JP2531315B2 - Rotating shaft support mechanism - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism capable of supporting a rotating shaft in ultrahigh vacuum and at high temperature. For example, it can be used for a rotating shaft portion of a molecular beam crystal growth apparatus (MBE), various measuring and analyzing apparatuses, MOCVD apparatus and the like.

[0002]

Bearings are used to support a rotating shaft. In many cases, rolling elements such as ball bearings and roll bearings are interposed between the inner ring and the outer ring to reduce the resistance. These ball bearings work effectively when used at room temperature and pressure. There are also sliding bearings that do not use rolling elements. However, ordinary bearings cannot be used under the conditions of ultra-high vacuum and high temperature. The higher the vacuum, the more friction. For this reason, a sliding motion of directly sliding the members becomes impossible. Even in the case of a ball bearing that uses rolling elements, the rolling frictional resistance itself increases as the degree of vacuum increases.

Therefore, as a bearing in an ultra-high vacuum, a sphere made of a metal sphere and a silver-coated or gold-coated sphere is used as a rolling element. It tries to reduce rolling resistance by using a flexible metal film. However, since it consists mainly of metal balls, it cannot withstand high temperatures. Thermal expansion and contraction remarkably occur between the two states of normal temperature and high temperature. The thermal expansion may cause a biting phenomenon, resulting in immobilization. Those using metal balls are at most 200 in ultra-high vacuum.
Can be used only up to ℃.

Ceramics are excellent in heat resistance and wear resistance. Bearings using ceramic balls have been developed for high temperatures. It is able to withstand high heat, but in an ultra-high vacuum, friction increases and wear is remarkable. Therefore, the life is abnormally short. After all, there are currently no bearings that can be used in ultra-high vacuum and at high temperatures. The inventor of the present invention considers that a bearing for supporting a shaft by rolling elements is not useful under such extreme conditions. It is an object of the present invention to provide a mechanism capable of rotatably supporting a shaft even in an ultrahigh vacuum and high temperature state.

[0005]

A rotary shaft support mechanism of the present invention is a mechanism for supporting a rotary shaft under high vacuum and high temperature, and a support cylinder surrounding the rotary shaft and a cylinder made by rolling a thin plate. It is composed of one or a plurality of flexible cylinders provided so as to be interposed between the support cylinder and the rotary shaft by deforming the cylindrical body, and a part of the flexible cylinder is fixed to the support cylinder. Part of the side is fixed to the rotating shaft, and the rotating shaft can be rotated within a certain angle range.

[0006]

The flexible cylinder formed by rolling a thin plate elastically connects the center rotation shaft and the support cylinder. Since it is elastically continuous, the rotating shaft can be rotated within a certain range. With the rotation of the rotary shaft, the thin plate forming the flexible cylinder flexes, and the contact surface between the flexible cylinder and the support cylinder changes. It is only the bending force of the thin plate that acts as resistance when rotating the rotating shaft. There is no slippage on the contact surface. This is an important feature. Conventional slide bearings and ball bearings have a large amount of resistance in a vacuum because of the presence of sliding and sliding friction. In the present invention, this is not the case, and since there is no slip, a sliding friction (sliding) resistance does not work. Therefore, the resistance does not increase even in an ultrahigh vacuum.

A single flexible cylinder may be used, but two or three flexible cylinders may be used with good symmetry. Further, in order to improve the balance, a number of flexible cylinders having different fixing points in the longitudinal direction may be provided. Since it is supported by the flexible cylinder, it is difficult to keep the rotary shaft in the exact center position.

However, since the rotary shaft is rotated from the outside by the rotary introducer, since the temperature of the portion where the rotary introducer is present is low, the rotary shaft can be supported by the conventional bearing. Even if it is cantilevered, since it is strictly supported by the bearing at the shaft end, even if the other end is supported by the flexible cylinder, the center position does not shift so much. The thin plate can be made of a refractory metal such as Ta. It must be a material that can withstand repeated bending.
If the temperature is relatively low up to 400 ° C, a thin stainless plate can be used. In the case of Ta, it can be used up to about 1500 ° C.

In addition to the drawback that the support point moves as described above, the support mechanism of the present invention may have a narrow range of rotation angle. The rotation angle range is determined by the outer diameter of the rotation shaft, the inner diameter of the support cylinder, the total length of the flexible cylinder, etc., but it is difficult to realize a rotation angle of one rotation or more (360 °). 9
This structure is suitable when a rotation angle of 0 ° to 180 ° is sufficient.

[0010]

FIG. 1 shows a rotary shaft support mechanism according to an embodiment of the present invention. This shows only the flange portion of the vacuum chamber, where the inside of the flange is vacuum and the outside is atmospheric pressure. The rotating shaft 1 at the center is surrounded by a flexible tubular body 2 on the outer periphery thereof. A cylindrical support cylinder 3 is installed outside the flexible cylinder 2. As shown in FIG. 2, three flexible cylinders are provided in this example. One end of the support cylinder 3 is fixed to the inner surface of the vacuum flange 3. A rotation introducing machine 5 is attached to the outside of the vacuum flange 3. The rotary shaft 1 and the introduction shaft 7 inside the vacuum are fixed by the fixing bracket 6.
Are linked. The rotation of the introduction shaft 7 is directly transmitted to the rotation shaft 1 inside the vacuum. The rotation introducing device 6 transmits a rotational force from the outside of the vacuum container to the inside of the vacuum container.

Rotary introducers are known. Since this is provided in a position which is in a vacuum but has a sufficiently low temperature, a metallic bearing can be used. Inside the rotary introduction machine, there are a bearing for holding the introduction shaft and a permanent magnet attached to the shaft. The outer cylinder also has a permanent magnet that can face it. By rotating the outer cylinder, the rotating shaft of the inner shaft can be rotated by the action of magnetic force. There are also rotation introduction machines that do not use magnets. The flexible tubular body 2 is formed by rolling a thin plate into a tubular shape, which is a cylinder in a free state, but it is thinly flexed and inserted between the support barrel and the rotary shaft. The flexible tubular body 2 is shaped like a blister.

A part of the flexible cylinder 2 is fixed to the inner wall of the support cylinder 3 by a fixing member 8. A part of the opposite side of the flexible cylinder 2 is also fixed to the rotating shaft 1 by the fixing fitting 9. The fixing member 9 prevents the shaft 1 and the flexible tubular body 2 from being displaced from each other. The fixing metal fitting 8 prevents the support cylinder 3 and the flexible cylinder body 2 from being displaced from each other. Since there is no deviation, no sliding friction resistance occurs.

FIG. 2 shows a state in which the rotary shaft 1 is just at the intermediate position. From this state, the rotary shaft 1 can be rotated left and right. When the rotary shaft 1 is rotated, the flexible portion of the thin plate moves, and the state shown in FIG. 3 is obtained. During this time, the rotating shaft 1,
The thin plate of the flexible cylinder and the inner wall of the support cylinder 3 are changed only in the contact and non-contact portions. With three flexible cylinders, the rotary shaft can rotate only 60 ° to 100 ° at most.

If it is desired to widen the range of the rotation angle, one flexible cylinder may be used for the entire circumference. Figure 4 shows such an example. The central angle surrounded by the flexible cylinder is about 240 °. The central angle is about 180 ° to 330 °. However, in this case, the elastic force acting around the rotary shaft 1 is not always balanced. There is a fear that the rotation axis will tilt because it is not balanced.

In order to avoid this, it is sufficient to divide the bending cylinder in the longitudinal direction and attach a plurality of bending cylinders so that the phases are different. FIG. 5 shows such a structure. This is because there are three equivalent flexible cylinders (2
a, 2b, 2c) attached. This balances the elastic force and prevents the shaft from tilting.

The rotary shaft support mechanism of the present invention is extremely novel in view of the conventional bearing. Since it is non-sliding, it is possible to overcome the problem of increased frictional resistance in ultra-high vacuum. However, there is a drawback that the rotation angle is limited. The limitation of the rotation angle can be easily understood by comparing FIG. 2 and FIG. 3, but it arises from the fact that the flexure-shaped flexible cylinder is fixed to the support cylinder by the fixing metal fitting 8. Such a restriction does not occur without the fixing fittings 8 and 9.

Assuming that the inner diameter of the support cylinder is d and the outer diameter of the rotary shaft is e, the flexible cylinder has a radius of curvature d in a portion in contact with the support cylinder, e in a portion in contact with the rotary shaft, and in a free space. The radius of curvature is r (= (d−e) / 2). Let P and Q be the centers of the bendable portion of the flexible cylinder at the radius r.
After all, the flexible cylinder can be deformed between PQ.
Let Θ be the effective center angle POQ of the flexible cylinder. The bending cylinder is Θ
The angular displacement can be made by the same way as a planetary gear, and the rotation axis rotates by (e + d) Θ / e.

If n flexible cylinders are used, the space between the rotary shaft and the support cylinder is divided into n equivalent spaces 2π / n. The maximum rotation amplitude can be obtained by using the largest bending cylinder. In this case, the maximum Θ _n is (P
Q) Since there are semi-circular arcs of radius r in both, Θ _n = 2π / n- (ed) / (e + d) (1). If this is converted into the maximum amplitude Φ of the rotation axis, Φ = (e + d) Θ / e = 2π (e + d) / ne− (ed) / e (2) The larger n (the number of divisions), the smaller the rotation angle, and the smaller d, the smaller the rotation angle. In practice, it is not possible to obtain the maximum amplitude determined by (2), so a value a little smaller than this must be satisfied.

[0019]

Although the frictional resistance is remarkably increased in an ultrahigh vacuum, in the present invention, since there is no sliding friction (sliding) portion, the resistance against rotational movement does not increase. Since the thin plate is made of a metal that can withstand high temperatures, it can withstand high temperatures. Thermal expansion occurs, but it is not a rigid body like balls, so it does not cause biting. It is possible to provide a reliable and inexpensive rotary shaft support mechanism for ultra-high vacuum and high temperature.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a rotary shaft support mechanism according to an embodiment of the present invention.

2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3 is a cross-sectional view of a state in which the rotary shaft has rotated from the state of FIG.

FIG. 4 is a cross-sectional view showing an example in which there is one flexible cylinder on the circumference.

FIG. 5 is a vertical cross-sectional view in the longitudinal direction showing an example in which one flexible cylinder is provided so that the phases thereof are different in the longitudinal direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotary shaft 2 flexible cylinder 3 support cylinder 4 vacuum flange 5 rotation introduction machine 6 connector 7 introduction shaft 8 fixing metal fitting 9 fixing metal fitting

Claims (1)

(57) [Claims] 1. A mechanism for supporting a rotating shaft under high vacuum and high temperature, comprising: a supporting cylinder surrounding the rotating shaft; and a cylindrical body formed by rolling a thin plate to be deformed between the supporting cylinder and the rotating shaft. And one or a plurality of flexible cylinders provided so as to intervene in the flexible cylinder, a part of the flexible cylinder is fixed to the support cylinder, and a part of the opposite side of the flexible cylinder is fixed to the rotating shaft. A rotating shaft support mechanism characterized in that the rotating shaft is configured to rotate within a certain angle range.