown) is attached to the hub 12.

The hub 12 is rotationally driven together with the shaft 1 by a drive motor M. A cylindrical rotor magnet 20 constituting the rotary drive motor M is attached to the inner diameter surface of the hub 12 so as to be able to rotate integrally therewith. A stator coil 21 facing the rotor magnet 20 is fixed to the cylindrical body of the sleeve 2 . Next, the effect will be explained.

Now, when the stator coil 21 of the rotary drive motor M is energized, a rotational force is generated in the rotor magnet 20 and the hub 12 rotates integrally with the shaft 1. When the shaft 1 rotates, the lubricant in the radial bearing gap 6 flows into the bent portion 7a of the herringbone groove due to the pumping action of the dynamic pressure generating groove 7 of the radial bearing R. The lubricant filling the bent portion 7a of the groove passes through the radial bearing clearance 6 and circulates to both ends of the radial bearing clearance 6 in the axial direction. In this embodiment, the pressure generated in the longer outer pattern grooves of the asymmetric herringbone dynamic pressure generating grooves 7 is greater than that in the shorter inner pattern grooves, and This effectively prevents lubricant from being sent out from the radial bearing R to the shaft end side.

In the thrust bearing S as well, the lubricant is circulated by the pumping action of the herringbone (or spiral) groove for generating dynamic pressure. In this way, in the radial bearing R, dynamic pressure is generated due to the pumping action of the groove 7 for generating dynamic pressure, and the pressure of the lubricant in the radial bearing clearance 6 increases, and the shaft 1 is pushed against the radial bearing surface 4 of the sleeve 2. Supported radially in contact. On the other hand, in the thrust bearing S, dynamic pressure is generated by the pumping action of the groove for generating dynamic pressure on the thrust bearing surface 17, and the shaft 1 is supported by the thrust shaft 17 of the thrust plate 16 in a non-contact manner.

Even if the amount of lubricant in the radial bearing clearance 6 decreases due to lubricant scattering out of the bearing and evaporation of the lubricant when starting and stopping the hydrodynamic bearing device and during rotation, The lubricant is automatically and effectively gradually replenished from the lubricant reservoir 10 through the radial bearing gap vicinity portion 11 by capillary action toward the narrower gap due to the taper. Therefore, there is no deterioration in bearing performance over a long period of time, and excellent durability can be obtained.

According to this embodiment, the lubricant reservoir 1
0 between the two radial bearings R, the span between the radial bearings R can be increased by the amount of the lubricant reservoir 10, and the bearing device can be made strong against external moments. Note that the groove 7 for generating dynamic pressure provided in the radial bearing R
The groove pattern does not necessarily have to be asymmetrical, and may be a symmetrical groove pattern.

Further, the groove 7 for generating dynamic pressure in the radial bearing R of the above embodiment is formed on the radial bearing surface 4 of the sleeve 2.
Alternatively, it may be provided on both the radial bearing surface 4 and the radial bearing surface 5. Furthermore, the groove 7 for generating dynamic pressure may be located only within the bearing clearance 6, and both ends of the groove 7 in the axial direction may protrude outward from the bearing clearance 6 in the axial direction. It may be located within the drug reservoir 10.

Further, in the above embodiment, shaft rotation is used, but sleeve rotation may also be used.

[0018]

[Effects of the Invention] As explained above, the hydrodynamic bearing device of the present invention has two radial bearing surfaces separated in the axial direction,
In the hydrodynamic bearing device, a herringbone-shaped groove is provided on at least one side of the radial bearing surface facing the radial bearing surface through the bearing clearance, and a lubricant reservoir is formed between the two bearing clearances. The portion of the lubricant reservoir near the bearing gap is connected to the bearing gap in a tapered shape with a taper angle of 2 to 8 degrees that becomes narrower toward the bearing gap. Therefore, even if the lubricant is gradually lost from the radial bearing clearance due to scattering, outflow, evaporation, etc., the lubricant held in the lubricant reservoir is forcibly replenished by capillary action, resulting in almost no deterioration in bearing performance and durability. A hydrodynamic bearing device with excellent properties can be obtained. Moreover, the manufacturing process is simple, the productivity is high, and the product can be provided at low cost.

[Brief explanation of the drawing]

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

[Explanation of symbols] 1 axis 2 Sleeve 4 Radial bearing surface 5 Radial bearing surface 6 Bearing clearance 7 Groove for generating dynamic pressure 10 Lubricant reservoir

Claims (1)

[Claims] Claim 1: The inner diameter surface of the sleeve has cylindrical radial bearing surfaces at two locations separated in the axial direction, and the shaft that fits into the sleeve has a radial bearing surface that faces the radial bearing surface with a bearing clearance therebetween. A herringbone-shaped groove for generating dynamic pressure is provided on at least one of the radial bearing surface and the radial bearing surface, and a portion between the two bearing gaps is provided with a lubricant with a gap larger than the bearing gap. In the hydrodynamic bearing device, which is a reservoir, a portion of the lubricant reservoir near the bearing clearance is tapered at a taper angle of 2 to 8 degrees, narrowing toward the bearing clearance, and connected to the bearing clearance. Hydrodynamic bearing device.