Method and device for resistance welding and coupling of forces between electrodes

Abstract

A welding device for joining components by resistance welding includes a pair of electrodes which can introduce an electrode force and an electrical welding current I.sub.S1 into the components, at least one further pair of electrodes which can introduce an electrode force and a further electrical welding current I.sub.S2 into the components, a power source which can generate the electrode forces, a coupling link which is mechanically connected between the power source and the pairs of electrodes and which can divide a total electrode force that can be generated by the power source into the electrode force and the further electrode force.

Claims

1. A welding device for joining components by resistance welding, comprising: a double inverter configured to generate a first electric welding current I.sub.S1 and to generate a second electric welding current I.sub.S2, a first electrode pair configured to introduce a first electrode force and the first electric welding current I.sub.S1 into the components, at least a second electrode pair configured to introduce a second electrode force and the second electric welding current I.sub.S2 into the components, a single source of force configured to generate the electrode forces, and a distribution linkage which is mechanically connected between the single source of force and the electrode pairs, the distribution linkage configured to divide a total electrode force that is generated by the single source of force into the first electrode force and the second electrode force, wherein: the distribution linkage is articulated to a first force transmission linkage by a first joint, the distribution linkage is articulated to a second force transmission linkage by a second joint, the first force transmission linkage is articulated to a first moving welding electrode of the first electrode pair by a first force transmission joint, the second force transmission linkage is articulated to a second moving welding electrode of the second electrode pair by a second force transmission joint, the electrode forces are transmitted by the first and second force transmission linkages, the single source of force is mechanically associated with the distribution linkage by a distribution joint that is arranged between the first joint and the second joint, and whereby the first moving welding electrode is mounted so that it is configured to be moved lengthwise by a first linear guide, and the second moving welding electrode is mounted so that it is configured to be moved lengthwise by a second linear guide.

2. The welding device according to claim 1, whereby the single source of force is configured as a linear source of force.

3. The welding device according to claim 1, whereby the first electrode pair has the first fixed welding electrode and the first moving welding electrode, and the second electrode pair has the second fixed welding electrode and the second moving welding electrode.

4. The welding device according to claim 1, whereby a rod of the single source of force that is configured to be moved lengthwise serves to transmit the total electrode force and said rod is articulated to the distribution linkage by the distribution joint.

5. The welding device according to claim 1, whereby the distribution joint is positioned in the middle between the first joint and the second joint.

6. A method for joining components by resistance welding, involving: generating a total electrode force by a single source of force, dividing the total electrode force between an electrode pair and another electrode pair by a distribution linkage and, as a result, pressing the components against each other that are arranged between the electrode pairs, wherein: the distribution linkage is articulated to a first force transmission linkage by a first joint, the distribution linkage is articulated to a second force transmission linkage by a second joint, the first force transmission linkage is articulated to the first electrode pair by a first force transmission joint, the second force transmission linkage is articulated to the second electrode pair by a second force transmission joint, the electrode forces are transmitted by the first and second force transmission linkages, and the single source of force is mechanically associated with the distribution linkage by a distribution joint that is arranged between the first joint and the second joint, and introducing a welding current I.sub.S1 and another welding current I.sub.S2 into the components via the electrode pairs in order to weld the components by resistance welding.

7. A welding device for joining components by resistance welding, comprising: a plurality of electrode pairs configured to introduce electrode forces and electric welding currents into the components, each electrode pair of the plurality of electrode pairs having a respective distribution linkage; and a single source of force configured to generate the electrode forces; wherein a first side of each distribution linkage is mechanically associated with a moving welding electrode of its respective electrode pair, and a second side of each distribution linkage is mechanically associated with the single source of force; whereby each of the moving welding electrodes is mounted so that it is configured to be moved lengthwise by a linear guide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Additional advantages, features and details of the invention can be gleaned from the description below in which embodiments are described in depth making reference to the drawing. The same, similar, and/or functionally equivalent parts are designated by the same reference numerals. The following is shown:

(2) FIG. 1 a three-dimensional front view at an angle from above of a welding device having two electrode pairs;

(3) FIG. 2 a three-dimensional front view at an angle from above of a coupling joint of the welding device shown in FIG. 1;

(4) FIG. 3 a wiring diagram of a double inverter for distributing a welding current among the welding electrode pairs of the welding device shown in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 shows a three-dimensional front view at an angle from above of a C-bracket 7 of a welding device 1. The welding device 1 has an electrode pair 15 and another electrode pair 17. Two or more components that are to be joined can be positioned between the electrode pairs 15, 17. A total electrode force 27 is exerted onto the electrode pairs 15 and 17 by means of a source of force 19. In this manner, the components that are to be joined are temporarily secured between the electrode pairs 15, 17 and pressed together in such a way that two welding currents supplied by a welding transformer 2 and by another welding transformer 3 cause the material of the components that are to be joined to melt, at least in certain areas, as a result of which the components are joined at two joining spots by means of resistance welding.

(6) The welding transformers 2 and 3 are connected via secondary current cables 6 to moving welding electrodes 39, 41 of the electrode pairs 15, 17. The current flows via fixed welding electrodes 35, 37 of the electrode pairs 15, 17, and finally back to the welding transformers 2 and 3 via the C-bracket 7.

(7) The moving welding electrode 39 is mounted so that it can be moved lengthwise by means of a linear guide 43. The other moving welding electrode 41 is mounted so that it can be moved lengthwise by means of another linear guide 45, and in particular, the moving welding electrodes 39 and 41 are mounted so that they can be moved lengthwise axis-parallel.

(8) The source of force 19, which is especially configured as a pneumatic cylinder, transmits the total electrode force 27 via a rod 10 to an advantageous distribution linkage 25. By means of the distribution linkage 25, the total electrode force 27 is divided into the individual electrode forces 21 and 23. For the further transmission, the moving electrodes 39 and 41 are mounted by means of sliding shafts 11 and 12 in the linear guides 43 and 45 so that they can be moved lengthwise.

(9) One current measuring coil 13 is connected in the welding current circuits for each electrode pair in order to ascertain the welding current.

(10) FIG. 2 shows a detailed view of the welding device of FIG. 1, likewise in a three-dimensional front view at an angle from above, whereby the coupling joint 25 and the linear guides 43 and 45 are shown.

(11) The interaction of the coupling joint 25 with the linear guides 43 and 45, and thus the division of the total electrode force 27 into the electrode force 21 of the electrode pair 15 and into the other electrode force 23 of the other electrode pair 17 will be explained in greater detail below.

(12) FIG. 2 shows a detailed view of the welding device of FIG. 1, likewise in a three-dimensional front view at an angle from above, whereby the distribution linkage 25 and the linear guides 43 and 45 are shown.

(13) The interaction of the distribution linkage 25 with the linear guides 43 and 45, and thus the division of the total electrode force 27 into the electrode force 21 of the electrode pair 15 and into the other electrode force 23 of the other electrode pair 17 will be explained in greater detail below.

(14) The distribution linkage 25 is articulated to the rod 10 by means of the distribution linkage 33. The distribution linkage 25 has other joints on both sides of the distribution linkage 33, namely, a joint 29 and another joint 31. A force transmission linkage 20 is articulated to the distribution linkage 25 by means of the joint 29. Another force transmission linkage 47 is articulated to the distribution linkage 25 by means of another joint 31.

(15) The total electrode force 27 of the source of force 19 is transmitted via the rod 10 that is configured, for example, as a piston rod of a pneumatic cylinder.

(16) The distribution linkage 25 fulfills the function of a compensation rocker and/or of a tilting lever.

(17) The force transmission linkages 20, 47 serve to transmit the electrode force 21 to the electrode pair 15, and to transmit the other electrode force 23 to the other electrode pair 17. For this purpose, the force transmission linkage 20 is articulated to the sliding shaft 53 of the electrode pair 15 by means of a force transmission joint 49. In order to transmit the other electrode force 23, the other force transmission linkage 47 is articulated by means of another distribution joint 51 to the other sliding shaft 55 of the other linear guide 45 of the other electrode pair 17.

(18) In order to transmit the electrode forces 21 and 23 to the moving welding electrode 39 and to the other moving welding electrode 41, the ends of each of the sliding shafts 53 and 55 opposite from the force transmission joints 49 and 51 have an electrode holder 59 or another electrode holder 61. In the direction of action of the electrode force 21, there is an electric insulator 63 below the electrode holder 59. Likewise, below the other electrode holder 61, there is another electric insulator 65. Thanks to this measure, it is possible to avoid a shunt via the compensation mechanism. The electrode holders 59, 61 each have four through holes via which a connection can be established between the appertaining sliding shaft 53, 55 and the appertaining moving welding electrode 39 and 41.

(19) In another embodiment, the two electric circuits are electrically insulated from each other in order to avoid a shunt.

(20) According to one embodiment, the source of force 19 is configured as a pneumatic device and, for this purpose, it has a pneumatic cylinder 8.

(21) The distribution joint 33 is a force path compensation device 9 and it converts a linear movement of the rod 10 of the pneumatic cylinder 8 first into pivoting and rotating movements of the distribution linkage 25 and of the force transmission linkages 20, 47. These pivoting and rotating movements are then converted back into linear movements of the sliding shafts 53 and 55. In this manner, the total electrode force 27 is advantageously divided into the individual electrode forces 21 and 23. Consequently, due to the pivoting movement of the distribution linkage 25, a tolerance compensation is achieved in the lengthwise direction of the linear guides 43 and 45. In spite of this tolerance compensation, advantageously, the total electrode force 27 is consistently distributed identically owing to the kinematics of the distribution linkage 25. This is advantageously not dependent on the pivoting position of the distribution linkage 25, but rather only on the position of the distribution joint 33 relative to the joints 29 and 31. In one embodiment, the distribution joint 33 is arranged exactly in the center between the joints 29 and 31, so that the electrode forces 21 and 23 are identical. Advantageously, the distribution linkage 25 is designed symmetrically, so that even the bearing forces that occur in the linear guides 43 and 45 as well as in the joints 29, 31, 49, 51 are likewise compensated for.

(22) When it comes to a divergent force distribution, it is possible to arrange the distribution joint 33 of the distribution linkage 25 in an asymmetrical division between the joints 29 and 31. Furthermore, it is conceivable to apply the principle of the distribution linkage 25 to more than two electrodes. In this context, symmetrically structured coupling joints can be provided for powers of two. If the numbers are different from this, asymmetrically coupling joints can be provided whereby appertaining coupling joints are permanently articulated on one side, if applicable.

(23) The linear guides 43 and 45 are screwed to a tong base element 4.

(24) In order to associate the C-bracket 7 of the welding device 1 with a robot device, the latter has a robot fastening plate 67 that especially has screwed connections or through holes by means of which screwed connections can be established to the robot device.

(25) Moreover, aside from the current measuring coil 13, a diode packet 5 is also provided in order to convert the welding current.

(26) FIG. 3 shows a wiring diagram of a double inverter 69.

(27) In FIG. 3, the letters L1, L2, L3 and PE designate a connection to a power network, especially to a power current connection.

(28) The double inverter 69 serves to generate an electric welding current I.sub.S1 and another electric welding current I.sub.S2. Appropriate measuring lines for the welding currents I.sub.S1 and I.sub.S2 are drawn in FIG. 3.

(29) A primary circuit U1, V1 and U2, V2 is provided for each electrode pair 15, 17, respectively. Voltages of the primary circuits U1 and V1, U2 and V2 are transformed by means of a transformer 71 and by another transformer 73. One of the diode packets 5 is situated downstream from each of the transformers 71, 73.

(30) Appropriate measuring lines are associated with each of the electrode pairs 15, 17 or their current circuits in order to measure a secondary voltage U.sub.S1 and U.sub.S2.

(31) Advantageously, two or more welding points can be created per work procedure and/or per target position. Advantageously, this can markedly shorten the production time. Advantageously, a defined electrode force 21 and 23 is nevertheless possible per welding spot. Thus, in spite of the placement of multiple welding spots, a high quality and process reliability of the welding procedure can advantageously be ensured. Advantageously, the distribution linkage 25 or the force path compensation device 9 is a low-wear and functional mechanism that is advantageously relatively compact and low-maintenance in comparison to two sources of force provided individually. Advantageously, the individual electrode forces 21 and 23 can reach the range from 2 to 5 kN, especially from 2.5 to 3.5 kN, especially about 1.5 to 3 kN.

(32) Advantageously, the process reliability is at the level of welding tongs having only one welding spot.

(33) According to FIGS. 1 and 2, the welding device 1 is configured with a C-shaped design and it has a C-bracket 7 for this purpose. According to an advantageous additional aspect of the invention, however, the welding device 1 can also be configured with an X-shaped design, having so-called X-shaped welding tongs. For this purpose, the distribution linkage 25 can be provided at the end of the tongs, analogously to the depiction of FIGS. 1 and 2. The transmission from the source of force is then, if applicable, via the X-shaped welding tongs and not directly via the rod 10 of the source of force 19.

(34) As an alternative or in addition, the source of force 19 can be configured in any desired manner, especially as a hydraulic source of force, and electric-motor source of force and/or the like.

(35) The fixed welding electrodes 35, 37 and the moving welding electrodes 39 and 41 of the electrode pairs 15, 17 are attached to tong arms of the welding device 1 in such a way that, when the tongs of the welding device 1 close, the result is two electric circuits via the components that are to be welded or joined. These are two electric circuits that can be regulated independently of each other, especially by means of the double inverter 69 shown in FIG. 3, having separately actuated transformers 71 and 73. The regulation here is carried out via a current measuring coil 75 of the electrode pair 15 and via another current measuring coil 77 of the other electrode pair 17, which is shown in FIG. 3.

(36) The welding tongs of the welding device 1 are equipped with the distribution linkage 25 of the force path compensation device 9, with which the total electrode force 27 generated by the tongs and/or the source of force 19 is divided between both electrode pairs 15, 17 at a given ratio, in this case, particularly in a ratio of 0.5:0.5, independently of the electrode position, in the area of the welding electrode in question, especially independently of the actual thickness of the components that are to be joined.

(37) In this manner, reproducible welding results are advantageously ensured. In addition, a path compensation is generated by means of the linear guides 43, 45 in order to compensate for different amounts of milling debris and/or different total metal thicknesses. The linear guides 43, 45 can be configured as sliding bearings with shafts and/or sliding rails with linear ball bearing units, or else as a combination of both of these. The compensation is especially implemented up to a vertical offset of 20 mm. Advantageously, pairs of caps of the electrode pairs 15, 17 can be machined one after the other with conventional milling cutters. As an alternative or in addition, double milling cutters can be used.

(38) A decisive advantage of the distribution linkage 25 of the force path compensation device 9 as compared to pneumatic cylinders oriented in parallel and/or servo motors is the fact that they occupy less space. As a result, the design freedom in terms of the joining materials in a production device is greatly enhanced. The distance between the electrode pairs 15, 17 or the linear guides 43 and 45 is especially between 20 mm and 300 mm, especially between 40 mm and 200 mm, especially between 50 mm and 180 mm, especially between 70 mm and 150 mm, especially between 90 mm and 100 mm. In the case of an electrode distance of, for example, 100 mm, welding spot distances of 50 mm, 33 mm, 25 mm or 20 mm can be achieved by means of so-called narrow gap welding. Accordingly, the electrode distance is divided into two, three, four or five individual distances by means of one, two, three or four inserted welding spots.

(39) The described welding device 1, especially robot welding tongs, can likewise be equipped with a pneumatic or servo-motor tong compensation means. According to another aspect, in particular, a movement of a fixed electrode arm towards the components that are to be joined is achieved by means of a robot movement, especially a 7-axis function.

LIST OF REFERENCE NUMERALS

(40) 1 welding device 2 welding transformer 3 welding transformer 5 diode packet 6 secondary current cable 7 C-bracket 8 pneumatic cylinder 9 force path compensation device 10 rod 13 current measuring coil 15 electrode pair 17 electrode pair 19 source of force 20 force transmission linkage 21 electrode force 23 electrode force 25 distribution linkage 27 total electrode force 29 joint 31 joint 33 distribution joint 35 welding electrode 37 welding electrode 39 welding electrode 41 welding electrode 43 linear guide 45 linear guide 47 force transmission linkage 49 force transmission joint 51 force transmission joint 53 sliding shaft 55 sliding shaft 59 electrode holder 61 electrode holder 63 insulator 65 insulator 67 robot fastening plate 69 double inverter 71 transformers 73 transformers 75 current measuring coil 77 current measuring coil