Vacuum pump and stator disc

Abstract

To provide a vacuum pump including a plurality of stages of Siegbahn exhaust mechanisms, and a stator disc of each of the Siegbahn exhaust mechanisms used in the vacuum pump enabling an exhaust process to be efficiently performed by connecting the plurality of stages of Siegbahn exhaust mechanisms in parallel without providing a communication port in a rotor disc In the vacuum pump including a Siegbahn exhaust mechanism according to an embodiment, a partition wall divides a flow channel to the Siegbahn exhaust mechanism into a plurality of channel systems, and gas divided by the partition wall is sent in parallel to the plurality of stages of exhaust mechanisms stacked on each other. This gas flows as indicated by the arrows in Fig. 6. In this manner, the Siegbahn exhaust mechanisms can be connected in parallel so that an exhaust speed can be improved without providing the communication port in the rotor disc.

Description

VACUUM PUMP AND STATOR DISC

[0001] The present invention relates to a vacuum pump and a stator disc used in the vacuum pump. Specifically, the present invention relates to a vacuum pump including radial flow type exhaust mechanisms (Siegbahn exhaust mechanisms) and a stator disc used in each of the radial flow type exhaust mechanisms, the vacuum pump being improved in exhaust efficiency by connecting a plurality of radial flow type exhaust mechanisms in parallel.[Background Art]

[0002] Vacuum pumps include a casing that forms a housing having an inlet port and an outlet port, and a structure that causes the corresponding vacuum pump to fulfill an exhaust function is housed inside the casing. The structure that fulfills the exhaust function includes a rotor portion fixed to a rotating shaft which is rotated at high speed and a stator portion fixed to the casing, when being roughly divided.Also, a motor is provided for rotating the rotating shaft at high speed, and when the rotating shaft is rotated at high speed by an operation of the motor, rotor blades (rotor discs) fixed to the rotating shaft are rotated together with the rotating shaft, and gas is sucked from an inlet port by interactions with stator blades (stator discs), and the gas is discharged from the outlet port.

[0003] The vacuum pumps are known to be of a type in which an exhaust mechanism (Y in Fig. 19) referred to as a vertical thread (Holweck type) is provided at a lower portion (an outlet port side) of an exhaust mechanism including a plurality of stator blades and a plurality of rotor blades illustrated in Fig. 19, and a type in which an exhaust mechanism referred to as a horizontal thread (hereinafter referred to as Siegbahn represented by X in Fig. 20) is provided at a lower portion (an outlet port side) of an exhaust mechanism including a plurality of stator blades and a plurality of rotor blades illustrated in Fig. 20.The Siegbahn vacuum pump includes a rotor disc (a rotor disk) and a stator disc installed to be separated from the rotor disc with clearance therebetween in an axial direction, and a spiral groove (radial thread groove) flow channel is engraved in a clearance-opposed front surface of at least one of the rotor disc or the stator disc. The vacuum pump exhausts gas by imparting, from the rotor disc,momentum to gas molecules diffused to flow into the spiral groove flow channel in a tangential direction of the rotor disc (that is, a tangential direction of a rotation direction of the rotor disc), thereby causing the spiral groove to generate favorable directionality from the inlet port to the outlet port.This Siegbahn vacuum pump can have a long flow channel for exhaust gas if the flow channel is formed in multiple stages, thus being excellent in backpressure performance. Also, because of the horizontal thread, the Siegbahn vacuum pump is characterized in that a height of the vacuum pump itself can be reduced as compared with the vertical thread.The type of vacuum pump including the exhaust mechanism referred to as the vertical thread is characterized in that the vacuum pump is simple in structure and excellent in stability. Also, because of the vertical thread, the vacuum pump is characterized in that a circumferential speed of the exhaust gas is constant.

[0004] Fig. 17 is a view for illustrating a conventional Siegbahn vacuum pump 1000, and illustrates an example of a schematic configuration of the conventional Siegbahn vacuum pump 1000. Arrows therein indicate flow of gas molecules.Fig. 18 is a view for illustrating a stator disc 5000 installed in the conventional Siegbahn vacuum pump 1000, and a cross-sectional view of the stator disc 5000 in a case of being viewed from an inlet port 101 side.The arrows in the stator disc 5000 indicate flow of gas molecules, and the arrow outside the stator disc 5000 indicates a rotation direction of a rotor disc (not illustrated).As is apparent from these figures, the Siegbahn vacuum pump imparts directionality of movement in a radial direction to gas. Therefore, a vacuum pump is proposed in which a plurality of stages of Siegbahn exhaust mechanisms are connected in parallel such that an exhaust process is performed in multiple stages at the same time to efficiently perform exhausting.[Patent Literature]

[0005] [PTL 1] Japanese Patent No. 4865321

[0006] In the invention described in PTL 1, a plurality of stages of Siegbahn exhaust mechanisms are arranged in parallel in an axial direction, and all suctionportions in each stage communicate with each other, so that gas is simultaneously exhausted in all the stages.The flow of gas in this conventional art is as represented by the arrows in Fig. 21. According to this structure, an exhaust speed in the Siegbahn exhaust mechanism can be increased by several times as high as possible since the exhaust can be simultaneously performed by the multiple stages of Siegbahn exhaust mechanisms.[Summary of Invention][Technical Problem]

[0007] Incidentally, in the invention described in PTL 1, a communication port needs to be provided in a rotor disc of the Siegbahn exhaust mechanism, and it is technically difficult to perform a machining process on the communication port. Also, the communication port provided in the rotor disc that is rotated at high speed unavoidably increases stress near the communication port, resulting in a problem in that it is not possible to increase revolutions per minute of the rotor disc.In this respect, an object of the present invention is to provide a vacuum pump including a plurality of stages of Siegbahn exhaust mechanisms, and a stator disc of each of the Siegbahn exhaust mechanisms used in the vacuum pump enabling an exhaust process to be efficiently performed by connecting the plurality of stages of Siegbahn exhaust mechanisms in parallel without providing a communication port in a rotor disc.[Solution to Problem]

[0008] The present invention provides a vacuum pump including an inlet port through which gas is sucked; an outlet port through which the gas sucked from the inlet port is exhausted; rotor discs held rotatably; stator discs installed opposite to the rotor discs, respectively; and a spiral protrusion provided on at least one of opposed surfaces of each of the rotor discs and each of the stator discs. From an outer side toward an inner side on a surface of each of the stator discs on the inlet port side, and from the inner side toward the outer side on a surface of each of the stator discs on the outlet port side, a plurality of stages of radial flow type exhaust mechanisms that exhaust gas in a radial direction are stacked. The vacuum pumpfurther includes a partition wall that divides a flow channel of the gas from the inlet port to the exhaust mechanisms into a plurality of channel systems, and the gas divided by the partition wall is sent in parallel to the plurality of stages of exhaust mechanisms stacked on each other.The vacuum pump may further include inflow ports to the exhaust mechanisms which are installed on surfaces of the stator discs on the inlet port side; and outflow ports from the exhaust mechanisms which are installed on surfaces of the stator discs on the outlet port side. The inflow port and the outflow port may have respective installation positions which are in phase with each other.The vacuum pump may further include inflow ports to the exhaust mechanisms which are installed on surfaces of the stator discs on the inlet port side. The inflow ports to the plurality of stages of exhaust mechanisms stacked on each other may have respective installation positions which are in phase with each other.The vacuum pump may further include outflow ports from the exhaust mechanisms which are installed on surfaces of the stator discs on the outlet port side. The outflow ports from the plurality of stages of exhaust mechanisms stacked on each other may have respective installation positions which are in phase with each other.The vacuum pump may further include inflow ports to the exhaust mechanisms which are installed on surfaces of the stator discs on the inlet port side. A starting position of each of the inflow ports may coincide with a back surface of the spiral protrusion in a rotation direction of the rotor discs.The vacuum pump may further include outflow ports from the exhaust mechanisms which are installed on surfaces of the stator discs on the outlet port side. An end position of each of the outflow ports may coincide with a front surface of the spiral protrusion in a rotation direction of the rotor discs.Each of the stator discs may have a projecting portion facing an outer circumferential surface each of the rotor discs.The partition wall may be installed at a predetermined angle with respect to the radial direction of the rotor discs.An additional exhaust mechanism having protrusions may be provided on the outlet port side of the plurality of stages of exhaust mechanisms stacked on each other, the number of protrusions preferably being a multiple of the number of the plurality of exhaust mechanisms.The present invention also provides a stator disc that is used in a radial flow type exhaust mechanism that exhausts gas in a radial direction and is installed opposite to a rotor disc held rotatably, the stator disc including: a spiral protrusion on an opposed surface of the stator disc opposite to the rotor disc, and from an outer side toward an inner side on a surface of the stator disc on an inlet port side, and from the inner side toward the outer side on a surface of the stator disc on an outlet port side, a partition wall that divides a flow channel of gas into a plurality of channel systems to exhaust gas in the radial direction.[Advantageous Effects of Invention]

[0009] According to the present invention, in the vacuum pump including the Siegbahn exhaust mechanisms, the Siegbahn exhaust mechanisms can be installed in a plurality of stages in parallel without providing a communication port in the rotor discs. Therefore, an exhaust speed can be increased without a risk of reliability.[Brief Description of Drawings]

[0010] Fig. 1 is a diagram illustrating a schematic configuration of a turbo-molecular pump according to an embodiment of the present invention.Fig. 2 is a diagram illustrating a circuit diagram of an amplifier circuit used in the embodiment of the present invention.Fig. 3 is a time chart illustrating control in a case where a detected value is smaller than a current command value in the embodiment of the present invention.Fig. 4 is a time chart illustrating control in a case where the detected value is larger than the current command value in the embodiment of the present invention.Fig. 5 is a view illustrating a schematic structural example of a Siegbahn vacuum pump according to an embodiment of the present invention.Fig. 6 is a view for illustrating an exhaust flow channel of a Siegbahn exhaust mechanism in the embodiment of the present invention.Fig. 7 is a cross-sectional view of a vacuum pump including a Siegbahn exhaust mechanism according to a first embodiment of the present invention.Fig. 8 is a view illustrating a stator disc (in a state in which upper and lower stages are coupled) in the first embodiment of the present invention.Fig. 9 is a view illustrating the stator disc (the lower stage of a single disc) in the first embodiment of the present invention.Fig. 10 is a cross-sectional view of a vacuum pump including a Siegbahn exhaust mechanism according to a second embodiment of the present invention.Fig. 11 is a view illustrating a stator disc (in a state in which upper and lower stages are coupled) in the second embodiment of the present invention (a ratio of an inflow port to an outflow port is 5:5).Fig. 12 is a view illustrating the stator disc (in a state in which the upper and lower stages are coupled) in the second embodiment of the present invention (a ratio of the inflow port to the outflow port is 7:3).Fig. 13 is a view illustrating a state in which the stator discs in the second embodiment of the present invention are stacked in three stages (a ratio of the inflow port to the outflow port is 7:3).Fig. 14 is a view illustrating the stator disc (the lower stage of the single disc) in the second embodiment of the present invention.Fig. 15 is a view for illustrating a relationship between the inflow and outflow ports and stator disc ridge portions in the embodiments.Fig. 16 is a view for illustrating an arrangement angle of partition walls in the embodiments.Fig. 17 is a cross-sectional view for illustrating a vacuum pump of a type including a conventional Siegbahn vacuum pump.Fig. 18 is a view for illustrating a stator disc disposed in the conventional Siegbahn vacuum pump.Fig. 19 is a cross-sectional view for illustrating a vacuum pump of a type including a conventional vertical thread exhaust mechanism (a Holweck exhaust mechanism).Fig. 20 is a cross-sectional view for illustrating a vacuum pump of a type including a conventional horizontal thread exhaust mechanism (a Siegbahn exhaust mechanism).Fig. 21 is a view for illustrating an exhaust flow channel in a vacuum pump in which conventional Siegbahn exhaust mechanisms are arranged in parallel.[Description of Embodiments]

[0011] (i) Overview of EmbodimentsIn a vacuum pump including Siegbahn exhaust mechanisms according to the present embodiment, a partition wall divides a flow channel to the Siegbahn exhaust mechanisms into a plurality of channel systems, and gas divided by the partition wall is sent in parallel to the plurality of stages of exhaust mechanisms stacked on each other. This gas flows as indicated by the arrows in Fig. 6.In this manner, the Siegbahn exhaust mechanisms can be connected in parallel so that an exhaust speed can be improved without providing a communication port in a rotor disc.

[0012] (ii) Details of EmbodimentsPreferred embodiments of the present invention will now be described in detail with reference to Figs. 1 to 16.In the present embodiment, the vacuum pump to which the present invention is applied is a vacuum pump (hereinafter referred to as a Siegbahn vacuum pump) including Siegbahn exhaust mechanisms in thread groove exhaust portions.First, a configuration of a turbo-molecular pump which is a general vacuum pump will be described, and next, this Siegbahn vacuum pump will be described.In the present embodiment, a direction perpendicular to a diametrical direction of the rotor disc is defined as an axial direction, and a horizontal direction is defined as a radial direction.Also, in the following description, an inlet port side of one stator disc is referred to as a Siegbahn vacuum pump upstream region, and an outlet port side thereof is referred to as a Siegbahn vacuum pump downstream region.

[0013] A vertical cross-sectional view of this turbo-molecular pump 100 is illustrated in Fig. 1. In Fig. 1, the turbo-molecular pump 100 has an inlet port 101formed at an upper end of an outer cylinder 127 having a cylindrical shape. Inside the outer cylinder 127, a rotating body 103 including a plurality of rotor blades 102 (102a, 102b, 102c, ...) formed radially in multiple layers on a circumferential portion thereof is provided, the rotor blades being turbine blades for sucking and exhausting gas. A rotor shaft 113 is attached to the center of the rotating body 103, and the rotor shaft 113 is supported in a levitative manner and position-controlled in the air by, for example, a five-axis controlled magnetic bearing. The rotating body 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0014] Upper radial electromagnets 104 include four respective electromagnets that are arranged in pairs on an X-axis and a Y-axis. Four upper radial sensors 107 are provided adjacent to the upper radial electromagnets 104 and corresponding to the upper radial electromagnets 104, respectively. As the upper radial sensor 107, for example, an inductance sensor or an eddy-current sensor having a conductive coil is used, and the position of the rotor shaft 113 is detected on the basis of a change in inductance of the conductive coil which is changed depending on the position of the rotor shaft 113. Each of the upper radial sensors 107 is configured to detect a radial displacement of the rotor shaft 113, that is, the rotating body 103 fixed thereto, and send a detection result to a control device 200.

[0015] In this control device 200, for example, a compensation circuit having a PID adjusting function generates an excitation control command signal for the upper radial electromagnet 104 on the basis of a position signal detected by the upper radial sensor 107, and an amplifier circuit 150 (to be described below) illustrated in Fig. 2 performs excitation control on the upper radial electromagnet 104 on the basis of this excitation control command signal, thereby adjusting a radial position of the rotor shaft 113 on an upper side.

[0016] The rotor shaft 113 is made of a high magnetic permeability material (iron, stainless steel, or the like), and is formed to be attracted by a magnetic force of the upper radial electromagnet 104. Such adjustments are performed independently in an X-axis direction and in a Y-axis direction, respectively. Also, lower radial electromagnets 105 and lower radial sensors 108 are arranged in the samemanner as the upper radial electromagnets 104 and the upper radial sensors 107, and adjust a radial position of the rotor shaft 113 on a lower side in the same manner as the radial position thereof on the upper side.

[0017] Further, axial electromagnets 106A and 106B are arranged to vertically sandwich a disc-shaped metal disc 111 provided at a lower portion of the rotor shaft 113. The metal disc 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect an axial displacement of the rotor shaft 113, and is configured to send an axial position signal thereof to the control device 200.

[0018] In the control device 200, for example, the compensation circuit having the PID adjusting function generates excitation control command signals for the axial electromagnets 106A and 106B, respectively, on the basis of the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 performs excitation control on both the axial electromagnet 106A and the axial electromagnet 106B on the basis of these excitation control command signals. In this manner, the axial electromagnet 106A attracts the metal disc 111 upward by the magnetic force, the axial electromagnet 106B attracts the metal disc 111 downward, and an axial position of the rotor shaft 113 is adjusted.

[0019] Consequently, the control device 200 is configured to appropriately adjust the magnetic force on the metal disc 111 which is generated by the axial electromagnets 106A and 106B, cause the rotor shaft 113 to magnetically levitate in the axial direction, and hold the rotor shaft 113 in a space in a non-contact manner. The amplifier circuit 150 that performs the excitation control on the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B will be described below.

[0020] Meanwhile, a motor 121 includes a plurality of magnetic poles arranged in a circumferential shape to surround the rotor shaft 113. Each magnetic pole is controlled by the control device 200 to rotatably drive the rotor shaft 113 by an electromagnetic force acting between the magnetic pole and the rotor shaft 113. Also, the motor 121 incorporates a rotation speed sensor such as a Hall element, a resolver, or an encoder (not illustrated), and a rotation speed of the rotor shaft 113 is detected by a detection signal from the rotation speed sensor.

[0021] Further, a phase sensor (not illustrated) is attached in the vicinity of, for example, the lower radial sensor 108 to detect a phase of rotation of the rotor shaft 113. The control device 200 is configured to use detection signals of both the phase sensor and the rotation speed sensor and detect positions of the magnetic poles.

[0022] A plurality of stator blades 123 (123a, 123b, 123c, ...) are arranged separate from the rotor blades 102 (102a, 102b, 102c, ...) with slight gaps therebetween. The rotor blades 102 (102a, 102b, 102c, ...) are all formed to be inclined by a predetermined angle from a plane perpendicular to an axis line of the rotor shaft 113 to transfer molecules of exhaust gas downward due to collision thereto. The stator blades 123 (123a, 123b, 123c, ...) are made of a metal such as aluminum, iron, stainless steel, copper, or a metal such as an alloy containing these metal as components, for example.

[0023] Similarly, the stator blades 123 are formed to be inclined by a predetermined angle from a plane perpendicular to the axis line of the rotor shaft 113, and are arranged toward an inside of the outer cylinder 127 in a staggered manner with respect to the layers of the rotor blades 102. Thus, outer circumferential ends of the stator blades 123 are supported in a state of being inserted between a plurality of stacked stator blade spacers 125 (125a, 125b, 125c, ...).

[0024] The stator blade spacer 125 is a ring-shaped member, and is made of, for example, a metal such as aluminum, iron, stainless steel, or copper, or a metal such as an alloy containing these metals as components. The outer cylinder 127 is fixed to outer circumferences of the stator blade spacers 125 with slight gaps therebetween. A base portion 129 is disposed at a bottom portion of the outer cylinder 127. An outlet port 133 is formed in the base portion 129 and communicates with the outside. Exhaust gas which has entered an inlet port 101 from a chamber (vacuum chamber) side and has been transferred to the base portion 129 is sent to the outlet port 133.

[0025] Further, depending on an application of the turbo-molecular pump 100, a threaded spacer 131 is disposed between a lower portion of the stator blade spacer 125 and the base portion 129. The threaded spacer 131 is a cylindricalmember made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals as components, and a plurality of helical thread grooves 131a are formed in an inner circumferential surface thereof. A direction of the helix of the thread groove 131a is a direction in which molecules of the exhaust gas are transferred toward the outlet port 133 when the molecules move in a rotation direction of the rotating body 103. A cylindrical portion 102d is suspended from a lowermost portion of the rotating body 103 which is connected to the rotor blades 102 (102a, 102b, 102c, ...). An outer circumferential surface of the cylindrical portion 102d has a cylindrical shape and projects toward an inner circumferential surface of the threaded spacer 131, and is close to the inner circumferential surface of the threaded spacer 131 with a predetermined gap therebetween. The exhaust gas transferred to the thread groove 131a by the rotor blade 102 and the stator blade 123 is sent to the base portion 129 while being guided by the thread groove 131a.

[0026] The base portion 129 is a disc-shaped member constituting a base bottom portion of the turbo-molecular pump 100, and is generally made of a metal such as iron, aluminum, or stainless steel. Since the base portion 129 physically holds the turbo-molecular pump 100 and also functions as a heat conduction path, it is desirable to use the base portion 129 made of a metal such as iron, aluminum, or copper, which has rigidity and high thermal conductivity.

[0027] In such a configuration, when the rotor blades 102 are rotatably driven together with the rotor shaft 113 by the motor 121, the rotor blades 102 and the stator blades 123 act to cause the exhaust gas to be sucked from a chamber through the inlet port 101. A rotation speed of the rotor blade 102 is usually 20,000 rpm to 90,000 rpm, and a circumferential speed at a distal end of the rotor blade 102 reaches 200 m / s to 400 m / s. The exhaust gas sucked from the inlet port 101 passes between the rotor blades 102 and the stator blades 123 and is transferred to the base portion 129. At this point, a temperature of the rotor blade 102 is increased due to conduction of frictional heat generated when the exhaust gas comes into contact with the rotor blade 102 or heat generated by the motor 121 , but the heat is transmitted to the stator blade 123 side due to radiation or conduction of gas molecules or the like of the exhaust gas.

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

[0029] In the above description, the threaded spacer 131 is disposed at an outer circumference of the cylindrical portion 102d of the rotating body 103, and the thread groove 131a is formed in the inner circumferential surface of the threaded spacer 131. However, on the contrary, a thread groove may be formed in an outer circumferential surface of the cylindrical portion 102d, and a spacer having a cylindrical inner circumferential surface may be disposed around the thread groove.

[0030] Also, depending on an application of the turbo-molecular pump 100, a periphery of an electrical installation portion is covered with a stator column 122 so that the gas sucked from the inlet port 101 does not infiltrate the electrical installation portion including 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 106Aand 106B, the axial sensor 109, and the like, and the inside of the stator column 122 may be kept at a predetermined pressure by a purge gas.

[0031] In this case, piping (not illustrated) is laid in the base portion 129, and the purge gas is introduced through the piping. The introduced purge gas is sent to the outlet port 133 through gaps between a protective bearing 120 and the rotor shaft 113, between a rotor and a stator of the motor 121, and between the stator column 122 and an inner circumferential side cylindrical portion of the rotor blade 102.

[0032] Here, a model of turbo-molecular pump 100 needs to be identified, and the turbo-molecular pump 100 needs to be controlled based on individually adjusted unique parameters (for example, characteristics corresponding to the model). In order to store these control parameters, the turbo-molecular pump 100 includes an electronic circuit unit 141 in a main body thereof. The electronic circuit unit 141 includes a semiconductor memory such as an EEP-ROM, an electronic component such as a semiconductor element for accessing the semiconductormemory, a substrate 143 for mounting the memory and component, and the like. The electronic circuit unit 141 is housed in a lower portion of the rotation speed sensor (not illustrated), for example, near the center of the base portion 129 constituting the lower portion of the turbo-molecular pump 100, and is closed by an airtight bottom cover 145.

[0033] Incidentally, in a semiconductor manufacturing process, the pressure of process gas introduced into a chamber is higher than a predetermined value. Otherwise, when the temperature thereof is lower than a predetermined value, some gas may have a property of becoming solid. Inside the turbo-molecular pump 100, a pressure of the exhaust gas is lowest at the inlet port 101 and highest at the outlet port 133. When the pressure of the process gas becomes higher than the predetermined value or the temperature thereof becomes lower than the predetermined value while being transferred from the inlet port 101 to the outlet port 133, the process gas becomes solid and is attached to and deposited inside the turbo-molecular pump 100.

[0034] For example, it can be found from a vapor pressure curve that, in a case where SiCI4 is used as the process gas in an Al etching device, a solid product (for example, AICI3) is precipitated and is attached to and deposited inside the turbo-molecular pump 100 at low vacuum (760 torr to 10-2 torr) and low temperature (about 20°C). Consequently, when a precipitate of the process gas is deposited inside the turbo-molecular pump 100, this deposit narrows a pump flow channel, causing the performance of the turbo-molecular pump 100 to be degraded. Thus, the above-described products are prone to solidifying and adhering to portions near the outlet port 133 and the threaded spacer 131 where the pressure is high.

[0035] In order to solve this problem, a heater (not illustrated) or an annular water-cooled pipe 149 is conventionally wound around an outer circumference of the base portion 129 or the like, and a temperature sensor (not illustrated) (for example, a thermistor) is embedded in the base portion 129, for example, and control of heating performed by the heater or cooling performed by the water-cooled pipe 149 (hereinafter, referred to as TMS, TMS; Temperature Management System) is performed so that the temperature of the base portion 129 ismaintained at a certain high temperature (a set temperature) based on a signal from the temperature sensor.

[0036] Next, the amplifier circuit 150 that performs the excitation control on the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B will be described with respect to the turbo-molecular pump 100 configured as described above. Fig. 2 illustrates a circuit diagram of the amplifier circuit 150.

[0037] In Fig. 2, an electromagnet coil 151 constituting the upper radial electromagnet 104 or the like has one end connected to a positive electrode 171a of a power source 171 via a transistor 161 and the other end 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 a source and a drain thereof.

[0038] At this point, the transistor 161 has a configuration in which a cathode terminal 161a of a diode thereof is connected to the positive electrode 171a, and an anode terminal 161b thereof is connected to one end of the electromagnet coil 151. Also, the transistor 162 has a configuration in which a cathode terminal 162a of a diode thereof is connected to the current detection circuit 181 , and an anode terminal 162b thereof is connected to the negative electrode 171b.

[0039] Meanwhile, a diode 165 for current regeneration has a configuration in which a cathode terminal 165a thereof is connected to one end of the electromagnet coil 151, and an anode terminal 165b thereof is connected to the negative electrode 171b. Similarly, a diode 166 for current regeneration has a configuration in which a cathode terminal 166a thereof is connected to the positive electrode 171a, and an anode terminal 166b thereof is connected to the other end of the electromagnet coil 151 via the current detection circuit 181. The current detection circuit 181 includes, for example, a Hall sensor type current sensor or an electric resistance element.

[0040] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, in a case where the magnetic bearing is under five-axis control, and a total of ten electromagnets 104, 105, 106A, and 106B are provided,the same amplifier circuit 150 is configured for each of the electromagnets, and the ten amplifier circuits 150 are connected to the power source 171, in parallel.

[0041] Further, an amplifier control circuit 191 is configured of, for example, a digital signal processor unit (hereinafter referred to as a DSP unit) (not illustrated) of the control device 200, and the amplifier control circuit 191 is configured to switch on / off of the transistors 161 and 162.

[0042] The amplifier control circuit 191 compares a current value detected by the current detection circuit 181 (a signal obtained by reflecting the current value is referred to as a current detection signal 191c) with a predetermined current command value. On the basis of this comparison result, magnitudes of pulse widths (pulse width times Tp1 and Tp2) generated in a control cycle Ts that is one cycle of the PWM control are determined. As a result, gate drive signals 191a and 191b having the pulse widths are output from the amplifier control circuit 191 to gate terminals of the transistors 161 and 162.

[0043] It is necessary to perform position control on the rotating body 103 at a high speed and in a strong force when the rotating body 103 passes a resonance point during rotation speed acceleration operation of the rotating body 103, when a disturbance occurs during constant speed operation, or the like. Therefore, for example, a voltage of about 50 V is used as the power source 171 so that a current flowing in the electromagnet coil 151 can be rapidly increased (or decreased). Also, a capacitor (not illustrated) is usually connected between the positive electrode 171a and the negative electrode 171b of the power source 171 in order to stabilize the power source 171.

[0044] In such a configuration, a current flowing in the electromagnet coil 151 (hereinafter referred to as an electromagnet current iL) is increased when both the transistors 161 and 162 are turned on, and the electromagnet current iL is decreased when both the transistors 161 and 162 are turned off.

[0045] Also, when one of the transistors 161 and 162 is turned on and the other thereof is turned off, a so-called flywheel current is held. Thus, the flywheel current flowing in the amplifier circuit 150 in this manner enables a hysteresis loss in the amplifier circuit 150 to be reduced and enables the power consumption of the entire circuit to be reduced low. Also, the control of the transistors 161 and162 in this manner enables high-frequency noise such as a harmonic wave generated in the turbo-molecular pump 100 to be reduced. Further, measurement of the flywheel current by the current detection circuit 181 enables the electromagnet current iL flowing in the electromagnet coil 151 to be detected.

[0046] That is, in a case where the detected current value is smaller than the current command value, both the transistors 161 and 162 are turned on only once during a control cycle Ts (for example, 100 ps) by a time corresponding to the pulse width time Tp1 as illustrated in Fig. 3. Therefore, the electromagnetic current iL during this period is increased toward a current value iLmax (not illustrated) that can flow from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[0047] Meanwhile, in a case where the detected current value is larger than the current command value, both the transistors 161 and 162 are turned off only once during the control cycle Ts by a time corresponding to the pulse width time Tp2 as illustrated in Fig. 4. Therefore, the electromagnet current iL during this period is decreased toward a current value iLmin (not illustrated) that can be regenerated from the negative electrode 171b to the positive electrode 171a via the diodes 165 and 166.

[0048] In either case, after the pulse width times Tp1 and Tp2 have passed, either the transistor 161 or 162 is turned on. Therefore, during this period, the flywheel current is held in the amplifier circuit 150.

[0049] The following description will be provided regarding a configuration of the Siegbahn type in which reversed exhausting is performed in that gas in the Siegbahn vacuum pump upstream region is exhausted from an outer diameter side to an inner diameter side, and gas in the Siegbahn vacuum pump downstream region is exhausted from the inner diameter side to the outer diameter side.

[0050] (ii-1) ConfigurationFig. 5 is a view illustrating a schematic structural example of a Siegbahn vacuum pump 1 according to an embodiment of the present invention.Fig. 5 illustrates a cross-sectional view of the Siegbahn vacuum pump 1 in an axial-line direction thereof.A casing 2 forming a housing of the vacuum pump 1 has a substantially cylindrical shape and constitutes a housing body of the Siegbahn vacuum pump 1 together with a base 3 provided at a lower portion (on the outlet port 133 side) of the casing 2. A gas transfer mechanism that is a structure causing the Siegbahn vacuum pump 1 to fulfill an exhaust function is accommodated in the housing body.This gas transfer mechanism includes a rotor portion held rotatably and a stator portion fixed to the housing body.

[0051] An inlet port 101 for introducing gas into the Siegbahn vacuum pump 1 is formed at an end portion of the casing 2. Also, a flange portion 5 projecting toward an outer circumferential side is formed on an end surface of the casing 2 on the inlet port 101 side.Also, the base 3 has an outlet port 133 through which gas is exhausted from the Siegbahn vacuum pump 1.

[0052] The rotor portion includes a shaft 7 which is a rotating shaft, a rotor 8 disposed on the shaft 7, a plurality of rotor discs 9 provided on the rotor 8, and a rotor cylinder 10. The shaft 7 and the rotor 8 constitute the rotor portion.Each of the rotor discs 9 is formed by a disk member having a disc shape that radially extends perpendicular to an axis line of the shaft 7.Also, the rotor cylinder 10 is formed by a cylindrical member having a cylindrical shape concentric with a rotational axis line of the rotor 8.

[0053] A motor portion 20 for rotating the shaft 7 at high speed is provided substantially in the middle of the shaft 7 in the axial-line direction.Further, radial magnetic bearing devices 30 and 31 for supporting the shaft 7 in a radial direction in a non-contact manner are provided on the inlet port 101 side and the outlet port 133 side of the shaft 7, respectively, with respect to the motor portion 20, and an axial magnetic bearing device 40 for supporting the shaft 7 in the axial-line direction (the axial direction) in a non-contact manner is provided at a lower end of the shaft 7.

[0054] A stator portion is formed on an inner circumferential side of the housing body. The stator portion includes a plurality of stator discs 50 provided on the inletport 101 side, and the stator discs 50 have spiral grooves including stator disc root portions 51 and stator disc ridge portions 52.The present embodiment employs a configuration in which a spiral groove is formed in the stator disc 50, but the present invention is not limited to this, and a spiral groove flow channel may be formed in a clearance-opposed surface of at least one of the above-described rotor disc 9 or the stator disc 50.Each of the stator discs 50 is formed by a disk member having a disc shape that radially extends perpendicular to the axis line of the shaft 7.The stator discs 50 of the respective stages are fixed to be separated from each other by a spacer 60 (the stator portion) having a cylindrical shape. The spacer 60 is formed to have a height in the axial direction which is decreased along the axial direction of the Siegbahn vacuum pump 1. In this manner a volume of the flow channel is gradually decreased toward the outlet port 133 of the Siegbahn vacuum pump 1 to compress the gas passing in the gas transfer mechanism. The arrows in Fig. 5 indicate the flow of gas.In the Siegbahn vacuum pump 1, the rotor discs 9 and the stator discs 50 are alternately arranged and are formed in a plurality of stages in the axial-line direction, but any number of rotor and stator components may be provided as needed to satisfy exhaust performance required for the vacuum pump.The Siegbahn vacuum pump 1 configured as described above may perform a vacuum exhaust process in a vacuum chamber (not illustrated) connected to the Siegbahn vacuum pump 1.

[0055] Next, a first embodiment will be described. Fig. 7 is a cross-sectional view of the vacuum pump 1 including Siegbahn exhaust mechanisms according to the first embodiment. Also, Fig. 8 is a view illustrating a stator disc (in a state in which upper and lower stages are coupled) in the first embodiment. Fig. 9 is a view illustrating the stator disc (the lower stage of a single disc) in the first embodiment.

[0056] In this first embodiment, partition walls 300 and side partition walls 302 are provided on an outer circumferential portion of the Siegbahn exhaust mechanism to divide the Siegbahn exhaust mechanism in a circumferential direction thereof, and as illustrated in Fig. 8, a flow channel toward a first-stage (lower-stage) Siegbahn exhaust mechanism and a flow channel toward a second-stage (upper-stage) Siegbahn exhaust mechanism are alternately provided. That is, the partition walls 300 and the side partition walls 302 provided on an outer circumference of the Siegbahn exhaust mechanism separate the exhaust gas from exhaust gas passing in the flow channel toward the first-stage Siegbahn exhaust mechanism and exhaust gas passing in the flow channel toward the second-stage Siegbahn exhaust mechanism. As a result, the plurality of stages of Siegbahn exhaust mechanisms (stator discs 50) can be arranged in parallel, and exhaust efficiency can be improved.In this first embodiment, the partition walls 300 have a function of covering the flow channel by extending vertically along the outer circumference of the Siegbahn exhaust mechanism.

[0057] In the first embodiment, as illustrated in Fig. 8, an entrance port (an inflow port) of the exhaust gas at an upper stage and a discharge port (an outflow port) of the exhaust gas at the upper stage are in the same phase, and an entrance port of the exhaust gas at a lower stage and a discharge port of the exhaust gas at the lower stage are in the same phase. That is, the entrance port and discharge port of each stage are at the same position. Therefore, the upper stage and the lower stage can be formed into completely the same shape, and the number of types of dies can be decreased when manufacturing is performed, and manufacturing costs can be reduced.The flow of the exhaust gas in the Siegbahn exhaust mechanism is as indicated by the arrows in the figure (Fig. 7). That is, the exhaust gas taken in from the inflow port provided on the outer circumference of the Siegbahn exhaust mechanism is sent inward in the radial direction and compressed to be discharged from the outflow port provided outward in the radial direction.Also, in a case where six stator disc ridge portions 52 (spiral protrusions) are provided, passages are provided at equal intervals at a pitch of 30 degrees. The entrance ports at the upper and lower stages are arranged to have phases shifted by a half pitch.Note that the rotor disc 9 is disposed at the upper portion of Fig. 8.

[0058] In the first embodiment, projecting portions 308 that extend the partition walls 300 in the axial direction may be provided, as illustrated in Fig. 8. Thisprojecting portions 308 enable angular positioning to be performed during manufacturing. Also, when the projecting portions 308 extends to a position facing an end surface of the rotor disc 9, leakage of the exhaust gas can be prevented.

[0059] Next, a second embodiment will be described. Fig. 10 is a cross-sectional view of the vacuum pump 1 including Siegbahn exhaust mechanisms according to the second embodiment. Also, Fig. 11 is a view illustrating a stator disc (in a state in which the upper and lower sides are coupled) in which a ratio of areas of the entrance port (the inflow port) and the discharge port (the outflow port) in the second embodiment is 5:5, and Fig. 12 is a view illustrating a stator disc (in a state in which the upper and lower sides are coupled) in which a ratio of areas of the inflow port to the outflow port in the second embodiment is 7:3.Further, Fig. 13 is a view illustrating a state in which three stages of stator discs are stacked in which a ratio of areas of the inflow port to the outflow port in the second embodiment is 7:3, and Fig. 14 is a view illustrating the stator disc (the lower stage of a single disc) in the second embodiment.

[0060] In this second embodiment, the partition walls 300 have a structure to cover sides one by one, and the entrance port at the upper stage and the entrance port at the lower stage are in the same phase, and the discharge port on the upper state and the discharge port at the lower stage are in the same phase. That is, the partition walls 300 that block only the lower side and the partition walls 300 that block only the upper side are arranged in different phases (alternately).An upper partition wall 304 and a lower partition wall 306 are provided to prevent backflow of the exhaust gas.The flow of the exhaust gas in the Siegbahn exhaust mechanism is as indicated by the arrows in Fig. 10.

[0061] In this second embodiment, since the inflow port and the outflow port of the exhaust gas are in the same phase, a ratio of areas of the inflow port to the outflow port can be easily changed by adjusting a position of the side partition wall 302.In an example illustrated in Figure 11 , a ratio of areas of the inflow port to outflow port is 5:5. However, in Figure 12 the ratio is 7:3.Generally, since exhaust gas is compressed in the Siegbahn exhaust mechanism, the exhaust efficiency tends to be increased if the entrance port is set to be wide and the discharge port is set to be narrow. Therefore, the ratio of the entrance port to the discharge port can be set appropriately in order to obtain desired exhaust efficiency.

[0062] Also, in this second embodiment, as illustrated in Fig. 13, the phases of the entrance port and discharge port are the same, so that the number of stages can be increased from two stages by stacking and overlapping the stator discs 50 having the same shape. By installing the upper partition wall 304 and the lower partition wall 306, the Siegbahn exhaust mechanism that can be connected in parallel in multiple stages can be configured.Also in this second embodiment, if the upper partition walls 304 and the lower partition walls 306 are separate components, the partition walls have the same shape, so that the number of types of the dies can be limited, and manufacturing costs can be reduced, in the same manner as in the first embodiment.

[0063] Next, modification examples of each embodiment will be described.As illustrated in Fig. 15, the starting position (represented by X in the figure) of the inflow port coincides with the back surface of the stator disc ridge portion 52 (the spiral protrusion) in the rotation direction of the rotor disc 9.Also, the starting position (represented by Y in the figure) of the outflow port coincides with the front surface of the stator disc ridge portion 52 (the spiral protrusion) in the rotation direction of the rotor disc 9.This is preferable because a pressure distribution in the Siegbahn exhaust mechanism can be efficiently produced.In Fig. 15, the arrows indicate the flow of the exhaust gas from the inflow port to the outflow port.

[0064] Next, as illustrated in Fig. 16, the partition walls 300 are installed at predetermined angles with respect to the radial direction of the rotor disc 9. The angle is preferably about 20 degrees. When the exhaust gas enters the Siegbahn exhaust mechanism, the relationship between the stator disc ridge portion 52 andthe partition wall 300 is set as described above, thereby enabling the exhaust gas to flow in and out smoothly.

[0065] Next, other modification examples will be described.An additional exhaust mechanism having stator disc ridge portions 52 (protrusions) is provided on the outlet port side of the plurality of stages of exhaust mechanisms stacked on each other, the number of stator disc ridge portions being a multiple of the plurality of the Siegbahn exhaust mechanisms. For example, three pairs of the Siegbahn exhaust mechanisms having six protrusions are connected in parallel, and the additional Siegbahn exhaust mechanism having 18 protrusions is connected. In this manner, more efficient exhaust can be performed.

[0066] In the vacuum pump in which the turbo-molecular pump is disposed upstream of the parallelly connected Siegbahn exhaust mechanisms according to the present embodiment, the pressure of the turbo-molecular pump provided upstream can be reduced. Therefore, not only the exhaust speed is simply improved, but also effects of reduction in power consumption of the motor and prevention of the vacuum pump itself from being heated can be achieved. That is, although characteristics of the gas allows the turbo-molecular pump to efficiently operate in a molecular flow region, exhaust efficiency is rapidly decreased in a pressure region in which working pressure is increased and causes an intermediate flow. As a result, the turbo-molecular pump has characteristics of a rapid increase in the power consumption of the motor or an increase in heat generation.Accordingly, in the vacuum pump including the turbo-molecular pump disposed upstream, an operation can be performed in a pressure region suitable for each performance, and the exhaust performance of the vacuum pump can be further improved.

[0067] Note that the embodiments and the modification examples of the present invention may be configured to combine each other as necessary.

[0068] Also, the present invention can be variously modified without departing from the spirit of the invention. It is needless to say that the present invention includes such various modifications.[Reference Signs List]

[0069] 1 Siegbahn vacuum pump2 Casing3 Base5 Flange portion7 Shaft8 Rotor9 Rotor disc10 Rotor cylinder20 Motor unit30 Radial magnetic bearing device31 Radial magnetic bearing device40 Axial magnetic bearing device50 Stator disc51 Stator disc root portion52 Stator disc ridge portion60 Spacer100 Turbo-molecular pump (vacuum pump) 101 Inlet port102 Rotor blade102d Cylindrical portion103 Rotating body113 Rotor shaft122 Stator column123 Stator blade125 Stator blade spacer127 Outer cylinder129 Base portion131 Threaded spacer131a Thread groove133 Outlet port200 Control device250 Rib portion260 Communication port (communication hole) 300 Partition wall302 Side partition wall304 Upper partition wall308 Projecting portion306 Lower partition wall1000 Siegbahn vacuum pump (conventional) 5000 Stator disc (conventional)

Claims

CLAIMS1. A vacuum pump comprising:an inlet port through which gas is sucked;an outlet port through which the gas sucked from the inlet port is exhausted;rotatable rotor discs arranged between the inlet port and the outlet port; stator discs arranged relative to the rotor discs such that at least one surface of each stator disc opposes a respective surface of a rotor disc; and spiral protrusions provided on at least one surface of each stator disc or on at least one surface of each rotor disc to define stacked radial flow type exhaust mechanisms that exhaust gas in a radial direction, each exhaust mechanism extending from an outer side toward an inner side of a surface of a respective stator disc which faces the inlet port, and from the inner side toward the outer side of a surface of the respective stator disc which faces the outlet port;the vacuum pump further comprising partition walls arranged on the outer side of the stator discs that divide a flow channel extending from the inlet port to the exhaust mechanisms into a plurality of channel systems which convey gas in parallel to a plurality of the exhaust mechanisms.

2. The vacuum pump according to claim 1, further comprising:inflow ports to the exhaust mechanisms which are installed on surfaces of the stator discs on the inlet port side; andoutflow ports from the exhaust mechanisms which are installed on surfaces of the stator discs on the outlet port side, whereinthe inflow ports and the outflow ports have respective installation positions which are in phase with each other.

3. The vacuum pump according to claim 1 , further comprisinginflow ports to the exhaust mechanisms which are installed on surfaces of the stator discs on the inlet port side, whereinthe inflow ports have respective installation positions which are in phase with each other.

4. The vacuum pump according to claim 1 or 3, further comprisingoutflow ports from the exhaust mechanisms which are installed on surfaces of the stator discs on the outlet port side, whereinthe outflow ports have respective installation positions which are in phase with each other.

5. The vacuum pump according to claim 1 , further comprisinginflow ports to the exhaust mechanisms which are installed on surfaces of the stator discs on the inlet port side, whereina starting position of each of the inflow ports coincides with a back surface of the spiral protrusion in a rotation direction of the rotor discs.

6. The vacuum pump according to claim 1 , further comprisingoutflow ports from the exhaust mechanisms which are installed on surfaces of the stator discs on the outlet port side, whereinan end position of each of the outflow ports coincides with a front surface of the spiral protrusion in a rotation direction of the rotor discs.

7. The vacuum pump according to claim 1 , wherein each of the stator discs has a projecting portion facing an outer circumferential surface of each of the rotor discs.

8. The vacuum pump according to claim 1 , wherein the partition walls are installed at a predetermined angle with respect to the radial direction of the rotor discs.

9. The vacuum pump according to claim 1, wherein each stator disc comprises a plurality of spiral protrusions, each spiral protrusion being provided on a respective surface of the stator disc.

10. A stator disc that is used in a radial flow type exhaust mechanism that exhausts gas in a radial direction, the stator disc comprising:a first spiral protrusion that extends from an outer side toward an inner side of one surface of the stator disc;a second spiral protrusion that extends from the inner side toward the outer side of the other surface of the stator disc; andpartition walls arranged on an outer side of the stator disc that divide a flow channel of gas into a plurality of channel systems which respectively convey gas towards the first spiral protrusion and convey gas away from the spiral protrusions.

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