Method for monitoring an attachment area during the laser welding of bent bar-type conductors containing copper

Patent metadata

Field	Value
Publication number	US-12533752-B2
Application number	US-202218054550-A
Country	US
Kind code	B2
Filing date	Nov 11, 2022
Priority date	May 15, 2020
Publication date	Jan 27, 2026
Grant date	Jan 27, 2026

Abstract

A method for monitoring an attachment area during laser welding of bent bar-type conductors containing copper, includes the steps of arranging a first bar-type conductor relative to a second bar-type conductor in partially overlapping fashion and welding the first and second bar-type conductors to one another using a processing laser beam, the welding including forming a weld bead interconnecting the bar-type conductors to one another. After the welding, at least one measurement variable is measured on at least one portion of the weld bead, wherein the at least one measurement variable changes with the temperature of the weld bead as a function of the time during a cooling down of the weld bead. A parameter depending on a heat capacity of the weld bead is determined from the at least one measured measurement variable, and the attachment area qualitatively or quantitatively determined from the parameter.

First claim

The invention claimed is:

1 . A method for monitoring an attachment area during laser welding of bent bar-type conductors containing copper, the method comprising:
arranging a first bar-type conductor relative to a second bar-type conductor in partially overlapping fashion; welding the first and second bar-type conductors to one another using a processing laser beam, the welding including forming a weld bead interconnecting the first and second bar-type conductors to one another; after the welding, measuring on at least one portion of the weld bead at least one measurement variable that changes with a temperature of the weld bead as a function of the time during a cooling down of the weld bead, wherein the at least one measurement variable comprises an intensity of a thermionic emission from a portion of the weld bead, and wherein the weld bead is observed using a camera or a photodiode, and the intensity of the thermionic emission is determined by a mean grayscale value from a partial region of an image recorded by the camera or a grayscale value recorded by the photodiode; determining a parameter depending on a heat capacity of the weld bead from the at least one measured measurement variable; and determining the attachment area qualitatively or quantitatively from the parameter.

2 . The method as claimed in claim 1 , wherein
the arranging of the first and second bar-type conductors is performed such that end regions of the first and second bar-type conductors are respectively parallel to one another and next to one another, end surfaces of the first and second bar-type conductors are located approximately level in relation to a direction of a longitudinal extent of the end regions, and the processing laser beam is directed at the two bar-type conductors in such a way that the weld bead is formed at the end surfaces of the bar-type conductors.

3 . The method as claimed in claim 1 , wherein the measuring of the at least one measurement variable includes observing the portion of the weld bead in a visible spectral range or in an infrared spectral range.

4 . The method as claimed in claim 3 , wherein the measuring of the at least one measurement variable is performed on the portion of the weld bead opposite to a second portion of the first and second bar-type conductors on which the processing laser beam acted.

5 . The method as claimed in claim 1 , wherein the intensity of the thermionic emission is measured in a restricted spectral range.

6 . The method as claimed in claim 1 , further comprising illuminating the weld bead using an observation light beam while the weld bead cools down,
wherein the at least one measurement variable comprises an intensity of the observation light beam reflected at a surface of the weld bead.

7 . The method as claimed in claim 6 , wherein the intensity of the reflected observation light beam is measured in a restricted spectral range about a central wavelength of the observation light beam.

8 . The method as claimed in claim 6 , further comprising disposing a polarization filter in front of a sensor device used to measure the intensity of the reflected observation light beam.

9 . The method as claimed in claim 1 , wherein the at least one measurement variable comprises the temperature on the portion of the weld bead.

10 . The method as claimed in claim 9 , wherein the temperature is measured using quotient pyrometry, with the intensity of the thermionic emission from the portion of the weld bead being measured at two different wavelengths.

11 . The method as claimed in claim 1 , wherein the parameter is a time duration that elapses between a first defined state and a second defined state while the weld bead cools down.

12 . The method as claimed in claim 11 , wherein the first defined state is an end of processing laser beam exposure.

13 . The method as claimed in claim 11 , wherein the second defined state is a complete solidification of the weld bead.

14 . The method as claimed in claim 11 , wherein the first defined state or the second defined state is recognized by the at least one measurement variable reaching a threshold value.

15 . The method as claimed in claim 11 , wherein the first defined state or the second defined state is recognized by a first time derivative or a second time derivative of the at least one measurement variable reaching a threshold value.

16 . The method as claimed in claim 1 , wherein the parameter is a gradient of the at least one measurement variable with respect to time and is determined at a specified time or averaged over a specified time period.

17 . The method as claimed in claim 1 , further comprising comparing the parameter or the attachment area to a decision value,
upon determining that the decision value is not reached, recognizing that the attachment area of the weld bead as being too small, and upon determining that the decision value is reached, recognizing the attachment area as being sufficiently large and permitting the first and second bar-type conductors to be used further.

18 . The method as claimed in claim 17 , further comprising determining a proportion of a cross section of the first and second bar-type conductors not covered by the weld bead using the camera, and recognizing the attachment area of the weld bead of the first and second bar-type conductors as being too small when the uncovered proportion of the cross section exceeds a limit value, even if the decision value is reached.

19 . A method for monitoring an attachment area during laser welding of bent bar-type conductors containing copper, the method comprising:
arranging a first bar-type conductor relative to a second bar-type conductor in partially overlapping fashion; welding the first and second bar-type conductors to one another using a processing laser beam, the welding including forming a weld bead interconnecting the first and second bar-type conductors to one another; after the welding, measuring on at least one portion of the weld bead at least one measurement variable that changes with a temperature of the weld bead as a function of time during a cooling down of the weld bead; determining a parameter depending on a heat capacity of the weld bead from the at least one measured measurement variable; determining the attachment area qualitatively or quantitatively from the parameter; and welding a multiplicity of pairs of bar-type conductors in succession, with one or more welding parameters being optimized and/or updated in a control loop when the pairs of bar-type conductors are welded such that the parameter or an-the attachment area quantitatively determined from the parameter is set to a specified target value for the pairs of welded bar-type conductors.

20 . An apparatus for laser welding bent bar-type conductors containing copper, the apparatus comprising:
a holding device configured to arrange two bar-type conductors in overlapping fashion, the holding device comprising a stator mount with a multiplicity of bar-type conductors to be welded; a laser processing head configured to provide a processing laser beam configured to weld the two bar-type conductors to one another such that a weld bead interconnecting the two bar-type connectors is formed; a sensor device configured to measure at least one measurement variable that changes with a temperature of the weld bead on a portion of the weld bead following an end of exposure to the processing laser beam and while the weld bead cools down, wherein the sensor

Assignees

• Trumpf Laser & Systemtechnik Gmbh

Inventors

• Bocksrocker Oliver
• Speker Nicolai

Classifications

• B23K2101/38

  Conductors · CPC title

• B23K26/22

  Spot welding · CPC title

• B23K31/125 Primary

  Weld quality monitoring · CPC title

• H02K15/35 Primary

  Form-wound windings · CPC title

• G01N2021/1761

  A physical transformation being implied in the method, e.g. a phase change · CPC title