KR20230062812A - vacuum pump - Google Patents

Abstract

(Problem) A vacuum pump capable of improving productivity by reducing the flow of gas (the number of gas molecules) toward the gap formed for insulation, reducing the amount of by-products deposited in the gap, and increasing the gap requiring maintenance. provides
(Means of solution) An outer cylinder 127 having an inlet port 101 and an exhaust port 133, a rotor shaft 113 freely rotatably supported inside the outer cylinder 127, and rotatable together with the rotor shaft 113 Multiple stages of rotary blades 102, multiple stages of stator blades 123 fixed to the outer cylinder and arranged between the multiple stages of rotation blades 102, and multiple stages of stator blades 123 are A cooling stator 110A and a heating stator 110B are provided, and an opening 114A of a gap 114 having a predetermined width to insulate between the cooling stator 110A and the heating stator 110B is provided. was formed at a position not facing the outer circumferential surface of the rotary blade 102 in the axial direction of the rotary body 103.

Description

vacuum pump

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

In recent years, in a process of forming a semiconductor element from a wafer as a processing target substrate, a method of manufacturing a semiconductor element of a product by processing the wafer in a process chamber of a semiconductor manufacturing apparatus maintained in a high vacuum has been taken. In a semiconductor manufacturing apparatus that processes wafers in a vacuum chamber, a vacuum pump having a turbo molecular pump unit, a screw groove pump unit, and the like is used to achieve and maintain a high degree of vacuum.

The turbo molecular pump unit has, inside the casing, rotatable rotor blades made of thin metal and fixed blades fixed to the casing. Then, the rotary blade is operated at a high speed of, for example, hundreds of m/sec, so that the process gas used for processing coming in from the intake port side is compressed inside the pump and exhausted from the exhaust port side.

By the way, the molecules of the process gas drawn in from the inlet side of the vacuum pump are at a high temperature immediately after being sucked in, and are cooled in the compression process associated with movement to the exhaust port side in accordance with the rotation of the rotary vane within the vacuum pump. When the process gas is cooled, it solidifies, and the solidified by-product adheres to the stator blade or the inner surface of the outer cylinder (casing) and deposits as a deposit. As a by-product, chlorine-based or sulfide-fluorine-based gases are common. For these gases, the degree of vacuum decreases and the sublimation temperature increases as the pressure increases, so that the gas tends to be solidified and deposited inside the vacuum pump. If the reaction product accumulates inside the vacuum pump, the passage of the reaction product may be narrowed and the compression performance and exhaust performance of the vacuum pump may deteriorate. On the other hand, in a gas transfer section using aluminum or stainless steel for the rotor blades or stator blades, if the temperature is too high, the strength of the rotor blades or stator blades may decrease and breakage may occur during operation. In addition, there is a concern that the electrical components installed in the vacuum pump and the electric motor that rotates the rotor may not exhibit desired performance when the temperature rises. Therefore, the vacuum pump requires temperature control to maintain a predetermined temperature.

Therefore, as a vacuum pump that suppresses the accumulation of reaction products, a structure is also known in which a cooling device or a heating device is installed around the stator to control the temperature in the gas passage and to transfer the gas in the gas passage without solidifying it. There is (see Patent Document 1, for example).

However, the sucked gas in the vacuum pump has a characteristic that the sublimation temperature increases as the vacuum degree increases and the pressure becomes higher, so that the gas tends to be solidified and deposited inside the vacuum pump. On the other hand, when the temperature is too high, the gas conveying unit composed of rotary blades or stator blades may have a problem in that strength is lowered or adversely affect the performance of electrical components and electric motors in the vacuum pump. Therefore, the solidification of the gas inside the vacuum pump can be suppressed while the vacuum pump is operated normally, without adversely affecting the performance of the electrical components and electric motors in the vacuum pump and without reducing the strength of the gas transfer section. It is preferable to perform temperature control.

So, for example, like the vacuum pump 10 shown in Figs. 9 and 10, the upper group gas conveying part 11 having the cooling stator 17A disposed within the cooling range requiring cooling and heating is required. divided into the lower gas conveying part 12 having the heating stator 17B disposed within the heating range for cooling, forming a gap 15 between the cooling stator 17A and the heating stator 17B, so that the cooling stator ( 17A) and the heating side stator 17B are independent of each other so that the temperature of the upper group gas transfer section 11 and the temperature of the lower group gas delivery section 12 do not influence each other. Further, between the cooling stator 17A and the heating stator 17B, the stator blade spacer 14 is pressed with a bolt 19 for positioning.

Japanese Patent Laid-Open No. 10-205486

In the structure in which the positioning between the cooling stator 17A and the heating stator 17B is pressed with a bolt 19, the magnitude of the force for tightening the bolt 19 and the amount of deformation of the O-ring 18 due to the tightening , or the type of stator blade spacer 14, etc., the size (size in the axial direction) of the gap 15 between the cooling stator 17A and the heating stator 17B changes. And, when the gap 15 is positioned in a state facing the circumferential surface in the radial direction of the rotor blade 16, when the rotor blade 16 rotates, the rotor blade 16 moves the tangential direction and the downstream direction. Molecules of the process gas transferred into the gap 15 are more likely to be directed (the number of gas molecules increases). Then, the gas entering the gap 15 is cooled by the cooling stator 17A, solidified in the gap 15, and deposited as a by-product. This deposit narrows the width of the gap 15, reduces the thermal insulation effect, and changes the temperature distribution in the pump. Therefore, maintenance work is required, such as disassembling the vacuum pump 10 on a regular basis, to remove deposits accumulated in the gap 15 . Due to this maintenance work, there was a problem that productivity was poor.

Therefore, a vacuum pump capable of improving productivity by reducing the flow of gas (the number of gas molecules) toward the gap installed for insulation, reducing the amount of by-products deposited in the gap, and increasing the interval requiring maintenance work. There is a technical problem to be solved in order to provide, and the present invention aims to solve this problem.

The present invention has been proposed to achieve the above object, and the invention described in claim 1 is a casing having an intake port and an exhaust port, a rotor shaft freely rotatably supported inside the casing, and rotatable together with the rotor shaft. A plurality of stages of rotary blades, a plurality of stages of stator blades fixed to the casing and arranged between the plurality of stages of rotor blades, a cooling stator holding the plurality of stages of stator blades at a predetermined interval, and heating A vacuum pump with side stators, wherein an opening of a gap of a predetermined width for thermal insulation between the cooling side stator and the heating side stator is formed at a position that does not face the outer circumferential surface of the rotary blade in the axial direction of the rotor shaft. , providing a vacuum pump.

According to this configuration, an opening with a predetermined width for thermal insulation between the cooling stator and the heating stator is formed at a position not facing the outer circumferential surface of the rotary blade in the axial direction of the rotor shaft. Therefore, even if a part of the gas is blown toward the inner circumferential surface of the stator due to the centrifugal force caused by the rotation of the rotor blades, since the opening of the gap is formed in a deflected position that does not face the outer circumferential surface of the rotor blade, the amount of gas entering the opening of the gap is also reduced. It is extremely small, and the amount of sediment deposited in the gap can be reduced. For this reason, the interval which requires maintenance work can be lengthened, and it contributes to the improvement of productivity.

In the invention according to claim 2, in the configuration according to claim 1, the shape of the gap is a first gap portion extending horizontally outward in a radial direction perpendicular to the axial direction; A vacuum pump having a second gap portion extending from an outer end of the gap portion further outward in the radial direction and along a downstream side in the axial direction.

According to this configuration, when the process gas entering the first gap portion from the opening is about to proceed further inward, it hits the wall of the next second gap portion once, so that the wall becomes a resistance This makes it possible to reduce the amount of process gas entering the gap from the opening, thereby reducing the amount of deposits produced in the process gas.

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

According to this configuration, when the process gas is about to enter the gap from the opening, the portion of the third gap facing downward becomes a wall and collides directly in front of the opening, thereby resisting the flow of the process gas toward the inside of the gap. . This makes it possible to reduce the amount of process gas entering the gap from the opening, thereby reducing the amount of deposits produced in the process gas.

In the invention according to claim 4, in the structure according to any one of claims 1 to 3, the shape of the gap is a fourth that extends outward in a radial direction perpendicular to the axial direction and further upstream in the axial direction. A vacuum pump having a gap portion is provided.

According to this configuration, the shape of the longitudinal section of the gap has a fourth gap portion extending outward in the radial direction perpendicular to the axial direction and further upstream in the axial direction. Accordingly, the process gas entering the gap from the opening part collides once with the fourth gap portion, and becomes resistance to the flow of the process gas toward the inside of the gap. This makes it possible to reduce the amount of process gas entering the gap from the opening, thereby reducing the amount of deposits produced in the process gas.

In the invention according to claim 5, in the structure according to any one of claims 1 to 4, the shape of the gap has an eaves protruding from the opening to the inside of the casing above the opening, the vacuum pump is provided.

According to this configuration, the shape of the longitudinal section of the gap is such that when the casing is longitudinally sectioned in the axial direction, the upper part of the opening of the gap formed on the inner circumferential surface of the casing is formed with the eaves protruding toward the inside of the casing from the opening. The flow of the process gas flowing out from the side is controlled to the eaves, so that it does not go in the direction of the opening of the gap, but can be directed to a different downstream side from the opening. This makes it possible to reduce the amount of process gas entering the gap from the opening, thereby reducing the amount of deposits produced in the process gas.

According to the present invention, it is possible to reduce the amount of process gas entering the gap formed for thermal insulation, thereby reducing the amount of deposits generated from the process gas deposited in the gap. For this reason, it is possible to increase productivity by increasing the interval required for maintenance work for removing deposits in the gap.

In addition, the insulation effect of the gap is also improved, and the temperature is controlled within a range that does not adversely affect the performance of the electrical components installed in the vacuum pump or the electric motor that rotates the rotor, and does not affect the strength of the rotor or stator. Fine control becomes possible.

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

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 amplifier circuit in the turbo molecular pump.
3 is a time chart showing a control example in the case where the current command value detected by the amplifier circuit in the turbo molecular pump is greater than the detected value.
4 is a time chart showing a control example in the case where the current command value detected by the amplifier circuit in the turbo molecular pump is smaller than the detected value.
5 is an enlarged cross-sectional view of a portion of the turbo molecular pump shown in FIG. 1, (a) is an enlarged view of portion A in FIG. 1, and (b) is a partially enlarged cross-sectional view to explain the shape of the gap.
6 shows a modified example of the present invention, (a) is a partially enlarged view corresponding to part A in FIG. 1, and (b) is a cross-sectional view of a part of (a) enlarged to explain the shape of the gap. am.
7 shows another modified example of the present invention, (a) is a partially enlarged view corresponding to part A in FIG. 1, and (b) is a cross-sectional view of a part of (a) enlarged to explain the shape of the gap. am.
8 shows another modified example of the present invention, (a) is a partially enlarged view corresponding to part A in FIG. 1, and (b) is a part of (a) enlarged to explain the shape of the gap it is a cross section
Fig. 9 is a longitudinal sectional view of a turbo molecular pump shown as an example of a conventional vacuum pump.
Fig. 10 is a partially enlarged view corresponding to section B in Fig. 9;

The present invention reduces the flow of gas (the number of gas molecules) toward the gap formed for insulation, reduces the amount of by-products deposited in the gap, and increases the interval requiring maintenance work, thereby improving productivity. In order to achieve the object of providing a vacuum pump, a casing having an intake port and an exhaust port, a rotor shaft freely rotatably supported inside the casing, and a plurality of stages of rotary blades rotatable together with the rotor shaft,

A vacuum pump comprising a plurality of stages of stator blades fixed to the casing and disposed between the plurality of stages of rotary blades, a heating stator and a cooling stator for holding the plurality of stages of stator blades at predetermined intervals. This was achieved by forming an opening with a predetermined width for thermal insulation between the heating stator and the cooling stator at a position not facing the outer circumferential surface of the rotary blade in the axial direction of the rotor shaft.

Example

Hereinafter, an embodiment according to an embodiment of the present invention will be described in detail based on the accompanying drawings. In addition, in the following embodiments, when referring to the number, numerical value, amount, range, etc. of components, unless specifically specified and in principle clearly limited to a specific number, it is not limited to that specific number, It does not matter whether it is more than or less than a specific number.

In addition, when referring to the shape and positional relationship of components, etc., substantially approximating or similar to the shape, etc. is included, except when it is specifically specified or when it is considered clearly not in principle.

In addition, drawings may exaggerate characteristic parts by enlarging or the like to make the characteristics easier to understand, and it cannot be said that the dimensional ratios and the like of constituent elements are the same as in reality. In cross-sectional views, hatching of some components may be omitted in order to make the cross-sectional structure of the components easier to understand.

Further, in the following description, expressions indicating directions such as up and down, left and right are not absolute, and are appropriate for the posture in which each part of the turbo molecular pump of the present invention is drawn, but when the posture changes, the posture changes. will have to be modified and interpreted accordingly. In addition, the same reference numerals are attached to the same elements throughout the description of the embodiments.

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.

1, in the turbo molecular pump 100, an intake port 101 is formed at the upper end of an outer cylinder 127 as a cylindrical housing. Inside the outer cylinder 127, a rotating body 103 having a plurality of rotary blades 102 (102a, 102b, 102c...), which are turbine blades for suctioning and exhausting gas, radially and in multiple stages formed on the periphery. It is available. A rotor shaft 113 is attached to the center of this rotating body 103, and this rotor shaft 113 is suspended in the air and its position is controlled by, for example, five-axis magnetic bearings.

In the upper radial electromagnet 104, four electromagnets are arranged in pairs on the X axis and the Y axis. In the vicinity of the upper radial electromagnet 104, four upper radial sensors 107 corresponding to each of the upper radial electromagnets 104 are provided. For the upper radial direction sensor 107, for example, an inductance sensor or an eddy current sensor having a conduction winding is used, and based on a change in inductance of the conduction coil that changes according to the position of the rotor shaft 113, The position of the rotor shaft 113 is detected. This upper radial direction sensor 107 is configured to detect the radial displacement of the rotor shaft 113, that is, the rotary body 103 fixed thereto, and send it to a control device (not shown).

In this control device, for example, a compensating circuit having a PID adjusting function generates an excitation control command signal for the upper radial electromagnet 104 based on the position signal detected by the upper radial sensor 107, , the amplifier circuit 150 shown in FIG. 2 (to be described later) controls the excitation of the upper radial electromagnet 104 based on this excitation control command signal, so that the upper radial position of the rotor shaft 113 is adjusted. do.

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

Further, the axial electromagnets 106A and 106B are disposed vertically sandwiching a disc-shaped metal disk 111 provided under the rotor shaft 113. The metal disk 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and the axial position signal is configured to be sent to a control device.

Then, in the control device, for example, a compensating circuit having a PID adjusting function, based on the axial position signal detected by the axial sensor 109, the axial electromagnet 106A and the axial electromagnet 106B Each excitation control command signal is generated, and the amplifier circuit 150 controls the excitation of the axial electromagnet 106A and the axial electromagnet 106B, respectively, based on these excitation control command signals, so that the axial electromagnet 106A ) attracts the metal disk 111 upward by magnetic force, and the axial electromagnet 106B attracts the metal disk 111 downward, so that the axial position of the rotor shaft 113 is adjusted.

In this way, the control device appropriately adjusts the magnetic force exerted by the axial electromagnets 106A and 106B on the metal disk 111 to magnetically levitate the rotor shaft 113 in the axial direction and maintain it in a non-contact space. has been The amplifier circuit 150 for controlling the excitation 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 arranged in a circumferential shape so as to surround the rotor shaft 113 . Each magnetic pole is controlled by a controller so as to rotationally drive the rotor shaft 113 through electromagnetic force acting between them and the rotor shaft 113 . In addition, a rotation speed sensor such as a Hall element, a resolver, an encoder, etc., not shown, is incorporated in the motor 121, and the rotation speed of the rotor shaft 113 is detected by the detection signal of this rotation speed sensor. there is.

Further, for example, a phase sensor (not shown) is attached near the lower radial direction sensor 108 to detect the rotational phase of the rotor shaft 113. In the control device, the position of the magnetic pole is detected using both the detection signals of the phase sensor and the rotational speed sensor.

A plurality of stator blades 123 (123a, 123b, 123c...) are disposed with a slight gap between the rotary blades 102 (102a, 102b, 102c...). The rotor blades 102 are formed inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 to transport exhaust gas molecules downward by collision.

In addition, the stator blades 123 are similarly formed inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are alternately arranged with the ends of the rotor blades 102 toward the inside of the outer cylinder 127. there is. The outer circumferential edge of the stator blade 123 is supported while being sandwiched between the stator blade spacers 125 (125a, 125b, 125c...) in which a plurality of stages are stacked.

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 an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer periphery of the stator blade spacer 125 with a slight gap therebetween. A base portion 129 is disposed at the bottom of the outer cylinder 127 . An exhaust port 133 is formed in the base portion 129 and communicates with the outside. Exhaust gas that enters the intake port 101 from the chamber side and is transported to the base portion 129 is sent to the exhaust port 133 .

In addition, depending on the purpose of the turbo molecular pump 100, a screwed spacer 131 is disposed between the lower portion of the fixed vane spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals as a component, and has a plurality of spiral screw grooves 131a on its inner circumferential surface. it is engraved The spiral direction of the screw groove 131a is the direction in which the molecules of the exhaust gas are transported to the exhaust port 133 when the molecules of the exhaust gas move in the direction of rotation of the rotating body 103 . A cylindrical portion 102E hangs down at the lowest portion of the rotating body 103 leading to the rotor blades 102 (102a, 102b, 102c...). The outer circumferential surface of this cylindrical portion 102E has a cylindrical shape and protrudes toward the inner circumferential surface of the threaded spacer 131, and approaches the inner circumferential surface of the threaded spacer 131 with a predetermined gap therebetween. The exhaust gas transported to the screw groove 131a by the rotary blade 102 and the stator blade 123 is sent to the base portion 129 while being guided by the screw groove 131a.

The base portion 129 is a disk-shaped member constituting the base portion of the turbo molecular pump 100, and is generally made of metal such as iron, aluminum, or stainless steel. The base part 129 not only physically holds the turbo molecular pump 100, but also functions as a heat conduction path, so a metal having rigidity such as iron, aluminum or copper and having high thermal conductivity is used. it is desirable to be

In this configuration, when the rotary blade 102 is rotationally driven by the motor 121 together with the rotor shaft 113, the rotary blade 102 and the fixed blade 123 act through the intake port 101. Exhaust gas is aspirated from the chamber. Exhaust gas taken in from the intake port 101 passes between the rotary blade 102 and the stator blade 123 and is transferred to the base portion 129 . At this time, the temperature of the rotor blades 102 rises due to frictional heat generated when the exhaust gas contacts the rotor blades 102 or the conduction of heat generated by the motor 121, and the like. is transmitted to the stator blade 123 side by conduction by gas molecules or the like.

The stator blade spacer 125 is bonded to each other at the outer periphery, and transfers heat received by the stator blade 123 from the rotary blade 102 or frictional heat generated when exhaust gas contacts the stator blade 123 to the outside. do.

In addition, in the above, the threaded spacer 131 is disposed on the outer circumference of the cylindrical portion 102E of the rotating body 103, and the threaded spacer 131 is engraved with a threaded groove 131a on the inner circumferential surface. Explained. However, in some cases, on the contrary, a screw groove is engraved on the outer circumferential surface of the cylindrical portion 102E, and a spacer having a cylindrical inner circumferential surface is disposed around it.

In addition, depending on the purpose of the turbo molecular pump 100, the gas sucked from the intake port 101 passes through the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, and the lower radial electromagnet 105. ), the lower radial sensor 108, the axial electromagnets 106A and 106B, the axial sensor 109, etc., so that the electric part does not intrude into the electric part, the stator column 122 covers the circumference, In some cases, the stator column 122 is maintained at a predetermined pressure with a purge gas.

In this case, a pipe (not shown) is disposed in the base portion 129, and the purge gas is introduced through the pipe. The introduced purge gas passes through gaps between the protective bearing 120 and the rotor shaft 113, between the rotor and the stator of the motor 121, and between the stator column 122 and the inner peripheral side cylindrical portion of the rotor blade 102. It is sent to the exhaust port 133.

Here, the turbo molecular pump 100 requires identification of the model and control based on individually adjusted unique parameters (eg, various characteristics corresponding to the model). To store these control parameters, the turbo molecular pump 100 has an electronic circuit section 141 in its main body. The electronic circuit section 141 is composed of semiconductor memories such as EEP-ROM, electronic components such as semiconductor devices for access thereto, and a mounting board 143 and the like. This electronic circuit portion 141 is housed in, for example, a lower portion of a rotational speed sensor (not shown) near the center of the base portion 129 constituting the lower portion of the turbo molecular pump 100, and forms an airtight bottom cover 145. is closed by

By the way, in a semiconductor manufacturing process, some of the process gases introduced into the chamber have the property of becoming solid when the pressure is higher than a predetermined value or the temperature is lower than a predetermined value. Inside the turbo molecular pump 100, the pressure of the exhaust gas is lowest at the intake port 101 and highest at the exhaust port 133. While the process gas is transferred from the inlet port 101 to the exhaust port 133, when the pressure is higher than a predetermined value or the temperature is lower than a predetermined value, the process gas becomes a solid, and the turbo molecular pump 100 It adheres to the inside and accumulates.

For example, when SiCl4 is used as a process gas in an Al etching device, a solid product (eg For example, it can be seen from the vapor pressure curve that AlCl3) is precipitated and deposited inside the turbo molecular pump 100. For this reason, when precipitates of the process gas are deposited inside the turbo molecular pump 100, the deposits narrow the pump passage and cause deterioration in the performance of the turbo molecular pump 100. In addition, the above-mentioned product was in a situation where it was easy to solidify and adhere in a high-pressure area near the exhaust port or near the threaded spacer 131.

Therefore, in order to solve this problem, conventionally, a heater or an annular water cooling tube 149 (not shown) is wound around the outer periphery of the base portion 129 or the like, and further, for example, the base portion 129 A temperature sensor (for example, a thermistor) not shown is embedded, and based on the signal of this temperature sensor, the temperature of the base part 129 is maintained at a constant high temperature (set temperature). Control of cooling by the water cooling tube 149 (hereinafter referred to as TMS. TMS; Temperature Management System) is performed.

Next, with respect to the turbo molecular pump 100 configured as described above, an amplifier circuit 150 for exciting and controlling the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B explain about A circuit diagram of this amplifier circuit 150 is shown in FIG.

2, one end of the electromagnet winding 151 constituting the upper radial electromagnet 104 and the like is connected to the anode 171a of the power source 171 via the transistor 161, and the other end thereof. It is connected to the cathode 171b of the power supply 171 via the current detection circuit 181 and the transistor 162 . The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between their source and drain.

At this time, in the transistor 161, the cathode terminal 161a of the diode is connected to the anode 171a, and the anode terminal 161b is connected to one end of the electromagnet winding 151. In the transistor 162, the cathode terminal 162a of the diode is connected to the current detection circuit 181, and the anode terminal 162b is connected to the cathode 171b.

On the other hand, the diode 165 for current regeneration has its cathode terminal 165a connected to one end of the electromagnet winding 151 and its anode terminal 165b connected to the cathode 171b. Similarly, in the current regeneration diode 166, the cathode terminal 166a is connected to the anode 171a, and the anode terminal 166b passes through the current detection circuit 181 to the electromagnet winding 151. ) is connected to the other end of The current detection circuit 181 is constituted by, for example, a Hall sensor type current sensor or an electrical resistance element.

The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, when the magnetic bearings are 5-axis controlled and the number of electromagnets 104, 105, 106A, 106B is 10 in total, the same amplifier circuit 150 is configured for each of the electromagnets, and 10 Amplifier circuits 150 are connected in parallel.

The amplifier control circuit 191 is constituted by, for example, a digital signal processor section (hereinafter referred to as a DSP section), not shown in the control device, and the amplifier control circuit 191 includes transistors ( 161, 162) to switch on/off.

The amplifier control circuit 191 compares the current value detected by the current detection circuit 181 (a signal reflecting this current value is referred to as a current detection signal 191c) and a predetermined current command value. Then, based on the comparison result, the size of the pulse width (pulse width time Tp1, Tp2) to be generated within the control cycle Ts, which is one cycle by PWM control, is determined. As a result, the gate drive signals 191a and 191b having this pulse width are output from the amplifier control circuit 191 to the gate terminals of the transistors 161 and 162 .

In addition, when the rotational speed of the rotating body 103 passes through a resonance point during accelerated operation or when a disturbance occurs during constant speed operation, it is necessary to control the position of the rotating body 103 at high speed and with strong force. Therefore, a high voltage of, for example, about 50 V is used as the power source 171 so that a rapid increase (or decrease) of the current flowing through the electromagnet winding 151 is possible. In addition, between the anode 171a and the cathode 171b of the power source 171, a normal capacitor is connected for stabilization of the power source 171 (not shown).

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

Also, when one of the transistors 161 and 162 is turned on and the other is turned off, a so-called flywheel current is maintained. And, by making the flywheel current flow through the amplifier circuit 150 in this way, hysteresis loss in the amplifier circuit 150 is reduced, and power consumption as a whole circuit can be suppressed to a low level. In addition, by controlling the transistors 161 and 162 in this way, high-frequency noise such as harmonics generated in the turbo molecular pump 100 can be reduced. In addition, by measuring this flywheel current in 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, as shown in FIG. 3 , the transistors 161 and 162 are switched only once during the control cycle Ts (for example, 100 μs) for a time corresponding to the pulse width time Tp1. ) are both turned on. Therefore, the electromagnet current iL during this period increases toward the current value iLmax (not shown) that can flow from the anode 171a to the cathode 171b through the transistors 161 and 162.

On the other hand, when the detected current value is greater than the current command value, as shown in Fig. 4, both transistors 161 and 162 are turned off for a time corresponding to the pulse width time Tp2 only once in the control cycle Ts. . Therefore, during this period, the electromagnet current iL decreases from the cathode 171b to the anode 171a through the diodes 165 and 166 toward a regenerable current value iLmin (not shown).

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

By the way, in the outer cylinder 127 as a casing, cooling-side stator 110A (stator blades 123a to 123f) and cooling-side rotor blades 102A (rotary blades 102a to 123f) disposed within a cooling range requiring cooling 102g)), heating-side stators 110B (fixed blades 123h to 123j) and cooling-side rotary blades 102B (rotary blades 102h to 123j) disposed within a heating range requiring heating. 102k)) and a lower group gas transfer unit. Then, an O-ring 112 is disposed between the cooling stator 110A and the heating stator 110B to separate the cooling stator 110A and the heating stator 110B by a predetermined amount to form a gap 114. By forming, the cooling stator 110A and the heating stator 110B are made independent, so that the temperature of the cooling stator 110A and the temperature of the heating stator 110B do not affect each other. In addition, between the cooling stator 110A and the heating stator 110B, the stator blade spacer 125 is pressed with a bolt 115 for positioning. Further, reference numeral 152 in FIG. 1 denotes a temperature sensor for detecting the temperature on the cooling stator 110A side, numeral 153 denotes a temperature sensor for detecting the temperature on the heating stator 110B side, and numeral 154 denotes a heating stator ( A heater for heating 110B), reference numeral 155, is a cooling pipe for cooling the cooling-side stator 110A.

On the other hand, the rotary blade 102g on the cooling side of the upper group gas transfer section, which is close to the opening 114A of the gap 114 between the cooling stator 110A and the heating side stator 110B, and the heating side of the lower group gas transfer section Between the rotary blades 102h, the outer circumferential surface of the cooling-side rotary blade 102g and the outer circumferential surface of the heating-side rotary blade 102h do not directly face the opening 114A of the gap 114. , the position of the rotary blade 102g and the rotary blade 102h is displaced in the axial direction, that is, the vertical direction, with respect to the opening 114A, respectively, so that the distance S between the rotary blade 102g and the rotary blade 102h is forming a gap. The distance S is determined when the position between the cooling stator 110A and the heating stator 110B is pressed with a bolt 115, either the cooling stator 110A or the heating stator 110B. Alternatively, it is preferable to ensure a size sufficient to prevent direct face-to-face contact with the opening 114A of the gap 114 even when both of them move in the axial direction.

In addition, as a preferable position of the opening 114A, considering the movement of molecules of the process gas by the rotor blade 102g and the rotor blade 102h, the distance between the rotor blade 102g and the rotor blade 102h in the axial direction is You can think about the middle. However, the position of the opening 114A is not limited to the approximate center, and may be located downstream from the approximately central position, for example, with emphasis on the movement of process gas molecules by the rotary blade 102g.

In addition, the size of the width of the opening 114A in the gap 114 (the dimension in the axial direction) is the mean free path, which is the average value of the distances that molecules of the process gas can travel without changing their paths by colliding with other molecules, or , in consideration of the insulation effect, etc., it is set to a size of a predetermined width that is difficult for molecules to enter as much as possible. For example, the size of the gap 114 and the opening 114A is 0.1 mm to 2.0 mm, more preferably 0.5 mm to 1.0 mm.

In addition, in the structure of this embodiment, as shown in FIG. 5 in an enlarged manner A of FIG. 1 , the shape of the longitudinal section of the gap 114 when the outer cylinder 127 serving as the casing is longitudinally sectioned in the axial direction is the opening A horizontal gap portion 114a as a first gap portion extending horizontally from 114A toward the outer side in a radial direction perpendicular to the axial direction, and a further radial outer side from the outer end of the horizontal gap portion 114a, further, It was set as the structure which integrally had the inclined gap part 14b as the inclined second gap part extending obliquely downward along the downstream side in the axial direction, and had the part formed in the inverted L shape from the opening part 114A. 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. In addition, the axial direction is the axial direction of the rotor shaft 113, and the radial direction is the direction perpendicular to the axial line, that is, the radial direction of the outer cylinder 127.

In the vacuum pump 10 structured as in this embodiment, the opening 14A of the gap 114 of a predetermined width that insulates the cooling stator 110A and the heating stator 110B is formed by rotating body 103. In the axial direction of the rotor blades 102 (rotary blades 102g and rotor blades 102h) are formed at positions that are not opposed to the outer circumferential surface and deviate from the axial direction. Therefore, even if a part of the process gas is blown toward the inner circumferential surfaces of the cooling stator 110A and the heating stator 110B of the cylindrical portion 102E due to the centrifugal force caused by the rotation of the rotary blade 102, the gap 114 Since the amount of process gas entering the opening 114A is extremely small, the amount of deposits deposited in the gap 114 can be reduced. As a result, it is possible to increase the interval required for maintenance work to remove deposits and the like accumulated in the gap 114, thereby contributing to improvement in productivity.

1 and 5, the shape of the longitudinal section of the gap 114 when the outer cylinder 127 serving as the casing is cross-sectioned in the axial direction is horizontally extended outward from the opening 114A. The horizontal gap part 114a and the inclined inclined gap part 114b extending obliquely along the outer side in the radial direction and further downstream in the axial direction from the outer end of the horizontal gap part 114a are integrally formed, A structure formed in a substantially inverted L-shape was shown.

In the structure shown in FIGS. 1 and 5, when entering the horizontal gap part 114a from the opening part 114A, then the inclined slope extending by bending downward obliquely outward from the outer end of the horizontal gap part 114a Since there is a gap part 114b, when it enters the horizontal gap part 114a from the opening part 114A and then flows into the inclined gap part 114b, the inclined gap part 114b collides with the wall, and the process gas It becomes the resistance of the flow going further inward. This can reduce the amount of process gas entering the gap 114 from the opening 114A, thereby reducing the amount of deposits produced in the process gas.

Note that the structure of the gap 114 is not limited to the structures shown in FIGS. 1 and 5 , and may be structures shown in FIGS. 6 , 7 , and 8 , for example. Incidentally, the slant gap portion 114b may be a gap portion that extends further outward in the radial direction from the outer end of the horizontal gap portion 114a and obliquely upward along the upstream side in the axial direction.

In the structure of the gap 114 shown in FIG. 6 , the shape of the longitudinal section of the gap 114 when the outer cylinder 127, which is a casing, is cross-sectioned in the axial direction is the downstream side in the axial direction as soon as the opening 114A is entered. A vertical gap part 114c as a third gap part facing and a horizontal gap part 114a extending horizontally from the lower end of the vertical gap part 114c toward the outer side in the radial direction are integrally formed, It is set as the structure which has the part currently formed in substantially I shape.

In the structure of FIG. 6 , the cross-sectional shape of the gap 114 is formed in a substantially I-shape, so that when the process gas is about to enter the gap 114 from the opening 114A, it enters the opening 114A and faces straight ahead. Where there is a wall of the vertical gap portion 114c facing axially downstream, the wall becomes resistance to the inward flow of the process gas. This makes it possible to reduce the amount of process gas entering the gap 114 from the opening 114A and, at the same time, to reduce the amount of deposits. Further, the vertical gap portion 114c has a structure that goes downstream in the axial direction as soon as it enters the opening 114A. Conversely, it may have a structure that goes upstream in the axial direction immediately after 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 cylinder 127, which is a casing, is cross-sectioned in the axial direction is immediately after entering the opening 114A, from the opening 11A. An inclined gap part 114d as a fourth gap part extending obliquely toward the outer side in the radial direction perpendicular to the axial direction and upstream in the axial direction, and the downstream side in the axial direction from the outer end of the inclined gap part 114d The slanted gap part 114e as the fifth gap part extending obliquely toward the above is integrally formed and has a structure having a part formed in a substantially inverted V shape from the opening part 114A.

In the structure of FIG. 7 , as soon as it enters the inclination gap portion 114d from the opening 114A, it rises outwardly obliquely upward, so the process gas entering from the opening 114A into the inclination gap portion 114d is outwardly obliquely upward. The inclined gap portion 114d becomes a wall and collides with it, and becomes 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, thereby reducing the amount of deposits produced in the process gas.

In addition, in the configuration of FIG. 7 , the warp gap portion 114d extending obliquely from the opening 114A in the outer side in the radial direction perpendicular to the axial direction and upstream in the axial direction, and the warp gap portion 114d An inclined gap portion 114e extending obliquely from the outer end toward the downstream side in the axial direction is integrally formed and has a structure having a portion formed in a substantially inverted V shape from the opening 114A, the opening 114A It is good also as a structure in which either the slant gap part 114d which extends obliquely upstream from ) or the slant gap part 114e which extends obliquely downstream from the opening part 114A is formed.

In the structure of the gap 114 shown in FIG. 8, when the outer cylinder 127, which is a casing, is cross-sectioned in the axial direction, the upper part of the opening 114A in the gap 114 formed on the inner peripheral surface of the outer cylinder 127, It is set as the structure in which the eaves 116 protruding toward the inner side of the outer cylinder 127 rather than the opening part 114A were formed. That is, the eaves 116 can create a step between the opening 114A and control the flow so that the process gas flowing from the upstream side does not go in the direction of the opening 114A, but proceeds directly to the downstream side. . In addition, the gap 114 has a vertical gap part 114c as a third gap part that faces downstream immediately after entering the opening 114A, and an outer side in the radial direction perpendicular to the axial direction from the lower end of the vertical gap part 114c. The horizontal gap part 114a extending horizontally towards the 114a is integrally formed, and it is set as the structure which has the part formed in the substantially I shape from the opening part 114A.

In the structure of FIG. 8 , the cross-sectional shape of the gap 114 is formed in a substantially I-shape, so that when the process gas is about to enter the gap 114 from the opening 114A, it enters the opening 114A and is directly in front. , since there is a wall of the vertical gap portion 114c that faces downward, the process gas hits the wall and becomes resistance to the flow of the process gas toward the inside. This can reduce the amount of process gas entering the gap 114 from the opening 114A, thereby reducing the amount of deposits produced in the process gas. Further, R-chamfering is applied to the lower edge portion (lower surface of the eaves portion) 116a of the eaves portion 116 and the lower edge portion 114g of the opening portion 114A, respectively. In the R-chamfering process, when a part of the process gas that the rotary blade 102 collided with and bounced up from within the outer cylinder 127 hit the lower edge part 116a or the lower edge part 114g, a part of the process gas that hit it Orient the direction of the rotor shaft 113 different from the inside of the opening 114A so as not to enter the opening 114A.

In addition, various modifications can be made to the present invention without departing from the spirit of the present invention, and it is natural that the present invention leads to the modification.

100: turbo molecular pump 101: intake port
102: rotary blade 102A: cooling side rotary blade
102B: Cooling side rotary blade 102E: Cylindrical part
102a: rotary wing 102b: rotary wing
102c: rotary wing 102d: rotary wing
102e: rotary blade 102f: rotary blade
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: lower radial sensor
109: Axial sensor 110A: Cooling side stator (upper group gas transfer part)
110B: Heating side stator (lower group gas transfer part)
111: metal disk 112: O-ring
113: rotor shaft 114: gap
114A: opening 114a: horizontal gap part (first gap part)
114b: inclination gap part (second gap part)
114c: vertical gap part (third gap part)
114d: inclined gap part (fourth gap part)
114e: inclined gap part (fifth gap part)
114g: lower edge part 115: bolt
116: eaves 116a: lower edge portion
120: protective bearing 121: motor
122: stator column 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
131: spacer with screw 131a: screw groove
133: exhaust port 141: electronic circuit
143: substrate 145: bottom cover
149: water cooling tube 150: amplifier 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 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: anode 171b: cathode
181: Current detection circuit 191: Amplifier control circuit
191a: gate driving signal 191b: gate driving signal
191c: current detection signal S: distance
Tp1: Pulse width time Tp2: Pulse width time
Ts: control cycle iL: electromagnet current
iLmax: current value iLmin: current value

Claims (5)

A casing having an intake port and an exhaust port;
Inside the casing, a rotor shaft freely supported for rotation;
A plurality of stages of rotary blades rotatable together with the rotor shaft;
A plurality of stator blades fixed to the casing and disposed between the plurality of stages of rotary blades;
A cooling-side stator and a heating-side stator holding the plurality of stator blades at predetermined intervals.
As a vacuum pump having a,
An opening of a gap having a predetermined width for thermal insulation between the cooling-side stator and the heating-side stator,
A vacuum pump characterized in that it is formed at a position not facing an outer circumferential surface of the rotor blade in the axial direction of the rotor shaft. The method of claim 1,
The shape of the gap is: a first gap portion extending horizontally outward in a radial direction perpendicular to the axial direction; , and also has a second gap portion extending along the downstream side in the axial direction. According to claim 1 or claim 2,
The vacuum pump characterized in that the shape of the gap has a third gap portion extending along the downstream side in the axial direction. The method according to any one of claims 1 to 3,
The shape of the gap has a fourth gap portion extending outward in a radial direction perpendicular to the axial direction and upstream in the axial direction. The method according to any one of claims 1 to 4,
The vacuum pump characterized in that the shape of the gap has an eaves protruding toward an inside of the casing from an upper portion of the opening portion.

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