JP6107675B2 - Welding quality inspection method and welding quality inspection device - Google Patents

Description

  The present invention relates to a welding quality inspection method and a welding quality inspection device, for example, by superimposing joint portions of a plurality of members to be welded, press-clamping the joint portions with a pair of electrodes, and current between the pair of electrodes. The present invention relates to a welding quality inspection method and a welding quality inspection device for inspecting the welding quality in lap resistance welding in which a plurality of members to be welded are joined together.

  In spot welding, which is a type of lap resistance welding, generally welded portions of a plurality of plate-like members to be welded (workpieces) are overlapped, and the welded portions of the workpieces are sandwiched and pressed by a pair of electrodes. A plurality of members to be welded are joined together by passing an electric current between the electrodes. The welded portion sandwiched between the electrodes is melted by Joule heat generated by current resistance and then solidified, so that a so-called nugget is formed in the welded portion, but this nugget is not formed properly, that is, the welding quality is poor. In such a case, re-welding or the like is performed so as to improve the welding quality.

  As a prior art for determining the quality of welding quality in such lap resistance welding, for example, a member to be welded becomes an inspection target every predetermined number of a plurality of spot welded members. Is known, which uses a hammer to strike a predetermined part of the welded portion, strikes it with a hammer, etc., and determines whether or not the welded part has been peeled off when the predetermined amount of hammer is driven (against check) ing.

  In recent years, it is also determined whether the quality of welding is good or bad based on a resistance value between electrodes during welding, and a conventional technique related to such a method is disclosed in Patent Document 1.

  The quality determination method disclosed in Patent Document 1 measures a resistance value between electrodes during welding, and generates a resistance value waveform that represents a change in resistance value with respect to energization time. Based on a resistance value waveform classification step of classifying the generated resistance value waveform into one of a plurality of resistance value waveform patterns due to various disturbances set in advance, and a criterion set in advance for each of the resistance value waveform patterns In the first welding quality pass / fail judgment step for judging whether or not the weld quality is good, and in the first weld quality pass / fail judgment step, it is determined that the spatter is generated from the resistance value waveform. A sputter presence / absence determination step for determining the presence / absence of a spatter and a change amount of the resistance value in the generated resistance value waveform when it is determined that spatter is generated, and a preset spa for each of the resistance value waveform patterns. A method of performing a second welding quality determining step of determining whether the welding quality is good based on the comparison between the change amount threshold of the resistance value when data occurs. Further, when it is determined that no spatter is generated in the sputter presence / absence determination step, the determination is further made by discriminant analysis such as multiple regression analysis / discriminant analysis.

  According to the quality determination method disclosed in Patent Literature 1, welding is performed for a resistance value waveform pattern classified in the resistance value waveform generated in the first welding quality pass / fail determination step that is similar to a good resistance value waveform. The resistance value generated in the second welding quality pass / fail determination step can be determined that the quality is good, and even in the welded portion determined in the first weld quality pass / fail determination step that the weld quality is not good. By simply comparing the resistance value change amount in the waveform with the resistance value change threshold value at the time of spattering set in advance for each resistance value waveform pattern, the nugget was formed properly, that is, the welding quality was good. It can be determined whether there is. Therefore, it is not necessary to set a threshold value for determining the welding quality according to the welding conditions for each welding location (spot), and the quality of the welding quality can be easily and accurately determined without being affected by various disturbances. can do.

JP 2011-240368 A

  By the way, when the quality of welding quality is judged using a preset judgment threshold as in the quality judgment method disclosed in Patent Document 1, for example, the judgment threshold is an error that leads to outflow of defective products to the market. Judgment (event that is judged to be good even though the product is defective) is set not to occur, and over judgment (event that is judged to be defective even though the product is good) ) Is known to occur. Therefore, in the lap resistance welding as described above, if the quality of the welding quality is continuously determined using a predetermined determination threshold value, a problem such as a decrease in productivity due to occurrence of an over determination, an operator, etc. There may be a problem that the number of work man-hours such as a chisel check due to increases.

  The present invention has been made in view of the above-described problems. For example, the joint portions of a plurality of members to be welded are superposed, the joint portions are pressed and clamped by a pair of electrodes, and a current is passed between the pair of electrodes. In lap resistance welding that joins a plurality of members to be welded together, the occurrence of over-determination can be suppressed and the weld quality of the joint part of the workpiece can be inspected precisely, thereby increasing productivity. An object of the present invention is to provide a welding quality inspection method and a welding quality inspection device that can suppress an increase in work man-hours such as a chisel check by an operator.

  In order to achieve the above object, the welding quality inspection method according to the present invention superimposes joint portions of a plurality of members to be welded, press-clamps the joint portions with a pair of electrodes, and supplies a current between the pair of electrodes. A welding quality inspection method for inspecting welding quality in lap resistance welding in which a plurality of members to be welded are joined to each other, wherein the joint portions of the members to be welded are sequentially conveyed to the welding apparatus having the pair of electrodes In the welding quality inspection method for sequentially inspecting the welding quality of the plurality of resistance value waveform patterns due to various preset disturbances, the resistance value waveform representing the change in the resistance value between the pair of electrodes during welding with respect to the energization time When the welding quality is judged to be poor in the first welding quality pass / fail judgment step and the first weld quality pass / fail judgment step for determining whether the weld quality is good or not, the presence or absence of spatter is determined from the resistance waveform. Size When the welding quality is determined to be poor in the second welding quality determining step for determining whether the welding quality is good and the second welding quality determining step, a basic variable obtained from the resistance value waveform is set in advance. In the third welding quality pass / fail judgment step and the third weld quality pass / fail judgment step for comparing the calculation result calculated by substituting into the judgment formula and a preset judgment threshold and judging the quality of the weld quality. A fourth welding quality pass / fail determination step for determining whether the weld quality is pass / fail by a method different from the first to third weld quality pass / fail determination steps when the welding quality is determined to be poor, and the fourth weld quality pass / fail determination step. When the welding quality is determined to be good in step 3, the calculation result closest to the determination threshold among the plurality of calculation results calculated in the third welding quality quality determination step at the time of the previous inspection is determined as the third welding quality quality determination. In the process A determination threshold value updating step of updating though Do determination threshold, a method has.

  Here, it is preferable that the plurality of calculation results in the determination threshold value update step include the calculation results calculated in the third welding quality pass / fail determination step at the time of inspection up to a preset number of times from this time. .

  Further, the welding quality inspection apparatus according to the present invention superimposes the joint portions of a plurality of members to be welded, press-clamps the joint portions with a pair of electrodes, and allows a current to flow between the pair of electrodes, A welding quality inspection device for inspecting welding quality in lap resistance welding for joining members to be welded, wherein the welding quality of joint portions of a plurality of members to be welded sequentially conveyed to the welding device having the pair of electrodes is sequentially determined. In the welding quality inspection apparatus to be inspected, welding is performed by classifying the resistance value waveform representing the change of the resistance value between the pair of electrodes during welding with respect to the energization time into a plurality of resistance value waveform patterns caused by various preset disturbances. When welding quality is determined to be poor by the first welding quality determining unit and the first welding quality determining unit for determining quality, welding is performed by determining the presence or absence of spatter from the resistance waveform. Good quality When the welding quality is determined to be poor by the second welding quality determining unit and the second welding quality determining unit, a basic variable obtained from the resistance value waveform is assigned to a predetermined determination formula. The welding result is determined to be poor by the third welding quality pass / fail judgment unit that compares the calculation result calculated with the preset determination threshold and judges the quality of the weld quality, and the third weld quality pass / fail judgment unit. When it is determined, the welding quality is determined by a fourth welding quality pass / fail determination unit that determines the quality of the weld quality by a method different from the first to third weld quality pass / fail determination units, and the fourth weld quality pass / fail determination unit. When it is determined as good, a calculation result closest to the determination threshold among the plurality of calculation results calculated by the third welding quality determination unit at the time of the previous inspection is newly set in the third welding quality determination unit. To be updated as a valid threshold And a threshold update unit, a a device having a.

  Here, it is preferable that the plurality of calculation results in the determination threshold value update unit include calculation results calculated by the third welding quality pass / fail determination unit at the time of inspection up to a preset number of times from this time. .

  As can be understood from the above description, according to the present invention, the welding quality is determined to be good in the fourth welding quality pass / fail determination step that determines the quality of the weld quality by a method different from the first to third weld quality pass / fail determination steps. When it is determined, the calculation result closest to the determination threshold value among the plurality of calculation results calculated in the third welding quality pass / fail determination process at the time of the previous inspection is updated as a new determination threshold value in the third weld quality pass / fail determination process. By doing, the determination threshold value in the 3rd welding quality quality determination process can be updated appropriately based on the determination result in the 4th welding quality quality determination process. Therefore, the occurrence of overjudgment can be suppressed and the weld quality of workpiece joints can be inspected precisely, which can improve productivity and suppress the increase in work man-hours such as chisel checks by workers etc. can do.

It is the whole block diagram which showed the whole structure of embodiment of the welding quality inspection apparatus of this invention. It is the flowchart explaining the welding quality inspection method by the welding quality inspection apparatus shown in FIG. It is explanatory drawing which demonstrated typically the determination threshold value update process shown in FIG.

  Embodiments of a welding quality inspection method and a welding quality inspection apparatus according to the present invention will be described below with reference to the drawings.

[Embodiment of welding quality inspection apparatus]
First, an embodiment of a welding quality inspection apparatus of the present invention will be described with reference to FIG. FIG. 1 is an overall configuration diagram showing an overall configuration of an embodiment of a welding quality inspection apparatus of the present invention.

  A welding quality inspection apparatus 1 shown in the figure superimposes joint portions of a plurality of welded members (workpieces) Wa, Wb,..., And welds the joint portions of the welded members Wa, Wb,. The pair of electrodes 2a, 2b are pressed and clamped, and a current is passed between the pair of electrodes 2a, 2b to join a plurality of members to be welded Wa, Wb,... The apparatus is an apparatus for sequentially inspecting the welding quality of the joint portion of each member to be welded that is sequentially conveyed to the welding robot 2 along the welding line. The welding quality inspection apparatus 1 includes a controller 3 that controls the operation of the welding robot 2, a monitor 4 that displays information in the controller 3, information on the welding quality of each welding location inspected by the welding quality inspection apparatus 1, and the like. Is communicably connected.

  The members to be welded by the welding robot 2 include, for example, a panel material constituting an automobile body, and the number of members to be welded and the thickness of each member to be welded are appropriately determined. Can be set. Further, as the welding robot 2, for example, an apparatus for spot welding using a C-type welding gun or an X-type welding gun, or an apparatus for continuously seam-welding a joint portion of a member to be welded with a roller-shaped or disk-shaped electrode. Etc. can be applied.

  The above-described welding quality inspection apparatus 1 mainly includes a resistance value measuring unit 9 that measures the resistance value between the electrodes 2a and 2b during welding, and a current value based on the resistance value measured by the resistance value measuring unit 9. A resistance value waveform generation unit 10 that generates a resistance value waveform representing a change in resistance value, and a first determination of whether the weld quality of the joint is good or not based on the resistance value waveform generated by the resistance value waveform generation unit 10 -4th welding quality quality determination part 11-14, and the determination threshold value update part 15 which updates the determination threshold value in the 3rd welding quality quality determination part 13 are provided.

  For example, the resistance value measuring unit 9 is configured such that a current value flowing between the electrodes 2a and 2b and a voltage value between the electrodes 2a and 2b every half cycle of the alternating current when an alternating current is passed between the electrodes 2a and 2b from the AC power source. And the resistance value between the electrodes 2a and 2b during welding can be measured by calculating the resistance value from the obtained current value and voltage value.

  The first welding quality acceptance / rejection determination unit 11 of the welding quality inspection apparatus 1 converts the resistance value waveform generated by the resistance value waveform generation unit 10 into one of a plurality of resistance value waveform patterns caused by various preset disturbances. The resistance value waveform thus classified is compared with a criterion set in advance for each resistance value waveform pattern to determine the quality of the welding quality, and the determination result is a second welding quality quality determination unit. 12 and the monitor 4 are transmitted.

  Factors that cause various disturbances in lap resistance welding include, for example, wear due to the use of tips at the tip of the electrode, straightness between the electrode and the workpiece, edge punching, plate clearance (workpiece joint gap), and sliding during welding. As the resistance value waveform pattern stored in advance in the first welding quality pass / fail judgment unit 11, for example, there are waveform patterns called general type, right-down type, root type, horizontal type, etc. A method of classifying the resistance value waveform generated by the value waveform generation unit 10 into one of a plurality of resistance value waveform patterns caused by various disturbances set in advance, or a criterion set in advance for each resistance value waveform pattern Since the method of determining the quality of the welding quality based on the above is well known (see Patent Document 1), the detailed description thereof is omitted here.

  The second welding quality quality determination unit 12 is a resistance value waveform generated by the resistance value waveform generation unit 10 when the first welding quality quality determination unit 11 determines that the welding quality is poor. The quality determination unit 11 determines the presence or absence of spatter from the resistance value waveform determined to have poor welding quality, and determines the quality of the welding quality. The determination result is the third welding quality quality determination unit 13. To the monitor 4 or the like.

  Here, the resistance value increases from the initial resistance value due to heat generation, and gradually decreases until reaching the maximum resistance value until spattering occurs. Further, it can be determined that sputtering has occurred when a large decrease is recognized, and it can be determined that sputtering has not occurred when such a rapid and large decrease in resistance value is not recognized.

  The third welding quality quality determination unit 13 determines the resistance generated by the resistance value waveform generation unit 10 when the second welding quality quality determination unit 12 determines that the welding quality is poor (that is, spatter is generated). The basic variable obtained from the value waveform is substituted into a preset judgment formula, and the calculation result calculated thereby is compared with a preset judgment threshold to judge the quality of the welding quality. The result is transmitted to the determination threshold update unit 15 and the determination result is transmitted to the fourth welding quality pass / fail determination unit 14, the determination threshold update unit 15, the monitor 4, and the like.

  Here, the basic variable includes, for example, an initial resistance value, a final resistance value, an average resistance value, a maximum resistance value, a minimum resistance value, a straight line connecting the initial resistance value and the final resistance value in the resistance value waveform, and a resistance value waveform. , The time required to reach the maximum resistance value from the start of energization, the time required to reach the minimum resistance value from the start of energization, and the like.

  In addition, as a determination formula for substituting the basic variable described above, for example, a determination formula represented by the following formula (1) can be used, and for example, 0 (zero) can be used as an initial value of the determination threshold. When the calculation result calculated by the determination formula is 0 or more, it is determined that the welding quality is poor, and when the calculation result calculated by the determination formula is less than 0, it can be determined that the welding quality is good. .

[Equation 1]
{2 × A + (B−E) / C} × D (1)
Here, A to D in Formula (1) are appropriate variables selected from the basic variables described above.

  The fourth welding quality pass / fail determination unit 14 is different from the first to third weld quality pass / fail determination units 11 to 13 when the third welding quality pass / fail determination unit 13 determines that the welding quality is poor. The quality of the welding quality is determined, and the determination result is transmitted to the determination threshold value updating unit 15, the monitor 4, or the like.

  Here, the fourth welding quality pass / fail judgment unit 14 can use any method as long as it can more reliably judge the weld quality of the joint than the first to third weld quality pass / fail judgment units 11 to 13 described above. For example, it is possible to apply a non-contact determination method using a chisel check by an operator, ultrasonic measurement, surface temperature measurement, or the like.

  The determination threshold value update unit 15, when it is determined that the welding quality is good by the fourth welding quality pass / fail determination unit 14, is the joint that is the current inspection target by the third welding quality pass / fail determination unit 13 during the previous inspection. Of the plurality of calculation results calculated for the part, the calculation result closest to the determination threshold is updated as a new determination threshold in the third welding quality determination unit 13. Specifically, the determination threshold value update unit 15 performs the current inspection during the inspection from the current time (the time when the fourth welding quality quality determination unit 14 determines that the welding quality is good) to the time that is set a predetermined number of times. Among the plurality of calculation results calculated by the third welding quality pass / fail determination unit 13 for the target joint, the calculation result closest to the determination threshold is set as a new determination threshold in the third weld quality pass / fail determination unit 13. Is to be updated.

[Embodiment of welding quality inspection method]
Next, with reference to FIG. 2 and FIG. 3, the welding quality inspection method (embodiment of the welding quality inspection method of this invention) by the welding quality inspection apparatus 1 shown in FIG. 1 is demonstrated more concretely. FIG. 2 is a flowchart for explaining the welding quality inspection method by the welding quality inspection apparatus shown in FIG. 1, and FIG. 3 is an explanatory view for schematically explaining the determination threshold value updating step shown in FIG. In addition, in FIG. 3, the determination threshold value at the time of inspection (at the time of welding) at each time (from the 1st time to the 8th time in the figure) of the joint portion where the welded member is sequentially conveyed to the welding robot 2 from the upper stage, The calculation result by a determination formula, the determination result in the 3rd welding quality quality determination process, and an example of the determination result in the 4th welding quality quality determination process are shown.

  As shown in FIG. 2, first, the welding quality inspection apparatus 1 measures the resistance value between the electrodes 2a and 2b during welding by the resistance value measuring unit 9 (S10). Next, the welding quality inspection device 1 generates a resistance value waveform representing a change in resistance value with respect to the energization time in the resistance value waveform generation unit 10 and calculates basic variables used for discriminant analysis described later from the resistance value waveform. (S11).

  Next, the welding quality inspection apparatus 1 converts the resistance value waveform generated in S11 into one of a plurality of resistance value waveform patterns due to various disturbances set in advance by the first welding quality pass / fail judgment unit 11. Classification is performed (S12), and the resistance value waveform thus classified is compared with a criterion set in advance for each resistance value waveform pattern to determine whether or not the welding quality is good (S13) (the first welding quality is good or bad) Judgment process). If it is determined in S13 that the welding quality is good, the determination result (non-defective product determination result) is transmitted to the monitor 4 (S19), and the process is terminated.

  On the other hand, if it is determined in S13 that the welding quality is not good (bad), the welding quality inspection apparatus 1 uses the resistance value waveform in which the welding quality is determined to be poor by the second welding quality good / bad determination unit 12. It is determined whether or not the spatter has been generated and whether or not the welding quality is good (S14) (second welding quality quality determination step). If it is determined in S14 that no spatter is generated and the welding quality is good, the determination result (non-defective product determination result) is transmitted to the monitor 4 (S19), and the process is terminated.

  On the other hand, when it is determined in S14 that spatter is generated and the welding quality is not good, the welding quality inspection apparatus 1 uses the discriminant analysis in the third welding quality inspection unit 13 to determine that the welding quality is good. It is determined whether or not there is (S15) (third welding quality quality determination step). Specifically, the basic variable obtained in S11 is substituted into a preset judgment formula, and the calculation result calculated thereby is compared with a preset judgment threshold value to determine whether the welding quality is good. Determine whether. If it is determined in S15 that the welding quality is good, the determination result (non-defective product determination result) is transmitted to the monitor 4 (S19), and the process is terminated.

  On the other hand, when it is determined in S15 that the welding quality is not good (bad), the welding quality inspection apparatus 1 uses the fourth welding quality pass / fail determination unit 14 to perform the first to third weldings such as a chisel check. It is a method that is different from the quality pass / fail judgment step (S13 to S15), and can more reliably judge the weld quality of the joint than the first to third weld quality pass / fail judgment steps (S13 to S15). It is determined whether or not the welding quality is good (S16) (fourth welding quality quality determination step). If it is determined in S16 that the welding quality is not good (defective), the determination result (defective product determination result) is transmitted to the monitor 4 (S18), and the process is terminated. The monitor 4 displays, for example, a warning signal regarding the poor welding quality.

  On the other hand, when it is determined in S16 that the welding quality is good, the welding quality inspection apparatus 1 transmits the determination result (non-defective product determination result) to the monitor 4 (S19) and also to the determination threshold update unit 15. Then, the determination threshold value used in the discriminant analysis of the third welding quality pass / fail determination step (S15) is updated (S17) (determination threshold update step).

  For example, as shown in FIG. 3, it is determined that the welding quality is good at the time of the sixth inspection (at the time of welding) for a joint portion with a member to be welded that is sequentially conveyed to the welding robot 2, and the sixth time Assuming that the determination threshold is set to be updated at the time of inspection and the number of retroactive times is set to 3, the welding quality inspection apparatus 1 performs the third welding at the time of inspection from the sixth time to the fourth time. Of the calculation results (3, 4, 2 in the figure) calculated in the quality pass / fail judgment step (S15), the calculation result closest to the determination threshold value (0 in the figure) at the time of the fourth inspection is shown. The calculation result (2 in the figure) is updated as a new determination threshold value in the third welding quality pass / fail determination step (S15). And the welding quality inspection apparatus 1 becomes an inspection object in the 3rd welding quality quality determination process (S15) using this new determination threshold value (2) at the time of the 7th inspection (at the time of welding). Judge the quality of the weld quality of the joint. The number of retroactive times means the number of retroactive times from this time (the time when the welding quality is determined to be good in the fourth welding quality pass / fail judgment step (S16)) (sixth time). And can be changed as appropriate according to the needs of the manager or the like.

  Thus, according to the present embodiment, when the first to third welding quality pass / fail judgment units 11 to 13 determine that the welding quality is poor, the first to third weld quality pass / fail judgment units 11. The quality of the welding quality is judged by the fourth welding quality judgment unit 14 that can judge the quality of the welding quality more reliably than -13, and the welding quality is judged to be good by the fourth welding quality judgment unit 14. In this case, the third welding quality pass / fail judgment unit obtains the computation result closest to the judgment threshold among the plurality of computation results calculated for the joint to be inspected by the third welding quality pass / fail judgment unit 13 during the previous inspection. By updating as a new determination threshold value in 13, the determination threshold value in the third welding quality acceptance / rejection determination unit 13 can be appropriately updated, and the occurrence of overdetermination can be suppressed and the welding quality of the joint portion of the welded member can be reduced. Elaborate It can be inspected. Therefore, productivity can be increased and an increase in work man-hours such as chisel check by an operator or the like can be suppressed.

  In addition, when a some to-be-welded part (welding location) exists in a to-be-welded member, it determines with the quality determination process of the welding quality by the above-mentioned 1st-4th welding quality quality determination part 11-14 about each junction. What is necessary is just to implement the determination threshold value update process by the threshold value update unit 15.

  Further, in the above-described embodiment, the description has been given of the embodiment in which the quality determination of the welding quality by the first to fourth welding quality quality determination units 11 to 14 is performed every time the joint of the member to be welded is welded. It is not necessary to carry out the quality judgment of the welding quality by the first to fourth welding quality judgment units 11 to 14 at the time of welding. For example, while performing the quality determination of the welding quality by the first to third welding quality quality determination units 11 to 13 every time the welded portion of the welded member conveyed to the welding robot 2 is welded, a predetermined value is determined from the welded member. Welded members to be inspected are extracted for each number of pieces, and the quality of the weld quality is judged by the fourth weld quality judging unit 14 only for the welded members thus extracted, and the quality of the fourth weld quality is judged. The determination threshold value in the third welding quality pass / fail determination unit 13 may be updated at an appropriate timing based on the determination result by the determination unit 14.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

DESCRIPTION OF SYMBOLS 1 ... Welding quality inspection apparatus, 2 ... Welding robot (welding apparatus), 2a, 2b ... Electrode, 3 ... Controller, 4 ... Monitor, 9 ... Resistance value measurement part, 10 ... Resistance value waveform generation part, 11 ... 1st welding Quality pass / fail judgment unit, 12 ... second weld quality pass / fail judgment unit, 13 ... third weld quality pass / fail judgment unit, 14 ... fourth weld quality pass / fail judgment unit, 15 ... determination threshold update unit, Wa, Wb ... welded member ( work)

Claims (4)

In lap resistance welding in which joint portions of a plurality of members to be welded are superposed, the joint portions are pressed and sandwiched by a pair of electrodes, and a current is passed between the pair of electrodes to join the plurality of members to be welded together A welding quality inspection method for inspecting welding quality, wherein the welding quality inspection method sequentially inspects the welding quality of the joints of a plurality of welded members that are sequentially conveyed to the welding apparatus having the pair of electrodes.
First, the resistance value waveform representing the change of the resistance value between the pair of electrodes during welding with respect to the energization time is classified into a plurality of preset resistance value waveform patterns due to various disturbances to determine whether the welding quality is good or bad. Welding quality pass / fail judgment process,
A second welding quality pass / fail determination step for determining whether or not the spatter is generated from the resistance waveform and determining the weld quality when the weld quality is determined to be poor in the first weld quality pass / fail determination step;
A calculation result calculated by substituting a basic variable obtained from the resistance value waveform into a predetermined determination formula when the welding quality is determined to be poor in the second welding quality pass / fail determination step, and a preset A third welding quality pass / fail judgment step for comparing the judgment threshold and judging the quality of the weld quality;
A fourth weld quality pass / fail determination step for determining pass / fail of weld quality by a method different from the first to third weld quality pass / fail determination steps when it is determined that the weld quality is poor in the third weld quality pass / fail determination step; ,
When it is determined that the welding quality is good in the fourth welding quality pass / fail determination step, the calculation result closest to the determination threshold among the plurality of calculation results calculated in the third weld quality pass / fail determination step during the previous inspection. And a determination threshold value updating step for updating as a new determination threshold value in the third welding quality pass / fail determination step.   The plurality of calculation results in the determination threshold value update step include calculation results calculated in the third welding quality pass / fail determination step at the time of inspection up to a preset number of times from this time. Welding quality inspection method. In lap resistance welding in which joint portions of a plurality of members to be welded are superposed, the joint portions are pressed and sandwiched by a pair of electrodes, and a current is passed between the pair of electrodes to join the plurality of members to be welded together A welding quality inspection apparatus for inspecting welding quality, wherein the welding quality inspection apparatus sequentially inspects the welding quality of the joints of a plurality of welded members that are sequentially conveyed to the welding apparatus having the pair of electrodes.
First, the resistance value waveform representing the change of the resistance value between the pair of electrodes during welding with respect to the energization time is classified into a plurality of preset resistance value waveform patterns due to various disturbances to determine whether the welding quality is good or bad. A welding quality pass / fail judgment unit;
A second welding quality pass / fail judgment unit that judges whether or not the spatter is generated from the resistance value waveform and judges the quality of the weld quality when the first weld quality pass / fail judgment unit judges that the weld quality is poor;
A calculation result calculated by substituting a basic variable obtained from the resistance waveform into a predetermined determination formula when the second welding quality determination unit determines that the welding quality is poor, and is set in advance. A third welding quality pass / fail determination unit that compares the determined threshold value to determine weld quality pass / fail,
A fourth weld quality pass / fail determination unit that determines the quality of weld quality by a method different from the first to third weld quality pass / fail determination units when the third weld quality pass / fail determination unit determines that the weld quality is poor. When,
When the fourth welding quality quality determination unit determines that the welding quality is good, the calculation closest to the determination threshold among the plurality of calculation results calculated by the third welding quality quality determination unit during the previous inspection A welding quality inspection apparatus comprising: a determination threshold value updating unit that updates a result as a new determination threshold value in the third welding quality quality determination unit.   The plurality of calculation results in the determination threshold value update unit include calculation results calculated by the third welding quality pass / fail determination unit at the time of inspection up to the number of times set in advance from this time. Welding quality inspection equipment.

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