KR19990083482A - Single-stage roots pump and multi-stage roots pump - Google Patents

Abstract

Once in the Roots pump, in order to increase the compression ratio, at least one intake port is constituted by three or more rotors between the first to nth rotors and defined by the (n-2) and (n-1) rotors. And the inlet openings defined by the (n-1) and nth rotors are open, and the exhaust ports defined by the (n-2) and (n-1) rotors are on the same side of the imaginary surface including a plurality of axes. The exhaust port communicated with the intake port defined by the (n-1) th and nth rotors and open by the (n-1) th nth rotor is opened.

In a multistage Roots pump, in order to communicate the exhaust port of the preceding stage pump chamber and the intake port of the subsequent stage pump chamber, the rotor between the first to nth rotors forms one set in the same tank, and in the pump chamber of the foremost stage, -2) one or more intake ports defined by the (n-1) rotor and an exhaust port defined by the (n-1) rotor n th rotor are open, and defined by the (n-1) and n th rotor The exhaust port communicates with the intake port defined by the (n-2) -rotor (n-1) rotor of the pump chamber of the subsequent stage on the same side of the imaginary surface including a plurality of shafts, and in the pump chamber except for the foremost stage and the rearmost stage, The exhaust port defined in the n-2) and (n-1) rotors communicates with the intake port defined by the (n-1) and nth rotors on the same side of the virtual surface, and in the pump chamber at the rearmost stage, the (n−) The exhaust port defined by 1) and the nth rotor is open.

Description

Single Roots Pump and Multistage Roots Pump {SINGLE-STAGE ROOTS PUMP AND MULTI-STAGE ROOTS PUMP}

The present invention includes a single Roots pump, which is driven by a rotary drive device such as a motor, and once performs a pumping operation by a pump chamber; A single pumping device in which the Roots pump and the rotary drive are manufactured as one unit; A multi-stage Roots pump driven by a rotary drive device and sequentially performing pumping operations in each stage; And a multistage pumping device in which the multistage Roots pump and the rotary drive device are integrally formed.

In a conventional single pumping device, the roots pump and the motor are integrally formed. Once the Roots pump has one pump chamber provided with an exhaust port and an inlet formed in the casing, a pair of rotors mounted on two axes in the casing are positioned side by side to interlock with each other. In the casing, both the inlet and exhaust ports of the pump chamber are open. One of the axes of the Roots pump is connected with a drive shaft which protrudes from the body of the motor. At the tip of one shaft connected to the drive shaft of the motor, the drive gear is fixed to transmit rotation in engagement with the driven gear once fixed to the tip of another shaft of the Roots pump.

In order to depressurize the inside by using the pumping device once to evacuate the chamber, the intake port of the Roots pump is open toward the chamber and the exhaust port is open toward the atmosphere. The Roots pump is then driven by a motor. As a result, each rotor is once rotated in the pump room of the Roots pump in an engaged state to perform the pumping operation, whereby the air in the chamber is released to the atmosphere to realize the pressure reduction in the chamber.

On the other hand, in the conventional multistage pumping apparatus, the multistage Roots pump and the motor are integrated. In a multi-stage Roots pump, a plurality of pump chambers each having an intake port and an exhaust port in a casing are formed side by side. In each pump room, a pair of (two) rotors are mounted on two side-by-side shafts which rotate in engagement with each other. The inlet port of the foremost pump chamber is open at the casing. A relatively long dividing wall in the axial direction is formed between the pump chamber of the preceding (previous) stage and the pump chamber of the subsequent (previous) stage, so that the intake port of the pump chamber of the preceding stage extends about 180 ° around the dividing wall, It communicates with the intake port of the pump chamber. The exhaust port of the rearmost pump chamber is open. On one shaft of the multistage Roots pump is connected a drive shaft protruding from the motor body for rotation transfer. At the tip of one shaft connected to the drive shaft of the motor, the drive gear is fixed to engage the driven gear fixed to the tip of another shaft of the multistage Roots pump to transmit rotation.

In order to vacuum the chamber by depressurizing the inside by using the multistage pumping device, the inlet port of the foremost pump chamber of the multistage Roots pump is open toward the pump chamber, the exhaust port of the rear pump system is open to the atmosphere, and the multistage Roots pump is Driven by a motor. As a result, each rotor is rotated in engagement with the pump chamber of the multi-stage Roots pump to perform the pumping operation, whereby the air in the chamber is released to the atmosphere to realize the pressure reduction in the chamber. However, in the conventional one-time Roots pump or one-time Roots pumping apparatus described above, although pressurized air for pumping operation is once supplied by the Roots pump, a paired rotor is placed in one pump chamber, so that the compression ratio is sufficiently high or large. Ensure that little is obtained. Therefore, the vacuum state is hardly realized even once the Roots pump or the pumping device is used.

Alternatively, in the above-described multistage Roots pump or multistage pumping apparatus, a relatively large compression ratio can be obtained because the multistage Roots pump has a plurality of pump chambers to realize an almost vacuum state.

However, in the above-described conventional multi-stage Roots pump or multi-stage pumping apparatus, a communication path surrounding the pump or the apparatus at about 180 ° is provided in order to sequentially communicate with the exhaust port of the preceding stage pump chamber and the intake port of the subsequent stage pump chamber. And a dividing wall provided between the pump chamber and the subsequent stage. For this reason, the dividing wall is longer in the axial direction, which makes the length of the multistage Roots pump or multistage pumping device longer, so that the setting area of the pump or device is expanded to such an extent that setting is difficult.

Of course, as introduced in Japanese Patent Laid-Open No. Hei 4-8891, it is possible to sequentially communicate the exhaust port of the preceding stage and the intake port of the subsequent stage in the multistage Roots pump by the additional or extra pipe. However, such a pipe arrangement has a problem of increasing the manufacturing cost.

In view of the above, it is a first object of the present invention to provide a single roots pump or a single pumping device in which a large compression ratio can be obtained.

In order to achieve the above object, once Roots pump according to the present invention comprises a casing forming one pump chamber having an inlet and an exhaust port; A plurality of motors mounted on a plurality of parallel axes to rotate in engagement with each other in the pump chamber; Three or more of said rotors from the first rotor to the nth rotor to rotate in engagement with each other to form a pair; At least one inlet port defined by the (n-2) rotor and the (n-1) rotor and an inlet port defined and opened by the (n-1) rotor and the nth rotor; (N-2) rotor and (n-1) rotor in communication with the inlet port defined by the (n-1) th rotor and the nth rotor on the same side of the imaginary surface including the plurality of axes to support the plurality of rotors An exhaust port defined by; And an exhaust port defined and opened by the (n-1) th rotor and the nth rotor.

In the Roots pump once, the pumping operation is performed by supplying the same compressed air as the conventional pump, but a set of rotors (rotor means) consisting of three rotors is applied differently from the conventional pump. If the sequentially engaged rotor is the first rotor, the second rotor,... If referred to as the (n-1) th rotor and the nth rotor, one pump chamber has two or more intake ports and two or more exhaust ports. These intake and exhaust ports are located in the pump chamber so that one or more intake port (s) and one or more exhaust port (s) are located on one side and another side of the imaginary surface defined by the plurality of axes to support the rotor. In this pump chamber, both the inlet port and the exhaust port are located adjacent to the same side of the virtual surface.

In connection with the above, the inlet port defined by the (n-1) rotor and the (n-2) rotor and the inlet port defined by the (n-1) rotor and the nth rotor are opened. In addition, the exhaust port defined by the first rotor and the second rotor communicates with the intake port defined by the second rotor and the third rotor at the same side of the virtual surface. Similarly, the exhaust port defined by the (n-2) rotor and the (n-1) rotor communicates with the intake port defined by the (n-1) rotor and the n th rotor on the same side of the virtual surface. The exhaust port defined by the (n-1) th rotor and the nth rotor is open.

Thus, a plurality of pumping operations can be performed in one pump room of this Roots pump so that the compression ratio can be set higher to improve the pumping operation for vacuum.

Two or more intake ports defining the intake ports defined by the (n-2) rotor and the (n-1) rotor and the intake ports defined by the (n-1) rotor and the n th rotor may be open at the Roots pump once. When the number of initial intake vents is increased, pumping operations such as evacuation can be improved.

When a pair of rotors consists of three or more rotors, if an even number of rotors constitutes a pair, one of the inlet or exhaust port numbers may be about one in one pump room on the same side of the imaginary plane defined by a plurality of axes. The number of is more than another one. The paired intake vents and exhaust vents can here be in communication with each other on the same side of the virtual plane, while the first intake vent and the last exhaust port are located on the side opposite to the virtual plane. To avoid this position, it is necessary to provide a communication path surrounding the pump or apparatus by about 180 ° and attach the pipe.

In contrast, when an odd number of rotors constitute one set, the same number of intake and exhaust ports exist in the pump chamber on the same side of the virtual surface. Here, the first inlet port and the last exhaust port are located on the same side of the virtual surface, so that no enclosing communication path or pipe attachment needs to be provided, resulting in excellent performance of the device.

When the exhaust port defined by the (n-2) rotor and the (n-1) rotor and the intake port defined by the (n-1) rotor and the nth rotor are communicated on the same side of the imaginary surface including a plurality of axes, These can be connected sequentially by an attachment pipe. However, the communication between the exhaust port and the inlet port by the communication groove formed on the casing is preferably omitted from the pipe attachment.

The pumping device once consists of the one-time Roots pump and a rotary drive device having a drive body and a drive shaft protruding from the drive body. Here, a timing gear train consisting of a drive gear fixed to the drive shaft of the rotary drive device and driven gears fixed to each shaft for supporting the rotor of the one end Roots pump driven by the drive gear is One end is inserted between the Roots pump and the rotary drive.

In one pumping device in which once a rotary drive such as a Roots pump and a motor are integrally formed, the driving force transmitted from the drive shaft of the rotary drive unit is converted into rotation via a timing gear train consisting of drive gears and driven gears and each axis. . Thus, no slipping that occurs when the pump is driven by the belt will occur, and once the influence of the axial torsion in the Roots pump is also reduced, the driving force of the rotary drive is driven by the rotation of all the rotors in each pump room. Can be switched. Therefore, the pumping operation can be performed smoothly in the pump chamber.

It is a further object of the present invention to provide a multistage Roots pump or multistage pumping apparatus that can reduce the manufacturing cost and facilitate its setting.

The multistage Roots pump of the first aspect of the present invention comprises a casing for forming a plurality of parallel pump chambers each having an inlet and an exhaust port, and a plurality of rotors mounted on a plurality of parallel shafts so as to rotate in engagement with each of the pump chambers. Equipped. The pump comprises three or more rotors out of the nth rotors in the same pair in the first rotor sequentially engaged; At least one inlet port defined by the (n-2) rotor and the (n-1) rotor and the inlet port defined by the (n-1) rotor and the n rotor are opened in the rearmost pump chamber; The (n-1) rotor and the (n-2) rotor of the pump chamber of the subsequent stage on the same side of the imaginary surface including the plurality of axes of the exhaust port defined by the (n-1) th rotor and the nth rotor Communicate with a defined intake vent; Except for the front end and the rear end, the exhaust port defined by the (n-2) rotor and the (n-1) rotor in the pump chamber of each stage has the (n-1) rotor and the first side on the same side of the virtual surface. communicate with an intake vent defined by the n rotor; And an exhaust port defined by the (n-1) th rotor and the nth rotor in the pump chamber of the rearmost stage.

When a multistage Roots pump uses more than one set of rotors consisting of three or more rotors, two or more intakes and two or more exhaust ports are present in each (same) stage pump room. At least one inlet and at least one outlet of these inlets and outlets is located in the same stage of the pumping chamber at both the one side and the other side of the virtual surface, and if necessary adjacent each other on the same side of the virtual surface.

For this reason, in the foremost pump chamber, at least one inlet port defined by the (n-2) rotor and the (n-1) rotor and the inlet port defined by the (n-1) rotor and the nth rotor are opened. There is; The exhaust port defined by the (n-1) rotor and the n rotor can communicate with the pump chamber of the subsequent stage defined by the (n-2) rotor and the (n-1) rotor on the same side of the virtual surface. . Here, the "sequential stage" includes the next stage and the stages following it.

In addition, in each stage of the pump chamber except for the front end and the rear end, the exhaust port defined by the first rotor and the second rotor may be in communication with the intake port defined by the second rotor and the third rotor on the same side of the virtual surface. Thus, the exhaust port defined by the (n-2) rotor and the (n-1) rotor can communicate with the intake port defined by the (n-1) rotor and the n th rotor on the same side of the virtual surface.

In the rearmost pump chamber, the exhaust port defined by the (n-1) th rotor and the nth rotor is opened.

Thus, it is not necessary to provide a communication path surrounding the pump or the device at about 180 ° to extend between the preceding pump chamber and the subsequent pump chamber for communication therebetween, or it is necessary to provide a long separation wall including the communication path, which is different from the prior art. No need to provide In addition, a pump having a partition wall as a simple partition between the pump chamber of the preceding stage and the pump chamber of the subsequent stage is sufficient. As a result, due to the shortened axial length of the pump, foot space can be minimized and the setup of the pump or device can be facilitated.

An attachment pipe can also be used when sequentially communicating the exhaust port of the preceding stage and the intake port of the subsequent stage on the same side of the virtual surface. Even in this case, since the pipes are located on the same side of the virtual surface, the pipe arrangement becomes easy enough to reduce the manufacturing cost. Thus, according to the multistage Roots pump of the first type, the setting of the pump or device is made easier due to the minimized foot space.

In a multi-stage Roots pump, when two or more intake ports are open from the inlet port defined by the (n-2) rotor and the (n-1) rotor and the inlet port defined by the (n-1) rotor and the nth rotor The number of initial intake vents can be increased, so that pumping effects such as vacuuming can be improved.

The multistage Roots pump of the second aspect according to the present invention includes a plurality of parallel pump chambers each having an intake port and an exhaust port, and a plurality of rotors mounted on a plurality of shafts so as to rotate in engagement with each of the pump chambers. In the pump, three or more rotors among the nth rotors in the sequentially engaged first rotors form the same pair of pairs; In the pump chamber of each stage except the rearmost stage forming a continuous stage, two or more intake ports defined by the (n-2) rotor and the (n-1) rotor, the (n-1) rotor and the nth rotor The intake vent defined by the rotor is open; The exhaust port defined by the (n-2) rotor and the (n-1) rotor and the exhaust port defined by the (n-1) rotor and the n-th rotor are pumped in subsequent stages on the same side of the imaginary surface including a plurality of axes Communicating with the intake port defined by the (n-2) rotor of the chamber and the (n-1) rotor; In the pump chambers of each stage except the foremost end and the rearmost end, the exhaust port defined by the (n-2) rotor and the (n-1) rotor has the (n-1) rotor and the n rotor on the same side of the virtual surface. Communicate with the intake vent defined by; And an exhaust port defined by the (n-1) th rotor and the nth rotor is opened in the pump chamber at the rearmost end.

In the second stage multistage Roots pump, in the pump stage of the same stage which constitutes a continuous stage including the foremost stage except the rearmost stage, two or more intake ports are opened, one of which is the (n-2) rotor and the first stage. It is limited by the (n-1) rotor, and another one of them is limited by the (n-1) th rotor and the nth rotor. In the same stage of the pumping chamber, the exhaust port defined by the (n-2) chamber and the (n-1) chamber and the exhaust port defined by the (n-1) rotor and the n-th rotor follow the same side of the virtual plane. However, it communicates with the inlet port defined by the (n-2) chamber and the (n-1) chamber of the pump chamber. Here, the "sequential stage" includes the next stage and the stage (s) consecutive to it.

In the pump chamber of the same stage except for the front end and the rear end, the exhaust port defined by the (n-2) rotor and the (n-1) rotor is connected to the (n-1) rotor and the n rotor in the same side of the virtual surface. Communication with the defined inlet port. In the rearmost pump chamber, the exhaust port defined by the (n-1) th rotor and the nth rotor is open.

Therefore, the increased number of initial intake ports of the multistage Roots pump can improve the pumping effect such as vacuuming.

When a set of rotors consists of three or more rotors, if an even number of rotors constitutes a set, one of the number of intake ports or the number of exhaust ports is one in the pump chamber of the same stage in the same side of the virtual surface defined by the plurality of axes. The degree is smaller than the number of another one of these. Here, the paired inlet and exhaust ports can communicate with each other on the same side of the virtual surface, but the first inlet and last exhaust port is located on the side opposite to the virtual surface. For this reason, it is possible to provide a communication path surrounding the pump or the device by about 180 ° and attach the pipe.

On the other hand, when an odd number of rotors constitute one set, the same number of intake and exhaust ports exist at the same stage in the same side of the virtual surface. Here, the first inlet port and the last exhaust port are located on the same side of the virtual surface, so that no enclosed communication path or pipe attachment needs to be provided, thus leading to excellent performance of the device.

When the exhaust port defined by the (n-2) rotor and the (n-1) rotor and the intake port defined by the (n-1) rotor and the nth rotor are communicated on the same side of the imaginary surface including a plurality of axes. It is possible to sequentially communicate these with the attachment pipe. However, preferably, the communication between the exhaust port and the intake port by the communication groove formed on the casing omits the pipe attachment.

In any case, the first and second multistage Roots pumps have the same exhaust port defined by the (n-2) rotor and the (n-1) rotor in the pump chamber of each stage except the foremost and rearmost stages. It has a common characteristic in that it communicates with the intake port defined by the (n-1) th rotor and the nth rotor from the side.

A third stage multistage Roots pump according to the present invention includes a casing for forming a plurality of parallel pump chambers each having an inlet and an exhaust port, and a plurality of rotors mounted on a plurality of shafts engaged with each other in the pump chamber. The pump consists of three or more rotors; The intake port of the foremost pump chamber is open; The exhaust port of the preceding stage pump chamber is sequentially communicated with the intake port of the subsequent stage pump chamber at the same side of the imaginary surface including the plurality of axes; And an exhaust port of the rearmost pump chamber in the casing is opened.

When a multi-stage Roots pump uses more than one set of rotors, each set consists of three or more rotors, with two or more inlets and two or more exhaust ports in each (same) stage pump room. Of these inlets and exhausts, one or more inlets and one or more outlets are located in the same stage of the pump chamber on both the one side and the other side of the virtual surface and, if necessary, located adjacent to each other on the same side of the virtual surface.

Thus, in both the pump chamber of the preceding stage and the pump chamber of the subsequent stage, if necessary, one or more inlet (s) and one or more exhaust port (s) are on the same side of the virtual surface, so that Intake ports are sequentially communicated on the same side of the virtual surface.

Therefore, it is not necessary to provide a communication path surrounding the pump or the device by about 180 ° between the preceding pump chamber and the subsequent pump chamber or to provide a long dividing wall including the communication path. In addition, as a simple partition, a device for forming a partition wall between the pump chamber of the preceding stage and the pump chamber of the subsequent stage is sufficient. As a result, the foot space can be minimized due to the shortened axial length of the pump, which facilitates the setup of the pump or device.

Although the pipes are used when sequentially communicating the exhaust ports of the preceding stage and the exhaust stages of the subsequent stage on the same side of the virtual plane, since the pipes are located on the same side of the virtual plane, pipe arrangement can be facilitated and manufacturing cost can be reduced. .

Thus, according to the third type multistage Roots pump, the setting of the pump or device is easier due to the minimized foot space.

When a set of rotors consists of three or more rotors, if an even number of rotors constitutes a set, one of the number of intake vents or the number of exhaust vents is about one another in the pump stage of the same stage on the same side of the virtual plane. Is less than Here, the paired inlet and exhaust ports can communicate with each other on the same side of the virtual surface, while the first inlet and the last exhaust port are located on the side opposite to the virtual surface.

On the other hand, when an odd number of rotors constitute one set, the same number of intake and exhaust ports exist in the pump chamber of the same stage in the same side of the virtual surface. Here, the first intake port and the last exhaust port are on the same side of the imaginary surface, so that no enclosing communication path or pipe attachment needs to be provided, thus leading to excellent performance of the device.

When the exhaust port defined by the (n-2) rotor and the (n-1) rotor and the exhaust port defined by the (n-1) rotor and the n-th rotor communicate on the same side of the imaginary surface including a plurality of axes, the pipe Communication grooves can be formed on the casing to omit attachment, which is also preferred.

In a multistage Roots pump consisting of a first-stage or third-stage multistage Roots pump and a drive device such as a motor, the inlet port of the foremost stage pump chamber and the exhaust port of the rearmost pump chamber are separated by a large distance, for the reason of This is because the intake port or the exhaust port of the rearmost pump chamber is located closest to the timing gear train. On the other hand, it is preferable that the exhaust port of the rearmost pump chamber is opened at the point closest to the timing gear train.

According to this position or configuration, the inlet port of the foremost stage pump chamber is opened at the furthest point from the timing gear train, so that oil attached to the timing gear train will not scatter in the chamber in which the inlet port is open. Thus, the pressure in the chamber can be reduced while maintaining the internal environment.

1 is a front sectional view of an end pumping apparatus according to a first embodiment;

2 is a cross-sectional view taken along the line 2-2 of FIG.

3 is a plan view of the first embodiment;

4 is a plan view of a lower plate used in the first embodiment.

5 is a schematic diagram illustrating an air flow in the first embodiment.

6 is a schematic diagram illustrating the air flow of the one-time pumping apparatus according to the second embodiment.

7 is a front sectional view of the multistage pumping apparatus according to the third embodiment;

8 is a sectional view taken along line 8-8 of FIG.

9 is a plan view of a third embodiment;

10 is a plan view of a lower plate used in the third embodiment.

11 is a schematic diagram illustrating an air flow of a third embodiment.

12 is a front sectional view of the multistage pumping apparatus according to the fourth embodiment;

13 is a plan view of a fourth embodiment.

14 is a plan view of a lower plate used in the fourth embodiment.

15 is a schematic view for explaining the air flow in the fourth embodiment;

16 is a front sectional view of the multistage pumping apparatus according to the fifth embodiment;

FIG. 17 is a cross sectional view taken along line 17-17 of FIG. 16;

18 is a plan view of a fifth embodiment;

19 is a plan view of a lower plate used in the fifth embodiment.

20 is a schematic view for explaining the air flow in the fifth embodiment;

FIG. 21 is a cross-sectional view of a modification of FIGS. 2, 8, and 17.

* Description of the symbols for the main parts of the drawings *

1: front housing 2, 3: cylinder block

4: rear housing 5, 6, 7: shaft

8, 9, 10: rotor F-F: virtual plane

P: Pump M: Motor

11: drive gear 12, 13: driven gear

2f, 2j: Intake vent 2g, 2k: Exhaust vent

22, 23, 24, 25, 26: cylinder block 28, 29, 30: axis

21a, 21b, 21c: bearings 31, 32, 33: rotor

22b, 22e, 23b, 23e, 25b, 25e: intake vent

22c, 22d, 23c, 23d, 25c, 25d: exhaust vent

22a, 23a, 24a, 25a: pump room

48c, 48d, 48e: communication groove

50a, 50b, 50c, 50d: communication groove

First embodiment

In the one-time pumping apparatus shown in FIGS. 1 and 2, the roots pump P is integrally coupled with the motor M once. In one roots pump P as shown in FIG. 1, the front housing 1, the first and second cylinder blocks 2, 3 and the rear housing 4 are via a sealing member (not shown). Stacked or stacked and interconnected by bolts (not shown) to form part of the casing.

Three axial holes are formed side by side and horizontally through the front housing 1, the first and second cylinder blocks 2, 3 and the rear housing 4. The first, second and third axes 5, 6, 7 are inserted into their respective axial holes so that the axes form a flat planar virtual surface F-F. A circular axial hole formed in the front housing 1, bearings 1a to 1c for supporting the first to third axes 5 to 7 are provided.

As shown in Fig. 2, in the front cylindrical block 2, a pump chamber 2a is formed on the rear side, consisting of three circular chamber portions whose centers are located in a straight line and adjacent portions overlap each other. . Grooves (not shown) are formed on the inner surface of the pump chamber 2a to accommodate the O-rings. On the right side, the center and left portions of the pump chamber 2a, the first rotor 8 mounted on the first shaft 5, the second rotor 9 mounted on the second shaft 6, and the third Each of the third rotors 10 mounted on the shaft 7 is provided. Each of the rotors 8, 9 and 10 has four leaf shapes that rotate in engagement with each other and form a set. A portion of the upper wall located between the portion for the first rotor 8 and the portion for the second rotor 9 is provided with an intake port 2b, and the portion for the second rotor 9 and the third rotor 10. In the part of the upper wall located between the portions for the vent holes 2c are respectively formed in the vertical direction. On the lower wall of the pump chamber 2a, in the part where the exhaust port 2d and the inlet port 2e are located between the portions for the first and second rotors 8 and 9, and the second and third rotors 9 , 10) are located between the parts located between them.

As shown in Fig. 1, in the second cylinder block, a gear chamber 3a having the same shape with respect to the upper gear chamber 2a is formed on the rear side, and for receiving the O-ring around this rear side. Grooves are provided. In the gear chamber 3a, a drive gear 11 is mounted on the second shaft 6 located at the center portion, and driven gears on the first and third shafts 5, 7 located at the right and left portions. 12 and 13 are respectively mounted to engage the drive gear 11 to form a timing gear train.

In each of the axial holes of the rear housing 4, bearings 4a to 4c are provided for supporting the first and third shafts 5 to 7. With respect to the rear housing 4, the drive main body 14 of the motor M is fixed by bolts (not shown), and the drive shaft 6 protrudes from this bolt, by means of a coupling (not shown). It is connected with the second shaft 6.

As shown in FIGS. 2 and 3, on the upper surface of the front housing 1, the first and second cylinder blocks 2, 3, and the rear housing 4, the upper plate 16 is fitted with a gasket 15. ), And are connected to them by bolts (not shown). As shown in Figs. 2 and 4, the communication grooves 18a for connecting the inlet port 2e and the exhaust port 2d of the first cylinder block 2 on the surface of the lower plate 18 are formed with the shafts 5 to 4. 7) orthogonal to.

Thus, a one-time pumping device, including a roots pump, is implemented so that the first to third rotors 8 to 10 forming a set of rotors have a minimum diameter.

Once this pumping device is used to evacuate the chamber to reduce the internal pressure, the inlet 16a on the top plate 16 is in communication with the chamber via a hose or the like, as shown in FIG. The exhaust port 16b on) is opened to the atmosphere via a hose or the like, and the Roots pump P is driven by the motor M once. As a result, the rotor 8, 9, 10 rotates in the pump chamber 2a of the Roots pump P once interlocked to sequentially perform the pumping operation therein, thereby releasing air inside the chamber to the atmosphere and Implement the decompression at.

Here, since such a single pumping apparatus uses a set of rotors composed of three (odd) rotors 8 to 10, two intake ports 2b and 2e and two exhaust ports 2d and 2c are provided in the pump chamber 2a. Is provided for In particular, above the imaginary surface FF defined by the axes of the first to third axes 5 to 7, one inlet port 2b and one exhaust port 2c exist in an adjacent relationship, if necessary, Below the imaginary surface, one intake port 2e and one exhaust port 2d exist in an adjacent relationship, if necessary. Therefore, the linear short communication groove 18a provided on the surface of the lower plate 18 has the exhaust port 2d and the intake port 2e of the pump chamber 2a at the bottom of the imaginary surface FF without using any pipe attachment or the like. Can communicate with each other.

As described above, in this one-time pumping apparatus, a plurality of pumping operations performed in one pump chamber 2a can increase the compression ratio in order to carry out efficient vacuuming. Further, the inlet port 2b and the exhaust port 2c of this one-time pumping device formed by protruding through the upper plate 16 exhibit excellent performance.

Further, in such a pumping apparatus, the driving force from the drive shaft of the motor M is first to third axes, and finally first to third, through the timing gear train consisting of the drive gear 11 and the driven gears 12 and 13. It is delivered to the third rotors 5 to 7 and is switched over. Thus, not only does any sleeping occur in the belt drive system, but also the first to third axes will not twist due to the short distance between the support at both ends and the geared center. As a result, the driving force of the motor M can be easily switched to the rotational force of the first to third rotors of the pump chamber 2a in order to smoothly execute the pumping operation.

Second embodiment

As shown in Fig. 6, in the pumping apparatus, one set of rotors is composed of four (first to fourth) rotors (not shown).

As a result, in this pump chamber 2a, two intake ports 2f and 2j and one exhaust port 2i exist above the imaginary surface FF, while one intake port 2h and two exhaust ports are provided. (2g, 2k) exists below the virtual surface FF. Here, the paired inlet port 2j and the exhaust port 2i, and the paired inlet port 2h and the exhaust port 2g are located on the same side of the virtual surface FF so that they can communicate with each other on both sides of the virtual surface. Can be. However, the first intake port 2f and the last exhaust port 2k are located on opposite sides of the imaginary surface F-F. In order to prevent this positioning, some communication path or the same pipe attachment surrounding the pumping device by about 180 ° is necessary.

Third embodiment

The multistage pumping apparatus is shown in FIGS. 7 to 11. As shown in Figs. 7 and 8, the multistage Roots pump P is formed integrally with the motor M. Figs. In the multistage Roots pump P as shown in FIG. 7, the front housing 21, the first, second, third, fourth and fifth cylinder blocks 22, 23, 24, 25, 26 and the rear The housings 27 overlap via sealing members (not shown) and are interconnected by bolts (not shown) to form part of the casing.

Through the front housing 21, the first to fifth cylinder blocks 22 to 26 and the rear housing 27, three axial holes are formed in parallel and in the horizontal direction. The first, second and third axes 28, 29, 30 are inserted into the axial holes so that the axes form a planar virtual surface F-F. In the circular axial housing formed in the front housing 21, bearings 21a-21c are provided for supporting the first to third shafts 28 to 30.

For the third cylinder block 24, in the first to fourth cylinder blocks 22 to 25 as shown in Fig. 8, a pump chamber 24a having the same shape as that of the first embodiment is formed on the rear side. And a groove (not shown) is formed on the inner surface to receive the O-ring. On the right side, the center and left portions of the pump chamber 24a, the first rotor 31 mounted on the first shaft 28, the two rotor 32 mounted on the second shaft 29, and the third shaft Each of the third rotors 33 mounted on the 30 is provided. These rotors 31, 32, 33 have four leaf shapes so as to rotate in engagement with each other and form one set. In the portion of the upper wall located between the portion for the first rotor 31 and the portion for the second rotor 32, the inlet port 24b is formed in the vertical direction, and the portion for the second rotor 32 In the portion of the upper wall located between the portions for the third rotor 33, an exhaust port 24c is formed, respectively. On the lower wall of the pump chamber 24a, the exhaust port 24d and the inlet port 24e are located at a portion located between the portions for the first and second rotors 31 and 32, and the second and third rotors 32, 33) is formed in each part located between.

As shown in Figs. 8, 9 and 11, for the first, second and fourth cylinder blocks 22, 23 and 25, three partially overlapping circular pump chambers 22a, 23a and 25a are provided. Located at the rear side, the inlet ports 22b, 22e; 23b, 23e; 25b, 25e, and the exhaust ports 22c, 22d; 23c, 23d; 25c, 25d are shown on the upper and lower walls of the pump chamber. It is shown in the vertical direction as shown in FIGS. 9 and 11. Thus, two intake ports 22d, 22e; 23d, 23e; 24b, 24e; 25b, 25e and two exhaust ports 22d, 22c; 23d, 23c in the pump chambers 22a, 23a, 24a, 25a of each stage; 24d, 24c; 25d, 25c) are present. In the pump chambers 22a, 23a, 25a, first to third rotors 34 to 36, 37 to 39 and 40 to 42 are located. Here, the foremost stage pump chamber 22a of the first cylinder block 22 is the longest, and the pump chambers 23a, 24a of the second and third cylinder blocks 23, 24 are the second and third longest, respectively, The rearmost end pump chamber 25a of the fourth cylinder block 25 is the shortest. Corresponding to the axial lengths of the pump chambers 22a, 23a, 24a, 25a, the first to third rotors 31 to 33, 34 to 36, 37 to 39, 40 to 42 are different from each other.

As shown in Fig. 8, in the fifth cylinder block 26, a gear chamber 26a having the same shape with respect to the upper pump chamber 22a is formed on the rear side, and the O-ring is wound around the gear chamber. Grooves are provided for receiving. In the gear chamber 36a, a drive gear 43 is mounted on the second shaft 29 located in the center portion, and driven gears on the first and third shafts 28, 30 located in the right and left portions. 44 and 45 are mounted so as to mesh with the drive gear 43, respectively, to form a timing gear train.

In each of the axial holes of the rear housing 27, bearings 27a to 27c are provided for supporting the first to third shafts 28 to 30. With respect to the rear housing 27, the drive main body 46 of the motor M is fixed by bolts (not shown), and the drive shaft protrudes from the main body so that the second shaft is formed by the coupling (not shown). It is connected with (29).

As shown in FIGS. 8 and 9, the upper plate 48 has a gasket 47 on the upper surface of the front bearing 21, the first to third cylinder blocks 22 to 26, and the rear housing 27. It is mounted via and interconnected with them by bolts (not shown). As shown in FIGS. 8 and 10, the lower plate 50 is provided with a gasket 49 on the lower surface of the front housing 10, the first to fifth cylinder blocks 22 to 26, and the rear housing 21. It is mounted via and interconnected by bolts (not shown). Thus, the upper and lower plates 48 and 50 form the rest of the casing.

As shown in FIG. 9, through the upper plate 48, an inlet port 48a in communication with the inlet port 22b of the first cylinder block 22, and an exhaust port 25c of the first cylinder block 25; An exhaust port 48a communicating with each other is formed in the vertical direction. In addition, on the rear surface of the upper plate 48, the oblique communication groove 48c and the second cylinder for communicating the exhaust port 22c of the first cylinder block 22 and the inlet port 23b of the second cylinder block 23 are made. An oblique communication groove 48d for communicating the exhaust port 23c of the block 23 and the inlet port 24b of the third cylinder block 24, and the exhaust port 24c and the fourth cylinder of the third cylinder block 24; An oblique communication groove 48e for communicating the inlet port 25b of the block 25 is formed, respectively.

Similarly, as shown in FIG. 10, on the front face of the lower plate 50, the oblique communication groove 50a and the second cylinder for communicating the exhaust port 22d of the first cylinder block 22 and the inlet port 22e. Oblique communication groove 50b for communicating the exhaust port 23d of the block 23 and the inlet port 23e, and oblique communication groove for communicating the exhaust port 24d and the intake port 24e of the third cylinder block 24 ( 50c) and an oblique communication groove 50d for communicating the exhaust port 25d of the fourth cylinder block 25 and the inlet port 25e are respectively provided. Here, all the communication grooves 50a to 50d are orthogonal to the axes 28 to 30.

Thus, a multistage pumping apparatus including a multistage Roots pump is implemented so that the first to third rotors 31 to 33, 34 to 36, 40 to 42, which respectively form a set of rotors, have a minimum diameter.

When this multistage pumping apparatus is used to evacuate the chamber to reduce the internal pressure, the intake chamber 48a on the upper plate 48 is in communication with the pump chamber via a hose or the like, as shown in FIG. The exhaust port 48b on the 48 is opened to the atmosphere via a hose or the like, and the multi-stage Roots pump P is driven by the motor M. As shown in FIG. As a result, the rotors 31 to 42 interlock with each other to perform the pumping operation in the respective pump chambers 22a, 23a, 24a, and 25a of the multistage Roots pump P, thereby releasing the air in the chamber to the atmosphere and A reduced pressure state is implemented.

Here, in this multistage pumping apparatus, four sets of rotors each consisting of three (odd) rotors 31 to 33, 34 to 36, 37 to 39, and 40 to 42 are used. As a result, the intake ports 22b, 22e; 23b, 23e; 24b, 24e; 25b, 25e, and the exhaust ports 22d, 22c; 23d, 23c; 24d, 24c; 25d, 25c are disposed, and the shafts 28 to 25 are disposed. One inlet port and one inlet port are present in each stage pump chamber 22a, 23a, 24a, 25a, both at the top and the bottom of the imaginary surface, including 30). In addition, the inlet ports 22b, 22e; 23b, 23e; 24b, 24e; 25b, 25e in the pump chambers 22a, 23a, 24a, 25a of each stage are provided with exhaust ports 22d, 22c; 23d, 23c; 24d, if necessary. , 24c; 25d, 25c) respectively.

Therefore, the communication grooves 48c, 48d, 48e formed on the rear surface of the upper plate 48 are sequentially exhausted from the preceding stage pump chambers 22a, 23a, 24a over the virtual surface FF without the need to attach a pipe. The 22c, 23c, 24c can communicate with the intake ports 23b, 23a, 24a of the pump chamber 23a, 24a, 25a of a subsequent stage. Similarly, the communication grooves 50a, 50b, 50c formed on the front face of the lower plate 50 are sequentially equipped with exhaust ports 22d, 23d, at each end below the imaginary surface FF, without the need to attach a pipe. 24d, 25d) can be communicated with (22e, 23e, 24e, 25e).

Therefore, a relatively long partition having a communication path surrounding the pumping device at about 180 ° while being located between the pump chambers 22a, 23a and 24a of the preceding stage and the pump chambers 23a, 24a and 25a of the subsequent stage, which is essential in the prior art. There is no need to form walls. Alternatively, as shown in FIG. 8, it is sufficient to form the partition walls 23f, 24f, 25f between the preceding pump chambers 22a, 23a, 24a and the subsequent pump chambers 23a, 24a, 25a as simple partitions. This can further shorten the axial length of the multistage Roots pump. As a result, the foot space can be minimized to facilitate setting of the multistage pumping apparatus and reduce manufacturing costs.

Further, in such a multistage pumping apparatus, the driving force from the drive shaft of the motor M is a timing gear train consisting of the drive gear 43, the driven gears 44 and 45, and the first to third axes 28 to 30. And are transferred to four sets of first to third rotors 31 to 42. Thus, not only does any slipping occur in the belt drive system, but also the short between the first end and the third axis 28 to 30 which are supported by the bearing and the center portion on which the gears 43 to 45 are mounted. You won't be warped by the distance. As a result, the driving force of the motor M can be easily switched from the respective pump chambers 22a to 25a to the first to third rotors 31 to 42 in order to smoothly perform the pumping operation.

In addition, in such a multistage pumping apparatus, the inlet port 48a is open at the position farthest from the timing gear train, and the exhaust port 48b is open at the closest position, which means that they are spaced at maximum distance, and thus the timing Lubrication oil in the gear train is prevented from scattering in the chamber in which the inlet port 48a is opened. Thus, the pressure in the chamber can be reduced while maintaining a good environmental condition.

Fourth embodiment

As shown in Figs. 12 to 15, the multistage pumping apparatus of this embodiment is different from the third embodiment in the structure of the front housing 51, the upper and lower plates 52, 53.

Specifically, as shown in FIG. 12, through the front housing 51, the inlet port 51a is formed in the vertical direction. In addition, as shown in Fig. 13, at the rear face and the front end of the upper plate 52, the inlet port 52a communicating with the inlet port 51a of the front housing 51, and the inlet port 51a, 52a and the first An axial communication groove 52b for communicating the inlet port 22b of the one cylinder block 22 is formed, respectively. In addition, as shown in FIG. 14, the axial communication grooves 53a for communicating the inlets 51a and 52a with the inlets 22e of the second cylinder block 22 on the front surface of the lower plate 53, And a cracked communication groove 53b for communicating the exhaust port 22d of the first cylinder block 22 and the exhaust port 23d of the second cylinder block 23 with the intake port 23e of the second cylinder block 23. Each is formed.

In this multistage pumping apparatus, the inlet port 22b defined by the first and second rotors 34 and 35, and the inlet port 22e defined by the second and third rotors 35 and 36 are the frontmost pump chamber 22a. Open at). Further, the exhaust port 22d of the foremost stage pump chamber 22a defined by the first and second rotors 34 and 35 is defined by the second and third rotors 38 and 39 under the virtual surface FF. It communicates with the inlet port 23e of the pump chamber 23a at the subsequent stage. In addition, the exhaust port 22c of the foremost stage pump chamber 22a defined by the second and third rotors 35 and 36 is defined by the first and third rotors 37 and 38 above the imaginary surface FF. It communicates with the intake port 23b of the pump chamber 23a of the subsequent stage. Therefore, in this multistage pumping apparatus, the increased number of intake openings 22b and 22e opened toward the first pump chamber 22a as compared with the third embodiment improves the vacuum operation.

Fifth Embodiment

The fifth embodiment introduced in FIGS. 16 to 20 differs from the third embodiment shown in FIGS. 7 to 11 in the following points. That is, the inlet port 61d is formed in the front housing 61, while the inlet port 67d is formed on the rear housing 67; Intake and exhaust operations are carried out in two roots of each stage; And the exhaust port of the preceding stage and the exhaust port of the subsequent stage are located on the same side of the virtual surface F-F. Hereinafter, parts or elements corresponding to those of the third embodiment are shown by reference numerals, where 60 is added in comparison with the third embodiment, and different parts or elements added are mainly described.

As shown in FIG. 16, the inlet port 61d is formed in the vertical direction on the front housing 61, and the exhaust port 67d is formed in the vertical direction on the rear housing 67. As shown in FIG. As shown in FIG. 18, at the front end and the rear end of the upper plate 91, the intake port 91a in communication with the intake port 61d and the exhaust port 91b in communication with the exhaust port 67c of the rear housing 67. Are formed in the vertical direction, respectively. On the rear surface of the upper plate 91, the axial communication groove 91c for communicating the intake ports 91a and 61d with the intake port 62b of the first cylinder block 62, the exhaust port of the first cylinder block 62. The inclined communication groove 91d for communicating 62c with the inlet port 63b of the cylinder block 62, and the exhaust port 63c of the second cylinder block 63 are provided with the inlet port 64b of the third cylinder block 64. Inclined communication groove 91e for communicating with each other), inclined communication groove 91f for communicating the inlet port 64c of the third cylinder block 64 with the inlet port 65b of the fourth cylinder block 65, And axially communicating grooves 91g for communicating the exhaust ports 65c of the fourth cylinder block 65 with the exhaust ports 91b and 67c, respectively.

Further, as shown in Fig. 19, on the front face of the lower plate 89, the axially communicating grooves 89a and the first through the inlet openings 91a and 61d communicate with the inlet openings 62e of the first cylinder 62. The inclined communication groove 89b for communicating the exhaust port 62d of the first cylinder block 62 with the inlet port 63e of the second cylinder block 63, and the exhaust port 63d of the second cylinder block 63 are removed. The inclined communication groove 89c for communicating with the inlet port 64e of the three cylinder block 64 and the exhaust port 64d of the third cylinder block 64 communicate with the inlet port 65e of the fourth cylinder block 65. The inclined communication groove 89d for making it, and the axial communication groove 89e for communicating the exhaust port 65d of the 4th cylinder block 65 with the exhaust ports 91b and 67c are formed, respectively.

Therefore, a multistage pumping apparatus including a multistage Roots pump, in which four sets of first to third rotors 71 to 73, 74 to 76, 77 to 79, 80 to 82, which respectively form a set of rotors, has a minimum diameter, Is implemented.

When such a multistage pumping apparatus is used to evacuate the chamber to reduce the pressure inside, the inlet 91a of the front housing 61 is in communication with the chamber via a hose or the like, as shown in FIG. The exhaust port 91b of the front housing 61 is opened to the atmosphere via a hose or the like, and the multi-stage Roots pump P is driven by the motor M. As shown in FIG. As a result, the rotors 71 to 82 rotate in the respective pump chambers 62a, 63a, 64a, 65a of the multi-stage Roots pump P interlocked in order to perform the pumping operation, so that the air in the chamber toward the atmosphere Released to achieve a reduced pressure.

Here, in this multistage pumping apparatus, four sets of rotors each consisting of three (odd) rotors 71 to 73, 74 to 76, 77 to 79, and 80 to 82 are used. As a result, in each stage pump chamber 62a, 63a, 64a, 65a, one inlet port 62b, 63b, 64b, 65b, and one exhaust port 62c, 63c, 64c, 65c are first to first. While above the imaginary surface FF including the third axes 68 to 70, one inlet port 62e, 63e, 64e, 65e, and one exhaust port 62d, 63d, 64d, 65d are virtual. It is below the face (FF). In other words, in both the preceding pump chambers 62a, 63a, 64a and the subsequent pump chambers 63a, 64a, 65a, one inlet port 63b, 64b, 64b and one exhaust port 62c, 63c, 64c are virtual. It exists above the surface FF, and one intake port 62e, 63e, 64e and one exhaust port 62b, 63b, 64d exist below the imaginary surface FF.

Accordingly, the communication grooves 91d, 91e, 91f formed on the rear surface of the upper plate 91 are sequentially exhausted from the preceding stage pump chambers 62a, 63a, 64a above the imaginary surface FF easily without using pipe attachment. The 62c, 63c, 64c can communicate with the inlet port 63b, 64b, 65b of the pump chamber 63a, 64a, 65a of a subsequent stage. Likewise, the communication grooves 89b, 89c, 89d formed on the front face of the lower plate 89 are easily connected to the leading ends 62a, 63a, 64a at each end below the imaginary surface FF without using pipe attachment. The exhaust ports 63d, 64d, 65d can be communicated with the inlets 63e, 64e, 65e of the subsequent ends 63a, 64a, 65a.

Therefore, it is not necessary to form a relatively long partition wall having a communication path surrounding the pumping device by about 180 ° while being located between the pump chamber of the preceding stage and the pump chamber of the subsequent stage. In addition, as shown in Fig. 16, it is sufficient to form a partition wall between the preceding stage pump chambers 62a, 63a, 64a and the subsequent stage pump chambers 63a, 64a, 65a as a simple partition, which is the axis of the multistage Roots pump. The direction length can be further shortened. As a result, the foot space can be minimized to facilitate the setting of the multistage pumping apparatus and to reduce its manufacturing cost.

Further, the driving force from the drive shaft of the motor M is first to third through the timing gear train consisting of the drive gear 83, the driven gears 84 and 85, and the first to third axes 68 and 70. Up to the rotors 71 to 82 and are diverted. Thus, not only does any sleeping occur, but the first to third axes 68 to 70 will not be twisted. As a result, the driving force of the motor M can be easily switched to the rotation of the first to third rotors 71 to 82 in the respective pump chambers 62a to 65a to smoothly perform the pumping operation.

In addition, since the inlet port 91a is opened at the outermost position from the timing gear train and the exhaust port 91b is opened at the position closest to it, the lubricant on the timing gear train is opened in the chamber in which the inlet port 91a is opened. Prevents dispersal Thus, the pressure in the chamber can be reduced while maintaining a good environmental condition.

Variant

As shown in Fig. 21, in the first to third embodiments, the first to third shafts 95 and 97 for supporting the first to third rotors 98 to 100 can be arranged, so that the predetermined A first portion (F1-F2) connecting the second and third axes (96, 97) so as to intersect at the second axis (96) by an angle, and an agent connecting the first and second axes (95, 96). The imaginary surface (F1-F2-F3) consists of two site | parts (F2-F3).

In addition, this arrangement of the rotor can communicate the intake port and the exhaust port sequentially with each other up and down the imaginary surface F1-F2-F3. In particular, on the lower side of the imaginary plane F1-F2-F3, it is sufficient to provide a relatively short communication passage in the circumferential direction even if a relatively long communication path is required on the upper side of the imaginary plane F1-F2-F3.

According to the present invention, there is an effect of providing a single roots pump or a single pumping device in which a large compression ratio can be obtained, and reducing a manufacturing cost and facilitating its setting.

Claims (31)

A casing constituting one pump chamber having an inlet port and an exhaust port, Has a plurality of rotors mounted on a plurality of shafts in the pump chamber to rotate with each other, Three or more of the rotors of the first to nth rotors are sequentially engaged with each other to form a pair, At least one of the intake port defined by the (n-2) rotor and the (n-1) rotor and the intake port defined by the (n-1) rotor and the nth rotor is opened, The exhaust port defined by the (n-2) rotor and the (n-1) rotor includes the (n-1) rotor on the same side of the imaginary surface including the plurality of axes for supporting the plurality of rotors. And the intake port defined by the nth rotor, The exhaust pump defined by the (n-1) th rotor and the nth rotor is open. The Roots pump as set forth in claim 1, wherein an odd number of rotors constitute one set. 3. The Roots pump as claimed in claim 2, wherein the odd number is three. The exhaust port defined in any one of claims 1, 2 and 3, wherein the exhaust port defined by the (n-2) rotor and the (n-1) rotor, the (n-1) rotor and the nth rotor The intake port defined by the first one is connected by a communication groove formed in the casing. The exhaust port defined by the first rotor and the second rotor communicates with the intake port defined by the second rotor and the third rotor on the same side of the imaginary surface, and in turn, the (n-2) rotor. And the exhaust port defined by the (n-1) rotor is in communication with the intake port defined by the (n-1) rotor and the n th rotor on the same side of the virtual surface thereof. The one-time Roots pump according to claim 1, wherein the imaginary surface comprises a first portion including a first axis and a second axis, and a second portion including a second axis and a third axis. Claims 1 to 3, 5 and 6, wherein the Roots pump of any one of the preceding, and a drive unit and a rotary drive device having a drive shaft protruding from the drive body, Between the one end Roots pump and the rotary drive unit, a drive gear fixed to the drive shaft of the rotary drive unit and each of the shafts for supporting the rotor of the one end Roots pump are driven by the drive gear. A pumping device once characterized in that a timing gear train comprising a driven gear is inserted. A casing which constitutes a plurality of pump chambers having inlet and exhaust ports in parallel, A plurality of rotors mounted on a plurality of shafts in each of the pump chambers to rotate with each other, Three or more of the rotors of the first to nth rotors are sequentially engaged with each other to form a pair, In the pump chamber of each stage except the foremost end and the rearmost end, the exhaust port defined by the (n-2) rotor and the (n-1) rotor has the (n) on the same side of the virtual surface. -1) is in communication with the intake port defined by the rotor and the n-th rotor, In the pump chamber at the foremost stage, the at least one intake port defined by the (n-2) rotor and the (n-1) rotor is opened, and is defined by the (n-1) rotor and the nth rotor. The exhaust port is the intake port defined by the (n-2) rotor and the (n-1) rotor of the pump chamber of the subsequent stage on the same side of the virtual surface including the plurality of shafts for supporting the plurality of rotors. In communication with The multistage Roots pump, characterized in that the exhaust port defined by the (n-1) th rotor and the nth rotor is opened in the rearmost pump chamber. A casing which constitutes a plurality of pump chambers having inlet and exhaust ports in parallel; A plurality of rotors mounted on a plurality of shafts in each of the pump chambers to rotate with each other, Three or more of the rotors of the first to nth rotors are sequentially engaged with each other to form a pair, In the pump chamber at the foremost stage, the at least one intake port defined by the (n-2) rotor and the (n-1) rotor and the intake port defined by the (n-1) rotor and the nth rotor Is open, and the exhaust port defined by the (n-1) th rotor and the nth rotor has the (n− 2) is in communication with the intake port defined by the rotor and the (n-1) rotor; The exhaust port defined by the (n-2) rotor and the (n-1) rotor in the pump chamber of each stage except the foremost stage and the rearmost stage is provided by the (n-1) rotor and the nth rotor. In communication with the defined intake port, And the exhaust port defined by the (n-1) th rotor and the nth rotor is opened in the rearmost pump chamber. 10. The multistage Roots pump according to claim 9, wherein an odd number of rotors constitute one set. 11. The multistage Roots pump according to claim 10, wherein the odd number is three. The exhaust port according to any one of claims 9, 10 and 11, wherein the exhaust port defined by the (n-2) rotor and the (n-1) rotor in the pump chamber of each stage, and (n-1) The intake port defined by the rotor and the n-th rotor is connected by a communication groove formed in the casing. 10. A pump according to claim 9, wherein in the pump chambers of each stage except the foremost and rearmost ends, the exhaust port defined by the first rotor and the second rotor is defined by the second rotor and the third rotor on the same side of the imaginary surface. The exhaust port communicated with the intake port and sequentially defined by the (n-2) rotor and the (n-1) rotor are defined by the (n-1) rotor and the nth rotor on the same side of the imaginary surface. Multi-stage Roots pump, characterized in that in communication with. 10. The system of claim 9, wherein the imaginary surface comprises a first portion comprising a first axis and a second axis, and a second portion including a second axis and a third axis, wherein the two portions intersect at the second axis. Multistage Roots pump, characterized in that. Claim 1 to 11, claim 13, wherein the multi-stage Roots pump according to any one of claims 14, and a rotation drive device having a drive body and a drive shaft protruding from the drive body, Between the multistage Roots pump and the rotary drive device, a drive gear fixed to the drive shaft of the rotary drive device and each of the shafts for supporting the rotor of the multistage Roots pump are driven by the drive gear. A multistage pumping apparatus, characterized in that a timing gear train comprising a plurality of driven gears is inserted. 16. The multistage pumping apparatus according to claim 15, wherein the intake port at the foremost end is opened at the position farthest from the timing gear train, and the exhaust port at the rear end is opened at the position closest to the timing gear train. A casing which constitutes a plurality of pump chambers having inlet and exhaust ports in parallel; A plurality of rotors mounted on a plurality of shafts in each of the pump chambers and engaged with each other to rotate, Three or more rotors of the first to nth rotors mesh with each other to form a pair of the same pair, In the pump chamber of each stage except the rearmost stage forming a continuous stage, the intake port defined by the (n-2) rotor and the (n-1) rotor, the (n-1) rotor and the At least one of the intake ports defined by the n rotor is open, and the exhaust port, the (n-1) rotor and the nth rotor defined by the (n-2) rotor and the (n-1) rotor are opened. The exhaust port defined by the second communication port is in communication with the inlet port defined by the n-th rotor and the n-th rotor of the pump chamber of the subsequent stage on the same side of the virtual surface including the plurality of axes for supporting the plurality of rotors, The exhaust port defined by the (n-2) rotor and the (n-1) rotor in the pump chamber of each stage except the foremost stage and the rearmost stage is connected to the (n-1) rotor on the same side of the virtual surface. Is in communication with the intake port defined by the nth rotor, And the exhaust port defined by the (n-1) th rotor and the nth rotor is opened in the rearmost pump chamber. 18. The multistage Roots pump according to claim 17, wherein an odd number of rotors constitute one set. 19. The multistage Roots pump according to claim 18, wherein the odd number is three. 20. The exhaust port according to any one of claims 17, 18 and 19, wherein the exhaust port defined by the (n-2) rotor and the (n-1) rotor in the pump chamber of each stage, and (n- 1) A multistage Roots pump, characterized in that the inlet port defined by the rotor and the nth rotor is communicated by a communication groove formed in the casing. 18. The exhaust port defined by the first rotor and the second rotor in the pump chamber of each stage except the foremost end and the rearmost end is defined by the second rotor and the third rotor on the same side of the imaginary surface. The exhaust port communicated with the intake port and sequentially defined by the (n-2) rotor and the (n-1) rotor are defined by the (n-1) rotor and the n-th rotor on the same side of the imaginary surface. Multistage Roots pump, characterized in that in communication with. 18. The multistage Roots pump according to claim 17, wherein the imaginary surface comprises a first portion including a first axis and a second axis, and a second portion including a second axis and a third axis. 23. A rotary drive system comprising the multistage Roots pump according to any one of claims 18, 19, 21 and 22, a drive body and a drive shaft protruding from the drive body. Between the multi-stage Roots pump and the rotary drive device, a drive gear fixed to the drive shaft of the rotary drive device, and the drive gear for supporting a plurality of rotors on each of the shafts of the multi-stage Roots pump A multistage pumping device, characterized in that a timing gear train comprising a plurality of driven gears is inserted. 24. The multistage pumping apparatus according to claim 23, wherein the intake port at the foremost end is opened at the position farthest from the timing gear train, and the exhaust port at the rear end is opened at the position closest to the timing gear train. A casing which constitutes a plurality of pump chambers each having an inlet port and an exhaust port in parallel; Each of the pump chambers has a plurality of rotors mounted on a plurality of shafts to rotate with each other, The rotor is a set of three or more In the casing, the intake port of the foremost front pump chamber is opened, The preceding stage exhaust port is sequentially communicated with the intake port of the subsequent stage on the same side of the imaginary surface including the plurality of axes, A multistage Roots pump, wherein said exhaust port of said rearmost pump chamber is opened. 27. The multistage Roots pump according to claim 25, wherein the odd number of rotors constitute one set. 27. The multistage Roots pump according to claim 26, wherein the odd number is three. 28. The multi-stage according to any one of claims 25, 26 and 27, wherein the exhaust port of the pump chamber at the preceding stage is in communication with the inlet port of the pump chamber at the subsequent stage by a communication groove formed in the casing. Roots pump. The multistage Roots pump according to claim 25, wherein the imaginary surface comprises a first portion including a first axis and a second axis, and a second portion including a second axis and a third axis. 30. A rotary drive system having the multistage Roots pump according to any one of claims 26, 27 and 29, a drive main body and a drive shaft protruding from the drive main body. Between the multi-stage Roots pump and the rotary drive, a drive gear fixed to the drive shaft of the rotary drive and a shaft for supporting a plurality of rotors of the multi-stage Roots pump are driven by the drive gear. A multistage pumping apparatus, characterized in that a timing gear train comprising a plurality of driven gears is inserted. 31. The multistage pumping apparatus according to claim 30, wherein the intake port at the foremost end is opened at the position farthest from the timing gear train, and the exhaust port at the rear end is opened at the position closest to the timing gear train.