DE102022208550A1 - Method for measuring at least one material layer of a vehicle tire using terahertz radiation - Google Patents

Abstract

The invention relates to a method for measuring at least one material layer (1) of a vehicle tire (2) using terahertz radiation, wherein the vehicle tire (2) is irradiated in a radial direction with terahertz radiation from a terahertz radiation source (3) and from which Vehicle tire (2) reflected terahertz radiation is received by a terahertz receiver (4), a diaphragm (5) being arranged between the terahertz radiation source (3) and the vehicle tire (2), through which the incident terahertz radiation is in the form of a line ( 6) is projected onto the vehicle tire (2), the reflection signals of the terahertz radiation generated on the at least one material layer (1) being detected by the terahertz receiver (4) and from the evaluation of these reflection signals taking into account the positional relationship between the terahertz Radiation source (3) and the terahertz receiver (4), the distance of the at least one material layer (1) from the terahertz radiation source (3) and / or from the terahertz receiver (4) is determined.

Description

The invention relates to a method for measuring at least one material layer of a vehicle tire using terahertz radiation, wherein the vehicle tire is irradiated in a radial direction with terahertz radiation from a terahertz radiation source and the terahertz radiation reflected by the vehicle tire is received by a terahertz receiver.

Vehicle tires usually consist of several different layers of material, which are successively applied to one another during tire production. Although there are measuring methods that can be used to determine the dimensions and positioning of an individual layer when it is applied, the application of additional layers as well as the final vulcanization step and the pressures and temperatures that occur can lead to shifts and/or deformation of individual layers which can affect the quality of the finished vehicle tire.

As part of quality controls, it is therefore necessary to examine the finished vehicle tire or the tire that has not yet been vulcanized or other preliminary stages of the tire during the manufacturing process with regard to the correct positioning and alignment of the individual material layers in order to, if necessary, select vehicle tires at an early stage to be able to reject items from the production line that do not meet the quality standards. Today, such investigations are preferably carried out non-destructively.

Different methods are already known for this. The surface, and here in particular the tread of the vehicle tire, can be examined using optical surface contour measurements, for example with the aid of infrared radiation or visible light. However, such methods are not suitable for measuring internal material layers such as the belt pack of a vehicle tire. A belt package is one or more internal layers of steel cord fabric that give the vehicle tire its strength and dimensional stability and prevent the penetration of foreign bodies. A deviation in the concentricity of the belt package has a significant impact on the quality of the vehicle tire. The measurement of the belt package in the finished or green tire is now often carried out using X-rays, the use of which, however, requires complex safety precautions, for example in the form of shielding cabins, due to their ionizing and therefore harmful effects on the human organism.

An alternative method in which terahertz radiation is used to test tires is from the EP 2 985 585 B1 already basically known. Terahertz radiation refers to electromagnetic radiation in a wavelength range of approximately 100µm to 6mm. It lies in the electromagnetic spectrum between infrared and microwave radiation. The frequencies of this radiation are in a range from approximately 50 GHz to 3000 GHz or 0.05 THz to 3 THz. Terahertz radiation is characterized by the fact that it has a high penetrating ability for certain materials such as rubber, but at the same time is non-ionizing and therefore essentially harmless to the human organism. It is therefore particularly suitable for the non-destructive testing of workpieces. Both the transmission behavior and the reflection behavior of the radiation can be examined and evaluated depending on the irradiated materials.

The object of the present invention is to provide an improved method for measuring at least one material layer, in particular an inner material layer, of a vehicle tire using terahertz radiation.

To solve the problem, a method with the features of patent claim 1 is proposed.

Advantageous refinements and further developments of the invention are the subject of the dependent claims.

According to claim 1, the invention is a method for measuring at least one material layer of a vehicle tire using terahertz radiation, the vehicle tire being irradiated in a radial direction with terahertz radiation from a terahertz radiation source and the terahertz radiation reflected by the vehicle tire from a Terahertz receiver is received. The invention is characterized in that a diaphragm is arranged between the terahertz radiation source and the vehicle tire, through which the incident terahertz radiation is projected onto the vehicle tire in the form of a line, with the reflection signals of the terahertz radiation generated on the at least one material layer from the terahertz -Receiver are detected and the distance of the at least one material layer from the terahertz is determined from the evaluation of these reflection signals, taking into account the positional relationship between the terahertz radiation source and the terahertz receiver hertz radiation source and/or is determined by the terahertz receiver.

In other words, the method according to the invention provides that a diaphragm is introduced into the beam path of the terahertz radiation emitted by a terahertz radiation source in such a way that the portion of radiation passing through the diaphragm strikes the vehicle tire at a defined angle of incidence and in the form of a line. This allows the terahertz radiation to be directed very precisely and with high spatial resolution onto the vehicle tire to be measured. The incident terahertz radiation is reflected on material interfaces of the vehicle tire. Depending on the structure of the vehicle tire, reflections can occur at different material interfaces. A first reflection takes place on the surface of the vehicle tire and therefore usually at an air-rubber transition. In a vehicle tire made up of several layers of material, part of the terahertz radiation passes through the outer rubber layer of the vehicle tire due to its high penetrating ability and hits, for example, the inner layer of the belt package made of steel cord fabric. A second reflection occurs at this transition between the rubber and the steel belt. Depending on the structure of the specific tire, further reflections can occur at other material interfaces.

The reflection signals of the individual reflections are detected by a terahertz receiver and subsequently evaluated. From the detected reflection signals, the distance of the at least one material layer from the terahertz radiation source and/or from the terahertz receiver can be deduced, taking into account the positional relationship between the terahertz radiation source and the terahertz receiver, i.e. the distance and the angle to one another. If several layers of material are present, the relative distance between the individual layers of material can also be deduced from one another, in particular, for example, the distance of an internal layer of material from the surface of the vehicle tire. Accordingly, the radius of individual material layers can also be deduced from knowledge of the distance between the center of the vehicle tire and the terahertz radiation source and/or terahertz receiver. Any displacements and/or deformations, such as a vertical run-out, a flat run-out or splices of individual material layers, in particular internal material layers such as the belt package, can be identified in this way and, as part of quality controls, vehicle tires in which the properties of one or more material layers differ If the components fall out of a specified tolerance range, they can be removed from the production line at an early stage.

The frequency of the irradiated terahertz radiation is in a range from approximately 0.05 THz to 3.0 THz in the method according to the invention. The frequency of the terahertz radiation is preferably in a range from approximately 0.05 THz to 1.0 THz, for example it can be 0.1 THz.

In the context of the present invention, the term “vehicle tires” means both finished, vulcanized tires and fully assembled but not yet vulcanized tires as well as various preliminary stages of these tires during the manufacturing process. In particular, such preliminary stages of a tire can be measured in which essentially all material layers of the tire are already arranged one above the other, but not all material layers have to be completely connected to one another.

According to one embodiment of the invention, the incident terahertz radiation is projected onto the vehicle tire through the aperture in the form of a line running perpendicular to the direction of travel of the vehicle tire.

The aperture provided according to the invention can be a slot-shaped aperture. In one embodiment of the invention, the opening of the slot-shaped panel has a length of approximately 20 mm to 400 mm and a width of approximately 0.01 mm to 1 mm.

Alternatively, the aperture can be a phase-modulating aperture made of plastic, in which a desired pattern, here a line, is generated by phase modulation of the terahertz radiation depending on the thickness of the aperture at the respective point. Such panels can be produced either ablatively, for example by etching or milling, or additively, for example by 3D printing or in a sintering process.

According to a proposal of the invention, the vehicle tire to be measured is mounted on a rotation device. In particular, when preliminary stages of the finished tire are examined, this can be, for example, the tire building drum on which the vehicle tire is assembled. In particular, a measurement of internal material layers can be carried out in a simple manner directly as part of the manufacturing process using the method according to the invention. The rotation device can also be, for example, a groove clamping head or a rim on which a finished vehicle tire is preferably measured.

According to a further proposal of the invention, the vehicle tire to be measured is rotated during the measurement. In this way, the tire can be measured over its entire circumference or over parts of its circumference without having to move the terahertz radiation source and the terahertz receiver. Alternatively, it is of course also possible to hold the tire and move the terahertz radiation source and/or the terahertz receiver.

It can be provided that a rotary encoder is used, through which the vehicle tire is rotated in defined angular steps Δα, the reflection signals of the terahertz radiation being detected for each rotation angle α set in this way. The rotary encoder can be arranged on the rotation device and can be designed as an incremental encoder or as an absolute encoder.

According to a proposal of the invention, the vehicle tire is rotated in angular steps Δα of 1°, with the reflection signals being recorded by the terahertz receiver for each rotation angle setting. In this way, 360 measurement signals are obtained over the entire circumference of the vehicle tire, which can subsequently be evaluated.

According to one embodiment of the method according to the invention, the reflection signals of the terahertz radiation generated at material interfaces of the vehicle tire are evaluated as a function of the rotation angle α. In this way, it is possible to determine the position of individual material layers and/or the relative distance between two or more material layers from one another over the entire circumference of the vehicle tire. Changes in the determined values along the circumference of the vehicle tire can be recorded quickly, whereby a deformation of one or more material layers, for example a vertical runout of the belt package, can be reliably detected.

According to a proposal of the invention, the terahertz receiver is designed as a sensor array. A sensor array includes several geometrically arranged sensor cells so that the reflection signals of the terahertz radiation can be received with spatial resolution using such a sensor array. The sensor array can be at least so large that it covers the entire relevant measuring range in both a vertical and a horizontal direction. Alternatively, it can be provided that the sensor array can be moved between different positions in a vertical and/or in a horizontal direction. In this way, the sensor array can be made smaller and therefore more cost-effective. The terahertz receiver can, for example, be designed as a so-called terahertz camera and receive the reflection signals of the terahertz radiation in a spatially resolved manner and thus, for example, over the entire width of the vehicle tire perpendicular to its running direction.

Alternatively, a sensor with just a single sensor cell can be used as a terahertz receiver. In order to obtain a corresponding spatial resolution here, such a sensor can be moved preferably linearly in a vertical and/or horizontal direction in order to detect the different reflection signals in the individual positions. Based on the angular relationships between the terahertz radiation source and the terahertz receiver, conclusions can be drawn about the material transitions examined. In this way, the method according to the invention can be carried out significantly more cost-effectively than with a terahertz receiver designed as a sensor array.

The terahertz receiver can also be assigned an evaluation unit which, for a given angle of rotation α, provides a graphical representation of the reflection signals of the terahertz radiation generated on the at least one material layer.

A terahertz receiver suitable for the purposes of the present invention is, for example, the Tera-4096 terahertz camera sold by TeraSense.

The distance between the terahertz radiation source and the aperture can be approximately 0 mm to 100 mm. In other words, the aperture can also be arranged directly on the radiation source. The distance between the bezel and the surface of the vehicle tire can be about 40mm to 200mm.

In addition to measuring the material layers of a vehicle tire, the proposed method also makes it possible in principle to measure individual components in vehicle tire construction before they are assembled into the finished vehicle tire, for example in order to determine overlap areas of individual material layers with regard to their characteristics such as width, thickness and size.

• 1: eine schematische Skizze einer Anordnung zur Durchführung des erfindungsgemäßen Verfahrens;
• 2: Strahlengang der einfallenden und reflektierten Terahertz-Strahlung in schematischer Darstellung;
• 3: schematische Darstellung der von dem Terahertz-Empfänger empfangenen und verarbeiteten Reflexionssignale für einen gegebenen Drehwinkel α.

The invention is explained in more detail below using an exemplary embodiment and with reference to the attached figures. Show it:

• 1 : a schematic sketch of an arrangement for carrying out the method according to the invention;
• 2 : Ray path of the incident and reflected terahertz radiation in a schematic representation;
• 3 : Schematic representation of the reflection signals received and processed by the terahertz receiver for a given angle of rotation α.

1 shows an arrangement, designated overall as 100, for carrying out the method according to the invention for measuring at least one material layer of a vehicle tire 2 using terahertz radiation. The vehicle tire 2 is rotatably mounted on a construction drum, not shown here. A rotary encoder, also not shown, is arranged on the construction drum, through which the vehicle tire 2 can be rotated in defined angular steps Δα.

The arrangement 100 includes a terahertz radiation source 3, which emits terahertz radiation 8 with a frequency of approximately 0.1 THz. The vehicle tire 2 is irradiated with the terahertz radiation 8 in a radial direction. A slot-shaped aperture 5 is arranged between the terahertz radiation source 3 and the surface 7 of the driving access 2. The aperture 5 includes a slot-shaped opening 9, which has a width of approximately 0.5 mm and a length of approximately 400 mm. The aperture 5 is arranged at a distance of approximately 60 mm from the terahertz radiation source 3 and at a distance of approximately 40 mm from the surface 7 of the vehicle tire 2.

The aperture 5 allows the incident terahertz radiation 8 to pass through only in a defined angular range, so that the terahertz radiation 10 that has passed through the aperture 5 hits the vehicle tire 2 at a defined angle of incidence and in the form of a line 6 running perpendicular to the running direction L of the vehicle tire 2. The size of the opening of the aperture 5 and the distances between the aperture 5, terahertz radiation source 3 and surface 7 of the vehicle tire 2 are selected so that the line 6 extends at least over the entire width of the vehicle tire 2 perpendicular to its running direction L. The terahertz radiation 10 is reflected on the vehicle tire 2, which is explained below and with reference to 2 will be explained in more detail, and the reflected terahertz radiation 11 is received by a terahertz receiver 4. The terahertz receiver 4 is a terahertz camera from TeraSense. From the evaluation of the reflection signals received by the terahertz receiver 4, as will be explained below, conclusions can be drawn about the position of individual material layers of the vehicle tire 2 and in particular about the relative distance of an internal material layer 1 from the surface 7 of the vehicle tire 2.

The 2 shows a schematic representation of the beam path of the terahertz radiation 10 and the reflected terahertz radiation 11 that passed through the aperture 5 and impinges on the vehicle tire 2. The vehicle tire 2 comprises two outer rubber layers 12, 13 and an inner material layer 1 lying between the two rubber layers 12, 13 Steel cord. The terahertz radiation 10 striking the vehicle tire 2 is already partially reflected on the surface 7 of the vehicle tire 2 and thus on the air-rubber boundary layer. This results in the portion of the reflected terahertz radiation 11, designated 11a. A portion of the incident terahertz radiation 10, on the other hand, passes through the outer rubber layer 12 and hits the inner material layer 1 made of steel cord, where further reflection takes place. This results in the portion of the reflected terahertz radiation 11, designated 11b. Both the portion 11a and the portion 11b of the reflected terahertz radiation 11 impinge on the terahertz receiver 4.

3 shows a schematic representation of the reflection signals received by the terahertz receiver 4 and processed into an image 14, namely for a fixed angle adjustment of the vehicle tire 2. The image 14 includes an upper line 15, which corresponds to the reflection of the terahertz radiation 10 on the surface 7 of the Vehicle tire 2 and thus on the outer rubber layer 12 can be assigned. Spaced from the line 15, the image 14 includes a further line 16, which is assigned to the reflection of the portion of the terahertz radiation 10 that has passed through the outer rubber layer 12 on the inner material layer 1 made of steel cord. The terahertz receiver 4 is designed to have spatial resolution, so that it receives the reflection signals over the entire width of the vehicle tire 2 perpendicular to its running direction L. The length of line 15 in the 3 corresponds to this width of the vehicle tire 2. This can be seen from the length of line 16 in the 3 that the internal material layer 1 does not extend over the entire width of the vehicle tire 2. Finally, the image 14 contains two further line sections 17, which result from reflections on the building drum. Here, both terahertz radiation 10 is reflected, which passes through the edge of the rubber layers 12, 13, as well as terahertz radiation 10, which passes the outside of the vehicle tire 2 and directly hits the construction drum. It can be seen that the inner material layer 1 made of steel cord acts like a mirror for the terahertz radiation 10 and is essentially not transparent to it.

From the distance between the two lines 15 and 16, the relative distance of the inner material layer 1 from the surface 7 of the vehicle tire 2 can be deduced. About this one To measure the distance over the entire circumference or parts of the circumference of the vehicle tire 2, the vehicle tire 2 can be rotated in defined angular increments Δα, for example in angular increments of 1°, and for each angular setting the recorded reflection signals can be processed and in an image 14 analogous to that Presentation in 3 being represented. From this, conclusions can be drawn about an angle-dependent change in the relative distance of the inner material layer 1 from the surface 7 of the vehicle tire 2 and thus about possible deviations in the positioning of the inner material layer 1 and the surface 7 of the vehicle tire 2 comprising the tread from predetermined tolerance values. In particular, the height runout of the inner material layer 1, for example the belt package of the vehicle tire 2, can be measured in this way.

Taking into account the positional relationship between the terahertz radiation source 3 and the terahertz receiver 4, the absolute distance of the inner material layer 1 and the surface 7 of the vehicle tire 2 from the terahertz radiation source 3 and/or from the terahertz receiver 4 can also be determined. If the distance between the center of the vehicle tire 2 and the terahertz radiation source 3 and/or the terahertz receiver 4 is also known, the radius of the individual material layers can also be determined. Deviations from these values along the circumference of the vehicle tire 2, which indicate a deformation of one or more material layers, can be reliably detected in this way.

Reference symbol list

1

material location

2

Vehicle tires

3

Terahertz radiation source

4

Terahertz receiver

5

cover

6

line

7

Surface of the vehicle tire

8th

Terahertz radiation

9

opening

10

Terahertz radiation

11

reflected terahertz radiation

11a

Proportion of reflected terahertz radiation

11b

Proportion of reflected terahertz radiation

12

outer rubber layer

13

outer rubber layer

14

Picture

15

line

16

line

17

Line sections

100

arrangement

L

Running direction

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2985585 B1 [0005]

Claims (13)

Method for measuring at least one material layer (1) of a vehicle tire (2) using terahertz radiation, wherein the vehicle tire (2) is irradiated in a radial direction with terahertz radiation from a terahertz radiation source (3) and which is emitted by the vehicle tire (2) reflected terahertz radiation is received by a terahertz receiver (4), characterized in that a diaphragm (5) is arranged between the terahertz radiation source (3) and the vehicle tire (2), through which the incident terahertz radiation is in the form of a line (6 ) is projected onto the vehicle tire (2), the reflection signals of the terahertz radiation generated on the at least one material layer (1) being detected by the terahertz receiver (4) and from the evaluation of these reflection signals taking into account the positional relationship between the terahertz radiation source (3) and the terahertz receiver (4) the distance of the at least one material layer (1) from the terahertz radiation source (3) and / or from the terahertz receiver (4) is determined. Procedure according to Claim 1 , characterized in that the incident terahertz radiation is projected onto the vehicle tire (2) through the aperture (5) in the form of a line (6) running perpendicular to the direction of travel of the vehicle tire (2). Procedure according to Claim 1 or 2 , characterized in that the vehicle tire (2) to be measured is mounted on a rotation device. Procedure according to one of the Claims 1 until 3 , characterized in that the vehicle tire (2) to be measured is rotated during the measurement. Procedure according to Claim 4 , characterized in that a rotary encoder is used, through which the vehicle tire (2) is rotated in defined angular steps Δα, the reflection signals of the terahertz radiation being detected for each rotation angle α set in this way. Procedure according to Claim 5 , characterized in that the vehicle tire (2) is rotated in angular steps Δα of 1°. Procedure according to Claim 5 or 6 , characterized in that the reflection signals of the terahertz radiation generated on the at least one material layer (1) are evaluated as a function of the rotation angle α. Procedure according to Claim 7 , characterized in that the terahertz receiver (4) is designed to have spatial resolution and comprises an evaluation unit which, for a given angle of rotation α, provides a graphical representation of the reflection signals of the terahertz radiation generated on the at least one material layer (1). Procedure according to one of the Claims 1 until 8th , characterized in that the panel (5) is designed as a slot-shaped panel (5), the length of the opening of the slot-shaped panel (5) being 20 mm to 400 mm and the width of the opening of the slot-shaped panel (5) being 0.01 mm to is 1 mm. Procedure according to one of the Claims 1 until 9 , characterized in that the distance between the terahertz radiation source (3) and the aperture (5) is 0 mm to 100 mm and that the distance between the aperture (5) and the surface (7) of the vehicle tire (2) is 40 mm up to 200 mm. Procedure according to one of the Claims 1 until 10 , characterized in that the terahertz receiver (4) is designed as a sensor array comprising several sensor cells. Procedure according to one of the Claims 1 until 10 , characterized in that the terahertz receiver (4) is designed as a single sensor cell, which can be moved in a vertical and/or horizontal direction. Procedure according to one of the Claims 1 until 12 , characterized in that the position of the belt package within the vehicle tire (2) is measured.

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