JPH0914186A - Turbo-molecular pump - Google Patents

Abstract

PURPOSE: To provide a turbo-molecular pump to reduce the occurrence of unfastening of a fastening part. CONSTITUTION: A fastening means 4 is provided to fasten together a rotary shaft 3 and a rotary vane 1 and the fastening means 4 is provided with a first screw and a second crew which form a male screw member for the rotary shaft 3 or the rotary vane. The first screw has a first male screw part and the second screw comprises a second male screw part having a female screw part engaged with the first male screw part and formed in an inner peripheral surface; and a third male screw part having an interior having a through-hole in which the first male screw is inserted and which is formed in the interior. A separation part is formed at least at a part between a second male screw part and a third male screw part. When the first screw and the second screw are joined in a screwed-in state with each other, the two male screw parts of the second screw are moved in different directions by the separation part. By anisotropy of a movement direction, a direction exerted on a substance to be fastened by each male screw part is differed and this constitution reduces the occurrence of unfastening exerted on a fastening means by means of a centrifugal force and vibration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pump for forming a vacuum state, and relates to a turbo molecular pump used for high vacuum exhaust.

[0002]

2. Description of the Related Art As a vacuum pump, there is a molecular drag pump which utilizes the transfer of gas molecules in one direction by the collision between a wall surface moving at high speed and gas molecules.
A turbo molecular pump using a turbine blade is known as this high-speed moving body. Conventionally, a rotary blade and a fixed blade provided so as to face the rotary blade are used as turbine blades that move at high speed, and the rotary blade is coaxially installed in a cylindrical fixed portion in which the fixed blade is installed on an inner peripheral surface. A turbo molecular pump having the above structure is known. In such a turbo molecular pump, there is a structure in which a rotary blade and a rotary shaft are coupled by fastening. Conventionally, in the coupling structure of a rotary blade and a rotary shaft by such fastening, assembly is usually performed while controlling fastening torque of fastening components such as screws.

The loosening of the fastening component caused by vibration or the like is suppressed by the frictional force that accompanies the reaction force generated when fastening the spring washer and the screw component.

[0004]

However, the conventional turbo-molecular pump has a problem that the fastening parts are loosened. The rotary blades of the turbo molecular pump are rotated at high speed of tens of thousands of times per minute when the turbo molecular pump is used, and are rapidly accelerated and decelerated when starting or stopping. Therefore, the fastening component is always subjected to centrifugal force in use, and the centrifugal force fluctuates due to acceleration and deceleration. The fastening component is subjected to a stress in the lateral direction with respect to the axial direction due to the centrifugal force and its fluctuation, and the spring washer and the screw component are slipped.

Further, the rotor blades vibrate in the rotation axis direction due to pressure fluctuations on the intake side and exhaust side of the turbo molecular pump,
As a result, the fastening component is also stressed in the axial direction, and the spring washer and the screw component are loosened. this,
When the fastening parts are loosened, contact occurs between the rotary blades and the fixed blades, and seizure or noise occurs, which causes a failure. Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional turbo molecular pump and to provide a turbo molecular pump capable of reducing looseness of fastening parts.

[0006]

SUMMARY OF THE INVENTION The present invention is a turbo-molecular pump having a fastening means for fastening a rotary shaft and a rotary blade, the fastening means being a male screw member for the rotary shaft or the rotary blade. It has a screw and a second screw. The first screw has a first male thread and the second screw has
A second male screw portion having an inner peripheral surface having a female screw portion to be screwed with the first male screw portion, and a third male screw portion having a through hole for passing the first male screw portion therein, A separating portion is formed at least in part between the second male screw portion and the third male screw portion. Then, the first screw portion and the second screw portion are screwed with each other to change the contact directions of the second male screw portion and the third male screw portion with respect to the rotary shaft or the rotary blade, thereby achieving the above object. is there.

In the fastening means of the present invention, the rotary shaft and the rotary blades are fastened. Then, the object to be fastened is on the female screw side, and the fastening means is on the male screw side for fastening.

By making the second male screw portion and the third male screw portion contact differently in the direction of contact with the object to be fastened, the fastening force of the fastening means having different acting directions is formed on the object to be fastened. It is possible to reduce loosening of fastening parts due to vibration and centrifugal force.

According to a first embodiment of the present invention, a separation surface formed between a second male thread portion and a third male thread portion has a cut surface having an angle other than a right angle with the axial direction of the first screw. According to this, the second male screw portion and the third male screw portion can be unidirectionally contacted with the object to be fastened in different directions.

According to the second embodiment of the present invention, the third male screw portion has a notch portion in the axial direction of the screw, whereby the gap between the third male screw portion and the female screw of the object to be fastened can be reduced. In addition, the gas remaining in the screw portion can be degassed.

According to a third embodiment of the present invention, the separating portion formed between the second male screw portion and the third male screw portion is constituted by a notch formed on the side surface of the second screw. Thus, the inclination directions of the second male screw portion and the third male screw portion with respect to the object to be fastened can be different.

According to a fourth embodiment of the present invention, the separating portion formed between the second male screw portion and the third male screw portion is constituted by an annular cutting surface, whereby
The second male screw portion and the third male screw portion can be different in the direction of the acting force on the object to be fastened.

[0013]

A fastening hole is formed in the object to be fastened of the rotary shaft and the rotary blade, and a female screw is formed on the inner peripheral surface of the hole. On the other hand, the first screw of the present invention is inserted into the through hole of the second screw of the present invention, and the first male screw portion of the first screw and the female screw portion of the second screw of the present invention are screwed together. Thus, the first screw and the second screw are integrally formed.

The integrated first screw and second screw are inserted into the fastening hole of the object to be fastened, and the second male screw portion and the third male screw portion of the second screw are screwed into the female screw in the fastening hole. Let Then, when the first screw is screwed in, the second male screw portion and the third male screw portion of the second screw move in different directions due to the separating portion formed therebetween. Due to the anisotropy of the moving direction, the direction in which the second male screw portion acts on the object to be fastened and the direction in which the third male screw portion acts on the object to be fastened can be made different from each other. The loosening that acts on the fastening means due to vibration can be reduced.

Further, the notch formed in the axial direction of the screw of the third male screw portion moves in a direction to widen the notch interval by screwing the first screw, and joins the third male screw portion and the female screw. The gap formed in the portion can be connected to the outside, and the residual gas trapped in the portion can be released to the outside for degassing.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment of the Present Invention) The configuration of the first embodiment of the present invention will be described with reference to FIG. In FIG. 1, a turbo molecular pump of the present invention stores a rotary blade 1 and a fixed blade 2 in a casing so that the blade portions face each other coaxially, and the rotary blade 3 is installed at an axial position. It can be rotated by. The rotary blade 1 is attached to one end of the rotary shaft 3 by a fastening means 4, and the drive motor 5 drives the rotary shaft 3 to rotate at high speed. Also, the rotating shaft 3
Are supported by bearing means such as a radial magnetic bearing 6 and a thrust magnetic bearing 7. The high-speed rotation of the rotary blade 1 causes the gas molecules to move with the fixed blade 2, so that the gas sucked from the intake port 9 is exhausted from the exhaust port to perform the exhaust action.

Since the structure of this turbo-molecular pump is a commonly known structure, its detailed description will be omitted. In the turbo molecular pump of the present invention, the rotary blade 1 and the rotary shaft 3 are composed of separate parts, and these parts are fastened by the fastening means 4 to be integrated. The fastening means 4 is installed at a position within a circle indicated by A in FIG. FIG. 2 is a schematic view showing these relations. The fastening means 4 has a rotary blade 1 and a rotary shaft 3 as an article to be fastened, and a female screw portion formed on the fastened object side and a male screw portion of the fastening means 4. The binding action is performed by coupling with.

FIG. 3 is a perspective view for explaining the construction of the first embodiment of the fastening means 4 of the present invention. In FIG. 3, the fastening means 4 includes a first screw 11 and a second screw 21, and constitutes a male screw portion for a female screw portion formed on the rotary blade 1 or the rotary shaft 3 side. The first screw 11 has a first head 13 formed at one end and a first head 13 at the other end.
Is formed with a male screw portion 12. On the other hand, the second screw 21
Is provided with two parts which are separated from each other at least in part and are in an adjacent state, and one of them has a second male screw part 22.
And a third male screw portion 23 is formed on the other side.

On the side where the second male screw portion 22 is formed, a female screw portion 24 is formed on the inner peripheral surface thereof so as to be screwed with the first male screw portion 12 of the first screw 11. A second head 27 is formed at one end on the side where the third male screw portion 23 is formed.
A through hole 26 is axially formed from 7 to the other end. Through the through hole 26, the first male screw portion 12
Can be passed through to the female screw 24 side. Further, the third male screw portion 23 is formed with a cutout portion 28 that communicates with the through hole 26 along the axial direction.

Incidentally, in the first embodiment shown in FIG.
The separating portion 25 is configured by an oblique cutting surface having an angle other than a right angle with the axial direction of the second screw 21, whereby the second screw 21 has a second male screw portion 22 and a third male screw portion 22. Is divided into two parts, that is, the part provided with the male screw part 23. The first screw 11 and the second screw 12 can be formed of a metal material, such as stainless steel, that releases a small amount of gas in a vacuum and has sufficient strength. In addition, in the first screw 11, the through hole 14 may be formed in the axial direction in order to degas the gas remaining in the screw hole on the rotor blade side.

Next, the operation of the embodiment of the present invention will be described with reference to FIG. FIG. 4A shows a side of the rotary blade 1 and the rotary shaft 3 to be fastened and a female screw portion 3 formed on the side.
1, the female screw portion 32 is shown. FIG. 4B shows the first screw 11 and the second screw 21 shown in FIG. FIG. 4C shows a fastening state obtained by attaching the first screw 11 and the second screw 21 to the object side and screwing in the first screw 11. FIG.
(D) shows the contact state of the first screw 11 and the second screw 21 with the object side in the fastened state. FIG.
As shown in (a) of FIG. 3, the rotary blade 1 and the rotary shaft 3 are used as the object side to be fastened, and holes and through holes for mounting the fastening means 4 of the present invention are formed on the fastened side, and the inner peripheral surface thereof is formed. The female screw 31 and the female screw 32 are threaded on the.

By the fastening means 4, the rotary blade 1 and the rotary shaft 2
4B, the first screw 11 is inserted into the through hole 26 of the second screw 21, and the first male screw portion 12 of the first screw 11 is inserted. And the second screw 21
Screwing the female screw 24 of the first screw 11
And the second screw 21 are integrated. Next, the integrated first screw 11 and second screw 21 are inserted into the through holes and holes formed in the rotary blade 1 and the rotary shaft 2, and the second screw 21
The second male screw part 22 and the female screw 31 are screwed together by turning the second head 27 of the third male screw part 2
3 and the female screw 32 are screwed together. By this screwing, the first
The screw 11 and the second screw 21 are attached to the rotary blade 1 and the rotary shaft 3.
Will be loosely tightened.

After that, when the first screw 11 is screwed into the object to be fastened, the first male screw portion 12 and the female screw 24 are screwed together. In this screwing, since the second head 27 is in contact with the rotating shaft 3 side, the portion provided with the third male screw portion 23 is fixed at the corresponding contact position. Therefore, the portion provided with the other second male screw portion 22 receives the force toward the rotating shaft 3 side. As a result, the rotary blade 1 also receives a force toward the rotary shaft 3 side, and a fastening force for fastening the rotary blade 1 and the rotary shaft 3 is generated. Further, in the embodiment of the present invention, the portion having the second male screw portion 22 and the portion having the third male screw portion 23 have the separating portion 2 formed by the cross section in the oblique direction.
Since they are adjacent to each other via 5, due to the fastening force,
Each of them receives forces in different directions as shown by arrows C and D in FIG.

The force in the direction of arrow C is applied to the second male screw portion 22.
By acting on the portion provided with, the separating portion 25 is slid to the lower right direction in the figure, the right side surface thereof is brought into close contact with the female screw of the object to be fastened (41 in the figure), and conversely, the left side surface is fastened. When it is separated from the female screw of the object (42 in the figure), it is in a state of one side contact. On the other hand, the force in the direction of the arrow D acts on the portion provided with the third male screw portion 23, slides the separating portion 25 in the upper left direction in the drawing, and makes the left side surface thereof closely contact with the female screw of the object to be fastened. (43 in the figure), on the contrary, the right side surface is separated from the female screw of the object to be fastened (44 in the figure), and a state of one-sided contact in the opposite direction is achieved.

As a result, the directions in which the male and female threads of the screw are abutted are opposite on both sides of the screw, and at least one of them acts against the centrifugal force and vibration against the external force. It is possible to prevent loosening of the fastening.

Further, the notch 28 formed in the side portion of the third male screw portion 23 along the axial direction up to the through hole 26 has a space of the thread groove portion between the third male screw 23 and the female screw 31 and the outside. To form a communication part through which the residual gas left in the space of the thread groove part is taken out through the communication part, and perform a degassing action in a vacuum atmosphere to improve the exhaust accuracy. You can

(Second Embodiment of the Present Invention) A second embodiment of the present invention will be described with reference to FIG. The second embodiment of the present invention has the same configuration of the turbo molecular pump shown in FIG. 1 and the relationship between the fastening means and the object to be fastened shown in FIG. Only explained. FIG. 5 is a perspective view and a sectional view for explaining the configuration and operation of the second embodiment of the fastening means 4 of the present invention. In FIG. 5, the fastening means 4 is the second screw 2
1 and a first screw 11 (not shown) to form a male screw portion for a female screw portion formed on the rotary blade 1 or the rotary shaft 3 side. Since the first screw 11 of the second embodiment is the same as that of the first embodiment, only the second screw of the fastening means 4 is omitted in FIGS. 5 (a) and 5 (b). Shows.

The second screw 21 is provided with two parts which are adjacent to each other with at least a part of the separation part 55 formed, one of which is formed with the second male screw part 22 and the other of which is formed with the third male screw. The part 23 is formed. The separating portion 55 has an arc shape in which a cut is made in the peripheral portion of the second screw 21 to join the remaining peripheral portions, and the side having the second male screw portion 22 projects to the side having the third male screw portion 23. Is forming. On the side where the second male screw portion 22 is formed, a female screw portion 24 is formed on the inner peripheral surface thereof so as to be screwed with the first male screw portion 12 of the first screw 11. Also, the third male screw part 23
The second head 27 is provided at one end on the side where the
Is formed, and a through hole 26 is opened in the axial direction from the second head 27 to the other end. This through hole 26
The first male screw portion 12 can be passed to the female screw 24 side via the.

Further, the third male screw portion 23 has a separating portion 5
A cut portion 28 is formed from the cut portion of 5 to the through hole 26 along the axial direction. In order to fasten the rotary blade 1 and the rotary shaft 2 by the fastening means 4 of the second embodiment, as in the first embodiment, the first screw 11 and the second screw 21 are integrated and then the rotary blade is joined. 1 and the rotary shaft 2 are inserted into the through holes and the holes, and the second male screw portion 22
The first screw 11 and the second screw 21 are loosely fastened to the rotary blade 1 and the rotary shaft 3 by screwing the male screw with the female screw 31 and with the third male screw portion 23 screwing with the female screw 31.

Thereafter, by screwing the first screw 11 into the object to be fastened, the portion having the second male screw portion 22 and the portion having the third male screw portion 23 are fastened to the object to be fastened. And act in opposite directions to each other to generate a fastening force that fastens the rotary blade 1 and the rotary shaft 3. Further, in the second embodiment, the part having the second male screw part 22 and the part having the third male screw part 23 are separated from each other by the notch 5 formed.
5 are adjacent to each other, the arrow E in FIG.
The third male screw portion 23 receives forces in different directions as indicated by arrows F and G in the figure by the fastening force indicated by.
The force in the direction of the arrow E acts on the portion provided with the second male screw portion 22 in a direction to reduce the distance between the cut portions of the separation portion 55. Then, the portion provided with the second male screw portion 22 and the portion provided with the third male screw portion 23 receive the action forces that rotate in opposite directions with the vicinity of the coupling portion of the separating portion 55 as a fulcrum, and are respectively reversed. It becomes a state of one-sided contact.

As a result, the directions in which the male screw and the female screw are abutted on opposite sides of the screw are opposite to each other, and at least one of them acts against the centrifugal force and vibration against the external force. It is possible to prevent loosening of the fastening. Further, when the portion having the second male screw portion 22 and the portion having the second male screw portion 22 come into contact with each other at the separating portion 55, the gap between the notches 28 widens, and the third male screw 23 and the female screw 31 are separated from each other. A communication portion is formed which allows the space of the thread groove portion between the space and the outside to communicate with the outside. Then, the residual gas left in the space of the thread groove portion can be taken out through the communicating portion to perform the degassing action in the vacuum atmosphere to improve the exhaust accuracy.

(Third Embodiment of the Present Invention) A third embodiment of the present invention will be described with reference to FIG. The third embodiment of the present invention is common in the configuration of the turbo-molecular pump shown in FIG. 1 and the relationship between the fastening means and the article to be fastened shown in FIG. Only explained. FIG. 6 is a perspective view for explaining the configuration and operation of the third embodiment of the fastening means 4 of the present invention. In FIG. 6, the fastening means 4 includes a second screw 21 and a first screw 11 (not shown).
It forms a male screw part for the female screw part formed on the side. The first screw 11 of the second embodiment is the same as that of the first embodiment.
5A and 5B, the fastening means 4
Only the second screw of the above is shown with the display of the screw portion omitted.

The second screw 21 is provided with two portions that are in an adjacent state via a separating portion 65 formed in an annular shape around the entire circumference of the screw, one of which is provided with a second male screw portion 22, and the other of which is provided on the other. Has a third male screw portion 23 formed therein. The annular separating portion 65 is formed in a mortar shape so that the side having the second male screw portion 22 is inserted into the side having the third male screw portion 23. Further, as in the first and second embodiments, the female screw portion 2
4 and a through hole 26 are formed, and a cut portion 28 is formed in the third male screw portion 23 so as to extend from the cut portion of the separation portion 65 to the through hole 26 along the axial direction.

By the fastening means 4 of the third embodiment, the rotary blade 1
In order to fasten the rotary shaft 3 to the rotary shaft 3, the first screw 11 and the second screw 21 are integrated as in the first and second embodiments, and then the through holes formed in the rotary blade 1 and the rotary shaft 3 are formed. And the second male screw portion 22 and the female screw 31 and the third male screw portion 23 and the female screw 31 by screwing the first screw 11 and the second screw 21 to each other. The rotation shaft 3 is loosely fastened. After that, by screwing the first screw 11 into the object to be fastened,
A portion provided with the second male screw portion 22 and a third male screw portion 23
The portion provided with acts on the object to be fastened in directions opposite to each other and generates a fastening force that fastens the rotary blade 1 and the rotary shaft 3.

In the third embodiment, the portion provided with the second male screw portion 22 and the portion provided with the third male screw portion 23 are adjacent to each other with the separation portion 65 formed in an annular and mortar shape. Therefore, the third male screw portion 23 receives forces in different directions as indicated by arrows I and J in FIG. 6 due to the fastening force indicated by arrow H in FIG. 6B. The force in the direction of arrow H acts on the portion provided with the second male screw portion 22 in a direction to reduce the gap of the separating portion 65, while the force in the directions of arrows I and J is the force of the third male screw portion 22. It acts on the portion provided with 23 in the direction of expanding the notch 28. The directions of these two acting forces are orthogonal to each other, and the fastening means can exert the fastening forces in different directions on the object to be fastened.

As a result, at least one of the centrifugal force and the vibration acts against the external force, and the loosening of the fastening can be prevented. Further, by expanding the cutout portion 28, a communication portion is formed which allows the space of the thread groove portion between the third male screw 23 and the female screw 31 to communicate with the outside. And through this communication part,
The residual gas left in the space of the thread groove portion can be taken out to the outside, and the gas can be released in a vacuum atmosphere to improve the exhaust accuracy.

(Effects of Embodiment) According to the above embodiment, the same effect as the double nut can be obtained by the two male screw portions of the fastening means in the female screw portion of the component to be fastened. Further, by generating the acting forces in different directions in the fastening means, it is possible to reduce the looseness of the fastening means due to the axial vibration of the rotary blade and the rotary shaft. Furthermore, by reducing the looseness of the fastening means, it is possible to stabilize the dynamic balance state of the rotor blades during high speed rotation.

[0038]

As described above, according to the present invention,
It is possible to provide a turbo molecular pump that can reduce the looseness of fastening parts.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view for explaining a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a diagram for explaining a relationship between a rotary blade and a rotary shaft.

FIG. 3 is a perspective view for explaining the configuration of the first embodiment of the fastening means of the present invention.

FIG. 4 is a schematic view for explaining the operation of the first embodiment of the fastening means of the present invention.

FIG. 5 is a schematic view for explaining a second embodiment of the fastening means of the present invention.

FIG. 6 is a schematic perspective view for explaining a third embodiment of the fastening means of the present invention.

[Explanation of Codes] 1 ... Rotary blade, 2 ... Fixed blade, 3 ... Rotary axis, 4 ... Fastening means,
5 ... Drive motor, 6, 7 ... Bearing, 8 ... Exhaust port, 9 ... Intake port, 11 ... First screw, 12 ... First male screw part, 13 ... First head, 14, 26 ... Through hole, 21 … Second screw, 2
2 ... 2nd external thread part, 23 ... 3rd external thread part, 24 ... internal thread part, 25, 55, 65 ... Separation part, 27 ... 2nd head, 28 ... Notch part, 31 ... internal thread.

Claims (1)

[Claims] 1. A turbo-molecular pump comprising fastening means for fastening a rotary shaft and a rotary blade, wherein the fastening means is a first
A male screw member for a rotating shaft or a rotary blade provided with a screw and a second screw, wherein the first screw has a first male screw part, and the second screw has a female screw part screwed with the first male screw part. A second male screw part having an inner peripheral surface and a third male screw part having a through hole for passing the first male screw part therein, and between the second male screw part and the third male screw part. At least part of which is formed with a separating portion, and the contact direction of the second male screw portion and the third male screw portion with respect to the rotary shaft or the rotary blade is made different by screwing the first screw and the second screw. A turbo molecular pump characterized by this.