Vacuum pump

Abstract

To provide a vacuum pump excellent in back pressure performance even when suction gas is hydrogen gas or the like.SOLUTION: A vacuum pump 100, which includes an exhaust part 114 including a turbine pump part 115 having plural steps of rotary blades 102 and a fixed blade 123, and a drag pump part 116 located on the exhaust downstream side further than the turbine pump part 115, uses the exhaust part 114 for exhausting suction gas sucked from a suction port 101, via a gas flow path FP1 from an exhaust port 133. It further includes an introduction flow path FP3 for introducing intermediate introduction gas having higher viscosity than suction gas, the introduction flow path FP3 being connected to a gas flow path FP1 at the exhaust downstream side further than the rotary blade 102 closest to a suction port 101 in the exhaust part 114, out of the plural steps of rotary blades 102.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vacuum pump. [Background technology]

[0002] Known vacuum pumps, such as turbomolecular pumps, include an exhaust section that includes a turbine pump section that is primarily intended to compress the molecular flow region, and a drag pump section that is primarily intended to compress the intermediate flow region to the viscous flow region (see, for example, FIG. 9 of Patent Document 1).

[0003] The vacuum pump shown in Patent Document 1 has a cylindrical casing with multiple stages of rotors and fixed vanes functioning as a turbine pump section, and a screw groove section functioning as a drag pump section. The casing has an intake port at the top and an exhaust port at the bottom. When the vacuum pump is driven, gas is sucked in through the intake port, and the gas passes through the turbine pump section and the drag pump section in that order before being exhausted through the exhaust port.

[0004] Generally, vacuum pumps have a back pressure dependency in which the performance of the pump is affected by the pressure on the exhaust port side (back pressure side). Conventionally, as a means for reducing the effect of back pressure (improving back pressure performance), it has been known to enlarge the diameter of the thread groove portion or to increase the axial length of the thread groove portion, as shown in Patent Document 1. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5689546 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the gas sucked by the vacuum pump is hydrogen gas, even if the above-mentioned means for improving the back pressure performance are used, sufficient back pressure performance may not be obtained compared to when, for example, nitrogen gas is sucked in. After extensive research into this point, the inventors of the present application have concluded that hydrogen gas has a lower viscosity than nitrogen gas, which reduces the compression effect in the exhaust section (especially the drag pump section), and that this is one of the causes of the deterioration of back pressure performance.

[0007] An object of the present invention is to provide a vacuum pump that has excellent back pressure performance even when the suction gas is hydrogen gas or the like. [Means for solving the problem]

[0008] The present invention is a vacuum pump comprising an exhaust section including a turbine pump section having multiple stages of rotors and fixed blades, and a drag pump section located downstream of the turbine pump section, and exhausting intake gas sucked in from an intake port by the exhaust section from the exhaust port via a gas flow path, the vacuum pump comprising an introduction flow path for introducing an intermediate introduction gas having a higher viscosity than the intake gas, the introduction flow path being connected to the gas flow path downstream of the rotor that is closest to the intake port in the exhaust section among the multiple stages of rotors.

[0009] Such a vacuum pump is provided with a purge gas flow passage that supplies a purge gas to the inside of a stator column provided on the inner periphery of a rotor on which the rotor blades are provided, and the introduction flow passage is branched off from the purge gas flow passage, and it is preferable that the purge gas is used as the intermediate introduction gas.

[0010] It is preferable that the purge gas flow path is composed of an outer purge gas flow path located outside the vacuum pump and an inner purge gas flow path located inside the vacuum pump, and that the introduction flow path branches off from the inner purge gas flow path and is connected to the gas flow path.

[0011] It is preferable that the inner diameter of at least a part of the introduction passage is smaller than the inner diameter of the purge gas passage.

[0012] The introduction passage preferably includes a valve capable of adjusting the flow rate of the intermediate introduction gas.

[0013] The introduction passage is preferably connected to the gas passage between the turbine pump section and the drag pump section. Effect of the Invention

[0014] The vacuum pump of the present invention is provided with an introduction passage for introducing an intermediate introduction gas having a higher viscosity than the intake gas, and this introduction passage is connected to the gas passage downstream of the rotor that is closest to the intake port in the exhaust section among the multiple stages of rotors. With this configuration, when the intake gas sucked in from the intake port by the exhaust section is exhausted from the exhaust port through the gas passage, the intake gas and the intermediate introduction gas flow in the gas passage. That is, the viscosity of the mixture of the intake gas and the intermediate introduction gas is higher than that of the intake gas alone, and therefore the compression effect in the exhaust section is improved. Therefore, according to the vacuum pump of the present invention, excellent back pressure performance can be obtained even if the suction gas is hydrogen gas or the like. [Brief description of the drawings]

[0015] [Figure 1] 1 is a vertical cross-sectional view that shows a schematic diagram of an embodiment of a vacuum pump according to the present invention. [Diagram 2] FIG. 2 is a circuit diagram of an amplifier circuit of the vacuum pump shown in FIG. [Diagram 3] 6 is a time chart showing control when a current command value is larger than a detection value. [Figure 4] 6 is a time chart showing control when a current command value is smaller than a detection value. [Diagram 5] FIG. 2 is a partially enlarged view of the vacuum pump shown in FIG. [Figure 6] 2 is a partial enlarged view showing a first modified example of the vacuum pump shown in FIG. [Figure 7] 1. FIG. 4 is a partially enlarged view showing a second modified example of the vacuum pump shown in FIG. [Figure 8] 1. FIG. 4 is a partially enlarged view showing a third modified example of the vacuum pump shown in FIG. [Figure 9] 1. FIG. 4 is a partial enlarged view showing a fourth modified example of the vacuum pump shown in FIG. [Figure 10] 6 is a graph showing the relationship between the back pressure and the suction pressure in the vacuum pump shown in FIGS. 1 and 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A turbomolecular pump, which is one embodiment of a vacuum pump according to the present invention, will be described below with reference to the drawings.

[0017] A longitudinal cross-sectional view of this turbomolecular pump 100 is shown in Fig. 1. The turbomolecular pump 100 has an intake port 101 formed at the upper end of a cylindrical outer tube 127. Inside the outer tube 127, a rotor 103 is provided, the rotor 103 having a plurality of rotors 102 (102a, 102b, 102c, ...) which are turbine blades for sucking in and exhausting gas (intake gas) and arranged radially and in multiple stages on its periphery. A rotor shaft 113 is attached to the center of the rotor 103, and the rotor shaft 113 is supported in the air and position-controlled by, for example, a five-axis controlled magnetic bearing. The rotor 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0018] The upper radial electromagnets 104 are arranged in pairs on the X-axis and the Y-axis. Four upper radial sensors 107 are provided adjacent to the upper radial electromagnets 104 and corresponding to each of the upper radial electromagnets 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors having conductive windings, and detect the position of the rotor shaft 113 based on the change in inductance of the conductive windings that changes according to the position of the rotor shaft 113. The upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed thereto, and send the detected displacement to a control device (not shown).

[0019] In this control device, 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.

[0020] The rotor shaft 113 is made of a material with high magnetic permeability (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnet 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. The lower radial electromagnet 105 and the lower radial sensor 108 are arranged in the same manner as the upper radial electromagnet 104 and the upper radial sensor 107, and adjust the lower radial position of the rotor shaft 113 in the same manner as the upper radial position.

[0021] Furthermore, axial electromagnets 106A and 106B are arranged above and below a circular metal disk 111 provided at the bottom of rotor shaft 113. Metal disk 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of rotor shaft 113, and an axial position signal is sent to a control device.

[0022] In the control device, a compensation circuit having, for example, a PID adjustment function generates an excitation control command signal for each of the axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of the axial electromagnets 106A and 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disk 111 upward by magnetic force and the axial electromagnet 106B attracts the metal disk 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0023] In this way, the control device appropriately adjusts the magnetic force that the axial electromagnets 106A, 106B exert on the metal disk 111, magnetically levitating the rotor shaft 113 in the axial direction and holding it in a non-contact manner in space. The amplifier circuit 150 that controls the excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A, 106B will be described later.

[0024] Meanwhile, motor 121 has a plurality of magnetic poles arranged circumferentially so as to surround rotor shaft 113. Each magnetic pole is controlled by a control device so as to rotate rotor shaft 113 via electromagnetic force acting between the magnetic pole and rotor shaft 113. Also, motor 121 incorporates a rotation speed sensor such as a Hall element, resolver, or encoder (not shown), and the rotation speed of rotor shaft 113 is detected by a detection signal from this rotation speed sensor.

[0025] Furthermore, for example, a phase sensor (not shown) is attached near the lower radial sensor 108 to detect the phase of rotation of the rotor shaft 113. The control device detects the position of the magnetic poles using the detection signals of both this phase sensor and the rotation speed sensor.

[0026] A plurality of fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap between them and the rotor blades 102 (102a, 102b, 102c...). The rotor blades 102 (102a, 102b, 102c...) are formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport the molecules of the intake gas downward by collision. The fixed blades 123 (123a, 123b, 123c...) are made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components.

[0027] Similarly, the fixed blades 123 are formed at an inclination at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged alternately with the stages of the rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported in a state where they are inserted between a plurality of stacked stages of fixed blade spacers 125 (125a, 125b, 125c, etc.).

[0028] The fixed vane spacer 125 is a ring-shaped member and is made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer periphery of the fixed vane spacer 125 with a small gap therebetween. A base portion 129 is disposed at the bottom of the outer cylinder 127. An exhaust port 133 is formed in the base portion 129 and communicates with the outside. The intake 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.

[0029] Furthermore, a threaded spacer 131 is disposed between the lower portion of the fixed vane spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals, and has a plurality of helical thread grooves 131a engraved on its inner peripheral surface. The helical direction of the thread grooves 131a is the direction in which the molecules of the intake gas are transferred toward the exhaust port 133 when they move in the rotation direction of the rotor 103. A cylindrical portion 102d hangs down from the lowest portion of the rotor 103, which is connected to the rotor vanes 102 (102a, 102b, 102c, etc.). The outer peripheral surface of the cylindrical portion 102d is cylindrical and protrudes toward the inner peripheral surface of the threaded spacer 131, and is adjacent to the inner peripheral surface of the threaded spacer 131 with a predetermined gap therebetween. The intake 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.

[0030] Here, a portion having a function of discharging the intake gas from intake port 101 toward exhaust port 133 is referred to as exhaust section 114, and a flow path through which the intake gas flows from intake port 101 to exhaust port 133 is referred to as gas flow path FP1. Exhaust section 114 is composed of turbine pump section 115 having multiple stages of rotors 102 and fixed blades 123, and drag pump section 116 having thread groove 131a and cylindrical section 102d.

[0031] The base portion 129 is a disk-shaped member that constitutes the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. The base portion 129 physically holds the turbomolecular pump 100 and also functions as a heat conduction path, so it is desirable to use a metal that has rigidity and high thermal conductivity, such as iron, aluminum, or copper.

[0032] In this configuration, when the rotor 102 is rotated together with the rotor shaft 113 by the motor 121, gas is sucked from the chamber through the intake port 101 by the action of the rotor 102 and the stator 123. The rotation speed of the rotor 102 is usually 20,000 rpm to 90,000 rpm, and the peripheral speed at the tip of the rotor 102 reaches 200 m / s to 400 m / s. The intake gas sucked from the intake port 101 passes between the rotor 102 and the stator 123 and is transferred to the base part 129. At this time, the temperature of the rotor 102 rises due to frictional heat generated when the intake gas comes into contact with the rotor 102 and conduction of heat generated by the motor 121, and the like, but this heat is transferred to the stator 123 side by radiation or conduction by gas molecules of the intake gas, and the like.

[0033] The fixed blade spacers 125 are joined to each other at their outer peripheries, and transmit to the outside heat received by the fixed blades 123 from the rotor blades 102 and frictional heat generated when the intake gas comes into contact with the fixed blades 123.

[0034] In the above description, the threaded spacer 131 is disposed on the outer periphery of the cylindrical portion 102d of the rotor 103, and the thread groove 131a is formed on the inner periphery of the threaded spacer 131. However, there are also cases where the thread groove is formed on the outer periphery of the cylindrical portion 102d, and a spacer having a cylindrical inner periphery is disposed around the outer periphery of the cylindrical portion 102d.

[0035] In the turbomolecular pump 100 of this embodiment, the intake gas sucked in from the intake port 101 does not enter 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., so that the electrical equipment section is surrounded by a stator column 122, and the inside of this stator column 122 is maintained at a predetermined pressure by purge gas.

[0036] A purge gas inlet 135 is provided in the base portion 129, and purge gas is introduced from this purge gas inlet 135 to the inside of the stator column 122. 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. Here, the flow path through which the purge gas flows from the purge gas inlet 135 to the stator column 122 is referred to as a purge gas flow path FP2.

[0037] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that are individually adjusted and identified as a model. In order to store these control parameters, the turbomolecular pump 100 has an electronic circuit section 141 in its main body. The electronic circuit section 141 is composed of a semiconductor memory such as an EEPROM, electronic components such as semiconductor elements for accessing the memory, and a substrate 143 for mounting these components. The electronic circuit section 141 is housed below a rotational speed sensor (not shown) near the center of a base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom cover 145.

[0038] In the semiconductor manufacturing process, some process gases introduced into the chamber have the property of becoming solid when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbomolecular pump 100, the pressure of the intake gas is lowest at the intake port 101 and highest at the exhaust port 133. If the pressure of the intake gas becomes higher than a predetermined value or the temperature falls below a predetermined value while the intake gas is being transferred from the intake port 101 to the exhaust port 133, the intake gas becomes solid and adheres to and accumulates inside the turbomolecular pump 100.

[0039] For example, when SiCl4 is used as a process gas in an Al etching apparatus, at low vacuum (760 [torr] to 10-2 [torr]) and low temperature (approximately 20 [°C]), a solid product (e.g., AlCl3) precipitates and adheres to and accumulates inside the turbomolecular pump 100, as can be seen from the vapor pressure curve. When precipitates of the process gas accumulate inside the turbomolecular pump 100, the deposits narrow the pump flow path, causing a decrease in the performance of the turbomolecular pump 100. The above-mentioned product is prone to solidification and adhesion in high pressure areas near the exhaust port 133 and near the threaded spacer 131.

[0040] Therefore, in order to solve this problem, in the past, a heater (not shown) or a circular water-cooled tube 149 was wrapped around the outer periphery of the base portion 129, and a temperature sensor (e.g., a thermistor) (not shown) was embedded in the base portion 129, and the heating of the heater and the cooling by the water-cooled tube 149 were controlled based on the signal from this temperature sensor to keep the temperature of the base portion 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS; Temperature Management System).

[0041] Furthermore, the turbomolecular pump 100 of this embodiment is provided with an intermediate introduction gas inlet 137 for introducing an intermediate introduction gas into the turbomolecular pump 100. Note that the intermediate introduction gas and the like will be described in detail later.

[0042] Next, regarding the turbo molecular pump 100 configured as described above, an amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B will be described. A circuit diagram of this amplifier circuit 150 is shown in FIG.

[0043] 2, one end of an electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to a positive electrode 171a of a power source 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power source 171 via a current detection circuit 181 and a transistor 162. The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between the source and drain.

[0044] At this time, the transistor 161 has a cathode terminal 161a of the diode connected to the positive electrode 171a, and an anode terminal 161b connected to one end of the electromagnet winding 151. The transistor 162 has a cathode terminal 162a of the diode connected to the current detection circuit 181, and an anode terminal 162b connected to the negative electrode 171b.

[0045] On the other hand, the current regeneration diode 165 has its cathode terminal 165a connected to one end of the electromagnet winding 151 and its anode terminal 165b connected to the negative electrode 171b. Similarly, the current regeneration diode 166 has its cathode terminal 166a connected to the positive electrode 171a and its anode terminal 166b connected to the other end of the electromagnet winding 151 via a current detection circuit 181. The current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or an electric resistance element.

[0046] The amplifier circuit 150 configured as above corresponds to one electromagnet. Therefore, when the magnetic bearing is controlled by five axes and there are a total of ten electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the ten amplifier circuits 150 are connected in parallel to the power supply 171.

[0047] Furthermore, the amplifier control circuit 191 is configured, for example, by a digital signal processor section (hereinafter referred to as a DSP section) of the control device (not shown), and this amplifier control circuit 191 switches the transistors 161 and 162 on / off.

[0048] The amplifier control circuit 191 is adapted to compare the current value detected by the current detection circuit 181 (a signal reflecting this current value is called a current detection signal 191c) with a predetermined current command value. Then, based on the result of this comparison, the magnitude of the pulse width (pulse width times Tp1, Tp2) to be generated within a control cycle Ts, which is one period of PWM control, is determined. As a result, gate drive signals 191a, 191b having this pulse width are output from the amplifier control circuit 191 to the gate terminals of the transistors 161, 162.

[0049] In addition, when the rotor 103 passes through a resonance point during an accelerating operation of the rotation speed, or when a disturbance occurs during a constant speed operation, it is necessary to control the position of the rotor 103 at high speed and with a strong force. For this reason, a high voltage of, for example, about 50 V is used as the power supply 171 so that the current flowing through the electromagnet winding 151 can be rapidly increased (or decreased). In addition, a capacitor (not shown) is usually connected between the positive pole 171a and the negative pole 171b of the power supply 171 to stabilize the power supply 171.

[0050] In this configuration, when both transistors 161, 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0051] Moreover, when one of the transistors 161, 162 is turned on and the other is turned off, a so-called flywheel current is maintained. By passing a flywheel current through the amplifier circuit 150 in this manner, the hysteresis loss in the amplifier circuit 150 can be reduced, and the power consumption of the entire circuit can be kept low. Furthermore, by controlling the transistors 161, 162 in this manner, high-frequency noise such as harmonics generated in the turbo molecular pump 100 can be reduced. Furthermore, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0052] That is, when the detected current value is smaller than the current command value, both of the transistors 161 and 162 are turned on for a time period corresponding to the pulse width time Tp1 only once in a control cycle Ts (e.g., 100 μs) as shown in Fig. 3. Therefore, the electromagnet current iL during this period increases toward a current value iLmax (not shown) that can flow from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[0053] On the other hand, when the detected current value is larger than the current command value, both of the transistors 161 and 162 are turned off for a time period corresponding to the pulse width time Tp2 only once during the control cycle Ts, as shown in Fig. 4. Therefore, the electromagnet current iL during this period decreases toward a current value iLmin (not shown) that can be regenerated from the negative pole 171b to the positive pole 171a via the diodes 165 and 166.

[0054] 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.

[0055] Here, the intermediate introduction gas will be described. The intermediate introduction gas is a gas with a higher viscosity than the intake gas. For example, when the intake gas is hydrogen gas, nitrogen gas or argon gas is used as the intermediate introduction gas. Note that the intermediate introduction gas is not limited to a gas different from the intake gas, and may be, for example, a gas of the same type as the intake gas, but with a higher temperature and higher viscosity.

[0056] In the turbomolecular pump 100 of this embodiment, the intermediate introduction gas is introduced into the turbomolecular pump 100 from an intermediate introduction gas inlet 137 shown in Fig. 5. The intermediate introduction gas introduced into the turbomolecular pump 100 flows through the introduction flow path FP3 shown in the figure. The fixed vane spacer 125a of this embodiment has a connection port 138 that penetrates the fixed vane spacer 125a in the radial direction, and as shown in the figure, the connection port 138 is located downstream of the rotor vane 102a in the exhaust direction. In other words, the introduction flow path FP3 is connected to the gas flow path FP1 by the connection port 138 downstream of the rotor vane 102a that is closest to the intake port 101 in the exhaust section 114.

[0057] According to the turbomolecular pump 100 configured in this manner, not only the intake gas sucked in from the intake port 101 but also the intermediate introduction gas that has passed through the connection port 138 flows through the gas flow path FP1. That is, the viscosity of the mixture of the intake gas and the intermediate introduction gas is higher than that of the intake gas alone, and therefore the compression effect in the exhaust section 114 (particularly the drag pump section 116) is improved. Therefore, according to the turbomolecular pump 100, even if the suction gas is a gas with a low viscosity such as hydrogen gas, it is possible to improve the back pressure performance compared to the case where the intermediate introduction gas is not introduced.

[0058] Here, the back pressure performance of the turbo molecular pump 100 in this embodiment will be described with reference to Fig. 10. In Fig. 10, the horizontal axis indicates the pressure (back pressure) at the exhaust port 133, and the vertical axis indicates 10 shows the pressure (suction pressure) at the intake port 101. The dashed line in Fig. 10 shows the relationship between the back pressure and the suction pressure when only intake gas is sucked in without introducing intermediate introduction gas, and the solid line in Fig. 10 shows the relationship between the back pressure and the suction pressure when intake gas is sucked in while introducing intermediate introduction gas. In Fig. 10, the intake gas is hydrogen gas, and the intermediate introduction gas is nitrogen gas.

[0059] As is clear from FIG. 10, when the back pressure increases, the suction pressure also increases. However, when the intermediate introduction gas is introduced, the increase in suction pressure is suppressed even when the back pressure increases, compared to when the intermediate introduction gas is not introduced, and it was confirmed that the back pressure performance is improved.

[0060] Various modifications are possible to the configuration relating to the intermediate gas introduction in the turbo molecular pump 100. For example, the turbo molecular pump 100 may be modified to the configuration shown in FIG.

[0061] The turbomolecular pump 100 shown in Fig. 6 includes a valve 139. Also, the connection port 138 is provided at the outlet of a through hole provided inside the threaded spacer 131. Note that in this embodiment, an introduction flow path FP3 through which the intermediate introduction gas flows is a flow path from the valve 139, via the intermediate introduction gas introduction port 137, to the connection port 138. And the valve 139 can adjust the flow rate of the intermediate introduction gas flowing through the introduction flow path FP3.

[0062] In the turbo molecular pump 100 shown in FIG. 6, the introduction flow path FP3 is connected to the vicinity of the middle of the drag pump section 116 in the exhaust section 114 by the connection port 138. That is, a mixed gas of the intake gas and the intermediate introduction gas flows downstream from the vicinity of the middle of the drag pump section 116 in the exhaust section 114, so the compression effect in this portion is improved compared to when only the intake gas flows through the gas flow path FP1. Therefore, even in the turbo molecular pump 100 shown in FIG. 6, the back pressure performance can be improved compared to when the intermediate introduction gas is not introduced. Note that if the amount of the intermediate introduction gas introduced into the gas flow path FP1 is too large or too small, the compression effect cannot be improved. On the other hand, if the valve 139 is provided as in this embodiment, the amount of the intermediate introduction gas can be easily changed, so that the back pressure performance can be further improved by adjusting the amount of the intermediate introduction gas.

[0063] Furthermore, the turbomolecular pump 100 may be modified to the configuration shown in Fig. 7. The turbomolecular pump 100 shown in Fig. 7 is provided with a connection port 138 between the turbine pump section 115 and the drag pump section 116 in the exhaust section 114. That is, the introduction flow path FP3 is connected to the gas flow path FP1 between the turbine pump section 115 and the drag pump section 116. With this configuration, the mixed gas of the intake gas and the intermediate introduction gas flows through the drag pump section 116, improving the compression effect in the drag pump section 116.

[0064] In the turbomolecular pump 100 shown in FIG. 6, the mixed gas of the intake gas and the intermediate introduction gas basically flows downstream from the middle of the drag pump section 116, while in the turbomolecular pump 100 shown in FIG. 7, the mixed gas basically flows through the entire drag pump section 116, so the compression effect is further improved. In addition, in the turbomolecular pump 100 shown in FIG. 5, the mixed gas of the intake gas and the intermediate introduction gas also flows through the entire drag pump section 116, so a further improvement in the compression effect is expected compared to the turbomolecular pump 100 shown in FIG. 6. In the turbomolecular pump 100 shown in FIG. 5, the number of gas molecules that come into contact with the rotor 102 and the fixed blades 123 when the mixed gas flows through the turbine pump section 115 increases compared to the case of only the intake gas, which increases the heat generation at the rotor 102 and the fixed blades 123, making it easier for the turbomolecular pump 100 to reach the upper limit temperature allowable. For this reason, it is necessary to suppress the allowable flow rate of the intake gas in order to suppress the temperature rise. On the other hand, in the turbo molecular pump 100 shown in FIG. 7, the mixed gas basically flows downstream of the turbine pump section 115, so the allowable flow rate of the intake gas can be increased compared to the turbo molecular pump 100 in FIG.

[0065] The turbomolecular pump 100 may be modified to the configuration shown in FIG. 8. In the turbomolecular pump 100 shown in FIG. 8, a purge gas joint 135a having a purge gas inlet 135 is branched into two on the outside of the base portion 129. One of the branched purge gas joints 135a is connected to the inside of the stator column 122, and the other of the branched purge gas joints 135a is connected to a connection port 138 located between the turbine pump portion 115 and the drag pump portion 116. In this embodiment, the purge gas flow path FP2 is a flow path from the purge gas inlet 135 to the stator column 122 via one of the purge gas joints 135a, and the introduction flow path FP3 is a flow path from the other purge gas joint 135a to the connection port 138. That is, the introduction flow path FP3 is branched from the purge gas flow path FP2, and a purge gas is used as an intermediate introduction gas flowing through the introduction flow path FP3.

[0066] According to the turbomolecular pump 100 shown in FIG. 8, the purge gas can be used as the intermediate introduction gas, so that the overall configuration of the turbomolecular pump 100, including the auxiliary equipment, can be simplified compared to the case where the purge gas and the intermediate introduction gas are prepared separately. Furthermore, when using the turbomolecular pump 100 shown in FIG. 8, it is particularly preferable that the suction gas is hydrogen gas and the purge gas is nitrogen gas. That is, since nitrogen gas has a higher viscosity than hydrogen gas, the back pressure performance can be improved compared to the case where nitrogen gas is not introduced as the intermediate introduction gas. Furthermore, since nitrogen gas is an inexpensive inert gas, the turbomolecular pump 100 can be operated safely and costs can be suppressed.

[0067] The turbomolecular pump 100 may be modified to the configuration shown in FIG. 9. In the turbomolecular pump 100 shown in FIG. 9, a through hole is provided inside the base portion 129 and the threaded spacer 131. The inlet of this through hole is connected to the purge gas flow path FP2. This through hole is also connected to a connection port 138 located between the turbine pump portion 115 and the drag pump portion 116. In this embodiment, the introduction flow path FP3 is a flow path from the inlet of this through hole to the connection port 138. Here, with regard to the purge gas flow path FP2 leading from the purge gas introduction port 135 to the inside of the stator column 122, the flow path located outside the turbomolecular pump 100 (i.e., inside the purge gas joint 135b) is referred to as an outer purge gas flow path FP2A, and the flow path located inside the turbomolecular pump 100 is referred to as an inner purge gas flow path FP2B.

[0068] In the turbomolecular pump 100 shown in Fig. 9, the introduction flow path FP3 branches off from the inner purge gas flow path FP2B and is connected to the gas flow path FP1. That is, in this turbomolecular pump 100 as well, the purge gas can be used as the intermediate introduction gas, so the overall configuration of the turbomolecular pump 100 can be simplified compared to the case where the purge gas and the intermediate introduction gas are prepared separately. In addition, in the turbomolecular pump 100 shown in Fig. 8, the introduction flow path FP3 is provided outside the turbomolecular pump 100, so a space is required for that, but in the turbomolecular pump 100 shown in Fig. 9, the introduction flow path FP3 is provided inside the turbomolecular pump 100, so a space can be secured around the turbomolecular pump 100.

[0069] When using a purge gas as an intermediate introduction gas as in the turbo molecular pump 100 shown in Figures 8 and 9, it is preferable that the inner diameter of at least a part of the introduction passage FP3 is smaller than the inner diameter of the purge gas passage FP2. In this embodiment, as shown in Figures 8 and 9, a connection port 138 having a relatively small diameter is used, and the inner diameter of at least this part is smaller than the inner diameter of the purge gas passage FP2.

[0070] The amount of purge gas used as the intermediate introduction gas is generally less than the amount of purge gas introduced into the stator column 122. Therefore, by making the inner diameter of at least a part of the introduction passage FP3 smaller than the inner diameter of the purge gas passage FP2, it becomes easier to achieve the desired back pressure performance from the beginning. Furthermore, when adjusting the amount of purge gas flowing through the introduction passage FP3 to improve the back pressure performance, it is easy to increase a small inner diameter, making the adjustment easier. The amount of purge gas flowing through the introduction passage FP3 may be adjusted using the above-mentioned valve 139 (see FIG. 6).

[0071] Although one embodiment of the present invention has been described above, the present invention is not limited to the specific embodiment, and various modifications, changes, and combinations are possible within the scope of the spirit of the present invention described in the claims unless otherwise specifically limited in the above description. Furthermore, the effects of the above embodiment are merely examples of the effects resulting from the present invention, and do not mean that the effects of the present invention are limited to the above effects.

[0072] For example, the drag pump section 116 is not limited to the above-mentioned Holweck type pump mechanism using the screw groove 131a, and may be configured with other pump mechanisms, such as a Sigburn type pump mechanism. [Explanation of symbols]

[0073] 100: Turbo molecular pump (vacuum pump) 101: Air intake 102: Rotor 103: Rotating body 114: Exhaust section 115: Turbine pump section 116:Drug pump section 122: Stator column 123: Fixed wing 133: Exhaust port 139: Valve FP1: Gas flow path FP2: Purge gas flow path FP2A: Outer purge gas flow path FP2B: Inner purge gas passage FP3: Inlet channel

Claims

1. A vacuum pump comprising an exhaust section including a turbine pump section having multiple stages of rotors and fixed vanes and a drag pump section located downstream of the turbine pump section, the vacuum pump exhausting intake gas sucked in from an intake port by the exhaust section through a gas flow path from the exhaust port, an introduction flow passage for introducing an intermediate introduction gas having a higher viscosity than the intake gas; a first impeller that is closest to the intake port in the exhaust section and that is connected to the gas flow passage downstream of the first impeller that is closest to the intake port in the exhaust section, the first impeller being connected to the gas flow passage downstream of the first impeller that is closest to the intake port in the exhaust section.

2. a purge gas flow passage for supplying a purge gas to an inside of a stator column provided on an inner circumferential side of a rotor on which the rotor blades are provided, 2. The vacuum pump according to claim 1, wherein the introduction passage is branched off from the purge gas passage, and the purge gas is used as the intermediate introduction gas.

3. the purge gas passage is composed of an outer purge gas passage located outside the vacuum pump and an inner purge gas passage located inside the vacuum pump, 3. The vacuum pump according to claim 2, wherein the introduction passage branches off from the inner purge gas passage and is connected to the gas passage.

4. 3. The vacuum pump according to claim 2, wherein an inner diameter of at least a part of the introduction passage is smaller than an inner diameter of the purge gas passage.

5. 2. The vacuum pump according to claim 1, wherein the introduction passage includes a valve capable of adjusting a flow rate of the intermediate introduction gas.

6. 2. The vacuum pump according to claim 1, wherein the introduction passage is connected to the gas passage between the turbine pump section and the drag pump section.

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