JPS63167121A - Dynamic pressure type field bearing device - Google Patents

Abstract

PURPOSE:To obtain a dynamic pressure type fluid bearing stable and high reliable even for high speed rotation, by providing a shaft, sleeve and a thrust bearing member and using grease, having density No.0 or less with fluorine oil serving as the basic oil, as the lubricant. CONSTITUTION:The whole unit of a herringbone groove 13A and a spiral groove 12A is filled with a lubricant 14. The lubricant 14 is grease manufactured by using a density increasing agent of teflon or the like for fluorine oil, and density of the grease 14 is set to No.0 or less for improving fluidity in a bearing clearance and decreasing bearing friction torque. If the fluorine grease of No.0 or less is used, necessary heat resistance as a dynamic pressure type fluid bearing is provided with no scattering and/or outflow, and stable rotary performance is obtained even for high speed rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a hydrodynamic bearing used in a disk drive device and the like and a lubricant therefor.

Conventional technology In recent years, as disk drive devices such as floppy disks and optical disks have become lighter, thinner, and smaller, the rotating main shaft, which is the heart of the device, has become smaller.In order to dramatically improve performance, conventional ball bearings and plain bearings have been There is a movement to adopt hydrodynamic bearings instead.

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

3 is the axis, and 3A is the Heson V' group.

4 is a lubricant, which is an oil such as a perfluoropolyether fully fluorinated oil (for example, Z-OS oil manufactured by Montefreos, hereinafter referred to as fluorine oil), mineral oil, or synthetic lubricating oil such as an ester type lubricant. 6 is the 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 thrust force.

One hole is a vent hole for discharging air bubbles accumulated near the Hesu/Gupone group 3A and the spiral group 2A. The operation of the hydrodynamic bearing configured as described above will be described below. Motor stator 7
When energized, a rotating magnetic field is generated, and the motor rotor 6,
It starts rotating together with the shaft 3 and 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 group 3A of the shaft 3 applies pumping pressure to the lubricant 4 in the bearing hole 1B, and at the same time, the two spiral groups of the thrust bearing member 2 pump the lower end surfaces of the thrust bearing member 2 and the shaft 3. Pumping pressure is applied to the lubricant 4 between them, and the shaft 3 floats on the sleeve and the thrust bearing member 4 and rotates without contact.

Problems to be Solved by the Invention However, the above configuration has the following problems. The first case is when the above-mentioned fluorine oil is used as the lubricant 14, but as shown in Fig. 4, when the rotation speed becomes high speed of several thousand rpm or more, the lubricant shown in A and B in the figure interacts with the atmosphere. 4A and 4B, the flow state changes from laminar flow to turbulent flow. This could cause the oil to scatter and cause oil to run out in the bearing. As shown in Figure 6, the principle of preventing lubricant from spilling is due to the force that tends to spill downward due to its own weight (ρq in the figure).
The component force of the centrifugal force (mrω2 in the figure) generated by rotation and rotation (
The oil tends to flow out due to the sum of mrω2groundθ in the figure, and is prevented from flowing out by the holding force of the oil's own surface tension (γ in the figure). , ω is the shaft angular velocity.) Fluorine oil has a surface tension γ
On the other hand, the lubricant cannot be retained against centrifugal force and turbulent flow at the gas-liquid interface under high-speed rotation conditions. , the lubricant could run out over time. In particular, a problem specific to hydrodynamic bearings is that if there is a herringbone group 3A near the gas-liquid interface (A and B in Figure 4), this will agitate the lubricant during high-speed rotation, increasing the outflow of the lubricant. was. As described above, a lubricant with excellent oil sealing properties, such as mineral oil or ester-based synthetic oil, has been desired.

The second case is when mineral oil or synthetic lubricating oil such as ester type lubricant is used as the lubricant 4, and although the oil seal performance is good, there are the following problems. When the bearing rotates at high speed, the bearing heats up to over 100'C due to heat generated by the bearing itself and the coil of the motor stator 7 near the bearing, but if continuous operation is continued at such high temperatures, the lubricant will deteriorate over time. In some cases, bearings deteriorated, and some of them even began to undergo thermal decomposition, making it impossible to guarantee long-term bearing performance. Particularly, a problem unique to this type of hydrodynamic bearing is that when one sleeve and the shaft 3 come into metal contact, the edges of the herringbone group 3A generate cutting wear, and the Because of this, there was a demand for a lubricant with good heat resistance, such as fluorine oil.

In view of the above-mentioned problems, the present invention provides a highly reliable hydrodynamic bearing that does not cause outflow of lubricant due to centrifugal force, has good heat resistance, and is highly reliable.

Means for Solving the Problems In order to solve the above problems, the hydrodynamic bearing of the present invention has a shaft, a sleeve, and a thrust bearing member, and uses a No. 0 or smaller grease with fluorine oil as a base oil as a lubricant. This is what was used.

Effects According to the present invention, with the above structure, the adhesive force of the grease prevents the lubricant from flowing out, and since fluorine oil is used as the base oil, a hydrodynamic bearing with excellent heat resistance and high reliability 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, 11A is the sleeve, 11B is the bearing hole, 1
2 is a thrust bearing member having a spiral-shaped dynamic pressure generating groove 12Ai. A shaft 13 has a herringbone-shaped dynamic pressure generating groove 13Af on its outer periphery, and a lower end surface 13B of the shaft 13 is machined to be flat and at right angles, and is in contact with the thrust bearing member 12. Reference numeral 14 indicates a lubricant that fills the entire herringbone group 13A and spiral group 12A, and reference numeral 110 indicates a vent hole for discharging air mixed inside the bearing. A hub 16 is fixed to the shaft 13, and a recording/reproducing disk (not shown) is fixed to the upper surface of the hub 15 and rotates. 16 is a motor rotor, 17 is a motor stator, and the motor rotor 16 is made of a permanent magnet and generates an attractive force (approximately 1.6 kilograms) as indicated by arrow F2 in the figure.

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/reproducing disk such as a magnetic disk or an optical disk (not shown) is attached to the hub 15. When rotation begins, the herringbone group 13A of the shaft 13 applies pumping pressure to the lubricant 14 in the bearing hole 11B, and the spiral group 12A of the mantle thrust member 12 also applies pumping pressure, causing the levitation to counteract F2 in the same figure. The shaft 13 generates a blade and the sleeve 1
1A, it floats on the thrust bearing member 12 and rotates without contact. In Fig. 2, the lubricant 14 is a fake grease made by using a thickener such as Teflon in fluorine oil (for example, Montefreos Z-03 or NOK Kluva S J-07, etc.), and the lubricant 14 is a grease made by using a thickener such as Teflon. The consistency of the grease 14 was set to 0 or less in order to improve the properties and reduce the bearing friction torque.

Fluorine grease 14 used in the hydrodynamic bearing of the present invention,
The differences in typical characteristics of conventional lubricants are shown below.

As shown in the table above, if you use fluorine grease of size 0 or less, (
1) Temperature characteristics of bearing torque, (threshold heat resistance, (3)
All three bearing performance requirements for oil sealing were satisfied. FIG. 2 shows the stable state of the lubricant 14 during high speed rotation. As described above, according to this embodiment, the lubricant 14 does not scatter or flow out, has the heat resistance necessary for a hydrodynamic fluid bearing, provides stable rotational performance even at high speed rotation, and provides a highly reliable dynamic bearing. A pressure type fluid bearing can be obtained.

Effects of the Invention As described above, the present invention makes it possible to obtain a hydrodynamic bearing that is stable and highly reliable even at high speed rotation by using fluorine grease with a stopper size of 0 or less.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a hydrodynamic bearing according to an embodiment of the present invention, Fig. 2 is a sectional view of a main part of Fig. 1, Fig. 3 is a sectional view of a conventional hydrodynamic bearing, and Fig. 4 is a sectional view of a conventional hydrodynamic bearing. Cross-sectional view of the main part of the figure, No. 6
The figure is a detailed view of part 0 of FIG. 4. 11... Frame, 11A mountain sleeve, 12
...Thrust bearing member, 12A... Thrust dynamic pressure generation groove, 13... - Shaft, 13A...
... Radial dynamic pressure generation groove, 13B ... - shaft end surface, 14 ... Fluorine grease. Name of agent: Patent attorney Toshio Nakao and one other person++
--Frame L-4 A-11 Frame L-Frame 3-Shaft 5-1 Hef. 0-171ta・υ-I 7-(-tastag Figure 4

Claims (1)

[Claims] a shaft, a sleeve, and a thrust bearing member that abuts the end surface of the shaft; a dynamic pressure generating groove is provided on either the outer periphery of the shaft or the inner periphery of the sleeve; the end surface of the shaft or the thrust bearing member 1. A hydrodynamic bearing device characterized in that either one of the two has a dynamic pressure generating groove, the base oil is perfluoropolyether fully fluorinated oil, and the grease is lubricated with a consistency of No. 0 or less.