JPH11354056A - Protecting method for in-vacuum working device and protecting method for x-ray generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply monitor the vacuum pressure in a sealed chamber without the use of a vacuum gauge such as an ion gauge and ensure safety work in the sealed chamber. SOLUTION: In an X-ray generator, by having electrons emitted from an electron gun against a target within a sealed chamber which is evacuated with a vacuum pump, X-rays are generated from the surface of the target. Motor load current I of a turbomolecular pump during an evacuation operation is monitored, and when the motor load current I of the turbomolecular pump during the evacuation operation was lowered than the specified lower limit value I1 , X-ray generating operation within the sealed chamber is permitted. When the motor load current I of the turbomolecular pump during evacuation operation was higher than a specified upper limit value I0 , the X-ray generating operation within the sealed chamber is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for securing a working device in a vacuum (for example, an X-ray generator) for performing a predetermined operation in a sealed chamber evacuated by a turbo-molecular pump.

[0002]

2. Description of the Related Art FIG. 4 is a schematic diagram showing a general configuration example of an X-ray generator. As shown in FIG. 1, the X-ray generator has an electron gun 2 and a target (anti-cathode) 3 arranged in a sealed chamber 1 so as to face each other, and electrons emitted from a filament of the electron gun 2 collide with the target 3. In this case, a configuration is provided in which X-rays generated from the surface of the target 3 are extracted from the transmission window 4. In order to efficiently discharge the electrons emitted from the filament of the electron gun 2 and maintain the life of the filament, it is necessary to discharge the molecules in the sealed chamber 1 to form a vacuum atmosphere. Is used.

However, it is inevitable that gas is generated in the sealed chamber 1 due to collision of electrons with the target 3 and the sealed chamber 1. In addition, the seal portion of the sealed chamber 1 may be worn out and cannot maintain high airtightness. If the vacuum pressure in the sealed chamber 1 becomes excessively high due to such a cause,
Discharge occurs in a portion where the gas concentration is high or the like, and when the discharge continues, a discharge path is formed in that portion, after which the breakdown voltage becomes extremely poor. In addition, there is a danger that each component in the sealed chamber 1 may be damaged.

Therefore, in the conventional X-ray generator, a vacuum gauge such as an ion gauge is provided in the sealed chamber 1.
The vacuum gauge constantly measures the vacuum pressure in the sealed chamber 1, and when the vacuum pressure is lower than a certain level (when a high vacuum state is reached), an operation for generating X-rays is permitted. In addition, a vacuum switch (security circuit) for forcibly stopping the X-ray generation operation when the vacuum pressure becomes higher than a certain level is provided.

[0005]

As described above, the conventional X-ray generator is provided with a vacuum switch using a vacuum gauge such as an ion gauge, but this type of vacuum gauge is generally expensive. Therefore, this has been a major barrier in reducing product costs.

Also, as is well known, an ion gauge has a filament for generating ions, but this filament is easily broken when energized at a low vacuum, and is easily consumed even under a vacuum pressure that does not break the wire. Low. Therefore, there has been a problem that the maintenance management cost is also high.
Furthermore, when the filament is damaged, it is necessary to stop the X-ray generation operation until the replacement operation is completed, which may adversely affect the operation efficiency.

[0007] The present invention has been made in view of the above circumstances, without using a vacuum gauge such as an ion gauge.
An object of the present invention is to easily monitor the vacuum pressure in a sealed chamber and to ensure safe operation in the sealed chamber.

[0008]

In order to achieve the above object, the present invention provides a vacuum working apparatus for performing a predetermined operation in a sealed chamber evacuated by a turbo molecular pump. In this method, the motor load current of the turbo molecular pump is monitored, and the operation in the sealed chamber is controlled based on the value of the motor load current.

When a vacuum atmosphere is formed in the sealed chamber and the turbo molecular pump motor enters a steady operation, the load on the motor is reduced, and the turbo molecular pump motor continues to operate at a low load current. However, when the vacuum pressure in the sealed chamber increases, the load on the motor of the turbo-molecular pump increases in order to discharge more gas than during normal operation, and the motor load current increases almost in proportion to the vacuum pressure. .

The present invention is characterized by controlling the operation of a working device in a vacuum, focusing on the relationship between the vacuum pressure in the sealed chamber and the motor load current of the turbo-molecular pump. For example, based on the value of the motor load current, the operation in the sealed room is controlled as in the following (A) or (B).

(A) When the motor load current of the turbo-molecular pump during execution of the vacuum suction operation becomes lower than a predetermined value, the operation in the sealed chamber can be executed. (B) When the motor load current of the turbo-molecular pump during execution of the vacuum suction operation becomes higher than a predetermined value, the operation in the sealed chamber is stopped.

In general, the turbo molecular pump is provided with a security circuit that stops the vacuum suction operation when the motor load current flows excessively. The present invention monitors the motor load current of the turbo-molecular pump in a state before the vacuum suction operation is stopped by the security circuit of the turbo-molecular pump (that is, during the execution of the vacuum suction operation), and the operation of the working device in the vacuum itself It controls work operation.

According to the present invention, X-rays are emitted from a target surface by firing electrons from an electron gun toward a target in a sealed chamber evacuated by a turbo-molecular pump.
In the X-ray generator for generating X-rays, focusing on the relationship between the above-described vacuum pressure in the sealed chamber and the motor load current of the turbo-molecular pump, the X-ray in the sealed chamber as shown in the following (a) or (b) It is characterized by controlling the line generation operation.

(A) The motor load current of the turbo-molecular pump during execution of the vacuum suction operation is monitored. When the motor load current of the turbo-molecular pump during execution of the vacuum suction operation becomes lower than a predetermined lower limit, X-ray generation operation in a sealed room is allowed. (B) Monitoring the motor load current of the turbo-molecular pump during the execution of the vacuum suction operation, and when the motor load current of the turbo-molecular pump during the execution of the vacuum suction operation becomes higher than a predetermined upper limit value, X-ray generation operation is stopped.

According to the present invention, the vacuum pressure in the sealed chamber can be easily measured by monitoring the motor load current of the turbo molecular pump, so that a vacuum gauge such as an ion gauge is not required, and the product cost is reduced. it can. In addition, there is an advantage that the maintenance and management cost of the vacuum gauge is not required, and the operating efficiency does not decrease due to the maintenance of the vacuum gauge.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. In this embodiment, an X-ray generator will be described as a working device in a vacuum that performs a predetermined operation in a sealed chamber that is evacuated by a turbo-molecular pump, and a method for securing the device will be specifically described.

As described above, the X-ray generator is provided in the sealed chamber 1.
An electron gun 2 and a target (anti-cathode) 3 are arranged opposite to each other, and electrons emitted from the electron gun 2 are made to collide with the target 3. 4 (see FIG. 4).

In order to efficiently discharge electrons emitted from the electron gun 2, it is necessary to discharge molecules in the sealed chamber 1 to form a high vacuum atmosphere. For this reason, a turbo molecular pump (hereinafter referred to as "TMP "May be abbreviated as").

FIG. 1 shows a TMP motor load current I, a motor voltage V, a motor speed R, and a vacuum pressure P in the sealed chamber 1 when the sealed chamber 1 of the X-ray generator is evacuated.
FIG. Sealed room 1 by auxiliary vacuum pump
After roughly exhausting the inside, the TMP is started. Immediately after the start, a large power is required to increase the rotation speed R of the motor, so the motor voltage V is set to a large value (period). At this time, since a large load acts on the motor, the motor load current I also shows a large value.

When the motor rotational speed R of the TMP increases and stabilizes at a predetermined rotational speed, the motor voltage V is switched to a small value (time point). After that, the motor maintains the high-speed rotation at a low torque due to the inertial force.
Is also smaller (period).

During the vacuum suction operation, the motor load current I gradually decreases as the interior of the sealed chamber 1 is evacuated, and then the vacuum pressure P is balanced with the gas generated in the sealed chamber 1. And the motor load current I also becomes constant. Here, when excessive gas is generated in the sealed chamber 1 and the vacuum pressure rises, the rotational load on the motor of the TMP increases. Therefore, the motor load current increases almost in proportion to the vacuum pressure in order to maintain the motor rotation speed of the TMP. FIG. 2 is an enlarged view showing a change in TMP motor load current corresponding to a change in vacuum pressure due to gas generation in the sealed chamber.

The security method according to this embodiment focuses on the change in motor load current I of the TMP in the vacuum suction operation is running as described above, when the motor load current I is smaller than the value I ₁ set in advance to, thereby permitting operation of generating X-rays, when the motor load current I exceeds the value I ₂ set in advance, are so forcibly stopping operation of generating X-rays. These set values I ₁ , I
₂ can be set arbitrarily. In this embodiment, I ₂ > I ₁ .

Various security circuits are added to the X-ray generator, and the security method according to this embodiment is also used as one of them, and is incorporated in the control program of the X-ray generator. The load applied to the motor is increased, the motor load current I exceeds a predetermined limit value _{I 0 (> I 2> I} 1), and is controlled to stop forcibly vacuum suction operation. Such security control for the TMP has been conventionally performed.

FIG. 3 is a flowchart showing the operation control of the X-ray generator to which the security method according to this embodiment is applied. First, the auxiliary pump is operated to roughly evacuate the sealed chamber 1 from the atmospheric pressure (S1), and the pressure in the sealed chamber 1 is reduced to a predetermined value. I is detected (S3).

[0025] Then, when the motor load current I is smaller than the set value _{I 1} (S4), to allow the X-ray generating operation (S5). The permission of the X-ray generation operation is displayed on the display unit of the X-ray generation device. When the X-ray generation operation is permitted, the operation of the X-ray generation device by the operator becomes valid, the X-ray generation device is operated, and the X-ray generation operation is executed (S
6).

The control unit of the X-ray generating apparatus, in X-ray generation operation, and receives a detection signal of the motor load current I of TMP, when the motor load current I exceeds the set value I ₂ (S
7) The X-ray generation operation is forcibly stopped (S8).

[0027] The present invention, besides the X-ray generator,
The present invention can be applied to various types of vacuum working devices that perform a predetermined work in a sealed chamber that is evacuated by a turbo molecular pump. Although the application of the present invention eliminates the necessity of installing a vacuum gauge, it is optional to install a vacuum gauge arbitrarily in addition to the security method of the present invention in order to monitor the vacuum pressure in the sealed chamber with higher accuracy. It is.

[0028]

As described above, according to the present invention, the vacuum pressure in the sealed chamber can be easily measured by monitoring the motor load current of the turbo-molecular pump, so that a vacuum gauge such as an ion gauge is not required. In addition, product cost can be reduced. In addition, maintenance and management costs for the vacuum gauge are not required, and a decrease in operating efficiency due to the maintenance of the vacuum gauge can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship among a TMP motor load current I, a motor voltage V, a motor rotation speed R, and a vacuum pressure P in a sealed chamber when the sealed chamber of the X-ray generator is evacuated.

FIG. 2 is an enlarged view showing a change in TMP motor load current corresponding to a change in vacuum pressure due to gas generation in a sealed chamber.

FIG. 3 is a flowchart showing operation control of the X-ray generator to which the security method according to the embodiment of the present invention is applied.

FIG. 4 is a schematic diagram illustrating a general configuration example of an X-ray generator.

[Explanation of symbols]

 1: Sealed room 2: Electron gun 3: Target 4: Transmission window

Claims (5)

[Claims] 1. A vacuum working apparatus for performing a predetermined operation in a sealed chamber evacuated by a turbo-molecular pump, wherein a motor load current of the turbo-molecular pump during execution of a vacuum suction operation is monitored. A method for securing a working device in a vacuum, comprising: controlling a work in the sealed chamber based on a value of an electric current. 2. The method for securing a working device in a vacuum according to claim 1, wherein when the motor load current of the turbo-molecular pump during execution of the vacuum suction operation becomes lower than a predetermined value, the sealing is performed. A method for securing a working device in a vacuum, wherein the working in a room can be performed. 3. The method for securing a working device in a vacuum according to claim 1, wherein a motor load current of the turbo-molecular pump during execution of the vacuum suction operation becomes higher than a predetermined value. A method for securing a working device in a vacuum, wherein the operation in the sealed chamber is stopped. 4. An X-ray generator that emits X-rays from the surface of a target by emitting electrons from an electron gun toward a target in a sealed chamber that is evacuated by a turbo-molecular pump. Monitoring the motor load current of the turbo-molecular pump of the above, when the motor load current of the turbo-molecular pump during the execution of the vacuum suction operation becomes lower than a predetermined lower limit, the X-ray generation operation in the sealed chamber A security method for an X-ray generator, characterized in that: 5. An X-ray generator that emits X-rays from the surface of a target by emitting electrons from an electron gun toward a target in a sealed chamber that is evacuated by a turbo-molecular pump. Monitoring the motor load current of the turbo-molecular pump of the above, when the motor load current of the turbo-molecular pump during the execution of the vacuum suction operation becomes higher than a predetermined upper limit, the X-ray generation operation in the sealed chamber And stopping the X-ray generator.