Vacuum pump and its rotor

Abstract

To provide a vacuum pump and a rotor, which can effectively prevent the stress corrosion crack of a rotor, and has excellent corrosion resistance.SOLUTION: In a vacuum pump (for example, a turbo molecular pump 100) exhausting gas by rotations of a rotor 103, the rotor 103 has a first area 1 covered by a first surface treatment layer 1A and a second area 2 covered by a second surface treatment layer 2A, on a surface thereof. A boundary portion 3 between the first area 1 and the second area 2 has an area where the respective surface treatment layers 1A and 2A are overlapped.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a vacuum pump and its rotor used as a gas exhaust means for process chambers and other chambers in semiconductor manufacturing equipment, flat panel display manufacturing equipment, and solar panel manufacturing equipment, and in particular to an excellent corrosion resistance that can effectively prevent stress corrosion cracking of the rotor. [Background technology]

[0002] A conventional example of this type of vacuum pump is the turbomolecular pump described in Patent Document 1. The turbomolecular pump in this document (hereinafter referred to as the "conventional vacuum pump") has a structure in which gas is exhausted by the rotation of a rotor (pump rotor 10) equipped with a plurality of rotor blades (moving blades 12).

[0003] In conventional vacuum pumps, a black Ni-plated surface treatment layer (S1) and a Ni-plated surface treatment layer (S4) are provided on the surface of the rotating body (pump rotor 10) to provide a difference in emissivity on the rotating body surface and to prevent corrosion of the rotating body due to process gas.

[0004] However, in conventional vacuum pumps, at the boundary between the black Ni-plated surface treatment layer (S1) and the Ni-plated surface treatment layer (S4), there is an area (S5) where the base material of the rotating body (pump rotor 10) is exposed, and no measures are taken to prevent corrosion of the base material at such a boundary. As a result, stress corrosion cracking of the rotating body cannot be effectively prevented, and the pump cannot be said to have excellent corrosion resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2015-229949 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above problems, and an object of the present invention is to provide a vacuum pump and a rotor thereof which can effectively prevent stress corrosion cracking of the rotor and have excellent corrosion resistance. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a vacuum pump that exhausts gas by rotating a rotor, the rotor having a first region covered with a first surface treatment layer and a second region covered with a second surface treatment layer on a surface thereof, and a boundary between the first region and the second region has a region where the respective surface treatment layers overlap. The rotor has a shape in which rotor blades are formed on the outer periphery of a cylindrical portion, the rotor blades are located at the upper portion of the rotor in the vertical direction, the boundary portion includes a first boundary portion located at the lower end portion of the rotor in the vertical direction, and the first boundary portion is located on the inner surface of the cylindrical portion. It is characterized by the above.

[0008] In the present invention, the rotating body At the center of teeth, A rotor shaft is attached via a fastening portion, and a tip end of the rotor shaft is fitted into a first hole on the rotating body side at the fastening portion. The boundary portion teeth , The opening edge of the first hole or its periphery Located in Includes the second boundary The present invention may be characterized in that:

[0009] In the present invention, A relief portion corresponding to the second boundary portion is provided on a surface of a member facing the opening edge portion of the first hole or its periphery. The present invention may be characterized in that:

[0010] Books invention teeth , A vacuum pump that exhausts gas by rotating a rotor, the rotor having a first region covered with a first surface treatment layer and a second region covered with a second surface treatment layer on a surface thereof, the boundary between the first region and the second region being an area where the respective surface treatment layers overlap, A rotor shaft is attached to the center of the rotor via a fastening portion, and a tip end of the rotor shaft is fitted into a first hole on the rotor side at the fastening portion, and the boundary portion teeth , located at or around the opening edge of the first hole a relief portion corresponding to the second boundary portion is provided on a surface of the member facing the opening edge portion of the first hole or its periphery, the relief portion including the second boundary portion; The present invention may be characterized as follows.

[0011] In the present invention, The second boundary portion is not on the inner surface of the first hole. thing of It may be a feature.

[0012] In the present invention, the center of the rotating body is The rotor shaft is attached via a fastening portion, and in the fastening portion, a bolt for fastening the rotor shaft to the rotor body is inserted from a second hole on the rotor body side, and the boundary portion includes a third boundary portion located on an inner surface of the second hole. The present invention may be characterized in that:

[0013] Books invention teeth , A vacuum pump that exhausts gas by rotating a rotor, the rotor having a first region covered with a first surface treatment layer and a second region covered with a second surface treatment layer on a surface thereof, the boundary between the first region and the second region being an area where the respective surface treatment layers overlap, A rotor shaft is attached to the center of the rotor via a fastening portion, and a bolt for fastening the rotor shaft to the rotor is inserted into a second hole on the rotor side at the fastening portion, and the boundary portion teeth , located on the inner surface of the second hole Including the third border The present invention may be characterized in that:

[0014] In the present invention, the first region may be provided on an outer surface of the cylindrical portion and a surface of the rotor, and the second region may be provided on an inner surface of the cylindrical portion.

[0015] In the present invention, the second surface treatment layer may have a higher emissivity than the first surface treatment layer.

[0016] The present invention also provides a rotor for a vacuum pump that exhausts gas, the rotor having a first region covered with a first surface treatment layer and a second region covered with a second surface treatment layer on a surface thereof, and a boundary between the first region and the second region has a region where the respective surface treatment layers overlap. The rotor has a shape in which rotor blades are formed on the outer periphery of a cylindrical portion, the rotor blades are located at the upper portion of the rotor in the vertical direction, the boundary portion includes a first boundary portion located at the lower end portion of the rotor in the vertical direction, and the first boundary portion is located on the inner surface of the cylindrical portion. It is characterized by the above. Effect of the Invention

[0017] In the present invention, as a specific configuration of a vacuum pump and its rotor, the rotor has a first region on its surface covered with a first surface treatment layer and a second region covered with a second surface treatment layer, and the boundary between the first and second regions has a region where the respective surface treatment layers overlap.As a result, the base material of the rotor is not exposed at the boundary, and there is almost no risk of the exposed base material being exposed to corrosive gases.This makes it possible to effectively prevent stress corrosion cracking of the rotor, and a vacuum pump and its rotor with excellent corrosion resistance can be provided. [Brief description of the drawings]

[0018] [Figure 1]1 is a vertical sectional view of a turbomolecular pump to which a vacuum pump according to the present invention is applied; [Diagram 2] Schematic diagram of the amplifier circuit. [Diagram 3] 5 is a time chart showing control when a current command value is larger than a detection value. [Figure 4] 5 is a time chart showing control when a current command value is smaller than a detection value. [Diagram 5] FIG. 2(a) is an explanatory diagram of the rotor and rotor shaft that constitute the turbomolecular pump in FIG. 1, and FIG. 2(b) is a view taken from the arrow A in FIG. [Figure 6] (a) is an explanatory diagram of the surface treatment configuration adopted in the turbo molecular pump of Figure 1, (b) is an enlarged view of part B in (a), and (c) is an enlarged view of part C in (a). [Figure 7] An enlarged view of part D in Figure 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] FIG. 1 is a longitudinal sectional view of a turbomolecular pump to which a vacuum pump according to the present invention is applied, FIG. 2 is a circuit diagram of an amplifier circuit, FIG. 3 is a time chart showing control when a current command value is larger than a detection value, and FIG. 4 is a time chart showing control when a current command value is smaller than a detection value.

[0020] 1, in a turbomolecular pump 100 in the figure, an intake port 101 is formed at the upper end of a cylindrical outer cylinder 127. Inside the outer cylinder 127, a rotor 103 is provided, in which a plurality of rotors 102 (102a, 102b, 102c, ...) which are turbine blades for sucking and exhausting gas are formed radially and in multiple stages on the periphery. As a specific configuration example of this rotor 103, in the turbomolecular pump 100 in FIG. 1, the rotor 103 is shaped such that the rotors 102 are formed on the outer periphery of a first cylindrical section 102e (see FIG. 5(a)).

[0021] A rotor shaft 113 is attached to the center of the rotating body 103 via a fastening part CN, 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 rotating body 103 is generally made of a metal such as aluminum or an aluminum alloy.

[0022] 1, the upper radial electromagnets 104 are arranged in pairs on the X-axis and the Y-axis. Four upper radial sensors 107 are provided adjacent to the upper radial electromagnets 104 and corresponding to each of the upper radial electromagnets 104. The upper radial sensors 107 are, for example, inductance sensors or eddy current sensors having conductive windings, and detect the position of the rotor shaft 113 based on the change in inductance of the conductive windings that changes according to the position of the rotor shaft 113. The upper radial sensors 107 are configured to detect the radial displacement of the rotor shaft 113, i.e., the rotating body 103 fixed thereto, and send the detected displacement to the control device 200.

[0023] In the control device 200, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for the upper radial electromagnet 104 based on a position signal detected by the upper radial sensor 107, and an amplifier circuit 150 (described later) shown in Figure 2 controls the excitation of the upper radial electromagnet 104 based on this excitation control command signal, thereby adjusting the upper radial position of the rotor shaft 113.

[0024] The rotor shaft 113 is made of a high magnetic permeability material (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnet 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction. In addition, 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.

[0025] 1, as a specific configuration example of a magnetic bearing, axial electromagnets 106A and 106B are arranged above and below a circular metal disk 111 provided at the bottom of a rotor shaft 113. The metal disk 111 is made of a highly magnetic permeable material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and an axial position signal is sent to a control device 200.

[0026] In the control device 200, a compensation circuit having, for example, a PID adjustment function generates an excitation control command signal for each of the axial electromagnets 106A and 106B based on the axial position signal detected by the axial sensor 109, and the amplifier circuit 150 controls the excitation of the axial electromagnets 106A and 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disk 111 upward by magnetic force and the axial electromagnet 106B attracts the metal disk 111 downward, thereby adjusting the axial position of the rotor shaft 113.

[0027] As described above, the control device 200 appropriately adjusts the magnetic force that the axial electromagnets 106A, 106B exert on the metal disk 111, magnetically levitates the rotor shaft 113 in the axial direction, and holds it in a non-contact manner in space. The amplifier circuit 150 that controls the excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A, 106B will be described later.

[0028] 1, the motor 121 has a plurality of magnetic poles arranged circumferentially so as to surround the rotor shaft 113. Each magnetic pole is controlled by a control device 200 so as to rotate the rotor shaft 113 via an electromagnetic force acting between the motor 121 and the rotor shaft 113. In addition, a rotational speed sensor such as a Hall element, resolver, or encoder (not shown) is incorporated in the motor 121, and the rotational speed of the rotor shaft 113 is detected by a detection signal from this rotational speed sensor.

[0029] 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 detects the position of the magnetic poles using the detection signals of both this phase sensor and the rotation speed sensor.

[0030] A plurality of fixed blades 123 (123a, 123b, 123c...) are arranged with a small gap between the rotor blades 102 (102a, 102b, 102c...). The rotor blades 102 (102a, 102b, 102c...) are formed at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transport exhaust gas molecules downward through collision. The fixed blades 123 (123a, 123b, 123c...) are made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components.

[0031] Similarly, the fixed blades 123 are formed at an inclination at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged alternately with the stages of the rotor blades 102 toward the inside of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported in a state where they are inserted between a plurality of stacked stages of fixed blade spacers 125 (125a, 125b, 125c, etc.).

[0032] The fixed wing spacer 125 is a ring-shaped member and is made of metal such as aluminum, iron, stainless steel, copper, or an alloy containing these metals as components. An outer cylinder 127 is fixed to the outer periphery of the fixed wing spacer 125 with a small gap therebetween. A base portion 129 is disposed at the bottom of the outer cylinder 127. An exhaust port 133 is formed in the base portion 129 and communicates with the outside. Exhaust gas that enters the intake port 101 from the chamber (vacuum chamber) side and is transferred to the base portion 129 is sent to the exhaust port 133.

[0033] Furthermore, depending on the application of the turbo molecular 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 a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals, and has a plurality of helical thread grooves 131a engraved on its inner peripheral surface. The helical direction of the thread groove 131a is the direction in which, when exhaust gas molecules move in the rotation direction of the rotor 103, the molecules are transported toward the exhaust port 133. At the bottom of the rotor 103, next to the rotor vanes 102 (102a, 102b, 102c, etc.), a second cylindrical part 102d is connected to a first cylindrical part 102e and hangs down (see FIG. 2(a)). The outer peripheral surface of the second 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 specified gap therebetween. The exhaust gas transferred to the thread groove 131a by the rotor 102 and the fixed blade 123 is sent to the base portion 129 while being guided by the thread groove 131a.

[0034] The base portion 129 is a disk-shaped member that constitutes the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. The base portion 129 physically holds the turbomolecular pump 100 and also functions as a heat conduction path, so it is desirable to use a metal that has rigidity and high thermal conductivity, such as iron, aluminum, or copper.

[0035] In this configuration, when the rotor 102 is rotated together with the rotor shaft 113 by the motor 121, the exhaust 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 exhaust gas sucked through 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 exhaust gas comes into contact with the rotor 102 and conduction of heat generated by the motor 121, and the like, but this heat is transferred to the fixed blade 123 side by radiation or conduction by gas molecules of the exhaust gas, and the like.

[0036] The fixed blade spacers 125 are joined to each other at their outer peripheries, and transmit heat received by the fixed blades 123 from the rotor blades 102, frictional heat generated when exhaust gas comes into contact with the fixed blades 123, and the like to the outside.

[0037] In the above description, the threaded spacer 131 is disposed on the outer periphery of the cylindrical portion 102d of the rotor 103, and the thread groove 131a is formed on the inner periphery of the threaded spacer 131. However, there are also cases where the thread groove is formed on the outer periphery of the cylindrical portion 102d, and a spacer having a cylindrical inner periphery is disposed around the outer periphery of the cylindrical portion 102d.

[0038] Depending on the application of the turbomolecular pump 100, in order to prevent the gas sucked in from the intake port 101 from entering the electrical equipment section, which is composed of the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, the lower radial electromagnet 105, the lower radial sensor 108, the axial electromagnets 106A and 106B, the axial sensor 109, etc., the electrical equipment section may be covered all around with a stator column 122, and the inside of this stator column 122 may be kept at a predetermined pressure by a purge gas.

[0039] In this case, piping (not shown) is provided in the base portion 129, and purge gas is introduced through this piping. The introduced purge gas is sent to the exhaust port 133 through gaps between the protective bearing 120 and the rotor shaft 113, between the rotor and stator of the motor 121, and between the stator column 122 and the inner cylindrical portion of the rotor blades 102.

[0040] Here, the turbomolecular pump 100 requires control based on specific parameters (e.g., various characteristics corresponding to the model) that are individually adjusted and identified as a model. In order to store these control parameters, the turbomolecular pump 100 has an electronic circuit section 141 in its main body. The electronic circuit section 141 is composed of a semiconductor memory such as an EEPROM, electronic components such as semiconductor elements for accessing the memory, and a substrate 143 for mounting these components. The electronic circuit section 141 is housed below a rotational speed sensor (not shown) near the center of a base section 129 that constitutes the lower part of the turbomolecular pump 100, and is closed by an airtight bottom cover 145.

[0041] In the semiconductor manufacturing process, some process gases introduced into the chamber have the property of becoming solid when their pressure exceeds a predetermined value or their temperature falls below a predetermined value. Inside the turbo molecular 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 becomes higher than 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 becomes solid and adheres to and accumulates inside the turbo molecular pump 100.

[0042] For example, SiCl is used as a process gas in an Al etching device. 4 When low vacuum (760[torr]~10 -2 At low temperatures (approximately 20°C) and at low temperatures (approximately 20°C), solid products (e.g., AlCl 3) precipitates and adheres to and accumulates inside the turbomolecular pump 100. As a result, 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 products are prone to solidification and adhesion in high-pressure areas near the exhaust port 133 and near the threaded spacer 131.

[0043] Therefore, in order to solve this problem, in the past, a heater (not shown) or a circular water-cooled tube 149 was wrapped around the outer periphery of the base portion 129, and a temperature sensor (e.g., a thermistor) (not shown) was embedded in the base portion 129, and the heating of the heater and the cooling by the water-cooled tube 149 were controlled based on the signal from this temperature sensor to keep the temperature of the base portion 129 at a constant high temperature (set temperature) (hereinafter referred to as TMS; Temperature Management System).

[0044] Next, an amplifier circuit 150 that controls excitation of the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B in the turbo molecular pump 100 configured as described above will be described. A circuit diagram of this amplifier circuit 150 is shown in FIG.

[0045] 8, one end of an electromagnet winding 151 constituting the upper radial electromagnet 104 etc. is connected to a positive electrode 171a of a power source 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power source 171 via a current detection circuit 181 and a transistor 162. The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between the source and drain.

[0046] At this time, the transistor 161 has a cathode terminal 161a of the diode connected to the positive electrode 171a, and an anode terminal 161b connected to one end of the electromagnet winding 151. The transistor 162 has a cathode terminal 162a of the diode connected to the current detection circuit 181, and an anode terminal 162b connected to the negative electrode 171b.

[0047] On the other hand, the current regeneration diode 165 has its cathode terminal 165a connected to one end of the electromagnet winding 151 and its anode terminal 165b connected to the negative electrode 171b. Similarly, the current regeneration diode 166 has its cathode terminal 166a connected to the positive electrode 171a and its anode terminal 166b connected to the other end of the electromagnet winding 151 via a current detection circuit 181. The current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or an electric resistance element.

[0048] The amplifier circuit 150 configured as above corresponds to one electromagnet. Therefore, when the magnetic bearing is controlled by five axes and there are a total of ten electromagnets 104, 105, 106A, and 106B, a similar amplifier circuit 150 is configured for each electromagnet, and the ten amplifier circuits 150 are connected in parallel to the power supply 171.

[0049] 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 switches the transistors 161 and 162 on / off.

[0050] The amplifier control circuit 191 is adapted to compare the current value detected by the current detection circuit 181 (a signal reflecting this current value is called a current detection signal 191c) with a predetermined current command value. Then, based on the result of this comparison, the magnitude of the pulse width (pulse width times Tp1, Tp2) to be generated within a control cycle Ts, which is one period of PWM control, is determined. As a result, gate drive signals 191a, 191b having this pulse width are output from the amplifier control circuit 191 to the gate terminals of the transistors 161, 162.

[0051] It is necessary to control the position of rotor 103 at high speed and with strong force when, for example, the rotor 103 passes through a resonance point during accelerated operation of the rotation speed or when a disturbance occurs during constant speed operation. For this reason, a high voltage of, for example, about 50 V is used as power supply 171 so that the current flowing through electromagnet winding 151 can be rapidly increased (or decreased). In addition, a capacitor (not shown) is usually connected between positive pole 171a and negative pole 171b of power supply 171 to stabilize power supply 171.

[0052] In this configuration, when both transistors 161, 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0053] Moreover, when one of the transistors 161, 162 is turned on and the other is turned off, a so-called flywheel current is maintained. By passing a flywheel current through the amplifier circuit 150 in this manner, the hysteresis loss in the amplifier circuit 150 can be reduced, and the power consumption of the entire circuit can be kept low. Furthermore, by controlling the transistors 161, 162 in this manner, high-frequency noise such as harmonics generated in the turbo molecular pump 100 can be reduced. Furthermore, by measuring this flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0054] That is, when the detected current value is smaller than the current command value, both of the transistors 161 and 162 are turned on for a time period corresponding to the pulse width time Tp1 only once in a control cycle Ts (e.g., 100 μs) as shown in Fig. 9. Therefore, the electromagnet current iL during this period increases toward a current value iLmax (not shown) that can flow from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[0055] On the other hand, when the detected current value is larger than the current command value, both of the transistors 161 and 162 are turned off for a time period corresponding to the pulse width time Tp2 only once during the control cycle Ts, as shown in Fig. 10. Therefore, the electromagnet current iL during this period decreases toward a current value iLmin (not shown) that can be regenerated from the negative pole 171b to the positive pole 171a via the diodes 165 and 166.

[0056] In either case, after the pulse width times Tp1 and Tp2 have elapsed, one of the transistors 161 and 162 is turned on. Therefore, a flywheel current is maintained in the amplifier circuit 150 during this period.

[0057] In Fig. 5, (a) is an explanatory diagram of the rotor and rotor shaft that constitute the turbomolecular pump of Fig. 1, and (b) is a view taken from the arrow A in Fig. 5(a). Also, in Fig. 6, (a) is an explanatory diagram of the surface treatment configuration adopted in the turbomolecular pump of Fig. 1, (b) is an enlarged view of part B in Fig. 5(a), and (c) is an enlarged view of part C in Fig. 5(a).

[0058] 6(a), (b) and (c), as a specific surface treatment configuration of the rotating body 103, in the turbomolecular pump 100 of FIG. 1, the rotating body 103 has on its surface a first region 1 covered with a first surface treatment layer 1A and a second region 2 covered with a second surface treatment layer 2A, and the boundary portion 3 between the first region 1 and the second region 2 has a region 3 (3A, 3B, 3C) where the respective surface treatment layers 1A, 2A overlap.

[0059] The definition of the boundary portion 3 is used not only to indicate the boundary between the respective surface treatment layers but also to indicate the overlapping region 3.

[0060] As a specific embodiment of the first and second regions 1, 2, in the turbomolecular pump 100 of FIG. 1, the first region 1 is configured so that a first surface treatment layer 1A is provided on the outer surfaces of the cylindrical portions 102d, 102e and on the surfaces of the rotor blades 102 (102a, 102b, 102c, etc.), and the second region 2 is configured so that a second surface treatment layer 2A is provided on the inner surfaces of the cylindrical portions 102d, 102e.

[0061] Here, "the outer surfaces of the cylindrical portions 102d, 102e" includes the outer surface of the first cylindrical portion 102d, the outer surface of the second cylindrical portion 102e, the lower end surface of the second cylindrical portion 102e, and the inner bottom surface and inner side surface of the recess 4 described later.

[0062] In addition, "the inner surfaces of the cylindrical portions 102d, 102e" includes the inner surface of the first cylindrical portion 102d, the inner surface of the second cylindrical portion 102e, the outer bottom surface (fastening surface 4A) of the recess 4 described later, the inner surface of the fitting hole 5 (the first hole on the rotating body 103 side), and the inner surface of the through hole 6 (the second hole on the rotating body 103 side).

[0063] As a specific configuration example of the above-mentioned first and second surface treatment layers 1A, 2A, in the turbo molecular pump of Fig. 1, the second surface treatment layer 2A is configured to have a higher emissivity than the first surface treatment layer 1A. Therefore, the heat accumulated in the rotor 103, specifically the rotor blades 102 (102a, 102b, 102c, ...) and the first or second cylindrical portion 102e, 102d, is mainly radiated from the second surface treatment layer 2A toward the member facing it (specifically the stator column 122).

[0064] As a means for providing the difference in emissivity as described above, in the turbomolecular pump 100 of Fig. 1, the first surface treatment layer 1A is formed by electroless nickel-phosphorus plating, and the second surface treatment layer 2A is formed by oxidizing the surface of the electroless nickel-phosphorus plating, but the difference in emissivity may be provided by a different means. In addition, the plating thickness, i.e., the thickness of the first and second surface treatment layers 1A is about 20 μm, but is not limited to this. The plating thickness can be appropriately changed as necessary, and a configuration in which the plating thickness is different between the first surface treatment layer 1A and the second surface treatment layer 2B may also be adopted.

[0065] Incidentally, in order to increase the heat emissivity from the rotor blades 102 (102a, 102b, 102c, etc.) and prevent stress corrosion cracking of the rotor blades 102, it is desirable to form the first surface treatment layer 1A of the rotor blades 102 by oxidation of electroless nickel-phosphorus plating, like the second surface treatment layer 2A. However, in the case of the turbomolecular pump 100 of FIG. 1, the rotor blades 102 are exposed to corrosive gases, and a surface treatment layer having an uppermost layer made of an oxide coating, such as the second surface treatment layer 2A, is easily eroded and deteriorated by corrosive gases. Therefore, in the turbomolecular pump 100 of FIG. 1, the portions of the entire rotor 102 that are particularly exposed to corrosive gases, specifically, the outer surfaces of the cylindrical portions 102d and 102e and the surface treatment layers (first surface treatment layer 1A) of the rotor blades 102 (102a, 102b, 102c, etc.) are formed by electroless nickel-phosphorus plating.

[0066] 6(a) and (b), the first boundary 3 (3A) is located on the inner surface of the second cylindrical portion 102d. Furthermore, as a specific example of the arrangement of the first boundary 3 (3A), in the example of FIG. 6(a) and (b), the first boundary 3 (3A) is arranged near the end of the inner surface of the second cylindrical portion 102d. This is to increase the bonding strength or peel strength between the first surface treatment layer 1A and the second surface treatment layer 2A at the boundary 3 (3A) by utilizing the centrifugal force of the rotor 103.

[0067] That is, (1) due to the shape or structure of the rotating body 103, the centrifugal force of the rotating body 103 becomes large near the end of the second cylindrical portion 102d, and (2) when the boundary portion 3 (3A) is arranged on the outer surface of the first or second cylindrical portion 102e, 102d, a centrifugal force acts on the boundary portion 3 in a direction away from the outer surface, whereas when the boundary portion 3 (3) is arranged on the inner surface of the first or second cylindrical portion 102e, 102d as shown in Figures 6(a) and (b), a centrifugal force acts on the boundary portion 3 in a direction toward the inner surface, thereby pressing the boundary portion 3 (3A) against the inner surface of the first or second cylindrical portion 102e, 102d. For this reason, in the example of Figures 6(a) and (b), as described above, the first boundary portion 3 (3A) is configured to be positioned near the end of the inner surface of the second cylindrical portion 102d, thereby making it possible to effectively prevent peeling between the first surface treatment layer 1A and the second surface treatment layer 2A at the first boundary portion 3 (3A).

[0068] 6(a) and (b), in order to increase the amount of heat radiation from the rotor 103 to the stator column 122, the first boundary portion 3 (3A) is configured to have the second surface treatment layer 2A superimposed on the first surface treatment layer 1A, thereby making the surface area of ​​the second surface treatment layer 2A as large as possible. However, this is not limited to this. It is also possible to adopt a configuration in which the first surface treatment layer 1A is superimposed on the second surface treatment layer 2A.

[0069] 5(a), 6(a) and 7, as a specific structural example of the fastening portion CN for attaching the rotor shaft 113 to the center of the rotor 103, in the turbo molecular pump 100 of FIG. 1, (1) a structure in which a recess 4 is provided at the end of the rotor 103, a fitting hole 5 is formed in the center of the inner bottom surface of this recess 4 as a first hole on the rotor 103 side, and a plurality of through holes 6, 6... are formed around the fitting hole 5 as second holes on the rotor 103 side; (2) The structure includes: an outer bottom surface of recess 4 is used as fastening surface 4A; a flange 7 facing this fastening surface 4A is formed on the outer periphery of rotor shaft 113; a structure in which the tip of rotor shaft 113 is fitted into fitting hole 5; and a bolt 8 for fastening rotating body 103 and rotor shaft 113 is inserted into through holes 6, 6 ... and then tightened and fixed into a screw hole (not shown) of flange 7; and a structure in which (4) a washer member 9 is arranged between the head of bolt 8 and flange 7.

[0070] As described above, at the fastening portion CN, the tip of the rotor shaft 113 is fitted into the fitting hole 5 (first hole) on the rotating body 103 side, and the second boundary portion 3 (3B) is located at or around the opening edge of the fitting hole 5, and there is no boundary portion 3 on the inner surface of the fitting hole 5.

[0071] Here, the "opening edge of the fitting hole 5 or its periphery" refers to the range in which a member (specifically, washer member 8) facing the opening edge of the fitting hole 5 (first hole) or its periphery contacts the inner bottom surface of the recess 4. Therefore, the second boundary portion 3 (3B) may be configured to be disposed within this range.

[0072] Incidentally, as another embodiment regarding the location of the second boundary portion 3 (3B), although not shown in the drawings, a configuration in which the second boundary portion 3 (3B) described above is arranged on the inner surface of the fitting hole 5 is also conceivable. However, the thickness of the second boundary portion 3 (3B) is thicker than the thickness of the other parts of the first surface treatment layer 1A and the second surface treatment layer 2A. For this reason, in the configuration in which the second boundary portion 3 (3B) is arranged on the inner surface of the fitting hole 5 as described above, for example, it is necessary to increase the press-fitting force during assembly or to further increase the temperature difference for shrink fitting, which may reduce the assembly workability. In addition, even after fitting, problems such as the rotor shaft 113 being tilted with the second boundary portion 3 (3B) as a base point and the rotor shaft 113 not being able to be fitted accurately into the fitting hole 5 are assumed.

[0073] However, in the turbomolecular pump of the embodiment of the present application shown in Figure 1, as described above, there is no second boundary portion 3 (3B) on the inner surface of the fitting hole 5 (first hole), so that the second boundary portion 3 (3B) does not hinder the fitting of the rotor shaft 113 into the fitting hole 5, and there is an advantage that the rotor shaft 113 can be fitted into the fitting hole 5 with high precision.

[0074] 7 and 6(c), in the turbo molecular pump according to the embodiment of the present application shown in Fig. 1, a relief portion 10 corresponding to the second boundary portion 3 (3B) is provided on the surface of the member facing the opening edge portion of the fitting hole 5 (first hole) or its periphery (specifically, the lower surface of the washer member 9 contacting the inner bottom surface of the recess 4). This relief portion 10 may be in the shape of a groove or a step.

[0075] As described above, the first surface treatment layer 1A and the second surface treatment layer 2A overlap at the second boundary portion 3 (3B), and therefore the thickness of the second boundary portion 3 (3B) is thicker than the thicknesses of the other portions of the first surface treatment layer 1A and the second surface treatment layer 2A. If the rotating body 103 and the rotor shaft 113 are fastened at the fastening portion CN without taking into consideration such partial thickness increase, for example, the washer member 9 may be disposed at an angle, and problems such as an unstable fastening state between the rotating body 103 and the rotor shaft 113 may be expected. However, in the turbomolecular pump 100 of the embodiment of the present application shown in Figure 1, as described above, a recess 10 corresponding to the second boundary portion 3 (3B) is provided, and the second boundary portion 3 (3B) is accommodated within the recess 10, thereby absorbing the thickness of the second boundary portion 3 (3B). Therefore, the thickness of the second boundary portion 3 (3B) does not affect the fastening state between the rotating body 103 and the rotor shaft 113, a stable fastening state is obtained, and there is no need to strictly control the thickness of the second boundary portion 3 (3B), thereby saving the trouble of such management.

[0076] Furthermore, in the fastening portion CN, as described above, the tip of the rotor shaft 113 is fitted into the fitting hole 5 (the first hole on the rotor side), and the bolt 8 for fastening the rotor 103 and the rotor shaft 113 is inserted from the through hole 6 (the second hole on the rotor side), and the third boundary portion 3 (3C) is located on the inner surface of the through hole 6 (see FIG. 6(c)). In this configuration, the third boundary portion 3 (3C) is located in a predetermined gap provided between the body of the bolt 8 and the through hole 6. Note that the through hole 6 does not require high-precision dimensional control compared to the fitting hole 5, so even if the third boundary portion 3 (3C), which is the overlapping portion of the surface treatment layer, is located, it does not cause a major problem.

[0077] Incidentally, as another embodiment regarding the location of the third boundary portion 3 (3C), although not shown in the drawings, a configuration in which the third boundary portion 3 (3C) is disposed at or around the opening edge portion of the through hole 6 is also conceivable. However, in this configuration, it is expected that there will be a decrease in the ease of assembly and problems (such as an unstable fastening state between the rotor 103 and the rotor shaft 113) similar to the case in which the above-mentioned relief portion 10 is not provided. On the other hand, in the turbo molecular pump 100 according to the embodiment of the present application shown in FIG. 1, as described above, the third boundary portion 3 (3C) is located on the inner surface of the through hole 6, and is therefore disposed in the gap between the through hole 6 and the body of the bolt 8. Therefore, the third boundary portion 3 (3C) does not affect the fastening state between the rotor 103 and the rotor shaft 113. In this respect, a stable fastening state can be obtained. In addition, there is no need to strictly manage the thickness of the third boundary portion 3 (3C), and the effort required for management can be saved.

[0078] As described above, in the vacuum pump and rotor of this embodiment, the rotor 103 has a first region 1 covered with a first surface treatment layer 1A on its surface, and a second region 2 covered with a second surface treatment layer 2A, and a boundary portion 3 between the first region 1 and the second region 2 has a region where the surface treatment layers 1A and 2A overlap. Therefore, the base material (metal such as aluminum or an aluminum alloy) of the rotor 103 is not exposed at the boundary portion 3, and there is almost no risk of the exposed base material being exposed to corrosive gas, so that stress corrosion cracking of the rotor 103 can be effectively prevented and the rotor has excellent corrosion resistance.

[0079] The present invention is not limited to the above-described embodiment, and many modifications are possible within the scope of the technical concept of the present invention using the ordinary creativity of those skilled in the art. [Explanation of symbols]

[0080] 1. First Area 1A First surface treatment layer 2. The second area 2A Second surface treatment layer 3. Boundary 3A First Boundary 3B Second Boundary 3C Third Boundary 4 Recess 5 Fitting hole (first hole on the rotating body side) 6 Through holes 7 Flange 8 Volts 9 Washer material 100 Turbomolecular Pump 101 Air intake 102 Rotor 102d Second cylindrical section 102e First cylindrical part 103 Rotating Body 104 Upper radial electromagnet 106A, 106B Axial electromagnet 107 Upper radial sensor 109 Axial Sensor 111 Metal Disc 113 Rotor shaft 120 Protective Bearing 121 Motor 122 Stator column 123 fixed wing 125 Fixed wing spacer 127 Outer cylinder 129 Base 131 Threaded spacer 131a Thread groove 133 Exhaust port 141 Electronic circuit section 149 Water cooled pipe 143 Substrate 145 Bottom lid 150 Amplifier circuit 171 Power supply 181 Current detection circuit 191 Amplifier control circuit 200 Control device CN fastening part

Claims

1. In a vacuum pump that exhausts gas by rotating a rotor, the rotating body has a first region covered with a first surface treatment layer and a second region covered with a second surface treatment layer on a surface thereof; a boundary between the first region and the second region includes a region where the surface treatment layers of the first region and the second region overlap each other; The rotor has a shape in which rotor blades are formed on the outer periphery of a cylindrical portion, The rotor is located at the top of the rotor in the vertical direction, the boundary portion includes a first boundary portion located at a lower end portion of the rotating body in the up-down direction, The first boundary portion is located on an inner surface of the cylindrical portion. A vacuum pump characterized by:

2. A vacuum pump that exhausts gas by rotating a rotor, the rotating body has a first region covered with a first surface treatment layer and a second region covered with a second surface treatment layer on a surface thereof; a boundary between the first region and the second region includes a region where the surface treatment layers of the first region and the second region overlap each other; A rotor shaft is attached to the center of the rotor via a fastening part, In the fastening portion, a tip end of the rotor shaft is fitted into a first hole on the rotating body side, the boundary portion includes a second boundary portion located at or around an opening edge portion of the first hole, a relief portion corresponding to the second boundary portion is provided on a surface of a member facing the opening edge portion of the first hole or its periphery; A vacuum pump characterized by:

3. The second boundary portion is not on the inner surface of the first hole.

3. The vacuum pump according to claim 2 .

4. A vacuum pump that exhausts gas by rotating a rotor, the rotating body has a first region covered with a first surface treatment layer and a second region covered with a second surface treatment layer on a surface thereof; a boundary between the first region and the second region includes a region where the surface treatment layers of the first region and the second region overlap each other; A rotor shaft is attached to the center of the rotor via a fastening part, In the fastening portion, a bolt for fastening the rotating body and the rotor shaft is inserted into a second hole on the rotating body side, the boundary portion includes a third boundary portion located on an inner surface of the second hole; A vacuum pump characterized by:

5. The first region is provided on an outer surface of the cylindrical portion and a surface of the rotor, The second region is provided on the inner surface of the cylindrical portion.

2. The vacuum pump according to claim 1 .

6. The second surface treatment layer has a higher emissivity than the first surface treatment layer.

6. A vacuum pump according to claim 1, wherein the first and second electrodes are arranged in a first direction.

7. A rotating body of a vacuum pump that exhausts gas, comprising: the rotating body has a first region covered with a first surface treatment layer and a second region covered with a second surface treatment layer on a surface thereof; a boundary between the first region and the second region includes a region where the surface treatment layers of the first region and the second region overlap each other; The rotor has a shape in which rotor blades are formed on the outer periphery of a cylindrical portion, The rotor is located at the top of the rotor in the vertical direction, the boundary portion includes a first boundary portion located at a lower end portion of the rotating body in the up-down direction, The first boundary portion is located on an inner surface of the cylindrical portion. A rotating body of a vacuum pump characterized by the above.

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