Vacuum pump, fixed disk, and retrofitted component

Abstract

[Problem] To provide a vacuum pump in which exhaust speed is improved while back pressure dependency performance is maintained, and a fixed disk and a retrofitted component used in the vacuum pump. [Solution] A vacuum pump according to the present embodiment is a Siegbahn element. In a fixed disk which is disposed opposing a rotary disk and in which a spiral groove having a valley part and a crest part is provided in an opposing surface, an inflow guide part for guiding inflow of gas is provided in a gas inflow port of the spiral groove. The inflow guide part has a shape in which the fixed disk crest part is extended farther outward than the outer diameter of the opposing rotary disk.

Description

Vacuum pumps, fixed discs and retrofit parts

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

[0002] A vacuum pump has a casing that forms an exterior body with an intake port and an exhaust port, and the casing houses a structure that enables the vacuum pump to perform its exhaust function. This structure is composed of a rotating part (rotor) that is rotatably held and a fixed part (stator) that is fixed to the casing. When this rotating part is rotated at high speed by a motor, the interaction between the rotor blades (rotating disk) and the stator blades (fixed disk) draws in gas through the intake port and exhausts it through the exhaust port.

[0003] Among vacuum pumps, a type known as a Sigburn molecular pump, which has a Sigburn configuration, is commonly used. This Sigburn vacuum pump includes a rotating disk and a fixed disk positioned axially away from the rotating disk with a clearance. A spiral groove (spiral flow path) is engraved on the surface of either the rotating disk or the fixed disk facing the clearance. The rotating disk imparts momentum in the tangential direction (i.e., the rotational direction) of the rotating disk to gas molecules that have diffused into the spiral groove, thereby providing preferential directionality from the intake port toward the exhaust port. Various types of Sigburn molecular pumps exist, including those with multiple stages of rotating-disk and fixed-disk pairs and those combined with fixed-vane and rotating-vane pairs (known as 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 port side has a portion that overlaps in the axial direction with the inlet of the spiral groove on the exhaust port side, thereby producing the effect of making it less likely that the dominant momentum in the exhaust direction will be lost.

[0004] JP 2015-102076 A

[0005] Generally, back pressure dependency and pumping speed can be cited as factors that indicate the pumping performance of a vacuum pump. Figure 14 is a graph showing the relationship between back pressure dependency, which is an index of pumping performance, and the suction pressure and back pressure at the pumping speed. Here, good (high) back pressure dependency 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 dependency is said to be poor (low). Vacuum pump users require a vacuum pump that can maintain a stable, constant suction pressure (good back pressure dependency), since 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. Using the Sigburn element described above is expected to improve back-pressure-dependent performance. On the other hand, to further improve back-pressure-dependent performance, measures such as increasing the number of Sigburn stages, lengthening the length, or shallowing the flow path depth are required. However, taking such measures increases the Sigburn inlet pressure, which in turn worsens the gas conductance and reduces the pumping speed. In other words, there is a trade-off between back-pressure-dependent performance and pumping speed.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a vacuum pump that improves pumping speed while maintaining back pressure dependent performance, as well as a fixed disk and retrofit parts for use in the vacuum pump.

[0008] According to a first aspect of the present invention, there is provided a vacuum pump comprising a casing, a rotor shaft disposed within the casing, a rotating disk rotatable together with the rotor shaft, and a fixed disk disposed opposite the rotating disk in the axial direction of the rotor shaft and having spiral grooves with valleys and peaks arranged on an opposing surface thereof, the vacuum pump evacuating gas through interaction between the rotating disk and the fixed disk, the vacuum pump being characterized in that an inflow guide portion for guiding the inflow of the gas is provided at a gas inlet of the spiral groove. According to a second aspect of the present invention, there is provided a vacuum pump according to the first aspect, characterized in that the inflow guide portion has a shape in which the peaks extend integrally outward beyond the outer diameter of the opposing rotating disk. According to a third aspect of the present invention, there is provided a vacuum pump according to the second aspect, characterized in that the inflow guide portion has a shape in which the peaks further extend integrally toward the intake port in the axial direction. A fourth aspect of the present invention provides the vacuum pump according to claim 1, characterized in that the inflow guide portion is configured to extend beyond the outer diameter of the opposing rotating disk by attaching an add-on component having a shape that extends the ridge portion beyond the outer diameter of the opposing rotating disk.A fifth aspect of the present invention provides the vacuum pump according to claim 4, characterized in that the inflow guide portion is configured by extending the add-on component further toward the intake port in the axial direction.A sixth aspect of the present invention provides the vacuum pump according to 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 on the stage of the fixed disks closest to the intake port.A seventh aspect of the present invention provides the vacuum pump according to any one of claims 1 to 5, characterized in that the inflow guide portion and the opposing fixed component are in contact with each other, with no gap between them. The invention described in claim 8 provides a fixed disk used in a vacuum pump that exhausts gas by interacting 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 has a shape in which the peaks are integrally extended 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 interacting with a rotating disk, and which is attached to a fixed disk that is arranged axially opposite the rotating disk and has a spiral groove with valleys and peaks on the opposing surface, and which is characterized in that the peaks extend outward beyond the outer diameter of the opposing rotating disk.

[0009] In the present invention, a Sigburn type pumping element can be used in a vacuum pump to increase pumping speed while maintaining back pressure dependent performance.

[0010] FIG. 1 is a diagram showing a schematic configuration example of a turbomolecular pump according to an embodiment of the present invention. FIG. 2 is a diagram showing a circuit diagram of an amplifier circuit used in an embodiment of the present invention. FIG. 3 is a time chart showing control when a detected value is greater than a current command value in an embodiment of the present invention. FIG. 4 is a time chart showing control when a detected value is smaller than a current command value in an embodiment of the present invention. FIG. 5 is a diagram showing a schematic configuration example of a conventional Sigburn molecular pump. FIG. 6 is an enlarged view for explaining a conventional fixed disk. FIG. 7 is a diagram showing a schematic configuration example of a conventional composite turbomolecular pump. FIG. 8 is a perspective view for explaining peaks forming spiral grooves provided on a fixed disk which is a Sigburn element in a conventional composite turbomolecular pump. FIG. 9 is a diagram showing a schematic configuration example of a composite turbomolecular pump according to a first embodiment of the present invention. FIG. 10 is a perspective view for explaining peaks forming spiral grooves provided on a fixed disk which is a Sigburn element in a composite turbomolecular pump according to the first embodiment of the present invention. FIG. 11 is a diagram showing a schematic configuration example of a composite turbomolecular pump according to a second embodiment of the present invention. FIG. 12 is a diagram showing a schematic configuration example of a composite turbomolecular pump according to a third embodiment of the present invention. FIG. 13 is a perspective view for explaining peaks forming spiral grooves provided on a fixed disk which is a Sigburn element in a composite turbomolecular pump according to the third embodiment of the present invention. 1 is a graph showing the relationship between back pressure dependent performance, which is an index of exhaust performance, and intake pressure and back pressure at exhaust speed.

[0011] (1) Overview of the embodiment The vacuum pump according to this embodiment is a Sigbahn element, and includes a fixed disk disposed opposite a rotating disk and having spiral grooves with peaks and valleys 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 that extends beyond the outer diameter of the opposing rotating disk from the peaks of the fixed 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 rotor and fixed vanes with a Sigbahn vacuum pump, or may be a vacuum pump that is a Sigbahn vacuum pump only. Therefore, the basic configurations of the turbomolecular pump and the Sigbahn vacuum pump will be described with reference to Figures 1 to 6.

[0013] As an example, a longitudinal cross-sectional view of the turbomolecular pump 100 described above 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 has a plurality of rotor blades 102 (102a, 102b, 102c, ...) formed radially and in multiple stages around its periphery, which are turbine blades for sucking and exhausting gas. A rotor shaft 113 is attached to the center of the rotor 103. The rotor shaft 113 is levitated and supported in the air and its position is controlled by, for example, a five-axis controlled magnetic bearing. The rotor 103 is generally made of a metal such as aluminum 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 upper radial electromagnet 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors having conductive windings, and detect the position of the rotor shaft 113 based on changes in the inductance of the conductive windings, which change depending on 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 electromagnets 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. The lower radial electromagnets 105 and the lower radial sensors 108 are arranged in the same manner as the upper radial electromagnets 104 and the upper radial sensors 107, and adjust the radial position of the lower side of the rotor shaft 113 in the same manner as the radial position of the upper side.

[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 highly magnetic permeable material such as iron. An axial sensor 109 is provided to detect the axial displacement of rotor shaft 113, and an axial position signal is sent to control device 200.

[0018] In the control device 200, a compensation circuit having, for example, a PID adjustment function generates excitation control command signals 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 each 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 forces that the axial electromagnets 106A and 106B exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in space without contact. The amplifier circuit 150 that controls the excitation of the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

[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. Motor 121 also incorporates a rotational speed sensor (not shown), such as a Hall element, resolver, or encoder, and the rotational speed of rotor shaft 113 is detected by the detection signal of this rotational speed sensor.

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

[0022] A plurality of 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 an angle of a predetermined degree 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 any of these metals as an ingredient.

[0023] Similarly, the fixed blades 123 are formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged in a staggered manner with the 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 by being inserted between a plurality of stacked fixed blade spacers 125 (125a, 125b, 125c, ...).

[0024] The fixed vane spacer 125 is a ring-shaped member made of a metal such as aluminum, iron, stainless steel, or copper, or an alloy containing any of these metals. An outer cylinder 127 is fixed to the outer periphery of the fixed vane spacer 125 with a small gap between them. A base 129 is disposed at the bottom of the outer cylinder 127. An exhaust port 133 is formed in the base 129 and communicates with the outside. Exhaust gas that enters the intake port 101 from the chamber (vacuum chamber) and is transferred to the base 129 is sent to the exhaust port 133.

[0025] Furthermore, depending on the application of the turbomolecular pump 100, a threaded spacer 131 is disposed between the lower portion of the fixed vane 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 any of these metals, and has multiple spiral thread grooves 131a engraved on its inner circumferential surface. The spiral direction of the thread grooves 131a corresponds to the direction in which exhaust gas molecules are transported toward the exhaust port 133 when they move in the rotational direction of the rotor 103. A cylindrical portion 102d hangs down from the lowest portion of the rotor 103, adjacent to the rotor vanes 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 adjacent to the inner circumferential surface of the threaded spacer 131 with a predetermined gap therebetween. The exhaust gas transferred to the thread groove 131 a by the rotor 102 and the fixed blade 123 is sent to the base portion 129 while being guided by the thread groove 131 a.

[0026] The base portion 129 is a disk-shaped member that forms the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. The base portion 129 not only physically holds the turbomolecular pump 100, but also functions as a heat conduction path, so it is desirable to use a metal that is rigid and has high thermal conductivity, such as iron, aluminum, or copper.

[0027] In this configuration, when the rotor 102 is rotated together with the rotor shaft 113 by the motor 121, the rotor 102 and the stator 123 act to draw exhaust gas from the chamber through the intake port 101. The rotational speed of the rotor 102 is typically 20,000 rpm to 90,000 rpm, and the peripheral speed at the tip of the rotor 102 reaches 200 m / s to 400 m / s. The exhaust gas drawn in through the intake port 101 passes between the rotor 102 and the stator 123 and is transported to the base 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, but this heat is transferred to the stator 123 side by radiation or conduction through gas molecules in the exhaust gas.

[0028] The stator spacers 125 are joined together at their outer peripheries and transmit to the outside heat received by the stator 123 from the rotor 102 and frictional heat generated when exhaust gas comes into contact with the stator 123 .

[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 circumferential surface of the threaded spacer 131. However, conversely, there are also cases where a thread groove is formed on the outer circumferential surface of the cylindrical portion 102d, and a spacer having a cylindrical inner circumferential surface is disposed around it.

[0030] Depending on the application of the turbomolecular pump 100, the electrical equipment section may be covered by a stator column 122 to prevent the gas sucked in from the intake port 101 from entering the electrical equipment section, which is composed of the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, the lower radial electromagnet 105, the lower radial sensor 108, the axial electromagnets 106A and 106B, the axial sensor 109, etc., and the interior of this stator column 122 may be kept at a predetermined pressure by purge gas.

[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 have been individually adjusted and identified for the model. To store these control parameters, the turbomolecular pump 100 is provided with an electronic circuit unit 141 within its body. The electronic circuit unit 141 is composed of a semiconductor memory such as an EEPROM, electronic components such as semiconductor devices for accessing the memory, and a substrate 143 for mounting these components. The electronic circuit unit 141 is housed below a rotational speed sensor (not shown) near the center of a base unit 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 a chamber have the property of solidifying when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the pressure of the exhaust gas is lowest at the inlet 101 and highest at the outlet 133. If the pressure of the process gas exceeds a predetermined value or the temperature falls below a predetermined value while the process gas is being transferred from the inlet 101 to the outlet 133, the process gas solidifies 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 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 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. The aforementioned product is prone to solidification and adhesion in high-pressure areas near the exhaust port 133 and the threaded spacer 131.

[0035] Therefore, in order to solve this problem, conventionally, a heater (not shown) or a circular water-cooled pipe 149 is wound around the outer periphery of the base portion 129 or the like, and a temperature sensor (not shown, for example, a thermistor) is embedded in the base portion 129, and heating by the heater and cooling by the water-cooled pipe 149 are controlled based on a signal from this temperature sensor so as to maintain the temperature of the base portion 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS; TMS; Temperature Management System).

[0036] Next, an amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B in the turbomolecular pump 100 will be described. 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 and the like is connected to the positive electrode 171a of the power supply 171 via a transistor 161, and the other end is connected to the negative electrode 171b of the power supply 171 via a current detection circuit 181 and a transistor 162. The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between the source and drain.

[0038] At this time, the transistor 161 has a diode cathode terminal 161a connected to the positive electrode 171a and an anode terminal 161b connected to one end of the electromagnet winding 151. The transistor 162 has a diode cathode terminal 162a connected to the current detection circuit 181 and an anode terminal 162b connected to the negative electrode 171b.

[0039] Meanwhile, the current regenerating 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 regenerating 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 detecting circuit 181. The current detecting circuit 181 is configured, for example, by 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 controlled in five axes and there are a total of ten electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the ten amplifier circuits 150 are connected in parallel to the power supply 171.

[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 in the figure of the control device 200, and this amplifier control circuit 191 is configured to switch the transistors 161 and 162 on / off.

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

[0043] It is necessary to control the position of the rotor 103 at high speed and with strong force when, for example, the rotor 103 passes through a resonance point during acceleration of its rotational speed or when a disturbance occurs during constant-speed operation. For this reason, a voltage of, for example, about 50 V is used as the power supply 171 so that a rapid increase (or decrease) in the current flowing through the electromagnet winding 151 can be achieved. In addition, a capacitor (not shown) is usually connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 to stabilize the power supply 171.

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

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

[0046] That is, when the detected current value is smaller than the current command value, both transistors 161 and 162 are turned on for a time period corresponding to a 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, if the detected current value is greater than the current command value, both transistors 161 and 162 are turned off for a time period corresponding to pulse width time Tp2 only once during the control cycle Ts, as shown in Fig. 4. Therefore, the electromagnet current iL during this period decreases toward a current value iLmin (not shown) that can be regenerated from the negative electrode 171b to the positive electrode 171a via 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. Arrows indicate the flow of gas molecules.

[0050] 6 is a diagram for explaining the fixed disk 501 disposed in the 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. Arrows inside the fixed disk 501 indicate the flow of gas molecules, and 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 molecular pump 1000 has a substantially cylindrical shape and, together with a base 700 provided at the bottom (exhaust port 60 side) of the casing 201, constitutes the housing of the Sigburn molecular pump 1000. A gas transfer mechanism, which is a structure that enables the Sigburn molecular pump 1000 to perform its exhaust function, is housed inside this housing. This gas transfer mechanism is broadly composed of a rotating part that is supported rotatably and a fixed part that is fixed to the housing. An intake port 401 for introducing gas into the Sigburn molecular pump 1000 is formed at the end of the casing 201. A flange portion 50 that protrudes outward is formed on the end face of the casing 201 on the intake port 401 side.

[0052] The base 700 is also formed with an exhaust port 60 for exhausting gas from the Sigbahn molecular pump 1000. The rotating part is composed of a shaft 701, which is a rotating axis, a rotor 801 arranged on the 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. 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 midway in the axial direction of the shaft 701. Furthermore, radial magnetic bearing devices 301, 310 for supporting the shaft 701 in a non-contact manner in the radial direction (diameter direction) are provided on the intake port 401 side and the exhaust port 60 side of the motor unit 202 of the shaft 701, and an axial magnetic bearing device 400 for supporting the shaft 701 in a non-contact manner in the axial direction is provided at the lower end of the shaft 701.

[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 the fixed disks 501 are engraved with spiral groove portions 530, which are spiral grooves composed of fixed disk valley portions 510 and fixed disk crest portions 520. Note that while the configuration in which the spiral grooves (spiral groove portions 530) are engraved on the fixed disks 501 has been described here, it is also possible to have the spiral grooves engraved on the rotating disk 901. In other words, it is sufficient that the spiral groove flow path formed by the spiral grooves is engraved on the gap-facing surface of at least one of the fixed disks 501 and the rotating disk 901.

[0055] Each fixed disk 501 is composed of a disk-shaped disk 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 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 components and stator components can be provided as needed to satisfy the evacuation performance required of the vacuum pump. The Sigburn molecular pump 1000 configured in this manner performs evacuation processing within a vacuum chamber (not shown) disposed in the Sigburn 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 illustrating a fixed disk crest 520 that forms 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. As is clear from FIGS. 7 and 8, in the compound turbomolecular pump 500, the fixed disk crest 520 that forms the spiral groove engraved on the uppermost fixed disk 501, which serves as the inlet of the Sigburn exhaust element, has the same outer diameter 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 that forms the uppermost spiral groove, which serves as the inlet of the Sigburn exhaust element, did not protrude beyond the outer diameter of the corresponding rotating disk 901.

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

[0058] As is clear from these figures, the fixed disk ridges 520 forming the spiral grooves on the fixed disk 501 are provided with inflow guide portions A that protrude beyond the outer diameter of the corresponding rotating disk 901. That is, the fixed disk ridges 520 are shaped to protrude beyond the outer diameter of the corresponding rotating disk 901. By providing these inflow guide portions A, the pressure downstream of the fixed disk ridges 520 (the back (opposite) side where the gas hits the inflow guide portions A) decreases, resulting in the gas flowing upstream of the fixed disk ridges 520 being sucked in. That is, the pressure increases where the gas collides with the inflow guide portions A, but decreases on the opposite side (downstream), causing the gas stagnating upstream to flow in as if being sucked in. Therefore, providing these inflow guide portions A can induce a vertical gas flow, which was previously lacking. Therefore, providing these inflow guide portions A improves the pumping speed while maintaining backpressure-dependent performance, resulting in improved pumping performance. The inflow guide portion A may be formed integrally with the fixed disk mountain portion 520, or may be formed by attaching a separate part afterward. The material may be the same as that of the fixed disk mountain portion 520, or may be a different material. The afterward part may be attached by fixing with screws, welding, or 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, too, the fixed disk ridges 520 forming spiral grooves on the fixed disk 501 are provided with inflow guide portions A that protrude beyond the outer diameter of the corresponding rotating disk 901. These inflow guide portions A are in contact with the opposing fixed-side component, with no gap between them. In other words, the inflow guide portions A protrude further than in the first embodiment.

[0060] According to the second embodiment, the inflow guide portion A and the opposing fixed component are in contact with each other, with no gap between them. This lack of a gap between them reduces the amount of gas flowing toward the rear side of the inflow guide portion A (the side opposite the surface the gas contacts), further reducing pressure on the rear side. This further promotes gas suction (introduction). This allows stagnant gas to be exhausted more efficiently, contributing to improved exhaust speed. In the second embodiment, as in the first embodiment, the inflow guide portion A may be integrally formed with the fixed disk ridge portion 520, or may be formed by attaching a separate component.

[0061] FIG. 12 is a diagram showing a schematic configuration example of a compound turbomolecular pump according to a third embodiment of the present invention, and FIG. 13 is a perspective view illustrating a fixed disk crest 520 forming a spiral groove on a fixed disk, which is a Sigbahn element of the compound turbomolecular pump according to the third embodiment of the present invention. In this third embodiment, the inflow guide portion A extends not only in the outer diameter direction but also integrally toward the axial intake port side. When extending axially toward the intake port side, it is desirable to keep the gap with the opposing rotating disk 901 as narrow as possible. A gap of approximately 1.5 mm, for example, that prevents contact between the rotating disk 901 and the pump during rotation is desirable. According to this third embodiment, the area of ​​the inflow guide portion A (the area on which gas contacts) is larger than that of the first embodiment, and less gas flows toward the back side (the side opposite the surface on which gas contacts). This further promotes gas suction.

[0062] In the third embodiment, as in the first and second embodiments, the inflow guide portion A may be integrally formed with the fixed disk crest portion 520, or may be formed by attaching a separate component. Also, as in the second embodiment, the inflow guide portion A may be in contact with the opposing fixed component, with no gap between them.

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

[0064] The embodiments and modifications of the present invention may be combined 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 also covers such modifications.

[0066] 100 Turbo molecular pump (vacuum pump) 101 Intake port 102 Rotor 102d Cylindrical portion 103 Rotor 113 Rotor shaft 122 Stator column 123 Fixed blade 125 Fixed blade spacer 127 Outer cylinder 129 Base portion 131 Threaded spacer 131a Thread groove 133 Exhaust port 200 Control device 500 Compound turbo molecular pump 501 Fixed disk 510 Fixed disk valley portion 520 Fixed disk crest portion 530 Spiral groove portion 901 Rotating disk 1000 Sigburn type molecular pump

Claims

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

2. A vacuum pump according to claim 1, characterized in that said inflow guide portion is shaped such that said ridge portion extends integrally outward beyond the outer diameter of the opposing rotating disk.

3. A vacuum pump according to claim 2, characterized in that said inflow guide portion is shaped such that said ridge portion is further integrally extended toward the intake port side in the axial direction.

4. The vacuum pump described in claim 1, characterized in that the inflow guide portion is configured to have a shape that extends outward beyond the outer diameter of the opposing rotating disk by attaching an add-on part having a shape that extends outward beyond the outer diameter of the opposing rotating disk.

5. A vacuum pump according to claim 4, characterized in that said inlet guide portion is shaped such that said retrofit part is further extended towards the intake port side in the axial direction.

6. A vacuum pump as claimed 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.

7. A vacuum pump as claimed in any one of claims 1 to 5, characterized in that the inflow guide portion and the opposing fixed part are in contact with each other, with no gap between them.

8. A fixed disk used in a vacuum pump which exhausts gas by interaction with a rotating disk, the fixed disk being arranged axially opposite the rotating disk, the fixed disk having a spiral groove with valleys and peaks on the opposing surface, and 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 part used in a vacuum pump that exhausts gas by interaction with a rotating disk, the retrofit part being attached to a fixed disk that is arranged axially opposite the rotating disk and has a spiral groove with valleys and peaks on the opposing surface, the peaks having a shape that extends outward beyond the outer diameter of the opposing rotating disk.

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