JPH0988900A - Oil diffusion pump device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the oil pollution in a vacuum container when the evacuating operation is stopped to continue the heating of a heater by reducing the power in a condition in which the high speed injection of the oil vapor is possible when a pump is stopped, and shutting down the power when the temperature in a pump chamber is dropped to the set value. SOLUTION: An oil diffusion pump device boils the oil in an oil pan 13 by the heat of a heater 12, the oil vapor is ejected from a jet 11, the gas molecule jumped from a suction port 16 is discharged through a discharge port 14 by the suction effect of an auxiliary pump to make a vacuum container connected to the suction port 16 in a high vacuum condition. When a control part 18 receives the evacuation stop command, a power supply part 19 is controlled so as to reduce the power to be supplied to the heater 12. Though the vacuum condition on the vacuum container side is kept, the temperature in a housing gradually rises, and when the detected temperature by a temperature sensor 17 is dropped to the set value, the power supply to the heater 12 is stopped to release the evacuating condition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an oil diffusion pump device used in a vacuum device.

[0002]

Oil diffusion pump devices are often used in vacuum pump devices to achieve high vacuum. FIG. 4 is a configuration diagram of a conventional oil diffusion pump device. Two-stage jet (steam jetting part) inside the housing 10 forming the pump chamber
11 is provided, and the heater 1 is provided in the oil sump 13 at the bottom thereof.
2 is installed in oil. An exhaust port 14 connected to an auxiliary pump (not shown) such as a rotary pump is provided below the side surface of the housing 10, and an air cooling fin 15 is provided above the exhaust port 14 so as to surround the housing 10. The intake port 16 on the upper part of the housing 10 is connected to a container (that is, a vacuum container) to be vacuumed. Electric power is supplied to the heater 12 from a power supply unit 21 controlled by the control unit 20.

During a steady operation of the apparatus having the above-mentioned structure, that is, during a vacuuming operation, the oil sump 13 is heated by the heater 12.
The oil inside boils and becomes oil vapor. The oil vapor is jetted downward from the jet 11 at supersonic speed (broken line arrow), and the gas molecules jumping from the intake port 16 by this jet flow are conveyed downward (solid line thick arrow). The oil vapor itself becomes a liquid on the inner wall of the side surface of the housing 10 that is cooled by the air-cooling fins 15, falls along the inner wall, and falls back to the oil sump 13. The gas molecules carried downward by the jet of oil vapor are discharged to the atmosphere side through the exhaust port 14 by the suction action of the auxiliary pump. In this way, the gas molecules that have jumped from the intake port 16 into the housing 10 are successively carried out to the atmosphere side, so that the vacuum container connected to the intake port 16 finally reaches a high vacuum state. The heater 12 is heated by the power supplied from the power supply unit 21, and the power supply is controlled by the control unit 2.
On / off is controlled by 0.

[0004]

Next, the processing operation and the phenomenon when the vacuuming operation is stopped will be described with reference to FIG. FIG. 5 is a diagram showing a temperature change of a main part of the oil diffusion pump device when the evacuation operation is stopped. In the figure,
The oil temperature is the temperature of the oil in the oil sump 13, and the housing temperature is the temperature of the wall surface of the housing 10, both of which are assumed values (not monitor values).

During the evacuation operation, the heater 12 continues to supply a sufficient amount of heat to the oil in the oil sump 13, so that the oil boils vigorously and the oil vapor rises vigorously. That is, the oil temperature becomes the boiling point TOB of the oil. At this time,
The housing 10 is in a state where the amount of heat supplied by heat conduction from high-temperature oil and the amount of heat taken away by the air-cooled fins 15 are in equilibrium, and are substantially maintained at a certain temperature lower than the oil temperature.

When the control unit 20 receives the vacuuming operation stop command (time t11), the power supply unit 21 causes the heater 12 to stop.
The power supplied to is shut off and heating stops. Although the oil temperature is initially higher than the housing temperature, the heat capacity of the oil is small, so that the oil is rapidly deprived of heat by the housing 10. Therefore, while the oil temperature rapidly decreases from the boiling point TOB, the housing temperature gradually decreases, and the two coincide with each other at time t12. After time t12, the cooling rate of the oil becomes slow due to heat conduction from the housing 10 to the oil. Therefore, the limit temperature TOE at which the oil evaporates after the oil temperature begins to drop
The time Δt1 required to reach (1) becomes considerably longer than that when the oil temperature continues to decrease at the cooling rate before time t12.

When the oil temperature falls below the boiling point TOB and ceases to be in a boiling state, the generation of oil vapor from the inside of the oil in the oil sump 13 is stopped, and the oil vapor only rises from the oil surface. As a result, the velocity of the jet flowing out of the jet 11 rapidly decreases, and the momentum for carrying the gas molecules downward is lost. Therefore, even if gas molecules fly in from the intake port 16, the gas molecules are not carried toward the exhaust port 14. At this time, the auxiliary pump is operating, but its suction force is not sufficient to maintain a high vacuum in the housing 10. Therefore, gas molecules that have entered the housing 10 from the exhaust port 14 gradually spread, and the inside of the housing 10 is gradually expanded. Also, the degree of vacuum inside the vacuum container decreases. As a result, the oil vapor leaked from the jet 11 gradually spreads and flows back to the vacuum container side through the intake port 16 and contaminates the inside of the vacuum container. Contamination due to the oil vapor continues until the oil temperature falls below the limit temperature TOE at which the oil evaporates, so the longer Δt1 is, the more severe the pollution becomes.

In order to prevent such a reverse flow of oil vapor, a structure such as a baffle or a trap was provided between the vacuum container and the intake port 16 in the conventional apparatus, but the structure is complicated and the cost is low. It was expensive. Further, as a result of the oil adhering to these structures, there is a problem that it interferes with the uptake of gas molecules and is liable to cause a failure such that the evacuation operation itself is not performed well.

The present invention has been made to solve the above problems, and an object thereof is to provide an oil diffusion pump device which reduces the oil contamination in the vacuum container when the vacuuming operation is stopped at a low cost. To provide.

[0010]

SUMMARY OF THE INVENTION The present invention, which has been made to solve the above-mentioned problems, discloses a method in which a heater is heated to heat and evaporate oil, and a high-speed injection of the oil vapor causes a gas to flow into a pump chamber. In an oil diffusion pump device that carries out molecules, a) a temperature sensor that detects the temperature of the pump chamber, b) power supply means that supplies power to the heater, and c) the temperature of the pump chamber when the pump operation is stopped. However, the temperature of the oil is reduced to such a degree that the high-speed injection of oil vapor can be maintained and the heater heating is continued, and then the temperature detected by the temperature sensor reaches a predetermined temperature. Control means for controlling the power supply means so as to cut off the power when the power goes down.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the oil diffusion pump device according to the present invention, the heater heating is not stopped immediately after the instruction to stop the vacuuming operation is given, and it is smaller than the heater heating power in the steady operation. The vacuum exhaust state is maintained by continuing to supply the heater with electric power that can substantially maintain the oil temperature. That is, the oil is in a state of boiling strongly by heating the heater during the evacuation operation, but after the vacuum evacuation operation stop command is given, as little electric power as possible is supplied to the heater within a range in which the oil boiling state can be maintained. . At this time, the temperature of the wall surface (housing) of the pump chamber gradually decreases. When the temperature of the housing detected by the temperature sensor has dropped to a predetermined temperature, the heater heating power supply is completely stopped. Therefore, both the oil temperature and the housing temperature start to drop.

As mentioned above, the cooling rate of oil is faster than that of the housing, so that at some point, the temperatures of both are the same,
After that, the decrease rate of the oil temperature becomes gentle due to the influence of the housing and atmosphere. However, since the housing has been cooled to a predetermined temperature in advance, the difference between the temperature when the oil temperature and the housing temperature match and the minimum limit temperature at which the oil evaporates is smaller than that in the conventional device. . As a result, the time required until the generation of oil vapor is stopped after the vacuum exhaust state is no longer maintained is considerably shortened as compared with the conventional device.

[0013]

Therefore, according to the oil diffusion pump device of the present invention, oil contamination on the vacuum container side can be reduced by a simple method of temperature sensor and power supply control.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the oil diffusion pump device according to the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of an oil diffusion pump device according to the present invention, FIG. 2 is a flow chart showing a heater heating control method, and FIG. 3 is a diagram showing power supplied to the heater and temperature changes.

In FIG. 1, a difference from the conventional device of FIG. 4 is that a temperature sensor 17 for detecting the temperature of the housing 10 is provided, and the controller 18 controls the power supply unit according to the detected temperature. It is configured so as to control 19.

In the steady operation state of evacuation, the control unit 18
By the control described above, sufficient electric power W1 is supplied from the power supply unit 19 to the heater 12, the oil in the oil sump 13 is heated, and the oil is in a state of intense boiling (step S1). When the control unit 18 receives a vacuuming operation stop command at time t21 (step S2), the power supply unit 19 is controlled to reduce the power supplied to the heater 12 to W2 (step S2).
3). The electric power W2 is set as small as possible within a range where the boiling state of the oil is maintained (that is, the oil temperature is maintained at the boiling point TOB). That is, since the boiling becomes mild, but the oil temperature is maintained at the boiling point TOB, the jet velocity from the jet 11 is maintained at supersonic speed, and thus the vacuum exhaust state is maintained. On the other hand, in the housing 10, since the amount of heat taken from the outside is larger than the amount of heat supplied by the heat transfer from the oil, the temperature thereof gradually decreases. Therefore, the housing temperature is gradually lowered while maintaining the vacuum state on the vacuum container side (state from t21 to t22 in FIG. 3).

When the housing temperature is lowered to the predetermined temperature T21 by the temperature detected by the temperature sensor 17 (step S4), the control unit 18 controls the power supply unit 19 to supply power to the heater 12 at the time t22. The supply is stopped (step S5). As a result, after time t22, the cooling rate of the housing 10 increases and the oil temperature also begins to drop rapidly.
As a result, the vacuum exhaust state is no longer maintained.

As described above, the cooling rate of the housing 10 is slower than the cooling rate of oil, so that at a certain time (time t
In 23), the oil temperature matches the housing temperature, and the oil cooling rate slows thereafter. However, the temperature T22 when the oil temperature and the housing temperature match becomes lower than the temperature T12 when the oil temperature and the housing temperature match in the conventional device. That is, it becomes closer to the limit temperature TOE at which the oil evaporates. Therefore, the time Δt2 required from reaching the temperature TOE after the oil temperature starts to decrease is considerably shorter than the time Δt1 in the conventional device. As a result, it is possible to reduce the possibility that the oil vapor will flow back to the vacuum container side through the intake port 16.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of an oil diffusion pump device according to the present invention.

FIG. 2 is a control flowchart of heater heating in the oil diffusion pump device of FIG.

FIG. 3 is a diagram showing a change in electric power and a change in temperature according to the control method of FIG.

FIG. 4 is a configuration diagram of a conventional oil diffusion pump device.

FIG. 5 is a diagram showing a temperature change due to a heater heating method in a conventional oil diffusion pump device.

[Explanation of symbols]

 10 ... Housing 11 ... Jet 12 ... Heater 13 ... Oil sump 14 ... Exhaust port 15 ... Air cooling fin 16 ... Intake port 17 ... Temperature sensor 18 ... Control part 19 ... Electric power supply part

Claims (1)

[Claims] 1. An oil diffusion pump device which heats and evaporates oil by heating a heater, and carries out gas molecules flowing into the pump chamber by high-speed injection of the oil vapor, a) detecting the temperature of the pump chamber A temperature sensor; b) a power supply means for supplying electric power to the heater; and c) a state in which the temperature of the pump chamber is lowered but the oil temperature is capable of high-speed injection of oil vapor when the pump operation is stopped. Control for controlling the power supply means so as to cut off the electric power when the temperature detected by the temperature sensor drops to a predetermined temperature after continuing the heater heating by reducing the electric power to the level An oil diffusion pump device comprising: