JPS62246619A - Dynamic pressure type fluid bearing device - Google Patents

Abstract

PURPOSE:To obtain a device to be formed into small thickness and high accuracy, by connecting a parallel groove with and between two helical grooves and filling a most area of the grooves with a lubricant. CONSTITUTION:While a shaft 23 is in rotation, bubbles 12E, 12F, contained in a lubricant, are discharged by two helical grooves 23A, 23B. This is because the lubricant of larger specific gravity is stronger pumped than the bubble of smaller specific gravity, as the result, the bubbles 12E, 12F are discharged. Bubbles 12G, contained in a central parallel groove 23C, are gradually discharged by the helical grooves 23A, 23B, and the bubbles in a bearing are almost removed. Accordingly, most of the whole unit of a bearing part is filled with the lubricant, and a disc device or the like can be oriented to small thickness and high performance.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a radial dynamic pressure type fluid bearing device used in a disk drive device or the like.

Conventional technology In recent years, floppy disks and hard disks.

As disk drive devices such as optical disks become lighter, thinner, and smaller,
In order to dramatically improve the size and performance of the rotating main shaft, which is the heart of the machine, there is a movement to adopt hydrodynamic bearings in place of conventional ball bearings and true circular slide bearings.

An example of the above-mentioned conventional hydrodynamic bearing device will be described below with reference to the drawings. 7 to 10 show cross-sectional views of conventional hydrodynamic bearing devices. 7th
In the figure, 1 is a frame, 1A is a sleeve, 1B is a bearing hole, 1C is a ventilation hole, 2 is a thrust member, 2A is a ventilation hole, 3 is a shaft, 3A.

3B is herringbone groove, 3C is pivot part, 4
5 is a lubricant, 5 is a table, 6 is a motor fist 3A-note, 7 is a motor stator, and 8 is a disk. The conventional example does not have the ventilation holes shown in FIG. In FIG. 8, 1 is a frame, 1A is a sleeve, 2 is a thrust member, and 4 is a lubricant, which is the same as in FIG. 9 is a shaft, and 9A and 9B are Herringhorn grooves. Two herringbone groups 9A and 9B are connected to each other.

In FIG. 9, 1 is a frame, 1A is a frame,
2 is a thrust member, which is the same as that shown in FIG.

1o is the axis and 1oA is the herringbone groove. This conventional herringbone group 10A has only one set.

In Fig. 10, 1 is a frame, 1A is a sleeve, 2
is a thrust member and is the same as in FIG. 11 is the axis,
11A is a groove.

Regarding the hydrodynamic bearing device configured as above,
The operation will be explained below. In FIG. 7, when the motor stator 7 is energized, the motor rotor rotates the shaft 3, table 5, and disk 8 at the same time. When rotation begins, herringbone grooves 3A and '3B release lubricant 4.
By generating a pumping pressure in the sleeve 1A
Rotates with high precision without contacting the object. The pivot portion 3C of the shaft 3 forms a pivot bearing with the thrust member 2. The disk rotated in this manner records and reproduces electrical signals using a magnetic head (not shown) or the like.

The ventilation hole 1C is for releasing the air inside the shaft shell 1B to the atmosphere and preventing a pressure difference from occurring.

The operations in FIGS. 8 to 1o are the same as in FIG. 7.

Problems to be Solved by the Invention However, with the above configuration, in the case of the conventional example shown in FIG. 7, a ventilation hole 1C is required, and the bearing span is There was a problem that sufficient bearing rigidity could not be obtained because the bearing length (or groove length) was 11+e2. Although ventilation holes are not required in FIGS. 8 to 10, there is a problem in that the bearing rigidity is not sufficient as described below.

In FIG. 8, when the shaft 9 starts rotating, air bubbles 12A, 12B contained in the lubricant 4 are discharged in the direction of the arrow in the figure due to the pumping action of the herringbone grooves 9A, 9B. be done.

Due to this discharge action, air accumulates in a band shape in the central part of the herringbone groove where the two sets are connected, indicated by e3 in the figure, and the bearing is filled with lubricant.
Since it is only 41+42, there was a problem that sufficient rigidity could not be obtained. The pressure generated at this time is as shown on the left side of the figure.

In Fig. 9, if the precision of the parts of the sleeve 1A is poor and there is a taper indicated by θ in the figure, when the shaft 1° begins to rotate, the entire herringbone groove will not be filled with lubricant, and Only the indicated part is satisfied. This is because the upper half of the herringbone groove has a large radial gap, making it difficult for pressure to increase, while the lower half has a small radial gap, making it easy for pressure to increase, so the pressure is balanced as shown on the left side of the figure. This is because it becomes stable.

In FIG. 10, even when the shaft 11 starts rotating, the parallel groove 11A has no effect of discharging bubbles, so the bubbles 12C and 12D are not completely discharged, but always come and go, and the lubricant is lost. Since the bearing was not filled sufficiently and many air bubbles were always mixed in, the rigidity of the bearing could not be obtained.

In this way, conventional bearing devices have insufficient rigidity, especially angular rigidity, when the bearing span is extremely short and the device is made thinner, resulting in large run-out and poor performance of disk drive devices, etc. The technical means of the present invention to solve the above-mentioned problems is to provide two helical grooves on either one of the abutment surfaces of the shaft and the sleeve, and to form two helical grooves between them. A set of groove groups is provided by connecting parallel grooves parallel to the axis.

Effect of the Invention The present invention has the above-mentioned configuration, in which the two helical grooves in the set of grooves discharge air bubbles in the lubricant and fill the grooves with the lubricant, and the central parallel groove fills the bearing hole a little. Since the taper is sufficiently filled with lubricant, a high-rigidity and high-precision hydrodynamic bearing device can be obtained even with a short bearing span.

EXAMPLE Hereinafter, a hydrodynamic bearing device according to one embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a sectional view of a hydrodynamic bearing device according to a first embodiment of the present invention. In FIG. 1, 21 is a frame, 21A is a sleeve, 21B is a bearing hole, 21 is a thrust member, 22A is a ventilation hole, 23 is a shaft, 23A and 23B are helical grooves, 23C is a central parallel groove, 24 is a lubricant, 2
5 is a table, 26 is a motor/rotor, 27 is a motor y
x data, 28 is a disk.

Regarding the hydrodynamic bearing device configured as above,
The operation will be explained below using FIGS. 1 to 4. First, FIG. 1 shows an embodiment of the cylinder 1 of the present invention. When the motor/stator 27 is energized, the motor/rotor 26 rotates the shaft 23, table 25, and disk 28 at the same time. When rotation starts, the helical grooves 23A, 23B and the central parallel groove 23C generate pumping pressure on the lubricant 24, thereby rotating with high precision without contacting the sleeve 21A. The pivot portion 23C of the shaft 3 constitutes a pivot bearing with the thrust member 22, and receives a thrust load. In this case, the thrust load is the rotating body (i.e. shaft 23. table 25° motor/rotor 26. disk 2
8) and the force with which the motor/rotor 26 attracts the motor/stator 27 is about 600 to 12 oQg. The disk 28 rotated in this way
Electric signals are recorded and reproduced using a magnetic head or an optical head unit (not shown). The ventilation hole 22A is for releasing the air in the pivot bearing portion to the atmosphere and preventing a pressure difference from occurring. In FIG. 2, while the shaft 23 is rotating, two helical grooves 23A, 23B discharge the air bubbles 12E, 12F contained in the lubricant 24. This pumps the lubricant 24 having a higher specific gravity more strongly than the bubbles having a lower specific gravity, and as a result, the bubbles 12E and 12F are expelled. The air bubbles 12G contained in the central parallel groove 23C remain in the lubricant at the beginning of rotation, but gradually form the helical grooves 23A and 23B.
The air bubbles inside the bearing are almost completely removed.

In this way, the bearing is entirely filled with the lubricant 24, as indicated by l in the figure, and high bearing rigidity is generated. The pressure distribution at this time is as shown in the second part on the left.

In general, the relationship between bearing length and bearing rigidity is such that, as shown in FIG. 3, when the bearing length is 1/2×l, when the bearing length is twice 1, the bearing rigidity is even greater than twice that. Therefore, much greater rigidity can be obtained than in the conventional example shown in FIG. 7, in which the bearing is divided into two parts.

This is an essential condition for achieving high rigidity with a short bearing span. Figure 4 shows a slight taper (
This is a diagram when there is θ) in the figure. In this case, the helical groove 23B is partially or
When the degree of taper is large, most of it is covered with air, but the central parallel groove 23C and the helical groove 23A are always covered with lubricant, so that sufficient rigidity as a bearing can be obtained. In addition, two helical grooves 23
A, angle β1 of 23B. β2 is selected to be 15 degrees to 45 degrees, which has a large bubble discharge effect.

As described above, according to this embodiment, by providing a parallel groove connected between two helical grooves and parallel to the axis, almost the entire bearing part is filled with lubricant.
Since sufficient rigidity can be obtained with a short bearing span, it is possible to achieve thinner disk devices and higher performance.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a diagram of the second embodiment. In the figure, 22 is a thrust member, and 29 is a shaft. In this embodiment, helical grooves 30D and 30E are provided on the inner surface of a sleeve 30A that is provided integrally with the frame 30.
Although a central parallel 11A groove 30G is provided, the feature of this embodiment is that three grooves 30D, 3oc, and 30E are provided in series.

The operation of the hydrodynamic bearing device configured as described above is the same as that of the first embodiment shown in FIGS. 1 to 4. In the second embodiment, as shown in FIG.
, 32B, and a pin 33 (for example, a known processing tool shown in Japanese Patent Publication No. 1988-6426) by inserting the machining tool 34 while applying a feed rate V and a rotational speed ω, three consecutive One groove aoD.

3oc and 30E are continuously formed by roughening. In the case of the first conventional example shown in FIG. 1, it is not possible to continuously roughen each groove.

As described above, by connecting the helical groove 30D, the central parallel groove 3oC, and the helical groove 3oE next to each other and providing three continuous grooves in one line, the grooves can be provided easily and at low cost. Other effects are the same as in the first embodiment.

Note that in the first embodiment, there are three grooves 23A.

23B and 23C were provided on the outer peripheral surface of the shaft, but sleeve 2
It may be provided on the inner peripheral surface of 1A.

In addition, in the second embodiment, three grooves 30D,
30C and 3oE are provided on the inner circumferential surface of the sleeve, but they may be provided continuously on the outer circumferential surface of the shaft 29.

Effects of the Invention As described above, the present invention provides a parallel groove connected adjacently between two helical grooves, so that most of the area of the groove is stably filled with lubricant. A thin, highly accurate hydrodynamic bearing device with short bearing span and high rigidity can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a hydrodynamic bearing device according to a first embodiment of the present invention, FIG. 2 is a sectional view of a main part of FIG. 1, and FIG. 3 is a bearing 13 of the hydrodynamic bearing device of the present invention. Page rigidity explanatory diagram, FIG. 4 is a sectional view of the main part of FIG. 1, FIG. 5 is a sectional view of a hydrodynamic bearing device according to the second embodiment of the present invention, and FIG. 6 is a groove shown in FIG. 5. An explanatory diagram of the processing method,
Fig. 7 is a sectional view of a conventional hydrodynamic bearing device, Fig. 8,
9 and 10 are cross-sectional views of other conventional hydrodynamic bearing devices. 21...Frame, 21A...Sleeve, 22...Thrust member, 23.29...
...Axis, 23A. 23B, 30D, 30E...Helical groove, 23G, 30G...Central parallel groove, 24...Lubricant, 26...Table. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure bearing length! (-) Fig. 4 2l-7L-z 21A--Three 7゛22--SuramataF ShumanX Fig. 5
22-m-thrust) 1129-axis? ? 2l--7L-me: Im, j2β-11-el f-1 1. -L Zu A-J warb lcl'A---m, 3 constant 2-s 9th) 8Pf1 3-axis 4-5 Myt@ 5-m-table &-t-tallof 7-1... ・S data special Kaisho 62-246G19 (6) E-7 and -heku- thrust 8P non-X

Claims (2)

[Claims] (1) A shaft, a sleeve, and a thrust member that abuts one end of the shaft, and one of the contact surfaces of the shaft and the sleeve has two helical grooves, and the center thereof has two helical grooves. a set of groove groups consisting of one parallel groove parallel to the axis connected adjacently to the helical groove, the groove group retaining a lubricant;
The two helical grooves have a predetermined angle with respect to the rotation direction so that pressure is generated in the intervening lubricant when the shaft rotates. (2) One of the two helical grooves and one of the parallel grooves connected to the center are continuous, and this continuous groove is
The hydrodynamic bearing device according to claim 1, having a set of groove groups including a plurality of grooves.