JPH0968474A - Air leak tester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely produce volume change of a specified quantity and produce stable pseud-leak. SOLUTION: A tank 9 is connected to an air passage 1b of the more downstream side than a valve 5b for a work through a pseud-leak valve 8. The tank 9 is released to the atmosphere through a three-way valve 4, the valve 5b and the valve 8 and the inside thereof is atmospheric pressure. After test pressure is supplied to the air passages 1a, 1b from a test pressure source 20, the valve 8 is opened in a state that a master valve 5a and the valve 5b are closed and the air passages 1a, 1b are shut, and pseud-leak is produced from the air passage 1b to the tank 9. Pressure change associating the pseud-leak is detected by a pressure sensor 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air leak tester, and more particularly to improvement of a pseudo leak generating means for generating a pseudo leak in an air passage.

[0002]

2. Description of the Related Art Conventionally, an air leak tester has been used for inspecting the tightness of a container (work) (presence of holes and cracks). In this air leak tester, a work to be inspected for leakage is connected to one end, and an air passage to which a test pressure source for supplying a test pressure is connected to the other end, and a work valve provided in the air passage. And a pressure sensor connected to the air passage on the downstream side of the work valve. In addition, this air leak tester uses a pseudo leak connected to the air passage downstream from the work valve in order to diagnose the pressure sensor and to accurately detect the atmospheric pressure conversion leak amount even when the work volume changes. It was equipped with a generating means.

As the pseudo leak generating means, a nozzle type and a cylinder type are known. In the nozzle type pseudo leak generating means, the nozzle is connected to the air passage downstream of the work valve via the pseudo leak valve. When the test pressure is supplied to the work, the pseudo leak valve is opened, a leak is generated from the air passage closed by the work valve into the atmosphere through the nozzle, and the pressure change is observed when a predetermined time has elapsed. In the cylinder type pseudo leak generating means, a cylinder is connected to an air passage downstream of the work valve. By moving the piston accommodated in this cylinder by a predetermined distance and changing the volume of the cylinder by a predetermined amount, a predetermined amount of leakage is generated from the air passage closed by the work valve toward the cylinder, which is accompanied by this. See pressure changes.

[0004]

By the way, in the above-mentioned pseudo leak generating means of the nozzle type, if dust adheres to the nozzle, the pseudo leak amount changes, so that a filter must be installed upstream of the nozzle. It was necessary to replace the filter regularly. In the cylinder type pseudo leak generating means, even if the stroke of the piston is set to a predetermined distance, a stroke error occurs, and a precise amount of pseudo leak cannot be generated. Further, when used for a long period of time, it was necessary to replace parts due to deterioration over time such as wear on the sliding surface between the piston and the cylinder and wear on the O-ring provided on the piston head.

[0005]

According to a first aspect of the present invention, an air passage is connected to one end thereof with a work to be inspected for leakage and to the other end thereof with a test pressure source for supplying a test pressure. A work valve provided in the air passage, a pressure sensor for detecting a pressure change in the air passage downstream of the work valve, and an air passage connected to the air passage downstream of the work valve In the air leak tester, the pseudo leak generating means includes a tank connected to an air passage downstream of the work valve, and the air leak and the tank. It is characterized in that it is provided with a pseudo leak valve interposed between the tank and a pressure supply means for supplying a pressure different from the test pressure to the tank.

According to a second aspect of the present invention, in the air leak tester according to the first aspect, the pressure supply means is provided in the work valve and an air passage between the work valve and the test pressure source. Including a three-way valve and the pseudo leak valve,
It is characterized in that the atmospheric pressure is supplied to the tank through these valves. According to a third aspect of the present invention, in the air leak tester according to the first aspect, the pressure supply means includes an auxiliary valve connected to the tank. According to a fourth aspect of the present invention, in the air leak tester according to the third aspect, the air leak tester further includes control means, and the control means closes the auxiliary valve and opens the pseudo leak valve toward a tank in an atmospheric pressure state. The pseudo leak is generated, then the pseudo leak valve is closed and the auxiliary valve is opened to bring the tank to the atmospheric pressure again, then the auxiliary valve is closed and the pseudo leak valve is opened to generate the pseudo leak again. The pseudo leak is performed multiple times. According to a fifth aspect of the present invention, in the air leak tester according to the third aspect, the pressure supply means includes an auxiliary pressure source, and the auxiliary pressure source is connected to the tank via the auxiliary valve. The air leak tester according to claim 3.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the air leak tester of the present invention will be described below with reference to FIG. The air leak tester includes an air passage 1. The air passage 1 has a common passage 1x and a pair of branch passages 1a and 1b branched from the common passage 1x. The compressed air source 2 is connected to the upstream end of the common passage 1x. One branch passage 1a
A master container M, which has been confirmed to be leak-free, is detachably connected to the downstream end 1m of the other branch passage 1b.
A work W whose leakage should be determined is detachably connected to the downstream end 1n.

The common passage 1x is provided with a regulator 3 and an electromagnetic three-way valve 4 in this order from the upstream side. The compressed air source 2 and the regulator 3 constitute a test pressure source 20. The branch passage 1a is provided with a normally open electromagnetic two-way valve 5a (master valve) and a normally open manual two-way valve 6a in order from the upstream side. Similarly, the branch passage 1b is also provided with an electromagnetic two-way valve 5b (workpiece valve) and a manual two-way valve 6b that are normally open from the upstream side.

A pair of input ports of the pressure sensor 7 are connected to the branch passages 1a and 1b between the electromagnetic two-way valves 5a and 5b and the manual two-way valves 6a and 6b, respectively. The pressure sensor 7 has a diaphragm 71 and outputs a signal according to the amount of deformation of the diaphragm 71 due to the differential pressure between the branch passages 1a and 1b.

In the branch passage 1b on the workpiece W side, a tank 9 is provided between the electromagnetic two-way valve 5b and the manual two-way valve 6b via a normally closed electromagnetic two-way valve 8 (pseudo leak valve). It is connected. The electromagnetic two-way valve 8 and the tank 9 constitute a pseudo leak generating means 30.

Further, the air leak tester includes a control unit 10.
(Control means). The control unit 10 includes a microcomputer, an input / output interface, a drive circuit and the like. A detection signal from the pressure sensor 7 is input to the control unit 10. The control unit 10 controls the electromagnetic three-way valve 4, the electromagnetic two-way valves 5a, 5b, 8 and the display (not shown), and also performs calculations and determinations described later.

The following leak test is performed by the leak tester having the above configuration. FIG. 1 shows an initial state. The master container M and the work W are connected to the downstream ends 1m of the branch passages 1a and 1b,
The test pressure source 20 and the branch passages 1a and 1b are made to communicate by turning on the electromagnetic three-way valve 4 in a state where they are respectively connected to 1n, and the test pressure P _T is supplied to the master container M and the work W. Thereafter, the electromagnetic two-way valves 5a and 5b are closed, and the pressure difference between the master side circuit and the work side circuit is detected by the pressure sensor 7. The master side circuit at this time includes a branch circuit 1a downstream of the electromagnetic two-way valve 5a and a master container M. The work side circuit includes a branch circuit 1b downstream of the electromagnetic two-way valve 5b and a work W. This differential pressure represents a pressure change in the work side circuit. When the work W is not damaged and air does not leak like the master container M, the differential pressure, that is, the pressure change ΔP _{T in the} work side circuit is zero. Work W
When there is a scratch or the like and air leakage occurs, a pressure change ΔP _T occurs. In the control unit 10, the pressure sensor 7
The atmospheric pressure conversion leakage amount V _L is calculated on the basis of the pressure change ΔP _T from, and when the atmospheric pressure conversion leakage amount V _L is less than the threshold value, it is judged as a good product, and when it exceeds the threshold value, it is judged as a defective product.

Generally, the atmospheric pressure conversion leakage amount V _L can be expressed by the following equation based on Boyle's law. V _L = ΔP _T · V _W / P ₀ (1) where V _W is the volume of the work side circuit. by the way,
When the work W changes, the volume V _{W of the} work side circuit also changes,
As is clear from the above equation (1), the relationship between the differential pressure ΔP _T and the atmospheric pressure conversion leakage amount V _L also changes. Therefore, it is necessary to obtain information on the volume V _W each time the work W to be tested changes, and for that purpose, a pseudo leak test is performed.

The pseudo leak test is performed as follows. First, the leak-free work W is connected to the branch passage 1b, and the master container M is connected to the branch passage 1a. Next, the electromagnetic two-way valve 8 is turned on and opened, the tank 9 is communicated with the atmosphere through the electromagnetic two-way valve 5b and the electromagnetic three-way valve 4, and the internal space thereof is brought to the atmospheric pressure P ₀ . Thus, valves 4, 5
b and 8 are pressure supply means 3 for supplying atmospheric pressure to the tank 9.
Play the role of 5.

Next, the electromagnetic two-way valve 8 is turned off and closed to disconnect the tank 9 from the work side circuit. Next, the electromagnetic three-way valve 4 is turned on, and the test pressure P is applied to the branch passages 1a and 1b.
Supply _T. Next, the electromagnetic two-way valves 5a and 5b are closed to close the work side circuit and the master circuit. Next, the electromagnetic two-way valve 8 is opened to communicate the tank 9 with the branch passage 1b, and a part of the compressed air flows out from the work side circuit to the tank 9 (pseudo leak). Then, the pressure sensor 7 detects the differential pressure ΔP _X after the pseudo leak, that is, the pressure change in the work side circuit before and after the pseudo leak. This pressure change ΔP _X and the volume V _W of the work side circuit have the following relationship according to Boyle's law. V _W = V ₀ · (P _T −P ₀ ) / ΔP _X (2) Here, V ₀ is the internal volume of the tank 9 (strictly speaking, the volume of the passage on the downstream side of the electromagnetic two-way valve 8 and the tank 9). Is the sum of the internal volume of).

By substituting the above equation (2) into the above equation (1), the following equation is obtained. V _L = V ₀ · (ΔP _T / ΔP _X ) · (P _T −P ₀ ) / P ₀ (3) In the control unit 10, a pseudo leak test is executed in advance to detect the pressure change ΔP _X. It is memorized, and in the leak test, from the detected pressure change ΔP _T and the stored pressure change ΔP _X in the pseudo leak test, the above (3)
The atmospheric pressure conversion leak amount _VL is calculated based on the equation. In addition,
In the equation (3), the tank volume V ₀ , the atmospheric pressure P ₀ , and the test pressure P _T are known.

By the way, the differential pressure between the master side circuit and the work side circuit causes the diaphragm 71 of the pressure sensor 7 to be deformed. This deformation is caused in the calculation of the atmospheric pressure conversion leakage amount V _L based on the above equation (3). Has almost no effect. This is because the differential pressure (pressure change) ΔP _T detected during the leak test and the differential pressure ΔP _X detected during the pseudo leak test both include factors due to the deformation of the diaphragm 71.
This is because this factor is almost canceled in the calculation of the atmospheric pressure conversion leak amount _{VL in} the equation (3).

Hereinafter, the reason why the influence of the deformation of the diaphragm 71 can be ignored will be described in detail. In the pseudo leak test, the following equation is established by the Boyle's law in the master side circuit. P _T · V _M = P ₁ · (V _M + ΔV) (4) However, P ₁ is the pressure of the master side circuit after the electromagnetic two-way valve 8 is opened to cause a pseudo leak to the tank 9 as described above. Is. ΔV is the volume change of the master side circuit due to the deformation of the diaphragm 71 of the pressure sensor 7. In the work side circuit, the following equation is established according to Boyle's law. P _T · V _W + P ₀ · V ₀ = P ₂ (V _W + V ₀ −ΔV) (5) where P ₂ is the work side after the electromagnetic two-way valve 8 is opened and the tank 9 is artificially leaked. The pressure of the circuit.

[0019] When the volume V _M of the master container M is equal to the volume V _W of the workpiece W, the equation (4) can be rewritten as the following equation. P _T · V _W = P ₁ · (V _W + ΔV) (4) ′ Substituting the equation (4) ′ into the equation (5) gives the following equation. P ₁ · (V _W + ΔV) = P ₂ (V _W + V ₀ −ΔV) −P ₀ · V ₀ (6) Here, the volume change ΔV due to the deformation of the diaphragm 71.
Is proportional to the differential pressure ΔP _X and can be expressed by KΔP _X (where K is a constant specific to the sensor). Further, assuming that P ₁ and P ₂ are approximately equal to the test pressure P _T , the following equation is obtained from the above equation (6). ΔP _X = P ₁ -P ₂ = V ₀ · (P _T −P ₀ ) / (V _W + 2 · K · P _T ) ... (7)

In the above equation (7), V _W '= V _W + 2 ·
Substituting K · P _T , the equation (7) can be rewritten as the following equation. V _W '= V ₀ · (P _T −P ₀ ) / ΔP _X (7)' As is clear from comparing the above equation (7) 'with the above equation (2), this value V _W ' It is understood that is the equivalent internal volume used in place of the internal volume V _W of the work side circuit when the deformation of the diaphragm is taken into consideration.

Next, the leak test will be described in consideration of the deformation of the diaphragm 71. Boyle's law at the time of the leak test can be expressed by the following equation. Master _{side: P T · V = P 1} '(V M + ΔV T) ... (8) work _{side: P T · V = P 2} ' (V W -ΔV T) + P 0 · V L ... (9) here P ₁ ′ and P ₂ ′ are pressures of the closed master side circuit and work side circuit. ΔV _T represents the volume change due to the deformation of the diaphragm of the pressure sensor 7. Here, V _M = V _W , P _T ≈P ₁ ′ ≈P ₂ ′, ΔV _T = K · Δ
Assuming P _T , the following equation is obtained from the above equations (8) and (9). P _X V _L = ΔP _T (V _W + 2K · P _T ) (10) The formula (10) can be rewritten as follows. V _L = V _W '.ΔP _T / P _X (10)' By substituting the formula (7) 'into the formula (10)', the following formula is obtained. V _L = V ₀ · (ΔP _T / ΔP _X ) · (P _T −P ₀ ) / P ₀ (11)

The equation (11) obtained as described above is the same as the equation (3). Therefore, upon operation of the atmospheric pressure conversion leakage amount V _L, it is possible to understand that can cancel the influence of the deformation of the diaphragm 71 of the pressure sensor 7, and thus, the atmospheric pressure conversion leakage amount V _L is the deformation of the diaphragm 71 It can be understood that it is possible to accurately obtain from the detected pressure changes ΔP _T and ΔP _X without calculating the equivalent internal volume V _W ′ based on

Next, the diagnosis of the leak tester including the pressure sensor 7 will be described. At the time of this diagnosis, the manual two-way valve 6
With the a and 6b closed, the pseudo leak test described above is performed to detect the pressure change ΔP _X. The pressure change ΔP _X at this time can be expressed by the following equation. ΔPx = V ₀ · (P _T −P ₀ ) / (Vset + 2 · K · P _T ) ... (12) Here, Vset is the electromagnetic two-way valve 5 b and the manual two-way valve 6 b.
It is the volume of the work side circuit between. The control unit 10 determines that there is no failure when the deviation between the pressure change ΔP _X obtained by the above equation (12) and the actual detected value is smaller than the allowable value, and determines that there is a failure when it is larger. .

As described above, in this embodiment, the tank 9 can be communicated with the circuit on the work side to perform the pseudo leak simply by opening the electromagnetic two-way valve 8, and the volume of the predetermined amount can be reliably ensured. Changes can occur. In addition, tank 9
Does not cause problems due to wear or dust,
It is possible to generate stable leaks over a long period of time without the hassle of replacing parts.

FIG. 2 shows a leak tester according to another embodiment. The leak tester of this embodiment differs from the embodiment of FIG. 1 in that an electromagnetic two-way valve 11 (auxiliary valve) is connected to the tank 9. The control unit 10 (see FIG. 1) executes the pseudo leak multiple times. More specifically, first, the electromagnetic two-way valves 8 and 1
Any one of 1 opens to bring the tank 9 to atmospheric pressure. next,
With the electromagnetic two-way valves 8 and 11 closed, the electromagnetic three-way valve 4 is turned on to supply the test pressure to the branch circuits 1a and 1b. Next, after closing the electromagnetic two-way valves 5a and 5b, the electromagnetic two-way valve 8 is opened to generate the pseudo leak as in the previous embodiment. Then, after the pressure sensor 7 detects a pressure change in the work side circuit, the electromagnetic two-way valve 8 is once closed, and then the electromagnetic two-way valve 11 is closed.
To open the tank 9 to the atmosphere. Then, the electromagnetic two-way valve 11 is closed again, and then the electromagnetic two-way valve 8 is opened to cause a similar pseudo leak. This embodiment is particularly effective when the test pressure is close to the atmospheric pressure P ₀ or when the tank 9 has a small volume. In this embodiment, the atmospheric pressure conversion leak amount _VL can be expressed by the following equation. V _L = N · V ₀ · (ΔP _T / ΔP _X ) · (P _T −P ₀ ) / P ₀ (13) Here, N is the number of repeated pseudo leaks. In this embodiment, the solenoid two-way valve 11 constitutes pressure supply means.

In the leak tester shown in FIG. 3, the auxiliary pressure source 40 different from the test pressure source 20 (FIG. 1) is the electromagnetic two-way valve 11.
It is connected to the tank 9 via. The electromagnetic two-way valve 11 is opened with the electromagnetic two-way valve 8 closed, the pressure of the auxiliary pressure source 30 is supplied to the tank 9, and then the electromagnetic two-way valve 11 is closed. In this state, the electromagnetic two-way valve 8 is opened and the pseudo leak is executed. The supply pressure from the auxiliary pressure source 40 to the tank 9 is generally lower than the test pressure, but may be higher than the test pressure or may be a negative pressure. In this embodiment, the electromagnetic two-way valve 11 and the auxiliary pressure source 40 constitute pressure supply means 45.

In the leak tester shown in FIG. 4, the tank 9
Is connected to the compressed air source 2 via the electromagnetic two-way valve 11 and the regulator 13. Prior to the execution of the pseudo leak, the electromagnetic two-way valve 11 is opened, and a pressure different from the test pressure is supplied to the tank 9 via the regulator 13. In this leak tester, the compressed air source and the regulator 13 constitute an auxiliary pressure source 50.

The present invention can be implemented in various modes without being restricted by the above embodiments. For example, the pressure sensor 7
Detects the differential pressure between the master side circuit and the work side circuit, but the branch passage 1a and the attached valve may be omitted and the pressure sensor 7 may detect the pressure change in the branch circuit 1b. The pseudo-leakage means of all the above-mentioned embodiments is provided with the master side circuit (between the electromagnetic similar valve 5a and the manual solenoid valve 6a).
However, in this case, the pseudo leaking means is used only for diagnosis. Further, instead of the compressed air source 2, a negative pressure source may be used.

[0029]

According to the first aspect of the present invention, the pseudo leak valve is opened to cause the pseudo leak from the air passage closed by the work valve to the tank. A leak can be generated reliably. Further, since the tank does not cause a defect due to abrasion or adhesion of dust or the like even if it is used for a long period of time, stable pseudo leak can be generated for a long period of time, and there is no trouble such as replacement of parts. According to the invention of claim 2, a pressure source different from the test pressure source is not required to bring the tank to the atmospheric pressure,
Further, since the pseudo leak valve, the work valve, and the three-way valve are used, it is not necessary to separately connect a valve for releasing the atmosphere to the tank, so that the structure is simplified. According to the third aspect of the invention, the auxiliary valve connected to the tank can relatively freely supply a pressure different from the test pressure to the tank. Claim 4
According to the invention, since the pseudo leak can be generated a plurality of times, the pressure sensor can reliably detect the pressure change due to the pseudo leak even if the volume of the tank is small.
According to the invention of claim 5, a pressure different from the atmospheric pressure can be supplied to the tank.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an air leak tester according to an embodiment of the present invention.

FIG. 2 is a view showing a main part of an air leak test of another form.

FIG. 3 is a diagram showing a main part of an air leak test of still another form.

FIG. 4 is a view showing a main part of an air leak test of still another form.

[Explanation of symbols]

 1 Air Passage 4 Electromagnetic Three-Way Valve 5b Electromagnetic Two-Way Valve (Work Valve) 7 Pressure Sensor 8 Electromagnetic Two-Way Valve (Pseudo Leakage Valve) 9 Tank 10 Control Unit (Control Means) 11 Electromagnetic Two-Way Valve (Auxiliary Valve) 20 Test pressure source 30 Pseudo leak generating means 35 Pressure supplying means 40 Auxiliary pressure source 45 Pressure supplying means 50 Auxiliary pressure source W Work

Claims (5)

[Claims] 1. An air passage having one end connected to a work to be inspected for leakage, and the other end connected to a test pressure source for supplying a test pressure, and a work valve provided in the air passage. A pressure sensor for detecting a pressure change in the air passage downstream of the work valve, and a pseudo-leakage generating unit connected to the air passage downstream of the work valve for producing pseudo-leakage from the air passage. In the air leak tester provided with, the pseudo leak generating means is a tank connected to an air passage downstream of the work valve, and a pseudo leak valve interposed between the air passage and the tank. An air leak tester, comprising: a pressure supply unit that supplies a pressure different from the test pressure to the tank. 2. The pressure supply means includes the work valve and
A three-way valve provided in an air passage between the work valve and the test pressure source, and the pseudo leak valve, and atmospheric pressure is supplied to the tank via these valves. Item 2. The air leak tester according to item 1. 3. The air leak tester according to claim 1, wherein the pressure supply means includes an auxiliary valve connected to the tank. 4. A control means is further provided, and this control means comprises:
The pseudo leak is generated toward the tank in the atmospheric pressure state by closing the auxiliary valve and opening the pseudo leak valve,
Next, close the pseudo leak valve and open the auxiliary valve to bring the tank back to atmospheric pressure, then close the auxiliary valve and open the pseudo leak valve to generate a pseudo leak again. The air leak tester according to claim 3, wherein 5. The air leak tester according to claim 3, wherein the pressure supply means includes an auxiliary pressure source, and the auxiliary pressure source is connected to the tank via the auxiliary valve.