JPH0792052A - Method for inspecting airtightness of hollow vessel - Google Patents

Abstract

PURPOSE:To provide a method for inspecting the airtightness of a hollow vessel in which a precise airtightness inspection can be executed with a simple facility at a low cost. CONSTITUTION:A fuel tank 1 is arranged in a vessel 4, the vessel 4 is made to be in a sealed state, and an incompressible fluid (water) is then charged into the vessel 4. Air is supplied into the fuel tank 1 and a standard tank 3 to pressurize the both with the same prescribed pressure, the differential pressure between the respective pressures in the fuel tank 1 and the standard tank 3 is detected, the differential pressure is also corrected with the internal pressure rise amount in the vessel 4 by the expansion of the fuel tank 1 to measure the internal pressure lowering amount by the leak of the fuel tank 1, and the presence of the leak from the fuel tank 1 is judged on the basis of the internal pressure lowering amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airtightness inspection method for a hollow container such as a fuel tank, and more particularly to a method for highly accurate airtightness inspection with a simple structure.

[0002]

2. Description of the Related Art Conventionally, an airtightness test has been carried out in order to guarantee the airtightness of an engine fuel supply system. As the airtightness inspection method, a differential pressure type leak check method is well known.

According to this differential pressure type leak check method, for example, when a leak check of the fuel tank 1 is performed, FIG.
As shown in FIG. 3, air is supplied into the fuel tank 1 to pressurize the fuel tank 1 with a pressure of, for example, 0.15 kg / cm ² , and at the same time, the reference tank 3 connected to the air leak tester 2 also has the same structure. Pressurize with pressure. Then, the differential pressure between the reference tank 3 and the fuel tank 1 is
The air leak tester 2 makes a measurement to check whether or not there is a leak in the fuel tank 1.

Incidentally, FIG. 6 shows a measurement pattern of the air leak tester 2. FIG. 7 is a basic circuit diagram of the air leak tester 2. The basic operation of the air leak tester 2 will be briefly described with reference to this figure. At the same time as the measurement is started, the solenoid valves SV-1, SV-2 and SV-3 are all opened. Air adjusted to a test pressure by the regulator A is supplied to the measurement object (workpiece) B and the reference object (master) C (pressurizing step). After stabilizing to the specified pressure, the solenoid valve SV-
2 and SV-3 are closed, and the differential pressure sensor D is sandwiched between the measurement object B.
Side and reference item C side are independent containers (equilibrium process). After the solenoid valves SV-2 and SV-3 are closed, the output of the differential pressure sensor D is output to the display / judgment unit F through the amplifier E with high sensitivity for the purpose of judgment, and the display value is zero-corrected. The pressure change (differential pressure) ΔP due to leakage is measured (detection step).

At this time, ΔP due to leakage changes as shown in the graph of FIG. Then, ΔP is NG within the specified time.
If it exceeds the set point, it is judged as NG, and if it does not exceed it, it is judged as OK. Then, the determination result is displayed by a lamp, the solenoid valves SV-2 and SV-3 are opened, the air inside the measurement object B is exhausted, and the measurement is completed.

[0006]

However, such a conventional differential pressure type leak check method has the following problems. That is, in recent years, the adoption of resin fuel tanks has been expanding. Due to the material of the resin fuel tank, expansion is likely to occur due to pressurization of air. Therefore, at the time of leak check, it is difficult to distinguish between the decrease in internal pressure of the fuel tank due to the leak and that due to the expansion of the fuel tank itself, and it is difficult to cope with the short tact time.
There is a problem that the detection accuracy is poor and an accurate airtightness test cannot be performed.

As an inspection method for solving such a problem,
Conventionally, there is one disclosed in JP-A-4-89542. In this inspection method, the hollow container is placed in the inspection chamber, and the hollow container and the inspection chamber are evacuated to a predetermined vacuum degree so that the inspection chamber has a higher vacuum degree than the hollow container. A specific gas is supplied to the chamber and the amount of gas leaked from the hollow container to the inspection chamber is measured by the gas measuring means.

Although this method can perform an accurate airtightness test, it requires a large amount of equipment and therefore has a problem that the equipment cost is high and it is not practical. Therefore,
The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a method for inspecting the airtightness of a hollow container capable of performing an accurate airtightness inspection with a simple and low-cost facility.

[0009]

Therefore, according to the present invention, a hollow container to be inspected is placed in a container, the container is sealed, and then an incompressible fluid is placed in the container. A step of filling, supplying gas into the hollow container and the reference tank, and pressurizing the both at the same predetermined pressure,
Detecting the pressure difference between the pressure inside the hollow container and the pressure inside the reference tank, measuring the amount of decrease in internal pressure due to leakage of the hollow container by correcting the pressure difference with the amount of increase in internal pressure due to expansion of the hollow container, and the internal pressure And a step of determining whether or not there is a leak from the hollow container based on the amount of decrease, and an airtightness inspection method for the hollow container.

[0010]

In such a method, in the differential pressure type leak check method, it is possible to separate the decrease in internal pressure due to expansion of the hollow container and the decrease in internal pressure due to leakage from the hollow container in the decrease in internal pressure of the hollow container. As a result,
During the leak check, the decrease in the internal pressure of the hollow container is distinguished from that due to the leakage and that due to the expansion of the hollow container itself, so that the detection accuracy can be improved and the accurate airtightness inspection can be executed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows the configuration of an example of an inspection apparatus for executing the airtightness inspection method for hollow containers according to the present invention. In this figure, the inspection device is a container body 4 with an open upper surface.
A, a container 4 including a lid 4B that opens and closes the upper surface of the container body 4A, a reference tank 3, and an air leak tester 2
A pressure sensor 5 provided in the container 4 as pressure detection means for detecting the internal pressure of the container 4, a water level sensor 7 for detecting the water level in the container 4, and a drain valve provided on the bottom wall of the container body 4A. 8, a water level control valve 9 provided on the lid 4B, and a control personal computer 6.

Here, as shown in FIG. 2, a gel seal material 10 is interposed between the upper end surface of the container body 4A and the lower surface of the lid 4B, and a manual lever 11 provided on the lid 4B is provided. The lid 4B can be brought into close contact with the container body 4A by engaging with the engagement piece 12 on the container body 4A side, and the inside of the container 4 can be sealed. Then, as an outline of the airtightness inspection method, the fuel tank 1 is set in the container 4, the container 4 is sealed, and then the container 4 is filled with water which is an incompressible fluid. Next, air is supplied to the fuel tank 1 and the reference tank 3 at, for example, 0.15 kg / c.
It is supplied at a pressure of m ² and sealed, and the inside of the fuel tank 1 and the inside of the reference tank 3 are pressurized. Then, the pressure difference between the reference tank 3 and the fuel tank 1 is measured by the air leak tester 2 as described with reference to FIG. 7, and it is checked whether or not the fuel tank 1 has a leak.

In this case, the pressure sensor 5 detects the pressure inside the container 4. Further, the amount of pressure increase in the container 4 due to the leakage of the fuel tank 1 is due to the compressive fluid (air) and has little influence. Therefore, the pressure sensor 5 detects a pressure increase in the container 4 due to the expansion of the fuel tank 1. Therefore, by correcting the differential pressure measured in the air leak tester 2 through the control personal computer 6 with this pressure increase, the decrease in internal pressure due to the leakage of the fuel tank 1 is measured.

The incompressible fluid (water) filled in the container 4 is managed as follows. That is, water is always filled in the container 4 up to a certain height of the water level sensor 7 except during inspection. After the fuel tank 1 is set in the container 4 and the container 4 is sealed, the container 4 is filled with water and the water level in the container 4 is set to the water level control valve 9 position. As described above, after the leak check, the drain valve 8 and the water level control valve 9 are opened, and the water is drained until the water level reaches a certain height of the water level sensor. The drained water will be circulated by a pump etc. so that it can be used again.

Next, the details of the airtightness inspection method for the fuel tank based on the above configuration will be described with reference to the configuration diagrams of FIGS. 1 and 2.
This will be described with reference to the inspection pattern diagram of FIG. 3 (the internal pressure of the fuel tank and the internal pressure of the container are not isometric) and the flowchart of FIG. First, an operator closes the holes of the fuel tank 1 and hoses (S1), sets the fuel tank 1 in the container body 4B (S2), and then the fuel tank 1
The air supply port of the air leak tester 2 is connected to the filler hose 13 and the manual lever 11 is operated, and the lower surface of the lid 4B is tightly fixed to the upper end surface of the container body 4A via the gel-like sealing material 10. And seal it (S
3). After that, the container 4 is filled with water (0 to t ₁ ).
(S4).

Next, the test start switch is operated (S
5) Air is enclosed in the fuel tank 1 and the reference tank 3 at a pressure of, for example, 0.15 kg / cm ² , and the fuel tank 1 and the reference tank 3 are pressurized to perform a leak check ( S6). On the other hand, the pressure sensor 5 provided in the container 4 detects the pressure increase amount ΔP ′ due to the expansion of the fuel tank 1 (t _{1 to} t ₂ ), and the control PC is detected by the pressure increase amount ΔP ′ due to the expansion of the fuel tank 1. The differential pressure ΔP measured by the air leak tester 2 through 6 is corrected to be smaller by the amount of pressure increase ΔP ′. With this correction, the amount of decrease in internal pressure due to the leakage of the fuel tank 1 is measured (S7). Whether the leak is OK or NG is determined by whether or not the amount of decrease in the internal pressure due to the leakage of the fuel tank 1 exceeds a reference value (t _{2 to} t).
₃ ) (S8). If the leak is OK, the OK determination lamp 14 is turned on and the OK determination buzzer is sounded (S9). If the leak is NG, the NG determination lamp 15 is turned on and the NG determination buzzer is sounded (S10). If the result is obtained in this way, drain the water in the container 4 (S
11), remove the lid 4B of the container 4 to release the seal (S
12), from the container 4 takes out the fuel tank _{1 (t 3 ~t 4) (} S13), and dried (S14).

If the fuel tank 1 has a leak NG, a re-inspection is performed, and if the fuel tank 1 is NG, it is discarded. According to the airtightness inspection method for such a fuel tank, the fuel tank 1 is placed in the container 4 and the container 4 is sealed, and then the incompressible fluid (water) is placed in the container 4.
And supplying air into the fuel tank 1 and the reference tank 3 to pressurize the both at the same predetermined pressure to detect the pressure difference between the fuel tank 1 and the reference tank 3 respectively. This differential pressure is corrected by the amount of increase in the internal pressure of the container 4 due to the expansion of the fuel tank 1, the amount of decrease in the internal pressure due to the leakage of the fuel tank 1 is measured, and the presence or absence of the leakage from the fuel tank 1 is determined based on the amount of the decrease in the internal pressure. Therefore, in the differential pressure type leak check method,
A decrease in internal pressure due to expansion of the fuel tank 1 and a decrease in internal pressure due to leakage from the fuel tank 1 in the decrease in internal pressure of the fuel tank 1 can be separated.

As a result, even in the case of resin-made fuel tanks, which have been increasingly used in recent years, at the time of a leak check, the internal pressure of the fuel tank drops due to leakage and due to expansion of the fuel tank itself. Differentiated, detection accuracy can be improved, and accurate airtightness inspection can be performed. Further, according to such a method, the conventional hollow container and the inspection chamber are evacuated to a predetermined vacuum degree, a specific gas is supplied to the hollow container, and the leak amount of the gas from the hollow container to the inspection chamber is measured by a gas measuring means. Compared with the method of measuring by, the equipment is simple, and the equipment cost is advantageous and practical.

As described above, the present invention has been described with reference to the specific embodiments, but the present invention is not limited to this, and is attached to the present invention by a person skilled in the art. Without departing from the scope of the appended claims
It should be noted that various changes and modifications are possible.

[0020]

As described above, according to the present invention, a hollow container to be inspected is placed in a container, the container is sealed, and then the container is filled with an incompressible fluid. And the step of pressurizing the inside of the hollow container and the inside of the reference tank with the same predetermined pressure, and detecting the pressure difference between the inside of the hollow container and the inside of the reference tank, the differential pressure by the expansion of the hollow container A method of measuring the internal pressure decrease due to the leakage of the hollow container by correcting the internal pressure increase, and determining the presence or absence of leakage from the hollow container based on the internal pressure decrease, Therefore, at the time of checking for leakage, the decrease in internal pressure of the hollow container is distinguished from that due to the leakage and that due to the expansion of the hollow container itself, so that the detection accuracy can be improved and an accurate airtightness test can be performed. , Made of resin with a large expansion problem The hollow container is effective.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for performing a method for inspecting the airtightness of a hollow container according to the present invention.

FIG. 2 is an enlarged view taken along arrow X in FIG.

FIG. 3 is an inspection pattern diagram of an airtightness inspection method.

FIG. 4 is an inspection flowchart of an airtightness inspection method.

FIG. 5 is a cross-sectional view illustrating an apparatus that executes a conventional airtightness inspection method.

FIG. 6 is a measurement pattern diagram of an air leak tester in the conventional device.

FIG. 7 is a basic circuit diagram of the above air leak tester.

FIG. 8 is a diagram showing a pressure change due to a leak of a fuel tank in the conventional device of the above.

[Explanation of symbols]

 1 Fuel tank 2 Air leak tester 3 Reference tank 4 Container 5 Pressure sensor 6 Control PC

Claims (1)

[Claims] 1. A step of placing a hollow container to be inspected in a container, sealing the container, and then filling the container with an incompressible fluid, and the inside of the hollow container and the reference tank. Supplying a gas, pressurizing the both with the same predetermined pressure, and detecting the pressure difference between the pressure inside the hollow container and the pressure inside the reference tank, and increasing the pressure inside the container due to the expansion of the hollow container. And measuring the amount of decrease in internal pressure due to leakage of the hollow container, and determining the presence / absence of leakage from the hollow container based on the amount of decrease in internal pressure.