JP3158622B2 - Vacuum exhaust device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum evacuation apparatus which is useful for protecting a vacuum pump and effectively continuing evacuation when a load exceeding the capacity is connected to the vacuum pump.

[0002]

2. Description of the Related Art A vacuum pump evacuates a container or the like for evacuation from a low vacuum to a desired degree of vacuum by being driven by an electric motor.

However, when a container having a capacity larger than the capacity of the vacuum pump is connected and a high load continues for a long time until the desired degree of vacuum is reached, blades in the vacuum pump may be damaged due to heat generation. In addition, there is a problem that the motor easily exceeds the rated current, which easily leads to pump down.

[0004] Therefore, a pump and an electric motor having an unnecessarily large capacity are used, or an intermittent operation of the pump is performed, so that the pump and the motor are exhausted without burden.

[0005]

However, as long as such means are employed, it is impossible to simultaneously reduce the capacity of the vacuum pump or the electric motor and shorten the exhaust time by continuous operation.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and the exhaust is performed while protecting the vacuum pump and the motor even when the connected load is large compared to the capacity of the vacuum pump and the motor. It is an object of the present invention to provide an evacuation apparatus that can effectively continue.

[0007]

In order to achieve the above object, the present invention employs the following configuration.

That is, the evacuation apparatus according to the present invention comprises:
A vacuum pump driven by an electric motor, an on-off valve provided at an upstream portion of an intake port of the vacuum pump and having a bypass system for communicating the upstream side and the downstream side at a closed position, and a detection for detecting a load current of the electric motor And a control means for holding the on-off valve in the closed position when the load current detected by the detection means exceeds a predetermined set value.

[0009]

The size of the container to be evacuated, etc., which is to be evacuated, is indirectly known from the magnitude of the load current. Therefore, if the on-off valve is closed when the load current exceeds a set value, the vacuum pump and the motor will It is possible to avoid operating with a high load. In this case, the on-off valve is provided with a bypass system path, and the upstream side and the downstream side are communicated via this system path. Therefore, if the conductance is made as small as possible within a range not exceeding the limit capacity of the vacuum pump and the electric motor, the exhaust to the exhaust container or the like can be effectively continued with the load reduced.

[0010]

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

1 and 2, a vacuum pump 1 has an intake port 1a and an exhaust port 1b opened upward.
The electric motor 2 is integrally mounted at a position where the vacuum pump 1 can be driven. In the present embodiment, for such a vacuum pump 1, an automatic pneumatic valve 3 serving as an on-off valve, a detection circuit 4 serving as a load current detecting means, and a control means 7 including a solenoid valve 5 and a current detection motor relay 6 are provided. Is attached, and a vacuum exhaust device is constituted as a whole.

As shown in FIG. 3, the pneumatic automatic valve 3 is provided with an upstream flow path 31a protruding from the body 3a and connected to the container C to be exhausted and a downstream side connected to the suction port 1a of the vacuum pump 1. A flow path 31b, a sheet 32 provided in the body 3a corresponding to the intersection of the two flow paths 31a, 31b, a rod 33 disposed in the body 3a, and a rod 33 supported by one end of the rod 33. A valve 34 that is attached to and detached from the seat 32 in accordance with the position of the rod 33 to selectively open and close between the flow paths 31a and 31b, and is fixed to the other end of the rod 32 and slides in the cylinder 35a at that position. A piston 35 which is fitted into the body 35a and a cylinder chamber 35b on one side of the piston 35 which is opened in the body 3a through an internal flow passage 3b.
And a second port B which is also opened in the body 3a and communicates with the cylinder chamber 35c on the other side of the piston 35 via the internal flow passage 3c. When the compressed air is introduced into the first port A and the second port B is opened, the piston 35
Is retracted to hold the valve 34 in the open position via the rod 33, and the compressed air is introduced into the second port B and the first port
When the port A is opened, the piston 35 is advanced to hold the valve 34 in the closed position via the rod 33. 34a is a packing.

In such an automatic pneumatic valve 3, the valve 34 has a hole 8 serving as a bypass system having a diameter φd smaller than the effective seat diameter D, which is bent and penetrated.
When the nozzle 4 is held at the closed position shown in the drawing, the upstream channel 31a and the downstream channel 31b can communicate with each other through the hole 8. The diameter φd of the hole 8 is set to a value such that the conductance becomes as small as possible without exceeding the limit capacity of the vacuum pump 1 and the electric motor 2.

The detection circuit 4 is capable of extracting a value a (hereinafter referred to as a load current value for convenience) proportional to the load current flowing through the secondary circuit of the electric motor 2. Input to the relay 6. On the other hand, a set value b is input to the relay 6 in advance, and the set value b is set when a limit load (for example, 30 Torr) is applied within a range where the blades of the vacuum pump 1 are not damaged by heat generation. It is set as the smaller value of the flowing load current or the rated current value of the motor. And the relay 6
When the load current value a exceeds the set value b, the contact is closed and the signal S is input to the solenoid valve 5. The relay 6 has a timer function, and once activated to output the signal S, the relay 6 continues to output the signal S until a predetermined time has elapsed.

The solenoid valve 5 has, for example, a function of switching between two positions and two directions as shown in FIG. 4. When the above-mentioned signal S is not inputted, the solenoid valve 5 is at the spring offset position shown in FIG. A is a compressed air source Q (for example, 4 kg / cm
² ) and open the second port B to the atmosphere,
When the signal S is input, the flow path is switched so that the compressed air source Q is connected to the second port B and the first port A
Is opened to the atmosphere.

With the vacuum evacuation apparatus having such a configuration, when the evacuation container C is evacuated from the atmospheric pressure to a predetermined degree of vacuum, a general pressure-power characteristic as shown in FIG. At the beginning of evacuation, an extremely large load is not applied to the vacuum pump 1 and the electric motor 2, and the load current value a input to the current detection motor relay 6 does not exceed the set value b. The valve 5 is held in the spring offset position, and the automatic pneumatic valve 3 is kept in the open position.
For this reason, the pump 1 driven by the electric motor 2 performs the exhaust by maximizing the exhaust capacity. Thereafter, when the inside of the container C is evacuated from 300 Torr to 100 Torr, the load applied to the vacuum pump 1 and the electric motor 2 becomes maximum as shown by the characteristic curve in FIG. If the evacuation is continued at this time, there is a risk that the vacuum pump 1 and the electric motor 2 may be damaged. When the load current value a corresponding to the size of the load exceeds the set value b (the limit load current value of the vacuum pump 1 or the rated current value of the electric motor 2), the current detection motor relay 6 operates. To output a signal S,
As a result, the solenoid valve 5 is driven, and the automatic pneumatic valve 3 is switched to the closed position. Therefore, the loads on the vacuum pump 1 and the electric motor 2 are reduced. Moreover, in this state, the container to be evacuated C and the vacuum pump 1 communicate with each other through a hole 8 provided in a valve 34 in the automatic pneumatic valve 3, and the hole 8 communicates with the vacuum pump 1 and the electric motor 2. The diameter φd is set so that the conductance becomes as small as possible without exceeding the limit capacity. Therefore, the exhaust to the exhaust container C can be effectively continued within a safe driving range. Thereafter, when a predetermined time has elapsed, the timer function of the relay 6 operates to stop the signal S. Valve 3
If the pressure in the container to be evacuated C passes through a pressure region that maximizes the load on the vacuum pump 1 or the electric motor 2 while the valve 4 is closed, the load current value a detected by the detection circuit 4 Becomes smaller than the set value b, the solenoid valve 5 returns to the spring offset position, holds the valve 34 again at the open position, and performs normal exhaust, but conversely, the load current value a still exceeds the set value b. If so, the relay 6 operates again to hold the valve 34 in the closed position for a certain period of time as described above. The timer function of the relay 6 prevents a chattering phenomenon in which the opening and closing operations change rapidly.

As described above, when this vacuum pumping apparatus is used, the vacuum pump 1 and the electric motor 2 can be used to evacuate the container to be evacuated C having a capacity exceeding the capacity of the vacuum pump 1 and the electric motor 2.
And the exhaust can be continued in the vicinity of the limit of those capabilities and exhaust can be completed in a short time.

The cross-sectional shape of the bypass system and the specific configuration of each part are not limited to those shown in the drawings, and various modifications can be made without departing from the spirit of the present invention.

[0019]

As described above, when the load exceeds the capacity of the vacuum pump or the electric motor, the vacuum exhaust system of the present invention closes the on-off valve to disconnect the load. In order to keep the load and the vacuum pump in communication with each other, the conductance of the bypass system should be as small as possible without exceeding the capacity of the vacuum pump and the motor, so that exhaust gas can be exhausted within the safe operation range. You can proceed effectively. Therefore, it is not necessary to use an unnecessarily large capacity vacuum pump and electric motor when evacuating the container to be evacuated,
The effect that exhaust can be completed in a short time is obtained as compared with the case of intermittent operation.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a left side view of FIG.

FIG. 3 is an enlarged front sectional view of a main part of FIG. 1;

FIG. 4 is a functional explanatory diagram of the solenoid valve used in the embodiment.

FIG. 5 is a graph showing exhaust characteristics of the example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum pump 1a ... Intake port 2 ... Electric motor 3 ... Opening / closing valve (automatic pneumatic valve) 4 ... Detection means (detection circuit) 7 ... Control means 8 ... Bypass system path (hole) a ... Load current value b ... Set value

Claims (1)

(57) [Claims] A vacuum pump driven by an electric motor;
An on-off valve provided at an intake port upstream portion of the vacuum pump and having a bypass system path for communicating the upstream side and the downstream side at a closed position, detection means for detecting a load current of the electric motor, and detection means for detecting the load current of the electric motor Control means for holding the on-off valve in the closed position when the load current exceeds a predetermined set value.