Vacuum pump and hermetic connector

Abstract

An object is to limit the manufacturing cost of a hermetic connector and achieve compactness and high performance. A vacuum pump (100) includes a hermetic connector (10), and the hermetic connector (10) includes pins (11, 12) configured to be electrically connected, a connector base portion (13) surrounding the pins (11, 12), and a sealing portion (14) providing a seal between the pins (11, 12) and the connector base portion (13). The sealing portion (14) is made of an insulating resin material.

Description

[Technical Field]

[0001] The present invention relates to a vacuum pump and a hermetic connector used for a vacuum pump.[Background Art]

[0002] As conventional art in this technical field, a vacuum pump described in PTL 1 includes a laterally elongate hermetic connector. A hermetic connector applied to a vacuum pump needs to have high airtightness and high heat resistance. To this end, a glass material is typically used to provide a seal between the connector base portion and the pins of a hermetic connector.[Citation List][Patent Literature]

[0003] [PTL 1] Japanese Patent No. 6912196[Summary of Invention][Technical Problem]

[0004] The manufacturing of the conventional hermetic connector described above involves the issue of increased cost because the step of sealing with a glass material is specialized. A hermetic connector used for a vacuum pump needs to be compact, have a large number of pins, and have a high level of leak rate performance. In particular, when used for a vacuum pump, any entry of the air into the interior through the hermetic connector would degrade the pump performance. Thus, there is a demand for manufacturing a compact, high-performance hermetic connector having a predetermined leak rate performance at a low cost.

[0005] In view of the above, it is an object of the present invention to limit the manufacturing cost of a hermetic connector and achieve compactness and high performance.[Solution to Problem]

[0006] To achieve the above object, a first aspect of the present invention relates to a vacuum pump including a hermetic connector, wherein the hermetic connector includes: a pin configured to be electrically connected; a connector base portion surrounding the pin; and a sealing portion providing a seal between the pin and the connector base portion, and the sealing portion is made of an insulating resin material.

[0007] In the above configuration, the sealing portion includes: a first sealing portion covering an outer surface of the pin; and a second sealing portion providing a seal between the first sealing portion and the connector base portion, the connector base portion is made of a metal material, the first sealing portion is made of a first resin material, and the second sealing portion is made of a second resin material.

[0008] In the above configuration, a linear expansion coefficient of the first resin material is greater than or equal to a linear expansion coefficient of the second resin material.

[0009] In the above configuration, the hermetic connector further includes a labyrinth structure that is disposed between the pin and the sealing portion to limit passage of gas.

[0010] In the above configuration, the labyrinth structure includes a projection and / or a recess disposed at an outer surface of the pin.

[0011] To achieve the above object, a second aspect of the present invention relates to a hermetic connector to be used for a vacuum pump, the hermetic connector including: a pin configured to be electrically connected; a connector base portion surrounding the pin; and a sealing portion providing a seal between the pin and the connector base portion, and the sealing portion is made of an insulating resin material.[Advantageous Effects of Invention]

[0012] According to the present invention, it is possible to limit the manufacturing cost of a hermetic connector and achieve compactness and high performance. Problems to be solved, configurations, and advantageous effects other than those described above will be recognized by the following description of embodiments.[Brief Description of Drawings]

[0013] [Fig. 1] Fig. 1 is a vertical cross-sectional view of a turbomolecular pump according to an embodiment of the present invention. [Fig. 2] Fig. 2 is a circuit diagram of an amplifier circuit of the turbomolecular pump shown in Fig. 1. [Fig. 3] Fig. 3 is a time chart showing control of an amplifier control circuit performed when a current command value is greater than a detected value. [Fig. 4] Fig. 4 is a time chart showing control of an amplifier control circuit performed when a current command value is less than a detected value. [Fig. 5] Fig. 5(a) is a front view of a hermetic connector according to the embodiment, and Fig. 5(b) is a cross-sectional view taken along line Vb-Vb. [Fig. 6] Fig. 6(a) is a front view of a hermetic connector according to a first modification, and Fig. 6(b) is a cross-sectional view taken along line VIb-VIb. [Fig. 7] Fig. 7(a) is a vertical cross-sectional view of a hermetic connector according to a second modification, and Fig. 7(b) is an enlarged view of part A. [Fig. 8] Figs. 8(a) to 8(c) are diagrams showing variations of a labyrinth structure. [Description of Embodiments]

[0014] Referring to the drawings, a vacuum pump according to the present invention is now described using a turbomolecular pump as an example.

[0015] Fig. 1 is a longitudinal cross-sectional view of the turbomolecular pump 100. As shown in Fig. 1, the turbomolecular pump 100 has a circular outer cylinder 127, which is a casing, having an inlet port 101 at its upper end. A rotating body 103 (rotor) in the outer cylinder 127 includes a plurality of rotor blades 102 (102a, 102b, 102c, ...), which are turbine blades for gas suction and exhaustion, in its outer circumference section. The rotor blades 102 extend radially in multiple stages. The rotating body 103 has a rotor shaft 113 in its center. The rotor shaft 113 is supported and suspended in the air and position-controlled by a magnetic bearing of 5-axis control, for example. The rotating body 103 is typically made of a metal such as aluminum or an aluminum alloy, or stainless steel.

[0016] Upper radial electromagnets 104 include four electromagnets arranged in pairs on an X-axis and a Y-axis. Four upper radial sensors 107 are provided in close proximity to the upper radial electromagnets 104 and associated with the respective upper radial electromagnets 104. Each upper radial sensor 107 may be an inductance sensor or an eddy current sensor having a conduction winding, for example, and detects a position of the rotor shaft 113 based on a change in the inductance of the conduction winding, which changes according to the position of the rotor shaft 113. The upper radial sensors 107 are configured to detect a radial displacement of the rotor shaft 113, that is, the rotating body 103 fixed to the rotor shaft 113, and send it to the controller 200.

[0017] In the controller 200, for example, a compensation circuit having a PID adjustment function generates an excitation control command signal for the upper radial electromagnets 104 based on a position signal detected by the upper radial sensors 107. Based on this excitation control command signal, an amplifier circuit 150 (described below) shown in Fig. 2 controls and excites the upper radial electromagnets 104 to adjust a radial position of an upper part of the rotor shaft 113.

[0018] The rotor shaft 113 may be made of a high magnetic permeability material (such as iron and stainless steel) and is configured to be attracted by magnetic forces of the upper radial electromagnets 104. The adjustment is performed independently in the X-axis direction and the Y-axis direction. Lower radial electromagnets 105 and lower radial sensors 108 are arranged in a similar manner as the upper radial electromagnets 104 and the upper radial sensors 107 to adjust the radial position of the lower part of the rotor shaft 113 in a similar manner as the radial position of the upper part.

[0019] Additionally, axial electromagnets 106A and 106B are arranged so as to vertically sandwich a metal disc 111, which has a shape of a circular disc and is provided in the lower part of the rotor shaft 113. The metal disc 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect an axial displacement of the rotor shaft 113 and send an axial position signal to the controller 200.

[0020] In the controller 200, the compensation circuit having the PID adjustment function may generate an excitation control command signal for each of the axial electromagnets 106A and 106B based on the signal on the axial position detected by the axial sensor 109. Based on these excitation control command signals, the amplifier circuit 150 controls and excites the axial electromagnets 106A and 106B separately so that the axial electromagnet 106A magnetically attracts the metal disc 111 upward and the axial electromagnet 106B attracts the metal disc 111 downward. The axial position of the rotor shaft 113 is thus adjusted.

[0021] As described above, the controller 200 appropriately adjusts the magnetic forces exerted by the axial electromagnets 106A and 106B on the metal disc 111, magnetically levitates the rotor shaft 113 in the axial direction, and suspends the rotor shaft 113 in the air in a non-contact manner. The amplifier circuit 150, which controls and excites the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B, is described below.

[0022] The motor 121 includes a plurality of magnetic poles circumferentially arranged to surround the rotor shaft 113. Each magnetic pole is controlled by the controller 200 so as to drive and rotate the rotor shaft 113 via an electromagnetic force acting between the magnetic pole and the rotor shaft 113. The motor 121 also includes a rotational speed sensor (not shown), such as a Hall element, a resolver, or an encoder, and the rotational speed of the rotor shaft 113 is detected based on a detection signal of the rotational speed sensor.

[0023] Furthermore, a phase sensor (not shown) is attached adjacent to the lower radial sensors 108 to detect the phase of rotation of the rotor shaft 113. The controller 200 detects the position of the magnetic poles using both detection signals of the phase sensor and the rotational speed sensor.

[0024] A plurality of stator blades 123 (123a, 123b, 123c, ...) are arranged slightly spaced apart from the rotor blades 102 (102a, 102b, 102c, ...). These rotor blades 102 in multiple stages and the stator blades 123 in multiple stages form a turbo pump portion. Each rotor blades 102 (102a, 102b, 102c, ...) is inclined by a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transfer exhaust gas molecules downward through collision. The stator blades 123 (123a, 123b, 123c, ...) are made of a metal such as aluminum, iron, stainless steel, copper, or a metal such as an alloy containing these metals as components.

[0025] The stator blades 123 are also inclined by a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113. The stator blades 123 extend inward of the outer cylinder 127 and alternate with the stages of the rotor blades 102. The outer circumference ends of the stator blades 123 are inserted between and thus supported by a plurality of layered stator blade spacers 125 (125a, 125b, 125c, ...).

[0026] The stator blade spacers 125 are ring-shaped members made of a metal, such as aluminum, iron, stainless steel, or copper, or an alloy containing these metals as components, for example. The outer cylinder 127 is fixed to the outer circumferences of the stator blade spacers 125 with a slight gap. A base portion 129 is located at the base of the outer cylinder 127. The base portion 129 has an outlet port 133 providing communication to the outside. The exhaust gas transferred toward the base portion 129 through the inlet port 101 from the chamber (vacuum chamber) is then sent to the outlet port 133.

[0027] According to the application of the turbomolecular pump 100, a threaded spacer 131, which functions as a thread groove pump portion, may be provided between the lower part of the stator blade spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, or iron, or an alloy containing these metals as components. The threaded spacer 131 has a plurality of helical thread grooves 131a engraved in its inner circumference surface. When exhaust gas molecules move in the rotation direction of the rotating body 103, these molecules are transferred toward the outlet port 133 in the direction of the helix of the thread grooves 131a. In the lowermost section of the rotating body 103 below the rotor blades 102 (102a, 102b, 102c, ...), a cylindrical portion 102d extends downward. The outer circumference surface of the cylindrical portion 102d is cylindrical and projects toward the inner circumference surface of the threaded spacer 131. The outer circumference surface is adjacent to but separated from the inner circumference surface of the threaded spacer 131 by a predetermined gap. The exhaust gas transferred to the thread groove 131a by the rotor blades 102 and the stator blades 123 is guided by the thread groove 131a to the base portion 129.

[0028] The base portion 129 is a disc-shaped member forming the base section of the turbomolecular pump 100, and is generally made of a metal such as iron, aluminum, or stainless steel. The base portion 129 physically holds the turbomolecular pump 100 and also serves as a heat conduction passage. As such, the base portion 129 is preferably made of rigid metal with high thermal conductivity, such as iron, aluminum, or copper. A hermetic connector 10 is provided at a side portion of the base portion 129. The controller 200 is connected through this hermetic connector 10. Details of the hermetic connector 10 will be described below.

[0029] In this configuration, when the motor 121 drives and rotates the rotor blades 102 together with the rotor shaft 113, the interaction between the rotor blades 102 and the stator blades 123 causes the suction of exhaust gas from the chamber through the inlet port 101. The rotational speed of the rotor blades 102 is usually 20000 rpm to 90000 rpm, and the circumferential speed at the tip of a rotor blades 102 reaches 200 m / s to 400 m / s. The exhaust gas taken through the inlet port 101 moves between the rotor blades 102 and the stator blades 123 and is transferred to the base portion 129. At this time, factors such as the friction heat generated when the exhaust gas comes into contact with the rotor blades 102 and the conduction of heat generated by the motor 121 increase the temperature of the rotor blades 102. This heat is conducted to the stator blades 123 through radiation or conduction via gas molecules of the exhaust gas, for example.

[0030] The stator blade spacers 125 are joined to each other at the outer circumference portion and conduct the heat received by the stator blades 123 from the rotor blades 102, the friction heat generated when the exhaust gas comes into contact with the stator blades 123, and the like to the outside.

[0031] In the above description, the threaded spacer 131 is provided at the outer circumference of the cylindrical portion 102d of the rotating body 103, and the thread grooves 131a are engraved in the inner circumference surface of the threaded spacer 131. However, conversely, thread grooves may be engraved in the outer circumference surface of the cylindrical portion 102d, while a spacer having a cylindrical inner circumference surface may be arranged around the outer circumference surface.

[0032] According to the application of the turbomolecular pump 100, to prevent the gas drawn through the inlet port 101 from entering an electrical portion, which includes the upper radial electromagnets 104, the upper radial sensors 107, the motor 121, the lower radial electromagnets 105, the lower radial sensors 108, the axial electromagnets 106A, 106B, and the axial sensor 109, the electrical portion may be surrounded by a stator column 122. The inside of the stator column 122 may be maintained at a predetermined pressure by purge gas.

[0033] In this case, the base portion 129 has a pipe (not shown) through which the purge gas is introduced. The introduced purge gas is sent to the outlet port 133 through gaps between a protective bearing 120 and the rotor shaft 113, between the rotor and the stator of the motor 121, and between the stator column 122 and the inner circumference cylindrical portion of the rotor blades 102. As shown in Fig. 1, the stator column 122 stands at the central position of the base portion 129. The present embodiment also has a water-cooled tube 149 serving as a cooling means in the base portion 129. Cooling water is supplied to this water-cooled tube 149, maintaining the base portion 129 and the stator column 122 at a suitable temperature.

[0034] The turbomolecular pump 100 requires the identification of the model and control based on individually adjusted unique parameters (for example, various characteristics associated with the model). To store these control parameters, the turbomolecular pump 100 includes an electronic circuit portion 141 in its main body. The electronic circuit portion 141 may include a semiconductor memory, such as an EEPROM, electronic components such as semiconductor elements for accessing the semiconductor memory, and a substrate 143 for mounting these components. The electronic circuit portion 141 is housed under a rotational speed sensor (not shown) near the center, for example, of the base portion 129, which forms the lower part of the turbomolecular pump 100, and is closed by an airtight bottom lid 145.

[0035] Some process gas introduced into the chamber in the manufacturing process of semiconductors has the property of becoming solid when its pressure becomes higher than a predetermined value or its temperature becomes lower than a predetermined value. In the turbomolecular pump 100, the pressure of the exhaust gas is lowest at the inlet port 101 and highest at the outlet port 133. When the pressure of the process gas increases beyond a predetermined value or its temperature decreases below a predetermined value while the process gas is being transferred from the inlet port 101 to the outlet port 133, the process gas is solidified and adheres and accumulates on the inner side of the turbomolecular pump 100.

[0036] For example, when SiCl4 is used as the process gas in an Al etching apparatus, according to the vapor pressure curve, a solid product (for example, AlCl3) is deposited at a low vacuum (760 [torr] to 10-2 [torr]) and a low temperature (about 20 [°C]) and adheres and accumulates on the inner side of the turbomolecular pump 100. When the deposits of the process gas accumulate in the turbomolecular pump 100, the accumulation may narrow the pump flow passage and degrade the performance of the turbomolecular pump 100. The above-mentioned product tends to solidify and adhere in areas with higher pressures, such as the vicinity of the outlet port 133 and the vicinity of the threaded spacer 131.

[0037] To solve this problem, conventionally, a heater or annular water-cooled tube 149 (not shown) is wound around the outer circumference of the base portion 129, and a temperature sensor (e.g., a thermistor, not shown) is embedded in the base portion 129, for example. The signal of this temperature sensor is used to perform control to maintain the temperature of the base portion 129 at a constant high temperature (set temperature) by heating with the heater or cooling with the water-cooled tube 149 (hereinafter referred to as TMS (temperature management system)).

[0038] The amplifier circuit 150 is now described that controls and excites the upper radial electromagnets 104, the lower radial electromagnets 105, and the axial electromagnets 106A and 106B of the turbomolecular pump 100 configured as described above. Fig. 2 is a circuit diagram of the amplifier circuit 150.

[0039] In Fig. 2, one end of an electromagnet winding 151 forming an upper radial electromagnet 104 or the like is connected to a positive electrode 171a of a power supply 171 via a transistor 161, and the other end is connected to a negative electrode 171b of the power supply 171 via a current detection circuit 181 and a transistor 162. Each transistor 161, 162 is a power MOSFET and has a structure in which a diode is connected between the source and the drain thereof.

[0040] In the transistor 161, a cathode terminal 161a of its diode is connected to the positive electrode 171a, and an anode terminal 161b is connected to one end of the electromagnet winding 151. In the transistor 162, a cathode terminal 162a of its diode is connected to a current detection circuit 181, and an anode terminal 162b is connected to the negative electrode 171b.

[0041] A diode 165 for current regeneration has a cathode terminal 165a connected to one end of the electromagnet winding 151 and an anode terminal 165b connected to the negative electrode 171b. Similarly, a diode 166 for current regeneration has a cathode terminal 166a connected to the positive electrode 171a and an anode terminal 166b connected to the other end of the electromagnet winding 151 via the current detection circuit 181. The current detection circuit 181 may include a Hall current sensor or an electric resistance element, for example.

[0042] The amplifier circuit 150 configured as described above corresponds to one electromagnet. Accordingly, when the magnetic bearing uses 5-axis control and has ten electromagnets 104, 105, 106A, and 106B in total, an identical amplifier circuit 150 is configured for each of the electromagnets. These ten amplifier circuits 150 are connected to the power supply 171 in parallel.

[0043] An amplifier control circuit 191 may be formed by a digital signal processor portion (not shown, hereinafter referred to as a DSP portion) of the controller 200. The amplifier control circuit 191 switches the transistors 161 and 162 between on and off.

[0044] The amplifier control circuit 191 is configured to compare a current value detected by the current detection circuit 181 (a signal reflecting this current value is referred to as a current detection signal 191c) with a predetermined current command value. The result of this comparison is used to determine the magnitude of the pulse width (pulse width time Tp1, Tp2) generated in a control cycle Ts, which is one cycle in PWM control. As a result, gate drive signals 191a and 191b having this pulse width are output from the amplifier control circuit 191 to gate terminals of the transistors 161 and 162.

[0045] Under certain circumstances such as when the rotational speed of the rotating body 103 reaches a resonance point during acceleration, or when a disturbance occurs during a constant speed operation, the rotating body 103 may require positional control at high speed and with a strong force. For this purpose, a voltage of about 50 V, for example, is used for the power supply 171 to enable a rapid increase (or decrease) in the current flowing through the electromagnet winding 151. Additionally, a capacitor is generally connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 to stabilize the power supply 171 (not shown).

[0046] In this configuration, when both transistors 161 and 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as an electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

[0047] Also, when one of the transistors 161 and 162 is turned on and the other is turned off, a freewheeling current is maintained. Passing the freewheeling current through the amplifier circuit 150 in this manner reduces the hysteresis loss in the amplifier circuit 150, thereby limiting the power consumption of the entire circuit to a low level. Moreover, by controlling the transistors 161 and 162 as described above, high frequency noise, such as harmonics, generated in the turbomolecular pump 100 can be reduced. Furthermore, by measuring this freewheeling current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0048] That is, when the detected current value is smaller than the current command value, as shown in Fig. 3, the transistors 161 and 162 are simultaneously on only once in the control cycle Ts (for example, 100 µs) for the time corresponding to pulse width time Tp1. During this time, the electromagnet current iL increases accordingly toward the current value iLmax (not shown) that can be passed from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[0049] When the detected current value is larger than the current command value, as shown in Fig. 4, the transistors 161 and 162 are simultaneously off only once in the control cycle Ts for the time corresponding to pulse width time Tp2. During this time, the electromagnet current iL decreases accordingly toward the current value iLmin (not shown) that can be regenerated from the negative electrode 171b to the positive electrode 171a via the diodes 165 and 166.

[0050] In either case, after pulse width time Tp1, Tp2 has elapsed, one of the transistors 161 and 162 is on. During this period, the freewheeling current is thus maintained in the amplifier circuit 150.<Hermetic Connector Structure>

[0051] The structure of the hermetic connector 10 used for the turbomolecular pump 100 is now described in detail. Fig. 5(a) is a front view of the hermetic connector 10. Fig. 5(b) is a cross-sectional view taken along line Vb-Vb in Fig. 5(a).

[0052] As shown in Figs. 5(a) and 5(b), the hermetic connector 10 according to the present embodiment includes multiple small-diameter pins 11 and large-diameter pins 12, which are configured to be electrically connected, a connector base portion 13, which has the shape of a laterally elongate rectangular frame and surrounds the multiple pins 11 and 12, and a sealing portion 14, which provides a seal between the multiple pines 11 and 12 and the connector base portion 13.

[0053] In this embodiment, the small-diameter pins 11 and the large-diameter pins 12 each have the shape of an elongate circular cylinder, but there is no limitation on their shape. For example, the pins 11 and 12 may have the shape of a circular cylinder with a step formed by circular cylinders of different diameters that are arranged coaxially and integrated to each other, or may be formed to have the shape of a prism.

[0054] The connector base portion 13 is made of a metal material such as stainless steel. The connector base portion 13 has a laterally elongate opening 13a in the center and holes 18 for bolting to the base portion 129 of the turbomolecular pump 100 at the four corners. The aspect ratio of the connector base portion 13 may be about 1:1.5 to 1:2, for example. Also, although the connector base portion 13 is formed in a plate shape, the shape is not limited to this. Any shape of connector base portion may be adopted.

[0055] The sealing portion 14 is made of an insulating resin material. Examples of the resin materials that may be used include polyamide / nylon (PA), polyphenylene ether (PPE), polyphenylene sulfide (PPS), and polybutylene terephthalate (PBT). As indicated by the hatch lines in Fig. 5(a), the space between the connector base portion 13 and the multiple pins 11 and 12 is filled with the sealing portion 14, and the connector base portion 13 and the pins 11 and 12 are formed integrally by means of the sealing portion 14. For example, the pins 11 and 12 may be formed in the sealing portion 14 through insert molding.

[0056] The advantageous effects of the present embodiment configured in this manner are now described.

[0057] Since the sealing portion 14 is made of an insulating resin material, the manufacturing process is simplified and the manufacturing cost of the hermetic connector 10 can be reduced as compared to a conventional structure filled with a glass material. Also, the hermetic connector 10 used for the turbomolecular pump 100 needs to accommodate a large number of wires for the power lines of the motor and electromagnets, sensors, and the like, and thus needs a large number of pins 11 and 12. Additionally, a high level of leak rate performance (sealing performance) is also needed. In the present embodiment, the connector base portion 13 and the pins 11 and 12 are formed integrally by means of the sealing portion 14, which is made of a resin material, thereby achieving a high level of leak rate performance.

[0058] Moreover, the connector base portion 13 is made of a metal material, allowing an O-ring to reliably provide a seal between the connector base portion 13 and the base portion 129 of the turbomolecular pump 100. As such, the hermetic connector 10 according to this embodiment is suitable for the turbomolecular pump 100. Additionally, the connector base portion 13 has a laterally elongate configuration, allowing the dimension in the axial direction (height direction) of the turbomolecular pump 100 to be small.

[0059] As described above, according to the present embodiment, a compact, high-quality hermetic connector 10 with high accuracy and a low leak rate can be achieved at a low cost. Also, incorporating the high-performance hermetic connector 10 into the turbomolecular pump 100 can prevent degradation in the exhaust performance of the turbomolecular pump 100.(First Modification)

[0060] The structure of a hermetic connector 20 according to a first modification is now described. Fig. 6(a) is a front view of the hermetic connector 20. Fig. 6(b) is a cross-sectional view taken along line VIb-VIb in Fig. 6(a).

[0061] As shown in Figs. 6(a) and 6(b), the hermetic connector 20 according to the first modification includes multiple small-diameter pins 21 and large-diameter pins 22, which are configured to be electrically connected, a connector base portion 23, which surrounds the multiple pins 21 and 22 and has the shape of a circular frame, and first sealing portions 25 and a second sealing portion 26, which provide a seal between the multiple pins 21 and 22 and the connector base portion 23.

[0062] The connector base portion 23 is made of a metal material such as stainless steel. The connector base portion 23 has a circular opening 23a in the center and holes 28 for bolting to the base portion 129 of the turbomolecular pump 100 at the four corners.

[0063] The first sealing portions 25 cover the outer surfaces (outer circumference surfaces) of the pins 21 and 22. The first sealing portions 25 are formed as cylinders conforming to the outer shapes of the pins 21 and 22. The second sealing portion 26 provides a seal between the first sealing portions 25 and the connector base portion 23. That is, the second sealing portion 26 provides a seal between the multiple pins 21 and 22, which are covered with the first sealing portions 25, and the connector base portion 23.

[0064] The first sealing portions 25 and the second sealing portion 26 are all made of insulating resin materials. Examples of the resin materials that may be used include polyamide / nylon (PA), polyphenylene ether (PPE), polyphenylene sulfide (PPS), and polybutylene terephthalate (PBT). However, the linear expansion coefficient α1 of the resin material (first resin material) of the first sealing portions 25 is greater than or equal to the linear expansion coefficient α2 of the resin material (second resin material) of the second sealing portion 26 (α1 ≥ α2).

[0065] The hermetic connector 20 according to the first modification has the same advantageous effects as the hermetic connector 10 according to the above-described embodiment. Additionally, since the linear expansion coefficient α1 of the first sealing portion 25 is greater than or equal to the linear expansion coefficient α2 of the second sealing portion 26, it is possible to maintain the airtightness even when a difference in thermal deformation arises between the connector base portion 23, which is made of a metal material, and the first sealing portions 25 and the second sealing portion 26, which are made of resin materials. In particular, the ambient temperature of the hermetic connector 20 increases during operation of the turbomolecular pump 100, resulting in a noticeable difference in thermal deformation between the connector base portion 23 and the first and second sealing portions 25 and 26. However, the use of two types of resin materials with different linear expansion coefficients can reduce the above difference in thermal deformation. Additionally, the linear expansion coefficients satisfy the relationship of α1 ≥ α2, preventing formation of gaps around the pins 21 and 22.

[0066] In the first modification, the first sealing portions 25 and the second sealing portion 26 may be made of the same resin material. In this case, the first sealing portions 25 and the second sealing portion 26 substitute the sealing portion 14 according to the embodiment described above. In other words, the first sealing portions 25 and the second sealing portion 26 are manufactured as separate members, and then eventually integrated to function as the sealing portion 14. This configuration still has the same advantageous effects as the above-described above embodiment.(Second Modification)

[0067] The structure of a hermetic connector 30 according to a second modification is now described. The hermetic connector 30 according to the second modification has the same basic configuration as the hermetic connector 10 shown in Figs. 5(a) and 5(b) but differs in that a labyrinth structure 31, which will be described below, is provided. The same reference numerals are given to the configurations of the hermetic connector 30 that are same as the corresponding configurations of the hermetic connector 10. Such configurations will not be described in detail.

[0068] Fig. 7(a) is a vertical cross-sectional view of the hermetic connector 30 according to the second modification. Fig. 7(b) is an enlarged view of part A in Fig. 7(a). The small-diameter pins 11 are not shown in Fig. 7(a). As shown in Figs. 7(a) and 7(b), the hermetic connector 30 according to the second modification includes a labyrinth structure 31. The labyrinth structure 31 includes projections 32 provided on a large-diameter pin 12 and recesses 33 provided in the sealing portion 14. More specifically, the large-diameter pin 12 has multiple projections 35 radially extending from its outer surface. The multiple projections 35 are provided at intervals in the axial direction of the large-diameter pin 12. Each projection 35 is formed in a disc shape (flange) projecting from the outer circumference surface of the large-diameter pin 12.

[0069] At the same time, since the sealing portion 14 is made of a resin material filling the space between the connector base portion 13 and the large-diameter pin 12, the recesses 36 conforming to the shapes of the projections 35 are formed. In a normal state, since the projections 35 and the recesses 36 are in close contact, the sealing performance is ensured. Each small-diameter pin 11 may also be provided with a labyrinth structure 31.

[0070] Since the ambient temperature of the hermetic connector 10 increases during operation of the turbomolecular pump 100, the difference in linear expansion coefficient may create a gap between the large-diameter pin 12 and the sealing portion 14. However, the second modification, in which the large-diameter pin 12 has the labyrinth structure 31, can limit passage of the air through a gap between the large-diameter pin 12 and the sealing portion 14. Accordingly, degradation in the leak rate performance of the hermetic connector 10 can be prevented, thereby maintaining the satisfactory exhaust performance of the turbomolecular pump 100. The labyrinth structure also has the advantage of preventing the large-diameter pin 12 from being pulled out.

[0071] Variations of the labyrinth structure are now described. Figs. 8(a), 8(b), and 8(c) are diagrams showing variations of the labyrinth structure.

[0072] A labyrinth structure 41 shown in Fig. 8(a) includes projections 42 that are bent into hooks. Accordingly, the recesses 43 formed in the sealing portion 14 have bent shapes conforming to the projections 42. This configuration still limits passage of the air through a gap between the large-diameter pin 12 and the sealing portion 14.

[0073] A labyrinth structure 51 shown in Fig. 8(b) includes a textured portion 52 in the surface of large-diameter pin 12 formed by knurling, sandblasting, or the like, and a textured portion 53 formed conforming to the textured portion 52. This configuration still limits passage of the air through a gap between the large-diameter pin 12 and the sealing portion 14.

[0074] A labyrinth structure 61 shown in Fig. 8(c) includes recesses 62 formed in the large-diameter pin 12 and projections 63 formed in the sealing portion 14 conforming to these recesses 62. This configuration still limits passage of the air through a gap between the large-diameter pin 12 and the sealing portion 14.

[0075] Providing a labyrinth structure between the large-diameter pin 12 and the sealing portion 14 as described above can stop gas from easily passing through any gap created between the large-diameter pin 12 and the sealing portion 14. In other words, any structure that makes it difficult for gas to pass through a gap between the large-diameter pin 12 and the sealing portion 14 can be adopted as the labyrinth structure of the present invention.

[0076] Although Figs. 7 and 8 illustrate the sealing portions 14 made of a resin material, the labyrinth structures 31, 41, 51, and 61 may also be adopted for a conventional sealing portion made of a glass material. That is, the labyrinth structure can be applied to any hermetic connector at a location between a pin and the sealing portion. By providing the labyrinth structure, even when a gap is formed between the pin and the sealing portion, it is possible to limit passage of gas through the gap, thereby preventing degradation in the leak rate performance of the hermetic connector 10. Furthermore, it is possible to prevent degradation in the exhaust performance of the turbomolecular pump.

[0077] In the present invention, the relationship between the internal pressure of the turbomolecular pump 100 and the external pressure determines the gas passing through the hermetic connector 10. When the internal pressure is higher than the external pressure, the exhaust gas present in turbomolecular pump 100 may pass through the hermetic connector 10 to the outside. In this case, the gas passing through the hermetic connector 10 is the exhaust gas present inside the turbomolecular pump 100. When the internal pressure is lower than the external pressure, the gas passing through the hermetic connector 10 is external gas (such as the air). The labyrinth structures 31, 41, 51, and 61 of the hermetic connector 10 can limit passage of gas regardless of the relationship between the internal pressure and the external pressure.

[0078] The present invention is not limited to the embodiment described above, and various modifications can be made without departing from the scope of the present invention. The present invention encompasses all technical matters included in the technical idea described in the claims. Although the foregoing embodiment illustrates preferred examples, other alternation, variations, modifications, and combinations, or improvements will be apparent to those skilled in the art from the content disclosed herein, and may be made without departing from the technical scope defined by the appended claims.

[0079] For example, the shape of the connector base portion of the hermetic connector is not limited to the shape of a laterally elongate rectangular frame and the shape of a circular frame described above. Any shape of connector base portion may be adopted. Also, the shape of the connector base portion may be a box shape instead of a frame shape.[Reference Signs List]

[0080] 10, 20, 30Hermetic connector 11, 21 Small-diameter pin (pin) 12, 22 Large-diameter pin (pin) 13, 23 Connector base portion 13a, 23a Opening 14 Sealing portion 18, 28 Hole 25 First sealing portion 26 Second sealing portion 31, 41, 51, 61 Labyrinth structure 32, 42, 62Projection 33, 43, 63Recess 52, 53 Textured portion 100 Turbomolecular pump (vacuum pump)

Claims

1. A vacuum pump comprising a hermetic connector, wherein the hermetic connector includes: a pin configured to be electrically connected; a connector base portion surrounding the pin; and a sealing portion providing a seal between the pin and the connector base portion, and the sealing portion is made of an insulating resin material.

2. The vacuum pump according to claim 1, wherein the sealing portion includes: a first sealing portion covering an outer surface of the pin; and a second sealing portion providing a seal between the first sealing portion and the connector base portion, the connector base portion is made of a metal material, the first sealing portion is made of a first resin material, and the second sealing portion is made of a second resin material.

3. The vacuum pump according to claim 2, wherein a linear expansion coefficient of the first resin material is greater than or equal to a linear expansion coefficient of the second resin material.

4. The vacuum pump according to claim 1, wherein the hermetic connector further includes a labyrinth structure that is disposed between the pin and the sealing portion to limit passage of gas.

5. The vacuum pump according to claim 4, wherein the labyrinth structure includes a projection and / or a recess disposed at an outer surface of the pin.

6. A hermetic connector to be used for a vacuum pump, the hermetic connector comprising: a pin configured to be electrically connected; a connector base portion surrounding the pin; and a sealing portion providing a seal between the pin and the connector base portion, wherein the sealing portion is made of an insulating resin material.

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