Vacuum pump and casing

Abstract

Provided is a structure for mitigating an impact in a radial direction of a flange axis when an impact is applied to a flange. A vacuum pump includes: a casing having an inlet port flange with a bolt hole formed therein; a rotor shaft disposed within the casing; and a rotor blade that is able to rotate together with the rotor shaft; wherein the inlet port flange includes a recessed portion that is formed continuously adjacent to the bolt hole in a radial direction of the rotor shaft and has a depth smaller than a thickness of the inlet port flange to leave a first thin portion, and a through hole formed adjacent to the bolt hole in a direction opposite to a rotational direction of the rotor shaft with a second thin portion interposed therebetween.

Description

2024-005 1 VACUUM PUMP AND CASING [Technical Field]

[0001] The present application relates to a vacuum pump and a casing. [Background Art]

[0002] As literature in which the background art of this technical field is disclosed, there is Japanese Patent Application Publication No. H10-274189 (PTL 1). This publication describes, “As shown in Fig. 3, the bolts 52 pass through the long holes 53 provided in the flanges 50a and 51a of the casing 50 and the vacuum vessel 51, and thus the casing 50 is attached to the vacuum vessel 51 from which the fluid sucked by the turbo molecular pump is supplied. A plurality of bolts 52 are all fixed to a plurality of long holes 53 at the ends on a side opposite thereto in a rotational direction of the exhaust blade body 2. Therefore, as described above, when the exhaust blade body 2 is damaged and the rotational energy thereof is transmitted to the casing 50, the casing 50 rotates relative to the vacuum vessel 51 by the length S against the fastening force of the bolts, and the rotational energy of the damaged exhaust blade body 2 is consumed as the energy required for the rotation, and thus the stress on the vacuum vessel 51 is weakened and they are not damaged.” (see paragraph

[0012] ). [Citation List] [Patent Literature]

[0003] [PTL 1] Japanese Patent Application Publication No. H10-274189 [Summary of Invention] [Technical Problem]

[0004] PTL 1 discloses that when the exhaust blade body is damaged and the rotational energy thereof is transmitted to the casing, the energy in the rotational direction of the exhaust blade body is consumed. However, in PTL 1, there is no mention of a structure for consuming the radial energy of the exhaust blade body in the same situation. The present invention has been made in view of the above circumstances and provides a structure for mitigating an impact in a radial direction of a flange axis when an impact is applied to a flange. [Solution to Problem]2024-005 2

[0005] In order to solve the above problems, for example, the configurations described in the claims are adopted. The present application includes a plurality of means for solving the above problems. One example thereof is a vacuum pump including: a casing having an inlet port flange with a bolt hole formed therein; a rotor shaft disposed within the casing; and a rotor blade that is able to rotate together with the rotor shaft; wherein the inlet port flange includes a recessed portion that is formed continuously adjacent to the bolt hole in a radial direction of the rotor shaft and has a depth smaller than a thickness of the inlet port flange to leave a first thin portion, and a through hole formed adjacent to the bolt hole in a direction opposite to a rotational direction of the rotor shaft with a second thin portion interposed therebetween. [Advantageous Effects of Invention]

[0006] According to the present invention, it is possible to provide a structure for mitigating an impact in a radial direction of a flange axis when an impact is applied to a flange. Objects, configurations, and effects other than those described above will be made clear by description of an embodiment below. [Brief Description of Drawings]

[0007] [Fig. 1] Fig. 1 shows an example of a vertical cross section of a turbo molecular pump 100. [Fig. 2] Fig. 2 shows an example of an amplifier circuit 150 for controlling a rotor shaft 113 of the turbo molecular pump 100. [Fig. 3] Fig. 3 shows an example of a time chart showing control in a case in which a current command value is larger than a detected value. [Fig. 4] Fig. 4 shows an example of a time chart showing control in a case in which the current command value is smaller than the detected value. [Fig. 5] Fig. 5 shows an example of an attachment form of the turbo molecular pump 100 to a vacuum vessel 501. [Fig. 6]2024-005 3 Fig. 6 is a plan view showing an example of a flange 502. [Fig. 7] Fig. 7 is an enlarged view of a portion A of Fig. 6. [Fig. 8] Fig. 8 is a perspective view of a fastening portion 601. [Fig. 9] Fig. 9 is a cross-sectional view along line B-B of Fig. 7. [Fig. 10] Fig. 10 is a conceptual diagram showing an example of an action of a recessed portion 703. [Fig. 11] Fig. 11 is a conceptual diagram showing an example of an action of a thin portion 705. [Fig. 12] Fig. 12 is a graph showing an example of a relationship between an amount of movement of a bolt 504 and a load acting on the bolt 504. [Fig. 13] Fig. 13 is a graph showing an example of a relationship between an amount of movement of the bolt 504 and a load acting on the bolt 504. [Description of Embodiments]

[0008] 1. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1-1. Overview of embodiment A turbo molecular pump is widely used for a vacuum vessel that requires a high vacuum, for example, in the exhaust of a semiconductor manufacturing apparatus or in an electron microscope. An inlet port of the turbo molecular pump is provided with a flange such that the flange can be fixed to an outlet port of the vacuum vessel with bolts or the like. An O-ring, a gasket, or the like is interposed between this flange and the outlet port of the vacuum vessel to maintain airtightness between the pump and the outlet port.

[0009] Inside the turbo molecular pump, there are provided a rotor portion that is rotatably supported and can be rotated at a high speed by a motor portion, and a stator portion that is fixed to a casing of the molecular pump.2024-005 4 In the turbo molecular pump, the rotor portion rotates at a high speed, and thus the rotor portion and the stator portion exhibit an exhaust action. Due to this exhaust action, gas is sucked through the inlet port of the pump and is exhausted through an outlet port of the pump. Typically, the turbo molecular pump exhausts gas in a molecular flow region (a region in which the degree of vacuum is high and the frequency of collisions between molecules is low). In order to exhibit an exhausting capacity in the molecular flow region, the rotor portion needs to rotate at a high speed, for example, about 30,000 revolutions per minute.

[0010] In a case in which some kind of trouble occurs during operation of such a turbo molecular pump and the rotor portion collides with the stator portion or another fixed member within the pump, the angular momentum of the rotor portion is transmitted to the stator portion or the fixed member, and a large torque that allows the entire pump to rotate in a rotational direction of the rotor portion is instantly generated. This torque also exerts a large stress on the vacuum vessel through the flange.

[0011] For this reason, in order to mitigate an impact caused by such a torque, in the present embodiment, a thin portion (see a thin portion 705 in Fig. 7) is provided at a portion facing in a direction opposite to a rotational direction of the rotor in a bolt attachment hole of the flange. In a case in which the impact caused by the torque occurs in the entire molecular pump due to the rotor portion coming into contact with the stator portion, this thin portion undergoes plastic deformation, thereby absorbing energy that allows the pump to rotate.

[0012] In addition, in the present embodiment, recessed portions (see recessed portions 703A and 703B in Fig. 7) are provided in the bolt attachment hole of the flange to be continuously adjacent to each other in a radial direction of a rotor shaft. In a case in which the impact caused by the torque occurs in the entire molecular pump due to the rotor portion coming into contact with the stator portion, the bolt is bent within this recessed portion. As a result, the impact in the radial direction which is applied to the pump is absorbed.

[0013] 1-2. Configuration of turbo molecular pump2024-005 5 A vertical cross-sectional view of the turbo molecular pump 100 is shown in Fig. 1. In Fig. 1, in the turbo molecular pump 100, an inlet port 101 is formed at the upper end of a cylindrical outer cylinder 127. A rotating body 103 in which a plurality of rotor blades 102 (102a, 102b, 102c, ...), which are turbine blades for sucking and exhausting gas, are formed radially and in multiple stages around a circumference is provided inside the outer cylinder 127. A rotor shaft 113 is attached to the center of the rotating body 103, and the rotor shaft 113 is supported and position-controlled while being levitated in the air by, for example, a magnetic bearing with five-axis control. The rotating body 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0014] As upper radial electromagnets 104, four electromagnets are disposed in pairs on an X axis and a Y axis. Four upper radial sensors 107 are provided close to these upper radial electromagnets 104 and corresponding to each of the upper radial electromagnets 104. As each of the upper radial sensors 107, for example, an inductance sensor having a conduction winding, an eddy current sensor, or the like is used to detect a position of the rotor shaft 113 on the basis of a change in an inductance of the conduction winding, which changes according to a position of the rotor shaft 113. This upper radial sensor 107 is configured to detect a radial displacement of the rotor shaft 113, that is, the rotating body 103 fixed thereto, and send it to a control device 200.

[0015] In this control device 200, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for the upper radial electromagnets 104 on the basis of the signal of the position detected by the upper radial sensors 107, and an amplifier circuit 150 shown in Fig. 2 (which will be described below) controls the excitation of the upper radial electromagnets 104 on the basis of this excitation control command signal, and thus the upper radial position of the rotor shaft 113 is adjusted.

[0016] The rotor shaft 113 is made of a high magnetic permeability material (iron, stainless steel, or the like) or the like, and is attracted by a magnetic force of the upper radial electromagnets 104. Such adjustment is performed independently in an X-axis direction and a Y-axis direction. Further, lower radial electromagnets 105 and lower radial sensors 108 are disposed similar to the upper radial2024-005 6 electromagnets 104 and the upper radial sensors 107, and the lower radial position of the rotor shaft 113 is adjusted similar to the upper radial position thereof.

[0017] Further, axial electromagnets 106A and 106B are disposed with a circular metal disk 111 provided below the rotor shaft 113 interposed vertically therebetween. 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 is configured to send an axial position signal to the control device 200.

[0018] Then, in the control device 200, for example, the compensation circuit having the PID adjustment function generates the excitation control command signals for the axial electromagnet 106A and the axial electromagnet 106B on the basis of the signal of the axial position detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of the axial electromagnet 106A and the axial electromagnet 106B on the basis of these excitation control command signals. Therefore, the axial electromagnet 106A attracts the metal disk 111 upward by a magnetic force and the axial electromagnet 106B attracts the metal disk 111 downward, and thus the axial position of the rotor shaft 113 is adjusted.

[0019] In this way, the control device 200 appropriately adjusts the magnetic force exerted on the metal disk 111 by the axial electromagnets 106A and 106B, magnetically levitates the rotor shaft 113 in the axial direction, and holds it in a space without contact. The amplifier circuit 150 that controls the excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B will be described below.

[0020] On the other hand, a motor 121 includes a plurality of magnetic poles disposed circumferentially to surround the rotor shaft 113. The magnetic poles are controlled by the control device 200 to rotationally drive the rotor shaft 113 through an electromagnetic force acting between the magnetic poles and the rotor shaft 113. Further, a rotational speed sensor (not shown) such as a Hall element, a resolver, an encoder, or the like is incorporated in the motor 121, and the rotational speed of the rotor shaft 113 is detected by a detection signal from the rotational speed sensor.2024-005 7

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

[0022] A plurality of stator blades 123 (123a, 123b, 123c, ...) are arranged with a slight gap between them and the rotor blades 102 (102a, 102b, 102c, ...). The rotor blades 102 (102a, 102b, 102c, ...) are each formed to be inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transfer molecules of the exhaust gas downward by collision. The stator blades 123 (123a, 123b, 123c, ...) are made of a metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components.

[0023] Further, the stator blades 123 are similarly formed to be inclined at a predetermined angle from the plane perpendicular to the axis of the rotor shaft 113 and are arranged inward of the outer cylinder 127 in alternating stages with the stages of the rotor blades 102. The outer circumferential ends of the stator blades 123 are supported in a state of being inserted between a plurality of stacked stator blade spacers 125 (125a, 125b, 125c, ...).

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

[0025] Furthermore, a threaded spacer 131 is provided between the lower the stator blade spacer 125 and the base portion 129, depending on the use of the turbo molecular pump 100. 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 is provided with a plurality of spiral thread grooves 131a engraved in its inner circumferential surface. A spiral direction of the thread groove 131a is a direction in which the molecules of the exhaust gas are transferred2024-005 8 toward the outlet port 133 when the molecules are transferred in a rotational direction of the rotating body 103. A cylindrical portion 102d is suspended from the lowest portion of the rotating body 103 following the rotor blades 102 (102a, 102b, 102c, ...). The outer circumferential surface of the cylindrical portion 102d is cylindrical, protrudes toward the inner circumferential surface of the threaded spacer 131, and is close to the inner circumferential surface of the threaded spacer 131 with a predetermined gap therebetween. The exhaust gas transferred to the thread groove 131a by the rotor blades 102 and the stator blades 123 is sent to the base portion 129 while being guided by the thread groove 131a.

[0026] The base portion 129 is a disk-shaped member that constitutes a base portion of the turbo molecular pump 100 and is generally made of a metal such as iron, aluminum, and stainless steel. The base portion 129 physically holds the turbo molecular pump 100 and also functions as a heat conduction path, and thus a metal with rigidity and high thermal conductivity such as iron, aluminum, or copper is desirably used.

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

[0028] The stator blade spacers 125 are joined to each other at the outer circumferential portion and transmit the heat received by the stator blades 123 from the rotor blades 102, the frictional heat generated when the exhaust gas comes into contact with the stator blade 123, or the like to the outside.2024-005 9

[0029] The above description has been made assuming that the threaded spacer 131 is disposed on the outer circumference of the cylindrical portion 102d of the rotating body 103, and that the threaded spacer 131 is provided with the thread groove 131a engraved in its inner circumferential surface. However, on the contrary, a thread groove may be formed in the outer circumferential surface of the cylindrical portion 102d, and a spacer having a cylindrical inner circumferential surface may be disposed around the thread groove.

[0030] Further, depending on the use of the turbo molecular pump 100, an electrical equipment unit may be surrounded by a stator column 122 and the inside of the stator column 122 may be maintained at a predetermined pressure with a purge gas such that the gas sucked from the inlet port 101 does not enter the electrical equipment unit constituted by the upper radial electromagnets 104, the upper radial sensors 107, the motor 121, the lower radial electromagnets 105, the lower radial sensors 108, the axial electromagnets 106A and 106B, the axial sensor 109, and the like.

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

[0032] Here, the turbo molecular pump 100 requires control based on specification of the model and unique parameters (for example, various characteristics corresponding to the model) that are individually adjusted. In order to store the control parameters, the turbo molecular pump 100 includes an electronic circuit unit 141 within its main body. The electronic circuit unit 141 is constituted by a semiconductor memory such as an EEP-ROM, electronic components such as semiconductor elements for accessing the semiconductor memory, a board 143 for mounting them, and the like. The electronic circuit unit 141 is housed in the base portion 129 constituting the lower portion of the turbo molecular pump 100, for example, under a rotational speed sensor (not shown) near the center of the base portion 129 and is closed by an airtight bottom cover 145.2024-005 10

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

[0034] For example, in a case where SiCl4 is used as a process gas in an Al etching apparatus, at a low vacuum (760 [torr] to 10−2 [torr]) and a low temperature (about 20 [°C]), solid products (for example, AlCl3) are precipitated to be adhered and deposited inside the turbo molecular pump 100, as can be seen from a vapor pressure curve. As a result, when the precipitates of the process gas is deposited inside the turbo molecular pump 100, the deposits narrow a pump flow path and cause a decrease in the performance of the turbo molecular pump 100. The above-mentioned products were likely to be coagulated and adhered to a high pressure portion near the outlet port 133 or the threaded spacer 131.

[0035] For this reason, in order to solve this problem, in the related art, a heater (not shown) or an annular water cooling tube 149 is wound around the outer circumference of the base portion 129 or the like, and a temperature sensor (for example, a thermistor) (not shown) is embedded in the base portion 129. Then, heating of the heater and cooling by the water cooling tube 149 are controlled to maintain the temperature of the base portion 129 at a constant high temperature (a set temperature) on the basis of a signal from this temperature sensor (hereinafter referred to as TMS. TMS: temperature management system).

[0036] Next, regarding the turbo molecular pump 100 configured as described above, the amplifier circuit 150 that controls the 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. 2.

[0037] In Fig. 2, an electromagnet winding 151 constituting each of the upper radial electromagnets 104 or the like has one end connected to a positive electrode 171a of a power source 171 via a transistor 161 and2024-005 11 the other end connected to a negative electrode 171b of the power source 171 via a current detection circuit 181 and a transistor 162. The transistors 161 and 162 are so-called power MOSFETs and have a structure in which a diode is connected between a source and a drain.

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

[0039] On the other hand, in a current regeneration diode 165, a cathode terminal 165a is connected to one end of the electromagnet winding 151, and an anode terminal 165b is connected to the negative electrode 171b. Further, similar to this, in a current regeneration diode 166, a cathode terminal 166a is connected to the positive electrode 171a, and an anode terminal 166b is connected to the other end of the electromagnet winding 151 via the current detection circuit 181. The current detection circuit 181 is constituted by, for example, a Hall sensor type current sensor or an electric resistance element.

[0040] The amplifier circuit 150 configured as described above corresponds to one electromagnet. For this reason, in a case in which the magnetic bearing is 5-axis controlled and there are a total of 10 electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each of the electromagnets, and 10 amplifier circuits 150 are connected in parallel to the power source 171.

[0041] Further, an amplifier control circuit 191 is constituted by, for example, a digital signal processor unit (hereinafter referred to as a DSP unit) of the control device 200, and this amplifier control circuit 191 is configured to turn on / off the transistors 161 and 162.

[0042] The amplifier control circuit 191 compares a 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. On the basis of this comparison result, a magnitude of a pulse width (a pulse width time Tp1, Tp2) to be generated within a control cycle Ts, which is one cycle of PWM control, is determined. As a result, gate drive signals 191a and 191b having this2024-005 12 pulse width are outputted from the amplifier control circuit 191 to gate terminals of the transistors 161 and 162.

[0043] It is necessary to control the position of the rotating body 103 at a high speed and with a strong force when the rotational speed of the rotating body 103 passes through a resonance point during an accelerated operation, or when a disturbance occurs during a constant speed operation. For this reason, in order to rapidly increase (or decrease) a current flowing through the electromagnet winding 151, a voltage of about 50 V, for example, is used as the power source 171. Further, a capacitor (not shown) is usually connected between the positive electrode 171a and the negative electrode 171b of the power source 171 in order to stabilize the power source 171.

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

[0045] Further, when one of the transistors 161 and 162 is turned on and the other thereof is turned off, a so-called flywheel current is maintained. By causing the flywheel current to flow 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 circuit as a whole can be kept low. Further, by controlling the transistors 161 and 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.

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

[0047] On the other hand, in a case where the detected current value is larger than the current command value, both transistors 161 and 162 are2024-005 13 turned off for a time equivalent to the pulse width time Tp2 only once during the control cycle Ts as shown in Fig. 4. For this reason, the electromagnet current iL during this period decreases toward a current value iLmin (not shown) that can be regenerated from the negative electrode 171b to the positive electrode 171a via the diodes 165 and 166.

[0048] In either case, either one of the transistors 161 and 162 is turned on after the pulse width time Tp1 or Tp2 has elapsed. For this reason, during this period, the flywheel current is maintained in the amplifier circuit 150.

[0049] Fig. 5 is a diagram showing an example of an attachment form of the turbo molecular pump 100 described above to a vacuum vessel 501. A flange 502 is formed on the inlet port of the turbo molecular pump 100, and an outlet port 133 is provided on an exhaust side of the turbo molecular pump 100. The vacuum vessel 501 constitutes a vacuum device for a semiconductor manufacturing apparatus, a mirror tower of an electron microscope, or the like, and a flange 503 is formed at an outlet port of the vacuum vessel 501.

[0050] In the flanges 502 and 503, a plurality of bolt holes are formed at the same concentric positions. Bolts 504 are inserted into these bolt holes, and nuts 505 are screwed onto these bolts 504 and tightened, and thus the turbo molecular pump 100 is attached and fixed to the lower portion of the vacuum vessel 501. Gas within the vacuum vessel 501 is sucked through the inlet port 101 of the turbo molecular pump 100 and exhausted through the outlet port 133. As a result, it is possible to exhaust, for example, a reactive gas for semiconductor manufacturing and other gases from the vacuum vessel 501.

[0051] In the example shown in this figure, the turbo molecular pump 100 is attached to the lower portion of the vacuum vessel 501, and the molecular pump is suspended from the vacuum vessel 501. However, the attachment position of the turbo molecular pump 100 is not limited to this. The turbo molecular pump 100 may be attached to the lateral side of the vacuum vessel 501 in a horizontal position, or may be attached to the upper portion of the vacuum vessel 501 with the inlet port 101 of the turbo molecular pump 100 facing downward.2024-005 14 Furthermore, a valve for adjusting the flow rate of an exhaust gas may be provided between the outlet port of the vacuum vessel 501 and the inlet port 101 of the turbo molecular pump 100. In addition, the outlet port 133 is generally connected to a roughing pump such as a rotary pump.

[0052] 1-3. Configuration of flange 502 Next, the flange 502 of the turbo molecular pump 100 will be described. This flange 502 is provided on a side of the inlet port 101 of the outer cylinder (in other words, the casing) 127. Fig. 6 is a plan view showing an example of the flange 502. The flange 502 shown in the figure has a circular ring shape. In this flange 502, twelve fastening portions 601 are formed at equal intervals in a circumferential direction.

[0053] Fig. 7 is an enlarged view of a portion A of Fig. 6. Fig. 7 is a plan view showing an example of each of the fastening portions 601. Fig. 8 is a perspective view of the fastening portion 601 shown in Fig. 7. Fig. 9 is a cross-sectional view along line B-B of Fig. 7. As shown in these figures, bolt holes 701 are formed in the flange 502. Each of the bolt holes 701 is a through hole having a circular cross section.

[0054] A long hole 702 is formed continuously adjacent to this bolt hole 701. The long hole 702 is a through hole extending in a radial direction of the rotor shaft 113 in a plan view. The long hole 702 is formed continuously adjacent to the bolt hole 701 in a direction opposite to a rotational direction of the rotor shaft 113. In addition, this long hole 702 is formed at a position at which a distance from the center of the bolt hole 701 is smaller than the inner diameter of the bolt hole 701.

[0055] In addition, recessed portions 703A and 703B are formed continuously adjacent to the bolt hole 701. The recessed portion 703A is a recessed portion formed continuously adjacent to the bolt hole 701 on an inner side in the radial direction of the rotor shaft 113 (in other words, on an inner side in the radial direction of the axis of the flange 502). The recessed portion 703A has a depth smaller than the thickness of the flange 502 to leave a plate-shaped thin portion 704A. On the other hand, the recessed portion 703B is a recessed portion formed continuously adjacent to the bolt hole 701 on an outer side in the radial direction of2024-005 15 the rotor shaft 113 (in other words, on an outer side in the radial direction of the axis of the flange 502). The recessed portion 703B has a depth smaller than the thickness of the flange 502 to leave a plate- shaped thin portion 704B. These recessed portions 703A and 703B are formed by, for example, counterboring. Hereinafter, the recessed portions 703A and 703B are collectively referred to as a “recessed portion 703.” In addition, the thin portions 704A and 704B are collectively referred to as a “thin portion 704.” The thin portion 704 is an example of a “first thin portion” according to the present invention.

[0056] In addition, a through hole 706 is formed adjacent to the bolt hole 701 with a plate-shaped thin portion 705 interposed therebetween. The through hole 706 has an oval cross section and extends in the radial direction of the rotor shaft 113 in a plan view. The length of this through hole 706 in the radial direction is approximately the same as that of the long hole 702, and the length of this through hole 706 in the rotational direction of the rotor shaft 113 is longer than that of the long hole 702. In addition, the through hole 706 is formed adjacent to the bolt hole 701 in a direction opposite to the rotational direction of the rotor shaft 113 (in other words, in a circumferential direction of the flange 502). The height of the plate-shaped thin portion 705 is set to a dimensional value smaller than the thickness of the flange 502. The height referred to here means a height in an axial direction of the bolt hole 701. The thin portion 705 is an example of a “second thin portion” according to the present invention.

[0057] Next, an action of the recessed portion 703 will be described. Fig. 10 is a conceptual diagram showing an example of an action of the recessed portion 703. Fig. 10(a) shows a state before an impact is applied to the flange 502. In the state shown in the figure, the bolt 504 is inserted through the bolt hole 701 of the flange 502 and a bolt hole 1001 of the flange 503 of the vacuum vessel 501. Fig. 10(b) shows a state after an impact is applied to the flange 502 in the same state as in Fig. 10(a). The impact referred to here is an impact in the radial direction of the rotor shaft 113 that occurs due to an unbalance defect or damage of the rotating body 103 including the rotor shaft.2024-005 16

[0058] When this impact in the radial direction is applied to the flange 502, the flange 502 moves relative to the flange 503 in the radial direction of the rotor shaft 113. As a result, a portion of the bolt 504 that is inserted through the flange 502 is displaced in the radial direction of the rotor shaft 113. At this time, in the present embodiment, the recessed portion 703A is formed continuously adjacent to the bolt hole 701, and thus the bolt 504 is bent without breaking. Due to this bending, it is possible to absorb the impact applied to the flange 502 in the radial direction.

[0059] Next, an action of the thin portion 705 will be described. Fig. 11 is a conceptual diagram showing an example of an action of the thin portion 705. Fig. 11(a) shows a state before an impact is applied to the flange 502. In the state shown in the figure, the bolt 504 is inserted through the bolt hole 701 of the flange 502. Fig. 11(b) shows a state after an impact is applied to the flange 502 in the same state as in Fig. 11(a). The impact referred to here is an impact in the rotational direction of the rotor shaft 113 that occurs due to the unbalance defect or damage of the rotating body 103.

[0060] When this impact in the rotational direction is applied to the flange 502, the flange 502 moves relative to the flange 503 (not shown) in the rotational direction of the rotor shaft 113. As a result, a portion of the bolt 504 that is inserted through the flange 502 is displaced in a direction opposite to the rotational direction of the rotor shaft 113. The displaced bolt 504 collides with the thin portion 705, and the impact causes the thin portion 705 to plastically deform. Due to this plastic deformation, it is possible to absorb the impact applied to the flange 502 in the rotational direction.

[0061] Next, the dimensional values of the recessed portion 703 and the thin portion 704 will be described. Fig. 12 is a graph showing an example of a relationship between an amount of movement of the bolt 504 and a load acting on the bolt 504 in the bolt 504 having a certain diameter size and the recessed portion 703 having a certain radial dimension (see arrow C in Fig. 11(a)) and a certain depth dimension. A horizontal axis of this graph indicates the amount of movement of the bolt 504, and a vertical axis of this graph indicates the load acting on the bolt 504 as the bolt 504 moves. The2024-005 17 movement referred to here means movement in the radial direction of the rotor shaft 113.

[0062] As the bolt 504 moves, the load acting on the bolt 504 gradually increases from x = a (around the position of collision with the thin portion 704) to x = c (around the position of collision with the recessed portion 703) in Fig. 12. The load then increases rapidly from x = c, and when the load reaches x = b, the bolt 504 breaks.

[0063] In view of this relationship, when setting the dimensional values of the recessed portion 703 and the thin portion 704, first, the amount of movement of the bolt 504 that is estimated by the impact that occurs due to the defect or damage of the rotating body 103 and the deformation of the casing 127 and the flange 502 is calculated. The amount of movement referred to here is the amount of relative movement of the bolt 504 in conjunction with the movement of the flange 502 in the radial direction.

[0064] Then, the dimensional values of the recessed portion 703 and the thin portion 704 are set such that the load does not reach a breaking point while the bolt 504 moves by the calculated amount. Specifically, a distance between an inner wall of the recessed portion 703 and the bolt 504 (see arrow C in Fig. 11(a)) and a thickness of the thin portion 704 are set to dimensional values that allow the bolt 504 to be pressed against the thin portion 704 and bent within the recessed portion 703 when an impact caused by the rotation of the rotor shaft 113 is applied to the flange 502 so as to prevent breakage of the bolt 504.

[0065] Specifically, the impact in the radial direction that occurs due to the defect or damage of the rotating body 103 and is applied to the flange 502 is expected to be an amount of energy indicated by a region g in the figure. The amount of the energy is consumed as energy that causes the plastic deformation of the thin portion 704 and the bolt 504. In other words, the energy (a region h) derived from the amount of movement in the radial direction and the load applied to the bolt 504 at that time is set to be equivalent to the energy due to the impact in the radial direction described above. At that time, the load applied to the bolt 504 is reduced compared to the case of the structure of the related art, as shown in the figure.2024-005 18

[0066] The thickness of the thin portion 704 (in other words, the depth of the recessed portion 703) is set to a dimensional value that does not cause plastic deformation due to the tightening axial force of the bolt 504.

[0067] Next, the dimensional value of the thin portion 705 will be described. Fig. 13 is a graph showing an example of a relationship between the amount of movement of the bolt 504 and the load acting on the bolt 504 in a structure having the thin portion 705 and the through hole 706 near the bolt 504 having a certain diameter size, as shown in Figs. 11(a) and 11(b). A horizontal axis of this graph indicates the amount of movement of the bolt 504, and a vertical axis of this graph indicates the load acting on the bolt 504 as the bolt 504 moves. The movement referred to here means movement in a direction opposite to the rotational direction of the rotor shaft 113.

[0068] First, the graph indicated by a thick solid line k in the figure will be described. The bolt 504 collides with the thin portion 705 at x = d in Fig. 13. As a result, the load begins to act on the bolt 504. The acted load is gradually increased until x = e. In this section, mainly the thin portion 705 is deformed. When the load acted on the bolt 504 reaches x = e, the thin portion 705 hits the side surface of the through hole 706 and is not deformed any further, and thereafter the bolt 504 is deformed. In the section in which the bolt 504 moves while being deformed, the load increases suddenly, and when the load reaches x = f, the bolt 504 breaks.

[0069] When the bolt 504 collides with the thin portion 705 in this manner, the thin portion 705 is deformed. Then, the bolt 504 that has collided with the thin portion 705 subsequently collides with the side surface of the through hole 706 and breaks. In other words, the bolt 504 does not break simply by colliding with the thin portion 705. For this reason, in the present embodiment, the plastic deformation strength of the thin portion 705 is set to be smaller than the breaking strength of the bolt 504. For this reason, the load required to break the bolt 504 is greater than the load required to deform the thin portion 705. For this reason, the thin portion 705 can be deformed to the maximum extent before the bolt 504 breaks. For this reason, it is possible to2024-005 19 prevent the bolt 504 from breaking before the thin portion 705 finishes the deformation, and the thin portion 705 can fully exhibit its cushioning effect.

[0070] Specifically, the impact in the rotational direction that occurs due to the defect or damage of the rotating body 103 and is applied to the flange 502 is expected to be an amount of energy indicated by a region i in the figure. The amount of the energy is consumed as energy that causes the plastic deformation of the thin portion 705. In other words, the energy (a region j) derived from the amount of movement in the rotational direction and the load applied to the bolt 504 at that time is set to be equivalent to the energy due to the impact in the rotational direction described above. At that time, the load applied to the bolt 504 is reduced compared to the case in which the thin portion 705 is not provided, as shown in the figure.

[0071] The plastic deformation strength of the thin portion 705 is determined by the thickness, height, and length of the thin portion 705, the thickness and material of the flange 502, and the like. If the thickness and height of the thin portion 705 are increased, or if the material of the flange 502 is made to have a strength greater than that shown by the thick solid line k in the graph, the load applied to the bolt 504 will increase more rapidly, and ultimately the load applied to the bolt in the amount of movement in the rotational direction will become higher (see the graph shown by the thin solid line m in the figure). On the other hand, the amount of movement in the rotational direction can be made small.

[0072] The thickness and height of the thin portion 705 are set to dimensional values that allow the thin portion 705 to collide with the bolt 504 and be crushed when an impact caused by the rotation of the rotor shaft 113 is applied to the flange 502 so as to absorb the impact. In addition, the thickness and height of the thin portion 705 are set to dimensional values that allow the amount of movement of the bolt 504 to be secured while causing the load applied to the bolt 504 to be suppressed when the same impact is applied to the flange 502. The same applies to the thickness and material of the flange 502.2024-005 20 The thickness of the thin portion 705 referred to here means a thickness in a direction approximately perpendicular to the axis of the bolt hole 701, and the height of the thin portion 705 referred to here means a height in the axial direction of the bolt hole 701.

[0073] The plastic deformation strength of the thin portion 705 may be set to be smaller than the strength at which the bolt 504 is deformed. In this case, the thickness and height of the thin portion 705 may be set to dimensional values that allow the thin portion 705 to be crushed without causing the bolt 504 to be bent when an impact caused by the rotation of the rotor shaft 113 is applied to the flange 502 so as to absorb the impact.

[0074] In the embodiment described above, the thin portion 705 is provided in the bolt hole 701 of the flange 502 at a portion facing in a direction opposite to the rotor rotational direction. In a case in which the impact caused by the torque occurs in the entire molecular pump due to the rotor portion coming into contact with the stator portion, the thin portion 705 undergoes plastic deformation. As a result, it is possible to absorb the energy that allows the pump to rotate.

[0075] In addition, in the present embodiment, the recessed portions 703 are provided in the bolt hole 701 of the flange 502 to be continuously adjacent to each other in the radial direction of the rotor shaft 113. In a case in which the impact caused by the torque occurs in the entire molecular pump due to the rotor portion coming into contact with the stator portion, the recessed portion 703 allows the bolt 504 to bend. When the bolt 504 is bent, it is possible to prevent the bolt 504 from breaking and to absorb the impact in the radial direction that is applied to the pump.

[0076] 2. Modification example The above embodiment may be modified as follows. The following modification examples may be combined with each other.

[0077] (1) The number of fastening portions 601 In the above embodiment, twelve fastening portions 601 are formed in the flange 502. However, the number 12 is merely an example. The number of fastening portions 601 may be appropriately selected depending on the usage conditions of the flange 502.

[0078] (2) Type of vacuum pump2024-005 21 In the above embodiment, the vacuum pump having the flange 502 is assumed to be a turbo molecular pump. However, a turbo molecular pump is merely an example of a vacuum pump. The flange 502 may be provided in a vacuum pump (for example, a thread groove type vacuum pump) other than a turbo molecular pump.

[0079] (3) Shape of recessed portion 703 As shown in Fig. 7 or the like, the shape of the recessed portions 703 in a plan view is merely an example. The shape of the recessed portion 703 in a plan view may be any other shape as long as it is continuously adjacent to the bolt hole 701 in the radial direction of the rotor shaft 113.

[0080] (4) Shape of through hole 706 In the embodiment described above, the through hole 706 has an oval cross section. However, this cross-sectional shape is merely an example. The through holes 706 may have a cross section (for example, a rectangular cross section) other than the oval cross section.

[0081] (5) Type of flange In the above embodiment, the fastening portion 601 is formed in the flange 502 on a side of the inlet port 101. However, the object in which the fastening portion 601 is formed is not limited to the inlet port flange. The fastening portion 601 may be formed in a flange other than the inlet port flange. In addition, the fastening portion 601 may be employed in the flange of a device other than a vacuum pump as long as the device requires a buffer mechanism for absorbing the impact of rotational torque.

[0082] (6) Height of thin portion 705 In the above embodiment, the height of the thin portion 705 is set to a dimensional value smaller than the thickness of the flange 502. However, this is not essential. The height of the thin portion 705 may be the same dimensional value as the thickness of the flange 502 as long as the dimensional value is a dimensional value that allows the thin portion 705 to collide with the bolt 504 and be crushed when an impact is applied to the flange 502 so as to absorb the impact.

[0083] (7) Others The present invention is not limited to the above-described embodiment, and various modification examples are included. For example, the above-described embodiment has been described in detail to clearly2024-005 22 explain the present invention, and the present invention is not necessarily limited to those with all the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to combine the configuration of one embodiment with the configuration of another embodiment. In addition, for a part of the configuration of each embodiment, addition of another configuration, deletion, or replacement is possible. The above-described embodiment discloses at least the configurations described in the claims. [Reference Signs List]

[0084] 100 Turbo molecular pump 101 Inlet port 102 Rotor blade 102d Cylindrical portion 103 Rotating body 104 Upper radial electromagnet 105 Lower radial electromagnet 106A, 106B Axial electromagnet 107 Upper radial sensor 108 Lower radial sensor 109 Axial sensor 111 Metal disk 113 Rotor shaft 120 Protective bearing 121 Motor 122 Stator column 123 Stator blade 125 Stator blade spacer 127 Outer cylinder 129 Base portion 131 Threaded spacer 131a Thread groove 133 Outlet port 141 Electronic circuit unit 143 Board2024-005 23 145 Bottom cover 149 Water cooling tube 150 Amplifier circuit 151 Electromagnet winding 161, 162 Transistor 161a Cathode terminal 161b Anode terminal 162a Cathode terminal 162b Anode terminal 165, 166 Diode 165a Cathode terminal 165b Anode terminal 166a Cathode terminal 166b Anode terminal 171 Power source 171a Positive electrode 171b Negative electrode 181 Current detection circuit 191 Amplifier control circuit 191a, 191b Gate drive signal 191c Current detection signal 200 Control device 501 Vacuum vessel 502, 503 Flange 504 Bolt 505 Nut 601 Fastening portion 701 Bolt hole 702 Long hole 703A, 703B Recessed portion 704A, 704B Thin portion 705 Thin portion 706 Through hole

Claims

2024-005 24 CLAIMS

1. A vacuum pump comprising: a casing having an inlet port flange with a bolt hole formed therein; a rotor shaft disposed within the casing; and a rotor blade that is able to rotate together with the rotor shaft; wherein the inlet port flange includes a recessed portion that is formed continuously adjacent to the bolt ole in a radial direction of the rotor shaft and has a depth smaller han a thickness of the inlet port flange to leave a first thin portion, nd a through hole formed adjacent to the bolt hole in a direction pposite to a rotational direction of the rotor shaft with a second thin ortion interposed therebetween. Claim 2] The vacuum pump according to claim 1, wherein a distance between a olt inserted into the bolt hole and an inner wall of the recessed ortion and a thickness of the first thin portion are set to dimensional alues that allow the bolt to be pressed by the first thin portion and ent within the recessed portion when an impact caused by rotation of the otor shaft is applied to the inlet port flange to prevent breakage of he bolt. Claim 3] The vacuum pump according to claim 1, wherein a thickness of the econd thin portion in a direction substantially perpendicular to an axis f the bolt hole is set to a dimensional value that allows the second hin portion to collide with a bolt inserted in the bolt hole and be rushed when an impact caused by rotation of the rotor shaft is applied o the inlet port flange to absorb the impact. Claim 4] The vacuum pump according to claim 3, wherein the thickness of the econd thin portion is set to a dimensional value that allows the second hin portion to be crushed without causing the bolt to be bent when an mpact caused by rotation of the rotor shaft is applied to the inlet port lange to absorb the impact.2024-005 25

5. The vacuum pump according to claim 3, wherein a height of the second thin portion in an axial direction of the bolt hole is set to a dimensional value that is smaller than the thickness of the inlet port 5 flange and allows an amount of movement of the bolt to be secured while causing a load applied to the bolt to be suppressed when an impact caused by rotation of the rotor shaft is applied to the inlet port flange. Claim 6] A casing having a flange with a bolt hole formed therein, wherein the flange includes a recessed portion that is formed continuously adjacent to the bolt ole in a radial direction of an axis of the flange and has a depth maller than a thickness of the flange to leave a first thin portion, and a through hole formed adjacent to the bolt hole in a circumferential irection of the flange with a second thin portion interposed herebetween. Claim 7] The casing according to claim 6, wherein the flange is an inlet port lange.

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