JP2012127326A - Vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum pump capable of reducing misalignment in a radial direction of a rotor, caused by deformation of the rotor.SOLUTION: The vacuum pump includes: a shaft 33 having a fastening surface 335 perpendicular to the axial center; positioning pins 40a, 40b vertically disposed on the fastening surface 335; a rotor 30 bolted to the fastening surface 335 and having respective through holes 301 through which the positioning pins 40a, 40b are inserted; and a motor rotating and driving the shaft 33. The positioning pin 40a is vertically disposed in a position on a line L1 which is perpendicular to the axial center, on the fastening surface 335. The positioning pin 40b is vertically disposed in a position on a line L2 which is perpendicular to the axial center and forms a prescribed angle θ with the line L1, on the fastening surface 335.

Description

  The present invention relates to a vacuum pump including a rotating body that rotates at a high speed, such as a turbo molecular pump or a molecular drag pump.

  2. Description of the Related Art Conventionally, in a turbo molecular pump, a rotating body structure in which a rotor in which rotor blades are formed on a shaft supported by a bearing (magnetic bearing or mechanical bearing) is bolted and integrated is common. The fastening structure employs a fitting structure in which the shaft on the shaft side is inserted into the hole provided on the rotor side, or conversely, the shaft provided on the rotor side is inserted into the hole provided on the shaft side. (For example, refer to Patent Document 1).

JP 2000-291586 A

  However, the diameter on the hole side increases due to the deformation due to centrifugal force or thermal expansion when the rotation rises or the temperature rises, or the diameter on the shaft side becomes smaller when the rotation decelerates or the temperature drops, and the fastening is loosened in the radial direction. There may be a radial shift between the shaft and the shaft. In such a case, the balance of the rotating body is greatly lost, and there is a possibility that the rotation drive becomes impossible.

According to a first aspect of the present invention, there is provided a vacuum pump comprising: a rotary shaft having a fastening surface perpendicular to the shaft core; first and second convex portions erected on the fastening surface; and bolt fastening to the fastening surface; 1st convex part provided with the rotor in which the 1st recessed part in which 1 convex part is inserted, and the 2nd recessed part in which the 2nd convex part is inserted, and the motor which rotationally drives a rotating shaft Is erected at a position on a first straight line orthogonal to the axis of the fastening surface, and the second convex part is on a second straight line that is orthogonal to the axial center of the fastening surface and forms a predetermined angle with the first straight line. It is erected at the position.
According to a second aspect of the present invention, in the vacuum pump according to the first aspect, the first and second convex portions are positioning pins.
According to a third aspect of the present invention, in the vacuum pump according to the first aspect, the first convex portion is a convex portion extending in the direction of the first straight line, and the second convex portion is extended in the direction of the second straight line. It is a convex part.
According to a fourth aspect of the present invention, in the vacuum pump according to the third aspect, the first and second convex portions are formed on the outer peripheral surface of the spline shaft. And the first and second recesses are spline grooves.

  ADVANTAGE OF THE INVENTION According to this invention, the radial direction shift | offset | difference of the rotor with respect to the rotating shaft resulting from rotor deformation | transformation can be suppressed.

It is a figure explaining the vacuum pump which concerns on this invention. FIG. 3 is a diagram illustrating a positioning structure of a rotor 30. It is a figure which shows an example of the rotor positioning structure in the conventional turbo molecular pump. It is a figure which shows the other example of the rotor positioning structure in the conventional turbo molecular pump. It is a figure explaining arrangement of pins 40a and 40b and position shift of rotor 30. It is a figure which shows the modification 1 of a rotor positioning structure. It is a figure which shows the other structure of convex part area | region 332a, 332b. It is a figure which shows the modification 2 of a rotor positioning structure. It is a figure which shows the cross-shaped convex part 322. FIG.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a vacuum pump according to the present invention, and is a cross-sectional view of a pump body 1 constituting a turbo molecular pump. The turbo molecular pump is composed of a pump body 1 shown in FIG. 1 and a control unit (not shown).

  The turbo molecular pump shown in FIG. 1 is a magnetic levitation turbo molecular pump, and the shaft 33 to which the rotor 30 is fastened is supported in a non-contact manner by a radial magnetic bearing 37 and a thrust magnetic bearing 38. The flying position of the shaft 33 is detected by a radial displacement sensor 27 and an axial displacement sensor 28. The shaft 33 magnetically levitated by the magnetic bearing is rotated at a high speed by a motor 36. 26 and 29 are emergency mechanical bearings, and the shaft 33 is supported by the mechanical bearings 26 and 29 when the magnetic bearing is not operating.

  The rotor 30 and the shaft 33 which is a rotating shaft are fastened by bolts 34. The positioning (centering) between the rotor 30 and the shaft 33 is performed by pins 40a and 40b. These positioning pins 40a and 40b prevent the rotor 30 from shifting in the radial direction with respect to the shaft 33 due to centrifugal force or thermal expansion during high-speed rotation.

  The rotor 30 is formed with a plurality of stages of rotating blades 32 and a cylindrical screw rotor 31 as vacuum evacuation function units. On the other hand, as the evacuation function section on the fixed side, a plurality of stages of fixed wings 22 arranged alternately with the rotary wings 32 in the axial direction and a screw stator 24 provided on the outer peripheral side of the screw rotor 31 are provided. . Each fixed wing 22 is placed on the base 20 via the spacer ring 23. When the pump casing 21 is fixed to the base 20, the stacked spacer ring 23 is sandwiched between the base 20 and the pump casing 21, and the fixed blade 22 is positioned.

  The base 20 is provided with an exhaust port 25, and a back pump is connected to the exhaust port 25. When the rotor 30 is magnetically levitated and driven at high speed by the motor 36, the gas molecules on the intake port 21a side are exhausted to the exhaust port 25 side.

  2A and 2B are views for explaining the positioning structure of the rotor 30. FIG. 2A is a view of the central portion of the rotor 30 provided with the pins 40a and 40b as viewed from the intake port 21a side, and FIG. It is A sectional drawing. The rotor 30 is fastened to an upper end surface (that is, a fastening surface) 335 of a flange portion 33 a formed at the upper end of the shaft 33. Two holes 330 are formed in the fastening surface 335 of the flange portion 33a. On the other hand, through holes 301 are also formed in the rotor 30 at positions facing the holes 330. As shown in FIG. 2A, the pins 40a and 40b are not arranged in a straight line with respect to the radial line passing through the axial center of the shaft 33, but are arranged at a position shifted by an angle θ from the straight line arrangement. Has been. In the example shown in FIG. 2, the distances from the axis center to the pins 40a and 40b are set equal, but they may be different.

  Each pin 40a, 40b is inserted and inserted in a form that is press-fitted into both the hole 330 and the through hole 301. In this case, the press-fitting allowance in the through hole 301 is set to be smaller than the press-fitting allowance in the hole 330, and the press-fitting between the pins 40a and 40b and the through hole 301 is light press-fitting. When the rotor 30 is fastened to the shaft 33, the pins 40a and 40b are previously press-fitted into the holes 330, and then the rotor 30 is mounted on the upper end surface of the flange portion 33a from above in FIG. The pins 40 a and 40 b are press-fitted into the respective through holes 301 of the rotor 30. Thereafter, the rotor 30 is fixed to the flange portion 33a by the bolt 34. The rotor 30 is restrained in the axial direction by a bolt 34.

  The present embodiment is characterized in that the rotor 30 is positioned (centered) by the pins 44a and 44b having the configuration shown in FIG. 2, and the operation and effect thereof will be described in comparison with the conventional structure. To do. In conventional turbo molecular pumps, a rotor positioning structure as shown in FIGS. 3 and 4 is generally employed.

  In the rotor positioning structure shown in FIG. 3, a shaft portion 331 for positioning is formed on the shaft 33. The shaft 30 is positioned (centered) by fitting the shaft 331 into a through-hole 302 formed in the rotor 30. In the structure shown in FIG. 3, the shaft portion 331 is press-fitted into the through hole 302 by shrink fitting.

  In a general turbo molecular pump, the rotor 30 is made of an aluminum material, and the shaft 33 is made of an iron material. Therefore, deformation due to centrifugal force or thermal expansion during high-speed rotation is greater in the rotor 30 than in the shaft 33. As a result, as illustrated in FIG. 3B, a gap is generated between the rotor-side through hole 302 and the shaft-side shaft portion 331. Note that the two-dot difference line indicates the rotor 30 before being deformed, and specifically indicates the inner diameter position of the rotor upper end recess where the through hole 302 is formed.

  On the other hand, in the rotor positioning structure shown in FIG. 4, a circular convex portion 303 is formed on the rotor side, and a hole 333 into which the convex portion 303 is inserted is formed on the shaft side. In this case, a gap fit is employed between the convex portion 303 and the hole 333. Since the rotor 30 using an aluminum system is larger in deformation due to centrifugal force or thermal expansion, if there is no gap between the convex portion 303 and the hole 333, deformation such that the fastening surface in the vicinity of the convex portion 303 is raised. May occur. Therefore, it is a gap fit. For this reason, the rotor 30 may be displaced in the radial direction and the balance of the rotating body may be lost.

  The rotor 30 is fastened to the shaft 33 by bolts 34, but accurate positioning in the radial direction of the rotor 30 that is a high-speed rotating body is difficult with the bolts 34. Therefore, when a gap as shown in FIG. 3B is generated, the rotor 30 tends to be displaced in the radial direction with respect to the shaft 33. As a result, the rotating body composed of the rotor 30 and the shaft 33 is out of balance, and the pump needs to be disassembled and rebalanced.

  FIG. 5A shows a case where the rotor 30 is deformed by centrifugal force or thermal expansion in the rotor positioning structure using the pins 40a and 40b of the present embodiment. In addition, a two-dot difference line shows the rotor 30 (inner diameter position of a rotor upper end recessed part) before a deformation | transformation. The pin 40a is disposed on a straight line L1 passing through the shaft core (axis center) on the fastening surface 335, and the pin 40b is disposed on a straight line L2 passing through the shaft core on the fastening surface 335 and forming an angle θ with the straight line L1. ing.

  Since the rotor 30 is deformed so as to expand in the outer peripheral direction, when the rotor 30 is deformed and the through-hole 301 becomes large, as shown in FIG. 5A, the pin 40a has a linear L1 direction (α1 direction) outside and A gap is generated in a direction (β1 direction) orthogonal to the straight line L1. On the other hand, with respect to the pin 40b, a gap is generated in the direction outside the straight line L2 (α2 direction) or in the direction perpendicular to the straight line L2 (β2 direction). Therefore, there is room for the rotor 30 to shift in the α1 direction with respect to the pin 40a, and there is room for the pin 40b to shift in the α2 direction. However, since the directions of the α1 direction and the α2 direction are shifted by an angle θ, the rotor 30 cannot actually shift in any direction.

  FIG. 5B shows a case where the pins 40a and 40b are arranged on the straight line L1. In this case, there is room for the rotor 30 to shift in the α1 direction for both pins 40a and 40b. Therefore, in such an arrangement, the rotor 30 can be displaced in the α1 direction, and the balance of the rotating body may be lost.

  For this reason, two or more positioning pins are required, and each pin needs to be arranged so that all the pins are not arranged on the same radial straight line passing through the axis center. That is, as shown in FIGS. 2 and 5A, at least one pin needs to be arranged at a position deviated from the straight line by a predetermined angle with respect to the radial line passing through the axis of the fastening surface 335. This angle deviation, that is, the angle θ of the straight line L2 shown in FIG. 5A is preferably set to 45 degrees or less in consideration of the arrangement shown by the dotted line B as the arrangement on the straight line L2. Further, as the material of the pins 4a and 40b, those having the same mechanical properties (Young's modulus and thermal expansion coefficient) as the shaft 33 are desirable. For example, stainless steel is preferable from the viewpoint of corrosion resistance. Moreover, you may use what gave corrosion-resistant plating to steel materials.

  Further, although the pins 40a and 40b are lightly press-fitted into the through hole 301 of the rotor 30, this fitting may be a gap fitting. In the case of clearance fitting, strictly speaking, a clearance is formed on the shaft core side with respect to the pins 40a and 40b before the rotor is deformed. However, if the clearance is about the clearance fitting, the rotor 30 cannot be driven even if it is displaced. There is no such thing. Furthermore, when the rotor 30 is deformed so as to expand to the outer peripheral side due to centrifugal force or thermal expansion, the above-described gap on the shaft core side is reduced, and displacement of the rotor 30 is suppressed compared to before the rotor is deformed. It will be. In the present embodiment, the through hole 301 is used, but the through hole 301 may not be penetrated.

(Modification 1)
FIG. 6 is a view showing a first modification of the rotor positioning structure of the present embodiment. 6A is a cross-sectional view showing a fastening portion between the rotor 30 and the shaft 33, and FIG. 6B is a plan view of a fastening surface 335 of the shaft 33 flange portion 33a. As shown in FIG. 6 (a), the fastening surface 335 (rotor facing surface) of the flange 33a is formed with a convex portion 332 having a bent planar shape as shown in FIG. 6 (b). On the fastening surface 30, a groove 304 having the same plane shape as the convex portion 332 and into which the convex portion 332 is inserted is formed.

  The convex portion 332 includes a convex region 332a extending in the straight line L1 direction and a convex region 332b extending in the straight line L2 direction. In other words, the convex portion 332 includes a convex portion region 332a disposed on the straight line L1 and a convex portion region 332b disposed on the straight line L2. Therefore, also in the case of the modification 1, there exists an effect similar to the case of the rotor positioning structure using the pins 40a and 40b mentioned above.

  In the example shown in FIG. 6, the convex regions 332a and 332b extend from the axial center to the edge of the flange portion 33a. However, as in the convex regions 332a and 332b shown in FIG. It does not need to extend to the edge of the part 33a. Further, as shown in FIG. 7B, the convex regions 332a and 332b may be arranged only in a region close to the edge of the flange portion 33a. In either case, since the convex regions 332a and 332b are arranged separately on the straight lines L1 and L2 forming the angle θ, the same action as that of the convex regions 332a and 332b shown in FIG. There is an effect.

  The fitting between the convex portion 322 and the groove 304 is preferably an interference fitting (that is, press-fitting), but may be a gap fitting as in the case of the pins 40a and 40b described above. Moreover, the shape of the convex part 322 may be a cross shape as shown in FIG. In such a case, if it is considered that the four convex regions 322a to 322d are formed at intervals of 90 degrees, it can be easily understood that the same effect as the convex portion 322 described above can be obtained.

(Modification 2)
In the rotor positioning structure of the second modification, a spline structure 50 composed of a hole side spline 50a and a shaft side spline 50b as shown in FIG. 8 is adopted as the positioning structure. 8A is a cross-sectional view showing a fastening portion between the rotor 30 and the shaft 33, and FIG. 8B is a view showing a spline 50a on the hole side formed on the rotor 30 side. In general, the spline is used for torque transmission, but the spline structure 50 in the modified example 2 is mainly used for positioning. The function of torque transmission is mainly performed by the bolt 34.

  In the hole-side spline 50a, a plurality of grooves 500 (500a, 500b) are formed radially from the inner peripheral surface of the hole toward the center. On the other hand, although not shown, the shaft-side spline 50b has a plurality of teeth (convex portions) fitted into the plurality of grooves 500 on the outer peripheral surface of the shaft erected at the axial center position of the fastening surface 335. Is formed. Also in such a spline structure 50, as shown in FIG. 8B, the pair of grooves 500a is arranged on the straight line L1, but the other pair of grooves 500b is a straight line L2 inclined with respect to the straight line L1. Is placed on top. That is, each groove 500 corresponds to the groove 304 of the first modification, and the teeth (convex parts) of the shaft-side spline 50b correspond to the convex parts 332 of the first modification. Therefore, as in the first modification described above. Has the effect of.

  Each of the embodiments described above may be used alone or in combination. This is because the effects of the respective embodiments can be achieved independently or synergistically. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired. For example, the present invention can be applied to a turbo molecular pump that is not a magnetic bearing type, and can also be applied to a vacuum pump such as a molecular drag pump described in JP-A-8-144992.

  1: pump body, 30: rotor, 33: shaft, 33a: flange, 34: bolt, 40a, 40b: pin, 50: spline structure, 50a: hole side spline, 50b: shaft side spline, 301: through hole, 304, 500, 500a, 500b: groove, 330: hole, 332: convex portion, 322a to 322d, 332a, 332b: convex region, 335: fastening surface, L1, L2: straight line

Claims (4)

A rotating shaft having a fastening surface perpendicular to the axis;
First and second protrusions erected on the fastening surface;
A rotor that is bolted to the fastening surface and has a first recess into which the first projection is inserted and a second recess into which the second projection is inserted;
A motor that rotationally drives the rotating shaft,
The first convex portion is erected at a position on a first straight line perpendicular to the axis of the fastening surface,
The vacuum pump characterized in that the second convex portion is erected at a position on a second straight line that is orthogonal to the axial center of the fastening surface and forms a predetermined angle with the first straight line. The vacuum pump according to claim 1, wherein
The vacuum pump characterized in that each of the first and second convex portions is a positioning pin. The vacuum pump according to claim 1, wherein
The first convex portion is a convex portion extending in the direction of the first straight line,
The vacuum pump, wherein the second convex portion is a convex portion extending in the direction of the second straight line. The vacuum pump according to claim 3,
A spline shaft erected at the axial position of the fastening surface;
The first and second convex portions are teeth formed on the outer peripheral surface of the spline shaft,
The vacuum pump characterized in that the first and second recesses are spline grooves.

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