JPH11270482A - Vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the operation and the exhaust speed in a vacuum pump comprising a male rotor and a female rotor engaged with each other in a casing, by forming a plurality of engagement parts on the male and female rotors at a specific distance, and mounting an intermediate plate having a communicating hole between the engagement parts. SOLUTION: A male rotor 1 and a female rotor 2 respectively comprising the engagement parts 11, 12 formed by the screw gears 1a, 2a, 1b, 2b are accomodated in a main casing 3 and a suction easing 4. On this occasion, the engagement parts 11, 12 are formed in such manner that the male rotor l and the female rotor 2 are located at a specific distance. An axial one end of the suction casing 4 is largely opened to be used as a gas intake port 13, and a discharge port is formed on an end plate 5 on the opposite side. Further an intermediate plate 20 is mounted on the end side of the engagement part 11 at a small interval so that it is not kept into contact with the end faces of the male rotor 1 and the female rotor 2, and an upper part of this intermediate plate 20 comprises a communicating hole 22 over both of the male rotor 1 side and the female rotor 2 side at the almost midway of the male rotor 1 and the female rotor 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vacuum pump,
In particular, the present invention relates to a vacuum pump suitable for a low / medium vacuum region from atmospheric pressure to a level of 10 ^-4 Torr.

[0002]

2. Description of the Related Art Conventionally, various types of vacuum pumps such as an oil rotary pump, a root pump and a diffusion pump have been used in a low / medium vacuum region. For example, in the semiconductor manufacturing field, a predetermined process is performed by storing a wafer in a container in a vacuum state. In this process, a vacuum pump is used while supplying an inert gas such as N ₂ gas into the container. Suction to remove impurities (O ₂ , CO _2, etc.) in the container,
And a vacuum of 0 ^over 4 Torr level. As a vacuum pump used in such a semiconductor manufacturing process, an oil rotary pump, a roots type mechanical booster pump, or the like is used.

[0003] However, in an oil rotary pump, the lubricating oil used is a gas (eg,
Arsenic, gallium, chlorine, Poly-Si, fluorine, etc.) to shorten the life as a lubricating oil, and oil molecules contaminate the inside of a semiconductor manufacturing container, which is undesirable in a semiconductor manufacturing process. There was a problem. Further, in the above-mentioned pump, since the pressure range for normal operation is narrow, it is necessary to switch and use several kinds of pumps until a predetermined pressure is reached, and one vacuum pump from atmospheric pressure to 10 ^-4 Torr level is used. There was a problem that it was not possible to exhaust.

To solve the above problem, Japanese Patent Application Laid-Open No.
A structure in which two pump bodies are formed as disclosed in Japanese Patent Application Laid-Open No. 2-168987 has been proposed. Referring to FIG. 4, the proposed vacuum pump includes a pair of male and female screw rotors 53 meshing with each other in a casing 52 having a suction port 50 on one side and a discharge port 51 on the other side.
The pump bodies 55 and 56 which are rotatably accommodated by appropriately disposing shaft sealing means 54 on both sides thereof are provided in two stages, and the casings 52 of the both bodies 55 and 56 are integrated to form a two-stage pump. Male and female rotors are provided coaxially and integrally rotatably, and the discharge port 55a of the first-stage pump body 55 and the suction port 56a of the second-stage pump body 56 are communicated by a pipe 57. Have. With such a configuration, the proposed vacuum pump connects the first suction port 50 to a place where the first suction port 50 is evacuated, for example, a vacuum tank, and discharges the gas sucked from the first suction port 50 to the first suction port. The inside of the tank can be evacuated by sending it from the outlet 55a to the second-stage discharge port 51 via the second-stage suction port 56a.

In order to solve the above-mentioned problem, Japanese Patent Laid-Open Publication No. Sho 60-2160897 has been proposed. This will be described with reference to FIG. FIG. 5 shows male and female rotors, and other parts are omitted. In FIG. 5, the male rotor 60 and the female rotor 61 are formed by portions 62 and 63 that perform suction and transfer operations and portions 64 and 65 that perform compression operations. The suction and transfer units 62 and 63 are
65, the twist angle θ is smaller and the L / D (length / diameter) is larger. As a result, a predetermined pressure can be obtained, and a large pumping speed can be obtained with the same size as that of a conventional general vacuum pump.

[0006]

SUMMARY OF THE INVENTION Incidentally, Japanese Patent Application Laid-Open
In the case of a vacuum pump as disclosed in JP-A-168987, it is necessary to connect a discharge port 55a of the first-stage pump main body 55 and a suction port 56a of the second-stage pump main body 56 by a pipe 57. , Resulting in a complicated pump structure. In addition, since the communication is established by the pipe 57, there is a technical problem that the conductance is reduced, the exhaust speed is slow, and it takes time to reach a predetermined pressure. Further, when a vacuum pump is used in a semiconductor manufacturing process or the like, there is a technical problem that a reaction product accumulates in the pipe 57 and eventually impairs a normal operation of the pump and the like.

In the case of a vacuum pump as disclosed in Japanese Patent Application Laid-Open No. Sho 60-2160897, a boundary portion 66 between portions 62 and 63 that perform suction and transfer and portions 64 and 65 that perform compression, that is, a twist angle. However, there is a technical problem that it is difficult to process a portion where the temperature changes rapidly. In addition, since the portions 62 and 63 that perform the transfer operation and the portions 64 and 65 that perform the compression operation are formed continuously, the cutting blade hits the already formed screw gear during cutting, and the tooth surface of the screw gear is used. There was a technical problem of cutting the steel.

An object of the present invention has been made to solve the above problems, for example 10 from atmospheric pressure (760 Torr) when used as a vacuum pump ^- in ⁴ Torr operating range of stable operation and pumping speed And a vacuum pump which can be easily manufactured.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a male rotor and a female rotor which mesh with each other.
A plurality of meshing portions formed at a fixed distance from the male and female rotors, a casing for accommodating both rotors, and a male and female rotor and a casing formed at the meshing portions. A working chamber, a gas inlet provided in the casing so as to be able to communicate with an end of the working chamber of the one meshing portion, and a casing so as to be able to communicate with an end of the working chamber of the other meshing portion. It is characterized by comprising: a provided gas discharge port; and an intermediate plate having a communication hole provided between the meshing portions. As described above, since a plurality of meshing portions are formed on the male and female rotors at a fixed distance, when manufacturing the screw gear portion constituting the meshing portion, the screw gear portion which has been already cut and the cutting blade are cut. Do not interfere with each other and do not break the cut screw gear portion. In addition, the provision of the intermediate plate is substantially equivalent to forming a screw gear for one lead, so that the compression ratio of the vacuum pump can be increased.

Here, there are provided a plurality of meshing portions formed on the male and female rotors, and an intermediate plate having a communication hole provided between the meshing portions, wherein the intermediate plate is in contact with an end face of the previous meshing portion. It is preferable that the gaps are arranged so as to have a small gap, and are formed so as to form a gap between the end face of the meshing portion of the next stage and the gas discharged from the meshing portion of the previous stage.
In this way, the intermediate plate is arranged with a minute gap from the end face of the previous meshing portion, and a gap is formed between the end face of the next meshing portion and the gas discharged from the previous meshing portion. As a result, the compression operation can be performed by the meshing portion at the next stage. In particular, since a gap for storing gas is formed, a stable pumping speed can be obtained over the entire operation range.

An intermediate plate having a communication hole is provided between a first meshing portion formed on the male and female rotors and a second meshing portion disposed at a stage subsequent to the first meshing portion. Wherein the intermediate plate is disposed with a minute gap from the end surface of the first meshing portion, and a gap for storing gas discharged from the first meshing portion is provided between the intermediate plate and the end surface of the second meshing portion. Preferably, they are arranged to be formed. By forming the first meshing portion and the second meshing portion on the male and female rotors as described above, the atmospheric pressure (760 Torr) when used as a vacuum pump.
10 r) ^- In ⁴ Torr operating range, it is possible to obtain a stable pumping speed.

Further, the first and second meshing portions formed on the male and female rotors are composed of screw gears, and the lead of the first meshing portion is larger than the lead of the second meshing portion. It is preferable that it is formed large. Thus, the lead of the first meshing portion is
Because it is formed larger than the lead of the second meshing part,
The first engagement portion can mainly perform suction and transfer operations, and the second engagement portion can mainly perform compression operations. In addition, since a supply portion to which an inert gas is supplied is formed close to a bearing rotatably supporting a male rotor and a female rotor that mesh with each other, oil molecules of a lubricant such as a bearing are formed. Can be prevented from entering the working chamber.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vacuum pump according to the present invention will be described with reference to the drawings. 1 and 2 show the schematic configuration of the vacuum pump. As shown in the figure, the male rotor 1 and the female rotor 2 are housed in a main casing 3 and a suction casing 4, and are rotatable by bearings 6 and 7 of an end plate 5 and bearings 9 and 10 of a sub-casing 8. Supported.

The male rotor 1 and the female rotor 2 have first and second meshing portions 11 and 12 having a pump function. The first and second meshing portions 11 and 12 are connected to the male rotor 1.
Gears 1a, 2a formed on the female rotor 2 and
a, 1b, and 2b. In the screw gears 1a, 2a, 1b, 2b, the helical helix angle is always constant, and the pitch in the rotation axis direction and the pitch in the plane perpendicular to the axis are also constant.

The first and second meshing portions 11 and 12
Are formed at a certain distance between the male rotor 1 and the female rotor 2. That is, the male rotor 1 and the female rotor 2
The screw gears 1a and 2a and the screw gears 1b and 2b are formed at regular intervals. This interval is determined in consideration of the distance where the cutting blade does not interfere with the tooth surface of the screw gear when cutting the screw gears 1a, 2a, 1b, 2b. The interval is determined by the thickness of the intermediate plate 20 and the second
Is determined by the size of the gap (storage portion) S for storing the gas discharged from the first meshing portion 11 formed on the side of the meshing portion 12. Therefore, when the screw gears 1a, 2a, 1b, 2b of the male rotor 1 and the female rotor 2 are formed by molding or the like instead of cutting, the thickness is determined by the thickness of the intermediate plate 20 and the size of the storage portion S. .

Although not shown exactly in the figure, the torsion angle θ ₁ of the screw gears 1 a and 2 a of the first meshing portion 11 that sucks gas into the vacuum pump and mainly transfers the gas is determined by the gas. Gear 1 of the second meshing portion 12 that compresses and discharges
The angle is smaller than the twist angle θ ₂ of b and 2b.
That is, the first gas is sucked into the vacuum pump and transferred.
The lead of the screw gears 1a and 2a of the meshing portion 11 is larger than the lead of the screw gears 1b and 2b of the second meshing portion 12 for compressing and discharging gas. With this configuration, the first meshing portion 11 can mainly perform the suction and transfer operations, and the second meshing portion 12 can mainly perform the compression operation. Moreover, the exhaust speed is determined by the length (size) of the lead on the intake side, but the first lead of the screw gears 1a, 2a of the second meshing portion 12 is shortened by the shortened lead.
Since the lead of the meshing portion 11 can be lengthened, a larger pumping speed can be obtained as compared with a vacuum pump having the same external dimensions.

The screw gear 1b of the second meshing portion 12
Since the lead 2b is formed short, the compression can be mainly performed by the second engagement portion 12. Also,
Since the leads of the screw gears 1b, 2b of the second meshing portion 12 are formed to be short, the backflow from the discharge port 14, which will be described later, can be reduced, and the heat generated by the compressed exhaust can be suppressed.

Further, as shown in FIG.
The casing 4 that covers the end face of the casing 4 has one end in the axial direction largely open as a gas inlet 13, and the opposite end plate 5.
Is provided with a discharge port 14. Except for these two ports, the casing 3 covers the male and female rotors 1 and 2 with a small gap, and the rotors 1 and 2 and the casing 3 form a V-shaped working chamber.

Timing gears 15 and 16 are attached to the shaft ends of the rotors 1 and 2, respectively.
Are adjusted so that the rotors do not contact each other. The bearings 6, 7, 9 and 10 are lubricated by splash lubrication, and the lubricating oil 13 accumulated in the auxiliary casing 8 is splashed by timing gears 15 and 16. In addition, a shaft seal portion 1 as a portion to be supplied with an inert gas is provided near the bearings 6, 7, and 16.
7, 18, and 19 are formed. An inert gas is supplied to the shaft seal portions 14, 15, 16 from an inert gas supply means (not shown) to prevent lubricating oil or outside air from entering the working chamber.

Since the temperature rises outside the main casing 3 due to the compression of the gas, a cooling jacket 3a is provided.
And compressed gas is cooled.

Next, the intermediate plate 20 provided with a small gap with respect to the end face of the first engagement portion 11 will be described with reference to FIGS. FIG. 3 is a side view of the first meshing portion 11 as viewed from the intermediate plate (a diagram viewed from the AA direction in FIGS. 1 and 2). As shown in FIG. An intermediate plate 20 is disposed at an end of the intermediate plate 20 at a minute interval without contacting the end surfaces of the male rotor 1a and the female rotor 2a. On the upper portion of the intermediate plate 20, a substantially one-way between the male rotor 1b and the female rotor 2b is provided, straddling both the male rotor 1b and the female rotor 2b. A communication hole 21 is formed.

Further, the intermediate plate 20 has a gap S between the intermediate plate 20 and the end face of the second meshing portion 12 for storing the gas discharged from the first meshing portion 11. Are located in By arranging the intermediate plate 20 between the first meshing portion 11 and the second meshing portion 12 of the male and female rotors 1 and 2 as described above, when the intermediate plate 20 is used as a vacuum pump in a predetermined operating range. , A stable pumping speed can be obtained. In particular, since the gap S for storing the gas discharged from the first meshing portion 11 is formed, a stable pumping speed can be obtained over the entire operation range.

Next, the operation of the vacuum pump according to the present invention will be described. When the male and female rotors 1 and 2 rotate, the gas in the tank (not shown) is sucked into the working chamber of the first meshing portion 11 from the suction port 13 by the first meshing portion 11. Then, it moves toward the intermediate plate 20 with the movement of the working chamber and is compressed. At this time, the screw gear of the first meshing portion 11
Since the door is formed larger than the second meshing portion 12, it also performs a compression action, but mainly performs a suction and transfer action.

When the airtight working chamber in the first meshing portion 11 reaches the communicating hole 21 of the intermediate plate 20 by the rotation of the rotor 1 or 2, the gas in the working chamber is discharged from the communicating hole 21. The gas discharged into the gap (storage portion) S between the second meshing portion 12 and the intermediate plate 20 is stored. Further, the gas stored in the gap S moves from the intermediate plate 20 toward the discharge port 14 by the movement of the working chamber of the second meshing portion 12 and is compressed. At this time, since the lead is formed smaller than that of the first meshing portion 11 of the screw gear of the second meshing portion, suction and transfer functions are also performed, but the compression function is mainly performed. Then, finally, the gas compressed by the second meshing portion 12 is exhausted from the discharge port 14.

The first and second engaging portions 11 and 12 are formed on the male and female rotors 1 and 2, and verification is performed using a vacuum pump in which the intermediate plate 20 is arranged as in the above embodiment. result, 10 from atmospheric pressure (760 Torr) ^- in ⁴ Torr operating range of, it was possible to obtain a stable pumping speed.
Further, the reaction product is finally exhausted from the discharge port 14 through the communication hole 21 of the intermediate plate 20 and the second meshing portion 12, so that the reaction product does not accumulate even if it enters the pump, and the normal operation can be performed. Was not inhibited.

[0026]

As is apparent from the above description, according to the vacuum pump of the present invention, a wide operating range can be obtained with a simple pump structure. In addition, since the pump is not communicated with the pipe as in the conventional case, the conductance does not decrease, and the reaction product is discharged out of the pump without accumulating even if it enters the pump. Operation can be stably obtained. Further, according to the vacuum pump of the present invention, since the gap portion is formed between the first pump and the second pump, the cutting blade may hit the meshing portion that has already been formed during cutting. Without it, it can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along line II-II of FIG. 2, showing an embodiment of a vacuum pump according to the present invention.

FIG. 2 is a sectional view taken along the line II of FIG. 1, showing an embodiment of the vacuum pump according to the present invention.

FIG. 3 is a side view showing an intermediate plate used in the vacuum pump according to the present invention.

FIG. 4 is a sectional view of a conventional vacuum pump.

FIG. 5 is a cross-sectional view of a conventional vacuum pump.
FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Male rotor 2 Female rotor 3 Main casing 4 Suction casing 5 End plate 8 Secondary casing 11 First meshing part 12 Second meshing part 13 Suction port 14 Discharge port 20 Intermediate plate 21 Communication hole S Gap (reservoir) θ ₁ θ ₂ Helix angle

Claims (6)

[Claims] A male rotor and a female rotor meshing with each other;
A plurality of engagement portions formed at a fixed distance from the male and female rotors, a casing for accommodating both rotors, and an operating chamber formed by the male and female rotors and the casing at the engagement portions A gas inlet provided in the casing so as to communicate with an end of the working chamber of the one meshing portion, and a gas inlet provided in the casing so as to communicate with an end of the working chamber of the other meshing portion. A vacuum pump comprising: a gas discharge port; and an intermediate plate having a communication hole provided between the meshing portions. 2. The vehicle according to claim 1, further comprising: a plurality of meshing portions formed on the male and female rotors; and an intermediate plate having a communication hole provided between the meshing portions. And a gap for storing the gas discharged from the previous meshing portion is formed between the first meshing portion and an end face of the next meshing portion. The vacuum pump according to 1. 3. An intermediate plate having a communication hole between a first meshing portion formed on the male and female rotors and a second meshing portion disposed at a stage subsequent to the first meshing portion. Wherein the intermediate plate is disposed with a minute gap from the end surface of the first meshing portion, and a gap for storing the gas discharged from the first meshing portion is provided between the intermediate plate and the end surface of the second meshing portion. The vacuum pump according to claim 1, wherein the vacuum pump is arranged to be formed. 4. The first and second meshing portions formed on the male and female rotors are composed of screw gears, and the lead of the first meshing portion is larger than the lead of the second meshing portion. The vacuum pump according to claim 3, wherein the vacuum pump is formed large. 5. The method according to claim 1, wherein the first engagement portion mainly sucks,
The vacuum pump according to claim 3, wherein the vacuum pump is configured to perform a transfer function and mainly perform a compression function by the second meshing portion. 6. A supply portion to which an inert gas is supplied is formed in the vicinity of a bearing rotatably supporting a male rotor and a female rotor which mesh with each other. 1
A vacuum pump according to claim 6.