The seam welding apparatus includes a pair of rotating electrodes, an electrode supporting frame, a distance measuring means, and a controller. The electrode supporting frame supports the pair of rotating electrodes. The distance measuring means is provided on the electrode supporting frame and measures a distance to an edge of the steel plate. The controller controls the robot to adjust a running direction of the rotating electrodes so that a deviation comes into zero when a distance actually measured by the distance measuring means deviates from a predetermined distance. Thereby, it is accomplished that the seam welding apparatus is downsized as well as uninfluenced by the surface state and/or shape of workpiece (steel plate).

The seam welding apparatus includes a pair of rotating electrodes, an electrode supporting frame, a distance measuring means, and a controller. The electrode supporting frame supports the pair of rotating electrodes. The distance measuring means is provided on the electrode supporting frame and measures a distance to an edge of the steel plate. The controller controls the robot to adjust a running direction of the rotating electrodes so that a deviation comes into zero when a distance actually measured by the distance measuring means deviates from a predetermined distance. Thereby, it is accomplished that the seam welding apparatus is downsized as well as uninfluenced by the surface state and/or shape of workpiece (steel plate).

A resistance welder controller controls a welding current flowing through an inverter transformer, detects the welding current flowing through the inverter transformer, measures an energizing time and a point time interval of the detected welding current, calculates a usage rate of the inverter transformer using the energizing time and the point time interval, stores an equivalent current curve indicating a relationship between a current value of the welding current and the usage rate of the inverter transformer when the inverter transformer is operated at a rated capacity, and determines whether a relationship between the current value and the calculated usage rate of the inverter transformer exceeds the rated capacity of the inverter transformer based on the equivalent current curve, continues an operation when the relationship does not exceed the rated capacity of the inverter transformer, and stops the operation when the relationship exceeds the rated capacity of the inverter transformer.

Provided is an inverter power supply including a measurement function of measuring deterioration of a rectifier element such as a diode.

The inverter power supply includes a step-down stabilization unit that applies a reverse voltage increasing gradually to diodes, an isolation amplifier that detects a current value of a current flowing to the diodes when the reverse voltage is applied, and an inverter control unit that decides that the diodes have deteriorated when the detected current value is larger than a determination current value for determining deterioration of the diodes, and decides that the diodes have not deteriorated when the detected current value is smaller than the determination current value.

Provided is an inverter power supply including a measurement function of measuring deterioration of a rectifier element such as a diode.

The inverter power supply includes a step-down stabilization unit that applies a reverse voltage increasing gradually to diodes, an isolation amplifier that detects a current value of a current flowing to the diodes when the reverse voltage is applied, and an inverter control unit that decides that the diodes have deteriorated when the detected current value is larger than a determination current value for determining deterioration of the diodes, and decides that the diodes have not deteriorated when the detected current value is smaller than the determination current value.

A resistance welding apparatus includes a welding tool with a welding electrode configured to contact a component. A welding transformer is configured to feed an electric current to the welding tool and a control device is configured to control a polarity of welding transformer by transmitting polarity information to the welding transformer such that a polarity of the welding transformer is switchable. A circuit including two transistors is operably connected in series between the welding tool and an output of the welding transformer and a polarity one of the transistors is rotated relative to the other transistor, such that a polarity of a welding voltage at the welding electrode is switchable with the switching of the polarity of the welding transformer, and such that a polarity of a welding current at the welding transformer is switchable with the switching of the polarity of the welding transformer.

The spot welding method of the present invention has steps of preliminary conduction, first conduction, second conduction, and third conduction: Preliminary conduction: Conduction method aimed at improving closeness of contact surfaces of steel sheets and reducing sheet gaps by gradually increasing the welding current (for example, upslope conduction). If rapidly applying current, current would be locally carried and that part would melt resulting in expulsion, so this is a conduction method gradually running current (for example upslope conduction) to avoid local heating. First conduction: Conduction method running a constant welding current and using the heat generated by the electrical contact resistance between steel sheets to cause the formation of a nugget when preliminary conduction results in close contact surfaces between the steel sheets. Second conduction: Conduction method making the current lower than the first conduction to suppress inside expulsion while making the nugget grow in the diametrical direction. Third conduction: Conduction method making the current higher than the second conduction and making the nugget grow not only in the diametrical direction, but also mainly in the sheet thickness direction when the nugget size becomes a certain extent of size at the second conduction step.

The spot welding method of the present invention has steps of preliminary conduction, first conduction, second conduction, and third conduction: Preliminary conduction: Conduction method aimed at improving closeness of contact surfaces of steel sheets and reducing sheet gaps by gradually increasing the welding current (for example, upslope conduction). If rapidly applying current, current would be locally carried and that part would melt resulting in expulsion, so this is a conduction method gradually running current (for example upslope conduction) to avoid local heating. First conduction: Conduction method running a constant welding current and using the heat generated by the electrical contact resistance between steel sheets to cause the formation of a nugget when preliminary conduction results in close contact surfaces between the steel sheets. Second conduction: Conduction method making the current lower than the first conduction to suppress inside expulsion while making the nugget grow in the diametrical direction. Third conduction: Conduction method making the current higher than the second conduction and making the nugget grow not only in the diametrical direction, but also mainly in the sheet thickness direction when the nugget size becomes a certain extent of size at the second conduction step.

Provided is an evaluation system including: an analog-to-digital converting section comprised of a programmable circuit and configured to convert an analog signal, the analog signal being acquired by a physical quantity acquiring section and indicative of a time-series change of at least one of (i) welding current, welding voltage, or load applied to pieces to be welded and (ii) a displacement, during welding, of a welding head; and an evaluating section configured to determine, based on a digital signal, whether or not the time-series change satisfies a predetermined condition, wherein configuration data for configuring the programmable circuit is arranged to be changeable by a user.

A resistance weld shielding control system includes a computer that is executed to control a fixture to receive and hold at least one part to be welded. The computer also controls one or more electrodes to apply electrical energy to the part for welding the at least one part, and controls a gas delivery system to direct an inert gas onto the part for shielding the part from the ambient atmosphere via a nozzle. The nozzle is configured in the fixture such that the fixture holds the nozzle in a fixed physical relationship to the part.