JP2009180147A - Flange structure of casing, turbo molecular pump, and vacuum pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flange structure efficiently absorbing the fracture energy of a rotor stored in a casing. <P>SOLUTION: In this structure, a flange 21 is provided at the end of the casing 2 storing the rotor 4 and fastened to a counter-member 71 through bolts 10. Longitudinal bottomed grooves 23 corresponding to the mounting positions of the bolts 10 are formed in a peripheral direction in the surface of the flange 21. The bottom surfaces of the bottomed grooves 23 are formed with bolt holes 22 passing the bolts 10 and opened in side edges in the rotational direction of the rotor, and oblong slit holes 24 communicating with the bolt holes 22, having width smaller than those of the bolt holes 22, and opened in opposite side edges in the rotational direction of the rotor 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flange structure of a casing, a turbo molecular pump, and a vacuum pump.

  Some turbo molecular pumps having a rotating body that rotates at a high speed in a casing absorb energy when the rotating body is broken by deformation of a flange (see, for example, Patent Document 1). In the flange described in Patent Document 1, a plurality of bolt holes through which casing mounting bolts are inserted are provided in the circumferential direction, and through holes are provided outside the respective bolt holes via thin portions. Thereby, at the time of destruction of a rotating body, a thin part is deformed by relative movement of a bolt, and energy of destruction of a rotating body is absorbed.

JP 2004-162696 A

  However, in the flange described in Patent Document 1, the course of the bolt is blocked by the deformation of the thin portion outside the bolt hole, the relative movement of the bolt is hindered, and the energy for destruction cannot be absorbed efficiently.

The present invention is a flange structure that is provided at an end of a casing that accommodates a rotor and is fastened to a mating member via a bolt, corresponding to the bolt mounting position, and extending in the circumferential direction on the surface of the flange. The bottomed groove has a bottomed groove, and a bolt hole through which a bolt penetrates at the rotation direction side end of the rotating body is opened on the bottom surface of the bottomed groove, and the first hole at least in the vicinity of the bolt hole A long hole-like slit hole narrower than the bolt hole is opened from the part to the second part which is the opposite end portion in the rotation direction of the rotating body.
A slit hole can be provided continuously with the bolt hole.
The bolt hole and the slit hole are preferably provided in the center in the width direction of the bottom surface of the bottomed groove.
The width of the slit hole in the first part can be formed wider than the width of the slit hole in the second part.
The width of the slit hole in the first part may be formed larger than the diameter of the bolt, and the width of the slit hole in the second part may be formed smaller than the diameter of the bolt.
The depth of the bottomed groove in the first part can be formed shallower than the depth of the bottomed groove in the second part.
The depth of the bottomed groove around the bolt hole may be formed shallower than the depth of the bottomed groove around the slit hole.
A cover member having a cylindrical portion for inserting a bolt may be attached to the bolt hole.
A turbo molecular pump according to the present invention has the above-described flange structure, a casing fastened to a member on the vacuum system side via a bolt, a rotor that is rotatably supported in the casing and has rotor blades formed thereon, And a stator having stator blades arranged corresponding to the rotor blades.
A vacuum pump according to the present invention has a flange structure described above, and corresponds to the casing that is fastened to a member on the vacuum system side via a bolt, a rotor that is rotatably supported in the casing, and the rotor. And an arranged stator.

  According to the present invention, the bottomed groove is formed in a longitudinal shape on the surface of the flange, and the bolt hole and the slit hole are opened in the bottomed groove. Therefore, the bolt is relatively moved along the slit hole when the rotor is broken. It can move and efficiently absorb the energy of breaking the rotor.

-First embodiment-
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view showing an overall configuration of a turbo molecular pump according to a first embodiment of the present invention, and FIG. 2 is a diagram showing an attached state of the turbo molecular pump. The turbo molecular pump is a vacuum pump used in, for example, a semiconductor manufacturing apparatus. For convenience of explanation, the vertical direction of the turbo molecular pump is defined below as shown in the figure.

  As shown in FIG. 1, a pump body 1 of a turbo molecular pump includes a substantially cylindrical outer casing 2, a base 3 attached to a lower portion of the outer casing 2, and is accommodated in the outer casing 2 and is rotatably supported by the base 3. And the rotor 4 to be operated.

  As shown in FIG. 2, the upper flange 21 of the outer casing 1 is fixed to the flange 71 of the vacuum chamber 7 on the semiconductor manufacturing apparatus side by bolts 10. The bolt 10 passes through the bolt hole 22 of the flange 21 and is screwed into a screw portion 72 provided on the flange 71. The configuration around the bolt hole 22 will be described later.

  As shown in FIG. 1, a plurality of stages of rotating blades 41 are formed on the outer peripheral surface of the rotor 4 at intervals in the vertical direction, and fixed blades 43 are alternately inserted between the rotating blades 41 of each stage. Yes. The fixed wings 43 at each stage are stacked via spacers 48. A rotating cylindrical portion 42 is formed below the rotor blade 41 of the rotor 4. On the base 3 side, a fixed cylindrical portion 44 is provided to face the rotating cylindrical portion 42, and a spiral groove is formed on the inner peripheral surface of the fixed cylindrical portion 44. The rotating blade 41 and the fixed blade 43 described above constitute a turbine blade portion, and the rotating cylindrical portion 42 and the fixed cylindrical portion 44 constitute a molecular drag pump portion.

  The rotor 4 is supported in a non-contact manner by a pair of upper and lower radial magnetic bearings 51 and an axial magnetic bearing 52 and is driven to rotate by a motor 6. The magnetic bearings 51 and 52 are provided with radial displacement sensors 53 and 54 and a thrust displacement sensor 55 for detecting the flying position of the rotor 4, respectively. The motor 6 is, for example, a DC brushless motor. A motor rotor 61 incorporating a permanent magnet is mounted on the shaft portion 45 of the rotor 4, and a motor stator 62 for forming a rotating magnetic field is provided on the base 3 side. .

  A sensor target 46 is provided at the lower end of the shaft portion 45, and a gap sensor 55 is provided at a position facing the sensor target 46. Reference numerals 56 and 57 are emergency mechanical bearings.

  In such a turbo molecular pump 1, gas molecules flow from the intake port 1a due to the high speed rotation of the rotor 4, and the gas molecules are exhausted from the exhaust port 1b through the gas passages of the turbine blade portion and the molecular drag pump portion, respectively. . As a result, the intake port 1a is in a high vacuum state. At this time, if the rotor 4 rotating at high speed is broken for some reason, the rotor 4 is scattered around by centrifugal force, and the scattered matter acts on the outer casing 2 in the same direction as the rotation direction of the rotor 4. . Since this rotational torque acts on the vacuum flange 71 via the upper flange 21, the vacuum system may be damaged. In order to prevent this, in this embodiment, the flange 21 of the pump body 1 is configured as follows.

  3A is a front view showing the configuration of the flange 21 according to the first embodiment (the view is taken along the line III in FIG. 1, and FIG. 3B is a line bb in FIG. 3A). Fig. 6 is a cross-sectional view of the upper surface of the flange 21 provided with a counterbore 23 (bottom groove) having a predetermined depth corresponding to the fastening position of the bolt 10. The counterbore 23 is a predetermined range in the circumferential direction. A plurality of thinly extending portions 21a are formed at equal intervals over (for example, about 5 ° to 10 °), and a thin flange portion 21a having a thin flange thickness is formed below the counterbore 23. The bolt 10 is formed to have a thickness that can be deformed by relative movement, and the bolt 10 is higher in hardness than the flange 21 so that the thin-walled portion 21a can be easily deformed, and the bolt 10 and the flange 21 have the same hardness. Also good.

  Bolt holes 22 having a diameter smaller than the width of the counterbore 23 are formed at the center of each counterbore 23 in the width direction and at the end in the rotation direction of the rotor 4. A slit hole 24 is formed in the center of the counterbore 23 in the width direction so as to extend to the opposite end of the rotor 4 in the rotational direction. The width of the slit hole 24 is smaller than the diameter of the through hole 22 and further smaller than the diameter of the bolt 10. Note that reference numeral 25 in FIG. 3A denotes a net stretched around the intake port 1a.

  Processing of the surface of the flange 21 is performed as follows. First, the counterbore 23 is processed into a long hole with a large-diameter end mill to form the thin portion 21a. Next, the slit hole 24 is processed with a small-diameter end mill, and the bolt hole 22 is processed with a drill.

  In the first embodiment, when the rotor 4 rotating at high speed is broken for some reason, the rotational torque due to the scattered matter of the rotor 4 acts on the casing 2 and the flange 21 rotates in the rotation direction of the rotor 4. At this time, since the bolt 10 is restrained by the flange 71, the bolt 10 does not follow the rotation of the flange 21. Therefore, as shown in FIG. 4, the bolt 22 bites into the slit hole 24 and the slit hole 24 is pushed and widened, and the bolt 22 relatively moves along the slit hole 24 on the side opposite to the rotation direction of the rotor 4. Thereby, the energy for breaking the rotor is consumed by the friction between the bolt 22 and the slit hole 24. As a result, the amount of torque transmitted from the flange 21 to the flange 71 can be reduced, and damage to the vacuum system device can be prevented.

According to 1st Embodiment, there can exist the following effects.
(1) A plurality of spot facings 23 are formed in the shape of a long hole on the surface of the flange 21 of the casing 2 in the circumferential direction, and bolt holes 22 are opened on one end side (rotor rotating direction side) of the spot facing 23, respectively. The slit holes 24 are opened to the bolt hole 22 and to the other end side of the counterbore 23 (on the opposite side of the rotor rotation direction). As a result, when the rotor 4 is broken, the bolt 10 is guided to the slit hole 24 and the bolt 10 moves relative to the flange 21 while expanding both sides of the slit hole 24, so that a frictional force acts around the bolt 10. , Can absorb the destruction energy efficiently. That is, since the thin portion 21a is deformed to the outside of the slit hole 24, the course of the bolt 10 is not obstructed even after the thin portion 21a is deformed, and the bolt 10 can be relatively moved along the slit hole 24. More frictional force can be applied to the peripheral surface.

(2) Since the counterbore 23 is provided on the surface of the flange 2, and the bolt hole 22 and the slit hole 24 are opened in the counterbore 23, processing is easy and the structure can be made at low cost.
(3) Since the slit hole 24 is provided in the center in the width direction of the spot facing 23 and the thin portions 21a are formed on both sides of the slit hole 24, a frictional force acts on both sides of the bolt 10 and the amount of energy absorption is large.
(4) Since the bolt hole 22 and the slit hole 24 are communicated with each other, when the rotor 4 is broken, the bolt 10 can be easily moved relatively from the bolt hole 22 to the slit hole 24, and desired shock absorption can be achieved. An effect is obtained.

-Second Embodiment-
A second embodiment of the present invention will be described with reference to FIG. Hereinafter, differences from the first embodiment will be mainly described.
The second embodiment is different from the first embodiment in the shape of the slit hole 24. That is, in the first embodiment, the width of the slit hole 24 is uniform in the longitudinal direction, but in the second embodiment, the width is gradually narrowed. FIG. 5 (a) is a front view showing the configuration of the flange 21 according to the second embodiment, FIG. 5 (b) is an enlarged view of a main part thereof, and FIG. 5 (c) is a diagram of FIG. 5 (a). It is a cc line sectional view. In addition, the same code | symbol is attached | subjected to the location same as FIG.

  As shown in FIG. 5, the slit hole 241 is tapered along the longitudinal direction, and the width of the slit hole 241 is maximum at the bolt hole side end 241 a and gradually decreases as the distance from the bolt hole 22 increases. ing. The dotted line in FIG. 5 (b) corresponds to the width of the slit hole 24 in FIG. 3, and the width of the bolt hole side end 241a is wider than that in FIG. Thus, when torque acts on the flange 21 due to the destruction of the rotor 4, the bolt 10 can be reliably guided to the slit 241 and a stable shock absorbing effect can be obtained. The slit holes 241 may not be all tapered along the longitudinal direction, but may be tapered halfway in the longitudinal direction, and the remaining width may be constant.

-Third embodiment-
A third embodiment of the present invention will be described with reference to FIG. Hereinafter, differences from the second embodiment will be mainly described.
The third embodiment differs from the second embodiment in the shape of spot facings 23. That is, in the second embodiment, the spot facing 23 is provided so that the thickness of the thin portion 21a is constant, but in the third embodiment, the depth of the spot facing is changed as follows. 6 (a) is a front view showing the configuration of the flange 21 according to the third embodiment, FIG. 6 (b) is an enlarged view of a main part thereof, and FIG. 6 (c) is a diagram of FIG. 6 (a). It is a cc line sectional view. In addition, the same code | symbol is attached | subjected to the location same as FIG.

  As shown in FIG. 6, the depth of the spot facing 231 around the bolt hole 22 is shallower than the depth of the spot facing 232 around the slit hole 241. Thereby, the thickness of the thin part 21a around the bolt hole 22 becomes thicker than that of FIG. For this reason, the flange rigidity around the bolt hole 22 is increased, and the flange 21 can be prevented from being deformed by the fastening force of the bolt 10. It should be noted that the thickness of the thin portion 21a around the bolt hole 22 in FIG.

-Fourth embodiment-
A fourth embodiment of the present invention will be described with reference to FIG. Hereinafter, differences from the third embodiment will be mainly described.
The fourth embodiment differs from the third embodiment in the shape of spot facings 23. That is, in the third embodiment, the depth of the spot facing 231 around the bolt hole 22 is made shallow, but in the fourth embodiment, the depth of the spot facing 232 around the slit hole 241 is further changed. . FIG. 7 (a) is a front view showing the configuration of the flange 21 according to the fourth embodiment, FIG. 7 (b) is an enlarged view of a main part thereof, and FIG. 7 (c) is a diagram of FIG. 7 (a). It is a cc line sectional view. In addition, the same code | symbol is attached | subjected to the location same as FIG.

  As shown in FIG. 7, the depth of the spot facing 232 around the slit hole 241 is gradually increased along the longitudinal direction from the bolt hole side end 241a to the opposite end 241b. That is, the spot facing 232B is deeper than the spot facing 232A, and the spot facing 232C is deeper than the spot facing 232B. Accordingly, as the width of the spot facing 232 becomes narrower, the thickness of the thin portion 21a becomes thinner, so that the bolt is more easily deformed to the end portion than that of FIG. As a result, the energy for breaking the rotor can be consumed over the entire length of the slit hole 241, so that the amount of energy consumption increases and the amount of torque transmitted to the flange 71 can be further reduced. In FIG. 7, the depth of the spot facing 232 is changed to three levels, but may be changed to two levels or four levels or more. The depth of the counterbore 23 shown in FIGS. 3 and 5 can be similarly changed.

-Fifth embodiment-
A fifth embodiment of the present invention will be described with reference to FIG.
In the fifth embodiment, the cover 26 is inserted between the bolt hole 22 and the bolt 10. FIG. 8A is a front view showing the configuration of the flange 21 according to the fifth embodiment, FIG. 8B is an enlarged view of the main part, and FIG. 8C is c in FIG. 8A. FIG. In addition, the same code | symbol is attached | subjected to the location same as FIG.

  The cover 26 includes a cylindrical cylindrical portion 261 and a ring-shaped washer portion 262 formed on one end side of the cylindrical portion 261. The outer diameter of the cylindrical portion 261 is substantially equal to the outer diameter of the bolt hole 22, the cylindrical portion 261 is inserted into the bolt hole 22 by press fitting, and the cover 26 is fixed integrally to the flange 21. The washer portion 262 contacts the flange surface, and the bolt 10 is inserted into the cylindrical portion 261. Note that the outer diameter of the bolt 10 may be smaller than the width of the slit hole 241.

  In the fifth embodiment, when torque acts on the flange 21 due to the destruction of the rotor 4, the cover 26 moves relative to the bolt 10 along the slit hole 241. Thereby, the energy of rotor destruction is consumed by the friction between the cover 26 and the slit hole 241 and the deformation of the cover member. In this case, the surface of the bolt 10 is covered with the cover 26, and the bolt itself does not bite into the slit hole 24. Therefore, the stress concentration on the screw thread portion and the screw trough portion on the bolt surface can be alleviated, and damage to the bolt 10 can be prevented. A stable shock absorbing effect can be obtained. The cover 26 is preferably made of a different type of metal from the flange 21 so as not to be seized when biting into the slit hole 241, and is made of a material harder than the flange 21 so as to easily deform the thin portion 21a. It is preferable to make it.

  In FIG. 8, the taper-shaped slit hole 241 is described as being provided. However, the cover 26 can be similarly inserted into one having the constant-width slit hole 24 (for example, FIG. 3). Further, not only when the cover 26 is inserted into the bolt hole 22 having a flat face facing surface, but also when the stepped spot facings 231 and 232 are provided as shown in FIGS. 9 (a) and 9 (b). Similarly, the cover 26 can be inserted. An example of deformation of the thin portion 21a in this case is shown in FIGS. 10 (a) and 10 (b). The shaded area in FIG. 10A is an area (deformation area) of the thin-walled part 21 a pushed outward by the cover 26. Although the shaft portion 10a of the bolt 10 is not deformed in FIG. 10B, the shaft portion 10a can be deformed as shown in FIG. As the bolt 10 is deformed in this way, more energy can be consumed due to the destruction of the rotor 4.

  FIG. 12 is a diagram illustrating an example of a shear test result of the bolt 10. In the figure, L1 (solid line) indicates the displacement of the flange 21 when a test force in the rotor rotation direction is applied to the flange 21 in a state where the flange 21 of the turbo molecular pump according to the fifth embodiment is fixed with the bolt 10. It is a characteristic showing the relationship between quantity and test force. Note that L2 (dotted line) is a comparative example of the present embodiment, and shows the relationship between the displacement of the flange and the test force when a test force in the rotor rotation direction is simply applied to the flange. According to the present embodiment, the amount of displacement of the flange 21 until the bolt 10 breaks is large and the maximum test force is large as compared with the case where a simple flange is used.

  In the above, the counterbore 23, that is, the bottomed groove is formed in the longitudinal shape on the surface of the flange 21 in the circumferential direction, but the shape of the bottomed groove is not limited to that described above. Bolt holes 22 are opened in the counterbore surface at the rotation direction side end of the rotor 4, and the bolt hole side end portion 241 a (first portion) connected to the end face 241 b (the second side opposite to the rotation direction of the rotor 4). However, the slit hole 24 may be provided separately from the bolt hole 22 as long as the bolt hole side end 241 a of the slit hole 24 is formed at least in the vicinity of the bolt hole 22. Although the bolt hole 22 and the slit hole 24 are provided in the center of the counterbore 23 in the width direction, they may be shifted from the center. In the fifth embodiment, the cover 26 is provided around the bolt, but the shape of the cover 26 as the cover member is not limited to the above. For example, the outer diameter of the cover 26 may be formed smaller than the inner diameter of the bolt hole 22, and the cover 26 may be inserted into the bolt hole 22 when the bolt 10 is fastened. In order to facilitate insertion into the bolt hole 22, an axial slit 26a may be provided in the cover 26 as shown in FIG.

  The structure of the flange 21 provided at the end of the casing 2 of the turbo molecular pump has been described above. However, the structure includes a rotor that is rotatably supported in the casing, and a stator that is disposed corresponding to the rotor. The same applies to the flange structure of a vacuum pump (for example, a drag pump). In addition, any casing that accommodates a rotor that rotates at high speed can be applied to casings other than vacuum pumps (for example, casings of gas turbines). That is, the present invention is not limited to the flange structure of the embodiment as long as the features and functions of the present invention can be realized.

1 is a cross-sectional view illustrating an overall configuration of a turbo molecular pump according to a first embodiment of the present invention. The figure which shows the attachment state of the turbo-molecular pump of FIG. The figure which shows the flange structure which concerns on 1st Embodiment. The figure which shows the operation | movement at the time of the rotor destruction in 1st Embodiment. The figure which shows the flange structure which concerns on 2nd Embodiment. The figure which shows the flange structure which concerns on 3rd Embodiment. The figure which shows the flange structure which concerns on 4th Embodiment. The figure which shows the flange structure which concerns on 5th Embodiment. The figure which shows the modification of FIG. The figure which shows an example of the operation | movement of FIG. The figure which shows the other example of operation | movement of FIG. The figure which shows an example of the shear test result of the volt | bolt by the flange structure which concerns on 5th Embodiment. The figure which shows the modification of the cover used for the flange structure which concerns on 5th Embodiment.

Explanation of symbols

2 Casing 4 Rotor 41 Rotor blade 43 Fixed blade 10 Bolt 21 Flange 21a Thin portion 22 Bolt hole 23, 231, 232, 232A to 232C Counterbore 24, 241 Slit hole 26 Cover

Claims (10)

It is provided at the end of the casing that houses the rotor, and is a flange structure that is fastened to the mating member via a bolt,
Corresponding to the mounting position of the bolt, it has a bottomed groove formed in a longitudinal shape in the circumferential direction on the surface of the flange,
A bolt hole through which the bolt penetrates is opened at the bottom of the bottomed groove in the rotation direction side of the rotor, and the rotation direction of the rotor is opposite from at least a first portion near the bolt hole. A flange structure of a casing, characterized in that an elongated slit hole having a width smaller than that of the bolt hole is opened to a second portion which is a side end portion. In the flange structure of the casing according to claim 1,
The casing flange structure, wherein the slit hole is provided continuously to the bolt hole. In the flange structure of the casing according to claim 1 or 2,
The casing flange structure, wherein the bolt hole and the slit hole are respectively provided in the center in the width direction of the bottom surface of the bottomed groove. In the flange structure of the casing according to any one of claims 1 to 3,
The width of the slit hole in the first part is formed wider than the width of the slit hole in the second part. In the flange structure of the casing according to claim 4,
The width of the slit hole in the first part is formed larger than the diameter of the bolt, and the width of the slit hole in the second part is formed smaller than the diameter of the bolt. Casing flange structure. In the flange structure of the casing according to claim 4 or 5,
The casing flange structure, wherein a depth of the bottomed groove in the first part is formed to be shallower than a depth of the bottomed groove in the second part. In the flange structure of the casing according to any one of claims 1 to 6,
The casing flange structure, wherein a depth of the bottomed groove around the bolt hole is shallower than a depth of the bottomed groove around the slit hole. In the flange structure of the casing according to any one of claims 1 to 7,
A flange structure of a casing, wherein a cover member having a cylindrical portion for inserting a bolt is attached to the bolt hole. A casing having the flange structure according to any one of claims 1 to 8, and fastened to a member on a vacuum system side via the bolt;
A rotor rotatably supported in the casing and having rotor blades formed thereon;
A turbomolecular pump comprising: a stator having stator blades disposed corresponding to the rotor blades. A casing having the flange structure according to any one of claims 1 to 8, and fastened to a member on a vacuum system side via the bolt;
A rotor rotatably supported in the casing;
A vacuum pump comprising: a stator disposed corresponding to the rotor.

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