Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
1999-02-22
2001-02-06
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S049700, C073S118040, C123S520000
Reexamination Certificate
active
06182502
ABSTRACT:
PRIOR ART
The invention relates to a diagnosis module for leak testing a container, in particular a tank ventilation system of a motor vehicle.
In a wide variety of technical fields, containers must be tested as to their functionality, i.e. leakproofness. It is thus important to leak test containers, for example in the chemical industry or in process technology. In addition, however, it is also necessary in automotive engineering to leak test containers, in particular tank systems. So for example, in some countries, the functionality of tank ventilation systems in vehicles must be tested with on-board means. Starting with the model year 1996, leaks of 1 mm must be detectable and starting with the model year 2000, even leaks 0.5 mm in size must be detectable. In order to detect such leaks, a so-called diagnosis module is installed, with which a leak test can be carried out from time to time.
The proposal has already been made to equip such a diagnosis module with an electric compressed air pump and a reversing valve that is embodied, for example, as a 4/2-way solenoid valve and to connect it on the valve end to the container to be monitored or to the tank ventilation system (DE 196 36 431). In its first switched position, the reversing valve shuts off the compressed air supply from the compressed air pump and ventilates the connection line between the reversing valve and the container and in its second switched position, connects the compressed air pump to the container with the connection line while simultaneously shutting off the ventilation. The reference leak, which is comprised of a throttle bore with a defined bore diameter, is disposed parallel to the reversing valve and connects the compressed air pump to the connection line between the reversing valve and the container. A measuring unit is connected to the electrical connection of the compressed air pump and measures the current consumption of the compressed air pump as a measurement for the volume flow supplied by the compressed air pump.
For leak testing, the supply volume flow of the compressed air pump is determined on the one hand, when the compressed air pump acts on the container in the second switched position of the reversing valve, and on the other hand, when the compressed air pump acts on only the reference leak in the first switched position of the reversing valve. A comparison of the two values makes it possible to tell whether a leak is still of a permissible size or has exceeded this amount.
With this diagnosis module, component tolerances and external influences such as temperature are largely precluded since the comparison of the two measurement values is made in relation to the reference measurement and external influences do not change decisively during the measurement. However, the reference leak is extremely important for correct measurement since it defines the threshold limit for a good/bad identification of leakproofness. It must therefore be assured that the cross section of the reference leak does not change with the passage of time, for example does not become smaller due to soiling. Since leak testing—as described at the beginning—is increasingly being accommodated to smaller leaks, the throttle bore of the reference leak in the known diagnosis module must likewise be made very small, as a result of which the susceptibility of the reference leak to soiling and thereby to a change of the opening cross section increases significantly and the measurements of leakproofness are no longer reliable.
ADVANTAGES OF THE INVENTION
The diagnosis module according to the invention has the advantage over the prior art that through the connection of a number of diaphragms in series, each with a throttle opening, the volume flow permitted for the reference measurement is adjusted with throttle openings that are relatively large in cross section, which in contrast to throttle bores with very small bore diameters, are relatively insensitive to soiling, deposits, impurities, etc. Therefore, in addition, the filters usually inserted before and after the reference leak in the known diagnosis module can be eliminated. For technical manufacturing reasons, the large cross section throttle openings are easier to produce than small ones so that rugged stamping tools can be used. The influences of stamping tolerances are just as noncritical as the influences of various deflashing qualities since they are of much less consequence than a significantly greater opening cross section.
Trials have shown that for example, the reference leak according to the invention, which is equipped with three diaphragms disposed in series and whose throttle openings each have a diameter of 1 mm, permits the same through flow, i.e. the same supply volume flow per unit time, as a single throttle bore with a diameter of 0.5 mm. With four and more diaphragms disposed in series, with the same size diameter of the throttle openings, the through flow quantity can be further reduced so that future requirements to discover extremely small leakages in the container can also be fulfilled with the diagnosis module according to the invention, without the diagnosis module measuring imprecisely or failing completely due to changes in the reference leak with long-term operation.
Advantageous improvements and updates of the diagnosis module disclosed are possible by means of the measures taken herein.
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Schwegler Helmut
Zimmermann Manfred
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
Wiggins David J.
Williams Hezron
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