Vacuum pump and fixing part

Abstract

The invention provides a vacuum pump and a fixing component, which can inhibit the generation of air holes and shrinkage cavities at thick wall parts of the fixing component formed by casting and can promote heat movement in the fixing component. A vacuum pump (210) is provided with: a housing (211); a rotor shaft (113) which is surrounded by the outer housing and is rotatably supported; a rotor (103) fixed to the rotor shaft (113) and rotating together with the rotor shaft (113); and a ring-shaped fixing member that exhausts the sucked gas in cooperation with the rotor (103). The fixing member is formed by casting and has: a first portion (246) and a second portion (245) which face each other with at least one reduction groove (255) extending in the circumferential direction of the fixing member and which reduces the volume therebetween; a bottom part (258) which is disposed so as to include at least the bottom of the reduction groove (255) and which connects the first portion (246) and the second portion (245); the fixing component is provided with a heat conduction improving structure (256) which improves heat conduction between the first part (246) and the second part (245).

Description

Technical Field

[0001] The invention relates to a vacuum pump and a fixing part. Background Art

[0002] Semiconductor manufacturing equipment, liquid crystal manufacturing equipment, electron microscopes, surface analysis equipment, or micro-processing equipment require that the environment inside the equipment be in a highly vacuum state. A vacuum pump is used to make the interior of these equipment highly vacuumed. As an example of a vacuum pump used, for example, a compound pump that combines a turbomolecular pump with a thread groove pump can be cited.

[0003] A vacuum pump combining a turbomolecular pump and a thread groove pump is, for example, as disclosed in Patent Document 1, in which a thread groove pump is arranged on the downstream side of a turbopump having rotating blades and stationary blades alternately arranged in the axial direction. Exhaust gas taken in from the air intake port is compressed by the turbomolecular pump and the thread groove pump and discharged from the exhaust port to the outside of the vacuum pump.

[0004] The thread groove pump is composed of a rotating rotor cylinder and a thread groove spacer on the housing side that accommodates the rotor. Thread grooves are formed on the opposite surfaces of the rotor cylinder or the thread groove spacer. Therefore, the gas can be transferred to the exhaust port side by the rotation of the rotor cylinder inside the thread groove spacer.

[0005] The exhaust gas exhibits the dynamics of molecular flow in the turbomolecular pump, but in the thread groove pump and the flow path downstream thereof, the pressure becomes relatively high, and the dynamics are similar to viscous flow. Therefore, by-products are easily precipitated in the flow of the thread groove pump and the flow path downstream thereof where the exhaust gas flows and settles. If the by-products precipitate in the flow path, the parts that are not in contact originally come into contact, which may damage the vacuum pump and cause the temperature distribution to change with the change of the thermal conductivity of the internal structure, thereby compromising safety and productivity.

[0006] Therefore, in the vacuum pump, the fixing parts (thread groove spacers) on the stator side of the thread groove pump that cooperate with the rotor are heated by other contacting members and maintained at a predetermined high temperature, thereby suppressing the generation of deposits.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2020-197152 Summary of the invention

[0010] Technical problem to be solved by the invention

[0011] The stationary parts that exhaust the sucked gas in cooperation with the rotor may have thick-walled parts for the purpose of improving the thermal conductivity of the heat path, promoting heat transfer, etc. However, if the stationary parts are formed by casting, which can be manufactured quickly and cheaply, there will be a difference in the speed of metal solidification between the thick-walled parts and the thin-walled parts of the stationary parts, and pores and shrinkage cavities (a type of pores) are likely to occur in the stationary parts.

[0012] The present invention is made to solve the above-mentioned technical problems, and its object is to provide a vacuum pump and a fixing part that can suppress the occurrence of pores and shrinkage holes in the thick-walled parts of the fixing part formed by casting and promote heat transfer in the fixing part.

[0013] Means for solving technical problems

[0014] The above object is achieved by the invention described in the following (1).

[0015] (1) The vacuum pump according to the present invention is characterized in that it comprises: an outer casing; a rotor shaft, which is enclosed by the outer casing and supported to rotate freely; a rotor, which is fixed to the rotor shaft and rotates together with the rotor shaft; and an annular fixing part, which cooperates with the rotor to exhaust the sucked gas; the fixing part is at least partially formed by casting and comprises: a first portion and a second portion, which are arranged with at least one reduction groove extending along the circumference of the fixing part to reduce the volume; and a bottom portion, which is arranged to include at least the bottom of the reduction groove and connect the first portion and the second portion; the fixing part has a heat conduction improving structure that is different from the bottom portion and improves the heat conduction between the first portion and the second portion.

[0016] Effects of the Invention

[0017] The vacuum pump described in (1) above can make the metal solidification rate during casting uniform and suppress the occurrence of pores and shrinkage holes by arranging reduction grooves in the thick-walled parts of the fixed parts formed by casting, and can also promote heat transfer between the first part and the second part that may be reduced by having the reduction grooves by means of a heat conductivity improvement structure.

[0018] (2) In the vacuum pump described in (1) above, the heat conduction improving structure may be a bridge structure connecting the first portion and the second portion that are opposite to each other with the reduction groove sandwiched therebetween. Thus, the vacuum pump effectively promotes heat transfer between the first portion and the second portion by means of the bridge structure while maintaining the effect of suppressing the occurrence of pores and shrinkage cavities brought about by the reduction groove.

[0019] (3) In the vacuum pump described in (1) or (2) above, the heat conductivity enhancing structure may be formed of a material having a higher thermal conductivity than the material of the cast portion of the fixing part. Thus, the vacuum pump can effectively promote heat transfer between the first portion and the second portion.

[0020] (4) In the vacuum pump described in any one of (1) to (3) above, the first portion and the second portion may be arranged so as to sandwich the reduction groove in the radial direction from the center of the annular fixing part. Thus, the vacuum pump can effectively transfer the heat to the radial inside via the heat conduction enhancement structure by supplying heat from the radial outside of the fixing part.

[0021] (5) In the vacuum pump described in any one of (1) to (4), the fixing part may be a part constituting the thread groove pump portion. Thus, the vacuum pump can heat the thread groove vicinity of the thread groove pump where gas is easily accumulated due to low temperature, thereby suppressing the occurrence of accumulation, while making the fixing part a casting.

[0022] (6) In the vacuum pump described in any one of (1) to (5), the fixing part may be formed as the thread groove pump part, including: a spiral groove having a spiral ridge and a spiral valley; and a threaded groove having a threaded ridge and a threaded valley. Thus, the vacuum pump can heat the spiral groove and the vicinity of the threaded groove where deposits are likely to form due to low temperatures, thereby suppressing the formation of deposits, by providing a heat conduction improving structure in the fixing part.

[0023] (7) In the vacuum pump described in any one of (1) to (6), the aforementioned reduction groove may be located on the surface of the aforementioned fixed part opposite to the surface on which the aforementioned thread groove pump portion is formed. Thus, the vacuum pump can effectively maintain the desired heat transfer to the thread groove pump portion for suppressing deposits while forming the reduction groove near the thick-walled thread groove pump portion of the fixed part.

[0024] (8) The fixing part of the present invention is a fixing part that cooperates with a rotatable rotor of a vacuum pump to exhaust the sucked gas, and is characterized in that at least a part is formed by casting, and has: a first portion and a second portion, at least one reduction groove extending along the circumferential direction of the fixing part is arranged to reduce the volume; and a bottom portion, which is arranged to include at least the bottom of the reduction groove and connect the first portion and the second portion; and a heat conduction improving structure that is different from the bottom portion and improves the heat conduction between the first portion and the second portion. Thus, by arranging the reduction groove in the thick-walled portion of the fixing part, the speed of metal solidification during casting can be made uniform to suppress the occurrence of pores and shrinkage cavities, and the heat transfer between the first portion and the second portion, which may be reduced by having the reduction groove, can be promoted by the heat conduction improving structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a longitudinal sectional view of the vacuum pump.

[0026] Figure 2 It is the circuit diagram of the amplifier circuit.

[0027] Figure 3 This is a timing chart showing control when the current command value is larger than the detected value.

[0028] Figure 4 This is a timing chart showing control when the current command value is smaller than the detected value.

[0029] Figure 5 It is a longitudinal sectional view of the vacuum pump according to the present embodiment.

[0030] Figure 6 This is a cross-sectional view showing a part of the thread groove spacer in an enlarged manner. (A) is Figure 5 A is an enlarged cross-sectional view of the range indicated by (B) Figure 6 (A) Magnified cross-sectional views of different phases.

[0031] Figure 7 It is a perspective view showing a thread groove spacer.

[0032] Figure 8 This is a plan view of the thread groove spacer viewed from the upstream side.

[0033] Fig. 9 This is a plan view of the thread groove spacer viewed from the downstream side.

[0034] Fig.10 It is along Figure 8 Cross-sectional view of line B-B

[0035] Fig.11 It is a longitudinal sectional view showing a part of a vacuum pump according to a modified example. DETAILED DESCRIPTION

[0036] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the dimensions of the accompanying drawings are exaggerated for the sake of convenience of description and may differ from the actual dimensions. In addition, in this specification and the accompanying drawings, for components having substantially the same functional structure, repeated descriptions are omitted by assigning the same reference numerals.

[0037] The vacuum pump 100 according to the embodiment of the present invention is a turbomolecular pump 100 that exhausts gas by ejecting gas molecules with the rotating blades of a rotating body rotating at high speed. The turbomolecular pump 100 is used, for example, to suck and exhaust gas from a chamber of a semiconductor manufacturing device. First, the basic structure of the turbomolecular pump 100 is described.

[0038] exist Figure 1 2 shows a longitudinal cross-sectional view of the turbomolecular pump 100. Figure 1 In the embodiment, the turbomolecular pump 100 has an air intake port 101 formed at the upper end of a cylindrical outer cylinder 127. Furthermore, a rotor 103 is provided inside the outer cylinder 127, which has a plurality of rotating blades 102 (102a, 102b, 102c...) formed radially and in multiple stages on the periphery as turbine blades for sucking and exhausting gas. A rotor shaft 113 is mounted at the center of the rotor 103, and the rotor shaft 113 is suspended and supported in the air by, for example, a 5-axis controlled magnetic bearing and position controlled. The rotor 103 is generally made of metal such as aluminum or aluminum alloy.

[0039] The upper radial electromagnet 104 has four electromagnets arranged in pairs on the X-axis and the Y-axis. Four upper radial sensors 107 are provided close to the upper radial electromagnet 104 and respectively corresponding to the upper radial electromagnet 104. The upper radial sensor 107 uses, for example, an inductance sensor or an eddy current sensor having a conductive coil, and detects the position of the rotor shaft 113 based on the change in the inductance of the conductive coil that changes according to the position of the rotor shaft 113. The upper radial sensor 107 is configured to detect the radial displacement of the rotor shaft 113, that is, the rotor 103 fixed thereto, and transmit it to the control device 200.

[0040] 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. Figure 2 The amplifier circuit 150 (described later) shown adjusts the upper radial position of the rotor shaft 113 by performing excitation control on the upper radial electromagnet 104 based on the excitation control command signal.

[0041] The rotor shaft 113 is formed of a high magnetic permeability material (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnet 104. The 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 the radial position of the lower side of the rotor shaft 113 is adjusted in the same manner as the radial position of the upper side.

[0042] Furthermore, the axial electromagnets 106A and 106B are arranged to sandwich a disc-shaped metal disk 111 provided at the lower part of the rotor shaft 113. The metal disk 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and is configured to send its axial position signal to the control device 200.

[0043] Moreover, in the control device 200, for example, a compensation circuit with a PID adjustment function generates respective excitation control command signals for the axial electromagnet 106A and the axial electromagnet 106B based on the axial position signal detected by the axial sensor 109. The amplification circuit 150 performs excitation control on the axial electromagnet 106A and the axial electromagnet 106B based on these excitation control command signals. 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.

[0044] In this way, the control device 200 appropriately adjusts the magnetic force of the axial electromagnets 106A and 106B acting on the metal disk 111, so that the rotor shaft 113 is magnetically suspended in the axial direction and is held in space without contact. In addition, the amplifier circuit 150 for controlling the excitation of these upper radial electromagnets 104, lower radial electromagnets 105, and axial electromagnets 106A and 106B will be described later.

[0045] On the other hand, the motor 121 has a plurality of magnetic poles arranged in a circumferential shape so as to surround the rotor shaft 113. Each magnetic pole is controlled by the control device 200 so as to drive the rotor shaft 113 to rotate via electromagnetic force acting between the magnetic poles and the rotor shaft 113. In addition, a rotation speed sensor such as a Hall element, an analyzer, an encoder, etc. (not shown) is installed in the motor 121, and the rotation speed of the rotor shaft 113 is detected by the detection signal of the rotation speed sensor.

[0046] Furthermore, for example, a phase sensor (not shown) is mounted near the lower radial sensor 108 to detect the rotation phase of the rotor shaft 113. The control device 200 detects the position of the magnetic pole using detection signals of the phase sensor and the rotation speed sensor.

[0047] A plurality of fixed blades 123 (123a, 123b, 123c...) are provided with a slight gap from the rotating blades 102 (102a, 102b, 102c...). The rotating blades 102 (102a, 102b, 102c...) are formed to be inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, because they transfer the molecules of the exhaust gas downward by collision. The fixed blades 123 (123a, 123b, 123c...) are made of metals such as aluminum, iron, stainless steel, copper, etc., or alloys containing these metals as components.

[0048] In addition, the fixed blades 123 are also formed to be inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged to be staggered with respect to the segments of the rotating blades 102 toward the inner side of the outer cylinder 127. The outer peripheral ends of the fixed blades 123 are supported in a state of being inserted between a plurality of stacked fixed blade spacers 125 (125a, 125b, 125c, ...).

[0049] The fixed blade spacer 125 is an annular member, and is made of a 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 blade spacer 125 with a slight gap. A base portion 129 is provided at the bottom of the outer cylinder 127. An exhaust port 133 is formed at the base portion 129, and is connected to the outside. The exhaust gas that enters the air intake port 101 from the chamber (vacuum chamber) side and is transferred to the base portion 129 is transported to the exhaust port 133.

[0050] Furthermore, according to the purpose of the turbomolecular pump 100, a thread groove spacer 131 (fixed component) is provided between the lower part of the fixed blade spacer 125 and the base part 129. The thread groove spacer 131 is a cylindrical component made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals as components, and a plurality of spiral thread grooves 131a are engraved on its inner circumference. The spiral direction of the thread groove 131a is the direction in which the molecules of the exhaust gas are transferred to the exhaust port 133 side when the molecules move in the rotation direction of the rotor 103. A cylindrical part 102d is vertically provided at the lowermost part of the rotor 103 that is continuous with the rotating blades 102 (102a, 102b, 102c, ...). The outer circumference of the cylindrical part 102d is cylindrical, and extends toward the inner circumference of the thread groove spacer 131, and is close to the inner circumference of the thread groove spacer 131 with a predetermined gap. The exhaust gas transferred to the thread groove 131 a by the rotary blade 102 and the fixed blade 123 is sent to the base portion 129 while being guided by the thread groove 131 a.

[0051] The base 129 is a disc-shaped member constituting the base of the turbomolecular pump 100, and is generally made of metal such as iron, aluminum, stainless steel, etc. Since the base 129 physically holds the turbomolecular pump 100 and also has the function of a heat conduction path, it is preferably made of a metal such as iron, aluminum, copper, etc. that has rigidity and high thermal conductivity.

[0052] In this structure, if the rotating blade 102 is driven to rotate together with the rotor shaft 113 by the motor 121, the exhaust gas is sucked from the chamber through the air inlet 101 by the action of the rotating blade 102 and the fixed blade 123. The rotation speed of the rotating blade 102 is usually 20000rpm to 90000rpm, and the circumferential speed at the front end of the rotating blade 102 reaches 200m / s to 400m / s. The exhaust gas sucked from the air inlet 101 passes between the rotating blade 102 and the fixed blade 123 and is transferred to the base portion 129. At this time, the temperature of the rotating blade 102 rises by the friction heat generated when the exhaust gas contacts the rotating blade 102, the conduction of heat generated by the motor 121, etc., but the heat is transferred to the fixed blade 123 side by radiation or conduction by gas molecules of the exhaust gas.

[0053] The stationary blade spacers 125 are joined to each other at the outer circumference, and transfer heat received by the stationary blades 123 from the rotary blades 102 , friction heat generated when the exhaust gas and the stationary blades 123 come into contact, and the like to the outside.

[0054] In the above description, it is assumed that the thread groove spacer 131 is disposed on the outer periphery of the cylindrical portion 102d of the rotor 103, and the thread groove 131a is engraved on the inner peripheral surface of the thread groove spacer 131. However, on the contrary, there is also a case where a thread groove is engraved on the outer peripheral surface of the cylindrical portion 102d, and a spacer having a cylindrical inner peripheral surface is disposed around it.

[0055] In addition, depending on the purpose of the turbomolecular pump 100, there may be the following situation: the electrical equipment consisting 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, 106B, the axial sensor 109, etc. is covered by the stator column 122, and the purge gas in the stator column 122 is maintained at a predetermined pressure so that the gas sucked from the air intake port 101 will not invade the electrical equipment.

[0056] In this case, a pipe (not shown) is provided in the base portion 129, and the cleaning gas is introduced through the pipe. The introduced cleaning gas passes through the gap between the protection 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 circumferential cylindrical portion of the rotary blade 102, and is sent to the exhaust port 133.

[0057] Here, the turbomolecular pump 100 requires the determination of the model and the control based on the inherent parameters (for example, the characteristics corresponding to the model) that are adjusted respectively. In order to save the control parameters, the turbomolecular pump 100 is equipped with an electronic circuit unit 141 in its main body. The electronic circuit unit 141 is composed of a semiconductor memory such as an EEP-ROM and electronic parts such as semiconductor elements for accessing it, and a substrate 143 for mounting them. The electronic circuit unit 141 is accommodated in the lower part of the base 129 constituting the lower part of the turbomolecular pump 100, for example, near the center, of the rotation speed sensor not shown in the figure, and is closed by an airtight bottom cover 145.

[0058] By the way, in the semiconductor manufacturing process, among the process gases introduced into the chamber, there is a gas having the property of becoming solid if its pressure becomes higher than a predetermined value or its temperature becomes lower than a predetermined value. Inside the turbomolecular pump 100, the pressure of the exhaust gas is the lowest at the air intake port 101 and the highest at the exhaust port 133. While the process gas is being transferred from the air intake port 101 to the exhaust port 133, if its pressure becomes higher than a predetermined value or its temperature becomes lower than a predetermined value, the process gas becomes solid and adheres to and accumulates inside the turbomolecular pump 100.

[0059] For example, when SiCl4 is used as a process gas in an Al etching device, it can be seen from the vapor pressure curve that in a low vacuum (760 [torr] ~ 10 －2 [torr]) and low temperature (about 20[°C]), solid products (such as AlCl3) precipitate and adhere to the inside of the turbomolecular pump 100. Therefore, if the precipitate of the process gas is deposited inside the turbomolecular pump 100, the deposit narrows the pump flow path and becomes a cause of performance degradation of the turbomolecular pump 100. In addition, the aforementioned products are in a state of being easily solidified and adhered in the high pressure parts near the exhaust port 133 and the screw groove spacer 131.

[0060] Therefore, in order to solve this problem, in the past, a heater not shown in the figure and an annular water-cooling tube 149 were wound on the outer periphery of the base part 129, and a temperature sensor not shown in the figure (such as a thermistor) was buried in the base part 129, and the heating of the heater and the cooling of the water-cooling tube 149 were controlled based on the signal of the temperature sensor to maintain the temperature of the base part 129 at a certain higher temperature (set temperature) (hereinafter referred to as TMS. TMS; Temperature Management System).

[0061] Next, the amplification circuit 150 for controlling the excitation of the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B of the turbomolecular pump 100 thus configured will be described. Figure 2 A circuit diagram of the amplifier circuit 150 is shown in FIG.

[0062] exist Figure 2 In the embodiment, one end of the electromagnet winding 151 constituting the upper radial electromagnet 104 and the like is connected to the positive electrode 171a of the power source 171 via the transistor 161, and the other end is connected to the negative electrode 171b of the power source 171 via the current detection circuit 181 and the transistor 162. The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between the source and the drain.

[0063] At this time, the cathode terminal 161a of the diode of transistor 161 is connected to the positive electrode 171a, and the anode terminal 161b is connected to one end of the electromagnet winding 151. In addition, the cathode terminal 162a of the diode of transistor 162 is connected to the current detection circuit 181, and the anode terminal 162b is connected to the negative electrode 171b.

[0064] On the other hand, the cathode terminal 165a of the diode 165 for current regeneration is connected to one end of the electromagnet winding 151, and the anode terminal 165b is connected to the negative electrode 171b. In addition, similarly, the cathode terminal 166a of the diode 166 for current regeneration is connected to the positive electrode 171a, and the anode terminal 166b is connected to the other end of the electromagnet winding 151 via the current detection circuit 181. And, the current detection circuit 181 is composed of, for example, a Hall sensor type current sensor or a resistor element.

[0065] Therefore, when the magnetic bearing is controlled in five axes and there are ten electromagnets 104, 105, 106A, 106B in total, the same amplifier circuit 150 is configured for each electromagnet, and ten amplifier circuits 150 are connected in parallel to the power supply 171.

[0066] Furthermore, the amplification control circuit 191 is constituted by, for example, a digital signal processor unit (hereinafter referred to as a DSP unit) not shown in the control device 200 , and switches the transistors 161 and 162 on and off.

[0067] The amplifier control circuit 191 compares the current value detected by the current detection circuit 181 (the signal reflecting the current value is referred to as the current detection signal 191c) with the predetermined current command value. Based on the comparison result, the size of the pulse width (pulse width time Tp1, Tp2) generated within one cycle of the PWM control, that is, the control cycle Ts, is determined. As a result, the gate drive signals 191a, 191b having the pulse width are output from the amplifier control circuit 191 to the gate terminals of the transistors 161, 162.

[0068] In addition, when the rotation speed of the rotor 103 passes through the resonance point during the acceleration operation, when interference occurs during the constant speed operation, etc., it is necessary to control the position of the rotor 103 at high speed and with strong force. Therefore, a high voltage of about 50V, for example, is used as the power supply 171 so that the current flowing into the electromagnet winding 151 can be increased (or decreased) sharply. In addition, between the positive electrode 171a and the negative electrode 171b of the power supply 171, a capacitor (not shown) is usually connected for the purpose of stabilizing the power supply 171.

[0069] In this configuration, when both transistors 161 and 162 are turned on, the current (hereinafter referred to as electromagnet current iL) flowing through the electromagnet winding 151 increases, and when both transistors 161 and 162 are turned off, the electromagnet current iL decreases.

[0070] In addition, if one of the transistors 161 and 162 is turned on and the other is turned off, the so-called flywheel current is maintained. Moreover, if the flywheel current is made to flow into the amplifier circuit 150 in this way, the hysteresis loss in the amplifier circuit 150 can be reduced, and the power consumption of the entire circuit can be suppressed to a low level. In addition, by controlling the transistors 161 and 162 in this way, high-frequency noise such as harmonics generated in the turbomolecular pump 100 can be reduced. Furthermore, by measuring the flywheel current with the current detection circuit 181, the electromagnet current iL flowing through the electromagnet winding 151 can be detected.

[0071] That is, when the detected current value is smaller than the current command value, Figure 3 As shown, the transistors 161 and 162 are turned on only once for a time corresponding to the pulse width time Tp1 in the control cycle Ts (e.g., 100 μs). Therefore, the electromagnet current iL during this period increases toward the current value iLmax (not shown) that can flow from the positive electrode 171a to the negative electrode 171b via the transistors 161 and 162.

[0072] On the other hand, when the detected current value is larger than the current command value, Figure 4As shown, both transistors 161 and 162 are turned off only once in the control cycle Ts for a time corresponding to the pulse width time Tp2. Therefore, the electromagnet current iL during this period decreases 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.

[0073] In either case, after the pulse width time Tp1 or Tp2 has elapsed, one of the transistors 161 and 162 is turned on. Therefore, during this period, the flywheel current is maintained in the amplifier circuit 150 .

[0074] <Present Implementation Method>

[0075] Next, the vacuum pump 210 according to the present embodiment will be described.

[0076] Vacuum pump 210 Figure 5 and Figure 6 As shown, the housing 211 (external body) forming the outer shell of the vacuum pump 210 is composed of a plurality of parts. Specifically, the housing 211 includes an upper box body 220 provided with an air inlet 101, a lower box body 230 provided with an air outlet 133, and a base portion 129. The housing 211 is formed in a substantially cylindrical shape with the base portion 129 as the bottom, and a threaded groove spacer 240 (fixed part) is provided in its internal space. The upper box body 220, the lower box body 230, and the threaded groove spacer 240 are arranged on the same axis and are integrally connected by a fastening member such as a bolt.

[0077] The lower box body 230 is formed in a cylindrical shape, and a plurality of setting holes 231 are formed on the outer peripheral surface, and a heating mechanism 260 is inserted into each setting hole 231. The lower box body 230 forms a heating side contact surface 232 that contacts a portion of the thread groove spacer 240 on the upstream side surface and a portion of the inner peripheral surface. The heating side contact surface 232 is formed in a ring shape when viewed from the upstream side. The heating side contact surface 232 includes a heating side upper contact surface 233 formed on the upstream side surface of the lower box body 230 and a heating side inner contact surface 234 formed on the inner peripheral surface of the lower box body 230. The heating side upper contact surface 233 and the heating side inner contact surface 234 are connected with a step difference. The lower box body 230 heated by the heating mechanism 260 can heat the thread groove spacer 131 with the help of the heating side contact surface 232.

[0078] The holes 231 are preferably arranged evenly along the circumferential direction, but may be arranged unevenly. The number of holes 231 is not particularly limited as long as it is one or more. The heating mechanism 260 is not particularly limited, and is a box heater in which a heating element is arranged inside a metal tube, and two terminals connected to the heating element are arranged on one end of the metal tube.

[0079] Since the upper box 220 and the lower box 230 need to function as the housing 211 for maintaining the vacuum, the material of the upper box 220 and the lower box 230 cannot be determined only by considering the thermal conductivity, but also by considering the material strength at the operating temperature. The upper box 220 and the lower box 230 are formed of, for example, stainless steel, which has less durability degradation at high temperatures than aluminum and is less likely to deform due to heat.

[0080] The thread groove spacer 240 is as follows Figures 5 to 10 As shown, it is an annular part that cooperates with the rotor 103 to exhaust the sucked gas. The thread groove spacer 240 is formed of a material with high thermal conductivity in order to transfer the heat transferred from the lower case 230 to the thread groove pump part that cooperates with the rotor 103. The material of the thread groove spacer 240 has a higher thermal conductivity than the material of the lower case 230. The material of the thread groove spacer 240 is preferably an aluminum alloy that can be cast (such as ADC12). In the present embodiment, the thread groove spacer 131 is formed by casting (such as die casting) using an aluminum alloy as a material. In addition, after the casting process, additional processing such as cutting and coating can be performed on a portion of the thread groove spacer 131. Since the thread groove spacer 240 is formed by casting, it can be manufactured quickly and cheaply.

[0081] The thread groove spacer 240 forms a part of a Holweg type thread groove pump having a threaded peak 241 and a threaded valley 242 which rotates around the axis and moves axially, and forms a part of a Siegbain type thread groove pump having a spiral peak 243 and a spiral valley 244 which allows it to rotate within the same plane around the axis and move away from (or approach) the axis.

[0082] The thread groove spacer 240 includes an annular connecting portion 250 having a heated side contact surface 251 that contacts and connects with the heating side contact surface 232 of the lower housing 230, and a cylindrical extension portion 254 that extends downstream from the inner peripheral surface side of the connecting portion 250. The thread groove spacer 131 has a spiral mountain portion 243 and a spiral valley portion 244 formed on the surface on the upstream side of the connecting portion 250, and a threaded mountain portion 241 and a threaded valley portion 242 formed on the inner peripheral surface of the extension portion 254. The heated side contact surface 251 includes a heated side lower contact surface 252 that contacts with the heating side upper contact surface 233 of the lower housing 230, and a heated side outer contact surface 253 that contacts with the heating side inner contact surface 234 of the lower housing 230. The heated side lower contact surface 252 is formed on the surface of the connection part 250 facing the downstream side, and the heated side outer contact surface 253 is formed on the surface facing the radially inner side and the radially outer side of the heated side lower contact surface 252. The heated side lower contact surface 252 and the heated side outer contact surface 253 are connected with a step difference. The thread groove spacer 131 is heated from the heated side contact surface 232 of the lower box body 230 heated by the heating mechanism 260 via the heated side contact surface 251.

[0083] The connection portion 250 has a plurality of reduction grooves 255 and a plurality of heat transfer enhancement structures 256 arranged in the circumferential direction formed radially inward of the heated side contact surface 251. The plurality of reduction grooves 255 and the plurality of heat transfer enhancement structures 256 are alternately arranged in the circumferential direction.

[0084] The reduction groove 255 is a portion where the wall thickness of the thread groove spacer 240 is partially reduced, and is formed on the surface (the surface on the downstream side) opposite to the surface (the surface on the upstream side) forming the spiral mountain portion 243 and the spiral valley portion 244 constituting the thread groove pump portion toward the upstream side. The reduction groove 255 is formed with a depth that does not penetrate the connecting portion 250. The connecting portion 250 is formed with a bottom 258 at the bottom of each reduction groove 255, which is reduced in thickness by forming the reduction groove 255. The reduction groove 255 is preferably not arranged on the heated side contact surface 251. As a result, the thread groove spacer 131 can fully ensure the heated side contact surface 251, which is exposed to heat, and prevent the reduction of heat conduction from the lower box 230 due to the reduction of the heated side contact surface 251. The width W (length in the radial direction) of the reduction groove 255 gradually decreases toward the depth direction. This can improve the mold releasability of the thread groove spacer 131 during casting, and can also make the flow of the material during casting smooth.

[0085] Each heat conduction improving structure 256 is arranged between two adjacent reduction grooves 255 in the circumferential direction, and is a portion where the reduction groove 255 is not formed. The thread groove spacer 240 includes a first portion 246 located radially inward of the reduction groove 255 and a second portion 245 located radially outward of the reduction groove 255, and the first portion 246 and the second portion 245 are opposed to each other with a plurality of reduction grooves 255 sandwiched therebetween. Moreover, the first portion 246 and the second portion 245 are connected by a plurality of heat conduction improving structures 256. That is, the heat conduction improving structure 256 is a bridge structure connecting the first portion 246 and the second portion 245 that are opposed to each other with the reduction groove 255 sandwiched therebetween. In the thread groove spacer 240, the heat transferred from the lower case 230 to the heated side contact surface 251 moves from the second portion 245 toward the first portion 246. A smooth concave curved surface 259 is formed on the surface of the connection portion between the heat conductivity improving structure 256 and the first portion 246. This can make the flow of the material during casting smooth, and can suppress the stress concentration between the thick-walled portion having the heat conductivity improving structure 256 and the thin-walled extension portion 254. Therefore, pores and shrinkage cavities are less likely to occur in the thread groove spacer 240 which is a casting, and damage due to stress concentration can be reduced.

[0086] Incidentally, in order to make the thread groove spacer 131 into a casting, it is necessary to change the material used to a material suitable for casting (for example, from A5056 of aluminum alloy to ADC12), which may reduce the thermal conductivity. In contrast, the thread groove spacer 131 has a heat conductivity improving structure 256, so that even if the thermal conductivity is reduced due to the change in material, a higher thermal conductivity performance can be obtained.

[0087] The number of each of the weight-reducing grooves 255 and the heat conduction improving structure 256 is not particularly limited, but it is preferable to provide a plurality of them. In the present embodiment, ten are provided for each.

[0088] In addition, a plurality of bolt holes 257 arranged in the circumferential direction are formed on the heated side lower contact surface 252 of the connection portion 250. Bolts inserted from the lower case 230 side are screwed into the bolt holes 257. The phase (circumferential position) of the bolt holes 257 preferably overlaps with the phase of the reduction groove 255 so as not to overlap with the phase of the heat conductivity improvement structure 256. Thus, it is possible to prevent the thermal conductivity of the heat conductivity improvement structure 256 from being reduced due to the bolt holes 257.

[0089] The axial thickness t2 of the bottom 258 of the connection portion 250 where the reduction groove 255 is formed is smaller than the axial thickness t3 of the second portion 245 of the connection portion 250. In addition, the radial thickness t1 of the cylindrical extension portion 254 is smaller than the axial thickness t3 of the second portion 245 of the connection portion 250. In addition, the circumferential thickness t4 of the heat conduction improvement structure 256 is smaller than the axial thickness t3 of the second portion 245 of the connection portion 250. Moreover, although there are some differences, the thickness t2 of the bottom 258, the thickness t1 of the extension portion 254, and the thickness t4 of the heat conduction improvement structure 256 are of the same degree.

[0090] Next, the operation of the vacuum pump 210 according to the present embodiment will be described.

[0091] In the present embodiment, the thread groove spacer 240 is formed by casting (for example, die casting) using an aluminum alloy as a material. Incidentally, during casting, if there is a deviation in the speed of metal solidification, pores and shrinkage cavities (a type of pores) are likely to occur inside the casting. In the thread groove spacer 240 which is a casting, since the axial thickness t3 of the second portion 245 of the annular connecting portion 250 is significantly greater than the radial thickness t1 of the cylindrical extension portion 254, when the connecting portion 250 does not have the reduction groove 255, a large deviation occurs in the speed of metal solidification between the connecting portion 250 and the extension portion 254. However, in the present embodiment, since the reduction groove 255 is formed in the connecting portion 250 to reduce the volume, the thickness t2 of the bottom 258, the thickness t1 of the extension portion 254, and the thickness t4 of the heat conduction improving structure 256 are of the same level. As a result, the dispersion of the metal solidification speed of the thread groove spacer 240 is reduced, and blowholes and shrinkage holes are less likely to occur in the thread groove spacer 240 .

[0092] In addition, the thread groove spacer 240 is provided with a reduction groove 255, such as Figure 6 As shown in (B), since the heat path needs to pass through the bottom 258, the heat path becomes longer and the cross-sectional area of ​​the heat path decreases, which increases the thermal resistance and may reduce the thermal conductivity. Figure 6As shown in (A), the thread groove spacer 240 has a heat conduction improving structure 256 for improving the heat conduction between the first portion 246 and the second portion 245 in addition to the bottom portion 258, so that the heat transferred from the lower case 230 can be effectively transferred to the extension portion 254. Therefore, the thread groove spacer 240 can effectively transfer the heat transferred from the heating side contact surface 232 of the lower case 230 to the heated side contact surface 251 to the spiral mountain portion 243 and the spiral valley portion 244 formed on the surface on the upstream side of the connecting portion 250 and the threaded mountain portion 241 and the threaded valley portion 242 formed on the inner peripheral surface of the extension portion 254. Therefore, it is possible to suppress the accumulation of gas in the thread groove pump due to low temperature. As an example, the thread groove spacer 240 is preferably temperature-controlled to 100°C or more as a whole.

[0093] Moreover, the thread groove spacer 240 is provided with the reduction groove 255 and the heat conduction improving structure 256, so that even if it is cast, it is possible to prevent the occurrence of pores and shrinkage holes due to the deviation of the solidification speed caused by the influence of thickness, etc., and make the axial thickness t3 of the second portion 245 of the connecting portion 250 thick. Therefore, it is possible to shorten the heat path from the heating mechanism 260 arranged in the lower box 230 to the upstream side surface of the thread groove spacer 240 and the thread groove of the inner peripheral surface of the extension portion 254. Therefore, the heat conduction performance of the thread groove spacer 240 can be improved. Furthermore, since the thread groove spacer 240 has a thick wall portion in the axial direction, the cross-sectional area of ​​the heat path from the heated side contact surface 251 to the inner peripheral surface of the extension portion 254 is increased, and the thermal resistance is reduced accordingly, which can promote the heat transfer from the heated side contact surface 251 to the threaded mountain portion 241 and the threaded valley portion 242 formed on the inner peripheral surface of the extension portion 254. Therefore, it is easy to make the thread groove spacer 240 reach the target temperature. In addition, by increasing the volume of the portion formed of the material with high thermal conductivity (the material of the thread groove spacer 240), the heat capacity of the thread groove spacer 240 becomes larger, and the temperature can be uniformed and stabilized at a desired temperature. In addition, since the thread groove spacer 240, which is a casting, is not prone to pores and shrinkage cavities, it is possible to suppress the decline in thermal conductivity, and it is possible to suppress the occurrence of portions with reduced strength, and to suppress damage during manufacturing and use.

[0094] As described above, the vacuum pump 210 according to the present embodiment includes a housing 211 (outer casing), a rotor shaft 113 enclosed in the outer casing and rotatably supported, a rotor 103 fixed to the rotor shaft 113 and rotating together with the rotor shaft 113, and an annular fixing part (thread groove spacer 240) that cooperates with the rotor 103 to exhaust the sucked gas; the fixing part is formed by casting and includes: a first portion 246 and a second portion 245, which are arranged with at least one reduction groove 255 extending along the circumferential direction of the fixing part to reduce the volume; and a bottom portion 258, which is arranged to include at least the bottom of the reduction groove 255 and connect the first portion 246 and the second portion 245; the fixing part includes a heat conduction improving structure 256 that is different from the bottom portion 258 and improves the heat conduction between the first portion 246 and the second portion 245. Thus, the vacuum pump 210 can make the metal solidification rate during casting uniform and suppress the occurrence of pores and shrinkage holes by arranging the reduction groove 255 in the thick-walled part of the fixed part (thread groove spacer 240) formed by casting, and can also promote heat transfer between the first part 246 and the second part 245 which may be lowered by having the reduction groove 255 by means of the heat conductivity improving structure 256.

[0095] The heat conduction improving structure 256 is a bridge structure connecting the first portion 246 and the second portion 245 which are opposite to each other with the reduction groove 255 interposed therebetween. Thus, the vacuum pump 210 can effectively promote heat transfer between the first portion 246 and the second portion 245 by means of the bridge structure while maintaining the effect of suppressing the occurrence of pores and shrinkage cavities brought about by the reduction groove 255. In addition, the bridge structure in this specification is as follows: Figure 6 , Figure 8 As shown, the portion where the reduction groove 255 is not formed is defined as including a structure in which the first portion 246 and the second portion 245 are connected to each other by an integral structure such as a wall extending in the axial direction from the bottom 258 .

[0096] The first portion 246 and the second portion 245 are arranged to sandwich the reduction groove 255 in the radial direction from the center of the annular fixed part. Thus, the vacuum pump 210 can effectively move the heat radially inward via the heat conduction enhancement structure 256 by being supplied with heat from the radially outer side of the fixed part. In addition, the vacuum pump 210 can not only promote the movement of heat from the heating mechanism 260 to the radially inner side of the thread groove pump of the fixed part (thread groove spacer 240), but also promote the movement of heat in the opposite direction to the radially outer side. For example, in order to reduce the temperature of the rotor 103 with the purpose of increasing the allowable flow rate of the gas (related to the heat resistance temperature of the material of the rotor 103, etc.), the vacuum pump 210 can also have the effect of actively dissipating the heat via the fixed part.

[0097] The fixing part may also be a part constituting the thread groove pump part. Thus, the vacuum pump 210 can heat the thread groove vicinity of the thread groove pump where gas is easily deposited due to low temperature, thereby suppressing the occurrence of deposits, while making the fixing part a casting.

[0098] The fixed part is formed as a thread groove pump part with a spiral groove having a spiral ridge 243 and a spiral valley 244 and a threaded groove having a threaded ridge 241 and a threaded valley 242. Thus, the vacuum pump 210 can heat the spiral groove and the vicinity of the threaded groove where deposits are likely to form due to low temperatures, thereby suppressing the formation of deposits by providing a heat conduction improvement structure 256 on the fixed part.

[0099] The reduction groove 255 is located on the surface of the fixed part opposite to the surface on which the thread groove pump part is formed. Thus, the vacuum pump 210 forms the reduction groove 255 near the thick-walled thread groove pump part of the fixed part, and since the reduction groove 255 does not face the gas flow path, the reduction groove 255 does not affect the exhaust performance, and the accumulation of deposits in the reduction groove 255 is suppressed, and the heat transfer to the thread groove pump part is effectively maintained.

[0100] In addition, the fixing part (thread groove spacer 240) of the present embodiment is a fixing part that cooperates with the rotatable rotor 103 of the vacuum pump 210 to exhaust the sucked gas, is formed by casting, and has: a first portion 246 and a second portion 245, which are arranged with at least one reduction groove 255 extending along the circumferential direction of the fixing part to reduce the volume; and a bottom portion 258, which is arranged to include at least the bottom of the reduction groove 255 and connect the first portion 246 and the second portion 245; and has a heat conduction improving structure 256 that improves the heat conduction between the first portion 246 and the second portion 245, which is different from the bottom portion 258. Therefore, the fixing part can make the metal solidification speed during casting uniform and suppress the occurrence of pores and shrinkage cavities by arranging the reduction groove 255 in the thick-walled portion, and can promote heat transfer between the first portion 246 and the second portion 245, which may be reduced by having the reduction groove 255, by the heat conduction improving structure 256.

[0101] In addition, the present invention is not limited to the above-mentioned embodiments, and can be variously changed and combined by those skilled in the art within the technical concept of the present invention. Fig.11As shown in the modified example, the thread groove spacer 240 (fixed component) may also be formed on the inner peripheral surface with a portion of a Holweg type thread groove pump having a threaded mountain portion 241 and a threaded valley portion 242 that rotates around the axis and moves in the axial direction, and no Sigband type thread groove pump is formed on the upstream side surface. In addition, the thread groove spacer 240 (fixed component) may not be formed on the inner peripheral surface of the Holweg type thread groove pump, and may be formed on the upstream side surface.

[0102] In addition, the heat conductivity enhancement structure 256 may be formed by another component installed in the casting having the first portion 246 and the second portion 245 by a method such as embedding or melting. In this case, the heat conductivity enhancement structure 256 may be formed by a material different from the material forming the casting having the first portion 246 and the second portion 245. Therefore, the heat conductivity enhancement structure 256 may be formed by a material having a higher thermal conductivity than the material of the cast portion of the fixed part. Thus, the vacuum pump 210 can effectively promote heat transfer between the first portion 246 and the second portion 245 by the heat conductivity enhancement structure 256 having a higher thermal conductivity.

[0103] In addition, as another embodiment of the heat conduction improving structure 256, substantially the entirety of the reduction groove 255 formed by casting or a portion of the reduction groove 255 may be filled with a material different from the material forming the casting.

[0104] In addition, the component that the thread groove spacer 240 (fixing component) contacts and receives heat is not limited to the lower case 230 .

[0105] In addition, the fixing member is not limited to the thread groove spacer 240, and may be a part of a device other than the vacuum pump, for example.

[0106] Description of Reference Numerals

[0107] 101 Inlet

[0108] 103 Rotor

[0109] 113 rotor shaft

[0110] 129 Base

[0111] 131 Thread groove spacer

[0112] 133 Exhaust port

[0113] 100, 210 Vacuum pump

[0114] 211 Shell (External Body)

[0115] 220 upper box

[0116] 230 lower box

[0117] 231 Setting hole

[0118] 232 Heating side contact surface

[0119] 233 Heating side upper contact surface

[0120] 234 Heating side inner contact surface

[0121] 240 Threaded Groove Spacers

[0122] 241 Spiral Mountain

[0123] 242 Threaded valley

[0124] 243 Spiral Mountain

[0125] 244 spiral valley

[0126] 245 Part 2

[0127] 246 Part 1

[0128] 250 Connection

[0129] 251 Heated side contact surface

[0130] 252 Lower contact surface of heated side

[0131] 253 External contact surface of heated side

[0132] 254 Extension

[0133] 255 Decrement slot

[0134] 256 Thermal conductivity enhancement structure

[0135] 257 Bolt Holes

[0136] 258 bottom

[0137] 259 curved face

[0138] 260 Heating mechanism

Claims

1. A vacuum pump, characterized in that: have: outer body; The rotor shaft is enclosed by the outer casing and supported rotatably; a rotor fixed to the rotor shaft and rotating together with the rotor shaft; and The annular fixed part cooperates with the aforementioned rotor to exhaust the sucked gas; The fixing part is at least partially formed by casting and comprises: a first portion and a second portion, which are arranged to sandwich at least one volume-reducing groove extending along the circumferential direction of the fixing part; and a bottom portion, which is arranged to include at least the bottom of the volume-reducing groove and connect the first portion and the second portion; The fixing part has a heat conduction improving structure that is different from the bottom portion and that improves heat conduction between the first portion and the second portion.

2. The vacuum pump according to claim 1, characterized in that The heat conduction improving structure is a bridge structure that connects the first portion and the second portion that are opposed to each other with the reduction groove interposed therebetween.

3. The vacuum pump according to claim 1, characterized in that The thermal conductivity enhancing structure is formed of a material having a higher thermal conductivity than a material of a cast portion of the fixing component.

4. The vacuum pump according to claim 1, characterized in that The first portion and the second portion are arranged to be aligned with each other in a radial direction with the reduction groove interposed therebetween from the center of the annular fixing part.

5. The vacuum pump according to any one of claims 1 to 4, characterized in that The aforementioned fixing parts are parts constituting the thread groove pump portion.

6. The vacuum pump according to claim 5, characterized in that The fixing part is formed as the thread groove pump part: A spiral groove portion having a spiral mountain portion and a spiral valley portion; and The thread-like groove portion has a thread-like mountain portion and a thread-like valley portion.

7. The vacuum pump according to claim 5, characterized in that The decrement groove is located on a surface of the fixing part opposite to a surface on which the thread groove pump portion is formed.

8. A fixed part that cooperates with a rotatable rotor of a vacuum pump to exhaust the sucked gas, characterized in that: At least a portion is formed by casting, and has: a first portion and a second portion, sandwiching at least one volume-reducing groove extending in the circumferential direction of the fixing part; and a bottom portion, which includes at least the bottom of the aforementioned reduction groove and is configured to connect the aforementioned first portion and the aforementioned second portion; A heat conduction improving structure that is different from the bottom portion and that improves heat conduction between the first portion and the second portion is provided.

Images