JPS5829870B2 - Leak test equipment - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a gas leak testing device, which uses a helium leak detector to detect and quantify a trace amount of gas leaking from an object to be inspected, and display it on a display (referred to as a meter). It is something.

As shown in FIG. 1, for example, this type of leak test apparatus has a helium leak detector 3 using a mass spectrometry leak tester connected to a test object 1 via a vacuum pipe 2.

Here, for test object 1, when using the vacuum method as a leak test method, the test object itself is used; on the other hand, when using the Pelger method, the test object filled with helium gas is stored in a test vacuum container. Use the one you made.

The helium leak detector 3 has a meter 4, and when helium gas leaks from the test object 1, the leak amount increases from the O level by a value H1 corresponding to the leak amount, as shown in FIG.

In this way, the meter 4 indicates O when there is no leakage, and the larger the leakage of the object to be inspected, the greater the swing of the meter 4. Therefore, normally, if the meter 4 does not swing, there is no leakage of the object to be inspected. It is determined that there is no leakage or that there is only a leakage so small that it cannot be detected.

As shown in FIG. 3, the helium detector 3 uses an analysis circuit 12 having a mass spectrometry tube 11 as a leak gas detection element.

The analysis tube 11 includes a filament 14 for emitting thermionic electrons heated by a power source 13 and an anode 15 facing the filament 14. Thermionic electrons emitted from the filament 14 are generated into an electron beam by a deflection electrode (not shown). Mass spectrometry is performed by ionizing a probe gas using this electron beam.

However, in the conventional mass spectrometer tube 11, thermionic current,
Therefore, in order to control the anode current at a constant level, a resistor 16 for detecting the anode current is provided in the loop through which the anode current flows, and an amplifier 17 detects and amplifies the variation in the voltage across the resistor 16.
The anode current is maintained at a constant value by controlling the filament current control circuit 18 (for example, a circuit having a transistor as a variable resistance element) inserted between the filament temperature and the filament temperature. There is.

Note that 19 is a high voltage power source for acceleration.

By the way, in the analysis circuit 12 having such a configuration, if the filament 15 of the mass spectrometry tube 11 is broken or the electron flow flowing through the mass spectrometry tube 11 becomes small, the mass spectrometry tube 11 will not be able to perform the analysis operation. , or the detection sensitivity of the entire leak testing device will be significantly reduced, so it is desirable to detect and deal with these accidents as soon as possible.

The present invention attempts to reliably fulfill such demands.

Hereinafter, an example of the present invention will be described in detail with reference to the drawings in which parts corresponding to those in FIG. 3 are denoted by the same reference numerals.

FIG. 4 shows a first embodiment of the present invention, in which a control signal D applied to the filament current control circuit 18 is shown.
T is given to the comparator 21 as a comparison detection input.

Note that this comparator 21 is supplied with a reference voltage signal SE for setting an alarm level from a reference voltage generation circuit 24 consisting of a reference power supply 22 and a variable resistor 23.

In the configuration shown in FIG. 4, as the filament 15 of the mass spectrometer tube 11 wears out and its resistance value increases, the output voltage DT of the amplifier 17 decreases, and in response, the filament current control circuit 18 Controlled to reduce resistance.

Therefore, the current flowing into the filament 14 increases, and thus the anode current of the mass spectrometer tube 11 is controlled to a substantially constant value by such servo operation.

However, in this state, if the consumption of the filament 14 becomes extremely large and exceeds the upper limit (or lower limit) of the above-mentioned loop servo operation permissible limit, the output DTII'i of the amplifier 17 will be reduced to the upper limit (or lower limit) of the controllable range. lower limit value).

Therefore, the comparison output ARM of the toki comparator 21 is maintained at a constant value, and as a result of this constant value, an abnormality occurs (that is, the anode current cannot be controlled to a constant value due to filament consumption). can be determined.

On the other hand, when the filament 14 is broken, its resistance appears to be infinite, which means that it exceeds the limit value of the controllable range.

Therefore, since the output of the comparator 21 is at the abnormality detection level, breakage of the filament 14 can be reliably detected.

As described above, according to the configuration shown in FIG. 4, consumption or breakage of the filament 14 can be detected reliably.

Note that an alarm circuit may be provided on the output side of the comparator 21 to issue an alarm when the output of the comparator 21 reaches a certain value.

FIG. 5 shows a second embodiment of the invention.

In the case of FIG. 4, the comparator 21 is used as a comparison means, but instead of this, a series circuit consisting of a zener diode 31 and a photocoupler 32 is provided, and the output DT of the amplifier 17 is applied to this series circuit, and the photocoupler 32 The output is sent as the abnormality detection output ARM.

In FIG. 5, when an operational amplifier with an IC configuration is used as the amplifier 17 and an operating voltage of 6 μ is used as the Zener diode 31, the output DT of the amplifier 17 is 4 to 5 when the filament 14 is operating normally. (2) At this time, no current flows through the zener diode 31, so the abnormality detection output ARM cannot be obtained from the photocoupler 32.

On the other hand, when the filament 14 wears out and constant control of the anode current becomes impossible, the output of the amplifier 17 increases by 10×1, and at this time, the zener diode 31 conducts, causing the photocoupler 32 to An abnormality detection output ARM is obtained.

As described above, according to the configuration shown in FIG. 5, by knowing the change in the anode current based on the increase in resistance caused by the consumption of the filament 14, breakage 2 of the filament 14 can be reliably predicted with a simple configuration. .

FIG. 6 shows a third embodiment of the present invention in which constant value control by the filament current control circuit 18 is not performed.

In this case, the heating power source 41 for the filament 14 is used as the power source, and a bridge circuit 42 with the filament 14 as one side
Configure.

That is, a series circuit of the filament 14 and the resistor 43 and a series circuit of the resistors 44 and 45 are connected in parallel to the power supply 41, and the midpoint of the connection between the filament 14 and the resistor 43 and the midpoint of the connection of the resistors 44 and 45 are connected in parallel. It is connected to a detection circuit 46 having a dynamic amplifier configuration.

In the configuration shown in FIG. 6, the output ARM of the detection circuit 46 changes in response to changes in the resistance value of the filament 14, and therefore, when the change exceeds a predetermined range, it can be determined that an abnormality has occurred.

In the case of FIG. 6, the power supply 41 for the filament 14 of the analysis tube 11 is shared as the power supply for the bridge circuit 42, but a dedicated power supply may be prepared separately from this power supply 41.

FIG. 7 shows a fourth embodiment of the present invention, which is another example of FIG.

In this case, in Fig. 4, the filament 14 and the power supply 1
The filament current control circuit 18 and the comparator 21 between the amplifiers 17 and 3 are omitted, and the output DT of the amplifier 17 is directly taken out as an abnormality detection output.

According to the configuration shown in FIG. 7, when the filament 14 is consumed and the anode current increases, the output of the amplifier 17 increases, so that this abnormality can be detected as in the case of FIG. Therefore, the simplification of the configuration can be further promoted.

FIG. 8 shows a fifth embodiment of the present invention, in which the anode current detection resistor 16 is omitted from FIG. The voltage across the terminal is sent out via the comparator 52 as an abnormality detection output ARM.

In the configuration shown in FIG. 8, if the resistance of the filament 14 increases dramatically due to wear and tear, the comparator 52 can detect an abnormality detection output ARM, and thus it is possible to reliably predict and detect a break in the filament 14.

Note that in FIG. 8, instead of the resistor 51 and comparator 52, an abnormality detection relay 53 may be provided as shown in FIG. 9.

In this case, detection of disconnection of the filament 14 can be realized with an extremely simple configuration.

In order to predict a disconnection, the relay 53 may select a predetermined electric current as required.

In the embodiments shown in FIGS. 4 and 5, a circuit that utilizes the equivalent resistance of a transistor was used as the filament current control circuit 18, but instead of this, a phase control method using a semiconductor element such as a 5CR1) LIAC is used. What was there,
Various methods can be applied, such as one using a current control method using a supersaturated reactor.

Further, in the above description, a direct heating type device in which thermionic electrons are directly emitted from a filament is used as the thermionic emission means, but instead of this, an indirect heating type device in which the cathode is heated by a filament may be used.

[Brief explanation of the drawing]

1 and 2 are block diagrams and signal waveform diagrams showing an outline of a leak test device to which the present invention can be applied, FIG. 3 is a connection diagram showing a conventional analysis circuit, and FIG. 4 is a diagram showing a conventional analysis circuit according to the present invention. A connection diagram showing an example of a leak test device, and FIGS. 5 to 9 are connection diagrams showing other examples of the present invention. 1...Test object, 2...Vacuum piping, 3
・・・・・・Helium leak detector, 4・・・・・・
Meter, 11... Mass spectrometry tube, 12...
・Analysis circuit, 13.41...Power supply, 14---
--Filament, 15... Anode, 16.
...Anode current detection resistor, 17...
amplifier, 18... filament current control circuit,
21゜52...Comparator, 24...
・Reference voltage generation circuit, 31... Zener diode, 32... Photo coupler, 42...
Bridge circuit, 46...Detection circuit, 51...
...Filament current detection resistor, 53...
Relay for abnormality detection.

Claims (1)

[Scope of Claims] 1. A gas leakage test device equipped with a mass spectrometry tube that generates an electron beam between a thermionic emission filament and an anode facing the same, and ionizes a probe gas with the electron beam, A gas leak test device comprising: an abnormality detection circuit that utilizes the change in resistance of the filament of the mass spectrometer tube as the filament wears out to obtain an output representing the change in resistance. 2. In the scope of claim 1, the abnormality detection circuit includes an anode current detection resistor and an amplifier that generates an output corresponding to the voltage across the anode current detection resistor, and is configured to obtain an abnormality detection output based on the output of the amplifier. Gas leak test equipment. 3. A gas leak test device according to claim 2, comprising comparison means for comparing the output of the amplifier with a reference value and generating an abnormality detection output when the output exceeds a predetermined limit value. 4. A gas leak test device according to claim 1, wherein the abnormality detection circuit is constituted by a bridge circuit including the filament on the τ side. 5. In the scope of claim 1, the abnormality detection circuit comprises a filament current detection resistor and an amplifier that generates an output corresponding to the voltage across the filament current detection circuit, and is configured to obtain an abnormality detection output based on the output of the amplifier. Gas leak test equipment. 6. A gas leak test device as claimed in claim 5, comprising comparison means for comparing the output of the amplifier with a reference value and generating an abnormality detection output when the output exceeds a predetermined limit value. 7. A gas leak test device according to claim 1, wherein the abnormality detection circuit comprises an abnormality detection relay connected in series to the filament.