JP2017020401A - Vacuum pump, rotor and rotor shaft of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum pump, a rotor and a rotor shaft of the same, which are suitable for obtaining stable fastening without a gap between the rotor shaft and the rotor.SOLUTION: A vacuum pump sucks and discharges a gas with a rotor 6, which is fastened to a rotor shaft 5, rotating around the axis of the rotor shaft 5. In the vacuum pump, fastening surfaces SF forming a fastening part between the rotor shaft 5 and the rotor 6 are formed in a tapered shape or a curved shape, which is inclined such that, when temperature of the rotor shaft 5 or the rotor 6 changes, a dimensional change in the radial direction compensates a dimensional change in the axial direction, or the dimensional change in the axial direction compensates the dimensional change in the radial direction, or the fastening surfaces are formed in surfaces including the tapered shape or the curved shape.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vacuum pump used as a gas exhaust means for a process chamber in a semiconductor manufacturing apparatus, a flat panel display manufacturing apparatus, a solar panel manufacturing apparatus, and other chambers, and a rotor and a rotor shaft thereof.

  FIG. 9 is a cross-sectional view of a conventional vacuum pump. The conventional vacuum pump P2 in FIG. 1 sucks and sucks in gas from the intake port 2 by rotating the rotor 6 (rotating member) fastened to the rotor shaft 5 around the axis of the rotor shaft 5. The gas is exhausted from the exhaust port 3 (see, for example, FIG. 9 of Patent Document 1).

  In the conventional vacuum pump P2 shown in FIG. 9, the rotor 6 is made of an aluminum alloy having a high specific strength, while the rotor shaft 5 is made of an iron-based material to be supported by a magnetic bearing. The rotor shaft 5 and the rotor 6 are fastened by shrink-fitting and fastened by a plurality of bolts BT that are located radially around the rotor shaft 5 (see, for example, FIGS. 1 and 2 of Patent Document 1). ).

  10 (a) to 10 (c) are explanatory views of a process for fastening the rotor shaft 5 and the rotor 6 in the conventional vacuum pump P2 of FIG.

  Referring to FIG. 10A, in the conventional vacuum pump P2 of FIG. 9, an end member 61 is integrally provided on the upper end side of the rotor 6, and a fitting hole 62 is formed in the end member 61, while shrink fitting. A fitting portion 51 to be fitted into the fitting hole 62 at the time of fastening is provided at the tip of the rotor shaft 5.

  In the shrink-fitting preparation step of FIG. 10A, a predetermined dimensional difference is set between the periphery of the fitting hole 62 and the fitting portion 51 by the heating around the fitting hole 62 described above.

  In the subsequent shrink fitting process of FIG. 10B, the outer peripheral surface of the fitting portion 51 and the inner peripheral surface of the fitting hole 62 in contact therewith, and the lower edge portion of the fitting hole 62 and the inner peripheral surface thereof. The lower edge part of the fitting part 51 to be contacted is set as the fastening surfaces SF and SF shown in FIG. 10A, and the fitting part 51 is inserted into the fitting hole 62 in a state where the above dimensional difference is set. Is inserted.

  Further, in the bolt tightening step shown in FIG. 10C that is performed thereafter, the rotor shaft 5 and the rotor 6 are firmly fastened by tightening the rotor shaft 5 and the rotor 6 with a plurality of bolts BT.

  By the way, in the conventional vacuum pump P2 of FIG. 9, in order to maintain a fastening state until the rotor 6 returns to normal temperature in the shrink fitting process of FIG. The jig T is pressed in the direction.

  However, in the conventional vacuum pump P2 of FIG. 9, the rotor 6 made of an aluminum alloy material contracts until it returns to room temperature. For this reason, in the conventional vacuum pump P2 of the same figure, when the force which presses the jig | tool T is inadequate, as shown in FIG. 11, the lower edge part of the fitting hole 62 set as fastening surface SF, and There is a problem that a gap Q is generated between the lower edge portion of the fitting portion 51 in contact with the fitting portion 51 and stable fastening without such a gap Q cannot be obtained.

  Further, when such a gap is generated, when the rotor shaft 5 and the rotor 6 are tightened with a plurality of bolts BT in the bolt tightening step of FIG. On the other hand, the axis of the rotor 6 is inclined, and the rotation balance of the entire rotating body including the rotor 6 may be deteriorated, or the vibration due to the rotation of the rotor 6 or the damage due to the collision of the rotor 6 may be easily caused. there were.

WO 2005/028874

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vacuum pump suitable for obtaining a stable fastening without a gap between the rotor shaft and the rotor, and the rotor and the rotor shaft. Is to provide.

  In order to achieve the above object, the present invention provides a vacuum pump that sucks and exhausts gas by rotation of a rotor fastened to a rotor shaft, and is a fastening that constitutes a fastening portion between the rotor shaft and the rotor The surface is inclined so that when the temperature of the rotor shaft or the rotor changes, a radial dimensional change compensates for the axial dimensional change, or an axial dimensional change compensates for the radial dimensional change. The taper shape or the curved shape, or the surface including the taper shape or the curved shape is characterized.

  In the present invention, the rotor shaft and the rotor are made of different materials, and the angle of the tapered shape or the curved shape is set based on the linear expansion coefficient of the rotor shaft or the rotor. May be a feature.

  In the present invention, the rotor shaft and the rotor are formed of different materials, and the angle of the tapered shape or the curved shape is set based on a contact position dimension on a contact surface of the rotor shaft and the rotor. It is good also as a feature.

  In the present invention, as means for fastening the rotor shaft and the rotor, a plurality of screw holes are formed in one of the rotor shaft and the rotor, and a plurality of bolt insertion holes corresponding to the screw holes are formed in the other. In addition, the rotor and the rotor shaft may be fixed in the axial direction by tightening bolts inserted into the respective bolt insertion holes with respect to the corresponding screw holes.

  In the configuration using the bolt in the present invention, the rotor shaft and the rotor are formed of different materials, and the angle of the tapered shape or the curved shape is determined by the rotor shaft, the rotor, or the bolt. It may be set based on a linear expansion coefficient.

  In the configuration using the bolt in the present invention, the rotor shaft and the rotor are formed of different materials, and the angle of the taper shape or the curved shape is a contact at the contact surface of the rotor shaft and the rotor. It may be set based on the position dimension.

  In the configuration using the bolt in the present invention, the tapered shape or the curved shape may be set in an inner range surrounded by at least the plurality of bolts or the screw holes.

  In the present invention, as means for constraining expansion in the rotor radial direction at the fastening portion between the rotor shaft and the rotor, a convex portion is provided on one of the rotor shaft and the rotor, and a concave portion is provided on the other. A configuration in which the portion and the concave portion are engaged may be employed.

  Further, the present invention provides the rotor of a vacuum pump, wherein the rotor used in the vacuum pump includes the tapered or curved fastening surface, or the rotor shaft used in the vacuum pump as the rotor shaft. A rotor shaft of a vacuum pump characterized by comprising the fastening surface having a tapered shape or the curved shape, or a rotor blade used on the outer peripheral surface of the rotor used in the vacuum pump, and the tapered shape or the curved shape. A vacuum pump rotor comprising the fastening surface.

  According to the present invention, as described above, the fastening surface constituting the fastening portion between the rotor shaft and the rotor has a radial dimensional change that compensates for the axial dimensional change when the temperature of the rotor shaft or the rotor changes. Thus, a taper shape or a curved shape inclined so that a dimensional change in the axial direction compensates for a dimensional change in the radial direction, or a surface including the tapered shape or the curved shape. For this reason, after the rotor is fastened to the rotor shaft, separation of the fastening surface due to a change in the dimensions of the rotor shaft or the rotor can be effectively prevented, and the fastening between the rotor shaft and the rotor can be obtained. It is possible to provide a vacuum pump, a rotor thereof, and a rotor shaft that are suitable for obtaining stable fastening.

  In the present invention, as described above, in the fastening between the rotor shaft and the rotor, a stable fastening without a gap is obtained. Therefore, conventional problems caused by the occurrence of a gap in such a fastening, for example, against the rotor shaft When the rotor is tightened with multiple bolts, the axis of the rotor tilts with respect to the rotor shaft, resulting in poor rotation balance of the entire rotating body including the rotor, vibration due to rotor rotation, It is possible to effectively prevent problems such as damage easily caused by a collision.

Sectional drawing of the vacuum pump which is embodiment of this invention. The enlarged view of the fastening part of a rotor axis | shaft and rotor in the vacuum pump of FIG. Explanatory drawing of other embodiment of this invention. Explanatory drawing which modeled the fastening relationship of the rotor and rotor shaft in the conventional vacuum pump shown in FIG. The explanatory view which modeled the fastening relation of the rotor and rotor axis in the vacuum pump which is the embodiment of the present invention shown in FIG. FIG. 2 is an enlarged view with XY coordinates of a rotor shaft in the vacuum pump of FIG. 1 and a vicinity of a fastening portion of the rotor (before tightening a bolt). FIG. 2 is an enlarged view with XY coordinates in the vicinity of a fastening portion of the rotor shaft and the rotor during operation of the vacuum pump of FIG. 1. Explanatory drawing of other embodiment regarding the contact surface (fastening surface) of the rotor axis | shaft and rotor in the vacuum pump of FIG. Sectional drawing of the conventional vacuum pump. (A)-(c) is explanatory drawing of the process of fastening a rotor axis | shaft and a rotor in the conventional vacuum pump of FIG. FIG. 10 is a diagram illustrating a state in which a gap due to a difference in thermal expansion coefficient is generated on the fastening surface when the rotor shaft and the rotor are fastened by shrink fitting in the conventional vacuum pump of FIG. 9.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.

  1 is a cross-sectional view of a vacuum pump according to an embodiment of the present invention, and FIG. 2 is an enlarged view of the vicinity of a rotor shaft and a fastening portion of the rotor in the vacuum pump of FIG. Note that hatching of the cross section of the rotor is omitted in order to make the main part of the present invention easy to see.

  The vacuum pump P1 in FIG. 1 is a vacuum pump that sucks and exhausts gas when the rotor 6 rotates around the axis of the rotor shaft 5, and its specific configuration is rotated inside the outer case 1. A blade exhaust portion Pt that sucks and exhausts gas by the blade 7 and the fixed blade 8, a screw groove exhaust portion Ps that sucks and exhausts gas using the screw groove 91, and a drive system thereof are included. ing.

  The outer case 1 has a bottomed cylindrical shape in which a cylindrical pump case 1A and a bottomed cylindrical pump base 1B are integrally connected with a fastening bolt in the cylinder axis direction, and the upper end side of the pump case 1A Is opened as an intake port 2 for inhaling gas, and an exhaust port 3 is provided on the side surface of the lower end of the pump base 1B as a means for exhausting the gas compressed by the screw groove exhaust part Ps to the outside of the outer case 1. Is provided.

  The intake port 2 is connected to a sealed chamber (not shown), which is a high vacuum, such as a process chamber of a semiconductor manufacturing apparatus, by a fastening bolt (not shown) provided on a flange 1C on the upper edge of the pump case 1A. The exhaust port 3 is connected in communication with an auxiliary pump (not shown).

  A cylindrical stator column 4 containing various electrical components is provided in the center of the pump case 1A. In the vacuum pump P1 of FIG. 1, the stator column 4 is formed as a separate component from the pump base 1B and fixed to the inner bottom of the pump base 1B by screws, so that the stator column 4 is erected on the pump base 1B. However, as another embodiment, the stator column 4 may be erected integrally with the inner bottom of the pump base 1B.

  A rotor shaft 5 is provided inside the stator column 4, and the rotor shaft 5 is arranged so that its upper end portion faces the intake port 2 and its lower end portion faces the pump base 1B. . The upper end portion of the rotor shaft 5 is provided so as to protrude upward from the cylindrical upper end surface of the stator column 4.

  The rotor shaft 5 is rotatably supported in the radial direction and the axial direction by two sets of radial magnetic bearings MB1 and one set of axial magnetic bearings MB2 as support means, and in this supported state, a drive motor as drive means It is configured to be rotationally driven by the MO. Since the radial magnetic bearing MB1, the axial magnetic bearing MB2 and the drive motor MO are well known, detailed description thereof will be omitted.

  A rotor 6 is provided as a rotating body on the outside of the stator column 4. The rotor 6 is enclosed in the pump case 1 </ b> A and the pump base 1 </ b> B and has a cylindrical shape surrounding the outer periphery of the stator column 4.

  The rotor 6 and the rotor shaft 5 are formed of different materials, and the rotor 6 is fastened to the rotor shaft 5 on the upper end side thereof by shrink fitting, for example.

  In the vacuum pump P1 shown in FIG. 1, (1) an end member 61 is integrally provided on the upper end side of the rotor 6 and a fitting hole 62 (see FIG. (Refer to FIG. 4), and a fitting portion 51 to be fitted into the fitting hole 62 at the time of fastening by shrink fitting is provided at the tip of the rotor shaft 5, and (2) an inner peripheral surface of the fitting hole 62 And the outer peripheral surface of the fitting portion 51 corresponding thereto is inclined at a predetermined angle θ (see FIG. 2) as a fastening surface SF (see FIG. 2) constituting a fastening portion between the rotor shaft 5 and the rotor 6. And (3) a predetermined gap is set around the fitting hole 62 and the fitting portion 51 by heating around the fitting hole 62. In this state, After inserting the fitting part 51, return to room temperature, and set We have adopted a structure in which the fastening surface SF is firmly fixed. Further, a predetermined gap may be set by cooling fit to cool the fitting portion 51, or the predetermined gap may be set by heating the periphery of the fitting hole 62 and cooling the fitting portion 51.

  The “predetermined angle θ”, that is, the inclination angle θ of the tapered fastening surface SF of the rotor 6 and the rotor shaft 5 (hereinafter referred to as “the angle of the contact surface (fastening surface SF)”) is the rotor shaft 5 or the rotor. The angle θ of the specific contact surface (fastening surface SF) is determined in consideration of the linear expansion coefficient of 6. As described later in paragraphs 0069 and 0070, the rotor shaft 5 or the rotor The linear expansion coefficient of 6 can be set, and the vacuum pump P1 of FIG. 1 employs such a setting for the angle θ of the contact surface (fastening surface SF).

  Further, in the vacuum pump P1 of FIG. 1, the rotor shaft 5 and the rotor 6 are fastened by bolts BT as means for restraining the expansion in the radial direction of the rotor 6 at the fastening portion between the rotor shaft 5 and the rotor 6.

  As a specific configuration of fastening by the bolt BT, in the vacuum pump P1 of FIG. 1, a plurality of screw holes NE are formed in the fastening surface SF of the rotor shaft 5 as shown in FIG. A plurality of corresponding bolt insertion holes H (not shown) are formed in the end member 61 of the rotor 6 and the bolts BT inserted into the respective bolt insertion holes H are tightened with respect to the corresponding screw holes NE. 6 and the rotor shaft 5 are fixed in the axial direction.

  When the rotor 6 and the rotor shaft 5 are fastened as described above, the rotor 6 can be rotated around the rotor shaft center by the radial magnetic bearing MB1 and the axial magnetic bearing MB2 via the rotor shaft 5. Supported.

<< Details of wing exhaust part Pt >>
The vacuum pump P1 of FIG. 1 is configured such that the upstream side from the substantially middle of the rotor 6 functions as the blade exhaust part Pt. Hereinafter, the blade exhaust part Pt will be described in detail.

  A plurality of rotor blades 7 are integrally provided on the outer peripheral surface of the rotor 6 on the upstream side from the substantially middle of the rotor 6. The plurality of rotor blades 7 are arranged in a radial pattern around the rotation center axis of the rotor 6 (the axis of the rotor shaft 5) or the axis of the outer case 1 (hereinafter referred to as “vacuum pump axis”). Yes.

  On the other hand, a plurality of fixed blades 8 are provided on the inner peripheral side of the pump case 1A, and the plurality of fixed blades 8 are also arranged in a radial pattern around the vacuum pump axis.

  In the vacuum pump P1 of FIG. 1, the blades of the vacuum pump P1 are arranged by arranging the rotary blades 7 and the fixed blades 8 arranged radially as described above alternately along the vacuum pump axis. The exhaust part Pt is configured.

  Each of the rotor blades 7 is a blade-like cut product that is cut and formed integrally with the outer diameter machining portion of the rotor 6 and is inclined at an angle that is optimal for exhausting gas molecules. All the fixed blades 8 are also inclined at an angle optimal for exhaust of gas molecules.

<< Exhaust operation explanation by blade exhaust part Pt >>
In the blade exhaust part Pt having the above configuration, the rotor shaft 5, the rotor 6, and the plurality of rotor blades 7 integrally rotate at a high speed when the drive motor MO is started, and the uppermost rotor blade 7 enters from the air inlet 2. Momentum in a downward direction (a direction from the intake port 2 toward the exhaust port 3) is imparted to the gas molecules. The gas molecules having the downward momentum are sent to the rotor blade 7 side of the next stage by the fixed blade 8. By applying the momentum to the gas molecules as described above and the feeding operation repeatedly in multiple stages, the gas molecules on the intake port 2 side are exhausted so as to sequentially move toward the downstream of the rotor 6.

<< Details of thread groove exhaust part Ps >>
The vacuum pump P1 in FIG. 1 is configured so that the downstream side from the substantially middle of the rotor 6 functions as the thread groove exhaust part Ps. Hereinafter, the thread groove exhaust portion Ps will be described in detail.

  The portion of the rotor 6 downstream from the substantially middle of the rotor 6 is a portion that rotates as a rotating member of the thread groove exhaust portion Ps, and is inserted and accommodated inside the thread groove exhaust portion stator 9 via a predetermined gap. Yes.

  The thread groove exhaust portion stator 9 is a cylindrical fixing member arranged so that the inner peripheral surface thereof faces the outer peripheral surface of the rotor 6, and surrounds the rotor 6 portion downstream from the substantially middle of the rotor 6. It is arranged.

  As a means for forming the screw groove exhaust passage R on the outer peripheral side of the rotor 6, a screw groove 91 that changes in a taper cone shape whose depth is reduced downward is formed in the inner peripheral portion of the screw groove exhaust portion stator 9. It is. The thread groove 91 is spirally engraved from the upper end to the lower end of the thread groove exhaust portion stator 9, and the screw groove exhaust portion stator 9 having such a thread groove 91 causes a gas to be disposed on the outer peripheral side of the rotor. A thread groove exhaust flow R for exhaust is formed. Although illustration is omitted, the above-described screw groove exhaust passage R may be provided by forming the screw groove 91 described above on the outer peripheral surface of the rotor 6.

  In the thread groove exhaust portion Ps, the gas groove is transferred while being compressed by the drag effect on the outer peripheral surface of the thread groove 91 and the rotor 6, and therefore the depth of the thread groove 91 is set on the upstream inlet side of the thread groove exhaust passage R ( It is set to be deepest at the flow path opening end closer to the intake port 2 and shallowest at the downstream outlet side (flow path opening end closer to the exhaust port 3).

  The inlet (upstream opening end) of the thread groove exhaust passage R is a gap (hereinafter referred to as “final gap G”) between the lowermost fixed blade 8E and the thread groove exhaust portion stator 9 among the fixed blades 8 arranged in multiple stages. And the outlet (downstream opening end) of the threaded groove exhaust flow path R is a flow path S on the pump exhaust port side (hereinafter referred to as “pump exhaust port side flow path S”). Through the exhaust port 3. Although not shown, the final gap G may be formed between the lowermost rotor blade of the rotor blades 7 arranged in multiple stages and the thread groove exhaust portion stator 9.

  The pump exhaust passage side flow path S has a predetermined gap between the lower end portion of the rotor 6 and the thread groove exhaust portion stator 9 and the inner bottom portion of the pump base 1B (in the vacuum pump P of FIG. By providing a gap in a form that makes a round around the outer periphery of the lower portion, it is formed so as to reach the exhaust port 3 from the outlet of the thread groove exhaust passage R.

<< Exhaust operation explanation in screw groove exhaust part Ps >>
The gas molecules that have reached the final gap G by the transfer by the exhaust operation of the blade exhaust part Pt described above are transferred to the screw groove exhaust flow path R. The transferred gas molecules move toward the exhaust port side flow path S in the pump while being compressed from the transition flow to the viscous flow by the drag effect generated by the rotation of the rotor 6. Then, the gas molecules that have reached the in-pump exhaust port side flow path S flow into the exhaust port 3 and are exhausted out of the outer case 1 through an auxiliary pump (not shown).

<Deformation due to temperature change of material>
A deformation amount ΔL of expansion and contraction due to a temperature change of the material is represented by the following formula (1).

<< When materials A and B are fastened on a non-inclined surface (corresponding to the conventional example) >>
FIG. 4 is an explanatory diagram modeling the fastening relationship between the rotor 6 and the rotor shaft 5 in the conventional vacuum pump P2 shown in FIG.

In FIG. 4, the material A is assumed to be an iron-based material used in the rotor shaft 5, and the material B is assumed to be an aluminum alloy material used in the rotor 6. Further, the fastening portion of the material A (the rotor shaft 5) and material B (rotor 6), the dimensions of the fastening before the material A is set to L _A, the dimensions of the material B is set to L _B.

When fastening two materials A having different linear expansion coefficients, B, each material A after fastening, the size of B (L A _'and L _B') is represented the following formula (2) in equation (3) The

In the process of fastening the rotor 6 and the rotor shaft 5, only the temperature of one of the materials A and B may be simply changed, but here the temperature of both the materials A and B is assumed to change. Yes. The deformation of the material A is caused by heating (temperature increase after cooling). On the other hand, since the deformation of the material B is caused by cooling (temperature decrease after heating), the deformation is opposite to the deformation of the material A. From this, in the following formula (2), the deformation amount (α _A L _A ΔT _A ) of the material A (rotor shaft 5) is a positive (+) value, and in the following formula (3), the material B (rotor 6) ) (Α _B L _B ΔT _B ) is a negative (−) value.

  During the fastening process, the material B (rotor 6) is restrained from being deformed in the axial direction by the jig T as shown in FIG. Then, at the initial stage of insertion in the fastening process, that is, when the relationship between the rotor shaft 5 and the rotor 6 shown in FIG. 10A becomes the state shown in FIG. 10B, the material A (the rotor shaft 5) and The fastening surface SF of the material B (rotor 6) is in contact with no gap.

  However, when the temperature difference between both materials A and B disappears, a gap Q as shown in FIG. 11 is generated on the fastening surface SF due to the difference in linear expansion coefficient between the materials A and B. Compared to the linear expansion coefficient of the iron-based material that is the material A of the rotor shaft 5, the linear expansion coefficient of the aluminum alloy material that is the material B of the rotor 6 is approximately doubled. This is because the shrinkage amount of the material B is smaller.

<< When the materials A and B are fastened on an inclined surface (corresponding to the embodiment of the present invention) >>
FIG. 5 is an explanatory diagram modeling the fastening relationship between the rotor 6 and the rotor shaft 5 in the vacuum pump P1 according to the embodiment of the present invention shown in FIG.

  In FIG. 5, it is assumed that the rotor shaft 5 is formed of the above-described material A (iron-based material) and the rotor 6 is formed of the above-described material B (aluminum alloy material).

In FIG. 5, the amount of deformation (ΔR) in the radial direction of the rotor shaft 5 (material A) due to temperature change is expressed by the following equation (4), similar to the equation (1). In addition, since there is anisotropy depending on the material structure and the like, the linear expansion coefficient is β in the following formula (4). That is, α is a linear expansion coefficient in the axial direction of the rotor 6 and the rotor shaft 5, whereas β is considered as a linear expansion coefficient in the radial direction.

In FIG. 5, the dimensions (R _A ′, R _B ′) after deformation due to temperature changes of the rotor shaft (material A) and the rotor 6 (material B) are expressed by the following formulas (5) and (6), respectively. Is done.

  In addition, about the deformation | transformation of the axial direction of the rotor shaft 5 (material A) and the rotor 6 (material B) by a temperature change, it becomes the same formula as said Formula (2) and Formula (3).

When the rotor shaft 5 (material A) and the rotor 6 (material B) are deformed due to a temperature change, the contact surface between the rotor shaft 5 and the rotor 6, that is, the fastening surface SF between the rotor shaft 5 and the rotor 6 before and after the deformation. The condition that the angle of the angle does not change (hereinafter referred to as “angle invariant condition”) is to satisfy the following expression (7).

Here, [Delta] L _A and [Delta] L _B in the formula (7), _{respectively, ΔL A = α A L A} ΔT A, the _{ΔL B = α B L B ΔT} B. When the rotor (6) and the rotor shaft (5) are fastened, the temperature change occurs in both the rotor (6) and the rotor shaft (5) by, for example, heating the rotor (6) and cooling the rotor shaft (5). It is an example when it occurs.

However, without cooling the rotor shaft 5, by heating the rotor 6, in the case of shrink fit fastening the rotor 6 and the rotor shaft 5, [Delta] L from the temperature change [Delta] T _A of the rotor shaft 5 is zero _A Since 0, the equation (7) becomes the following equation (7-1). Further, in the case of a cold fit in which the rotor 6 is not heated and the rotor shaft 5 is cooled and the rotor 6 and the rotor shaft 5 are fastened, the temperature change ΔT _B of the rotor 6 is zero, so that ΔL _B Since 0, the equation (7) becomes the following equation (7-2).

Therefore, the inclination angle of the tapered shape described above, that is, the angle of the contact surface (fastening surface SF) may be calculated from the above formula (7), formula (7-1), or formula (7-2). That is, the angle θ of the contact surface (fastening surface SF) can be set using the axial and radial displacement amounts due to the deformation of the rotor shaft 5 or the rotor 6. By setting the angle θ of the contact surface (fastening surface SF) in this way, the radial displacement (dimensional change) compensates for the axial displacement (dimensional change) due to temperature change. From the above equation (7), the angle invariant condition can be expressed by the following equation (8).

  The angle-invariant conditional expressions shown in the equations (7) and (8) also indicate that the dimensional change in either the radial direction or the axial direction is compensated by the dimensional change in the other direction. Yes. For example, when the temperature of the rotor changes during operation or the like, if only the dimensional change in the axial direction causes a gap between the fastening surfaces SF, the fastening of the taper angle θ is caused by the dimensional change in the radial direction of the rotor 6. It deform | transforms so that surface SF may be maintained, and it becomes possible for fastening surface SF to maintain favorable fastening without a gap.

Here, ΔL _A , ΔL _B , ΔR _A , and ΔR _B in the formula (8) can be expressed as formula (9), formula (10), formula (11), and formula (12), respectively. .

When the formula (9) to the formula (12) are respectively substituted into the formula (8), the formula (8) becomes the following formula (8 ′).

Moreover, when organizing the formula (8 '), the rotor shaft 5 (material A) and the rotor 6 in the axial direction in the (material B) the length _L A, _{L B} and the radial length _R A, of _{R B} relationship Becomes the following formula (8 ″).

<< Consideration of Formula (8 '') >>
Α _A / α _B in the equation (8 ″) is a ratio of linear expansion coefficients in the axial direction of the rotor shaft 5 (material A) and the rotor 6 (material B), and in the equation (8 ″) Β _B / β _A is the ratio of the linear expansion coefficient in the radial direction for the rotor shaft 5 (material A) and the rotor 6 (material B). From this, the angle θ of the contact surface (fastening surface SF) can be set based on the linear expansion coefficients of the rotor shaft 5 (material A) and the rotor 6 (material B), and the angle set as such. Since the taper-shaped fastening surface inclined by θ, that is, the contact surface (fastening surface SF) satisfies the above-mentioned angle invariant condition, even if the rotor shaft 5 and the rotor 6 are deformed due to temperature changes during fastening, The angle θ of the contact surface (fastening surface SF) does not change before and after the deformation.

For this reason, in the vacuum pump P1 of FIG. 1, after the rotor shaft 5 and the rotor 6 are fastened, separation of the fastening surface SF due to a difference in linear expansion coefficient between the rotor shaft 5 and the rotor 6 can be effectively prevented. The fastening between the rotor shaft 5 and the rotor 6 is stable in that a fastening without a gap can be obtained. In the case of shrink fitting, the temperature change ΔT _A of the rotor shaft 5 is assumed to be zero, and in the case of cold fitting, the above equation may be used assuming that the temperature change ΔT _B of the rotor 6 is zero. Further, in the present embodiment, considering that there is anisotropy depending on the material structure and the like, the linear expansion coefficient in the axial direction and the radial direction are different from each other. However, for isotropic materials, the axial direction And the linear expansion coefficient in the radial direction may be set to the same value. In this case, the angle θ of the contact surface (fastening surface SF) is determined by the dimensions of the rotor shaft 5 and the rotor 6.

  By the way, when the angle θ of the contact surface (fastening surface SF) is set at least within the range surrounded by the bolt BT or the screw hole NE described above, the fastening between the rotor shaft 5 and the rotor 6 is stabilized. Therefore, outside the range, the setting of the angle θ of the contact surface (fastening surface SF) as described above may be omitted or may not be omitted.

<< Consideration of Formula (7) >>
FIG. 6 is an enlarged view with XY coordinates in the vicinity of the rotor shaft and the fastening portion of the rotor (before fastening with bolts) in the vacuum pump of FIG. 1.

The coordinate axis XY in FIG. 6 has an origin O at the point where the rotation center axis of the rotor shaft 5 (material A) and the end face of the rotor 6 (material B) intersect. Further, “l _A ” in the figure is the contact position dimension in the axial direction of the rotor shaft 5 on the contact surface (fastening surface SF) of the rotor shaft 5 and the rotor 6, and “r _A ” is the dimension of the rotor shaft 5 on the contact surface. The radial contact position dimension, “l _B ”, is the axial contact position dimension of the rotor 6 on the contact surface, and “r _B ” is the radial contact position dimension of the rotor 6 on the contact surface.

  In FIG. 6, the “contact position dimension” is the length of a perpendicular drawn from the contact surface (fastening surface SF) to the coordinate axis XY, and in particular, when “the contact position dimension in the axial direction” is referred to, the rotor axis 5 means the length of a perpendicular line drawn from the contact surface (fastening surface SF) of the rotor 6 to the coordinate axis X, and the “diameter contact position dimension” refers to the coordinate axis from the contact surface (fastening surface SF). It means the length of the perpendicular line dropped to Y.

Δl _A / _{Δr A} is the ratio of .DELTA.l _A and [Delta] r _A in FIG. 6 corresponds to [Delta] L _A / [Delta] R _A is the ratio of [Delta] L _A and [Delta] R _A in FIG. 5, .DELTA.l _B and [Delta] r _B in FIG. 6 is the ratio of Δl _B / Δr _B corresponding to [Delta] L _B / [Delta] R _B is the ratio of [Delta] L _B and [Delta] R _B in FIG. Therefore, the angle invariant conditional expression shown in the expression (7) can be expressed as the following expression (7 ′).

Moreover, the said Formula (7 ') becomes like the following formula (7-1') or the following formula (7-2 ') for the same reason as the said Formula (7).

Here, the “l _A ”, “l _B ”, “r _A ”, and “r _B ” are the following formulas (9 ′), (10 ′), (11 ′), and (12 ′), respectively. It can be expressed as

When the formula (10 ′) and the formula (12 ′) are substituted into the formula (7-1 ′), the formula (7-1 ′) becomes the following formula (7-1 ″).

When the formula (9 ′) and the formula (11 ′) are substituted into the formula (7-2 ′), the formula (7-2 ′) becomes the following formula (7-2 ″).

From the above formulas (7-1 ″) and (7-2 ″), the angle θ of the contact surface (fastening surface SF) in the fastening process is determined by the rotor shaft 5 (material A) or the rotor 6 (material B). Is set based on the linear expansion coefficient (α _A , β _A or α _B , β _B ) of the rotor, and the contact position dimensions (l _A , r _{A of the} rotor shaft 5 (material A) and the rotor 6 (material B)). , L _B , r _B ).

<< Example in consideration of thermal expansion of rotating body during operation of vacuum pump P1 >>
Due to the operation of the vacuum pump P1, the temperature of the rotating body (including the bolt BT) composed of the rotor 6, the rotor shaft 5 and the like increases and thermally expands. Due to such thermal expansion during operation of the vacuum pump P1, the contact state on the contact surface (fastening surface SF) of the rotor 6 and the rotor shaft 5 changes from the initial setting state, that is, the state set in the fastening step, and the rotor If a gap is left between the contact surface (fastening surface SF) between the rotor shaft 5 and the rotor shaft 5, problems such as unstable fastening between the rotor shaft 5 and the rotor 6 are assumed.

  Therefore, it is necessary to maintain the contact state on the contact surface (fastening surface SF) so as not to change from the initial setting state (the state set in the fastening process) even during the operation of the vacuum pump P1.

  FIG. 7 is an enlarged view with XY coordinates near the fastening portion of the rotor shaft and the rotor during operation of the vacuum pump of FIG.

  A coordinate axis XY in FIG. 7 has an origin O at a point where the rotation center axis of the rotor shaft 5 (material A) and the end face of the rotor 6 (material B) intersect. In the same figure, “l” is the axial contact position dimension on the contact surface (fastening surface SF) between the rotor shaft 5 and the rotor 6, and “r” is on the contact surface (fastening surface SF) of the rotor shaft 5 rotor 6. It is a contact position dimension of radial direction.

  In FIG. 7, the “contact position dimension” is a length of a perpendicular drawn from the contact surface (fastening surface SF) to the coordinate axis XY, and in particular, “a contact position in the axial direction on the contact surface (fastening surface SF)”. The term “dimension” means the length of the perpendicular drawn from the contact surface (fastening surface SF) to the coordinate axis X, and the term “diameter contact position dimension in the contact surface (fastening surface SF)” means the same contact. It means the length of a perpendicular line drawn from the surface (fastening surface SF) to the coordinate axis Y.

In FIG. 7, when the temperature changes by ΔT (° C.) during the operation of the vacuum pump P1, the equations considering the elongation amount of the bolt BT due to thermal expansion are expressed as the following equations (13) and (14). . In addition, since the radial extension amount (α _C ΔT · R) of the bolt BT (material C) due to thermal expansion is smaller than the axial extension amount, the following equation (13) shows that the radial extension of the bolt BT due to thermal expansion. The quantity (α _C ΔT · R) is omitted.

As can be seen from the equation (13), since the linear expansion coefficients β _A and β _B are different, a gap is left in the contact surface (fastening surface SF) due to thermal expansion of the rotating body during operation of the vacuum pump P1. This gap usually occurs in such a form that the contact surface (fastening surface SF) opens in the radial direction of the rotor shaft 5 or the rotor 6. Therefore, such a radial gap is compensated by an axial displacement of the contact surface (fastening surface SF), specifically, a displacement satisfying the following formula (15).

  When the formula (15) is modified, the formula (15) becomes the following formula (16). Θ in the following formula (16) is an angle of the contact surface (fastening surface SF) necessary for the axial displacement of the contact surface (fastening surface SF) to be a displacement that compensates for the radial gap described above.

When the formula (13) and the formula (14) are substituted into the formula (16), the formula (16) becomes the following formula (17).

As can be seen from the equation (17), the angle θ of the contact surface (fastening surface SF) is determined by five linear expansion coefficients (α _A , α _B , α _C , β _A , β _B ), the rotor shaft 5 and the rotor. 6 on the contact surface dimension (l, r) on the contact surface (fastening surface SF). In this case, since the deformation in the radial direction of the bolt BT (material C) is ignored, β _C does not appear in the equation (17).

  By the way, although the above description considers the elongation amount of the bolt BT as the thermal expansion of the rotating body during the operation of the vacuum pump P1, the elongation amount of the bolt BT is made as small as possible by selecting the material of the bolt BT. In this case, it is not necessary to consider the amount of elongation of the bolt BT.

When the material structure is isotropic, the linear expansion coefficient is equal in the axial direction and the radial direction (α _A = β _A , α _B = β _B ), and further, when the amount of elongation of the bolt BT in the axial direction is not considered, Since the linear expansion coefficient α _{C in} the axial direction of the bolt BT (material C) is 0, the above equation (17) is expressed by the following equation (17 ′).

  Therefore, when it is not necessary to consider the amount of elongation of the bolt BT as described above, the contact position dimension (1, L) on the contact surface (fastening surface SF) of the rotor shaft 5 and the rotor 6 from the above equation (17 ′). Based on r), the angle θ of the contact surface (fastening surface SF) can be determined.

<< Modification of Formula (17) >>
The equation (17) can be transformed into the following equation (17 ″).

  The expression (17 ″) indicates the contents of the following << Expression consideration 1 >> and << Expression consideration 2 >>.

《Formula consideration 1》
The coordinates (r, l) of an arbitrary point P in the contact surface (fastening surface SF) is a straight line of a linear function having a predetermined slope, specifically, linear expansion coefficients (α _A , α _B , α _C , Β _A , β _B ) and a tangent angle (tan θ), a straight line (l = f (α _A , α) having a slope (f (α _A , α _B , α _C , β _A , β _B , tan θ)) determined by _B , α _C , β _A , β _B , tan θ) · r). Therefore, “a region where the tangent line is a straight line passing through the origin O of the XY coordinate axes” exists in the contact surface (fastening surface SF). If the surface has such a region, the contact surface (fastening surface SF) described above is not limited to the tapered shape shown in FIGS. Alternatively, it may be a surface including such a tapered shape or a curved shape.

  Further, in the present embodiment, considering that there is anisotropy depending on the material structure and the like, the linear expansion coefficient in the axial direction and the radial direction are different from each other. However, when considering an isotropic material, the axial direction And the linear expansion coefficient in the radial direction may be set to the same value, and the equation can be further simplified.

<Formula consideration 2>
If the angle θ of the contact surface (fastening surface SF) is always constant, the extension line of the contact surface (fastening surface SF) always passes through the origin O of the XY coordinate axis.

<< Other embodiments >>
In the vacuum pump P1 of FIG. 1, the embodiment in which the rotor shaft 5 and the rotor 6 are fastened with the bolt BT is adopted as a means for restraining the expansion of the rotor 6 in the radial direction at the fastening portion between the rotor shaft 5 and the rotor 6. However, the present invention is not limited to this embodiment.

  As for the restraining means, for example, as shown in FIG. 3, while the convex portion 10 is provided on the rotor 6 side, the concave portion 11 is provided on the rotor shaft 5 side, and the rotor shaft 5 and the rotor 6 are fastened together. In addition, a configuration in which the convex portion 10 and the concave portion 11 are engaged with each other may be employed. In this case, as shown in the figure, the convex portion 11 on the rotor 6 side is formed so as to protrude from the fastening surface SF of the rotor 6 described above toward the fastening surface SF of the rotor shaft 5. Further, the concave portion 11 on the rotor shaft 5 side can be formed so as to be open toward the convex portion 10 on the fastening surface SF of the rotor shaft 5 described above.

  Although not shown in the figure, the means for restraining may be configured such that the convex portion 10 described above is provided on the rotor shaft 5 side while the concave portion 11 described above is provided on the rotor 6 side. It is.

  When the above-described restraint is sufficient only by fastening with the bolt BT described above, the above-described engagement structure between the convex portion 10 and the concave portion 11 may be omitted, and the above-described restraint structure only with the engagement structure. Is sufficient, the fastening with the bolt BT may be omitted.

  In the vacuum pump P1 of FIG. 1, a plurality of bolts BT (see FIG. 2) are employed as means for constraining the radial expansion of the rotor 6 at the fastening portion between the rotor shaft 5 and the rotor 6. As shown in FIG. 3, for example, as shown in FIG. 3, a screw groove is formed on the outer peripheral surface of the tip of the rotor shaft 5 protruding from the end member 61 of the rotor 6, and a nut NA is tightened in the screw groove. A configuration in which the rotor 6 and the rotor shaft 5 are fixed in the axial direction may be employed. Further, such a nut NA and the plurality of bolts BT can be used in combination.

  Although not shown, the bolt BT through hole is provided in the rotor shaft 5, the bolt BT screw hole NE is provided in the rotor 6, and the bolt BT is inserted and fixed from below the fastening surface SF of the rotor shaft 6 in FIG. You may make it the structure to do.

  The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the art within the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Exterior case 1A Pump case 1B Pump base 1C Flange 2 Intake port 3 Exhaust port 4 Stator column 5 Rotor shaft 51 Insertion part 6 Rotor 61 End member 62 of a rotor Fitting hole 7 Rotary blade 8 Fixed blade 9 Screw groove exhaust part stator 91 Screw groove 10 Convex part 11 Concave part BT Bolt G Final gap MB1 Radial magnetic bearing MB2 Axial magnetic bearing MO Motor NE Screw hole NA Nut P1 Vacuum pump P2 of the present invention Conventional vacuum pump Pt Blade exhaust part Ps Screw groove exhaust part R Screw groove Exhaust passage S Pump exhaust side flow path SF Fastening surface T Jig θ The angle of inclination of the fastening surface

Claims (11)

A vacuum pump that sucks and exhausts gas by rotating a rotor fastened to a rotor shaft,
The fastening surface that forms the fastening portion between the rotor shaft and the rotor is arranged such that when the temperature of the rotor shaft or the rotor changes, the dimensional change in the radial direction compensates for the dimensional change in the axial direction. A vacuum pump characterized in that the dimensional change is a tapered shape or a curved shape inclined so as to compensate for a dimensional change in the radial direction, or a surface including the tapered shape or the curved shape. The rotor shaft and the rotor are formed of different materials,
2. The vacuum pump according to claim 1, wherein an angle of the tapered shape or the curved shape is set based on a linear expansion coefficient of the rotor shaft or the rotor. The rotor shaft and the rotor are formed of different materials,
2. The vacuum pump according to claim 1, wherein an angle of the tapered shape or the curved shape is set based on a contact position dimension on a contact surface of the rotor shaft and the rotor. As means for fastening the rotor shaft and the rotor, a plurality of screw holes are formed in one of the rotor shaft and the rotor, a plurality of bolt insertion holes corresponding to the screw holes are formed on the other, and 4. The rotor and the rotor shaft are fixed in the axial direction by tightening a bolt inserted into the bolt insertion hole with respect to the corresponding screw hole. 5. Vacuum pump. The rotor shaft and the rotor are formed of different materials,
5. The vacuum pump according to claim 4, wherein an angle of the tapered shape or the curved shape is set based on a linear expansion coefficient of the rotor shaft, the rotor, or the bolt. The rotor shaft and the rotor are formed of different materials,
6. The vacuum pump according to claim 4, wherein an angle of the tapered shape or the curved shape is set based on a contact position dimension on a contact surface of the rotor shaft and the rotor. 7. The vacuum pump according to claim 4, wherein the tapered shape or the curved shape is set in an inner range surrounded by at least a plurality of the bolts or the screw holes. As means for constraining expansion in the rotor radial direction at the fastening portion between the rotor shaft and the rotor, a convex portion is provided on one of the rotor shaft and the rotor, and a concave portion is provided on the other, and the convex portion and the concave portion are engaged. A vacuum pump according to any one of claims 1 to 7, characterized in that a combined configuration is employed.   A rotor for a vacuum pump, comprising the fastening surface having the tapered shape or the curved shape as a rotor used in the vacuum pump according to claim 1.   A rotor shaft for a vacuum pump, comprising the fastening surface having the tapered shape or the curved shape as a rotor shaft used in the vacuum pump according to claim 1.   A rotor for a vacuum pump comprising: a rotor used in the vacuum pump according to any one of claims 1 to 8; and a rotor blade on an outer peripheral surface thereof, and the fastening surface having the tapered shape or the curved shape. .

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