阅读说明：本技术 用于对至少一个构件进行电阻焊接的电阻焊接装置和电阻焊接方法 (Resistance welding device and resistance welding method for resistance welding at least one component ) 是由 R.肖尔茨 于 2020-04-08 设计创作，主要内容包括：本发明涉及用于对至少一个构件进行电阻焊接的电阻焊接装置和电阻焊接方法。所述电阻焊接装置包括焊接工具、至少一个焊接变压器、由两个晶体管构成的串联线路和控制机构,焊接工具带有为了焊接应与所述至少一个构件接触的至少一个焊接电极,焊接变压器用于在焊接所述至少一个构件时将电流输送给焊接工具,两个晶体管被连接到焊接工具和焊接变压器的输出端之间,控制机构用于通过将极性信息发送给所述至少一个焊接变压器来控制所述至少一个焊接变压器的极性,其中串联线路的一个晶体管的极性相对于另一个晶体管的极性翻转,从而能够转换所述至少一个焊接变压器的极性,以在焊接变压器处实现能转换极性的焊接电压和能转换极性的焊接电流。(The present invention relates to a resistance welding apparatus and a resistance welding method for resistance welding at least one member. The resistance welding device comprises a welding tool with at least one welding electrode which is to be in contact with the at least one component for welding, at least one welding transformer for supplying a current to the welding tool when welding the at least one component, two transistors being connected between the welding tool and an output of the welding transformer, a series connection of two transistors, and a control mechanism for controlling the polarity of the at least one welding transformer by transmitting polarity information to the at least one welding transformer, wherein the polarity of one transistor of the series line is reversed with respect to the polarity of the other transistor, so that the polarity of the at least one welding transformer can be switched, to achieve a welding voltage capable of reversing polarity and a welding current capable of reversing polarity at the welding transformer.)

1. Resistance welding device (2; 3; 3A, 4) for resistance welding at least one component (6, 7), comprising a welding tool (10), at least one welding transformer (30), a series connection of two transistors (41, 42; 43, 44), and a control means (20), wherein the welding tool (10) has at least one welding electrode (11, 12) which is to be brought into contact with the at least one component (6, 7) for welding, wherein the at least one welding transformer (30) is used for supplying a current to the welding tool (10) during welding of the at least one component (6, 7), wherein the two transistors (41, 42; 43, 44) are connected between the welding tool (10) and an output of the welding transformer (30), and wherein the control means (20) is used for controlling the welding of the at least one component by supplying polarity information (25A, 25B; 26A, 27A; 28A, 29A) to the at least one welding transformer (30), wherein one transistor (42; 44) with respect to the polarity of the other transistor (41; 43) so that the polarity of the at least one welding transformer (30) can be switched to achieve a polarity-switchable welding voltage (U21, U22) and a polarity-switchable welding current (I2) at the welding transformer (30).

2. Resistance welding device (2; 3; 3A, 4) according to claim 1, wherein the control mechanism (20) is configured for a voltage (U) at a primary side applied to the at least one welding transformer (30)_W) Providing the polarity information (25A, 25B).

3. Resistance welding device (2; 3; 3A, 4) according to claim 1 or 2, wherein the control means (20) are configured for providing the polarity information (26A, 27A) in the form of a digital signal.

4. Resistance welding device (2; 3; 3A, 4) according to any of the preceding claims, wherein the voltage (U) is other than for the voltage that should be applied at the primary side of the at least one welding transformer (30)_W) The control mechanism (20) and the at least one welding transformer (30; 300) is also guided through at least one guide path (26, 27; 28. 29) and wherein the control mechanism (20) is configured for controlling the movement of the at least one guide path (26, 27; 28. 29) transmitting the polarity information (26A, 27A; 28A, 29A) to the welding transformer (30; 300).

5. Resistance welding device (2; 3; 3A, 4) according to one of the preceding claims, wherein the at least one welding transformer (30) has a polarity conversion mechanism (35), the polarity conversion mechanism (35) being configured for evaluating the polarity information (25A, 25B; 26A, 27A; 28A, 29A), and the polarity conversion mechanism (35) being configured for converting the polarity of the at least one welding transformer (30) on the basis of the evaluation result.

6. Resistance welding device (2; 3; 3A, 4) according to any of the preceding claims, wherein the at least one welding transformer (30) is constituted by a parallel line of at least two transformers (30 _1, 30_ 2).

7. Resistance welding device (2; 3; 3A, 4) according to claims 5 and 6, wherein the polarity switching mechanism (35) is configured for switching all at least two transformers (30 _1, 30_ 2) in parallel always into the same polarity.

8. Resistance welding device (2; 3; 3A, 4) according to any of the preceding claims, furthermore having a detection means (15), the detection means (15) being adapted to detect a voltage (U) between the two welding electrodes (11, 12) when welding with the welding tool (10)_E) Detection is carried out, wherein the control means (20) are configured to pass the voltage (U) to be detected by the detection means (15)_E) With said voltage (U)_E) Is compared against a predetermined reference value to check for a polarity reversal.

9. Resistance welding device (2; 3; 3A, 4) according to one of the preceding claims, wherein the welding transformer (30) has two outputs (31, 33), at which outputs (31, 33) a series connection of two transistors (41, 42; 43, 44) is connected in front of the welding tool (10), respectively.

10. Resistance welding device (2; 3; 3A, 4) according to any of the preceding claims, wherein the two transistors (41, 42; 43, 44) are metal oxide semiconductor field effect transistors.

11. Resistance welding device (2; 3; 3A, 4) according to any of the preceding claims, wherein the welding tool (10) is a welding tongs with two welding electrodes (11, 12), the at least one component (6, 7) being arranged between the welding electrodes (11, 12) when welding.

12. Apparatus (1) for processing articles (5) having a resistance welding device (2, 3; 3A, 4) according to any one of the preceding claims, wherein the resistance welding device (2, 3; 3A, 4) is provided for resistance welding at least one component (6, 7), the at least one component (6, 7) being provided for processing at least one of the articles (5).

13. The apparatus (1) according to claim 12, wherein the apparatus (1) is configured for producing a crude body of a transport means or a heating body or a chain as the object (5).

14. Resistance welding method for resistance welding at least one component (6, 7) by means of a resistance welding device (2; 3; 3A, 4), wherein the resistance welding device (2; 3; 3A, 4) has a welding tool (10), at least one welding transformer (30), a series connection of two transistors (41, 42; 43, 44) and a control means (20), the welding tool (10) has at least one welding electrode (11, 12) which is to be brought into contact with the at least one component (6, 7) for welding, the at least one welding transformer (30) is used for supplying a current to the welding tool (30) during welding of the at least one component (6, 7), the two transistors (41, 42; 43, 44) are connected between the welding tool (10) and an output of the welding transformer (30), wherein the resistance welding method has the steps of: sending polarity information (25A, 25B; 26A, 27A; 28A, 29A) to the at least one welding transformer (30) by means of the control device (20) for controlling the polarity of the at least one welding transformer (30); the polarity of the two transistors (41, 42; 43, 44) is switched in such a way that: switching on one of the transistors (41; 43) in dependence on the polarity information (25A, 25B; 26A, 27A; 28A, 29A); and in synchronous operation with current, the transistors (42; 44) connected in series with the connected transistors (41; 43) are switched on in a positively conducting manner, so that the polarity of one transistor (42; 44) of the series circuit is reversed with respect to the polarity of the other transistor (41; 43) of the series circuit in order to achieve a welding voltage (U21, U22) and a welding current (I2) of a switchable polarity at the welding transformer (30).

Technical Field

The present invention relates to a resistance welding apparatus and a resistance welding method for resistance welding at least one member.

Background

Resistance welding of various sheet metal combinations is used, for example, in automated vehicle production, in which a welding device establishes a welded connection, for example, on the body of a vehicle, such as a motor vehicle, a truck, an aircraft, or the like. In this case, as in other production plants, such as, for example, production lines for furniture, heating bodies, etc., the metal parts are joined by welding by means of a welding tool of a welding device.

Furthermore, welding devices, in particular resistance welding devices, can also be used in the single-piece production.

Magnetization of the welded components may occur due to the direct current during welding. Which makes further processing of the welded metal parts difficult.

Due to possible magnetization of the equipment parts, contamination and malfunctions in the welding equipment may occur.

Furthermore, due to the different alloys, different plate thickness combinations and the peltier effect (peltier effect) for the welded plates, undesirable burning or material creep (material walking) at the welding electrode may occur depending on the welding current direction in the case of aluminum.

These effects occur, inter alia, when resistance welding is performed on the chain links and when welding is performed on the heating body.

In order to avoid magnetization effects, it is conceivable to use a rectifier with four thyristors instead of the conventional diode rectifier, which is usually installed in a resistance welding device for providing a welding current.

However, this solution has the disadvantage that, in comparison with diode rectifiers, rectifiers with four thyristors require on the one hand twice the installation space. Due to the double construction space, a rectifier with four thyristors becomes very awkward and inefficient in terms of operation. This is not only disadvantageous for devices for moving the resistance welding device in space, such as for example robots.

On the other hand, a rectifier with four thyristors shows worse operation characteristics than a diode rectifier because the rectifier with four thyristors has higher losses and lower power. The worse operating characteristics are undesirable in view of the economical use of resources. Furthermore, the poorer operating characteristics result in higher costs for the operator of the resistance welding device.

Furthermore, it is possible to reverse the polarity of the welding voltage for the welding tool. In such cases, however, cables must be provided between a welding transformer, which is arranged in the welding tool, which is operated in particular by the robot, and a current transformer in the welding control, which is arranged in a stationary manner. A 24V signal can be transmitted via the cable, and the polarity of the welding voltage can be changed by means of this 24V signal. Such additional cabling in connection with robots is limited by the principle that implies a high risk with regard to e.g. cable defects, especially cable breaks and/or open plugs at the transformer and/or cable replacements. This requires that a feedback signal is additionally fed back from the transformer to the welding control unit and that the feedback signal is monitored in the transformer and/or the control unit. This monitoring also has the aspect of quality assurance as to the strength of the weld. If multiple transformers are to be connected in parallel, all transformers have to be connected to additional cables. This means a large space requirement for the respective connection at the transformer and a large wiring outlay.

Disclosure of Invention

It is therefore the object of the present invention to provide a resistance welding device and a resistance welding method for resistance welding at least one component, with which the above-mentioned problems can be solved. In particular, a resistance welding device and a resistance welding method for resistance welding at least one component are to be provided, for which a disturbing magnetization effect is avoided very effectively, in a trouble-free, cost-effective manner and with high reliability.

This object is achieved by a resistance welding device for resistance welding at least one component according to claim 1. The resistance welding device comprises a welding tool, at least one welding transformer, a series circuit formed by two transistors and a control mechanism, the welding tool is provided with at least one welding electrode which is to be contacted with at least one component for welding, the at least one welding transformer is for delivering current to the welding tool while welding at least one component, the two transistors being connected between the welding tool and an output of the welding transformer, the control mechanism being configured to control the polarity of the at least one welding transformer by sending polarity information to the at least one welding transformer, wherein the polarity of one transistor of the series line is reversed with respect to the polarity of the other transistor of the series line, the polarity of at least one welding transformer can thereby be switched in order to achieve a welding voltage with switchable polarity and a welding current with switchable polarity at the welding transformer.

In the case of the resistance welding device, no additional cables have to be routed between the stationary welding control and the welding transformer in order to achieve a polarity reversal of the transformer of the welding device. This represents a great advantage, since the welding transformer is usually moved in space together with the welding tool. This makes it possible to construct the welding transformer in a small overall size and with low losses, without having to accept safety losses as a result. The welding transformer is preferably designed as a medium-frequency direct-current transformer (MF-DC transformer) and is also referred to as a transformer rectifier unit.

With the described configuration, the described resistance welding device can be used to avoid disturbing magnetization effects in conventional diode rectifiers very effectively, without problems, cost-effectively and with high reliability.

The claimed resistance welding device has smaller losses and less installation space but higher power than the thyristor solution described above. Furthermore, the resistance welding device claimed in the claims has similar properties and a similar construction space but smaller losses compared to MF-DC transformers with diode rectifiers according to the prior art.

Overall, with the claimed resistance welding device, a trouble-free, executable and checkable polarity reversal of the welding transformer can be achieved with small overall dimensions, with small losses and with little effort.

Further advantageous embodiments of the device are specified in the dependent claims.

It is possible that the control unit is designed to provide polarity information in the voltage applied to the primary side of the at least one welding transformer.

It is conceivable that the control means are designed to provide the polarity information in the form of a digital signal.

In addition to the connection for the voltage to be applied to the primary side of the at least one welding transformer, the control device and the at least one welding transformer can be connected by at least one line, wherein the control device is designed to transmit polarity information to the welding transformer via the at least one line.

The at least one welding transformer can have a polarity-switching mechanism configured to evaluate the polarity information and to switch the polarity of the at least one welding transformer based on the evaluation.

Optionally, the at least one welding transformer is formed by a parallel connection of at least two transformers.

The polarity switching mechanism can be designed to switch all of the at least two transformers connected in parallel to the same polarity.

It is also possible that the resistance welding device is further provided with a detection device for detecting a voltage between the two welding electrodes during welding with the welding tool, wherein the control device is designed to check the polarity reversal by comparing the voltage detected by the detection device with a predetermined reference value for the voltage.

The welding transformer can have two outputs, to each of which a series connection of two transistors is connected upstream of the welding tool.

The two transistors may alternatively be metal oxide semiconductor field effect transistors.

In one embodiment, the welding tool is a welding tongs with two welding electrodes, between which at least one component is arranged during welding.

The resistance welding apparatus described above can be part of an apparatus arranged for processing an object. The resistance welding device can be provided for resistance welding at least one component, which is provided for processing at least one of the objects. The device can be designed for producing a transport vehicle raw body or a body-in-white (Fahrzeugrohkarossen) or a heating body or a chain as an object.

The object is also achieved by a resistance welding method for resistance welding at least one component according to claim 14. The resistance welding method is carried out using a resistance welding device having a welding tool with at least one welding electrode which is to be brought into contact with at least one component for welding, at least one welding transformer for supplying a current to the welding tool during welding of the at least one component, a series circuit of two transistors which are connected between the welding tool and an output of the welding transformer, and a control mechanism. Here, the resistance welding method includes the steps of: sending polarity information to the at least one welding transformer with the control mechanism for controlling the polarity of the at least one welding transformer; switching the polarities of the two transistors by: turning on one of the transistors according to the polarity information; and in synchronous operation with current, the transistors connected in series with the connected transistors are switched on in a positive-conducting manner, whereby the polarity of one transistor of the series circuit is reversed with respect to the polarity of the other transistor of the series circuit in order to achieve a welding voltage of switchable polarity and a welding current of switchable polarity at the welding transformer.

The resistance welding method achieves the same advantages as mentioned above in connection with the resistance welding device.

Other possible embodiments of the invention also include combinations of features or embodiments not explicitly mentioned above or below in connection with the examples. A person skilled in the art will also add individual aspects here as an improvement or supplement to the corresponding basic form of the invention.

Drawings

The invention is further described below with reference to the drawings and in accordance with embodiments. Wherein:

fig. 1 shows a block diagram of an apparatus with a resistance welding device according to a first embodiment;

fig. 2 shows a first example of a first part of a profile of the network supply voltage for a welding transformer of the resistance welding device according to the first embodiment;

fig. 3 shows a second example of a first part of a profile of the network supply voltage for a welding transformer of the resistance welding device according to the first embodiment;

fig. 4 shows a block diagram of a parallel circuit of a transformer of the resistance welding device according to the second embodiment;

fig. 5 shows a block diagram of a parallel circuit of a transformer of the resistance welding apparatus according to the modification, i.e., the third embodiment; and is

Fig. 6 shows a block diagram of a device with a resistance welding apparatus according to a fourth embodiment.

In the figures, identical or functionally identical elements are provided with the same reference symbols, unless otherwise indicated.

Detailed Description

Fig. 1 very schematically shows an apparatus 1 with a resistance welding device 2. The device 1 can be, for example, a production device for articles 5, such as, for example, transport means, furniture, heating bodies, etc.

In the production apparatus 1, the metal members 6, 7 can be thus connected by resistance welding, thereby establishing the welded connection 8. It is possible here for example for the two edges of the individual components 6 to be connected to one another by resistance welding with one or more weld connections 8. Whatever the number of components 6, 7 are connected to each other by means of a welded connection 8, which welded connection 8 can be a spot weld or a weld seam or a combination thereof.

For welding, the resistance welding device 2 has a welding tool 10 in the form of a welding tongs with two welding electrodes 11, 12, a counter electrode voltage U arranged on the welding tool 10_EA detection device 15 for detection, a welding control device or control device 20 (welding control device or control device 20 having a converter 22 connected thereto with an output 25), a welding transformer 30 having three outputs 31, 32, 33 and an evaluation unit 35, a rectifier branch or rectifier circuit 40 formed by a first transistor 41, a second transistor 42, a third transistor 43, a fourth transistor 44, and a device 50 for actuating the welding tool 10.

The resistance welding device 2 is capable of establishing a weld connection 8 with a welding tool 10 under the control of the control mechanism 20. For this purpose, the converter 22 provides an ac voltage U at its output for supplying power to a transformer 30_W. The alternating voltage U_WAn input U to the transformer 30 is connected to the primary side of the transformer 30₁The above. The alternating voltage U_WFor powering the transformer 30 for providing the welding current I2.

On the secondary side of the welding transformer 30, a first secondary voltage U21 is present between the first and second output 31, 32 of the welding transformer 30. Furthermore, a second secondary voltage U22 is applied between the second and third outputs 32, 33 of the welding transformer 30. The first secondary voltage U21 and the second secondary voltage U22 form a welding voltage U21, U22, which welding voltage U21, U22 induces a welding current I2.

The first transistor 41 is connected to the first output 31 of the welding transformer 30. A second transistor 42 is connected in series with the first transistor 41. Thereby, a series line composed of the first and second transistors 41, 42 is connected between the welding transformer 30 and the welding tool 10. More precisely, the series connection of the first and second transistors 41, 42 is connected between the welding transformer 30 and the first welding electrode 11.

The second welding electrode 12 is directly connected to a second output 32 of the welding transformer 30.

The third transistor 43 is connected to the third output 32 of the welding transformer 30. A fourth transistor 44 is connected in series with the third transistor 43. Thereby, a series line composed of the third and fourth transistors 43, 44 is connected between the welding transformer 30 and the welding tool 10. More precisely, the series line formed by the third and fourth transistors 43, 44 is connected between the welding transformer 30 and the first welding electrode 11.

The control means 20 can be operated by means of an alternating voltage U shown in fig. 2 with respect to time t_WTogether with the polarity switching module 35 of the transformer 30, the transistors 41, 42, 43, 44 are switched as described below for changing the polarity of the transformer 30. According to FIG. 2, the alternating voltage U_WFor this purpose, polarity information 25A, 25B is provided, i.e. information about how the polarity of the transformer 30 should be switched.

The polarity switching module 35 switches the polarity of the transformer 30 to the ac voltage U_WThe polarity information 25A, 25B of (a) was evaluated. The polarity switching module 35 is capable of performing an evaluation at least in part by means of software running on the polarity switching module 35.

For example, the polarity switching module 35 is adjusted such that the alternating voltage U is present_WThe polarity information 25A, 25B of (a) was evaluated assuming that: at the beginning of the welding time T, the first power pulse from the converter 22 to the transformer 30 is always applied as a connection U to the primary side of the transformer 30₁Upper positive voltage U_WAs shown in fig. 2. In one embodiment, this positive voltage U forming polarity information 25A_WIt can be evaluated by the converter 22 and/or the polarity switching module 35 in such a way that the positive polarity is to be switched on for the transformer 30. Thus, the polarity switching module 35 control transistors 41, 42, 43, 44 for setting a predetermined positive polarity of transformer 30.

For the connection U at the primary side of the transformer 30₁First negative voltage U_WIn other words, this negative voltage can be recognized by the polarity switching module 35 as a negative output voltage U of the control means 20_W. The first negative voltage U_WPolarity information 25B is thus formed, as shown in fig. 2. The polarity switching module 35 therefore controls the transistors 41, 42, 43, 44 for setting the transformer 30 from the positive polarity of the transformer 30 to the now predetermined negative polarity.

FIG. 3 shows the voltage U of FIG. 2_WAn alternative to (2). In the alternative according to fig. 3, the polarity switching module 35 is adjusted in such a way that the alternating voltage U is present_WThe polarity information 25A, 25B of (a) was evaluated assuming that: at the beginning of the welding time T, the first power pulse from the converter 22 to the transformer 30 is always applied as a connection U to the primary side of the transformer 30₁Negative voltage U of_WTo be implemented. Therefore, the polarity of the transformer 30 can be switched accordingly, as preset in the polarity switching module 35.

The control means 20 of fig. 1 can thus be operated by applying an alternating voltage U to the alternating voltage U_WIs provided to predetermine how the polarity of the transformer 30 should be switched. The control of the transistors 41 to 44 is then performed by the polarity switching module 35, which polarity switching module 35 switches the ac voltage U_WWas evaluated for polarity. The polarity switching module 35 is designed to be dependent on the alternating voltages U, respectively_WAnd a polarity pre-selection to turn on one of the transistors 41, 42, 43, 44. In synchronous operation with current, the series-connected transistors of the transistors 41, 42, 43, 44 are then switched on in negative conduction.

For example, the control means 20 switches on the first transistor 41 in accordance with the output voltage and the polarity preselection, respectively. The second transistor 42 connected in series is then switched on in negative conduction during synchronous operation with current.

In principle, it is suitable that the transistor pair for polarity selection is positively conducting, while the transistor pair for synchronous rectification is negatively conducting. Therefore, it is applicable in the above-described embodiment that the transistors 41, 43 for polarity selection are positively turned on, and the transistors 42, 44 for synchronous rectification are negatively turned on. The transistors 41, 43 of fig. 1 can be omitted if no pole switching is required. Alternatively, the transistors 42, 44 of fig. 1 can be omitted.

In particular, the transistors 41, 42 are N-channel MOSFETs. The same applies to the transistors 43, 44.

Thus, for each rectifier, two transistors, i.e. in this exemplary embodiment transistors 41, 42, are then switched on in series in the rectifier branch or rectifier line 40. The same applies in the same way to a series connection of third and fourth transistors 43, 44 with further rectifiers as rectifier branches or rectifier lines 40.

In this way, a welding voltage U21, U22 of switchable polarity and a welding current 12 of switchable polarity can be achieved at the welding transformer 30.

Thus, the polarity information 25A, 25B is associated with the power connections of the transformer 30. Thus, no cables are required between the additional 24V output at the converter 22 and the corresponding input at the transformer 39 for pole switching. Furthermore, a feedback signal for informing the actual polarity of the transformer 30 as a function of the evaluation by the polarity module 35 can be dispensed with. Instead, the detection means 15 can detect the electrode voltage U for welding that is present according to the standard on the basis of the reference value that is made during commissioning_EThe polarity monitoring is performed in such a way that the polarity is correctly connected. In other words, the polarity module 35 and/or the control device 20 can utilize the voltage U at the electrodes 11, 12 during welding by means of the detection device 15_EAnd said voltage U_EAnd the voltage U at the electrodes 11, 12_ETo perform said polarity monitoring. The reference value can be stored in the polarity module 35 and/or in the control means 20.

Independently of the two variants according to fig. 2 and 3, the following procedure is used when controlling by means of the control device 20, and also when welding components of different thicknesses, such as sheet metal or the like. In this case, the great advantages described below are achieved in particular for aluminum plates but not only for such components.

For such components, the control device 20 controls the pole change in such a way that the positive electrode of the welding tool 10 rests on, for example, the thicker component 6 and the negative electrode of the welding tool 10 rests on the thinner component 7. The weld nugget or the weld connection 8 is thereby drawn more into the thicker component 6, since the positive electrode or the electrode cap arranged thereon is always hotter than the negative electrode or the electrode cap arranged thereon during welding, and furthermore the thinner component 7 is in principle hotter than the thicker component 6. The hottest spot during welding is thereby always shifted in the direction of the positive electrode, i.e. in this case in the direction of the thicker component 6 against which the positive electrode is applied.

Thus, depending on which component 6, 7 is assigned to which electrode 11, 12 of the welding tool 10, the electrodes 11, 12 of the welding tool 10 can be switched quickly and reliably from negative to positive or reverse by means of the pole change controlled in this way, in order to establish a high-quality weld connection 7. Thus, there is no need to flip the bonding tool 10 from one bonding location to another. This is particularly advantageous because the turning of the bonding tool 10 is time-consuming and requires a large amount of control and is therefore costly. Furthermore, the tilting of the welding tool 10 may be associated with a high risk of collision or even not possible at all due to the narrow spatial conditions at the components.

Another advantage of the control by the control mechanism 20 described above is that the cap burn-out at the electrodes 11, 12 is evenly adjusted by the pole switching. That is, a correspondingly greater cap burn-out occurs at the hotter positive electrode than at the negative electrode. The cap is milled out when the maximum burn-out is reached and replaced after a number of mills, which causes downtime in production. Since each of the electrodes 11, 12 is connected as a positive electrode or as a negative electrode as required by the pole change, milling is less necessary and the cap needs to be replaced less frequently. The described control by the control means 20 thus enables a more efficient use of the time for production. Furthermore, valuable resources and costs are saved due to the infrequent need for cap replacement.

The resistance welding device 2 can thus be used particularly advantageously in sheet metal combinations in which undesirable burning or material creep of the welding electrodes 11, 12 occurs when the welding tongs are used as a welding tool 10. Furthermore, the resistance welding device 3 can be used particularly advantageously when welding links and when welding heating bodies.

Fig. 4 shows a resistance welding device 3 according to a second embodiment. The resistance welding device 3 is constructed in many parts in the same manner as described for the resistance welding device 2 according to the previous embodiment.

Unlike the resistance welding apparatus 2 according to the previous embodiment, the resistance welding apparatus 3 according to the present embodiment has a welding transformer 300, and the welding transformer 300 is constituted by a parallel line of two transformers 30_1, 30_ 2. Each of the two transformers 30_1, 30_2 can be designed like the transformer 30 according to fig. 1. Each of the two transformers 30_1, 30_2 is connected to the output 25 of the control means 20.

Furthermore, the transformer 30_1 is connected to the control unit 20 via a bus line 26. Furthermore, the transformer 30_1 is connected to the control unit 20 via a bus line 27. The bus lines 26, 27 form a bus via which the data 260, 270 can be transmitted, preferably in real time. Polarity information 26A, 27A can be transmitted in the data 260, 270. In particular, the communication takes place over said bus using the Sercos protocol or the ethernet protocol or the CAN protocol or any other industrial bus.

"real-time" refers to the operation of the computing system in which the processing of the generated data takes place according to section 9 (process flow) of the standard DIN 44300 (information processing) which is supplanted by DIN ISO/IEC 2382 during this timeThe program of data is prepared to run continuously in such a way that the processing result is available within a predetermined time period. The data can be generated according to a random distribution over time or at predetermined times, depending on the application. The control means 20 and the polarity switching module 35 are therefore designed in such a way that no delays are caused and occur by their hardware and software, which delays prevent compliance with these conditions. Therefore, the switching of the polarity of the transformers 30_1, 30_2, 300 for the voltage U is performed sufficiently fast enough_WSo as not to be influenced by said voltage U_WA delay is generated in the execution of the welding process at least one component 6, 7.

Therefore, the polarity of the parallel-connected transformers 30_1, 30_2 is controlled for the transformer 300 via the bus lines 26, 27. The polarity information 26A, 27A transmitted via the bus lines 26, 27 can be evaluated by means of the polarity switching modules 35_1, 35_ 2. The polarity information 26A, 27A can also have the actual polarity of the associated transformer 30_1, 30_ 2. The polarity of the respective transformer 30_1, 30_2 can be switched with the polarity switching module 35_1, 35_ 2. The polarity switching modules 35_1, 35_2 are designed to switch the polarity of the transformers 30_1, 30_2 in such a way that the polarity of the transformers 30_1, 30_2 is always the same. By means of the detection means 15, it is possible to use the voltage U for the electrodes, which is present as a standard during welding_EAnd the electrode voltage U on said electrodes 11, 12_EThe polarity monitoring is performed by comparison of the reference values of (a).

The previously described control of the polarity of the transformer 300 by means of the power connection 25 with the correct polarity represents a very safe solution in terms of transformer parallel lines, since each transformer 30_1, 30_2 has the same power supply.

In the variant of fig. 4, therefore, no additional wiring complexity is required either, but the polarity of the transformer 300 is switched using the existing bus lines 26, 27.

Of course, in a modification of the present embodiment, the welding transformer 300 can be constituted by a parallel line of two or more transformers 30_1, 30_ 2. In this case, further transformers are also connected to the bus lines formed by the bus lines 26, 27, respectively.

Alternatively, the previously described polarity reversal can also be carried out with the aid of the information 26A, 27A and the bus lines 26, 27 in the case of the transformer 30 of fig. 1, i.e. without further transformers connected in parallel. In this case, in addition to or as an alternative to the polarity information 25A, 25B, one of the pieces of information 26A, 27A can be provided and used by means of one of the bus lines 26, 27 for carrying out the polarity reversal. Redundancy can thereby also be ensured. Furthermore, it can be selected that the voltage U is used_WShould also use the information 26A, 27A obtained by means of one of the bus conductors 26, 27.

Fig. 5 shows a resistance welding apparatus 3A according to a third embodiment. The resistance welding device 3A is constructed in many parts in the same manner as described for the resistance welding device 3 according to the previous embodiment.

Unlike the resistance welding device 3 according to the preceding embodiment, the resistance welding device 3A according to the present embodiment has discrete connections or lines 28, 29, with which connections or lines 28, 29 the control of the polarity reversal of the transformers 30_1, 30_2 and thus of the transformer 300 is effected. The polarity information 28A, 29A is transmitted in the form of digital signals through discrete connectors or guides 28, 29. The signal has at least two different values during the course of time t, which have a sufficient distance in order to transmit different polarities as information 28A, 29A.

By means of a variant of the transformers 30_1, 30_2, 300, the polarity of the transformers 30_1, 30_2, 300 can be controlled discretely, for example for an external control unit. Thus, the welding control means at the upper stage that controls the plurality of welding tools 10 can operate the transformers 30_1, 30_2, and 300. Furthermore, the polarity or the switching thereof can be monitored in the control unit 20 by additional wiring by means of discrete connections or lines 28, 29.

Another advantage of such a control of the polarity of the transformers 30_1, 30_2, 300 is that the MOSFET transformers up to now, together with their supply of 24V, are easily exchanged for transformers 30_1, 30_2, 300 with pole switching, which is necessary subject to the process. Such a replacement can be carried out for a correspondingly adapted converter 22 without changing the existing cable set of the device 10, since no additional connections are required at the transformers 30_1, 30_2, 300.

As an alternative, the previously described polarity reversal can also be implemented for the transformer 30 of fig. 1 by means of the information 28A, 29A and the lines 28, 29. In addition or as an alternative to the polarity information 25A, 25B, one of the information 28A, 29A can be provided and used via one of the guides 28, 29 for performing the polarity reversal. Redundancy can thereby also be ensured.

Fig. 6 shows a resistance welding device 4 according to a second embodiment. The resistance welding device 4 is constructed in many parts in the same manner as described for the resistance welding device 2 according to the first embodiment.

Unlike the resistance welding apparatus 2 according to the first embodiment, in the resistance welding apparatus 4 according to the present embodiment, the transistors 41, 42, 43, 44 are each configured exclusively as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET). The mosfets are connected in anti-parallel in the resistance welding device 4.

As shown in fig. 6, the primary voltage U1 on the primary side of the welding transformer 30 is generated by the bridge circuit 70 of the semiconductor switches 71, 72, 73, 74. The semiconductor switches 71, 72, 73, 74 can in particular each be a Bipolar Transistor (IGBT = Insulated-Gate Bipolar Transistor) of a current transformer having an Insulated Gate electrode.

In the circuit 70, the first semiconductor switch 71 and the second semiconductor switch 72 are connected in series. Furthermore, the third semiconductor switch 73 is connected in series with the fourth semiconductor switch 74. Between a first connection node 81 arranged between the first and second semiconductor switches 71, 72 and a second connection node 82 arranged between the third and fourth semiconductor switches 73, 74, a primary voltage U1 is formed at the primary side of the welding transformer 30.

On the secondary side of the welding transformer 30, a first secondary voltage U21 is applied between the first and second outputs 31, 32 of the welding transformer 30. Furthermore, a second secondary voltage U22 is applied between the second and third outputs 32, 33 of the welding transformer 30. The first secondary voltage U21 and the second secondary voltage U22 form welding voltages U21, U22.

The welding transformer 30 converts the primary voltage U1 into first and second secondary voltages U21, U22. Here, the sum of the secondary voltages U21, U22 is smaller than the value of the primary voltage U1. Furthermore, the welding transformer 30 converts a primary current I1 at the primary side of the welding transformer 30 into a secondary current I2 at the secondary side of the welding transformer 30. The secondary current 12, which can also be referred to as welding current, has a higher value than the primary current I1.

The circuit of the welding device 4 shown in fig. 6 is connected by the control means 20 in the same way as described in relation to the previous embodiment.

The welding device 4 can be used in the apparatus 1 according to the first embodiment instead of the welding device 2. In particular, the rectifier 400 can be constructed in the same manner as described in relation to the first and second embodiments.

The welding device 4 can also be used particularly advantageously in sheet metal combinations for which different degrees of burning of the welding electrode occur in the welding tongs. Furthermore, the welding device 4 can be used particularly advantageously when welding links and when welding heating bodies.

All of the previously described embodiments of the device 1, the resistance welding apparatuses 2, 3A, 4 and the resistance welding method can be used individually or in all possible combinations. In particular, all features and/or functions of the embodiments described above can be combined arbitrarily. In particular, the following modifications can be additionally taken into account.

The components shown in the figures are illustrated schematically and can differ from the forms shown in the figures in the precise design, as long as the previously described function thereof is ensured.

The transistors 41, 42, 43, 44 can also be bipolar transistors, but are preferably designed as Metal Oxide Semiconductor Field Effect Transistors (MOSFETs).

Alternatively or additionally, it is possible that not (only) the polarity module 35 but also the control device 20 is designed to switch the series-connected transistors 41, 43 in negative conduction during synchronous operation with current.