JPH09166515A - Leak test device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a leak test device to test plural kinds of works without complicating a pneumatic circuit and reduce the cost. SOLUTION: In the leak test device, after preset pressure supplied to both of a work W and a comparison work 10 is lowered to a test pressure, according to the change of a differential pressure between both within a fixed time, the air-tightness of the work W is tested. A pressure sensor 25 for detecting the supplied pressure is disposed in a second path (b) for supplying the compressed air from an air source 1 to the work W and the comparison work 10. A controller for controlling the device is provided with a storage means, thereby storing pre-pressure data showing the pre-pressure corresponding to the kind of a work. At the time of testing, pressurizing data corresponding to the kind of a work to be tested is read out, and on the other hand, when the pressure detected by the pressure sensor 25 reaches the preset pressure shown by the read-out pressurizing data, the supply of compressed air to the work W and the comparison work 10 is ended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leak test device for inspecting air tightness in a work.

[0002]

2. Description of the Related Art Conventionally, this type of leak test apparatus has been
For example, there is the one shown in FIG. That is, in the leak test apparatus, the compressed air supplied from the air source 1 in the factory is supplied to the first path a provided with the first electromagnetic valve 2 and the first stop valve 3 and the first regulator 4. , The air relay 5, and the second path b provided with the second stop valve 6 to supply the work W to the work W, while a part of the work is supplied to the air relay 5, the second and third solenoid valves 7, 8 and the structure which supplies to the comparison work 10 which is a reference | standard master via the 3rd stop valve 9. In addition, comparison work 1
0 has the same shape as the work to be inspected, and has no leak at all because the internal airtightness is secured.

The air relay 5 is connected to a pressure switch 11 which operates when the internal pressure of the air relay 5 reaches a predetermined pressure and closes the air relay 5. A fourth solenoid valve 12 and a second regulator 13 are provided between the air source 1 and the second solenoid valve 7, and further detect the differential pressure between the work W side and the comparison work 10 side. The differential pressure sensor 14 is provided in parallel with the second solenoid valve 7. The output of the differential pressure sensor 14 is amplified by the amplifier 15 and can be directly read by the meter 16 connected thereto. In addition, a fourth stop valve 17 is provided between the first and second paths a and b, and the first stop path a of the air flow rate supplied to the work W and the comparison work 10 is provided in the first path a. A master flow meter 18 for setting a limit value is connected via a fifth stop valve 19 and a throttle valve 20.

In the leak test apparatus having such a configuration, the leak test of the work is performed by the following operation under the control of the controller (not shown). First, the first to third solenoid valves 2, 7, 8 are opened, and compressed air is supplied from the air source 1 to the work W and the comparative work 10 at the same time. Then, when the pressure on the work W side and the comparison work 10 side rises to a predetermined pressure, that is, a set preload determined by the type of work, the pressure switch 11 operates to move from the second path b to the work W and the comparison work 10. The compressed air supply is shut off. At the same time, the first solenoid valve 2 is closed and the fourth solenoid valve 12 is opened, the surplus air pressure is released by flowing back through the second regulator 13, and the sealed air pressure of the workpiece W and the comparative workpiece 10 is tested from the set preload. The pressure automatically drops. The heat exchange between the work W and the air is accelerated in a short time by this pressurization and discharge. And
This state has passed a predetermined time (several seconds) and the work W
When the pressure on the side of the comparison workpiece 10 becomes stable, the second and fourth
The electromagnetic valves 7 and 13 are closed, and the differential pressure sensor 14 detects the differential pressure between the work W side and the comparison work 10 side.

Then, the quality of the work W is judged based on the fluctuation amount of the differential pressure within a fixed time. That is,
When the variation amount of the differential pressure exceeds the upper limit set value, it is determined that the workpiece W is defective because the leak amount in the work W exceeds the allowable range, while the variation amount of the differential pressure is set to the upper limit set value. If the value does not exceed the lower limit set value, the work W is determined to be normal. Further, as described above, before the test pressure is supplied to the work W and the comparative work 10, the set preload larger than the test pressure is once supplied, so that the work W and the comparative work 1
The time to stabilize the pressure on the 0 side can be shortened.

[0006]

However, in such a conventional leak test apparatus, the pressure switch 11 detects that the internal pressures of the workpiece W and the comparative workpiece 10 have reached the set preload during inspection. The structure was such that the set preload was fixed. Therefore, in order to inspect different types of workpieces W with the same leak tester, a plurality of pressure switches capable of detecting the set preload suitable for only the types of workpieces W to be inspected are prepared, and if necessary, those switches are used. Must have a switchable structure. As a result, the air circuit is complicated and the cost of the device is high.

The present invention has been made in view of such conventional problems, and provides a leak test apparatus capable of inspecting a plurality of types of works without complicating the air circuit and at a low cost. The purpose is to do.

[0008]

In order to solve the above-mentioned problems, according to the present invention, a set preload is supplied to both the work and the comparison master, and the internal pressure of both is once reduced to the test pressure. , In a leak test device for inspecting the airtightness of the work based on the change in the differential pressure between the work and the comparison master within a fixed time, a plurality of preload data indicating set preloads respectively corresponding to different types of works are provided. Pre-stored storage means, pre-load data reading means for reading pre-load data indicating the set pre-load corresponding to the workpiece to be inspected from the storage means, and a pressure sensor for detecting internal pressure in both the workpiece and the comparison master. The pressure detected by the pressure sensor is the set preload indicated by the preload data read by the preload data reading means. When matched, was that a signal output means for outputting a signal indicative thereof.

In such a configuration, during the inspection, the preload data reading means reads out the preload data indicating the set preload corresponding to the work to be inspected from the storage means, while the preload data is supplied to the work and the comparison master by the pressure sensor. When the detected pressure matches the set preload indicated by the preload data read from the storage means, the signal output means outputs a signal notifying it. Therefore, it is possible to supply different set preloads to different types of works using the same pressure sensor without providing a pressure switch for each type of works to be inspected as in the conventional case.

Further, based on a temperature sensor for detecting the temperature of the work and the temperature detected by the temperature sensor,
With the correction means for correcting the set preload indicated by the preload data read by the preload data reading means, the set preload is automatically corrected to a pressure according to the temperature of the work.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. That is, FIG. 1 is an air circuit diagram in the case where the present invention is applied to the leak test device described with reference to FIG. Hereinafter, the same parts as those in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described. In the leak test device according to the present embodiment, a pressure sensor 25 is provided in the second path b described above, instead of the first regulator 4, the air relay 5, and the pressure switch 11 described above. The pressure sensor 25 detects the internal pressure of the workpiece W and the comparative workpiece 10 and outputs the internal pressure to the controller 26 shown in FIG. The controller 26 includes a pressure sensor 25
And the first to fourth solenoid valves 2, 7, 8, 12 and the amplifier 1
5. Temperature sensor 2 detachably attached to the work W
7 are respectively connected.

Although not shown, the controller 26 includes a CPU for controlling the entire apparatus according to a predetermined program, a ROM storing the program, preload data indicating a plurality of set preloads corresponding to different kinds of works, and A RAM that is a storage unit that stores in advance various data necessary for the operation of the controller 26, and that has a backup power supply and that can hold the stored data;
It is composed of a timer and the like. The CPU implements the preload data reading means, the signal output means, and the correction means of the present invention. Although not shown, the controller 26 is connected with “OK” lamps and “NG” lamps that notify the inspection result by lighting, an input device for inputting various data, and the like. Various signals can be output to other devices in the factory.

Next, the operation at the time of inspection in the leak test apparatus having the above configuration will be described according to the control flowchart of the controller 26 shown in FIG. That is, the controller 26 reads the preload data corresponding to the work W from the RAM at the start of the inspection (S1), and then the set preload indicated by the preload data read based on the temperature of the work W detected by the temperature sensor 27. Is corrected (S2). More specifically, the temperature of the work W is calculated by a predetermined calculation formula using the detected temperature and a temperature compensation coefficient determined by various conditions unique to each work W such as the inner volume, shape, and material of the work W. The most suitable preload for is calculated. After that, the sensitivity of the meter 16 is reduced by reducing the magnification of the amplifier 15, while the first to third electromagnetic valves 2, 7, 8 are opened, and the work W and the comparison tank 10 side are simultaneously opened from the air source 1. Compressed air is supplied, and the timer is turned on at this time to start measuring the pressurization time (S3).

Thereafter, it is judged whether or not the pressures of the work W and the comparative work 10 detected by the pressure sensor 25 have reached the corrected preload obtained in step S2 (S4), and the result of this judgment is NO. In the case of, it is continuously determined whether or not the pressurizing time has elapsed (S5). If the preload time has not elapsed (NO in S5), step S4
On the other hand, when the preload time has already passed, that is, when the work W has a large leak (Y in S5).
(ES) After outputting a signal indicating a work abnormality to the outside to notify it (S6), the inspection is ended. on the other hand,
When the pressures of the work W and the comparative work 10 reach the corrected preload and the determination result of step S4 is YES, the first solenoid valve 2 is closed and the fourth solenoid valve 12 is opened (S7). As a result, the excess air pressure is released by flowing back through the second regulator 13, and the enclosed air pressure of the work W and the comparative work 10 is automatically reduced to the test pressure. At this time, the timer is reset and turned on again at the same time to start measuring the balance time.

Subsequently, it is determined whether or not the balance time has elapsed (S8), and the state is maintained until the balance time has elapsed (NO in S8). After that, when the balance time has elapsed (YES in S8), the second solenoid valve 7 and the fourth solenoid valve 12 are closed, the timer is reset, and at the same time, it is turned on again to start measuring the test time (S9). Then, the differential pressure sensor 14 detects the differential pressure between the work W side and the comparative work 10 side, that is, the minute leak of the work, and stores the detected differential pressure in the RAM (S1).
0). At this time, the meter is switched to high sensitivity.
Next, it is determined whether the test time has passed (S
11) The state is maintained until the test time elapses (NO in S11). After that, when the test time elapses (YES in S11), the work W side and the comparison work 10 are compared again.
The differential pressure with the side is detected (S12), the previously detected differential pressure is read from the RAM, and the variation value N with the newly detected differential pressure is calculated (S13).

Subsequently, the variation value N is discriminated (S14), and if the variation value N is equal to or greater than the preset upper limit value MAX,
While the work W is judged to be defective and the "NG" lamp is turned on (S15), when the value is below the preset lower limit value MIN, the comparative work 10 is judged to be abnormal and a signal indicating this is output to the outside. By informing it by doing so (S16), the inspection ends. Then, when the variation value N is within the range that does not exceed the preset upper limit value MAX and the lower limit value MIN, the work W is determined to be normal and "OK".
After turning on the lamp (S17), the inspection is finished. Even when the variation value N is "0", the work W is determined to be normal and the "OK" lamp is turned on.

As described above, in the leak test apparatus shown in this embodiment, the pressure switch 11 is provided for each type of the workpiece W to be inspected as described in the conventional example.
It is possible to supply different set preloads to different types of workpieces W by one pressure sensor 25 without providing the above.
Therefore, the number of components of the air circuit is reduced, and it is possible to inspect a plurality of types of works without complicating the air circuit, so that the cost of the device can be reduced. Moreover, unlike the one in which a plurality of pressure switches 11 are switched and used, the air circuit is the same regardless of the type of the work W, so that the same inspection accuracy can be ensured regardless of the type of the work W.

Further, during the inspection, the set preload, which varies depending on the type of the work W, is automatically corrected to the pressure corresponding to the temperature of the work W, so the preload supplied to the work W is always most suitable for that temperature. It can be pressure. Although the temperature of the work W is directly obtained by the temperature sensor 27 detachably attached to the work W in the present embodiment, the present invention is not limited to this.
The temperature may be indirectly obtained from the outside air temperature.

[0019]

As described above, in the leak test apparatus of the present invention, the same pressure sensor is used at the time of inspection without providing a pressure switch for each type of work to be inspected as in the conventional case, and different types of works are inspected. Since different set preloads can be supplied to the device, the number of components of the air circuit can be reduced, and the cost of the device can be reduced because the air circuit is not complicated. Moreover, unlike the conventional device that switches a plurality of pressure switches to be used, since the air circuit is the same regardless of the type of work, the same inspection accuracy can be secured regardless of the type of work.

Further, there are provided a temperature sensor for detecting the temperature of the work, and a correcting means for correcting the set preload indicated by the preload data read by the preload data reading means based on the temperature detected by the temperature sensor. By what
Since the set preload can be automatically corrected to the best pressure according to the temperature of the work, the preload supplied to the work can always be the most suitable pressure for that temperature.

[Brief description of the drawings]

FIG. 1 is an air circuit diagram showing an embodiment of the present invention.

FIG. 2 is a block configuration diagram in the same embodiment.

FIG. 3 is a flowchart showing an operation of the controller in the same embodiment.

FIG. 4 is an air circuit diagram showing a conventional leak test apparatus.

[Explanation of symbols]

 2 1st solenoid valve 7 2nd solenoid valve 8 3rd solenoid valve 12 4th solenoid valve 10 Comparison work (comparison master) 14 Differential pressure sensor 25 Pressure sensor 26 Controller 27 Temperature sensor

Claims (2)

[Claims] 1. A set preload is supplied to both the work and the comparison master, the internal pressures of both are once reduced to a test pressure, and then a change in the differential pressure between the work and the comparison master is made within a certain period of time. Based on the above, in the leak test device for inspecting the airtightness of the work, a storage means in which a plurality of preload data indicating preset preloads corresponding to different kinds of works are stored in advance, and a preset preload corresponding to the work to be inspected A preload data reading unit that reads out preload data from the storage unit, a pressure sensor that detects internal pressures in both the work and the comparison master, and a pressure detected by the pressure sensor is read by the preload data reading unit. When the set preload indicated by the issued preload data matches, the signal output hand that outputs a signal notifying it Leak test apparatus characterized by comprising a, the. 2. A temperature sensor for detecting the temperature of the work, and a correction means for correcting the set preload indicated by the preload data read by the preload data reading means based on the temperature detected by the temperature sensor. The leak test apparatus according to claim 1, further comprising: