Vacuum pump and fixed disc

Abstract

To provide a vacuum pump equipped with a multi-stage Sigburn exhaust mechanism, which allows for the parallel connection of multiple Sigburn exhaust mechanisms without providing communication ports on the rotating disc, thereby enabling efficient exhaust processing, and to provide a fixed disc for the Sigburn exhaust mechanism used in the vacuum pump. [Solution] The vacuum pump including the Sigburn exhaust mechanism according to this embodiment divides the flow path to the Sigburn exhaust mechanism into multiple systems by a partition wall, and sends the gas divided by the partition wall in parallel to each of the multiple stacked exhaust mechanisms. This gas flow is as shown by the arrows in Figure 6. By connecting the Sigburn exhaust mechanisms in parallel in this way, the exhaust speed can be improved without providing a communication port on the rotating disc.

Description

Technical Field

[0001] The present invention relates to a vacuum pump and a fixed disk used in the vacuum pump. Specifically, in a vacuum pump provided with a radial flow type exhaust mechanism (Sigbahn exhaust mechanism), the present invention relates to a vacuum pump with improved exhaust efficiency by connecting a plurality of radial flow type exhaust mechanisms in parallel and a fixed disk used in the radial flow type exhaust mechanism.

Background Art

[0002] A vacuum pump includes a casing that forms an exterior body having an intake port and an exhaust port, and inside the casing, a structure that enables the vacuum pump to perform an exhaust function is housed. The structure that enables the exhaust function is roughly composed of a rotating part (rotor part) fixed to a rotating shaft that rotates at high speed and a fixed part (stator part) fixed to the casing. In addition, a motor for rotating the rotating shaft at high speed is provided. When the rotating shaft rotates at high speed due to the action of this motor, the rotor blades (rotating disks) fixed to the rotating shaft rotate together with the rotating shaft, and gas is sucked from the intake port and discharged from the exhaust port due to the interaction with the stator blades (fixed disks).

[0003] This vacuum pump includes a type provided with an exhaust mechanism (Y in the figure) called a vertical screw (Holbeck type) at the lower part (exhaust port side) of an exhaust mechanism composed of a plurality of fixed blades and a plurality of rotating blades shown in FIG. 19, and a type provided with an exhaust mechanism called a horizontal screw (hereinafter referred to as Sigbahn, X in the figure) at the lower part (exhaust port side) of an exhaust mechanism composed of a plurality of fixed blades and a plurality of rotating blades shown in FIG. 20. [[ID=1】 Among these, the Sigburn type vacuum pump comprises a rotating disc and a fixed disc installed with an axial gap (clearance) between them. A spiral groove (radial screw groove) flow path is engraved on the gap-facing surface of at least one of the rotating disc or the fixed disc. The rotating disc imparts momentum to the gas molecules that diffuse into the spiral groove flow path in the tangential direction of the rotating disc (i.e., the tangential direction of the rotation of the rotating disc), thereby giving the gas a dominant directionality from the intake to the exhaust port, and thus performing exhaust. This Sigburn-type vacuum pump, when configured in multiple stages, allows for a longer exhaust gas flow path, resulting in superior back pressure performance. Furthermore, its horizontal screw design allows for a lower overall height compared to pumps with vertical screw connections. Vacuum pumps equipped with an exhaust mechanism called a vertical screw have the characteristics of a simple structure and excellent stability. In addition, because of the vertical screw, the peripheral velocity of the exhaust gas is constant.

[0004] Figure 17 is a diagram illustrating a conventional Sigburn-type vacuum pump 1000, and shows a schematic configuration example of a conventional Sigburn-type vacuum pump 1000. The arrows indicate the flow of gas molecules. Figure 18 is a diagram illustrating a fixed disc 5000 installed in a conventional Sigburn-type vacuum pump 1000, and is a cross-sectional view of the fixed disc 5000 as seen from the intake port 101 side. The arrows inside the fixed disk 5000 indicate the flow of gas molecules, while the arrows outside the fixed disk 5000 indicate the direction of rotation of the rotating disk (not shown). As is clear from these figures, in a Sigburn-type vacuum pump, the gas is given a radial direction of motion. Therefore, a vacuum pump has been proposed that efficiently exhausts gas by connecting multiple Sigburn exhaust mechanisms in parallel and performing exhaust processing in multiple stages simultaneously. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 4865321

[0006] In the invention described in Patent Document 1, the Sigburn exhaust mechanism is arranged in parallel in multiple stages in the axial direction, and the intake sections in each stage are all connected so that gas is exhausted simultaneously in all stages. The gas flow in this conventional technology is as shown by the arrows in Figure 21. With this structure, exhaust can be performed simultaneously in multiple stages of the Sigburn exhaust mechanism, thereby increasing the exhaust speed in the Sigburn exhaust mechanism by several times. [Overview of the project] [Problems that the invention aims to solve]

[0007] Incidentally, in the invention described in Patent Document 1, it is necessary to provide a communication port on the rotating disc of the Sigburn exhaust mechanism, and it was technically difficult to manufacture this communication port. Furthermore, providing a communication port on a rotating disc that rotates at high speed inevitably increases the stress near the communication port, which creates the problem that the rotational speed of the rotating disc cannot be increased. Therefore, the object of the present invention is to provide a vacuum pump equipped with a multi-stage Sigburn exhaust mechanism that can efficiently perform exhaust processing by connecting multiple stages of Sigburn exhaust mechanisms in parallel without providing communication ports on the rotating disc, and a fixed disc for the Sigburn exhaust mechanism used in the vacuum pump. [Means for solving the problem]

[0008] The invention described in claim 1 provides a vacuum pump comprising a plurality of stacked radial flow type exhaust mechanisms, each comprising an intake port for drawing in gas, an exhaust port for exhausting the gas drawn in from the intake port, a rotatably held rotating disc, a fixed disc installed opposite the rotating disc, and a spiral-shaped projection installed on at least one of the opposing surfaces of the rotating disc and the fixed disc, wherein the gas is exhausted radially from the outside to the inside on the intake port side surface of the fixed disc and from the inside to the outside on the exhaust port side surface of the fixed disc, and further comprising a partition wall that divides the gas flow path from the intake port to the exhaust mechanism into a plurality of systems, and the gas divided by the partition wall is sent in parallel to each of the plurality of stacked exhaust mechanisms. The invention described in claim 2 provides a vacuum pump according to claim 1, comprising an inlet to the exhaust mechanism installed on the intake side surface of the fixed disc and an outlet from the exhaust mechanism installed on the exhaust side surface of the fixed disc, wherein the phases of the installation positions of the inlet and the outlet coincide. The invention described in claim 3 provides a vacuum pump according to claim 1, characterized in that it is provided with an inlet to the exhaust mechanism installed on the intake side surface of the fixed disc, and the phases of the installation positions of the inlets to the multiple stacked exhaust mechanisms coincide. The invention described in claim 4 provides a vacuum pump according to claim 1 or 3, characterized in that it includes an outlet from the exhaust mechanism installed on the exhaust port side surface of the fixed disc, and the phases of the installation positions of the outlets from the multiple stacked exhaust mechanisms coincide. The invention described in claim 5 provides a vacuum pump according to claim 1, characterized in that it is provided with an inlet to the exhaust mechanism installed on the intake side surface of the fixed disc, and the starting position of the inlet coincides with the back surface of the spiral projection with respect to the rotation direction of the rotating disc. The invention described in claim 6 provides a vacuum pump according to claim 1, characterized in that it is provided with an outlet from the exhaust mechanism installed on the exhaust port side surface of the fixed disc, and the end position of the outlet coincides with the front surface of the spiral projection with respect to the rotation direction of the rotating disc. The invention described in claim 7 provides a vacuum pump according to claim 1, characterized in that the fixed disc is provided with a protrusion facing the outer circumferential surface of the rotating disc. The invention described in claim 8 provides a vacuum pump according to claim 1, characterized in that the partition wall is installed at a predetermined angle with respect to the radial direction of the rotating disk. The invention described in claim 9 provides a vacuum pump according to claim 1, characterized in that an additional exhaust mechanism having multiple times the number of protrusions of the exhaust mechanism is installed on the exhaust port side of the multi-stage stacked exhaust mechanism. The invention described in claim 10 provides a fixed disc used in a radial flow type exhaust mechanism for exhausting gas in the radial direction, which is installed opposite a rotatably held rotating disc, and which has a spiral projection on the surface facing the rotating disc, and is provided with a partition wall that divides the gas flow path into multiple systems in order to exhaust gas radially from the outside to the inside on the surface of the fixed disc on the intake side and from the inside to the outside on the surface of the fixed disc on the exhaust side. [Effects of the Invention]

[0009] According to the present invention, in a vacuum pump equipped with a Sigburn exhaust mechanism, multiple Sigburn exhaust mechanisms can be installed in parallel without providing communication ports on the rotating disc. Therefore, the exhaust speed can be improved without incurring reliability risks. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows a schematic configuration of a turbomolecular pump according to an embodiment of the present invention. [Figure 2] This figure shows a circuit diagram of an amplifier circuit used in an embodiment of the present invention. [Figure 3] A time chart showing control when the detected value in the embodiment of the present invention is smaller than the current command value. [Figure 4] A time chart showing control when the detected value in the embodiment of the present invention is larger than the current command value. [Figure 5] A diagram showing a schematic configuration example of a Sigburn type vacuum pump according to an embodiment of the present invention. [Figure 6] A diagram for explaining an exhaust passage of a Sigburn exhaust mechanism in an embodiment of the present invention. [Figure 7] A cross-sectional view of a vacuum pump including a Sigburn exhaust mechanism in the first embodiment of the present invention. [Figure 8] A diagram showing a fixed disk (in a state where the upper and lower stages are combined) in the first embodiment of the present invention. [Figure 9] A diagram showing a fixed disk (a single lower stage) in the first embodiment of the present invention. [Figure 10] A cross-sectional view of a vacuum pump including a Sigburn exhaust mechanism in the second embodiment of the present invention. [Figure 11] A diagram showing a fixed disk (in a state where the upper and lower stages are combined) in the second embodiment of the present invention (the ratio of the inlet to the outlet is 5:5). [Figure 12] A diagram showing a fixed disk (in a state where the upper and lower stages are combined) in the second embodiment of the present invention (the ratio of the inlet to the outlet is 7:3). [Figure 13] A diagram showing a state where three fixed disks are stacked in the second embodiment of the present invention (the ratio of the inlet to the outlet is 7:3). [Figure 14] A diagram showing a fixed disk (a single lower stage) in the second embodiment of the present invention. [Figure 15] A diagram for explaining the relationship between the inlet and outlet and the mountain portion of the fixed disk in each embodiment. [[ID=​​​​This is a cross-sectional view illustrating a type of vacuum pump equipped with a conventional Sigburn vacuum pump. [Figure 18] This is a diagram illustrating the fixed disc installed in a conventional Sigburn-type vacuum pump. [Figure 19] This is a cross-sectional view illustrating a type of vacuum pump equipped with a conventional vertical screw exhaust mechanism (Holbeck exhaust mechanism). [Figure 20] This is a cross-sectional view illustrating a type of vacuum pump equipped with a conventional lateral screw exhaust mechanism (Sigburn exhaust mechanism). [Figure 21] This diagram illustrates the exhaust flow path in a vacuum pump with a conventional Sigburn exhaust mechanism arranged in parallel. [Modes for carrying out the invention]

[0011] (i) Outline of the embodiment The vacuum pump including the Sigburn exhaust mechanism according to this embodiment divides the flow path to the Sigburn exhaust mechanism into multiple systems by a partition wall, and sends the gas divided by the partition wall in parallel to each of the multiple stacked exhaust mechanisms. This gas flow is as shown by the arrows in Figure 6. By connecting these Sigburn exhaust mechanisms in parallel, the exhaust speed can be increased without providing communication ports on the rotating disc.

[0012] (ii) Details of the embodiment Hereinafter, preferred embodiments of the present invention will be described in detail with reference to Figures 1 to 16. In this embodiment, the vacuum pump to which the present invention is applied is a vacuum pump equipped with a Sigburn exhaust mechanism in the screw groove exhaust section (hereinafter referred to as a Sigburn type vacuum pump). First, I will explain the configuration of a typical vacuum pump, the turbomolecular pump, and then I will explain the Sigburn type vacuum pump. In this embodiment, the direction perpendicular to the diameter of the rotating disk is defined as the axial direction, and the horizontal direction is defined as the radial direction. Furthermore, in the following explanation, the intake side of a single fixed disc will be referred to as the upstream region of the Sigburn-type vacuum pump, and the exhaust side as the downstream region of the Sigburn-type vacuum pump.

[0013] Figure 1 shows a longitudinal cross-sectional view of the turbomolecular pump 100. In Figure 1, the turbomolecular pump 100 has an intake port 101 formed at the upper end of a cylindrical outer cylinder 127. Inside the outer cylinder 127 is a rotating body 103, which has multiple rotating blades 102 (102a, 102b, 102c...) formed radially and in multiple stages around its circumference, serving as turbine blades for drawing in and exhausting gas. A rotor shaft 113 is attached to the center of this rotating body 103, and this rotor shaft 113 is levitated and supported in the air and its position is controlled by, for example, a 5-axis controlled magnetic bearing. The rotating body 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0014] The upper radial electromagnet 104 consists of four electromagnets arranged in pairs along the X and Y axes. Four upper radial sensors 107 are provided in close proximity to the upper radial electromagnet 104, and each sensor corresponds to one of the upper radial electromagnets 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors with conduction windings, and detect the position of the rotor shaft 113 based on the change in the inductance of these conduction windings, which changes according to the position of the rotor shaft 113. These upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed to it, and send the data to the control device 200.

[0015] In this control device 200, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for the upper radial electromagnet 104 based on the position signal detected by the upper radial sensor 107, and the 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.

[0016] The rotor shaft 113 is made of a high-permeability material (such as iron or stainless steel) and is attracted by the magnetic force of the upper radial electromagnet 104. This adjustment is performed independently in the X-axis and Y-axis directions. The lower radial electromagnet 105 and lower radial sensor 108 are arranged in the same way as the upper radial electromagnet 104 and upper radial sensor 107, and adjust the lower radial position of the rotor shaft 113 in the same way as the upper radial position.

[0017] Furthermore, axial electromagnets 106A and 106B are positioned above and below a disc-shaped metal disk 111 located at the bottom of the rotor shaft 113. The metal disk 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 its axial position signal is sent to the control device 200.

[0018] Then, in the control device 200, for example, a compensation circuit having a PID adjustment function generates excitation control command signals for the axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 excites the axial electromagnets 106A and 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disk 111 upward with magnetic force, and the axial electromagnet 106B attracts the metal disk 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0019] Thus, the control device 200 appropriately adjusts the magnetic force exerted by the axial electromagnets 106A and 106B on the metal disk 111, causing the rotor shaft 113 to levitate axially and be held in contact with space. The amplifier circuit 150 that excites and controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

[0020] On the other hand, the motor 121 is equipped with multiple magnetic poles arranged circumferentially around the rotor shaft 113. Each magnetic pole is controlled by the control device 200 to rotate the rotor shaft 113 via the electromagnetic force acting between it and the rotor shaft 113. The motor 121 also incorporates a rotational speed sensor, such as a Hall element, resolver, or encoder (not shown), and the rotational speed of the rotor shaft 113 is detected by the detection signal from this rotational speed sensor.

[0021] Furthermore, for example, a phase sensor (not shown) is attached near the lower radial sensor 108 to detect the phase of rotation of the rotor shaft 113. The control device 200 uses both the detection signals from this phase sensor and the rotational speed sensor to detect the position of the magnetic pole.

[0022] Multiple fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap between them and the rotating blades 102 (102a, 102b, 102c...). Each of the rotating blades 102 (102a, 102b, 102c...) is formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward by collision. The fixed blades 123 (123a, 123b, 123c...) are made of metals such as aluminum, iron, stainless steel, copper, or alloys containing these metals as components.

[0023] Similarly, the fixed wing 123 is formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and is arranged alternately with the stages of the rotor blade 102 toward the inside of the outer cylinder 127. The outer edge of the fixed wing 123 is supported by being fitted between a plurality of stacked fixed wing spacers 125 (125a, 125b, 125c, etc.).

[0024] The fixed-wing spacer 125 is a ring-shaped member and is made of a metal such as aluminum, iron, stainless steel, or copper, or an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer circumference of the fixed-wing spacer 125 with a small gap in between. A base portion 129 is provided at the bottom of the outer cylinder 127. An exhaust port 133 is formed in 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 transferred to the base portion 129 is sent to the exhaust port 133.

[0025] Furthermore, depending on the application of the turbomolecular pump 100, a threaded spacer 131 is provided between the lower part of the fixed-blade spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals, and has multiple helical screw grooves 131a engraved on its inner circumferential surface. The direction of the helix of the screw grooves 131a is such that when exhaust gas molecules move in the direction of rotation of the rotating body 103, these molecules are transported toward the exhaust port 133. A cylindrical portion 102d hangs down from the lowest part of the rotating body 103 following the rotor blades 102 (102a, 102b, 102c...). The outer circumferential surface of this cylindrical portion 102d is cylindrical and protrudes toward the inner circumferential surface of the threaded spacer 131, and is in close proximity to the inner circumferential surface of the threaded spacer 131 with a predetermined gap between them. The exhaust gas, which has been transferred to the screw groove 131a by the rotor blade 102 and the fixed blade 123, is guided through the screw groove 131a and sent to the base section 129.

[0026] The base portion 129 is a disc-shaped component that forms the base of the turbomolecular pump 100, and is generally made of a metal such as iron, aluminum, or stainless steel. 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.

[0027] In this configuration, when the rotor blade 102 is rotated by the motor 121 together with the rotor shaft 113, exhaust gas is drawn in from the chamber through the intake port 101 due to the action of the rotor blade 102 and the fixed blade 123. The rotational speed of the rotor blade 102 is usually 20,000 rpm to 90,000 rpm, and the peripheral speed at the tip of the rotor blade 102 reaches 200 m / s to 400 m / s. The exhaust gas drawn in from the intake port 101 passes between the rotor blade 102 and the fixed blade 123 and is transferred to the base section 129. At this time, the temperature of the rotor blade 102 rises due to frictional heat generated when the exhaust gas comes into contact with the rotor blade 102 and heat conduction generated by the motor 121, but this heat is transferred to the fixed blade 123 side by radiation or conduction by gas molecules of the exhaust gas.

[0028] The fixed-wing spacers 125 are joined to each other at their outer circumference, and they transmit heat received by the fixed wing 123 from the rotor blade 102, as well as frictional heat generated when exhaust gases come into contact with the fixed wing 123, to the outside.

[0029] In the above description, the threaded spacer 131 is positioned on the outer circumference of the cylindrical portion 102d of the rotating body 103, and a threaded groove 131a is engraved on the inner surface of the threaded spacer 131. However, conversely, there are also cases where a threaded groove is engraved on the outer circumference of the cylindrical portion 102d, and a spacer having a cylindrical inner surface is positioned around it.

[0030] Furthermore, depending on the application of the turbomolecular pump 100, the electrical components, which consist of an upper radial electromagnet 104, an upper radial sensor 107, a motor 121, a lower radial electromagnet 105, a lower radial sensor 108, axial electromagnets 106A, 106B, and an axial sensor 109, may be covered by a stator column 122 to prevent the gas drawn in from the intake port 101 from entering the electrical components, and the inside of this stator column 122 may be maintained at a predetermined pressure with purge gas.

[0031] In this case, piping (not shown) is provided in the base section 129, and purge gas is introduced through this piping. The introduced purge gas is sent to the exhaust port 133 through the 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 part of the rotor blade 102.

[0032] Here, the turbomolecular pump 100 requires model identification and control based on individually adjusted unique parameters (e.g., characteristics corresponding to the model). To store these control parameters, the turbomolecular pump 100 is equipped with an electronic circuit section 141 within its body. The electronic circuit section 141 consists of electronic components such as semiconductor memory such as EEP-ROM and semiconductor elements for accessing it, and a substrate 143 for mounting them. This electronic circuit section 141 is housed, for example, below a rotational speed sensor (not shown) near the center of the base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom cover 145.

[0033] Incidentally, in the semiconductor manufacturing process, some process gases introduced into the chamber have the property of becoming solid when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the exhaust gas pressure is lowest at the intake port 101 and highest at the exhaust port 133. If the process gas's pressure exceeds a predetermined value or its temperature falls below a predetermined value while it is being transferred from the intake port 101 to the exhaust port 133, the process gas becomes solid and adheres to and accumulates inside the turbomolecular pump 100.

[0034] 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 to 10⁻² torr) and low temperature (approximately 20°C), solid products (e.g., AlCl3) precipitate and adhere to the inside of 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 aforementioned products tended to solidify and adhere in areas with high pressure, such as near the exhaust port 133 and near the threaded spacer 131.

[0035] Therefore, in order to solve this problem, conventional methods involve wrapping a heater (not shown) or an annular water-cooling pipe 149 around the outer circumference of the base portion 129, and embedding a temperature sensor (e.g., a thermistor) (not shown) in the base portion 129. Based on the signal from this temperature sensor, heating by the heater and cooling by the water-cooling pipe 149 are controlled (hereinafter referred to as TMS; Temperature Management System) to maintain the temperature of the base portion 129 at a constant high temperature (set temperature).

[0036] Next, we will describe an amplifier circuit 150 that energizes and controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B of the turbomolecular pump 100 configured in this way. The circuit diagram of this amplifier circuit 150 is shown in Figure 2.

[0037] In Figure 2, the electromagnet winding 151, which constitutes the upper radial electromagnet 104, has one end connected to the positive terminal 171a of the power supply 171 via transistor 161, and the other end connected to the negative terminal 171b of the power supply 171 via current detection circuit 181 and transistor 162. Transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between their source and drain.

[0038] In this configuration, transistor 161 has its diode cathode terminal 161a connected to the positive terminal 171a, and its anode terminal 161b connected to one end of the electromagnet winding 151. Transistor 162 has its diode cathode terminal 162a connected to the current detection circuit 181, and its anode terminal 162b connected to the negative terminal 171b.

[0039] On the other hand, the diode 165 for current regeneration has its cathode terminal 165a connected to one end of the electromagnet winding 151, and its anode terminal 165b connected to the negative terminal 171b. Similarly, the diode 166 for current regeneration has its cathode terminal 166a connected to the positive terminal 171a, and its anode terminal 166b connected to the other end of the electromagnet winding 151 via the current detection circuit 181. The current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or an electrical resistance element.

[0040] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, if the magnetic bearing is 5-axis controlled and there are a total of 10 electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and 10 amplifier circuits 150 are connected in parallel to the power supply 171.

[0041] Furthermore, the amplifier control circuit 191 is configured, for example, by a digital signal processor (hereinafter referred to as the DSP section) of the control device 200 (not shown), and this amplifier control circuit 191 is configured to switch transistors 161 and 162 on and off.

[0042] The amplifier control circuit 191 compares the current value detected by the current detection circuit 181 (the signal reflecting this current value is called the current detection signal 191c) with a predetermined current command value. Based on this comparison, it determines the magnitude of the pulse width (pulse width time Tp1, Tp2) to be generated within the control cycle Ts, which is one period of PWM control. As a result, gate drive signals 191a and 191b with this pulse width are output from the amplifier control circuit 191 to the gate terminals of transistors 161 and 162.

[0043] Furthermore, when the rotating body 103 passes a resonance point during accelerated rotational speed operation, or when disturbances occur during constant-speed operation, it is necessary to control the position of the rotating body 103 with high speed and strong force. For this reason, a voltage of approximately 50V is used for the power supply 171 so that the current flowing through the electromagnet winding 151 can be rapidly increased (or decreased). In addition, a capacitor is usually connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 to stabilize the power supply 171 (not shown).

[0044] In this configuration, when both transistors 161 and 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as the electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0045] Furthermore, by turning one of transistors 161 and 162 on and the other off, a so-called flywheel current is maintained. By allowing this flywheel current to flow through the amplifier circuit 150, hysteresis loss in the amplifier circuit 150 can be reduced, and the overall power consumption of the circuit can be kept low. In addition, by controlling transistors 161 and 162 in this way, high-frequency noise such as harmonics generated in the turbomolecular pump 100 can be reduced. Moreover, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0046] In other words, if the detected current value is smaller than the current command value, both transistors 161 and 162 are turned on only once during the control cycle Ts (e.g., 100 μs) for a duration corresponding to the pulse width time Tp1, as shown in Figure 3. Therefore, the electromagnet current iL during this period increases from the positive electrode 171a to the negative electrode 171b, towards the current value iLmax (not shown) that can flow through transistors 161 and 162.

[0047] On the other hand, if the detected current value is greater than the current command value, both transistors 161 and 162 are turned off only once during the control cycle Ts for a duration corresponding to the pulse width time Tp2, as shown in Figure 4. Therefore, during this period, the electromagnet current iL decreases from the negative electrode 171b towards the positive electrode 171a, towards a regenerative current value iLmin (not shown) via diodes 165 and 166.

[0048] In either case, after the pulse width time Tp1 and Tp2 have elapsed, one of transistors 161 or 162 is turned on. Therefore, during this period, the flywheel current is maintained in the amplifier circuit 150.

[0049] Next, we will explain the configuration of a Sigburn-type vacuum pump that exhausts gas in the upstream region from the outer diameter side to the inner diameter side, and then exhausts gas in the downstream region from the inner diameter side to the outer diameter side, in a reverse exhaust process.

[0050] (ii-1) Configuration Figure 5 is a diagram showing a schematic configuration example of a Sigburn-type vacuum pump 1 according to an embodiment of the present invention. Figure 5 shows a cross-sectional view of the Sigburn-type vacuum pump 1 in the axial direction. The casing 2 that forms the exterior of the Sigburn-type vacuum pump 1 is roughly cylindrical in shape and, together with the base 3 provided at the lower part of the casing 2 (on the exhaust port 133 side), constitutes the housing of the Sigburn-type vacuum pump 1. Inside this housing is the gas transfer mechanism, which is the structure that enables the Sigburn-type vacuum pump 1 to perform its exhaust function. This gas transfer mechanism is broadly composed of a rotating part that is held to rotate freely and a fixed part that is fixed to the housing.

[0051] An air intake port 101 for introducing gas into the Sigburn-type vacuum pump 1 is formed at the end of the casing 2. In addition, a flange portion 5 that protrudes outward is formed on the end face of the casing 2 on the side of the air intake port 101. Furthermore, the base 3 has an exhaust port 133 formed therein for exhausting gas from the Sigburn-type vacuum pump 1.

[0052] The rotating part (rotor part) consists of a shaft 7 which is the axis of rotation, a rotor 8 disposed on the shaft 7, multiple rotating discs 9 provided on the rotor 8, and a rotating cylinder 10. The rotor part is composed of the shaft 7 and the rotor 8. Each rotating disc 9 consists of a disc-shaped member that extends radially perpendicular to the axis of the shaft 7. Furthermore, the rotating cylinder 10 consists of a cylindrical member that is concentric with the rotation axis of the rotor 8.

[0053] A motor unit 20 for rotating the shaft 7 at high speed is provided in the middle of the shaft 7 in the axial direction. Furthermore, radial magnetic bearing devices 30, 31 are provided on the intake port 101 side and the exhaust port 133 side of the motor section 20 of the shaft 7 to support the shaft 7 in the radial direction without contact, and an axial magnetic bearing device 40 is provided at the lower end of the shaft 7 to support the shaft 7 in the axial direction without contact.

[0054] A fixed section (stator section) is formed on the inner circumference of the housing. This fixed section consists of multiple fixed discs 50 provided on the intake port 101 side, and spiral grooves are engraved on the fixed discs 50, which are composed of fixed disc valleys 51 and fixed disc peaks 52. In this embodiment, a spiral groove is engraved on the fixed disc 50, but the invention is not limited to this configuration. It is sufficient if the spiral groove flow path is engraved on at least one of the gap-facing surfaces of the rotating disc 9 or the fixed disc 50. Each fixed disc 50 is composed of disc-shaped members that extend radially perpendicular to the axis of the shaft 7. Each stage of the fixed disc 50 is separated from and fixed by cylindrical spacers 60 (stator section). The axial height of the spacers 60 is formed to decrease along the axial direction of the Sigburn-type vacuum pump 1, thereby gradually reducing the volume of the flow path toward the exhaust port 133 of the Sigburn-type vacuum pump 1 and compressing the gas passing through the gas transfer mechanism. The arrows in Figure 5 indicate the flow of gas. In the Sigburn-type vacuum pump 1, the rotating disc 9 and the stationary disc 50 are arranged alternately and formed in multiple stages in the axial direction. However, in order to meet the discharge performance required of the vacuum pump, any number of rotor and stator components can be provided as needed. The Sigburn-type vacuum pump 1 configured in this way is used to perform vacuum evacuation in the vacuum chamber (not shown) located within the Sigburn-type vacuum pump 1.

[0055] Next, the first embodiment will be described. Figure 7 is a cross-sectional view of the vacuum pump 1 including the Sigburn exhaust mechanism in the first embodiment. Figure 8 shows the fixed disc (with the upper and lower sections joined together) in the first embodiment, and Figure 9 shows the fixed disc (lower section alone) in the first embodiment.

[0056] In this first embodiment, a partition wall 300 and a side partition wall 302 are provided around the outer periphery of the Sigburn exhaust mechanism, dividing it in the circumferential direction. As shown in Figure 8, a flow path toward the first stage (lower stage) Sigburn exhaust mechanism and a flow path toward the second stage (upper stage) Sigburn exhaust mechanism are alternately arranged. That is, by providing a partition wall 300 and a side partition wall 302 around the outer periphery of the Sigburn exhaust mechanism, the exhaust gas is separated into exhaust gas passing through the flow path toward the first stage Sigburn exhaust mechanism and exhaust gas passing through the flow path toward the second stage Sigburn exhaust mechanism. As a result, multiple Sigburn exhaust mechanisms (fixed discs 50) can be arranged in parallel to improve exhaust efficiency. In this first embodiment, the partition wall 300 extends vertically around the outer circumference of the Sigburn exhaust mechanism, thereby covering the flow path.

[0057] In this first embodiment, as shown in Figure 8, the exhaust gas inlet and outlet of the upper stage, and the exhaust gas inlet and outlet of the lower stage are in the same phase. That is, the inlets and outlets of each stage are in the same position. Therefore, the upper and lower stages can be made to have exactly the same shape, which reduces the number of molds used during manufacturing and lowers manufacturing costs. The flow of exhaust gas within the Sigburn exhaust mechanism is as shown by the arrows in the figure (Figure 7). Specifically, exhaust gas taken in from the inlet located on the outer circumference of the Sigburn exhaust mechanism is sent radially inward, compressed, and discharged from the outlet on the radially outward side. Furthermore, if there are six fixed disc peaks 52 (spiral-shaped protrusions), the passages are installed at equal intervals with a 30-degree pitch. The entrances to the upper and lower levels are then positioned with a half-pitch phase difference. A rotating disk 9 is positioned at the top of Figure 8.

[0058] In the first embodiment, as shown in Figure 8, a projection 308 extending axially from the partition wall 300 may be provided. This projection 308 allows for angular positioning during manufacturing. Furthermore, by extending it to a position opposite the end face of the rotating disc 9, exhaust gas leakage can be prevented.

[0059] Next, a second embodiment will be described. Figure 10 is a cross-sectional view of the vacuum pump 1 including the Sigburn exhaust mechanism in the second embodiment. Figure 11 is a diagram showing the fixed disc (upper and lower sections combined) in the second embodiment with an inlet (inlet area) to outlet (outlet area) ratio of 5:5, and Figure 12 is a diagram showing the fixed disc (upper and lower sections combined) in the second embodiment with an inlet to outlet area ratio of 7:3. Furthermore, Figure 13 shows a state in which three fixed discs with an inlet-to-outlet area ratio of 7:3 in the second embodiment are stacked, and Figure 14 shows a fixed disc (the lower single disc) in the second embodiment.

[0060] In this second embodiment, the partition wall 300 has a structure that covers one side at a time, with the upper inlet and the lower inlet being in the same phase, and the upper outlet and the lower outlet being in the same phase. In other words, the partition wall 300 that closes only the lower side and the partition wall 300 that closes only the upper side are arranged in different phases (alternating). Furthermore, an upper bulkhead 304 and a lower bulkhead 306 are provided to prevent backflow of exhaust gases. The flow of exhaust gas within the Sigburn exhaust system is as shown by the arrows in the figure (Figure 10).

[0061] In this second embodiment, since the exhaust gas inlet and outlet are in the same phase, the ratio of the inlet and outlet areas can be easily changed by adjusting the position of the side partition wall 302. In the example shown in Figure 11, the ratio of the inlet to outlet areas is 5:5, but in Figure 12, the ratio is 7:3. Generally, since exhaust gases are compressed within a sigburn exhaust system, setting a wider inlet and a narrower outlet tends to increase exhaust efficiency. Therefore, the ratio of the inlet to the outlet can be appropriately set to obtain the desired exhaust efficiency.

[0062] Furthermore, in this second embodiment, as shown in Figure 13, since the inlet and outlet have the same phase, the number of stages can be increased from two by stacking fixed discs 50 of the same shape. By installing an upper bulkhead 304 and a lower bulkhead 306, a multi-stage parallel-connectable Sigburn exhaust mechanism can be constructed. In this second embodiment as well, if the upper partition wall 304 and the lower partition wall 306 are made as separate parts, they will have the same shape, so the type of mold can be limited as in the first embodiment, and manufacturing costs can be reduced.

[0063] Next, we will describe some variations of each embodiment. As shown in Figure 15, the starting position of the inlet (indicated by X in the figure) is aligned with the back surface of the fixed disc peak 52 (spiral-shaped projection) with respect to the rotation direction of the rotating disc 9. Furthermore, the end position of the outlet (indicated by Y in the figure) is aligned with the front surface of the fixed disc peak 52 (spiral-shaped projection) with respect to the rotation direction of the rotating disc 9. This is preferable because it allows for the efficient creation of a pressure distribution within the Sigburn exhaust mechanism. In Figure 15, the arrows indicate the flow of exhaust gas from the inlet to the outlet.

[0064] Next, as shown in Figure 16, the partition wall 300 is installed at a predetermined angle with respect to the radial direction of the rotating disc 9. The angle is preferably around 20 degrees. By arranging the relationship between the fixed disc peak 52 and the partition wall 300 in this way, the inflow and outflow of exhaust gas can be made smooth when the exhaust gas enters the ignition system.

[0065] Next, I will explain other variations. An additional exhaust mechanism is installed on the exhaust port side of a multi-stage stacked Sigburn exhaust mechanism, equipped with multiple times the number of fixed circular plate peaks 52 (projections) of the Sigburn exhaust mechanism. For example, three pairs of Sigburn exhaust mechanisms, each with 6 projections, are connected in parallel, and an additional Sigburn exhaust mechanism with 18 projections is connected to them. This allows for more efficient exhaust.

[0066] In this embodiment, a vacuum pump in which a turbomolecular pump is placed upstream of a parallel-connected Sigburn exhaust mechanism can reduce the pressure of the upstream turbomolecular pump. Therefore, not only is the exhaust speed improved, but the power consumption of the motor is also reduced and the vacuum pump itself does not overheat. In other words, while a turbomolecular pump operates efficiently in the molecular flow region of the gas, its exhaust efficiency decreases sharply in the pressure region where the operating pressure increases and the flow becomes intermediate. As a result, the power consumption of the motor increases sharply and the amount of heat generated increases. Therefore, in a vacuum pump with a turbomolecular pump positioned upstream, it is possible to operate within a pressure range suitable for each of its performance characteristics, thereby further improving the exhaust performance of the vacuum pump.

[0067] Furthermore, the embodiments and variations of the present invention may be combined as needed.

[0068] Furthermore, the present invention can be modified in various ways, as long as it does not depart from the spirit of the invention. Naturally, the present invention extends to such modified versions. [Explanation of symbols]

[0069] 1. Sigburn type vacuum pump 2 Casing 3 base 5. Flange section 7 shafts 8 rotors 9. Rotating disk 10 Rotating Cylinders 20 Motor section 30 Radial magnetic bearing device 31 Radial magnetic bearing device 40 Axial magnetic bearing device 50 Fixed disc 51 Fixed disk valley 52 Fixed disc mountain section 60 Spacer 100 Turbomolecular Pumps (Vacuum Pumps) 101 Air intake 102 Rotary blades 102d Cylindrical section 103 Solids of revolution 113 Rotor shaft 122 Status Column 123 Fixed wing 125 Fixed-wing spacers 127 Outer cylinder 129 Base section 131 Screw-on spacer 131a Screw groove 133 Exhaust vent 200 Control device 250 Rib section 260 Communication port (communication hole) 300 Bulkhead 302 Side bulkhead 304 Upper bulkhead 308 Protrusion 306 Lower Bulkhead 1000 Sigburn type vacuum pump (conventional) 5000 Fixed disc (conventional)

Claims

1. An air intake port for drawing in gas, An exhaust port for exhausting the gas drawn in from the aforementioned intake port, A rotating disk held to rotate freely, A fixed disc is installed opposite the rotating disc, The device comprises a spiral projection installed on at least one of the opposing surfaces of the rotating disk and the stationary disk, On the surface of the fixed disc on the intake port side, from the outside to the inside, On the surface of the fixed disc facing the exhaust port, from the inside outwards, A vacuum pump comprising multiple stages of radial flow type exhaust mechanisms that exhaust gas in a radial direction, The system includes a partition wall that divides the gas flow path from the intake port to the exhaust mechanism into multiple systems. A vacuum pump characterized by sending the gas separated by the partition wall in parallel to each of the multiple stacked exhaust mechanisms.

2. An inlet to the exhaust mechanism is installed on the surface of the fixed disc on the side of the intake port, The fixed disc comprises an outlet from the exhaust mechanism installed on the exhaust port side surface of the fixed disc, The vacuum pump according to claim 1, characterized in that the phases of the installation positions of the inlet and the outlet coincide.

3. The fixed disc is provided with an inlet for the exhaust mechanism, which is installed on the surface of the fixed disc on the side of the intake port, The vacuum pump according to claim 1, characterized in that the phases of the installation positions of the inlets to the multi-stage stacked exhaust mechanism are aligned.

4. The fixed disc is provided with an outlet for the exhaust mechanism located on the exhaust port side, The vacuum pump according to claim 1 or 3, characterized in that the phases of the installation positions of the outlets from the multi-stage stacked exhaust mechanism are aligned.

5. The fixed disc is provided with an inlet for the exhaust mechanism, which is installed on the surface of the fixed disc on the side of the intake port, The vacuum pump according to claim 1, characterized in that the starting position of the inlet and the back surface of the spiral projection coincide with the rotation direction of the rotating disc.

6. The fixed disc is provided with an outlet for the exhaust mechanism located on the exhaust port side, The vacuum pump according to claim 1, characterized in that the end position of the outlet and the front surface of the spiral projection coincide with the rotation direction of the rotating disc.

7. The vacuum pump according to claim 1, characterized in that the fixed disc is provided with a projection facing the outer circumferential surface of the rotating disc.

8. The vacuum pump according to claim 1, characterized in that the partition wall is installed at a predetermined angle with respect to the radial direction of the rotating disk.

9. The vacuum pump according to claim 1, characterized in that an additional exhaust mechanism having multiple times the number of protrusions of the exhaust mechanism is installed on the exhaust port side of the multi-stage stacked exhaust mechanism.

10. A fixed disc used in a radial flow type exhaust mechanism that exhausts gas in the radial direction, which is installed opposite a rotatably held rotating disc, The surface facing the rotating disc is provided with spiral-shaped protrusions, On the surface of the fixed disc on the intake port side, from the outside to the inside, On the surface of the fixed disc facing the exhaust port, from the inside outwards, A fixed disc characterized by having partitions that divide the gas flow path into multiple systems in order to exhaust gas in the radial direction.

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