JP2009092039A - Two-stage screw type vacuum pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of supporting a rotating rotor on a rotating shaft, adaptable to expansion due to heat with rotation, simple in structure, and easy to assemble/disassemble. <P>SOLUTION: In a two-stage screw type vacuum pump, the suction port of a second screw type vacuum pump is connected to the exhaust port of a first screw type vacuum pump whose suction port is connected to a vacuum chamber. The screw rotors of the first screw type vacuum pump and the second screw type vacuum pump are supported in a cantilevered fashion and arranged in vertical. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a structure of a two-stage screw type vacuum pump having a cantilever rotor used in a semiconductor manufacturing process.

Conventionally, a vacuum pump used in a semiconductor manufacturing process has a first pump called a booster pump whose inlet is connected to a vacuum vessel (reaction chamber), and an inlet of the first pump connected to the exhaust of the first pump. This is a two-stage pump called a pump. The first pump is necessary to obtain the exhaust speed in the pressure range required in the manufacturing process, but when the exhaust port is at atmospheric pressure, the pressure range of 0.1 to 500 Pa required for the intake pressure in the manufacturing process Therefore, the first pump that emphasizes sealing performance is required.
In general, the first pump uses a rooted structure with a horizontally supported double-sided bearing support and a single-stage rotor, and the second pump has a horizontally-supported double-supported structure. A rotor type having a multi-stage root type or a screw type, and a screw type (FIG. 7) in which the bearing support is vertically cantilevered are used. Usually, the first pump having an inlet for connecting to the vacuum vessel is disposed on the upper part of the second pump and is contained in one frame.
The vacuum dry pump used in this semiconductor manufacturing process exhausts various process gases. However, depending on the manufacturing process, it is necessary to exhaust the powder generated in the process, and in such a case, the powder is in the meshing part of the rotor of the first pump or the second pump or the rotor and the casing part. It often happens that the pump stops due to clogging.

If the pump stops, it is possible to minimize the time to stop the production line if it is possible to remove the powder clogged between the rotor meshing part and between the rotor and the casing. In this configuration, since the first pump is a double-sided structure, even if there is no abnormality in the bearing part and the seal part separating the bearing part and the rotor part, the powder in the rotor part cannot be removed without removing them. If the first pump is not removed from the upper part of the second pump, the powder removal operation of the second pump cannot be performed. At the site where the pump is installed, a crane or the like is required to remove the first pump weighing about 100 kg or more from the frame. No. Also, disassembly and reassembly of bearings and seals in an atmosphere with powder may cause powder to adhere to the bearings and seals and damage the bearings and seals. It was impossible to remove the body.

Therefore, even if there is no abnormality in the bearing part and the seal part, the pump must be removed from the pipe connected to the vacuum vessel, transferred to a place where it can be overhauled, disassembled, powder removed, and reassembled. Restoration required a lot of effort. Further, in order to continue the production of the semiconductor, it is necessary to prepare another alternative pump, and it is necessary to always prepare an extra pump extra.
Japanese Utility Model Publication No. 7-28965

In the present invention, the rotor of the first pump and the second pump is a screw type, and further, the screw rotor is cantilevered and vertically placed,
The first pump and the second pump can be taken down from the top of the second pump and moved to another place for disassembly and reassembly, or without disassembling the bearings and seals. The purpose is to make it possible to easily remove the powder adhering to the rotor part of the rotor, to recover the pump in a short time, and to eliminate the need to prepare another pump only for replacement within the recovery period And

  According to the two-stage screw type vacuum pump of the present invention, the inlet port of the second screw type vacuum pump is connected to the exhaust port of the first screw type vacuum pump connected to the vacuum vessel (reaction chamber). Further, in the two-stage screw type vacuum pump, the screw rotors of the first screw type vacuum pump and the second screw type vacuum pump were cantilever-supported, and were placed vertically. By adopting such a configuration, it is possible to remove powder clogged in the meshing part of the rotor or between the rotor and the casing on the spot without taking down the first pump from the upper part of the second pump. Is possible.

  According to the two-stage screw type vacuum pump of the present invention, the exhaust port of the first screw type vacuum pump and the intake port of the second screw type vacuum pump are arranged so as to face each other at a substantially horizontal position. . By adopting such a configuration, the exhaust port of the first screw type vacuum pump and the intake port of the second screw type vacuum pump can be connected by a substantially straight shortest path. There is no influence on the conductance, and the area to which the powder can adhere can be minimized without deteriorating the exhaust performance. (If the path between the first pump and the second pump is long, the area where the powder adheres increases, and the powder adhered for some reason peels off, causing the first pump or the second pump to The probability of biting the powder with the rotor part of is increased.)

  According to the two-stage screw type vacuum pump of the present invention, the first housing that covers the screw rotor of the first screw type vacuum pump and the second housing that covers the screw rotor of the second screw type vacuum pump, Each of them is divided into at least two parts, and the screw rotor can be exposed by removing one of the housing members divided into at least two parts. By adopting such a configuration, if the biting of the powder is only at the upper part of the rotor, the powder can be removed by removing only the upper end housing.

  According to the two-stage screw type vacuum pump of the present invention, the design pumping speed of the first screw type vacuum pump is made larger than the design pumping speed of the second screw type vacuum pump, and the first screw type vacuum pump is used. The volume was compressed by a pump so that it could be exhausted. With this configuration, the second screw vacuum pump is smaller than the first screw vacuum pump, and the second screw vacuum pump is perpendicular to the first screw vacuum pump. The selection range of the relative position becomes wide. For example, even if the exhaust port of the first screw-type vacuum pump and the intake port of the second screw-type vacuum pump are connected by a substantially linear path, the second screw-type vacuum is more effective than the first screw-type vacuum pump. Since the pump can be made smaller, it is possible to prevent the length of the two-stage screw vacuum pump from extending in the direction of the rotation axis.

  According to the first aspect of the present invention, a two-stage system in which the intake port of the second screw type vacuum pump is connected to the exhaust port of the first screw type vacuum pump connected to the vacuum vessel (reaction chamber). In the screw-type vacuum pump, the first pump is lifted from the upper part of the second pump by supporting the screw rotors of the first screw-type vacuum pump and the second screw-type vacuum pump in a cantilevered manner and vertically. Even if it is not lowered, it is possible to remove the powder clogged between the meshing part of the rotor or between the rotor and the casing on the spot.

  According to the invention of claim 2 of the present application, the exhaust port of the first screw type vacuum pump and the intake port of the second screw type vacuum pump are arranged opposite to each other in a substantially horizontal position. The exhaust port of the screw type vacuum pump and the intake port of the second screw type vacuum pump can be connected by a substantially straight shortest path, so there is no effect on the conductance of the second pump and the exhaust performance is reduced. Without this, the area to which the powder can adhere can be minimized.

 According to the invention of claim 3, the first housing that covers the screw rotor of the first screw-type vacuum pump and the second housing that covers the screw rotor of the second screw-type vacuum pump each include at least The screw rotor is exposed by removing one housing member divided into at least two parts. By adopting such a configuration, if the biting of the powder is only at the upper part of the rotor, the powder can be removed by removing only the upper end housing.

  According to the invention of claim 4 of the present application, the second screw type vacuum pump is smaller than the first screw type vacuum pump, and the second screw type vacuum pump is perpendicular to the first screw type vacuum pump. The selection range of the relative position in the direction can be widened.

Embodiments of a vacuum pump according to the present invention will be described below with reference to the drawings. FIG. 5 is a sectional view schematically showing an embodiment of a two-stage screw type vacuum pump according to the present invention.
Here, the first screw-type vacuum pump (first vacuum pump, rotary rotor pump, cantilever rotary pump, pre-stage vacuum pump or booster pump) 1A of FIG. 5 will be described with reference to FIGS. To do.
FIG. 1 is a cross-sectional view schematically showing an embodiment of a first screw vacuum pump (first vacuum pump, rotary rotor pump, cantilever rotary pump, pre-stage vacuum pump or booster pump) 1A. FIG. 2 is a cross-sectional view taken along the line AA in FIG.
As shown in the figure, the first screw-type vacuum pump 1A includes a pair of screw rotors 102 and 103 arranged vertically, and the pair of screw rotors 102 and 103 is housed inside an exhaust chamber housing 171. ing. A housing (exhaust chamber housing) 171 forming the exhaust chamber is constituted by the rotor housing 104, the upper end housing 172, and the bearing housing 173.

  A plurality of working chambers 107 are formed by the pair of screw rotors 102 and 103 and the exhaust chamber housing 171. The working chamber 107 sucks process gas (reaction product gas) from an intake port 153 formed in the rotor housing 104 and the upper end housing 172, and process gas (reaction product gas) as the pair of screw rotors 102 and 103 rotates. Is exhausted from an exhaust port (exhaust port) 154 formed on the side surface of the rotor housing 104.

  The screw rotors 102 and 103 and the exhaust chamber housing 171 are partitioned so that the intake port 153 and the exhaust port (exhaust port) 154 do not always communicate with each other. The exhaust chamber 168 is separated by the screw rotors 102 and 103 on the intake side and the exhaust chamber housing 171. In the position until the intake side is closed, a recess 173 for accommodating a reaction product is provided at the lower end of the intake port 153 formed in the rotor housing 104. Further, a baffle plate 174 is arranged at the intake port 153 above the screw rotors 102 and 103 so that a lump of reaction products does not fall directly into the exhaust chamber 168.

  Between the screw rotors 102 and 103 and the exhaust chamber housing 171, there is a minute gap including the end surfaces of the screw rotors 102 and 103, but the second screw-type vacuum pump that is disposed on the atmosphere side and requires an air sealing function. The gap may be larger than that.

  Further, the second screw vacuum pump (the latter stage vacuum pump or the main stage pump) has a large power for exhausting to the atmosphere by being volume-compressed and exhausted by the first screw type vacuum pump (first stage vacuum pump or booster pump) 1A. Tap pump) 1B can be reduced in size and energy is saved.

  The screw rotor 102 includes a rotor member 156 and a rotating shaft member 105. The rotor member 156 is made of an aluminum material, and the rotary shaft member 105 is made of an iron material. The rotor member 156 is a hollow rotor, and a cylindrical member 157 made of an iron-based material is shrink-fitted or cold-fitted in the hollow portion. In this way, the cylindrical member 157 made of an iron-based material is shrink-fitted or cold-fitted to the rotor member 156 made of an aluminum-based material, so that the aluminum-based material is more iron-based when the temperature rises. Even if the thermal expansion is greater, the compression of the iron-based material and the expansion of the aluminum-based material due to shrink fitting or cold fitting are buffered, and a gap is less likely to be generated between the rotor member 156 and the cylindrical member 157. Further, the joint surface between the rotor member 156 and the cylindrical member 157 has a cylindrical shape so that the rotational axes of both members can be easily aligned. A step portion 166 is provided at the lower end of the cylindrical member 157 so that the relative position in the axial direction of the rotor member 156 does not change. Further, a taper that narrows toward the upper part is provided on the inner periphery of the cylindrical member 157, and a taper that has the same shape as the taper of the cylindrical member 157 that becomes thinner toward the end also at the upper end of the rotary shaft member 105 is provided. It is. Then, the rotating shafts of the rotor member 156 and the cylindrical member 157 are made to coincide with each other by bringing the tapered portions of the cylindrical member 157 and the rotating shaft member 105 into pressure contact with each other. The cylindrical member 157 and the rotating shaft member 105 are the same iron-based material, and there is almost no difference in the amount of thermal expansion due to a temperature change. The cylindrical member 157 and the rotating shaft member 105 are brought into pressure contact with each other by disposing a disc spring 158 between the upper surface of the cylindrical member 157 and a bolt 159 fastened to the upper end of the rotating shaft member 105. A lid 160 is fastened to the upper end portion of the screw rotor 102 so that reactive organisms do not accumulate in the hollow portion of the rotor member 156.

  Similarly, the screw rotor 103 includes a rotor member 161 and a rotating shaft member 108. The rotor member 161 is made of an aluminum material, and the rotary shaft member 108 is made of an iron material. The rotor member 161 is a hollow rotor, and a cylindrical member 162 made of an iron-based material is shrink-fitted or cold-fitted in the hollow portion. In this way, the cylindrical member 162 made of an iron-based material is shrink-fitted or cold-fitted to the rotor member 161 made of an aluminum-based material, so that when the temperature rises, the aluminum-based material is more iron-based material. Even if the thermal expansion is greater than that, the compression of the iron-based material and the expansion of the aluminum-based material due to shrink fitting or cold fitting are buffered, and it is possible to make it difficult to form a gap between the rotor member 161 and the cylindrical member 162. Further, the joint surface between the rotor member 161 and the cylindrical member 162 is formed in a cylindrical shape so that the rotation axes of both members can be easily aligned. A step portion 167 is provided at the lower end of the cylindrical member 162 so that the relative position in the axial direction with the rotor member 161 does not change. Further, a taper that narrows toward the upper part is provided on the inner periphery of the cylindrical member 162, and a taper that has the same shape as the taper of the cylindrical member 162 that narrows toward the end also at the upper end of the rotary shaft member 108. is there. Then, the rotating portions of the rotor member 161 and the cylindrical member 162 are made to coincide with each other by pressing the taper portions of the cylindrical member 162 and the rotating shaft member 108 together, and further, the rotating shaft of the rotating shaft member 108 is also made to coincide. The cylindrical member 162 and the rotating shaft member 108 are the same iron-based material, and there is almost no difference in the amount of thermal expansion due to temperature change. The cylindrical member 162 and the rotary shaft member 108 are brought into pressure-contact with each other by disposing a disc spring 163 between the upper surface of the cylindrical member 162 and a bolt 164 fastened to the upper end of the rotary shaft member 108. A lid 165 is fastened to the upper end portion of the screw rotor 103 so that reactive organisms do not accumulate in the hollow portion of the rotor member 161.

  The screw rotors 102 and 103 can be rotated at a high speed by increasing the resonance frequency by providing a lightweight aluminum-based material and a hollow portion like the screw rotors 102 and 103 to make the screw rotors 102 and 103 as light as possible. . As a result, the first vacuum pump (previous vacuum pump or booster pump) can be reduced in size and the sealing performance can be improved, so that the first vacuum pump (previous vacuum pump or booster pump) with good exhaust efficiency can be configured. .

  In the screw rotor 102, a rotary shaft portion 105 of the rotor is rotatably supported in a rotor housing 104 by bearings 106 and 101 provided at an upper portion below the rotary shaft portion 105 and a bearing 123 provided at a lower portion. . In order to prevent the process gas (reaction product gas) in the exhaust chamber from leaking to the bearing side and accumulating on the bearing or contaminating the lubricating oil between the bearing 106 and the exhaust chamber 168, the lubricating oil on the bearing side 106 is further exhausted. A shaft seal 169 is provided so as not to leak to the chamber 168 side. The bearings 106, 101, 123 are pressurized by a disc spring (not shown).

  Similarly, in the screw rotor 103, the rotating shaft portion 108 of the rotor can be rotated in the rotor housing 104 by bearings 109 and 110 provided at the upper portion below the rotating shaft portion 108 and a bearing 124 provided at the lower portion. It is supported. In order to prevent process gas (reaction product gas) in the exhaust chamber from leaking to the bearing side and accumulating on the bearing or contaminating the lubricating oil between the bearing 109 and the exhaust chamber 168, the lubricating oil on the bearing side 109 is further exhausted. A shaft seal 170 is provided so as not to leak to the chamber 168 side. The bearings 109, 110, and 124 are pressurized by a disc spring (not shown) or the like.

  The outer rings of the bearings 106 and 101 are press-fixed to the inner periphery of a cylindrical bearing support member 175 made of an iron-based material, and the outer peripheral portion of the bearing support member 175 is press-contacted to a bearing housing 175 made of an aluminum-based material. It is fixed. A projecting portion 180 is formed at the lower end of the bearing support member 175 in the radial direction of the rotary shaft so as to be easily positioned in the axial direction with respect to the outer ring of the bearing and the bearing housing 175. Similarly, the outer rings of the bearings 109 and 110 are pressure-fixed to a bearing support member 177 made of an iron-based material, and the bearing support member 177 is pressure-fixed to a bearing housing 176 made of an aluminum-based material. At the lower end of the bearing support member 177, a protruding portion 181 is formed in the radial direction of the rotary shaft so as to be easily positioned in the axial direction with respect to the outer ring of the bearing and the bearing housing 176. In this way, it is fixed to the bearing housing 176 made of an aluminum-based material having a different thermal expansion coefficient through the bearing support members 175 and 177 having substantially the same thermal expansion coefficient as the outer rings of the bearings 106, 101, 109, and 110. By doing so, it is possible to prevent a gap from being changed between the outer rings of the bearings 106, 101, 109, and 110 and the bearing support members 175 and 177.

  Further, the bearing housing 176 is formed with a hollow portion 182 for thermally insulating the bearings 106, 101, 109, 110 and the exhaust chamber 168. Thus, heat between the exhaust chamber 168 and the bearings 106, 101, 109, 110 is prevented so that heat such as compression heat of the exhaust gas generated in the exhaust chamber 168 is not transmitted to the bearings 106, 101, 109, 110. Providing a space in the conduction path makes it difficult for heat to be transferred to the bearings 106, 101, 109, and 110, and prevents breakage due to the high temperature of the bearings 106, 101, 109, and 110. By providing the hollow portion 182 around the bearings 106, 101, 109, and 110, a heat conduction path through which heat is transmitted to the bearings 106, 101, 109, and 110 through the bearing housing 176 can be lengthened, so that a more heat insulating effect can be obtained. improves. Further, when the reaction product gas is exhausted, and further when the reaction product gas that becomes solid at low temperature flows, a path through which the reaction product gas flows (intake port 153 → exhaust chamber 168 → exhaust port) so that the reaction product does not accumulate. It is necessary to operate the vacuum pump at a high temperature 154), but the heat around the exhaust chamber 168 maintained at a high temperature by the hollow portion 182 is prevented from being transmitted to the bearings 106, 101, 109, 110. There is also an effect.

  The rotor housing 104, the upper end housing 172 and the bearing housing 173 constituting the exhaust chamber housing 171 are made of the same aluminum material as the rotor member 161 made of an aluminum material, and have the same thermal expansion coefficient. This prevents the gap between the screw rotors 102 and 103 and the exhaust chamber housing 171 from changing with temperature. Further, since the exhaust chamber housing 171 is made of an aluminum-based material, the heat conductivity is good and the heat generated near the exhaust port 153 can be easily transferred to the intake port 154 side, and the temperature of the exhaust chamber 168 can be made uniform.

  A heat transfer plate 183 made of an aluminum material for controlling the temperature in the exhaust chamber 168 is in close contact with the periphery of the rotor housing 104. A passage 184 for flowing a cooling medium (water or the like) or a heating medium (high-temperature and high-pressure steam or the like) is formed in the heat transfer plate, and heating and cooling are performed with these media. For example, when exhausting a reaction product gas that solidifies at a high temperature and low temperature (a temperature close to normal temperature) such as tungsten, the exhaust chamber needs to be maintained at a low temperature, and cooling water is supplied to the path 184.

A cooling plate 185 made of an aluminum-based material is disposed at a position at the lower end of the bearing housing 176 and in contact with a heat conduction path through which heat is transferred to the bearings 106, 101, 109, 110 via the bearing housing 176. When the bearings 106, 101, 109, and 110 cannot be sufficiently maintained at a low temperature only by the hollow portion 182, the amount of heat conducted to the bearings 106, 101, 109, and 110 can be reduced by arranging the cooling plate 185. Therefore, the temperature rise of the bearings 106, 101, 109, 110 can be suppressed.
The cooling plate 185 is provided with a cooling path 186 for allowing a medium such as cooling water to flow, thereby further improving the cooling efficiency.

  Further, the cooling plate 185 is in contact with the motor housing 187, and the motor 113 can be cooled. Further, a second cooling plate 188 is in close contact with the outer periphery of the motor housing 187, and the motor 113 is also cooled by the second cooling plate 188. Further, the second cooling plate 188 is formed with a cooling path 189 for flowing a medium such as cooling water, thereby further improving the cooling efficiency.

  A timing gear 111 is provided at the lower end portion of the rotating shaft portion 105, and a timing gear 112 is provided at the lower end portion of the rotating shaft portion 108. When the timing gears 111 and 112 mesh with each other, the screw rotors 102 and 103 are engaged. Are configured to rotate in a non-contact manner synchronously.

  A permanent magnet type rotor 150 of the motor 113 is fixed between the bearing 110 and the timing gear 112 of the rotating shaft portion 108, and canned by a can 151. When the vacuum pump is driven and the inside of the exhaust chamber 168 is evacuated, the motor 113 side is also evacuated, so the can 151 prevents the rotor 150 side from being separated from the atmosphere, thereby preventing atmospheric leakage to the exhaust chamber 168. . Further, when the pressure of the exhaust port 153 becomes higher than the atmospheric pressure at the start of operation, the process gas in the exhaust chamber 168 may leak to the motor 113 side. In this case, the process gas can be prevented from leaking to the atmosphere due to the motor being canned. An electromagnet stator 152 of the motor 113 is fixed outside the can 151, and the rotational speed of the screw rotor 103 is controlled by an inverter. Furthermore, the screw rotors 102 and 103 are configured to rotate in a non-contact manner synchronously by transmitting the rotational motion to the screw rotor 102 via the timing gears 111 and 112.

  The timing gears 111 and 112 are housed in an oil chamber 127 in which lubricating oil 126 partitioned by an oil housing 125 is stored. The timing gears 111 and 112 are configured to be supplied with lubricating oil by a lubricating oil supply means (not shown). Further, by changing the axial thickness of the timing gears 111 and 112 and aligning the bottom surfaces in the axial direction, the lubricating oil blown from the timing gear 111 to the timing gear 112 due to the centrifugal force of rotation is exchanged with the timing gear 112. Stopped at the stepped portion, the meshing portion with the timing gears 111 and 112 is lubricated.

Next, the second screw type vacuum pump (rotary rotor type pump, cantilever type rotary pump, rear vacuum pump or main pump) 1B of FIG. 5 will be described with reference to FIGS.
FIG. 3 is a sectional view schematically showing an embodiment of the second screw type vacuum pump (rotary rotor type pump, cantilever type rotary pump, rear vacuum pump or main pump) 1B. 4 is a cross-sectional view taken along the line BB in FIG.
As shown in the figure, the screw type vacuum pump 1 B includes a pair of screw rotors 202 and 203 arranged vertically, and the pair of screw rotors 202 and 203 are housed inside an exhaust chamber housing 271. The exhaust chamber housing 271 includes a rotor housing 204, an upper end housing 272, and a bearing housing 276.

  A plurality of working chambers 207 are formed by the pair of screw rotors 202 and 203 and the exhaust chamber housing 271. The plurality of working chambers 207 suck process gas (reaction product gas) from an intake port 253 formed in the upper end housing 272 and transfer the process gas (reaction product gas) as the pair of screw rotors 202 and 203 rotate. Then, the air is exhausted from an exhaust port (exhaust port) 254 formed on the side surface of the lower end of the rotor housing 204.

  At the upper end of the upper end housing 272, that is, the cantilevered screw rotors 202, 203 having the structure described below, an exhaust port 154 of the first screw type vacuum pump 1A and an intake port 253 of the second screw type vacuum pump 1B are provided. A pulsation prevention space 290 for buffering the pulsation is formed when the intermediate pressure between the two pulsates. For example, when the atmospheric pressure is suddenly exhausted from the vacuum state as an extreme case, the maximum pressure of the pulsation becomes equal to or higher than the atmospheric pressure (in some cases, more than several times the atmospheric pressure), and the exhaust port 154 of the first screw type vacuum pump 1A. And pulsation between the suction port 253 of the second screw type vacuum pump 1B and process gas leaks to the bearing 109 side of the first screw type vacuum pump 1A having a low pressure, causing a failure. Further, when a pulsation with a large pressure change occurs in the intermediate pressure, in the case of cantilever screw rotors such as the first screw vacuum pump 1A and the second screw vacuum pump 1B, the screw rotor is biased in the bending direction. A force is generated, causing contact between the screw rotor or between the screw rotor and the housing, causing damage. In particular, the first screw-type vacuum pump has a plurality of working chambers formed in parallel, for example, a pair of screw rotors such as three, four, four, and six, and is exhausted by volume compression. The pressure of each working chamber at the exhaust end face is different, and the force in the direction of bending with respect to the screw rotor increases. The second screw-type vacuum pump has a structure in which both screw rotors are single and exhausted without volume compression. Since the shaft diameter is smaller than the screw rotor of the first screw-type vacuum pump, Compared to the vacuum pump, the force in the direction of bending with respect to the screw rotor is not so great.

  A trap member 291 is disposed in the pulsation prevention space 290 formed in the upper end housing 272 so as to partition the intake port 253 and the exhaust chamber 268 so that reaction products do not enter the exhaust chamber 268. The trap member 291 has a hollow structure that tapers from the lower end to the upper end, and is configured such that reaction products accumulate in a groove 292 formed between the upper end housing 272 and the trap member 291. By configuring the upper end housing 272 as a side housing in which the upper surface flange and the air inlet 253 are formed, the reaction product accumulated in the groove portion 292 can be cleaned only by removing the upper surface flange.

  A small gap is formed between the screw rotors 202 and 203 and at least the rotor housing 204.

  The next screw rotor 202 includes a rotor member 256 and a rotating shaft member 205. The rotor member 256 and the rotating shaft member 205 are made of an iron-based material. The rotor member 256 is a hollow rotor, and a taper that narrows toward the upper part is provided on the inner periphery of the rotor member 256, and further, the taper of the rotor member 256 that becomes narrower toward the end also on the upper end of the rotary shaft member 205. A taper of the same shape is provided. Then, the rotating shafts of the rotor member 156 and the rotating shaft member 205 can be easily matched by press-contacting the tapered portions of the rotor member 256 and the rotating shaft member 205 with each other. The rotor member 256 and the rotating shaft member 205 are the same iron-based material, and there is almost no difference in the amount of thermal expansion due to temperature change. The rotor member 256 and the rotary shaft member 205 are pressure-contacted by a tapered portion by disposing a disc spring 258 between the hollow inner upper surface of the rotor member 256 and the bolt 259 fastened to the upper end of the rotary shaft member 205. . A lid 260 is fastened to the upper end portion of the screw rotor 202 so that reactive organisms do not accumulate in the hollow portion of the rotor member 256.

  Similarly, the screw rotor 203 includes a rotor member 261 and a rotating shaft member 208. The rotor member 261 and the rotating shaft member 208 are made of an iron-based material. The rotor member 261 is a hollow rotor, and is provided with a taper that becomes narrower toward the upper part of the inner periphery of the rotor member 261. Further, the upper end of the rotary shaft member 208 becomes thinner toward the end, and the taper of the rotor member 261 is reduced. A taper of the same shape is provided. Then, the rotating shafts of the rotor member 261 and the rotating shaft member 208 can be easily matched by pressing the tapered portions of the rotor member 261 and the rotating shaft member 208 together. The rotor member 261 and the rotating shaft member 208 are the same iron-based material, and there is almost no difference in the amount of thermal expansion due to temperature change. The rotor member 261 and the rotary shaft member 208 are pressure-contacted by a tapered portion by disposing a disc spring 264 between the hollow inner upper surface of the rotor member 261 and the bolt 264 fastened to the upper end of the rotary shaft member 208. . A lid 265 is fastened to the upper end portion of the screw rotor 203 so that reactive organisms do not accumulate in the hollow portion of the rotor member 261.

In the first screw-type vacuum pump, in order to obtain the exhaust capacity, the screw rotor becomes large, and the weight of the rotating part becomes heavy. However, the exhaust chamber 168 in operation is in the vicinity of the molecular flow region, and the gap between the screw rotor and between the screw rotor and the rotor casing can be widened. Therefore, even a material having a large thermal expansion coefficient can be used. Therefore, the screw rotor of the first screw type vacuum pump is optimally made of an aluminum-based material that has a large thermal expansion coefficient but is lightweight.
On the other hand, the second screw type vacuum pump has a smaller exhaust capacity than the first screw type vacuum pump, so the screw rotor part is small, but it needs a sealing function to suppress the backflow of the atmosphere. It is necessary to narrow the gap between the screw rotor and the rotor casing. Therefore, the screw rotor of the second screw-type vacuum pump is optimally an iron-based material having a high density but a low thermal expansion coefficient.

  In the screw rotor 202, the rotary shaft portion 205 of the rotor is rotatably supported in the rotor housing 204 by bearings 206 and 201 provided in the upper portion below the rotary shaft portion 205 and a bearing 223 provided in the lower portion. . In order to prevent the process gas (reaction product gas) in the exhaust chamber from leaking to the bearing side and accumulating on the bearing between the bearing 206 and the exhaust chamber 268, the lubricating oil on the bearing side 206 is further removed. A shaft seal 269 is provided so as not to leak to the exhaust chamber 268 side. The bearings 206, 201, and 223 are pressurized by a disc spring (not shown).

  Similarly, in the screw rotor 203, the rotary shaft portion 208 of the rotor can be freely rotated in the rotor housing 204 by the bearings 209 and 210 provided in the upper portion below the rotary shaft portion 208 and the bearing 224 provided in the lower portion. It is supported. In order to prevent the process gas (reaction product gas) in the exhaust chamber from leaking to the bearing side and accumulating on the bearing between the bearing 209 and the exhaust chamber 268, the lubricating oil on the bearing side 209 is further removed. A shaft seal 270 is provided so as not to leak to the exhaust chamber 268 side. The bearings 206, 201, and 223 are pressurized by a disc spring (not shown) or the like.

The outer rings of the bearings 206 and 201 are fixed to the inner periphery of a cylindrical bearing support member 275 made of an iron-based material, and the outer peripheral portion of the bearing support member 275 is pressed against a bearing housing 276 made of an iron-based material. It is fixed. At the lower end of the bearing support member 275, a protrusion 280 is formed in the radial direction of the rotary shaft so as to be easily positioned with respect to the outer ring of the bearing and the bearing housing 276 in the rotary shaft direction. Similarly, the outer rings of the bearings 209 and 210 are press-fixed to a bearing support member 277 made of an iron-based material, and the bearing support member 277 is press-fixed to a bearing housing 276 made of an iron-based material. At the lower end of the bearing support member 277, a protruding portion 281 is formed in the radial direction of the rotary shaft so as to be easily positioned with respect to the outer ring of the bearing and the bearing housing 276 in the rotary shaft direction. The bearing support members 275 and 277 are disposed so as to support the bearing in the empty portion 282 described later.
Thus, by fixing the outer ring of the bearings 206, 207, 209, 210 to the bearing housing 276 via the bearing support members 275, 277, the hollow portion 282 and the bearings 206, 207, 209, 210 are connected in series in the rotation axis direction. The axial length of the vacuum pump can be shortened without being arranged in the above.

  Further, the bearing housing 276 is formed with a hollow portion 282 for thermally insulating the bearings 206, 207, 209, 210 and the exhaust chamber 268. Thus, heat between the exhaust chamber 268 and the bearings 206, 207, 209, 210 is prevented so that heat such as compression heat of the exhaust gas generated in the exhaust chamber 268 is not transmitted to the bearings 206, 207, 209, 210. By providing a space in the conduction path, it becomes difficult for heat to be transferred to the bearings 206, 207, 209, and 210, and breakage due to a high temperature of the bearings 206, 207, 209, and 210 can be prevented. By providing the hollow portion 282 around the bearings 206, 207, 209, and 210, a heat conduction path through which heat is transmitted to the bearings 206, 207, 209, and 210 via the bearing housing 176 can be lengthened, so that a more heat insulating effect can be obtained. improves. Further, when the reaction product gas is exhausted, it is necessary to operate the vacuum pump with a high temperature in the path (intake port 253 → exhaust chamber 268 → exhaust port 254) through which the reaction product gas flows so that the reaction product does not accumulate. However, there is an effect that heat around the exhaust chamber 268 maintained at a high temperature by the hollow portion 282 is prevented from being transmitted to the bearings 206, 207, 209, and 210.

  The rotor housing 204, the upper end housing 272, and the bearing housing 276 constituting the exhaust chamber housing 271 are made of the same iron-based material as the rotor member 161 made of an iron-based material, and have the same thermal expansion coefficient. Thus, the gap between the screw rotors 202 and 203 and the exhaust chamber housing 271 is prevented from changing with temperature.

  A heat transfer plate 283 made of an aluminum material for controlling the temperature in the exhaust chamber 268 is in close contact with the periphery of the rotor housing 204. A passage 284 for flowing a cooling medium (water or the like) or a heating medium (high-temperature high-pressure steam or the like) is formed in the heat transfer plate 283, and heating / cooling is performed with these media. For example, when exhausting a reaction product gas that solidifies at a high temperature and low temperature (temperature close to normal temperature) such as tungsten, the exhaust chamber needs to be maintained at a low temperature, and cooling water is supplied to the path 284. In this way, the heat transfer plate 283 made of an aluminum material having a thermal conductivity better than that of an iron material is brought into close contact with the rotor housing 204 to equalize the temperature of the rotor housing 204.

A cooling plate 285 made of an aluminum-based material is disposed at a position at the lower end of the bearing housing 276 and in contact with a heat conduction path through which heat is transferred to the bearings 206, 207, 209, and 210 via the bearing housing 276. When the bearings 206, 207, 209, and 210 cannot be sufficiently maintained at a low temperature only by the hollow portion 282, the cooling plate 285 is disposed to reduce the amount of heat conducted to the bearings 206, 207, 209, and 210. Therefore, the temperature rise of the bearings 206, 207, 209, and 210 can be suppressed.
The cooling plate 285 is provided with a cooling path 286 for allowing a medium such as cooling water to flow, thereby further improving the cooling efficiency.

  Further, the cooling plate 285 is in contact with the motor housing 287, and the motor 213 can be cooled. Further, a second cooling plate 288 is in close contact with the outer periphery of the motor housing 287, and the motor 213 is also cooled by the second cooling plate 288. The second cooling plate 288 is provided with a cooling path 289 for allowing a medium such as cooling water to flow, thereby further improving the cooling efficiency.

  A timing gear 211 is provided at the lower end portion of the rotating shaft portion 205, and a timing gear 212 is provided at the lower end portion of the rotating shaft portion 208. When the timing gears 211 and 212 mesh with each other, the screw rotors 202 and 203 are engaged. Are configured to rotate in a non-contact manner synchronously.

  A permanent magnet type rotor 250 of the motor 213 is fixed between the bearing 210 of the rotating shaft portion 208 and the timing gear 212, and canned by a can 251. When the exhaust port 254 side of the second screw type vacuum pump is clogged, the pressure in the vicinity of the exhaust port 254 may become higher than the atmospheric pressure, and the process gas in the exhaust chamber 268 leaks to the motor 213 side. In this case, since the motor 213 is canned, the process gas can be prevented from leaking to the atmosphere. An electromagnet stator 252 of the motor 213 is fixed outside the can 251 and the rotational speed of the screw rotor 203 is controlled by an inverter. Furthermore, the screw rotors 202 and 203 are configured to rotate in a non-contact manner synchronously by transmitting the rotational motion to the screw rotor 202 via the timing gears 211 and 212.

  The timing gears 211 and 212 are housed in an oil chamber 227 in which lubricating oil 226 partitioned by an oil housing 225 is stored. The timing gears 211 and 212 are configured to be supplied with lubricating oil by a lubricating oil supply means (not shown). Furthermore, by changing the axial thickness of the timing gears 211 and 212 and arranging the axial bottom surfaces together, the lubricating oil that has been blown from the timing gear 211 to the timing gear 212 by the centrifugal force of rotation is exchanged with the timing gear 212. Stopped at the stepped portion, the meshing portion with the timing gears 211 and 212 is lubricated.

  Since some reaction product gases tend to solidify when the pressure increases, an inert gas is injected into the exhaust chamber on the side of the rotor housing 204 of the second screw vacuum pump 1B disposed on the atmosphere side. An inert gas injection path 295 is provided for diluting the reaction product gas to make it difficult to produce a reaction product.

  Finally, referring to FIG. 5, the exhaust port 154 of the first screw type vacuum pump 1A and the intake port 253 of the second screw type vacuum pump 1B are connected in series and the vertical two-stage screw type vacuum pump 300 is connected. The configuration will be described.

As shown in FIG. 5, the exhaust path formed by the exhaust port 154 of the first screw-type vacuum pump 1A, the intake port 253 of the second screw-type vacuum pump 1B, and the intermediate pipe 301 is horizontal. By disposing, the exhaust port 154 of the first screw type vacuum pump 1A and the intake port 253 of the second screw type vacuum pump 1B can be connected with almost no decrease in conductance.
Further, the exhaust port 154 of the first screw-type vacuum pump 1A and the intake port 253 of the second screw-type vacuum pump 1B may be connected without using the intermediate pipe 301.

  When repairing or maintaining the screw rotor part, the fastening between the bearing housing and the rotor housing of each of the first screw type vacuum pump and the second screw type vacuum pump is released, and the upper part of the rotor housing together with the rotor housing. By removing the upper end housing and the like disposed on the screw rotor portion, the screw rotor portion can be easily exposed to the operator, so that workability is improved and assembly is facilitated.

  It can be applied to a rotary rotor type fluid pump, a cantilever type rotary fluid pump, a rotary rotor type vacuum pump, a cantilever type rotary vacuum pump, and the like. In particular, it can be applied to a cantilever screw vacuum pump for exhausting process gas used in semiconductor manufacturing processes, and in particular, to a multi-stage cantilever screw vacuum pump in which a plurality of cantilever screw vacuum pumps are connected in series. .

It is sectional drawing which shows typically embodiment of the 1st screw type vacuum pump of the two-stage screw type vacuum pump which concerns on this invention. It is AA sectional drawing of FIG. It is sectional drawing which shows typically embodiment of the 2nd screw type vacuum pump of the two-stage screw type vacuum pump which concerns on this invention. It is BB sectional drawing of FIG. It is sectional drawing which shows typically embodiment of the two-stage screw type vacuum pump which concerns on this invention. It is explanatory drawing which showed the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A 1st screw type vacuum pump 102,103 Screw rotor 104 Rotor housing 105 Rotary shaft member 101,106,109,110,123,124 Bearing 107 A working chamber is formed 113 Motor 111,112 Timing gear 125 Oil housing 126 Lubricating oil 150 Rotor 151 Can 152 Stator 153 Intake port 154 Discharge port (exhaust port)
156 Rotor member 157 Cylinder member 166 Stepped portions 158 and 163 Disc springs 159 and 164 Bolt 160 and 165 Lid 168 Exhaust chamber 169 and 170 Shaft seal 171 Exhaust chamber housing 172 Upper end housing 173 Bearing housing 174 Baffle plates 175 and 177 Bearing support member 182 Hollow part 183 Heat transfer plate 184 Path 185 Cooling plate 186, 189 Cooling path 188 Second cooling plate

Claims (4)

  In the two-stage screw vacuum pump in which the suction port of the second screw type vacuum pump is connected to the exhaust port of the first screw type vacuum pump whose suction port is connected to the vacuum vessel, the first screw type vacuum pump and A two-stage screw-type vacuum pump characterized in that the screw rotor of the second screw-type vacuum pump is cantilevered and is vertically installed.   2. The two-stage according to claim 1, wherein an exhaust port of the first screw type vacuum pump and an intake port of the second screw type vacuum pump are disposed so as to face each other at a substantially horizontal position. Screw type vacuum pump.   The first housing that covers the screw rotor of the first screw-type vacuum pump and the second housing that covers the screw rotor of the second screw-type vacuum pump are each at least divided into two and at least divided into two The two-stage screw vacuum pump according to claim 1 or 2, wherein the screw rotor is exposed by removing the housing member.   The design pumping speed of the first screw-type vacuum pump is made larger than the design pumping speed of the second screw-type vacuum pump, and the first screw-type vacuum pump can be evacuated by volume compression. The two-stage screw type vacuum pump according to any one of claims 1 to 3.

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