JP2014173433A - Vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum pump in which a rotor and a shaft can be easily fastened and disassembled.SOLUTION: A fitting part between a rotor side fitting hole 301 and a shaft side fitting shaft 331 and a fitting part between a rotor side fitting protrusion 302 and a shaft side fitting groove 332 are provided in a vacuum pump. Diameters A to D of the respective parts are set so that a clearance Cr between the rotor side fitting hole 301 and the shaft side fitting shaft 331 is smaller than a clearance Cs between the rotor side fitting protrusion 302 and the shaft side fitting groove 332 at ordinary temperatures. In addition, the diameters A to D of the respective parts are set so that the clearance Cs between the rotor side fitting protrusion 302 and the shaft side fitting groove 332 is smaller than the clearance Cr between the rotor side fitting hole 301 and the shaft side fitting shaft 331 when the temperatures of a rotor 30 and a shaft 33 exceed a predetermined temperature Ts.

Description

  The present invention relates to a vacuum pump.

  2. Description of the Related Art Conventionally, in a turbo molecular pump, a rotating body structure in which a rotor having rotor blades formed on a rotor shaft supported by a bearing (magnetic bearing or mechanical bearing) is bolted and integrated is generally used. In the fastening structure, the rotor shaft side engagement shaft is inserted into the engagement hole provided on the rotor side, or conversely, the engagement hole provided on the rotor shaft side is engaged on the rotor side. A fitting structure for inserting the shaft is adopted. As a fitting structure of a turbo molecular pump in which the rotor and the rotor shaft rotate at a high speed and a strict balance is required, “shrink fit” is generally used (see Patent Document 1, paragraph 40).

JP 2007-239464 A

In “shrink fitting”, although the looseness of the fitting portion during operation is small, it is necessary to heat the engagement hole side and cool the engagement shaft side when fastening. For this reason, assembly takes time.
Further, in the turbo molecular pump, the rotor blades and the rotor main body are peeled off and deteriorated, and therefore it is necessary to repair or replace the rotor at a predetermined frequency. However, in “shrink fitting”, once disassembled, it is difficult to remove the engagement shaft from the engagement hole unless the fitting part is punched out by pressing. It took a lot of time.

(1) A vacuum pump according to a first aspect of the present invention includes a shaft having a shaft-side shaft-like fitting portion and a shaft-side hole-like fitting portion, and a rotor-side hole-like shape fitting with the shaft-side shaft-like fitting portion. A rotor-side shaft-like fitting portion that fits with the fitting portion and the shaft-side hole-like fitting portion, and has a linear expansion coefficient different from that of the shaft, and a rotor fixed to the shaft. A first gap formed between the shaft-like fitting portion and the rotor-side hole-like fitting portion, and a second gap formed between the shaft-side hole-like fitting portion and the rotor-side shaft-like fitting portion In normal temperature setting, one of the first and second gaps, which is the gap between the shaft-like fitting part having the smaller linear expansion coefficient and the hole-like fitting part having the larger linear expansion coefficient, is one of the first and second gaps. The size of the gap becomes smaller than the size of the other gap. The size was configured to be smaller than the size of one gap.
(2) A vacuum pump according to a seventh aspect of the present invention is a shaft having a shaft-side shaft-like fitting portion, a rotor-side shaft-like fitting portion, and a rotor-side hole shape fitting with the shaft-side shaft-like fitting portion. It has a fitting part, has a linear expansion coefficient different from that of the shaft, has a rotor fixed to the shaft, and a fixing member side hole fitting part that fits the rotor side shaft-like fitting part. A first clearance formed between the shaft-side shaft-like fitting portion and the rotor-side hole-like fitting portion; and a rotor-side shaft-like shape, each having a same expansion coefficient and a fixing member that fixes the rotor to the shaft. In setting the second gap formed between the fitting portion and the fixed member side hole-like fitting portion, at the normal temperature, the shaft shape having the smaller linear expansion coefficient among the first and second gaps. The size of one gap, which is the gap between the fitting portion and the hole-like fitting portion with the larger linear expansion coefficient, The size of the gap is smaller than the size of one of the gaps if the size of the other gap is smaller than the size of the gap and exceeds a predetermined temperature during operation.

  ADVANTAGE OF THE INVENTION According to this invention, the fastening operation | work and disassembly operation | work with a rotor and a shaft can be facilitated, and the position shift of the radial direction of a rotor and a shaft can be made small at the time of high temperature.

It is a figure explaining the vacuum pump of 1st Embodiment. It is an expanded sectional view of the part II of FIG. It is a graph which shows the relationship between the clearance gap between a rotor side fitting hole and a shaft side fitting axis | shaft, the clearance gap between a rotor side fitting protrusion, and a shaft side fitting groove, and temperature. It is sectional drawing explaining the fitting structure of the rotor and shaft in 2nd Embodiment. It is a figure explaining a modification. It is a figure explaining a modification.

--- First embodiment ---
A first embodiment of a vacuum pump according to the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating the vacuum pump according to the first embodiment, 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 a rotor shaft (shaft) 33 to which a rotor 30 is fastened is not contacted by a radial magnetic bearing 37 and a thrust magnetic bearing 38. Supported. 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.

  A rotor disk 35 is attached to the lower surface of the shaft 33 via a mechanical bearing 29. A mechanical bearing 26 is provided on the upper side of the shaft 33. The mechanical bearings 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 are fastened by bolts 34. A portion indicated by reference numeral II is a fitting portion between the rotor 30 and the shaft 33. By adopting such a fitting structure, the rotor 30 is displaced in the radial direction with respect to the shaft 33 due to centrifugal force during high-speed rotation. Is preventing.

  The rotor 30 is formed with a plurality of stages of rotating blades 32 and a cylindrical screw rotor 31. On the other hand, on the fixed side, there are provided a plurality of stages of fixed blades 22 arranged alternately with the rotary blades 32 in the axial direction, and a screw stator 24 provided on the outer peripheral side of the screw rotor 31. 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. In the vacuum pump (turbo molecular pump) of the present embodiment, the rotor blades 32 and the screw rotor 31 constitute a rotary-side vacuum exhaust function unit, and the fixed blades 22 and the screw stator 24 constitute a fixed-side vacuum exhaust function unit. ing.

  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.

  FIG. 2 is an enlarged cross-sectional view of the portion II of FIG. 1, and the details of the fitting structure of the rotor 30 and the shaft 33 will be described below. As described above, the rotor 30 is fastened to the upper end of the shaft 33 by the bolt 34. A rotor-side fitting hole 301 having a circular cross section that extends along the axial direction of the shaft 33 is provided at the center of the rotor 30. Further, on the lower surface of the rotor 30 in contact with the upper surface of the shaft 33, a rotor-side fitting protrusion 302 having a thick short cylindrical shape protruding downward in the figure is provided.

  A cylindrical shaft-side fitting shaft 331 that protrudes upward in the figure is provided on the upper portion of the shaft 33. An annular shaft-side fitting groove 332 is provided around the base end portion of the fitting shaft 331. When the rotor 30 is attached to the upper end of the shaft 33, the shaft-side fitting shaft 331 is inserted into the rotor-side fitting hole 301 and fitted. Further, when the rotor 30 is attached to the upper end of the shaft 33, the rotor side fitting protrusion 302 is inserted into the shaft side fitting groove 332 to be fitted.

  The radial fitting between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331 and the fitting between the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332 in the radial direction have gaps, respectively. It is set to fit (clear fit) as possible. Here, the diameter of the shaft-side fitting shaft 331 is A, the diameter of the rotor-side fitting hole 301 is B, the diameter of the rotor-side fitting protrusion 302 is C, and the diameter of the shaft-side fitting groove 332 is D. And The radial gap between the rotor side fitting hole 301 and the shaft side fitting shaft 331 is represented by B-A, and the radial gap between the rotor side fitting projection 302 and the shaft side fitting groove 332 is It is represented by DC. In the following description, the radial gap formed between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331 is also called a gap Cr, and the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332 The gap in the radial direction formed between them is also called a gap Cs.

  In the present embodiment, the material of the rotor 30 is an aluminum alloy, and the material of the shaft 33 is stainless steel or steel. The linear expansion coefficient of the aluminum alloy that is the material of the rotor 30 is larger than the linear expansion coefficient of stainless steel or steel that is the material of the shaft 33. When the temperature of the rotor 30 and the shaft 33 rises due to the difference in the linear expansion coefficient, the clearance Cr between the rotor side fitting hole 301 and the shaft side fitting shaft 331 increases, and the rotor side fitting protrusion 302 and the shaft side are increased. The gap Cs with the fitting groove 332 is reduced. Further, when the temperatures of the rotor 30 and the shaft 33 are lowered, the clearance Cr between the rotor side fitting hole 301 and the shaft side fitting shaft 331 is reduced, and the rotor side fitting protrusion 302 and the shaft side fitting groove 332 are formed. The gap Cs increases.

Therefore, in the present embodiment, as will be described later, the diameters A to D of the respective parts are set so as to satisfy both the following conditions (a) and (b).
(A) At normal temperature (when cold), that is, when the temperature of the rotor 30 and the shaft 33 is normal temperature, the following equation (1) is satisfied.
Clearance Cr <Clearance Cs
B−A <D−C (1)
(B) When the temperature is high, that is, when the temperature of the rotor 30 and the shaft 33 exceeds the predetermined temperature Ts due to the operation of the turbo molecular pump, the following equation (2) is satisfied.
Clearance Cs ≦ Clearance Cr
DC ≦ B−A (2)

  That is, at room temperature, the clearance Cr between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331 is smaller than the clearance Cs between the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332. The diameter AD of each part is set. Therefore, at the normal temperature, the radial position between the rotor 30 and the shaft 33 is prevented from being shifted by the fitting portion between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331 having a smaller gap.

  However, as described above, the clearance Cr between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331 increases as the temperature of the rotor 30 and the shaft 33 increases due to the operation of the turbo molecular pump. Therefore, when the configuration is such that only the fitting portion between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331 prevents radial displacement between the rotor 30 and the shaft 33, the rotor 30 and the shaft 33 There is a possibility that the deviation of the radial position becomes large.

  On the other hand, as described above, the gap Cs between the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332 becomes smaller as the temperature of the rotor 30 and the shaft 33 becomes higher due to the operation of the turbo molecular pump. When the temperature of the rotor 30 and the shaft 33 exceeds the predetermined temperature Ts, as described in the condition (b), the clearance Cr between the rotor side fitting hole 301 and the shaft side fitting shaft 331, and the rotor side The magnitude relationship between the gap Cs between the fitting protrusion 302 and the shaft-side fitting groove 332 is reversed.

  That is, in this embodiment, when the temperature of the rotor 30 and the shaft 33 exceeds the predetermined temperature Ts, the gap is smaller, and the rotor is fitted by the fitting portion between the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332. 30 and the shaft 33 are configured to prevent the radial positions from being shifted.

  FIG. 3 shows the relationship between the temperature and the clearance Cr between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331 and the clearance Cs between the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332. It is a graph. As shown in FIG. 3, as the temperature rises, the clearance Cr between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331 increases, and the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332 become larger. The gap Cs is reduced. Further, at the above-described predetermined temperature Ts, the size of the gap Cr between the rotor side fitting hole 301 and the shaft side fitting shaft 331 and the gap Cs between the rotor side fitting projection 302 and the shaft side fitting groove 332 are set. The size matches.

  That is, in the present embodiment, when the temperatures of the rotor 30 and the shaft 33 are equal to or lower than the predetermined temperature Ts, the radial displacement between the rotor 30 and the shaft 33 causes the rotor-side fitting hole 301 and the shaft-side fitting. It is regulated by the gap Cr with the shaft 331. Further, when the temperatures of the rotor 30 and the shaft 33 are equal to or higher than the predetermined temperature Ts, the radial displacement between the rotor 30 and the shaft 33 is caused between the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332. It is regulated by the gap Cs.

  In other words, when the temperatures of the rotor 30 and the shaft 33 are equal to or lower than the predetermined temperature Ts, the maximum value of the radial positional deviation between the rotor 30 and the shaft 33 is the rotor-side fitting hole 301 and the shaft-side fitting shaft. This is the value (B−A) of the gap Cr with 331. When the temperatures of the rotor 30 and the shaft 33 are equal to or higher than the predetermined temperature Ts, the maximum value of the radial positional deviation between the rotor 30 and the shaft 33 is the rotor-side fitting protrusion 302, the shaft-side fitting groove 332, and the like. This is the value of the gap Cs (DC).

  In this embodiment, at the maximum temperature Tmax of the rotor 30 and the shaft 33 that are allowed in design, the diameters A to D of the respective parts are set so that both of the two fitting parts described above are clearance fits. ing. That is, the values of the clearance Cr and the clearance Cs at the maximum temperature Tmax are both positive values.

The value Cr (t) of the gap Cr at an arbitrary temperature t and the value Cs (t) of the gap Cs are given by the following equations (3) and (4).
Cr (t) = {B0 + (t−t1) · α1 · B0}
-{A0 + (t-t1) · α2 · A0} (3)
Cs (t) = {D0 + (t−t1) · α2 · D0}
− {C0 + (t−t1) · α1 · C0} (4)
Here, t1 is a temperature at room temperature (for example, 20 ° C.). A0, B0, C0, and D0 are values of A, B, C, and D, respectively, at room temperature. α1 is a linear expansion coefficient for a material (for example, an aluminum alloy) constituting the rotor 30, and α2 is a material for a material for the shaft 33 (for example, an aluminum alloy having a linear expansion coefficient different from that of stainless steel, steel, or the rotor). Linear expansion coefficient.

  As described above, the linear expansion coefficient α1 for the material constituting the rotor 30 (for example, an aluminum alloy) is the same as the material constituting the shaft 33 (for example, an aluminum alloy having a linear expansion coefficient different from that of stainless steel, steel, or the rotor). Is larger than the linear expansion coefficient α2.

The first embodiment described above has the following operational effects.
(1) As a fitting portion between the rotor 30 and the shaft 33, a fitting portion between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331, a rotor-side fitting protrusion 302, and a shaft-side fitting groove 332 The fitting part is provided. At a normal temperature, the gap Cr between the rotor side fitting hole 301 and the shaft side fitting shaft 331 is smaller than the gap Cs between the rotor side fitting projection 302 and the shaft side fitting groove 332. The diameter AD of each part was set. When the temperature of the rotor 30 and the shaft 33 exceeds a predetermined temperature Ts, the gap Cs between the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332 is fitted to the rotor-side fitting hole 301 and the shaft-side fitting. The diameters A to D of the respective portions were set so as to be smaller than the gap Cr with the shaft 331.

  As a result, of the two fitting portions whose sizes change according to the temperatures of the rotor 30 and the shaft 33, the fitting portion with the smaller gap size in the radial direction between the rotor 30 and the shaft 33. The position can be prevented from shifting. Therefore, even if the rotor 30 and the shaft 33 are not fastened by shrink fitting, the radial displacement between the rotor 30 and the shaft 33 can be suppressed, so that the fastening work and the disassembling work between the rotor 30 and the shaft 33 are easy. Can be Further, the work time required for the fastening work and the disassembling work can be shortened. Therefore, the manufacturing cost of the vacuum pump and the maintenance cost of the rotor 30 and the shaft 33 can be reduced.

(2) When the temperature of the rotor 30 and the shaft 33 rises due to the difference in material between the rotor 30 and the shaft 33, that is, the difference in linear expansion coefficient, the clearance Cr between the rotor side fitting hole 301 and the shaft side fitting shaft 331 The gap Cs between the rotor-side fitting projection 302 and the shaft-side fitting groove 332 is reduced. Thereby, even if the temperature of the rotor 30 and the shaft 33 changes, it is possible to prevent the maximum value of the radial displacement between the rotor 30 and the shaft 33 from fluctuating greatly. Therefore, even if the temperature of the rotor 30 and the shaft 33 rises, deviation in the radial position between the rotor 30 and the shaft 33 can be suppressed, and occurrence of abnormal vibration or the like due to an imbalance of balance can be prevented. This also improves the durability of each part of the vacuum pump.

(3) At the maximum temperature Tmax of the rotor 30 and the shaft 33 allowed by design, the fitting portion between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331, and the rotor-side fitting protrusion 302 and the shaft side The diameters A to D of each part were set so that any of the fitting parts with the fitting groove 332 was a clearance fit. Thereby, it can suppress that the thermal stress acts in these fitting parts repeatedly, and the durability of the rotor 30 and the shaft 33 can be improved.

--- Second Embodiment ---
A second embodiment of the vacuum pump according to the present invention will be described with reference to FIG. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and different points will be mainly described. Points that are not particularly described are the same as those in the first embodiment. The present embodiment is different from the first embodiment mainly in that a member different from the rotor 30 and the shaft 33 and a fitting portion with the rotor 30 are provided.

  FIG. 4 is a cross-sectional view for explaining a fitting structure of the rotor 30 and the shaft 33 in the second embodiment. In the present embodiment, a balancing plate 40 for balancing the rotation of the rotor 30 and the shaft 33 is further provided. The balancing plate 40 is provided with a plate-side fitting groove 41 that fits into a rotor-side fitting projection 303 described later, and a bolt through hole 42 through which the bolt 34 passes. When the balancing plate 40 is fixed to the shaft 33 by the bolts 34, the rotor 30 is sandwiched between the upper surface of the shaft 33 and the lower surface of the balancing plate 40.

  On the upper surface of the rotor 30, there is provided a rotor-side fitting protrusion 303 that protrudes upward and engages with the plate-side fitting groove 41. In the present embodiment, the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332 provided in the first embodiment are not provided.

  Here, when the diameter of the rotor-side fitting protrusion 303 is C and the diameter of the plate-side fitting groove 41 is D, the gap between the rotor-side fitting protrusion 303 and the plate-side fitting groove 41 is D−. Represented by C. In the following description, the gap between the rotor-side fitting protrusion 303 and the plate-side fitting groove 41 is also referred to as a gap Cp.

  When the temperatures of the rotor 30 and the shaft 33 rise, the gap Cr between the rotor side fitting hole 301 and the shaft side fitting shaft 331 increases, and the gap Cp between the rotor side fitting protrusion 303 and the plate side fitting groove 41. Becomes smaller. Further, when the temperatures of the rotor 30 and the shaft 33 are lowered, the clearance Cr between the rotor side fitting hole 301 and the shaft side fitting shaft 331 is reduced, and the rotor side fitting protrusion 303 and the plate side fitting groove 41 are not formed. The gap Cp increases.

  Therefore, in the present embodiment, the diameters A to D of each part in the present embodiment are set so as to satisfy both the conditions (a) and (b) in the first embodiment described above. By setting the diameters A to D of the respective parts in this way, the same operational effects as the operational effects of the first embodiment described above can be obtained.

  In the present embodiment, the balancing plate 40 has both the function of balancing the rotation of the rotor 30 and the shaft 33, the function of fixing the rotor 30, and the function of preventing the rotor 30 from shifting. Points can be reduced and costs can be reduced.

---- Modified example ---
(1) In the first embodiment described above, as an example in which two fitting portions are provided between the rotor 30 and the shaft 33, as shown in FIG. Although the fitting shaft 331 and the annular shaft side fitting groove 332 are provided, the present invention is not limited to this. That is, the contents described by way of illustration in the respective embodiments described above are examples, and the present invention is not limited to this.

  FIG. 5A is a diagram schematically showing a fitting portion between the rotor 30 and the shaft 33 in the first embodiment. As shown in FIG. 5A, in the first embodiment, a shaft-like fitting portion (that is, a shaft-side fitting shaft 331) is provided on the center side of the shaft 33, and a groove shape (hole shape) is provided around the shaft-like fitting portion. ) Fitting portion (that is, the shaft side fitting groove 332). And the hole-shaped fitting part (namely, rotor side fitting hole 301) was provided in the center side of the rotor 30, and the shaft-shaped fitting part (namely, rotor side fitting protrusion 302) was provided in the circumference | surroundings.

  On the other hand, for example, as shown in FIG. 5B, the concave-convex relationship in each fitting portion may be reversed from the first embodiment. That is, a hole-shaped fitting portion (that is, the shaft-side fitting hole 334) is provided on the center side of the shaft 33, and a shaft-shaped fitting portion (that is, the shaft-side fitting shaft 335) is provided around the hole. Then, a shaft-like fitting portion (that is, the rotor-side fitting protrusion 304) is provided on the center side of the rotor 30, and a groove-like (hole-like) fitting portion (that is, the rotor-side fitting groove 305) is provided around the shaft-like fitting portion. Provide.

  A radial gap formed between the rotor side fitting protrusion 304 and the shaft side fitting hole 334 is also called a gap Cr ′, and is formed between the rotor side fitting groove 305 and the shaft side fitting shaft 335. The radial gap is also referred to as a gap Cs ′. As described above, the linear expansion coefficient of the shaft 33 is smaller than the linear expansion coefficient of the rotor 30. Therefore, when the temperatures of the rotor 30 and the shaft 33 rise, the gap Cs ′ between the rotor-side fitting groove 305 and the shaft-side fitting shaft 335 increases, and the rotor-side fitting protrusion 304 and the shaft-side fitting hole 334 The gap Cr ′ becomes smaller. Further, when the temperatures of the rotor 30 and the shaft 33 are lowered, the gap Cs ′ between the rotor side fitting groove 305 and the shaft side fitting shaft 335 is reduced, and the rotor side fitting protrusion 304 and the shaft side fitting hole 334 are The gap Cr ′ increases.

  Therefore, as in the condition (a) of the first embodiment, the size of the gap Cs ′ whose size increases as the temperature rises is smaller than the size of the gap Cr ′ at room temperature. Set the dimensions of each part as follows. That is, at room temperature, out of the gap Cs ′ and the gap Cr ′, the shaft-like fitting portion having the smaller linear expansion coefficient (that is, the shaft-side fitting shaft 335) and the hole-like fitting portion having the larger linear expansion coefficient. The dimension of each part is set so that the size of one gap (that is, the gap Cs ′) that is the gap with the rotor-side fitting groove 305 is smaller than the size of the other gap (that is, the gap Cr ′). To do.

  Further, as in the condition (b) of the first embodiment, when the temperature of the rotor 30 and the shaft 33 exceeds a predetermined temperature Ts, the size of the gap decreases as the temperature increases. The size of each part is set so that the size of the gap Cr ′ is smaller than the size of the gap Cs ′. That is, when the predetermined temperature Ts is exceeded, the shaft-shaped fitting portion having a larger linear expansion coefficient (that is, the rotor-side fitting protrusion 304) and the hole-shaped fitting portion having a smaller linear expansion coefficient (that is, the linear fitting coefficient) The dimension of each part is set so that the size of the gap (that is, the gap Cr ′) with the shaft side fitting hole 334) is smaller than the size of the one gap (that is, the gap Cs ′).

(2) In the above-described first embodiment, the linear expansion coefficient α1 for the material constituting the rotor 30 has been described as being greater than the linear expansion coefficient α2 for the material constituting the shaft 33. Is not limited to this. That is, the linear expansion coefficient α1 for the material constituting the rotor 30 may be smaller than the linear expansion coefficient α2 for the material constituting the shaft 33. In this case, unlike the first embodiment described above, when the temperature of the rotor 30 and the shaft 33 rises, the gap Cr between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331 becomes small, A gap Cs between the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332 increases. Further, when the temperatures of the rotor 30 and the shaft 33 are lowered, the clearance Cr between the rotor side fitting hole 301 and the shaft side fitting shaft 331 increases, and the rotor side fitting protrusion 302 and the shaft side fitting groove 332 are separated from each other. The gap Cs is reduced.

  Therefore, when the linear expansion coefficient α1 for the material constituting the rotor 30 is smaller than the linear expansion coefficient α2 for the material constituting the shaft 33, the diameters A to D of the respective parts are set so as to satisfy the following conditions. do it. That is, when the temperature of the rotor 30 and the shaft 33 is normal temperature, the clearance Cs <the clearance Cr, and when the temperature of the rotor 30 and the shaft 33 exceeds the predetermined temperature Ts, the clearance Cr ≦ the clearance What is necessary is just to set the diameter AD of each part so that it may become Cs.

  In other words, at the normal temperature, the size of one gap that is a gap between the shaft-shaped fitting portion having the smaller linear expansion coefficient and the hole-shaped fitting portion having the larger linear expansion coefficient among the gap Cs and the gap Cr. However, the dimension of each part is set so that it may become smaller than the magnitude | size of the other clearance gap. Further, when the predetermined temperature Ts is exceeded, a gap (that is, the other gap) between the shaft-like fitting portion having the larger linear expansion coefficient and the hole-like fitting portion having the smaller linear expansion coefficient. What is necessary is just to set the dimension of each part so that a magnitude | size may become smaller than the magnitude | size of one clearance gap.

(3) In the above description, at the maximum temperature Tmax, the fitting portion between the rotor-side fitting hole 301 and the shaft-side fitting shaft 331, and the rotor-side fitting protrusion 302 and the shaft-side fitting groove 332 The diameters A to D of each part were set so that any of the fitting parts had a clearance fit. That is, in the above description, the values of the gap Cs and the gap Cr are both set to exceed zero at the maximum temperature Tmax, but this is not essential in the present invention. For example, as shown in FIG. 6, the diameters A to D of the respective parts may be set so that the size of the gap Cs becomes zero or less at the maximum temperature Tmax. In this case, since the allowable range of the positional deviation in the radial direction between the rotor 30 and the shaft 33 is narrowed, it is possible to effectively prevent the occurrence of abnormal vibration or the like due to an imbalance. In addition, this can further improve the durability of each part of the vacuum pump.

(4) In the above description, a turbo molecular pump has been described as an example of a vacuum pump. However, the present invention is not limited to this and may be applied to other vacuum pumps such as a drag pump.
(5) You may combine each embodiment and modification which were mentioned above, respectively.

The present invention is not limited to the embodiment described above, and includes a shaft having a shaft-side shaft-like fitting portion and a shaft-side hole-like fitting portion, and a shaft-side shaft-like fitting portion. A rotor-side hole-like fitting portion to be mated, and a rotor-side shaft-like fitting portion to be fitted to the shaft-side hole-like fitting portion, the linear expansion coefficient being different from the shaft, and a rotor fixed to the shaft A first gap formed between the shaft-side shaft-like fitting portion and the rotor-side hole-like fitting portion, and formed between the shaft-side hole-like fitting portion and the rotor-side shaft-like fitting portion. In setting the second gap, at room temperature, of the first and second gaps, the shaft-like fitting part having the smaller linear expansion coefficient and the hole-like fitting part having the larger linear expansion coefficient The size of one of the gaps is smaller than the size of the other gap and exceeds a predetermined temperature during operation. When the size of the other gaps are those comprising a vacuum pump arrangement the various structures to be smaller than the size of one of the gaps.
Further, the present invention is not limited to the embodiment described above, and the shaft having the shaft-side shaft-like fitting portion, the rotor-side shaft-like fitting portion, and the shaft-side shaft-like fitting portion and the fitting. A rotor-side hole-like fitting part that has a linear expansion coefficient different from that of the shaft, and a rotor fixed to the shaft, and a fixing member-side hole-like fitting part that fits the rotor-side shaft-like fitting part. A first clearance formed between the shaft-side shaft-like fitting portion and the rotor-side hole-like fitting portion, the shaft having the same linear expansion coefficient as the shaft, and a fixing member that fixes the rotor to the shaft. And the second gap formed between the rotor-side shaft-like fitting portion and the fixing member-side hole-like fitting portion, the linear expansion coefficient of the first and second gaps is set at normal temperature. One gap that is the gap between the shaft-shaped fitting portion with the smaller linearity and the hole-shaped fitting portion with the larger linear expansion coefficient The size of the other gap is smaller than the size of the other gap, and when the temperature exceeds a predetermined temperature during operation, the size of the other gap becomes smaller than the size of the one gap. Is included.

DESCRIPTION OF SYMBOLS 1 Pump main body, 30 Rotor, 33 Rotor shaft (shaft), 40 Balancing plate, 41 Plate side fitting groove, 301 Rotor side fitting hole, 302 Rotor side fitting protrusion, 331 Shaft side fitting shaft, 332 shaft Side mating groove

Claims (7)

A shaft having a shaft-side shaft-like fitting portion and a shaft-side hole-like fitting portion;
A rotor-side hole-like fitting portion that fits with the shaft-side shaft-like fitting portion; and a rotor-side shaft-like fitting portion that fits with the shaft-side hole-like fitting portion. The expansion coefficient is different, and includes a rotor fixed to the shaft,
A first gap formed between the shaft-side shaft-like fitting portion and the rotor-side hole-like fitting portion, and between the shaft-side hole-like fitting portion and the rotor-side shaft-like fitting portion. In setting the formed second gap,
At normal temperature, the size of one of the first and second gaps, which is a gap between the shaft-like fitting part having the smaller linear expansion coefficient and the hole-like fitting part having the larger linear expansion coefficient. Is a vacuum pump configured so that the size of the other gap becomes smaller than the size of the other gap, and the size of the other gap becomes smaller than the size of the one gap when a predetermined temperature is exceeded during operation. The vacuum pump according to claim 1, wherein
When the linear expansion coefficient of the shaft is smaller than the linear expansion coefficient of the rotor,
At normal temperature, when the first gap is smaller than the second gap and exceeds a predetermined temperature during operation, the second gap becomes smaller than the first gap. A vacuum pump that is smaller than the size of the gap. The vacuum pump according to claim 2,
The size of the first gap increases as the temperature increases,
The size of the second gap is a vacuum pump that decreases as the temperature increases. The vacuum pump according to claim 1, wherein
When the linear expansion coefficient of the shaft is larger than the linear expansion coefficient of the rotor,
When the size of the second gap is smaller than the size of the first gap at room temperature and exceeds a predetermined temperature during operation, the size of the first gap becomes the second size. A vacuum pump that is smaller than the size of the gap. The vacuum pump according to claim 4,
The size of the second gap increases as the temperature increases,
The size of the first gap is a vacuum pump that decreases with increasing temperature. In the vacuum pump as described in any one of Claims 1-5,
The size of the first and second gaps is a vacuum pump that is larger than zero even when the predetermined temperature is exceeded during operation. A shaft having a shaft-side axial fitting portion;
A rotor having a rotor-side shaft-like fitting portion and a rotor-side hole-like fitting portion that fits with the shaft-side shaft-like fitting portion, having a linear expansion coefficient different from that of the shaft, and being fixed to the shaft When,
A fixing member side hole-like fitting portion that fits with the rotor-side axial fitting portion, the shaft has the same linear expansion coefficient, and a fixing member that fixes the rotor to the shaft;
A first gap formed between the shaft-side shaft-like fitting portion and the rotor-side hole-like fitting portion, and between the rotor-side shaft-like fitting portion and the fixing member-side hole-like fitting portion. In setting the second gap formed in
At normal temperature, the size of one of the first and second gaps, which is a gap between the shaft-like fitting part having the smaller linear expansion coefficient and the hole-like fitting part having the larger linear expansion coefficient. Is a vacuum pump configured so that the size of the other gap becomes smaller than the size of the other gap, and the size of the other gap becomes smaller than the size of the one gap when a predetermined temperature is exceeded during operation.

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