Vacuum pump and casing

Abstract

To provide a structure for relaxing an impact in the radial direction of a flange axis when the impact is applied to a flange.SOLUTION: A vacuum pump includes a casing having a suction port flange in which a bolt hole is formed, a rotor shaft disposed in the casing, and a rotor blade rotatable together with the rotor shaft, in which the suction port flange includes a recessed portion formed continuously with the bolt hole in a radial direction of the rotor shaft and having a depth smaller than a thickness of the suction port flange so as to leave a first thin portion, and a through-hole formed adjacent to the bolt hole across a second thin portion in a direction opposite to a rotation direction of the rotor shaft.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Japanese Patent Laid-Open Publication No. 10-274189 (Patent Document 1) discloses background art in this technical field. This publication states, "The casing 50 is attached to a vacuum vessel 51, which supplies fluid sucked by a turbomolecular pump, by passing bolts 52 through elongated holes 53 formed in flanges 50a, 51a of the casing 50 and the vacuum vessel 51, as shown in FIG. 3. The bolts 52 are all fixed to the elongated holes 53 at the ends opposite the rotation direction of the exhaust vanes 2. Therefore, as described above, when the exhaust vanes 2 are broken and their rotational energy is transmitted to the casing 50, the casing 50 rotates relative to the vacuum vessel 51 by a length S against the tightening force of the bolts. The rotational energy of the broken exhaust vanes 2 is consumed as the energy required for that rotation, so the stress on the vacuum vessel 51 is weakened and the vacuum vessel 51 is not broken" (see paragraph

[0012] ). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-274189 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses that when an exhaust vane is damaged and the rotational energy is transmitted to the casing, the rotational energy of the exhaust vane is consumed. However, Patent Document 1 does not mention a structure for consuming the radial energy of the exhaust vane in the same situation. The present invention has been made in view of the above circumstances, and provides a structure for absorbing impact in the radial direction of the flange axis when an impact is applied to the flange. [Means for solving the problem]

[0005] In order to solve the above problems, for example, the configurations described in the claims are adopted. The present application includes a number of means for solving the above-described problems. One example is a vacuum pump comprising: a casing having an intake flange with bolt holes formed therein; a rotor shaft arranged within the casing; and a rotor blade rotatable together with the rotor shaft, wherein the intake flange comprises: a recess formed adjacent to the bolt holes in the radial direction of the rotor shaft, the recess having a depth smaller than the thickness of the intake flange so as to leave a first thin-walled portion; and a through hole formed adjacent to the bolt holes in the opposite direction to the rotational direction of the rotor shaft, separated by a second thin-walled portion. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a structure for absorbing an impact in the radial direction of the flange axis when an impact is applied to the flange. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 shows an example of a vertical cross section of a turbomolecular pump 100. As shown in FIG. [Figure 2] FIG. 2 shows an example of an amplifier circuit 150 for controlling the rotor shaft 113 of the turbomolecular pump 100. [Figure 3] FIG. 3 shows an example of a time chart illustrating control when the current command value is larger than the detected value. [Figure 4] FIG. 4 shows an example of a time chart illustrating control when the current command value is smaller than the detected value. [Figure 5]FIG. 5 shows an example of how the turbomolecular pump 100 is attached to a vacuum vessel 501. [Figure 6] FIG. 6 is a plan view showing an example of the flange 502. As shown in FIG. [Figure 7] FIG. 7 is an enlarged view of a portion A of FIG. [Figure 8] FIG. 8 is a perspective view of the fastening portion 601. As shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view taken along line BB in FIG. [Figure 10] FIG. 10 is a conceptual diagram showing an example of the function of the recess 703. [Figure 11] FIG. 11 is a conceptual diagram showing an example of the function of the thin-walled portion 705. As shown in FIG. [Figure 12] FIG. 12 is a graph showing an example of the relationship between the amount of movement of the bolt 504 and the load acting on the bolt 504. [Figure 13] FIG. 13 is a graph showing an example of the relationship between the amount of movement of the bolt 504 and the load acting on the bolt 504. DETAILED DESCRIPTION OF THE INVENTION

[0008] 1. Example Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1-1. Overview of the Example Turbomolecular pumps are widely used, for example, for exhausting gas from semiconductor manufacturing equipment and in vacuum vessels that require high vacuum, such as electron microscopes. A flange is provided at the intake port of the turbomolecular pump, allowing it to be fixed to the exhaust port of the vacuum vessel with bolts, etc. An O-ring or gasket is placed between this flange and the exhaust port of the vacuum vessel to maintain airtightness between the pump and the exhaust port.

[0009] Inside the turbomolecular pump, there are provided a rotor section that is rotatably supported and can be rotated at high speed by a motor section, and a stator section that is fixed to the casing of the molecular pump. In a turbomolecular pump, the rotor and stator rotate at high speed, causing the pump to draw in gas through the pump's intake port and expel it from the exhaust port. Typically, turbomolecular pumps exhaust gas in the molecular flow region (a region where the degree of vacuum is high and molecules rarely collide with each other). In order to demonstrate its exhaust capacity in the molecular flow region, the rotor must rotate at a high speed, for example, around 30,000 revolutions per minute.

[0010] If a problem occurs during operation of such a turbomolecular pump and the rotor collides with the stator or other fixed components within the pump, the angular momentum of the rotor is transferred to the stator or fixed components, instantly generating a large torque that rotates the entire pump in the direction of the rotor's rotation. This torque also exerts a large stress on the vacuum vessel through the flange.

[0011] Therefore, in this embodiment, in order to mitigate such impacts due to torque, a thin-walled portion (see thin-walled portion 705 in FIG. 7) is provided in the bolt mounting hole of the flange in the portion facing in the direction opposite to the rotor rotation direction. When an impact due to torque occurs to the entire molecular pump, for example, when the rotor portion comes into contact with the stator portion, this thin-walled portion undergoes plastic deformation, thereby absorbing the energy that rotates the pump.

[0012] In this embodiment, recesses (see recesses 703A and 703B in Figure 7) are provided in the bolt mounting holes of the flange, connected in the radial direction of the rotor shaft. If the rotor comes into contact with the stator, for example, and a torque shock is generated across the entire molecular pump, the bolts bend within these recesses. This absorbs the radial shock applied to the pump.

[0013] 1-2.Configuration of turbomolecular pump A longitudinal cross-sectional view of a 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 cylinder 127. Inside the outer cylinder 127, a rotor 103 is provided, the rotor 103 having a plurality of rotors 102 (102a, 102b, 102c, etc.), which are turbine blades for sucking in and exhausting gas, formed radially and in multiple stages around its periphery. A rotor shaft 113 is attached to the center of the rotor 103, and the rotor shaft 113 is levitated and supported in the air and its position is controlled by, for example, a five-axis controlled magnetic bearing. The rotor 103 is generally made of metal such as aluminum or an aluminum alloy.

[0014] 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 upper radial electromagnet 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 changes in the inductance of the conductive windings, which change 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.

[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 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.

[0016] The rotor shaft 113 is made of a high magnetic permeability material (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnets 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. The lower radial electromagnets 105 and the lower radial sensors 108 are arranged in the same manner as the upper radial electromagnets 104 and the upper radial sensors 107, and adjust the radial position of the lower side of the rotor shaft 113 in the same manner as the radial position of the upper side.

[0017] 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 highly magnetic permeable 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.

[0018] In the control device 200, a compensation circuit having, for example, a PID adjustment function generates excitation control command signals for the axial electromagnet 106A and the axial electromagnet 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of the axial electromagnet 106A and the axial electromagnet 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disc 111 upward by magnetic force, and the axial electromagnet 106B attracts the metal disc 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0019] In this way, the control device 200 appropriately adjusts the magnetic forces that the axial electromagnets 106A and 106B exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in space without contact. The amplifier circuit 150 that controls the excitation of the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

[0020] 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. Motor 121 also incorporates a rotational speed sensor (not shown), such as a Hall element, resolver, or encoder, and the rotational speed of rotor shaft 113 is detected by the detection signal of this rotational speed sensor.

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

[0022] A plurality of fixed blades 123 (123a, 123b, 123c...) are arranged at small gaps from the rotating blades 102 (102a, 102b, 102c...). Each of the rotating blades 102 (102a, 102b, 102c...) is formed at an angle of a predetermined degree 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 any of these metals as an ingredient.

[0023] Similarly, the fixed blades 123 are formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged in a staggered manner with the rows of rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported by being inserted between a plurality of stacked rows of fixed blade spacers 125 (125a, 125b, 125c, etc.).

[0024] The fixed vane spacer 125 is a ring-shaped member made of a metal such as aluminum, iron, stainless steel, or copper, or an alloy containing any of these metals. An outer cylinder 127 is fixed to the outer periphery of the fixed vane spacer 125 with a small gap between them. 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.

[0025] Furthermore, depending on the application of the turbomolecular pump 100, a threaded spacer 131 is disposed between the lower portion of the stator spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing any of these metals, and has multiple spiral thread grooves 131a engraved on its inner circumferential surface. The spiral direction of the thread grooves 131a corresponds to the direction in which exhaust gas molecules are transported toward the exhaust port 133 when they move in the rotational direction of the rotor 103. A cylindrical portion 102d hangs down from the lowest portion of the rotor 103, adjacent to the rotor blades 102 (102a, 102b, 102c, etc.). The outer circumferential surface of this cylindrical portion 102d is cylindrical and protrudes toward the inner circumferential surface of the threaded spacer 131, and is adjacent 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 102 and the fixed blade 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 forms the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. The base portion 129 not only physically holds the turbomolecular pump 100, but also functions as a heat conduction path, so it is desirable to use a metal that is rigid and has high thermal conductivity, such as iron, aluminum, or copper.

[0027] In this configuration, when the rotor 102 is rotated together with the rotor shaft 113 by the motor 121, the action of the rotor 102 and the stator 123 draws exhaust gas from the chamber through the intake port 101. The rotational speed of the rotor 102 is typically 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 drawn in through the intake port 101 passes between the rotor 102 and the stator 123 and is transported to the base 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, but this heat is transferred to the stator 123 side by radiation or conduction through gas molecules of the exhaust gas.

[0028] The stator spacers 125 are joined together at their outer peripheries and transmit to the outside heat received by the stator 123 from the rotor 102 and frictional heat generated when exhaust gas comes into contact with the stator 123.

[0029] 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 circumferential surface of the threaded spacer 131. However, there are also cases where the thread groove is formed on the outer circumferential surface of the cylindrical portion 102d, and a spacer having a cylindrical inner circumferential surface is disposed around the outer circumferential surface of the cylindrical portion 102d.

[0030] Depending on the application of the turbomolecular pump 100, the electrical equipment section may be surrounded by a stator column 122 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., and the interior of this stator column 122 may be kept at a predetermined pressure by purge gas.

[0031] 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.

[0032] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that have been individually adjusted and identified for the model. To store these control parameters, the turbomolecular pump 100 is provided with an electronic circuit section 141 within its 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 lid 145.

[0033] In the semiconductor manufacturing process, some process gases introduced into a chamber have the property of solidifying when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the pressure of the exhaust gas is lowest at the inlet port 101 and highest at the outlet port 133. If the pressure of the process gas exceeds a predetermined value or the temperature falls below a predetermined value while the process gas is being transferred from the inlet port 101 to the outlet port 133, the process gas solidifies and adheres to and accumulates inside the turbomolecular pump 100.

[0034] 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 [torr]) 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 process gas precipitates 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 the threaded spacer 131.

[0035] Therefore, in order to solve this problem, conventionally, a heater (not shown) or a circular water-cooled pipe 149 is wrapped around the outer periphery of the base portion 129, etc., and a temperature sensor (e.g., a thermistor) (not shown) is embedded in the base portion 129, and the heating of the heater and the cooling by the water-cooled pipe 149 are controlled based on the signal from this temperature sensor to maintain the temperature of the base portion 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS; Temperature Management System).

[0036] Next, a description will be given of the amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B in the turbomolecular pump 100. A circuit diagram of this amplifier circuit 150 is shown in FIG.

[0037] 2, one end of the electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to a positive electrode 171a of a power supply 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power supply 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.

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

[0039] Meanwhile, current regeneration diode 165 has its cathode terminal 165a connected to one end of electromagnet winding 151 and its anode terminal 165b connected to negative electrode 171b. Similarly, current regeneration diode 166 has its cathode terminal 166a connected to positive electrode 171a and its anode terminal 166b connected to the other end of electromagnet winding 151 via current detection circuit 181. Current detection circuit 181 is configured, for example, with a Hall sensor type current sensor or an electrical resistance element.

[0040] The amplifier circuit 150 configured as above corresponds to one electromagnet. Therefore, if the magnetic bearing is controlled in 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.

[0041] 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 in the figure of the control device 200, and this amplifier control circuit 191 is configured to switch the transistors 161 and 162 on / off.

[0042] The amplifier control circuit 191 compares 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. Based on the comparison result, the amplifier control circuit 191 determines the size of the pulse width (pulse width times Tp1 and Tp2) to be generated within a control cycle Ts, which is one period under PWM control. As a result, gate drive signals 191a and 191b having these pulse widths are output from the amplifier control circuit 191 to the gate terminals of the transistors 161 and 162.

[0043] It is necessary to control the position of rotor 103 at high speed and with strong force when, for example, rotor 103 passes through a resonance point during acceleration of its rotational speed or when a disturbance occurs during constant-speed operation. For this reason, a voltage of, for example, about 50 V is used as power supply 171 so that the current flowing through electromagnet winding 151 can be rapidly increased (or decreased). In addition, a capacitor (not shown) is usually connected between positive electrode 171a and negative electrode 171b of power supply 171 to stabilize power supply 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 electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0045] Furthermore, when one of the transistors 161 and 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, 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 and 162 in this manner, high-frequency noise such as harmonics generated in the turbomolecular 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, when the detected current value is smaller than the current command value, both transistors 161 and 162 are turned on for a time period corresponding to pulse width time Tp1 only once in a control cycle Ts (for example, 100 μs), as shown in Fig. 3. Therefore, during this period, the electromagnet current iL 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, if the detected current value is greater than the current command value, both transistors 161 and 162 are turned off for a time period corresponding to 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 diodes 165 and 166.

[0048] 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.

[0049] FIG. 5 is a diagram showing an example of how the turbomolecular pump 100 described above is attached to a vacuum vessel 501. The turbo molecular pump 100 has a flange 502 formed at its intake port, and an exhaust port 133 provided on its exhaust side. The vacuum vessel 501 constitutes a vacuum device such as a semiconductor manufacturing device or a column of an electron microscope, and has a flange 503 formed at the exhaust port.

[0050] A plurality of bolt holes are formed concentrically at the same positions in the flanges 502 and 503. Bolts 504 are inserted into these bolt holes and nuts 505 are screwed onto these bolts 504 to fasten them, thereby attaching and fixing the turbomolecular pump 100 to the bottom of the vacuum vessel 501. Gas within the vacuum vessel 501 is sucked in through the intake port 101 of the turbomolecular pump 100 and exhausted through the exhaust port 133. This allows, for example, reaction gases used in semiconductor manufacturing and other gases to be exhausted from the vacuum vessel 501.

[0051] In the example shown in the figure, the turbomolecular pump 100 is attached to the bottom of the vacuum vessel 501, and the molecular pump is suspended from the vacuum vessel 501. However, the attachment position of the turbomolecular pump 100 is not limited to this. The turbomolecular pump 100 may be attached horizontally to the side of the vacuum vessel 501, or may be attached to the top of the vacuum vessel 501 with the intake port 101 of the turbomolecular pump 100 facing downwards. Furthermore, a valve for adjusting the flow rate of the exhaust gas may be provided between the exhaust port of the vacuum vessel 501 and the intake port 101 of the turbo molecular pump 100 . Moreover, the exhaust port 133 is generally connected to a roughing pump such as a rotary pump.

[0052] 1-3. Configuration of flange 502 Next, a description will be given of the flange 502 of the turbo molecular pump 100. This flange 502 is provided on the intake port 101 side of the outer cylinder (in other words, the casing) 127. Figure 6 is a plan view showing an example of this flange 502. The flange 502 shown in the figure has a circular ring shape, and is formed with 12 fastening portions 601 at equal intervals in the circumferential direction.

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

[0054] An oblong hole 702 is formed adjacent to this bolt hole 701. This oblong hole 702 is a through hole that extends in the radial direction of rotor shaft 113 in a plan view. This oblong hole 702 is formed adjacent to bolt hole 701 in the opposite direction to the rotation direction of rotor shaft 113. In addition, this oblong hole 702 is formed at a position where the distance from the center of bolt hole 701 is smaller than the inner diameter of bolt hole 701.

[0055] Furthermore, recesses 703A and 703B are formed adjacent to bolt hole 701. Recess 703A is a recess formed adjacent to bolt hole 701 on the radially inner side of rotor shaft 113 (in other words, radially inward of the axis of flange 502). Recess 703A has a depth smaller than the thickness of flange 502 so as to leave a plate-shaped thin portion 704A. On the other hand, recess 703B is a recess formed adjacent to bolt hole 701 on the radially outer side of rotor shaft 113 (in other words, radially outward of the axis of flange 502). Recess 703B has a depth smaller than the thickness of flange 502 so as to leave a plate-shaped thin portion 704B. Recesses 703A and 703B are formed, for example, by spot facing. Hereinafter, recesses 703A and 703B will be collectively referred to as "recesses 703." Furthermore, thin-walled portions 704A and 704B will be collectively referred to as "thin-walled portion 704." This thin-walled portion 704 is an example of a "first thin-walled portion" according to the present invention.

[0056] Furthermore, a through hole 706 is formed adjacent to the bolt hole 701, separated by a plate-shaped thin portion 705. 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 the through hole 706 in the radial direction is approximately the same as that of the elongated hole 702, and the length of the through hole 706 in the rotational direction of the rotor shaft 113 is longer than that of the elongated hole 702. The through hole 706 is formed adjacent to the bolt hole 701 in the opposite direction to the rotational direction of the rotor shaft 113 (in other words, in the circumferential direction of the flange 502). The height of plate-shaped thin portion 705 is set to a dimension value smaller than the thickness of flange 502. Note that the height referred to here refers to the height in the axial direction of bolt hole 701. The thin portion 705 is an example of the "second thin portion" according to the present invention.

[0057] Next, the function of the recess 703 described above will be explained. Fig. 10 is a conceptual diagram showing an example of the function of the recess 703. Fig. 10(a) shows a state before an impact is applied to the flange 502. In the state shown in Fig. 10, bolts 504 are inserted through bolt holes 701 in the flange 502 and bolt holes 1001 in 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. Note that the impact referred to here is an impact in the radial direction of the rotor shaft 113 that occurs due to imbalance or damage to the rotating body 103 including the rotor shaft.

[0058] When this radial impact is applied to flange 502, flange 502 moves relative to flange 503 in the radial direction of rotor shaft 113. As a result, the portion of bolt 504 that is inserted into flange 502 is displaced in the radial direction of rotor shaft 113. At this time, in this embodiment, because recess 703A is formed adjacent to bolt hole 701, bolt 504 bends without breaking. This bending makes it possible to absorb the radial impact applied to flange 502.

[0059] Next, the function of the thin-walled portion 705 will be described. FIG. 11 is a conceptual diagram showing an example of the function of the thin-walled 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 into 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. Note that the impact referred to here is an impact in the rotational direction of the rotor shaft 113 that occurs due to imbalance or damage to the rotating body 103.

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

[0061] Next, the dimensional values ​​of the recess 703 and the thin-walled portion 704 will be described. FIG. 12 is a graph showing an example of the relationship between the amount of movement of bolt 504 and the load acting on bolt 504, in a case where bolt 504 has a certain diameter and recess 703 has a certain radial dimension (see arrow C in FIG. 11(a)) and depth dimension. The horizontal axis of this graph indicates the amount of movement of bolt 504, and the vertical axis indicates the load acting on bolt 504 as bolt 504 moves. Note that movement here refers to movement along the radial direction of rotor shaft 113.

[0062] 12 (around the collision position with thin-walled portion 704) to x=c (around the collision position with recess 703).The load then increases rapidly from x=c, and when it reaches x=b, bolt 504 breaks.

[0063] In view of this relationship, when setting the dimensional values ​​of recessed portion 703 and thin-walled portion 704, first determine the estimated movement of bolt 504 due to the impact caused by a malfunction or breakage of rotating body 103 and the deformation of casing 127 and flange 502. The movement here refers to the amount of relative movement of bolt 504 in conjunction with the radial movement of flange 502.

[0064] Then, the dimensional values ​​of recess 703 and thin-walled portion 704 are set so that bolt 504 does not reach the breaking point while moving the calculated amount. Specifically, the distance between the inner wall of recess 703 and bolt 504 (see arrow C in FIG. 11(a)) and the thickness of thin-walled portion 704 are set to dimensional values ​​that will prevent bolt 504 from breaking when bolt 504 is pressed against thin-walled portion 704 and bent within recess 703 when an impact caused by the rotation of rotor shaft 113 is applied to flange 502.

[0065] Specifically, the radial impact that occurs due to a malfunction or breakage of the rotor 103 and is applied to the flange 502 is expected to have the amount of energy shown in region g in the figure. This amount of energy is consumed as energy that causes plastic deformation of the thin-walled portion 704 and the bolt 504. In other words, the energy (area h) derived from the amount of radial movement and the load applied to the bolt 504 at that time is set to be equivalent to the energy caused by the radial impact described above. As shown in the figure, the load applied to the bolt 504 at this time is reduced compared to the case of the conventional structure.

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

[0067] Next, the dimensional values ​​of the thin-walled portion 705 will be described. 11(a) and 11(b), which has a thin-walled portion 705 and a through-hole 706 near bolt 504 of a certain diameter. The horizontal axis of this graph represents the amount of movement of bolt 504, and the vertical axis represents the load acting on bolt 504 as bolt 504 moves. Note that the movement referred to here refers to movement in the direction opposite to the rotation direction of rotor shaft 113.

[0068] First, the graph indicated by the thick solid line k in the figure will be explained. Bolt 504 collides with thin-walled portion 705 at x=d in FIG. 13. As a result, a load begins to act on bolt 504. The acting load gradually increases until x=e. In this section, thin-walled portion 705 is mainly deformed. When bolt 504 reaches x = e, thin-walled portion 705 hits the side surface of through-hole 706 and does not deform any further, and bolt 504 continues to deform. In the section where bolt 504 moves while deforming, the load increases rapidly, and when bolt 504 reaches x = f, bolt 504 breaks.

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

[0070] Specifically, the impact in the rotational direction that occurs due to a malfunction or breakage of the rotor 103 and that is applied to the flange 502 is expected to have the amount of energy shown in region i in the figure. This amount of energy is consumed as energy that causes plastic deformation of thin-walled portion 705. In other words, the energy (area j) derived from the amount of rotational movement and the load applied to bolt 504 at that time is set to be equivalent to the energy due to the impact in the rotational direction described above. As shown in the figure, the load applied to the bolt 504 at this time is reduced compared to when the thin-walled portion 705 is not provided.

[0071] The plastic deformation strength of thin-walled portion 705 is determined by the thickness, height, and length of thin-walled portion 705, the thickness and material of flange 502, etc. If the thickness or height of thin-walled portion 705 were increased, or if the material of flange 502 were made stronger than that indicated by thick solid line k in the graph, the load applied to bolt 504 would increase more rapidly, and ultimately the load applied to the bolt per rotational movement would increase (see the graph indicated by thin solid line m in the figure). On the other hand, the amount of rotational movement can be reduced.

[0072] The thickness and height of thin-walled portion 705 are set to dimensional values ​​that allow it to collide with bolt 504, crush, and absorb the impact when an impact caused by the rotation of rotor shaft 113 is applied to flange 502. Furthermore, the thickness and height of thin-walled portion 705 are set to dimensional values ​​that allow it to increase the amount of movement of bolt 504 while suppressing the load applied to bolt 504 when the impact is applied to flange 502. The same applies to the thickness and material of flange 502. The thickness of the thin-walled portion 705 referred to here is the thickness in a direction approximately perpendicular to the axis of the bolt hole 701, and the height of the thin-walled portion 705 is the height in the axial direction of the bolt hole 701.

[0073] The plastic deformation strength of thin-walled portion 705 may be set to be smaller than the strength at which bolt 504 deforms. In this case, the thickness and height of thin-walled portion 705 may be set to dimensional values ​​that allow bolt 504 to be crushed without bending when an impact caused by the rotation of rotor shaft 113 is applied to flange 502, thereby absorbing the impact.

[0074] In the embodiment described above, a thin-walled portion 705 is provided in the bolt hole 701 of the flange 502 in the portion facing in the direction opposite to the rotor rotation direction. This thin-walled portion 705 undergoes plastic deformation when a torque shock occurs to the entire molecular pump, for example, when the rotor portion comes into contact with the stator portion. This makes it possible to absorb the energy that rotates the pump.

[0075] In this embodiment, a recess 703 is provided in the bolt hole 701 of the flange 502, connected in the radial direction of the rotor shaft 113. This recess 703 allows the bolt 504 to bend when an impact due to torque occurs to the entire molecular pump, for example, when the rotor part comes into contact with the stator part. Bending of the bolt 504 prevents the bolt 504 from breaking and makes it possible to absorb the radial impact applied to the pump.

[0076] 2. Variations The above embodiment may be modified as follows: The following modifications may be combined with each other.

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

[0078] (2) Vacuum pump type In the above embodiment, a turbomolecular pump is assumed as the vacuum pump having the flange 502. However, a turbomolecular pump is merely one example of a vacuum pump. The flange 502 may be provided on a vacuum pump other than a turbomolecular pump (for example, a screw groove type vacuum pump).

[0079] (3) Shape of the recess 703 7 and the like is merely an example. The shape of recess 703 in plan view may be any other shape as long as it is connected to bolt hole 701 in the radial direction of rotor shaft 113.

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

[0081] (5) Flange type In the above embodiment, the fastening portion 601 is formed on the flange 502 on the intake port 101 side. However, the object on which the fastening portion 601 is formed is not limited to the intake port flange. The fastening portion 601 may also be formed on a flange other than the intake port flange. Furthermore, if a buffer mechanism for absorbing the impact of rotational torque is required, the fastening portion 601 may be used on the flange of a device other than a vacuum pump.

[0082] (6) Height of thin-walled section 705 In the above embodiment, the height of thin-walled portion 705 is set to a dimension value smaller than the thickness of flange 502. However, this is not essential. The height of thin-walled portion 705 may be the same dimension value as the thickness of flange 502, as long as the dimension value is such that when an impact is applied to flange 502, thin-walled portion 705 collides with bolt 504, crushes, and can absorb the impact.

[0083] (7) Other The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace 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. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with another configuration. The above-described embodiment discloses at least the configurations described in the claims. [Explanation of symbols]

[0084] 100... turbomolecular pump, 101... intake port, 102... rotor, 102d... cylindrical portion, 103... rotor, 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... fixed blade, 125... fixed blade spacer, 127... outer cylinder, 129... base portion, 131... threaded spacer, 131a... thread groove, 133... exhaust port, 141... electronic circuit portion, 143... board, 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 supply, 171a...positive electrode, 171b...negative electrode, 181...current detection circuit, 19 1...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...recess, 704A, 704B...thin portion, 705...thin portion, 706...through hole

Claims

1. a casing having an intake flange with bolt holes formed therein; a rotor shaft disposed within the casing; a rotor blade rotatable together with the rotor shaft; A vacuum pump comprising: The intake flange is a recess formed adjacent to the bolt hole in a radial direction of the rotor shaft, the recess having a depth smaller than a thickness of the intake port flange so as to leave a first thin-walled portion; a through hole formed adjacent to the bolt hole in a direction opposite to the rotation direction of the rotor shaft, with a second thin-walled portion therebetween; A vacuum pump comprising:

2. 2. The vacuum pump according to claim 1, wherein a distance between the bolt inserted into the bolt hole and an inner wall of the recess and a thickness of the first thin-walled portion are set to dimensional values ​​that allow the bolt to be pressed by the first thin-walled portion and bent within the recess when an impact caused by rotation of the rotor shaft is applied to the intake port flange, thereby preventing the bolt from breaking.

3. 2. The vacuum pump according to claim 1, wherein a thickness of the second thin-walled portion in a direction substantially perpendicular to an axis of the bolt hole is set to a dimension value that allows the second thin-walled portion to collide with a bolt inserted in the bolt hole and crush when an impact caused by rotation of the rotor shaft is applied to the intake port flange, thereby absorbing the impact.

4. 4. The vacuum pump according to claim 3, wherein the thickness of the second thin-walled portion is set to a dimension value that allows, when an impact caused by rotation of the rotor shaft is applied to the intake port flange, to be crushed without bending the bolt, thereby absorbing the impact.

5. 4. The vacuum pump according to claim 3, wherein a height of the second thin-walled portion in the axial direction of the bolt hole is smaller than a thickness of the intake port flange, and is set to a dimension that can increase the movement of the bolt while suppressing the load applied to the bolt when an impact caused by rotation of the rotor shaft is applied to the intake port flange.

6. A casing having a flange with bolt holes formed therein, The flange is a recess formed adjacent to the bolt hole in a radial direction of the axis of the flange, the recess having a depth smaller than the thickness of the flange so as to leave a first thin-walled portion; a through hole formed adjacent to the bolt hole in the circumferential direction of the flange, with a second thin-walled portion separating the through hole from the bolt hole; A casing comprising:

7. 7. A casing according to claim 6, wherein the flange is an inlet flange.

Images