JP2005274528A - Leak inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leak inspection device capable of simultaneously inspecting a plurality of detection objects. <P>SOLUTION: Two detection objects are provided for a common reference tank, and a pressure difference generated between the reference tank and each of the two objects is detected by each differential pressure detector. The detection outputs are added at a reversed polarity by a first adder, and an inspection object having a leak is specified by the polarity of the addition result. Whether or not the leak quantity exceeds an allowable value is determined, and the detection outputs of the differential detectors are added at the same polarity by a second adder, and whether the leak close to the same quantity of the object is present or not is determined by the addition result. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a leakage inspection apparatus used for automatically inspecting various containers for leakage.

In general, as shown in FIG. 3, a leakage inspection apparatus applies air pressure to one inspection object 9 and one reference tank 11, and determines whether or not a pressure difference occurs between them. It is determined whether or not 9 is leaked. First, this general leak inspection apparatus will be briefly described.
In the figure, reference numeral 1 denotes an air pressure source. The air pressure generated by the air pressure source 1 is given to the regulating valve 3 through the pipe line 2, stabilized at a constant air pressure by the regulating valve 3, and given to the three-way electromagnetic valve 4. A branch pipe 5 is connected to the outlet side of the three-way solenoid valve 4, and the air pressure supplied from the pneumatic pressure source 1 is branched into two branch paths 6 and 7 by the branch pipe 5.

Shutoff valves 8A and 8B are inserted in the two branch paths 6 and 7, respectively, and the air pressure output from the air pressure source 1 is applied to the object 9 and the reference tank 11 through the shutoff valves 8A and 8B. The first part of the shutoff valves 8A and 8B inserted in the branch paths 6 and 7 (the branch path between the object to be inspected 9 and the reference tank 11) is defined as branch paths 6 'and 7'. A differential pressure detector 12 is passed between the branch paths 6 'and 7' so that the differential pressure between the branch paths 6 'and 7' can be measured. Note that a pressure gauge 17 may be connected to the branch path 6 'as necessary.
Whether the detection output of the differential pressure detector 12 is amplified by the amplifier 13, and the amplified output signal is given to the pass / fail determination device 14 to determine whether the device under test 9 is leaking and display the determination result on the display 15. Alternatively, the defective / non-defective product can be automatically sorted by operating the good / bad sorting device.

Leakage inspection is performed as follows. The three-way solenoid valve 4 is controlled to a first state in which A and B communicate with each other, and the shutoff valves 8A and 8B are controlled to be opened to apply air pressure to the object 9 and the reference tank 11. This state is referred to as a pressurizing mode (FIG. 4).
The shut-off valves 8A and 8B are closed after a certain time after pressurization (stable mode). The reference tank 11 is composed of a container having the same internal volume as the object to be inspected 9 and having no leakage. Therefore, if there is no leakage in the inspection object 9, no pressure difference is generated between the branch paths 6 'and 7'. However, if there is a leakage in the inspection object 9, the branch paths 6 'and 7' pass over time. A pressure difference occurs between them. This pressure difference is detected by the differential pressure detector 12, this detection output signal is amplified by the amplifier 13, and it is determined by the pass / fail determination device 14 that there is a leak when the detected differential pressure value after a predetermined time has reached a predetermined value or more. Yes (inspection mode).

After the inspection is finished, the three-way solenoid valve 4 is switched to the second state in which B-C communicates, and the shutoff valves 8A and 8B are controlled to be opened to thereby adjust the air pressure applied to the inspection object 9 and the reference tank 11 in three directions. Release from the exhaust port C of the solenoid valve 4 (exhaust mode), one test cycle is completed, and the object to be inspected 9 is replaced. Reference numeral 16 denotes a controller for controlling these processes.
In the leakage inspection apparatus shown in FIG. 3, since the reference tank 11 is fixed and the inspected objects 9 are sequentially replaced, air pressure is repeatedly applied to the reference tank 11 sequentially. Due to the supply of air pressure, the temperature of the reference tank rises, and a temperature difference is generated between the reference tank 11 and the object 9 to be inspected, and this temperature difference has a drawback that disturbance such as zero point fluctuation occurs.

In order to eliminate this drawback, the present applicant, as disclosed in Patent Document 1, connects two test objects to a common reference tank, and connects the reference tank and each of the two test objects. Measure the pressure difference generated by the differential pressure measuring device, add the measured values, identify the inspected object with the polarity of the addition result, and determine whether the leakage amount exceeds the allowable amount A leakage inspection device was proposed.
FIG. 5 shows an example of the configuration. The controller 16 controls the three-way solenoid valve 4 and the shutoff valves 8A, 8B, and 8C to control the pressurization mode, the inspection mode, and the exhaust mode, which is the same as the leak inspection apparatus shown in FIG.

3 differs from FIG. 3 in that a three-way branch pipe 18 is provided on the output side of the three-way solenoid valve 4, and shut-off valves 8A, 8B, and 8C are connected to the branch paths 6A, 6B, and 7 of the three-way branch pipe 18, respectively. Here, the branch path on the output side that has passed through the shutoff valves 8A, 8B, and 8C will be referred to as branch paths 6A ', 7', and 6B '. The reference tank 11 is connected to the branch path 7 ', and the test objects 9A and 9B are connected to the branch paths 6A' and 6B ', respectively.
At the same time, differential pressure detectors 12A and 12B are passed between the branch path 7 'leading to the reference tank 11 and the branch path 6A' leading to one of the inspected objects 9A and between 7 'and the branch path 6B', respectively. Provide. With this connection structure, the differential pressure detector 12A detects the pressure difference between the reference tank 11 and the inspection object 9A, and the differential pressure detector 12B detects the pressure difference between the reference tank 11 and the inspection object 9B. To detect.

The characteristic configuration of the leakage inspection apparatus proposed in Patent Document 1 is that the adder 19 adds the detection output signals of these two differential pressure detectors 12A and 12B. That is, in the differential pressure detector 12A, when there is a leak in the inspection object 9A, the diaphragm DF is displaced in the direction indicated by the dotted line and, for example, transmits a positive polarity detection signal V _A. The diaphragm DF of the pressure difference detector 12B If leakage is present in the pressure difference detector 12B in the test subject 9B displaced in the direction indicated by the dotted line, transmitting the example, a negative polarity of the detection signal -V _B. The two detection signals V _A and −V _B are added by the adder 19, and the presence or absence of leakage and the inspection target on the side having leakage can be specified by the polarity of the addition result.

That is, when there is a leak in the inspection object 9A and there is no leakage in the inspection object 9B, the positive detection signal _VA is transmitted, and the negative detection signal -V _B is -V _B = 0. The addition result of the adder 19 is positive. Therefore, in this case, it can be seen that there is a leak in the inspection object 9A. When there is a leak in the inspection object 9B, the addition result of the adder 19 is negative.
Here, immediately after the temperature of the reference tank 11 is increased as a result of repeated pressurization and the air pressure is applied, the air in the reference tank 11 is thermally expanded due to this temperature increase, and immediately after the air pressure is applied, the temperature rises. If the pressure in the reference tank 11 increases, the pressure increase causes the diaphragms DF of the two differential pressure detectors 12A and 12B to be displaced to the same extent in opposite directions. When the movement of the diaphragm DF is viewed from the output of the adder 19, ΔV _A + (− ΔV _B ) ≈0. That is, it can be seen that the temperature rise of the reference tank 11 or the disturbance caused by the deformation pipe is removed. Therefore, the configuration shown in FIG. 5 is equivalent to measuring the pressure difference between the objects to be inspected 9A and 9B, and it is possible to obtain a highly accurate inspection result in which the temperature rise of the reference tank 11 and the disturbance due to the deformation pipe are removed. .

Accordingly, the addition result of the adder 19 is amplified by the amplifier 13, and the amplified output is input to the pass / fail judgment device 14, so that the pass / fail judgment device 14 determines the signal to be inspected 9A by the polarity of the input signal and the voltage value. It is possible to determine which of 9B has a leak and whether or not the leak amount is within an allowable range, and the determination result can be displayed on the display 15, for example. FIG. 6 shows an example of display on the display 15. The leakage amount of the inspection object 9A is displayed on the positive side of the indicator, and the leakage amount of the inspection object 9B is displayed on the negative side. Therefore, when the pointer 15A swings to the positive side, it indicates that there is a leak in the inspection object 9A, and when it moves to the negative side, it indicates that the inspection object 9B has a leakage. When the pointer 15A swings to the defective zone A, the inspection target 9A is determined to be defective, and when the pointer 15A swings to the defective zone B, the inspection target 9B is determined to be defective. When the pointer 15A is in the range of the center good zone, it is determined to be good.
Japanese Patent No. 2126343

According to the leak inspection apparatus proposed in Patent Document 1, it is possible to compare and inspect the reference tank 11 and the two inspected objects 9A and 9B at a time, so that it is applied when inspecting a large number of inspected objects. It is effective. However, even if the temperature of the reference tank 11 fluctuates independently, the pressure change accompanying the fluctuation can be offset by adding the detection outputs of the two differential pressure detectors 12A and 12B. .
By the way, in the above description, it has been described that it can be determined which of the inspected objects 9A and 9B is leaked by the polarity of the added value of the adder 19. However, this determination method cannot make a correct determination strictly. For example, even if the addition value of the adder 19 is positive and the pointer 15A swings to the defective zone A, the addition value of the adder 19 is V _A + (− V _B ), and therefore there is a leak in the inspection object 9B. Even if V _A + (− V _B )> 0, the pointer 15A swings to the positive side, and if the value of V _A is larger, it may be possible to reach the defective zone A. Therefore, since V _A + (− V _B )> 0, it is dangerous to determine that “only the subject 9A is leaking”.

In order to eliminate this drawback, as shown in FIG. 7, the detection results of the differential pressure detectors 12A and 12B are separately input to the pass / fail judgment devices 14B and 14C, and the respective inspected objects 9A and 9B are leaked separately. If each of the detected differential pressure values is zero and the addition result of the adder 19 is also zero, both the inspected objects 9A and 9B are accurately determined if it is determined that there is no leakage. Become.
Further, if the addition result of the adder 19 is positive and the individual inspection result of the inspection object 9A is “leakage”, and the inspection result of the inspection object 9B is “no leakage”, the inspection object Only 9A can be determined to have “leakage”. Further, if the addition result of the adder 19 is negative and the individual inspection result of the inspection object 9B is “leakage”, and the individual inspection result of the inspection object 9A is “no leakage”, only the inspection object 9B. It can be determined that there is a leak.

As described above, when the presence or absence of leakage of the two test objects is determined based on the addition result of the adder 19, a true determination result can be obtained. However, there is a drawback that the scale of the inspection apparatus becomes large because the pass / fail determination must be made individually for each of the inspected objects 9A and 9B.
Furthermore, since the differential pressure detection signals input to the quality determination means 14A and 14B provided individually include drift components generated due to temperature fluctuations of the reference tank 11, the individual quality determination devices 14A and 14B. In this determination, a defect can be detected only when the leak is larger than the drift component. That is, there is a disadvantage that it is impossible to detect the presence or absence of leakage smaller than the drift component. As a result, even if the leak inspection apparatus shown in FIG. 7 is used, if the inspected objects 9A and 9B have the same level of leakage smaller than the drift component, the leakage cannot be detected. .

The object of the present invention is to propose a leakage inspection apparatus capable of detecting the leakage even when the two inspection objects 9A and 9B have similar leakage in the leakage inspection apparatus shown in FIG. is there.
Still another object of the present invention is to propose a leak inspection apparatus that can eliminate the effect of drift that occurs when detecting the presence of similar leaks in the two test objects 9A and 9B. is there.

  According to the first aspect of the present invention, a three-way branch pipe that branches the air pressure supplied from the pneumatic pressure source in three directions, a shut-off valve connected to each pipeline branched by the three-way branch pipe, and the take-off valve are taken out. A standard tank connected to one pipe line of air pressure, a pair of test objects connected to the two pipes of air pressure taken out through the shutoff valve, and a pipe line communicating with the pair of test objects A pair of differential pressure detectors that respectively detect a pressure difference generated between the standard tank and each object to be inspected by being passed between the pipes communicating with the reference tank, and the pair of differential pressure detections A first adder for adding the detection outputs of the detectors in reverse polarity, a first pass / fail judgment device for judging the presence or absence of leakage of each object to be inspected based on the addition result of the adders, and detection by a pair of differential pressure detectors A second adder for adding the outputs in the same polarity, and this second addition Drift correction means for subtracting the drift correction value from the addition result, a second pass / fail judgment device for judging the presence or absence of leakage of each object to be inspected based on the correction result drift-corrected by the drift correction means, an air pressure source and the three-way The first state is connected between the branch pipes and the air pressure supplied from the air pressure source is applied to the three-way branch pipe side, and the second state is closed by closing the air pressure source side and releasing the three-way branch pipe to the atmosphere. The three-way solenoid valve, the three-way solenoid valve is switched to the first state, the shut-off valve is opened, the pressurizing mode for supplying air pressure to the reference tank and each object to be inspected, and the shut-off valve is closed. In this state, the detection output of the differential pressure detector is measured to determine the presence or absence of leakage of each inspection object, and the three-way solenoid valve is switched to the second state to be applied to the reference tank and each inspection object. Exhaust that discharges fresh air to the atmosphere Suggest leakage inspection apparatus is constituted by a controller for controlling over de switching.

According to a second aspect of the present invention, in the leak inspection apparatus according to the first aspect, the drift correction means stores the drift correction value acquired in the calibration mode and the drift correction value stored in the drift memory is the second. This invention proposes a leakage inspection apparatus characterized by comprising a subtracter that subtracts from the added output value of an adder.
According to a third aspect of the present invention, in the leak inspection apparatus according to the first or second aspect, the drift correction value stored in the drift memory applies air pressure to the pair of inspected objects and the reference tank, and the timing at the time of the inspection. The initial addition value obtained by the second adder at the first timing substantially equal to the first addition value, and the true leakage obtained from the second adder at the second timing after the time when drift is expected to converge from the first timing. We propose a leakage inspection device characterized by the difference between the measured values.

According to the leakage inspection apparatus according to the present invention, since the second adder for adding the detection outputs of the two differential pressure detectors with the same polarity is provided, if the two inspection objects have the same level of leakage, the first adder Even if the output of the adder is 0, 2ΔA is output as the addition result of the second adder if the differential pressure detection value of one of the differential pressure detectors is ΔA. As a result, if there is a similar leak in the two test objects, it can be detected.
Further, in the present invention, since the drift correction means is provided before the addition result of the second adder is input to the pass / fail judgment device, even if a drift component is included in the addition result of the second adder, this drift correction means. Since the drift component is removed by this, it is possible to avoid making an erroneous determination due to the drift component.

  In particular, the drift memory provided in the drift correction means stores the drift correction value acquired by a technique called mastering. Therefore, the drift correction value is highly reliable, and the influence of drift can be reliably removed. Therefore, a highly reliable leak test can be performed.

FIG. 1 shows an embodiment of a leak inspection apparatus according to the present invention. The parts corresponding to those in FIG. 5 are denoted by the same reference numerals, and repeated description thereof is omitted. In the present invention, the adder 19 described in FIG. 5 is the first adder, and the pass / fail judgment device 14 is the first pass / fail judgment device. In addition, the first feature is a configuration in which the second adder 21 and the second pass / fail judgment device 22 are provided.
Further, the configuration in which the drift correction means 23 is provided on the output side of the second adder 21 is a second feature.
Furthermore, the third feature is that the drift correction value stored in the drift memory 23B provided in the drift correction means 23 is acquired by a technique called mastering.

The features of each feature will be described below.
Since the first adder 19 adds the detection outputs of the differential pressure detectors 12A and 12B with opposite polarities (V _A -V _B ), there is a leak in one of the two inspected objects 9A and 9B. For example, a detection signal having a positive polarity or a negative polarity can be obtained as a result of the addition, and it can be determined which of the inspected objects has a leak based on the polarity of the addition output signal.
In contrast, the second adder 21 adds the detection output signals of the two differential pressure detectors 12A and 12B with the same polarity (V _A + V _B ). The inverter 26 shown in FIG. 1 is provided for polarity inversion. When the same polarity is added and the inspected objects 9A and 9B have the same value of leakage, an added value 2ΔP that is twice the differential pressure value ΔP detected by one of the differential pressure detectors 12A and 12B is obtained. calculate. Accordingly, the second pass / fail judgment device 22 compares the added value 2ΔP with the set value, and if it exceeds the set value, it determines that both of the inspected objects 9A and 9B have “leakage” and displays it on the display 25. . Therefore, it is possible to detect the same leakage that cannot be detected by the first pass / fail judgment device 14.

  Next, the second feature will be described. The second feature is that the drift correcting means 23 is provided in the subsequent stage of the second adder 21. The drift is a state in which air pressure is applied to the inspected objects 9A and 9B and the reference tank 11, and a drift component generated by adiabatic change of air or the like is generated in the two differential pressure detectors with the same polarity. Therefore, since the second adder 21 adds the differential pressure detection signals detected by the two differential pressure detectors 12A and 12B with the same polarity, it is included in the differential pressure detection signals output by the two differential pressure detectors 12A and 12B. Drift components to be added to each other. As a result, there is a possibility that even if the inspected objects 9A and 9B do not have the same leakage, it may be determined that “there is leakage” only by the drift component.

The drift component is removed by the drift correction means 23, and the result of removing the drift component is input to the second pass / fail judgment device 22 through the amplifier 24, whereby the influence of the drift component can be removed. As a drift component removal method, a drift correction value is stored in the drift memory 23B, and this drift correction value is subtracted from the addition result output from the second adder 21 by the subtractor 23A. Can be taken.
The third feature of the present invention is that the drift correction value stored in the drift memory 23B is the drift correction value acquired by mastering. A method for obtaining the drift correction value by mastering will be described below.

A curve P1 shown in FIG. 2 indicates the addition value of the second adder 21 in a state where the addition output value of the second adder 21 is reset to zero at the end of the equilibrium period T2 and the inspection is started. The added output curve P1 substantially includes a drift value P2 and a leakage amount P3 (here, it is assumed that the inspection objects 9A and 9B have leakage).
The differential pressure P3 generated by leakage is represented by a straight line that rises at a certain increase rate from the start of the inspection period T3. On the other hand, the drift amount P2 generated by the adiabatic change caused by pressurizing the air increases exponentially due to the temperature difference between the internal air temperature and the object to be inspected immediately after the start of the inspection period T3. Saturates and maintains a constant value.

  Therefore, if the leak amount is measured in a state where the drift amount P2 converges to a constant value, the true leak amount can be measured. That is, the addition output D1 of the second adder 21 is measured at the end of the inspection period T3, the measurement state is further maintained from that point, and the addition value is obtained when a predetermined time, for example, about several tens of seconds elapses. D2 is measured, and after the same period T3 (about several seconds) as the inspection period T3 has elapsed from the measurement time point, the added value D3 is measured again. By this measurement, D3-D2 is a pressure change value due to leakage. Therefore, if the presence or absence of leakage is determined based on whether the subtraction result of D3-D2 is larger or smaller than the determination value NG, a correct determination can be made without being affected by drift.

However, when this inspection method is adopted, since the inspection time is several tens of seconds, it cannot be used for actual inspection. For this reason, in general, when ΔD3 = D3−D2 is calculated and the leakage amount ΔD3 is subtracted from the first measured value D1, the remainder becomes a drift value. That is, the drift value D is
D = D1−ΔD3 (1)
Is required. By recording this drift value D as a drift correction value, the leakage amount from which the drift value has been removed can be calculated in a short time if the drift correction value D is removed from the first measurement value D1 in the next and subsequent inspections. The correct judgment can be made. The operation of measuring the measured values D1, D2, and D3 and obtaining the drift value D is generally called mastering. Mastering is performed as appropriate when the ambient temperature changes significantly, and the drift correction value is updated according to changes in the environment.

  As described above, since the drift correction value acquired by mastering is calculated based on the leakage amount obtained in a state where the drift amount converges to a constant value, the drift correction value is highly reliable. By storing this highly reliable drift correction value in the drift memory 23B, the reliability of the inspection can be improved.

  The leak inspection apparatus according to the present invention can be used for inspecting whether there is a leak in a package for storing food or a package for storing medicine.

The block diagram for demonstrating embodiment of the leak inspection apparatus by this invention. The graph for demonstrating the mastering used for this invention. The block diagram for demonstrating the leak test | inspection apparatus used very generally. The graph for demonstrating the operation | movement of the leak test | inspection shown in FIG. The block diagram for demonstrating the leak inspection apparatus proposed previously. The figure for demonstrating an example of the quality determination indicator which can be used for the leak test | inspection apparatus shown in FIG. The block diagram which shows the other example of a prior art.

Explanation of symbols

1 Pneumatic pressure source 14 First pass / fail judgment device
2 pipeline 15, 25 indicator
3 Control valve 19 First adder
4 Three-way solenoid valve 21 Second adder 6A, 6B, 6A ', 6B' Branch path 22 Second pass / fail judgment device
7, 7 'Branch 23 Drift correction means
8A-8C Shut-off valve 23A Subtractor
9A, 9B Inspected object 23B Drift memory
11 Reference tank 26 Inverter
12A, 12B Differential pressure detector
13, 24 Amplifier

Claims (3)

A. A three-way branch pipe that branches the air pressure supplied from the air pressure source in three directions;
B. A shutoff valve connected to each pipe branched by the three-way branch pipe;
C. A standard tank connected to one line of air pressure taken through this shut-off valve;
D. A pair of objects to be inspected connected to two pipes of air pressure taken out through the shutoff valve;
E. A pair of pipes communicating with the pair of objects to be inspected and a pipe line communicating with the reference tank to detect a pressure difference generated between the standard tank and each object to be inspected. A differential pressure detector;
F. A first adder for adding the detection outputs of the pair of differential pressure detectors in reverse polarity;
G. A first pass / fail judgment device for judging the presence / absence of leakage of each object to be inspected based on the addition result of the adder;
H. A second adder for adding the detection outputs of the pair of differential pressure detectors with the same polarity;
I. Drift correction means for subtracting the drift correction value from the addition result of the second adder;
J. et al. A second pass / fail judgment device for judging the presence or absence of leakage of each object to be inspected based on a correction result obtained by drift correction by the drift correction means;
K. A first state in which the air pressure source is connected to the three-way branch pipe and the air pressure supplied from the air pressure source is applied to the three-way branch pipe side; and the air pressure source side is closed and the three-way branch pipe is released to the atmosphere. A three-way solenoid valve that switches to the state of 2,
L. The three-way solenoid valve is switched to the first state, the shut-off valve is opened, the pressurizing mode for supplying air pressure to the reference tank and each object to be inspected, and the shut-off valve is closed. An inspection mode in which the detection output of the differential pressure detector is measured to determine the presence or absence of leakage of each object to be inspected, and the three-way solenoid valve is switched to the second state to be applied to the reference tank and each object to be inspected. A controller for controlling the exhaust mode to release the discharged air to the atmosphere;
Leakage inspection device configured by   2. The leak inspection apparatus according to claim 1, wherein the drift correction means stores a drift correction value acquired in the calibration mode, and the drift correction value stored in the drift storage is added to the second adder. A leak inspection apparatus comprising: a subtracter that subtracts from a value. In either of the leak inspection apparatuses of Claim 1 or 2,
The drift correction value stored in the drift storage device applies an air pressure to the pair of inspected objects and the reference tank, and an initial addition value obtained from the second adder at a first timing substantially equal to the timing at the time of inspection, A leak inspection apparatus characterized in that a difference value from a measured value corresponding to a true leak obtained from the second adder is obtained at a second timing when a time at which the drift is expected to converge from the first timing is passed. .

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