Resistance Welding Transistor Polarity Switching
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Solution Overview
Problem
Resistance welding devices face challenges such as magnetization effects, slow cycle times, and increased costs due to the need for multiple robots and complex electrode management when welding different metal combinations, especially aluminum, which requires breaking through oxide layers and handling varying material thicknesses.
Innovation Solution
A resistance welding device with a welding tool and transformer system utilizing a series connection of transistors for polarity switching, allowing for quick current decay and efficient polarity changeover, reducing cycle times and space requirements, and minimizing magnetization effects through a medium-frequency direct current transformer design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional resistance welding devices are used, then welding can be performed on metal components, but the cycle time is too long to meet the demand for shorter cycle times in automated production
Solution Approach 1:
The patent applies periodic action by using pulsed welding current with alternating polarity. The control device switches the polarity of the welding current periodically during the welding process, creating time-varying current pulses that effectively break through aluminum oxide layers while reducing overall cycle time compared to conventional continuous welding methods.
Solution Approach 2:
The patent changes the parameter of welding current polarity dynamically during the welding process. By switching the polarity between positive and negative half-cycles, the system adapts to different welding stages - using one polarity to break oxide layers and another for stable welding, thereby reducing total welding time and improving productivity.
2Reliability
If direct current is used during welding, then welding can be performed, but magnetization effects occur on the welded parts making further processing difficult
Solution Approach 1:
The patent uses alternating current with periodic polarity reversal instead of direct current. The control device switches the current polarity at regular intervals, preventing the accumulation of magnetic flux and avoiding magnetization effects on the welded parts, thereby eliminating the harmful magnetic effects while maintaining reliable welding quality.
Solution Approach 2:
Instead of using unidirectional direct current that causes magnetization, the patent inverts the current polarity periodically. This inversion approach reverses the magnetic field direction during the welding process, preventing net magnetization of the workpiece and eliminating the associated processing difficulties.
3Productivity
If two robots with welding guns are used to meet cycle times, then welding productivity increases, but space requirement and operating costs increase
Solution Approach 1:
The patent enables a single robot to achieve high welding speeds through periodic polarity switching of the welding current. This allows one welding gun to perform what would otherwise require two robots, thereby reducing space requirements and operating costs while maintaining high productivity through the time-varying current control method.
4Reliability
If welding current is not switched off quickly, then the welding process can be maintained, but the time required to produce welded connections increases
Solution Approach 1:
The control device implements periodic action by automatically switching off the welding current after a predetermined number of alternating polarity cycles. This ensures the welding process completes effectively while minimizing idle time, as the current is terminated promptly after achieving the welding objective, thereby reducing overall connection production time without compromising quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables faster cycle times, reduced costs, and improved handling of diverse metal combinations by quickly switching off the welding current and avoiding magnetization, thus meeting production demands with a single robot and minimizing resource usage.
Implementation Method 1
a series connection of two transistors between the welding tool and an output of the welding transformer are connected, with the polarity of one transistor in the series connection being rotated relative to the polarity of the other transistor in the series connection
Implementation Method 2
at least one welding transformer for supplying an electric welding current to the welding tool when welding the at least one component
Implementation Method 3
a control device for switching the series connection made up of two transistors during a converter-controlled welding time in a first operating mode and for switching the series connection off two transistors, at the end of the inverter-controlled welding time, in a second operating mode
Data Source
Figure 1~2
Figure 3~4
AI summary
A resistance welding device (2; 3) and a resistance welding process for resistance welding of at least one component (5, 6) are provided. The resistance welding device (2; 3) comprises a welding tool (10) with at least one welding electrode (11, 12) which is to be contacted with the at least one component (5, 6) for welding, at least one welding transformer (30) for supplying an electric welding current (I2) to the welding tool (10) when welding the at least one component (5, 6), a series circuit of two transistors (41, 42; 43, 44) which are connected between the welding tool (10) and an output of the welding transformer (30), wherein the polarity of one transistor (42; 44) of the series circuit is reversed relative to the polarity of the other transistor (41; 43) of the series circuit, and a control device (20) for switching the series circuit of two transistors (41, 42;43, 44) during an inverter-controlled welding time (T1) in a first operating mode (B1) and for switching the series circuit of two transistors (41, 42; 43, 44), at the end of the inverter-controlled welding time (T1) for a predetermined duration (T2; T3) in a second operating mode (B2; B200), which differs from the first operating mode (B1).