JP2015206345A - vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum pump in which a gap between a boss part of a rotor and a concave part of a shaft is eliminated during low-speed rotation and downtime as well as high-speed rotation of a rotor assembly.SOLUTION: A boss part 21 of a rotor 20 is engaged with a concave part 31 of a shaft 30. The boss part 21 of the rotor 20 is hollow. A female thread 21c that is a parallel thread is engraved on an inner peripheral surface of the boss part 21. A plug 40 has a truncated cone shape. An outer peripheral surface of the plug 40 has a tapered shape of which a diameter is reduced from the side of the concave part 31 toward an upper surface 26 of the rotor 20. A male thread 40b is engraved on the outer peripheral surface. When the male thread 40b is screwed into the female thread 21c, the boss part 21 is thereby engaged with the plug 40. When the screwing progresses, the plug 40 thereby expands the boss part 21 toward the side of an outer periphery and brings the boss part 21 into contact with the concave part 31, and the rotor 20 and the shaft 30 are fastened.

Description

  The present invention relates to a vacuum pump.

  A vacuum pump represented by a turbo molecular pump is attached to a vacuum chamber such as a dry etching apparatus or a CVD apparatus. The turbo molecular pump includes a rotor assembly having a rotor formed with rotor blades and a rotor cylindrical portion, a shaft that is fastened to the rotor, and a motor that rotationally drives the shaft. The motor rotates the shaft at a high speed of several tens of thousands of revolutions per minute. The rotor fastened to the shaft also rotates at high speed as the shaft rotates. By rotating the rotor (rotor assembly) at a high speed, the rotor blades and the stator blades cooperate, and the rotor cylindrical portion and the cylindrical stator cooperate to exhaust the gas in the vacuum chamber to achieve a high vacuum state. To produce.

  For the purpose of centering (alignment) when the rotor and the shaft are fastened, a boss portion (convex portion) is provided on the rotor, and a concave portion that engages with the boss portion is provided on the top surface of the shaft. A clearance (clearance) is provided between the outer peripheral surface of the boss portion of the rotor and the inner peripheral surface of the concave portion of the shaft from the viewpoint of assemblability and decomposability. The formation of this gap has caused the weight balance of the rotor assembly to deteriorate.

  In Patent Document 1, the boss portion of the rotor expands in the radial direction rather than the recess portion of the shaft due to the centrifugal force generated at the time of high-speed rotation, so that the outer peripheral surface of the rotor boss portion contacts the inner peripheral surface of the recess portion of the shaft. An invention is described in which the rotor assembly is aligned. However, in the invention described in Patent Document 1, when the rotor assembly does not rotate at a high speed, that is, when the rotor assembly rotates at a low speed or stops, a gap is formed between the rotor boss and the shaft recess, There was a risk that the weight balance would be lost.

JP 2006-57805 A

  Therefore, it has been desired to eliminate the gap between the rotor boss and the shaft recess not only when the rotor assembly rotates at high speed but also when the rotor assembly rotates at low speed or stops.

(1) A vacuum pump according to a preferred embodiment of the present invention is a vacuum pump including a shaft that transmits a rotational driving force, and a rotor that is fastened to the shaft by a fastening structure and rotates by transmitting the rotational driving force from the shaft. is there. The fastening structure includes a concave portion provided on the end surface of the shaft, a hollow boss portion extending from the rotor toward the concave portion and having a first screw engraved on the inner peripheral surface, and a hollow boss portion from the bottom surface side of the concave portion. And an expansion member provided on the outer circumferential surface with a second screw that is screwed to the first screw and bulges the outer circumferential surface of the hollow boss toward the inner circumferential surface of the recess.
(2) In a further preferred embodiment, the expansion member is provided with a transmission portion that faces the hollow hole of the hollow boss portion and transmits the tightening torque.
(3) In a further preferred embodiment, the first screw of the hollow boss portion is a parallel screw, and the second screw of the expansion member is a taper screw whose diameter is reduced from the recessed portion side toward the upper surface side of the rotor.
(4) In a further preferred embodiment, the first screw of the hollow boss portion is a taper screw having a diameter reduced from the concave portion side toward the upper surface side of the rotor, and the second screw of the expansion member is a parallel screw.
(5) In a more preferred embodiment, the first screw of the hollow boss portion and the second screw of the expansion member are taper screws that are reduced in diameter from the recess side toward the upper surface side of the rotor.
(6) In a more preferred embodiment, the expansion member is provided with a through hole that communicates the space surrounded by the hollow boss portion, the concave portion, and the expansion member with the outside.
(7) In a more preferred embodiment, the screwing of the second screw of the expansion member and the first screw of the hollow boss portion is set in a direction to advance when the rotation of the rotor is accelerated.

  According to the present invention, it is possible to eliminate a gap between the rotor boss and the shaft recess not only when the rotor assembly is rotated at a high speed but also when the rotor assembly is rotated or stopped at a low speed. As a result, the weight balance of the rotor assembly can be maintained well. Therefore, for example, the rotation of the rotor assembly can be kept stable.

The figure which shows a turbo-molecular pump. The figure which showed the rotor, the shaft, and the plug. The figure which showed the periphery of the fastening structure of a rotor and a shaft. The figure shown about the shape of a boss | hub part and a plug, and those engagement. The figure which showed the plug of embodiment and the modification.

The vacuum pump of the present invention will be described by taking a composite turbo molecular pump as an example. The present invention can also be applied to vacuum pumps such as an all-blade turbomolecular pump and a molecular drag pump.
-Embodiment-
FIG. 1 is a cross-sectional view showing a schematic configuration of the turbo molecular pump 100. The rotor assembly 10 is rotatably provided in the casing 90 of the turbo molecular pump 100. The turbo molecular pump 100 is a magnetic bearing type pump, and the rotor assembly 10 is supported in a non-contact manner by an upper radial electromagnet 82, a lower radial electromagnet 84, and a thrust electromagnet 86.

  The rotor assembly 10 includes a rotor 20, a shaft 30, a plug 40, a bolt 50, and a rotor disk 60. The bolt 50 and the plug 40 are members for fastening the rotor 20 and the shaft 30. The fastening by the plug 40 will be described later with reference to FIG.

  The rotor 20 includes a rotor base 29, a plurality of stages of rotor blades 22 provided on the peripheral surface of the rotor base 29, and a rotor cylindrical portion 24 provided at the lower end of the rotor base 29. A plurality of stages of stator blades 70 are provided between the plurality of stages of rotor blades 22 in the axial direction, and a cylindrical stator 72 is provided on the outer peripheral side of the rotor cylindrical portion 24. Each stator blade 70 is disposed on the base 94 via a spacer 92. When the casing 90 is fixed to the base 94, the stacked spacers 92 are sandwiched between the base 94 and the casing 90, and the respective stator blades 70 are positioned.

  The base 94 is provided with an exhaust port 96, and a back pump is connected to the exhaust port 96. As the rotor assembly 10 is magnetically levitated by the upper radial electromagnet 82, the lower radial electromagnet 84, and the thrust electromagnet 86, the motor 80 is driven to rotate at high speed, whereby the gas molecules on the intake port 98 side are exhausted to the exhaust port 96 side. The

  2A is a cross-sectional view of the rotor 20, FIG. 2B is a plug 40, and FIG. FIG. 5A is an enlarged view of FIG. Each part of the rotor 20, the plug 40, and the shaft 30 will be described with reference to FIGS. 2 and 5A.

  As shown in FIG. 2A, a boss portion 21 protrudes from the lower surface 27 of the rotor 20. Further, a through hole 25 is formed in the rotor 20 from the lower end 21a of the boss portion 21 to the upper surface of the rotor 20, that is, the surface 26 on the upstream side of the vacuum exhaust. Therefore, the boss portion 21 is hollow inside and has a cylindrical shape. A female screw 21 c is engraved on the peripheral surface of the through hole 25 on the boss portion 21 side, that is, the inner peripheral surface 21 b of the boss portion 21. The through hole 25 is a parallel hole, and the female screw 21c is also a parallel screw. The boss portion 21 has an outer peripheral surface 21d.

  The plug 40 has a truncated cone shape. Further, as shown in FIGS. 2B and 5A, the outer peripheral surface 40a of the base portion 40h of the plug 40 has a tapered shape whose diameter is reduced from the lower surface 40g side toward the upper surface 40e side. . A male screw 40b is engraved on the outer peripheral surface 40a, and the male screw 40b is also a tapered screw having a diameter reduced from the lower surface 40g side toward the upper surface 40e side. That is, the plug 40 is a tapered plug having a diameter reduced from the lower surface 40g side toward the upper surface 40e side. In other words, since the upper surface 40 e of the plug 40 faces the rotor 20, the taper screw of the plug 40 arranged in the rotor assembly 10 is reduced in diameter from the concave portion 31 side of the shaft 30 to the rotor 20 side.

  The male screw 40b of this embodiment will be further described with reference to FIG. FIG. 5A shows the plug 40 of the above embodiment. In the plug 40, the outer peripheral surface 40a of the base portion 40h has a tapered shape. On top of that, a male screw 40b is provided. The thread height of the male screw 40b is constant. However, as described above, since the outer peripheral surface 40a of the base portion 40h is tapered, the male screw 40b is a tapered screw. As a result, the plug 40 becomes a tapered plug.

  As shown in FIGS. 2B and 5A, a chamfer 40c is provided on the upper end side of the outer peripheral surface 40a of the plug 40 in order to facilitate insertion of the rotor 20 into the boss portion 21. Since the plug 40 is screwed into the boss portion 21 of the rotor 20 to connect the shaft 30 to the rotor 20, the plug 40 has a concave portion 40d (hexagonal hole 40d) for inserting a tightening tool (hexagonal wrench) on the top surface. 40e. The plug 40 is screwed into the boss portion 21 of the rotor 20 from the upper surface 40e side. The hexagonal hole 40d is a transmission part for transmitting the tightening torque of the hexagon wrench to the plug 40. Further, the plug 40 is provided with a through hole 40f that allows the bottom surface of the recess 40d to communicate with the lower surface 40g. The through hole 40f is provided for adjusting the atmospheric pressure (described later).

  As shown in FIG. 2 (c), a recess 31 is formed at the upper end 30 a of the shaft 30. The recess 31 has an inner peripheral surface 31a and a bottom surface 31b.

  FIG. 3 is a view showing the periphery of the fastening structure of the rotor 20 and the shaft 30. The fastening of the rotor 20 and the shaft 30 will be described with reference to FIG.

  First, the plug 40 is loosely screwed into the boss portion 21 of the rotor 20. That is, the female screw 21c of the boss portion 21 and the male screw 40b of the plug 40 are screwed together. At this time, the boss portion 21 of the rotor 20 does not receive an outward force from the plug 40.

  Next, the boss portion 21 of the rotor 20 to which the plug 40 is loosely screwed is engaged with the concave portion 31 of the shaft 30. As described above, since the boss portion 21 of the rotor 20 has not yet received an outward force from the plug 40, the outer peripheral surface 21 d of the boss portion 21 of the rotor 20 is in contact with the inner peripheral surface 31 a of the concave portion 31 of the shaft 30. They are separated, or only a part contacts and others are separated.

  Then, the rotor 20 and the shaft 30 are temporarily fixed by the bolt 50. At this time, the rotor 20 and the shaft 30 can move with respect to each other to the extent of play of the through hole in which the bolt 50 is inserted.

  Here, a hexagon wrench (not shown), which is a tightening tool, is engaged with the hexagonal hole 40d of the plug 40 through a through hole 25 provided in the rotor 20, and a tightening torque is applied to the plug 40. Thereby, the plug 40 moves upward in the figure.

  In FIG. 4A, the direction in which the plug 40 advances (arrow in the center in the figure) and the force (left arrow and right arrow in the figure) received by the boss portion 21 of the rotor 20 from the plug 40 are indicated by arrows. As described above, the female screw 21c of the boss portion 21 of the rotor 20 is a parallel screw, and the male screw 40b of the plug 40 is a taper screw. Therefore, as shown in FIG. 4A, when the screwing of the male screw 40b of the plug 40 and the female screw 21c of the boss portion 21 of the rotor 20 proceeds to a certain extent, the plug 40 moves against the boss portion 21 of the rotor 20. To give outward force. That is, the plug 40 is an expansion member that bulges the peripheral wall of the boss portion 21 of the rotor 20.

  Further explanation will be made with reference to FIG. 3. The outer peripheral surface 21 d of the boss portion 21 of the rotor 20 receives the outward force from the plug 40 described above and extends over the entire inner periphery 31 a of the concave portion 31 of the shaft 30. Abut. This is a fastening structure of the rotor 20 and the shaft 30 by the plug 40.

  After the fastening structure of the rotor 20 and the shaft 30 by the plug 40 is completed, the bolt 50 is finally tightened, and the fastening structure of the rotor 20 and the shaft 30 by the bolt 50 is completed.

  The above-described through hole 40f of the plug 40 is provided to equalize the atmospheric pressure between the space 12 surrounded by the boss portion 21 of the rotor 20, the plug 40, and the concave portion 31 of the shaft 30, and the outside. By providing the through hole 40f, gas can quickly flow out of the space 12 during evacuation.

  The male screw 40b of the plug 40 and the female screw 21c of the boss portion 21 of the rotor 20 are set so that when the rotation of the rotor 20 is accelerated, the screwing proceeds, that is, so-called tightening is achieved. ing. Specifically, the male screw 40 b and the female screw 40 b are rotated so that the rotation direction of the male screw 40 b when the male screw 40 b of the plug 40 is screwed to the female screw 21 c of the boss portion 21 is opposite to the rotation direction of the rotor 20. A screw 21c is formed.

According to the embodiment described above, the following operational effects can be obtained.
(1) The turbo-molecular pump 100 includes a shaft 30 that transmits a rotational driving force, and a rotor 20 that is fastened to the shaft 30 by a fastening structure and rotates by receiving the rotational driving force from the shaft 30.
The fastening structure has a recess 31 provided on the end surface of the upper end 30a of the shaft 30, and extends from the rotor 20 toward the recess 31 coaxially with the recess 31, and a female screw 21c is engraved on the inner peripheral surface 21b. The hollow and cylindrical boss portion 21 is screwed into the female screw 21c of the boss portion 21 from the bottom surface 31b side of the concave portion 31 so that the outer peripheral surface 21d of the boss portion 21 bulges toward the inner peripheral surface 31a of the concave portion 31. The male screw 40b includes a plug 40 that is an expansion member provided on the outer peripheral surface 40a. In addition, you may provide the recessed part 31, the boss | hub part 21, and the plug 40 each in multiple numbers (for example, 2 sets or 4 sets), and in that case, it provides in the circumferential direction at equal intervals.

  With the above configuration (1), the following effects (1A) to (1D) can be achieved.

(1A) The gap between the outer peripheral surface 21d of the boss portion 21 of the rotor 20 and the inner peripheral surface 31a of the concave portion 31 of the shaft 30 is maintained even when the rotor 20 is stopped at normal temperature or when the rotor 20 is rotated at low speed at normal temperature. Can be eliminated. As a result, the radial displacement between the rotor 20 and the shaft 30 due to the centrifugal force during acceleration of the turbo molecular pump 100 can be prevented, and the center of gravity balance of the rotor assembly 10 can be prevented from being lost.

(1B) The outer peripheral surface 21d of the boss portion 21 of the rotor 20 contacts the inner peripheral surface 31a of the concave portion 31 of the shaft 30 over the entire periphery, and the gap between the outer peripheral surface 21d and the inner peripheral surface 31a can be eliminated. Since the outer peripheral surface 21d of the boss portion 21 of the rotor 20 is in contact with the inner peripheral surface 31a of the concave portion 31 of the shaft 30 over the entire circumference, the alignment between the central axis of the rotor 20 and the central axis of the shaft 30 is reduced. An effect can also be produced.

  By preventing the collapse of the center-of-gravity balance described in (1A) above and the alignment effect described in (1B), the occurrence of run-out can be suppressed and the rotation of the rotor assembly 10 can be stabilized. .

(1C) The fastening operation to eliminate the gap between the outer peripheral surface 21d of the boss portion 21 of the rotor 20 and the inner peripheral surface 31a of the concave portion 31 of the shaft 30 is easier than shrink fitting or cold fitting. Therefore, the refastening operation of the rotor 20 and the shaft 30 during repair or overhaul is facilitated.

(1D) The outer peripheral surface 21d of the boss portion 21 of the rotor 20 abuts the inner peripheral surface 31a of the concave portion 31 of the shaft 30 over the entire periphery, and the gap between the outer peripheral surface 21d and the inner peripheral surface 31a can be eliminated. Since the clearance between the outer peripheral surface 21d and the inner peripheral surface 31a is a factor that creates the degree of freedom of the position of the boss portion 21 in the recess 31, the present invention improves the reproducibility of the fastening structure by eliminating the clearance. As a result, for example, fastening before plating of the rotor 20 can be reproduced even after plating of the rotor 20.

  The above (1D) will be specifically described. The rotor 20 may be plated. At that time, normally, the rotor assembly 10 is assembled before the rotor 20 is plated, the weight balance of the rotor assembly 10 is adjusted, the rotor assembly 10 is disassembled and the rotor 20 is plated, and then the rotor assembly 10 is again mounted. After assembling, the weight balance of the rotor assembly 10 is adjusted again. Conventionally, a lot of time and labor has been devoted to adjusting the weight balance again. However, in the present invention, since the reproducibility of the fastening structure is good, it is easy to adjust the weight balance again, reducing the burden on the operator. it can.

(2) The plug 40, which is an expansion member, faces the through hole 25, which is a hollow hole of the boss portion 21, and has a concave portion 40d (hexagonal hole 40d) that is a transmission portion for transmitting a tightening torque from a hexagon wrench. Is provided.
Thereby, a hexagon wrench can be inserted into the hexagonal hole 40d from the upper surface 26 side of the rotor 20. For this reason, workability at the time of tightening the plug 40 is also ensured.

(3) The female screw 21c of the boss portion 21 is a parallel screw. The male screw 40b of the plug 40, which is an expansion member, is a taper screw having a diameter reduced from the concave portion 31 side of the shaft 30 to the rotor 20 side.
As a result, when the female screw 21c of the boss portion 21 and the male screw 40b of the plug 40 are screwed together, the boss portion 21 bulges to the outer peripheral side, and the rotor 20 and the shaft 30 are fastened. If the plug 40 standardized by JIS is used, an increase in cost can be suppressed.

(4) When the rotation of the rotor 20 is accelerated, the male screw 40b of the plug 40, which is an expansion member, and the female screw 21c of the boss portion 21 are set to advance.
Thereby, as the rotor 20 accelerates, the screwing of the rotor 20 and the plug 40 becomes stronger, and as a result, the degree of bulging of the boss portion 21 of the rotor 20 toward the outer peripheral side increases, The fastening of the shaft 30 becomes stronger.
Note that the magnitude of the acceleration (negative acceleration) at the time of rotational deceleration of the rotor 20 is not as great as the magnitude of the acceleration (positive acceleration) at the time of rotational acceleration of the rotor 20. For this reason, when the rotation of the rotor 20 is decelerated, no force acts between the boss portion 21 and the plug 40 as the rotation of the rotor 20 is accelerated. Therefore, as described above, the setting is such that it is tightened when the rotation of the rotor 20 is accelerated.

(5) The plug 40 is provided with a through hole 40f that communicates the space 12 surrounded by the boss portion 21 of the rotor 20, the plug 40, and the concave portion 31 of the shaft 30, and the outside.
Thereby, gas can flow out quickly from the space 12 toward the outside during vacuum evacuation, and the pressure adjustment between the space 12 and the outside becomes easy.

(6) Generally, the boss portion 21 of the rotor 20 is made of an aluminum alloy, and the concave portion 31 of the shaft 30 is made of iron. In that case, the expansion coefficient of the rotor 20 at the time of high speed rotation or high temperature is larger than that of the shaft 30. As a result, the outer peripheral surface 21d of the boss portion 21 of the rotor 20 is pressed against the inner peripheral surface 31a of the concave portion 31 of the shaft 30 more than when rotating at a low speed, stopping, and at room temperature. Therefore, the fastening of the rotor 20 and the shaft 30 at the time of high speed rotation or high temperature becomes stronger than that at the time of low speed rotation, stop, and normal temperature.

  The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.

  Modifications 1A, 1B, 1C, and 1D shown in FIGS. 4B, 4C, 4D, and 4E are the boss portion 21 and the plug 40 in the embodiment shown in FIG. It is a modification regarding engagement (screwing). These modified examples also have the same operational effects as the embodiment. Hereinafter, differences from the embodiment will be described.

-Modification 1A-
4B, the female screw 21c of the boss portion 21 of the rotor 20 is a taper screw having a diameter reduced from the lower end 21a side of the boss portion 21 toward the upper surface 26 (see FIG. 2A) side of the rotor 20. It has become. On the other hand, the male screw 40b of the plug 40 does not change in diameter from the lower surface 40g side of the plug 40 to the upper surface 40e side, and is a parallel screw. Even if it is such engagement (screwing) of a female screw and a male screw, there exists an effect similar to embodiment.

-Modification 1B-
In FIG. 4C, the female screw 21 c of the boss portion 21 of the rotor 20 is a taper screw having a diameter reduced from the lower end 21 a side of the boss portion 21 toward the upper surface 26 (see FIG. 2A) side of the rotor 20. It has become. The male screw 40b of the plug 40 is also a tapered screw having a diameter reduced from the lower surface 40g side of the plug 40 toward the upper surface 40e side. However, the taper angle θ1 of the female screw 21c is set smaller than the taper angle φ1 of the male screw 40b. Even if it is such engagement (screwing) of a female screw and a male screw, there exists an effect similar to embodiment.

-Modification 1C-
4D, the female screw 21c of the boss portion 21 of the rotor 20 is a taper screw having a diameter reduced from the lower end 21a side of the boss portion 21 toward the upper surface 26 (see FIG. 2A) side of the rotor 20. It has become. The male screw 40b of the plug 40 is also a tapered screw having a diameter reduced from the lower surface 40g side of the plug 40 toward the upper surface 40e side. However, the taper angle θ2 of the female screw 21c is set larger than the taper angle φ2 of the male screw 40b. Even if it is such engagement (screwing) of a female screw and a male screw, there exists an effect similar to embodiment.

  Here, in the modified example 1A and the modified example 1C, the plug 40 is in contact with the boss portion 21 at the corner portion 40i on the upper surface 40e side. The contact portion between the plug 40 and the boss portion 21 is preferably located in the vicinity of the lower end 21 a of the boss portion 21. This is to facilitate the boss portion 21 to bulge to the outer peripheral side. In the embodiment and the modification 1B, the lower end of the female screw 21c (the lower end 21a of the boss portion 21) naturally becomes the contact portion between the plug 40 and the boss portion 21 by setting the plug 40 and the boss portion 21. In Modification 1D (see FIG. 4E) shown below, the contact portion between the plug 40 and the boss portion 21 is a region from the lower end 21a to the upper surface 40e.

-Modification 1D-
4E, the female screw 21c of the boss portion 21 of the rotor 20 is a taper screw having a diameter reduced from the lower end 21a side of the boss portion 21 toward the upper surface 26 (see FIG. 2A) side of the rotor 20. It has become. The male screw 40b of the plug 40 is also a tapered screw having a diameter reduced from the lower surface 40g side of the plug 40 toward the upper surface 40e side. However, the taper angle θ3 of the female screw 21c is set equal to the taper angle φ3 of the male screw 40b. Thus, since the taper angle of both is set equal, the contact part of the plug 40 and the boss | hub part 21 becomes an area | region from the lower end 21a to the upper surface 40e. That is, the plug 40 and the boss portion 21 are in surface contact. Even if it is such engagement (screwing) of a female screw and a male screw, there exists an effect similar to embodiment.

  Modified examples 2A and 2B shown in FIGS. 5B and 5C are modified examples of the plug 40 in the embodiment shown in FIG. These are particularly different from the embodiment in “the shape of the outer peripheral surface of the base” and “the height of the thread of the male screw”. Only different configurations are denoted by reference numerals different from those of the embodiment. Even the plugs shown in these modified examples have the same effects as the plug 40 of the embodiment.

-Modification 2A-
FIG. 5B shows a plug 41 of this modification. The outer peripheral surface 40a of the base portion 40h of the plug 41 has a tapered shape as in the embodiment. The height of the thread of the male screw 41b of the plug 41 is changed so that the diameter decreases from the lower surface 40g toward the upper surface 40e. Therefore, the male screw 41b of this modification is also a taper screw like the male screw 40b of the plug 40 of the embodiment. And the plug 41 becomes a taper plug. Even such a plug 41 has the same effects as the plug 40 of the embodiment.

-Modification 2B-
FIG. 5C shows the plug 42 of this modification. Unlike the embodiment, the outer peripheral surface 42a of the base portion 42h of the plug 42 does not change in diameter. Further, the thread height of the male screw 42b of the plug 42 is changed so that the diameter of the male screw 42b is reduced from the lower surface 40g toward the upper surface 40e. Therefore, the male screw 42b of this modification also becomes a taper screw like the male screw 40b of the plug 40 of the embodiment. The plug 42 becomes a tapered plug. Even such a plug 42 has the same effect as the plug 40 of the embodiment.

  In the above, an example of a composite turbo molecular pump has been given as the vacuum pump of the present invention, but the present invention can also be applied to vacuum pumps such as an all-wing turbo molecular pump and a molecular drag pump.

  Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

10: rotor assembly,
20: rotor,
21: Boss part,
21a: lower end,
21b: inner peripheral surface,
21c: female screw,
21d: outer peripheral surface,
22: Rotor wing,
24: Rotor cylindrical part,
25: through hole,
26: top surface,
27: lower surface,
30: shaft,
30a: upper end,
31: recess,
31a: inner peripheral surface,
31b: bottom surface,
40: Plug,
40a: outer peripheral surface,
40b: male screw,
40d: recess (hexagonal hole),
40e: top surface,
40f: through hole,
40 g: bottom surface,
40h: base,
40i: corner,
41: plug,
41b: male screw,
42: plug,
42a: outer peripheral surface,
42b: male screw,
42h: base,
50: Bolt,
60: rotor disk,
70: Stator wing,
72: cylindrical stator,
80: motor,
82: Upper radial electromagnet,
84: Lower radial electromagnet,
86: Thrust electromagnet,
90: casing,
92: Spacer,
94: Base,
96: exhaust port,
98: Inlet,
100: Turbo molecular pump

Claims (7)

A shaft that transmits rotational driving force;
In a vacuum pump provided with a rotor that is fastened to the shaft by a fastening structure and that is rotated by a rotational driving force transmitted from the shaft,
The fastening structure is
A recess provided on the end face of the shaft;
A hollow boss portion extending from the rotor toward the concave portion and having a first screw engraved on an inner peripheral surface;
A second screw that is screwed into the first screw of the hollow boss portion from the bottom surface side of the concave portion and bulges the outer peripheral surface of the hollow boss portion toward the inner peripheral surface of the concave portion is provided on the outer peripheral surface. And an expansion member. The vacuum pump according to claim 1, wherein
The vacuum pump, wherein the expansion member is provided with a transmission portion that transmits a tightening torque facing the hollow hole of the hollow boss portion. The vacuum pump according to claim 1 or 2,
The first screw of the hollow boss is a parallel screw,
The second screw of the expansion member is a vacuum pump that is a taper screw having a diameter reduced from the concave side toward the upper surface side of the rotor. The vacuum pump according to claim 1 or 2,
The first screw of the hollow boss portion is a taper screw having a diameter reduced from the concave side toward the upper surface side of the rotor,
A vacuum pump in which the second screw of the expansion member is a parallel screw. The vacuum pump according to claim 1 or 2,
The first screw of the hollow boss portion and the second screw of the expansion member are taper screws that are reduced in diameter from the concave portion toward the upper surface of the rotor. In the vacuum pump as described in any one of Claims 1-5,
A vacuum pump in which the expansion member is provided with a through hole that communicates the space surrounded by the hollow boss portion, the recess, and the expansion member with the outside. In the vacuum pump as described in any one of Claims 1-6,
The vacuum pump in which the screwing of the second screw of the expansion member and the first screw of the hollow boss portion is set in a direction to advance when the rotation of the rotor is accelerated.

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