WO2025041797A1 - Vacuum pump - Google Patents

Abstract

[Problem] To propose a vacuum pump that offers excellent back pressure performance even when the suction gas is hydrogen gas or the like. [Solution] A vacuum pump 100 comprising an exhaust part 114 that includes: a turbine pump section 115 with a plurality of stages of rotary blades 102 and fixed blades 123; and a drag pump section 116 positioned on the exhaust downstream side of the turbine pump section 115. Intake gas sucked in from an intake port 101 by the exhaust part 114 is discharged from an exhaust port 133 via a gas flow passage FP1. The vacuum pump 100 is characterized by comprising an introduction flow passage FP3 for introducing intermediate introduction gas having a higher viscosity than the intake gas. The vacuum pump 100 is also characterized in that the introduction flow passage FP3 is connected to the gas flow passage FP1 on the exhaust downstream side of the rotary blade 102 closest to the intake port 101 among the plurality of stages of rotary blades 102 in the exhaust part 114.

Description

Vacuum pump

The present invention relates to a vacuum pump.

Among vacuum pumps, such as turbomolecular pumps, there is known a vacuum pump with 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, Figure 9 of Patent Document 1).

The vacuum pump shown in Patent Document 1 has multiple stages of rotors and fixed vanes inside a cylindrical casing that function as a turbine pump section, and also has a screw groove section that functions as a drag pump section. The casing also has an intake port at the top and an exhaust port at the bottom. When the vacuum pump is operated, gas is sucked in through the intake port, and this gas passes through the turbine pump section and drag pump section in that order before being exhausted from the exhaust port.

Generally, vacuum pumps have a backpressure dependency in which the performance of the pump is affected by the pressure on the exhaust port side (backpressure side). Conventionally, known means of reducing the effect of backpressure (improving backpressure performance) include enlarging the diameter of the thread groove portion or lengthening the axial length of the thread groove portion, as shown in Patent Document 1.

Patent No. 5689546

However, when the gas being sucked into the vacuum pump is hydrogen gas, even if the above-mentioned means for increasing 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 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 factors that causes the back pressure performance to decrease.

The present invention aims to provide a vacuum pump that has excellent back pressure performance even when the suction gas is hydrogen gas or the like.

The present invention is a vacuum pump that includes an exhaust section that includes a turbine pump section having multiple stages of rotors and fixed blades and a drag pump section that is located downstream of the turbine pump section, and exhausts intake gas sucked in from an intake port by the exhaust section through a gas flow path from the exhaust port, and is characterized in that it includes an introduction flow path that introduces an intermediate introduction gas that has a higher viscosity than the intake gas, and the introduction flow path is 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.

Such a vacuum pump is provided with a purge gas flow passage that supplies purge gas to the inside of a stator column that is provided on the inner periphery of the 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.

The purge gas flow path is preferably 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 the introduction flow path is preferably branched off from the inner purge gas flow path and connected to the gas flow path.

It is preferable that the inner diameter of at least a portion of the introduction passage is smaller than the inner diameter of the purge gas passage.

It is also preferable that the introduction passage is equipped with a valve capable of adjusting the flow rate of the intermediate introduction gas.

The introduction passage is preferably connected to the gas passage between the turbine pump section and the drag pump section.

The vacuum pump of the present invention is provided with an introduction flow passage for introducing an intermediate introduction gas having a higher viscosity than the intake gas, and this introduction flow passage is connected to the gas flow 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 via the gas flow passage, the intake gas and the intermediate introduction gas flow in the gas flow passage. In other words, 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, with 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.

1 is a vertical cross-sectional view that shows a schematic diagram of an embodiment of a vacuum pump according to the present invention. FIG. 2 is a circuit diagram of an amplifier circuit of the vacuum pump shown in FIG. 1 . 6 is a time chart showing control when a current command value is larger than a detection value. 6 is a time chart showing control when a current command value is smaller than a detection value. FIG. 2 is a partially enlarged view of the vacuum pump shown in FIG. 1 . FIG. 2 is a partial enlarged view showing a first modified example of the vacuum pump shown in FIG. 1 . FIG. 2 is a partial enlarged view showing a second modified example of the vacuum pump shown in FIG. 1 . FIG. 2 is a partial enlarged view showing a third modified example of the vacuum pump shown in FIG. 1 . FIG. 4 is a partial enlarged view showing a fourth modified example of the vacuum pump shown in FIG. 6 is a graph showing the relationship between back pressure and suction pressure in the vacuum pump shown in FIGS. 1 and 5 .

Below, we will explain a turbomolecular pump, which is one embodiment of a vacuum pump according to the present invention, with reference to the drawings.

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, with a plurality of rotors 102 (102a, 102b, 102c, ...) which are turbine blades for drawing in and exhausting gas (intake gas) and arranged radially around its periphery in multiple stages. A rotor shaft 113 is attached to the center of this rotor 103, and this rotor shaft 113 is supported in the air and its position is controlled by, for example, a five-axis controlled magnetic bearing. The rotor 103 is generally made of a metal such as aluminum or an aluminum alloy.

The upper radial electromagnets 104 are arranged in pairs on the X-axis and 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 winding, which 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 it to a control device (not shown).

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 the position signal detected by the upper radial sensor 107, and the amplifier circuit 150 (described later) shown in FIG. 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.

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.

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 the axial position signal is sent to the control device.

Then, in the control device, 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 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.

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 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, 106B will be described later.

On the other hand, the motor 121 has multiple magnetic poles arranged circumferentially to surround the rotor shaft 113. Each magnetic pole is controlled by a control device so as to rotate the rotor shaft 113 via electromagnetic forces acting between the magnetic poles and the rotor shaft 113. In addition, the motor 121 incorporates a rotational speed sensor such as a Hall element, resolver, or encoder (not shown), and the rotational speed of the rotor shaft 113 is detected by the detection signal of this rotational speed sensor.

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 uses the detection signals of both this phase sensor and the rotation speed sensor to detect the position of the magnetic pole.

Several fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap between the rotating blades 102 (102a, 102b, 102c...). The rotating 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 intake gas molecules downwards by collision. The fixed blades 123 (123a, 123b, 123c...) are made of metals such as aluminum, iron, stainless steel, copper, etc., or alloys containing these metals as components.

The fixed blades 123 are also formed 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 end of the fixed blades 123 is supported by being inserted between a plurality of stacked fixed blade spacers 125 (125a, 125b, 125c, etc.).

The fixed wing spacer 125 is a ring-shaped member 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 wing 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 is connected to 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.

Furthermore, a threaded spacer 131 is disposed between the lower portion of the fixed blade spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of 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 transported 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 rotors 102 (102a, 102b, 102c, etc.). The outer peripheral surface of this 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 guided by the thread groove 131a and sent to the base part 129.

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

The base portion 129 is a disk-shaped member that forms the base of the turbomolecular pump 100, and is generally made of a metal such as iron, aluminum, or stainless steel. 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.

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

The fixed blade spacers 125 are joined together at their outer periphery 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.

In the above, it has been explained that the threaded spacer 131 is disposed on the outer periphery of the cylindrical portion 102d of the rotor 103, and that the thread groove 131a is engraved on the inner periphery of the threaded spacer 131. However, conversely, there are also cases where a thread groove is engraved on the outer periphery of the cylindrical portion 102d, and a spacer having a cylindrical inner periphery is disposed around it.

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, upper radial sensor 107, motor 121, lower radial electromagnet 105, lower radial sensor 108, axial electromagnets 106A and 106B, and axial sensor 109, etc., and the electrical equipment section is surrounded by a stator column 122, and the inside of this stator column 122 is kept at a predetermined pressure by purge gas.

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 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 the purge gas flow path FP2.

Here, the turbomolecular pump 100 requires control based on the model identification and individually adjusted unique parameters (for example, various characteristics corresponding to the model). To store these control parameters, the turbomolecular pump 100 has an electronic circuit section 141 inside its body. The electronic circuit section 141 is composed of a semiconductor memory such as an EEP-ROM, electronic components such as semiconductor elements for accessing the memory, and a substrate 143 for mounting these components. This electronic circuit section 141 is housed below a rotational speed sensor (not shown) near the center of the base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom cover 145.

In the semiconductor manufacturing process, some process gases introduced into the 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 intake gas is lowest at the intake port 101 and highest at the exhaust port 133. If the pressure of the intake gas exceeds 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 solidifies and adheres to and accumulates inside the turbomolecular pump 100.

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

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

Furthermore, the turbomolecular pump 100 of this embodiment is equipped with an intermediate introduction gas inlet 137 for introducing intermediate introduction gas into the turbomolecular pump 100. A detailed explanation of the intermediate introduction gas etc. will be given later.

Next, regarding the turbomolecular pump 100 configured in this manner, we will explain 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. A circuit diagram of this amplifier circuit 150 is shown in Figure 2.

In FIG. 2, one end of the electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to the positive pole 171a of the power supply 171 via the transistor 161, and the other end is connected to the negative pole 171b of the power supply 171 via the current detection circuit 181 and the 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.

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

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 pole 171b. Similarly, the current regeneration diode 166 has its cathode terminal 166a connected to the positive pole 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 electrical resistance element.

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.

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 and off.

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. Then, based on the result of this comparison, it determines the size of the pulse width (pulse width times Tp1, Tp2) to be generated within a control cycle Ts, which is one period under PWM control. 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 transistors 161, 162.

In addition, when the rotating body 103 passes through a resonance point during accelerated operation of the rotation speed, or when a disturbance occurs during constant speed operation, it is necessary to control the position of the rotating body 103 at high speed and with strong force. For this reason, a high voltage of about 50 V, for example, is used for 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.

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

Furthermore, when one of the transistors 161, 162 is turned on and the other 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 is 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 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.

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

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 equivalent to pulse width time Tp2 only once during control cycle Ts, as shown in FIG. 4. Therefore, during this period, electromagnet current iL decreases toward current value iLmin (not shown) that can be regenerated from negative pole 171b to positive pole 171a via diodes 165 and 166.

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

Here, we will explain the intermediate introduction gas mentioned above. 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 of a different type from the intake gas, and may be, for example, a gas of the same type as the intake gas, but with its viscosity increased by increasing its temperature.

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

With 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. In other words, 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, with the turbomolecular pump 100, even if the intake gas is a low-viscosity gas such as hydrogen gas, the back pressure performance can be improved compared to the case where the intermediate introduction gas is not introduced.

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 the pressure (suction pressure) at the intake port 101. The dashed line in Fig. 10 indicates the relationship between the back pressure and the suction pressure when only the intake gas is sucked without introducing the intermediate introduction gas, and the solid line in Fig. 10 indicates the relationship between the back pressure and the suction pressure when the intake gas is sucked while introducing the intermediate introduction gas. In Fig. 10, the intake gas is hydrogen gas, and the intermediate introduction gas is nitrogen gas.

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

The configuration related to the intermediate gas introduction in the turbomolecular pump 100 can be modified in various ways. For example, the turbomolecular pump 100 may be modified to the configuration shown in FIG. 6.

The turbomolecular pump 100 shown in FIG. 6 is equipped with a valve 139. The connection port 138 is provided at the outlet of a through hole provided inside the threaded spacer 131. In this embodiment, the introduction flow path FP3 through which the intermediate introduction gas flows is a flow path from the valve 139 through the intermediate introduction gas introduction port 137 to the connection port 138. The valve 139 can adjust the flow rate of the intermediate introduction gas flowing through the introduction flow path FP3.

In the turbomolecular 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, downstream of the vicinity of the middle of the drag pump section 116 in the exhaust section 114, a mixture of intake gas and intermediate introduction gas flows, so the compression effect in this part is improved compared to when only intake gas flows through the gas flow path FP1. Therefore, even in the turbomolecular 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 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 a valve 139 is provided as in this embodiment, the amount of intermediate introduction gas can be easily changed, so that the back pressure performance can be further improved by adjusting the amount of intermediate introduction gas.

The turbomolecular pump 100 may also 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.

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, the mixed gas of the intake gas and the intermediate introduction gas also flows through the entire drag pump section 116 in the turbomolecular pump 100 shown in FIG. 5, so a further improvement in the compression effect is expected compared to the turbomolecular pump 100 in FIG. 6. In the turbomolecular pump 100 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 in the rotor 102 and the fixed blades 123, making it easier to reach the upper limit temperature of the turbomolecular pump 100 that is permissible. 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 turbomolecular 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 turbomolecular pump 100 in FIG. 5.

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 fitting 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 fittings 135a is connected to the inside of the stator column 122, and the other of the branched purge gas fittings 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 fittings 135a, and the introduction flow path FP3 is a flow path from the other purge gas fitting 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.

The turbomolecular pump 100 shown in FIG. 8 allows the purge gas to be used as the intermediate introduction gas, and therefore the overall configuration of the turbomolecular pump 100, including associated equipment, can be simplified compared to when 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 when 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 reduced.

The turbomolecular pump 100 may be modified to the configuration shown in FIG. 9. The turbomolecular pump 100 shown in FIG. 9 has through holes in the base portion 129 and the threaded spacer 131. The inlet of the through hole is connected to the purge gas flow path FP2. The 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 the through hole to the connection port 138. Here, for the purge gas flow path FP2 that leads 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 the outer purge gas flow path FP2A, and the flow path located inside the turbomolecular pump 100 is referred to as the inner purge gas flow path FP2B.

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, the purge gas can also be used as the intermediate introduction gas, so the overall configuration of the turbomolecular pump 100 can be simplified compared to when 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 space is required, but in the turbomolecular pump 100 in FIG. 9, the introduction flow path FP3 is provided inside the turbomolecular pump 100, so space can be secured around the turbomolecular pump 100.

When using a purge gas as an intermediate introduction gas, as in the turbomolecular pump 100 shown in Figures 8 and 9, it is preferable that the inner diameter of at least a portion of the introduction flow path FP3 is smaller than the inner diameter of the purge gas flow path FP2. In this embodiment, as shown in Figures 8 and 9, a relatively small diameter connection port 138 is used, and the inner diameter of at least this portion is smaller than the inner diameter of the purge gas flow path FP2.

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 portion of the introduction flow path FP3 smaller than the inner diameter of the purge gas flow path 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 flow path 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 flow path FP3 may be adjusted using the valve 139 (see Figure 6) described above.

The above describes one embodiment of the present invention, but the present invention is not limited to the specific embodiment, and unless otherwise limited in the above description, various modifications, changes, and combinations are possible within the scope of the spirit of the present invention described in the claims. 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.

For example, the drag pump section 116 is not limited to the Holweck pump mechanism that uses the screw groove 131a described above, but may be configured with other pump mechanisms, such as a Sigburn pump mechanism.

100: Turbo molecular pump (vacuum pump)
101: Intake port 102: Rotor 103: Rotor 114: Exhaust section 115: Turbine pump section 116: Drag pump section 122: Stator column 123: Fixed blade 133: Exhaust port 139: Valve FP1: Gas flow path FP2: Purge gas flow path FP2A: Outer purge gas flow path FP2B: Inner purge gas flow path FP3: Introduction flow path

Claims (6)

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. 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 provided with the rotor blades,
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. 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. The vacuum pump of claim 2, characterized in that the inner diameter of at least a portion of the introduction passage is smaller than the inner diameter of the purge gas passage. The vacuum pump of claim 1, characterized in that the inlet passage is equipped with a valve capable of adjusting the flow rate of the intermediate inlet gas. 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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