Vacuum pump and cover used therefor

Abstract

To provide a vacuum pump capable of inhibiting foreign objects, such as particles, which are generated by a process gas from entering a semiconductor wafer manufacturing step etc.SOLUTION: A vacuum pump includes: a casing 127 having an air inlet 101; and a rotating body 103 having a recessed part 201, which is open to the air inlet 101, and fastened to a rotor shaft 113 by a fastening bolt 205 disposed in the recessed part 201. The vacuum pump further includes: a cover 202 which contacts with an upper end surface 103a, which faces the air inlet 101, of the rotating body 103 at its outer peripheral part 202b, is formed into a shape protruding toward the air inlet 101 side, and covers the recessed part 201.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vacuum pump that can be used in a pressure range from low vacuum to ultra-high vacuum, and a cover used for the vacuum pump, and in particular to a vacuum pump and a cover used for the vacuum pump that can suppress the generation of particles remaining in the vacuum pump and foreign matter caused by rust, etc. [Background technology]

[0002] Conventionally, when manufacturing semiconductors such as memories and integrated circuits, it is necessary to perform doping and etching on high-purity semiconductor substrates (wafers) in a chamber under high vacuum conditions to avoid the effects of dust in the air, etc. Furthermore, the process gas used here is exhausted by a vacuum pump such as a compound pump that combines a turbomolecular pump and a threaded groove pump.

[0003] As such a vacuum pump, for example, one that includes a cylindrical casing, a cylindrical stator that is nested and fixed in the casing and has a threaded portion, and a rotor that is bolted to a rotor shaft that is supported in the stator so as to be rotatable at high speed. The process gas is transferred upstream of the threaded pump by being given downward momentum by the rotating blades of the rotor. The process gas is then compressed by the threaded pump and exhausted to the outside.

[0004] In semiconductor manufacturing chambers, there are many processes in which corrosion-resistant process gas is applied to semiconductor wafers. When the process gas inside the chamber is exhausted with a vacuum pump, the process gas can cause corrosion or rust on the tip of the rotor shaft or on the surface of the bolts fastening the rotor shaft to the rotating body, or can generate particles (fine particles, dust, etc.) due to physicochemical changes in the components in the process gas.

[0005] Then, as the pressure in the chamber is repeatedly reduced and increased, the process gas containing foreign matter such as rust on the bolt surfaces and particles may flow back into the chamber, and the foreign matter may adhere to the semiconductor wafer, degrading the processing quality of the semiconductor wafer. In order to prevent the process gas containing such foreign matter from flowing back into the chamber, Patent Document 1 discloses a vacuum pump equipped with a cover that is fitted into the recess of the rotor and arranged to cover the rotor shaft and the fastening parts of the bolts.

[0006] However, in the vacuum pump disclosed in Patent Document 1, when assembling the vacuum pump, a small gap is provided between the cover and the rotor to absorb dimensional errors of the components, which allows process gas to pass through, and this can cause rust on the bolt surfaces or particles remaining in the recesses to flow back into the chamber.

[0007] 12, for example, a vacuum pump is disclosed that includes a flexible cover 2, the outer periphery of which is supported on an end face 1a facing the intake port of the rotor 1, and the central part 2a of which is elastically deformed to fit into the recess 3 of the rotor 1 and cover the recess 3, so that the process gas does not pass through a small gap between the rotor 1 and the flexible cover 2 and thus prevents the process gas from passing into the recess 3. In this configuration, the flexible cover 2 covers the recess 3 of the rotor 1, so that the bolts 5 that fasten the rotor 1 to the rotating shaft 4 are not exposed to the process gas, and corrosion and rusting of the bolts 5 are suppressed, thereby suppressing the backflow of foreign matter into the chamber. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6190580 [Patent Document 2] Patent No. 6644813 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the invention described in Patent Document 2, the flexible cover 2 is provided so that the central portion 2a is elastically deformed to fit into the recess 3 of the rotor 1 and cover the recess 3, and so there is a risk that particles may remain in the portion 6b between the central portion 2a that is recessed into the recess 3 and the bolt 5. Furthermore, if the design is not appropriate for the deformation of the central portion 2a to fit into the recess 3, the outer periphery 2b of the flexible cover 2 covering the recess 3 of the rotor 1 may be rolled up and lifted from the end face 1a of the rotor 1, and particles may remain between the lifted portion 6a and the end face 1a of the rotor 1, and there is a problem that the remaining particles may flow back into the chamber.

[0010] Therefore, a technical problem arises that must be solved in order to prevent foreign matter such as particles originating from the process gas from entering the semiconductor wafer manufacturing process, etc., and the present invention has an object to solve this problem. [Means for solving the problem]

[0011] The present invention has been proposed to achieve the above object, and the invention described in claim 1 is a vacuum pump including a casing having an intake port, and a rotor having a recess that opens toward the intake port and is fastened to a rotor shaft by a bolt disposed in the recess, wherein an outer periphery of the rotor is in contact with an end face facing the intake port, and a bolt is formed in a convex shape toward the intake port and covers the recess. Flexible With cover The cover has a contact area increasing structure in which, when an end of the outer periphery is pressed against the end surface, a part of the outer periphery is deflected to come into planar contact with the end surface. The present invention provides a vacuum pump.

[0012] According to this configuration, the recess of the rotor that opens toward the intake port is covered with a cover that is convex toward the intake side, and the outer periphery of the cover is attached in contact with the end face of the rotor. Therefore, when the cover is pressed toward the end face of the rotor during installation, the convex cover maintains its convex shape and the outer periphery of the cover is strongly pressed against the end face of the rotor, so that the outer periphery of the cover becomes parallel to the end face of the rotor and is disposed in close contact with the end face of the rotor. This makes it possible to eliminate foreign matter such as particles remaining in the center of the cover and between the outer periphery of the cover and the end face of the rotor. As a result, there is no backflow of particles from inside the vacuum pump to the chamber side.

[0014] moreover When the cover is attached, the bolts are fastened to press the cover firmly against the rotor, and the outer periphery of the cover is pressed even more firmly against the end face of the rotor in proportion to the fastening force of the bolts, increasing the contact area where the outer periphery of the cover is parallel to the end face of the rotor, and the outer periphery of the cover and the end face of the rotor are arranged in closer contact with each other.

[0015] Claim 2 The invention described in claim 1 to In the described configuration, the end surface is provided with a step portion that receives the outer circumferential portion and restricts the expansion of the cover.

[0016] According to this configuration, when the cover is attached and the outer periphery of the cover spreads outward, the outer periphery of the cover hits the step, which prevents the outer periphery from spreading outward more than specified. It also prevents the cover from shifting in position relative to the end face of the rotor. This prevents the outer periphery of the cover from curling away from the end face of the rotor and prevents the cover from shifting in position relative to the end face of the rotor, allowing the outer periphery of the cover to come into closer contact with the end face of the rotor.

[0017] Claim 3 The invention described in claim 1 or 2In the vacuum pump according to the above configuration, an opposing surface of the outer circumferential portion that faces the end surface is formed to be convexly curved toward the end surface.

[0018] With this configuration, when the cover is attached, the cover is pressed firmly against the rotor and the outer periphery of the cover slides over the end face of the rotor and expands outward; the convexly curved portion of the outer periphery slides over the end face of the rotor in line contact, preventing scratches on the end face of the rotor.

[0019] Claim 4 The invention described in claim 1 3 In the vacuum pump according to any one of the above, a restraining portion is further provided that holds the cover and restricts the cover from expanding.

[0020] With this configuration, in cases where the rigidity of the cover is low, the restraining portion can restrict the spread of the entire cover while maintaining the specified convex shape of the cover, thereby making it possible to press the outer periphery of the cover against the end face of the rotating body while maintaining the specified shape of the cover.

[0021] Claim 5 The invention described in claim 1 4 In the vacuum pump according to any one of the above aspects, the cover is provided with a rigidity increasing structure that increases rigidity so as to suppress the cover from expanding.

[0022] According to this configuration, the rigidity increasing structure satisfies both the flexibility and rigidity of the cover, and it is possible to expand the entire cover while maintaining the specified convex shape of the cover. This makes it possible to press the outer periphery of the cover against the end face of the rotor while maintaining the specified shape of the cover.

[0023] Claim 6 The invention described in claim 1 5In the configuration described in any one of the above, the cover provides a vacuum pump that is corrosion-resistant and rust-proof.

[0024] According to this configuration, the cover itself has corrosion resistance and rust prevention properties, so that corrosion and rusting of the cover due to the exhausted process gas is suppressed.

[0025] Claim 7 The invention described in claim 1 6 In the vacuum pump according to any one of the above aspects, the cover has a surface that is subjected to a coating treatment for corrosion resistance and rust prevention.

[0026] According to this configuration, the surface of the cover is subjected to a coating treatment for corrosion resistance and rust prevention, so that corrosion and rusting of the cover surface due to the exhausted process gas can be effectively prevented.

[0027] Claim 8 The invention described in is a cover used for a vacuum pump including a casing having an intake port, a rotor having a recess that opens toward the intake port and is fastened to a rotor shaft by a bolt disposed in the recess, the cover having an outer periphery contacting an end face of the rotor facing the intake port, formed in a convex shape toward the intake port, and covering the recess. The outer circumferential portion has a contact area increasing structure that is flexible and can be brought into planar contact with the end surface when an end portion of the outer circumferential portion is pressed against the end surface. , provide cover.

[0028] According to this configuration, the end face around the recess of the rotor in the vacuum pump can be tightly covered, so that particles and the like resulting from the process gas are prevented from remaining in the recess of the rotor, and corrosion and rust of the vacuum pump due to the exhausted process gas, for example, can be effectively prevented. Effect of the Invention

[0029] According to the present invention, the recess of the rotor that opens toward the intake port is covered with a cover that is convex toward the intake side, and the outer periphery of the cover is parallel to the end face of the rotor and is attached in contact with the end face of the rotor, so that when the cover is attached, the outer periphery of the cover and the end face of the rotor are positioned in a state of more intimate contact, and the recess of the rotor can be blocked by the cover. This makes it possible to eliminate foreign matter such as particles remaining in the center of the cover and between the outer periphery of the cover and the end face of the rotor, and also suppresses corrosion and rusting of the bolts, thereby preventing foreign matter from flowing back from inside the vacuum pump to the chamber. [Brief description of the drawings]

[0030] [Figure 1] 1 is a vertical sectional view of a turbomolecular pump shown as an example of a vacuum pump according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing an example of an amplifier circuit in the turbo molecular pump. [Diagram 3] 4 is a time chart showing an example of control when a current command value detected by an amplifier circuit in the turbo molecular pump is larger than a detection value. [Figure 4] 5 is a time chart showing an example of control when a current command value detected by an amplifier circuit in the turbo molecular pump is smaller than a detection value. [Diagram 5] 2A and 2B are partially enlarged views showing the structure around the cover of the turbo molecular pump shown in FIG. 1, in which (a) is a plan view and (b) is a schematic cross-sectional view taken along line AA in (a). [Figure 6] FIG. 6 is an exploded side view of the cover surrounding structure shown in FIG. 5. [Figure 7] 6A shows the cover alone shown in FIG. 5, where (a) is a plan view of the cover, (b) is a schematic cross-sectional view taken along line BB in (a), and (c) is a partially enlarged view of (b). [Figure 8] 6 shows a first modified example of the cover alone shown in FIG. 5, in which (a) is a plan view of the cover, (b) is a schematic cross-sectional view taken along line CC of (a), (c) is a partially enlarged view of (b), and (d) is an enlarged view of a portion corresponding to (c) for explaining an example in which the first modified example is further modified. [Figure 9] 6A and 6B show a second modified example of the cover alone shown in FIG. 5, in which (a) is a plan view of the cover, (b) is a schematic cross-sectional view taken along line DD in (a), and (c) is a partially enlarged view of (b). [Figure 10] 6A and 6B show a third modified example of the cover alone shown in FIG. 5, in which (a) is a plan view of the cover, (b) is a schematic cross-sectional view taken along line EE of (a), and (c) is a partially enlarged view of (b). [Figure 11] 5A is a partially enlarged view showing a modified example of the cover surrounding structure of the turbo molecular pump shown in FIG. 1, where FIG. 5A is a schematic cross-sectional view of a portion corresponding to line AA in FIG. 5A, and FIG. 5B is an exploded cross-sectional view showing the portion in FIG. 5A in an exploded form. [Figure 12] 1 is a cross-sectional view illustrating a problem with a conventional vacuum pump. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] In order to achieve the object of providing a vacuum pump capable of preventing foreign matter such as particles resulting from process gas from entering a semiconductor wafer manufacturing process, etc., the present invention provides a vacuum pump comprising: a casing having an intake port; and a rotor having a recess opening towards the intake port and fastened to a rotor shaft by a bolt disposed within the recess, wherein an outer periphery of the rotor is in contact with an end face facing the intake port, and the rotor is provided with a cover formed convexly towards the intake port and covering the recess. EXAMPLES

[0032] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the following embodiment, when the number, value, amount, range, etc. of components are mentioned, the number is not limited to the specific number, and may be more or less than the specific number, unless otherwise specified or when it is clearly limited to a specific number in principle.

[0033] In addition, when referring to the shape or positional relationship of components, etc., this includes things that are substantially similar or approximate to those shapes, etc., unless otherwise specified or considered to be clearly different in principle.

[0034] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional ratios of the components may not be the same as the actual ones. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0035] In the following description, the expressions indicating directions such as up, down, left, right, etc. are not absolute, but are appropriate when each part of the vacuum pump of the present invention is in the illustrated position, but if the position is changed, the expressions should be interpreted in accordance with the change in position. Also, the same elements are given the same symbols throughout the description of the embodiments.

[0036] A longitudinal cross-sectional view of this turbomolecular pump 100 is shown in Fig. 1. In Fig. 1, the turbomolecular pump 100 has an intake port 101 formed at the upper end of a cylindrical outer tube 127. Inside the outer tube 127, a rotor 103 is provided, the rotor 103 having a plurality of rotors 102 (102a, 102b, 102c, ...) which are turbine blades for sucking in and exhausting gas, formed radially on its periphery in multiple stages. A rotor shaft 113 is attached to the center of the rotor 103, and the rotor shaft 113 is supported in the air and position-controlled by, for example, a five-axis controlled magnetic bearing. The rotor 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0037] The upper radial electromagnets 104 are arranged in pairs on the X-axis and the Y-axis. Four upper radial sensors 107 are provided adjacent to the upper radial electromagnets 104 and corresponding to each of the upper radial electromagnets 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors having conductive windings, and detect the position of the rotor shaft 113 based on the change in inductance of the conductive windings that changes according to the position of the rotor shaft 113. The upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed thereto, and send the detected displacement to the control device 200.

[0038] In this control device 200, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for the upper radial electromagnet 104 based on a position signal detected by the upper radial sensor 107, and an amplifier circuit 150 (described later) shown in Figure 2 controls the excitation of the upper radial electromagnet 104 based on this excitation control command signal, thereby adjusting the upper radial position of the rotor shaft 113.

[0039] The rotor shaft 113 is made of a material with high magnetic permeability (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnet 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. The lower radial electromagnet 105 and the lower radial sensor 108 are arranged in the same manner as the upper radial electromagnet 104 and the upper radial sensor 107, and adjust the lower radial position of the rotor shaft 113 in the same manner as the upper radial position.

[0040] Furthermore, axial electromagnets 106A and 106B are arranged above and below a circular metal disk 111 provided at the bottom of rotor shaft 113. Metal disk 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of rotor shaft 113, and an axial position signal is sent to control device 200.

[0041] In the control device 200, a compensation circuit having, for example, a PID adjustment function generates an excitation control command signal for each of the axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of the axial electromagnets 106A and 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disk 111 upward by magnetic force and the axial electromagnet 106B attracts the metal disk 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0042] In this way, the control device 200 appropriately adjusts the magnetic force that the axial electromagnets 106A, 106B exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in a non-contact manner in space. The amplifier circuit 150 that controls the excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A, 106B will be described later.

[0043] Meanwhile, motor 121 has a plurality of magnetic poles arranged circumferentially so as to surround rotor shaft 113. Each magnetic pole is controlled by control device 200 so as to rotate rotor shaft 113 via electromagnetic force acting between the magnetic pole and rotor shaft 113. Also, motor 121 incorporates a rotation speed sensor such as a Hall element, resolver, or encoder (not shown), and the rotation speed of rotor shaft 113 is detected by a detection signal from this rotation speed sensor.

[0044] Furthermore, for example, a phase sensor (not shown) is attached near the lower radial sensor 108 to detect the phase of rotation of the rotor shaft 113. The control device 200 detects the position of the magnetic poles using the detection signals of both this phase sensor and the rotation speed sensor.

[0045] A plurality of fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap between the rotor blades 102 (102a, 102b, 102c...). The rotor blades 102 (102a, 102b, 102c...) are formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward through collision. The fixed blades 123 (123a, 123b, 123c...) are made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components.

[0046] Similarly, the fixed blades 123 are formed at an inclination at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged alternately with the stages of the rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported in a state where they are inserted between a plurality of stacked stages of fixed blade spacers 125 (125a, 125b, 125c, etc.).

[0047] The fixed vane spacer 125 is a ring-shaped member and is made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer periphery of the fixed vane spacer 125 with a small gap therebetween. A base portion 129 is disposed at the bottom of the outer cylinder 127. An exhaust port 133 is formed in the base portion 129 and communicates with the outside. Exhaust gas that enters the intake port 101 from the chamber (vacuum chamber) side and is transferred to the base portion 129 is sent to the exhaust port 133.

[0048] Furthermore, depending on the application of the turbo molecular pump 100, a threaded spacer 131 is disposed between the lower part of the fixed vane spacer 125 and the base part 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals, and has a plurality of helical thread grooves 131a engraved on its inner peripheral surface. The helical direction of the thread groove 131a is the direction in which, when the molecules of the exhaust gas move in the rotation direction of the rotor 103, the molecules are transferred toward the exhaust port 133. A cylindrical part 102d hangs down from the lowest part of the rotor 103, which is connected to the rotor vanes 102 (102a, 102b, 102c, etc.). The outer peripheral surface of this cylindrical part 102d is cylindrical and protrudes toward the inner peripheral surface of the threaded spacer 131, and is adjacent to the inner peripheral surface of the threaded spacer 131 with a predetermined gap therebetween. The exhaust gas transferred to the thread groove 131a by the rotor 102 and the fixed blade 123 is sent to the base portion 129 while being guided by the thread groove 131a.

[0049] The base portion 129 is a disk-shaped member that constitutes the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. The base portion 129 physically holds the turbomolecular pump 100 and also functions as a heat conduction path, so it is desirable to use a metal that has rigidity and high thermal conductivity, such as iron, aluminum, or copper.

[0050] In this configuration, when the rotor 102 is rotated together with the rotor shaft 113 by the motor 121, the exhaust gas is sucked from the chamber through the intake port 101 by the action of the rotor 102 and the fixed blade 123. The rotation speed of the rotor 102 is usually 20,000 rpm to 90,000 rpm, and the peripheral speed at the tip of the rotor 102 reaches 200 m / s to 400 m / s. The exhaust gas sucked through the intake port 101 passes between the rotor 102 and the fixed blade 123 and is transferred to the base part 129. At this time, the temperature of the rotor 102 rises due to frictional heat generated when the exhaust gas comes into contact with the rotor 102 and conduction of heat generated by the motor 121, and the like, but this heat is transferred to the fixed blade 123 side by radiation or conduction by gas molecules of the exhaust gas, and the like.

[0051] The fixed blade spacers 125 are joined to each other at their outer peripheries, and transmit heat received by the fixed blades 123 from the rotor blades 102, frictional heat generated when exhaust gas comes into contact with the fixed blades 123, and the like to the outside.

[0052] In the above description, the threaded spacer 131 is disposed on the outer periphery of the cylindrical portion 102d of the rotor 103, and the thread groove 131a is formed on the inner periphery of the threaded spacer 131. However, there are also cases where the thread groove is formed on the outer periphery of the cylindrical portion 102d, and a spacer having a cylindrical inner periphery is disposed around the outer periphery of the cylindrical portion 102d.

[0053] Depending on the application of the turbomolecular pump 100, in order to prevent the gas sucked in from the intake port 101 from entering the electrical equipment section, which is composed of the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, the lower radial electromagnet 105, the lower radial sensor 108, the axial electromagnets 106A and 106B, the axial sensor 109, etc., the electrical equipment section may be covered all around with a stator column 122, and the inside of this stator column 122 may be kept at a predetermined pressure by a purge gas.

[0054] In this case, piping (not shown) is provided in the base portion 129, and purge gas is introduced through this piping. The introduced purge gas is sent to the exhaust port 133 through gaps between the protective bearing 120 and the rotor shaft 113, between the rotor and stator of the motor 121, and between the stator column 122 and the inner cylindrical portion of the rotor blades 102.

[0055] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that are individually adjusted and identified as a model. In order to store these control parameters, the turbomolecular pump 100 has an electronic circuit section 141 in its main body. The electronic circuit section 141 is composed of a semiconductor memory such as an EEPROM, electronic components such as semiconductor elements for accessing the memory, and a substrate 143 for mounting these components. The electronic circuit section 141 is housed below a rotational speed sensor (not shown) near the center of a base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom cover 145.

[0056] In the semiconductor manufacturing process, some process gases introduced into the chamber have the property of becoming solid when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbo molecular pump 100, the pressure of the exhaust gas is lowest at the intake port 101 and highest at the exhaust port 133. If the pressure of the process gas becomes higher than a predetermined value or the temperature falls below a predetermined value while the process gas is being transferred from the intake port 101 to the exhaust port 133, the process gas becomes solid and adheres to and accumulates inside the turbo molecular pump 100.

[0057] For example, when SiCl4 is used as the process gas in an Al etching apparatus, the vapor pressure curve shows that at low vacuum (760 [torr] to 10-2) and low temperature (approximately 20 [°C]), solid products (e.g., AlCl3) precipitate and adhere to and accumulate inside the turbomolecular pump 100. As a result, when precipitates of the process gas accumulate inside the turbomolecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. Furthermore, the above-mentioned products are prone to solidification and adhesion in high pressure areas near the exhaust port 133 and near the threaded spacer 131.

[0058] Therefore, in order to solve this problem, in the past, a heater (not shown) or a circular water-cooled tube 149 was wrapped around the outer periphery of the base portion 129, and a temperature sensor (e.g., a thermistor) (not shown) was embedded in the base portion 129, and the heating of the heater and the cooling by the water-cooled tube 149 were controlled based on the signal from this temperature sensor to keep the temperature of the base portion 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS; Temperature Management System).

[0059] Next, regarding the turbo molecular pump 100 configured as described above, an amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B will be described. A circuit diagram of this amplifier circuit 150 is shown in FIG.

[0060] 2, one end of an electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to a positive electrode 171a of a power source 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power source 171 via a current detection circuit 181 and a transistor 162. The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between the source and drain.

[0061] At this time, the transistor 161 has a cathode terminal 161a of the diode connected to the positive electrode 171a, and an anode terminal 161b connected to one end of the electromagnet winding 151. The transistor 162 has a cathode terminal 162a of the diode connected to the current detection circuit 181, and an anode terminal 162b connected to the negative electrode 171b.

[0062] On the other hand, the current regeneration diode 165 has its cathode terminal 165a connected to one end of the electromagnet winding 151 and its anode terminal 165b connected to the negative electrode 171b. Similarly, the current regeneration diode 166 has its cathode terminal 166a connected to the positive electrode 171a and its anode terminal 166b connected to the other end of the electromagnet winding 151 via a current detection circuit 181. The current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or an electric resistance element.

[0063] The amplifier circuit 150 configured as above corresponds to one electromagnet. Therefore, when the magnetic bearing is controlled by five axes and there are a total of ten electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the ten amplifier circuits 150 are connected in parallel to the power supply 171.

[0064] Furthermore, the amplifier control circuit 191 is configured, for example, by a digital signal processor section (hereinafter referred to as a DSP section) (not shown) of the control device 200, and this amplifier control circuit 191 switches the transistors 161 and 162 on / off.

[0065] The amplifier control circuit 191 is adapted to compare the current value detected by the current detection circuit 181 (a signal reflecting this current value is called a current detection signal 191c) with a predetermined current command value. Then, based on the result of this comparison, the magnitude of the pulse width (pulse width times Tp1, Tp2) to be generated within a control cycle Ts, which is one period of PWM control, is determined. As a result, gate drive signals 191a, 191b having this pulse width are output from the amplifier control circuit 191 to the gate terminals of the transistors 161, 162.

[0066] In addition, when the rotor 103 passes through a resonance point during an accelerating operation of the rotation speed, or when a disturbance occurs during a constant speed operation, it is necessary to control the position of the rotor 103 at high speed and with a strong force. For this reason, a high voltage of, for example, about 50 V is used as the power supply 171 so that the current flowing through the electromagnet winding 151 can be rapidly increased (or decreased). In addition, a capacitor (not shown) is usually connected between the positive pole 171a and the negative pole 171b of the power supply 171 to stabilize the power supply 171.

[0067] In this configuration, when both transistors 161, 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0068] Moreover, when one of the transistors 161, 162 is turned on and the other is turned off, a so-called flywheel current is maintained. By passing a flywheel current through the amplifier circuit 150 in this manner, the hysteresis loss in the amplifier circuit 150 can be reduced, and the power consumption of the entire circuit can be kept low. Furthermore, by controlling the transistors 161, 162 in this manner, high-frequency noise such as harmonics generated in the turbo molecular pump 100 can be reduced. Furthermore, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0069] That is, when the detected current value is smaller than the current command value, both of the transistors 161 and 162 are turned on for a time period corresponding to the pulse width time Tp1 only once in a control cycle Ts (e.g., 100 μs) as shown in Fig. 3. Therefore, the electromagnet current iL during this period increases toward a current value iLmax (not shown) that can flow from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[0070] On the other hand, when the detected current value is larger than the current command value, both of the transistors 161 and 162 are turned off for a time period corresponding to the pulse width time Tp2 only once during the control cycle Ts, as shown in Fig. 4. Therefore, the electromagnet current iL during this period decreases toward a current value iLmin (not shown) that can be regenerated from the negative pole 171b to the positive pole 171a via the diodes 165 and 166.

[0071] In either case, after the pulse width times Tp1 and Tp2 have elapsed, one of the transistors 161 and 162 is turned on. Therefore, a flywheel current is maintained in the amplifier circuit 150 during this period.

[0072] In the configuration of the vacuum pump according to this embodiment, i.e., the turbo molecular pump 100, a recess 201 is formed in the upper end face 103a of the rotor 103, and the recess 201 is covered by a flexible cover 202. The structure in which the recess 201 is covered by the flexible cover 202 will be described in further detail with reference to Figs. 5 to 7.

[0073] Fig. 5 is an enlarged view of the main part of Fig. 1, that is, a partially enlarged view showing the peripheral structure of the flexible cover 202 in the turbo molecular pump 100, where (a) is a plan view and (b) is a schematic cross-sectional view taken along line AA in Fig. 5(a). Fig. 6 is an exploded side view of the peripheral structure of the cover shown in Fig. 5. Fig. 7 shows the flexible cover 202 shown in Fig. 5, where (a) is a plan view of the flexible cover 202, (b) is a schematic cross-sectional view taken along line BB in (a), and (c) is a partially enlarged view of (b).

[0074] A flexible cover 202 that covers the recess 201 is fastened integrally to the rotor shaft 113 together with a washer 203 and a sleeve 204 by means of a fastening bolt 205 made of stainless steel.

[0075] The flexible cover 202 is a thin disk formed in a truncated cone shape, and is made of, for example, stainless steel or aluminum alloy, and is formed to a thickness of about 1 to 3 mm. The outer diameter of the flexible cover 202 is set to be about 3 to 10 mm larger than the inner diameter of the recess 201 of the rotating body 103, and the central portion 202a rises gently upward in a convex shape, and the outer circumferential portion 202b descending from the central portion 202a is in contact with the upper end surface 103a of the rotating body 103. A through hole 206 through which a fastening bolt 205 is inserted is formed approximately at the center of the central portion 202a.

[0076] The washer 203 is interposed between the fastening bolt 205 and the flexible cover 202, and is made of, for example, stainless steel, and has a through hole 207 formed in the center, into which the fastening bolt 205 is attached.

[0077] The sleeve 204 is disposed between the flexible cover 202 and the rotor shaft 113. The sleeve 204 is formed in a substantially cylindrical shape and is made of, for example, stainless steel or an aluminum alloy. The sleeve 204 has a through hole 208 formed in the center thereof, through which the fastening bolt 205 is inserted.

[0078] The flexible cover 202, the washer 203, the sleeve 204, and the fastening bolt 205 are coated with a corrosion-resistant and rust-resistant coating, which can suppress corrosion and rusting of each component.

[0079] 5(a) and 5(b), the fastening bolt 205 is passed through the through hole 207 of the washer 203, the through hole 206 of the flexible cover 202, and the through hole 208 of the sleeve 204 in this order to integrate the washer 203, the flexible cover 202, and the sleeve 204. In this state, the fastening bolt 205 is inserted into the recess 201 as shown in FIG. 1 and attached to the screw hole 113a provided at the upper end of the rotor shaft 113. In this case, the outer periphery 202b of the flexible cover 202 is abutted against the upper end face 103a of the rotating body 103 to cover and close the recess 201 with the flexible cover 202, and the fastening bolt 205 is tightened to the rotor shaft 113 until the gap between the upper end face 103a and the outer periphery 202b becomes tight, and the flexible cover 202 together with the washer 203 and the sleeve 204 is fixed to the rotating body 103. That is, flexible cover 202 is attached such that outer periphery 202b contacts upper end surface 103a of rotor 103 facing intake port 101, and convex central portion 202a faces intake port 101.

[0080] In this manner, in the turbomolecular pump 100 according to the present embodiment, by covering and sealing the recess 201 of the rotor 103, the rotor shaft 113 and the bolts 209 fastening the rotor 103 to the rotor shaft 113 are not exposed to the process gas, and corrosion and rusting of the rotor shaft 113 and the bolts 209 can be suppressed.

[0081] In addition, when the flexible cover 202 is pressed against the upper end surface 103a of the rotor 103 during attachment, the convex flexible cover 202 has an end of the outer periphery 202b of the flexible cover 202 pressed strongly against the upper end surface 103a of the rotor 103 while maintaining the convex shape, and the end portion of the outer periphery 202b of the flexible cover 202 is brought into contact with the upper end surface 103a of the rotor 103 in a parallel state. That is, the outer periphery 202b of the flexible cover 202 is disposed in a state of being in close contact with the upper end surface 103a of the rotor 103. This makes it possible to eliminate foreign matter such as particles remaining between the end of the outer periphery 202b of the flexible cover 202 and the upper end surface 103a of the rotor 103. As a result, it is possible to eliminate particles flowing back from inside the turbo molecular pump 100 to the chamber side.

[0082] Also, the flexible cover 202 may be configured so that the flexible cover 202 itself is flexible, and when an end of the outer periphery 202b is strongly pressed against the upper end face 103a of the rotating body 103, a part of the outer periphery 202b of the flexible cover 202 is bent and comes into planar contact with the upper end face 103a of the rotating body 103 to increase the contact area, that is, the flexible cover 202 itself may be configured to have the effect of a contact area increasing structure. In this case, when the flexible cover 202 is strongly pressed against the upper end face 103a of the rotating body 103 by the fastening force of the fastening bolt 205 during attachment of the flexible cover 202, the flexible cover 202 is bent in proportion to the fastening force of the fastening bolt 205, and the outer periphery 202b expands while sliding on the upper end face 103a with the bending, and the outer periphery 202b of the flexible cover 202 is pressed even more strongly against the upper end face 103a of the rotating body 103. This increases the area of ​​parallel contact between the central portion of the flexible cover 202 and between the outer periphery 202b of the flexible cover 202 and the upper end face 103a of the rotating body 103, and thus allows the flexible cover 202 to be arranged more densely, thereby further eliminating foreign matter such as particles that remain between the end of the outer periphery 202b of the flexible cover 202 and the upper end face 103a of the rotating body 103.

[0083] In addition, when the flexible cover 202 is attached, the fastening force of the fastening bolt 205 presses the flexible cover 202 strongly against the upper end face 103a of the rotating body 103. As examples of the flexible cover 202 having a mechanical structure having a contact area increasing means that enables the outer periphery 202b of the flexible cover 202 to come into planar contact with the upper end face 103a of the rotating body 103 in proportion to the fastening force of the fastening bolt 205, in addition to the above, there are structures such as those shown in Figures 8 and 9.

[0084] Fig. 8 shows a first modified example of the flexible cover 202 shown in Fig. 5, where (a) is a plan view of the flexible cover 202, (b) is a schematic cross-sectional view along line CC in (a), and (c) is a partially enlarged view of (b). The flexible cover 202 shown in Fig. 8 has a mechanical contact area increasing structure having a means for enabling the outer circumferential portion 202b to come into planar contact with the upper end face 103a of the rotating body 103 in proportion to the fastening force of the fastening bolt 205 when the flexible cover 202 is strongly pressed against the upper end face 103a of the rotating body 103 by the fastening force of the fastening bolt 205 during attachment of the flexible cover 202.

[0085] The flexible cover 202 here is also formed of a thin disk in a truncated cone shape, for example, made of stainless steel or aluminum alloy, formed to a thickness of about 1 to 3 mm, and further coated with corrosion and rust resistance. The outer diameter of the flexible cover 202 is set to be about 3 to 10 mm larger than the inner diameter of the recess 201 of the rotating body 103, and the central part 202a rises gently upward in a convex shape, and the outer periphery 202b descending from the central part 202a is in contact with the upper end surface 103a of the rotating body 103. Furthermore, a through hole 206 through which a fastening bolt 205 is inserted is formed in the approximate center of the central part 202a.

[0086] 8 has a structure in which outer circumferential portion 202b contacts upper end surface 103a of rotor 103 facing intake port 101, and central portion 202a forming a convex shape is attached facing intake port 101. An annular flange portion 210 is integrally provided on the outside of outer circumferential portion 202b, extending substantially horizontally from outer circumferential portion 202b to the outside, going around the outside of outer circumferential portion 202b.

[0087] 8 is used, when the flexible cover 202 is attached, the fastening force of the fastening bolt 205 presses the flexible cover 202 strongly against the upper end face 103a of the rotating body 103, and the flange portion 210 provided on the outside of the outer circumferential portion 202b is pressed against the upper end face 103a in surface contact in proportion to the fastening force of the fastening bolt 205. When pressed further, the outer circumferential portion 202b and the flange portion 210 bend and slide on the upper end face 103a, spreading outward, and further, a part of the outer circumferential portion 202b bends and comes into surface contact with the upper end face 103a, increasing the surface contact area between the flexible cover 202 and the upper end face 103a of the rotating body 103, thereby obtaining a closer contact.

[0088] In order to prevent scratches or the like from occurring on the upper end face 103a of the rotating body 103 due to the outer circumferential portion 202b of the flexible cover 202 sliding over the upper end face 103a, it is advisable to configure the lower surface side of the flange portion 210 of the flexible cover 202 to have a cross-section that is convex toward the upper end face 103a (convex portion 202c), as shown in (d) of Figure 8.

[0089] In order to prevent the outer circumferential portion 202b of the flexible cover 202 from expanding beyond a predetermined amount due to the strong fastening force of the fastening bolts 205, a regulating wall 211 serving as a step may be provided on the upper end face 103a of the rotating body 103 to which the flexible cover 202 is attached, so as to surround the entire outside of the flexible cover 202. That is, when the outer circumferential portion 202b tries to expand outward beyond a predetermined amount, the outer circumferential portion 202b hits the regulating wall 211, and the expansion beyond the predetermined amount can be prevented. Furthermore, by providing the regulating wall 211, it becomes possible to prevent the flexible cover 202 from being displaced relative to the upper end face 103a.

[0090] As a further effect, in addition to the surface contact between the bottom surface of flange portion 210 and upper end surface 103a of rotating body 103, close contact is obtained by contact between the side surface of flange portion 210 and the side wall of regulating wall 211, thereby increasing the area of ​​surface contact.

[0091] Fig. 9 shows a second modified example of the flexible cover 202 shown in Fig. 5, where (a) is a plan view of the flexible cover 202, (b) is a schematic cross-sectional view taken along the DD line in (a), and (c) is a partially enlarged view of (b). The flexible cover 202 shown in Fig. 9 has a structure in which, when the flexible cover 202 is strongly pressed against the upper end face 103a of the rotor 103 by the fastening force of the fastening bolt 205 during attachment of the flexible cover 202, the outer circumferential portion 202b bends in proportion to the fastening force of the fastening bolt 205 and comes into planar contact with the upper end face 103a to increase the contact area, i.e., has an inner flange portion 212 as a mechanical contact area increasing structure.

[0092] More specifically, the flexible cover 202 of the second modification shown in Fig. 9 is provided with an annular inner flange portion 212 that extends from the outer periphery 202b diagonally downward inwardly, in a manner that goes around the inner side of the outer periphery 202b. The flexible cover 202 here is also formed in a cone shape from a thin disk, for example, made of stainless steel or aluminum alloy, formed to a thickness of about 1 to 3 mm, and further subjected to a coating treatment for corrosion resistance and rust resistance. The outer diameter of the flexible cover 202 is set to be about 3 to 10 mm larger than the inner diameter of the recess 201 of the rotating body 103, and the central portion 202a rises in a gently convex shape toward the upper side, and the outer periphery 202b and the inner flange portion 212 that extend downward from the central portion 202a are capable of contacting the upper end surface 103a of the rotating body 103. Furthermore, a through hole 206 through which a fastening bolt 205 is inserted is formed approximately at the center of the central portion 202a.

[0093] In the flexible cover 202 of the second modification, when the flexible cover 202 is strongly pressed against the upper end face 103a of the rotating body 103 by the fastening force of the fastening bolt 205 during installation, the inner flange portion 212 is first pressed against the upper end face 103a of the rotating body 103 in proportion to the fastening force of the fastening bolt 205, and the inner flange portion 212 becomes parallel to the upper end face 103a of the rotating body 103, increasing the contact area with the upper end face 103a. In addition, after substantially the entire inner flange portion 212 has finished contacting the upper end face 103a, a part of the outer circumferential portion 202b is then crushed to become parallel to the upper end face 103a, providing the flexible cover 202 with a mechanical contact area increasing structure that allows contact with the upper end face 103a. This allows the area of ​​close contact between the inner flange portion 212 and outer peripheral portion 202b of the flexible cover 202 and the upper end face 103a of the rotating body 103 to be increased, further eliminating foreign matter such as particles that remain between the end of the outer peripheral portion 202b of the flexible cover 202 and the upper end face 103a of the rotating body 103.

[0094] Fig. 10 shows a third modified example of the flexible cover 202 shown in Fig. 5, where (a) is a plan view of the flexible cover 202, (b) is a schematic cross-sectional view taken along the E-ED line in (a), and (c) is a partially enlarged view of (b). The flexible cover 202 shown in Fig. 10 has a plurality of elongated rod-shaped aggregates 213 (eight in this example) made of, for example, stainless steel or aluminum alloy attached to the inside of the flexible cover 202. The plurality of aggregates 213 are radially arranged from a central portion 202a, which is the apex of the convex shape, toward an outer circumferential portion 202b and at approximately equal intervals in the outer circumferential direction.

[0095] The flexible cover 202 here is also formed of a thin disk in a truncated cone shape, for example, made of stainless steel or aluminum alloy, and formed to a thickness of about 1 to 3 mm, and furthermore, the flexible cover 202 and the aggregate 213 are each subjected to a corrosion-resistant and rust-resistant coating treatment. The outer diameter of the flexible cover 202 is set to be about 3 to 10 mm larger than the inner diameter of the recess 201 of the rotor 103, and the central portion 202a rises in a gently convex shape toward the upper side, and the outer circumferential portion 202b descending from the central portion 202a is in contact with the upper end surface 103a of the rotor 103. Furthermore, a through hole 206 through which a fastening bolt 205 is inserted is formed in the approximate center of the central portion 202a.

[0096] 10, when the flexible cover 202 is attached, the fastening force of the fastening bolt 205 presses the flexible cover 202 strongly against the upper end face 103a of the rotating body 103, and the outer periphery 202b is first pressed against the upper end face 103a and bent inward in proportion to the fastening force of the fastening bolt 205, thereby increasing the contact area. Next, the aggregate 213 is bent inward together with the flexible cover 202, and the outer periphery 202b of the flexible cover 202 further comes into contact with the upper end face 103a of the rotating body 103, thereby increasing the contact area. This mechanical contact area increasing structure is provided. In this case, when the rigidity of the flexible cover 202 is low, the rigidity of the aggregate 213 can be added, and the combination of the flexibility of the flexible cover 202 and the rigidity of the aggregate 213 can be utilized to increase the contact area between the outer periphery 202b of the flexible cover 202 and the upper end face 103a of the rotating body 103.

[0097] 11A and 11B are partially enlarged views showing a modified example of the peripheral structure of the flexible cover 202 of the turbo molecular pump 100 shown in FIG. 1, in which (a) is a schematic cross-sectional view of a portion corresponding to line AA in FIG. 5A, and (b) is an exploded cross-sectional view showing the portion of FIG. 5A in an exploded form.

[0098] In the structure shown in FIG. 11, a flexible cover 202 covering a recess 201 is fastened integrally to a rotor shaft 113 together with a first washer 203a, a second washer 203b, and a sleeve 204 by using a stainless steel fastening bolt 205. The flexible cover 202 is a thin disk formed in a truncated cone shape, and is made of, for example, stainless steel or an aluminum alloy, and is formed to a thickness of about 1 to 3 mm. The outer diameter of the flexible cover 202 is set to be about 3 to 10 mm larger than the inner diameter of the recess 201 of the rotor 103, and the central portion 202a rises in a gently convex shape toward the upper side, and the outer periphery 202b descending from the central portion 202a is in contact with the upper end surface 103a of the rotor 103. A through hole 206 through which the fastening bolt 205 is inserted is formed at the approximate center of the central portion 202a.

[0099] In the flexible cover 202 formed in a gentle convex shape using a thin material like this, if the rigidity of the flexible cover 202 is low, there is a risk that the convex central portion 202a will be significantly crushed and the shape of the flexible cover 202 will be significantly damaged when the cover is fastened with the fastening bolt 205. Therefore, in this modified example, the flexible cover 202 is sandwiched between first and second washers 203a and 203b, respectively, to achieve a structure in which the flexible cover 202 is fastened while maintaining an appropriate convex shape.

[0100] The first washer 203a is interposed between the fastening bolt 205 and the flexible cover 202, and is made of, for example, stainless steel, with a through hole 207 formed in the center to which the fastening bolt 205 is attached. The lower surface 203aa facing the flexible cover 202 is formed in a curved shape that follows the shape of the upper surface of the central portion 202a of the flexible cover 202 and generally corresponds to the central portion 202a of the flexible cover 202, so that when the flexible cover 202 is sandwiched together with the second washer 203b, the lower surface 203aa comes into contact with the upper surface of the flexible cover 202 in a generally intimate contact manner.

[0101] The second washer 203b is interposed between the sleeve 204 and the flexible cover 202, and is made of, for example, stainless steel, with a through hole 207 formed in the center to which the fastening bolt 205 is attached. Furthermore, the upper surface 203ba facing the flexible cover 202 is formed in a curved shape that follows the shape of the lower surface (inner surface) of the central portion 202a of the flexible cover 202 and generally corresponds to the central portion 202a of the flexible cover 202, so that when the flexible cover 202 is sandwiched together with the first washer 203a, the upper surface 203ba comes into contact with the lower surface of the flexible cover 202 in a generally intimate contact manner.

[0102] The flexible cover 202, the first washer 203a, and the second washer 203b are also subjected to a coating treatment for corrosion resistance and rust resistance, so that corrosion and rusting of each member can be suppressed.

[0103] 11(a) and 11(b), the fastening bolt 205 passes through the through hole 207 of the first washer 203a, the through hole 206 of the flexible cover 202, the through hole 207 of the second washer 203b, and the through hole 208 of the sleeve 204 in this order, thereby integrating the first washer 203a, the flexible cover 202, the second washer 203b, and the sleeve 204. Here, the upper surface of the flexible cover 202 is in close contact with the lower surface 203aa of the first washer 203a, and the lower surface (inner surface) of the flexible cover 202 is in close contact with the upper surface 203ba of the second washer 203b, and they are integrated.

[0104] 1, the fastening bolt 205 is inserted into the recess 201 and attached to the screw hole 113a provided at the upper end of the rotor shaft 113 together with the first washer 203a, the flexible cover 202, the second washer 203b, and the sleeve 204. In this case, the outer periphery 202b of the flexible cover 202 is abutted against the upper end face 103a of the rotor 103 to cover and close the recess 201 with the flexible cover 202, and the fastening bolt 205 is tightened to the rotor shaft 113 until the gap between the upper end face 103a and the outer periphery 202b becomes tight, and the flexible cover 202 is fixed to the rotor shaft 113 together with the washer 203 and the sleeve 204. That is, flexible cover 202 is attached such that outer periphery 202b is in close contact with upper end surface 103a of rotor 103 facing intake port 101, and convex central portion 202a faces intake port 101.

[0105] In the structure of the embodiment shown in Figure 11, the upper and lower surfaces of the flexible cover 202 are tightly sandwiched between the lower surface 203aa of the first washer 203a, which conforms to the shape of the central portion 202a of the flexible cover 202, and the upper surface 203ba of the second washer 203b. Therefore, even if the flexible cover 202 is pressed toward the upper end face 103a of the rotating body 103, the convex flexible cover 202 retains its convex shape and the outer periphery 202b of the flexible cover 202 is pressed firmly against the upper end face 103a of the rotating body 103, so that a portion of the outer periphery 202b of the flexible cover 202 and the upper end face 103a of the rotating body 103 are tightly arranged in parallel contact with each other. This makes it possible to eliminate foreign matter such as particles remaining in the center of the flexible cover 202 and between the outer periphery 202b of the flexible cover 202 and the upper end face 103a of the rotating body 103, and prevents particles from flowing back from inside the vacuum pump to the chamber.

[0106] Additionally, the upper portion of the sleeve 204 may have the structure of the upper surface 203ba of the second washer 203b. [Industrial Applicability]

[0107] The present invention can be modified in various ways without departing from the spirit of the present invention, and it is natural that the present invention covers such modifications. [Explanation of symbols]

[0108] 100: Turbo molecular pump 101: Air intake 102: Rotor 102d: Cylindrical section 103: Rotating body 103a: Upper end surface 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 111: Metal disc 113: Rotor shaft 113a: Screw hole 120: Protective bearing 121: Motor 122: Stator column 123:Fixed wing 125: Fixed wing spacer 127: Outer cylinder 129: Base section 131: Threaded spacer 131a: Thread groove 133: Exhaust port 141:Electronic circuit section 143: Substrate 145: Bottom lid 149:Water cooled pipe 150: Amplifier circuit 151: Electromagnet winding 161: Transistor 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: Positive electrode 171b: Negative electrode 181: Current detection circuit 191: Amplifier control circuit 191a: Gate drive signal 191b: Gate drive signal 191c: Current detection signal 200: Control device 201: Recess 202: Flexible cover 202a: central part 202a: central part 202b: Outer periphery 202c:Convex part 203: Washer 203a: First washer 203aa: Bottom surface 203b: Second washer 203ba:Top surface 204: Sleeve 205: Fastening bolt 206: Through hole 207: Through hole 208:Through hole 209: Bolt 210: Flange part 211: Regulatory wall 212: Inner flange 213: Aggregate Tp1: Pulse width time Tp2: Pulse width time Ts: Control cycle iL: Electromagnet current iLmax: Current value iLmin: Current value

Claims

1. A vacuum pump comprising: a casing having an intake port; and a rotor having a recess that opens toward the intake port and is fastened to a rotor shaft by a bolt disposed in the recess, a flexible cover having an outer circumferential portion in contact with an end surface of the rotor facing the intake port, the flexible cover being formed in a convex shape toward the intake port and covering the recess, The cover has a contact area increasing structure that enables a portion of the outer circumferential portion to bend and come into planar contact with the end surface when an end portion of the outer circumferential portion is pressed against the end surface.

2. 2. The vacuum pump according to claim 1, wherein the end surface is provided with a step portion that receives the outer periphery and restricts the cover from expanding.

3. 3. The vacuum pump according to claim 1, wherein a surface of the outer circumferential portion facing the end face is curved convexly toward the end face.

4. 4. The vacuum pump according to claim 1, further comprising a restraining portion that clamps the cover and restricts the cover from expanding.

5. 5. The vacuum pump according to claim 1, wherein the cover is provided with a rigidity increasing structure that increases rigidity so as to suppress the cover from expanding.

6. 6. The vacuum pump according to claim 1, wherein the cover is corrosion-resistant and rust-resistant.

7. 7. The vacuum pump according to claim 1, wherein the cover has a surface that is coated with a corrosion-resistant and rust-resistant coating.

8. A cover for use in a vacuum pump, the cover comprising: a casing having an intake port; and a rotor having a recess that opens toward the intake port and is fastened to a rotor shaft by a bolt disposed in the recess, an outer circumferential portion of the rotor is in contact with an end surface of the rotor facing the intake port, the outer circumferential portion is formed in a convex shape toward the intake port, the outer circumferential portion covers the concave portion, and the outer circumferential portion is flexible; A cover characterized in that it has a contact area increasing structure that allows a part of the outer periphery to bend and come into planar contact with the end surface when the end of the outer periphery is pressed against the end surface.

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