Vacuum pump and fixed disc

Abstract

To provide a vacuum pump that can restrain heat transfer between a plurality of fixed disks, and provide the fixed disks.SOLUTION: A turbo molecular pump (vacuum pump) 100 comprises an outer cylinder (casing) 127, a rotor shaft (rotating shaft) 113 rotatably supported inside the outer cylinder 127, a plurality of rotating disks 200 to be rotated together with the rotor shaft 113, and a plurality of fixed disks 201 alternately arranged between the plurality of rotating disks 200, and exhausts gas by interaction between the plurality of rotating disks 200 and the plurality of fixed disks 201. The plurality of fixed disks 201 include a first fixed disk 201a, and a second fixed disk 201b adjacent to the first fixed disk 201a in an axial direction. The first fixed disk 201a comprises an outer peripheral side convex part (first contact part) 210 for performing positioning by being in contact with the second fixed disk 201b. The outer peripheral side convex part 210 comprises a space part 216 provided between itself and the second fixed disk 201b.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a vacuum pump and a fixed disk. [Background technology]

[0002] As background art in this technical field, for example, Patent Document 1 describes a turbomolecular pump including: a rotor on which multiple stages of moving blades are formed; multiple stages of stator vanes arranged alternately with respect to the moving blades; a pump casing on which an intake port flange is formed; and multiple spacers that are sandwiched so as to be stacked between a spacer locking portion of the pump casing and a pump base and hold the multiple stages of stator vanes in predetermined positions, wherein one of the contact surfaces of a pair of spacers sandwiching one stage of the multiple stages of stator vanes therebetween is made uneven.

[0003] According to Patent Document 1, "by making one of the contact surfaces of a pair of spacers sandwiching a stator vane uneven to reduce the contact area between the spacers, or by making the contact surface of the spacer locking portion with the spacer uneven to reduce the contact area with the spacer, it is possible to reduce the heat conducted from the pump casing to the spacer. As a result, the temperature rise of the spacers and stator vanes is suppressed, and the temperature rise of the rotor due to heat radiation from the stator vanes can be suppressed." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-152958 [Patent Document 2] Patent No. 6353195 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, some vacuum pumps are configured with a Sigburn pumping mechanism (see Patent Document 2). The Sigburn pumping mechanism is a mechanism that exhausts gas through the interaction between multiple fixed disks with spiral grooves and multiple rotating disks. In the Sigburn pumping mechanism, the downstream side of the gas flow is heated by a heater, while the upstream side is cooled by a cooling medium. Therefore, it is very important to prevent heat from transferring from the high-temperature side to the low-temperature side via the multiple fixed disks. However, while Patent Document 1 mentions suppressing temperature increases in the spacers and stator vanes, it does not mention anything about suppressing heat transfer between the multiple fixed disks.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a vacuum pump and fixed disks that can suppress the transfer of heat between a plurality of fixed disks. [Means for solving the problem]

[0007] In order to achieve the above object, one aspect of the present invention is a vacuum pump comprising a casing, a rotating shaft rotatably supported inside the casing, a plurality of rotating disks that rotate together with the rotating shaft, and a plurality of fixed disks that are alternately arranged between the plurality of rotating disks, and which exhausts gas by interaction between the plurality of rotating disks and the plurality of fixed disks, wherein the plurality of fixed disks include a first fixed disk and a second fixed disk that is adjacent to the first fixed disk in the axial direction, the first fixed disk having a first abutment portion that abuts against the second fixed disk to position it relative to the second fixed disk at least in the axial direction, and the first abutment portion having a space portion provided at a contact point with the second fixed disk. the first abutment portion is provided along the periphery of the first stationary disk and includes an annular first outer peripheral convex portion that abuts against the second stationary disk to position the second stationary disk in the axial direction, and an annular first inner peripheral convex portion that is provided radially inward from the first outer peripheral convex portion and engages with the second stationary disk to position the second stationary disk in at least one of the radial direction and the circumferential direction, the space portion is a first recess formed between the first outer peripheral convex portion and the first inner peripheral convex portion, the second stationary disk has a second abutment portion that abuts against the first abutment portion, the second abutment portion includes a second outer peripheral convex portion having an annular shape provided along the periphery of the second fixed disk, a second inner peripheral convex portion having an annular shape provided radially inward from the second outer peripheral convex portion, and a second recess portion formed between the second outer peripheral convex portion and the second inner peripheral convex portion, wherein the first outer peripheral convex portion abuts against the second outer peripheral convex portion, thereby positioning the first fixed disk and the second fixed disk in the axial direction, and the first inner peripheral convex portion engages with the second inner peripheral convex portion, thereby positioning the first fixed disk and the second fixed disk in the radial and circumferential directions. It is characterized by:

[0010] In the above configuration, a Sigburn exhaust mechanism having a spiral groove is provided on the opposing surface of either at least one of the plurality of rotating disks or at least one of the plurality of fixed disks facing the at least one rotating disk.

[0011] In the above configuration, the first fixed disk and the second fixed disk are each divided into a plurality of pieces.

[0012] In the above configuration, a circumferential positioning portion is provided on at least one of the first inner circumferential convex portion or the second inner circumferential convex portion, and the circumferential positioning portion causes the outlet side opening and the inlet side opening of at least one of the spiral grooves of the folded portion to coincide when viewed from the axial direction.

[0013] In order to achieve the above object, another aspect of the present invention is a vacuum pump having a plurality of rotating disks that rotate together with the rotary shaft of the vacuum pump. Multiple A fixed disc, Multiple The fixed disc is the first fixed disk has a first abutment portion that abuts against the second fixed disk to position the first fixed disk in at least the axial direction, the first abutment portion has a space portion provided at a contact point with the second fixed disk, the first abutment portion is provided along the periphery of the first fixed disk and includes: an annular first outer peripheral convex portion that abuts against the second fixed disk to position the second fixed disk in the axial direction; and an annular first inner peripheral convex portion that is provided radially inward from the first outer peripheral convex portion and engages with the second fixed disk to position the second fixed disk in at least one of the radial direction and the circumferential direction, a first recess formed between a first outer peripheral convex portion and the first inner peripheral convex portion, the second fixed disk having a second abutment portion abutting against the first abutment portion, the second abutment portion including a second outer peripheral convex portion having an annular shape provided along the periphery of the second fixed disk, a second inner peripheral convex portion having an annular shape provided radially inward from the second outer peripheral convex portion, and a second recess formed between the second outer peripheral convex portion and the second inner peripheral convex portion, the first fixed disk and the second fixed disk being positioned in the axial direction by the first outer peripheral convex portion abutting against the second outer peripheral convex portion, and the first inner peripheral convex portion engaging with the second inner peripheral convex portion being positioned in the radial direction and the circumferential direction. It is characterized by: [Effects of the Invention]

[0014] According to the present invention, it is possible to suppress the transfer of heat between a plurality of fixed disks. Note that problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a vertical cross-sectional view of a turbomolecular pump according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a circuit diagram of an amplifier circuit of the turbomolecular pump shown in FIG. [Figure 3] 10 is a time chart showing the control of the amplifier control circuit when a current command value is larger than a detection value. [Figure 4] 10 is a time chart showing the control of the amplifier control circuit when a current command value is smaller than a detection value. [Figure 5] FIG. 2 is an enlarged view of part A shown in FIG. [Figure 6] FIG. [Figure 7] FIG. [Figure 8]10 is an explanatory diagram showing an inner peripheral convex portion of the fixed disk. FIG. [Figure 9] FIG. 6 is an enlarged view of part B shown in FIG. [Figure 10] FIG. 7 is an enlarged view of part C shown in FIG. [Figure 11] FIG. 8 is an enlarged view of a portion D shown in FIG. [Figure 12] 10 is an explanatory diagram showing a circumferential positioning state of the fixed disk. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a vacuum pump according to the present invention will be described with reference to the drawings, taking a turbomolecular pump as an example.

[0017] A longitudinal cross-sectional view of this turbomolecular pump 100 is shown in FIG. 1. In FIG. 1, the turbomolecular pump 100 has an intake port 101 formed at the upper end of a cylindrical outer tube 127. Inside the outer tube 127 is provided a rotor 103, which has a plurality of rotors 102 (102a, 102b, 102c, etc.), which are turbine blades for sucking in and exhausting gas, formed radially and in multiple stages around its periphery. A rotor shaft 113 is attached to the center of this rotor 103, and this rotor shaft 113 is levitated and supported in the air and its position is controlled by, for example, a five-axis controlled magnetic bearing. The rotor 103 is generally made of a metal such as aluminum, an aluminum alloy, or stainless steel.

[0018] 1, a water-cooled spacer 128 and an outer wall 126, which are peripheral components, are arranged on the outer periphery of the rotating body 103. The water-cooled spacer 128 is a ring-shaped member that incorporates an annular cooling pipe 110, which serves as a temperature adjustment means, and a temperature sensor (not shown). Cooling water is supplied to the cooling pipe 110, thereby cooling the components around the water-cooled spacer 128. In other words, 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 approximately the lower half of the turbomolecular pump 100. The water-cooled spacer 128 and the outer wall 126 are arranged below the outer cylinder 127, coaxially aligned with the outer cylinder 127. The outer cylinder 127, the water-cooled spacer 128, and the outer wall 126 are fastened together with a plurality of bolts 115, and together with the base portion 129, form an exterior body (casing) of the turbomolecular pump 100 that houses the rotor 103.

[0019] Here, the water-cooled spacer 128 also functions as a fixed vane spacer 125, which will be described later. That is, the water-cooled spacer 128 (specific spacer) constitutes one (one stage) of the multiple fixed vane spacers 125. The water-cooled spacer 128 is made of a material with higher thermal conductivity than the outer cylinder 127 and the outer wall 126, such as aluminum.

[0020] The upper radial electromagnets 104 are arranged in pairs on the X-axis and the Y-axis. Four upper radial sensors 107 are provided adjacent to the upper radial electromagnets 104 and corresponding to each upper radial electromagnet 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors having conductive windings, and detect the position of the rotor shaft 113 based on changes in the inductance of the conductive windings, which change according to the position of the rotor shaft 113. The upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed thereto, and send the detected displacement to the control device 195.

[0021] In this control device 195, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for the upper radial electromagnet 104 based on a position signal detected by the upper radial sensor 107, and an amplifier circuit 150 (described later) shown in Figure 2 controls the excitation of the upper radial electromagnet 104 based on this excitation control command signal, thereby adjusting the upper radial position of the rotor shaft 113.

[0022] The rotor shaft 113 is made of a high magnetic permeability material (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnets 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. The lower radial electromagnets 105 and the lower radial sensors 108 are arranged in the same manner as the upper radial electromagnets 104 and the upper radial sensors 107, and adjust the radial position of the lower side of the rotor shaft 113 in the same manner as the radial position of the upper side.

[0023] Furthermore, axial electromagnets 106A and 106B are arranged above and below a circular metal disk 111 provided at the bottom of rotor shaft 113. Metal disk 111 is made of a highly magnetic permeable material such as iron. An axial sensor 109 is provided to detect the axial displacement of rotor shaft 113, and an axial position signal is sent to control device 195.

[0024] In the control device 195, a compensation circuit having, for example, a PID adjustment function generates excitation control command signals for each of the axial electromagnet 106A and the axial electromagnet 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of each of the axial electromagnet 106A and the axial electromagnet 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disc 111 upward by magnetic force, and the axial electromagnet 106B attracts the metal disc 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0025] In this way, the control device 195 appropriately adjusts the magnetic forces that the axial electromagnets 106A and 106B exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in space without contact. The amplifier circuit 150 that controls the excitation of the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

[0026] Meanwhile, motor 121 has a plurality of magnetic poles arranged circumferentially so as to surround rotor shaft 113. Each magnetic pole is controlled by control device 195 so as to rotate rotor shaft 113 via electromagnetic force acting between the magnetic pole and rotor shaft 113. Motor 121 also incorporates a rotational speed sensor (not shown), such as a Hall element, resolver, or encoder, and the rotational speed of rotor shaft 113 is detected by the detection signal of this rotational speed sensor.

[0027] Furthermore, a phase sensor (not shown) is attached, for example, near the lower radial sensor 108, to detect the phase of rotation of the rotor shaft 113. The control device 195 uses the detection signals from both this phase sensor and the rotational speed sensor to detect the position of the magnetic pole.

[0028] A plurality of stator blades 123 (123a, 123b, 123c...) are arranged with a small gap between them and the rotor blades 102 (102a, 102b, 102c...). These multiple stages of rotor blades 102 and multiple stages of stator blades 123 form a turbo pump section. Each of the rotor blades 102 (102a, 102b, 102c...) is inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward through collisions. The stator blades 123 (123a, 123b, 123c...) are made of metals such as aluminum, iron, stainless steel, copper, or alloys containing these metals. The water-cooled spacer 128 mentioned above is in thermal contact with one of the multiple stator blades 123, which are interior components.

[0029] Similarly, the fixed blades 123 are formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged in a staggered manner with the rows of rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported by being inserted between a plurality of stacked rows of fixed blade spacers 125 (125a, 125b, 125c, etc.).

[0030] The fixed vane spacer 125 is a ring-shaped member made of a metal such as aluminum, iron, stainless steel, or copper, or an alloy containing any of these metals. An outer cylinder 127 is fixed to the outer periphery of the fixed vane spacer 125 with a small gap between them. A base portion 129 is disposed at the bottom of the outer cylinder 127 (more specifically, at the bottom of the outer wall 126). An exhaust port 133 is formed above the base portion 129 and communicates with the outside. Exhaust gas that enters the intake port 101 from the chamber (vacuum chamber) side and is transported toward the base portion 129 is sent to the exhaust port 133.

[0031] Furthermore, a Sigburn type pump section 131 is disposed between the lower part of the stator spacer 125 and the base section 129. The Sigburn type pump section 131 is formed so as to be spatially continuous with the next stage of the upper turbo pump section constituted by the rotors 102 (102a, 102b, 102c, etc.), the stator vanes 123 (123a, 123b, 123c, etc.), etc.

[0032] The Sigburn type pump section 131 has a plurality of rotating disks 200 that rotate together with the rotor shaft 113, and a plurality of fixed disks 201 that are alternately arranged between the plurality of rotating disks 200. These rotating disks 200 and fixed disks 201 are made of a metal such as aluminum, iron, stainless steel, copper, or an alloy containing any of these metals as an ingredient.

[0033] The rotating disk 200 is formed integrally with the cylindrical rotating body 103, and rotates in the same direction as the rotor shaft 113 and the rotating body 103 as the rotating body 103 rotates. In other words, the rotating disk 200 rotates integrally with the rotor blades 102 (102a, 102b, 102c, etc.).

[0034] The fixed disk 201 is provided integrally with the main body casing (the combination of the outer cylinder 127 and the base part 129). The fixed disk 201 is inserted between two stages of upper and lower rotating disks 200 arranged in the axial direction of the rotor shaft 113.

[0035] Although details will be described later, a number of ridges 202 having a cross-sectional shape of a set are formed to protrude between the fixed disk 201 and the rotating disk 200. Furthermore, a Sigburn spiral groove 203, which is a spiral groove flow path, is formed between adjacent ridges 202. The exhaust gas transported by the rotor 102 and the fixed blades 123 is guided by the Sigburn spiral groove 203 of the Sigburn type pump section 131 and sent to the base section 129.

[0036] The exhaust gas guided into the Sigburn spiral groove 203 is sent to the annular space 135 formed above the base 129, and while circulating around the annular space 135, is discharged to the outside through the exhaust port 133. This annular space 135 is an annular space partitioned by the fixed disk 201 of the Sigburn type pump section 131, the heater spacer 153, and the base 129.

[0037] Here, the heater spacer 153, which is a fixed component, is a cylindrical member and, in this embodiment, is configured separately from the Sigburn type pump section 131. Of course, the heater spacer 153 may be configured integrally with the Sigburn type pump section 131 and constitute a part of the Sigburn type pump section 131. The heater spacer 153 is configured from a metal such as aluminum or stainless steel. A heater 190 serving as a heating means is inserted into the heater spacer 153, and the heater 190 generates heat, thereby heating the Sigburn type pump section 131 via the heater spacer 153. The heater 190 also heats the exhaust gas flowing through the annular space 135. This suppresses the formation of deposits due to a drop in the temperature of the exhaust gas. The inner spacer 154 is a cylindrical member configured from a metal such as stainless steel, and provides thermal insulation between the water-cooled spacer 128 and the fixed vane spacer 125 and the Sigburn type pump section 131 below the water-cooled spacer 128.

[0038] The base portion 129 is a disk-shaped member that forms the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. The base portion 129 not only physically holds the turbomolecular pump 100, but also functions as a heat conduction path, so it is desirable to use a metal that is rigid and has high thermal conductivity, such as iron, aluminum, or copper.

[0039] In this configuration, when the rotor 102 is rotated together with the rotor shaft 113 by the motor 121, the rotor 102 and the stator 123 act to draw exhaust gas from the chamber through the intake port 101. The rotational speed of the rotor 102 is typically 20,000 rpm to 90,000 rpm, and the peripheral speed at the tip of the rotor 102 reaches 200 m / s to 400 m / s. The exhaust gas drawn in through the intake port 101 passes between the rotor 102 and the stator 123 and reaches the Sigmund Freud pump unit 131. At this time, the temperature of the rotor 102 rises due to frictional heat generated when the exhaust gas comes into contact with the rotor 102 and conduction of heat generated by the motor 121, but this heat is transferred to the stator 123 by radiation or conduction through gas molecules of the exhaust gas.

[0040] Furthermore, the gas that reaches the Sigburn pump section 131 flows into the most upstream Sigburn spiral groove section 203 and passes through a passage that gradually narrows in the depth direction (axial direction of the rotor shaft 113). The gas then passes through a turning section (see FIG. 5) and the Sigburn spiral groove section 203 of a fixed depth, and is transported to the base section 129.

[0041] The fixed blade spacers 125 are joined together at their outer peripheries and transmit to the outside heat received by the fixed blades 123 from the rotor blades 102 and frictional heat generated when exhaust gas comes into contact with the fixed blades 123.

[0042] Depending on the application of the turbomolecular pump 100, the electrical equipment section may be surrounded by a stator column 122 to prevent the gas sucked in from the intake port 101 from entering the electrical equipment section, which is composed of the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, the lower radial electromagnet 105, the lower radial sensor 108, the axial electromagnets 106A and 106B, the axial sensor 109, etc., and the interior of this stator column 122 may be kept at a predetermined pressure by purge gas.

[0043] In this case, purge gas is introduced through a purge port 160 provided in the base portion 129. The introduced purge gas passes through gaps between the protective bearing 120 and the rotor shaft 113, between the rotor and stator of the motor 121, and between the stator column 122 and the inner cylindrical portion of the rotor blades 102, and is discharged to the outside through an exhaust port 133. As shown in FIG. 1 , the stator column 122 is erected at the center of the base portion 129. In this embodiment, a water-cooled pipe 149 is provided in the base portion 129 as a cooling means. Cooling water is supplied to this water-cooled pipe 149, thereby maintaining the base portion 129 and the stator column 122 at an appropriate temperature.

[0044] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that have been individually adjusted and identified for the model. To store these control parameters, the turbomolecular pump 100 is provided with an electronic circuit section 141 within its body. The electronic circuit section 141 is composed of a semiconductor memory such as an EEPROM, electronic components such as semiconductor elements for accessing the memory, and a substrate 143 for mounting these components. The electronic circuit section 141 is housed below a rotational speed sensor (not shown) near the center of a base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom lid 145.

[0045] In the semiconductor manufacturing process, some process gases introduced into a chamber have the property of solidifying when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the pressure of the exhaust gas is lowest at the inlet port 101 and highest at the outlet port 133. If the pressure of the process gas exceeds a predetermined value or the temperature falls below a predetermined value while the process gas is being transferred from the inlet port 101 to the outlet port 133, the process gas solidifies and adheres to and accumulates inside the turbomolecular pump 100.

[0046] For example, when SiCl4 is used as the process gas in an Al etching apparatus, the vapor pressure curve shows that at low vacuum (760 [torr] to 10-2 [torr]) and low temperature (approximately 20 [°C]), solid products (e.g., AlCl3) precipitate and adhere to and accumulate inside the turbomolecular pump 100. As a result, when precipitates of the process gas accumulate inside the turbomolecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. Furthermore, the above-mentioned products are prone to solidification and adhesion in high-pressure areas near the exhaust port 133 and the Sigbahn-type pump section 131.

[0047] Therefore, in order to solve this problem, conventionally, a heater (not shown) or a circular water-cooled pipe 149 is wrapped around the outer periphery of the base portion 129, etc., and a temperature sensor (e.g., a thermistor) (not shown) is embedded in the base portion 129, and the heating of the heater and the cooling by the water-cooled pipe 149 are controlled based on the signal from this temperature sensor to maintain the temperature of the base portion 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS; Temperature Management System).

[0048] Next, a description will be given of the amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B in the turbomolecular pump 100. A circuit diagram of this amplifier circuit 150 is shown in FIG.

[0049] 2, one end of the electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to a positive electrode 171a of a power supply 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power supply 171 via a current detection circuit 181 and a transistor 162. The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between the source and drain.

[0050] At this time, the transistor 161 has a diode cathode terminal 161a connected to the positive electrode 171a and an anode terminal 161b connected to one end of the electromagnet winding 151. The transistor 162 has a diode cathode terminal 162a connected to the current detection circuit 181 and an anode terminal 162b connected to the negative electrode 171b.

[0051] Meanwhile, current regeneration diode 165 has its cathode terminal 165a connected to one end of electromagnet winding 151 and its anode terminal 165b connected to negative electrode 171b. Similarly, current regeneration diode 166 has its cathode terminal 166a connected to positive electrode 171a and its anode terminal 166b connected to the other end of electromagnet winding 151 via current detection circuit 181. Current detection circuit 181 is configured, for example, with a Hall sensor type current sensor or an electrical resistance element.

[0052] The amplifier circuit 150 configured as above corresponds to one electromagnet. Therefore, if the magnetic bearing is controlled in five axes and there are a total of ten electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the ten amplifier circuits 150 are connected in parallel to the power supply 171.

[0053] Furthermore, the amplifier control circuit 191 is configured, for example, by a digital signal processor section (hereinafter referred to as a DSP section) not shown in the figure of the control device 195, and this amplifier control circuit 191 is configured to switch the transistors 161 and 162 on / off.

[0054] The amplifier control circuit 191 compares the current value detected by the current detection circuit 181 (a signal reflecting this current value is called a current detection signal 191c) with a predetermined current command value. Based on the comparison result, the amplifier control circuit 191 determines the size of the pulse width (pulse width times Tp1 and Tp2) to be generated within a control cycle Ts, which is one period under PWM control. As a result, gate drive signals 191a and 191b having these pulse widths are output from the amplifier control circuit 191 to the gate terminals of the transistors 161 and 162.

[0055] It is necessary to control the position of rotor 103 at high speed and with strong force when, for example, rotor 103 passes through a resonance point during acceleration of its rotational speed or when a disturbance occurs during constant-speed operation. For this reason, a voltage of, for example, about 50 V is used as power supply 171 so that the current flowing through electromagnet winding 151 can be rapidly increased (or decreased). In addition, a capacitor (not shown) is usually connected between positive electrode 171a and negative electrode 171b of power supply 171 to stabilize power supply 171.

[0056] In this configuration, when both transistors 161 and 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0057] Furthermore, when one of the transistors 161 and 162 is turned on and the other is turned off, a so-called flywheel current is maintained. By passing a flywheel current through the amplifier circuit 150 in this manner, hysteresis loss in the amplifier circuit 150 can be reduced, and the power consumption of the entire circuit can be kept low. Furthermore, by controlling the transistors 161 and 162 in this manner, high-frequency noise such as harmonics generated in the turbomolecular pump 100 can be reduced. Furthermore, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0058] That is, when the detected current value is smaller than the current command value, both transistors 161 and 162 are turned on for a time period corresponding to pulse width time Tp1 only once in a control cycle Ts (for example, 100 μs), as shown in Fig. 3. Therefore, during this period, the electromagnet current iL increases toward a current value iLmax (not shown) that can flow from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[0059] On the other hand, if the detected current value is greater than the current command value, both transistors 161 and 162 are turned off for a time period corresponding to pulse width time Tp2 only once during the control cycle Ts, as shown in Fig. 4. Therefore, the electromagnet current iL during this period decreases toward a current value iLmin (not shown) that can be regenerated from the negative pole 171b to the positive pole 171a via diodes 165 and 166.

[0060] In either case, after the pulse width times Tp1 and Tp2 have elapsed, one of the transistors 161 and 162 is turned on. Therefore, a flywheel current is maintained in the amplifier circuit 150 during this period.

[0061] Next, the Sigbahn type pump section 131, which is a characteristic part of the turbomolecular pump 100 according to this embodiment, will be described in detail.

[0062] FIG. 5 is an enlarged view of portion A shown in FIG. 1, showing the gas flow path of the Sigburn type pump portion 131. FIG. 6 is a plan view of the fixed disk 201. FIG. 7 is a rear view of the fixed disk 201. FIG. 8 is an explanatory diagram showing the inner peripheral side convex portion of the fixed disk 201. FIG. 9 is an enlarged view of portion B shown in FIG. 5. FIG. 10 is an enlarged view of portion C shown in FIG. 6. FIG. 11 is an enlarged view of portion D shown in FIG. 7. FIG. 12 is an explanatory diagram showing the circumferential positioning state of the fixed disk 201.

[0063] The Sigburn pump section 131 includes multiple stationary disks 201 stacked along the axial direction of the rotor shaft 113. In the following description, the three stationary disks 201 stacked in the axial direction will be described, designated 201a, 201b, and 201c, starting from the top. The bottom stationary disk 201c is formed as a single annular member and is fixed to the heater spacer 153 in a circumferentially positioned state. Positioning pins may be used, for example, for circumferential positioning. The remaining top and second stationary disks 201a and 201b are formed as split halves. Forming the stationary disks 201a and 201b as split members in this way allows each split stationary disk 201 to be installed from the side of the rotor shaft 113, improving assembly workability.

[0064] A number of protruding ridges 202 with a rectangular cross section are formed on the surface of the fixed disk 201. Furthermore, Sigburn spiral grooves 203, which are spiral groove channels, are formed between adjacent ridges 202. The top and second fixed disks 201a and 201b have a number of ridges 202 formed on both the front and back surfaces. The bottom fixed disk 201c has a number of ridges 202 formed only on the front surface.

[0065] The first stage of the fixed disk 201 is inserted between the two stages of the rotating disks 200, upper and lower, arranged in the axial direction of the rotor shaft 113, thereby forming a gas flow path passing through the interior of the Sigburn pump unit 131, as shown by the arrows in Fig. 5. That is, the gas that has reached the Sigburn pump unit 131 flows into the Sigburn spiral groove 203 from the outer periphery of the uppermost rotating disk 200 and the uppermost fixed disk 201a, passes through the Sigburn spiral groove 203, and reaches the uppermost turning portion (part B in Fig. 5). The gas then passes from the uppermost turning portion through the Sigburn spiral groove 203 to the next turning portion, and is further transferred from the next turning portion through the Sigburn spiral groove 203 to the base unit 129.

[0066] 6 and 7, outer peripheral convex portions 210 are formed along the periphery on the plate surface of fixed disk 201. As described above, the top and second tier fixed disks 201a, 201b are two-piece pieces, and when the two pieces are combined, fixed disks 201a, 201b have annular outer peripheral convex portions 210 formed along the periphery of the plate surface on both the front and back sides.

[0067] An inner circumferential convex portion 211 is formed on the front plate surface of the fixed disk 201, and is located radially inward of the outer circumferential convex portion 210. An inner circumferential convex portion 212 is formed on the back plate surface of the fixed disk 201, and is located radially inward of the outer circumferential convex portion 210. The inner circumferential convex portion 211 on the front side has an L-shaped cross section, and the inner circumferential convex portion 212 on the back side has an inverted L-shaped cross section. That is, in the fixed disks 201a and 201b in a state where the two halves are combined, the outer circumferential convex portion 210 is formed in an annular shape along the periphery of the front plate surface, and the inner circumferential convex portion 211 is formed in an annular shape radially inward of the outer circumferential convex portion 210. The outer circumferential convex portion 210 is formed in an annular shape along the periphery of the back plate surface, and the inner circumferential convex portion 212 is formed in an annular shape radially inward of the outer circumferential convex portion 210. Furthermore, for the lowest fixed disc 201c, an outer circumferential convex portion 210 is formed in a circular ring shape along the periphery of the front plate surface, and an inner circumferential convex portion 211 is formed in a circular ring shape radially inward from the outer circumferential convex portion 210.

[0068] Annular recesses 213 are formed between the outer peripheral convex portion 210 and the inner peripheral convex portion 211 on the front side, and between the outer peripheral convex portion 210 and the inner peripheral convex portion 212 on the back side. Furthermore, as shown in FIGS. 8 and 12, a positioning groove 214 is formed in the inner peripheral convex portion 211 on the front side of the fixing disk 201. Furthermore, as shown in FIGS. 8 and 12, a positioning protrusion 215 is formed in the inner peripheral convex portion 212 on the back side of the fixing disk 201 at a position facing the positioning groove 214. The half-split fixing disk 201 shown in FIGS. 6 and 10 has one positioning groove 214 and one positioning protrusion 215, but the fixing disk 201, which is made by combining two halves, has positioning grooves 214 formed in two locations 180 degrees apart on the front plate surface, and positioning protrusions 215 formed in two locations facing the positioning grooves 214 on the back plate surface of the fixing disk 201. Conversely, the positioning protrusion 215 may be formed on the front plate surface of the fixed disk 201, and the positioning groove 214 may be formed on the back plate surface. Furthermore, it is sufficient that the pair of the positioning groove 214 and the positioning protrusion 215 is formed in at least two places on the fixed disk 201. For example, the pair of the positioning groove 214 and the positioning protrusion 215 may be formed on the plate surface of the fixed disk 201 at an interval of 120 degrees.

[0069] 5 and 9, the two axially overlapping fixed disks 201 are positioned in the axial direction by the abutment of outer circumferential convex portions 210 formed on the lower and upper fixed disks 201. Furthermore, the radial positioning is achieved by the projections and recesses of the inner circumferential convex portion 211 formed on the lower fixed disk 201 and the inner circumferential convex portion 212 formed on the upper fixed disk 201. However, the inner circumferential convex portions 211 and 212 are not in contact with each other in the axial direction (i.e., there is a slight gap between them), and are not involved in axial positioning.

[0070] 12, the two axially overlapping fixed disks 201 are positioned in the circumferential direction by fitting a positioning protrusion 215 formed on the inner peripheral convex portion 212 of the upper fixed disk 201 into a positioning groove 214 formed on the inner peripheral convex portion 211 of the lower fixed disk 201. When the two upper and lower fixed disks 201 are positioned in the circumferential direction in this manner, the outlet opening and the inlet opening of the Sigburn spiral groove portion 203 can be aligned in the axial direction at the turning portion of the gas flow path shown in FIG. 5. The positioning groove 214 and the positioning protrusion 215 are also not in contact with each other in the axial direction and are not involved in axial positioning. Therefore, even if there is some dimensional error in the fixed discs 201, the two fixed discs 201 that overlap in the axial direction are positioned axially at the abutment points of their outer peripheral convex portions 210, radially positioned at the engagement points of their inner peripheral convex portions 211, 212, and circumferentially positioned reliably at the engagement points of the positioning grooves 214 and the positioning protrusions 215.

[0071] The radial position of the outer peripheral convex portion 210 is the same for the contact position between the outer cylinder 127 and the stator spacer 125, the contact position between the stator spacers 125, the contact position between the stator spacers 125 and the water-cooled spacer 128, and the contact position between the stator spacer 125 and the fixed disk 201. As a result, the load applied when the outer cylinder 127 is fixed with the bolts 115 is applied in a straight line in the axial direction at the above-mentioned radial positions, so even in a structure in which the contact area is limited for thermal insulation, no force that causes tilting of the fixed disk 201 is applied, making it possible to stably fix the outer cylinder 127.

[0072] In the multiple stages of fixed disks 201 stacked while being positioned in the axial, radial, and circumferential directions in this manner, the recesses 213 existing between the outer peripheral convex portions 210 and the inner peripheral convex portions 211 and between the outer peripheral convex portions 210 and the inner peripheral convex portions 212 are connected at the top and bottom to form multiple spaces 216 aligned along the axial direction. These spaces 216 function as heat insulating portions, and suppress the transfer of heat from the heater spacer 153 to the cooling portion above the Sigburn type pump unit 131 via the multiple stages of fixed disks 201.

[0073] That is, the underside of the Sigburn pump section 131 is in contact with the heater spacer 153, and heat from the heater 190 heats the fixed disk 201 via the heater spacer 153, thereby overheating the gas flowing through the gas flow path of the Sigburn pump section 131. This prevents the gas flowing through the gas flow path from liquefying or solidifying, and in particular prevents gas molecules from accumulating as solid products in the gas flow path. However, because the Sigburn pump section 131 has a structure in which multiple stages of fixed disks 201 are stacked in the axial direction, if heat from the heater spacer 153 is transmitted to the water-cooled spacer 128 via the multiple stages of fixed disks 201, the cooling effect of the water-cooled spacer 128 on the upstream interior of the turbomolecular pump 100 will be reduced.

[0074] In this embodiment, a plurality of spaces 216 are formed along the axial direction between the outer circumferential convex portion 210 and the inner circumferential convex portions 211, 212 of the fixed disks 201 stacked in multiple layers, and the spaces 216 make it difficult for heat from the heater spacer 153 to be transmitted to the water-cooled spacer 128.

[0075] Next, the effects of this embodiment configured as above will be described.

[0076] In the turbomolecular pump 100 according to this embodiment, the Sigbahn type pump section 131, which is disposed below a pump section consisting of the rotor blades 102, the fixed blades 123, etc., has a plurality of rotating disks 200 that rotate together with the rotor shaft 113 and a plurality of fixed disks 201 that are disposed alternately between the plurality of rotating disks 200, and the fixed disks 201 are stacked in multiple stages and have a plurality of spaces 216 that are aligned along the axial direction, thereby making it difficult for heat from the heater spacer 153 to be transmitted to the water-cooled spacer 128. Therefore, it is possible to suppress a decrease in the cooling effect of the water-cooled spacer 128 while ensuring the heating effect of the heater spacer 153 on the fixed disks 201.

[0077] Furthermore, in this embodiment, with regard to an assembly of fixed disks 201, which are components of the Sigburn pump unit 131, two axially overlapping fixed disks 201 can be stacked while being positioned not only axially but also radially and circumferentially. Specifically, the axial positioning is achieved by the outer circumferential convex portions 210 formed on the lower and upper fixed disks 201 abutting against each other, and the radial positioning is achieved by the concave-convex engagement between the inner circumferential convex portion 211 formed on the lower fixed disk 201 and the inner circumferential convex portion 212 formed on the upper fixed disk 201. Furthermore, the radial positioning is achieved by the concave-convex engagement between the inner circumferential convex portion 211 formed on the lower fixed disk 201 and the inner circumferential convex portion 212 formed on the upper fixed disk 201.

[0078] Furthermore, the inner circumferential side protrusions 211 and 212, which position the disks in the radial direction, do not contact each other in the axial direction. Similarly, the positioning grooves 214 and positioning protrusions 215, which position the disks in the circumferential direction, do not contact each other in the axial direction, and neither of these structures contributes to axial positioning. Therefore, even if there is some dimensional error in the fixed disks 201, the two fixed disks 201 overlapping in the axial direction are positioned axially at the contact points of the outer circumferential side protrusions 210, positioned radially at the engagement points of the inner circumferential side protrusions 211 and 212, and positioned circumferentially at the engagement points (fitting points) of the positioning grooves 214 and the positioning protrusions 215. In this embodiment, the radial and circumferential positions are simultaneously achieved by the engagement of the inner circumferential side protrusions 211 and 212. However, it is also possible to position the fixed disks in one of the radial and circumferential directions by the inner circumferential side protrusions 211 and 212, and position the fixed disks in the other direction by a separate member.

[0079] Furthermore, in this embodiment, of the multiple fixed disks 201, the remaining fixed disks 201a and 201b, except for the bottommost fixed disk 201c, are formed as two-half divided pieces, so that each divided fixed disk 201 can be assembled from the side of the rotor shaft 113, improving assembly workability. Note that the number of stacked fixed disks 201 is not limited to three, and the number of divided fixed disks 201 is not particularly limited either. Furthermore, the number of divided fixed disks 201 is not limited to two, but may be three or more.

[0080] In this embodiment, of the two fixed discs 201 overlapping in the axial direction, the upper fixed disc 201 is the first fixed disc, and the lower fixed disc 201 is the second fixed disc. That is, when looking at the top fixed disc 201a and the second fixed disc 201b, the top fixed disc 201a corresponds to the first fixed disc, and the second fixed disc 201b corresponds to the second fixed disc. Also, when looking at the second fixed disc 201b and the third fixed disc 201b, the second fixed disc 201b corresponds to the first fixed disc, and the third fixed disc 201b corresponds to the second fixed disc.

[0081] Of the fixed disk 201 (e.g., fixed disk 201a) corresponding to the first fixed disk, the outer peripheral convex portion 210 (first outer peripheral convex portion), the inner peripheral convex portion 212 (first inner peripheral convex portion), and the concave portion 213 (first concave portion) correspond to the first abutment portion of the present invention (see FIG. 9). Of these, the outer peripheral convex portion 210 abuts against the outer peripheral convex portion 210 of the fixed disk 201 (e.g., fixed disk 201b) corresponding to the second fixed disk on the lower side, thereby positioning the fixed disk in the axial direction, and the inner peripheral convex portion 212 engages with the inner peripheral convex portion 211 of the fixed disk 201b, thereby positioning the fixed disk in the circumferential and radial directions. The concave portion 213 is a space 216 provided at the abutment point between the fixed disk 201a and the fixed disk 201b.

[0082] Furthermore, of the fixed disk 201 (e.g., fixed disk 201b) corresponding to the second fixed disk, the outer peripheral convex portion 210 (second outer peripheral convex portion), the inner peripheral convex portion 211 (second inner peripheral convex portion), and the concave portion 213 (second concave portion) correspond to the second abutment portion of the present invention (see FIG. 9). Of these, the outer peripheral convex portion 210 abuts against the outer peripheral convex portion 210 of the fixed disk 201 (e.g., fixed disk 201a) corresponding to the first fixed disk on the upper stage side, thereby positioning the fixed disk in the axial direction, and the inner peripheral convex portion 211 engages with the inner peripheral convex portion 212 of the fixed disk 201a, thereby positioning the fixed disk in the circumferential and radial directions. The concave portion 213 is a space 216 provided at the abutment point between the fixed disk 201b and the fixed disk 201a.

[0083] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various alternatives, modifications, variations, combinations, or improvements from the contents disclosed in this specification, and these are included in the technical scope described in the appended claims. [Explanation of symbols]

[0084] 100 Turbomolecular pump (vacuum pump) 101 Air intake 102 Rotor 103 Rotating Body 113 Rotor shaft (rotating shaft) 123 Fixed wing 127 Casing 128 Water cooling spacer 129 Base 131 Sigburn type pump section 133 Exhaust port 153 Heater Spacer 190 Heater 200 Rotating Disc 201(201a, 201b, 201c) Fixed disc 202 Yamabe 203 Sigburn spiral groove 210 Outer periphery side convex part (1st contact part, 2nd contact part) 211, 212 Inner circumferential convex portion (first contact portion, second contact portion) 213 Recess (first contact portion, second contact portion) 214 Positioning groove 215 Positioning protrusion 216 Spatial section

Claims

1. A casing; a rotating shaft rotatably supported inside the casing; a plurality of rotating disks that rotate together with the rotating shaft; a plurality of fixed discs alternately arranged between the plurality of rotating discs; A vacuum pump that exhausts gas by interaction between the plurality of rotating disks and the plurality of fixed disks, the plurality of fixed disks include a first fixed disk and a second fixed disk adjacent to the first fixed disk in the axial direction, the first fixed disk has a first abutment portion that abuts against the second fixed disk to position the second fixed disk at least in the axial direction, the first contact portion has a space provided at a contact point with the second fixed disk, The first contact portion is a first outer peripheral convex portion having an annular shape, the first outer peripheral convex portion being provided along a periphery of the first stationary disk and contacting the second stationary disk to position the second stationary disk in the axial direction; a first annular inner peripheral convex portion that is provided radially inward of the first outer peripheral convex portion and engages with the second fixed disk to position the second fixed disk in at least one of the radial direction and the circumferential direction, the space is a first recess formed between the first outer circumferential convex portion and the first inner circumferential convex portion, the second fixed disk has a second abutment portion that abuts against the first abutment portion, The second contact portion is a second outer peripheral convex portion having an annular shape provided along the periphery of the second fixed disk; a second inner peripheral convex portion having an annular shape and provided radially inward of the second outer peripheral convex portion; a second recess formed between the second outer circumferential convex portion and the second inner circumferential convex portion, the first outer peripheral convex portion abuts against the second outer peripheral convex portion, thereby positioning the first fixed disk and the second fixed disk with respect to the axial direction; The first inner circumferential convex portion engages with the second inner circumferential convex portion, thereby positioning the first fixed disk and the second fixed disk in the radial and circumferential directions. A vacuum pump characterized by:

2. 2. The vacuum pump according to claim 1, a Sigburn exhaust mechanism having a spiral groove formed on an opposing surface of either at least one of the plurality of rotary disks or at least one of the plurality of fixed disks facing the at least one rotary disk; A vacuum pump characterized by:

3. 2. The vacuum pump according to claim 1, The first fixed disk and the second fixed disk are each divided into a plurality of disks. A vacuum pump characterized by:

4. In the vacuum pump according to claim 2, a circumferential positioning portion provided on at least one of the first inner circumferential convex portion and the second inner circumferential convex portion, the circumferential positioning portion causes an outlet-side opening and an inlet-side opening of at least one of the spiral grooves of the folded-back portion to coincide with each other when viewed from the axial direction; A vacuum pump characterized by:

5. A plurality of fixed disks disposed between a plurality of rotary disks that rotate together with the rotary shaft of the vacuum pump, the plurality of fixed disks include a first fixed disk and a second fixed disk adjacent to the first fixed disk in the axial direction, the first fixed disk has a first abutment portion that abuts against the second fixed disk to position the second fixed disk at least in the axial direction, the first contact portion has a space provided at a contact point with the second fixed disk, The first contact portion is a first outer peripheral convex portion having an annular shape, the first outer peripheral convex portion being provided along a periphery of the first stationary disk and contacting the second stationary disk to position the second stationary disk in the axial direction; a first annular inner peripheral convex portion that is provided radially inward of the first outer peripheral convex portion and engages with the second fixed disk to position the second fixed disk in at least one of the radial direction and the circumferential direction, the space is a first recess formed between the first outer circumferential convex portion and the first inner circumferential convex portion, the second fixed disk has a second abutment portion that abuts against the first abutment portion, The second contact portion is a second outer peripheral convex portion having an annular shape provided along the periphery of the second fixed disk; a second inner peripheral convex portion having an annular shape and provided radially inward of the second outer peripheral convex portion; a second recess formed between the second outer circumferential convex portion and the second inner circumferential convex portion, the first outer peripheral convex portion abuts against the second outer peripheral convex portion, thereby positioning the first fixed disk and the second fixed disk with respect to the axial direction; The first inner circumferential convex portion engages with the second inner circumferential convex portion, thereby positioning the first fixed disk and the second fixed disk in the radial and circumferential directions. A fixed disc characterized by:

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