Method for characterizing a weld

Abstract

A method for characterizing at least one joined connection between at least two components, whereby an eddy-current sensor is consecutively moved several times over the at least one weld, thereby generating a plurality of data sets of the detected measuring signals in various parallel sectional planes of the weld, and whereby, on the basis of the plurality of data sets, a projection data set is subsequently determined as the measure of the spatial distribution of the measuring signals along the at least one joined connection.

Claims

1. A method for characterizing at least one joined connection between at least two joined components, comprising: consecutively moving an eddy-current sensor several times over the at least one joined connection, thereby generating a plurality of data sets of detected measuring signals in various parallel sectional planes of the joined connection, determining, on the basis of the plurality of data sets, a projection data set as a measure of a spatial distribution of the measuring signals along the at least one joined connection, adding the data sets in order to determine the projection data set along a direction (y) that is oriented perpendicular to the sectional planes, adapting a curve progression to the projection data set, whereby, on the basis of the adapted curve progression, flaws and/or defects of the at least one joined connection are determined, comparing the projection data set to a stored reference data set, and characterizing the joined components as rejects if a flaws and/or defect in the projection data set reaches or exceeds a reference threshold value of the reference data set.

2. The method according to claim 1, further comprising passing the eddy-current sensor over a number of adjacent joined connections of the components, whereby a shared projection data set is determined as the measure of the spatial distribution of the measuring signals along each joined connection.

3. The method according to claim 1, further comprising tilting and/or swiveling the eddy-current sensor over the course of consecutive movements along the at least one joined connection.

4. The method according to claim 1, for a production of a battery element, further comprising: joining together at least two battery components situated adjacent to each other by means of a welded connection, whereby at least one weld is made as the joined connection.

5. A device for the production of a battery element, comprising a welding apparatus configured to create an integrally bonded welded connection of at least two battery components that are arranged so as to be stacked above each other, an eddy-current sensor configured to generate and detect eddy currents in the vicinity of at least one joined connection that has been created by the welding apparatus, and a controller for execution of the method according to claim 1.

6. The device according to claim 5, wherein the eddy-current sensor is configured as a fork sensor having a transmission geometry.

7. A vehicle battery of a motor vehicle that is or can be electrically powered, comprising at least one battery element produced according to the method of claim 4.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will be described in greater detail below on the basis of a drawing. The latter contains the following in simplified and schematic depictions:

(2) FIG. 1 shows a top view of a device for the production of a battery element,

(3) FIGS. 2 to 4 show each a top view of the battery element with an arrester tab and collector foil, which are integrally bonded by means of a number of welds,

(4) FIG. 5 shows several partial views of a method according to the invention for characterizing at least one weld, and

(5) FIGS. 6 and 7 show a perspective view of an eddy-current sensor configured as a fork sensor, for examining the weld.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIGS. 1 to 4 each show a battery element 2 of a vehicle battery (not shown here in greater detail). The battery element 2 has two battery components 4, 6 as parts.

(7) The battery element 2 is, for example, a battery cell, whereby the battery component 4 here is especially configured as a battery electrode having a coating 8 and a collector foil 10, and whereby the battery component 6 is especially configured as an arrester tab. In order to improve the attachment in the vicinity of the battery component or of the arrester tab 6 to a housing part of the battery element 2 (not shown here in greater detail), a so-called pre-sealing tape 12 is arranged in the vicinity of the battery component 6. The pre-sealing tape 12 effectuates a minimum distance for purposes of electric insulation between the voltage-carrying arrester tab 6 and the housing part.

(8) FIG. 1 also schematically shows a highly simplified depiction of a device 14 for the production of the battery element 2.

(9) The device 14 here has a welding apparatus 16 for creating the integrally bonded welded connection of the battery components 4 and 6, which are arranged so as to be stacked above each other, at least in certain sections. The welding apparatus 16 is suitable and configured, for instance, for ultrasonic welding or laser beam welding. In this context, the welding apparatus 16 is moved, for instance, along a joining direction F, a process in which the battery components 4, 6 are integrally bonded by means of at least one joint or weld 18.

(10) The device 14 also has an eddy-current sensor 20 for characterizing or inspecting the at least one weld 18. The eddy-current sensor 20 here is suitable and configured for generating and detecting eddy currents in the vicinity of the at least one weld 18.

(11) The welding apparatus 16 and the eddy-current sensor 20 are coupled to a controller 22, that is to say, to a control unit.

(12) In the embodiment shown in FIG. 1, the battery element 2 has a single, longitudinal weld 18. In other words, the battery components 4 and 6, especially the arrester tab 6 and the collector foil 10, are welded together by means of a weld 18.

(13) The embodiment shown in FIG. 2 depicts the battery element 2 with four longitudinal welds 18 distributed along the joining direction F. In the embodiments shown in FIG. 3 and FIG. 4, the battery components 4 and 6 are each connected to a plurality of approximately punctiform welds (welding points) 18, which are arranged so as to be distributed, for example, in two rows perpendicular to the joining direction F. In the embodiment shown in FIG. 3, the rows are arranged so as to be stacked above each other, whereas in the embodiment shown in FIG. 4, the rows are arranged offset with respect to each other. The welds 18 shown in the figures are provided with reference numerals only by way of an example.

(14) A method according to the invention for characterizing or inspecting at least one weld 18 is explained in greater detail below making reference to FIG. 5. The depiction in FIG. 5 has four sections 24, 26, 28 and 30 arranged horizontally one above the other. Each section shows one method step for characterizing the at least one weld 18.

(15) In the first method step depicted in section 24, the eddy-current sensor 20 is consecutively moved several times along the at least one weld 18. In this process, the eddy current sensor 20 is moved linearly along the joining direction F and thereby consecutively passed several times over the weld site that is to be examined and/or tested. The measured data or measuring signals (sensor signals) 32 are transmitted to the controller 22 for evaluation.

(16) With every pass, a data set of the appertaining measuring signals 32 is created and stored in a memory of the controller 22. The measuring signals 32 are generated over the course of various passes in various parallel sectional planes 34, 36, 38 of the weld 18, whereby FIG. 5 shows three sectional planes 34, 36, 38 by way of an example.

(17) During the course of the successive movements or passes along the weld 18, the eddy-current sensor 20 is, for example, tilted and/or swiveled. This is shown schematically in section 24 by means of a double arrow 40.

(18) The weld 18 shown in FIG. 5 has a somewhat punctiform defect 42. The defect 24 is, for example, a pore, an impurity phase or a phase boundary located inside the weld 18. The transfer function of the measuring signals 32 of the eddy-current sensor 20 shown in section 26, in other words, the course of the measuring signals 32 during the scanning of the defect 42, exhibits a well-defined, for instance, circular or circular-ring shaped structure.

(19) In a subsequent method step, the controller 22 generates a projection data set 44 which is shown in section 28 and which has been created by superimposing the data sets of the measuring signals 32 stemming from the individual sectional planes 34, 36, 38. For this purpose, the measuring signals 32 or density values or the plurality of data sets along a direction y oriented essentially perpendicular to the sectional planes are summed up. In other words, the plurality of data sets is summed up or added up to form the projection data set 44. Thus, the size of the data sets is effectively reduced. As can be seen in section 28, the projection data set 44 is essentially a two-dimensional data set in a plane oriented perpendicular to the longitudinal or joining direction F.

(20) In the method step depicted in section 30, the controller 22 adapts or fits a curve progression or fit 46 to the data of the projection data set 44. The weld 18 is characterized on the basis of the adapted curve progression 46, whereby the position and/or intensity of the defect 42 inside the weld 18 are determined.

(21) In order to adapt or fit the curve progression 46, preferably several uniformly distributed functions are employed that result from the shape of the well-defined structure. In the embodiment shown, a hump shaped curve progression 46 results from the circular or circular-ring shaped structure of the measuring signals 32 (section 26).

(22) In the embodiment shown, for example, two Gaussian peaks that are arranged next to each other and whose distance from each other falls only within a well-defined range are used to adapt or fit the curve progression 46.

(23) On the basis of the intensity or amplitude of the curve progression 46 on the shapes of the data of the projection data set 44, the controller 22 is suitable and configured in such a way that essential properties of the defect 42, especially its dimension 48 and/or position 50 inside the weld 18, can be easily determined at the appertaining position. This allows a simple evaluation of the measuring signals 32, even in the case of defects 42 that are very close to each other, whereby, due to the number of fit functions, the defects 42 can essentially be resolved individually.

(24) The curve progression 46 and/or the projection data set 44 are compared, for instance, by means of the controller 22, to a stored reference data set for threshold values of a reference sample or exemplary sample. Preferably, a characterization of the signal or curve progression 46, for example, by means of neural networks, takes place here.

(25) The controller 22 controls and/or regulates the production process of the battery elements 2, preferably on the basis of the characterization of the created welds 18. In this context, it is possible for the battery element 2 to be characterized as a reject if, on the basis of a comparison of a threshold value to the reference data set, for instance, an intensive defect 42 is detected in the projection data set 44 and/or in the curve progression 46.

(26) In several welds 18—such as, for instance, in the embodiments of FIGS. 2 to 4—the eddy-current sensor 20 can be guided along the joining direction F over several adjacent welds 18. In this process, the controller 22 suitably determines a shared projection data set 48 as the measure for the spatial distribution of the measuring signals 32 along the welds 18, said projection data set being evaluated according to the projection data set 44 of a single weld 18.

(27) FIGS. 6 and 7 show an embodiment of the eddy-current sensor 20 in the form of a transmission fork sensor.

(28) In this context, the fork sensor 20 has, for instance, an approximately horseshoe-shaped or U-shaped (sensor) housing 50, whereby a transmitting coil and a receiving coil situated across from it are arranged in the vicinity of the free end of the vertical U-leg. In this context, the coils (not shown in greater detail here) are connected to the controller according to a transformer principle. In this process, the excitation frequency of the coils is selected in such a way as to ensure sufficient penetration through the electrically conductive material of the welded connection 18.

(29) The invention being claimed here is not restricted to the embodiments described above. Rather, the person skilled in the art can also derive other variants of the invention within the scope of the disclosed claims without departing from the subject matter of the invention being claimed here. In particular, all of the individual features described in conjunction with the embodiment within the scope of the disclosed claims can also be combined in a different manner without departing from the subject matter of the invention being claimed here.

LIST OF REFERENCE NUMERALS

(30) 2 battery element 4 battery component/part 6 battery component/part/arrester tab 8 coating 10 collector foil 12 pre-sealing tape 14 device 16 welding apparatus 18 joined connection/weld 20 eddy-current sensor/fork sensor 22 controller 24, 25, 28, 30 section 32 measuring signals 34, 36, 38 sectional plane 40 arrow 42 defect 44 projection data set 46 curve progression 48 projection data set 50 housing F joining direction Y direction