JPH09311091A - Air leak test method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately detect the leak amount converted to an atmo spheric pressure with taking consideration into a deformation of a diaphragm in an air leak tester using a diaphragm-type differential sensor. SOLUTION: In a first process of a measurement mode, two-way solenoid valves 5a, 5b set at branching air paths 1a, 1b are closed, and an open valve 9 connected to a branching air path 1a at the master side is opened. A work W is closed at an atmospheric pressure and a master container M is opened to the air. In this state, a volume-changing device 8 connected to the branching air path 1b is driven to change a volume of a closing system at the work side. A differential pressure is detected by a differential pressure sensor 7. In a second process of the measurement mode, the open valve 9 is closed and, not only a system including the work, but a system including the master container are closed at the atmospheric pressure. In this state, the volume is changed in the same manner as above and a differential pressure is detected. In a leak inspection mode, the leak amount converted to the atmospheric pressure is detected by a deformation compensation volume of the closing system of the work side obtained from the detected differential pressures and a test pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air leak test method capable of accurately detecting an atmospheric pressure conversion leak amount.

[0002]

2. Description of the Related Art An air leak tester is used to inspect a sealed container for leakage. The air leak test apparatus includes a common air passage whose one end is connected to the test pressure source, and first and second branch air passages branched from the other end of the common air passage. The first and second branch air passages each have a connection end for the master container and a connection end for the work. A three-way solenoid valve is provided in the common air passage, and a two-way solenoid valve is provided in the pair of branch air passages. A diaphragm type differential pressure sensor for detecting the pressure difference is provided between the first and second branch air passages on the connection end side of the two-way solenoid valve.

In the air leak test apparatus having the above-mentioned structure, the test pressure source supplies the test pressure to the master container and the work through the three-way solenoid valve, and thereafter the pair of two-way solenoid valves are closed, whereby the master pressure is reduced. The system including the container and the system including the work are closed by the test pressure, and in this state, the presence or absence of leakage from the work is determined based on the differential pressure detected by the differential pressure sensor. This determination is generally performed by comparing the atmospheric pressure conversion leakage amount with a threshold value. The calculation of the atmospheric pressure-converted leak amount requires information on the detected differential pressure and the volume of the work-side closed system to be inspected. In particular, in order to detect the atmospheric pressure conversion leakage amount with high accuracy, it is necessary to set the volume of the work side closed system as the volume of deformation compensation in consideration of the influence of the deformation of the diaphragm of the differential pressure sensor.

From the above viewpoint, the air leak test method of Japanese Patent Publication No. 4-66307 has been developed. According to this method, in the measurement mode, a master container is connected to the first branch air passage, and a leak-free workpiece having the same shape as the inspection target is connected to the second branch air passage. And the volume of the work side closing system is changed by the volume changer, and based on the differential pressure information detected by the differential pressure sensor after this volume change and the volume change amount, the work side closing system Deformation compensation volume is calculated.
In the leak inspection mode, the atmospheric pressure conversion leak amount is detected based on the detected differential pressure and the deformation compensation volume.

[0005]

In the above air leak test method, since the deformation compensation volume of the work side closed system at the test pressure is obtained, the measurement mode must be executed again when the test pressure is changed. It was troublesome.

[0006]

According to a first aspect of the present invention, there is provided a common air passage having one end connected to a test pressure source, and a connection end for branching from the other end of the common air passage and for a master container. A first branch air passage, a second branch air passage branched from the other end of the common air passage and having a connection end for a work, valve means provided in each of the branch air passages, and these valve means A diaphragm type differential pressure sensor for detecting a pressure difference between the first and second branch air passages on the side of the connection end, and a valve connected between the valve means and the connection end in the second branch air passage. Using an air leak test device with a volume changer,
In the method of performing measurement mode and leak check mode,
In the measurement mode, (i) the first branch air passage is opened to the atmosphere, a leak-free work having the same shape as the work to be inspected is connected to the second branch air passage, and the second branch air passage is connected by the valve means.
A first step in which the volume of the work-side closed system is changed by the volume changer while the branch air passage is closed at atmospheric pressure, and the differential pressure is detected by the differential pressure sensor after the volume is changed; The volume of the work-side closing system is changed by the volume changer in a state where the master container and the leak-free work are connected to the first and second branch air passages, respectively, and the branch air passages are closed by the valve means at atmospheric pressure. Then, the second step of detecting the differential pressure with the differential pressure sensor after the volume change,
In the leak inspection mode, the master container and the workpiece to be inspected are connected to the connection ends of the first and second branch air passages, and the valve means is closed while the test pressure is applied to the master container. And the work is closed with a test pressure, and based on the differential pressure detected by the differential pressure sensor and the deformation compensation volume of the work-side closing system that compensates for the deformation of the diaphragm of the differential pressure sensor, the leak amount converted to atmospheric pressure. The deformation compensation volume of the work-side closed system is obtained from information including the differential pressure detected in the first and second steps of the measurement mode.

According to a second aspect of the present invention, in the air leak test method according to the first aspect, the detected differential pressure obtained in the first step of the measurement mode and the volume change amount by the volume changer in the first step. And the proportional constant of the differential pressure sensor, that is, the proportional constant relating to the differential pressure applied to the differential pressure sensor and the volume change amount of the work side closing system due to the deformation of the differential pressure sensor, the diaphragm of the differential pressure sensor is The volume of the work-side closed system when not deformed, that is, the initial volume is calculated, and the detected differential pressure obtained in the second step of the measurement mode and the volume change amount by the volume changer in the second step, The deformation compensation constant is calculated based on the initial volume of the work-side closing system, and in the leak inspection mode, the test pressure is multiplied by the compensation constant to add the volume of the work-side closing system to the work-side closing system. System A shape compensating volume, based on the detected differential pressure in the deformation compensation volume and the leakage inspection mode, and calculates the atmospheric pressure conversion leakage amount.

According to a third aspect of the invention, in the air leak test method according to the first aspect, the detected differential pressure obtained in the first step of the measurement mode and the volume change amount by the volume changer in the first step. And the proportional constant of the differential pressure sensor, that is, the proportional constant relating to the differential pressure applied to the differential pressure sensor and the volume change amount of the work side closing system due to the deformation of the differential pressure sensor, the diaphragm of the differential pressure sensor is The volume of the work-side closed system when not deformed, that is, the initial volume is calculated, and the detected differential pressure obtained in the second step of the measurement mode and the volume change amount by the volume changer in the second step, Based on the initial volume of the work-side closed system and the above proportionality constant related to the deformation of the diaphragm, the volume of the master container-side closed system when the diaphragm of the differential pressure sensor is not deformed, that is, the initial volume is calculated. In the inspection mode, the initial volume of the work-side closed system, the initial volume of the master-side closed system, the deformation-compensated volume of the work-side closed system obtained from the information of the proportional constant and the test pressure, and the differential pressure detected in the leak inspection mode. Based on and
It is characterized in that an atmospheric pressure conversion leak amount is calculated.

According to a fourth aspect of the invention, in the first branch air passage, one port of the open valve is connected between the valve means and the connecting end, and the other port of the open valve is open to the atmosphere. The air leak test method according to any one of claims 1 to 3, wherein in the measurement mode, a master container is provided at a connection end of the first and second branch air passages over the first and second steps. And the workpieces to be inspected and the leak-free workpieces having the same shape are continuously connected, and in the first step, the pair of valve means are set to the closed position,
By opening the release valve to the open position, the system on the master container side is opened to the atmosphere and the system on the work side is closed at atmospheric pressure.In this state, the volume changer is operated to change the differential pressure with the differential pressure sensor. In the second step, by closing the pair of valve means and closing the open valve, not only the system on the workpiece side but also the system on the master container side are closed at atmospheric pressure, and the volume in this state is increased. The changer is actuated to detect the differential pressure with the differential pressure sensor, and in the leak inspection mode, the master container and the workpiece to be inspected are connected to the connection ends of the first and second branch air passages. The test pressure is supplied to the master container and the work by opening the pair of valve means, and then the system on the master container side and the system on the work side are closed by the test pressure by closing the pair of valve means. By differential pressure sensor And detecting the pressure.

According to a fifth aspect of the present invention, in the air leak test method according to any one of the first to third aspects, a test pressure supply for communicating the pair of branch air passages with a test pressure source is provided in the common air passage. A three-way valve for selecting either a position or an atmosphere open position where the pair of branch air passages are disconnected from the test pressure source and opened to the atmosphere is provided. In the measurement mode, the three-way valve is used for the first and second steps. First and second
The master container and the non-leakage work having the same shape as the inspection target work are continuously connected to the connection end of the branch air passage of No. 1, and in the first step, the valve means of the first branch air passage is opened. By closing the valve means of the second branch air passage and setting the three-way valve to the atmosphere open position, the system on the master container side is opened to the atmosphere and the system on the work side is closed at atmospheric pressure. The differential pressure sensor is operated to detect the differential pressure, and in the second step, by setting the pair of valve means to the closed position, not only the system on the workpiece side but also the system on the master container side at atmospheric pressure. In the closed state, the volume changer is operated in this state to detect the differential pressure by the differential pressure sensor. In the leak inspection mode, the master container and the workpiece to be inspected are connected to the connection ends of the first and second branch air passages. Connect the above-mentioned pair of valve hands Open the above three-way valve to the test pressure supply position to supply the test pressure to the master container and the work, and then close the pair of valve means to test the system on the master container side and the work side. It is characterized in that the differential pressure is detected by a differential pressure sensor after that.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
~ It demonstrates in detail with reference to FIG. First, an outline of the air leak test apparatus will be described with reference to FIG. The air leak test apparatus includes an air passage 1. The air passage 1 includes a common air passage 1x and the common air passage 1x.
It has the 1st, 2nd branch air passages 1a and 1b branched from. A compressed air pressure source 2 (test pressure source) is connected to the upstream end of the common air passage 1x. At the downstream end (connection end) of the first branch air passage 1a, a master container M that is confirmed to be leak-free is detachably connected, and
The work W is detachably connected to the downstream end (connection end) of the branch air passage 1b.

The common air passage 1x is provided with a regulator 3 and a three-way solenoid valve 4 in this order from the upstream side. The three-way solenoid valve 4 blocks the test pressure supply position where the pair of branch air passages 1a and 1b communicate with the compressed air source 2 and the pair of branch air passages 1a and 1b from the compressed air source 2 and opens to the atmosphere. One of the open positions is selected, and the open position is set in the off state. The branch air passages 1a and 1b each have a normally open two-way solenoid valve 5
a and 5b (valve means) are provided.

A pair of input ports of the differential pressure sensor 7 are connected to the branch air passages 1a and 1b on the downstream side of the two-way solenoid valves 5a and 5b, respectively. The differential pressure sensor 7 has a diaphragm 71 inside and converts the deformation of the diaphragm 71 according to the pressure difference between the pair of input ports into a voltage and outputs the voltage.

A volume changer 8 is connected to the work-side branch air passage 1b downstream of the two-way solenoid valve 5b. Further, one port of an open valve 9 composed of a normally closed two-way valve is connected to the master side branch air passage 1a downstream of the two-way solenoid valve 5a. The other port of the open valve 9 is open to the atmosphere.

Further, the air leak test apparatus has a control section (measurement mode executing means, leak inspection executing means) 10. The control unit 10 includes a microcomputer, a memory, an input / output interface, a drive circuit and the like. A detection signal from the differential pressure sensor 7 is also input to the control unit 10. The control unit 10 includes a three-way solenoid valve 4 and a two-way solenoid valve 5.
a, 5b control, control of the motor 21 of the drive means 20 described later, indicator 11, pass lamp 12, fail lamp 13
Is to control.

As shown in FIG. 2, the volume changer 8 and the release valve 9 are driven by a common drive means 20. More specifically, the drive means 20 is
It has a motor 21 and a drive shaft 22 rotated by this motor 21. The drive shaft 22 has
Volume changer drive cam 31, release valve drive cam 32
Are fixed at intervals in the extending direction of the drive shaft 22. As shown in FIG. 3A, the cam 31 has an elliptical shape. As shown in FIG. 3B, the cam 32
Has a circular shape, and a notch 32a is formed in the cam 32 in a relatively large angle range. The volume changer 8 and the release valve 9 are arranged side by side in the extending direction of the drive shaft 22 and face the cams 31 and 32, respectively.

As shown in FIG. 4, the volume changer 8 has a cylinder 80 extending in a direction orthogonal to the drive shaft 22 and having one end closed, and an accommodating space 80a of the cylinder 80 in the axial direction (drive shaft 22). And a plunger 81 accommodated so as to be slidable in a direction (perpendicular to the direction). The accommodating space 80a of the cylinder 80 is connected to the branch air passage 1b via a communication port 80b opening on the upper surface of the cylinder 80. One end of the plunger 81 projects from the cylinder 80, and a cam follower 85 is rotatably supported by the projecting end.
The plunger 81 is biased toward the drive shaft 22 by a spring 86. As shown in FIG. 2, an L-shaped locking bracket 8 is provided on the upper surface of the cylinder 80.
7 is fixed, and the protrusion amount of the plunger 81 is regulated by the tip locking portion 87a (see FIG. 4) of the locking bracket 87. As a result, the cam follower 85
Is the cam 31 at the initial position of the cam 31 shown in FIG.
The cam 31 comes into contact with the cam 31 when it is rotated by a predetermined angle.

As shown in FIG. 5, the open valve 9 is provided with a tubular body 90 orthogonal to the drive shaft 22 and a plunger 91 slidably accommodated in the body 90. The body 90 has two ports 92a and 92b and a flow passage 93 connecting the ports 92a and 92b. The port 92a is connected to the master side branch air passage 1a, and the port 92b is open to the atmosphere. The plunger 91 has a valve element 91a at the inner end, and the valve element 91a is seated on a valve seat 93a at one end of the flow path 93 to allow the flow path 93 to be formed.
Is closed and separated from the valve seat 93a, the flow path 9
3 is open. A cam follower 95 is rotatably supported on the protruding end of the plunger 91. The plunger 91 is urged toward the drive shaft 22 by the spring 96, which causes
The cam follower 95 is in contact with the cam 32.

The control unit 10 of the air leak test apparatus having the above-described configuration executes two operation modes in response to the operation of the start button (not shown). One is the measurement mode and the other is the normal leak inspection mode. This measurement mode is periodically executed when the work W or the master container M is changed or in order to maintain the accuracy of the leak inspection in the leak inspection mode.

First, a measurement mode for obtaining information necessary for the deformation compensation volume of the work-side closed system, which will be described later, will be described. This measurement mode includes the first step and the second step. Prior to executing the first step, a leak-free work W having the same shape as the inspection target is connected to the branch air passage 1b, and the master container M is connected to the branch air passage 1a.
The master container M and the work W remain connected to the branch air passages 1a and 1b until the second step of the measurement mode is completed.

First, the first step will be described. When the measurement mode start button is pressed in a state where the solenoid valves 4, 5a, 5b are off and the master container M and the work W are open to the atmosphere, in response to this, the control unit 10
Closes the two-way solenoid valves 5a and 5b by turning them on. Simultaneously with this or after waiting for a predetermined short time, the motor 21 of the driving means 20 is driven. At the start of driving the motor 21, the cams 31 and 32 are in the states shown in FIGS. 3 (A) and 3 (B). Therefore, the volume changer 8 is in the maximum volume state with the plunger 81 projecting outward as much as possible, as shown in FIG. Further, the plunger 91 of the release valve 9 is shown in FIG.
As shown in, the flow path 93 is closed by being pushed in.
Therefore, not only the system including the work W but also the system including the master container M is temporarily closed at atmospheric pressure.

When the cam 32 is rotated by the drive of the motor 21, the cam follower 95 is formed in the notch 32a of the cam 32.
Enters. As a result, the plunger 91 of the release valve 9 projects towards the drive shaft 22 and the valve element 91a
Lifts from the valve seat 93a. As a result, the flow path 93 of the opening valve 9 is opened, and the system including the master container M is opened to the atmosphere.

Further, by driving the motor 21, the cam 3
When 1 rotates, the circumferential surface of the cam 31 comes into contact with the cam follower 95, and the plunger 81 is pushed in with this rotation, and the volume of the accommodation space 80a of the cylinder 80 is reduced. When the cam 31 rotates 90 ° from the initial position,
The volume of this accommodation space 80a becomes the minimum.

As described above, the system including the master container M is opened to the atmosphere, and the work side closed system (volume changer 8 and
The volume of the branch air passage 1b on the downstream side of the two-way solenoid valve 5b and the system including the work W) is set by the set volume V _C (the difference between the maximum value and the minimum value of the volume of the volume changer 8, that is, the volume change amount). Reduce. The control unit 10 reads the detected differential pressure ΔP ₁ from the differential pressure sensor 7 at the time when the cams 31, 32 rotate 90 °.

When Boyle's law is applied to the state before the volume change and the state after the volume change in the first step, the following equation is obtained. P ₀ V _W = (P ₀ + ΔP ₁ ) (V _W −V _C + ΔV ₁ ) ... (1) Here, P ₀ is the pressure of the work-side closed system before volume change, that is, atmospheric pressure, and (P ₀ + ΔP ₁ ) is the pressure of the work W closed system after the volume change. V _W is the volume (initial volume) of the work-side closed system before the volume change, that is, in the state where the diaphragm 71 is not deformed, and is (V _W −V _C +
ΔV ₁ ) is the volume of the system including the work W after the volume change. It should be noted that ΔV ₁ is the volume increase (volume change amount) of the work side closed system corresponding to the deformation of the diaphragm 71 caused by the generation of the differential pressure due to the volume change.

The above equation (1) can be rewritten as the following equation. _{P 0 V W = P 0 V} W + ΔP 1 V W -P 0 (V C over [Delta] V ₁₎ over [Delta] P ₁ (V _C over ΔV ₁₎ ... (2) change in volume due to deformation of the diaphragm is [Delta] V ₁ = K
It is represented by ΔP ₁ . Here, K is a proportional constant relating to the deformation of the diaphragm 71. By substituting this into the above equation (2) and rearranging, the following equation is obtained. _{V W = (P 0 + ΔP} 1) (V C -KΔP 1) / ΔP 1 ... (3) where, if approximated to _{(P 0 + ΔP 1) ≒} P 0, the following equation is obtained. V _W = P ₀ {(V _C / ΔP ₁ ) −K} (4) In the control unit 10, the atmospheric pressure value P ₀ and the volume by the volume changer 8 are calculated according to the above formula (3) or (4). Change V _C
And the detected differential pressure ΔP ₁ and the proportional constant K of the diaphragm 71.
Based on and, the initial volume V _W of the work-side closed system is calculated and stored in the memory.

Subsequently, the control section 10 executes the second step in the measurement mode. That is, the motor 21 is continuously driven. Then, with the rotation of the cam 31, the plunger 81 of the volume changer 8 projects toward the drive shaft 22, and returns to the maximum volume again at the 180 ° rotation position. The cam follower 95 is disengaged from the notch 32a of the cam 32 within the rotation angle range where the plunger 81 is locked by the locking bracket 87 and the maximum volume is maintained, whereby the valve element 91a of the opening valve 9 is closed. The flow path 93 is closed by hitting the seat 93a. As a result, the system including the master container M is closed at atmospheric pressure.

After the system including the master container M is closed, the accommodation space 8 of the cylinder 80 is rotated along with the rotation of the cam 31.
The volume of 0a decreases again. When the drive shaft 22 and the cam 31 rotate 270 ° from the initial position, the volume of the accommodation space 80a becomes the minimum again.

As described above, the control unit 10 closes the system on the master container side at atmospheric pressure as in the work-side closed system, and sets the volume of the closed system including the work W to the same set volume V as in the first step.
At the time when the pressure is reduced by _C (the difference between the maximum value and the minimum value of the volume of the volume changer 8, that is, the volume change amount), the detected differential pressure ΔP ₂ from the differential pressure sensor 7 is read.

When Boyle's law is applied to the state before the volume change and the state after the volume change in the second step, the following equation is obtained. Work _{side: P 0 V W = P W} (V W -V C + ΔV 2) ... (5) _{master: P 0 V M = P M} (V M -ΔV 2) ... (6) where, P _W is It is the pressure on the work side after the volume is changed, and P _M
Is also the pressure on the master side after the volume change. V _M is
This is the volume (initial volume) of the master container side closed system before the volume is changed, that is, in the state where the diaphragm 71 is not deformed.
(V _M −ΔV ₂ ) and (V _W −V _C + ΔV ₂ ) are the volumes of the master container side closed system and the work side closed system after the volume change.
It should be noted that ΔV ₂ is the master side closing system corresponding to the deformation of the diaphragm 71 caused by the generation of the differential pressure due to the volume change,
This is the volume increase (volume change amount) of the work-side closed system.

The following equation is obtained by summing the above equations (5) and (6). _{P M V W (V M -ΔV} 2) = P W V M (V W -V C + ΔV 2) ... (7) Equation (7) can be rewritten as follows. P _M V _W V _M over _{P M V W · ΔV 2 =} P W V M V W -P W V M V C + P W V M · ΔV 2 ... (8) and to organize expression (8) as follows become. _{P W V M V C = (} P W -P M) V M V W + (P M V W + P W V M) ΔV 2 ... (9) where the detection differential pressure [Delta] P ₂ in the second step, ΔP ₂ = P _W
Since it is expressed by −P _M and ΔV ₂ = KΔP ₂ , the above equation (9) can be rewritten as follows. _{P W V M V C = ΔP} 2 · V M V W + KΔP 2 (P M V W + P W V M) ... (10) is rewritten above equation (10), the following equation. KΔP ₂ (P _M V _W + P _W V _M ) = P _W V _M V _C −ΔP ₂ · V _M V _W (11) Further, the above formula (11) can be rewritten as the following formula. K (P _M V _W / P _W V _M +1) = V _C / ΔP ₂ −V _W / P _W (12) Here, V _W >> V _C and P ₀ >> ΔP ₂ , so P _W
≈P _M ≈P ₀ holds, and by substituting this equation into equation (12), the following equation is obtained. K (V _W / V _M +1) = V _C / ΔP ₂ −V _W / P ₀ (13)

The left side of the equation (13) represents a compensation constant R described later. According to the equation (13), the volume change amount V _C by the volume changer 8, the differential pressure ΔP ₂ detected in the second step, the initial volume V _W of the work side closed system obtained in the first step, and the large value The compensation constant R can be obtained based on the atmospheric pressure value P ₀ . This compensation constant R is also stored in the memory. In this embodiment, the initial volume V _M of the master-side closed system remains unknown and is not calculated. The motor 21 is
It makes one rotation and returns to the original initial state and then stops. Then, the two-way solenoid valves 5a and 5b are opened. In this way, the measurement mode ends.

Next, the normal leak inspection mode will be described below. In this mode, the motor 21 is not driven, the cams 31 and 32 are at the initial positions shown in FIGS. 3A and 3B, and the open valve 9 is closed.

The master container M is connected to the first branch air passage 1a, and the work W to be inspected for leakage is connected to the second branch air passage 1b. In the initial state, the solenoid valves 4, 5a,
5b is off, and the master container M and the work W are open to the atmosphere. In response to the ON operation of the leak inspection start button, the control unit 10 turns on the three-way solenoid valve 4 while keeping the two-way solenoid valves 5a and 5b off, that is, while keeping them open, and sets the branch air passages 1a and 1b to the compressed air pressure source. The test pressure P _T set by the regulator 3 is supplied to the master container M and the work W.

Next, by closing the two-way solenoid valves 5a and 5b, the system including the master container M and the system including the work W are closed at the test pressure P _T. If no leaks in the workpiece W, the diaphragm is not deformed, the volume of the system including the volume of the system including the master container M, the workpiece W is maintained respectively remain initial volume V _M, V _W, detected difference The pressure is also zero. When the work W leaks, the diaphragm 71 is deformed as the pressure of the work-side closed system is reduced, and the volume of the system including the master container M is increased by the volume ΔV _T (V _M + ΔV). _T ) and the volume of the system including the work W is ΔV
_{It is} reduced by _T to become (V _W −ΔV _T ). The pressure of the system including the master container M is P _XM , and the pressure of the system including the work W is P _XW .

In the closed system on the master container side, the following equation is established according to Boyle's law. The _{P T V M = P XM (} V M + ΔV T) ... (14) Similarly workpiece side closed system, the following equation is established. P _T V _W = P _XW (V _W −ΔV _T ) + P _{0 VL} (15) Here, V _L is the atmospheric pressure conversion leakage amount. Above (14),
If P _T is deleted from the equation (15), the following equation is obtained. P _XM (V _M + ΔV _T ) / V _M = {P _XW (V _W −ΔV _T ) + P _{0 VL} } / V _W (16) The above equation (16) can be rewritten as follows. _{P 0 V L V M = (} P XM -P XW) V M V W + ΔV T (P XM V W + P XW V M) ... (17) here, (P _XM over _{P XW) = ΔP T, ΔV} T = KΔP _T (where K is a proportional constant) is substituted into the above equation (17),
The following equation is obtained. _{V L = {V W + K} (P XM V W / V M + P XW)} ΔP T / P 0 ... (18) Further, P _XM ≒ P _T, when the _{P XW ≒ P T, (18} ) equation follows Can be rewritten as V _L = {V _W + KP
_T (1 + V _W / V _M )} ΔP _T / P ₀ (19) Further, the formula (19) can be rewritten as the following formula by substituting R = K (1 + V _W / V _M ). it can. V _L = (V _W + R · P _T ) ΔP _T / P ₀ (20)

According to the above equation (20), the work-side closed system V _W obtained in the first step of the measurement mode, the compensation constant R obtained in the second step of the measurement mode, the test pressure P _T, and the leak check The atmospheric pressure conversion leakage amount V _L is detected based on the detected differential pressure ΔP _T in the mode and the atmospheric pressure value P ₀ .

By the way, in the equation (20), (V _W +
R · P _T ) can be defined as the deformation compensation volume VE of the work-side closed system, and the equation (20) can be rewritten as the following equation. V _L = VE · (ΔP _T / P ₀ ) ... (21) Therefore, calculating the atmospheric pressure conversion leakage amount _VL based on the above equation (20) is equivalent to the deformation compensation volume VE of the work side closed system. This means that the atmospheric pressure conversion leak amount _VL is detected based on the detected differential pressure ΔP _T and the atmospheric pressure value P ₀ . The deformation compensation volume VE need not be calculated, but may be calculated and stored in the memory.

As described above, by using the deformation compensating volume VE instead of the initial volume V _W of the work-side closed system, it is possible to obtain the highly accurate atmospheric pressure conversion leak amount _VL in consideration of the deformation of the diaphragm 71. You can The deformation compensation volume VE is the initial volume V _{W of the} system including the work _W and the compensation constant R
And the test pressure P _T. Initial volume V _W ,
The compensation constant R is measured under the atmospheric pressure condition in the above-described measurement mode, and even if the test pressure is changed, it is not necessary to re-measure the initial volume V _W and the compensation constant R, which is complicated. Can be resolved. In addition, the pressure sensor provided in the common air passage 1x on the downstream side of the regulator 3 measures the test pressure in each leak inspection mode,
By substituting the measured test pressure into, it is possible to obtain an accurate atmospheric pressure conversion leak amount V _L even for a minute change in the test pressure. Since the proportionality constant R is based not only on the initial volume V _W of the work-side closed system but also on the initial volume V _{M of the} system including the master container M, these initial volumes V _M , V _W
Is changed, it is necessary to re-measure the initial volume V _W and the proportional constant by executing the measurement mode prior to the leak inspection mode.

The control unit 10 displays the atmospheric pressure conversion leakage amount V _L obtained as described above on the display device 11 and compares it with a threshold value to make a leakage determination. When the leakage amount V _L is smaller than the threshold value, the work W is determined to be non-defective and the pass lamp 12 is turned on. When the leak amount _VL is larger than the threshold value, it is determined that the work W is defective and the fail lamp 13 is turned on.

Finally, the control unit 10 controls the two-way solenoid valve 5a,
The two-way solenoid valve 5b is turned off and opened, and the three-way solenoid valve 4 is turned off to open the master container M and the work W to the atmosphere. After performing the leak test in this manner, the work W is removed from the branch air passage 1b, replaced with a new work W, and the above-described leak inspection mode is repeated.

In the above-described embodiment, the work W may be connected to the branch air passage 1b and the master container M may be connected to the branch air passage 1a before the measurement mode is started. Since it is possible to save the trouble of connecting the master container M, the measurement mode can be smoothly performed. Further, since the volume changer 8 is actuated by the motor-driven cams 31 and 32 together with the opening valve 9, workability is better than when the volume changer 8 is manually operated, and another drive system is used. The configuration is simpler than the case where it is operated by the following method. Further, the operation timings of the open valve 9 and the volume changer 8 can be surely obtained. Further, since there is no heat generation due to the operation of the release valve 9, the differential pressure can be accurately measured, and the accuracy of the air leak test can be improved.

In the measurement mode, the two-way solenoid valves 5a and 5b may be temporarily opened after the first step and then closed again at the beginning of the second step. In measurement mode,
The solenoid valves 4, 5a, 5b may be controlled similarly to the leak inspection mode. In this case, the test pressure source and the branch air passage are shut off by the manual valve provided in the regulator 3.

Next, a second embodiment will be described. In this embodiment, the open valve 9 is omitted from the first embodiment described above, and only the measurement mode in the control unit 10 is changed, and illustration thereof is omitted. In the present embodiment, the control unit 10 closes the two-way solenoid valve 5b in the first step of the measurement mode,
The two-way solenoid valve 5a is maintained in the open state without being closed, and the system including the master container M is kept open to the atmosphere. In the second step of the measurement mode, the system including the master container M is closed at atmospheric pressure by closing the two-way solenoid valve 5a before changing the volume. The two-way solenoid valve 5 is provided between the first step and the second step.
The work W may be once opened to atmospheric pressure by opening b.

The third embodiment relates to how to obtain information, and can be applied to both the first and second forms. More specifically, although in the first step of the measurement mode obtains an initial volume V _W of the first embodiment as well as the work side closed system described above, in the second step to obtain the initial volume V _M of the master container side. The following equation can be derived from the above equation (13). _{V M = V W ΔP 2 K} / {V C over _{(V W + P 0 K)} ΔP 2 / P 0} ... (22) initial volume V _M calculated by the equation (12) is stored in the memory . In the leak inspection mode, the above equation (1
According to 9), the atmospheric pressure conversion leak amount is calculated based on the initial volumes V _W , V _M , the detected differential pressure ΔP _T in the leak inspection mode, the test pressure P _T , and the atmospheric pressure value P ₀ . V _L = {V _W + K _{P T} (1 + V _W / V _M )} ΔP _T / P ₀ (19) Here, {V _W + KP _T (1 + V _W / V _M )} corresponds to the deformation compensation volume VE. , It is not necessary to directly calculate.

As another form, the volume changer may be driven so as to increase the volume of the work-side closing system. In this case, the above equation (3) can be rewritten as follows. V _W = if (P ₀ over _{ΔP 1) (V C -KΔP 1} ) / ΔP 1 ... (3) ' is approximated obtains the initial volume of the work side closed system in the same manner as described above (4) .

In the measurement mode, the volume change amount (set volume) when measuring the initial volume of the system including the work W and when measuring the initial volume of the system including the master container may be different. The motor 21 may be stopped for a predetermined time before the differential pressure is detected by the differential pressure sensor 7, and the differential pressure may be detected after the differential pressure becomes stable. As a result, a more accurate differential pressure is detected. The test pressure may be negative pressure. In the measurement mode, only the detected differential pressures ΔP ₁ and ΔP ₂ are stored in the memory, and in the leak inspection mode, the initial volume V _W and the compensation constant R of the work closing system or the initial volume V of the work side closing system are stored. _W and the initial volume V _M of the master side, may be calculated.

In this leak inspection mode, the initial volume V of the work-side closed system obtained in the first step is calculated by the following equation.
_W , the detected differential pressure ΔP ₂ obtained in the second step, the proportional constant K,
The direct atmospheric pressure conversion leak amount _VL may be calculated by the following equation based on the volume change amount V _C , the test pressure P _T , the detected differential pressure ΔP _T , and the atmospheric pressure value P ₀ . V _L = {V _W + KP _T (V _C / ΔP ₂ −V _W / P ₀ )} ΔP _T / P ₀ (23) Of course, the calculation of the atmospheric pressure conversion leakage amount V _L is not direct, either. This means that the deformation compensation volume VE is substantially obtained. Further, as the calculation method in the leak inspection mode, the detected differential pressures ΔP ₁ and ΔP obtained in the measurement mode are calculated according to the expression (3) or (4) substituted into the above expression (23).
The atmospheric pressure conversion leakage amount may be calculated based on various information including P ₂ .

[0049]

According to the first aspect of the present invention, a highly accurate leak amount converted to atmospheric pressure is obtained substantially based on the deformation compensating volume of the work side closing system including the deformation of the diaphragm of the differential pressure sensor. be able to. In addition, the first and second measurement modes
In the step, the detected differential pressure is detected under the atmospheric pressure condition, and based on the information including the detected differential pressure, the deformation compensation volume is substantially obtained, so that the test pressure is changed, It is not necessary to re-measure these information, and the complexity can be eliminated. Further, when the test pressure is measured each time in the leak inspection mode, an accurate atmospheric pressure conversion leak amount can be obtained even for a minute change in the test pressure. According to the invention of claim 2, the initial volume of the work-side closed system when the diaphragm is not deformed and the compensation constant are obtained based on the detected differential pressures obtained in the first and second steps of the measurement mode. Since the deformation compensation volume is obtained from the information and the test pressure, the accurate atmospheric pressure conversion leakage amount can be obtained by a simple calculation. According to the invention of claim 3, the initial volume of the work side closed system and the master container side when the diaphragm of the differential pressure sensor is not deformed based on the detected differential pressure obtained in the first and second steps of the measurement mode. Since the deformation compensating volume is obtained from these initial volumes and the information and the test pressure, the accurate leak amount converted to atmospheric pressure can be obtained by a simple calculation. Claim 4,
According to the invention of 5, the measurement mode can be continued while the master container is set, so that the measurement mode can be smoothly performed with good workability.

[Brief description of drawings]

FIG. 1 is a system diagram of the air leak test apparatus.

FIG. 2 is a plan view showing a main part of the air leak test apparatus.

3A and 3B show initial positions of cams used in the air leak test apparatus.

FIG. 4 is an enlarged horizontal sectional view of a volume changer in the air leak test apparatus.

FIG. 5 is an enlarged horizontal sectional view of an opening valve in the air leak test apparatus.

[Explanation of symbols]

1x Common air passage 1a Branch air passage 1b Branch air passage 2 Compressed air pressure source (test pressure source) 4 Three-way solenoid valve (three-way valve) 5a, 5b Two-way solenoid valve (two-way valve, valve means) 7 ... Differential pressure sensor 8 ... Volume changer 9 ... Open valve 10 ... Control unit (measurement mode execution means, leak inspection mode execution means)

Claims (5)

[Claims] 1. A common air passage having one end connected to a test pressure source, and a first branch air passage branched from the other end of the common air passage and having a connection end for a master container.
A second branch air passage branched from the other end of the common air passage and having a connection end for a work, valve means provided in each of the branch air passages, and the first branch air passage on the connection end side of the valve means. 1, a diaphragm type differential pressure sensor for detecting a pressure difference between the second branch air passage, and a volume changer connected between the valve means and the connection end in the second branch air passage. A method of executing a measurement mode and a leak inspection mode using an air leak test apparatus, wherein in the measurement mode, (i) the first branch air passage is opened to the atmosphere, and a leak-free workpiece having the same shape as the workpiece to be inspected. Is connected to the second branch air passage, and the volume of the work-side closing system is changed by the volume changer in a state where the second branch air passage is closed at atmospheric pressure by the valve means. A first step of detecting the differential pressure with the differential pressure sensor after changing the product, and (ii) connecting the master container and the leak-free work to the first and second branch air passages, respectively, and connecting the branch air passages with valve means. A second step in which the volume of the work-side closing system is changed by the volume changer in a state of being closed at atmospheric pressure, and the differential pressure is detected by the differential pressure sensor after the volume is changed; , Connecting the master container and the workpiece to be inspected to the connection ends of the first and second branch air passages,
By closing the valve means with the test pressure applied,
Based on the differential pressure detected by the differential pressure sensor after closing the master container and the work with the test pressure and the deformation compensation volume of the work side closed system that compensates the deformation of the diaphragm of the differential pressure sensor, the atmospheric pressure conversion is performed. An air leak test method for detecting a leak amount, wherein the deformation compensating volume of the work-side closed system is obtained from information including a differential pressure detected in the first and second steps of the measurement mode. 2. A differential pressure detected in the first step of the measurement mode, a volume change amount by a volume changer in the first step, and a proportional constant of the differential pressure sensor, that is, a differential pressure sensor. Based on the proportional constant related to the differential pressure and the amount of change in the volume of the work-side closed system due to the deformation of the differential pressure sensor, determine the volume of the work-side closed system when the diaphragm of the differential pressure sensor is not deformed, that is, the initial volume. The deformation compensation constant is calculated on the basis of the detected differential pressure obtained in the second step of the measurement mode, the volume change amount by the volume changer in the second step, and the initial volume of the work side closed system. In the leak inspection mode, the value obtained by multiplying the test pressure by the compensation constant and the volume of the work-side closed system is calculated as the deformation-compensated volume of the work-side closed system. Detected differential pressure Based on the air leak test method according to claim 1, characterized in that for calculating the atmospheric pressure conversion leakage amount. 3. A differential pressure detected in the first step of the measurement mode, a volume change amount by a volume changer in the first step, and a proportional constant of the differential pressure sensor, that is, a differential pressure sensor. Based on the proportional constant related to the differential pressure and the amount of change in the volume of the work-side closed system due to the deformation of the differential pressure sensor, determine the volume of the work-side closed system when the diaphragm of the differential pressure sensor is not deformed, that is, the initial volume. The detected differential pressure calculated in the second step of the measurement mode, the volume change amount by the volume changer in the second step, the initial volume of the work side closing system, and the proportional constant relating to the deformation of the diaphragm. Based on the above, the volume of the master container side closed system when the diaphragm of the differential pressure sensor is not deformed, that is, the initial volume is calculated.In the leak inspection mode, the initial volume of the work side closed system and the master side closed system are calculated. It is characterized in that an atmospheric pressure conversion leak amount is calculated based on the deformation volume of the work side closed system obtained from the information of the period volume, the proportional constant and the test pressure, and the detected differential pressure in the leak inspection mode. The air leak test method according to claim 1. 4. One port of an open valve is connected between the valve means and the connection end in the first branch air passage,
The other port of this release valve is open to the atmosphere, and in the measurement mode, the master container and the inspection target are connected to the connection ends of the first and second branch air passages over the first and second steps. The work and the leak-free work having the same shape are continuously connected, and in the first step, the system on the master container side is opened by setting the pair of valve means to the closed position and the open valve to the open position. At the same time as opening to the atmosphere, the system on the side of the work is closed at atmospheric pressure, and in this state, the volume changer is operated to detect the differential pressure by the differential pressure sensor. In the second step, the pair of valve means are closed and By closing the opening valve, not only the system on the work side but also the system on the master container side are closed at atmospheric pressure, and the volume changer is operated in this state to detect the differential pressure by the differential pressure sensor, In leak check mode Supplies a test pressure to the master container and the work by opening the pair of valve means in a state where the master container and the work to be inspected are connected to the connection ends of the first and second branch air passages. Next, by closing the pair of valve means, the system on the master container side and the system on the work side are closed by a test pressure, and then the differential pressure is detected by a differential pressure sensor. Air leak test method according to any one. 5. A test pressure supply position for connecting the pair of branch air passages and a test pressure source to the common air passage, and the pair of branch air passages are cut off from the test pressure source to open to the atmosphere. A three-way valve that selects one of the atmosphere open positions is provided. In the measurement mode, the master container and the inspection target are connected to the connection ends of the first and second branch air passages over the first and second steps. The work and the leak-free work having the same shape are continuously connected, and in the first step, the valve means of the first branch air passage is opened and the valve means of the second branch air passage is closed, and the three-way valve is opened to the atmosphere. By setting to the position, the system on the master container side is opened to the atmosphere and the system on the work side is closed at atmospheric pressure. In this state, the volume changer is operated to detect the differential pressure by the differential pressure sensor. In the process, the above pair By closing the valve means to the closed position, not only the work side system but also the master container side system is closed at atmospheric pressure.In this state, the volume changer is operated to detect the differential pressure with the differential pressure sensor. In the leak inspection mode, the master container and the workpiece to be inspected are connected to the connection ends of the first and second branch air passages,
By opening the pair of valve means and setting the three-way valve to the test pressure supply position, the test pressure is supplied to the master container and the work, and then by closing the pair of valve means, the system on the master container side and the work side. The air leak test method according to any one of claims 1 to 3, wherein the system is closed with a test pressure, and then the differential pressure is detected by a differential pressure sensor.