Method for leak testing a container

Abstract

Method for sensory leak testing of a container (1) pressurized by means of a gaseous measuring fluid, characterized by the following steps: a) Provision of a container to be tested (1), b) Provision of an optoelectronic system for detecting the shape and type of container (1), c) Provision of at least one robot-guided sensor (7, 8) for the sensory detection of measuring fluid escaping from any leak in the container (1), d) optoelectronic detection of the container (1), generation of an image file (3) of said container (1), comparison of the same with a plurality of image files of reference images of different container types stored in an electronic database and conclusion about a specific container type, e) Fixing and sealing fluid connections (13) of the container (1), f) Filling the container (1) with the measuring fluid, g) depending on the detected container type and a test cycle stored in the said database, control of the robot (5, 6) guiding the sensor (7, 8) and guiding the sensor (7, 8) on a predetermined test path, and h) in the event that a leak in the container (1) is detected as a result of measuring fluid escaping from it, marking of the detected leak directly on the container (1) and / or display of a real image of the container (1) including marking of the detected leak and / or generation of an electronic file at least with regard to the location of the detected leak and electronic storage of the file in an electronic database.

Description

[0001] According to the preamble of claim 1, the invention relates to a method for sensory leak testing of a container pressurized by means of a gaseous measuring fluid.

[0002] From DE 41 40 725 A1, a method and an arrangement for leak testing of containers using imaging optics are known. Essentially, this document proposes filling the interior of the container with a pressurized measuring fluid, imaging the container surface by generating a two-dimensional raster image on an optoelectronic receiver, and using image evaluation electronics to generate a leak image with correspondingly positioned leak points by comparing the raster image with a reference image. Hot air is proposed as the measuring fluid, for example, which is located by an infrared-sensitive CCD receiver as it escapes from a leak point.

[0003] German patent DE 10 2012 008 857 A1 discloses a method and a test system for leak testing a gas system of a motor vehicle, for example, a CNG system (CNG = Compressed Natural Gas). The method essentially proposes to automatically move a detection element (gas detection sensor) mounted on a robot arm to at least one test point of a component installed in the vehicle and to check for any leakage. A resulting signal is transmitted to a detection device. The test is performed at measuring pressures from 10 bar to 100 bar.

[0004] German patent DE 10 2012 014 129 A1 describes a method for leak testing a vehicle, in particular an enclosed space, such as its interior. This involves pressurizing the interior with a test gas, such as helium, measuring the concentration of the test gas in at least one test area of ​​the space using a test probe, and finally determining the leak tightness of the enclosed space as a function of the measured test gas concentration. This is achieved by defining a sealing line or sealing surface of the enclosed space as the test area, scanning this area with a test probe, and locating any leaks. Detected leaks can be visualized using an imaging technique.

[0005] For the state of the art, reference is also made to DE 196 81 664 T5, US 2009 / 0 210 175 A1 and US 2010 / 0 288 020 A1.

[0006] The object of the invention is to provide an alternative method, in view of the prior art, for the sensory leak testing of a container pressurized with a measuring fluid, which can be carried out quickly and cost-effectively with minimal technical equipment requirements.

[0007] The problem is solved by a method for the sensory leak test of a container pressurized with a gaseous measuring fluid, which is characterized by the following steps: a) Provision of a container to be tested, b) Provision of an optoelectronic system for detecting the shape and type of container, c) Provision of at least one robot-guided sensor for the sensory detection of measuring fluid escaping from any leak in the container, d) optoelectronic detection of the container, generation of an image file of said container, comparison of this file with a plurality of image files of reference images of different container types stored in an electronic database and conclusion about a specific container type, e) Securing and sealing fluid connections of the container, f) Filling the container with the measuring fluid, g) depending on the detected container type and a test cycle stored in the said database, control of the robot guiding the sensor and guidance of the sensor on a predetermined test path, and h) In the event that a leak is detected in the container due to escaping measuring fluid, the detected leak shall be marked directly on the container and / or a real image of the container shall be displayed including the marking of the detected leak and / or an electronic file shall be generated, at least with regard to the location of the detected leak, and the file shall be stored electronically in an electronic database.

[0008] The above method offers the advantage, in light of the state of the art, of a faster and more reliable, less time-consuming and costly detection of any leaks in the container under test. This test can be carried out in extremely short process times of 60 seconds or less, even with different container types, for example, in the case of fuel tanks.

[0009] The dependent claims describe preferred further developments or embodiments of the invention.

[0010] Accordingly, with regard to step a), a fuel tank is preferably used as the container to be tested, which is further preferably a fuel tank made of a plastic or a composite material. As the invention further provides, with regard to step b), an optoelectronic system is preferably used which includes at least one stereo camera. With regard to step d), it is further provided that the reference images are preferably generated from CAD data (CAD = computer-aided design) stored in the electronic database. The measures described above have the advantage that high-quality images of the container currently being sensed can be created and compared with high-quality reference images, which leads to a reliable identification of the container type in question.To reliably detect any leakage point with regard to step g), a sensor is preferably used which is designed to sensing, depending on the selected measuring fluid, specifically the measuring fluid used and / or a density difference of the gas in the area of ​​the test path and / or an acoustic signal resulting from the escape of the measuring fluid from the leak. As further provided by the invention, a forming gas, a noble gas, or air is preferably used as the measuring fluid, wherein a forming gas is understood to be a gas mixture of nitrogen and hydrogen. Regarding the aforementioned noble gas, helium is particularly suitable. Air in the form of compressed air can be used, in particular, if a potential leak is audibly noticeable through escaping air and is thus detected.According to a further preferred embodiment of the method according to the invention, the measuring fluid in the container is subjected to a relatively low pressure of 50 mbar to 400 mbar, preferably 100 mbar to 300 mbar, which is particularly well withstood by said containers made of plastic or a composite material.

[0011] According to the state of the art (DE 10 2012 008 857 A1), much higher measuring pressures are used for leak testing, which are at 10 bar or 100 bar.

[0012] A system for carrying out the method of the type described above, comprising an optoelectronic system for detecting the shape and type of a container to be tested for leakage and at least one robot-guided sensor for the sensory detection of measuring fluid escaping from any leak in the container, is characterized in particular by the fact that the sensor is designed to detect leak rates of up to 10 -12The sensor is designed to detect pressure in mbar I / s, thereby enabling the detection of even the smallest amounts of escaping measuring fluid, which in turn leads to a particularly high safety standard for said containers, especially fuel tanks. A suitable embodiment of said at least one sensor is characterized in that it is formed by a sensor for point leak testing, particularly of attached components and / or connection points of the container, or by an elongated or rod-shaped sensor, particularly for leak testing of joint seams of the container.

[0013] The invention is explained in more detail below with reference to an exemplary embodiment schematically illustrated in a drawing. However, it is not limited to this embodiment, but encompasses all embodiments defined by the patent claims.

[0014] The only Fig.Figure 1 schematically depicts a system for the sensory leak test of a container 1 that can be pressurized or is pressurized by means of a gaseous measuring fluid. According to this embodiment, said container 1 is a fuel tank for a motor vehicle. The fuel tank preferably consists of a plastic, in particular a thermoplastic such as polyethylene (PE), or of a composite material, in particular a multilayer composite material. It is certainly easy for those skilled in the art to understand that a multitude of vehicle types results in a multitude of container types, which must be tested for leak tightness using the test system in question.

[0015] In this respect, the testing system initially comprises an optoelectronic system for detecting the shape and type of the container 1 to be tested. The said optoelectronic system has a stereo camera 2, which in turn is electrically or wirelessly connected to an electronic control unit (ECU).

[0016] During the detection of container 1, the stereo camera 2 takes a stereoscopic photograph or a 3D image of said container 1 and generates a corresponding image file 3, which is stored in an electronic database of the electronic control unit (ECU). This image file 3 is then compared with image files of reference images of various container types, and the result is used to determine the specific container type. These reference images are preferably CAD data (CAD = computer-aided design) and are also stored in the electronic database of the electronic control unit (ECU). In addition, the position and orientation of container 1 are determined using preferably six axis data points 4, and the container is fixed in place. These axis data points 4 are also provided to the higher-level control system in the form of the electronic control unit (ECU) and processed therein.

[0017] Furthermore, the test system comprises at least one, and according to this embodiment two, sensors 7, 8, each guided by a robot 5, 6, for the sensory detection of measuring fluid escaping from any leak in the container 1. According to an extremely simple embodiment of the invention, shown here only as an example, the measuring fluid is supplied by means of a known pressurized gas cylinder 9 with a fitting 10 for adjusting the desired gas pressure and is fed to the container 1 via a known gas pressure hose 11, which is fixed to a fluid connection 13 of the container 1 by means of a coupling tool 12 and tightly connected to it. It is understood that any further connections of the container 1, not shown here, are pressure-tight sealed.Preferably, a gas pressure of 50 mbar to 400 mbar, and more preferably 100 mbar to 300 mbar, is generated in container 1 using the measuring fluid. Such a relatively low gas pressure compared to the prior art is sufficient for reliable leakage measurement according to the inventive method and is particularly well suited for leak tightness testing of the exemplary fuel tanks made of plastic or a composite material.

[0018] The preferred measuring fluids are a forming gas, a noble gas, or air, whereby a forming gas is understood to be a gas mixture of nitrogen and hydrogen. Regarding the noble gas, helium is particularly suitable. Air in the form of compressed air is used especially when a potential leak is audibly detectable by escaping air and is thus sensed. Sensors 7 and 8 are used here, which are designed to detect, depending on the selected measuring fluid, specifically the measuring fluid used and / or a density difference of the gas in the area of ​​a test path and / or an acoustic signal resulting from the escape of the measuring fluid from the leak.

[0019] Once the position and orientation of the container 1 to be inspected are determined, the robots 5, 6 are controlled by means of corresponding control signals 14, 15 on the basis of a test cycle assigned to the determined container type, programmed and stored in the database of the electronic control unit (ECU), so that the sensors 7, 8 are guided over a predetermined test path.

[0020] If a leak is detected in container 1 due to escaping measuring fluid, the detected leak can be marked directly on the container 1, for example, by means of a color code or similar. Preferably, however, a suitable measurement signal 16, 17 is generated with regard to the location and, if applicable, the size of the detected leak and provided to the electronic control unit (ECU), which in turn creates a real-world image of container 1 on a monitor 18, including an electronic marking of the leak, for quick viewing and orientation by, for example, a testing engineer. Furthermore, it can be advantageous to generate an electronic file of the aforementioned real-world image including the detected leak and to store it in an electronic database for possible later or further evaluation (not shown in the drawing).Subsequent or further evaluation can lead to a decision as to whether a tested container 1 is repairable or is rejected as defective. Any combination of the aforementioned measures for outputting the measurement results is, of course, also covered by the invention.

[0021] For cycle time optimization, a sensor 7 is provided for point leak testing of, in particular, attachments and / or connections of the container 1, e.g., for leak testing of a connection of a gasoline pump or a tank neck not shown in the drawing, as well as an elongated or rod-shaped sensor 8 for, in particular, leak testing of joint seams of the container 1. Reference symbol list 1 container 2 stereo cameras 3 image files (container 1) 4 axle data 5 robots 6 robots 7 Sensor 8 Sensor 9 pressurized gas cylinders 10 fittings 11 Gas pressure hose 12 coupling tools 13 Fluid connection (container 1) 14 Control and regulation signal 15 Control and regulation signal 16 Measurement signal 17 Measurement signal 18" Monitor ECU electronic control unit

Claims

[1] Method for sensory leak testing of a container pressurized by means of a gaseous measuring fluid (1), characterized by the following steps: a) Provision of a container to be tested (1), b) Provision of an optoelectronic system for detecting the shape and type of container (1), c) Provision of at least one robot-guided sensor (7, 8) for the sensory detection of measuring fluid escaping from any leak in the container (1), d) optoelectronic detection of the container (1), generation of an image file (3) of said container (1), comparison of the same with a plurality of image files of reference images of different container types stored in an electronic database and conclusion about a specific container type, e) Fixing and sealing fluid connections (13) of the container (1), f) Filling the container (1) with the measuring fluid, g) depending on the detected container type and a test cycle stored in the said database, control of the robot (5, 6) guiding the sensor (7, 8) and guiding the sensor (7, 8) on a predetermined test path, and h) in the event that a leak in the container (1) is detected as a result of measuring fluid escaping from it, marking of the detected leak directly on the container (1) and / or display of a real image of the container (1) including marking of the detected leak and / or generation of an electronic file at least with regard to the location of the detected leak and electronic storage of the file in an electronic database. [2] Method according to claim 1, characterized by , that with regard to the step a) a fuel tank is used as the container to be tested (1). [3] Method according to claim 2, characterized bythat a fuel tank made of a plastic or composite material is used. [4] Method according to claim 1, characterized by , that with regard to step b) an optoelectronic system is used which includes at least one stereo camera (2). [5] Method according to claim 1, characterized by , that with regard to step d), the reference images are created using CAD data stored in the electronic database. [6] Method according to claim 1, characterized by , that with regard to step g) a sensor (7, 8) is used which is designed to specifically sense the gaseous measuring fluid used and / or a density difference of the gas in the area of ​​the test path and / or an acoustic signal resulting from an escape of the measuring fluid from the leak. [7] Method according to any one of the preceding claims, characterized bythat a forming gas, a noble gas or air is used as the measuring fluid. [8] Method according to any one of the preceding claims, characterized by , that the measuring fluid located in the container (1) is subjected to a pressure of 50 mbar to 400 mbar, preferably of 100 mbar to 300 mbar.

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