The invention concerns a method of laser beam welding of galvanic cells in the process of production of a battery module.

Disclosed in document US 2019/0326623 Al is an apparatus, and a method of using the apparatus, for holding a circuit against a battery module to facilitate welding the circuit to the battery module, in particular, laser welding using a robot arm. The disclosed method includes providing a set of first fixtures for holding a set of first conductive tabs of the circuit against a corresponding set of positive terminals of the battery module, and providing a set of second fixtures for holding a set of second conductive tabs of the circuit against a corresponding set of negative terminals of the battery module. The method further includes providing a rigid plate having a set of first structures therein for receiving the set of first fixtures and having a set of second structures therein for receiving the set of second fixtures. Each of the set of first structures and each of the set of second structures includes a top recessed portion and a bottom recessed portion. Additionally, the method includes engaging the set of first fixtures and the set of second fixtures with the rigid plate such that each of the first structure receives one of the set of first fixtures and each of the second structure receives one of the set of second fixtures. The method further includes disposing the rigid plate onto the circuit such that each of the set of first fixtures engages one of the set of first tabs to hold the one first tab against one corresponding positive terminal, and each of the set of second fixtures engages one of the set of second tabs to hold the one second tab against one corresponding negative terminal. Upon welding of circuit onto battery module, each of the set of first tabs of circuit is physically and electrically connected to one corresponding positive terminal of one battery cell, and each of the set of second tabs of circuit is physically and electrically connected to one corresponding negative terminal of one battery cell.

Known from document US 2913/0183574 Al is a battery system which includes battery cells, metal plates, and welding rings. The battery cell includes terminal rods. The battery cells are connected to each other through the metal plates. The welding rings are arranged on the metal plates, and have insertion holes into which the terminal rods are inserted. The surface of the insertion hole is welded to the terminal rod. The periphery of the welding ring is welded to the metal plate after the terminal rod is inserted into the insertion hole. The terminal rods are electrically connected to the metal plates through the welding rings. The terminal rod and/or the welding ring includes a stopper that temporarily holds the welding ring at a predetermined position with the welding ring being connected to the terminal rod. The temporarily held position is the position where the periphery of the welding ring is in contact with the metal plate.

Known from document EP 3 686 956 Al is a battery module which comprising a housing, cylindrical battery cells and a bus-bar to which the electrode terminals of the cylindrical cell are welded. In particular, there is disclosed a battery module including a plurality of cylindrical battery cells including electrode terminals respectively formed at a top and a bottom of the plurality of cylindrical cells, the plurality of cylindrical battery cells being arranged in columns and rows in a horizontal direction, a module housing including an accommodation portion having a plurality of hollow structures to accommodate the plurality of cylindrical battery cells inserted into the module housing, and a bus bar configured to contact the electrode terminals of the plurality of cylindrical battery cells to electrically connect between the plurality of cylindrical battery cells, wherein the bus bar includes, a main body portion that is positioned at a top or a bottom of the plurality of cylindrical battery cells and has a plate shape having upper and lower surfaces that are broader than a lateral surface of the main body portion in a horizontal direction, and a contact portion that is configured to electrically contact and be connected to an electrode terminal formed in one of the plurality of cylindrical battery cells, extends and protrudes from the main body portion in a horizontal direction, is stepped from the main body portion in a direction toward where the electrode terminal is positioned, and includes a branched structure bifurcated in two directions with respect to a direction in which the contact portion extends and protrudes from the main body portion, wherein an embossed protrusion protruding toward where the electrode terminal is positioned is formed in the branched structure, and a contact area is set to allow a welding rod to establish electrical connection around the embossed protrusion in the branched structure.

Known from document US 2021/0367287 Al is a battery module having a plurality of battery cells which are each electrically conductively interconnected with one another in series and/or in parallel, and a switching device, which has a first terminal and a second terminal, wherein a first connecting element of electrically conductive design electrically conductively connects the first terminal to a voltage tap of a battery cell arranged at an end and a second connecting element of electrically conductive design electrically conductively connects the second terminal to a voltage tap of the battery module, wherein the first connecting element and/or the second connecting element are received in a thermally conductive manner in a receptacle of the housing of the battery module.

This invention solves the problem of increasing efficiency of the process of galvanic cell welding in the process of producing electric battery modules.

According to the invention, a method of laser beam welding of galvanic cells in the process of production of a battery module, consisting in physical connection and electric serial and/or parallel connection of galvanic cell electrodes via a connecting element of an electrically-conducting structure under the laser beam welding method is characterised in that the process of laser beam welding of galvanic cell electrodes is preceded by a non-contact three- dimensional measurement of the position of the connecting elements which connect the galvanic cell electrodes, where the measurement is taken using a measurement taking system, following which, based on the said three- dimensional measurement, the position of welds is determined and the result is sent to the software controlling the welding head, whereupon the said welding head is used to carry out the process of laser beam welding of the connecting elements to the galvanic cell electrodes to achieve the pre-determined connection thereof, where during the said non-contact three-dimensional measurement of the position of the electrodes of the galvanic cells and during the laser beam welding process the connecting element(s) is (are) pressed to the said galvanic cells.

Preferably, the connecting element(s) is (are) pressed to the galvanic cells using a pressing mask which features openings positioned in correspondence to the pattern of position of the said galvanic cell electrodes, where the mask is fitted on the battery module with the connecting element(s) on.

Preferably, during the three-dimensional measurement of the position of the connecting elements which connect the galvanic cell electrodes, the measurement taking system moves over the battery module, or the battery module moves under the welding head.

Preferably, during laser beam welding of the connecting elements to the galvanic cell electrodes the welding head moves over the battery module, or the battery module moves under the welding head, or the battery module and the welding head do not change their positions.

Preferably, laser beam welding is performed under the protection of shielding gases, or under the blow of air, or under the protection of a medium distributed by the pressing mask, or the laser beam welding is performed without the protection of shielding gases.

The solution according to the invention enables precise, non-contact measurement of the height of the connecting element, which substantially improves efficiency of the process of galvanic cell welding in the process of producing an electric battery module.

Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.

In the drawings:

Fig. 1 shows a block diagram of an example of the method of laser beam welding of galvanic cells in the process of production of a battery module; Fig. 2 presents the pressing mask in a orthographic projection from the top; Fig. 3 shows the pressing mask in a perspective view from the top;

Fig. 4 depicts the pressing mask in an orthographic projection from the bottom;

Fig. 5 shows the pressing mask in a perspective view from the bottom;

Fig. 6 presents a galvanic cell module prepared for taking measurement of the position of galvanic cell electrodes, and for running the laser beam welding process, in a perspective view;

Fig. 7 depicts the galvanic cell module as in Fig. 6 in an orthographic projection from the top;

Fig. 8 presents the galvanic cell module as in Fig. 6 in an orthographic projection from the side;

Fig 9 shows the station of non-contact measurement of the position of the elements which connect the galvanic cell electrodes;

Fig. 10 depicts the connecting element with the position of the welds marked; Fig. 11 shows the station of laser beam welding of the connecting elements to the galvanic cell electrodes;

Fig. 12 presents a welded galvanic cell module viewed from the top.

According to the invention embodiment, a method of laser beam welding of galvanic cells in the process of production of a battery module consists in physical connection and electrical serial and/or parallel connection of galvanic cell electrodes via a connecting element of an electrically conducting structure, such as copper plate(s), under the laser beam welding method (Fig. 1). The process of laser beam welding of the connecting elements 3 to the electrodes of the galvanic cells 2 is preceded by a non-contact three-dimensional measurement of the position of the connecting elements 3 which connect the electrodes of the galvanic cells 2 using a measurement taking system, such as a laser profilometer 8 with an encoder mounted on a movable axis (Fig. 9). The measurement-taking system sends precise information about the position of all connections in the plane of the connecting element 3, for example using pattern matching algorithms, and the distance to the measurement taking system, for example by measuring the profile of a specific connection, it also sends corrected welding positions to the software which controls the welding head. With a specific structure of the connecting element 3 applied, the measurement taking system is able to detect a gap between the connecting element 3 and the electrode of the galvanic cell 2. The said measurement is used as the basis for determining the position of the welds (Fig. 10) and sent to the software which controls the welding head 7, following which the said welding head 7 is used to perform the process of laser beam welding of the connecting elements 3 to the electrodes of the galvanic cells 2 according to their set connection (Fig. 11). During the said non-contact three-dimensional measurement of the position of the electrodes of the galvanic cells 2 and during the process of laser beam welding the connecting element(s) is (are) pressed to the said galvanic cells for example with a pressing mask 4, for example made of the POM plastic, where the mask features openings 5 positioned in correspondence to the pattern of position of the said electrodes of the galvanic cells 2, as shown in Fig. 2 - Fig. 5, where the connecting element(s) 3 which connect the electrodes of the galvanic cells 2 is (are) placed on the galvanic cells 2, whereupon mounted on the battery module 1 is the pressing mask 4 which presses the said connecting element(s) 3 to the said galvanic cells 2, as shown in Fig. 6 - Fig. 8. The connecting element 3 is pressed individually to each galvanic cell 2 in the area where the welding is performed to eliminate the potential gap between the said elements. Shown in Fig. 12 is a battery module 1 welded with the connecting element 3 which connects the electrodes of the galvanic cells 2, with visible welds 6.

In one embodiment of the invention, the measurement taking system moves over the battery module when measuring the position of the elements connecting the electrodes of the galvanic cells, while in another embodiment the battery module moves under the measurement taking system.

In one embodiment of the invention, the welding head moves over the battery module during the laser beam welding of the connecting elements to the electrodes of the galvanic cells, in another embodiment the battery module moves under the welding head, and in yet another embodiment the battery module and the welding head do not change their positions.

In all embodiments described above laser beam welding may be performed under the protection of shielding gases, or under the blow of air, or under the protection of a medium distributed by the pressing mask, or without the protection of shielding gases.

List of numerical references

1 - battery module

2 - galvanic cell

3 - connecting element

4 - pressing mask

5 - openings in the mask

6 - welds

7 - welding head

8 - measurement taking system, laser profilometer