JP7546412B2 - Vacuum pumps, stators and spacers - Google Patents

Description

The present invention relates to a vacuum pump, a fixed vane, and a spacer, and more specifically to a structure that improves the exhaust efficiency of a vacuum pump.

2. Description of the Related Art In the past, vacuum pumps such as turbomolecular pumps, which perform exhaust processing by rotating a rotor part (shaft or rotor) and a rotating part including a rotor blade and a rotating cylinder at high speed inside a casing having an intake port and an exhaust port, have been widely used.
In these vacuum pumps, exhaust processing is performed by the interaction between multiple stages of rotor blades rotating at high speed and multiple stages of fixed blades fixed to the casing.
As shown in Figure 30, the stator 123 used here is composed of a plurality of blades 550, an inner rim 600 that holds and fixes the inner side (the rotor side when installed) of the plurality of blades 550, and an outer rim 700 that holds and fixes the outer side (the casing side when installed). Figure 31 is a partially enlarged view of the dashed circle portion of the stator 123 shown in Figure 30.
Note that fixed wings 123 of a type that does not have an outer rim 700 (a type in which the blade 550 is held and fixed only by the inner rim 600) as shown in FIG. 32 are also used.
32 shows the fixed wing 123 in a halved state, and FIG. 33 is a partially enlarged view of the portion circled by the dashed line in FIG.
However, in this vacuum pump, due to design requirements, the outer diameter of one of the multiple stages of rotors is smaller on the exhaust port side than on the intake port side, or the inner diameter of one of the multiple stages of rotors is larger on the exhaust port side than on the intake port side.

34 and 35 are diagrams for explaining the prior art.
FIG. 34 is a cross-sectional view for explaining a case where a fixed vane 123 (of the type shown in FIG. 30) having an inner rim 600 and an outer rim 700 is used in a conventional turbo-molecular pump.
FIG. 35 is a partially enlarged view of FIG.
As shown in FIG. 35, the flow of exhaust gas is in the direction indicated by the arrow from the intake port side to the exhaust port side.
As shown in FIG. 35, the inner rim 600 (outer side) and the outer rim 700 (inner side) of the fixed vanes 123 were arranged horizontally with respect to the exhaust direction, and did not play any particular role in the exhaust operation of the turbomolecular pump.
In addition, on the upper surface of the fixed blade spacer at the position where the outer diameter of the rotor is reduced, there is a portion that is perpendicular to the exhaust direction, resulting in a structure that reflects gas molecules transferred by the upstream rotor directly toward the intake port, which is a factor that reduces exhaust performance.

JP 2007-2692 A JP 2018-35718 A

In the vacuum pumps disclosed in the above-mentioned Patent Documents 1 and 2, the outer rim and inner rim of the fixed vanes are arranged horizontally with respect to the gas exhaust direction, and do not contribute to the exhaust efficiency.
In recent years, there has been a demand for improving the pumping efficiency of vacuum pumps without increasing the size of the pump or the rotational speed of the rotor portion.

The present invention aims to provide a vacuum pump with improved exhaust performance by improving the fixed vanes (inner rim and outer rim) and spacers installed in the vacuum pump.

In the invention of claim 1, the present invention comprises a casing having an intake port and an exhaust port, a rotating shaft rotatably supported inside the casing, multiple stages of rotors fixed to the rotating shaft and rotatable together with the rotating shaft, and multiple stages of fixed blades fixed to the casing and disposed between the rotors, wherein an outer diameter of at least one of the multiple stages of rotors is formed to be smaller on the exhaust port side than on the intake port side, or an inner diameter of at least one of the multiple stages of rotors is formed to be smaller on the exhaust port side than on the intake port side. The present invention provides a vacuum pump in which the exhaust port side is formed with a larger diameter, and a tapered surface having a downward slope toward the exhaust port side is provided on the outer and inner peripheral parts of a fixed blade, which is located directly above the rotating blade, which is formed with a small outer diameter, or directly above the rotating blade, which is formed with a large inner diameter , and the fixed blade has a plurality of blades arranged radially, and an inner rim and an outer rim that hold these plurality of blades, and the tapered surface is provided on the outer peripheral surface of the inner rim and the inner peripheral surface of the outer rim .
The invention described in claim 2 provides a vacuum pump described in claim 1, characterized in that the fixed vane has a plurality of blades arranged radially and a spacer portion that holds the plurality of blades and positions the fixed vane in the height direction, and the inner surface of the spacer portion is provided with a tapered surface that has a downward slope toward the exhaust port side.
In accordance with a third aspect of the present invention, there is provided a vacuum pump according to the second aspect, characterized in that the surfaces of the plurality of blades of the fixed vane on the exhaust port side are undercut.
In accordance with a fourth aspect of the present invention, there is provided a vacuum pump according to the second aspect, characterized in that a vertical surface or a tapered surface is provided behind the plurality of blades of the fixed vane.
In a fifth aspect of the present invention, there is provided a vacuum pump comprising a casing having an intake port and an exhaust port, a rotating shaft rotatably supported inside the casing, multiple stages of rotors fixed to the rotating shaft and rotatable together with the rotating shaft, and multiple stages of fixed blades fixed to the casing and disposed between the rotors, wherein an outer diameter of at least one of the multiple stages of rotors is smaller on the exhaust port side than on the intake port side, or an inner diameter of at least one of the multiple stages of rotors is larger on the exhaust port side than on the intake port side. The present invention provides a vacuum pump characterized in that a tapered surface having a downward slope toward the exhaust port side is provided on the outer and inner peripheral portions of a fixed blade that is located directly above the rotor blade that is formed with a small outer diameter or directly above the rotor blade that is formed with a large inner diameter, a protrusion is provided that protrudes within a range of the height direction of the fixed blade from a spacer portion that holds the casing side of the fixed blade and positions the fixed blade in the height direction, and a tapered surface having a downward slope toward the exhaust port side is provided on at least a portion of the inner peripheral surface of the spacer portion and the protrusion.
The invention described in claim 6 provides a fixed impeller for use in a vacuum pump equipped with a casing having an intake port and an exhaust port, the fixed impeller having a plurality of radially arranged blades and an inner rim and an outer rim which hold the plurality of blades, the outer peripheral surface of the inner rim and the inner peripheral surface of the outer rim being provided with tapered surfaces having a downward slope toward the exhaust port side.
The invention described in claim 7 provides a spacer for use in a vacuum pump equipped with a casing having an intake port and an exhaust port, the spacer having a spacer part that holds the casing side and positions the fixed vane in the height direction when positioning the fixed vane having a plurality of radially arranged blades, a protrusion part is provided that protrudes from the spacer part within a range of the height direction of the fixed vane, and a tapered surface having a downward slope toward the exhaust port side is provided on the inner surface of the spacer part and at least a part of the protrusion part.

According to the present invention, the exhaust performance of a vacuum pump can be further improved by devising the shape of the inner rim or outer rim or spacer of the fixed vanes in the vacuum pump.

1 is a diagram showing a schematic configuration example of a turbomolecular pump according to an embodiment of the present invention; FIG. 2 is a circuit diagram of an amplifier circuit used in an embodiment of the present invention. 5 is a time chart showing control when a current command value is larger than a detection value in the embodiment of the present invention. 5 is a time chart showing control when a current command value is smaller than a detection value in the embodiment of the present invention. 1 is a diagram showing a schematic configuration example of a turbomolecular pump according to a first embodiment of the present invention; FIG. 6 is a partial enlarged view of the turbomolecular pump according to the first embodiment shown in FIG. 5 . A figure showing a fixed wing having a tapered surface on the inner rim in the first embodiment A. A figure showing a fixed wing having a tapered surface on the inner rim in accordance with the first embodiment B, as well as a vertical surface and a circumferential surface. A figure showing a fixed wing having tapered surfaces on the inner rim and outer rim in the first embodiment C. A figure showing a fixed wing having tapered surfaces on the inner rim and outer rim, as well as vertical and circumferential surfaces, in accordance with the first embodiment D. This figure shows a fixed wing in which tapered surfaces are provided on the inner rim and outer rim in the first embodiment E, and also has a tapered surface above (below) the blade of the outer rim. A figure showing a fixed wing in which tapered surfaces are provided on the inner rim and outer rim in the first embodiment F, and the inner circumferential surface is located above (below) the blade. This figure shows a fixed wing in the first embodiment G, in which the inner rim and outer rim have tapered surfaces, the inner circumferential surface is located above (below) the blade of the outer rim, and a vertical surface is provided. This figure shows a fixed wing in accordance with the first embodiment H, in which tapered surfaces are provided on the inner and outer rims, and also a tapered surface is provided above (below) the blade of the outer rim, and a vertical surface is provided. FIG. 13 is a diagram showing a fixed wing having tapered surfaces and flanges on the inner rim and outer rim according to the first embodiment I. This is a diagram showing a fixed wing having tapered surfaces, flanges, and vertical surfaces on the inner rim and outer rim of the first embodiment J. FIG. 5 is a partial enlarged view showing a schematic configuration example of a turbomolecular pump according to a second embodiment of the present invention. A figure showing a fixed wing having a tapered surface and an inner circumferential surface on an outer rim in accordance with the second embodiment A. A figure showing a fixed wing having a tapered surface and an inner circumferential surface on an outer rim and a flange in accordance with the second embodiment B. A figure showing a fixed wing in which an outer rim in accordance with the second embodiment C is provided with a tapered surface and an inner peripheral surface, and also with an inner rim vertical surface and an outer rim vertical surface. A figure showing a fixed wing having a tapered surface and an inner circumferential surface on an outer rim and a flange in accordance with the second embodiment D. FIG. 11 is a partially enlarged view of a turbomolecular pump according to a third embodiment. FIG. 13 is a partially enlarged view of a turbomolecular pump according to a fourth embodiment. A figure showing a fixed wing having an inner rim tapered surface on the inner rim of the fourth embodiment A. A figure showing a fixed wing in which an inner rim according to the fourth embodiment B is provided with an inner rim tapered surface and an inner rim vertical surface. FIG. 13 is a partially enlarged view of a turbomolecular pump according to a fifth embodiment. FIG. 13 is a diagram showing the external appearance of a fixed wing spacer according to the fifth embodiment A. FIG. 13 is a diagram showing the external appearance of a fixed wing spacer according to the fifth embodiment B. FIG. 13 is a diagram for explaining a taper angle. FIG. 1 is a diagram showing a conventional fixed wing. FIG. 31 is a partially enlarged view of the fixed wing shown in FIG. 30. FIG. 1 shows a conventional fixed wing without an outer rim. FIG. 33 is a partially enlarged view of the fixed wing shown in FIG. 32. FIG. 1 is a diagram showing a schematic configuration example of a conventional turbomolecular pump. FIG. 35 is a partially enlarged view of the turbomolecular pump shown in FIG. 34.

(i) Overview of the embodiment In this embodiment, in a vacuum pump in which the outer diameter of at least one of the multiple stages of rotors is smaller on the exhaust port side, or the inner diameter of at least one of the multiple stages of rotors is larger on the exhaust port side, a tapered surface (inclined surface) having a downward slope towards the exhaust port side is provided on at least one of the outer periphery or inner periphery of a fixed vane that is located directly above the rotor with a small outer diameter or directly above the rotor with a large inner diameter.
By providing this tapered surface, when molecules enter, they are reflected at a right angle, sending them to the inner circumference, where they are struck by the upper rotor and sent to the next exhaust stage.

In this way, the outer or inner periphery of the fixed blades, which did not affect the exhaust in the conventional technology, also contributes to the exhaust, improving the exhaust efficiency of the vacuum pump.

(ii) Details of the Embodiments Preferred embodiments of the present invention will now be described in detail with reference to FIGS.
(Vacuum Pump Configuration)
1 is a diagram showing a schematic configuration example of a turbomolecular pump 100 according to an embodiment of the present invention, in which 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 and exhausting gas, formed radially on its periphery in multiple stages. A rotor shaft 113 is attached to the center of the rotor 103, and the rotor shaft 113 is supported in the air and its position is controlled by, for example, a five-axis controlled magnetic bearing.

The upper radial electromagnets 104 are arranged in pairs on the X-axis and Y-axis. Four upper radial sensors 107 are provided in close proximity 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, 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 the control device 200.

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 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 control device 200.

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 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 200 appropriately adjusts the magnetic force 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.

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 the control device 200 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 200 uses the detection signals of both this phase sensor and the rotation speed sensor to detect the position of the magnetic pole.

Multiple fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap between the rotor blades 102 (102a, 102b, 102c...). Each rotor blade 102 (102a, 102b, 102c...) is formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward by collision.

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 in a staggered manner with 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, ...).

The fixed wing spacer 125 is a ring-shaped member, and is made of metals such as aluminum, iron, stainless steel, copper, or alloys 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. Exhaust gas that enters the intake port 101 from the chamber side and is transferred to the base portion 129 is sent to the exhaust port 133.

Furthermore, depending on the application of the turbomolecular pump 100, a threaded spacer 131 is disposed between the lower part of the fixed vane spacer 125 and the base part 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 groove 131a is the direction in which the molecules of the exhaust gas are transported toward the exhaust port 133 when they move in the rotation direction of the rotor 103. A cylindrical part 102d hangs down from the lowest part of the rotor 103, which is connected to the rotor vanes 102 (102a, 102b, 102c, ...). The outer peripheral surface of this cylindrical part 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 exhaust 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 portion 129.

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 by the motor 121 together with the rotor shaft 113, exhaust gas is drawn from the chamber through the intake port 101 by the action of the rotor 102 and the fixed blades 123. The exhaust gas drawn in from the intake port 101 passes between the rotor 102 and the fixed blades 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 fixed blades 123 side by radiation or conduction by gas molecules of the exhaust 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 exhaust gas comes into contact with the fixed blades 123.

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 engraved on the inner periphery of the threaded spacer 131. However, there are also cases where the opposite is true, that is, 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.

Depending on the application of the turbomolecular pump 100, 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, may be covered with a stator column 122 and a predetermined pressure may be maintained inside the stator column 122 with purge gas to prevent the gas sucked in from the intake port 101 from entering the electrical equipment section.

In this case, piping (not shown) is provided in the base portion 129, and purge gas is introduced through this piping. The introduced purge gas is sent to the exhaust port 133 through the 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.

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 in its main 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. The 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 exhaust gas is lowest at the intake port 101 and highest at the exhaust 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 intake port 101 to the exhaust port 133, the process gas solidifies and adheres to and accumulates inside the turbomolecular pump 100.

For example, when _SiCl4 is used as a process gas in an Al etching device, at low vacuum (760 [torr] to 10 ^-2 [torr]) and low temperature (about 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. 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 and near the threaded spacer 131.

Therefore, in order 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, etc., and a temperature sensor (e.g., a thermistor) (not shown) is embedded in the base portion 129, and the heating of the heater and the cooling by the water-cooled tube 149 are 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; TMS; Temperature Management System).

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 on 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) (not shown) of the control device 200, and this amplifier control circuit 191 is configured to switch 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 of 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.

When the rotor 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 rotor 103 at high speed and with 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.

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 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.

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 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, the electromagnet current iL decreases from negative pole 171b to positive pole 171a toward a current value iLmin (not shown) that can be regenerated 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.

(First embodiment)
Next, a first embodiment will be described with reference to FIGS.
FIG. 5 is a diagram showing a schematic configuration example of a turbomolecular pump according to the first embodiment, and FIG. 6 is a partially enlarged view of the turbomolecular pump according to the first embodiment shown in FIG.
In this first embodiment, the inner rim 600 or the outer rim 700 or both of the fixed wing 123 are provided with tapered surfaces (inner rim tapered surface 610, outer rim tapered surface 710) having a downward slope toward the exhaust port side.
The tapered surface is provided at a location where the outer diameter of one of the multiple rotor stages is smaller on the exhaust port side, or where the inner diameter of one of the multiple rotor stages is larger on the exhaust port side. A fixed blade 123 with a tapered surface is disposed between these rotor stages.

FIG. 7 is a diagram showing a fixed blade 123 having a tapered surface on the inner rim according to the first embodiment A.
As shown in this figure, the inner rim 600 is provided with an inner rim tapered surface 610 that has a downward slope toward the exhaust port side. When molecules sent to this inner rim tapered surface 610 hit it, they are reflected at a right angle, struck by the upper stage rotor, and sent to the next stage. From this point of view, the inner rim 600 also contributes to the exhaust action by providing the inner rim tapered surface 610.
As is apparent from this figure, the blade 550 of the stator 123 is held and fixed by an inner rim 600 and an outer rim 700 .

8 is a diagram showing a fixed wing 123 having an inner rim with a tapered surface according to the first embodiment B. The fixed wing 123 according to the first embodiment B has an inner rim vertical surface 620 and an inner rim circumferential surface 630 formed thereon.
The fixed blades 123 are made of a material such as aluminum, and are manufactured as a casting using a mold, or by cutting.
When the product is produced as a casting in a metal mold, it is necessary to remove the product from the metal mold, so there is an inner rim vertical surface 620. On the underside of the blade 550, at the location where the inner rim vertical surface 620 is formed, there is formed an inner rim circumferential surface 630 that is parallel to the outer rim 700.

9 is a diagram showing a fixed vane 123 having tapered surfaces on the inner rim and outer rim according to the first embodiment C. As shown in this figure, not only the inner rim 600 but also the outer rim 700 is provided with an outer rim tapered surface 710 having a downward slope toward the exhaust port side.
In this first embodiment C, not only the inner rim 600 but also the outer rim 700 contributes to the exhaust action.
In this first embodiment C, both the inner rim 600 and the outer rim 700 are provided with tapered surfaces (610, 710), but the outer rim tapered surface 710 may be provided only on the outer rim 700.

FIG. 10 is a diagram showing a fixed blade 123 according to the first embodiment D, in which tapered surfaces are provided on the inner rim and the outer rim, and also vertical surfaces and circumferential surfaces are provided.
As in the first embodiment B, when the product is produced as a casting in a mold, it is necessary to remove the product from the mold, so an outer rim vertical surface 720 is provided. On the underside of the blade 550, an outer rim circumferential surface 730 parallel to the inner rim 600 is formed at the location where the outer rim vertical surface 720 is formed.

11(a) and (b) are diagrams showing a fixed wing 123 having tapered surfaces on the inner rim and outer rim in the first embodiment E, and also having a tapered surface above (below) the blade of the outer rim.
In this first embodiment E, the inner rim 600 side has the same shape as the first embodiment A and embodiment C, but the configuration of the outer rim 700 is different from that of the first embodiment C. That is, in the embodiment shown in Fig. 11(a), the outer rim tapered surface 710 is formed above the surface of the blade 550, and a surplus portion 740 exists.
On the other hand, in the embodiment shown in FIG. 11( b ), the outer rim tapered surface 710 is formed below the rear surface of the blade 550 , and an excess portion 740 exists.
The presence of this excess portion 740 makes it easy to determine the axial dimension of the fixed wing 123. In other words, height adjustment can be performed within a range not affected by the blade 550.
In this first embodiment E, both the inner rim 600 and the outer rim 700 are provided with tapered surfaces (610, 710), but it is also possible to provide the outer rim tapered surface 710 only on the outer rim 700.
It should be noted that this first embodiment E is manufactured by cutting since there are no vertical surfaces.

FIG. 12 is a diagram showing a fixed wing 123 according to a first embodiment F, in which tapered surfaces are provided on the inner and outer rims and the inner circumferential surface is located above (below) the blades.
In this first embodiment F, the inner rim 600 side has the same shape as the first embodiment A and embodiment C, but the configuration of the outer rim 700 is different from that of the first embodiment C. That is, an outer rim inner circumferential surface 760 is formed above (below) the surface of the blade 550. Unlike the outer rim tapered surface 710, the outer rim inner circumferential surface 760 is a surface parallel to the axial direction of the turbo molecular pump 100.
By providing this outer rim inner peripheral surface 760 and adjusting the axial dimension, it is possible to perform axial positioning when installing the fixed vanes 123 inside the turbo molecular pump 100 .
In this first embodiment F, both the inner rim 600 and the outer rim 700 are provided with tapered surfaces (610, 710), but the tapered surface 710 may be provided only on the outer rim 700.
It should be noted that this first embodiment F is manufactured by cutting since there are no vertical surfaces.

13 is a diagram showing a fixed wing 123 having tapered surfaces on the inner and outer rims, an inner peripheral surface above (below) the blades of the outer rim, and a vertical surface according to the first embodiment G. The difference between this embodiment G and the first embodiment F is that an inner rim vertical surface 620 and an outer rim vertical surface 720 are provided.
By providing this outer rim inner peripheral surface 760 and adjusting the axial dimension, it is possible to perform axial positioning when installing the fixed vanes 123 inside the turbo molecular pump 100 .
In this first embodiment G, both the inner rim 600 and the outer rim 700 are provided with tapered surfaces (610, 710), but the outer rim tapered surface 710 may be provided only on the outer rim 700.

14(a) and (b) are diagrams showing a fixed wing 123 according to the first embodiment H, in which tapered surfaces are provided on the inner rim and outer rim, and also a tapered surface is provided above (below) the blade of the outer rim, and a vertical surface is provided. (a) is an external view seen from above, and (b) is an external view seen from below.
The difference between this embodiment and the first embodiment E is that an inner rim vertical surface 620 and an outer rim vertical surface 720 are provided.
The presence of the excess portion 740 makes it easier to define the axial dimension of the stator 123 .
In this first embodiment H, both the inner rim 600 and the outer rim 700 are provided with tapered surfaces (610, 710), but the tapered surface 710 may be provided only on the outer rim 700.

FIG. 15 is a diagram showing a fixed wing 123 according to the first embodiment I, in which tapered surfaces are provided on the inner rim and the outer rim, and a flange is provided.
In this embodiment I, a flange 750 is provided that protrudes outward (toward the outer cylinder 127 when installed) from the outer rim 700 .
The flange 750 can position and hold the fixed wing 123 in the axial direction. That is, the thickness (height in the axial direction) of the flange 750 can be adjusted to position the fixed wing 123 in the axial direction, and the flange 750 can be clamped to fix the fixed wing 123 to the outer cylinder 127.
In this first embodiment I, both the inner rim 600 and the outer rim 700 are provided with tapered surfaces (610, 710), but the outer rim tapered surface 710 may be provided only on the outer rim 700.
It should be noted that this first embodiment I is manufactured by cutting since there are no vertical surfaces.

FIG. 16 is a diagram showing a fixed wing 123 according to the first embodiment J, in which tapered surfaces are provided on the inner rim and outer rim, inner rim vertical surfaces and outer rim vertical surfaces are provided, and flanges are provided.
In this embodiment J, similarly to embodiment I, a flange 750 is provided that protrudes outward from the outer rim 700 (toward the outer cylinder 127 when installed).
The flange 750 can position and hold the fixed wing 123 in the axial direction. That is, the fixed wing 123 can be positioned in the axial direction by adjusting the thickness (axial height) of the flange 750, and can be fixed to the outer cylinder 127 by clamping the flange 750.
The difference between this embodiment J and the first embodiment I is that an inner rim vertical surface 620 and an outer rim vertical surface 720 are provided.
In this first embodiment J, both the inner rim 600 and the outer rim 700 are provided with tapered surfaces (610, 710), but the outer rim tapered surface 710 may be provided only on the outer rim 700.

Second Embodiment
Next, a second embodiment will be described with reference to FIGS.
FIG. 17 is a partial enlarged view of the turbomolecular pump according to the second embodiment.
In the second embodiment, the outer rim 700 of the fixed vane 123 is provided with an outer rim tapered surface 710 having a downward slope toward the exhaust port side, and an outer rim inner circumferential surface 760. That is, the outer rim 700 is characterized in that the outer rim tapered surface 710 and the outer rim inner circumferential surface 760 coexist. Note that the inner rim 600 is similar to that of the first embodiment.

FIG. 18 is a diagram showing a fixed blade 123 having a tapered surface and an inner peripheral surface on an outer rim according to the second embodiment A.
The outer rim tapered surface 710 is disposed at a position corresponding to the blade 550. An outer rim inner peripheral surface 760 is provided below the outer rim tapered surface 710. This outer rim inner peripheral surface 760 is not inclined and is parallel to the axial direction of the turbo molecular pump 100.
The position of the fixed blade 123 can be determined by adjusting the height direction of this outer rim inner circumferential surface 760. Since no blade 550 exists in a position corresponding to this outer rim inner circumferential surface 760, adjustment can be easily performed.
In this second embodiment A, both the inner rim 600 and the outer rim 700 are provided with tapered surfaces (610, 710), but the outer rim tapered surface 710 may be provided only on the outer rim 700.
In addition, this second embodiment A is manufactured by cutting since there are no vertical surfaces.

FIG. 19 is a diagram showing a fixed blade 123 according to the second embodiment B, in which a tapered surface and an inner peripheral surface are provided on the outer rim, and a flange is also provided.
The outer rim tapered surface 710 is disposed at a position corresponding to the blade 550. An outer rim inner peripheral surface 760 is provided below the outer rim tapered surface 710.
The difference between the second embodiment B and the second embodiment A is that a flange 750 is provided on the outer side of the outer rim 700 (toward the outer cylinder 127 when installed).
The flange 750 can position and hold the fixed wing 123 in the axial direction. That is, the fixed wing 123 can be positioned in the axial direction by adjusting the thickness (axial height) of the flange 750, and can be fixed to the outer cylinder 127 by clamping the flange 750.
In this second embodiment B, both the inner rim 600 and the outer rim 700 are provided with tapered surfaces (610, 710), but the outer rim tapered surface 710 may be provided only on the outer rim 700.
In addition, this second embodiment B is manufactured by cutting since there are no vertical surfaces.

FIG. 20 is a diagram showing a fixed wing 123 according to the second embodiment C, in which a tapered surface and an inner peripheral surface are provided on the outer rim, and an inner rim vertical surface and an outer rim vertical surface are also provided.
The outer rim tapered surface 710 is disposed at a position corresponding to the blade 550. An outer rim inner peripheral surface 760 is provided below the outer rim tapered surface 710.
The difference between this embodiment C and the second embodiment A is that when the product is produced as a casting in a mold, it is necessary to remove the product from the mold, so an inner rim vertical surface 630 and an outer rim vertical surface 720 are provided.
In this second embodiment C, both the inner rim 600 and the outer rim 700 are provided with tapered surfaces (610, 710), but it is also possible to provide the outer rim tapered surface 710 only on the outer rim 700.

FIG. 21 is a diagram showing a fixed blade 123 according to the second embodiment D, in which a tapered surface and an inner peripheral surface are provided on an outer rim, and a flange is also provided.
The outer rim tapered surface 710 is disposed at a position corresponding to the blade 550. An outer rim inner peripheral surface 760 is provided below the outer rim tapered surface 710.
The difference between the second embodiment D and the second embodiment C is that a flange 750 is provided that protrudes outward from the outer rim 700 (toward the outer cylinder 127 when installed).
The flange 750 can position and hold the fixed wing 123 in the axial direction. That is, the fixed wing 123 can be positioned in the axial direction by adjusting the thickness (height in the axial direction) of the flange 750, and can be fixed to the outer cylinder 127 by clamping the flange 750.
In this second embodiment D, both the inner rim 600 and the outer rim 700 are provided with tapered surfaces (610, 710), but the outer rim tapered surface 710 may be provided only on the outer rim 700.

Third Embodiment
Next, a third embodiment will be described with reference to FIG.
FIG. 22 is a partial enlarged view of the turbomolecular pump according to the third embodiment.
In the third embodiment, the fixed blades 123 used in the first embodiment are arranged in the opposite direction or in the same direction. At least the fixed blades 123 in the final stage are arranged in the opposite direction.
By arranging the fixed wings 123 in this manner, it is possible to use products of the same size (fixed wings 123) for both purposes, thereby reducing manufacturing costs.
Furthermore, since the outer rim tapered surface 710 is continuous, no gap is required for the spacer.

Fourth Embodiment
Next, a fourth embodiment will be described with reference to FIGS.
FIG. 23 is a partial enlarged view of a turbomolecular pump according to the fourth embodiment.
In the fourth embodiment, an inner rim tapered surface 610 having a downward slope toward the exhaust port side is provided on the inner rim 600 of the fixed vane 123. That is, the inner rim tapered surface 610 is provided on the inner rim 600 located at a location where the root diameter of the blade 550 of the fixed vane 123 located upstream is smaller than the root diameter of the blade 550 of the fixed vane 123 located downstream.

Fig. 24 shows a fixed wing 123 having an inner rim 600 according to the fourth embodiment A provided with an inner rim tapered surface 610. The inner rim 600 shown in Fig. 24 does not have an inner rim vertical surface 620, and is therefore manufactured by cutting.
Fig. 25 shows a fixed wing 123 having an inner rim tapered surface 610 and an inner rim vertical surface provided on an inner rim 600 according to a fourth embodiment B. The inner rim 600 shown in Fig. 25 is manufactured by casting using a metal mold because it has an inner rim vertical surface 620.
Although both Figures 24 and 25 show a fixed wing 123 of a type that does not have an outer rim 700, this embodiment 4 can also be applied to a fixed wing 123 of a type that has an outer rim 700.

Fifth Embodiment
Next, a fifth embodiment will be described with reference to FIGS.
FIG. 26 is a partial enlarged view of the turbomolecular pump according to the fifth embodiment.
The fifth embodiment relates to a fixed wing spacer 800 having a fixed wing spacer portion 870 that holds the outer frame 127 side and positions the fixed wing 123 in the height direction.
27 (Fifth embodiment A) and 28 (Fifth embodiment B) are diagrams showing the appearance of this fixed wing spacer 800. As shown in these figures, this fixed wing spacer 800 is provided with a protruding portion 860 that protrudes in the height direction from a spacer portion 870 within the height direction range of the fixed wing 123, and a fixed wing spacer tapered surface 810 having a downward slope toward the exhaust port side is formed on at least a part of an inner circumferential surface 830 of the fixed wing spacer portion 870 and the protruding portion 860. The range in which the inner circumferential surface 830 of the fixed wing spacer portion 870 and the protruding portion 860 protrude within the height direction range of the fixed wing 123 is also defined as the "outer periphery of the fixed wing".

Between each of the protrusions 860, there is provided a blade fitting groove 820 into which the blade 550 of the stator 123 is fitted and held when installed.
The fixed wing spacer 800 shown in Fig. 28 is further provided with a fixed wing spacer flange 850. This fixed wing spacer flange 850 allows the fixed wing spacer 800 to be positioned in the height direction, and by being clamped, the fixed wing spacer 800 can be held and fixed.

(About the angle of the tapered surface)
The angle of the tapered surface in each of the first to fifth embodiments will be described.
There are no particular limitations on the angle of the tapered surface, so long as it is a tapered surface (inclined surface) that has a downward gradient toward the exhaust port side.
29(a) is a cross-sectional view of a fixed blade 123 corresponding to the first embodiment H. In the example shown in this figure, a tapered surface is provided on the fixed blade 123 at an angle of a line (imaginary line) connecting an inner diameter lower end A of the fixed blade spacer 125 and an inner diameter upper end B of the fixed blade spacer 125.
29(b) is a cross-sectional view of the fixed blade 123 corresponding to the second embodiment D. In the example shown in this figure, the fixed blade 123 is provided with a tapered surface at an angle of either a line (imaginary line) connecting the intersection point H of a perpendicular line drawn from the tip X of the rotor 102 in the upper stage to the fixed blade 123 in the lower stage to each point (1) (the root of the blade 550 of the fixed blade 123) or (2) (the lower surface of the inner circumference of the fixed blade 123).
Thus, the angle of the tapered surface can be various, and can be determined appropriately depending on various circumstances.

In addition, in each embodiment, a gently curved surface may be used in place of a tapered surface.

The embodiments and variations of the present invention may be combined as necessary.

Furthermore, the present invention can be modified in various ways without departing from the spirit of the invention, and it goes without saying that the present invention also covers such modifications.

100 Turbo molecular pump 101 Intake port 102 Rotor 103 Rotor 113 Rotor shaft 123 Stator 125 Stator spacer 127 Outer cylinder 129 Base portion 133 Exhaust port 200 Control device 550 Blade 600 Inner rim 610 Inner rim tapered surface 620 Inner rim vertical surface 630 Inner rim circumferential surface 700 Outer rim 710 Outer rim tapered surface 720 Outer rim vertical surface 730 Outer rim circumferential surface 740 Excess portion 750 Flange 760 Outer rim inner peripheral surface 800 Stator spacer 810 Stator spacer tapered surface 820 Blade fitting groove 830 Stator spacer inner peripheral surface 850 Stator spacer flange 860 Protruding portion 870 Stator spacer portion

Claims (7)

a casing having an intake port and an exhaust port;
a rotating shaft rotatably supported inside the casing;
A plurality of stages of rotors fixed to the rotary shaft and rotatable together with the rotary shaft;
a plurality of stages of fixed blades fixed to the casing and disposed between the rotor blades;
a vacuum pump in which an outer diameter of at least one of the plurality of rotor stages is smaller on the exhaust port side than on the intake port side, or an inner diameter of at least one of the plurality of rotor stages is larger on the exhaust port side than on the intake port side,
a tapered surface having a downward slope toward the exhaust port is provided on an outer circumferential portion and an inner circumferential portion of a fixed vane that is disposed directly above the rotor vane having a small outer diameter or directly above the rotor vane having a large inner diameter ;
The fixed wing has a plurality of blades arranged radially, and an inner rim and an outer rim that hold the plurality of blades,
A vacuum pump according to claim 1, wherein the tapered surface is provided on an outer peripheral surface of the inner rim and an inner peripheral surface of the outer rim . The fixed wing has a plurality of blades arranged radially and a spacer portion that holds the plurality of blades and positions the fixed wing in a height direction,
2. The vacuum pump according to claim 1, wherein the spacer portion has an inner peripheral surface provided with a tapered surface having a downward slope toward the exhaust port. 3. The vacuum pump according to claim 2 , wherein the surfaces of the plurality of blades of the fixed vane on the exhaust port side are undercut. 3. The vacuum pump according to claim 2 , wherein a vertical surface or a tapered surface is provided behind each of the plurality of blades of the fixed vane. a casing having an intake port and an exhaust port;
a rotating shaft rotatably supported inside the casing;
A plurality of stages of rotors fixed to the rotary shaft and rotatable together with the rotary shaft;
a plurality of stages of fixed blades fixed to the casing and disposed between the rotor blades;
a vacuum pump in which an outer diameter of at least one of the plurality of rotor stages is smaller on the exhaust port side than on the intake port side, or an inner diameter of at least one of the plurality of rotor stages is larger on the exhaust port side than on the intake port side,
a tapered surface having a downward slope toward the exhaust port is provided on an outer circumferential portion and an inner circumferential portion of a fixed vane that is disposed directly above the rotor vane having a small outer diameter or directly above the rotor vane having a large inner diameter;
a protrusion protruding from a spacer portion that holds the casing side of the fixed blade and positions the fixed blade in the height direction within a range of the fixed blade,
a spacer portion having an inner circumferential surface and at least a portion of the protrusion, the spacer portion having a tapered surface that slopes downward toward the exhaust port side, the spacer portion having an inner circumferential surface and at least a portion of the protrusion, the spacer portion having an inner circumferential surface and the protrusion, A fixed vane for use in a vacuum pump having a casing with an intake port and an exhaust port,
The blade assembly has a plurality of blades arranged radially, and an inner rim and an outer rim that hold the plurality of blades,
A fixed vane, in which an outer peripheral surface of the inner rim and an inner peripheral surface of the outer rim are provided with tapered surfaces having a downward slope toward the exhaust port side. A spacer for use in a vacuum pump having a casing with an intake port and an exhaust port,
a spacer portion that holds the casing and positions the stator in a height direction when arranging the stator having a plurality of radially arranged blades,
a protrusion protruding from the spacer portion within a range in the height direction of the fixed wing is provided,
A spacer, characterized in that an inner circumferential surface of the spacer portion and at least a part of the protruding portion are provided with a tapered surface having a downward slope toward the exhaust port side.

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