JPH07197884A - Oil steam reverse flow preventing device for evacuation line - Google Patents

Abstract

PURPOSE:To provide an oil steam reverse flow preventing device in an evacuation line which is constituted to maintain a pressure in the evacuation line at a constantly given value to prevent the reverse flow of oil steam from an evacuating device and reduce a flow rate of purge gas as much as possible. CONSTITUTION:A vent valve 4, an automatic shut-off valve 5, and a main valve 6 are interconnected, in the order, from an evacuating device 1 in a line 2 through which the evacuating device 1 is connected to a vacuum vessel 3. A purge gas feed line part 8 through which purge gas is introduced from a gas source 9 is connected to a line part 2a between the main valve 6 and the automatic shut-off valve 5, and a purge gas flow rate control valve 10 and a purge gas introduction valve 11 are located therein. A pressure gauge 7 is connected to the line part 2a, and a detecting output therefrom is fed to a controller 20. Based on a detecting output, the opening and/or opening and closing of a purge gas flow rate control valve and/or the purge gas introduction valve 11 is controlled. This constitution maintains a pressure in the line part 2a at a given value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil vapor backflow prevention device in a vacuum exhaust pipe line, and more particularly to a vacuum pump using oil in a gas compression process of an oil rotary vacuum pump, or a roots pump for exhausting gas to be oil lubricated. The present invention relates to an oil vapor backflow prevention device in a vacuum exhaust pipe line which is optimal for preventing backflow of oil vapor from a vacuum exhaust device using a vacuum pump communicating with a chamber to the vacuum container side.

[0002]

2. Description of the Related Art Conventionally, as a method for preventing the backflow of oil vapor from a vacuum exhaust device using an oil rotary vacuum pump or a roots pump, for example, a bibliography "Vacuum Technology" (Kyoritsu Shuppan, July 1985) As described in pages 203 to 207 of “D. Clean Araki system”, a purge gas is introduced into the suction side pipe of the vacuum exhaust device and 13 Pa (1
The flow rate of the purge gas is set to 0 ⁻¹ Torr) or more to prevent the oil molecules from being pushed away and the oil vapor from entering the vacuum container side. Further, a method is described in which an adsorbent or a cooling surface is provided in the middle of the intake pipe at a pressure lower than 13 Pa to adsorb oil molecules.

Further, Japanese Patent Publication No. 56-7067 and Japanese Unexamined Patent Publication No.
No. 49978 describes a method for preventing oil intrusion by providing a complicated opening in a small pipe for ejecting gas in the pipe and making a purge gas flow at a constant speed and in a constant direction toward the suction direction of the vacuum pump. . Alternatively, an expensive dry pump that does not use oil may be used in the gas compression process in a method completely different from such an oil rotary vacuum pump.

However, recently, in the vacuum apparatus, the oil vapor flowing back from the vacuum exhaust apparatus has many applications in which the products processed in the vacuum apparatus are affected. On the other hand, among the above-mentioned conventional techniques, in the method described in the bibliographical "vacuum technique", the inlet pressure is 13 Pa or higher, which is higher than the pressure required by the operating conditions, or the trap is regularly maintained. I had to do it.

Further, Japanese Patent Publication No. 56-7067 and Japanese Unexamined Patent Publication No.
The method disclosed in Japanese Patent No. 49978 requires an opening having a complicated shape inside the pipe of the purge gas introducing portion,
If the position where the purge gas is introduced is inappropriate, the oil vapor may flow back into the vacuum vessel, and the purge gas flow rate is not controlled by the inlet pressure or the pipe flow velocity, so the purge gas flow rate is stable. Without doing so, the oil vapor may flow back into the vacuum container, or a large amount of purge gas may flow, reducing the effective exhaust rate and consuming unnecessary purge gas.

Further, when the oil rotary vacuum pump is urgently stopped for some reason, it is impossible to cope with a mistake in valve operation or the like. For this reason, at present, the vacuum exhaust device using an expensive dry pump is predominantly used even in the purpose of obtaining a vacuum state without oil vapor by exhausting air or an inert gas. However, even if an expensive drive pump is used, it does not have a check valve with a high sealing property, so that the atmosphere on the exhaust side instantaneously flows back at the time of emergency stop, and the pressure of the vacuum container rises.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the ultimate pressure is, for example, less than 13 Pa without significantly reducing the exhaust pressure under the conventional working pressure, and the oil to the vacuum container is not reached. It is an object of the present invention to provide an inexpensive oil vapor backflow prevention device in a vacuum exhaust pipe line that can reliably prevent backflow of steam.

[0008]

[Means for Solving the Problems] The above object is to provide a vacuum pump using a vacuum pump that uses oil in a gas compression process, or a vacuum pump in which the gas to be exhausted communicates with the oil lubrication chamber. , A vacuum container is connected at least through a main valve by a vacuum exhaust pipe line, and the oil vapor from the vacuum exhaust device in the vacuum exhaust pipe line is vacuumed by a purge gas introduced into the vacuum exhaust pipe line. In an oil vapor backflow prevention device in a vacuum exhaust pipe for preventing backflow into a container, a purge gas introduction valve and / or a purge gas flow rate control are provided in a purge gas supply pipe connecting the vacuum exhaust pipe and a purge gas supply source. A valve is provided, and a pressure gauge or an anemometer is provided in the vacuum exhaust pipe line, and a detection output of the pressure gauge or the flow meter is supplied to a controller, and based on the detection output from the controller. The pressure in the vacuum exhaust line is set by supplying a drive signal for opening and closing the purge gas introduction valve and / or a control signal for controlling the flow rate of the purge gas flow rate control valve to the purge gas introduction valve and / or the purge gas flow rate control valve. Alternatively, it is achieved by an oil vapor backflow prevention device in the vacuum exhaust pipe line, characterized in that the gas flow velocity is controlled to a predetermined value.

[0009]

A pressure gauge or a velocity meter is connected to the vacuum exhaust pipe line, and the vacuum exhaust pipe is controlled by the purge gas introduction valve and / or the purge gas flow rate control valve connected to the purge gas supply pipe line by the detection output. The pressure in the line can be maintained by the purge gas at a predetermined pressure, for example below 13 Pa. As a result, it is possible to reliably prevent the oil vapor from flowing back into the vacuum container from the vacuum exhaust device side.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An oil vapor backflow prevention device in a vacuum exhaust pipe according to an embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the vacuum evacuation device 1 uses an oil rotary vacuum pump, and this intake port is connected to a vacuum container 3 via a pipe 2. A vent valve 4, an automatic shutoff valve 5, and a main valve 6 are sequentially connected to the inside of the pipe 2 from the vacuum exhaust device 1 side. When the automatic shutoff valve 5 is opened by receiving a drive signal from the controller 20, the pipe 2 is communicated on both sides.
When closed, shut off both sides. Main valve 6 is vacuum container 3
It is a valve that is conventionally used as an accessory and connects and disconnects the vacuum container 3 and the vacuum exhaust device 1.
Also in this embodiment, the controller 20 controls the opening and closing.

According to this embodiment, a pressure gauge 7 is connected to the conduit 2. A purge gas supply pipe 8 is connected to the vacuum exhaust device 1 side, and in the present embodiment, atmospheric air is supplied from the purge gas source 9 through a filter under a predetermined pressure, and the purge gas flow rate is supplied to the pipe 8. The control valve 10 and the purge gas introduction valve 11 are connected to each other, and the purge gas flow rate control valve 10 receives a drive signal from the controller 20 and controls the opening degree based on the detection output of the pressure gauge 7. Has been done. Further, the purge gas introduction valve 11 also receives a detection signal from the pressure gauge 7 by the controller 20, and receives a drive signal from the controller 20 to open and close based on the detection signal. In any case, the pressure in the pipe 2 is controlled to be less than 13 Pa in this embodiment. Further, in this embodiment, the main valve 6 and the automatic shutoff valve 5 are
The length L of the conduit portion 2a between and is: L> β ₁ · β ₂ · 4 × 10 ⁻²⁴ · (T · c · α · a) /
(Q · δ ² ) where β _{1 is} a coefficient depending on the type of purge gas β ₂ is a coefficient depending on the type of oil used in the vacuum evacuation device T is an atmospheric temperature, a is a sectional area of a pipe, Q is a gas flow rate, and is δ ^2. Oil molecule diameter α; maximum probability velocity of oil vapor molecule, c; v / α
(V; molecular velocity in the molecular group of oil vapor).

Further, the purge gas supply line 8 is provided with a bypass line 12, in which the valve 1 is provided.
4 ', a purge gas reservoir tank 13 and a vent valve 14 are connected. Reservoir tank 13 serves to mitigate a sudden change in pressure in pipeline 2 when vent valve 14 is opened and closed. Similarly to the above-mentioned valve, the vent valve 14 also receives a drive signal from the controller 20 and also supplies the controller 20 with a monitor signal for monitoring the open / closed state of the drive signal.

Further, according to the present embodiment, the controller 20 has a monitor signal for monitoring the driving state of the vacuum exhaust device 1, a monitor signal for monitoring the open / closed states of the vent valves 4, 14, as well as the automatic shutoff valve 5, A monitoring signal for monitoring the open / closed state of the purge gas flow control valve 10, the purge gas introduction valve 11, and the main valve 6 is supplied.

The oil vapor backflow prevention device in the vacuum exhaust pipe according to the embodiment of the present invention is constructed as described above, and its operation will be described below.

FIG. 2 is a time chart of the operation of each part of the system shown in FIG.
Is the opening / closing of the vacuum exhaust device 1, B is the opening / closing of the automatic shutoff valve 5 and the valve 14 ′, C is the first and second vent valves 4,
14 shows opening / closing, D shows opening / closing of the main valve 6, E shows pressure in the pipe 2, and F shows opening / closing of the purge gas introduction valve 11.
When the evacuation device 1, that is, the oil rotary vacuum pump is started to be driven, the vent valves 4 and 14 are simultaneously changed from the open state to the closed state in response to the drive signal from the controller 20. That is, the inside of the conduit 2 is cut off from the atmosphere. The main valve 6
Remains closed. At the same time, the purge gas introduction valve 11 is also opened by the drive signal of the controller 20. Therefore, the air purified by the filter from the gas source 9 is introduced into the purge gas supply pipe line 8. The vent valves 4 and 14 are closed and the purge gas introduction valve 11 is opened at the same time as the driving of the vacuum exhaust device 1 is started, and the automatic shutoff valve 5 is opened after a predetermined time from this. Therefore, the evacuation device 1 starts to exhaust the pipe line 2. At the same time, the pressure in the pipe 2 decreases as indicated by E in FIG.
When the pressure detected by the pressure gauge 7 is below 13 Pa, the main valve 6 is opened. As a result, as shown by E in FIG.
Although it decreased to Pa and fell slightly below, the pipe pressure rapidly increased with the opening of the main valve 6 and reached almost atmospheric pressure. On the other hand, by opening the main valve 6, the vacuum container 3 and the pipeline 2 were separated. Communicate. Therefore, the pressure in the pipeline 2 drops sharply,
Below 13 Pa. Further, the main valve 6 is opened and the purge gas introduction valve 11 is closed as shown by F in FIG.
This causes a sharp drop as described above.
When it goes below a, it opens again. In this embodiment, when the pressure exceeds 13 Pa or decreases below, the opening of the flow control valve 10 is adjusted by the drive signal from the controller 20 by the detection output of the pressure gauge 7 so that the pressure in the pipeline 2 becomes less than 13 Pa. It is adjusted to a predetermined value. As a result, the pressure in the conduit 2 is maintained at a predetermined value of less than 13 Pa. Therefore, even if the oil vapor flows from the vacuum exhaust device 1 to the vacuum container 3 side, it is reliably pushed back by the purge gas, and the oil vapor does not enter the vacuum container 3. Further, according to the present embodiment, since the length of the conduit 2a between the main valve 6 and the automatic shutoff valve 5 is set as the above-mentioned L, the introduction amount of the purge gas from the gas source 9 is minimized. Can be

Next, when the vacuum exhaust apparatus 1 is stopped, it is stopped by a stop signal from the controller 20,
At the same time, the main valve 6, the automatic shutoff valve 5, and the valve 14 'are closed as shown in the charts B and E of FIG.
After a predetermined time, the purge gas introduction valve 11 is closed by the drive signal from the controller 20. Further, after a predetermined time has elapsed, the vent valves 4 and 14 are opened. As a result, the pipe line between the automatic shutoff valve 5 and the vacuum exhaust device 1 is set to the atmospheric pressure. Further, between the automatic shutoff valve 5 and the main valve 6, the purge gas introduction valve 11 has been introduced for a predetermined time even after the automatic shutoff valve 5 is closed, and the vent valve 14 is opened to the atmospheric pressure. Therefore, since the main valve 6 is closed, all parts except the vacuum container 3 are at atmospheric pressure.

As described above, it is possible to reliably prevent the oil vapor from flowing back to the vacuum container 3, but according to the present embodiment, the vacuum exhaust device 1 and the valves 4, 5, 6 are further provided. The monitoring signal for monitoring the open / closed state is supplied to the controller 20, 11, 14, 14 ′, so that, for example, some failure of the vacuum exhaust device 1 itself may occur during the oil vapor prevention operation. In the event of an emergency stop, the controller 20 detects that the stop has occurred despite the drive signal being given, thereby closing the valves in the same order as in the chart shown in FIG. Therefore, it is possible to prevent the oil vapor from flowing back into the vacuum container 3 even when the vacuum exhaust device 1 is urgently stopped.
Further, the open / closed state of each valve 4, 5, 6, 10, 11, 14 is also monitored, and if any of these valves fails due to the monitoring signal being supplied to the controller 20, it is shown in FIG. The valves are opened and closed in the order shown in the chart, and the system shown in FIG. 1 is controlled so that all the systems are placed at atmospheric pressure, so that oil vapor does not flow back into the vacuum container 3 in any case. Therefore, the quality of each work processed in the vacuum container 3 can be guaranteed.

Although the embodiments of the present invention have been described above, needless to say, the present invention is not limited to these, and various modifications can be made based on the technical idea of the present invention.

For example, in the above embodiments, the length of the pipe portion 2a is L as described above, but the pipe portion 2a is made smaller by partially reducing the diameter of the portion to which the purge gas supply pipe line 8 is connected. Can be further shortened to maintain a predetermined pressure, that is, less than 13 Pa, and the amount of purge gas for this can be made small.

Further, in the above embodiment, the pressure gauge 7 was connected to the conduit portion 2a, but instead of this, a velocity meter was connected,
The detection signal may be used to control the opening or opening or closing of the purge gas flow valve 10 and the purge gas introduction valve 11 by the drive output of the controller 20.

In the above embodiment, the gas source 9 is a filter that cleans the air in the atmosphere and introduces it into the purge gas supply pipe 8. However, a gas selective membrane is used instead of the filter. Alternatively, the inert gas in the atmosphere may be extracted and introduced into the purge gas supply pipe line 8. Alternatively, the gas source 9 itself may be used as an inert gas generator to apply a predetermined pressure and introduce the gas into the purge gas supply conduit 8.

In the above embodiment, the purge gas flow control valve 10 and the purge gas introduction valve 11 are provided in the purge gas supply pipe line 8. However, even if either one of them is omitted, the pressure in the pipe line portion 2a is reduced. Can be maintained at a predetermined value.

In the above embodiment, the oil rotary pump is used as the vacuum exhaust device 1. However, instead of this, a vacuum pump in which the gas to be exhausted communicates with the oil lubrication chamber, that is, a roots pump may be used. The effect of the present invention can be obtained.

Further, in the above embodiment, the vacuum evacuation device 1, the valves 4, 5, 6, 10, 11, 14 and the controller 20 are all described as separate bodies in FIG.
0, valves 4, 5, 6, 10, 11, 14, 14 ′ are integrated with a pressure gauge 7, ports are provided in this casing, and these ports are connected by a gas source 9 as shown in FIG. You may make it connect to the purge gas reservoir tank 13, the vacuum container 3, the vacuum exhaust device 1, etc. by piping.
Of course, in this case, the entire system can be made compact. In particular, with the recent development of microcomputers, the controller 20 itself can be made extremely small. Therefore, even if it is integrated with these valves, the vacuum evacuation device 1, the vacuum container 3, and the gas source 9 do not increase in size so much. It is possible to easily attach and connect to any of them without restricting the attachment position to such.

In the above embodiment, when the pressure in the pipe 2 exceeds or falls below 13 Pa after opening the main valve 6, the purge gas introduction valve 11 remains open.
The opening of the purge gas flow control valve 10 is adjusted by the drive signal from the controller 20 so that the pressure in the pipe 2 is adjusted to a predetermined value of less than 13 Pa. In some cases, the purge gas flow control valve is adjusted. Alternatively, the pressure in the conduit 2 may be controlled to 13 Pa by omitting 10 and repeating opening and closing of the purge gas introduction valve 11. Alternatively, the purge gas introduction valve 11 may be omitted, and the pressure in the pipeline 2 may be adjusted to a predetermined value of less than 13 Pa simply by changing the opening degree of the purge gas flow rate control valve 10. Although the timing of opening and closing each valve is determined by the predetermined time in the above embodiment, instead of this, the timing may be determined based on a signal that monitors whether each valve is completely opened or closed. Good.

[0027]

As described above, according to the oil vapor backflow prevention device in the vacuum exhaust device according to the present invention, the amount of the purge gas is minimized and the pressure in the vacuum exhaust pipe line is maintained at a predetermined value for vacuuming. It is possible to reliably prevent the oil vapor from the exhaust device from entering the vacuum container.

[Brief description of drawings]

FIG. 1 is a piping system diagram showing an evacuation device provided with an oil vapor backflow prevention device according to an embodiment of the present invention.

FIG. 2 is a time chart showing the operation of the same system.

[Explanation of symbols]

 1 Vacuum Evacuation Device 2 Piping 3 Vacuum Container 4 Vent Valve 5 Automatic Shutoff Valve 6 Main Valve 7 Pressure Gauge 8 Purge Gas Supply Pipeline 9 Gas Source 10 Purge Gas Flow Control Valve 11 Purge Gas Introduction Valve 20 Controller

Claims (9)

[Claims] 1. A vacuum pump using a vacuum pump that uses oil in a gas compression stroke, or a vacuum pump in which the gas to be exhausted communicates with the oil lubrication chamber, and a vacuum container via at least a main valve. To prevent the oil vapor from the vacuum exhaust device from flowing back to the vacuum container by the purge gas introduced into the vacuum exhaust pipe line. In the oil vapor backflow prevention device in the vacuum exhaust pipe line, the purge gas introducing valve and / or the purge gas flow control valve is provided in the purge gas supply pipe line connecting the vacuum exhaust pipe line and the purge gas supply source, and the vacuum exhaust pipe line is provided. Is equipped with a pressure gauge or an anemometer, supplies the detection output of the pressure gauge or the anemometer to the controller, and opens or closes the purge gas introduction valve based on the detection output from the controller. The drive signal and / or the control signal for controlling the flow rate of the purge gas flow rate control valve to the purge gas introduction valve and / or the purge gas flow rate control valve so that the pressure in the vacuum exhaust pipe or the gas flow rate is predetermined. An oil vapor backflow prevention device in a vacuum exhaust pipe line, which is controlled to a value. 2. A vacuum shutoff valve and a first vent valve are further provided between the main valve and the vacuum exhaust device in the vacuum exhaust pipe line, and a bypass pipe line is connected to the purge gas supply pipe line. A purge gas reservoir tank and a second vent valve are provided in the passage, and at the start of driving the vacuum exhaust device, the controller closes the first and second vent valves and opens the purge gas introduction valve. The shut-off valve is opened after a predetermined time, and when the vacuum exhaust device is not driven, the shut-off valve is closed together with the shut-off valve. After a second predetermined time from the shut-off valve, the purge gas introduction valve is closed and then the third shut-off valve. The oil vapor backflow prevention device in the vacuum exhaust line according to claim 1, wherein the first and second vent valves are opened after a predetermined time. 3. The oil vapor backflow prevention in the vacuum exhaust pipe line according to claim 1, wherein the vacuum exhaust pipe line is provided with a portion having a small diameter, and the purge gas supply pipe line is connected to the portion. apparatus. 4. The oil vapor backflow prevention device in a vacuum exhaust pipe line according to claim 1, wherein the purge gas supply source has a device for supplying an inert gas. 5. The purge gas supply source has a gas selective membrane to extract an inert gas from the atmosphere.
The oil vapor backflow prevention device in the vacuum exhaust line according to. 6. The vacuum exhaust pipe according to claim 1, wherein the purge gas supply source has a filter, and the atmosphere is introduced into the purge gas supply pipe line through the filter. Oil vapor backflow prevention device in the road. 7. When the evacuation device fails and stops, the controller closes the shutoff valve together with the evacuation device, and after a fourth predetermined time from this, the purge gas introduction valve is closed. After a predetermined time of 5, the first,
The oil vapor backflow prevention device in the vacuum exhaust pipe line according to any one of claims 1 to 6, wherein the second vent valve is opened. 8. The length L of the conduit portion between the main valve and the shutoff valve in the vacuum exhaust conduit is L> β ₁ · β ₂ · 4 × 10 ⁻²⁴ · (T · c · α ・ a) /
(Q · δ ² ) where β _{1 is} a coefficient depending on the type of purge gas β ₂ is a coefficient depending on the type of oil used in the vacuum evacuation device T is an atmospheric temperature, a is a sectional area of a pipe, Q is a gas flow rate, and is δ ^2. Oil molecule diameter α; maximum probability velocity of oil vapor molecule, c; v / α
(V; molecular velocity in the molecular group of oil vapor). The oil vapor backflow prevention device in the vacuum exhaust pipe line according to any one of claims 1 to 7. 9. The controller, the purge gas introduction valve and / or the purge gas flow rate control valve, the velocity meter or pressure gauge, the shutoff valve, and the first and second vent valves are integrated. The oil vapor backflow prevention device in the vacuum exhaust pipe line according to any one of claims 2 to 8.