JPS63167112A - Dynamic pressure type field bearing - Google Patents

Abstract

PURPOSE:To obtain a dynamic pressure type fluid bearing with a sufficient amount of floating even in a low speed, by combining an unsymmetrical herringbone grooved radial bearing with a spiral grooved thrust bearing and injecting a lubricant so as to communicate with these bearings. CONSTITUTION:A thrust bearing member 12 has a spiral groove 12A. A shaft 13, which has on its periphery a herringbone groove 13A of unsymmetrical shape forming a bottom end surface 13B of the shaft 13 to be flatly further vertically machined, is adapted to the thrust bearing member 12. If rotation is started, the herringbone groove 13A of the shaft 13 gives a pressure as shown by P1 to a lubricant 14 in a bearing hole 11B by the pumping action.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a hydrodynamic bearing used in disk drives and the like.

Conventional technology In recent years, as disk drive devices such as floppy disks and original disks have become lighter, thinner, shorter, and smaller, the rotating main shaft, which is the heart of the disk drive, has become smaller and more sophisticated. There is a movement to adopt hydrodynamic bearings instead of bearings.

A conventional hydrodynamic bearing will be described below with reference to the drawings. FIG. 3 shows a cross-sectional view of a conventional hydrodynamic bearing. 1 is the frame.

1A is a sleeve, 1B is a bearing hole, and 2 is a thrust bearing member, which has two spiral groups.

3 is an axis, and 3A is a herringbone group.

4 is a lubricant, 6 is a hub, 6 is a motor rotor, and 7 is a motor stator. In many cases, the motor rotor 6 attracts the motor stator 7 with a force of about 1 kilogram or more, generating a large slamming force. 1A is a ventilation hole for discharging the air bubbles that have accumulated in the vicinity between the herringbone group 3A and the two members of the Snowy/Iraruguru group. The operation of the hydrodynamic bearing configured as described above will be described below. When the motor stator 7 is energized, a rotating magnetic field is generated, and the motor rotor 6 is connected to the shaft 3. It starts rotating together with hub 5. A recording/reproducing disk such as a magnetic disk or an optical disk (not shown) is attached to the hub 5. When rotation starts, the herringbone glue 3A of shaft 3 is attached to bearing hole 1.
A pumping pressure is applied to the lubricant 4 in B, and at the same time the spiral group 2A of the thrust bearing member 2 applies a pumping pressure to the lubricant 4 between the thrust bearing member 2 and the lower end face of the shaft 3, and the shaft 3 is 1A and the thrust bearing member 4 and rotates without contact.

Problems to be Solved by the Invention However, in the above configuration, since the herringbone group 3A of the radial bearing and the spiral group 3A of the thrust bearing are close to each other, a common lubricant 4 is used for each lubricant. There is.

Furthermore, in order to minimize the motor current consumption of the entire device, a low-viscosity oil or grease with low bearing friction torque must be used as the lubricant. As a result, the spiral group 2A generates a pressure P in Fig. 3 due to its pumping action, causing the spiral group to float in the thrust direction with a force F1 (more than 1 kg) in the figure, but the viscosity of the lubricant 4 Because of the low flying height, the flying height was only 1 to 2 micrometers, as shown by C1 in the figure, and at 1 o'clock there was not enough flying height, causing distortion and damage to the bearing.

Means for Solving the Problems In order to solve the above problems, a hydrodynamic bearing of the present invention includes a shaft, a sleeve, and a thrust member.

It has an asymmetrical herringbone group and a spiral group, and a lubricant is applied to communicate with both groups.

Operation The present invention uses the above-described configuration to ensure sufficient flying height of the thrust bearing due to the axial pressure generated by the asymmetrically shaped herringbone group of the radial bearing and the pressure generated by the spiral group of the thrust bearing, and the reliability is high even at low speed rotation. A dynamic pressure fluid bearing with high torque can be obtained.

Example Below, the first example of a hydrodynamic bearing according to an example of the present invention will be described.
This will be explained with reference to FIGS. In Figure 1, 1
1 is the frame, 11Au sleeve.

11B is a bearing hole, and 12 is a thrust bearing member having a spiral group 12Ai shown in FIG.

In FIG. 1, reference numeral 13 denotes a shaft, which has an asymmetrical herringbone group 13A on its outer periphery, and the lower end surface 1 of the shaft 13.
3B is machined flat and at right angles.

It is in contact with the thrust bearing member 12. 14 is a herringbone group 13A and a spiral group 12A
It is a lubricant that fills the whole area. 15 is a hub fixed to the shaft 13, and a recording/reproducing disk (not shown) is attached to this hub 1.
It is fixed on the top surface of 6 and rotates. 16 is a motor rotor, 1
7 is the motor stator, and the motor rotor 1θ is a permanent magnet, and the attraction force (approximately 1.6 kilograms) is indicated by arrow F2 in the figure.
is occurring. Reference numeral 18 denotes a mechanical seal such as a three-ring ring that prevents the pressure generated and the lubricant 14 from leaking.

The operation of the hydrodynamic bearing constructed as described above will be described below with reference to FIG. 1. Motor stator 17
When energized, a rotating magnetic field is generated and the motor rotor 16 is
Axis 13. It starts rotating together with the hub 16. A recording and reproducing disk such as a magnetic disk and an original disk (not shown) is attached to the hub 15. When rotation begins, the herringbone group 13A of the shaft 13 applies a pressure shown in P1 to the lubricant 14 in the bearing hole 11B by a pumping action. At this time, there are three conditions in terms of bearing configuration.

These are: (1) The herringbone group 13A has an asymmetrical shape in which the thrust bearing member 12 side is short.

(The lubricant 14 filling the herringbone group 13A also communicates with the thrust bearing member 12. is sealed by means such as incorporating a mechanical seal such as a 5-ring.By satisfying these conditions, the herringbone group 13A is formed as shown at P2 in the figure.
The lubricant in the gap between and spiral group 12A is P2.
pressure. On the other hand, the spiral group 12A generates a slight pressure of P3 due to rotation, and the maximum pressure of the thrust bearing is P2 + P3, generating force F2 in the figure, but at this time, due to the pressure P2 effect of the herringbone group, As shown at 02 in the figure, a sufficient bearing flying height of about 10 micrometers can be obtained. In addition, when designing the asymmetrical shape of the herringbone group 13A, the inner diameter of the bearing hole 11B is determined, and the pressure generated in the thrust direction by the herringbone group 13A is P2% in the figure.
If the thrust load is F1 in the figure, the pressure P2P2〈4×F
The pattern shape of the herringbone group 1aA is set to be 2/π×D2. If the pressure P2.

When P2>4×F2/πXD2, the flying height is too large and stable rotation may not be obtained.

In addition, in the hydrodynamic bearing of the present invention, a mass of air bubbles 19A in the lubricant near the boundary between the herringbone group 13A and the spiral group 12A is difficult to remove, and if a large amount accumulates, the bearing rigidity may decrease and rotational runout may occur. Ta. However, by making the herringbone ring meter or deeper and making it deeper than the conventional (3 to 6 micron meter), air bubbles can be gradually discharged to the outside of the bearing as shown in 19B and 19G in the figure as it rotates for a long time. confirmed. Therefore, in the present invention, the groove depth of the herringbone group 13A is set to 8 micrometers or more.

In the example, the shaft diameter is 4 mm and the number of rotations is 3.
00 to 500 rpm, and a low viscosity silicone grease (with a consistency of No. 1.6 and containing solid additives such as carbon fluoride) or a low viscosity fluorine grease (with a consistency of No. 0 or less) was used as the lubricant.

As described above, according to the embodiment of the present invention, by combining an asymmetric herringbone group radial bearing and a snow radial group thrust bearing and applying lubricant so that both groups communicate with each other, a sufficient thrust floating amount can be obtained even at low speeds. Therefore, a highly reliable hydrodynamic bearing can be obtained. Furthermore, since a low viscosity lubricant can be used, the bearing torque is small and the current consumption of the product can be reduced.

In the present embodiment shown in FIG. 1, the herringbone group 13A may be formed on the inner peripheral surface of the bearing hole 11B of the sleeve 11A. Further, the same applies even if the spiral group 12A is provided on the lower end surface 13B of the shaft 13.

Effects of the Invention As described above, the present invention combines an asymmetrical herringbone group radial bearing and a spiral group thrust bearing, and by applying lubricant so that they communicate with each other, a sufficient flying height can be obtained even at low speeds, and it is reliable. A hydrodynamic bearing with high performance and low torque can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a hydrodynamic bearing according to an embodiment of the present invention, FIG. 2 is a detailed view of the thrust bearing member in FIG. 1, and FIG.
The figure is a cross-sectional view of a conventional hydrodynamic bearing. 11... Frame, 11A... Three 7", 12... Thrust bearing member, 12A...
...Spiral group%13- ...Axis, 1
3A... Herringbone group, 14...
...Lubricant, 18...Mechanical seal. Name of agent: Patent attorney Toshio Nakao and one other person
---F L-4 1ri A--1 ring and roof. Fig. 2 1-11F U-4 LA, - One-pronged leaf ゛2°゛-Alternatively detailed copy τ 3A---Herring digit; ---r, pu・ni---@-taυ-da'f---5-g entered theda

Claims (2)

[Claims] (1) It has a shaft, a sleeve, and a thrust bearing member that contacts the shaft end surface and is fixed to one end of the sleeve, and has a herringbone group on either the outer periphery of the shaft or the inner periphery of the sleeve. a spiral group on either the end face of the thrust bearing member or the shaft; the herringbone group has an asymmetrical shape with a shorter end on the thrust bearing member side; and the end face of the sleeve and the thrust bearing 1. A hydrodynamic bearing, characterized in that a space between the members is sealed, and a lubricant is applied so that the herringbone group and the spiral group communicate with each other. (2) The hydrodynamic bearing according to claim 1, wherein the asymmetrical herringbone group has a depth of 6 micrometers or more.