JP4183855B2 - Air leak test method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air leak test method and apparatus.
[0002]
[Prior art]
A general differential pressure type air leak test apparatus called a balanced type will be briefly described. A master side and a work side branch passage are connected to a common passage extending from a test pressure source. A master container is connected to the master side branch passage, and a workpiece is connected to the workpiece side branch passage. The master container has the same shape, volume, and material as the workpiece, and it has been confirmed that there is no leakage.
In the above apparatus, after a test pressure is applied to the two branch passages from the test pressure source, these branch passages are blocked to form a closed system independent of each other. Thereafter, the differential pressure between the two closed branch passages is monitored to detect a workpiece leak.
[0003]
By the way, when the test pressure is applied, the air temperature in the workpiece and the master container once rises due to the heat generated by the adiabatic compression, and then settles to the ambient temperature due to heat radiation. Even after closing the branch passage, the heat dissipation continues, and the pressure of the two branch passages in the closed state decreases, but the pressure drop of the two branch passages due to this heat dissipation is because the heat dissipation characteristics of the master container and the workpiece are equal, Equal to each other. Therefore, the differential pressure is not affected by the pressure drop due to the heat radiation, and the pressure drop corresponding to the leakage of the workpiece can be reliably detected.
[0004]
However, if the master container has the same shape, material, and volume as the workpiece as described above, many types of master containers are required in the production line for many types and small quantities, which increases equipment costs and management costs. .
Therefore, recently, an unbalanced type apparatus has been developed in which a master container having a predetermined shape, volume and material is used without changing the master container even if the workpieces are different. In this apparatus as well, the test pressure is applied to the two branch passages, and when the predetermined waiting time elapses, the branch passage is closed and the differential pressure is detected. The master container has a heat dissipation characteristic different from that of the workpiece. Therefore, even if there is no leakage in the workpiece, a differential pressure is generated due to the difference in the heat dissipation characteristic, so the waiting time needs to be increased. This is because after waiting for almost no heat dissipation, the branch passage is closed and only the differential pressure due to leakage is detected. As a result, there is a disadvantage that the test time becomes long.
[0005]
Therefore, in the leak test apparatus disclosed in Japanese Examined Patent Publication No. 4-19440, an initial pressure higher than the test pressure is first applied, and then the test pressure is set. When an initial pressure higher than the test pressure is applied, the heat generated by the adiabatic compression is larger than that when the test pressure is applied, and the air temperature in the workpiece is higher than when the test pressure is applied. As a result, the amount of heat dissipation increases. Then, when the pressure is lowered to the test pressure, heat is taken away along with the adiabatic expansion, so that the air temperature in the work is forcibly lowered to the ambient temperature. Therefore, it is possible to detect the leakage based on the differential pressure by closing the branch passage without waiting for a long time for heat radiation, and to shorten the test time.
[0006]
[Problems to be solved by the invention]
In the apparatus disclosed in the above publication, the air temperature in the work is forced to the ambient temperature by radiating heat after applying the initial pressure and depriving the heat by adiabatic expansion in the process of changing from the initial pressure to the test pressure. This eliminates the influence of heat dissipation characteristics. Therefore, the time from the start of applying the initial pressure to the test pressure and the difference between the initial pressure and the test pressure are set optimally. However, since these settings are fixed, if the ambient temperature changes, the air temperature in the workpiece will not be equal to the ambient temperature after switching the test pressure, and the effect of heat dissipation will remain even after the branch passage is closed. Sometimes it was not possible to do it accurately.
[0007]
The above discussion can also be applied to a simple air leak test apparatus that is not a differential pressure type. In this apparatus, a test pressure source is connected to the upstream end of the passage, and a workpiece is connected to the downstream end. After applying the test pressure, the passage is closed, and workpiece leakage is detected based on a change in pressure in the closed passage. Even in this device, in order to eliminate the effect of pressure fluctuation due to heat radiation, the passage is closed after the test pressure is applied until the heat radiation has settled, or after the passage is closed, the pressure changes linearly and waits for leakage based on pressure. Because it was detected, the test time was long. In addition, when adopting a method that lowers the test pressure to the test pressure after applying the initial pressure and forcibly matches the air temperature in the workpiece with the ambient temperature, the leak detection cannot be performed accurately due to fluctuations in the ambient temperature as described above. was there.
[0008]
[Means for Solving the Problems]
According to a first aspect of the present invention, in the differential pressure type air leak test method, in the normal test mode, the initial pressure is supplied from the pressure supply means to the master side and the work side branch passage through the common passage, and then the test pressure is supplied. After that, the on-off valve is closed and the branch passage on the master side and the work side is closed in an independent state, and after waiting for a predetermined waiting time in this closed state, from the differential pressure detected by the differential pressure sensor, Detects leakage of workpieces connected to the workpiece side branch passage,
Further, a special test mode is executed as necessary or periodically. In this special test mode, the initial pressure supply and test pressure supply are performed under the same conditions as in the normal test mode, and the on-off valve is closed. Then, after waiting for a longer waiting time than the normal test mode, the differential pressure component that changes linearly due to leakage is subtracted from the detected differential pressure of the differential pressure sensor to obtain a differential pressure component that does not change. Adjust the time from the start of the initial pressure supply in the normal test mode to the switch to the test pressure and / or the pressure difference between the initial pressure and the test pressure so that the differential pressure component that does not change is zero. It is characterized by.
[0009]
According to a second aspect of the present invention, in the differential pressure type air leak test apparatus, in the normal test mode, the control means controls the pressure supply means to initially set the master side and work side branch passages via the common passage. Pressure, then test pressure, then close the open / close valve to close the master and work side branch passages in an independent state, wait for a predetermined waiting time in this closed state, and then the differential pressure sensor Detects the leakage of the workpiece connected to the workpiece side branch passage from the differential pressure detected at
The control means also executes a special test mode. In this special test mode, the initial pressure supply and test pressure supply are performed under the same conditions as in the normal test mode, and the on-off valve is closed. After waiting for a longer waiting time than the test mode, the differential pressure component that changes linearly due to leakage is subtracted from the detected differential pressure of the differential pressure sensor to obtain a differential pressure component that does not change. It is characterized by adjusting the time from the start of the initial pressure supply in the normal test mode to switching to the test pressure, the pressure difference between the initial pressure and the test pressure or both so that the pressure component becomes zero. It is characterized by doing.
[0010]
According to a third aspect of the present invention, in the simple air leak test method, in the normal test mode, the initial pressure is supplied to the work through the passage by controlling the pressure supply means, and then the test pressure is supplied. After that, close the on-off valve to close the work, wait for a predetermined waiting time in this closed state, detect the work leakage from the pressure detected by the pressure sensor,
A special test mode is executed as necessary or periodically. In this special test mode, the initial pressure supply and test pressure supply are performed under the same conditions as in the normal test mode, and the on-off valve is closed. After waiting for a longer waiting time than in the normal test mode, the pressure component that changes linearly due to leakage is subtracted from the detected pressure of the pressure sensor to obtain a pressure component that does not change, and this pressure component that does not change becomes zero. The time from the start of the initial pressure supply in the normal test mode to the switch to the test pressure, the pressure difference between the initial pressure and the test pressure, or both are adjusted. And
[0011]
According to a fourth aspect of the present invention, in the simple air leak test apparatus, in the normal test mode, the control unit controls the pressure supply unit to supply the initial pressure to the workpiece through the passage, and then performs the test. Supply pressure, then close the on-off valve to close the work, wait for a predetermined waiting time in this closed state, detect the work leakage from the pressure detected by the pressure sensor,
The control means also executes a special test mode. In this special test mode, the initial pressure supply and test pressure supply are performed under the same conditions as in the normal test mode, and the on-off valve is closed. After waiting for a longer waiting time than the test mode, the pressure component that changes linearly due to leakage is subtracted from the detected pressure of the pressure sensor to obtain a pressure component that does not change, and this pressure component that does not change becomes zero. As described above, the time from the start of the initial pressure supply in the normal test mode to the switching to the test pressure, the pressure difference between the initial pressure and the test pressure is adjusted, or both, To do.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. A differential pressure type air leak test apparatus shown in FIG. 1 includes a pressure supply means 10, a common passage 20 having an upstream end connected to the pressure supply means 10, a master side branch passage 21 branched from the common passage 20, and a work side. And a branch passage 22.
[0013]
The pressure supply means 10 includes a positive pressure air pressure source 11, a source flow passage 12 connected to the air pressure source 11, an initial pressure supply passage 13 and a test pressure supply passage 14 branched from the source flow passage 12, Relief type regulators 15 and 16 provided in the passages 13 and 14 respectively, and a 2-position 3-port electromagnetic switching valve 17 connected to the downstream ends of the passages 13 and 14 are provided. The regulators 13 and 14 are set to an initial pressure and a test pressure, respectively. The initial pressure is higher than the test pressure (absolute value is large). The switching valve 17 selectively connects the common passage 20 to either the initial pressure supply passage 13 or the test pressure supply passage 14. In the present embodiment, the common passage 20 is connected to the initial pressure supply passage 13 at the off position, and is connected to the test pressure supply passage 14 at the on position.
[0014]
A two-position three-way electromagnetic switching valve 23 is provided in the middle of the common passage 20. The switching valve 23 blocks the downstream portion of the common passage 20 from the upstream portion at the off position and opens it to the atmosphere, and connects the downstream portion to the upstream portion at the on position.
[0015]
The branch passages 21 and 22 are provided with normally open electromagnetic on-off valves 27 and 28, respectively. Further, two ports of a differential pressure sensor 29 are connected to the branch passages 21 and 22 on the downstream side of the on-off valves 27 and 28.
[0016]
A master container M is connected to the downstream end of the master side branch passage 21. The master container M has a predetermined shape, volume, and material, and is different from a workpiece W described later. The master container M is devised so that the heat release after adiabatic compression is completed in a short time by reducing the volume and attaching a heat radiating fin. Further, the master container itself may be omitted and the downstream end of the master side branch passage 21 may be closed. A work W to be inspected is connected to the downstream end of the work side branch passage 22.
[0017]
The air leak test apparatus according to the present embodiment further includes a control means 30. The control means 30 sequentially controls the switching valves 17 and 23 and the on-off valves 27 and 28 based on the measurement time of a built-in timer. Further, the control means receives the detection signal from the differential pressure sensor 29 and controls the display 31, the pass lamp 32 and the fail lamp 33.
[0018]
The operation of the apparatus having the above configuration will be described focusing on the operation of the control means 30. First, valve control in a normal test mode will be described with reference to FIG. The initial pressure supply circuit 13 is communicated with the branch passages 21 and 22 by turning on the switching valve 23 and communicating the upstream portion and the downstream portion of the common passage 20. Thereby, the initial pressure is supplied to the branch passages 21 and 22, the master container M, and the workpiece W. When a predetermined time Ta has elapsed from the start of the initial pressure supply, the switching valve 17 is turned on to switch the connection of the common passage 20 from the initial pressure supply circuit 13 to the test pressure supply circuit 14. As a result, the test pressure is supplied to the branch passages 21, 22, the workpiece W and the master container M through the common passage 20. Then, when a predetermined time Tb has elapsed from the time of switching to the test pressure, the on-off valves 27 and 28 are closed, and the branch passages 21 and 22 are made an independent closed system. When a predetermined time Tc elapses from the closing time of the on-off valves 27, 28, the on-off valves 27, 28 are opened and the switching valve 23 is turned off to open the master container M and the workpiece W to the atmosphere, and the test is completed. To do.
[0019]
Next, changes in the pressure of the workpiece W and the air temperature in the workpiece at each time Ta, Tb, and Tc will be described in detail with reference to FIGS. First, at a predetermined time Ta from the initial pressure supply start time, the pressure in the workpiece W reaches the initial pressure over time T1. At this time T1, heat is generated mainly by adiabatic compression in the workpiece W (more precisely, all the components downstream of the switching valve 23). Therefore, the air temperature in the workpiece W rises from the ambient temperature.
[0020]
The workpiece W is maintained at the initial pressure for the remaining time T2 of the predetermined time Ta after reaching the initial pressure. At time T2, heat is dissipated in the workpiece W that has become higher than the ambient temperature, and the air temperature in the workpiece W decreases toward the ambient temperature while drawing an exponential curve. At this time, the larger the temperature difference is, the larger the heat radiation is, so that a large temperature drop can be obtained even in the short time T2 at the initial stage of heat generation.
[0021]
When the test pressure is switched to when the time Ta elapses, the compressed air is released from the regulator 16. This means adiabatic expansion, and heat is taken away from the regulator 16 on the downstream side. Therefore, in the compressed air discharge time T3, the air temperature in the work W is rapidly decreased to be equal to the ambient temperature. As a result, thereafter, the work W no longer has a pressure drop due to heat dissipation. It should be noted that a short time T4 obtained by subtracting the actual discharge time T3 at the predetermined time Tb from the test pressure switching time ensures that the test pressure is completely reached, and a slight temperature between the workpiece W and the ambient temperature. It is time to eliminate the difference.
[0022]
At a predetermined time Tc after closing the on-off valves 27 and 28, a detection time T6 is set after the waiting time T5. This waiting time T5 is a time for waiting for the pressure fluctuation generated in the branch passages 21 and 22 to settle with the closing operation of the on-off valves 27 and 28.
[0023]
In the detection time T6, leakage is detected from the differential pressure detected by the differential pressure sensor 29. Specifically, the leakage amount is obtained from the gradient of the differential pressure change at the detection time T6. The leakage amount is preferably an atmospheric pressure equivalent leakage amount per unit time calculated from the differential pressure information and the test pressure.
[0024]
By using adiabatic expansion as described above, pressure fluctuations associated with heat dissipation can be eliminated in a short time, and when the on-off valves 27 and 28 are closed, the air temperature in the workpiece W becomes equal to the ambient temperature. Therefore, since the pressure drop due to heat radiation does not occur, the detected differential pressure includes only the differential pressure component caused by the leakage of the workpiece W. As a result, leak detection can be performed accurately. The leak amount is displayed on the display 31. When the leak amount is lower than the allowable value, the pass lamp 32 is turned on, and when it is higher, the fail lamp 33 is turned on.
[0025]
The operation in the normal test mode described above is the same as that of the apparatus disclosed in the aforementioned publication. In this normal test mode, the difference ΔPx between the initial pressure and the test pressure and the time Ta from the start of the initial pressure supply to the switch to the test pressure are the environments where the ambient temperature is at a standard temperature, for example, 25 ° C. The temperature of the air in the workpiece W is set to exactly match the ambient temperature due to the decrease in temperature due to the dissipation of the adiabatic compression heat and the adiabatic expansion during test pressure switching. However, in reality, the ambient temperature when the test is performed is different from the standard temperature, and varies depending on the season, time, air conditioning environment, and the like. If the ambient temperature is significantly different from the standard temperature, the air temperature in the workpiece W is higher or lower than the ambient temperature when the on-off valves 27 and 28 are closed, and heat is dissipated to the detected differential pressure at the detection time T6. , A differential pressure component due to endotherm is included, and accurate leak detection cannot be performed. That is, as shown exaggeratedly in FIG. 4, the detected differential pressure ΔPd indicated by the solid line includes not only the differential pressure component ΔPm due to leakage indicated by the alternate long and short dash line but also the differential pressure component ΔPh caused by heat dissipation indicated by the broken line. It is.
[0026]
Therefore, in the present embodiment, a special test mode is executed as necessary or periodically (for example, every predetermined time or every time a normal test mode is performed a predetermined number of times). In this special test mode, the control until the on-off valves 27 and 28 are closed is the same as that in the normal test mode described above, and thus the description thereof is omitted.
[0027]
In a special test mode, the time Tc ′ from when the on-off valves 27 and 28 are closed to when the on-off valves 27 and 28 are reopened and opened to the atmosphere is made several times longer than the time Tc in the normal test mode. More specifically, the waiting time T5 ′ from the closing time of the on-off valves 27 and 28 is set longer than the waiting time T5 in the normal test mode, and the detection time T6 ′ is about the same as the detection time T6 in the normal test mode. To do.
[0028]
As described above, if the air temperature in the workpiece W differs from the ambient temperature when the on-off valves 27 and 28 are closed, heat dissipation or heat absorption at the workpiece W occurs and the pressure of the workpiece W fluctuates. Ingredients are produced. Hereinafter, the case where heat is generated in the workpiece W will be described with reference to FIG. 4 again. In the special test mode, since the waiting time T5 ′ is long as described above, when the waiting time T5 ′ elapses, the heat dissipation of the workpiece W is finished, and the air temperature in the workpiece W matches the ambient temperature. ing. Therefore, at the detection time T6 ′, the differential pressure component ΔPh accompanying the heat radiation is not changed and is included in the detected differential pressure ΔPd as a constant value. However, since the differential pressure component ΔPm due to leakage changes linearly, the detected differential pressure ΔPd also changes linearly. The control means 30 can accurately calculate the differential pressure component ΔPm associated with leakage by translating the linear line of the detected differential pressure ΔPd until it becomes zero when the on-off valves 27 and 28 are closed, Based on this, an accurate leak amount can be detected as in the normal test mode.
[0029]
By subtracting the differential pressure component ΔPm caused by leakage from the detected differential pressure ΔPd, it is possible to obtain a constant differential pressure component ΔPh caused by the heat radiation of the workpiece W described above. Then, from the differential pressure component ΔPh, when the on-off valves 27 and 28 are closed, the time Ta during which the air temperature in the workpiece W can be matched with the ambient temperature is calculated. In the next normal test mode, The switching valve 17 is turned on at a timing based on the updated time Ta.
[0030]
The increase / decrease of the time Ta based on the differential pressure component ΔPh is performed using a map created in advance. When the differential pressure component ΔPh is positive, it means that the air temperature in the work W is higher than the ambient temperature when the on-off valves 27 and 28 are closed. Therefore, the work at the initial pressure is increased by increasing the time Ta. Increase the heat dissipation of W. When the differential pressure component ΔPh is negative, it means that the air temperature in the workpiece W is lower than the ambient temperature when the on-off valves 27 and 28 are closed. Therefore, the time Ta is shortened to dissipate heat at the initial pressure. suppress.
[0031]
Next, a second embodiment of the present invention will be described with reference to FIG. This embodiment relates to a simple air leak test apparatus rather than a differential pressure type. In this apparatus, the upstream end of the passage 20 ′ is connected to the pressure supply means 10, and the downstream end is connected to the workpiece W. A switching valve 23 and an opening / closing valve 27 are provided in the passage 20 ′, and a pressure sensor 29 ′ is connected to the downstream side of the opening / closing valve 27.
[0032]
In the above apparatus, the switching valves 17 and 23 and the on-off valve 27 are sequence-controlled by control means (not shown) in the same manner as in the first embodiment, and a special test mode is executed in addition to the normal test mode. This is exactly the same as in the first embodiment. The only difference is that the pressure sensor 29 'detects not the differential pressure but the pressure of the workpiece W. Therefore, the description of the operation of the second embodiment is omitted by replacing the differential pressure with the pressure in the description of the operation of the first embodiment.
[0033]
In the first and second embodiments, in the special test mode, the time Ta is adjusted so that the differential pressure component ΔPh (pressure component) due to heat dissipation and heat absorption is zero, but instead of this time Ta The pressure difference ΔPx between the initial pressure and the test pressure may be adjusted. That is, when the differential pressure component ΔPh is positive, the pressure difference ΔPa is increased, and when the differential pressure component ΔPh is negative, the pressure difference ΔPa is decreased. Further, both the time Ta and the pressure difference ΔPa may be adjusted based on the differential pressure component ΔPh.
[0034]
In the first and second embodiments, a pressure sensor is disposed in the passage near the work, and the elapsed time after the detected pressure of the pressure sensor reaches the initial pressure (corresponding to time T2 in FIG. 2) is adjusted. May be. This time adjustment is included in the adjustment of the time Ta.
[0035]
The setting of the time Ta and the pressure difference ΔPx in the special test mode may be the same as the normal test mode performed immediately before as described above, or may be set conditions when the ambient temperature is at the standard temperature.
[0036]
In the first and second embodiments, the initial pressure and the test pressure may be set to a negative pressure by using a negative pressure air source instead of the compressed air source. In this case, the same circuit as in FIGS. 1 and 5 is used, but the pressure source side is defined as the upstream side. In this case, the air temperature in the workpiece decreases due to adiabatic expansion when an initial pressure whose absolute value is larger than the test pressure is applied, and in the initial pressure applied state, the air temperature in the workpiece increases toward the ambient temperature due to the endothermic effect. Then, the air temperature in the workpiece further rises to the ambient temperature due to the adiabatic compression heat when the test pressure is switched to the next.
[0037]
【The invention's effect】
As described above, according to the first and second aspects of the present invention, in the normal test mode, the leak test can be executed in a short time by switching from the initial pressure to the test pressure. By adjusting the control conditions in this normal test mode in a special test mode that is periodically performed, accurate leak detection can be performed regardless of changes in the ambient temperature.
According to the third and fourth aspects of the present invention, similar effects can be obtained even in a simple air leak test.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a differential pressure type air leak test apparatus according to a first embodiment of the present invention.
FIG. 2 is a graph showing a time lapse of a work pressure obtained by valve control in the same device.
FIG. 3 is a diagram showing a time course of the air temperature in the workpiece obtained by valve control in the apparatus.
FIG. 4 is a diagram showing changes in detected differential pressure after closing an on-off valve, changes in differential pressure component due to heat dissipation, and changes in differential pressure component due to leakage.
FIG. 5 is a circuit diagram of a simple air leak test apparatus according to a second embodiment of the present invention.
[Explanation of symbols]
10 pressure supply means 20 common passage 20 'passage 21 master side branch passage 22 work side branch passages 27, 28 on-off valve 29 differential pressure sensor 29' pressure sensor 30 control means W work

Claims (4)

A pressure supply means capable of supplying a test pressure and an initial pressure having an absolute value larger than this, a common passage connected to the pressure supply means, a master side branch passage and a work side branch passage branched from the common passage; In an air leak test method using an on-off valve provided in these branch passages, and a differential pressure sensor for detecting a differential pressure between a master side and a work side branch passage on the downstream side of these on-off valves,
In the normal test mode, the initial pressure is supplied from the pressure supply means to the master side and the work side branch passage through the common passage, and then the test pressure is supplied, and then the on-off valve is closed to close the master side. The workpiece side branch passage is closed in an independent state, and after waiting for a predetermined waiting time in this closed state, the workpiece connected to the workpiece side branch passage is leaked from the differential pressure detected by the differential pressure sensor. Detect
Further, a special test mode is executed as necessary or periodically. In this special test mode, the initial pressure supply and the test pressure supply are performed and the on-off valve is closed as in the normal test mode. After waiting for a longer waiting time than the normal test mode, the differential pressure component that changes linearly due to leakage is subtracted from the detected differential pressure of the differential pressure sensor to obtain a differential pressure component that does not change, and this change The time from the start of supplying the initial pressure in the normal test mode to the switch to the test pressure, the pressure difference between the initial pressure and the test pressure, or both, should be adjusted so that the differential pressure component is not zero. An air leak test method characterized by comprising. A pressure supply means capable of supplying a test pressure and an initial pressure having an absolute value larger than this, a common passage connected to the pressure supply means, a master side branch passage and a work side branch passage branched from the common passage; In an air leak test apparatus comprising an opening / closing valve provided in these branch passages, a differential pressure sensor for detecting a differential pressure between the branch passage on the master side and the workpiece side on the downstream side of these on / off valves, and a control means,
This control means supplies the initial pressure to the master side and work side branch passages through the common passage by controlling the pressure supply means in the normal test mode, and then supplies the test pressure, Thereafter, the on-off valve is closed and the master side and work side branch passages are closed in an independent state, and after waiting for a predetermined waiting time in this closed state, the work side branch is taken from the differential pressure detected by the differential pressure sensor. Detects leakage of workpieces connected to the aisle,
The control means also executes a special test mode. In this special test mode, the initial pressure supply and test pressure supply are performed in the same manner as in the normal test mode, and the on-off valve is closed. After waiting for a longer waiting time than the test mode, the differential pressure component that changes linearly due to leakage is subtracted from the detected differential pressure of the differential pressure sensor to obtain a differential pressure component that does not change. It is characterized by adjusting one or both of the pressure difference between the initial pressure and the test pressure, the time from the start of the initial pressure supply in the normal test mode to the switch to the test pressure, so that the component becomes zero. An air leak test apparatus characterized by that. Pressure supply means capable of supplying a test pressure and an initial pressure having a larger absolute value than this, a passage connecting the pressure supply means and the workpiece, an on-off valve for closing the passage, and a passage on the downstream side of the on-off valve In an air leak test method using an apparatus provided with a pressure sensor for detecting the pressure of
In the normal test mode, the initial pressure is supplied to the work through the passage by controlling the pressure supply means, and then the test pressure is supplied, and then the open / close valve is closed to close the work. , After waiting for a predetermined waiting time in this closed state, the leakage of the work is detected from the pressure detected by the pressure sensor,
A special test mode is executed as needed or periodically. In this special test mode, the initial pressure supply and test pressure supply are performed in the same manner as the normal test mode, and the on-off valve is closed. After waiting for a longer waiting time than the test mode, the pressure component that changes linearly due to leakage is subtracted from the detected pressure of the pressure sensor to obtain a pressure component that does not change, and this pressure component that does not change becomes zero. As described above, the time from the start of the initial pressure supply in the normal test mode to the switching to the test pressure, the pressure difference between the initial pressure and the test pressure is adjusted, or both, Air leak test method. Pressure supply means capable of supplying a test pressure and an initial pressure having a larger absolute value than this, a passage connecting the pressure supply means and the workpiece, an on-off valve for closing the passage, and a passage on the downstream side of the on-off valve In an air leak test apparatus provided with a pressure sensor for detecting the pressure of and a control means,
The control means controls the pressure supply means in a normal test mode, thereby supplying the initial pressure to the workpiece through the passage, then supplying the test pressure, and then closing the on-off valve. After the workpiece is closed, after waiting for a predetermined waiting time in this closed state, the leakage of the workpiece is detected from the pressure detected by the pressure sensor, and the control means further executes a special test mode. In the normal test mode, after supplying the initial pressure and the test pressure as in the normal test mode and closing the on-off valve, after waiting for a longer waiting time than in the normal test mode, the detected pressure of the pressure sensor The normal test mode is used to subtract the pressure component that changes linearly due to leakage to obtain a pressure component that does not change, and to make this unchanged pressure component zero. Initial time from pressure supply start to switching to the test pressure, the air leak test apparatus characterized by and adjusting either or both of the pressure difference between the initial pressure and the test pressure at.

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