Spot welding system and spot welding method and nugget diameter estimation system and nugget diameter estimation method
First Claim
Patent Images
1. A spot welding system comprising:
- a first and a second electrode adaptive for a relative advancement to each other to hold therebetween a welding spot of a work and for a relative retreat form each other to set free the welding spot;
a mechanism for biasing either electrode of the first and the second electrode with a controlled pressure in a direction in which the either electrode makes the relative advancement;
a power supply for supplying a controlled voltage between the first and the second electrode;
a detector for detecting a variation of a distance between the first and the second electrode; and
a controller for controlling a welding quality of the welding spot on a basis of a detected variation of the distance, the controller comprising;
an extrenum holder for holding an extrenum of the detected variation before a spattering at the welding spot;
a base setter for setting a base to be the detected variation upon a restart of a thermal expansion of the welding spot after the spattering with a continued welding current conducted through the welding spot;
an adder for adding a difference between the base and the detected variation to the extrenum to provide a corrected variation;
an integrator for determining a time integration of the corrected variation;
an estimator for estimating a size of a nugget of the welding spot on a basis of the time integration; and
a decision-maker for making a decision on a conformity of the welding quality on a basis of an estimated size of the nugget.
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Accused Products
Abstract
A welding spot is held between electrodes either biased with a controlled pressure, having a controlled voltage applied thereacross, and variations of an inter-electrode distance are detected for a welding quality control, in which the distance variations are time-integrated, a nugget size is estimated on a basis of the integration, and a decision is made of a conformity of welding quality based on an estimated nugget size.
32 Citations
37 Claims
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1. A spot welding system comprising:
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a first and a second electrode adaptive for a relative advancement to each other to hold therebetween a welding spot of a work and for a relative retreat form each other to set free the welding spot; a mechanism for biasing either electrode of the first and the second electrode with a controlled pressure in a direction in which the either electrode makes the relative advancement; a power supply for supplying a controlled voltage between the first and the second electrode; a detector for detecting a variation of a distance between the first and the second electrode; and a controller for controlling a welding quality of the welding spot on a basis of a detected variation of the distance, the controller comprising; an extrenum holder for holding an extrenum of the detected variation before a spattering at the welding spot; a base setter for setting a base to be the detected variation upon a restart of a thermal expansion of the welding spot after the spattering with a continued welding current conducted through the welding spot; an adder for adding a difference between the base and the detected variation to the extrenum to provide a corrected variation; an integrator for determining a time integration of the corrected variation; an estimator for estimating a size of a nugget of the welding spot on a basis of the time integration; and a decision-maker for making a decision on a conformity of the welding quality on a basis of an estimated size of the nugget. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A spot welding system comprising:
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a first and a second electrode adaptive for a relative advancement to each other to hold therebetween a welding spot of a work and for a relative retreat from each other to set free the welding spot; a mechanism for biasing either electrode of the first and the second electrode with a controlled pressure in a direction in which the either electrode makes the relative advancement; a power supply for supplying a controlled voltage between the first and the second electrode; a detector for detecting a variation of a distance between the first and the second electrode; and controlling means for controlling a welding quality of the welding spot on a basis of the detected variation of the distance, the controlling means comprising; extrenum holding means for holding an extrenum of the detected variation before a spattering at the welding spot; base setting means for setting a base to be the detected variation upon a restart of the thermal expansion of the welding spot after the spattering with a continued welding current conducted through the welding spot; adding means for adding a difference between the base and the detected variation to the extrenum to provide a corrected variation; integrating means for determining a time integration of the corrected variation; estimating means for estimating a size of a nugget of the welding spot on a basis of the time integration; and deciding means for making a decision on conformity of the welding quality on a basis of an estimated size of the nugget. - View Dependent Claims (16)
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17. A spot welding method comprising the steps of:
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having a first and a second electrode making a relative advancement to each other to hold therebetween a welding spot of a work; biasing either electrode of the first and the second electrode with a controlled pressure in a direction in which the either electrode makes the relative advancement; supplying a controlled voltage between the first and the second electrode; detecting a variation of a distance between the first an the second electrode; and controlling a welding quality of the welding spot on a basis of the detected variation of the distance, the controlling step comprising; holding an extrenum of the detected variation before a spattering at the welding spot; setting a base to be the detected variation upon a restart of the thermal expansion of the welding spot after the spattering with a continued welding current conducted through the welding spot; adding a difference between the base and the detected variation to the extrenum to provide a corrected variation; determining a time integration of the corrected variation; estimating a size of a nugget of the welding spot on a basis of the time integration; and making a decision on a conformity of the welding quality on a basis of an estimated size of the nugget. - View Dependent Claims (18)
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19. A nugget size estimation system comprising:
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an extrenum holder for holding an extrenum of a detected variation of a distance between electrode that have a welding spot held therebetween under pressure, as the extrenum has occurred before a spattering at the welding spot; a base setter for setting a base to be the detected variation upon a restart of a thermal expansion of the welding spot after the spattering with a continued welding current conducted through the welding spot; an adder for adding a difference between the base and the detected variation to the extrenum to provide a corrected variation; an integrator for determining a time integration of the corrected variation; and an estimator for estimating a size of a nugget of the welding spot on a basis of the time integration. - View Dependent Claims (20)
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21. A nugget size estimation system comprising:
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extrenum holding means for holding an extrenum of a detected variation of a distance between electrodes that have a welding spot held therebetween under pressure, as the extrenum has occurred before a spattering at the welding spot; base setting means for setting a base to be the detected variation upon a restart of a thermal expansion of the welding spot after the spattering with a continued welding current conducted through the welding spot; adding means adding a difference between the base and the detected variation to the extrenum to provide a corrected variation; integrating means for determining a time integration of the corrected variation; and estimating means for estimating a size of a nugget of the welding spot on a basis of the time integration. - View Dependent Claims (22)
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23. A nugget size estimation method comprising the steps of:
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holding an extrenum of a detected variation of a distance between electrodes that have a welding spot held therebetween under pressure, as the extrenum has occurred before spattering at the welding spot; setting a base to be the detected variation upon a restart of a thermal expansion of the welding spot after the spattering with a continued welding current conducted through the welding spot; adding a difference between the base and the detected variation to the extrenum to provide a corrected variation; determining a time integration of the corrected variation; and estimating a size of a nugget of the welding spot on a basis of the time integration. - View Dependent Claims (24)
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25. A method of estimating a nugget diameter in a spot welding, the method comprising the steps of:
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holding a welding spot between electrodes under pressure to detect an inter-electrode displacement therebetween; conducting a welding current through the electrodes and the welding spot, causing a thermal expansion of the welding spot; detecting a spattering occurred at the welding spot during the thermal expansion; identifying an extrenum of detected values of the inter-electrode displacement before the spattering; processing detected values of the inter-electrode displacement after the spattering to determine a growth of the thermal expansion after the spattering; adding the growth to the extrenum to provide substitute values for the detected values after the spattering; integrating detected values of the inter-electrode displacement, using the substitute values, to make a time integration of the inter-electrode displacement; and estimating a nugget diameter of the welding spot on the basis of the time integration. - View Dependent Claims (26)
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27. A method of estimating a nugget diameter in a spot of welding, the method comprising the steps of:
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holding a welding spot between electrodes under pressure, to detect an inter-electrode displacement therebetween; detecting an initial value of the inter-electrode displacement before conducting a welding current through the electrodes and the welding spot, continuing a conduction of the welding current, causing a thermal expansion of the welding spot; detecting a spattering occurred at the welding spot during the thermal expansion; interrupting the conduction of the welding current, causing a thermal shrinkage of the welding spot; detecting a final value of the inter-electrode displacement associated with the thermal shrinkage; adding a difference between the initial and final values to detected values of the inter-electrode displacement after the spattering, to provide substitute values for the detected values; identifying an extrenum of the detected values of the inter-electrode displacement before the spattering; integrating detected values of the inter-electrode displacement using the substitute values, to make a time integration of the inter-electrode displacement; and estimating a nugget diameter of the welding spot on a basis of the time integration. - View Dependent Claims (28)
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29. A method estimating a nugget diameter in spot welding, the method comprising the step of:
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estimating an actual weld nugget diameter by an integration of an inter-electrode displacement due to a thermal expansion during a conduction of a welding current, wherein the integration of the inter-electrode displacement due to the thermal expansion is performed within an integration interval defined by a combination of an integration start point and an integration end point, the integration start point is one of; an integration start point determined in advance on basis of welding conditions; an integration start point determined as a point during a current conduction, where the inter-electrode displacement reaches or exceeds a predetermined level; and an integration start point determined as a point where a predetermined period of time has elapsed from a start of a current conduction, and the integration end point is one of; an integration end point determined in advance on basis of the welding conditions; an integration end point determined as a point during or after a current conduction, where the inter-electrode displacement as it has once exceeded a maximum value, decreases to or exceeds a predetermined level; integration end point determined as a point where a predetermined period of time has elapsed from the integration start point; an integration end point determined as a point where a thermal expansion rate based on the inter-electrode displacement during a current conduction becomes a 0; and an integration end point determined as a point where a predetermined period of time has elapsed from a start of a current conduction, and a regression expression is computed for determining an estimated nugget diameter on a basis of an inter-electrode displacement integration value calculated by integrating the inter-electrode displacement due to the thermal expansion during a conduction of a welding current, a welding current value, a current conducting time and a welding pressure, while searching a statistical model on a basis of multivariate data to estimate the actual weld nugget diameter, such that
space="preserve" listing-type="equation">y=b0+b1x1+b2x2+b3x3+b4x4 and
space="preserve" listing-type="equation">Yi=a+byi+e,where y;
estimated nugget diameterx1;
inter-electrode displacement integration valuex2;
welding currentx3;
current conducting timex4;
welding pressureYi;
i-th measured nugget diameteryi;
i-th estimated nugget diametera;
interceptb;
b0 to b4;
regression coefficientse;
error. - View Dependent Claims (30)
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31. A method of estimating a nugget diameter in a spot welding, the method comprising the step of:
estimating an actual weld nugget diameter by integrating an inter-electrode displacement due to a thermal shrinkage after a finish of a conduction of a welding current, wherein the integration process of the inter-electrode displacement due to the thermal shrinkage is performed within an integration interval defined by a combination of an integration start point and an integration end point, the integration start point is one of; an integration start point determined as a finish point of a current conduction; an integration start point determined as a point after a finish of a current conduction, where the inter-electrode displacement reaches or exceeds a predetermined lever; and an integration start point determined as a point where a predetermined period of time has elapsed from a finish of a current conduction, and the integration end point is one of; an integration end point determined in advance on basis of the welding conditions; an integration end point determined as a point where a predetermined period of time has elapsed from the integration start point; an integration end point determined as a point where a thermal expansion rate based on the inter-electrode displacement during a current conduction becomes a 0; and an integration end point determined as a point where a predetermined period of time has elapsed from a finish of a current conduction, and a regression expression is computed for determining an estimated nugget diameter on a basis of an inter-electrode displacement integration value calculated by integrating the inter-electrode displacement due to the thermal shrinkage after a finish of conduction of a welding current, a welding current, a current conducting time and a welding pressure, while searching a statistical model on a basis of multivariate data to estimate the actual weld nugget diameter, such that
space="preserve" listing-type="equation">y=b0+b1x1+b2x2+b3x3+b4x4 and
space="preserve" listing-type="equation">Yi=a+byi+e,where y;
estimated nugget diameterx1;
inter-electrode displacement integration valuex2;
welding currentx3;
current conducting timex4;
welding pressureYi;
i-th measured nugget diameteryi;
i-th estimated nugget diametera;
interceptb;
b0 to b4;
regression coefficientse;
error.- View Dependent Claims (32)
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33. A method of estimating a nugget diameter in a spot welding, the method comprising the step of
estimating an actual weld nugget diameter by an integration of an inter-electrode displacement due to a thermal expansion during a conduction of a welding current, wherein the integration of the inter-electrode displacement due to the thermal expansion is performed within an integration interval defined by a combination of an integration start point and an integration end point, the integration start point is one of: -
an integration start point determined in advance on basis of welding conditions; an integration start point determined as a point during a current conduction, where the inter-electrode displacement reaches or exceeds a predetermined level; and an integration start point determined as a point where a predetermined period of time has elapsed from a start of a current conduction, and the integration end point is one of; an integration end point determined in advance on basis of the welding conditions; an integration end point determined as a point during or after a current conduction, where the inter-electrode displacement, as it has once exceeded a maximum value, decreases to or exceeds a predetermined level; an integration end point determined as a point where a predetermined period of time has elapsed from the integration start point; an integration end point determined as a point where a thermal expansion rate based on the inter-electrode displacement during a current conduction becomes a 0; and an integration end point determined as a point where a predetermined period of time has elapsed from a start of a current conduction, and a regression expression is computed for determining an estimated nugget diameter on a basis of an inter-electrode displacement integration value calculated by integrating the inter-electrode displacement due to the thermal expansion during a conduction of a welding current, and a thickness, a material, a joining type and a surface preparation of welding plates, while searching a statistical model on a basis of multivariate data to estimate the actual weld nugget diameter; and
the regression expression, such that
space="preserve" listing-type="equation">y=b0+b1x1+b2x2+b3x3+b4x4+b5x5 and
space="preserve" listing-type="equation">Yi=a+byi+e,where y;
estimated nugget diameterx1;
inter-electrode displacement integration valuex2;
welding plate thicknessx3;
welding plate materialx4;
welding plate joining typex5;
welding plate surface preparationYi;
i-th measured nugget diameteryi;
i-th estimated nugget diametera;
interceptb;
b0 to b5;
regression coefficientse;
error.
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34. A method of estimating a nugget diameter in a spot welding, the method comprising the step of:
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estimating an actual weld nugget diameter by an integration of an inter-electrode displacement due to a thermal expansion during a conduction of a welding current, wherein the integration of the inter-electrode displacement due to the thermal expansion is performed within an integration interval defined by a combination of an integration start point and an integration end point, the integration start point is one of; an integration start point determined in advance on basis of welding conditions; an integration start point determined as a point during a current conduction, where the inter-electrode displacement reaches or exceeds a predetermined level; and an integration start point determined as a point where a predetermined period of time has elapsed from a start of a current conduction, and the integration start point is one of; an integration end point determined in advance on basis of the welding conditions; an integration end point determined as a point during or after a current conduction, where the inter-electrode displacement as it has once exceeded a maximum value, decreases to or exceeds a predetermined level; an integration end point determined as a point where a predetermined period of time has elapsed from the integration start point; an integration end point determined as a point where a thermal expansion rate based on the inter-electrode displacement during a current conduction becomes a 0; and an integration end point determined as a point where a predetermined period of time has elapsed from a start of a current conduction, and a regression expression is computed for determining an estimated nugget diameter on a basis of an inter-electrode displacement integration value calculated by integrating the inter-electrode displacement due to the thermal shrinkage after a finish of conduction of a welding current, and a thickness, a material, a joining type and a surface preparation of welding plates, while searching a statistical model on a basis of multivariate data to estimate the actual weld nugget diameter; and
the regression expression is, such that
space="preserve" listing-type="equation">y=b0+b1x1+b2x2+b3x3+b4x4+b5x5 and
space="preserve" listing-type="equation">Yi=a+byi+e,where y;
estimated nugget diameterx1;
inter-electrode displacement integration valuex2;
welding plate thicknessx3;
welding plate materialx4;
welding plate joining typex5;
welding plate surface preparationYi;
i-th measured nugget diameteryi;
i-th estimated nugget diametera;
interceptb, b0 to b5;
regression coefficientse;
error.
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35. A method of estimating a nugget diameter in a spot welding, the method comprising the step of:
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estimating an actual weld nugget diameter by an integration of an inter-electrode displacement due to a thermal expansion during a conduction of a welding current, wherein the integration of the inter-electrode displacement due to the thermal expansion is performed within an integration interval defined by a combination of an integration start point and an integration end point, the integration start point is one of; an integration start point determined in advance on basis of welding conditions; an integration start point determined as a point during a current conduction, where the inter-electrode displacement reaches or exceeds a predetermined level; and an integration start point determined as a point where a predetermined period of time has elapsed from a start of a current conduction, and the integration end point is one of; an integration end point determined in advance on basis of the welding conditions; an integration end point determined as a point during or after a current conduction, where the inter-electrode displacement, as it has once exceeded a maximum value, decreases to or exceeds a predetermined level; an integration end point determined as a point where a predetermined period of time has elapsed from the integration start point; an integration end point determined as a point where a thermal expansion rate based on the inter-electrode displacement during a current conduction becomes a 0; and an integration end point determined as a point where a predetermined period of time has elapsed from a start of a current conduction, and a correction coefficient is calculated from an inter-electrode displacement integration value associated with the thermal expansion during a conduction of a welding current and an inter-electrode displacement integration value associated with the thermal shrinkage after a finish of conduction of a welding current, such that the correction coefficient =(the inter-electrode displacement integration value associated with the thermal shrinkage)/(the inter-electrode displacement integration value associated with the thermal expansion), and the inter-electrode displacement integration value associated with the thermal expansion is multiplied by the correction coefficient to correct an attenuation of an inter-electrode displacement due to an electrode tip contact area.
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36. A system for estimating a nugget size of a welding spot, the system comprising:
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a spot welder for holding a welding spot between electrodes under pressure, detecting an inter-electrode displacement therebetween, and conducting a welding current through the welding spot; a spattering detector for detecting a spattering occurred at the welding spot; a first selector for selecting a first value of the inter-electrode displacement detected before the spattering; a second selector for selecting a second value of the inter-electrode displacement detected after the spattering, the second value being different from the first value; a corrector for correcting detected values of the inter-electrode displacement after the spattering, depending on a difference between the first and second values; an integrator for integrating detected values of the inter-electrode displacement, using corrected values thereof as applicable, to make a time integration of the inter-electrode displacement; and an estimator for estimating a nugget size of the welding spot on a basis of the time integration.
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37. A method of estimating a nugget size in a spot welding, the method comprising:
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holding a welding spot between electrodes under pressure, detecting an inter-electrode displacement therebetween; conducting a welding current through the welding spot; detecting a spattering occurred at the welding spot; selecting a first value of the inter-electrode displacement detected before the spattering; selecting a second value of the inter-electrode displacement detected after the spattering, the second value being different from the first value; correcting detected values of the inter-electrode displacement after the spattering, depending on a difference between the first and second values; integrating detected values of the inter-electrode displacement, using corrected values thereof as applicable, to make a time integration of the inter-electrode displacement; and estimating a nugget size of the welding spot on a basis of the time integration.
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Specification