HU205303B - Method for non-destructive determining fault in the course of fatigue testing tyres by infrared camera - Google Patents

Abstract

The present invention relates to a tire test (1) for the determination of a non-destructive defect location by means of a tire test, wherein the tire (1) is rotated and exposed to the load, while the tire is synchronized with one or more infrared cameras (3, 4, 5) synchronized with rotation in the frame rate. (1) a running and / or lateral surface (2) is observed, and the thermogram thus obtained is digitized by pixels and transformed to values linearly related to the temperature, if necessary. Recording of digital thermograms (1) rendered by the camera (3) or cameras (3,4,5), which map the surface (2) of the tire (1), is repeated at a given time interval to be a time difference ratio of the consecutive, spacially spaced thermogram pixel values, then the differential ratios and the points where the pixel values formed by their respective difference ratios differ by more than the predetermined value are considered to be fault locations. As a further advantage, product identification is also performed at the same time as defining a non-destructive defect location, selecting tires as representative samples (1), subjecting them to qualifying fatigue testing, and classifying tires (1) according to whether or not they are found to be defective. V 3 _Figure EN 205 303 B Scope of the description: 6 pages (including 1 sheet)

Description

(57) EXTRAS

The present invention relates to a tire (1) method for determining a non-destructive fault location by fatigue testing, wherein the tire (1) is rotated and subjected to a load while synchronizing with one or more infrared cameras (3, 4, 5) (1) the running and / or side surfaces (2) are observed, and the resulting thermogram is digitized per pixel and transformed, if necessary, into values that are linearly related to temperature.

The digital thermograms provided by the camera (3) or the cameras (3,4,5), mapping the surface (2) of the tire (1), are repeated at intervals to form a time difference of successive spatially consistent thermogram pixel values, and The points where the pixel values of their respective difference coefficients deviate more than the predetermined mean are considered to be errors.

As a further advantage, defining a non-destructive site is accompanied by product qualification by selecting tires (1) as a representative sample, subjecting them to a qualifying fatigue test, and by evaluating the tires (1) according to whether or not they are found.

FIG

Scope of the description: 6 pages (including 1 page figure)

HU 205 303 B

HU 205 303 Β

FIELD OF THE INVENTION The present invention relates to a method of determining a non-destructive defect location during tire fatigue testing by rotating and exposing a tire while synchronizing the image with one or more infrared cameras, The resulting thermogram is digitized per pixel and transformed, if necessary, to a value linearly related to temperature.

Made in different sizes, structures, patterns, etc. for different applications. tire rating internationally recommended (recommended) or test bench lifetime, speed, etc. developed by some tire manufacturers. runs on the basis of the failure of the bench.

Among the fatigue tests, the qualifying tests of the given code are bounded by ambient temperature, load, tire pressure, etc. parameters and load for a specified amount of time.

From time to time, during lifetime tests, brief stops are made for visual inspection, size control, pressure and spot temperature measurement, the results of which are recorded on a log sheet.

A state-of-the-art solution is a computing solution that continuously measures, registers, and processes the initial parameters that are set and changes during the process. (Speed, load, tire pressure, interior air temperature, etc.).

Detection of mileage failure in bench test procedures in general

- visual inspection of downtime,

- mechanical sensors of the equipment,

- in the case of continuous-instrument parameter check eg. rapid change (drop) in tire pressure,

- subjective (operator) evaluation of sound and resonance phenomena immediately preceding failure.

"Failure" results in such an extreme physical and technical condition that the post-analysis technician can only determine direct errors and localized errors based on his experience.

It would be advisable to stop the load and to locate the fault before the explosive event of the failure.

Testing of vehicle tires is described in U.S. Patent No. 3,542,340.

In addition, several process solutions are known which have been developed for various measurements in the infrared, that is, the thermal radiation range. Thus, a temperature mapping system is disclosed in U.S. Patent No. 4,685,898, and U.S. Patent No. 3,720,832 is used for similar non-destructive testing.

Some of the above solutions measure physical state variables with conventional direct measuring devices, while others use infrared radiation as a material test method. There is no known method for modeling the occurrence of defects by imitating the practical application or loading of a given material, or for such product qualification.

There is a known test procedure (7th Annual Meeting of the Tire Society, Akron, Ohio, March 23, 1988; conference proceedings) in which the tire is rotated to expose it to conditions similar to the actual one. The tire is examined by thermal imaging, infrared heat imaging, looking for the temperature distribution and its changes. This method attempts to explore the relationship between tire pressure and wear and load and strain, and consequently, only the temperature distribution along the tire profile, without taking into account changes in the circumference of the entire tire, is investigated. Therefore, the method cannot be adapted to a specific fault location or product classification based on it.

The object of the present invention was to develop a unique measuring technique which, in accordance with the tire test and bench test procedures known and accepted in technical practice, is a direct source of error. allows you to identify errors by exploration.

The findings underlying the invention are as follows. Existing or already existing structural changes to the sidewall or tread of the running tire - eg. layer separation - results in well identifiable local warming. Continuous detection of spatial and temporal temperature changes in these areas, infrared camera thermal sensing, and high-speed computer data entry and data processing provide the opportunity for non-destructive fault location. Thus, the load test can be stopped in time before an explosive failure occurs, which also makes it difficult to determine faults.

Thus, a general solution of our object is a method of repeating the recording of digital tire thermograms provided by the cameras at intervals of time to form a temporal diffusion coefficient of consecutive spatially consistent thermogram pixel values, where the corresponding pixel values of the corresponding difference multipliers differ more than the predetermined mean from the mean, errors are considered.

Figure 1 illustrates the invention.

A preferred device arrangement for the process of the present invention is shown in Figure 1.

The means of observation is an infrared (3) camera. It is expedient to design a rotation sensor which preferably operates by optical or infrared synchronous signaling. Using this signal as a synchronous pulse, the camera (3) provides picture synchronization2

EN 205 303 Β. If necessary, we can use more than one sensor or camera. In our example, the camera (3) scans the tread of the tire (1), while the cameras (4 and 5) arranged on both sides scan the side surface of the tire. Of course, everything we wrote about image synchronization applies to all cameras (3, 4, 5).

Continuous - rotational thermodynamic evaluation is possible by obtaining the thermal map of the tire (1) lateral or tread (2) as a series of thermograms in an expanded form.

Maintaining a constant rpm during a lifetime test or a discrete change / increase in rpm during a speed test provides a high degree of accuracy in locating selected points or microspheres (e.g., within 0.4% error at 600 rpm). Any point on each thermogram - e.g. on the display screen - belonging to the same tire surface point. This is ensured by synchronization.

A / D converter is used in the cameras or as a separate unit connected thereto. The sampling and quantizing unit is of conventional design in digital television technology and is not detailed. Dividing pixels and treating them as numerical values is the application of computing, and therefore real-time or real-time computing. helps with automatic tests.

The process of the invention is as follows. The tire (1) to be tested is rotated and loaded. This means that it is mounted on the chassis of a vehicle designed to accommodate a test bench or special measuring equipment. Then, by rotating the wheel and the tire (1) with it, a synchronization signal arrangement, preferably of an optical or infrared design, ensures that the tire (1) is infrared scanned periodically, i.e., it is continuously mapped to locations and pixels of the resulting image. 4, 5) through image synchronization of cameras. One frame time should match the rotation time. The entire surface to be examined (2) is scanned together by the camera (3, 4 and 5). The cameras operating in the infrared range (3,4,5) are arranged at an angle, preferably at right angles, to the motion vector of the rotating tire to be mapped. You can use a monitor or hard-copy device (printer, drawing machine, etc.) to display sequentially scanned images.

The tire (1) warms up under load, better at structural defects than elsewhere. We can recognize and detect this in two ways, according to our purpose. The first option is to form a planar gradient of the digital image. Where the gradient is large, that is, a temperature surge, a fault is likely to occur. By "big" we usually mean a rating obtained by comparison with empirical values obtained from experience, This is from a tire type, and more. also depends on other test conditions. Another possibility is the temporal examination, that is, the training of the differential ratio of the series of images over time. The evaluation is similar to the previous one. Since we have periodic thermograms for measurements, instead of the theoretical differential defined as limit values, we produce a difference fraction by generating the difference between successive thermograms, subtracting. The difference values are a point-by-point characteristic of the rate of temperature change - warming up. Experience shows that at warming points this warming accelerates significantly, with good approximation, exponentially. If we can detect this in time, we can prevent explosive failure and, at the same time, locate the fault on the essentially undamaged (1) tire.

To do this, it is necessary to determine the extent to which an error rate is likely to be exceeded when the differential rate is exceeded. This depends on many factors, e.g. the size, tread, material, etc. of the tire (1). It can be said that this threshold should be set separately for a given product. It is advisable to look at the rate of warming not by itself but by reference to the average warming of the entire tire surface. The average rate of temperature increase depends on the current load and the temperature already reached.

It is also desirable to evaluate the behavior of not only one point but also of several adjacent points and not only one difference factor but also several successive difference ratios. This eliminates the possibility of detecting the occurrence of momentary point errors during measurement.

The original and / or gradient and / or difference ratio images may be displayed.

The best way to display the image is as follows. The one or more (3, 4, 5) cameras produce a monochromatic signal which, depending on the magnitude of the signal values, is visualized or printed on a color display to a pseudochrome image. this allows the operator to identify the fault location by the appearance of a particular color.

As shown, in a typical embodiment of the invention, the tire (1) is mounted on a test bench, its surface (2), in particular its most critical tread, being monitored by an infrared camera (3). If necessary, similar cameras (4, 5) are mounted on the boat so that they capture the sidewalls in their picture fields.

The procedure can be performed in several steps, whereby the tread and sidewall are examined separately, one after the other.

By exploring and locating the location of the detected, locally and timely identified fault, it is possible to identify primary faults that are not distorted by the physical process of extensive failure.

Qualifying testing of (1) tires is also performed by fatigue testing. In this case, a representative sample of the tires (1) to be taken out of production shall be taken. Manufacturers apply detailed specifications, available for each type, for load, load duration, error type, and frequency for performance of qualification tests. Thus, defining locations is, of course, an examination of such qualifiers3

EN 205 303 B case is also suitable. Classification is based on whether or not a defect occurs under the given conditions for a representative sample.

The information thus provided to the person skilled in the art is significantly more valuable than what can be traditionally obtained.

By printing the thermograms, you can document the thermodynamic behavior of the tire on the test bench, which can be included as an attachment to your product artwork.

The process assembly can also be carried out in a portable, mobile form, and can be safely solved in a short time during installation and relocation to the test stations.

Claims (5)

PATIENT INDIVIDUAL POINTS 1. A method for determining a non-destructive defect location in a tire fatigue test, wherein the tire (1) is rotated and subjected to a load, and at the same time rotationally synchronized with one or more cameras (3,4,5) operating in the infrared range (3,4). running and / or lateral surfaces ( 2) observe the thermogram obtained by digitizing the pixels and, if necessary, transforming them to values linearly related to the temperature, characterized by the surface of the tire (1) supplied by the camera or cameras (3,4,5); repeating the imaging digital thermograms at specific intervals, sequentially matching the corresponding pixel values corresponding to each other in time, the average of the time difference differences is calculated, and the points where the pixel values corresponding to the difference coefficients differ more than the predetermined value from the average considered. The method according to claim 1, characterized in that at the same time as the determination of the non-destructive defect location, product qualification is performed by selecting tires as representative samples (1), they are subjected to qualifying fatigue testing and the tires (1) are classified as found. or not. Method according to claim 1 or 2, characterized in that the digital thermograms and / or the difference coefficients formed by the camera or cameras (3, 4, 5), which map the surface (2) of the tire (1) displayed and / or recorded on a recording medium and / or printed. Method according to any one of claims 1, 2 or 3, characterized in that the fatigue testing of the tires (1) is carried out on a test bench. Method according to claim 1, characterized in that the points of error are those where the pixel values formed by the difference ratios differ by more than 5% from the average. EN 205 303 Β Int. Cl. ⁵ : B 60 Q 1/00 l.ábra