JP2002174175A - Evacuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evacuator high in energy efficiency at the time when pressure on the air intake side is arrival pressure or vacuum to a certain degrees by reducing motive power by differential pressure. SOLUTION: The multistage type evacuator 100 furnished with a roughing pump B and a booster pump A is constituted to be high in energy efficiency by installing a ceiling pump C on the atmospheric air side of the final stage roughing pump B and making designed exhaust speed of the ceiling pump C in size enough to function as the ceiling pump even though it is lower than designed exhaust speed of the roughing pump B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum exhaust device used for exhausting a vacuum chamber or the like of a semiconductor manufacturing facility.

[0002]

2. Description of the Related Art In a semiconductor vacuum apparatus, a vacuum degree of about 0.01 Pa can be obtained in a chamber to be evacuated.
It is particularly important that no oil molecules enter the evacuated chamber. Therefore, as such a vacuum pump that can satisfy such demands, a screw vacuum pump, a roots vacuum pump, a claw vacuum pump, a scroll vacuum pump, a diaphragm vacuum pump, a piston vacuum pump, etc. There has been proposed an oil-free dry vacuum pump that can achieve a degree of vacuum up to about 0.01 Pa and is oil-free.

[0003] However, if these vacuum pumps are used alone, power consumption is increased, and it is difficult to achieve a sufficient vacuum ultimate pressure. In order to solve such a problem, conventionally, two or more stages of different types of vacuum pumps are combined in series.

[0004]

However, when these two or more stages of vacuum pumps are used, a dry vacuum pump having a relatively large displacement is used as a booster pump on the vacuum chamber side and a booster pump is used on the atmospheric exhaust side. It is common to use a roughing vacuum pump with a small displacement.
In this case, there are the following inherent problems.

Since the volume of the transfer chamber is smaller than that of a single-stage roughing pump used in the atmosphere, when the reactive gas is exhausted, the pump is formed by accumulating products in the transfer chamber and the like. The problem is that the adverse effect on the vehicle is greatly increased, and long-term continuous operation is likely to be hindered.

Conventionally, the following solutions have been proposed to solve such a problem. Since the reaction gas is exhausted as a gas without solidifying in a specific temperature range, a heater is attached to the atmosphere-side vacuum pump to keep the inside of the chamber at this temperature range. Furthermore, a problem can be solved by creating a refuse space for storing products and the like on the exhaust side of the pump for easy maintenance.

However, in this case, although the size of the roughing pump is small, the heater must be relatively large in order to control the temperature of the roughing pump, and the burden on the production cost and power consumption is large. Would. It is an object of the present invention to solve such a problem.

[0008]

In order to solve the above-mentioned problems, a vacuum pumping apparatus according to the present invention is a vacuum pumping apparatus having a roughing pump and a booster pump. The pump is designed and equipped with a sealing pump to seal the backflow. The design pumping speed of the sealing pump (“design pumping speed” is the gas transfer volume per rotation of the input shaft and the unit of the input shaft. A value obtained by multiplying the number of rotations over time, the same applies hereinafter) is smaller than the designed pumping speed of the roughing pump but functions as a sealed pump.

A heater for preventing the backflow of the atmosphere into the roughing pump and using a sealed pump having a designed pumping speed smaller than that of the pump to suppress the deposition of the reactive gas. Even if the heater is used, the heater may be attached to the sealing pump, and the sealing pump can be made smaller, so that the heater can be made smaller. Even if the sealed pump is affected by the reaction gas, the sealed pump is small, lightweight and compact, so that it can be easily attached and detached and exchanged with a spare sealed pump. Therefore, maintenance time can be reduced.

Further, since the design pumping speed of the sealed pump is smaller than that of the roughing pump, the motor for operating the sealed pump can be downsized. Here, it is the sealed pump that receives a load due to the pressure difference between the atmosphere side and the vacuum side during the steady operation. Therefore, power consumption during steady operation can be reduced.

Further, in the vacuum evacuation apparatus according to the present invention, the roughing pump and the sealing pump are driven until the suction side pressure of the booster pump drops from the atmosphere to about 13300 Pa, and the suction side pressure of the booster pump is about 13300 Pa or less. Then, the booster pump is driven when it becomes With this configuration, the power required to drive the booster pump, the roughing pump, and the sealed pump may be small, and the driving motor may have a small capacity.

Further, in the vacuum exhaust system according to the present invention, in a vacuum exhaust system in which a plurality of stages of vacuum pumps are connected in series or in parallel, it is possible to prevent the atmosphere from flowing back into the exhaust port of the final stage roughing pump. Wherein the designed pumping speed of the sealed pump is smaller than the designed pumping speed of the final-stage roughing pump but large enough to function as a sealed pump.

In this case, even if a heater for suppressing the deposition of the reactive gas is used, the heater may be mounted on the sealing pump, and the sealing pump can be made smaller, so that the heater can be downsized. Even if the sealed pump is affected by the reaction gas, the sealed pump is small, lightweight and compact, so that it can be easily attached and detached and exchanged with a spare sealed pump. In addition, power consumption during steady operation can be reduced.

Further, the vacuum pumping apparatus of the present invention is provided with a bypass valve for bypassing the sealed pump between the final-stage roughing pump and the pumping pipe, and the suction pressure of the first pump of the plurality of vacuum pumps on the exhaust chamber side is compared. In a relatively high range, the bypass valve is opened to reduce the exhaust time, and exhaust from the valve is enabled.When the discharge pressure of the final-stage roughing pump reaches the ultimate pressure or a relatively low pressure, the bypass valve is opened. The valve is closed and the pump is evacuated only from the sealed pump. With this configuration, the evacuation time from the atmospheric pressure can be reduced.

Further, the vacuum pumping apparatus of the present invention is characterized in that the designed pumping speed of the sealed pump is 1/5 to 1/100 of the designed pumping speed of the roughing vacuum pump. With this configuration, it is possible to more reliably obtain a vacuum exhaust device having higher energy efficiency as compared with the related art.

[0016]

Preferred embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIG.
The evacuation device 100 according to the embodiment will be described.

The vacuum evacuation apparatus 100 includes a screw type vacuum pump A as a mechanical booster pump, a screw type vacuum pump B as a roughing pump, and a screw type vacuum pump C as a sealing pump.

In the following terms, "main" means "booster screw vacuum pump", "sub" means "roughing screw vacuum pump", and "seal" means "sealed screw pump".

The evacuation apparatus 100 includes a main screw rotor 130 (a screw rotor of a booster screw vacuum pump), a sub screw rotor 150 having a smaller outer diameter than the main screw rotor 130 (a screw rotor of a roughing screw vacuum pump), A seal screw rotor 200 having a smaller outer diameter than the screw rotor 150 (a screw rotor of a sealing screw vacuum pump). Main screw rotor 1
30 includes male and female screw rotors 130f and 130m, sub-screw rotor 150 includes male and female screw rotors 150f and 150m, and seal screw rotor 200 includes male and female screw rotors 2.
00f and 200 m.

The main screw rotor 130 is provided with a main rotor storage chamber 11 formed inside the housing 110.
0b. In detail, 130f
Is rotatably supported by the housing 110 by bearings 131 and 132, and the male rotor 130m is rotatably supported by the housing 110 by bearings 133 and 134. Here, the seals 137 and 138 are
1, 132, 133 and 134 and main rotor storage room 1
10b and bearings 131, 132, 133 and 1
34 prevents leakage of the lubricating oil into the main rotor storage chamber 110b.
Foreign matter is prevented from entering the bearings 131, 132, 133 and 134 from the outside.

The sub-screw rotor 150 has a sub-rotor storage chamber 110d formed inside the housing 110.
It is stored in. More specifically, the female rotor 150f is connected to the housing 110 by bearings 161, 162 and 163.
The rotor 150m is rotatably supported by the male rotor 150m.
4, 165 and 166 rotatably supported by the housing 110. Here, the seals 167, 16
8, 169 and 170 are bearings 161, 162, 163,
164, 165 and 166 and sub rotor storage room 110d
And bearings 161, 162, 163, 164, 1
65 and 166 are prevented from leaking into the sub rotor storage chamber 110d, and the sub rotor storage chamber 1
From 10d, bearings 161, 162, 163, 164, 16
5 and 166 are prevented from entering a foreign substance.

The seal screw rotor 200 has a seal rotor storage chamber 11 formed inside the housing 110.
0f. Specifically, the female rotor 200f
Is the housing 2 by the bearings 211, 212 and 213.
00 and the male rotor 200m
14, 215 and 216 rotatably supported by the housing 110. Here, the seals 217, 21
8, 219 and 220 are bearings 211, 212, 213,
214, 215 and 216 and the sub rotor storage chamber 110e
And bearings 211, 212, 213, 214, 2
15 and 216 are prevented from leaking into the sub rotor storage chamber 110e.
From 10e, bearings 211, 212, 213, 214, 21
5 and 216 are prevented from entering foreign matter.

The designed pumping speed (a value obtained by multiplying the gas transfer volume per one rotation of the input shaft and the number of rotations per unit time of the input shaft) of the screw type vacuum pump C as a sealed pump is 5 liters.
/ min (rated rotation speed of the motor 223: 3000 rpm)
The designed pumping speed of the screw type vacuum pump B as a roughing pump is 420 l / min (rated rotation speed of the motor 173 is 4500 rpm), and the designed pumping speed of the screw type vacuum pump A as a mechanical booster pump is 850.
0 liter / min (rated speed of motor 143: 6800r
pm). That is, the designed pumping speed of the sealed pump C is about 1/100 of that of the roughing pump B,
The designed pumping speed of the roughing pump B is about 1 times that of the booster pump A.
/ 20. Thus, the fact that the designed pumping speed of the sealed pump C is smaller than that of the roughing pump B means that the volume of the exhaust-side transfer chamber 200A communicating with the atmosphere of the sealed pump C also increases as shown in FIG. It is correspondingly smaller. Accordingly, the volume of the exhaust-side transfer chamber 200A of the sealed pump C is sufficiently smaller than the volume of the intake-side transfer chamber 150A of the roughing pump B. The relationship between the right end face in FIG. 2 of the exhaust side transfer chamber 200A communicating with the atmosphere of the sealed pump C in FIG. 2 and the left end face (housing inner wall) in FIG. 2 of the exhaust port 110g is obtained while securing a necessary exhaust passage area. The exhaust-side transfer chamber 200A communicating with the atmosphere is designed to have a minimum volume. Specifically, the volume of the exhaust-side transfer chamber 200A can be reduced to about 1/5 of the volume of the suction-side transfer chamber 150B of the roughing pump itself.

The main rotor storage chamber 110b is formed in the wall of the housing 110, and communicates with the outside of the housing 110 through an intake port 110a for sucking a compressive fluid from the outside of the housing 110 into the inside of the housing 110. The main rotor storage chamber 110b and the sub rotor storage chamber 110d communicate with each other through a communication path 110c formed inside the housing 110, and the sub rotor storage chamber 110d and the seal rotor storage chamber 110f communicate with each other through a communication path formed inside the housing 110. 110e, and the seal rotor storage chamber 110f is connected to the housing 11
0, and is communicated with the outside of the housing 110 by an exhaust port 110g for discharging a compressive fluid from the inside of the housing 110 to the outside of the housing 110. Here, the intake port 110a communicates with a vacuum container having a fixed volume (not shown), and the exhaust port 110g communicates with the atmosphere.

At one end of the male and female rotors 130f and 130m of the main screw rotor 130, timing gears 141 and 142 for rotating one of them with the other are fixed so as to mesh with each other. Further, at one end of the male rotor 130m,
The main motor 143 is integrally connected.

One end of each of the male and female rotors 150f and 150m of the sub-screw rotor 150 is provided with a timing gear 1 for rotating one of them with the other.
71 and 172 are fixed so as to mesh with each other. Further, a sub motor 173 is integrally connected to one end of the female rotor 150f.

Timing gears 221 and 222 for rotating one of the male and female rotors 200f and 200m of the seal screw rotor 200 in accordance with the rotation of one of them are fixed to mesh with each other. Further, at one end of the female rotor 200f,
The sub motor 223 is integrally connected.

The housing 110 includes a main housing first member 111, a main housing second member 112, a main housing third member 113, a main housing fourth member 114, a sub housing first member 115, a sub housing second member 116, a sub housing Housing third member 117,
The sub-housing fourth member 118, the seal housing first member 119, the seal housing second member 120, the seal housing third member 121, and the seal housing fourth member 122 are formed.

In this embodiment, the main male and female rotors 130
f, the number of screw teeth of 130m is 6: 5, the ratio of screw teeth of the sub-side male and female rotors 150f and 150m is also 6: 5, and the ratio of screw teeth of the male and female rotors 200f and 200m is also 6: 5. Each is configured. The number of screw turns of the main-side male and female rotors 130f and 130m is 1 (the "number of turns" here is the female screw 130f
(6 teeth) means the number of turns. When the number of teeth of the male and female screws is different, the "number of turns" refers to the number of turns of the screw having the larger number of teeth, as described above. ), The number of screw turns of the sub-side male and female rotors 150f and 150m is five, and the number of screw turns of the seal-side male and female rotors 200f and 200m is three. The screw lead angle of the main female rotor 120f is about 45 degrees, the screw lead angle of the sub female rotor 150f is about 12 degrees, and the screw lead angle of the seal female rotor 200f is about 12 degrees.
Each time, each is configured.

Here, the main-side male and female rotors 12
The number of turns of the screw of 0f and 120m is substantially one, or at least one gas transfer chamber (for example, a closed chamber in a compression step as shown by 120B in FIG. 3) which is not communicated with any of the intake port 110a and the exhaust port 110c. The number of turns formed may be sufficient. Booster pump A in this embodiment
This is because the sealing performance does not need to be improved due to the relationship between the designed pumping speed of the roughing pump B and the sealing performance. Also,
Also for the roughing pump B, it is not necessary to make the sealing performance so good because of the relationship between the designed pumping speed of the seal pump C and the sealing performance.

Next, the evacuation device 10 according to the present embodiment
The operation of 0 will be described. First, a case will be described in which the gas in the chamber is evacuated by the roughing screw vacuum pump B until the pressure in the vacuum container (not shown) changes from around atmospheric pressure to around 13300 Pa. By driving the submotor 173, the male and female rotors 150f and 150m rotate, and exhaust the gas in the vacuum exhaust chamber. At this time, the gas in the vacuum evacuation chamber is supplied to the intake port 110 of the booster pump A.
a, is sucked into the sealing pump C via the communication path 110c between the booster pump A and the booster pump A and the roughing pump B, and the communication path 110e between the roughing pump B and the roughing pump B and the sealing pump C, It is discharged into the atmosphere from the exhaust port 110f. At this time, the sealing pump drives the seal motor 223 simultaneously with the driving of the sub motor 223, thereby preventing the male and female rotors 200f and 200m from rotating and preventing gas from flowing back from the atmosphere side into the vacuum exhaust chamber. At this point, since the amount of gas to be exhausted is large, it cannot be exhausted in a short time with the exhaust amount of the seal pump. Therefore, when the suction side pressure of the sealed pump is larger than about 13300 Pa, not only the sealed pump but also the rough pump is evacuated through the bypass valve 250.

When the pressure on the suction side of the booster screw vacuum pump A becomes about 13300 Pa or less due to the exhaustion, the rotor 150 of the roughing screw vacuum pump B is turned off.
f, Start driving the booster pump A while maintaining the rotation of 150 m. That is, by driving the main motor 143, the male and female rotors 130m and 130f are rotated, and the diluted gas in the vacuum exhaust chamber is transferred and exhausted to the roughing pump B side. The roughing pump B transfers and compresses the gas transferred from the booster pump A to the sealed pump C side and discharges the gas from the exhaust port 110g to the atmosphere. As described above, the pressure of the container having the vacuum volume is reduced to the ultimate pressure. Here, since the booster pump A discharges a gas having a low pressure, the power required to drive the booster pump A may be small. Therefore, the drive motor can be of a small capacity. Further, the roughing pump B also discharges a gas having a low pressure under a steady operation, so that the load on the motor is reduced and the power consumption thereof can be reduced.

In this embodiment, the designed pumping speed of the screw type vacuum pump C as the sealing pump of the vacuum pump 100 is 5 liter / min (the rated rotation speed of the motor 173 is 3000 rpm).
pm), the designed pumping speed of the screw type vacuum pump B as the roughing pump is 420 L / min (rated rotation speed of the motor 173 is 4500 rpm), and the designed pumping speed of the screw type vacuum pump A as the booster pump is 8500 L / m.
in (the rated rotational speed of the motor 143 is 6800 rpm). That is, the pumping speed of the sealed pump C is designed to be about 1/100 of that of the roughing pump B, and the pumping speed of the roughing pump B is designed to be about 1/20 that of the booster pump A. Power due to pressure can be reduced, and energy efficiency can be increased when the pressure on the intake side is the ultimate pressure or a certain degree of vacuum.

Here, the power consumption can be reduced as the designed pumping speed of the sealed pump C is smaller than the designed pumping speed of the roughing pump B, but the designed pumping speed of the sealed pump is reduced. If it is made too small, the evacuation time will be prolonged in the transition period from when the pressure of the vacuum container is changed from the atmospheric pressure to the ultimate pressure. In order to solve this problem, a bypass valve is provided between the roughing pump and the sealing pump so as to directly exhaust the gas from the atmospheric pressure to a vacuum pressure of about 13300 Pa from the roughing pump. However, although the bypass valve is attached, the design pumping speed of the sealed pump cannot be reduced without limitation, and both the power consumption and the pumping time are taken into consideration, and the sealed pump pump speed relative to the designed pumping speed of the roughing pump B is considered. The designed pumping speed of C is preferably set to 1/5 to 1/100.

As described above, since the designed pumping speed of the sealed pump C is sufficiently small as described above, the fluid transfer space can be narrowed, and the screw diameter can be reduced. Therefore, the gap variation due to the thermal expansion in the radial direction is also reduced, so that the radial gap can be further reduced. As a result, the total gas leakage space is reduced, and the sealing performance can be improved. Therefore, the sealing pump C does not need to be devised to improve the sealing performance, and the size of the entire shaft can be kept small. Further, even if the accuracy of the gap between the screw of the roughing pump B and the housing is not so good due to the sealing property of the sealing pump C, a high degree of vacuum can be obtained and the axial length of the booster screw pump A can be increased. Can be shortened.

Here, the number of turns of the male and female screws 130f and 130m of the booster screw pump A is approximately 1 or a gas which does not communicate with either the intake port or the exhaust port of the booster pump in consideration of the ultimate vacuum and the axial size. The number of turns in which at least one transfer chamber is formed may be sufficient. Male and female screws 130f, 130 of roughing screw pump B
The number of turns of m may be about 3 to 10 since the sealing property of the present invention is improved as described above. Further, the number of turns of the male and female screws 170f and 170m of the sealing pump C is preferably as large as possible in relation to the sealing property.
It may be about 10.

As described above, since the axial length of the booster pump A can be kept short, even if the conductance is increased by increasing the lead angle of the screw of the booster pump A, the axial length becomes excessive. Not even.

Here, the lead angle of the female screw 130f of the booster screw pump A is preferably about 30 ° to 60 ° in order to make it easier for the gas molecules on the intake side to enter the screw groove. In particular, in order to improve the knocking effect of the gas molecules on the intake side due to the screw tooth surface, 45 °
Preferably, it is near. The lead angle of the female screw 150f of the roughing screw pump B does not need to be large, and may be about 8 ° to 15 ° in consideration of processing and axial length. Screw 200f for sealed pump C
Does not need to be large, and may be about 8 ° to 15 ° in consideration of processing and the length in the axial direction.

When a screw vacuum pump having a simple structure is employed as the sealing pump, the exhaust passage becomes simple and short. Therefore, the reaction product is unlikely to be clogged in the exhaust passage, and even if clogged or attached, maintenance such as removal is easy. Furthermore, even when other vacuum pumps including a screw type vacuum pump are used, the sealed pump is small, light and compact, so that the manufacturing cost is low and the mounting and dismounting can be easily performed, so that the replacement with the spare sealed pump is easy. I can do it.

The evacuation device 10 according to the present embodiment
Since the rotation axis of the main screw rotor 130, the rotation axis of the sub screw rotor 150, and the rotation axis of the seal screw rotor 200 are different from each other, these rotors can be designed more freely than the conventional example shown in FIG. it can. Therefore, the main screw rotor 130 can be designed to have both a large screw outer diameter and a large lead so that the suction conductance is large. In addition, the seal screw rotor 200 has a small outer diameter so that the power due to the differential pressure is small, that is, the exhaust-side transfer chamber 200A has a small volume, and sealing performance, workability, rotation balance, and the like are taken into consideration. Therefore, the lead angle θ1 can be designed to a value most suitable for processing.

With such a configuration, the sealed pump that exhausts to the atmosphere side is the place where the most torque load is applied to the motor due to the pressure difference between the suction side and the exhaust side. The torque load due to the same differential pressure from the atmosphere can be reduced as the volume of the pump is reduced. The use of a sealed pump having a small volume reduces power consumption due to the pressure difference during steady operation, reduces vibration and noise.

(Second Embodiment) FIG. 4 shows an embodiment of a viscous pump portion when a viscous pump is used as the sealing pump. In FIG. 4, reference numeral 41 denotes a housing;
Is a screw, and 43 is a bypass valve.

(Third Embodiment) As shown in FIG. 5, in a vacuum exhaust device 300 according to a third embodiment, the booster pump A is a screw pump, the roughing pump B is a scroll pump, and the sealing pump C is a screw pump. It is characterized by using a pump. A vacuum exhaust device 300 according to a third embodiment of the present invention will be described with reference to FIG. However, only the points that are substantially different from the first embodiment will be described, and the description of the same configuration as the first embodiment will be omitted.

FIG. 5 shows the overall structure of the vacuum pump of this embodiment. The roughing scroll type vacuum pump B shown in FIG. 5 is fitted on the first frame 2 and the second frame 3 with the axes thereof aligned with the first frame 1 and the second frame 2 with the wraps facing each other. The first fixed scroll 3 and the second fixed scroll 4 and the wrap are opposed to each other so as to be sandwiched between the first fixed scroll 3 and the second fixed scroll 4 so as to be able to move eccentrically around the axis. The orbiting scroll 5 and a crankshaft that is rotationally driven via a motor 6 for driving the orbiting scroll 5 and bearings 7 and 8 that are arranged so that their axes are aligned with the first fixed scroll 3 and the second fixed scroll 4. 9, a suction pipe 10 and a discharge port 11.

By using a scroll pump having a very high compression ratio as a roughing pump, a booster pump having a low compression ratio can be used in the present configuration.
Further, since the scroll pump is operated in a steady state at a relatively low rotation speed, vibration and noise can be suppressed.

In each of the embodiments described above, a case has been described in which a screw pump is used as a booster pump, a screw type or scroll type pump is used as a roughing pump, and a screw type or viscous pump is used as a sealing pump. However, in the present invention, a roots pump, a claw pump, a scroll pump, a diaphragm pump, or a piston pump may be used as the booster pump. Roots type, claw type, diaphragm type,
In addition to a piston type pump and a diffusion pump, an oil rotary pump can be used if it is operated in such a manner that oil does not flow backward to the booster pump side. As for the sealed pump attached to the two-stage or multi-stage vacuum pumps composed of these vacuum pumps, pumps of the roots type, claw type, scroll type, diaphragm type, piston type, etc., or oil rotary type are also available. Can be used.

[0048]

As described above, the vacuum pumping apparatus of the present invention seals the backflow of the atmosphere into the final-stage roughing pump with respect to the multistage vacuum pump composed of the roughing pump and the booster pump. A sealing pump is attached to the exhaust port of the roughing pump in order to reduce the design pumping speed of the sealing pump.
Vacuum pump that is sufficiently smaller than the designed pumping speed of the roughing pump but has a size that functions as a sealed pump, has a simple structure, low power consumption, low vibration and noise, can achieve high vacuum pressure, and is easy to maintain. Equipment can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of an evacuation apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a screw-type sealing pump of the evacuation device shown in FIG.

FIG. 3 is a partially exploded view of a screw of a roughing pump and a sealing pump of the evacuation apparatus shown in FIG. 1;

FIG. 4 is an enlarged sectional view of a viscous pump type sealing pump of the vacuum evacuation device shown in FIG.

FIG. 5 is a cross-sectional view of a vacuum exhaust device according to a second embodiment of the present invention.

[Explanation of symbols]

 A roughing pump B booster pump C sealed pump 100, 300 Vacuum exhaust device 110a intake port 110f exhaust port 130A intake-side transfer chamber 150A exhaust-side transfer chamber

Claims (6)

[Claims] 1. A vacuum exhaust device comprising a roughing pump and a booster pump, wherein a sealing pump for sealing a backflow of the atmosphere into the pump is mounted on an exhaust port of the roughing pump. A vacuum pumping apparatus characterized in that the designed pumping speed of the sealed pump is smaller than the designed pumping speed of the roughing pump, but is large enough to function as a sealed pump. 2. A bypass valve is provided between the roughing pump and the exhaust pipe so as to bypass the sealed pump. In a range where the suction pressure of the booster pump on the exhaust chamber side is relatively high, the exhaust time is reduced. By opening the bypass valve to enable exhaust from the valve, and when the discharge side pressure of the roughing pump reaches the ultimate pressure or a relatively low pressure, close the bypass valve and exhaust only from the sealed pump. The evacuation apparatus according to claim 1, wherein: 3. A bypass valve is provided between the roughing pump and the exhaust pipe so as to bypass the sealed pump. In a range where the suction pressure of the booster pump on the exhaust chamber side is relatively high, the exhaust time is reduced. By opening the bypass valve to enable exhaust from the valve, and when the discharge side pressure of the roughing pump reaches the ultimate pressure or a relatively low pressure, close the bypass valve and exhaust only from the sealed pump. The evacuation apparatus according to claim 1, wherein: 4. A vacuum pumping apparatus in which a plurality of vacuum pumps are connected in series or in parallel, and a sealed pump for preventing a backflow of the atmosphere into the pump is provided at an exhaust port of the final-stage roughing pump. A vacuum evacuation apparatus characterized in that the design pumping speed of the sealed pump is smaller than the designed pumping speed of the final-stage roughing pump but is large enough to function as a sealed pump. 5. A bypass valve for bypassing the sealed pump is provided between the final-stage roughing pump and the exhaust pipe, and the exhaust time is reduced when the suction pressure of the first-stage pump on the exhaust chamber side is relatively high. Therefore, the bypass valve is opened to allow exhaust from the valve, and when the discharge pressure of the final-stage roughing pump reaches the ultimate pressure or a relatively low pressure, the bypass valve is closed and exhaust is performed only from the sealed pump. The vacuum evacuation apparatus according to claim 4, wherein the evacuation is performed. 6. The vacuum pump according to claim 1, wherein the designed pumping speed of the sealed pump is 1/5 to 1/100 of the designed pumping speed of the roughing vacuum pump. The evacuation device according to item 1.