JPS588981Y2 - Pivot bearing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in pivot bearing devices used in lubricating oil.

Generally, a pivot bearing device used in lubricating oil has a casing 1 formed in the shape of a cylinder with a bottom, as shown in FIG.
A lubricating oil 2 is contained therein, and a bearing seat 3 is installed therein, and a pivot shaft 5 connected to a vertical rotating body 4 is supported on the bearing seat 3 within the lubricating oil 2.

By the way, when this type of bearing device is used as a bearing for a rotating body that is operated at a rotation speed higher than a critical rotation speed, the casing 1 is usually connected to the casing 1 via a ball bearing 6, as shown in FIG. The housing γ is housed with a radial gap 8 between it and the housing γ, and lubricating oil is also interposed in the radial gap 8 to form a cylindrical oil film of the lubricating oil. The buffering effect absorbs the vibration energy generated in the rotating body 4 when the rotational speed passes through the critical rotational speed, thereby suppressing the vibration generated in the rotating body 4 during the passage.

However, as described above, this type of conventional bearing device which also has an allocation function has the following problems.

That is, the conventional device changes the gap length of the radial gap 8 between the outer surface of the side wall of the casing 1 and the inner surface of the side wall of the housing T when vibration energy is transmitted from the rotating body 4 via the pivot shaft 5. The squeezing effect of the oil film produced by this change absorbs vibration energy and dampens it.

With this method of damping vibration by changing the gap length,
When the gap length changes greatly and drastically, such as when passing the critical rotation speed, a pressure drop occurs due to the squeeze effect.
Bubbles are likely to be generated in the oil film, and the generation of these bubbles significantly reduces the buffering effect, and as a result, there is a high risk that the rotating body 4 will not be able to pass through the critical speed and that the rotating body 4 will be damaged. .

In particular, when the rotating body 4 is used in an atmosphere close to vacuum, the growth of bubbles is promoted, so in order to safely pass the critical rotation speed under such an atmosphere, precise balancing of the rotating body 4 is required. It took.

Furthermore, when used in a vacuum atmosphere, air bubbles contained in the lubricating oil have a sensitive effect on the reduction of the damping effect, so there is also the drawback that a long period of degassing is required after assembly.

The present invention was devised in view of these circumstances, and its purpose is to provide a pivot bearing that is easy to manufacture and that can suppress the vibration of the rotating body well even when the rotational speed is passed through the critical rotation speed. The goal is to provide equipment.

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

In Fig. 2, 11 is a flange 1 at the upper opening edge.
A base l is provided at the inner bottom of this casing 11, which is a casing having a lubricating oil 13 and containing a lubricating oil 13 inside.

The base 1 includes, for example, a protrusion 15 that protrudes from the inner surface of the bottom wall of the casing 11 to a large diameter, and an annular plate 1T fixed to the upper surface of the protrusion 15 with bolts 16.

A movable body U is disposed above the base H with a minute gap 18 of, for example, 20 to 200 microns between it and the upper surface of the annular plate 17.

The movable body U is roughly divided into a disc 20 facing the upper surface of the base U, and a bearing seat 21 fixed to the center of the upper surface of the disc 20.

The minute gap 18 is maintained between the disc 20 and the protrusion 15, supporting the thrust load applied downward and moving the movable body in the direction parallel to the base l and in the horizontal direction. Ball bearing 2 that supports movability
2 is a plurality of them interposed at equal intervals.

The disk 20 has a small diameter protrusion 23 on the lower surface of the center thereof.
A movable body 19 is formed on the protrusion 23 and the protrusion 15 of the base l opposite to the protrusion 23 at a predetermined position on the base l due to the magnetic attraction force generated between them.
Permanent magnets 25° and 26 are embedded in each to always restrain the l
It is.

Additionally, a recess 27 is formed in the center of the upper surface of the disc 20, and the bearing seat 21 is fitted and fixed into this recess 27.

A hemispherical recess 31 is formed in the center of the upper surface of the bearing seat 21 to support a curved surface 30 at the lower end of the pivot shaft 29 whose base end, that is, the upper end in the figure, is connected to the rotating body 28. .

Therefore, the movable body L'', the chair, the disk 20, and the bearing seat 17
And the total mass md of the permanent magnet 25 is now expressed as KS O, OIMR≦md≦MR, where MR is the mass of the rotating body 28, KS is the composite spring constant of the pivot shaft 29, and KR is the stiffness of the rotating body 28. It is set so that the conditions are satisfied.

Note that 32 in the figure indicates pins (these are provided at two symmetrical locations) for preventing the movable body l from rotating.

), and 33 indicates a hole provided in the disc 20 for inserting the pin 31 in a loosely fitted state.

Further, the lubricating oil 13 is contained at a level such that at least a portion below the curved surface portion 30 is submerged.

With such a configuration, when the lubricating oil 13 is housed in the casing 11 in the above relationship, the lubricating oil 13 penetrates into the minute gap 18 formed between the base l and the movable body U, and the minute gap 18 is filled with the lubricating oil 13. An oil film is formed inside the tank that extends only in the horizontal direction.

When the pivot shaft 29 rotates, the lubricating oil 13 penetrates between the curved surface portion 30 and the recessed portion 31, and smooth support is achieved by this lubricating oil.

Furthermore, when the rotational speed of the rotating body 28 connected to the pivot shaft 29 increases and attempts to pass the critical rotational speed, the rotating body 28
A large vibration energy is generated at 8, and this energy is transmitted to the movable body U through the pivot shaft 29 as a force that causes the movable body U to vibrate.

Therefore, the movable body U vibrates in the direction perpendicular to the axis, but since an oil film is formed in the minute gap 18 between the movable body L and the base L4, this oil film and the movable body U vibrate. Energy is absorbed by the viscous friction that occurs between the two.

In this case, the base Ll and the movable body 1'' are connected to the pivot shaft 29.
A minute gap 1B is set between the two so that they face each other in the axial direction, and an oil film extending horizontally is formed in the minute gap 18, and the movable body U is moved in a direction perpendicular to the axis. Since it is provided so as to be movable in the horizontal direction, no matter what vibration force is transmitted to the movable body U via the pivot shaft 29, the gap length of the minute gap 18 will not change. Since there is no generation of bubbles that are likely to be generated in the oil film due to pressure fluctuations when the gap length fluctuates drastically, a good vibration energy absorption function, that is, a vibration damping function can be always performed.

Of course, even in an atmosphere close to vacuum, a good vibration damping effect can be achieved simply by removing air bubbles within the minute gap 18 by short-term degassing.

In addition, since the facing surfaces of the base L'' forming the minute gap 18 and the movable body U may be flat, manufacturing can be greatly facilitated.

Since the mass md of the bent movable body U is set to the above-described value, the limiting action can be reliably exerted even when the rotating body 28 reaches the critical rotational speed, and as a result, the critical rotational speed can be safely reached. can be passed.

That is, the vibration system consisting of the rotating body 28 and the pivot bearing device can be represented by the equivalent circuit shown in FIG. 3, and from this diagram, the composite spring constant (KS) of the pivot shaft 29 can be determined as follows.

In addition, in FIG. 3 and equation (1), K R... Rigidity of rotating body 28 (kg/crrL) MR
... Mass of rotating body (ky - S 2 / crn ) KT
Aq: Equivalent rigidity of the end of the rotating body (kg/cIIL) K
s... Composite spring constant of the pivot shaft 29 (kg/crf
L) Kd...Support spring constant of movable body 19 (kg/cf
rL) md...Mass of moving part (kg・S2/cIf
L).

However, in this vibration system, generally KR>>Ks
>>Kd Therefore, Fig. 3 can be considered equivalent to the vibration system shown in Fig. 4. Therefore, in the vibration system shown in Fig. 4, the primary resonant frequency (fs) of the bearing part is If you ask for it, you will get .

Further, the critical resonance frequency (fc) of the rotating body 28 is approximately determined by the characteristics specific to the rotating body.

Here, when the rotating body 28 passes through the critical rotation speed, in order to transmit the force generated in the rotating body 28 to the bearing section with a gain of 1 or less and to cause the bearing section to perform a stable distribution action, the following relationship is satisfied. need to be done.

Substituting equations (2) and (3) into equation (4) above, we get:

Here, Kd and Ks are as described above, Ks>>Kd
Since there is the relationship, the above equation (6) becomes as follows.

On the other hand, from the perspective of mechanical strength, the mass of the moving part m
The lower limit of d is 0, OIMR≦md −...(8
) must be met.

Therefore, in order to satisfy the above formula (4), md should be It is necessary to set it within the range of .

In the device according to the present invention, since md is set within the range shown by the above equation (9), the allocation function can be reliably performed even when the rotating body 28 reaches the critical rotation speed.

Therefore, the critical rotation speed can be passed safely.

As detailed above, according to the present invention, not only can it perform well as a bearing, but it also prevents air bubbles from forming in the oil film used for distribution no matter what kind of vibration force is transmitted from the rotating body side. In addition, even when passing the critical rotation speed, the vibration energy can be well absorbed, and the vibrations generated in the rotating body can be sufficiently suppressed, so the rotating body can be It is possible to provide a pivot bearing device that enables ultra-high speed rotation and is also easy to manufacture.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing a conventional example, Fig. 2 is a cross-sectional view showing an embodiment of the present invention, Fig. 3 is an explanatory view showing a vibration system consisting of a rotating body and a pivot bearing device, and Fig. 4 is a cross-sectional view showing an embodiment of the present invention. FIG. 4 is an explanatory diagram showing a vibration system equivalent to FIG. 3; 11...Casing, 13...Lubricating oil, 14...
Base, 18--Minute gap, U...Movable body, 20-.
・Disk, 21...Bearing seat, 22...Ball bearing, 25° 26...-Magnet, 28...Rotating body, 29.
...Pivot axis.

Claims (1)

[Claims for Utility Model Registration] A base provided in a stationary state in lubricating oil, and a central portion of the upper surface disposed on the base with a small gap capable of forming an oil film extending only in the horizontal direction between the base and the base. a movable body having a bearing portion at the bottom; a pivot shaft whose tip end is supported by the bearing portion of the movable body while immersed in the lubricating oil and whose base end portion is connected to the rotating body; and the base. and a bearing that is interposed between the base and the movable body and supports the movable body so as to be movable in a horizontal direction; a magnet that restrains the movable body in a fixed position, and the mass of the movable part that is integral with the movable body is 0.01.
MR-K8MR (where KR MR is the mass of the rotating body, KS is the composite spring constant of the pivot shaft, and KR is the rigidity of the rotating body).