Resistance spot welding method and resistance spot welding apparatus

Patent metadata

Field	Value
Publication number	US-11247292-B2
Application number	US-201916294086-A
Country	US
Kind code	B2
Filing date	Mar 6, 2019
Priority date	Mar 9, 2018
Publication date	Feb 15, 2022
Grant date	Feb 15, 2022

Abstract

Provided are a method and an apparatus for resistance spot welding in which preliminary current application is executed and then main welding is executed in accordance with master patterns of various parameters obtained during the preliminary current application. The main welding is executed under welding conditions of the master patterns, and whether a welding abnormality has occurred and whether the welding abnormality is likely to occur are determined. When the welding abnormality is likely to occur, the welding conditions for the main welding are corrected so as to prevent the welding abnormality. When the welding abnormality is unlikely to occur, the welding conditions for the main welding are corrected so as to match the master patterns.

First claim

What is claimed is:

1. A resistance spot welding method in which a workpiece formed by a plurality of metal sheets placed on top of one another is held between a pair of electrodes, and the metal sheets are melted and joined together by applying a current between the electrodes, the resistance spot welding method comprising:
acquiring information on the workpiece, and executing preliminary current application under a welding condition that is set based on the information;
measuring an execution state during the preliminary current application, and based on the execution state, setting a master pattern of a welding condition for main welding;
executing the main welding under the welding condition of the master pattern, and when a current application time in the main welding is within a predetermined time, determining whether a welding abnormality has occurred;
when the welding abnormality has not occurred, determining whether the welding abnormality is likely to occur;
when the welding abnormality is likely to occur, continuing current application after correcting the welding condition for the main welding so as to prevent the welding abnormality;
when the welding abnormality is unlikely to occur, continuing current application after correcting the welding condition for the main welding so as to match the master pattern; and
when the welding abnormality has occurred, changing the welding condition for the main welding to a preset abnormality-response welding condition, and notifying occurrence of the welding abnormality.

2. The resistance spot welding method according to claim 1 , wherein, during execution of the main welding, whether a melting amount of the metal sheets has reached a predetermined amount as a target is determined, and when the melting amount of the metal sheets has not reached the predetermined amount at a point in time when the current application time in the main welding has reached a set welding end time in the master pattern, a welding prolongation process of continuing current application in the main welding is performed.

3. The resistance spot welding method according to claim 2 , wherein when the melting amount of the metal sheets has not reached the predetermined amount at a point in time when the current application time in the main welding has reached a predetermined time beyond the set welding end time, the main welding is forcibly ended and occurrence of the welding abnormality is notified.

4. The resistance spot welding method according to claim 1 , wherein the execution state during the preliminary current application is a pressure applied by the electrodes to the workpiece, an electrode displacement between the electrodes, and an electrical resistance between the electrodes.

5. The resistance spot welding method according to claim 4 , wherein:
the welding abnormality is expulsion occurring during the welding;
when the pressure is below an expulsion-determining threshold value, or when the electrode displacement is above an expulsion-determining threshold value, or when the electrical resistance is above an expulsion-determining threshold value, it is determined that the welding abnormality has occurred; and
when the pressure is below an expulsion likelihood-determining threshold value, or when the electrode displacement is above an expulsion likelihood-determining threshold value, or when the electrical resistance is above an expulsion likelihood-determining threshold value, it is determined that the welding abnormality is likely to occur.

6. A resistance spot welding apparatus that has a pair of electrodes between which a workpiece formed by a plurality of metal sheets placed on top of one another is held, and that melts and joins together the metal sheets by applying a current between the electrodes holding the workpiece, the resistance spot welding apparatus comprising:
a control device configured to acquire information on the workpiece, and to execute preliminary current application under a welding condition that is set based on the information on the workpiece;
a measurement device configured to measure an execution state during the preliminary current application; and
a notification device configured to notify occurrence of a welding abnormality when the welding abnormality has occurred,
wherein the control device registers a master pattern of a welding condition for main welding based on the execution state measured by the measurement device, and executes the main welding under the welding condition of the master pattern, and
wherein the control device measures a current application time in the main welding, and when the current application time in the main welding is within a predetermined time, determines whether the welding abnormality has occurred and whether the welding abnormality is likely to occur, and when the welding abnormality is likely to occur, corrects the welding condition for the main welding so as to prevent the welding abnormality, and when the welding abnormality is unlikely to occur, corrects the welding condition for the main welding so as to match the master pattern, and when the welding abnormality has occurred, changes the welding condition for the main welding to a preset abnormality-response welding condition.

7. The resistance spot welding apparatus according to claim 6 , wherein:
the measurement device includes an applied pressure measurement device configured to measure a pressure applied by the electrodes to the workpiece, an electrode displacement measurement device configured to measure an electrode displacement between the electrodes, a voltage measurement device configured to measure a voltage across the electrodes, and a current measurement device configured to measure a welding current flowing between the electrodes; and
the execution state during the preliminary current application is the pressure, the electrode displacement, and an electrical resistance between the electrodes that is calculated based on the voltage and the welding current, during execution of the preliminary current application.

8. The resistance spot welding apparatus according to claim 7 , wherein:
the welding abnormality is expulsion occurring during the welding;
when the pressure is below an expulsion-determining threshold value, or when the electrode displacement is above an expulsion-determining threshold value, or when the electrical resistance is above an expulsion-determining threshold value, the control device determines that the welding abnormality has occurred; and
when the pressure is below an expulsion likelihood-determining threshold value, or when the electrode displacement is above an expulsion likelihood-determining threshold value, or when the electrical resistance is above an expulsion likelihood-determining threshold value, the control device determines that the welding abnormality is likely to occur.

Assignees

• Toyota Motor Co Ltd

Inventors

• Nomura Koji
• Ogura Shuhei
• Kawakita Atsushi
• Kato Naoya
• Hioki Toru
• Fukushima Kenji
• Kato Shun
• Goto Takashi

Classifications

• B23K11/115 Primary

  by means of two electrodes placed opposite one another on both sides of the welded parts · CPC title

• B23K11/36

  Auxiliary equipment (B23K11/31 takes precedence) · CPC title

• B23K11/314

  Spot welding guns, e.g. mounted on robots · CPC title

• B23K11/253

  the measured parameter being a displacement or a position · CPC title

• B23K11/11

  Spot welding · CPC title