JP2005017107A - Calibration method for leak inspection device and leak inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always correctly compensate drift by estimating a drift compensation quantity of a leak inspection device from a drift characteristic curve. <P>SOLUTION: After estimating a value of differential pressure caused between an inspection body and a reference tank as a first measured value D1, the variation of the differential pressure caused during elapsing of a specific time from a time point having passed longer time than the specific time is obtained as a second measured value ΔD3. Gaining the first measured value and the second measured value by using the inspection body set at a different temperature from a reference ambient temperature and a seal jig maintained at nearly equal temperature to the reference ambient temperature is executed at every plurality of temperature difference by changing the temperature of the inspection body. The first characteristic curve X1 of each temperature difference vs the first measured value D1, and the second characteristic curve X2 of each temperature difference vs the first measured value ΔD3 are recorded. The temperature characteristics of the drift value included in the first characteristic curve X1 is obtained from the difference between the first characteristic curve X1 and the second characteristic curve X2. By utilizing the temperature characteristics of the drift value in the inspection mode, the drift compensation value is obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a leak inspection apparatus for inspecting the presence or absence of leakage in various containers, gas appliances, engine cylinder blocks, and the like.
[0002]
[Prior art]
In the inspection device called leak tester, especially air leak tester,
B) Enclose air pressure into the test object, monitor the change in the air pressure, and when the air pressure falls below the specified value, determine that the object to be inspected has a leak pressure system,
(B) A differential pressure type in which air pressure is sealed in both the object to be inspected and a reference tank, and whether there is a leak or not is determined by whether or not a differential pressure is generated between the two.
Exists.
[0003]
The gauge pressure type has a simple structure, but its detection sensitivity is low, so it is not practically used at present. In general, a differential pressure type leak inspection apparatus is widely used.
The biggest drawback of the air leak tester is that various adverse effects resulting from the use of air pressure occur. In other words, air is affected by the temperature of the object to be inspected, the temperature of the jig etc. that contacts the object to be inspected, and the temperature due to the adiabatic change of the pressurized air. (This is called drift), making it difficult to determine the presence or absence of leakage.
[0004]
For this reason, the present applicant has conventionally made various proposals regarding various leak inspection methods and drift correction of inspection apparatuses. (Patent Literature 1, Patent Literature 2, Patent Literature 3).
FIG. 4 shows a schematic configuration of a conventional differential pressure detection type leak inspection apparatus. This type of leakage inspection apparatus includes an air pressure source 10 such as a compressor, a pressure adjusting valve 11 that adjusts a compressed air pressure supplied from the air pressure source 10, and a pressure value of the air pressure adjusted by the pressure adjusting valve 11. A pressure gauge 12 to be measured and displayed, a three-way solenoid valve 13, solenoid valves 14A and 14B, and a sealing jig 16 for closing the opening of the subject 17 and applying a compressed air pressure to the subject 17; The reference tank 18, the differential pressure detector 15 that measures the differential pressure between the object 17 to be inspected, and the reference tank 18, the temperature and the temperature difference between the sealing jig 16 and the object 17 to be inspected, or the outside air temperature. In response to the temperature sensors 16A and 17A for measuring the temperature and the temperature difference with the device under test 17, the variable gain amplifier 19 for amplifying the output signal of the differential pressure detector 15, and the output signal of the variable gain amplifier 19 Determination means 20 for determining the presence or absence of leakage Constituted by a display device 21 for displaying the determination result of the determining unit 20.
[0005]
In the non-inspection mode, the solenoid valves 14A and 14B are in a state where the three-way solenoid valve 13 is conductive between A and B.
Is maintained in a closed state, and in this state, the air pressure from the air pressure source 10 is adjusted by the pressure regulating valve 11, and a desired test pressure is displayed on the pressure gauge 12.
In the inspection mode, the electromagnetic valves 14A and 14B are controlled to be in an open state, and compressed air is applied to the device under test 17 and the reference tank 18 through the electromagnetic valves 14A and 14B. This application state of compressed air is referred to as a pressurization period T1 as shown in FIG.
[0006]
When the pressurization period T1 elapses (T1 = several seconds), the solenoid valves 14A and 14B are closed, and a stable period of a certain period is provided. This stable period is generally called an equilibrium period T2. If the differential pressure detector 15 outputs a large differential pressure detection signal ΔDS (see FIG. 5) exceeding the determination value NG during the equilibrium period T2, the determination means 20 is then connected to the sealing jig 16 at that time. The inspection body 17 determines that there is a large leak, displays the determination result on the display 21, and ends the inspection.
[0007]
If the differential pressure detection value does not exceed the determination value NG within the equilibrium period T2, it is determined that there is no major leakage, and the detection signal of the differential pressure detector 15 is forcibly reset to zero. After the zero reset, the gain of the variable gain amplifier 19 is switched to a high gain and enters a test period T3.
If the detection signal of the differential pressure detector 15 does not exceed the determination value NG in the inspection period T3, it is determined that “there is no slight leakage”. If the differential pressure detection signal exceeds the determination value NG within the inspection period T3, it is determined that “there is a slight leak” in this case.
[0008]
When the inspection period T3 ends, the three-way solenoid valve 13 is controlled to be in a conductive state between B and C, and the solenoid valves 14A and 14B are controlled to be in an open state, so that the compressed air in the object 17 and the reference tank 18 is discharged. Exhaust to atmosphere and return to initial state.
By the way, in this type of differential pressure detection type leak inspection apparatus, there is a phenomenon in which a differential pressure detection signal is generated even though there is no leakage due to disturbance factors such as a change in temperature of the object 17 and a change in ambient temperature. This phenomenon is generally called drift. Due to the occurrence of drift, there is a problem that it is determined that “there is no leakage even though there is no leakage” or “no leakage even though there is leakage”.
[0009]
In order to eliminate this inconvenience, drift correction is performed. A conventional drift correction method will be described with reference to FIGS. A curve P1 shown in FIG. 6 shows a differential pressure detection signal output from the differential pressure detector 15. This differential pressure detection signal includes the drift amount indicated by the curve P2 and the leakage amount indicated by the curve P3.
The differential pressure generated by leakage is represented by a straight line that rises at a certain rate from the start of the equilibrium period T2. On the other hand, the drift amount due to 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, but eventually becomes saturated. , Maintain a constant value.
[0010]
Therefore, if the leakage amount is measured in a state where the drift converges to a constant value, the true leakage amount can be measured. That is, the differential pressure value D1 is measured at the end of the inspection period T3, the differential pressure measurement state is further maintained from that time, and the differential pressure value D2 is obtained when a predetermined time, for example, several tens of seconds elapses. The differential pressure value D3 is measured again after elapse of the same period T3 (about several seconds) as the inspection period T3 from the measurement time point. 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.
[0011]
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 the drift value D, in the next and subsequent inspections, if the drift value D is removed from the first measured value D1, the leakage amount from which the drift value has been removed can be calculated in a short time, and a correct determination is made. be able to. The operation of measuring the measured values D1, D2, and D3 and obtaining the drift value D is generally called mastering.
[0012]
[Patent Document 1]
JP 2001-50854 A
[Patent Document 2]
JP 2002-22592 A
[Patent Document 3]
JP 2003-106923 A
[0013]
[Problems to be solved by the invention]
Although it has been described that correct drift correction can be performed by removing the drift value D obtained by the above equation (1) from the first measurement value D1, the object 17 is not always at room temperature in reality. Inconvenience may occur. The reason will be described below. FIG. 7 shows a situation in which the drift correction can be correctly performed by removing the drift amount D obtained by the equation (1) from the first measurement value D1. That is, the horizontal axis shown in FIG. 7 indicates the temperature difference between the sealing jig 16 and the inspection object 17 measured as the environmental temperature, and the vertical axis indicates the differential pressure value. X1 is a first characteristic curve obtained by plotting the first measured values D1-1, D2-2, D3-3, ... measured for each temperature difference, and X2 is a second measured value ΔD3- measured for each temperature difference. 1, the 2nd characteristic curve calculated | required by plotting (DELTA) D3-2 and (DELTA) D3-3 is shown. In addition, when measuring X1 and X2, a test object without leakage is used. Since the drift amount of the adiabatic change becomes zero by using the inspected object without leakage, the second characteristic curve X2 can obtain a curve passing through the origin. The reason why the slope of the second characteristic curve X2 does not become zero despite the mastering using the inspected object without leakage is due to the temperature difference between the inspected object 17 and the sealing jig 16. This is because heat exchange occurs between the object to be inspected 17 and the sealing jig 16, and this heat exchange causes a temperature change to the air in the object to be inspected 17 to cause drift.
[0014]
As shown in FIG. 7, the first characteristic curve X1 and the first characteristic curve X1 are obtained when the temperature difference between the sealing jig 16 and the inspection object 17 is limited to a certain range centering on zero (no disturbance factor). The two characteristic curve X2 can be regarded as a substantially straight line. Further, when the first characteristic curve X1 and the second characteristic curve X2 are substantially parallel, the second characteristic curve X1 is obtained by subtracting the drift amount D from the measured value D1-n of any inspection regardless of the temperature difference. A value corresponding to the measured value ΔD3-n can be obtained, and correct drift correction can be performed.
[0015]
On the other hand, as shown in FIG. 8, the slope of the first characteristic curve X1 of the first measurement value D1 and the second characteristic curve X2 of the second measurement value ΔD3 are different due to the temperature characteristic of drift due to adiabatic change. The drift correction amount is D for each temperature difference._A, D_B, D_CSince different values are taken as described above, correct drift correction cannot be performed at a temperature outside the range of the temperature at which the drift correction amount is obtained, and therefore, inconvenience that mastering must be performed every time the environmental temperature changes occurs.
[0016]
In such a case, it is conceivable that mastering is performed for each temperature difference between the object to be inspected and the sealing jig or the outside air temperature, and the drift correction value is obtained and recorded in advance, but the work is enormous and difficult to realize. It is. In particular, the work must be performed for each type of object to be inspected.
As shown in FIG. 8, the object of the present invention is other than the temperature at which drift calibration is performed, even when the first characteristic curve X1 of the first measurement value D1 and the second characteristic curve X2 of the second measurement value ΔD3 are different in slope. A leak inspection apparatus that can correct the characteristic of the first characteristic curve X1 correctly even at a temperature of which the correct leak amount can be obtained from the corrected drift characteristic curve, and a leak inspection that operates using this calibration method The device is to be provided.
[0017]
[Means for Solving the Problems]
According to the first aspect of the present invention, the same air pressure is sealed in both the object to be inspected and the reference tank, and a differential pressure is generated between the object to be inspected and the reference tank while a predetermined time elapses after the sealing. In a calibration method for a leak inspection apparatus that measures whether or not there is a leak in the object to be inspected, a temperature equal to the reference environment temperature at the opening of the inspected dry object that does not leak in the calibration mode In this closed state, air pressure is sealed between the object to be inspected and the reference tank, and the differential pressure generated between the object to be inspected and the reference tank after a predetermined time has passed after the air pressure is sealed. The value is acquired as the first measurement value D1, and after the first measurement value D1 is acquired, the time between the inspected object and the reference tank has elapsed during a time substantially equal to the predetermined time from the time when the time longer than the predetermined time has elapsed. Is obtained as a second measured value ΔD3. In the drift value acquisition method, the first measurement value and the second measurement value are acquired using a test object set to a temperature different from the reference environment temperature and a seal jig maintained at a temperature substantially equal to the reference environment temperature. Is performed for each of a plurality of temperature differences by changing the temperature of the object to be inspected, and the first characteristic curve X1 of each temperature difference versus the first measured value D1 and the second characteristic curve of each temperature difference versus the second measured value ΔD3. X2 is recorded, and from the difference between the first characteristic curve X1 and the second characteristic curve X2, the temperature characteristic of the drift value generated by the adiabatic change of the air generated immediately after the application of air pressure included in the first characteristic curve X1 is obtained, Provided is a method for calibrating a leakage inspection apparatus for obtaining a drift correction value at an arbitrary environmental temperature other than the environmental temperature using the temperature characteristic of the drift value in an inspection mode.
[0018]
According to a second aspect of the present invention, in the calibration method for a leakage inspection apparatus according to the first aspect, the first measured value D1 when the temperatures of the object to be inspected and the sealing jig are both at the reference environmental temperature is set to the reference temperature drift value A1, The slopes of the first characteristic curve and the second characteristic curve when ΔT is changed from the reference environmental temperature are a1 / ΔT and a2 / ΔT, the difference between the environmental temperature during inspection and the reference environmental temperature during calibration is ΔT1, and the seal jig temperature When the temperature difference between the test object and the object to be inspected is ΔT2, the drift correction value A2 is calculated as A2 = A1 + (a1−a2) ΔT1 / ΔT + a1 · ΔT2 / ΔT for each inspection, and the drift correction value A2 is inspected. There is provided a calibration method for a leakage inspection apparatus that subtracts the first measurement value D1 acquired from time to time and compares the subtraction result with a determination value to determine the presence or absence of leakage.
[0019]
According to claim 3 of the present invention, air pressure is sealed in both the object to be inspected and the reference tank, and whether or not a differential pressure is generated between the object to be inspected and the reference tank during a predetermined time after the sealing. In the leak inspection apparatus for determining whether or not the inspection object leaks, an environmental temperature measurement means for measuring the environmental temperature, a temperature difference measurement means for measuring a temperature difference between the inspection object and the environmental temperature, and a calibration mode are requested. The first and second characteristic curve records for recording the first characteristic curve and the second characteristic curve obtained from the first measured value D1 and the second measured value D2 at the reference environmental temperature acquired by the calibration method according to Item 1. And the first characteristic curve and the second characteristic curve recorded in the first characteristic curve recording means and the second characteristic curve recording means, the first characteristic curve when the temperature of the object to be inspected and the sealing jig are both the reference temperature. 1 measured value D1 as reference temperature drift Adiabatic characteristic calculation for obtaining slopes a1 / ΔT and a2 / ΔT of the first characteristic curve and the second characteristic curve at the temperature difference ΔT from the reference temperature drift value acquisition means extracted as the value A1, and the first characteristic curve and the second characteristic curve If the difference between the environmental temperature at the time of leakage inspection and the reference environmental temperature at the calibration mode is ΔT1, and the difference between the temperature of the sealing jig at the time of leakage inspection and the temperature of the object to be inspected is ΔT2, the drift correction value A2 is
A2 = A1 + (a1-a2) ΔT1 / ΔT + a1 · ΔT2 / ΔT
The drift correction value calculation means calculated by the above, a subtraction means for subtracting the drift correction value A2 calculated by the drift correction value calculation means from the first measured value D1 acquired at the time of leak inspection, and the subtraction result subtracted by the subtraction means There is provided a leak inspection apparatus comprising a determination means for comparing a determination value and determining the presence or absence of leakage.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
By grasping the temperature characteristics of the drift caused by the adiabatic change of air that occurs immediately after the air pressure is applied to the object to be inspected, a highly reliable leak test was realized without any hassle.
FIG. 1 shows an embodiment of a leak inspection apparatus according to the present invention. Parts corresponding to those in FIG. 4 are denoted by the same reference numerals, and redundant description thereof is omitted. A feature of the present invention is that a drift correcting device 30 provided between the variable gain amplifier 19 and the judging means 20 is characterized. The drift correction device 30 characterized by the present invention includes an environmental temperature measurement means 31, a temperature difference measurement means 32, a first characteristic curve recording means 33, a second characteristic curve recording means 34, and a reference temperature drift acquisition means 35. The adiabatic characteristic calculating means 36, the drift value calculating means 37, and the subtracting means 38 are configured.
[0021]
The environmental temperature measuring means 31 acquires the measured value of the temperature sensor 16A that measures the temperature of the sealing jig 16 as the environmental temperature (outside air temperature). The temperature difference measuring means 32 measures the temperature difference between the temperature of the sealing jig 16 and the inspection object 17. For this purpose, the measured values of the temperature sensor 16A for measuring the temperature of the sealing jig 16 and the temperature sensor 17A for measuring the temperature of the inspection object 17 are taken in, and the difference value is output.
The first characteristic curve recording means 33 and the second characteristic curve recording means 34 are the first measurement values D1-1, D1-2, D1-3,... And the second measurement value ΔD3-1 acquired by the mastering described in FIG. , ΔD3-2, ΔD3-3, etc., and the first measured values D1-1, D1-2D, D1-3,... And the second measured values ΔD3-1, ΔD3-2, ΔD3-3,. The first characteristic curve X1 and the second characteristic curve X2 are obtained by plotting by interpolation calculation or the like, and the first characteristic curve X1 and the second characteristic curve X2 are recorded.
[0022]
The reference temperature drift acquisition unit 35 corresponds to a state in which the temperature difference between the environmental temperature in the plurality of first measured values D1 recorded as the first characteristic curve X1 in the first characteristic curve recording unit 33 and the temperature of the object to be inspected 17 is zero. The first measurement value D1 is acquired as the reference temperature drift value A1, and the acquired value is output to the drift value calculation means 37.
The adiabatic characteristic calculating means 36 calculates the difference between the first characteristic curve X1 and the second characteristic curve X2 from the first characteristic curve recording means 33 and the second characteristic curve recording means 34, and sends the calculation result to the drift value calculating means 37. input.
[0023]
In the drift value calculation means 37, the environmental temperature given from the environmental temperature measurement means 31, the temperature difference between the environmental temperature given from the temperature difference measurement means 32 and the object to be inspected 17, and the reference temperature drift value acquisition means 35 give The drift correction value A2 at the environmental temperature given from the environmental temperature measuring means 31 is calculated by the equation (2) using the reference temperature drift value A1 and the gradients a1 / ΔT and a2 / ΔT given from the adiabatic characteristic calculating means 36. .
[0024]
A2 = A1 + (a1-a2) ΔT1 / ΔT + a1 · ΔT2 / ΔT (2)
Here, ΔT1 represents a temperature difference between the reference environmental temperature determined in the calibration mode and the environmental temperature measured for each inspection in the inspection mode. That is, when the mask ring is performed in the calibration mode, the environmental temperature in which the temperature difference between the sealing jig 16 and the object to be inspected 17 is zero is determined as the reference environmental temperature. In the inspection mode, every time a leakage inspection is performed, the temperature of the sealing jig 16 is measured as the environmental temperature, and the difference between the measured temperature and the reference environmental temperature is output to the drift value calculating means 37 as ΔT1. .
[0025]
ΔT2 is a drift value in which the temperature difference between the sealing jig 16 and the inspection object 17 is measured for each inspection of each inspection object in the inspection mode, and the temperature difference is ΔT2 and the temperatures of the inspection object and the sealing jig are different. Is input to the drift value calculating means 37.
Every time the leakage inspection of the inspection object 17 is performed, the equation (2) is calculated to obtain the drift value A2. The drift value A2 obtained by the equation (2) is input to the subtracting means 38, and is subtracted from the measured value by the subtracting means 38, and the drift amount is removed from the measured value. The determination means 20 compares the differential pressure value due to true leakage from which the drift has been removed with the determination value NG, and if the differential pressure value is smaller than the determination value NG, it is determined that there is no leakage, and if it is larger, it is determined that there is leakage.
[0026]
The drift value obtained by the equation (2) is corrected according to the temperature characteristic of the drift generated along with the adiabatic change of the air generated at the time when the air pressure is sealed in the object to be inspected 17, and mastering was performed in the calibration mode. A correct drift correction value can be obtained even under an ambient temperature other than the reference ambient temperature. In order to clarify the reason, the derivation process of equation (2) will be described below.
The graph shown in FIG. 2 uses a dry inspected object 17 having no leakage, changes the temperature of the inspected object 17, and performs mastering of the first characteristic curve X1 of the first measured value D1 and the second measured value ΔD3. The second characteristic curve X2 is sampled and represented in the same graph.
[0027]
In FIG. 2, 25 ° C. is set as the reference environmental temperature. Therefore, both the inspected object 17 and the sealing jig 16 are in a state where there is no temperature difference at 25 ° C., and the state where this temperature difference is zero is the reference environment temperature, and the drift value due to the adiabatic change at 25 ° C. A1) is referred to as drift. Assuming that the slope of only the adiabatic change included in the measured value D1 is b1 / ΔT,
b1 / ΔT = a1 / ΔT−a2 / ΔT (3)
Naturally, if the slope of the adiabatic change is zero,
a1 = a2
It is.
[0028]
Further, b1 = a1 if there is no heat transfer between the device under test 17 and the sealing jig 16.
Next, when the environmental temperature changes from 25 ° C. to 25 ° C. + ΔT1 (see FIG. 2), that is, the drift component due to the adiabatic change when the temperature of the device under test 17 and the sealing jig 16 are both 25 ° C. + ΔT1 is obtained. If b1 is an increase in drift due to adiabatic change when there is a temperature change of ΔT,
A1 + (b1 / ΔT) ΔT1 = A1 + (a1−a2) ΔT1 / ΔT (4)
The second term on the right side of the equation (4) is an increase in drift due to adiabatic change caused by the temperature of the object 17 and the sealing jig 16 being simultaneously changed to the same temperature of 25 ° C. + ΔT1.
[0029]
Next, when the temperature of 25 ° C. + ΔT1 (sealing jig temperature) is used as a reference, the drift component A2 of the first measured value D1 when the temperature of the inspection object 17 is 25 ° C. + ΔT1 + ΔT2 (see FIG. 2) is
A2 = A1 + (a1-a2) ΔT1 / ΔT + a1 · ΔT2 / ΔT
Thus, the above equation (2) is obtained.
When the temperature of the sealing jig 16 is affected by the temperature of the object 17 to be inspected, ΔT1 is the difference between the reference environmental temperature during calibration (25 ° C. in this example) and the environmental temperature during the inspection mode. ΔT2 is a temperature difference between the temperature of the inspection object 17 and the sealing jig 16.
[0030]
Correction of characteristic curve by mastering
In the range where the first characteristic curve X1 and the second characteristic curve X2 are linear, any inspection object 17 can be obtained without correcting the characteristic of the characteristic curve X1 (mainly the reference temperature drift value A1) by mastering during inspection. The drift correction amount A2 can be obtained by the equation (2) at the temperature of the sealing jig 16 and the temperature of the sealing jig 16, but the characteristic curve X1 can be corrected by mastering at any temperature of the sealing jig 16 and the object to be inspected 17. it can. Thus, the characteristic curve X1 can be used in a wide temperature range. The reason will be described below.
[0031]
When the temperature of the inspection object 17 is TX + ΔTX at an arbitrary sealing jig temperature TX, the differential pressure measurement value of the first measurement value D1 is AX and the second measurement value ΔD3 is a2x by mastering. Assuming
In FIG. 2, when the temperature difference ΔTX of the second measured value ΔD3, the measured differential pressure value is a2x ′, so the differential pressure δX due to leakage is
δX = a2x−a2x ′ (5)
The measurement value AX of the first measurement value D1 includes a leakage component obtained in the inspection mode, a component due to adiabatic change, and a drift component due to a temperature difference ΔTX (drift component due to heat transfer). The drift component AX ′ of only adiabatic change at the temperature TX + ΔTX is
AX ′ = AX− (a2x−a2x ′) − a2x ′ = AX−a2x (6)
That is, the drift value of the adiabatic change to be corrected is a value obtained by subtracting the value of the second measurement value ΔD3 from the measurement value of the first measurement value D1. (However, it is assumed that the temperature difference between the device under test 17 and the sealing jig 16 does not change when the first measurement value D1 and the second measurement value ΔD3 are measured). In this case, the temperature drift AX ′ of the adiabatic change is equal to the drift value of TX + ΔTX when the temperatures of the inspection object 17 and the sealing jig 16 are equal.
[0032]
In the equation (2), A1 is corrected to AX ′, the reference environment temperature is changed to TX + ΔTX, and the slope of the characteristic curve does not change. It can be graphed from the first characteristic curve X1 and the second characteristic curve X2. A curve C indicated by a dotted line in FIG. 3 represents a temperature characteristic of the adiabatic change. If the temperature characteristics of the adiabatic change can be graphed, it can be determined how much the ambient temperature changes should be corrected by the mastering. In other words, the temperature characteristic of the adiabatic change is the reference environment temperature T₀Is represented by a curve passing through A1. The temperature characteristic of the adiabatic change can be corrected in the temperature range in which this is represented by a straight line.
[0033]
The temperature characteristic of the adiabatic change can be obtained by (first characteristic curve X1−second characteristic curve X2). The drift correction amount due to the temperature difference between the object to be inspected 17 and the sealing jig 16 corresponds to the third term of the equation (2). In FIG. 3, the horizontal axis of the temperature characteristic of the adiabatic change is represented by the difference between the temperature of the inspected object 17 and the reference environment temperature, which is drawn by combining the graphs of the first characteristic curve X1 and the second characteristic curve X2. This is because the difference between the reference ambient temperature and the ambient temperature at the time of inspection is correct on the horizontal axis as far as the temperature characteristics of the adiabatic change are concerned. This is because the temperature characteristic of the adiabatic change is corrected for the environmental temperature change. When the object to be inspected and the sealing jig are insulated, the slope of the characteristic of X2 becomes zero, so the characteristic curve of X1 represents the temperature characteristic curve of the adiabatic change. The drift correction amount A2 in this case can be obtained from the characteristic curve of X1 from the temperature difference between the temperature of the object to be inspected and the reference environmental temperature during calibration.
[0034]
About humidity correction
The wetness of the object to be inspected is one of the causes of drift that cannot be ignored. It is also caused by wetting that makes temperature drift correction difficult. Drift due to wetting is affected by the temperature of the object to be inspected. If the object to be inspected is wet, the internal pressure of the object to be inspected is increased by evaporation of moisture (in the case of a dry object to be inspected, the internal pressure is decreased when the temperature of the object to be inspected is high), so that the detection sensitivity of the leak inspection is lowered. Wet correction is performed by measuring changes in the in-vivo pressure in the atmospheric pressure state, or by measuring the vapor pressure change on the surface of the inspected object from the outside at atmospheric pressure or negative pressure, as in the method of measuring the temperature of the inspected object. What is necessary is just to measure as a change. For details, see “Japanese Patent Application No. 2003-167252” (filed on Jun. 12, 2003). In order to shorten the test cycle, it is necessary to measure wetness outside rather than inside. In this case, it is practical to devise a sealing jig and measure the wet state of the workpiece surface with negative pressure. If measured at negative pressure, the effect of seal deformation is small, and it is sensitive to changes in vapor pressure.
[0035]
【The invention's effect】
According to the present invention, from the first characteristic curve X1 and the second measurement curve X2 obtained from the first measurement value D1 and the second measurement value ΔD3 acquired for each temperature difference between the reference environment temperature and the object to be inspected in the calibration mode, Due to the difference, it is possible to obtain the temperature characteristic of the drift generated by the adiabatic change of the air pressure. Therefore, even if leakage inspection is performed at any temperature other than the reference environment temperature at the time of calibration, a correct drift correction value can be obtained by calculation without calibrating the first characteristic curve X1 by mastering, and this drift correction value is used. By doing so, correct drift correction can be performed and the reliability of the leak test can be improved. In particular, since the user is provided with an inspection device that does not need to perform mastering each time the environmental temperature changes, there is an advantage that a leakage inspection device that is easy to handle can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram for explaining Embodiment 1 of the present invention;
FIG. 2 is a graph for explaining the operation of the embodiment 1 shown in FIG. 1;
FIG. 3 is a graph for explaining a main part of the first embodiment shown in FIG. 1;
FIG. 4 is a block diagram for explaining a conventional technique.
FIG. 5 is a timing chart for explaining the operation of a conventional leakage inspection apparatus.
FIG. 6 is a graph for explaining the content of drift occurring in the leakage inspection apparatus.
FIG. 7 is a graph for explaining an example of a drift correction method of the leakage inspection apparatus.
FIG. 8 is a graph for explaining another example of the drift correction method of the leakage inspection apparatus.
[Explanation of symbols]
10 Pneumatic pressure source 30 Drift correction device
11 Pressure regulating valve 31 Ambient temperature measuring means
12 Pressure gauge 32 Temperature difference measuring means
13 Three-way solenoid valve 33 First characteristic curve recording means
14A, 14B Solenoid valve 34 Second characteristic curve recording means
15 Differential pressure detector 35 Reference temperature drift acquisition means
16 Sealing jig 36 Adiabatic characteristic calculation means
17 Inspected object 37 Drift value calculation means
18 Reference tank 38 Subtraction means
19 Variable gain amplifier
20 judgment means
21 Display

Claims (3)

The same air pressure is sealed in both the object to be inspected and the reference tank, and it is measured whether or not a differential pressure is generated between the object to be inspected and the reference tank while a predetermined time elapses after the sealing. In the calibration method of the leakage inspection apparatus for determining whether or not there is leakage in the inspection object,
In the calibration mode, the opening of the inspected and dried object to be inspected is closed with a sealing jig whose temperature is equal to the reference environment temperature. In this closed state, air pressure is sealed in the object to be inspected and the reference tank. After the predetermined time elapses, a differential pressure value generated between the object to be inspected and the reference tank is acquired as the first measured value D1, and after acquiring the first measured value D1, a time longer than the predetermined time is acquired. In the drift value acquisition method for acquiring, as the second measured value ΔD3, the differential pressure change value generated between the object to be inspected and the reference tank during a time substantially equal to the predetermined time from the elapsed time, the reference environment The first measurement value and the second measurement value are obtained using the inspection object set to a temperature different from the temperature and the sealing jig maintained at a temperature substantially equal to the reference environmental temperature. Change the temperature to multiple The first characteristic curve X1 of each temperature difference versus the first measured value D1 and the second characteristic curve X2 of each temperature difference versus the second measured value ΔD3 are recorded for each temperature difference, and these first characteristic curves X1 and The temperature characteristic of the drift value generated by the adiabatic change of the air generated immediately after application of the air pressure included in the first characteristic curve X1 is obtained from the difference of the second characteristic curve X2,
A calibration method for a leak inspection apparatus, characterized in that a drift correction value at an arbitrary environmental temperature other than the environmental temperature is obtained by using the temperature characteristic of the drift value in an inspection mode. 2. The method of calibrating a leakage inspection apparatus according to claim 1, wherein the first measured value D1 when the temperatures of the object to be inspected and the sealing jig are both at the reference environmental temperature is determined from the reference temperature drift value A1 and the reference environmental temperature. The slopes of the first characteristic curve and the second characteristic curve when ΔT changes are a1 / ΔT and a2 / ΔT, and when the difference between the environmental temperature at the time of inspection and the reference environmental temperature at the time of calibration is ΔT1, When the temperature difference with the object to be inspected is ΔT2, the drift correction value A2 is calculated as A2 = A1 + (a1−a2) ΔT1 / ΔT + a1 · ΔT2 / ΔT for each inspection, and this drift correction value A2 is calculated during the inspection. A method for calibrating a leakage inspection apparatus that subtracts the obtained first measurement value D1 and compares the subtraction result with a determination value to determine the presence or absence of leakage. Air pressure is sealed in both the object to be inspected and the reference tank, and depending on whether or not a differential pressure is generated between the object to be inspected and the reference tank during a predetermined time after the sealing, In a leak inspection device that determines the presence or absence of leakage,
A. Environmental temperature measuring means for measuring environmental temperature;
B. Temperature difference measuring means for measuring the temperature difference between the object to be inspected and the environmental temperature;
C. The first and second characteristic curves for recording the first characteristic curve and the second characteristic curve obtained from the first measurement value D1 and the second measurement value D2 at the reference environmental temperature obtained by the calibration method according to claim 1 in the calibration mode. Two characteristic curve recording means;
D. Based on the first characteristic curve and the second characteristic curve recorded in the first characteristic curve recording unit and the second characteristic curve recording unit, the first measurement is performed when both the temperature of the object to be inspected and the sealing jig are the reference temperature. A reference temperature drift value acquisition means for taking out the value D1 as a reference temperature drift value A1,
E. Adiabatic characteristic calculating means for obtaining slopes a1 / ΔT and a2 / ΔT of the first characteristic curve and the second characteristic curve at a temperature difference ΔT from the first characteristic curve and the second characteristic curve;
F. When the difference between the environmental temperature at the time of leak inspection and the reference environmental temperature at the time of the calibration mode is ΔT1, and the temperature difference between the seal jig temperature at the time of leak inspection and the temperature of the object to be inspected is ΔT2, the drift correction value A2 is A2 = A1 + (A1-a2) ΔT1 / ΔT + a1 · ΔT2 / ΔT
Drift correction value calculating means for calculating in
G. Subtracting means for subtracting the drift correction value A2 calculated by the drift correction value calculating means from the first measured value D1 acquired at the time of the leak inspection;
H. A leakage inspection apparatus comprising: a determination unit that compares a subtraction result subtracted by the subtraction unit with a determination value to determine the presence or absence of leakage.

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