JP2011185094A - Turbo-molecular pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an impact applied to a case member by a rotor split by abnormality in a structure formed with a throttle part smaller than the diameter of a rotor blade on an intake opening side of the case member. <P>SOLUTION: A blade exhaust part 2 formed by piling rotor blades 4a of a rotor 4 and stator blades 6 in multiple stages is provided in an upper case 12 having an intake opening 15. The stator blade 6 is fitted, being pinched by spacers 5 arranged in upper and lower. The top surface of the spacer 5 of the highest stage is arranged on an intake opening 15 side than the top surface of the rotor blade 4a of the highest stage, and an impact interfering member 20 is provided on the spacer 5 of the highest stage separately from the inner surface of the throttle part 12a of the upper case 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a turbo molecular pump.

A turbo molecular pump is used when a semiconductor manufacturing apparatus or an analysis apparatus is changed from a medium vacuum to an ultra-high vacuum.
The turbo molecular pump increases the rotational speed of the rotor to increase the exhaust speed and the diameter of the rotor blades as much as possible. For this reason, the diameter of the rotor blades of the turbo molecular pump may be larger than the diameter of the exhaust system of the apparatus to which the turbo molecular pump is attached. In this case, it is necessary to adjust the diameter of the inlet of the turbo molecular pump to the size of the device to be attached. For this purpose, the case member is provided with a throttle portion that covers the outer peripheral portion of the rotor blade, and the diameter of the intake port provided in the case member is made smaller than the diameter of the rotor blade.

  By the way, in a turbo molecular pump that rotates at a high speed, abnormal vibrations from the outside and abnormal situations inside can occur, and if the rotor breaks down, the rotor with large rotational energy is split and scattered. Will do. A structure in which an internal case is provided between the case member and the outer periphery of the rotor blade is known in order to prevent the case member from being deformed or broken by the broken pieces directly hitting the case member ( For example, see Patent Document 1). Since the inner case absorbs the rotational energy of the broken pieces of the rotor, the impact on the case member can be reduced.

JP-A-11-62879

In the turbo molecular pump described in the above prior art document, since the inner case is provided between the case member and the outer periphery of the rotor blade, the impact of the case member in the radial direction of the rotor is reduced.
However, when the rotor is split, axially thrust force is applied to the rotor along with radial outward force due to centrifugal force. Therefore, the fragments are scattered on the inlet side while drawing a spiral.
For this reason, for a turbomolecular pump having a case member having a suction port smaller than the diameter of the rotor blade and thus having a throttle portion smaller than the diameter of the rotor blade, the inner case described in the above-mentioned prior document The impact on the case member cannot be reduced.

  The turbomolecular pump of the present invention has a case member in which a stator blade supported by a spacer and a rotor blade are stacked in the axial direction of the rotor, and an intake port is formed on the uppermost rotor blade side. In the turbo molecular pump in which the diameter of the inlet of the case member is smaller than the diameter of the rotor blade, at least one is provided between the inner surface of the case member on the upper surface side of the uppermost rotor blade and the upper surface of the uppermost rotor blade. An impact interference member having a portion spaced apart from the inner surface of the case member is provided.

  According to the present invention, the rotational energy of the rotor fragments scattered on the inlet side can be absorbed by the impact interference member.

Sectional drawing which shows Embodiment 1 of the turbo-molecular pump of this invention. FIG. 2 is a perspective view of the impact interference member and the uppermost spacer shown in FIG. 1. Sectional drawing which shows Embodiment 2 of the turbo-molecular pump of this invention. The perspective view which shows the modification 1 of the impact interference member of this invention. The perspective view which shows the modification 2 of the impact interference member of this invention. The perspective view which shows the modification 3 of the impact interference member of this invention.

(Embodiment 1)
FIG. 1 illustrates the best mode for carrying out the present invention with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of a turbo molecular pump according to the present invention. The turbo molecular pump 1 illustrated in FIG. 1 is a magnetic bearing type turbo molecular pump. The turbo molecular pump 1 includes a case member 11 in which an upper case 12 and a base 13 are sealed from the outside by a seal member 42. In the center of the case member 11, a rotor 4 having a plurality of stages of rotor blades 4a is rotatably arranged.

  The turbo molecular pump 1 is a composite type turbo molecular pump having a blade exhaust part 2 in an internal space of an upper case 12 and a thread groove exhaust part 3 in an internal space of a base 13. The blade exhaust part 2 is composed of a plurality of stages of rotor blades 4 a and a plurality of stages of stator blades 6, and the thread groove exhaust part 3 is composed of a rotor cylindrical part 4 b and a screw stator 7.

  The rotor blades 4a and the stator blades 6 are alternately arranged in the axial direction of the pump (the vertical direction in the drawing). A plurality of ring-shaped spacers 5 are laminated on the inner surface of the upper case 12 on the base 13, and the outer peripheral portion of each stator blade 6 is sandwiched and held by the upper and lower spacers 5. A screw groove (not shown) is formed on the inner peripheral surface of the cylindrical screw stator 7. At the lower part of the rotor 4, a rotor cylindrical portion 4 b is formed in which an outer peripheral surface is formed with a screw groove facing the inner peripheral surface of the screw stator 7 with a slight gap. The screw stator 7 is fixed to the base 13 with bolts 41.

  The rotor 4 in which the multistage rotor blades 4 a and the rotor cylindrical portion 4 b are formed is supported in a non-contact state by a radial magnetic bearing 31 and a thrust magnetic bearing 32 provided on the base 13. The rotor 4 supported in a non-contact manner by the magnetic bearings 31 and 32 is driven to rotate by the motor 9. The magnetic levitation position of the rotor 4 is detected by gap sensors 33a, 33b, and 33c. Reference numeral 34 denotes a mechanical protective bearing that supports the rotor 4 in a state where the rotor 4 is not levitated by the magnetic action of the magnetic bearings 31 and 32.

An intake port 15 is formed in the upper part of the upper case 12. The diameter D _in the inlet 15 has a diameter D _R smaller size of the rotor blades 4a. Therefore, the upper case 12, the upper portion of the blade pumping section 2, in other words, the upper part of the uppermost rotor blade 4a, the diaphragm portion 12a to be smaller than the diameter D _R of the rotor blade 4a is formed Yes.

  Gas molecules flowing in from the intake port 15 are struck by the rotor blade 4 a rotating at high speed in the blade exhaust section 2 and applied to the stator blade 6. Although not shown, the rotor blades 4a and the stator blades 6 have opposite blade inclination directions, and the gas molecules are unlikely to reverse from the front side, which is the high vacuum side, to the downstream side, which is the downstream side. The angle has been changed. The gas molecules are compressed in the blade exhaust part 2 and transferred to the screw exhaust part 3 below the figure.

  In the screw exhaust portion 3, when the rotor cylindrical portion 4b rotates at a high speed with respect to the screw stator 7, an exhaust function by a viscous flow is generated, and the gas transferred from the blade exhaust portion 2 to the thread groove exhaust portion 3 is exhausted while being compressed. It is transferred in the direction of the mouth 45 and evacuated. In the present embodiment, the screw groove exhaust portion 3 having a screw groove configuration is used. However, a portion that exhibits an exhaust function by viscous flow, including configurations other than the screw groove configuration, may be referred to as a drag pump portion.

  An impact interference member 20 is installed on the upper part of the uppermost rotor blade 4a. The impact interference member 20 is disposed between the upper surface of the uppermost rotor blade 4 a and the inner surface of the throttle portion 12 a of the upper case 12. The upper surface of the uppermost spacer 5 is positioned above the upper surface of the uppermost rotor blade 4 a, that is, on the intake port 15 side, and the impact interference member 20 is placed on the upper surface of the uppermost spacer 5.

  FIG. 2 is a perspective view of the impact interference member 20 and the uppermost spacer 5 (hereinafter, the uppermost spacer 5 is simply referred to as the spacer 5). The spacer 5 includes a lower portion 51 having an outer surface 51 a that contacts the inner surface of the upper case 12, and an upper portion 52 having an outer diameter smaller than that of the lower portion 51 and formed integrally with the lower portion 51. The outer surface 52 a of the upper part 52 is located inside the outer surface 51 a of the lower part 51. The impact interference member 20 has a ring shape having a base portion 21 and an inclined portion 22 formed integrally with the base portion 21, and the lower surface of the base portion 21 is placed on the upper surface of the upper portion 52 of the spacer 5.

The inclined portion 22 of the impact interference member 20 has a ring shape that is inclined along the throttle portion 12a so as to be approximately several mm away from the throttle portion 12a of the upper case 12. The inclined portion 22 is formed with an opening 24 having a diameter D _o smaller than the inner diameter D _s of the throttle portion 12a. The inclined portion 22 has a large number of circular openings 23 penetrating in the thickness direction.

Here, when an abnormality occurs inside and outside the device, and the rotor 4 that rotates at high speed is split, a thrust force in the axial direction acts on the rotor 4 along with a radially outward force due to centrifugal force. The debris scatters toward the intake port 15 while drawing a spiral.
However, in the turbo molecular pump of the present invention, the impact interference member 20 is disposed on the front surface of the throttle portion 12a of the upper case 12. The broken pieces of the rotor 4 collide with the impact interference member 20, and the impact interference member 20 is deformed, so that the kinetic energy of the fragments is absorbed.

  In this case, since the impact interference member 20 is disposed away from the inner surface of the upper case 12, the impact is not directly transmitted to the upper case 12 when deformed. Moreover, the impact interference member 20 is merely placed on the upper surface of the spacer 5 and is not attached to the upper case 12. Therefore, when the impact interference member 20 absorbs the kinetic energy of the fragments, the impact interference member 20 rotates on the spacer 5 along the inner surface of the upper case 12, and the impact on the upper case 12 can be further reduced.

Inclined portion 22 of the impact interference member 20, the diameter D _o of the inner circumference side tip has an inner diameter D _s is smaller than the size of the aperture portion 12a. For this reason, it becomes resistance of the gas drawn in from the inlet 15 of the upper case 12. Therefore, in the embodiment of the turbo molecular pump 1 according to the present invention, the opening 23 is formed in the impact interference member 20. That is, the opening 23 formed in the inclined portion 22 is for relaxing the resistance of vacuum exhaust. The opening 23 is sized such that the inclined portion 22 satisfies the relaxation of the resistance of the vacuum exhaust while ensuring the rigidity necessary for absorbing the kinetic energy of the fragmented rotor 4 fragments.

  If it is not intended to limit but a suitable example of the material of the impact interference member 20 is shown, SUS304, structural carbon steel S25C, S35C, S45C, etc. are mentioned. It is desirable to apply a plating layer of nickel or the like to the outer surface of the base 21 of the impact interference member 20, including the case of SUS304, that is, the surface facing the inner surface of the upper case 12. Further, in the case of a material having insufficient corrosion resistance such as carbon steel, it is necessary to form a plating layer such as nickel for preventing corrosion on the entire surface.

(Embodiment 2)
The turbo molecular pump 1 according to the first embodiment has only the impact interference member 20 disposed between the uppermost rotor blade 4a and the throttle portion 12a of the upper case 12.
Considering the scattering motion of the divided rotor 4, the turbo molecular pump 1 shown in the first embodiment can sufficiently reduce the impact on the case member 11.
The turbo molecular pump 1A shown in FIG.
One difference between the turbomolecular pump 1A shown in FIG. 3 and the turbomolecular pump 1 of the first embodiment is that a protective inner case 61 is provided in the case member 11 together with the impact interference member 20. is there. Another difference is that the screw stator 63 is formed integrally with the inner case 61 by molding.

  The inner case 61 has a large-diameter portion 62 located on the upper case 12 side and a small-diameter portion 63 located on the base 13 side. The inner case 61 is attached to the base 13 with a bolt 41 between the large-diameter portion 62 and the small-diameter portion 63. Yes. The outer surface of the large-diameter portion 62 is disposed several mm away from the inner surface of the upper case 12. On the inner surface side of the large diameter portion 62, a plurality of stages of spacers 5 and stator blades 6 are alternately stacked. The uppermost spacer 5 is fixed to the large diameter portion 62 of the inner case 61 with bolts 43.

  The upper surface of the uppermost spacer 5 is located above the upper surface of the uppermost rotor 4 a, and the impact interference member 20 is placed on the upper surface of the uppermost spacer 5. The shape, function, and the like of the impact interference member 20 are as described in the first embodiment.

The outer surface of the small diameter portion 63 of the inner case 61 is arranged several mm away from the inner surface of the base 13. On the inner peripheral surface of the small-diameter portion 63, a screw groove facing the screw groove formed on the outer peripheral surface of the rotor cylindrical portion 4b with a slight gap is formed.
Other configurations and functions are the same as those in the first embodiment, and the same components are denoted by the same reference numerals and description thereof is omitted.

  Also in the turbo molecular pump 1 </ b> A shown in the second embodiment, the impact interference member 20 is disposed between the uppermost rotor blade 4 a and the throttle portion 12 a of the upper case 12. For this reason, the broken pieces of the rotor 4 collide with the impact interference member 20, and the impact interference member 20 is deformed to absorb the movement energy of the fragments, and the impact is not directly transmitted to the upper case 12. Moreover, since the impact interference member 20 is merely placed on the upper surface of the spacer 5, when absorbing the kinetic energy of the fragments, the impact interference member 20 rotates on the spacer 5 along the inner surface of the upper case 12, The impact on the upper case 12 can be reduced.

At the same time, the turbo molecular pump 1A shown in the second embodiment includes a protective inner case 62 having a large-diameter portion 62 located on the upper case 12 side and a small-diameter portion 63 located on the base 13 side. For this reason, even when the fragmented pieces of the rotor 4 are scattered toward the region corresponding to the blade exhaust part 2 of the upper case 12 and the region corresponding to the screw exhaust part 2 of the base 13, the shock wave spreads to the case member 11. Can be relaxed.
The impact interference member 20 is not limited to the structure shown in FIG. 2 and can be used with various modifications. Below, several modifications of the impact interference member 20 are shown.

(Modification 1 of impact interference member)
FIG. 4 is a perspective view showing Modification 1 of the impact interference member. The impact interference member 70 illustrated in FIG. 4 includes a base 71 and a large number of protrusions 72 formed integrally with the base 71. The protrusions 72 are inclined so as to rise toward the center, and the protrusions 72 are separated by slit-like openings 73.
That is, in the first modification, the impact interference member 70 is formed with a slit-like opening provided to reduce the resistance of evacuation.

(Modification 2 of the impact interference member)
FIG. 5 is a perspective view showing Modification Example 2 of the impact interference member. The impact interference member 80 shown in FIG. 5 has a flat shape as a whole.
The impact interference member 80 is provided with a large number of slit-shaped openings 83 communicating with each other on the inner peripheral side of a ring-shaped base 81, and a large number of protrusions 82 separated from each other by the openings 83. ing. In other words, the impact interference material 70 shown in Modification 1 has a shape that is flat as a whole.
In this case, the slit-shaped opening 83 communicating with the inner peripheral side may be a circular or elliptical through hole that does not communicate with the inner peripheral side.

(Modification 3 of the impact interference member)
FIG. 6 is a perspective view showing Modification 3 of the impact interference member. The impact interference member 90 illustrated in FIG. 6 has a structure in which a mesh portion 92 is provided on a base portion 91.
The mesh portion 92 is formed of a metal woven fabric in which fine metal wires are woven so that a large number of pores are formed, or a metal plate on which innumerable pores are formed. In FIG. 6, the mesh portion 92 is formed to be inclined with respect to the base portion 91, but may be formed flat with the base portion 91.

The impact interference member is not limited to one having a size in which the diameter D _{o of the} opening is smaller than the inner diameter D _s of the aperture 12 a of the upper case 12. The diameter D _o of the opening of the impact interference member may be the same as or smaller than the inner diameter D _s of the throttle portion 12a of the case member 11. When the diameter D _o of the opening of the impact interference member is the same as or smaller than the inner diameter D _s of the throttle portion 12a, the influence of the evacuation resistance is reduced, so that the opening penetrating in the thickness direction 23, 73, 83, etc. need not be formed.

  Further, the impact interference member is not limited to a flat shape or an inclined portion. It may be formed in a step shape or a zigzag shape. Even in the case of a shape having an inclined portion, the inclined portion is not limited to a shape having a linear cross section, and the cross section may have a concave or convex shape. Moreover, you may have a composite shape which combined a part of above-mentioned each shape.

  Further, although the magnetic bearing type turbo molecular pump has been described as an embodiment, the present invention is not limited to the shaft bearing type and can be applied. In addition, the present invention can be applied in various modifications within the scope of the invention. In short, the stator blades supported by the spacers and the rotor blades are stacked in the axial direction of the rotor. In the turbo molecular pump having a case member having an inlet formed on the uppermost rotor blade side, and the diameter of the inlet of the case member is smaller than the diameter of the rotor blade, the upper surface of the uppermost rotor blade Any impact interference member that is at least partially separated from the inner surface of the case member may be provided between the inner surface of the case member and the upper surface of the uppermost rotor blade.

DESCRIPTION OF SYMBOLS 1, 1A Turbo molecular pump 4 Rotor 4a Rotor blade 5 Spacer 6 Stator blade 11 Case member 12 Upper case 13 Base 15 Inlet 20, 70, 80, 90 Impact interference member 22 Inclined portion 23, 73, 83 Opening portion

Claims (6)

The stator blades supported by the spacer and the rotor blades are stacked in the axial direction of the rotor, and have a case member in which an intake port is formed on the uppermost rotor blade side, and the diameter of the intake port of the case member In a turbomolecular pump having a size smaller than the diameter of the rotor blade,
An impact interference member at least partially separated from the inner surface of the case member is provided between the inner surface of the case member and the upper surface of the uppermost rotor blade on the upper surface side of the uppermost rotor blade. A turbo-molecular pump that is characterized.   2. The turbo molecular pump according to claim 1, wherein the impact interference member has a ring shape that is rotatable by being guided by an inner surface of the case member. 3.   3. The turbo molecular pump according to claim 1, wherein the uppermost spacer has an upper surface closer to the inlet side than an upper surface of the uppermost rotor blade, and the impact interference member includes an upper surface of the uppermost spacer. A turbo molecular pump characterized by being mounted on an upper surface.   4. The turbo molecular pump according to claim 1, wherein an inner surface of the case member in a region where the stator blades and the rotor blades are stacked is separated from the inner surface of the case member for protection. A turbomolecular pump characterized by an inner case.   5. The turbo molecular pump according to claim 1, wherein the impact interference member has an opening penetrating in a thickness direction. 6. The turbo-molecular pump according to any one of claims 1 to 5, wherein the impact interference member is formed integrally with a flat base portion and the base portion, and an inner peripheral side is an upward slope toward the intake port side. A turbo molecular pump characterized by having an inclined portion.

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