CN116018464A

CN116018464A - Vacuum pump

Info

Publication number: CN116018464A
Application number: CN202180053111.7A
Authority: CN
Inventors: 三轮田透; 高井庆行; 坂口祐幸
Original assignee: Edwards Japan Ltd
Current assignee: Edwards Japan Ltd
Priority date: 2020-09-10
Filing date: 2021-09-03
Publication date: 2023-04-25
Also published as: EP4212729A1; KR20230062812A; IL300575A; US20240011495A1; JP2022046347A; WO2022054717A1

Abstract

The invention provides a vacuum pump, which can reduce the flow of gas (the number of gas molecules) towards a gap arranged for heat insulation, reduce the amount of byproducts accumulated in the gap, prolong the interval required for maintenance and improve the productivity. The vacuum pump comprises an outer cylinder (127), a rotor shaft (113), a plurality of layers of rotating wings (102), a plurality of layers of fixed wings (123), a cooling side stator (110A) and a heating side stator (110B), wherein the outer cylinder (127) is provided with an air inlet (101) and an air outlet (133), the rotor shaft (113) is rotatably supported on the inner side of the outer cylinder (127), the plurality of layers of rotating wings (102) can rotate together with the rotor shaft (113), the plurality of layers of fixed wings (123) are fixed relative to the outer cylinder and are arranged between the plurality of layers of rotating wings (102), the cooling side stator (110A) and the heating side stator (110B) hold the plurality of layers of fixed wings (123) at a predetermined interval, and an opening part (114A) of a predetermined width for insulating heat between the cooling side stator (110A) and the heating side stator (110B) is arranged at a position not opposite to the outer circumferential surface of the rotating wings (102) in the axial direction of the rotating body (103).

Description

Vacuum pump

Technical Field

The present invention relates to a vacuum pump, and more particularly, to a vacuum pump capable of reducing the amount of deposits (generally referred to as "deposits") generated by solidification of a gas in the vacuum pump and the like deposited in a gap.

Background

In recent years, in a process of forming a semiconductor device from a wafer as a substrate to be processed, a method of processing the wafer in a processing chamber of a semiconductor manufacturing apparatus kept in a high vacuum to manufacture a semiconductor device as a product has been adopted. In a semiconductor manufacturing apparatus for processing a wafer in a vacuum chamber, a vacuum pump having a turbo molecular pump unit, a screw groove pump unit, and the like is used to maintain a high vacuum.

The turbo-molecular pump section has a thin metal rotatable rotor and a stationary rotor fixed to the casing. The rotary vane is operated at a high speed of several hundred m/s, for example, and the process gas for the processing, which has entered from the inlet side, is compressed in the pump and discharged from the outlet side.

However, molecules of the process gas sucked from the suction port side of the vacuum pump are cooled in the compression process in which the molecules are heated immediately after being sucked and moved toward the discharge port side along with the rotation of the rotary vane in the vacuum pump. The process gas solidifies upon cooling, and the solidified byproducts adhere to the stationary wing, the inner surface of the outer tube (shell), and the like, and accumulate as a deposit. By-products are generally chlorine-based and fluorine sulfide-based gases. The sublimation temperature of these gases increases as the vacuum degree decreases and the pressure increases, so that the gases are easily solidified and accumulated in the vacuum pump. When the reaction product accumulates in the vacuum pump, the flow path of the reaction product may be narrowed, and the compression performance and the exhaust performance of the vacuum pump may be degraded. On the other hand, when the temperature of the gas transfer portion made of aluminum, stainless steel, or the like is too high for the rotor blade or the stator blade, the strength of the rotor blade or the stator blade may be lowered, and breakage may occur during operation. Further, there is a possibility that electric components provided in the vacuum pump and an electric motor for rotating the rotor may not exhibit desired performance when the temperature is high. Therefore, the vacuum pump needs to be temperature-controlled to maintain a predetermined temperature.

Therefore, as a vacuum pump for suppressing the accumulation of reaction products, there is also known a structure in which a cooling device or a heating device is provided around a stator to control the temperature in a gas flow path so that the gas in the gas flow path can be transferred without solidifying (for example, refer to patent document 1).

However, the sucked gas in the vacuum pump has a characteristic that the sublimation temperature increases as the vacuum degree increases and the pressure increases, and the gas is easily solidified and accumulated in the vacuum pump. On the other hand, the gas transfer portion including the rotary vane, the fixed vane, and the like has a problem in that strength is lowered when the temperature is too high, and may adversely affect performance of electric components and electric motors in the vacuum pump. Therefore, it is preferable to perform temperature control so that the solidification of the gas in the vacuum pump can be suppressed while the vacuum pump is operated normally without adversely affecting the performance of the electric components and the electric motor in the vacuum pump and without lowering the strength of the gas transfer portion.

Therefore, for example, like the vacuum pump 10 shown in fig. 9 and 10, the upper layer gas transfer unit 11 includes a cooling side stator 17A disposed in a cooling range to be cooled, and the lower layer gas transfer unit 12 includes a heating side stator 17B disposed in a heating range to be heated, and a gap 15 is provided between the cooling side stator 17A and the heating side stator 17B so that the cooling side stator 17A and the heating side stator 17B are independent from each other, and the temperature of the upper layer gas transfer unit 11 and the temperature of the lower layer gas transfer unit 12 do not affect each other. The fixed vane spacer 14 is pressed between the cooling side stator 17A and the heating side stator 17B by the bolts 19 to be positioned.

Patent document 1: japanese patent laid-open No. 10-205486.

In the structure in which the cooling side stator 17A and the heating side stator 17B are positioned by being pressed by the bolts 19, the size (axial dimension) of the gap 15 between the cooling side stator 17A and the heating side stator 17B varies according to the magnitude of the force of the fastening bolts 19, the deformation amount of the O-rings 18 due to the fastening, the type of the fixed wing spacers 14, and the like. When the gap 15 is positioned so as to face the radial circumferential surface of the rotor blade 16, molecules of the process gas transferred in the tangential direction and the downstream direction by the rotor blade 16 tend to face the gap 15 (the number of gas molecules increases) when the rotor blade 16 rotates. The gas introduced into the gap 15 is cooled by the cooling side stator 17A, solidified in the gap 15, and deposited as a by-product. The deposit narrows the width of the gap 15, thereby reducing the heat insulating effect and changing the temperature distribution in the pump. Therefore, maintenance work is required to remove the deposited material stored in the gap 15 by periodically disassembling the vacuum pump 10. This maintenance work has a problem of deterioration in productivity.

Disclosure of Invention

Accordingly, an object of the present invention is to solve the above-described problems by providing a vacuum pump capable of improving productivity by reducing the flow of gas (the number of gas molecules) into a gap provided for heat insulation, reducing the amount of by-products deposited in the gap, and extending the interval at which maintenance work is required.

The present invention has been made in order to achieve the above object, and an object of the present invention is to provide a vacuum pump according to claim 1, wherein the vacuum pump includes a casing having an air inlet and an air outlet, a rotor shaft rotatably supported inside the casing, a plurality of layers of rotary vanes rotatably supported on the inside of the casing, the plurality of layers of rotary vanes being fixed to the casing and disposed between the plurality of layers of rotary vanes, the plurality of layers of rotary vanes being held by the plurality of layers of rotary vanes at predetermined intervals, a plurality of layers of rotary vanes, a cooling side stator and a heating side stator, wherein an opening portion of a gap of a predetermined width for insulating heat between the cooling side stator and the heating side stator is provided at a position not facing an outer peripheral surface of the rotary vanes in an axial direction of the rotor shaft.

According to this configuration, the opening of the gap of a predetermined width for insulating heat between the cooling side stator and the heating side stator is provided at a position not facing the outer peripheral surface of the rotor blade in the axial direction of the rotor shaft. Therefore, even if a part of the gas flies toward the inner peripheral surface of the stator due to the centrifugal force caused by the rotation of the rotor blade, the opening of the gap is provided at a position not offset to face the outer peripheral surface of the rotor blade, so that the amount of the opening entering the gap is extremely small, and the amount of the deposit deposited in the gap can be reduced. This can lengthen the intervals at which maintenance work is required, contributing to improvement in productivity.

The invention described in claim 2 provides the vacuum pump according to claim 1, wherein the gap has a 1 st gap portion and a 2 nd gap portion, the 1 st gap portion extends horizontally outward in a radial direction perpendicular to the axial direction, and the 2 nd gap portion extends further outward in the radial direction from an outer end of the 1 st gap portion and extends downstream in the axial direction.

According to this structure, when the process gas having entered the 1 st gap portion from the opening portion is to enter further into the interior, the process gas collides with the wall of the 2 nd gap portion once, so that the wall becomes resistance to the flow into the gap. This reduces the amount of process gas entering the gap from the opening, and can further reduce the amount of deposits generated by the process gas.

The invention described in claim 3 provides the vacuum pump according to claim 1 or 2, wherein the gap has a 3 rd gap portion extending along a downstream side in the axial direction.

According to this configuration, when the process gas is to enter the gap from the opening, the 3 rd gap portion facing the lower side becomes a wall at the position immediately before entering the front of the opening, and collides with the wall, thereby causing resistance to the flow of the process gas into the gap. This can reduce the amount of process gas entering the gap from the opening, and can further reduce the amount of deposition generated by the process gas.

The invention described in claim 4 provides the vacuum pump according to any one of claims 1 to 3, wherein the gap has a 4 th gap portion in a shape extending radially outward perpendicular to the axial direction and upstream in the axial direction.

According to this configuration, the shape of the longitudinal section of the gap has a 4 th gap portion extending outward in the radial direction perpendicular to the axial direction and extending toward the axially upstream side. Therefore, the process gas entering the gap from the opening collides with the 4 th gap portion once, and becomes a resistance to the flow of the process gas into the gap. This can reduce the amount of process gas entering the gap from the opening, and can further reduce the amount of deposition generated by the process gas.

The invention described in claim 5 provides the vacuum pump according to any one of claims 1 to 4, wherein the gap has a shape having a flange portion protruding from the opening portion toward the inside of the casing at an upper portion of the opening portion.

According to this configuration, since the flange portion protruding from the opening portion toward the inside of the case is provided at the upper portion of the opening portion of the gap formed in the inner peripheral surface of the case when the case is longitudinally sectioned in the axial direction, the flow of the process gas from the upstream side toward the flange portion is controlled so as not to enter in the direction of the opening portion of the gap but to be directed toward the downstream side different from the opening portion. This can reduce the amount of process gas entering the gap from the opening, and can further reduce the amount of deposition generated by the process gas.

Effects of the invention

According to the present invention, the amount of process gas entering the gap provided for heat insulation can be reduced, and the amount of deposits generated by the process gas accumulating in the gap can be reduced. This can lengthen the interval between maintenance operations that require removal of deposits in the gap, thereby improving productivity.

Further, the heat insulating effect of the gap is also improved, and the temperature can be finely controlled within a range in which the performance of the electric motor for rotating the rotor and the electric components provided in the vacuum pump are not adversely affected, and within a range in which the strength of the rotor and the stator is not affected.

In addition, the normal operation of the vacuum pump can be achieved while controlling the curing of the process gas.

Drawings

Fig. 1 is a longitudinal sectional view of a turbo molecular pump shown as an example of a vacuum pump according to an embodiment of the present invention.

Fig. 2 is a diagram showing an example of an amplification circuit of the turbo molecular pump.

Fig. 3 is a timing chart showing a control example of the case where the current command value detected by the amplification circuit of the turbo molecular pump is larger than the detected value.

Fig. 4 is a timing chart showing a control example of the case where the current command value detected by the amplification circuit of the turbo molecular pump is smaller than the detected value.

Fig. 5 is an enlarged partial cross-sectional view of the turbo molecular pump shown in fig. 1, (a) is an enlarged view of a portion a in fig. 1, and (b) is a cross-sectional view in which a part of the shape for explaining the gap is further enlarged.

Fig. 6 shows a modification of the present invention, (a) is a partial enlarged view corresponding to the portion a in fig. 1, and (b) is a cross-sectional view of a part of the portion (a) for explaining the shape of the gap.

Fig. 7 shows another modification of the present invention, (a) is a partial enlarged view corresponding to the portion a in fig. 1, and (b) is a cross-sectional view of a part of the portion (a) for explaining the shape of the gap.

Fig. 8 shows still another modification of the present invention, (a) is a partial enlarged view corresponding to the portion a in fig. 1, and (b) is a cross-sectional view of a part of the portion (a) for explaining the shape of the gap.

Fig. 9 is a longitudinal sectional view of a turbo molecular pump as an example of a conventional vacuum pump.

Fig. 10 is a partial enlarged view corresponding to the portion B of fig. 9.

Detailed Description

The present invention is achieved in order to achieve the object of providing a vacuum pump capable of improving productivity by reducing the flow of gas (the number of gas molecules) toward a gap provided for heat insulation, reducing the amount of by-products deposited in the gap, and extending the interval at which maintenance work is required, by: the vacuum pump is provided with a casing, a rotor shaft, a plurality of layers of rotating wings, a plurality of layers of fixed wings, a heating side stator and a cooling side stator, wherein the casing is provided with an air inlet and an air outlet, the rotor shaft is rotatably supported on the inner side of the casing, the plurality of layers of rotating wings can rotate together with the rotor shaft, the plurality of layers of fixed wings are fixed relative to the casing and are arranged between the plurality of layers of rotating wings, the heating side stator and the cooling side stator hold the plurality of layers of fixed wings at a preset interval, and the vacuum pump is characterized in that an opening part for insulating a gap with a preset width between the heating side stator and the cooling side stator is arranged at a position which is not opposite to the outer peripheral surface of the rotating wings in the axial direction of the rotor shaft.

Examples

An example of an embodiment of the present invention will be described in detail below based on the drawings. In the following examples, the numbers, values, amounts, ranges, and the like of the constituent elements are mentioned, and unless otherwise specifically indicated, the number is obviously limited to a specific number, and the number is not limited to the specific number, and may be a specific number or more or a specific number or less.

When referring to the shape and positional relationship of the constituent elements, the shape and the like are included in the present invention, except for the case where they are particularly clear and the case where they are not considered as such in principle, the shape and the like are substantially similar or analogous to the shape and the like.

In the drawings, the feature portions may be exaggerated for easy understanding of the features, and the dimensional ratios of the constituent elements are not limited to the same as the actual ones. In the cross-sectional view, a cross-sectional line of a part of the constituent elements may be omitted in order to facilitate understanding of the cross-sectional structure of the constituent elements.

In the following description, the expressions indicating the vertical direction, the horizontal direction, and the like are not absolute, and the description is applicable to the case of describing the posture of each part of the turbomolecular pump of the present invention, but should be interpreted as a change in the posture, and changes in accordance with the change in the posture. In addition, the same reference numerals are given to the same elements throughout the description of the embodiments.

Fig. 1 shows an embodiment of a turbo molecular pump 100 as a vacuum pump according to the present invention, and fig. 1 is a longitudinal sectional view thereof.

In fig. 1, a turbo molecular pump 100 has an intake port 101 formed at the upper end of an outer tube 127 that is a cylindrical cover. The outer tube 127 includes a rotor 103 inside, and the rotor 103 includes a plurality of rotor blades 102 (102 a, 102b, 102 c) which are turbine blades for sucking and discharging gas, formed radially and in multiple layers on a peripheral portion. A rotor shaft 113 is mounted in the center of the rotor 103, and the rotor shaft 113 is supported in suspension in the air by a 5-axis controlled magnetic bearing, for example, and is position-controlled.

The upper radial electromagnet 104 is configured by 4 electromagnets in pairs in the X-axis and the Y-axis. In the vicinity of the upper radial electromagnet 104, 4 upper radial sensors 107 are provided corresponding to the upper radial electromagnet 104. The upper radial sensor 107 detects the position of the rotor shaft 113 based on a change in inductance of a conductive winding that changes in correspondence with the position of the rotor shaft 113, for example, using an inductance sensor having the conductive winding, an eddy current sensor, or the like. The upper radial sensor 107 is configured to detect a radial displacement of the rotor shaft 113, that is, the rotor 103 fixed to the rotor shaft 113, and to send the radial displacement to a control device, not shown.

In this control device, 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 amplification circuit 150 (described later) shown in fig. 2 performs excitation control for the upper radial electromagnet 104 based on the excitation control command signal, thereby adjusting the upper radial position of the rotor shaft 113.

The rotor shaft 113 is made of a high magnetic permeability material (iron, stainless steel, or the like) or the like, and is attracted by the magnetic force of the upper radial electromagnet 104. The adjustment is performed independently in the X-axis direction and the Y-axis direction, respectively. The lower radial electromagnet 105 and the lower radial sensor 108 are disposed in the same manner as the upper radial electromagnet 104 and the upper radial sensor 107, and the radial position of the lower side of the rotor shaft 113 is adjusted in the same manner as the radial position of the upper side.

The

axial electromagnets

106A and 106B are disposed so as to sandwich a disk-shaped metal disk 111 provided at the lower portion of the rotor shaft 113. The metal disk 111 is made of a high magnetic permeability material such as iron. The axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and the axial position signal is sent to the control device.

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

In this way, the control device appropriately adjusts the magnetic force acting on the metal disk 111 by the

axial electromagnets

106A and 106B, and magnetically suspends the rotor shaft 113 in the axial direction and holds it in a spatially non-contact manner. The amplification circuit 150 for performing excitation control of the upper radial electromagnet 104, the lower radial electromagnet 105, and the

axial electromagnets

106A and 106B will be described later.

On the other hand, the motor 121 includes a plurality of magnetic poles circumferentially arranged so as to surround the rotor shaft 113. Each magnetic pole is controlled by the control device such that the rotor shaft 113 is rotationally driven via electromagnetic force acting between the magnetic pole and the rotor shaft 113. Further, a rotational speed sensor, not shown in the drawings, such as a hall element, an analyzer, an encoder, or the like, is incorporated in the motor 121, and the rotational speed of the rotor shaft 113 is detected by a detection signal of the rotational speed sensor.

Further, for example, a phase sensor, not shown in the figure, is mounted near the lower radial sensor 108, and detects the phase of the rotation of the rotor shaft 113. The control device detects the position of the magnetic pole by using the detection signals of the phase sensor and the rotational speed sensor together.

A plurality of fixing wings 123 (123 a, 123b, 123 c) are arranged with a small gap from the rotating wings 102 (102 a, 102b, 102 c). The rotary wing 102 is formed to be inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transfer the molecules of the exhaust gas downward by collision.

The fixed blades 123 are also formed to be inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are disposed alternately with the layers of the rotor blades 102 inside the outer tube 127. The outer peripheral ends of the fixed wings 123 are supported in a state of being interposed between a plurality of stacked fixed wing spacers 125 (125 a, 125b, 125 c).

The fixed wing spacer 125 is an annular member, and is made of a metal such as aluminum, iron, stainless steel, copper, or an alloy including these metals as components. An outer tube 127 is fixed to the outer periphery of the fixed wing spacer 125 with a small gap. A base portion 129 is disposed at the bottom of the outer tube 127. An exhaust port 133 is formed in the base portion 129 and communicates with the outside. The exhaust gas transferred from the chamber side inlet 101 to the base portion 129 is sent to the exhaust port 133.

Further, according to the use of the turbomolecular pump 100, a threaded spacer 131 is disposed between the lower portion of the fixed wing spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals as components, and a plurality of spiral thread grooves 131a are engraved in the inner peripheral surface thereof. The direction of the spiral of the screw groove 131a is a direction in which molecules of the exhaust gas are transferred to the exhaust port 133 when the molecules move in the rotation direction of the rotating body 103. The cylindrical portion 102E hangs down at the lowermost portion continuous with the rotation wings 102 (102 a, 102b, 102 c) of the rotation body 103. The outer peripheral surface of the cylindrical portion 102E is cylindrical, and protrudes toward the inner peripheral surface of the threaded spacer 131, and is close to the inner peripheral surface of the threaded spacer 131 with a predetermined gap. The exhaust gas transferred to the screw groove 131a by the rotating fin 102 and the fixed fin 123 is guided by the screw groove 131a and sent to the base portion 129.

The base portion 129 is a disk-shaped member constituting the base portion of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, or stainless steel. The base portion 129 physically holds the turbomolecular pump 100 and also has a function of a heat conduction path, and therefore, it is desirable to use a metal having rigidity and high thermal conductivity such as iron, aluminum, or copper.

In this configuration, when the rotor shaft 113 is driven to rotate together with the rotor 102, the exhaust air is sucked from the chamber through the inlet 101 by the action of the rotor 102 and the stator 123. The exhaust gas sucked through the inlet 101 passes between the rotary vane 102 and the fixed vane 123, and is transferred to the base portion 129. At this time, the temperature of the rotary vane 102 increases due to frictional heat generated when the exhaust gas contacts the rotary vane 102, conduction of heat generated by the motor 121, and the like, but the heat is transferred to the fixed vane 123 side by conduction of radiation, gas molecules of the exhaust gas, and the like.

The fixed vane spacers 125 are joined to each other at the outer peripheral portions, and transmit heat received by the fixed vane 123 from the rotary vane 102, frictional heat generated when the exhaust gas comes into contact with the fixed vane 123, and the like to the outside.

In the above description, the threaded spacer 131 is disposed on the outer periphery of the cylindrical portion 102E of the rotating body 103, and the thread groove 131a is engraved on the inner peripheral surface of the threaded spacer 131. However, in contrast, a screw groove may be engraved in the outer peripheral surface of the cylindrical portion 102E, and a spacer having a cylindrical inner peripheral surface may be disposed around the screw groove.

In addition, depending on the application of the turbomolecular pump 100, the following may be the case: the electric component is covered with the stator pole 122 so that the gas sucked from the inlet 101 does not enter the electric component 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

106A and 106B, the axial sensor 109, and the like, and the inside of the stator pole 122 is kept at a predetermined pressure by the purge gas.

In this case, a pipe, not shown in the drawing, is provided in the base portion 129, and the purge gas is introduced through the pipe. The introduced purge gas is sent to the exhaust port 133 through gaps between the protection bearing 120 and the rotor shaft 113, between the rotor and the stator of the motor 121, and between the stator post 122 and the inner circumferential side cylindrical portion of the rotor wing 102.

Here, the turbo molecular pump 100 needs to control the intrinsic parameters (for example, characteristics corresponding to the model) that are adjusted based on the model determination. In order to store the control parameter, the turbo molecular pump 100 includes an electronic circuit 141 in its main body. The electronic circuit 141 is composed of a semiconductor memory such as an EEP-ROM, electronic components such as a semiconductor device for access, a board 143 for mounting the same, and the like. The electronic circuit portion 141 is housed in a lower portion of a rotational speed sensor, not shown, for example, near the center of the base portion 129, and is closed by an airtight bottom cover 145, and the base portion 129 constitutes a lower portion of the turbomolecular pump 100.

However, in the process of manufacturing a semiconductor, there is a substance having a property that the pressure of the process gas introduced into the chamber becomes higher than a predetermined value or the temperature thereof becomes lower than a predetermined value and becomes solid. Inside the turbo molecular pump 100, the pressure of the exhaust gas is lowest at the intake port 101 and highest at the exhaust port 133. When the pressure of the process gas is higher than a predetermined value and the temperature thereof is lower than a predetermined value while the process gas is being transferred from the inlet 101 to the outlet 133, the process gas is in a solid state and is deposited inside the turbo molecular pump 100.

For example, siCl is used for Al etching device ₄ In the case of the process gas, it is known from the vapor pressure curve that the low vacuum (760 torr]～10 ^-2 [ torr) and low temperature (about 20 DEG C]) When solid products (e.g. AlCl ₃ ) The precipitate is deposited and deposited in the turbo molecular pump 100. As a result, when the deposition of the process gas accumulates in the turbo molecular pump 100, the deposition narrows the pump flow path, which causes a decrease in the performance of the turbo molecular pump 100. And, the foregoingThe product is in a state of being easily solidified and attached in a portion where the pressure is high in the vicinity of the exhaust port and the vicinity of the threaded spacer 131.

Therefore, in order to solve this problem, a heater, which is not shown in the drawings, and a ring-shaped water-cooled tube 149 are conventionally wound around the outer periphery of the base portion 129 or the like, and a temperature sensor (for example, a thermistor), which is not shown in the drawings, is embedded in the base portion 129, for example, and control of heating the heater and cooling the water-cooled tube 149 is performed so that the temperature of the base portion 129 is kept at a constant high temperature (set temperature) based on a signal of the temperature sensor (hereinafter, referred to as tms. Tms; temperature Management System).

Next, the turbomolecular pump 100 configured as described above will be described with respect to the amplification circuit 150 that performs excitation control of the upper radial electromagnet 104, the lower radial electromagnet 105, and the

axial electromagnets

106A and 106B. Fig. 2 shows a circuit diagram of the amplification circuit 150.

In fig. 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 source 171 via the transistor 161, and the other end thereof is connected to the negative electrode 171b of the power source 171 via the current detection circuit 181 and the transistor 162. The transistors 161 and 162 are so-called power field effect transistors, and have a structure in which diodes are connected between source and drain.

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

On the other hand, the current-regenerating diode 165 has a cathode terminal 165a connected to one end of the electromagnet winding 151, and an anode terminal 165b connected to the negative electrode 171 b. In the same manner as above, 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 the current detection circuit 181. The current detection circuit 181 is composed of, for example, a hall sensor type current sensor and a resistor element.

The amplification circuit 150 configured as described above corresponds to one electromagnet. Therefore, when the magnetic bearing is 5-axis controlled and the total number of

electromagnets

104, 105, 106A, 106B is 10, the same amplifying circuit 150 is configured for each electromagnet, and 10 amplifying circuits 150 are connected in parallel to the power source 171.

The amplification control circuit 191 is constituted by, for example, a digital signal processor unit (hereinafter referred to as DSP unit) not shown in the figure of the control device, and the amplification control circuit 191 switches the on/off of the transistors 161 and 162.

The amplification control circuit 191 compares the current value detected by the current detection circuit 181 (a signal reflecting the current value is referred to as a current detection signal 191 c) with a predetermined current command value. Based on the comparison result, the magnitude of the pulse width (pulse width times Tp1, tp 2) generated in the control period Ts, which is one period of PWM control, is determined. As a result, the gate drive signals 191a and 191b having the pulse width are output from the amplification control loop 191 to the gate terminals of the transistors 161 and 162.

In addition, when the rotational speed of the rotor 103 passes a resonance point during acceleration operation, when external disturbance occurs during constant speed operation, or the like, it is necessary to perform high-speed and strong position control of the rotor 103. Therefore, in order to enable a rapid increase (or decrease) in the current flowing to the electromagnet winding 151, a high voltage of, for example, about 50V is used as the power source 171. In order to stabilize the power source 171, a capacitor is typically connected between the positive electrode 171a and the negative electrode 171b of the power source 171 (not shown).

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

When one of the transistors 161 and 162 is turned on and the other is turned off, so-called fly wheel current is maintained. In addition, by flowing the flywheel current through the amplification circuit 150 in this way, hysteresis loss of the amplification circuit 150 is reduced, and power consumption of the entire circuit can be suppressed to be low. Further, by controlling the transistors 161 and 162 in this manner, high-frequency noise such as high-frequency modulation generated in the turbo molecular pump 100 can be reduced. Further, by measuring the flywheel current through the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

That is, when the detected current value is smaller than the current command value, both the transistors 161 and 162 are turned on 1 time for a time corresponding to the pulse width time Tp1 in the control period Ts (for example, 100 μs), as shown in fig. 3. Accordingly, the electromagnet current iL during this period increases from the positive electrode 171a toward the negative electrode 171b to a current value iLmax (not shown) that can flow through the transistors 161 and 162.

On the other hand, when the detected current value is larger than the current command value, both the transistors 161 and 162 are turned off 1 time for a time corresponding to the pulse width time Tp2 in the control period Ts, as shown in fig. 4. Accordingly, the electromagnet current iL in this period decreases from the negative electrode 171b to the positive electrode 171a to a current value iLmin (not shown) that can be regenerated via the diodes 165 and 166.

In either case, after the pulse width times Tp1 and Tp2 have elapsed, either of the transistors 161 and 162 is turned on. Therefore, during this period, the flywheel current at the amplifying circuit 150 is maintained.

However, the outer tube 127 as a case is constituted by an upper layer group gas transfer portion having cooling side stators 110A (fixed fins 123a to 123 f) and cooling side rotating fins 102A (rotating fins 102A to 102 g) arranged in a cooling range to be cooled, and a lower layer group gas transfer portion having heating side stators 110B (fixed fins 123h to 123 j) and cooling side rotating fins 102B (rotating fins 102h to 102 k) arranged in a heating range to be heated. An O-ring 112 is disposed between the cooling side stator 110A and the heating side stator 110B, and a gap 114 is provided between the cooling side stator 110A and the heating side stator 110B so as to be away from each other by a predetermined amount, whereby the cooling side stator 110A and the heating side stator 110B are independent, and the temperature of the cooling side stator 110A and the temperature of the heating side stator 110B do not affect each other. Further, the fixed vane spacer 125 is pressed and positioned between the cooling side stator 110A and the heating side stator 110B by the bolts 115. In fig. 1, reference numeral 152 denotes a temperature sensor that detects the temperature of the

cooling side stator

110A, 153 denotes a temperature sensor that detects the temperature of the

heating side stator

110B, 154 denotes a heater that heats the heating side stator 11OB, and 155 denotes a cooling pipe that cools the cooling side stator 110A.

On the other hand, between the cooling-side rotating vane 102g of the upper layer group gas transfer unit and the heating-side rotating vane 102h of the lower layer group gas transfer unit, which are adjacent to the opening 114A of the gap 114 between the cooling-side stator 110A and the heating-side stator 11OB, the positions of the rotating vane 102g and the rotating vane 102h are shifted in the axial direction, that is, in the up-down direction, with respect to the opening 114A so that the outer peripheral surfaces of the cooling-side rotating vane 102g and the heating-side rotating vane 102h do not face the opening 114A of the gap 114, respectively, and a gap of a distance S is provided between the rotating vane 102g and the rotating vane 102 h. Preferably, the distance S is ensured to be of the following magnitude: when the cooling side stator 110A and the heating side stator 110B are positioned by being pressed by the bolts 115, the opening 114A of the gap 114 does not face from the front to the back even if either one or both of the cooling side stator 110A and the heating side stator 110B move in the axial direction.

Further, as a preferable position of the opening 114A, considering the movement of molecules of the process gas by the

rotating fins

102g and 102h, it is conceivable that the axial distance between the

rotating fins

102g and 102h is approximately the center. However, the position of the opening 114A is not limited to the substantially central position, and may be, for example, a position located downstream of the substantially central position with importance attached to the movement of molecules of the process gas by the rotating fins 102 g.

The size (axial dimension) of the width of the opening 114A of the gap 114 is set to a predetermined width that makes it as difficult for molecules to enter as possible, considering the average free path, the heat insulating effect, and the like, which are average values of the distances that the molecules of the process gas can travel without colliding with other molecules and changing the travel path. For example, the size of the gap 114 and the opening 114A is 0.1mm to 2.0mm, and more preferably 0.5mm to 1.0mm.

In the structure of this embodiment, as shown by an enlarged portion a of fig. 1 in fig. 5, a horizontal clearance portion 114A and an inclined clearance portion 114b are integrally formed in the shape of a longitudinal section of the clearance 114 when the outer tube 127 as a case is cut longitudinally in the axial direction, and the horizontal clearance portion 114A is formed in an inverted L shape from the opening portion 114A, the 1 st clearance portion horizontally extends from the opening portion 114A to the outside in the radial direction perpendicular to the axial direction, the inclined clearance portion 114b is formed as a 2 nd clearance portion, the 2 nd clearance portion further extends radially outward from the outside end of the horizontal clearance portion 114A and obliquely downward in the downstream side in the axial direction, and the inclined clearance portion 114b is inclined. In the following description, the upstream side in the axial direction is the intake port 101 side, and the downstream side in the axial direction is the exhaust port 133 side. The axial direction refers to the axial direction of the rotor shaft 113, and the radial direction refers to a direction perpendicular to the axis, that is, the radial direction of the outer tube 127.

In the vacuum pump 10 configured as in this embodiment, an opening 114A of a gap 114 of a predetermined width for insulating heat between the cooling side stator 110A and the heating side stator 110B is provided at a position not opposed to the outer peripheral surface of the rotor 102 (the rotor 102g and the rotor 102 h) in the axial direction of the rotor 103 and offset in the axial direction. Therefore, even if a part of the process gas flies toward the inner peripheral surfaces of the cooling side stator 110A and the heating side stator 110B of the cylindrical portion 102E due to the centrifugal force caused by the rotation of the rotating fins 102, the amount of the process gas entering the opening 114A of the gap 114 is very small, and the amount of the deposit deposited in the gap 114 can be reduced. This can lengthen the interval at which maintenance work is required to remove the deposited material or the like deposited in the gap 114, contributing to improvement in productivity.

In the embodiment shown in fig. 1 and 5, the shape of the longitudinal section of the gap 114 when the outer tube 127 as the case is cut in the axial direction is shown as a structure in which a horizontal gap portion 114A and an inclined gap portion 114b are integrally provided, the horizontal gap portion 114A extends horizontally outward from the opening 114A, the inclined gap portion 114b extends obliquely outward in the radial direction and downstream in the axial direction from the outer end of the horizontal gap portion 114A, and the inclined gap portion 114b is inclined.

In the structure shown in fig. 1 and 5, when the process gas enters the horizontal gap portion 114A from the opening 114A, there is a slope gap portion 114b, and the slope gap portion 114b extends from the outer end of the horizontal gap portion 114A to bend obliquely downward toward the outside, so when the process gas enters the horizontal gap portion 114A from the opening 114A and then flows into the slope gap portion 114b, the slope gap portion 114b collides as a wall, and the process gas flows further toward the inside. This can reduce the amount of process gas entering the gap 114 from the opening 114A, and can further reduce the amount of deposition generated by the process gas.

The structure of the gap 114 is not limited to the structures shown in fig. 1 and 5, and may be, for example, the structures shown in fig. 6, 7, and 8. Further, the inclined gap portion 114b may be a gap portion extending further radially outward and axially upstream from the outer end of the horizontal gap portion 114a to an obliquely upper side.

In the structure of the gap 114 shown in fig. 6, the vertical gap portion 114c and the horizontal gap portion 114A are integrally formed in the shape of a longitudinal section of the gap 114 when the outer tube 127 as the case is cut in the axial direction, and have a portion formed in a substantially I-shape from the opening 114A, and the vertical gap portion 114c is a 3 rd gap portion which is immediately directed to the downstream side in the axial direction when entering the opening 114A, and the horizontal gap portion 114A horizontally extends from the lower end of the vertical gap portion 114c to the outer side in the radial direction.

In the structure of fig. 6, when the process gas is to enter the gap 114 from the opening 114A by forming the gap 114 in a substantially I-shaped cross-sectional shape, a wall of the vertical gap portion 114c facing the axially downstream side is present at a position immediately before entering the opening 114A, and therefore, the wall becomes a resistance to the flow of the process gas inward. This can reduce the amount of process gas entering the gap 114 from the opening 114A, and can further reduce the amount of deposits that may be generated. The vertical gap portion 114c is configured to be oriented toward the axially downstream side when entering the opening 114A, but may be configured to be oriented toward the axially upstream side when entering the opening 114A.

In the structure of the gap 114 shown in fig. 7, the shape of the longitudinal section of the gap 114 when the outer tube 127 as a case is cut in the axial direction is configured such that the inclined gap portion 114d and the inclined gap portion 114e are integrally provided to have a portion formed in a substantially inverted V shape from the opening 114A, the inclined gap portion 114d is a 4 th gap portion, the 4 th gap portion extends obliquely from the opening 114A to the outside in the radial direction perpendicular to the axial direction and to the upstream side in the axial direction when the gap portion 114A is entered, the inclined gap portion 114e is a 5 th gap portion, and the 5 th gap portion extends obliquely from the outer end of the inclined gap portion 114d to the downstream side in the axial direction.

In the structure of fig. 7, since the process gas having entered the inclined gap 114d from the opening 114A is lifted obliquely upward to the outside when entering the inclined gap 114d, the inclined gap 114d inclined obliquely upward to the outside collides with the process gas as a wall, and the process gas is prevented from flowing inward. This can reduce the amount of process gas entering the gap 114 from the opening 114A, and can further reduce the amount of deposition generated by the process gas.

In the structure of fig. 7, the inclined gap portion 114d and the inclined gap portion 114e are integrally provided to have a portion formed in a substantially inverted V shape from the opening 114A, the inclined gap portion 114d extending obliquely from the opening 114A to the outside in the radial direction perpendicular to the axial direction and upstream in the axial direction, and the inclined gap portion 114e extending obliquely from the outer end of the inclined gap portion 114d to the downstream side in the axial direction, but it is also possible to provide either the inclined gap portion 114d extending obliquely from the opening 114A to the upstream side or the inclined gap portion 114e extending obliquely from the opening 114A to the downstream side.

In the structure of the gap 114 shown in fig. 8, when the outer tube 127 serving as a case is cut in the axial direction, a flange 116 protruding inward of the outer tube 127 than the opening 114A is provided at an upper portion of the opening 114A of the gap 114 formed on the inner peripheral surface of the outer tube 127. That is, the flange 116 forms a step with the opening 114A, and the gas flow can be controlled so that the process gas flowing from the upstream side directly enters the downstream side without going in the direction of the opening 114A. The gap 114 is configured such that a vertical gap portion 114c and a horizontal gap portion 114A are integrally provided, and a portion formed in a substantially I-shape from the opening 114A is provided, the vertical gap portion 114c being a 3 rd gap portion facing the downstream side immediately after entering the opening 114A, and the horizontal gap portion 114A extending horizontally from the lower end of the vertical gap portion 114c to the outside in the radial direction perpendicular to the axial direction.

In the structure of fig. 8, when the process gas is to enter the gap 114 from the opening 114A by forming the gap 114 in a substantially I-shape in cross section, a wall of the vertical gap portion 114c facing downward is present at a position immediately before entering the opening 114A, and therefore, the process gas collides with the wall and becomes resistance to flow of the process gas toward the inside. This can reduce the amount of process gas entering the gap 114 from the opening 114A, and can further reduce the amount of deposition generated by the process gas. Further, R chamfering is performed on the lower surface edge portion (flange distal lower surface) 116a of the flange portion 116 and the lower side edge portion 114g of the opening portion 114A, respectively. When a part of the process gas in the outer tube 127 that has been returned by the rotating fins 102 collides with the lower surface edge portion 116a or the lower side edge portion 114g, the R chamfering process makes a part of the collided process gas face in a direction of the rotor shaft 113 different from that in the opening 114A, and does not enter the opening 114A.

In addition, the present invention can be variously modified without departing from the spirit of the present invention, and it is apparent that the present invention also relates to the modification.

Description of the reference numerals

100: turbomolecular pump

101: suction port

102: rotary wing

102A: cooling side rotary wing

102B: cooling side rotary wing

102E: cylindrical portion

102a: rotary wing

102b: rotary wing

102c: rotary wing

102d: rotary wing

102e: rotary wing

102f: rotary wing

102g: rotary wing

103: rotating body

104: upper radial electromagnet

105: lower radial electromagnet

106A: axial electromagnet

106B: axial electromagnet

107: upper radial sensor

108: underside radial sensor

109: axial sensor

110A: cooling side stator (upper layer gas transfer part)

110B: heating side stator (lower layer gas transfer part)

111: metal disc

112: o-shaped ring

113: rotor shaft

114: gap of

114A: an opening part

114a: horizontal gap portion (1 st gap portion)

114b: inclined gap portion (gap portion 2)

114c: vertical gap portion (3 rd gap portion)

114d: inclined gap portion (4 th gap portion)

114e: inclined gap portion (5 th gap portion)

114g: lower side edge portion

115: bolt

116: flange part

116a: lower surface edge portion

120: protective bearing

121: motor with a motor housing

122: stator post

123: fixed wing

123a: fixed wing

123b: fixed wing

123c: fixed wing

123d: fixed wing

123e: fixed wing

123f: fixed wing

123g: fixed wing

123h: fixed wing

123i: fixed wing

125: fixed wing spacer

127: outer cylinder

129: base portion

131: threaded spacer

131a: thread groove

133: exhaust port

141: electronic circuit part

143: substrate board

145: bottom cover

149: water cooling pipe

150: amplifying circuit

151: electromagnet winding

152: temperature sensor

153: temperature sensor

154: electromagnet winding

155: water cooling pipe

161: heater

161a: cathode terminal

161b: anode terminal

162: transistor with a high-voltage power supply

162a: cathode terminal

162b: anode terminal

165: diode

165a: cathode terminal

165b: anode terminal

166: diode

166a: cathode terminal

166b: anode terminal

171: power supply

171a: positive electrode

171b: negative electrode

181: current detection loop

191: amplifying control loop

191a: gate drive signal

191b: gate drive signal

191c: current detection signal

S: distance of

Tpl; pulse width time

Tp2; pulse width time

Ts: control period

iL: electromagnet current

iLmax: current value

illimin: a current value.

Claims

1. A vacuum pump having a casing, a rotor shaft, a plurality of rotary vanes, a plurality of stationary vanes, a cooling side stator, and a heating side stator,

The aforementioned housing has an air suction port and an air discharge port,

the rotor shaft is rotatably supported inside the housing,

the multi-layered rotor wing is rotatable with the rotor shaft,

the multi-layered stationary blades are fixed to the housing and disposed between the multi-layered rotating blades,

the cooling side stator and the heating side stator hold the multi-layered fixed wing at a predetermined interval,

the aforementioned vacuum pump is characterized in that,

an opening portion of a gap of a predetermined width is provided at a position not facing the outer peripheral surface of the rotor blade in the axial direction of the rotor shaft, the gap thermally insulating between the cooling side stator and the heating side stator.

2. The vacuum pump according to claim 1, wherein,

the shape of the aforementioned gap has a 1 st gap portion and a 2 nd gap portion,

the 1 st gap portion extends horizontally to the outside in the radial direction perpendicular to the axial direction,

the 2 nd gap portion extends further outward in the radial direction than the outer end of the 1 st gap portion and downstream in the axial direction.

3. A vacuum pump according to claim 1 or 2, wherein,

the gap has a 3 rd gap portion extending along a downstream side in the axial direction.

4. A vacuum pump according to any one of claim 1 to 3,

the gap has a 4 th gap portion, and the 4 th gap portion extends radially outward perpendicular to the axial direction and upstream in the axial direction.

5. A vacuum pump according to any one of claim 1 to 4,

the gap has a flange protruding from the opening toward the inside of the case at an upper portion of the opening.