Vacuum pump, fixed disc and retrofit component

Abstract

To provide a vacuum pump capable of improving an exhaust speed while maintaining back pressure dependency performance, and a fixed disc and a retrofit component used in the vacuum pump.SOLUTION: A vacuum pump according to the present embodiment is a Sigbahn element, and has a fixed disc that is arranged so as to face a rotating disc and in which a spiral groove has valleys and peaks is disposed on a facing surface, where an inflow guide part for guiding the inflow of gas is provided at a gas inflow port of the spiral groove. The inflow guide part has a shape in which the peaks of the fixed disc are extended outside an outer diameter of the opposing rotating disc.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a vacuum pump, a fixed disk and a retrofit part for use in the vacuum pump. [Background technology]

[0002] A vacuum pump has a casing that forms an exterior body with an intake port and an exhaust port, and a structure that allows the vacuum pump to exhibit exhaust performance is housed inside the casing. This structure that exhibits exhaust performance is composed of a rotating part (rotor part) that is held rotatably and a fixed part (stator part) that is fixed to the casing. By rotating this rotating part at high speed with a motor, the interaction between the rotor blades (rotating disk) and the stator blades (fixed disk) sucks in gas from the intake port and exhausts it to the exhaust port.

[0003] Among vacuum pumps, a type called a Sigburn type molecular pump, which has a Sigburn type configuration, is used. This Sigburn type vacuum pump includes a rotating disk and a fixed disk arranged with a gap (clearance) in the axial direction from the rotating disk, and a spiral groove (spiral flow path) is engraved on the surface facing the gap of either the rotating disk or the fixed disk. Then, the gas molecules that have diffused into the spiral groove are given momentum in the tangential direction of the rotating disk (i.e., the rotation direction of the rotating disk) by the rotating disk, so that the spiral groove gives a preferential direction from the intake port to the exhaust port, and exhaust is performed. There are various types of Sigburn molecular pumps, including a type that has multiple stages of pairs of rotating and fixed disks, and a type that is used in combination with pairs of fixed and rotating blades (called turbo stages). In the document described in Patent Document 1, in a Sigburn type vacuum pump, the outlet of the spiral groove on the intake side has a portion that overlaps with the inlet of the spiral groove on the exhaust side in the axial direction, thereby producing the effect of preventing the loss of dominant momentum in the exhaust direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-102076 A Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, the pumping performance of a vacuum pump can be expressed by its back pressure dependency and pumping speed. FIG. 14 is a graph showing the relationship between back pressure dependent performance, which is an index of exhaust performance, and the suction pressure and back pressure at the exhaust speed. Here, good (high) back pressure dependence performance means that an increase in back pressure (exhaust port pressure) is unlikely to affect the suction pressure (intake port pressure). In other words, if an increase in back pressure immediately affects the suction pressure, the back pressure dependence performance is said to be bad (low). Vacuum pump users require vacuum pumps that can maintain a stable, constant intake pressure (good back pressure dependent performance) because pressure varies depending on how the vacuum pump is used.

[0006] On the other hand, pumping speed refers to the ability to form a vacuum faster when pumping under the same conditions, and the faster the pumping speed, the better the pumping performance. By using the above-mentioned Sigburn element, it is expected that the back pressure dependent performance can be improved. On the other hand, in order to further improve the back pressure dependent performance, it is necessary to take measures such as increasing the number of Sigburn stages, increasing the length, and making the flow path shallower. However, when such a measure is taken, the Sigburn inlet pressure increases, while the gas conductance deteriorates, and the pumping speed deteriorates. In other words, there is a trade-off between back pressure dependent performance and pumping speed.

[0007] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a vacuum pump that improves pumping speed while maintaining back pressure dependent performance, as well as a fixed disk and a retrofit part for use in said vacuum pump. [Means for solving the problem]

[0008] The invention described in claim 1 provides a vacuum pump comprising a casing, a rotor shaft arranged within the casing, a rotating disk rotatable together with the rotor shaft, and a fixed disk arranged opposite the rotating disk in the axial direction of the rotor shaft and having a spiral groove having valleys and peaks on the opposing surface, the vacuum pump evacuating gas by interaction between the rotating disk and the fixed disk, characterized in that an inflow guide portion for guiding the inflow of the gas is provided at a gas inlet of the spiral groove. The invention described in claim 2 provides the vacuum pump described in claim 1, characterized in that the inflow guide portion has a shape in which the ridge portion is integrally extended outward beyond the outer diameter of the opposing rotating disk. The invention described in claim 3 provides the vacuum pump described in claim 2, characterized in that the inflow guide portion has a shape in which the ridge portion is further integrally extended toward the intake port side in the axial direction. The invention described in claim 4 provides the vacuum pump described in claim 1, characterized in that the inflow guide portion has a shape in which the ridge portion extends outward beyond the outer diameter of the opposing rotating disk by attaching an add-on part having a shape in which the ridge portion extends outward beyond the outer diameter of the opposing rotating disk. The invention recited in claim 5 provides the vacuum pump recited in claim 4, characterized in that the inflow guide portion has a shape in which the add-on part is further extended toward the intake port side in the axial direction. The invention described in claim 6 provides a vacuum pump described in any one of claims 1 to 5, characterized in that the rotating disk and the fixed disk are arranged in a plurality of stages, and the inflow guide portion is provided in the stage closest to the intake port among the plurality of stages of the fixed disks. The invention recited in claim 7 provides a vacuum pump recited in any one of claims 1 to 5, characterized in that the inflow guide portion and the opposing fixed side component are in contact with each other and there is no gap between them. The invention described in claim 8 provides a fixed disk used in a vacuum pump that exhausts gas by interaction with a rotating disk, characterized in that the fixed disk is arranged axially opposite the rotating disk, has a spiral groove with valleys and peaks on the opposing surface, and is equipped with an inflow guide portion that extends integrally outward beyond the outer diameter of the opposing rotating disk. The invention described in claim 9 provides an add-on component used in a vacuum pump that exhausts gas by interaction with a rotating disk, arranged axially opposite the rotating disk, and attached to a fixed disk having a spiral groove with valleys and peaks on the opposing surface, characterized in that the peaks have a shape that extends outward beyond the outer diameter of the opposing rotating disk. Effect of the Invention

[0009] In the present invention, a Sigburn type pumping element is used in a vacuum pump to increase pumping speed while maintaining back pressure dependent performance. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a schematic configuration example of a turbomolecular pump according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a circuit diagram of an amplifier circuit used in an embodiment of the present invention. [Diagram 3] 5 is a time chart showing control when a detection value is greater than a current command value in the embodiment of the present invention. [Figure 4] 5 is a time chart showing control when a detection value is smaller than a current command value in the embodiment of the present invention. [Diagram 5] FIG. 1 is a diagram showing a schematic configuration example of a conventional Sigburn type molecular pump. [Figure 6] FIG. 13 is an enlarged view for explaining a conventional fixed disk. [Figure 7] FIG. 1 is a diagram showing a schematic configuration example of a conventional compound turbomolecular pump. [Figure 8]FIG. 1 is a perspective view for explaining a ridge portion forming a spiral groove provided on a fixed disk which is a Sigburn element in a conventional compound turbomolecular pump. [Figure 9] 1 is a diagram showing a schematic configuration example of a compound turbomolecular pump according to a first embodiment of the present invention. [Figure 10] FIG. 2 is a perspective view for explaining a ridge portion forming a spiral groove provided on a fixed disk which is a Sigburn element in the compound turbo-molecular pump according to the first embodiment of the present invention. [Figure 11] FIG. 4 is a diagram showing a schematic configuration example of a compound turbomolecular pump according to a second embodiment of the present invention. [Figure 12] FIG. 13 is a diagram showing a schematic configuration example of a compound turbomolecular pump according to a third embodiment of the present invention. [Figure 13] FIG. 11 is a perspective view illustrating a ridge portion forming a spiral groove provided on a fixed disk which is a Sigburn element in a compound turbo-molecular pump according to a third embodiment of the present invention. [Figure 14] 1 is a graph showing a relationship between back pressure dependent performance, which is an index of exhaust performance, and suction pressure and back pressure at exhaust speeds. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (1) Overview of the embodiment The vacuum pump according to this embodiment is a Sigbahn element, and is provided with a fixed disk opposite a rotating disk, the fixed disk having a spiral groove with valleys and peaks on the opposing surface, and an inflow guide portion for guiding the inflow of gas at the gas inlet of the spiral groove. This inflow guide portion has a shape in which the fixed disk ridge portion extends outward beyond the outer diameter of the opposing rotating disk.

[0012] (2) Details of the embodiment The vacuum pump according to this embodiment may be a composite vacuum pump that combines a turbomolecular pump having multiple stages of pairs of rotors and fixed vanes with a Sigburn type vacuum pump, or may be a vacuum pump that is only a Sigburn type vacuum pump. Therefore, the basic configurations of a turbomolecular pump and a Sigmoid type vacuum pump will be described with reference to FIGS.

[0013] As an example, a longitudinal cross-sectional view of the above-mentioned 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, a rotor 103 is provided, the rotor 103 having a plurality of rotors 102 (102a, 102b, 102c, ...) which are turbine blades for sucking in and exhausting gas, formed radially on its periphery in multiple stages. A rotor shaft 113 is attached to the center of the rotor 103, and the rotor shaft 113 is levitated in the air and positionally controlled by, for example, a five-axis controlled magnetic bearing. The rotor 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0014] 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 of the upper radial electromagnets 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 the change in inductance of the conductive windings that changes 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 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 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.

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

[0017] 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 high magnetic permeability 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 200.

[0018] In the control device 200, a compensation circuit having, for example, a PID adjustment function generates an excitation control command signal for each of the axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of 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 by magnetic force and the axial electromagnet 106B attracts the metal disk 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0019] In this way, the control device 200 appropriately adjusts the magnetic force that the axial electromagnets 106A, 106B exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in a non-contact manner in space. The amplifier circuit 150 that controls the excitation of the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A, 106B will be described later.

[0020] 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 200 so as to rotate rotor shaft 113 via electromagnetic force acting between the magnetic pole and rotor shaft 113. Also, motor 121 incorporates a rotation speed sensor such as a Hall element, resolver, or encoder (not shown), and the rotation speed of rotor shaft 113 is detected by a detection signal from this rotation 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 detects the position of the magnetic poles using the detection signals of both this phase sensor and the rotation speed sensor.

[0022] A plurality of fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap between the rotor blades 102 (102a, 102b, 102c...). The rotor blades 102 (102a, 102b, 102c...) are 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 through collision. The fixed blades 123 (123a, 123b, 123c...) are made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components.

[0023] Similarly, the fixed blades 123 are formed at an inclination at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged alternately with the stages of the rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported in a state where they are inserted between a plurality of stacked stages of fixed blade spacers 125 (125a, 125b, 125c, etc.).

[0024] The fixed wing spacer 125 is a ring-shaped member and is made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer periphery of the fixed wing spacer 125 with a small gap therebetween. A base portion 129 is disposed 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 turbo molecular pump 100, a threaded spacer 131 is disposed between the lower part of the fixed vane spacer 125 and the base part 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 a plurality of helical thread grooves 131a engraved on its inner peripheral surface. The helical direction of the thread groove 131a is the direction in which, when the molecules of the exhaust gas move in the rotation direction of the rotor 103, the molecules are transferred toward the exhaust port 133. A cylindrical part 102d hangs down from the lowest part of the rotor 103, which is connected to the rotor vanes 102 (102a, 102b, 102c, etc.). The outer peripheral surface of this cylindrical part 102d is cylindrical and protrudes toward the inner peripheral surface of the threaded spacer 131, and is adjacent to the inner peripheral surface of the threaded spacer 131 with a predetermined gap therebetween. The exhaust gas transferred to the thread groove 131a by the rotor 102 and the fixed blade 123 is sent to the base portion 129 while being guided by the thread groove 131a.

[0026] The base portion 129 is a disk-shaped member that constitutes the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. The base portion 129 physically holds the turbomolecular pump 100 and also functions as a heat conduction path, so it is desirable to use a metal that has rigidity and high thermal conductivity, such as iron, aluminum, or copper.

[0027] In this configuration, when the rotor 102 is rotated together with the rotor shaft 113 by the motor 121, the exhaust gas is sucked from the chamber through the intake port 101 by the action of the rotor 102 and the fixed blade 123. The rotation speed of the rotor 102 is usually 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 sucked through the intake port 101 passes between the rotor 102 and the fixed blade 123 and is transferred to the base part 129. 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, and the like, but this heat is transferred to the fixed blade 123 side by radiation or conduction by gas molecules of the exhaust gas, and the like.

[0028] The fixed blade spacers 125 are joined to each other at their outer peripheries, and transmit heat received by the fixed blades 123 from the rotor blades 102, frictional heat generated when exhaust gas comes into contact with the fixed blades 123, and the like to the outside.

[0029] In the above description, the threaded spacer 131 is disposed on the outer periphery of the cylindrical portion 102d of the rotor 103, and the thread groove 131a is formed on the inner periphery of the threaded spacer 131. However, there are also cases where the thread groove is formed on the outer periphery of the cylindrical portion 102d, and a spacer having a cylindrical inner periphery is disposed around the outer periphery of the cylindrical portion 102d.

[0030] Depending on the application of the turbomolecular pump 100, in order 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., the electrical equipment section may be covered all around with a stator column 122, and the inside of this stator column 122 may be kept at a predetermined pressure by a purge gas.

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

[0032] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that are individually adjusted and specified for the model. In order to store these control parameters, the turbomolecular pump 100 has an electronic circuit section 141 in its main 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 the 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 cover 145.

[0033] 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 turbo molecular pump 100, the pressure of the exhaust gas is lowest at the intake port 101 and highest at the exhaust port 133. If the pressure of the process gas becomes higher than a predetermined value or the temperature falls below a predetermined value while the process gas 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 turbo molecular pump 100.

[0034] For example, when SiCl4 is used as a process gas in an Al etching apparatus, at low vacuum (760 [torr] to 10-2 [torr]) and low temperature (approximately 20 [°C]), a solid product (e.g., AlCl3) precipitates and adheres to and accumulates inside the turbomolecular pump 100, as can be seen from the vapor pressure curve. When precipitates of the process gas accumulate inside the turbomolecular pump 100, the deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. The above-mentioned product is prone to solidification and adhesion in high pressure areas near the exhaust port 133 and near the threaded spacer 131.

[0035] Therefore, in order to solve this problem, in the past, a heater (not shown) or a circular water-cooled tube 149 was wrapped around the outer periphery of the base portion 129, and a temperature sensor (e.g., a thermistor) (not shown) was embedded in the base portion 129, and the heating of the heater and the cooling by the water-cooled tube 149 were controlled based on the signal from this temperature sensor to keep the temperature of the base portion 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS; Temperature Management System).

[0036] 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 turbo molecular pump 100 configured as described above. A circuit diagram of this amplifier circuit 150 is shown in FIG.

[0037] 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 source 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power source 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.

[0038] At this time, the transistor 161 has a cathode terminal 161a of the diode 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 cathode terminal 162a of the diode connected to the current detection circuit 181, and an anode terminal 162b connected to the negative electrode 171b.

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

[0040] The amplifier circuit 150 configured as above corresponds to one electromagnet. Therefore, when the magnetic bearing is controlled by 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.

[0041] 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) of the control device 200, and this amplifier control circuit 191 switches the transistors 161 and 162 on / off.

[0042] The amplifier control circuit 191 is adapted to compare 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. Then, based on the result of this comparison, the magnitude of the pulse width (pulse width times Tp1, Tp2) to be generated within a control cycle Ts, which is one period of PWM control, is determined. As a result, gate drive signals 191a, 191b having this pulse width are output from the amplifier control circuit 191 to the gate terminals of the transistors 161, 162.

[0043] It is necessary to control the position of rotor 103 at high speed and with strong force when, for example, the rotor 103 passes through a resonance point during accelerated operation of the rotation 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 pole 171a and negative pole 171b of power supply 171 to stabilize power supply 171.

[0044] In this configuration, when both transistors 161, 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.

[0045] Moreover, when one of the transistors 161, 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, the 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, 162 in this manner, high-frequency noise such as harmonics generated in the turbo molecular 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.

[0046] That is, when the detected current value is smaller than the current command value, both of the transistors 161 and 162 are turned on for a time period corresponding to the pulse width time Tp1 only once in a control cycle Ts (e.g., 100 μs) as shown in Fig. 3. Therefore, the electromagnet current iL during this period 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.

[0047] On the other hand, when the detected current value is larger than the current command value, both of the transistors 161 and 162 are turned off for a time period corresponding to the 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 the diodes 165 and 166.

[0048] 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.

[0049] 5 is a diagram for explaining a conventional Sigburn type molecular pump 1000, and is a diagram showing a schematic configuration example of the conventional Sigburn type molecular pump 1000. The arrows indicate the flow of gas molecules.

[0050] 6 is a diagram for explaining a fixed disk 501 disposed in a conventional Sigburn type molecular pump 1000, and is a cross-sectional view of the fixed disk 501 as viewed from the intake port 101 (FIG. 5) side of the conventional Sigburn type molecular pump 1000. The arrows inside the fixed disk 501 indicate the flow of gas molecules, and the arrows outside the fixed disk 501 indicate the rotation direction of the rotating disk 901 (FIG. 5).

[0051] The casing 201 forming the exterior of the Sigburn type molecular pump 1000 has a substantially cylindrical shape, and constitutes the housing of the Sigburn type molecular pump 1000 together with a base 700 provided at the lower part (exhaust port 60 side) of the casing 201. Inside this housing, a gas transfer mechanism, which is a structure that allows the Sigburn type molecular pump 1000 to exert an exhaust function, is housed. This gas transfer mechanism is roughly composed of a rotating part that is supported so as to be freely rotatable, and a fixed part that is fixed to the housing. An intake port 401 for introducing gas into the Sigburn type molecular pump 1000 is formed at the end of the casing 201. In addition, a flange portion 50 is formed on the end face of the casing 201 on the intake port 401 side, protruding outward toward the outer periphery.

[0052] Further, the base 700 is formed with an exhaust port 60 for exhausting gas from the Sigburn type molecular pump 1000 . The rotating part is composed of a shaft 701 which is a rotating shaft, a rotor 801 disposed on this shaft 701, a plurality of rotating disks 901 provided on the rotor 801, and a rotating cylinder 110. The shaft 701 and the rotor 801 form the rotor part. Each rotating disk 901 is made of a disk-shaped member extending radially perpendicular to the axis of the shaft 701 . Moreover, the rotating cylinder 110 is made of a cylindrical member having a cylindrical shape concentric with the rotation axis of the rotor 801 .

[0053] A motor unit 202 for rotating the shaft 701 at high speed is provided in the middle of the shaft 701 in the axial direction. Furthermore, radial magnetic bearing devices 301, 310 are provided on the intake port 401 side and exhaust port 60 side of the motor section 202 of the shaft 701 for supporting the shaft 701 in a non-contact manner in the radial direction (diameter direction), and an axial magnetic bearing device 400 is provided at the lower end of the shaft 701 for supporting the shaft 701 in a non-contact manner in the axial direction (axial direction).

[0054] A fixed portion (stator portion) is formed on the inner periphery of the housing. This fixed portion is composed of a plurality of fixed disks 501 provided on the intake port 401 side, and spiral groove portion 530, which is a spiral groove composed of fixed disk valley portion 510 and fixed disk crest portion 520, is engraved on fixed disk 501. Although the configuration in which the spiral groove (spiral groove portion 530) is engraved on the fixed disk 501 has been described here, it is also possible to adopt a configuration in which the spiral groove is engraved on the rotating disk 901. That is, it is sufficient that the spiral groove flow path formed by the spiral groove is engraved on the gap-facing surface of at least one of the fixed disk 501 and the rotating disk 901.

[0055] Each fixed disk 501 is composed of a disk-shaped member extending radially perpendicular to the axis of the shaft 701 . The fixed disks 501 of each stage are fixed and spaced from each other by cylindrical spacers 601. The arrows in Figure 5 indicate the flow of gas. In the Sigburn type molecular pump 1000, the rotating disks 901 and the fixed disks 501 are arranged alternately to form multiple stages in the axial direction, but any number of rotor parts and stator parts can be provided as necessary to satisfy the discharge performance required of the vacuum pump. The Sigburn type molecular pump 1000 configured in this manner is adapted to perform evacuation processing within a vacuum chamber (not shown) disposed in the Sigburn type molecular pump 1000 .

[0056] Fig. 7 is a diagram showing a schematic configuration example of a conventional compound turbomolecular pump (a pump in which a turbomolecular pump and a Sigburn element are integrated), and Fig. 8 is a perspective view for explaining a fixed disk crest portion 520 forming a spiral groove provided on a fixed disk which is a Sigburn element in a conventional compound turbomolecular pump. In Fig. 7, the portion indicated by S is the Sigburn element. 7 and 8, in the compound turbomolecular pump 500, the outer diameter of the fixed disk crest 520 forming the spiral groove engraved in the uppermost fixed disk 501, which is the inlet of the Sigburn exhaust element, is the same size as the outer diameter of the corresponding rotating disk 901. This is because the fixed disk 501 and the rotating disk 901 are the same size. Thus, in the past, the fixed disk crest 520 forming the uppermost spiral groove, which is the inlet of the Sigburn exhaust element, did not protrude from the outer diameter of the corresponding rotating disk 901.

[0057] FIG. 9 is a diagram showing a schematic configuration example of a composite turbomolecular pump according to a first embodiment of the present invention, and FIG. 10 is a perspective view for explaining fixed disk crest portion 520 forming a spiral groove provided in the fixed disk which is a Sigburn element in the composite turbomolecular pump according to the first embodiment of the present invention.

[0058] As is clear from these figures, the fixed disk ridge 520 forming the spiral groove provided in the fixed disk 501 is provided with an inflow guide portion A that protrudes beyond the outer diameter of the corresponding rotating disk 901. That is, in terms of shape, the fixed disk ridge 520 is disposed so as to protrude beyond the outer diameter of the corresponding rotating disk 901. By providing this inflow guide portion A, the pressure drops downstream of the fixed disk ridge portion 520 (the back (opposite) side where the gas hits the inflow guide portion A), and the gas flowing upstream of the fixed disk ridge portion 520 is sucked in. That is, the pressure rises where the inflow guide portion A and the gas collide, but the pressure drops on the opposite side (downstream side), and it is thought that the gas that was stagnant on the upstream side flows in as if it were being sucked in. Therefore, by providing this inflow guide A, it is possible to induce a vertical gas flow, which was previously poor. Therefore, by providing this inflow guide portion A, it is possible to improve the pumping speed while maintaining the back pressure dependent performance, and as a result, it is possible to improve the pumping performance. This inflow guide portion A may be formed integrally with the fixed disk crest portion 520, or may be formed by attaching a later-installed part (a separate part). The material may be the same as that of the fixed disk crest portion 520, or may be a different material. This later-installed part may be attached by fixing with a screw, by welding, or by fitting.

[0059] 11 is a diagram showing a schematic configuration example of a compound turbomolecular pump according to a second embodiment of the present invention. In this second embodiment, fixed disk crest 520 forming a spiral groove provided in fixed disk 501 is provided with inflow guide portion A protruding from the outer diameter of corresponding rotating disk 901. This inflow guide portion A contacts the opposing fixed side component, and there is no gap between them. That is, in comparison with the first embodiment, inflow guide portion A protrudes further.

[0060] According to the second embodiment, the inflow guide part A and the opposing fixed part are in contact with each other, and there is no gap between them. In this way, because there is no gap between them, less gas flows into the back side of the inflow guide part A (the side opposite to the surface that the gas hits), and the pressure on the back side is further reduced. This makes it possible to further promote the suction (introduction) of gas. Therefore, the stagnant gas can be exhausted more efficiently, which contributes to improving the exhaust speed. In the second embodiment, similarly to the first embodiment, the inflow guide portion A may be integrally formed with the fixed disk mountain portion 520, or may be formed by attaching an add-on part (a separate part).

[0061] FIG. 12 is a diagram showing a schematic configuration example of a composite turbomolecular pump according to a third embodiment of the present invention, and FIG. 13 is a perspective view for explaining fixed disk crest portion 520 forming a spiral groove provided in the fixed disk which is a Sigburn element in the composite turbomolecular pump according to the third embodiment of the present invention. In the third embodiment, the inflow guide portion A is extended not only in the outer diameter direction but also integrally toward the intake port side in the axial direction. When extending toward the intake port side in the axial direction, it is desirable to make the gap with the opposing rotating disk 901 as narrow as possible. A gap that does not contact the rotating disk 901 while rotating, for example, about 1.5 mm, is desirable. According to the third embodiment, the area of ​​the inflow guide portion A (the area that the gas hits) is larger than that of the first embodiment, and the gas flows less toward the back side (the side opposite to the surface that the gas hits). Therefore, the intake of the gas can be further promoted.

[0062] In this third embodiment, similarly to the first and second embodiments, the inflow guide portion A may be integrally formed with the fixed disk mountain portion 520, or may be formed by attaching an add-on part (a separate part). Also, as in the second embodiment, the inflow guide portion A may be in contact with the opposing fixed side component, with no gap therebetween.

[0063] In the first to third embodiments, when there are multiple stages of Sigburn elements, it is desirable to provide the inflow guide portion A in the axially uppermost stage (the stage closest to the intake port). Also, in a Sigbahn type vacuum pump having multiple stages of Sigbahn elements only, it is preferable to provide the inflow guide portion A in the axially uppermost stage (the stage closest to the intake port). However, the inflow guide portion A may be provided in other stages as well as the uppermost stage.

[0064] The embodiments and modifications of the present invention may be combined with each other as necessary.

[0065] Furthermore, the present invention can be modified in various ways without departing from the spirit of the present invention, and it goes without saying that the present invention covers such modifications. [Explanation of symbols]

[0066] 100 Turbo molecular pump (vacuum pump) 101 Air intake 102 Rotor 102d Cylindrical section 103 Rotating Body 113 Rotor shaft 122 Stator column 123 Fixed wing 125 Fixed wing spacer 127 Outer cylinder 129 Base 131 Threaded spacer 131a Thread groove 133 Exhaust port 200 Control device 500 Compound turbomolecular pump 501 Fixed disc 510 Fixed disc valley 520 Fixed disk mountain part 530 Spiral groove 901 Rotating disc 1000 Sigburn type molecular pump

Claims

1. A casing; A rotor shaft disposed within the casing; a rotating disk rotatable together with the rotor shaft; a fixed disk disposed opposite the rotating disk in the axial direction of the rotor shaft, the fixed disk having a spiral groove having a valley portion and a peak portion on an opposing surface thereof, A vacuum pump that exhausts gas by interaction between the rotating disk and the fixed disk, A vacuum pump comprising an inflow guide portion at a gas inlet of the spiral groove for guiding the inflow of the gas.

2. 2. The vacuum pump according to claim 1, wherein the inflow guide portion has a shape in which the ridge portion is integrally extended outward beyond an outer diameter of the opposing rotary disk.

3. 3. The vacuum pump according to claim 2, wherein the inflow guide portion has a shape in which the ridge portion is further integrally extended toward the intake port in the axial direction.

4. 2. The vacuum pump according to claim 1, wherein the inflow guide portion is configured to have the ridge portion extended outwardly beyond the outer diameter of the opposing rotating disk by attaching an add-on part having a shape in which the ridge portion extends outwardly beyond the outer diameter of the opposing rotating disk.

5. 5. The vacuum pump according to claim 4, wherein the inflow guide portion is shaped such that the retrofit part is further extended toward the intake port in the axial direction.

6. The rotating disks and the fixed disks are arranged in a plurality of stages, 6. The vacuum pump according to claim 1, wherein the inflow guide portion is provided on a stage of the fixed disks that is closest to the intake port side among the plurality of stages of the fixed disks.

7. 6. The vacuum pump according to claim 1, wherein the inflow guide portion and the opposing fixed part are in contact with each other, with no gap therebetween.

8. A fixed disk used in a vacuum pump that exhausts gas by interaction with a rotating disk, the fixed disk being characterized in that it is arranged axially opposite the rotating disk, has a spiral groove having valleys and peaks on the opposing surface, and is provided with an inflow guide portion having a shape in which the peaks are integrally extended outward beyond the outer diameter of the opposing rotating disk.

9. A retrofit component used in a vacuum pump that exhausts gas by interaction with a rotating disk, the retrofit component being attached to a fixed disk that is disposed axially opposite the rotating disk and has a spiral groove having a valley portion and a peak portion on an opposing surface thereof, the retrofit component comprising: A retrofit part, characterized in that the ridge portion has a shape that extends outward beyond the outer diameter of the opposing rotating disk.

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