JPS6325348Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a dual oil rotary vacuum pump device comprising a pair of oil rotary vacuum pumps.

Conventionally, as a vacuum pump device for achieving a high degree of vacuum, for example, a device in which a pair of oil rotary vacuum pumps are connected in series via an intermediate exhaust passage is known. However, when a pair of oil rotary vacuum pumps are connected in series, the pumping speed in the low vacuum region is almost the same as when using a single oil rotary vacuum pump, so the first half of the pumping work is In the high-pressure region that occupies the area where the vacuum pump is located, there is no point in operating both vacuum pumps together; on the contrary, it is uneconomical to use more power than when using a single vacuum pump.

One possible way to deal with such problems is to install two oil rotary vacuum pumps and use a switching valve to select either series connection or parallel connection to operate the pumps. It will be done. However, when the switching valve is manually switched, not only is the operation cumbersome, but also problems arise in that it is difficult to detect the appropriate time to switch.

Therefore, it may be possible to detect the operating state of the pump using a pressure sensor, etc., determine when to switch based on the detection result, and operate an electromagnetic actuator etc. based on the determination result to switch the switching valve. It will be done. However, such a device requires various sensors, judgment circuits, special actuators, etc., and therefore tends to have a complicated structure. Therefore, there is a problem that it is difficult to ensure high reliability over a long period of time.

The present invention was developed in light of these circumstances, and uses a three-way valve that switches a pair of oil rotary vacuum pumps connected in series using only spring force and differential pressure as actuating sources to properly exhaust the air. By making it possible to automatically switch to parallel connection in the progress stage, it is possible to effectively utilize the capacity of the double-oil rotary vacuum pump to perform efficient evacuation work, and it is also easy to operate. The purpose of the present invention is to provide a dual oil rotary vacuum pump device that is simple in structure and maintains high reliability over a long period of time, without the trouble of being troublesome or making it easy to change the timing incorrectly. be.

An embodiment of the present invention will be described below with reference to the drawings.

The exhaust port 1b of the oil rotary vacuum pump 1 at the front stage and the intake port 2a of the oil rotary vacuum pump 2 at the rear stage are communicated via the intermediate exhaust passage 3, and the gas is sucked in from the intake port 1a of the oil rotary vacuum pump 1 at the front stage. can be discharged through both pumps 1 and 2 from the exhaust port 2b of the oil rotary vacuum pump 2 in the latter stage. The oil rotary vacuum pumps 1 and 2 are installed at eccentric positions within cylindrical cylinders 1c and 2c.
Vanes 1d..., 2d that are in constant sliding contact with the inner circumferential surface of 2c.
The exhaust port 2b of the oil rotary vacuum pump 2 in the latter stage is configured to rotatably house rotors 1e and 2e holding... The opening is below the oil level. Note that 4 is a relief valve provided in the middle of the intermediate exhaust passage 3.

In the pump device thus constructed, one end is connected to the inlet port 1a of the oil rotary vacuum pump 1 in the previous stage.
A detour passage 5 is provided, the other end of which communicates with the intermediate exhaust passage 3 and faces the middle of the intermediate exhaust passage 3.
A three-way valve 6 is provided to divide the downstream passage 3a into an upstream passage 3a and a downstream passage 3b, and to selectively communicate the downstream passage 3b with the upstream passage 3a or the detour passage 5. The three-way valve 6 is formed to be elongated upward and downward to intersect with the intermediate exhaust passage 3, and has an upper end, that is, one end, communicated with the detour passage 5, and a lower end, that is, the other end, communicates with the relief valve through the fluid flow passage 7. a valve holding hole 8 opened in the valve seat portion of No. 4;
A communication passage 9 that communicates the upper end vicinity of one end of the valve holding hole 8 with the rear passage 3b, a piston valve 11 housed in the valve holding hole 8 so as to be able to rise and fall, and the piston valve 11. It is equipped with a spring 12 that urges the bottom dead center, that is, the other dead center. The piston valve 11 has a stepped cylindrical shape with a small diameter portion 11a on the upper end side and has a through hole 11b near the lower end. Its small diameter part 1
1a closes the communication passage 9, and the through hole 11b allows communication between the front passage 3a and the rear passage 3b.

Next, the operation of this embodiment will be explained. At the beginning of the exhaust work, the oil rotary vacuum pump 1 in the previous stage was
Since the intake pressure at the intake port 1a is relatively high, the piston valve 11 of the three-way valve 6 is pressed against the spring 12.
As shown in FIG. 2, it is held at the bottom dead center by the urging force of . Therefore, communication between the rear passage 3b and the front passage 3a is cut off by the piston valve 11, and the latter passage 3b is communicated with the detour passage 5 via the communication passage 9 and the valve holding hole 8. I will do it. Therefore, in this case, a portion of the intake air flows through the bypass passage 5 and the three-way valve 6.
The liquid is directly guided to the downstream side passage 3b through the downstream oil rotary vacuum pump 2 and discharged to the outside world. Note that the other intake air is guided to the oil rotary vacuum pump 1 in the previous stage and exhausted to the outside world through the relief valve 4. That is, in the low vacuum region, the oil rotary vacuum pump 1 at the front stage and the oil rotary vacuum pump 2 at the rear stage are connected in parallel for one load. As the exhaust progresses and the degree of vacuum increases and the intake pressure at the intake port 1a decreases, the pressure inside the upper end of the valve holding hole 8 communicating with the intake port 1a and the pressure inside the valve holding hole 8 opened to the atmosphere decrease. A large difference will be generated between the pressure inside the lower end and the piston valve 11 will rise against the biasing force of the spring 12 due to this pressure difference. Then, as shown in FIG. 3, the communication passage 9 is closed by the small diameter portion 11a of the piston valve 11, cutting off communication between the downstream passage 3b and the detour passage 5, and the piston valve 11 is closed. The through hole 11b matches the intermediate exhaust passage 3, and the rear passage 3b and the front passage 3a are brought into communication. Therefore, in this case, all the intake air sequentially passes through the double oil rotary vacuum pumps 1 and 2 and is discharged to the outside world via the pump oil A from the exhaust port 2b of the oil rotary vacuum pump 2 in the latter stage. That is, in the high vacuum region, the oil rotary vacuum pump 1 at the front stage and the oil rotary vacuum pump 2 at the rear stage are connected in series as before.

As described above, according to the pump device having such a configuration, in order to achieve a high degree of vacuum, the pair of oil rotary vacuum pumps 1 and 2 connected in series are used in the low vacuum region that occupies the first half of the exhaust work. Since it is possible to switch to a parallel connection at , it is possible to effectively utilize the capabilities of these two oil rotary vacuum pumps 1 and 2 to perform efficient evacuation work. In other words, as shown in Fig. 4, a device in which a pair of oil rotary vacuum pumps are connected in series has the drawback that the pumping speed in the low vacuum region is relatively low (see the dashed line a), and the In a device in which two oil rotary vacuum pumps are connected in parallel, the amount of leakage in the high vacuum region is large, and the pumping capacity is likely to reach its limit before reaching a high degree of vacuum (dashed line b).
However, according to the vacuum pump device according to the present invention, it is possible to switch a pair of oil rotary vacuum pumps from a parallel connection state to a series connection state at the stage of transition from a low vacuum region to a high vacuum region. Therefore, the above-mentioned drawbacks can be wiped out and excellent characteristics can be obtained, such as being able to perform evacuation at a high speed in the low vacuum region and finally achieving a high degree of vacuum (see solid line c). In addition, in this vacuum pump device, the relief valve 4 provided in the intermediate exhaust passage 3 can be effectively used as an exhaust valve when connected in parallel, so simple elements such as a bypass passage 5 and a three-way valve 6 are added. The above-mentioned characteristics can be obtained by simply using the method described above, and it is easy to implement.

Moreover, the three-way valve 6 is configured to switch the flow path by a piston valve 11 that is operated by a combination of the biasing force of a spring 12 and the force due to the differential pressure between the intake air and the atmosphere acting on both ends. Because there is
The above-described switching operation can be automatically performed during the exhaust operation. The switching characteristics can be appropriately set by selecting the pressure receiving areas at both ends of the piston valve 11 and the elastic modulus of the spring 12. Therefore, when transitioning from a low vacuum region to a high vacuum region, the oil rotary vacuum pumps 1 and 2, which form a pair, can always be appropriately switched from parallel connection to series connection, allowing highly efficient pumping operation to be performed without error. You can make it happen. Moreover, since the three-way valve 6 uses only spring force and differential pressure as its operating sources, it has a simple structure, reliable operation, and can maintain high reliability over a long period of time.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, with FIG. 1 being a principle explanatory diagram, FIGS. 2 and 3 being partial sectional views showing essential parts, and FIG. 4 being a characteristic curve diagram. 1... Front stage oil rotary pump, 2... Back stage oil rotary pump, 3... Intermediate exhaust passage, 4... Relief valve, 5... Detour passage, 6... Three-way valve, 3a... Front stage side passage, 3b...Late stage side passage, 8...Valve holding hole, 9...Communication passage, 11...Piston valve, 11
b...Through hole, 12...Spring.

Claims (1)

[Scope of Claim for Utility Model Registration] In a vacuum pump device in which an oil rotary vacuum pump at the front stage and an oil rotary vacuum pump at the rear stage are connected in series via an intermediate exhaust passage having a relief valve, one end is connected to the oil rotary vacuum pump at the front stage. A detour passage is provided which communicates with the intake port of the pump and has its other end facing halfway through the intermediate exhaust passage, and the intermediate exhaust passage is divided into a front passage having the relief valve and a rear passage. A three-way valve is provided, and the three-way valve is provided with a valve holding hole that is provided to intersect with the intermediate exhaust passage and has one end communicating with the detour passage and the other end open to the atmosphere, and one end of the valve holding hole. a communication passage whose side communicates with the latter passage, and a piston which is accommodated in the valve holding hole so as to be freely advanced and retracted and which closes the communication passage at one dead center and cuts off communication between the former passage and the latter passage. a valve, a spring that biases the piston valve toward the other dead center side of the valve holding hole, and a spring provided on the piston valve, which is provided in the piston valve and when the piston valve is located at one dead center, the front passageway and the rear passageway. What is claimed is: 1. A dual oil rotary vacuum pump device, characterized in that it has a through hole for communicating with the two.