Resistance welding monitor
First Claim
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1. A resistance welding monitor comprising:
- input means for inputting data representing material characteristics of a material of a work to be welded, data representing a thickness of said work and data representing the shape of a pair of electrodes of a resistance welder,a current sensor for detecting a welding current in welding operation,welding voltage detection means for detecting a welding voltage which is a true output voltage of a power source of said resistance welder, on the basis of said welding current and said interelectrode voltage, detected by interelectrode voltage measuring means for measuring an interelectrode voltage received through a pair of coupling wire from said pair of electrodes,calculation means for deriving a contact diameter which is a diameter of a current-pass between said electrode and work and an interplate current-pass diameter which is a diameter of a contact part of plural plates of said work, on the basis of an electrode resistance of the resistance of said electrode, a contact resistance of a resistance between said electrode and the surface of the work and a work resistance which is a ratio between said welding voltage and said welding current,means for deriving a temperature distribution in said work on the basis of said welding voltage, welding current, contact diameter and interplate current pass diameter,nugget diameter calculation means for deriving a nugget diameter which is formed between said plural plates on the basis of said temperature distribution,input means for inputting data of a reference nugget diameter of a target diameter, andcomparison means for comparing said nugget diameter with said reference nugget diameter and for outputting a comparison result.
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Abstract
A welding voltage output from a power source of a resistance welder is derived on the basis of a welding current and an interelectrode voltage, and diameter of a nugget which is formed in a sheetlike work to be welded is estimated on the basis of the welding current, the welding voltage, data of material constant and a thickness of the sheetlike work, subsequently, the estimated diameter of nugget is composed with a target diameter of nugget, and thereby quality of the resistance welding is determined.
84 Citations
11 Claims
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1. A resistance welding monitor comprising:
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input means for inputting data representing material characteristics of a material of a work to be welded, data representing a thickness of said work and data representing the shape of a pair of electrodes of a resistance welder, a current sensor for detecting a welding current in welding operation, welding voltage detection means for detecting a welding voltage which is a true output voltage of a power source of said resistance welder, on the basis of said welding current and said interelectrode voltage, detected by interelectrode voltage measuring means for measuring an interelectrode voltage received through a pair of coupling wire from said pair of electrodes, calculation means for deriving a contact diameter which is a diameter of a current-pass between said electrode and work and an interplate current-pass diameter which is a diameter of a contact part of plural plates of said work, on the basis of an electrode resistance of the resistance of said electrode, a contact resistance of a resistance between said electrode and the surface of the work and a work resistance which is a ratio between said welding voltage and said welding current, means for deriving a temperature distribution in said work on the basis of said welding voltage, welding current, contact diameter and interplate current pass diameter, nugget diameter calculation means for deriving a nugget diameter which is formed between said plural plates on the basis of said temperature distribution, input means for inputting data of a reference nugget diameter of a target diameter, and comparison means for comparing said nugget diameter with said reference nugget diameter and for outputting a comparison result. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A welding voltage measuring apparatus of a resistance welder comprising:
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a current sensor for detecting a welding current and for outputting a detected voltage, interelectrode voltage detection means for detecting an interelectrode voltage across a pair of electrodes of said resistance welder, first calculation means for deriving a ratio of said detected voltage to said interelectrode voltage at a point of time of the rise edge of said welding current, second calculation means for multiplying one of said detected voltage and said interelectrode voltage by said ratio derived by said first calculation means, and for equalizing both values of said detected voltage and said interelectrode voltage at said point of time of the rise edge, and third calculation means for deriving a voltage difference between said equalized detected voltage and interelectrode voltage.
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8. A welding voltage measuring apparatus of a direct current resistance welder comprising:
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a current sensor for detecting a welding current and for outputting a detected voltage, interelectrode voltage detection means for detecting an interelectrode voltage across a pair of electrodes of said resistance welder, first voltage detection means for detecting a first detected voltage and a first interelectrode voltage at a first time immediately after said welding current has changed from decreasing phase to increasing phase, a second voltage detection means for detecting a second detected voltage and a second interelectrode voltage at a second time point immediately before said welding current will change from decreasing phase to increasing phase, first calculation means for deriving a first absolute value of a difference between said first detected voltage and said second detected voltage, and a second absolute voltage of a difference between said first interelectrode voltage and said second interelectrode voltage, and deriving a ratio of said first absolute value to said second absolute value, second calculation means for equalizing both the values of said detected voltage and said interelectrode at one of said first time and said second time by multiplying one of said detected voltage and said interelectrode voltage by said ratio, and third calculation means for deriving a voltage difference between said equalized detected voltage and said interelectrode voltage. - View Dependent Claims (9, 10, 11)
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Specification