EP4707606A1

EP4707606A1 - Vacuum pump and fixed disk

Info

Publication number: EP4707606A1
Application number: EP24800080.4A
Authority: EP
Inventors: Kenta Kataoka; Shigeyoshi Nakatsuji
Original assignee: Edwards Japan Ltd
Current assignee: Edwards Japan Ltd
Priority date: 2023-05-01
Filing date: 2024-04-24
Publication date: 2026-03-11
Also published as: CN121039399A; TW202447084A; KR20260002826A; JP7721592B2; WO2024228349A1; JP2024160584A

Abstract

[Problem] To provide a vacuum pump and a stator disc that can suppress transfer of heat between a plurality of stator discs.

[Solving Means] Provided is a turbo molecular pump (vacuum pump) 100 that includes an outer cylinder (casing) 127, a rotor shaft (rotating shaft) 113 that is rotatably supported inside the outer cylinder 127, a plurality of rotor discs 200 that rotate together with the rotor shaft 113, and a plurality of stator discs 201 that are alternately arranged between the plurality of rotor discs 200, the turbo molecular pump exhausting gas by interaction between the plurality of rotor discs 200 and the plurality of stator discs 201, wherein the plurality of stator discs 201 include a first stator disc 201a and a second stator disc 201b that is adjacent to the first stator disc 201a in an axial direction, the first stator disc 201a has an outer peripheral side protruding portion (first contact portion) 210 that contacts the second stator disc 201b to perform positioning in the axial direction, and the outer peripheral side protruding portion 210 has a spatial portion 216 that is provided between the outer peripheral side protruding portion 210 and the second stator disc 201b.

Description

The present invention relates to a vacuum pump and a stator disc.
As a background art in the field of this technology, for example, PTL 1 describes "a turbo molecular pump including: a rotor having a plurality of stages of moving blades formed thereon; a plurality of stages of stator blades alternately arranged with respect to the moving blades; a pump casing having an inlet port flange formed thereon; and a plurality of spacers that are sandwiched between the spacer locking portion of the pump casing and a pump base so as to be laminated and that hold the plurality of stages of stator blades at prescribed positions, wherein one of the contact surfaces of a pair of spacers sandwiching one of the plurality of stages of stator blades is formed to be a concavo-convex surface."
Further, according to PTL 1, "one of the contact surfaces of the pair of spacers sandwiching the stator blade is formed to be the concavo-convex surface to reduce the contact area between the spacers, or the contact surface of the spacer locking portion with respect to the spacers is formed to be a concavo-convex surface to reduce a contact surface with respect to the spacers, whereby conduction heat from the pump casing to the spacers can be reduced. As a result, an increase in the temperature of the spacers or the stator blades is suppressed, and an increase in the temperature of the rotor due to heat radiation from the stator blades can be suppressed."

[PTL 1] Japanese Patent Application Laid-open No. 2006-152958
[PTL 2] Japanese Patent No. 6353195

Meanwhile, some vacuum pumps have a configuration including a Siegbahn exhausting mechanism (PTL 2). The Siegbahn exhausting mechanism is a mechanism to exhaust gas by interaction with a plurality of stator discs formed with spiral grooves and a plurality of rotor discs. In the Siegbahn exhausting mechanism, the downstream side of a gas flow is heated by a heater, while the upstream side thereof is cooled by a cooling medium. Therefore, it is extremely important to prevent the transfer of heat from a high temperature side to a low temperature side via the plurality of stator discs. PTL 1 refers to the suppression of an increase in the temperature of the spacers or the stator blades but does not refer to the suppression of the transfer of heat between the plurality of stator discs.
In view of this, the present invention has an object of providing a vacuum pump and a stator disc that can suppress the transfer of heat between a plurality of stator discs.
In order to achieve the above object, an aspect of the present invention provides a vacuum pump including: a casing; a rotating shaft that is rotatably supported inside the casing; a plurality of rotor discs that rotate together with the rotating shaft, and a plurality of stator discs that are alternately arranged between the plurality of rotor discs, the vacuum pump exhausting gas by interaction between the plurality of rotor discs and the plurality of stator discs, wherein the plurality of stator discs include a first stator disc and a second stator disc that is adjacent to the first stator disc in an axial direction, the first stator disc has a first contact portion that contacts the second stator disc to perform positioning in at least the axial direction with respect to the second stator disc, and the first contact portion has a spatial portion that is provided at a contact place with the second stator disc.
In the above configuration, the first contact portion includes an annular first outer peripheral side protruding portion that is provided along a peripheral edge of the first stator disc and contacts the second stator disc to perform positioning in the axial direction with respect to the second stator disc, and an annular first inner peripheral side protruding portion that is provided further on an inner side in a radial direction than the first outer peripheral side protruding portion and engages the second stator disc to perform positioning in at least one of the radial direction and a circumferential direction with respect to the second stator disc, and the spatial portion is a first recessed portion that is formed between the first outer peripheral side protruding portion and the first inner peripheral side protruding portion.
In the above configuration, the second stator disc has a second contact portion that contacts the first contact portion, the second contact portion includes an annular second outer peripheral side protruding portion that is provided along a peripheral edge of the second stator disc, an annular second inner peripheral side protruding portion that is provided further on an inner side in a radial direction than the second outer peripheral side protruding portion, and a second recessed portion that is formed between the second outer peripheral side protruding portion and the second inner peripheral side protruding portion, the first stator disc and the second stator disc are positioned in the axial direction when the first outer peripheral side protruding portion contacts the second outer peripheral side protruding portion, and the first stator disc and the second stator disc are positioned in the radial direction and a circumferential direction when the first inner peripheral side protruding portion engages the second inner peripheral side protruding portion.
In the above configuration, the vacuum pump includes: a Siegbahn exhausting mechanism in which spiral grooves are provided on an opposed surface of one of at least one of the plurality of rotor discs and at least one of the plurality of stator discs that is opposed to the at least one rotor disc.
In the above configuration, each of the first stator disc and the second stator disc is divided into a plurality of parts.
In the above configuration, the vacuum pump includes: a circumferential positioning portion that is provided on at least one of the first inner peripheral side protruding portion and the second inner peripheral side protruding portion, wherein an exit-side opening portion and an entrance-side opening portion of at least one of the spiral grooves at a turning-back portion are aligned with each other in the axial direction by the circumferential positioning portion.
Further, in order to achieve the above object, another aspect of the present invention provides a stator disc arranged between a plurality of rotor discs that rotate together with a rotating shaft of a vacuum pump, wherein the stator disc has a contact portion that contacts another stator disc adjacent in an axial direction to perform positioning in at least the axial direction, and the contact portion has a spatial portion that is provided at a contact place with the other stator disc.
According to the present invention, the transfer of heat between a plurality of stator discs can be suppressed. Note that problems, configurations, and effects other than the above are made obvious by the description of the following embodiments.

[Fig. 1]
Fig. 1 is a vertical cross-sectional view of a turbo molecular pump according to a first embodiment of the present invention.
[Fig. 2]
Fig. 2 is a circuit diagram of the amplifier circuit of the turbo molecular pump shown in Fig. 1.
[Fig. 3]
Fig. 3 is a time chart showing the control of an amplifier controlling circuit performed when a current command value is greater than a detected value.
[Fig. 4]
Fig. 4 is a time chart showing the control of the amplifier controlling circuit performed when the current command value is smaller than the detected value.
[Fig. 5]
Fig. 5 is an enlarged view of an A-portion shown in Fig. 1.
[Fig. 6]
Fig. 6 is a plan view of a stator disc.
[Fig. 7]
Fig. 7 is a rear view of the stator disc.
[Fig. 8]
Fig. 8 is an explanatory view showing the inner peripheral side protruding portion of the stator disc.
[Fig. 9]
Fig. 9 is an enlarged view of a B-portion shown in Fig. 5.
[Fig. 10]
Fig. 10 is an enlarged view of a C-portion shown in Fig. 6.
[Fig. 11]
Fig. 11 is an enlarged view of a D-portion shown in Fig. 7.
[Fig. 12]
Fig. 12 is an explanatory view showing a positioning state in the circumferential direction of the rotor disc.

Hereinafter, embodiments of a vacuum pump according to the present invention will be described with reference to the drawings using a turbo molecular pump as an example.
Fig. 1 shows a vertical cross-sectional view of a turbo molecular pump 100. In Fig. 1, the turbo molecular pump 100 has an inlet port 101 at the upper end of a cylindrical outer cylinder 127. Inside the outer cylinder 127, the rotating body 103 is provided in which a plurality of rotor blades 102 (102a, 102b, 102c, etc.) serving as turbine blades for sucking and exhausting gas are formed at a peripheral portion radially and in multiple stages. At the center of the rotating body 103, a rotor shaft 113 is attached. The rotor shaft 113 is supported to be floated and position-controlled in the air by, for example, a magnetic bearing that performs five-axis control. The rotating body 103 is generally made of metal such as aluminum and an aluminum alloy, or stainless.
Further, as shown in Fig. 1, a water-cooled spacer 128 and an outer wall 126 that are outer peripheral components are arranged on the outer peripheral side of a rotating body 103. The water-cooled spacer 128 is a ring-shaped member in which an annular cooling pipe 110 that is a temperature adjusting means and a temperature sensor (not shown) are embedded. Components on the periphery of the water-cooled spacer 128 are cooled as cooling water is supplied to the cooling pipe 110. That is, heat generated by the rotation of the rotating body 103 is cooled by the water-cooled spacer 128. The outer wall 126 is a cylindrical member that surrounds the substantially lower half of the turbo molecular pump 100. Below the outer cylinder 127, the water-cooled spacer 128 and the outer wall 126 are arranged in order to be coaxial with the outer cylinder 127. The outer cylinder 127, the water-cooled spacer 128, and the outer wall 126 are fastened and integrated with each other by a plurality of bolts 115 and constitute the housing (casing) of the turbo molecular pump 100 that accommodates the rotating body 103 with a base portion 129.
Here, the water-cooled spacer 128 also has a function as a stator blade spacer 125 that will be described later. That is, the water-cooled spacer 128 (specific spacer) constitutes one (one stage) of a plurality of stator blade spacers 125. Note that the water-cooled spacer 128 is made of a material having a higher heat conducting ratio than the outer cylinder 127 or the outer wall 126, for example, an aluminum material.
Upper radial electromagnets 104 have four electromagnets arranged in pairs in X and Y axes. Four upper radial sensors 107 are provided so as to be close to the upper radial electromagnets 104 and correspond to the respective upper radial electromagnets 104. Inductance sensors, eddy-current sensors, or the like having a conductive coil are, for example, used as the upper radial sensors 107. The position of the rotor shaft 113 is detected on the basis of a change in the inductance of the conductive coil that changes in accordance with the position of the rotor shaft 113. The upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, that is, the radial displacement of the rotating body 103 fixed to the rotor shaft 113 and transmit the detected displacement to the controlling device 195.
In the controlling device 1950, for example, a compensating circuit having a PID adjusting function generates an excitation control command signal for the upper radial electromagnets 104 on the basis of a position signal detected by the upper radial sensors 107, and an amplifier circuit 150 (that will be described later) shown in Fig. 2 performs the excitation control of the upper radial electromagnets 104 on the basis of the excitation control command signal. Thus, the upper radial position of the rotor shaft 113 is adjusted.
Further, the rotor shaft 113 is made of a high permeability material (such as iron and stainless steel) or the like and sucked by the magnetic forces of the upper radial electromagnets 104. The adjustment is separately performed in each of an X-axis direction and a Y-axis direction. Further, lower radial electromagnets 105 and lower radial sensors 108 are arranged like the upper radial electromagnets 104 and the upper radial sensors 107 and adjust the lower radial position of the rotor shaft 113 like the upper radial position.
In addition, axial electromagnets 106A and 106B are arranged with a disc-shaped metal disc 111 at the lower portion of the rotor shaft 113 held therebetween in a vertical direction. The metal disc 111 is made of a high permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and an axial position signal detected by the axial sensor 109 is configured to be transmitted to the controlling device 1950.
Then, in the controlling device 195, for example, the compensating circuit having the PID adjusting function generates an excitation control command signal for each of the axial electromagnet 106A and the axial electromagnet 106B on the basis of the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 performs the excitation control of each of the axial electromagnet 106A and the axial electromagnet 106B on the basis of these excitation control command signals. Thus, the axial electromagnet 106A sucks the metal disc 111 upward by a magnetic force, and the axial electromagnet 106B sucks the metal disc 111 downward by a magnetic force, so that the axial position of the rotor shaft 113 is adjusted.
As described above, the controlling device 195 appropriately adjusts a magnetic force applied to the metal disc 111 by the axial electromagnets 106A and 106B, and magnetically floats the rotor shaft 113 in an axial direction and retains the same in a non-contact manner in a space. Note that the amplifier circuit 150 that performs the excitation control of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B will be described later.
Meanwhile, a motor 121 includes a plurality of magnetic poles circumferentially arranged so as to surround the rotor shaft 113. The respective magnetic poles are controlled by the controlling device 195 so as to rotate and drive the rotor shaft 113 via an electromagnetic force applied between the respective magnetic poles and the rotor shaft 113. Further, a rotating speed sensor such as a hall element, a resolver, and an encoder not shown is, for example, incorporated into the motor 121, and the rotating speed of the rotor shaft 113 is detected by the detection signal of the rotating speed sensor.
In addition, a phase sensor not shown is attached near, for example, the lower radial sensors 108, and detects the phase of the rotation of the rotor shaft 113. The controlling device 195 detects the positions of the magnetic poles using both the detection signals of the phase sensor and the rotating speed sensor.
A plurality of stator blades 123 (123a, 123b, 123c, etc.) are disposed with a slight gap with respect to the rotor blades 102 (102a, 102b, 102c, etc.). A turbo pump portion is constituted by a plurality of stages of the rotor blades 102 and a plurality of stages of the stator blades 123. Each of the rotor blades 102 (102a, 102b, 102c, etc.) is formed to be inclined by a prescribed angle from a plane perpendicular to the axial line of the rotor shaft 113 to transfer the molecules of exhaust gas downward by collision. The stator blades 123 (123a, 123b, 123c, etc.) are made of, for example, metal such as aluminum, iron, stainless steel, and copper or metal such as an alloy containing these metal as components. Note that the water-cooled spacer 128 described above thermally contacts one of the plurality of stator blades 123 that are interior components.
Also, the stator blades 123 are similarly formed to be inclined by a prescribed angle from the plane perpendicular to the axial line of the rotor shaft 113 and disposed alternately with the stages of the rotor blades 102 toward the inside of the outer cylinder 127. Further, the outer peripheral ends of the stator blades 123 are supported in a state of being fitted and inserted between a plurality of stacked stator blade spacers 125 (125a, 125b, 125c, etc.).
The stator blade spacers 125 are ring-shaped members and made of, for example, metal such as aluminum, iron, stainless steel, and copper or metal such as an alloy containing these metal as components. The outer cylinder 127 is fixed to the outer periphery of the stator blade spacers 125 with a slight gap. A base portion 129 is disposed at the bottom of the outer cylinder 127 (more specifically, the bottom of the outer wall 126). An outlet port 133 is formed above the base portion 129 and communicates with an outside. Exhaust gas transferred toward the base portion 129 after entering the inlet port 101 from the side of a chamber (vacuum chamber) is supplied to the outlet port 133.
In addition, a Siegbahn-type pump portion 131 is disposed between the lower portion of the stator blade spacers 125 and the base portion 129. The Siegbahn-type pump portion 131 is formed at a stage next to an upper turbo pump portion constituted by the rotor blades 102 (102a, 102b, 102c, etc.), the stator blades 123 (123a, 123b, 123c, etc.), or the like so as to be spatially continuous.
The Siegbahn-type pump portion 131 has a plurality of rotor discs 200 that rotate with the rotor shaft 113 and a plurality of stator discs 201 that are alternately arranged between the plurality of rotor discs 200. The rotor discs 200 and the stator discs 201 are made of, for example, metal such as aluminum, iron, stainless steel, and copper or metal such as an alloy containing these metals as components.
The rotor discs 200 are integrally formed with the cylindrical rotating body 103, and rotate in the same direction as the rotor shaft 113 and the rotating body 103 as the rotating body 103 rotates. That is, the rotor discs 200 also rotate integrally with the rotor blades 102 (102a, 102b, 102c, etc.).
The stator discs 201 are integrally provided on a body casing (a combination of the outer cylinder 127 and the base portion 129). Further, one stage of the stator disc 201 is inserted between two vertical stages of the rotor discs 200 aligned in the axial direction of the rotor shaft 113.
As will be described in detail later, a multiplicity of ridge portions 202 having an assembly-shaped cross section are formed to protrude between the stator discs 201 and the rotor discs 200. In addition, Siegbahn spiral groove portions 203 that are spiral groove flow paths are formed between the adjacent ridge portions 202. Exhaust gas transferred by the rotor blades 102 and the stator blades 123 is sent to the base portion 129 while being guided by the Siegbahn spiral groove portions 203 of the Siegbahn-type pump portion 131.
Then, the exhaust gas guided by the Siegbahn spiral groove portions 203 is sent to an annular space 135 formed above the base portion 129, and exhausted to the outside via the outlet port 133 while circulating in the annular space 135. The annular space 135 is an annular space partitioned by the stator discs 201 of the Siegbahn-type pump portion 131, a heater spacer 153, and the base portion 129.
Here, the heater spacer 153 that is a stator component is a member formed into a cylindrical shape, and is constituted separately from the Siegbahn-type pump portion 131 in the present embodiment. Of course, the heater spacer 153 may be formed integrally with the Siegbahn-type pump portion 131 and constitute a part of the Siegbahn-type pump portion 131. The heater spacer 153 is made of, for example, metal such as aluminum and stainless steel. A heater 190 that serves as a heating means is inserted into the heater spacer 153. The Siegbahn-type pump portion 131 is also heated via the heater spacer 153 as the heater 190 generates heat. Further, the exhaust gas flowing through the annular space 135 is heated by the heater 190. Thus, the generation of a deposit due to a reduction in the temperature of the exhaust gas is suppressed. Further, an inner spacer 154 is, for example, a cylindrical member made of metal such as stainless steel, and insulates the water-cooled spacer 128 from the stator blade spacers 125 and the Siegbahn-type pump portion 131 that are arranged on the lower side of the water-cooled spacer 128.
The base portion 129 is a disc-shaped member constituting the base portion of the turbo molecular pump 100, and is generally made of metal such as iron, aluminum, and stainless steel. Since the base portion 129 serves also as a heat conducting path besides physically retaining the turbo molecular pump 100, metal such as iron, aluminum, and copper having stiffness and high heat conductivity is desirably used as such.
According to the above configuration, exhaust gas is sucked from the chamber via the inlet port 101 by the operation of the rotor blades 102 and the stator blades 123 when the rotor blades 102 are rotationally driven by the motor 121 together with the rotor shaft 113. The rotor blades 102 generally have a rotating speed of 20,000 rpm to 90,000 rpm, and a peripheral speed at the tip ends of the rotor blades 102 reaches 200 m/s to 400 m/s. The exhaust gas sucked from the inlet port 101 passes through between the rotor blades 102 and the stator blades 123, and reaches the Siegbahn-type pump portion 131. At this time, the temperature of the rotor blades 102 increases due to friction heat generated when the exhaust gas contacts the rotor blades 102, the conduction of heat generated by the motor 121, or the like. However, the heat is transmitted to the side of the stator blades 123 through radiation or conduction by the gas molecules or the like of the exhaust gas.
Further, the gas having reached the Siegbahn-type pump portion 131 flows into the Siegbahn spiral groove portion 203 on the most upstream side, and passes through a path that is gradually narrowed in a depth direction (in the axial direction of the rotor shaft 113). After that, the gas is transferred to the base portion 129 via turning-back portions (see Fig. 5) or the Siegbahn spiral groove portions 203 having a certain depth.
Note that the stator blade spacers 125 are bonded to each other at an outer peripheral portion, and transmit heat received by the stator blades 123 from the rotor blades 102, friction heat generated when exhaust gas contacts the stator blades 123, or the like to the outside.
Further, depending on the use of the turbo molecular pump 100, there is also a case that the surrounding area of an electrical portion including the upper radial electromagnets 104, the upper radial sensors 107, the motor 121, the lower radial electromagnets 105, the lower radial sensors 108, the axial electromagnets 106A and 106B, the axial sensor 109, or the like is covered with a stator column 122, and that the pressure inside the stator column 122 is retained at a prescribed pressure by a purge gas in order to prevent gas sucked via the inlet port 101 from entering the electrical portion.
In this case, a purge gas is introduced via a purge port 160 provided on the base portion 129. The introduced purge gas is delivered from the outlet port 133 to the outside via a gap between a protecting bearing 120 and the rotor shaft 113, a gap between the rotor and the stator of the motor 121, and a gap between the stator column 122 and a cylindrical portion on the inner peripheral side of the rotor blades 102. Note that the stator column 122 is erected at the central position of the base portion 129 as shown in Fig. 1. Further, in the present embodiment, a water-cooled pipe 149 that serves as a cooling means is provided in the base portion 129. The base portion 129 and the stator column 122 are retained at a suitable temperature as cooling water is supplied to the water-cooled pipe 149.
Here, the turbo molecular pump 100 requires control based on the specification of a model and separately adjusted unique parameters (for example, various characteristics corresponding to the model). In order to store the control parameters, the turbo molecular pump 100 includes an electronic circuit portion 141. The electronic circuit portion 141 includes electronic components such as a semiconductor memory like an EEP-ROM and a semiconductor element for accessing the semiconductor memory, a substrate 143 for mounting the electronic components, or the like. The electronic circuit portion 141 is accommodated at, for example, the lower portion of a rotating speed sensor not shown near the center of the base portion 129 constituting the lower portion of the turbo molecular pump 100 and is closed by an airtight bottom lid 145.
Meanwhile, in a semiconductor manufacturing process, some process gases introduced into a chamber have the property of becoming solid when their pressure becomes higher than a prescribed value or when their temperature becomes lower than a prescribed value. Inside the turbo molecular pump 100, the pressure of exhaust gas is the lowest at the inlet port 101 and the highest at the outlet port 133. When the pressure of a process gas becomes higher than a prescribed value or when the temperature of the process gas becomes lower than a prescribed value during the transfer of the process gas from the inlet port 101 to the outlet port 133, the process gas becomes solid and is attached to and deposited inside the turbo molecular pump 100.
For example, when SiCl4 is used as a process gas in an Al etching device, it appears from a vapor pressure curve that a solid product (for example, AlCl3) separates out and is attached to and deposited inside the turbo molecular pump 100 in a low vacuum condition (from 760 [torr] to 10-2 [torr]) and at a low temperature (about 20[°C]). Therefore, when the precipitate of a process gas is deposited inside the turbo molecular pump 100, the precipitate narrows down a pump flow path, which causes a reason for a reduction in the performance of the turbo molecular pump 100. Further, the product described above is liable to be solidified and attached to a high-pressure portion near the outlet port 133 or the Siegbahn-type pump portion 131.
Therefore, in order to solve the above problem, a heater or an annular water-cooled pipe 149 is conventionally wound on the periphery of the base portion 129 or the like, and a temperature sensor (for example, a thermistor) is embedded in, for example, the base portion 129. Then, heating is performed by the heater or cooling control is performed by the water-cooled pipe 149 (hereinafter called TMS (Temperature Management System)) so that the temperature of the base portion 129 is retained at a constant high temperature (setting temperature) on the basis of a signal from the temperature sensor.
Next, in regard to the turbo molecular pump 100 thus configured, the amplifier circuit 150 that performs the excitation control of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B will be described. Fig. 2 shows a circuit diagram of the amplifier circuit 150.
In Fig. 3, an electromagnet coil 151 constituting the upper radial electromagnets 104 or the like has one end thereof connected to a positive electrode 171a of a power supply 171 via a transistor 161 and the other end thereof connected to a negative electrode 171b of the power supply 171 via a current detecting circuit 181 and a transistor 162. Further, the transistors 161 and 162 are so-called power MOSFETs and have a structure in which a diode is connected between a source and a drain.
On this occasion, a cathode terminal 161a of the diode of the transistor 161 is connected to the positive electrode 171a, and an anode terminal 161b thereof is connected to one end of the electromagnet coil 151. Further, a cathode terminal 162a of the diode of the transistor 162 is connected to the current detecting circuit 181, and an anode terminal 162b thereof is connected to the negative electrode 171b.
On the other hand, a cathode terminal 165a of a diode 165 for current regeneration is connected to one end of the electromagnet coil 151, and an anode terminal 165b thereof is connected to the negative electrode 171b. Further, a cathode terminal 166a of a diode 166 for current regeneration is similarly connected to the positive electrode 171a, and an anode terminal 166b thereof is connected to the other end of the electromagnet coil 151 via the current detecting circuit 181. Further, the current detecting circuit 181 includes, for example, a hall sensor type current sensor or an electric resistance element.
The amplifier circuit 150 thus configured corresponds to one electromagnet. Therefore, in a case in which the magnetic bearing performs five-axis control and the total number of the electromagnets 104, 105, 106A, and 106B is ten, the same amplifier circuit 150 is constituted for each of the electromagnets, and the ten amplifier circuits 150 are connected in parallel to the power supply 171.
In addition, an amplifier controlling circuit 191 includes, for example, a digital signal processor portion (hereinafter called a DSP portion) not shown of the controlling device 195. The amplifier controlling circuit 191 switches the ON/OFF of the transistors 161 and 162.
The amplifier controlling circuit 191 compares a current value (a signal reflecting the current value is called a current detecting signal 191c) detected by the current detecting circuit 181 with a prescribed current command value. Then, on the basis of a result of the comparison, the amplifier controlling circuit 191 determines the size (pulse width time Tp1 or Tp2) of a pulse width to be generated in a control cycle Ts showing one cycle in PWM control. As a result, the amplifier controlling circuit 191 outputs gate driving signals 191a and 191b having the pulse width to the gate terminals of the transistors 161 and 162.
Note that when passing through a resonance point during the accelerating operation of the rotation of the rotating body 103 or when disturbance occurs during an operation at a constant speed, the position of the rotating body 103 is required to be controlled at a high speed and with a great force. Therefore, a voltage of, for example, about 50 V is used as the power supply 171 so that a rapid increase (or decrease) in a current flowing through the electromagnet coil 151 is enabled. Further, a capacitor is generally connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 to stabilize the power supply 171 (not shown).
In the configuration, a current (hereinafter called an electromagnet current iL) flowing through the electromagnet coil 151 increases when both the transistors 161 and 162 are turned ON, and the electromagnet current iL decreases when both the transistors 161 and 162 are turned OFF.
Further, a so-called flywheel current is retained when one of the transistors 161 and 162 is turned ON and the other thereof is turned OFF. Then, the feeding of the flywheel current to the amplifier circuit 150 as described above leads to a decrease in hysteresis loss in the amplifier circuit 150, which makes it possible to reduce the power consumption of the whole circuit. Further, the control of the transistors 161 and 162 as described above enables a reduction in high-frequency noise such as a higher harmonic wave caused in the turbo molecular pump 100. In addition, the measurement of the flywheel current with the current detecting circuit 181 enables the detection of the electromagnet current iL flowing through the electromagnet coil 151.
That is, when a detected current value is smaller than a current command value, the amplifier circuit 150 turns ON both the transistors 161 and 162 for a period corresponding to the pulse width time Tp1 only once in the control cycle Ts (for example, 100 us) as shown in Fig. 3. Therefore, in the period, the electromagnet current iL increases toward a value iLmax (not shown) of the current capable of flowing through the transistors 161 and 162 from the positive electrode 171a to the negative electrode 171b.
On the other hand, when the detected current value is greater than the current command value, the amplifier circuit 150 turns OFF both the transistors 161 and 162 for a period corresponding to the pulse width time Tp2 only once in the control cycle Ts as shown in Fig. 4. Therefore, in the period, the electromagnet current iL decreases toward a value iLmin (not shown) of the current capable of being regenerated through the diodes 165 and 166 from the negative electrode 171b to the positive electrode 171a.
Then, in both cases, the amplifier circuit 150 turns ON one of the transistors 161 and 162 after the elapse of the pulse width time Tp1 or TP2. Therefore, the flywheel current is retained in the amplifier circuit 150 in the period.
Next, the Siegbahn-type pump portion 131 that is the characteristic of the turbo molecular pump 100 according to the present embodiment will be described in detail.
Fig. 5 is an enlarged view of an A-portion shown in Fig. 1, and shows the gas flow path of the Siegbahn-type pump portion 131. Fig. 6 is a plan view of a stator disc 201. Fig. 7 is a rear view of the stator disc 201. Fig. 8 is an explanatory view showing the inner peripheral side protruding portion of the stator disc 201. Fig. 9 is an enlarged view of a B-portion shown in Fig. 5. Fig. 10 is an enlarged view of a C-portion shown in Fig. 6. Fig. 11 is an enlarged view of a D-portion shown in Fig. 7. Fig. 12 is an explanatory view showing a positioning state in the circumferential direction of the stator disc 201.
The Siegbahn-type pump portion 131 includes a plurality of stator discs 201 overlapping each other in the axial direction of the rotor shaft 113. In the following description, three stator discs 201 overlapping each other in the axial direction will be denoted by symbols 201a, 201b, and 201c, respectively, in order from an upper stage. Here, the stator disc 201c of the lowermost stage is formed as an annular integrated part and fixed on the heater spacer 153 in a state of being positioned in the circumferential direction. Here, a positioning pin may be, for example, used to position the stator disc 201c in the circumferential direction. Further, the remaining stator discs 201a and 201b of the uppermost stage and the second stage are halved divided parts. When the stator discs 201a and 201b are formed as divided parts as described above, the incorporation of the respective divided stator discs 201 from the lateral side of the rotor shaft 113 is enabled, which makes assembling workability excellent.
On the plate surfaces of the stator discs 201, a multiplicity of ridge portions 202 having a rectangular cross section are formed so as to protrude. In addition, the Siegbahn spiral groove portions 203 that are spiral groove flow paths are formed between the adjacent ridge portions 202. As for the stator discs 201a and 201b of the uppermost stage and the second stage, the multiplicity of ridge portions 202 are formed on both their front and rear plate surfaces. Further, as for the stator disc 201c of the lowermost stage, the multiplicity of ridge portions 202 are formed only on its front plate surface.
Further, one stage of the stator disc 201 is inserted between two upper and lower stages of the rotor discs 200 aligned in the axial direction of the rotor shaft 113, whereby the gas flow path passing through the inside of the Siegbahn-type pump portion 131 is formed as shown by arrows in Fig. 5. That is, the gas having reached the Siegbahn-type pump portion 131 flows into the Siegbahn spiral groove portions 203 from the outer peripheral side of the rotor disc 200 of the uppermost stage and the stator disc 201a of the uppermost stage, and reaches the turning-back portion (the B-portion in Fig. 5) of the uppermost stage via the Siegbahn spiral groove portion 203. After that, the gas reaches the turning-back portion of the next stage via the Siegbahn spiral groove portions 203 from the turning-back portion of the uppermost stage. In addition, the gas is transferred to the base portion 129 via the Siegbahn spiral groove portions 203 from the turning-back portion of the next stage.
As shown in Figs. 6 and 7, an outer peripheral side protruding portion 210 arranged along a peripheral edge is formed on the plate surface of the stator disc 201. As described above, the stator discs 201a and 201b of the uppermost stage and the second stage are halved divided parts. In the stator discs 201a and 201b in which the halved divided parts are combined together, the outer peripheral side protruding portions 210 are formed into an annular shape along the peripheral edges of the plate surfaces on both the front and rear sides.
On the plate surface on the front side of the stator disc 201, an inner peripheral side protruding portion 211 arranged on an inner side in a radial direction than the outer peripheral side protruding portion 210 is formed. Further, on the plate surface on the rear side of the stator disc 201, an inner peripheral side protruding portion 212 arranged on an inner side in the radial direction than the outer peripheral side protruding portion 210 is formed. The inner peripheral side protruding portion 211 on the front side has an L-shaped cross section, and the inner peripheral side protruding portion 212 on the rear side has a reverse L-shaped cross section. That is, in the stator discs 201a and 201b in which the halved divided parts are combined together, the outer peripheral side protruding portion 210 is formed into an annular shape along the peripheral edge of the plate surface on the front side, and the inner peripheral side protruding portion 211 is formed into an annular shape on the inner side in the radial direction than the outer peripheral side protruding portion 210. Further, the outer peripheral side protruding portion 210 is formed into an annular shape along the peripheral edge of the plate surface on the rear side, and the inner peripheral side protruding portion 212 is formed into an annular shape on the inner side in the radial direction than the outer peripheral side protruding portion 210. In addition, as for the stator disc 201c of the lowermost stage, the outer peripheral side protruding portion 210 is formed into an annular shape along the peripheral edge of the plate surface on the front side, and the inner peripheral side protruding portion 211 is formed into an annular shape on the inner side in the radial direction than the outer peripheral side protruding portion 210.
Between the outer peripheral side protruding portion 210 and the inner peripheral side protruding portion 211 on the front side and between the outer peripheral side protruding portion 210 and the inner peripheral side protruding portion 212 on the rear side, an annular recessed portion 213 is each formed. Further, as shown in Figs. 8 and 12, a positioning groove 214 is formed on the inner peripheral side protruding portion 211 on the front side of the stator disc 201. In addition, as shown in Figs. 8 and 12, a positioning protruding portion 215 is formed at a position opposed to the positioning groove 214 on the inner peripheral side protruding portion 212 on the rear side of the stator disc 201. In the halved stator discs 201 shown in Figs. 6 and 7, the positioning groove 214 and the positioning protruding portion 215 are formed alone. However, on the plate surface on the front side of the stator disc 201 in which the halved divided parts are combined together, the positioning grooves 214 are formed at two places separated by 180 degrees. On the plate surface on the rear side of the stator disc 201, the positioning protruding portions 215 are formed at two places opposed to the positioning grooves 214. Conversely, the positioning protruding portions 215 may be formed on the plate surface on the front side of the stator disc 201, and the positioning grooves 214 may be formed on the plate surface on the rear side thereof. Further, pairs of the positioning grooves 214 and the positioning protruding portions 215 may only be formed at least at two places of the stator disc 201. For example, the pairs of the positioning grooves 214 and the positioning protruding portions 215 may be formed on the plate surfaces of the stator disc 201 at an interval of 120 degrees.
As shown in Figs. 5 and 9, the two stator discs 201 overlapping each other in the axial direction are positioned in the axial direction when the outer peripheral side protruding portions 210 formed on the stator discs 201 of the lower stage and the upper stage contact each other. Further, the two stator discs 201 are positioned in the radial direction when the inner peripheral side protruding portion 211 formed on the stator disc 201 of the lower stage and the inner peripheral side protruding portion 212 formed on the stator disc 201 of the upper stage engage each other in a recessed and protruding manner However, the inner peripheral side protruding portion 211 and the inner peripheral side protruding portion 212 do not contact each other in the axial direction (that is, the inner peripheral side protruding portion 211 and the inner peripheral side protruding portion 212 have a slight gap therebetween), and are irrelevant to their positioning in the axial direction.
In addition, as shown in Fig. 12, the two stator discs 201 overlapping each other in the axial direction are positioned in a circumferential direction when the positioning protruding portions 215 formed on the inner peripheral side protruding portion 212 of the stator disc 201 of the upper stage are fitted into the positioning grooves 214 formed on the inner peripheral side protruding portion 211 of the stator disc 201 of the lower stage. When the stator discs 201 of the two upper and lower stages are positioned in the circumferential direction as described above, the exit-side opening portion and the entrance-side opening portion of the Siegbahn spiral groove portions 203 can be aligned with each other in the axial direction at the turning-back portion of the gas flow path shown in Fig. 5. Note that the positioning grooves 214 and the positioning protruding portions 215 do not also contact each other in the axial direction, and are irrelevant to positioning in the axial direction. Accordingly, even if there are some dimensional errors between the stator discs 201, the two stator discs 201 overlapping each other in the axial direction are reliably positioned in the axial direction at the contact place between the outer peripheral side protruding portions 210, positioned in the radial direction at the engagement place between the inner peripheral side protruding portions 211 and 212, and positioned in the circumferential direction at the fitting places between the positioning grooves 214 and the positioning protruding portions 215.
Further, the position in the radial direction of the outer peripheral side protruding portions 210 is such that the contact positions between the outer cylinder 127 and the stator blade spacers 125, the contact positions between the stator blade spacers 125, the contact positions between the stator blade spacers 125 and the water-cooled spacer 128, and the contact positions between the stator blade spacers 125 and the stator discs 201 are all the same in the radial direction. Thus, a load applied when the outer cylinder 127 is fixed by the bolts 115 is applied straightly in the axial direction at the position in the radial direction described above. Therefore, even in a structure in which a contact area is reduced for heat insulation, a force by which the stator discs 201 are inclined does not act, which enables secured fixation.
In the plurality of stages of the stator discs 201 overlapping each other in a state of being positioned in the axial direction, the radial direction, and the circumferential direction, the recessed portions 213 existing between the outer peripheral side protruding portion 210 and the inner peripheral side protruding portion 211 and between the outer peripheral side protruding portion 210 and the inner peripheral side protruding portion 212 are vertically connected to each other, whereby a plurality of spatial portions 216 aligned along the axial direction are formed. These spatial portions 216 function as heat insulating portions, and suppress the transfer of heat from the heater spacer 153 to a cooling portion above the Siegbahn-type pump portion 131 via the plurality of stages of the stator discs 201.
That is, the lower surface of the Siegbahn-type pump portion 131 is in contact with the heater spacer 153, and the stator discs 201 are heated by heat from the heater 190 via the heater spacer 153. As a result, gas flowing through the gas flow path of the Siegbahn-type pump portion 131 is heated. Thus, the liquefaction or solidification of the gas flowing through the gas flow path can be prevented, and particularly, the deposition of gas molecules that are solid products inside the gas flow path can be prevented. However, the Siegbahn-type pump portion 131 has a structure in which the plurality of stages of the stator discs 201 overlap each other in the axial direction. Therefore, when the heat from the heater spacer 153 is transferred to the water-cooled spacer 128 via the plurality of stages of the stator discs 201, an interior cooling effect by the water-cooled spacer 128 on the upstream side of the turbo molecular pump 100 is reduced.
In the present embodiment, the plurality of spatial portions 216 aligned along the axial direction are formed between the outer peripheral side protruding portions 210 and the inner peripheral side protruding portion 211 and 212 of the stator discs 201 overlapping each other in the plurality of stages. Therefore, the transfer of the heat from the heater spacer 153 to the water-cooled spacer 128 is made difficult by the spatial portions 216.
Next, the effects of the present embodiment thus configured will be described.
In the turbo molecular pump 100 according to the present embodiment, the Siegbahn-type pump portion 131 arranged below the pump portion including the rotor blades 102, the stator blades 123, or the like has the plurality of rotor discs 200 that rotate with the rotor shaft 113 and the plurality of stator discs 201 that are alternately arranged between the plurality of rotor discs 200, and has the plurality of spatial portions 216 aligned along the axial direction between the stator discs 201 overlapping each other in the plurality of stages. Therefore, the turbo molecular pump 100 has a structure in which the transfer of heat from the heater spacer 153 to the water-cooled spacer 128 is made difficult. Accordingly, the turbo molecular pump 100 can suppress a reduction in the cooling effect by the water-cooled spacer 128, while securing the effect of heating the stator discs 201 by the heater spacer 153.
Further, the present embodiment relates to the assembly of the stator discs 201 that are the constituting members of the Siegbahn-type pump portion 131, and the two stator discs 201 overlapping each other in the axial direction can be laminated together in a state of being positioned not only in the axial direction but also in the radial direction and the circumferential direction. Specifically, the two stator discs 201 are positioned in the axial direction when the outer peripheral side protruding portions 210 formed on the stator discs 201 of the lower stage and the upper stage contact each other, and positioned in the radial direction when the inner peripheral side protruding portion 211 formed on the stator disc 201 of the lower side and the inner peripheral side protruding portion 212 formed on the stator disc 201 of the upper stage engage each other in a recessed and protruding manner. In addition, the two stator discs 201 are positioned in the radial direction when the inner peripheral side protruding portion 211 formed on the stator disc 201 of the lower stage and the inner peripheral side protruding portion 212 formed on the stator disc 201 of the upper stage engage each other in a recessed and protruding manner.
Furthermore, the inner peripheral side protruding portion 211 and the inner peripheral side protruding portion 212 that are positioned in the radial direction do not contact each other in the axial direction, and the positioning grooves 214 and the positioning protruding portions 215 that are positioned in the circumferential direction do not also contact each other in the axial direction. In both states, the inner peripheral side protruding portions 211 and 212, the positioning grooves 214, and the positioning protruding portions 215 are irrelevant to positioning in the axial direction. Accordingly, even if there are some dimensional errors between the stator discs 201, the two stator discs 201 overlapping each other in the axial direction are reliably positioned in the axial direction at the contact place between the outer peripheral side protruding portions 210, positioned in the radial direction at the engagement place between the inner peripheral side protruding portions 211 and 212, and positioned in the circumferential direction at the engagement places (fitted places) between the positioning grooves 214 and the positioning protruding portions 215. Note that the two stator discs 201 are positioned in the radial direction and the circumferential direction at the same time by the engagement between the inner peripheral side protruding portions 211 and 212 in the present embodiment. However, the two stator discs 201 may be positioned in one of the radial direction and the circumferential direction by the inner peripheral side protruding portions 211 and 212, and may be positioned in the other direction by another member.
Further, in the present embodiment, the remaining stator discs 201a and 201b other than the stator disc 201c of the lowermost stage among the plurality of stator discs 201 are formed as halved divided parts. Therefore, the incorporation of the respective divided stator discs 201 from the lateral side of the rotor shaft 113 is enabled, which makes assembling workability excellent. Note that the number of the laminated stator discs 201 is not limited to three, and the number of the divided stator discs 201 is not also particularly limited. Further, the number of the divisions of the stator discs 201 is not limited to two but may be three or more.
Note that in the present embodiment, the stator disc 201 of the upper stage and the stator disc 201 of the lower stage among the two stator discs 201 overlapping each other in the axial direction are a first stator disc and a second stator disc, respectively. That is, as for the stator disc 201a of the uppermost stage and the stator disc 201b of the second stage, the stator disc 201a of the uppermost stage and the stator disc 201b of the second stage correspond to the first stator disc and the second stator disc, respectively. Further, as for the stator disc 201b of the second stage and the stator disc 201b of the third stage, the stator disc 201b of the second stage and the stator disc 201b of the third stage correspond to the first stator disc and the second stator disc, respectively.
In the stator disc 201 (for example, the stator disc 201a) corresponding to the first stator disc, the outer peripheral side protruding portion 210 (first outer peripheral side protruding portion), the inner peripheral side protruding portion 212 (first inner peripheral side protruding portion), and the recessed portion 213 (first recessed portion) correspond to first contact portions of the present invention (see Fig. 9). Among them, the outer peripheral side protruding portion 210 contacts the outer peripheral side protruding portion 210 of the stator disc 201 (for example, the stator disc 201b) corresponding to the second stator disc of the lower stage to perform positioning in the axial direction, and the inner peripheral side protruding portion 212 engages the inner peripheral side protruding portion 211 of the stator disc 201b to perform positioning in the circumferential direction and the radial direction. Further, the recessed portion 213 is the spatial portion 216 provided at the contact place between the stator disc 201a and the stator disc 201b.
In the stator disc 201 (for example, the stator disc 201b) corresponding to the second stator disc, the outer peripheral side protruding portion 210 (second outer peripheral side protruding portion), the inner peripheral side protruding portion 211 (second inner peripheral side protruding portion), and the recessed portion 213 (second recessed portion) correspond to second contact portions of the present invention (see Fig. 9). Among them, the outer peripheral side protruding portion 210 contacts the outer peripheral side protruding portion 210 of the stator disc 201 (for example, the stator disc 201a) corresponding to the first stator disc of the upper stage to perform positioning in the axial direction, and the inner peripheral side protruding portion 211 engages the inner peripheral side protruding portion 212 of the stator disc 201a to perform positioning in the circumferential direction and the radial direction. Further, the recessed portion 213 is the spatial portion 216 provided at the contact place between the stator disc 201b and the stator disc 201a.
Note that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the gist of the present invention. All technical matters included in technical idea described in claims are the targets of the present invention. Although the embodiments show suitable examples, persons skilled in the art could realize various substituting examples, correction examples, modified examples, combined examples, or improved examples from the contents disclosed in the present specification. These examples are included in the technical scope described in the attached claims.

100: Turbo molecular pump (Vacuum pump)
101: Inlet port
102: Rotor blade
103: Rotating body
113: Rotor shaft (Rotating shaft)
123: Stator blade
127: Outer cylinder (Casing)
128: Water-cooled spacer
129: Base portion
131: Siegbahn-type pump portion
133: Outlet port
153: Heater spacer
190: Heater
200: Rotor disc
201 (201a, 201b, 201c): Stator disc
202: Ridge portion
203: Siegbahn spiral groove portion
210: Outer peripheral side protruding portion (first contact portion, second contact portion)
211, 212: Inner peripheral side protruding portion (first contact portion, second contact portion)
213: Recessed portion (first contact portion, second contact portion)
214: Positioning groove
215: Positioning protruding portion
216: Spatial potion

Claims

A vacuum pump comprising:
a casing;

a rotating shaft that is rotatably supported inside the casing;

a plurality of rotor discs that rotate together with the rotating shaft; and

a plurality of stator discs that are alternately arranged between the plurality of rotor discs,

the vacuum pump exhausting gas by interaction between the plurality of rotor discs and the plurality of stator discs, wherein

the plurality of stator discs include a first stator disc and a second stator disc that is adjacent to the first stator disc in an axial direction,

the first stator disc has a first contact portion that contacts the second stator disc to perform positioning in at least the axial direction with respect to the second stator disc, and

the first contact portion has a spatial portion that is provided at a contact place with the second stator disc.
The vacuum pump according to claim 1, wherein
the first contact portion includes

an annular first outer peripheral side protruding portion that is provided along a peripheral edge of the first stator disc and contacts the second stator disc to perform positioning in the axial direction with respect to the second stator disc, and

an annular first inner peripheral side protruding portion that is provided further on an inner side in a radial direction than the first outer peripheral side protruding portion and engages the second stator disc to perform positioning in at least one of the radial direction and a circumferential direction with respect to the second stator disc, and

the spatial portion is a first recessed portion that is formed between the first outer peripheral side protruding portion and the first inner peripheral side protruding portion.
The vacuum pump according to claim 2, wherein
the second stator disc has a second contact portion that contacts the first contact portion,

the second contact portion includes

an annular second outer peripheral side protruding portion that is provided along a peripheral edge of the second stator disc,

an annular second inner peripheral side protruding portion that is provided further on an inner side in a radial direction than the second outer peripheral side protruding portion, and

a second recessed portion that is formed between the second outer peripheral side protruding portion and the second inner peripheral side protruding portion,

the first stator disc and the second stator disc are positioned in the axial direction when the first outer peripheral side protruding portion contacts the second outer peripheral side protruding portion, and

the first stator disc and the second stator disc are positioned in the radial direction and a circumferential direction when the first inner peripheral side protruding portion engages the second inner peripheral side protruding portion.
The vacuum pump according to any one of claims 1 to 3, comprising:
a Siegbahn exhausting mechanism in which spiral grooves are provided on an opposed surface of one of at least one of the plurality of rotor discs and at least one of the plurality of stator discs that is opposed to the at least one rotor disc.
The vacuum pump according to any one of claims 1 to 3, wherein
each of the first stator disc and the second stator disc is divided into a plurality of parts.
The vacuum pump according to claim 4, comprising:
a circumferential positioning portion that is provided on at least one of the first inner peripheral side protruding portion and the second inner peripheral side protruding portion, wherein

an exit-side opening portion and an entrance-side opening portion of at least one of the spiral grooves at a turning-back portion are aligned with each other in the axial direction by the circumferential positioning portion.
A stator disc arranged between a plurality of rotor discs that rotate together with a rotating shaft of a vacuum pump, wherein
the stator disc has a contact portion that contacts another stator disc adjacent in an axial direction to perform positioning in at least the axial direction, and

the contact portion has a spatial portion that is provided at a contact place with the other stator disc.