JP2014181628A - Vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum pump that can increase the allowable rotation speed of the pump.SOLUTION: The vacuum pump comprises: a rotor 30 made of an aluminum alloy; and a rotating cylinder part 32 made of a fiber reinforced plastic material and externally fitted and fixed to a ring part 30a of the rotor 30. A convex part 301 is formed on an outer peripheral surface of the rotor 30 to which the rotating cylinder part 32 is externally fitted and fixed, and a concave part 320 into which the convex part 301 is inserted is formed on an inner peripheral surface of the rotating cylinder part 32. Because the rotating cylinder part 32 is externally fitted and fixed to the ring part 30a so that the convex part 301 is inserted into the concave part 320 in this way, the range of increase in temperature or rotation speed within an expansion limit can be extended when the rotor 30 (the ring part 30a) is expanded to the outside (the rotating cylinder part 32 side) by increase in temperature or rotation speed.

Description

  The present invention relates to a vacuum pump.

  Conventionally, a turbomolecular pump has an all-blade type turbomolecular pump having only rotor blades and fixed blades, a turbo pump stage composed of rotor blades and fixed blades, and a screw groove in the rotation side cylinder portion or the fixed side cylinder portion. There is a hybrid turbomolecular pump consisting of a formed drug pump stage. In addition, there is a pump consisting only of a drag pump stage, and since there is essentially no influence below, it will be described as a combined turbo molecular pump including this.

  In the composite turbo molecular pump, generally, the rotation-side cylindrical portion of the drag pump stage is formed integrally with the rotor blade, and a metal material such as an aluminum alloy is used as the material thereof. On the other hand, in order to reduce the weight of the rotor, a configuration is known in which the rotation-side cylindrical portion of the drag pump stage is formed of carbon fiber reinforced plastic (CFRP) or the like having a low specific gravity (see, for example, Patent Document 1).

  In the vacuum pump described in Patent Document 1, an annular support plate made of CFRP material is adhesively press-fitted to the outer periphery of the lower end portion of an aluminum alloy rotor, and a cylindrical rotor made of CFRP material is press-fitted to the outer periphery of the support plate. It is fixed. CFRP has a lower specific gravity, a higher Young's modulus, and a lower coefficient of thermal expansion than aluminum.

Japanese Patent No. 3098139 JP 2011-214558 A

  The turbo molecular pump has a wide temperature range from a storage lower limit temperature (for example, allowable to ambient temperature −25 ° C.) to an operation upper limit temperature (for example, allowable to about 120 ° C. at the rotor temperature), and a high rotation speed (for example, 500 rps level). Therefore, in the case of the structure in which the CFRP annular member is bonded and press-fitted to the outer periphery of the aluminum rotor as described above, there is a large difference in thermal expansion between the rotor and the annular member and the elastic expansion due to centrifugal force. . As a result, at the maximum rotational speed, the adhesive press-fit portion between the rotor and the annular member is in an interference fit state, and there is a tensile strength limit on the annular member on the outer peripheral side.

  On the other hand, in the low temperature state of the storage lower limit temperature, the fitting relationship in the adhesive press-fitting portion between the rotor and the annular member is a gap fit if there is no adhesive. Therefore, the joint between the rotor and the annular member is maintained by the extension displacement of the adhesive itself between the rotor and the annular member. This extension displacement has an allowable limit for preventing peeling, and the allowable limit of extension displacement is further reduced in consideration of repetition.

  That is, in the turbo molecular pump configured as described above, the pump use conditions are limited by the tensile strength limit of the CFRP annular member and the allowable displacement limit of the adhesive. In particular, there is a problem that the rotational speed and temperature during pump operation are limited by the limit of the tensile strength of the CFRP annular member.

A vacuum pump according to a preferred embodiment of the present invention includes: a pump rotor made of an aluminum alloy; and a cylindrical member that is formed of a fiber-reinforced plastic material and is externally fixed to the pump rotor. A convex portion is formed on the outer peripheral surface to be inserted and fixed, and a concave portion into which the convex portion is inserted is formed on the inner peripheral surface of the cylindrical member.
In a more preferred embodiment, the vacuum pump has a plurality of convex portions formed in axial symmetry along the circumferential direction of the outer peripheral surface, and the concave portions are respectively formed at positions facing the plurality of convex portions on the inner peripheral surface. Yes.
In a more preferred embodiment, the convex portion is a spherical convex portion, and the concave portion is a spherical concave portion or a conical concave portion.
In a more preferred embodiment, the spherical convex portion is configured by substituting with a ceramic sphere or a metal sphere inserted into the concave portion of the outer peripheral surface of the pump rotor.
In a more preferred embodiment, the convex portion is a convex portion that has a longer circumferential dimension than the axial dimension and is elongated in the circumferential direction.
In a further preferred embodiment, the cylindrical member is a cylindrical rotor that functions as a low vacuum side pump part.
In a further preferred embodiment, the pump rotor has a cylindrical rotor as a low vacuum side pump part, and the cylindrical member is extrapolated to the outer peripheral surface of the cylindrical rotor.
In a more preferred embodiment, a plating layer is formed on the concave and convex portions.

  According to the present invention, the allowable temperature range can be widened, and the allowable rotational speed of the pump can be further increased.

FIG. 1 is a cross-sectional view showing a schematic configuration of a turbo molecular pump. FIG. 2 is a cross-sectional view of a portion indicated by reference symbol A in FIG. FIG. 3 is a diagram illustrating an example of an adhesive press-fitting configuration. FIG. 4 is a diagram showing changes in the radius Ra and the radius Rc due to thermal expansion. FIG. 5 is a diagram for explaining displacement due to centrifugal force. FIG. 6 shows changes in the radii Ra1 and Ra2 with respect to the ring portion 30a and changes in the radii Rc1 and Rc2 with respect to the rotating cylindrical portion 32 due to thermal expansion. FIG. 7 is a diagram for explaining displacement due to centrifugal force. FIG. 8 is a sectional view (horizontal section) of the ring portion 30a. FIG. 9 is a cross-sectional view showing the concave portion 320 of the rotating cylindrical portion 32 and the convex portion 301 in a state of being fitted therein. FIG. 10 is a diagram illustrating a state in which the convex portion 301 fits in the central direction of the concave portion 320 as the ring portion 30a expands. FIG. 11 is a diagram illustrating a second modification. FIG. 12 is a diagram illustrating a third modification. FIG. 13 is a diagram for explaining the second embodiment.

-First embodiment-
Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of a magnetic levitation turbomolecular pump. A turbo molecular pump 1 is connected to a power supply device (not shown) and is driven and controlled by the power supply device.

  The shaft 31 to which the rotor 30 is attached is supported in a non-contact manner by electromagnets 37, 38 and 39 provided on the base 20. The electromagnet 39 constituting the axial magnetic bearing is arranged so as to sandwich the rotor disk 35 provided at the lower end of the shaft 31 in the axial direction. The flying position of the shaft 31 is detected by radial displacement sensors 27 and 28 and an axial displacement sensor 29.

  The rotating body (rotor 30 and shaft 31) magnetically levitated so as to be freely rotatable by the magnetic bearing is driven to rotate at high speed by the motor 36. For example, a brushless DC motor is used as the motor 36. The motor stator 36a is provided on the base 20, and the motor rotor (permanent magnet) 36b is provided on the shaft 31 side.

  The rotation of the rotor 30 is detected by the rotation sensor 33. A sensor target 34 is provided at the lower end of the shaft 31 that is rotationally driven by the motor 36. The sensor target 34 rotates integrally with the shaft 31. The axial displacement sensor 29 and the rotation sensor 33 described above are disposed at positions facing the lower surface of the sensor target 34. When the magnetic bearing is not operating, the shaft 31 is supported by emergency mechanical bearings 26a and 26b.

  The turbo molecular pump 1 shown in FIG. 1 has a turbo pump stage composed of a rotating blade 30b and a fixed blade 22, and a drag pump stage (thread groove pump) composed of a rotating cylindrical portion 32 and a screw stator 24. doing. The rotor 30 made of aluminum alloy is formed with a plurality of stages of rotating blades 30b. The plurality of stages of fixed blades 22 are alternately arranged with the rotary blades 30b in the axial direction. Each fixed wing 22 is placed on the base 20 via the spacer ring 23. When the fixing flange 21c of the pump casing 21 is fixed to the base 20 with a bolt, the stacked spacer ring 23 is sandwiched between the base 20 and the pump casing 21, and the fixed blade 22 is positioned.

  A ring portion 30a is formed at the lower end in the axial direction of the rotor 30, and the above-described rotating cylindrical portion 32 is fixed so that the upper end portion thereof is extrapolated to the ring portion 30a. The rotary cylinder portion 32 is fixed to the rotor 30 by press-fitting by cold fitting. A screw stator 24 that is a fixed-side drag pump stage is provided on the outer peripheral side of the rotating cylindrical portion 32. The screw stator 24 is attached to the base 20 so that a predetermined gap is formed between the screw stator 24 and the rotating cylindrical portion 32.

  For the rotating cylindrical part 32, fiber reinforced plastics (FRP: Fiber Reinforced Plastics) such as CFRP having a low specific gravity is used to reduce the weight of the rotor. As a base material (matrix) of fiber reinforced plastic, generally, thermosetting resin such as unsaturated polyester is often used, and epoxy resin, polyamide resin, phenol resin, and the like are also used. Details of the joint structure between the rotating cylindrical portion 32 and the rotor 30 will be described later. In the following description, it is assumed that the rotating cylindrical portion 32 is formed of a CFRP material.

  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 a cross-sectional view of a portion indicated by reference symbol A in FIG. 1, that is, a joint portion between the rotating cylindrical portion 32 and the rotor 30. As described above, since the rotary cylindrical portion 32 and the rotor 30 are press-fitted by cold fitting, the inner peripheral surface of the rotary cylindrical portion 32 and the outer peripheral surface of the rotor 30 are fitted with no gap. In FIG. 2, the inner peripheral surface and the outer peripheral surface are illustrated with a gap so as to be easily understood.

  A convex portion 301 is formed on the outer peripheral surface of the ring portion 30 a of the rotor 30. In the example shown in FIG. 2, the convex part 301 is a columnar convex part (for example, cylinder), Comprising: A plurality is formed along the circumferential direction of an outer peripheral surface. The plurality of convex portions 301 are preferably formed symmetrically so as not to cause imbalance in the rotating body. On the other hand, a recess 320 is formed on the inner peripheral surface of the rotating cylindrical portion 32 at a position facing the protrusion 301.

  In FIG. 2, Ra1 is the radius of the outer peripheral surface of the ring portion 30a, Ra2 is the radius of the tip portion of the convex portion 301, Rc1 is the radius of the inner peripheral surface of the rotating cylindrical portion 32, and Rc2 is the radius of the bottom portion of the concave portion 320. Here, the radius is a radius from the center of each axis. As will be described later, the magnitude relationship between Ra1 and Rc1 varies depending on the temperature and the centrifugal force during rotation, but the dimensional relationship when fitting the rotating cylindrical portion 32 to the ring portion 30a by cold fitting is Rc1> It is set like Ra1 and Ra2. Rc2 is set so that a gap is always formed.

  Next, the relationship between Ra1 and Rc1 when a temperature change occurs and when the rotor rotational speed changes will be described. First, with reference to FIGS. 3 to 5, a conventional configuration in which the rotary cylindrical portion 32 is adhesively press-fitted into the ring portion 30 a will be described. FIG. 3 is a diagram showing an example of the adhesive press-fitting configuration, and is a cross-sectional view of the same part as FIG. A groove 302 for filling the adhesive is formed in the ring portion 30a. In FIG. 3, the adhesive in the groove 302 is not shown.

  Also in this case, the ring portion 30a and the rotating cylindrical portion 32 are fitted by cold fitting. That is, the rotor 30 side is cooled to a cold fitting temperature (about −100 ° C.), and the ring portion 30 a is inserted into the rotating cylindrical portion 32. When the temperature returns to room temperature, the ring portion 30a expands and becomes an interference fit state, and the rotating cylindrical portion 32 is fixed to the ring portion 30a. Further, the rotating cylindrical portion 32 and the ring portion 30a are bonded together by the adhesive in the groove 302.

  FIG. 4 is a diagram illustrating a change in radius Ra1 due to thermal expansion of the rotor 30 alone having the ring portion 30a and a change in radius Rc1 due to thermal expansion of the rotating cylindrical portion 32 alone. In the operation of assembling the CFRP rotating cylindrical portion 32 to the aluminum alloy ring portion 30a, generally, a cold fit is employed in which the rotor 30 is cooled by liquid nitrogen or the like and thermally contracted. Therefore, when the radius Ra1 of the outer peripheral surface of the ring portion 30a at the time of assembly (at the time of heat shrinkage) is Ra10 and the radius Rc1 of the inner peripheral surface of the rotating cylindrical portion 32 is Rc10, at the room temperature so that Ra10 <Rc10 is satisfied. Ra1 and Rc1 are set.

  When the temperature of the rotor 30 and the rotating cylindrical portion 32 rises from the temperature during assembly (for example, −100 ° C.), the radii Ra1 and Rc1 increase due to thermal expansion. Since the thermal expansion coefficient of the aluminum alloy rotor 30 is larger than that of the CFRP rotary cylinder 32, the radius Ra1 has a larger degree of change as shown in FIG. When the temperature Tc1 is exceeded, the magnitude relationship is reversed such that Ra1> Rc1 (tightened fit state).

  When the temperature further rises, the tightening margin increases as the temperature rises, and the tensile stress of the rotating cylindrical portion 32 extrapolated to the ring portion 30a increases. In this case, since there is a strength limit in the rotating cylindrical portion 32, the upper limit temperature Tmax1 of the rotating cylindrical portion 32 is determined from the upper limit of the tensile stress (the upper limit considering the margin). When the temperature decreases and T <Tc1, the gap is fitted again, but the bonding between the ring portion 30a and the rotating cylindrical portion 32 is caused by the extension displacement of the adhesive itself between the ring portion 30a and the rotating cylindrical portion 32. Is preserved.

  However, this extension displacement has an allowable limit for preventing peeling. Furthermore, when considering repeated expansion and contraction due to temperature changes, the extension displacement limit is further reduced. The temperature Tmin is a lower temperature limit value determined from an allowable limit for preventing peeling. That is, the rotor temperature (the temperature of the rotor 30 and the rotating cylindrical portion 32) T is limited to Tmin ≦ T ≦ Tmax1. The dimension Li is a tightening margin at the temperature Tmax1, that is, a limit value of the tightening margin. On the other hand, the dimension Ld is the gap dimension at the time of Tmin and is the limit of the extension displacement of the adhesive. Therefore, the lower limit of the pump storage temperature must be set to Tmin or more.

  The thermal expansion displacement shown in FIG. 4 indicates the displacement state when the centrifugal force due to rotation is assumed to be constant (for example, the number of rotations = 0). On the other hand, FIG. 5 is a diagram for explaining displacement due to centrifugal force. FIG. 5 also shows changes in the radii Ra1 and Rc1 due to changes in the rotational speed when the rotor 30 and the rotating cylindrical portion 32 are independent. In general, the displacement is proportional to the square of the rotational speed ω. Ra11 and Rc11 are radii Ra1 and Rc1 when ω = 0, and if the pump temperature T1 is higher than Tmin shown in FIG. 4, the gap dimension (Rc1−Ra1) is smaller than Ld. As the rotational speed ω increases, the gap size (Rc1-Ra1) decreases, the magnitude relationship is reversed at the rotational speed ωc1, and a tight fit is established when ω> ωc1.

  As described above, the interference between the ring portion 30 a and the rotating cylindrical portion 32 has a limit value Li depending on the strength limit of the rotating cylindrical portion 32. When a centrifugal force is applied, a force from the ring portion 30a and a force due to the centrifugal force of the rotating cylindrical portion 32 itself act on the rotating cylindrical portion 32 that is extrapolated to the ring portion 30a. The rotational speed ωmax1 in FIG. 5 is a rotational speed when the tightening margin becomes the limit value Li. When the pump temperature T2 is T2> T1, the rotational speed ω at which the tightening margin becomes the limit value Li is also reduced.

  As described above, it is necessary to set the difference between the radius Rc10 and the radius Ra10 at the time of assembly so that the lower limit temperature is limited from the limit of the extension displacement of the adhesive and the lower limit temperature is lower than the storage lower limit temperature. When this difference increases, the temperature Tmin at which the gap dimension becomes the limit value Ld also increases, and the storage lower limit temperature may be limited. On the other hand, if the difference between the radius Rc10 and the radius Ra10 is reduced, the temperature at which the tightening margin reaches the limit value Li is lowered, and the upper limit of the use temperature may be limited.

  6 and 7 are diagrams for explaining the displacement when the connection structure between the ring portion 30a and the rotating cylindrical portion 32 is as shown in FIG. FIG. 6 is a view corresponding to FIG. 4 and shows changes in the radii Ra1 and Ra2 with respect to the ring portion 30a and changes in the radii Rc1 and Rc2 with respect to the rotating cylindrical portion 32 due to thermal expansion. In this case, the radius Ra20 of the tip of the convex portion 301 of the ring portion 30a at the cold-fitting temperature is set to be smaller than the radius Rc10 of the inner peripheral surface of the rotating cylindrical portion 32 so that the assembly operation by the cold-fitting can be performed. . That is, Rc10> Ra20 is satisfied.

  In the case of the structure shown in FIG. 2, in order to prevent the rotating cylindrical portion 32 from being detached from the ring portion 30a at the pump storage temperature (Tmin in FIG. 4), the convex portion 301 of the ring portion 30a rotates at that time. It is only necessary that Ra2> Rc1 be fitted in the concave portion 320 of the cylindrical portion 32, and there is no restriction on the peeling of the adhesive as in the conventional case. Therefore, as can be seen from FIG. 6, Ra20 is set such that Rc10> Ra20> Ra10, but the cooling fit temperature (about −100 ° C.) is sufficiently lower than the storage temperature (−25 ° C.). Therefore, there is no problem in workability during cold-fitting work.

  The broken line shown in FIG. 6 shows the change of the radius Ra1 in FIG. As described above, the radius Ra10 of the ring portion 30a during the cold fitting operation in FIG. 6 is set smaller than the radius Ra10 in FIG. Therefore, the temperature Tc2 at which the gap fitting state is switched to the interference fitting state is higher than the temperature Tc1 in the case of FIG. 4, and the temperature Tmax2 at which the difference between the radius Ra1 and the radius Rc1 becomes the fastening margin limit value Li is It becomes higher than the temperature Tmax1 in the case of FIG. That is, it can be seen that the allowable temperature range ΔT2 (= Tmax2−Tmin) in the case of the configuration of FIG. 2 extends to the higher temperature side than the allowable temperature range ΔT1 in the case of the structure using the adhesive.

  FIG. 7 is a diagram for explaining displacement due to centrifugal force as in the case of FIG. 5. The curve Ra1 'in FIG. 7 is the same as the curve Ra1 shown in FIG. As in the case described with reference to FIG. 6, the radius Ra11 at ω = 0 in FIG. 7 is set to be smaller than the radius Ra11 when the adhesive is used, so that the rotational speed ωc2 at which the gap fit is switched to the interference fit. However, it becomes larger than the rotational speed ωc1 in the case of FIG. As a result, the rotational speed ωmax2 at which the tightening margin is the limit value Li is ωmax2> ωmax1, and the allowable rotational speed range Δω2 is expanded to a higher temperature than the allowable rotational speed range Δω1 in FIG.

  As described above, the thermal expansion and the centrifugal force expansion have been individually examined. However, even when both are actually considered together, the present invention has an operation range (temperature range) as compared with the conventional case of fixing with an adhesive. And the rotation speed range) can be widened, and the rotation speed can be increased. In particular, the effect of the present invention is remarkable in a large pumping speed pump having a large rotor size. Conventionally, CFRP cylinders that were applied to small pumps are also applied to FPD (flat panel displays) that are normally used up to the limit temperature of aluminum rotors at high pumping speeds, and large pumps that are used in semiconductor etching applications. it can. Thereby, it is possible to save power and reduce costs by reducing the weight of the rotor.

  In the embodiment described above, the convex portion 301 is a columnar convex portion (for example, a cylinder), but various shapes are possible. 8-10 is a figure which shows the 1st modification of the convex part 301 and the recessed part 320. As shown in FIG. FIG. 8 is a sectional view (horizontal section) of the ring portion 30a. Four convex portions 301 are provided on the outer peripheral surface of the ring portion 30a at intervals of 90 °. The convex portion 301 is a spherical convex portion. FIG. 9 is a cross-sectional view showing the concave portion 320 of the rotating cylindrical portion 32 and the convex portion 301 in a state of being fitted therein.

  A recess 320 shown in FIG. 9A is a spherical recess. The curvature radius R2 of the concave portion 320 is set larger than the curvature radius R1 of the convex portion 301. FIG. 9A shows an interference fit state, and the outer peripheral surface of the ring portion 30 a is in contact with the inner peripheral surface of the rotating cylindrical portion 32. In this state, the convex portion 301 is set to a dimension (Ra2 <Rc2) that does not contact the concave portion 320. The recess 320 shown in FIG. 9B has a conical shape.

  As shown in FIG. 9, when the convex portion 301 is a spherical surface and the concave portion 320 is a spherical surface or a conical surface, the convex portion 301 is expanded when the ring portion 30 a expands and becomes an interference fit with respect to the rotating cylindrical portion 32. Is caught on the inner peripheral surface of the recess 320 to prevent the balancing state from deteriorating. In FIG. 9B, the concave conical tip is shown as being sharp, but since stress concentration occurs as the tip curvature decreases, it is preferable to implement a design that appropriately rounds the tip. FIG. 10 is a diagram illustrating a state in which the convex portion 301 fits in the central direction of the concave portion 320 as the ring portion 30a expands in the process of increasing the temperature or rotating speed. A two-dot chain line indicates a relationship between the ring portion 30a after expansion and the rotating cylindrical portion 32. Since the final fitting state is determined by the dimensional accuracy of the convex portion and the concave portion, the processing accuracy is ensured according to the necessary balance accuracy.

  FIG. 11 is a diagram showing a second modification. In the example shown in FIG. 8, the spherical convex portion 301 is integrally formed on the outer peripheral surface of the ring portion 30a. However, in the example shown in FIG. 11, a spherical concave portion is formed on the outer peripheral surface of the ring portion 30a. Ceramic or metal balls 303 were arranged. The shape of the concave portion 320 on the rotating cylindrical portion 32 side may be spherical as shown in FIG. 11 or may be a conical surface as shown in FIG. Also in this case, the same effects as those in FIGS.

  FIG. 12 is a diagram illustrating a third modification. 12A is a cross-sectional view of a portion where the convex portion 304 of the ring portion 30a is formed, and FIG. 12B is a front view of a portion where the convex portion 304 is formed. In the example shown in FIGS. 2 and 8, the shape of the convex portion 301 is a columnar shape or a spherical shape, but may be a convex portion 304 that is elongated in the circumferential direction as shown in FIG. 12. Further, a metal plating layer such as nickel plating may be formed on the surfaces of the recesses 320 and the protrusions 301. By forming the metal plating layer, the above-described effect of preventing the occurrence of imbalance can be further enhanced. As shown in FIG. 10, when the surface of CFRP or aluminum material is rough in the expansion process of the ring portion 30a, the frictional force increases, and the convex portion 301 becomes a rotating cylindrical portion when moving like a two-dot chain line. 32 may be caught on the inner peripheral surface. However, the formation of the metal plating layer can reduce the occurrence of catching.

-Second Embodiment-
In the first embodiment described above, the mounting structure of the rotating cylindrical portion 32 to the rotor 30 has been described. However, the present invention can also be applied to a mounting structure as shown in FIG. In the configuration shown in FIG. 13, the rotating cylindrical portion 32 is formed integrally with the lower portion of the rotor 30. A CFRP ring member 40 is fixed to the upper outer peripheral surface of the rotating cylindrical portion 32 by cold fitting.

  The ring member 40 is provided to prevent the crack from progressing when a crack occurs in the rotating cylindrical portion 32 made of an aluminum alloy (see, for example, Japanese Patent Application Laid-Open No. 2011-214558). The outer peripheral surface of the rotating cylindrical part 32 has a thread groove structure (a thread part 322 and a thread groove part 323). Therefore, if it is assumed that the rotating cylindrical portion 32 that rotates at a high speed is cracked due to excessive centrifugal force, the stepped portion at the lower end of the rotating cylindrical portion 32 (the stepped portion between the screw thread portion 322 and the screw groove portion 323) is cracked. Is likely to occur. When a crack occurs, the crack progresses in the direction of the upper end of the rotating cylindrical portion 32, and there is a possibility that the rotating cylindrical portion 32 and further the entire rotor 30 may eventually be destroyed. Therefore, a ring member 40 for stopping the progress of cracks is provided on the upper portion of the rotating cylindrical portion 32.

  The fixing structure of the ring member 40 has the same configuration as the fixing structure of the ring portion 30a and the rotating cylindrical portion 32 described in the first embodiment. That is, a concave portion 401 is formed on the inner peripheral surface of the CFRP ring member 40, and a convex portion 301 formed on the outer peripheral surface of the rotating cylindrical portion 32 is fitted in the concave portion 401. Although not described here, the dimensional relationship between the convex portion 301 of the rotating cylindrical portion 32 and the concave portion 401 of the ring member 40 is the same as the dimensional relationship between the ring portion 30a and the rotating cylindrical portion 32 described above. As a result, the allowable upper limit temperature and the allowable upper limit rotation speed can be improved.

  As described above, the vacuum pump according to the present embodiment includes the rotor 30 made of aluminum alloy and the rotating cylindrical portion that is formed by FRP material and is extrapolated to the ring portion 30a provided on the rotor 30 by cold fitting. 32, the ring portion 30a on which the rotating cylindrical portion 32 is fixed by extrapolation has a convex portion 301 on the outer peripheral surface, and the rotating cylindrical portion 32 has an inner periphery opposed to the ring portion 30a fixed by extrapolation. The surface has a concave portion 320 into which the convex portion 301 is inserted. As described above, since the rotating cylindrical portion 32 is extrapolated and fixed to the ring portion 30a so that the convex portion 301 is inserted into the concave portion 320, the ring portion 30a is moved outward (rotating cylindrical portion 32 side) due to a rise in temperature or a rotational speed. In the case of expansion, the temperature increase or rotation speed increase until reaching the expansion limit can be expanded to a wider range as shown in FIGS.

  Furthermore, an increase in the amount of unbalance of the rotor 30 can be suppressed by providing a plurality of convex portions and concave portions in axial symmetry.

  The above description is merely an example, and when interpreting the invention, there is no limitation or restriction on the correspondence between the items described in the above embodiment and the items described in the claims. For example, in the embodiment described above, the composite turbo molecular pump having the rotating cylindrical portion 32 has been described as an example. However, as long as it has an FRP cylindrical portion that rotates at high speed, the turbo molecular pump is not limited to the turbo molecular pump. It can be applied to a vacuum pump.

  1: turbo molecular pump, 30: rotor, 30a: ring part, 32: rotating cylindrical part, 40: ring member, 301, 304: convex part, 320, 401: concave part

Claims (8)

An aluminum alloy pump rotor;
A cylindrical member that is formed of a fiber reinforced plastic material and is externally fixed to the pump rotor,
On the outer peripheral surface of the pump rotor on which the cylindrical member is extrapolated and fixed, a convex portion is formed,
A vacuum pump in which a concave portion into which the convex portion is inserted is formed on an inner peripheral surface of the cylindrical member. The vacuum pump according to claim 1, wherein
A plurality of the convex portions are formed axisymmetrically along the circumferential direction of the outer peripheral surface,
The said recessed part is a vacuum pump currently formed in the position facing the said some convex part of the said internal peripheral surface, respectively. The vacuum pump according to claim 2,
The convex portion is a spherical convex portion,
The said recessed part is a vacuum pump which is a spherical recessed part or a conical recessed part. The vacuum pump according to claim 3,
The spherical convex portion is a vacuum pump configured by a ceramic sphere or a metal sphere inserted into a concave portion of the outer peripheral surface of the pump rotor. The vacuum pump according to claim 2,
The said convex part is a vacuum pump whose circumferential direction dimension is long compared with an axial direction dimension, and is a convex part elongate in the circumferential direction. The vacuum pump according to claim 1 or 2,
The said cylindrical member is a vacuum pump which is a cylindrical rotor which functions as a low vacuum side pump part. The vacuum pump according to claim 1 or 2,
The pump rotor has a cylindrical rotor as a low vacuum side pump part,
The said cylindrical member is a vacuum pump extrapolated and fixed to the outer peripheral surface of the said cylindrical rotor. The vacuum pump according to any one of claims 1 to 7,
A vacuum pump in which a plating layer is formed on the concave and convex portions.

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