JP2601098B2 - Leakage inspection method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leakage inspection method and apparatus for inspecting an amount of leakage of an object having a cavity therein, such as a fuel injection nozzle or a fuel injection pump.

[0002]

2. Description of the Related Art Various methods have been proposed for inspecting gas or liquid leaking from a cavity to the outside of a test object having a cavity. Then, as one of the inspection methods, a high-pressure gas is introduced into the cavity of the test object to make the inside of the cavity a test pressure, and then the test object is closed from a pressure source. There is a method of detecting a pressure change with a pressure gauge or the like and measuring a leak amount.

[0003]

However, according to this method, when the volume of the cavity of the object to be inspected is large, only a small pressure fluctuation occurs, and the detection accuracy of the leak amount is low. In the above method, when the test pressure of the gas introduced into the test object is high, the temperature of the gas rises higher than the outside air temperature due to adiabatic compression during pressurization, and then the heat is radiated from the test object to the outside air to be inspected. The temperature of the gas inside the body gradually decreases, and as a result, the gas inside the body to be inspected fluctuates even if the body to be inspected does not leak.

If the temperature of the test object is different from the temperature of the surrounding gas, the temperature of the test object and the temperature of the gas change after the test pressure is applied, so that the temperature becomes the same. Pressure fluctuation occurs in the air pressure inside the test object. For this reason, this pressure fluctuation affects the leakage amount, and lowers the detection accuracy. Further, in order to avoid this, it is necessary to measure the pressure fluctuation due to leakage after the temperature of the gas inside the test object reaches equilibrium (after it does not change), and the inspection requires a long time.

In view of the conventional problems, the present invention can detect a small amount of leakage even when the volume of the cavity is large, and is not affected by the magnitude of the test pressure or the temperature of the test object. And a highly accurate leak inspection method and apparatus.

[0006]

According to the present invention, a test object having a cavity is placed in a sealable test tank containing a liquid, the test object is buried in the liquid, and a gas volume is provided above the liquid. After the test tank is closed, the gas volume is reduced and the pressurized fluid is introduced into the cavity of the test object. The leakage inspection method is characterized by measuring the amount of leakage of the object to be inspected by detecting the leakage.

In the present invention, it is most remarkable that the object to be inspected is buried in a sealable inspection tank containing a liquid and a gas volume is formed above the inspection tank. The inspection tank is closed and the gas volume is decompressed. On the other hand, a pressurized fluid is introduced into the cavity of the test object, and the pressure change in the gas volume depressurized is detected. Is to do.

As the above-mentioned inspection object, there are, for example, those having a relatively large volume of a hollow portion, such as a fuel injection nozzle and a fuel injection pump used for a diesel engine. Of course, the present invention can also be applied to a method of inspecting a test object for leaks in which the volume of the cavity is small. As a liquid for burying the test object,
Usually, water is used, but there are light oil, brake oil, cleaning oil, and the like.

The gas volume is a gas remaining portion formed between the upper surface of the liquid and the ceiling of the test tank when the test object is buried in the liquid. This gas volume is depressurized prior to the leakage inspection. A pressurized fluid for leak inspection is introduced into the cavity of the inspection object. As the pressurized fluid, a pressurized gas is usually used, but a pressurized liquid can also be used. Examples of the gas include air and nitrogen gas.

[0010] As an apparatus for carrying out the above-mentioned leak inspection method, a sealable inspection tank for holding an object to be inspected having a cavity, and a liquid supply for introducing a liquid into the inspection tank via a sealing valve are provided. , A pressure reducing device for reducing the gas volume formed above the liquid in the inspection tank, a pressure measuring device for detecting a pressure change in the gas volume, and pressurizing the cavity of the device under test. Based on the pressurizing device that introduces fluid and the result of pressure change
Measuring device for measuring the amount of pressurized fluid leakage from the test object
There is a leak inspection device characterized by comprising a device.

There is a pump as a liquid supply device for introducing a liquid into the inspection tank. As a decompression device for decompressing the gas volume, there is a piston cylinder. As a pressure measuring device for detecting a pressure change, for example, there are various pressure sensors using a strain gauge or the like. Further, when a calibration piston capable of changing the volume by a certain amount is used as shown in the embodiment as the pressure reducing device, the leak amount can be detected more accurately and automatically. Ma
Also, as shown in the embodiment,
It has the function of calculating the amount of body leakage. That is, the measurement
The position is based on the pressure change detected by the above pressure gauge.
And only the presence or absence of leakage of pressurized fluid
In addition, the amount of leakage can be accurately measured.

[0012]

In the leak inspection method of the present invention, the object to be inspected is buried in the liquid in the sealable inspection tank, and a gas volume is left above the inspection tank. The above-mentioned gas volume in the test tank in the state is set to a reduced pressure state, while a pressurized fluid is introduced into the cavity of the test object. After that, it is left for a certain period of time, and the pressure change in the gas volume is detected. At this time, if there is a leak in the test object, the pressure of the gas volume part in the decompressed state increases. If there is no leak, there is no pressure change. Therefore, the leak amount can be calculated from the pressure change amount and the gas volume.

In the present invention, in the leak amount inspection, a small volume of the gas volume is formed above the inspection tank, and a pressure change per predetermined time is detected. Therefore, even if the amount of leakage is very small, the above-described pressure change appears significantly, and the amount of leakage can be accurately detected. Therefore, the leak amount can be detected accurately even in the case of the test object having a large cavity volume.

Further, in the present invention, the pressure change is detected after the gas volume is depressurized. Therefore, even if there is a leak in the inspection tank, the leak acts in the direction of increasing the pressure similarly to the leak from the test object.
Therefore, even if there is a leak in the inspection tank, a defective product (large leak amount) of the test object is not determined to be a good product (small leak amount). That is, fail safe
It also has functions.

Further, the liquid in which the object to be inspected is buried has a much larger heat capacity than gas. Therefore, even if the temperature of the gas inside the test object rises due to pressurization, or if there is a relatively large temperature difference between the test object and the liquid during the test, the liquid temperature change is small and the liquid tank Has little effect on the gas pressure change in the gas volume formed above.

Further, whatever the amount of liquid to be introduced into the inspection tank, it is sufficient if there is an amount by which the object to be inspected is buried. That is, since the present invention detects the pressure change in the gas volume, the amount of liquid introduced into the inspection tank is irrelevant. Therefore, preparation for inspection is easy. In addition, the same effect can be obtained in the above inspection apparatus. Therefore, according to the present invention, even when the volume of the cavity is large, a small amount of leakage can be detected, and a high-precision leakage inspection method that is not affected by the magnitude of the test pressure or the temperature of the test object. And an inspection device can be provided.

[0017]

【Example】

Embodiment 1 A leakage inspection method and apparatus according to an embodiment of the present invention will be described with reference to FIGS. First, as shown in FIG. 1, an inspection apparatus according to the present embodiment includes a sealable inspection tank 2 in which an object to be inspected 1 having a hollow portion is inserted, and the inspection tank 2.
It has a liquid supply device 25 for introducing the liquid 21 therein through a sealing valve 261 and a pressure reducing device 3 for reducing the pressure of the gas volume 22 formed above the liquid 21 in the inspection tank 2.

Further, it has a pressure measuring device 40 for detecting a pressure change in the gas volume section 22 and a pressurizing device 13 for introducing a pressurized fluid into the cavity of the device under test 1. The liquid 21 is
It is stored in a liquid tank 210 provided separately from the inspection tank 2. Water is used as the liquid 21. As the liquid supply device 25, a liquid pump is used. A liquid introduction pipe 2 is provided between the liquid tank 210 and the inspection tank 2.
51 are connected.

On the other hand, a return pipe 252 for returning the liquid overflowing in the inspection tank 2 to the tank 210 is provided between the upper part of the inspection tank 2 and the liquid tank 210.
Is provided. Electromagnetic sealing valves 261 and 262 for sealing the inside of the inspection tank 2 are interposed between the liquid introduction pipe 251 and the return pipe 252, respectively. A pressurized fluid introduction pipe 11 is connected to the test object 1 between a cavity (not shown) and a pressurizing device 13 via an electromagnetic sealing valve 12. As the pressurizing device 13, an air compressor is used.

Next, the pressure reducing device 3 and the pressure measuring device 40 are connected to the gas volume 22 of the inspection tank 2 via a measuring pipe 41. The pressure reducing device 3 has cylinders 32 and 35. The cylinder 32 has a pressure reducing chamber 30 and a rear chamber 322 via the calibration piston 31. The decompression chamber 30 is connected to the measurement pipe 41 via a pipe 33.

The cylinder 35 is provided with a working piston 35.
A first chamber 351 and a second chamber 352 are provided through the first chamber 351. The calibration piston 31 and the working piston 350 are integrally connected by a connecting rod 37. 1st room 351, 2nd room 3
52 is connected to an operating air source 381 via pipes 361 and 362 switching valve 38. On the other hand, the pressure measuring device 40 is connected to a measurement control device 45 via an amplifier 42. The measurement control device has a display unit 43 and a recording unit 44.

Next, the inspection method will be described. First, the test object 1 to which the pressurized fluid introduction pipe 11 is connected is put into the test tank 2. Further, the lid 20 of the inspection tank 2 is sealed. Next, the sealing valves 261 and 262 are opened, and water as the liquid 21 is introduced from the liquid supply device 25 into the inspection tank 2. Then, when the inspection object 1 in the inspection tank 2 is buried in the liquid 21 and the liquid 21 overflows from the inspection tank 2, the sealing valves 261 and 262 are closed.

As a result, a gas volume 22 is formed above the inspection tank 2, and the inspection tank 2 is sealed.
The sealing valves 261 and 262 are opened and closed by a signal from the measurement control device 45. Next, the pressure reducing device 3 is operated to bring the gas volume 22 into a reduced pressure state. That is, the switching valve 3
8 is actuated by the measurement control device 45, and pressurized working air is injected into the first chamber 351 side of the cylinder 35. As a result, the working piston 350 is pushed toward the second chamber. Therefore, the calibration piston 31 of the cylinder 32 is pulled toward the rear chamber 322 by the connecting rod 37.

It is important to note that the calibration piston 31
As a result, the pressure in the decompression chamber 30 is reduced, and the pipe 33, the measuring pipe 41, and the gas volume 22 are also reduced in pressure. Further, when the calibration piston 31 retreats by the distance A, a constant volume change ΔV is given in the decompression chamber 30 (refer to a calculation formula described later). In this state, the calibration piston 31 is stopped and the gas volume 2
The reduced pressure state in 2 is measured by the pressure measuring device 40 and the measurement control device 45.

That is, the pressure inside the gas volume section 22 becomes lower than the atmospheric pressure as shown in FIG. 2, and the reduced pressure amount is recorded as Pcal. Next, the pressurized fluid introduction pipe 1 is inserted into the cavity of the test object 1 placed in the test tank 2.
1, pressurized air (for example, 10 k
g / cm ² ). This introduction is performed by opening and closing the sealing valve 12 by the measurement control device 45.

Thereafter, while maintaining this state, the amount of leakage in a certain time is detected. FIGS. 2 and 3 show the detection results of the leakage amount. FIG. 2 shows a case where there is a leak in the test object, and FIG. 3 shows a case where there is no leak. When there is a leak, as shown in FIG. 2, the pressure in the gas volume increases by ΔP over a certain period of time (for example, 10 seconds), starting from the time of pressurizing the test object 1.

In the same figure, a line 81 indicates a period before the operation of the calibration piston, a line 82 indicates a reduced pressure state during the operation of the calibration piston, and a line 83 indicates a pressure change during the inspection. FIG. 3 shows the same relationship as FIG. 2, but shows a parallel line 830 at a constant pressure even after pressurization because there is no leakage.

Therefore, the measurement control device 45 calculates the leakage amount _VL according to the following equation based on the measurement results shown in FIG. V _L = (ΔV / Pcal) × ΔP × (60 / t) V _L ; Leakage amount (cm ³ / min) ΔV; Volume change of calibration piston (cm ³ ) Pcal; Pressure change during operation of calibration piston (mmH)
Pressure change in detection time _{(mmH 2 O) t;;} 2 O) ΔP detection time (in seconds)

The leak amount obtained by the above equation is compared with a reference value, and the pass / fail is displayed and recorded on the display 43 and the recorder 44. As is known from the above, in this example, a small gas volume 22
Is formed, and the pressure change ΔP is detected. Therefore, even if the leakage amount is very small, the pressure change ΔP is large, so that the leakage amount can be accurately detected. Therefore, the leak amount can be detected with high accuracy even in a test object having a large cavity volume.

Further, since the pressure change is detected after the gas volume 22 is depressurized, even if the inspection tank 2 is leaked, the leak acts in the direction of increasing the pressure of the gas volume 22. Therefore, the test object 1 with a large leak amount is
There is no fail-safe function, and it has a fail-safe function. In this example, since the pressure is reduced by providing the calibration piston 31 in the cylinder 32,
The above volume change (ΔV) from the movement amount A of the calibration piston 31
Can be easily measured.

The liquid 21 buried in the test object 1 is
It is water and has a much larger heat capacity than air. Therefore, even if the temperature difference between the liquid 21 and the test object 1 is large, the change in pressure is not affected. Inspection is performed in the gas volume 22
Since the pressure change is detected, the inspection tank 2
The liquid 21 in the inside may be an amount that buryes the test object 1, and the amount does not need to be the same for each measurement. Therefore,
Preparation for inspection is also easy. In this example, the volume change ΔV
Was performed by the calibration piston 31, but this volume change can be performed by a bolt screw method other than the calibration piston.

Embodiment 2 A specific measurement example using the inspection apparatus of Embodiment 1 will be described. Inspection tank volume; . . 3600 cm ³ gas volume; . . Gas volume change of 7 cm ³ calibration piston; ΔV = 0.027 cm
³ Pressure change during calibration piston operation; Pcal = 26 mmH
Pressure change during ₂ O detection time; ΔP = 5 mmH ₂ O detection time; t = 10 seconds

When the above measured value is calculated by the above equation, the leakage amount V _L (cm ³ / min) is as follows. V _L = (ΔV / Pcal) × ΔP × (60 / t) = (0.027 / 26) × 5 × (60/10) = 0.031 (cm ³ / min)

[Brief description of the drawings]

FIG. 1 is an overall explanatory diagram of an inspection apparatus according to a first embodiment.

FIG. 2 is a diagram showing a pressure change when a test object has a leak in the first embodiment.

FIG. 3 is a diagram showing a pressure change when the object to be inspected has no leak in the first embodiment.

[Explanation of symbols]

 1. . . Test object, 13. . . Pressure device, 2. . . Inspection tank, 21. . . Liquid, 22. . . Gas volume, 25. . . Liquid feeder, 3. . . Decompression device, 31. . . Calibration piston, 30. . . Decompression chamber, 40. . . Pressure measuring instrument,

Claims (2)

(57) [Claims] 1. A test object having a cavity is placed in a sealable test tank containing a liquid, the test object is buried in the liquid, and a gas volume is formed above the liquid. After the test tank is closed, the gas volume is depressurized and a pressurized fluid is introduced into the cavity of the test object, and then the pressure change in the gas volume is detected. A leakage inspection method characterized by measuring the amount of leakage of an object to be inspected. 2. A test tank having a cavity, which is capable of being closed and containing an object to be tested, a liquid supply device for introducing a liquid into the test tank via a sealing valve, a decompressor also depressurizing the gas volume portion formed above, a pressure measuring device for detecting a pressure change in the gas volume, and the pressure device for introducing a pressurized fluid into the cavity of the test subject, the pressure Based on the detection result of pressure change in the measuring instrument
A leakage inspection device comprising: a measurement device for measuring a leakage amount of a pressurized fluid from a test object.