JPS6182138A - Inspecting method of pressure leak - Google Patents

Abstract

PURPOSE:To obtain the measurement result of easy, high-precision quality inspection by supplying fluid of the same pressure to a molding to be inspected and a master in the same shape, and comparing and measuring the pressure and deciding whether the molding is normal or not, and discharging the fluid to the outside every time a measurement is taken. CONSTITUTION:Compressed air from an air supply source 20 is passed through a filter 22, pressure regulator 24, and pressure gauge 26 and branched in two directions through an electromagnetic change-over valve 28. The air is sent to the body 36 to be inspected and the reference master 38 in the same shape with it through electromagnetic changeover valves 30a and 30b, filters 32a and 32b, and throttle valves 34a and 34b. A difference detector 40 measures a difference in internal air pressure between conduits 31a and 31b. The differential pressure is sent to a display device 44 through an amplifier 42 and a meter 44. A defect of the object body 36 such as cracking and a pinhole is detected from the differential pressure. When the inspection is finished, the air is discharged through a valve 48 and next inspection is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for inspecting pressure leaks in molded products including holes.
More specifically, for example, compressed air is supplied to the water jacket, cam chamber, crank chamber, oil hole, etc. of the engine part, and at the same time, the same is applied to a normal standard molded product with no pressure leaks (hereinafter referred to as the standard master). The present invention relates to a pressure leak testing method in which pressurized air is supplied and the pressure difference between a molded product to be inspected and a reference master is compared and measured over time to determine whether the molded product to be inspected is good or defective.

Water jackets for the engine parts of automobiles,
Holes in the cam chamber, crank chamber, etc. must be formed completely without air leakage, but due to casting defects, for example, cracks, pinholes, etc. may occur on the walls of the holes.

Conventionally, the walk jacket of the engine part, the cam chamber,
The following two methods are widely adopted as methods for inspecting pressure leaks due to cracks, pinholes, etc. from the wall surface of a hole in a crank chamber or the like. First of all, one of them is
This method tests for pressure leaks in the holes by supplying air in a sealed manner to the holes in the molded product, placing the molded product in a water tank, and observing whether air bubbles are generated.

However, with this method, the inspector must constantly observe the presence or absence of air bubbles, which requires a dedicated person.
In addition, there is the inconvenience that accurate inspection cannot be performed because it is performed manually. Another method is to supply air at the same pressure to the molded product to be inspected and a reference master that has the same shape as the molded product and has no pressure leaks, and then compare and measure the presence or absence of a pressure difference between each within a predetermined time. However, if a value greater than a predetermined pressure difference can be confirmed on the side of the inspected object, there is a method of determining it as a defective product. However, in this latter method, the reference master is repeatedly used, especially when mass-produced test objects are to be inspected, and thus exposes the following drawbacks. In other words, the air supplied to the reference master is not discharged to the outside, but is constantly flowing in and out of the reference master and the air pipes that circulate through this master. Heat buildup occurs on the tube wall due to air compression, which increases the air temperature in the master and in the conduit. If the inspection is continued in this state, the temperature of the air inside the reference master will become higher than the temperature of the air inside the molded product to be inspected. This is because air in the factory atmosphere is used for each inspection of the molded product that is covered and inspected, so the air temperature inside the molded product does not rise. This creates a difference in the temperature of the air supplied to the reference master and the molded product to be inspected, which manifests itself as a pressure difference. Further, during the test, a difference appears in the rate of temperature drop of the internal air between the two, which causes pressure noise and impedes accurate testing.

Therefore, as a result of intensive research and efforts, the inventors of the present invention vented the air supplied inside the reference master to the outside for each inspection, and used air at the same temperature as the object to be inspected at all times during the inspection. By doing so, the same conditions can be set for the reference master and the object to be inspected, the inspection results obtained will be extremely reliable, and a pressure leak inspection method that allows accurate inspection will be obtained, eliminating the above-mentioned disadvantages. It turned out that it would be done.

Accordingly, an object of the present invention is to provide a pressure leakage testing method that allows simple and highly accurate measurement results to be obtained in quality testing of objects to be tested in a mass production process.

In order to achieve the above object, the present invention supplies a fluid of the same pressure to a molded product to be inspected and a reference master having the same shape as the molded product, so that the pressure in the molded product and the reference master are equal to each other. The method is characterized in that the pressure is comparatively measured to determine the quality of the molded product, and the fluid supplied into the reference master is further exhausted to the outside after each measurement.

Next, the pressure leak testing method according to the present invention will be described in detail below with reference to the accompanying drawings, citing preferred embodiments in relation to the apparatus for carrying out the method.

FIG. 1 shows a piping system for carrying out the pressure leak inspection method according to the present invention.

Reference numeral 20 indicates an air supply source, this air supply source 20
The discharge side of is connected to a pressure regulator 24 via a filter 22.
connected to. The output side of the pressure regulator 24 is connected to an electromagnetic switching valve 28 . In this case, a gauge 26 is interposed between the pressure regulator 24 and the electromagnetic switching valve 28, if necessary.

On the other hand, the output side of the electromagnetic switching valve 28 is branched and connected to a first electromagnetic switching valve 30a and a second electromagnetic switching valve 30b, respectively. A pipe line 3 extending from the first electromagnetic switching valve 30a
1a further passes through a filter 32a and a throttle valve 34a to a molded product to be inspected (hereinafter referred to as an inspected object) 3.
Connect to 6 airtightly.

Similarly, a conduit 31b extending from the second electromagnetic switching valve 30b is airtightly connected to the reference master 38 from the filter 32b via the throttle valve 34b. In this case, it is preferable to interpose a relief valve 48 between the throttle valve 34b and the reference master 38, which is opened and closed by a cock.

In such a configuration, in the present invention, the electromagnetic switching valve 30a
, 30b, a differential pressure detector 4o is disposed between the pipes 31a and 31b. The output side of the differential pressure detector 40 is connected to a display 46 via a pressure amplifier 42 and a meter 44.

Therefore, a method for inspecting the presence or absence of pressure leaks in a molded product using the pressure leak inspection device having the circuit configuration as described above will be described.

Pressurized air from the air supply source 20 passes through a filter 22 to remove dust, and its pressure is adjusted to a predetermined value by a pressure regulator 24. A gauge 26 indicates the output of this pressure regulator 24. Next, the electromagnetic switching valve 2
The air branched into two directions by 8 is supplied to the inspection object 36 through the electromagnetic switching valve 30a, filter 32a and throttle valve 34a on one side, and passes through the electromagnetic switching valve 30b, filter 32b and throttle valve 34b on the other hand to the standard. The signal is supplied to the master 38. In this way, air at a predetermined pressure is introduced into the inspected object 36 and the reference master 38 under the same conditions. Therefore, the differential pressure detector 40 measures the difference in internal air pressure between the pipe line 31a and the pipe line 31b.

This measurement result is sent to a display 46 via an amplifier 42 and a meter 44. If the differential pressure is greater than a predetermined value after a predetermined time has elapsed, it is confirmed that the inspected object 36 has a defect such as a crack or a pinhole. Therefore, this inspection object 36 can be taken out as a defective product.

By the way, in the present invention, after the inspection is once completed, the air in the reference master 38 is exhausted from the air release valve 48, and air under the same conditions is supplied to the inspected object 36 and the reference master 38 during the next inspection. do.

That is, the air supplied to the object to be inspected 36 and the reference master 38 in the inspection process is cooled by the outside air during the inspection and its temperature decreases, resulting in pressure fluctuations. If the temperature of the air supplied is the same, the temperature drop and pressure fluctuation during the inspection will be the same and will not pose a problem during the inspection.

Here, Fig. 2 shows the relationship between the number of inspections and the measured values by the pressure leak inspection method according to the present invention and the conventional method.The inspection conditions were: pressurized at a pressure of 2 kg/ad for 5 seconds, balanced for 10 seconds; Measurement was performed for 5 seconds. Further, the time required for evacuation was 5 seconds.

As is clear from the figure, with the conventional method, as the number of tests increases, the measured values vary; for example, after 10 tests, the measured value has an error of up to 0.3 ^^. In this inspection method, which exhausts the air after each inspection, the measured value is almost constant, and the variation is 0.1 even after 10 inspections.
It was found that accurate testing is possible at all times because the amount is very small (mAq).

Therefore, according to the present invention, by exhausting the air in the reference master for each inspection, air is always kept at the same temperature, that is,
External air is supplied to the test object and the reference master. Therefore, even if the number of inspections increases, measurement errors can be kept to a low level. This means that it is possible to repeatedly measure test objects of the same standard produced in a mass production process using the same reference master.

Although the present invention has been described above with reference to a preferred embodiment, the present invention is not limited to this embodiment. For example, the reference master may be provided with an air exhaust port instead of an air relief valve. Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

Figure 1 is a piping diagram of an air supply system for carrying out the pressure leak inspection method according to the present invention, and Figure 2 is a graph showing the comparison between the number of inspections and measured values by the inspection method according to the present invention and the conventional method. be. 20...Air supply source 22...Filter 24...
・Pressure regulator 26...Gauge 28...Solenoid switching valves 30a, 30b...Solenoid switching valves 31a, 31b...Pipe line 32a132b...Filter

Claims (1)

[Claims] (1) Fluid of the same pressure is supplied to the molded product to be inspected and a reference master having the same shape as the molded product, and the pressure in the molded product and the pressure in the reference master are compared and measured. A pressure leak testing method characterized by determining pass/fail and further evacuating the fluid supplied into the reference master to the outside for each measurement.