Foreign matter accumulation amount estimation device and vacuum pump

Abstract

To provide a foreign matter accumulation amount estimation device capable of estimating an accumulation amount of foreign matter.SOLUTION: A foreign matter accumulation amount estimation device 210 is used in a turbo-molecular pump 100 including an intake port and an exhaust port, and includes an exhaust member 212 connectable to the exhaust port 133, and is disposed inside the exhaust member 212, and at least a part thereof has a gap t with respect to an inner peripheral surface 213 of the exhaust member 212. The turbo molecular pump 100 includes a conductor member 214 to which a voltage for detecting an electrostatic capacity is applied between an exhaust member 212 and itself, a measuring device 216 for measuring the electrostatic capacity between the exhaust member 212 and the conductor member 214, and an arithmetic device 218 for estimating a deposition amount of foreign matter inside the turbo molecular pump 100 from a change in the electrostatic capacity.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a foreign matter accumulation amount estimation device that can be used in, for example, a vacuum pump, and a vacuum pump equipped with the foreign matter accumulation amount estimation device. [Background technology]

[0002] Turbomolecular pumps are commonly known as a type of vacuum pump. These turbomolecular pumps are used, for example, for exhausting gases in manufacturing equipment for semiconductors, flat panels, and the like. In turbomolecular pumps, a motor inside the pump body is energized to rotate rotors, which eject gas molecules (gas molecules) from the gas (process gas) drawn into the pump body, thereby exhausting the gas. Some turbomolecular pumps are equipped with heaters and cooling tubes to properly manage the temperature inside the pump.

[0003] In vacuum pumps used for exhausting gas from semiconductor and flat panel manufacturing equipment, reaction products (foreign matter) produced during the manufacturing process of semiconductors and flat panels can accumulate inside the vacuum pump. If a large amount of foreign matter accumulates, it can disrupt the gas flow inside the vacuum pump or collide with rotating parts, causing problems. For this reason, technology has been devised to detect the amount of foreign matter accumulated based on changes in capacitance so that the timing of vacuum pump maintenance can be determined in advance.

[0004] In the invention disclosed in Patent Document 1 (paragraphs 0035 to 0039, Figure 2, etc.) listed below, a change in capacitance due to deposits accumulated between parallel plate electrodes is measured. In the invention disclosed in Patent Document 2 (paragraphs 0073, 0074, Figure 7, etc.), a change in capacitance due to deposits on the surfaces of interdigital electrodes is measured. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-159632 [Patent Document 2] Patent Publication No. 2021-195893 Summary of the Invention [Problem to be solved by the invention]

[0006] The invention disclosed in Patent Document 1 has the following problems. (1) Due to the lack of sufficient installation space, only small sensors can be installed, and sufficient detection sensitivity cannot be obtained. (2) The sensor blocks the gas flow path, adversely affecting exhaust performance. (3) It is not easy to extract the sensor signal from inside the pump to the outside.

[0007] In contrast, in the invention disclosed in Patent Document 2, the sensor is thin and can be installed on the surface of the gas flow path, so it does not block the gas flow path as in the invention disclosed in Patent Document 1. However, although it is possible to detect deposits when the thickness is small (thin), there is a problem in that as the thickness increases, the sensitivity decreases and detection becomes difficult.

[0008] An object of the present invention is to provide a foreign matter accumulation amount estimation device capable of estimating the amount of accumulated foreign matter, and a vacuum pump. [Means for solving the problem]

[0009] In order to achieve the above object, a foreign matter deposition amount estimation device according to the present invention comprises: A foreign matter accumulation amount estimation device used in a vacuum pump having an intake port and an exhaust port, an exhaust member connectable to the exhaust port; a conductor disposed inside the exhaust member, at least a portion of which is spaced a predetermined distance from an inner surface of the exhaust member, and to which a voltage for detecting capacitance is applied between the conductor and the exhaust member; a measuring device for measuring the capacitance between the exhaust member and the conductor; a computing device that estimates the amount of foreign matter accumulated inside the vacuum pump from the change in capacitance; Equipped with. Furthermore, a vacuum pump according to the present invention includes the above foreign matter accumulation amount estimation device. [Effects of the Invention]

[0010] According to the above invention, it is possible to provide a foreign matter accumulation amount estimation device capable of estimating the accumulation amount of foreign matter, and a vacuum pump. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an explanatory diagram schematically illustrating the configuration of a foreign matter deposition amount estimation device and a turbomolecular pump according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a circuit diagram of an amplifier circuit. [Figure 3] 10 is a time chart showing control when a current command value is larger than a detection value. [Figure 4] 10 is a time chart showing control when a current command value is smaller than a detection value. [Figure 5] 1 is an explanatory diagram showing an enlarged view of a foreign matter deposition amount estimation device according to a first embodiment. [Figure 6] FIG. 10 is an explanatory diagram showing a modified foreign matter deposition amount estimating device that controls temperature. [Figure 7] FIG. 10 is a perspective view showing a modified foreign matter deposition amount estimating device in which the conductive member has one communication opening. [Figure 8] FIG. 10 is a cross-sectional view showing a modified foreign matter deposition amount estimating device in which the conductive member has one communication opening. [Figure 9] FIG. 10 is an explanatory diagram schematically showing the configuration of a foreign matter deposition device and a turbomolecular pump according to a second embodiment of the present invention. [Figure 10] FIG. 6 is an explanatory diagram showing an enlarged view of a foreign matter deposition amount estimation device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Outline of the first embodiment> 1 shows a vacuum pump (here, a turbomolecular pump 100) according to a first embodiment of the present invention, and a foreign matter deposition amount estimation device 210 attached to the turbomolecular pump 100. The turbomolecular pump 100 is adapted to be connected to a vacuum chamber (not shown) of a target device such as a semiconductor manufacturing device.

[0013] Here, it is also possible to combine the turbomolecular pump 100 and the foreign matter deposition amount estimation device 210 and regard them as, for example, a vacuum pumping system. Furthermore, in the following, the turbomolecular pump 100 and the foreign matter deposition amount estimation device 210 will be described as separate devices, but this is not limiting, and for example, the foreign matter deposition amount estimation device 210 can also be regarded as part of the turbomolecular pump 100.

[0014] We are considering correcting the parts marked in red. <<Turbomolecular Pump 100>> 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, ...) which are turbine blades for sucking in and exhausting gas and which are 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] Furthermore, axial electromagnets 106A and 106B are arranged above and below a circular metal disk (also called an "armature 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 from the axial sensor 109 is sent to control device 200.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] A plurality of fixed blades 123 (123a, 123b, 123c...) are arranged at small gaps (predetermined intervals) from the rotating blades 102 (102a, 102b, 102c...). Each of the rotating blades 102 (102a, 102b, 102c...) is inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward through collision.

[0024] 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.).

[0025] 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.

[0026] Furthermore, depending on the application of the turbomolecular pump 100, a screw stator 131 is disposed inside the base portion 129. The screw stator 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 a plurality of 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 rotation direction of the rotor 103. A rotor lower cylindrical portion 103b hangs down from the lower part of the rotor main body 103a on which the rotor blades 102 (102a, 102b, 102c, etc.) of the rotor 103 are formed. The outer circumferential surface of this rotor lower cylindrical portion 103b is cylindrical and protrudes toward the inner circumferential surface of the screw stator 131, and is adjacent to the inner circumferential surface of the screw stator 131 with a predetermined gap therebetween. The exhaust gas transferred to the thread grooves 131a by the rotor 102 and the fixed blades 123 is guided along the thread grooves 131a and sent to the base portion 129. In this way, the screw stator 131 and the rotor lower cylindrical portion 103b facing it constitute a Holweck type exhaust mechanism portion 204. The Holweck type exhaust mechanism portion 204 gives directionality to the exhaust gas by the rotation of the rotor lower cylindrical portion 103b relative to the screw stator 131, thereby improving the exhaust characteristics of the turbomolecular pump 100.

[0027] 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.

[0028] In the configuration of the turbomolecular pump 100, when the rotor 102 is rotationally driven together with the rotor shaft 113 by the motor 121, exhaust gas is drawn from the chamber through the intake port 101 by the action of the rotor 102 and the stator 123. The exhaust gas drawn in through the intake port 101 passes between the rotor 102 and the stator 123 and is transferred to the base portion 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 by gas molecules (gas molecules) of the exhaust gas, etc.

[0029] 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.

[0030] In the above description, the screw stator 131 is disposed on the outer periphery of the rotor lower cylindrical portion 103b of the rotor 103, and the screw grooves 131a are formed on the inner circumferential surface of the screw stator 131. However, conversely, there are also cases where a screw groove is formed on the outer circumferential surface of the rotor lower cylindrical portion 103b, and a spacer having a cylindrical inner circumferential surface is arranged around it.

[0031] 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.

[0032] In this case, a purge gas port (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 inner cylindrical portion of the rotor blades 102 (lower cylindrical portion 103b of the rotor) and the stator column 122 or the base portion 129.

[0033] 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.

[0034] 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.

[0035] For example, when SiCl4 is used as the process gas in an Al etching system, the low vacuum (760 [torr] to 10 -2The vapor pressure curve shows that at temperatures of 100[torr]) and low temperatures (approximately 20[°C]), solid products (e.g., AlCl3, also called "reaction products") precipitate and adhere to and accumulate inside the turbomolecular pump 100. As a result, when process gas deposits accumulate inside the turbomolecular pump 100, these deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. The aforementioned products are prone to solidification and adhesion in high-pressure areas near the exhaust port 133 and the screw stator 131.

[0036] Therefore, in order to solve this problem, conventionally, a heater (not shown) or a circular water-cooled pipe 149 is wound around the outer periphery of the base portion 129 or the like, and a temperature sensor (e.g., a thermistor) (not shown) is embedded in the base portion 129, and heating by the heater and cooling by the water-cooled pipe 149 are controlled based on a signal from the 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). In this embodiment, the screw stator 131 is heated by a heater (not shown) embedded in the screw stator 131, and the base portion 129 is cooled by the water-cooled pipe 149 embedded in the bottom cover 145.

[0037] Next, regarding the turbomolecular pump 100 configured as described above, we will explain 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. A circuit diagram of this amplifier circuit is shown in Figure 2.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] It is necessary to control the position of rotor 103 at high speed and with strong force when, for example, the 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 high 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 1 (the side of the intake port 101) is an intake section connected to the target device, and the lower side (the side where the exhaust port 133 of the base part 129 is provided) is an exhaust section connected to an auxiliary pump (back pump) or the like (not shown). The turbomolecular pump 100 can be used not only in the vertical position shown in FIG. 1, but also in an inverted position, a horizontal position, or an inclined position.

[0051] In the turbomolecular pump 100, the aforementioned outer cylinder 127 and base portion 129 are combined to form a single case. Hereinafter, the outer cylinder 127 and base portion 129 may be collectively referred to as the "casing" or the "main body casing." Alternatively, only the outer cylinder 127 or only the base portion 129 may be referred to as the "casing." The turbomolecular pump 100 is electrically (and structurally) connected to a box-shaped electrical equipment case (not shown), and the aforementioned control device 200 is incorporated into the electrical equipment case.

[0052] The internal configuration of the main body casing of the turbomolecular pump 100 (here, a combination of the outer cylinder 127 and the base portion 129) can be divided into a rotation mechanism portion 136 that rotates the rotor shaft 113 and the like by the motor 121, and an exhaust mechanism portion 137 that is rotationally driven by the rotation mechanism portion 136. The exhaust mechanism portion 137 can also be divided into a turbomolecular pump mechanism portion 138 that is composed of the rotor blades 102, the fixed blades 123, and the like, and a thread groove pump mechanism portion (Hollweck type exhaust mechanism portion 204) that is composed of the rotor lower cylindrical portion 103b, the screw stator 131, and the like.

[0053] The aforementioned purge gas (protective gas) is used to protect the bearing parts and the rotor 102, etc., to prevent corrosion caused by the exhaust gas (process gas), and to cool the rotor 102. This purge gas can be supplied by a general method.

[0054] For example, the aforementioned purge gas port (not shown) extending linearly in the radial direction is provided at a predetermined position (such as a position 90 degrees or 120 degrees away from the exhaust port 133) of the base portion 129. Then, purge gas is supplied to this purge gas port (not shown) from the outside of the base portion 129 via a purge gas cylinder (such as an N2 gas cylinder), a flow rate regulator (valve device), or the like.

[0055] The aforementioned protective bearings 120 are also called "touchdown (T / D) bearings" or "backup bearings." These protective bearings 120 prevent the position or attitude of the rotor shaft 113 from changing significantly, even in the unlikely event of a problem with the electrical system or atmospheric inrush, and prevent damage to the rotor blades 102 and their surrounding areas.

[0056] In FIG. 1 showing the structure of the turbo molecular pump 100 and the rotor 103, hatching showing cross sections of components is omitted to avoid cluttering the drawing.

[0057] <Foreign matter accumulation amount estimation device 210> As described above, reaction products (foreign matter) may accumulate inside the turbomolecular pump 100. In this embodiment, a foreign matter accumulation amount estimation device 210 as shown in Figures 1 and 5 is used to estimate the accumulation amount of foreign matter generated inside the turbomolecular pump 100, outside the turbomolecular pump 100. The configuration and functions of the foreign matter accumulation amount estimation device 210 will be described below.

[0058] Fig. 5 shows an enlarged view of the foreign matter deposition amount estimation device 210 of Fig. 1. As shown in Fig. 5, the foreign matter deposition amount estimation device 210 includes an exhaust member 212 and a conductive member 214. Furthermore, the foreign matter deposition amount estimation device 210 includes a measuring device 216 and a computing device 218.

[0059] As will be described in detail later, exhaust member 212 and conductive member 214 constitute foreign object detection device (foreign object detection section) 220. Foreign object detection device 220 is electrically connected to measuring device 216, and the occurrence status of foreign objects in foreign object detection device 220 is measured by measuring device 216. The measurement results of measuring device 216 are transmitted to computing device 218, and the occurrence status of foreign objects is determined based on the results of calculations by computing device 218.

[0060] 7 and 8, the foreign object detector 220 has a double-pipe structure made up of an exhaust member 212 and a conductive member 214. The foreign object detector 260 in FIGS. 7 and 8 and the foreign object detector 220 in FIGS. 1 and 5 differ in the number of communication holes 236 (described later) and the size relationship between the exhaust member 212 and the conductive member 214 in the axial direction.

[0061] However, here, the foreign object detection device 220 shown in Figures 1 and 5 will be described with reference to Figures 7 and 8 regarding the commonalities between the foreign object detection device 220 shown in Figures 1 and 5 and the foreign object detection device 260 shown in Figure 8, which is also used. Note that the foreign object detection device 220 in Figures 1 and 5 and the foreign object detection device 260 shown in Figure 8, which is also used, are shown facing in opposite axial directions. Furthermore, in Figure 7, which is also used, the exhaust member 212 and the conductive member 214 are shown with different shading densities.

[0062] 1 and 5, the exhaust member 212 and the conductive member 214 are formed by processing a conductive material, such as aluminum, iron, stainless steel, copper, or an alloy containing any of these metals, into a cylindrical shape. Of these, the exhaust member 212 is a single tubular member including a cylindrical portion 222, a tip flange portion 224, and an intermediate flange portion 226. One end of the cylindrical portion 222 of the exhaust member 212 (the end on the side where the tip flange portion 224 is not provided) is connected to an exhaust port 133 (described later) of the turbomolecular pump 100.

[0063] The exhaust member 212 is connected to the exhaust port 133 by bolting using a bolt (hexagon socket head bolt) 225, with one end inserted inside the exhaust port 133. The bolt 225 is screwed into a mounting seat (reference number omitted) of the base portion 129, with an intermediate flange portion 226 sandwiched between the bolt 225. The exhaust member 212 (foreign matter detector 220) is provided so as to be detachable from the turbomolecular pump 100 via the bolt 225.

[0064] The method of connecting the exhaust member 212 to the exhaust port 133 is not limited to this, and may be a method using a clamp (a vacuum piping clamp). The exhaust member 212 (foreign matter detection device 220) may also be connected to the turbomolecular pump 100 by, for example, welding. Welding can be classified as a connection method that does not allow the exhaust member 212 (foreign matter detection device 220) to be detached.

[0065] The conductor member 214 is also formed in a single tube shape, and the outer diameter of the conductor member 214 is set to be smaller than the inner diameter of the exhaust member 212. The wall thickness of the conductor member 214 is thinner than the wall thickness of the exhaust member 212. The conductor member 214 is arranged concentrically (coaxially) inside the exhaust member 212. A gap t (FIG. 5) is present between an outer peripheral surface 215 of the conductor member 214 and an inner peripheral surface 213 of the exhaust member 212. This "gap" is also referred to as, for example, a "spacing," "distance," or "inter-electrode distance." The size of the gap t is, for example, 2 mm.

[0066] The conductor member 214 is supported inside the exhaust member 212 while being suspended by a conductive pin 230. The conductive pin 230 and the conductor member 214 can be fixed together, for example, by screwing the tip of the conductive pin 230 into a connecting hole 232 of the conductor member 214. In the modification shown in FIG. 8, the portion of the conductor member 214 into which the conductive pin 230 is screwed is partially thickened to ensure a sufficient contact area (fastening force). This type of structure may be employed for the conductor member 214 of the foreign object detecting device 220 shown in FIG. 5.

[0067] In both foreign object detection devices 220 and 260, the conductive pin 230 and the conductive member 214 can be fixed together by various methods, including not only screwing but also press-fitting, as long as electricity can flow between the conductive pin 230 and the conductive member 214.

[0068] The conductive pin 230 is formed by processing a conductive material such as aluminum, iron, stainless steel, copper, or an alloy containing any of these metals into a stepped cylindrical shape. The conductive pin 230 is inserted into a through hole 228 formed in the intermediate flange portion 226. The through hole 228 extends in the radial direction of the exhaust member 212 (and the intermediate flange portion 226).

[0069] O-rings 227, 227 are attached to the relatively small-diameter portion of the conductive pin 230. The O-rings 227, 227 are arranged spaced apart from each other in the axial direction of the conductive pin 230. The O-rings 227, 227 provide an airtight seal between the conductive pin 230 and the exhaust member 212 inside the through-hole 228. Therefore, the O-rings 227, 227 provide a vacuum sealing function. Furthermore, the conductive pin 230 is fixed to the exhaust member 212 via the tightening force of a fixing nut 229 arranged on the outside of the intermediate flange portion 226.

[0070] The fixing nut 229 is formed using a conductive material such as stainless steel. A rectangular insulating plate 233 made of an electrically insulating material and a round terminal (crimp terminal) 234 are sandwiched between the fixing nut 229 and the intermediate flange portion 226. The insulating plate 233 is in contact with a flattened seating surface of the intermediate flange portion 226. An electric wire (not shown) extends from the round terminal 234, and the round terminal 234 is used to connect the electric wire (not shown) to the conductive pin 230.

[0071] As shown with reference to Fig. 7, two fixing screws 238a and 238b are used to fix the insulating plate 233, and a round terminal 234 is also sandwiched between the head of one of the fixing screws 238a and the insulating plate 233. Electrical wiring (not shown) also extends from the round terminal 234 connected to the fixing screw 238a. The two round terminals 234 are used to apply a voltage to the conductive pin 230 and one of the fixing screws 238a for foreign object detection. The method of foreign object detection will be described later.

[0072] 1 and 5, the conductor member 214 is provided with a plurality of communication openings 236 (seven in the example of FIG. 5). The communication openings 236 penetrate the exhaust member 212 in the thickness direction (radial direction) and are arranged in a row at equal intervals along the axial direction of the conductor member 214. Furthermore, the opening dimensions of the communication openings 236 are the same. However, the foreign object detection device 260 according to the modified example shown in FIGS. 7 and 8 is provided with only one communication opening 236, and in this respect, the foreign object detection device 220 shown in FIGS. 1 and 5 differs from the foreign object detection device 260 shown in FIGS. 7 and 8.

[0073] In the example of FIGS. 1 and 5, a spacer 240 is inserted into the rightmost communication opening 236 among the multiple communication openings 236 lined up in a row. In FIG. 5, the spacer 240 is hatched for emphasis. An example of this spacer 240 is shown in FIG. 7, which is incorporated herein by reference. In the example of FIG. 7, only one spacer 240 is used, and it is inserted into only one communication opening 236. In addition, in the example of FIG. 7, there is no communication opening (communication opening 236) into which a spacer 240 is not inserted. In these respects as well, the foreign object detection device 220 of FIGS. 1 and 5 differs from the foreign object detection device 260 of the modified example shown in FIGS. 7 and 8.

[0074] 7, spacer 240 is formed by processing an electrically insulating material such as rubber (including other synthetic resins) or ceramics into a stepped pin shape. One axial end of spacer 240 is formed relatively thin and is inserted into communication opening 236.

[0075] The other axial end of the spacer 240 (the outer end of the conductor member 214) faces the inner circumferential surface 213 of the exhaust member 212. One end of the spacer 240 is in contact with the inner circumferential surface 213 of the exhaust member 212 and is interposed between the conductor member 214 and the exhaust member 212. The spacer 240 maintains a gap between the conductor member 214 and the exhaust member 212, while preventing the conductor member 214 from rotating (whirling) around the conductive pin 230 as a central axis.

[0076] In FIG. 7, two spacers 240 are arranged at positions 180 degrees apart in phase in the circumferential direction of the conductive member 214. Furthermore, three or more spacers 240 (and communication ports 236) may be arranged at 120-degree or 90-degree intervals in the circumferential direction. Furthermore, the spacer 240 may be attached to the communication port 236 located at the end closest to the turbomolecular pump 100. Furthermore, the spacer 240 may be attached to a communication port 236 located at a position midway in a row. Furthermore, the spacer 240 may be attached to a plurality of communication ports 236 in a row.

[0077] <Major components for estimating the amount of foreign matter deposited in the turbomolecular pump 100> As described above, the foreign object detector 220 is connected to the exhaust port 133 of the turbomolecular pump 100 (FIGS. 1 and 5). The exhaust port 133 is an opening formed in the side surface of the base portion 129 that constitutes the turbomolecular pump 100. The exhaust port 133 constitutes one end (a radially outer portion) of an intra-base exhaust flow path 272 that is formed inside the base portion 129. The intra-base exhaust flow path 272 is spatially connected to the outside of the turbomolecular pump 100 via the exhaust port 133.

[0078] The other end of the intra-base exhaust flow path 272 extends parallel to the axial direction of the turbomolecular pump 100. Furthermore, the other end of the intra-base exhaust flow path 272 opens toward the thread groove pump mechanism (Hollweck type exhaust mechanism 204). The thread groove pump exhaust flow path 274 faces the thread groove pump mechanism (Hollweck type exhaust mechanism 204), and the intra-base exhaust flow path 272 is spatially connected to the thread groove pump exhaust flow path 274.

[0079] In this embodiment, the thread groove pump exhaust flow path 274 is an exhaust flow path that connects to the downstream side of the thread groove 131a in the thread groove pump mechanism (Hollweck-type exhaust mechanism 204). The thread groove pump exhaust flow path 274 is an exhaust flow path that is different from the thread groove 131a. Gas that is pressurized by the thread groove 131a flows into the thread groove pump exhaust flow path 274. The gas that flows into the thread groove pump exhaust flow path 274 flows through the intra-base exhaust flow path 272 and into the foreign object detection device 220.

[0080] A wiring passage 276 for electrical connection is also formed in the base portion 129. In the example of Fig. 1, the wiring passage 276 is formed at a position 180 degrees out of phase with the base internal exhaust flow path 272 in the circumferential direction (of the base portion 129). Although not shown, wiring led from electrical components such as the board 143 is passed through the wiring passage 276 and is electrically connected to a male connector member 280 on which an electrode 278 is formed. A female connector member 284 of an electrical cable 282 is connected to the male connector member 280.

[0081] As described above, a voltage (high-frequency voltage) for detecting foreign objects is supplied to the foreign object detection device 220. The value of the high-frequency voltage can be, for example, about 3 V (either a peak value or an effective value). Wiring and electrodes for supplying this voltage can be provided in the electrical cable 282, the male connector member 280, and the female connector member 284. The female connector member 284 can be electrically connected to the fixing screw 238 a and the conductive pin 230 of the foreign object detection device 220. Furthermore, the wiring and electrodes can be provided separately from the electrical cable 282, the male connector member 280, and the female connector member 284.

[0082] <Detection of capacitance C> Fixing screw 238a is electrically connected to exhaust member 212, and conductive pin 230 is electrically connected to conductor member 214. When a voltage is applied to exhaust member 212 and conductor member 214 via fixing screw 238a and conductive pin 230, a potential difference occurs between exhaust member 212 and conductor member 214. Because a gap t exists between exhaust member 212 and conductor member 214, an electric charge Q (= CV) corresponding to the potential difference and electrostatic capacitance is stored between exhaust member 212 and conductor member 214.

[0083] In the above-mentioned Q=CV equation (hereafter referred to as "Equation (1)"), C is the capacitance and V is the potential difference. Since the potential difference V is known, the capacitance C can be calculated by detecting (measuring) the charge Q and performing the calculation (C=Q / V). Furthermore, by calculating the difference between the capacitances calculated at different times, the change in capacitance C (ΔC) over that time can be calculated.

[0084] Furthermore, the capacitance of a parallel plate conductor can be calculated by the formula C=εS / d (hereinafter referred to as "formula (2)"). The meanings of the symbols in formula (2) are as follows: C: capacitance ε: Dielectric constant (relative permittivity) of the material between the conductors S: opposing area of ​​conductor d: distance between conductors

[0085] 1 and 5, the exhaust member 212 and the conductive member 214 are cylindrical and concentrically arranged. The capacitance between the exhaust member 212 and the conductive member 214 can be expressed using the equation C=(2πε) / (ln(b / a)) (hereinafter referred to as "Equation (3)"), which is the equation for capacitance of a coaxial cylindrical conductor. Here, the meaning of each symbol is as follows: C: capacitance π: Pi ε: Dielectric constant (relative permittivity) of the material between the conductors a: outer diameter of the conductive member 214 b: inner diameter of exhaust member 212 Also, ln is the natural logarithm.

[0086] As described above, the exhaust member 212 and the conductive member 214 are connected to the measuring device 216, which is connected to the computing device 218. The exhaust member 212 and the conductive member 214 serve as electrodes, forming a capacitance sensor. The measuring device 216 measures the electric charges of the exhaust member 212 and the conductive member 214, and the computing device 218 calculates the capacitance and changes in capacitance at different times based on the measurement results of the measuring device 216. Note that the roles of the measuring device 216 and the computing device 218 are not limited to these. For example, some of the calculations may be performed in the measuring device 216, or all of the calculations may be performed in the computing device 218. Furthermore, the measuring device 216 and the computing device 218 may be integrated. Furthermore, the computing device 218 may be integrated with the control device 200 (FIG. 1).

[0087] Gas from the turbomolecular pump 100 flows into the foreign matter detection device 220, and the flowing gas flows between the exhaust member 212 and the conductive member 214 and inside the conductive member 214. The gas comes into contact with both the inner circumferential surface 213 of the exhaust member 212 and the outer circumferential surface 215 of the conductive member 214. As a result, foreign matter (reaction products) is generated and accumulates on both the inner circumferential surface 213 of the exhaust member 212 and the outer circumferential surface 215 of the conductive member 214. As the operating time of the turbomolecular pump 100 accumulates, the amounts of foreign matter accumulated on the exhaust member 212 and the conductive member 214 gradually increase.

[0088] As the thickness of the foreign matter increases, the gap t between exhaust member 212 and conductive member 214 gradually closes, and as gap t narrows, the capacitance between exhaust member 212 and conductive member 214 increases. Then, measuring device 216 measures the capacitance, and computing device 218 calculates the amount of change in this capacitance, etc.

[0089] Because gas is introduced into the foreign matter detection device 220 from the turbomolecular pump 100, it can be considered that changes in capacitance in the foreign matter detection device 220 are linked to the accumulation of foreign matter inside the turbomolecular pump 100 and reflect the state of foreign matter accumulation. Therefore, by monitoring changes in capacitance in the foreign matter detection device 220, the amount of foreign matter accumulated inside the turbomolecular pump 100 can be estimated.

[0090] In order to estimate the amount of foreign matter accumulation, a mathematical expression (relational expression) is created in advance through experiments, which expresses the relationship between the amount of foreign matter accumulated in the foreign matter detection device 220 and the amount of accumulation inside the turbo molecular pump 100. For example, this relational expression can be expressed as follows: A and the conversion coefficient α are calculated as the deposition amount T B Let,T B =αT A An example is an equation such as the following (hereinafter referred to as "equation (4)").

[0091] The relational expression is not limited to the above-mentioned formula (4), and various other expressions can be created and used. By using such a relational expression, for example, the amount of foreign matter accumulation can be estimated by (Method 1) or (Method 2) described below.

[0092] (Method 1) Using a relational expression, the deposition amount inside the turbomolecular pump 100 is calculated and estimated from the deposition amount inside the foreign matter detection device 220. This calculation and estimation is performed by having a computer (conversion device) execute a software program (deposition amount estimation software, deposition amount estimation application) created for deposition amount estimation.

[0093] According to Method 1, various relational equations can be written into the software program based on experimental results. After the software program is installed on a computer, it is possible to easily handle many types of sediments by applying the relational equations that suit the conditions. However, Method 1 requires a computer (conversion device) to perform estimations based on the relational equations.

[0094] (Method 2) Based on the relational expression, the gap (distance) t between the exhaust member 212 and the conductive member 214 is set in advance to be smaller than the gap between predetermined portions inside the turbomolecular pump 100. According to this method 2, a computer (conversion device) is not required to perform estimation based on the relational expression. Furthermore, because a conversion device is not required, costs can be reduced. Furthermore, the component configuration can be simplified.

[0095] As described above, the foreign matter deposition amount estimation device 210 of this embodiment can estimate the deposition amount using a plurality of methods by utilizing the relational expressions. One of these methods may be selected in advance and adopted in the foreign matter deposition amount estimation device 210, or multiple methods may be adopted so that the user can select one as needed. Also, a method may be constructed that combines multiple methods. For example, when Method 1 and Method 2 are combined, it is conceivable to set the gap (distance) t in Method 2 and then perform estimation using a computer (conversion device) in Method 1.

[0096] The computer (conversion device) of the above method 1 may be integrated with the arithmetic device 218. Alternatively, the functions of the computer (conversion device) of the above method 1 may be incorporated into the arithmetic device 218. Furthermore, the computer (conversion device) of the above method 1 may be integrated with the arithmetic device 218 and the measurement device 216. Furthermore, the computer (conversion device) of the above method 1 may be integrated with the control device 200 (FIG. 1).

[0097] <Utilizing temperature control> The above-mentioned relational expression can also be created based on the relationship between the temperature inside the turbomolecular pump 100 and the temperature inside the foreign object detection device 220. In other words, the amount of foreign object deposition varies depending on the pressure and temperature of the surrounding environment and the gas composition (type of gas). Of these parameters, the pressure does not vary significantly between the inside of the turbomolecular pump 100 and the inside of the exhaust member 212 of the foreign object detection device 220. Furthermore, the gas composition (type of gas) is usually known in advance once the user and application have been determined. For this reason, the conversion coefficient α can be determined by previously clarifying the relationship between the temperature inside the turbomolecular pump 100 and the temperature inside the exhaust member 212 through experiments.

[0098] For example, if it is known in advance that the temperature inside the exhaust member 212 will be half that of the temperature inside the turbo molecular pump 100, foreign matter will accumulate at twice the rate inside the exhaust member 212. B =T A You can create a relational expression such as / 2.

[0099] If the relationship between the internal temperature of the turbo molecular pump 100 and the internal temperature of the exhaust member 212 is known, the accumulation amount T A For example, the value obtained by simply doubling the amount of deposition T B In this case, the multiple (which may be a decimal point) is input in advance into a computer (conversion device), and the amount of foreign matter accumulation T A It is possible to perform a conversion by multiplying the measurement and calculation results.

[0100] Furthermore, as described above, since the estimation of the foreign matter deposition amount is greatly affected by the relationship between the temperature inside the turbomolecular pump 100 and the temperature inside the exhaust member 212, it is conceivable to control the temperature inside the foreign matter detection device 220 so that it becomes the same as the temperature inside the turbomolecular pump 100. To achieve this, for example, as shown in Fig. 6, it is possible to attach, for example, an annular heater 290 to the outer periphery of the exhaust member 212, and control the heater 290 with a temperature control device 292 to adjust the temperature inside the foreign matter detection device 220.

[0101] If the internal temperature of the turbomolecular pump 100 during operation (e.g., during rated operation) is known and constant, the temperature of the heater 290 can be adjusted by the temperature control device 292 to match the known internal temperature of the turbomolecular pump 100.

[0102] Furthermore, in cases where the internal temperature of the turbomolecular pump 100 changes or is unknown, it is also possible to measure the internal temperature of the turbomolecular pump 100 and control the temperature of the heater 290 using a temperature control device 292 based on the measurement results, although this configuration is not shown.

[0103] Furthermore, if the temperature of the foreign matter detection device 220 is adjusted to be the same as the temperature inside the turbomolecular pump 100, the temperature conditions of the foreign matter detection device 220 can be made the same as the state of the gas flow path inside the turbomolecular pump 100, making it possible to accurately estimate the amount of foreign matter accumulated inside the turbomolecular pump 100 without requiring the conversion coefficient α described above.

[0104] The temperature inside the exhaust member 212 need not necessarily be adjusted to be the same as the temperature inside the turbomolecular pump 100, but may be adjusted to a temperature that maintains a certain relationship other than the same temperature (for example, 1 / 2 times, 3 / 5 times, 1.5 times, 2 times, etc.). The temperature control device 292 may be integrated with the arithmetic device 218 or the control device 200 (FIG. 1).

[0105] <Representative Advantages of the Foreign Matter Deposition Amount Estimation Device 210 and the Turbomolecular Pump 100 According to the First Embodiment> According to the foreign matter deposition amount estimation device 210 of the first embodiment described above and the turbomolecular pump 100 equipped with the foreign matter deposition amount estimation device 210, the foreign matter detection device 220 is connected to the exhaust port 133 of the turbomolecular pump 100. This makes it possible to estimate the amount of foreign matter deposited inside the turbomolecular pump 100 based on the amount of foreign matter deposited outside the turbomolecular pump 100 (outside the outer cylinder 127 and the base portion 129).

[0106] Furthermore, compared to the invention disclosed in Patent Document 1, for example, there is no need to place a capacitance sensor inside the pump, and there are fewer constraints on the sensor installation space (high degree of freedom). Furthermore, capacitance can be detected using a relatively large space, making it easy to increase the size of the capacitance sensor. Furthermore, it is easy to ensure a large electrode area (charged area) in the capacitance sensor, making it easy to improve detection sensitivity. Furthermore, the exhaust member 212 and the conductive member 214, which serve as electrodes, are cylindrical, making it easier to ensure a large area compared to when the electrodes are flat. Furthermore, because the electrodes can be placed along (or along) the shape of the pipe, the detection direction of the electrodes can be aligned with the direction of foreign matter accumulation (e.g., the radial direction of the pipe, a direction perpendicular to the axis of the pipe, etc.), and the amount of foreign matter accumulated in the pipe can be more accurately determined.

[0107] Furthermore, because the conductive member 214 is cylindrical and disposed concentrically within the exhaust member 212, the capacitance sensor can be made smaller in proportion to the cross-sectional area of ​​the gas flow path. This prevents the capacitance sensor from blocking the gas flow path inside the pump and adversely affecting exhaust performance. Furthermore, there is no need to route the wiring connected to the capacitance sensor through narrow spaces inside the pump, such as the threaded pump exhaust flow path 274 (FIG. 5), or spaces where multiple components are closely spaced, making wiring easier.

[0108] As a result, it becomes possible to determine the timing of cleaning and to make a maintenance plan after properly understanding the operating state of the pump inside the turbomolecular pump 100. By performing maintenance appropriately, it is possible to prevent deposits from coming into contact with the rotor blades 102 (102a, 102b, 102c, etc.) inside the turbomolecular pump 100.

[0109] The determination of when cleaning should be performed may be made manually based on the calculation results of the calculation device 218. Alternatively, the determination of when cleaning should be performed may be made in a predetermined computer device based on commands written in a predetermined software program. Examples of the predetermined computer device include the control device 200 of the turbomolecular pump 100, an integrated control device owned by a user of the turbomolecular pump 100, and an inspection terminal device carried by a maintenance worker for the turbomolecular pump 100, etc.

[0110] Furthermore, the arithmetic device 218 can estimate the amount of foreign matter deposited inside the turbomolecular pump 100 based on the relationship between the change in capacitance C, the dielectric constant of the foreign matter, and the ratio of the amount of foreign matter deposited inside the turbomolecular pump 100 to the amount of foreign matter deposited on the exhaust member 212, which is measured in advance by an experiment or the like. This is effective when the type of foreign matter is known in advance.

[0111] The above-mentioned "ratio of the amount of foreign matter deposited inside the turbomolecular pump 100, measured in advance by experiment or the like, to the amount of foreign matter deposited on the exhaust member 212" can be, for example, "the ratio of the rate of foreign matter deposition inside the turbomolecular pump 100, measured in advance by experiment or the like, to the rate of foreign matter deposition on the exhaust member 212." The "deposition rate" here can be, for example, "the amount of deposition per predetermined time" or "the time required for a predetermined amount of foreign matter to deposit."

[0112] Furthermore, the "amount of foreign matter deposited on exhaust member 212" can be replaced with, for example, the "amount of foreign matter deposited on conductive member 214," the "sum of the amount of foreign matter deposited on exhaust member 212 and the amount of foreign matter deposited on conductive member 214," or the "amount of foreign matter deposited on foreign matter detection device 220." Furthermore, the above-mentioned "amount of foreign matter deposited on foreign matter detection device 220" may be the "amount of foreign matter deposited on exhaust member 212," the "amount of foreign matter deposited on conductive member 214," or the "sum of the amount of foreign matter deposited on exhaust member 212 and the amount of foreign matter deposited on conductive member 214."

[0113] Furthermore, the distance (size of the gap t) between the exhaust member 212 and the conductive member 214 can be set to be equal to (within ±20%) or smaller than the width of the narrowest part of the gas flow path inside the turbomolecular pump 100. This is effective when the state of foreign matter accumulation inside the turbomolecular pump 100 is the same (does not change significantly) as inside the exhaust member 212 (inside the foreign matter detection device 220).

[0114] Specifically, the "gas flow passages inside the turbo molecular pump 100" mentioned here may include, for example, the following: (1) A gas flow path between the rotor 102 and the fixed blade 123 in the turbomolecular pump mechanism 138 (FIG. 1). (2) The screw groove 131a in the screw groove pump mechanism part (the Holweck type exhaust mechanism part 204). (3) A screw groove pump exhaust flow path 274 connected to the downstream side of the screw groove 131a. (4) Each part of the base internal exhaust flow path 272 formed inside the base part 129.

[0115] The "narrowest portion" here can be the narrower portion of the gas flow path between the rotor 102 and the stator 123 according to (1) above, compared with the "narrowest portion" of the thread groove 131a according to (2) above. These portions are also the portions where foreign matter is more likely to be generated and accumulate than other portions inside the turbomolecular pump 100.

[0116] The distance (size of gap t) between the exhaust member 212 and the conductive member 214 should be equal to or smaller than the flow path width (spacing, distance) of this "narrowest portion." In this case, gap t will be smaller than the flow path width of the "narrowest portion." For example, if the deposition rate of gap t and the "narrowest portion" is the same, gap t and the "narrowest portion" will be filled with deposits at the same time, or gap t will be filled with deposits faster, and the capacitance of gap t will be saturated first. Therefore, even if the dielectric constant of the deposits is unknown, it is possible to detect that the "narrowest portion" is about to be filled with deposits by detecting saturation of capacitance.

[0117] Furthermore, according to the foreign matter detection device 220 (FIGS. 1 and 5) of the foreign matter deposition amount estimation device 210, the conductive member 214 has communication openings 236 that penetrate the conductive member 214 in the thickness direction. Therefore, gas that has flowed into the inside of the conductive member 214 can be guided to the gap t via the communication openings 236. This makes it easy for the gas to enter the gap t, and the gas has good fluidity. Furthermore, since a plurality of communication openings 236 are provided along the axial direction of the conductive member 214, it is possible to easily cause the gas to flow throughout the entire gap t.

[0118] More specifically, if the conductive member 214 were not provided with the communication port 236, the gas that has flowed into the conductive member 214 would flow toward the tip flange portion 224 of the exhaust member 212, which is located on the opposite side of the turbomolecular pump 100. Furthermore, since the conductive member 214 is formed in a cylindrical shape, the gas inlet into the gap t would be limited to the end of the exhaust member 212 on the turbomolecular pump 100 side.

[0119] As a result, foreign matter tends to be generated in a concentrated manner near the entrance to the gap t, and tends to be unevenly deposited near the entrance to the gap t. As a result, the area near the entrance to the gap t becomes filled with deposits, making it difficult for gas to flow into the inner part of the gap t. Further gas is then prevented from flowing into the gap t, making it difficult for gas to spread throughout the entire gap t.

[0120] However, by providing the communication port 236 in the conductive member 214, it becomes possible to introduce the gas from the inside of the conductive member 214 to the inner part of the gap t through the communication port 236. This makes it easier for the gas to penetrate the entire gap t, improving the fluidity of the gas. As a result, it is possible to prevent foreign matter from being unevenly accumulated near the entrance of the gap t. This also makes it possible to more accurately measure the capacitance between the exhaust member 212 and the conductive member 214.

[0121] Furthermore, since a plurality of communication ports 236 are provided along the axial direction of the conductive member 214, it is possible to easily cause gas to flow throughout the entire gap t. This also makes it possible to more accurately measure the capacitance between the exhaust member 212 and the conductive member 214. Here, the arrangement of the plurality of communication ports 236 is not limited to a single row, and may be multiple rows or a staggered arrangement. Furthermore, the conductive member 214 may be formed using a punched metal or the like having a large number of holes.

[0122] In order to improve the fluidity of the gas, the conductor member 214 may be formed to have, for example, a semicircular (semi-cylindrical, arc-shaped) cross section, thereby opening a portion of the side surface (circumferential surface) of the conductor member 214. However, even in this case, there is a possibility that foreign matter may be unevenly deposited near the entrance of the gap t between the conductor member 214 with a semicircular (semi-cylindrical, arc-shaped) cross section and the exhaust member 212. Therefore, providing multiple communication ports 236 in the axial direction in the conductor member 214 makes it easier to guide the gas throughout the gap t. Furthermore, even when the conductor member 214 has a semicircular (semi-cylindrical, arc-shaped) shape or another shape, the conductor member 214 may be formed using a punched metal or the like having a large number of holes.

[0123] Second Embodiment Next, a foreign matter deposition amount estimating device 310 according to a second embodiment of the present invention will be described with reference to Figures 9 and 10. Note that the same parts as those in the first embodiment are given the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0124] Fig. 9 shows a turbomolecular pump 100 equipped with a foreign matter detection device 320 of a foreign matter deposition amount estimation device 310, and Fig. 10 shows an enlarged view of the foreign matter detection device 320 of Fig. 9, together with the measuring device 216 and the computing device 218. In the example of Figs. 9 and 10, the foreign matter detection device 320 is provided with two conductor members (a main conductor member 314A and a sub-conductor member 314B). As will be described in detail later, the sub-conductor member 314B functions as an auxiliary conductor.

[0125] The main conductor member 314A and the secondary conductor member 314B are both formed in a cylindrical shape and are arranged in a row inside the exhaust member 312 along the axial direction of the exhaust member 312. The secondary conductor member 314B is arranged closer to the turbomolecular pump 100 than the main conductor member 314A. Furthermore, the main conductor member 314A and the secondary conductor member 314B are arranged concentrically with the exhaust member 312.

[0126] The opposing ends 372, 374 of the main conductor member 314A and the secondary conductor member 314B are machined at an angle to the axial direction, and the end 372 of the main conductor member 314A and the end 374 of the secondary conductor member 314B are parallel and angled to each other.

[0127] A relatively large protruding portion (portion protruding in the axial direction) at end 372 of main conductor member 314A reaches the inside (radially inward) of intermediate flange portion 326 of exhaust member 312. Furthermore, the tip of conductive pin 330A inserted into intermediate flange portion 326 reaches main conductor member 314A.

[0128] The main conductor member 314A is fixed to the conductive pin 330A and is supported inside the exhaust member 312 while being supported by the conductive pin 330A. Here, the conductive pin 330A can be the same as the conductive pin 230 in the first embodiment. The main conductor member 314A can be fixed to the conductive pin 330A by a method such as screwing, in the same manner as the conductor member 214 in the first embodiment is fixed to the conductive pin 230. The main conductor member 314A can be fixed to the conductive pin 330A in the same manner as the example shown in FIGS. 1 and 5, or the example shown in FIGS. 7 and 8.

[0129] A relatively large protruding portion (portion protruding in the axial direction) at the end 372 of the secondary conductor member 314B reaches the inside (radial inner side) of the intermediate flange portion 326 of the exhaust member 312. Furthermore, the tip of the conductive pin 330B inserted into the intermediate flange portion 326 reaches the secondary conductor member 314B.

[0130] The secondary conductor member 314B is fixed to the conductive pin 330B and is supported inside the exhaust member 312 while being suspended by the conductive pin 330B. Here, the conductive pin 330B may be the same as the conductive pin 230 in the first embodiment. The secondary conductor member 314B can be fixed to the conductive pin 330B by a method such as screwing, in the same manner as the conductive member 214 in the first embodiment is fixed to the conductive pin 230. The conductive member 214 may be fixed to the conductive pin 330B in the same manner as the examples in FIGS. 1 and 5, or the examples in FIGS. 7 and 8.

[0131] A gap t is formed between the outer peripheral surface 315A of the main conductor member 314A and the inner peripheral surface 313 of the exhaust member 312. A (distance between electrodes, Fig. 5) is present. A The size of the gap is the same as the gap t in the first embodiment (for example, 2 mm).

[0132] A gap t is formed between the outer peripheral surface 315B of the secondary conductor member 314B and the inner peripheral surface 313 of the exhaust member 312. B (distance between electrodes, FIG. 5) is interposed. The outer diameter of the secondary conductor member 314B is set to be larger than the outer diameter of the primary conductor member 314A. Therefore, the gap t B The size of the gap t A smaller than (t A >t B ) and the gap t B The size can be, for example, less than 2 mm (0.5 to 1.9 mm, preferably 0.8 to 1.6 mm, more preferably 1 mm to 1.4 mm).

[0133] In this way, by providing the secondary conductor member 314B, which has a different inter-electrode distance from the main conductor member 314A, within the exhaust member 312, it is possible to arrange two (or multiple) capacitance sensors in a common environment, one of which (some of which) reaches capacitance saturation earlier and at different times. The capacitance sensors are formed by the combination of the main conductor member 314A and the exhaust member 312, and the combination of the secondary conductor member 314B and the exhaust member 312. Furthermore, the combination of the main conductor member 314A and the exhaust member 312 functions as a main electrode, and the combination of the secondary conductor member 314B and the exhaust member 312 functions as a secondary electrode.

[0134] Then, under the same environment, gaps of different sizes t A、 t B By forming the small side gap t B is the gap on the larger side t A The capacitance sensor (on the main conductor member 314A side) is filled with foreign matter more quickly than the capacitance sensor (on the secondary conductor member 314B side), and the capacitance C is saturated. This makes it possible to form a capacitance sensor (on the main conductor member 314A side) that saturates later and a capacitance sensor (on the secondary conductor member 314B side) that saturates earlier. By using the output signals related to the main conductor member 314A and the output signals related to the secondary conductor member 314B, it is possible to determine the type (component) of foreign matter using one electrode (the secondary conductor member 314B in this case), and then estimate the amount of foreign matter accumulation using the other electrode (the main conductor member 314A in this case).

[0135] More specifically, the gap t B In the capacitance sensor on the narrower side (the side of the secondary conductor member 314B), the gap t A The gap t B The gap t on the wider side is filled with foreign matter, and the capacitance becomes saturated. A Even in this case, the narrow gap t B It is thought that foreign matter has accumulated to a thickness similar to that of the narrow gap t B Since the size of is known, the gap on the wide side t A The thickness of the deposits at the site can be estimated.

[0136] Furthermore, the permittivity (relative permittivity) ε of the foreign matter can then be calculated from the above-mentioned equation (2) relating to the capacitance of the parallel plate conductor and equation (3) relating to the capacitance of the coaxial cylindrical conductor. Also, it is possible to estimate the type of foreign matter based on the calculated value of the permittivity. Also, the amount of foreign matter inside the turbomolecular pump 100 can be calculated by the gap t A It is possible to estimate the capacitance using the capacitance sensor on the wider side (the side of the main conductor member 314A).

[0137] Here, the distance between the exhaust member 312 and the main conductor member 314A (gap t A Similarly to the gap t in the first embodiment, the size of the gap t can be set to be equal to or smaller than the narrowest part of the gas flow path inside the turbo molecular pump 100.

[0138] In the second embodiment, the main conductor member 314A is located on the downstream side of the tip flange portion 224, and the sub conductor member 314B is located on the upstream side of the turbomolecular pump 100, but this is not limiting. For example, the main conductor member 314A may be located on the upstream side (the turbomolecular pump 100 side), and the sub conductor member 314B may be located on the downstream side (the tip flange portion 22A side).

[0139] In the second embodiment, the opposing ends 372, 374 of the main conductor member 314A and the secondary conductor member 314B are machined at an angle, but this is not limiting. Although not shown, for example, the opposing ends 372, 374 of the main conductor member 314A and the secondary conductor member 314B may be machined perpendicular (perpendicular) to the axial direction. In this case, for example, the thickness of the intermediate flange portion 226 may be increased to offset the positions of the conductive pins 330A, 330B in the axial direction of the exhaust member 312, thereby connecting them to the main conductor member 314A and the secondary conductor member 314B. Alternatively, the main conductor member 314A and the secondary conductor member 314B may each be machined into a semicircular shape and arranged facing each other in the vertical direction in FIG. 10 . In FIG. 10 , the spacer 240 is hatched for emphasis.

[0140] <Inventions that can be extracted from the embodiments> The following inventions can be extracted from the above-described embodiments. (1) A foreign matter deposition amount estimation device (such as the foreign matter deposition amount estimation device 210) used in a vacuum pump (such as the turbomolecular pump 100) equipped with an intake port (such as the intake port 101) and an exhaust port (such as the exhaust port 133), an exhaust member (such as exhaust member 212) connectable to the exhaust port; The exhaust member is disposed inside the exhaust member, and at least a part of the exhaust member is spaced a predetermined distance (gap t, t A a conductor (such as the conductor member 214 or the main conductor member 314A) to which a voltage for detecting capacitance is applied between the exhaust member and the conductor (such as the conductor member 214 or the main conductor member 314A) with a gap (such as the size of the conductor member 214 or the main conductor member 314A) between the exhaust member and the conductor member; a measuring device (such as measuring device 216) that measures the capacitance between the exhaust member and the electrical conductor; a computing device (e.g., computing device 218) that estimates the amount of foreign matter accumulated inside the vacuum pump from the change in capacitance; A foreign matter deposition amount estimation device comprising: (2) The arithmetic unit A change in the capacitance (such as capacitance C), The dielectric constant of the foreign matter (dielectric constant ε, etc.), estimating the amount of foreign matter deposited inside the vacuum pump based on a relationship between the amount of foreign matter deposited inside the vacuum pump and a ratio of the amount of foreign matter deposited on the exhaust member, which is measured in advance; The foreign matter deposition amount estimation device according to (1) above, characterized in that: (3) The predetermined distance is The width of the gas flow path inside the vacuum pump must be equal to or smaller than the narrowest part (e.g., the narrower part when comparing the "narrowest part" of the gas flow path between the rotor 102 and the fixed blade 123 with the "narrowest part" of the screw groove 131a). The foreign matter deposition amount estimation device according to (1) above, characterized in that: (4) A distance different from the predetermined distance (gap tB Auxiliary conductors (e.g., auxiliary conductor members 314B) are disposed in the Based on the difference between the change in the capacitance output measured by the conductor and the change in the capacitance output measured by the auxiliary conductor, determine whether or not there is saturation in the capacitance output (saturation of capacitance, filling of the gap t with foreign matter, etc.). The foreign matter deposition amount estimation device (such as the foreign matter deposition amount estimation device 310 in FIGS. 9 and 10) according to the above (3) is characterized by the above. (5) The exhaust member and the conductor are both cylindrical, and the exhaust member and the conductor are arranged coaxially. The foreign matter deposition amount estimation device according to (1) above, characterized in that: (6) At least one of the exhaust member and the conductor is separable from the vacuum pump. The foreign matter deposition amount estimation device according to (1) above, characterized in that: (7) The conductor has a communication hole (such as the communication hole 236) that penetrates the conductor in the thickness direction. The foreign matter deposition amount estimation device according to (1) above, characterized in that: (8) An exhaust member temperature control device (such as the temperature control device 292) is provided to control the temperature of the exhaust member. The foreign matter deposition amount estimation device according to (1) above, characterized in that: (9) A vacuum pump equipped with the foreign matter deposition amount estimation device according to any one of (1) to (8) above (such as the turbomolecular pump 100 connected to the foreign matter deposition amount estimation device 210, 310).

[0141] <Other> The present invention is not limited to the above-described embodiments, and various modifications and combinations of the embodiments are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0142] 100: Turbomolecular pump 101: Air intake 102: Rotor 123:Fixed wing 129, 429: Base part 131: Screw stator 131a: Thread groove 133: Exhaust port 210, 310: Foreign matter accumulation amount estimation device 212: Exhaust parts 213: Inner surface 214: Conductive material 215: Outer surface 216: Measuring equipment 218: Arithmetic device 220, 260: Foreign object detection device 236: Connecting port 240: Spacer 290: Heater 292: Temperature control device 310: Foreign matter accumulation amount estimation device 312: Exhaust components 313: Inner surface 314A: Main conductor member 314B: Sub-conductor member 315A: Outer surface 315B: Outer surface 320: Foreign object detection device t: gap t A :gap t B :gap

Claims

1. A foreign matter accumulation amount estimation device used in a vacuum pump having an intake port and an exhaust port, an exhaust member connectable to the exhaust port; a conductor disposed inside the exhaust member, at least a portion of which is spaced a predetermined distance from an inner surface of the exhaust member, and to which a voltage for detecting capacitance is applied between the conductor and the exhaust member; a measuring device for measuring the capacitance between the exhaust member and the conductor; a computing device that estimates the amount of foreign matter accumulated inside the vacuum pump from the change in capacitance; A foreign matter deposition amount estimation device comprising:

2. The computing device the change in capacitance; and The dielectric constant of the foreign matter; estimating the amount of foreign matter deposited inside the vacuum pump based on a relationship between the amount of foreign matter deposited inside the vacuum pump and a ratio of the amount of foreign matter deposited on the exhaust member, which is measured in advance; 2. The foreign matter deposition amount estimation device according to claim 1,

3. The predetermined distance is The width of the gas flow path inside the vacuum pump must be equal to or less than the narrowest part of the flow path.

2. The foreign matter deposition amount estimation device according to claim 1,

4. An auxiliary conductor is disposed at a distance different from the predetermined distance, determining whether or not the capacitance output is saturated based on the difference between the change in capacitance output measured by the conductor and the change in capacitance output measured by the auxiliary conductor; 4. The foreign matter deposition amount estimation device according to claim 3, wherein:

5. The exhaust member and the conductor are both cylindrical, and the exhaust member and the conductor are arranged coaxially.

2. The foreign matter deposition amount estimation device according to claim 1,

6. At least one of the exhaust member and the conductor is separable from the vacuum pump.

2. The foreign matter deposition amount estimation device according to claim 1,

7. The conductor has a communication hole that penetrates the conductor in the thickness direction.

2. The foreign matter deposition amount estimation device according to claim 1,

8. An exhaust member temperature control device is provided to control the temperature of the exhaust member.

2. The foreign matter deposition amount estimation device according to claim 1,

9. A vacuum pump equipped with the foreign matter deposition amount estimation device according to any one of claims 1 to 8.

Images