JPH10253486A - Device and method for detecting leak from airtight housing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable leaks from the junction of a carburetor to be detected easily. SOLUTION: An opening in a carburetor 1 except an inlet and an outlet for a test fluid is hermetically closed, and the test fluid is circulated inside the carburetor 1. Under these conditions, an AE(acoustic emission) signal produced by the circulation of the test fluid is detected using an acoustic sensor 8 mounted on the exterior wall surface of the carburetor 1 and the level of the AE signal is determined to detect whether or not the junction of the carburetor 1 is having a leak. In particular, the AE signal obtained by the acoustic sensor 18 is squared and integrated to determine its level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembly structure in which a plurality of block bodies are joined together, and the joint can be easily leaked in an airtight housing through which fluid flows, for example, a carburetor used in an internal combustion engine. Further, the present invention relates to a leak detecting device and a leak detecting method for an airtight housing capable of detecting with high accuracy.

[0002]

2. Description of the Related Art A carburetor used in an internal combustion engine is for forming a mixture of fuel and air. For example, a carburetor includes a first block body forming a carburetor body having a throttle valve and the like incorporated therein. , And a second block body that constitutes a fuel float chamber. The carburetor body has a structure in which a venturi is formed between the air inlet and the air-fuel mixture outlet, and a fuel injection nozzle is provided inside the venturi.

[0003] By the way, the integration of the above-mentioned block body is performed as follows.
The joint is hermetically sealed with a sealing member such as an O-ring interposed on the mounting surface forming the joint. The hermetic sealing of this joint not only prevents fuel leakage from the float chamber formed by the second block body, but also maintains the negative pressure obtained by the venturi of the carburetor body, and Thus, it plays an important role in sucking up fuel from the float chamber and mixing it with air. By the way, if the airtightness at the joint is not sufficiently ensured, for example, it is impossible to secure a negative pressure due to air entering from the leak, and it is difficult to suck up fuel from the float chamber and mix it with air. Becomes

[0004] An airtightness test of a joint in an assembly structure such as the carburetor described above, a so-called airtight housing,
As a simple test method, all of the openings are closed and immersed in a test liquid such as soapy water in this state to cause air leakage from the inside of the airtight housing (assembled structure). This is done by visually observing whether or not bubbles are generated. For this reason, there is a problem that the test efficiency is very poor, and furthermore, a quantitative leak determination cannot be performed. It has also been difficult to detect minute leaks with high accuracy.

On the other hand, to detect leakage in a pressure-resistant container or the like,
The use of acoustic sensors has been proposed. For example, Japanese Patent Application Laid-Open Nos. 53-100292 and 7-15920
Japanese Patent Application Laid-Open No. 7-1995 discloses detecting an AE wave (acoustic emission) generated by leakage of pressurized or depressurized fluid (air) contained in a container using the acoustic sensor, and for example, detecting the frequency spectrum pattern thereof. A technique is disclosed in which a flaw that causes a leak is analyzed to analyze the flaw.

[0006]

However, the above-described technique for detecting a leak in a pressure-resistant container or the like using an acoustic sensor is as follows.
Since air at a predetermined pressure is sealed in a container or the like to be inspected and the inspection is performed in a sealed state, it is undeniable that the inspection itself becomes large-scale. In addition, since it is necessary to seal the container under a predetermined pressure, there is a problem that the configuration of the inspection apparatus for realizing the sealed structure becomes large.

Japanese Patent Application Laid-Open No. 1-98938 discloses that an acoustic sensor is attached to a cylinder body, and the cylinder is operated by applying a predetermined pressure.
There is disclosed a technique of detecting an E wave and detecting a minute internal leak (leakage) of the cylinder from the number of appearances of an AE signal exceeding the noise level. According to this technique, it is not necessary to seal the cylinder, so that there is an advantage that the leak test can be performed relatively easily. However, since the cylinder must be actuated each time, it is not suitable for use in applications such as the carburetor described above, which is to be inspected before being mounted on the internal combustion engine, that is, in a state where the carburetor is just assembled. is there.

The present invention has been made in view of such circumstances, and an object thereof is to provide an assembly structure in which a plurality of block bodies are joined together, such as a carburetor used for an internal combustion engine, for example. An object of the present invention is to provide a leak detecting device and a leak detecting method for a hermetic housing having a simple configuration capable of easily and accurately detecting a leak at a joint portion in a hermetic housing through which a fluid flows.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is used for an airtight housing, such as an internal combustion engine, which comprises an assembled structure in which a plurality of blocks are joined, and through which a fluid flows. The present invention relates to a leak detection device that detects a leak at a joint portion of a carburetor, and particularly, hermetically closes an opening of the hermetic housing except for an inlet for a test fluid and an outlet for the test fluid, and connects the inlet and the outlet. Means for allowing a test fluid to flow through the closed airtight housing, an acoustic sensor attached to an outer wall surface of the airtight housing, and an acoustic sensor when the test fluid flows through the airtight housing. A obtained
AE measuring means for discriminating an E signal and detecting a leak in the hermetic housing.

In particular, when the airtight housing is formed of a carburetor, the acoustic sensor is provided in close contact with a flat bottom surface of a block constituting a float chamber of the carburetor. It is characterized in that the level of the square integration value of the obtained AE signal is determined and the degree of leakage in the hermetic housing is discriminated.

Further, in the method for detecting leakage of an airtight housing according to the present invention, the opening of the airtight housing is airtightly closed except for an inlet for a test fluid and an outlet for the test fluid, and the test fluid is sealed inside the airtight housing. And an AE signal generated by the flow of the test fluid is detected via an acoustic sensor attached to an outer wall surface of the hermetic housing, thereby detecting a leak in the hermetic housing.

That is, according to the present invention, an opening of an airtight housing composed of an assembly structure such as a carburetor is closed, and a test is performed inside the airtight housing through a predetermined inlet and an outlet for a test fluid. A fluid, for example dry air, is passed. When the test fluid flows, A is detected by an acoustic sensor attached to the outer wall surface of the airtight housing.
By discriminating the signal level of the E signal obtained by, for example, a square integration process, the leak at the joint of the hermetic housing can be easily and quantitatively detected.

That is, attention is paid to the fact that the acoustic signal (AE signal) generated by the test fluid flowing through the airtight housing changes due to the presence of the leak at the joint, and the level is discriminated. Is distinguished.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a leak detecting device and a leak detecting method for an airtight housing according to an embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a leak detection device according to this embodiment, and 1 is a carburetor used for an internal combustion engine to be inspected. The carburetor 1 has an assembled structure in which a first block 2 forming a carburetor body having a throttle valve and the like incorporated therein and a second block 3 forming a float chamber for fuel are joined and integrated. An airtight housing consisting of a body and having a joint is formed. The carburetor 1 is assembled by joining and joining the first and second block bodies 2 and 3 to each other by hermetically joining the mounting surface forming the joining portion with a sealing member such as an O-ring interposed therebetween and forming a peripheral flange. It is performed by screwing the part.

The leak detecting apparatus has a base 11 on which the carburetor 1 to be inspected is placed and which supports the bottom surface of the second block 3 constituting the float chamber of the carburetor 1 described above. A pair of columns 12, 13 provided on both sides of the base 11 have first and second closing bodies 14, 15 for airtightly closing the air introduction port 4 and the air-fuel mixture outlet 5 of the carburetor 1, respectively. Is attached. These closing bodies 14 and 15 are provided with a sealing material made of synthetic rubber or the like on the contact surface with the air inlet 4 and the air / fuel mixture outlet 5, and the air inlet 4 and the air / fuel mixture outlet 5 are provided. A function of closing the opening in an airtight manner by being pressed against a predetermined pressure.

Incidentally, in the structure shown in FIG.
Of the carburetor 1 is attached to the tip of a screw body 16 screwed to the support column 12.
And is pressed against the air introduction port 4 to hermetically close the opening. Further, the second closing body 15 is fixedly attached to the support 13, and is moved in a direction facing the air-fuel mixture outlet 5 of the carburetor 1 by adjusting the positioning of the support 13 with respect to the base 11, The opening is closed by being pressed against the air / fuel mixture outlet 5.

Further, other openings of the carburetor 1, for example, a tube 6 forming an air bypass passage are hermetically closed by connecting the tube 6 itself or by sandwiching the tube 6 with a clip 16. However, the fuel supply port 7 communicating with the fuel float chamber of the carburetor 1 is kept open, for example, as an inlet for dry air as a test fluid. A discharge pipe 17 communicating with the inside of the carburetor 1 is provided at a central portion of the second closing member 15 as a discharge port for dry air introduced into the carburetor 1 from the fuel float chamber through the fuel supply port 7. Is attached.

That is, the carburetor 1 mounted on the base 11 has an opening except for a fuel supply port 7 used as an inlet for dry air as a test fluid and a discharge pipe 17 forming the discharge port. Each part is airtightly closed. A pressure gauge P for monitoring the introduction pressure of the dry air is attached to a dry air introduction pipe connected to the fuel supply port 7. The discharge pipe 1
A flowmeter (anemometer) F for measuring the amount of air discharged from the carburetor 1 is attached to the tip of the carburetor 1. As the introduction pipe and the discharge pipe 17, those having a length of, for example, 1 m or more are used so as not to affect detection of an acoustic (AE) signal described later. That is, care is taken so that external vibrations and the like are not applied to the carburetor 1 through these pipes.

On the other hand, the base 11 is provided with an acoustic sensor 18 which is in close contact with a flat bottom surface of the second block 3 forming the fuel float chamber of the carburetor 1 mounted on the base 11. Have been. In particular, the acoustic sensor 18 is provided on the base 11 via a cushion member 19,
The carburetor 1 is supported by the weight of the carburetor 1 on the flat bottom surface of the second block body 3 so that the sensor surface thereof comes into close contact with the carburetor 1 uniformly.

The acoustic sensor 18 is composed of, for example, an AE (acoustic emission) sensor with a built-in head amplifier, and has an acoustic (A) frequency of 180 to 300 kHz.
E) Plays the role of detecting signals with high sensitivity. The acoustic (AE) signal detected by the acoustic sensor 18 is guided to an AE measuring device 20 configured as shown in FIG. 2 and is used for leak detection at a joint of the carburetor 1.

As shown in FIG. 2, the AE measuring device 20 includes a preamplifier 21 for amplifying an acoustic (AE) signal obtained from the acoustic sensor 18 to a predetermined signal processing level.
And a filter 22 for filtering the output of the preamplifier 21 in a predetermined frequency range to remove noise components. Further, the AE measuring device 20 includes, for example, a microprocessor, and performs a square integration process on a level of the AE signal extracted through the filter 22 according to a predetermined arithmetic program. AE signal level (double integrated value)
A discriminator 24 for discriminating the leakage at a predetermined decision level (threshold) to determine whether or not a leak is recognized at the joint of the carburetor 1; and a display 25 for displaying a discrimination result by the discriminator 24. It is composed.

To detect a leak at the joint of the carburetor (airtight housing) 1 using the leak detecting device configured as described above, the carburetor 1 is set on the base 11 as described above, and the air inlet 4 and the like are set. With the opening closed, dry air is introduced from the fuel supply port 7 at a low pressure of about 0.2 to 0.4 kg / cm ² , and the dry air is supplied to the carburetor 1 as shown by a dashed line X in FIG. This is performed by detecting an acoustic (AE) signal required via the acoustic sensor 18 while discharging from the discharge pipe 17 through the inside of the device. That is, while controlling the pressure and flow rate of the dry air flowing through the carburetor 1 using the pressure gauge P and the flow meter F, the leak test is performed in a state where the flow state is stabilized. Then, in a state where dry air as a test fluid is flowing through the carburetor 1 stably, for example, in a state where the introduction pressure of the dry air is constant, an acoustic signal generated in the dry air as the flowing fluid is supplied to the acoustic sensor. This is done by detecting via 18.

In particular, sound (AE) detected as described above
The sound (AE) signal is evaluated by performing a square integration process on the signal and effectively obtaining an average value of the signal level. The effective signal level is determined as a predetermined determination level (threshold). The comparison discriminates whether or not a leak has occurred at the joint of the carburetor 1.

Thus, according to the leak detection method executed in this manner, when there is no leak at the joint of the carburetor 1, the dry air introduced into the carburetor 1 is discharged without stagnating inside thereof. It is discharged outside through a pipe 17. At this time, since the dry air flowing through the carburetor 1 only receives the flow resistance caused by the internal structure of the carburetor 1, the level of the acoustic signal generated by the flow of the dry air does not increase so much. It is kept at an almost constant low level.

However, if there is a leak at the joint of the carburetor 1, the flow of the dry air is disturbed by the leak, and the level of the acoustic signal generated by the flow of the dry air is increased due to the disturbance. Moreover, a new acoustic signal is generated due to the leakage of dry air from the joint. Then, the acoustic sensor 18 detects an acoustic (AE) signal in a state where the acoustic signal component caused by the leakage is added, so that the signal level is significantly increased.

For example, as shown in FIG. 3, the level of the acoustic (AE) signal in a state where there is no leakage is relatively low and substantially constant as shown by a characteristic A. On the other hand, when a leak occurs at the joint, an acoustic signal component due to the leakage of dry air from the joint is added.
As shown in FIG. 5, the level of the acoustic (AE) signal increases depending on the degree of the leakage, and the level of the leakage shows a large variation with time. The AE measuring device 20 monitors the effective level of the sound (AE) signal that changes in this way, and compares the level with a predetermined determination level D to detect the presence or absence of leakage at the joint. It has become something.

Therefore, according to the leak detecting device and the leak detecting method for detecting the leak at the joint portion of the carburetor 1 as described above, the acoustic signal is detected while the dry air as the test fluid is passed. It is not necessary to particularly increase the pressure of the dry air introduced into the carburetor 1,
A leak test can be easily performed at low pressure. Moreover, since it is different from the one that detects the leakage of the air sealed in the container, such as a leak test in a closed container, it is not necessary to instantaneously detect the acoustic signal generated by the leakage, and the dry air flows. It can be detected constantly over a period of time. Therefore, the configuration of the detection device itself can be simplified.

Further, since it is not necessary to seal the inside of the carburetor 1 at a high pressure, the structure for hermetically closing the opening can be simplified, and the configuration of the entire apparatus can be simplified. . In particular, according to the leak inspection apparatus having the structure shown in FIG. 1, the installation (set) of the carburetor 1 to be inspected and the replacement thereof are easy, so that effects such as the efficiency of the inspection work can be achieved.

The acoustic signal generated in the dry air flowing through the carburetor 1 also changes due to the presence of a slight leak. Therefore, the above-described inspection method enables highly accurate leak detection. In addition, it is possible to quantitatively evaluate the magnitude of the leak as a change in the level of the acoustic signal. Therefore, in a shipping inspection stage or the like in a state in which the carburetor 1 is assembled as a single unit, the airtightness at the joint thereof can be simplified, and a highly accurate and objective inspection can be performed.

In the structure shown in FIG. 1 described above, low-pressure dry air is introduced into the carburetor 1 from the fuel supply port 7 thereof, and the dry air is supplied from the discharge pipe 17 attached to the mixture supply port 5. While discharging, an acoustic signal generated at that time in the dry air was detected. That is, a leak test was performed by flowing dry air from the float chamber formed by the second block body 3 toward the carburetor body.

However, according to the usage of the carburetor 1, since the float chamber is maintained at a negative pressure, the fuel supply port 7 is closed airtight by a clip or the like as shown in FIG. Alternatively, dry air may be introduced from above. That is, in this case, the first closing member 14 that closes the air inlet 4 is provided with a dry air inlet pipe communicating with the air inlet 14, and a predetermined pressure is introduced into the carburetor body through the inlet pipe. Dry air may be introduced. Then, the introduced dry air may be discharged from the mixture air outlet 5 via the discharge pipe 17.

In this way, the dry air introduced into the carburetor body generates a negative pressure when passing through the venturi and sucks the air in the float chamber, so that the pressure in the float chamber is reduced. Then, if there is a leak at the joint, air will enter from the leaked part due to the negative pressure, so that the flow of dry air is disturbed as in the above-described embodiment, and Is changed, and a new sound signal is generated by the air entering from the leak portion. Therefore, by measuring the sound signal that changes in this way as described above, it is possible to quantitatively and easily inspect the leak at the joint, as in the previous embodiment. That is, the leak test can be performed in the same manner only by the difference between the positive pressure and the negative pressure in the float chamber.

Depending on the form of the hermetic seal defect at the joint, the degree of leakage may change between the above-described positive pressure and negative pressure cases. For example, leakage may easily occur from the float chamber to the outside depending on the state of the sealing member interposed at the joint, but may not easily occur in the reverse direction. Therefore, it goes without saying that the above-described two types of inspections may be performed, and the inspection results may be comprehensively evaluated to determine the airtightness of the joint. In addition, if such an inspection form is adopted, it is possible to determine the degree of leakage (the form of leakage) and to estimate the cause thereof, and so forth.

The present invention is not limited to the above embodiment. For example, since the level of an acoustic signal due to leakage greatly changes depending on the degree of leakage, the determination level is set as a plurality of levels, and the degree of leakage is objectively determined according to the result of discrimination at each level. You may do it. In this way, it is possible to make a certain determination as to whether the leakage is due to a failure in fastening the joint or a result of a sealing member such as an O-ring.

Further, in the embodiment, the acoustic sensor 18 is provided so as to be in close contact with the flat bottom surface of the second block 3 constituting the fuel float chamber of the carburetor 1. Of course, it is also possible to configure so as to adhere. Further, an assembly structure other than the carburetor 1, for example, a structure formed of a pipe joint, a joint structure between a fluid nozzle to be mounted on the carburetor and a carburetor body, or a hermetic housing such as a valve structure including a check valve or a pump. It goes without saying that the present invention can be similarly applied to leak inspection. Similarly, the present invention can be applied to an airtightness inspection of a joint in measuring instruments having a waterproof / explosion-proof structure. In short, the present invention can be variously modified and implemented without departing from the gist thereof.

[0036]

As described above, according to the leak detection device and the leak test method according to the present invention, the test fluid, such as dry air, is passed through an airtight housing composed of an assembly structure while flowing the dry fluid. The leak at the joint of the hermetic housing is detected by detecting an acoustic signal generated by the above and discriminating an accidental level of the acoustic signal, so that a leak test can be performed easily and efficiently. . In particular, since the leak detection can be performed only by passing a low-pressure test fluid without pressurizing or depressurizing the inside of the hermetic housing, the operation procedure of the leak inspection is very simple.

Furthermore, since the airtight housing is essentially different from the one in which high-pressure air is sealed, there is no need to instantaneously detect an acoustic signal caused by a leak, and during the period when the test fluid is flowing, The leak test can be performed while constantly detecting the acoustic signal over the entire area. Therefore, it is not necessary to take measures such as increasing the processing speed in the AE measuring device or devising the sampling timing of the acoustic signal, and further, it is not necessary to devise such as storing the acoustic signal and providing it to the signal processing. Discrimination against leakage can be easily performed only by general-purpose signal processing of a general processing speed. In addition, there is a great effect in practical use such as a leak test can be quantitatively and accurately performed from the level of the acoustic signal while simplifying the configuration of the entire detection device and reducing the cost thereof. Especially when the airtight housing is a carburetor,
Since it is required to evaluate its characteristics before installation in an internal combustion engine, the practical advantages obtained by the leak detection device and the leak detection method according to the present invention are significant.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a leak detecting device for an airtight housing according to an embodiment of the present invention, and a leak detecting method thereof.

FIG. 2 is a diagram showing a configuration example of an AE measurement device in the leak detection device shown in FIG.

FIG. 3 is a diagram for explaining the operation of sound signal level determination in the leak detection device and the leak detection method according to the present invention.

FIG. 4 is a diagram showing a schematic configuration of a leak detecting device for an airtight housing according to another embodiment of the present invention, and a leak detecting method thereof.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 carburetor (airtight housing) 11 base 14 first closed body 15 second closed body 17 discharge pipe 18 acoustic sensor 20 AE measuring device 23 signal processing circuit (square integration) 24 discriminator

Claims (3)

[Claims] 1. A leak detecting device comprising an assembled structure in which a plurality of block bodies are joined and detecting leakage of an airtight housing through which a fluid flows, wherein an opening of the airtight housing is provided with a test fluid. Means for hermetically closing except for the inlet and its outlet, means for allowing a test fluid to flow inside the hermetically closed housing except for the inlet and outlet, and An acoustic sensor mounted on a wall surface; and AE measuring means for detecting a leak in the hermetic housing by discriminating an AE signal obtained through the acoustic sensor when the test fluid flows through the hermetic housing. A leak detecting device for an airtight housing. 2. The airtight housing comprises a carburetor for mixing fuel and air, and the acoustic sensor is provided in close contact with a flat bottom surface of a block constituting a float chamber of the carburetor, 2. The leak of the hermetic housing according to claim 1, wherein the AE measuring section determines a level of a square integral value of an AE signal obtained by the acoustic sensor to determine a degree of the leak in the hermetic housing. 3. Detection device. 3. When detecting leakage of an airtight housing through which a fluid flows therein, an opening of the airtight housing is provided with an inlet for a test fluid and its discharge. Except for the outlet, the test fluid flows through the airtight housing by being airtightly closed except for the outlet, and an AE signal generated by the flow of the test fluid is detected via an acoustic sensor attached to the outer wall surface of the airtight housing. And detecting a leak in the hermetic housing.