JP2013022635A - Method for evaluating resistance welding, method for controlling resistance welder, device for controlling the resistance welder and the resistance welder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resistance welder having a simple configuration, easily and accurately determining whether a joining state of welded materials is good or not during welding, and capable of taking measures against a disturbance which prevents the good joining state when it is determined that the joining state of the welded materials is not good.SOLUTION: The resistance welder includes: electrodes 1, 2 pressurizing the plurality of materials W to be welded; a power supply device 3; and a control device 4 for performing control to successfully join the materials W to be welded. The control device 4 includes: a means 5 for detecting melting start timing of the materials W to be welded; and a timer 6 comparing the detected melting start timing of the materials W to be welded with predetermined melting start timing of the materials W to be welded, determining whether the joining state of the materials W to be welded is good or not, on the basis of whether the difference of the both timing is within a preset range or not, and changing a welding condition when it is determined that the joining state of the welded materials W is not good.

Description

  The present invention relates to a resistance welding evaluation method, a resistance welding machine control method, a resistance welding machine control device, and a resistance welding machine.

  In resistance welding such as spot welding, the welded material is melted and joined by applying Joule heating by pressurizing the welded material with an electrode and energizing it. A resistance welding machine for performing such resistance welding generally includes an electrode for pressurizing a material to be welded, and means such as a power supply device for supplying a current to the electrode.

  In such resistance welding, generally, a plurality of materials to be welded are overlapped, these materials to be welded are pressurized with electrodes, and a current is supplied from the power supply device to the materials to be welded via the electrodes. During this time, the welded portion was softened and pressed without first reaching the welded material melting, and the inside of the pressure welded portion was melted by further Joule heating while expanding the pressure welded portion. When the melted part is formed and the energization is stopped and the melted part is solidified, a nugget is formed and the welded materials are joined to each other. In order to join the materials to be welded appropriately, for example, it is necessary to form a nugget having an appropriate diameter according to the thickness of the materials to be welded. In order to appropriately join the workpieces in this manner, the workpieces W1 and W2 are appropriately pressurized by the electrodes 1 and 2 as shown by “no disturbance” in FIG. It is necessary to secure an appropriate current-carrying area and an appropriate current density.

  On the other hand, as shown by “with a gap” in FIG. 14B, there is a so-called gap that is one of disturbances due to insufficient pressurization of the overlapped workpieces W1 and W2. When it occurs, the current-carrying area of the material W to be welded is reduced, and as a result, the current density supplied from the electrodes 1 and 2 is increased, and the melted part is formed in a state where the press-contact part is not sufficiently formed, The diameter of the pressure contact part (pressure contact diameter) is substantially the same as the diameter of the melted part (melting diameter), and the molten metal scatters from between the welded materials W1 and W2, generating dust, and a nugget with a sufficient diameter is not formed. For this reason, the bonding strength is insufficient, and furthermore, scattered dust adheres to the workpiece W and the surroundings are soiled.

  In addition, when the energized area is increased due to disturbance such as the electrodes 1 and 2 being worn out or not shaped into an appropriate shape, the current density of the electrodes 1 and 2 is reduced. The formation of the pressure contact part and the melted part by heating is delayed. On the other hand, the energization of the electrodes 1 and 2 to the material W to be welded is generally cut off after a specified time has elapsed since the energization was started. Therefore, the nugget cannot be formed with a sufficient diameter between the materials to be welded. As a result, the joining strength is insufficient or the materials to be welded W1 and W2 are not joined, so-called peeling occurs. It becomes.

  By the way, in resistance welding, since a nugget is formed between materials to be welded together, it is difficult to directly observe the nugget. Therefore, for example, Patent Document 1 is known as a related conventional technique for evaluating a joining state by resistance welding. This patent document 1 relates to a method for evaluating a welded portion formed by spot welding.

  In Patent Document 1, after obtaining an electrical resistance value between electrodes from a measured voltage value and a measured current value between electrodes at the time of energization in spot welding, the maximum value of the electrical resistance value and energization from the start of energization to 40 ms are disclosed. Disclosed is a method for evaluating spot weldability of a steel sheet, characterized in that an average value of electrical resistance values from the start to the end is obtained, and spot weldability of the steel sheet is evaluated based on the maximum value with respect to the average value. ing.

  That is, in Patent Document 1, as an index for evaluating the spot weldability of a steel sheet, the electrical resistance value between the electrodes for 40 ms from the start of energization and the electrical resistance value from the start to the end of energization. The average value is used. And in patent document 1, since it calculates | requires the average value of the electrical resistance value between energization start to completion | finish, it evaluates after welding is completed.

JP 2005-334935 A

  In Patent Document 1, since the evaluation is performed after the welding is completed, it is impossible to determine whether the joining state of the welded material is good or not during the welding. For this reason, there is a problem in that it is impossible to take measures against disturbances that cause the joining state to be unsatisfactory when the judgment of the joining state of the workpiece is not good.

  In Patent Document 1, the electrical resistance value between the electrodes for 40 ms from the start of energization and the average value of the electrical resistance values from the start to the end of energization are used as indicators for determination. This is used to evaluate the spot weldability of the steel sheet.Therefore, when disturbances such as electrode wear as well as the sheet gap occur, the evaluation results will vary, and the start point of energization Since the starting point is used, there is a problem in that the joining state cannot be accurately evaluated when the actual melting of the workpiece is delayed.

The present invention has been made in view of the above-described problems, and provides a resistance welding evaluation method that can easily and accurately determine the quality of a welded material in a simple configuration during welding. For the purpose.
In addition, the present invention has been made in view of the above-described problems, and with a simple configuration, it is possible to easily and accurately determine the quality of the welding state of the welded material during welding, so that the welding state of the welded material is determined. It is an object of the present invention to provide a resistance welding machine control method capable of taking measures against disturbances that cause the joining state not to be good when the determination is not good.
Furthermore, the present invention has been made in view of the above-described problems, and with a simple configuration, whether or not the joining state of the welded material is easily and accurately determined during welding, and the joining state of the welded material is determined. An object of the present invention is to provide a resistance welding machine control device and a resistance welding machine capable of taking measures against disturbances that cause the joining state not to be good when the determination is not good.

In order to achieve the above object, the resistance welding evaluation method according to claim 1 is a resistance welding in which the welded material is melted and joined by Joule heating by pressurizing the welded material with an electrode and energizing it. A method for evaluating a joining state of the welding material, the step of detecting the timing of the melting start of the welding material, and the timing of the melting start of the detected welding material, which are determined in advance A step of comparing the welding start timing of the material to be welded and a step of determining whether or not the joining state of the material to be welded is good based on whether or not the difference between the timings is within a preset range. It is characterized by this.
In order to achieve the above object, the invention according to the control method for a resistance welder according to claim 2 is a resistance welder that melts and joins the material to be welded by pressurizing the material to be welded with an electrode and energizing it. In the method for controlling the welded material to be satisfactorily joined, the step of detecting the melting start timing of the welded material, the detected melting start timing of the welded material, The step of comparing the welding start timing of the welded material determined in advance and whether or not the joining state of the welded material is acceptable is determined based on whether or not the difference between the timings is within a preset range. And a step of changing welding conditions when the joining state is not good in the determination.
In order to achieve the above object, the resistance welding machine according to claim 3 is a resistance welding machine that melts and joins the materials to be welded by pressurizing the materials to be welded with electrodes and energizing them. A control device for controlling the welding materials to be satisfactorily joined, the means for detecting the melting start timing of the welding materials, and the detected melting start timing of the welding materials; , Comparing the welding start timing of the welded material determined in advance, and determining whether the joining state of the welded material is good or not based on whether or not the difference between both timings is within a preset range. And means for changing the welding condition when the joined state is not good in the determination.
In order to achieve the above object, the resistance welding machine according to claim 4 includes an electrode for pressurizing the welded material, and means for supplying an electric current to the electrode. A resistance welding machine that performs Joule heating by pressing and energizing to melt and join a material to be welded, and is characterized in that the control device according to claim 3 is provided.

According to the first aspect of the present invention, the step of detecting the melting start timing of the welded material, the detected timing of melting start of the welded material, and the predetermined timing of starting melting of the welded material, And a step of determining whether the welding state of the welded material is good or not based on whether or not the difference between both timings is within a preset range. It is possible to provide a resistance welding evaluation method capable of easily and accurately determining whether or not the joining state is good during welding.
According to the second aspect of the present invention, the step of detecting the melting start timing of the welded material, the detected timing of melting start of the welded material, and the predetermined timing of melting start of the welded material, A step of judging whether or not the joining state of the welded material is good based on whether or not the difference between both timings is within a preset range, and when the joining state is not good in the judgment In a simple configuration comprising a step of changing the welding conditions, it is possible to easily and accurately determine the quality of the welding state of the welded material during welding, and when the determination of the bonding state of the welded material is not good, It is possible to provide a control method for a resistance welder that can change the welding conditions and take measures against disturbances that cause the joining state to not be improved.
According to the invention of claim 3, the means for detecting the start timing of melting of the workpiece, the detected timing of starting melting of the workpiece, and the predetermined timing of starting melting of the workpiece And means for determining whether the welding condition of the welded material is good based on whether or not the difference between the two timings is within a preset range, and welding if the bonding condition is not good in the determination. With a simple configuration that includes a means for changing the condition, it is possible to easily and accurately determine the quality of the welding state of the welded material during welding, and when the determination of the bonding state of the welded material is not good, It is possible to provide a control device for a resistance welding machine capable of taking measures against disturbances that cause welding conditions to be changed by changing welding conditions.
According to the invention of claim 4, it is possible to easily and accurately determine whether or not the welding state of the welded material is welded with a simple configuration in which the control device according to claim 3 is provided in the resistance welder. Thus, it is possible to provide a resistance welding machine capable of taking measures against disturbances that cause the joining state to be not improved by changing the welding conditions when the judgment of the joining state of the workpiece is not good. it can.

(Aspect of the Invention)
In the following, the invention that is claimed to be claimable in the present application (hereinafter referred to as “claimable invention”. The claimable invention is at least the “present invention” to the invention described in the claims. Some aspects of the present invention, including subordinate concept inventions of the present invention, superordinate concepts of the present invention, or inventions of different concepts) will be illustrated and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is for the purpose of facilitating the understanding of the claimable invention, and is not intended to limit the combinations of the constituent elements constituting the claimable invention to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention. In each of the following terms, (1) corresponds to claim 1, (7) corresponds to claim 2, (13) corresponds to claim 3, and (19) claims. This corresponds to item 4.

(1) In resistance welding in which a welded material is pressurized with an electrode and energized to perform Joule heating to melt and weld the welded material, a method for evaluating the joining state of the welded material,
Detecting the start of melting of the workpiece,
A step of comparing the detected start timing of melting of the welded material with a predetermined start timing of melting of the welded material;
And a step of judging whether or not the joining state of the workpieces is good based on whether or not the difference between the two timings is within a preset range.

  In the invention described in the item (1), a current is supplied to the material to be welded that has been pressurized by the electrodes, and the timing of the start of melting of the material to be welded is detected. Then, the timing of the start of melting of the welded material detected is compared with the predetermined timing of the start of melting of the welded material, and whether or not the difference between both timings is within a preset range. If the difference between both timings is within a preset range, the welding condition of the welded material is good, and if the difference between both timings is not within the preset range, the welded material Is determined to be defective. Since the quality of the welding condition of the welded material is determined based on the start of melting of the welded material, it is possible to easily and accurately evaluate the bonded condition of the welded material without being affected by disturbance during welding. can do.

  (2) The ultrasonic wave is transmitted between the electrodes of the material to be welded, and the timing of the melting start of the material to be welded is detected by detecting the change of the ultrasonic wave. Evaluation method for resistance welding.

  In the invention described in the item (2), in the invention described in the item (1), an ultrasonic wave is transmitted between the electrodes of the material to be welded, and a reflected wave or a transmitted wave of the transmitted ultrasonic wave is received. By detecting the change, it is possible to accurately detect the melting start timing of the welded material. In order to detect a change in the received ultrasonic wave, specifically, energy (intensity), transmittance or reflectance, spectral intensity, amplitude, and the like can be measured.

  (3) The resistance welding evaluation method according to (1), wherein the timing of melting start of the welded material is detected by calculating energy input between the electrodes of the welded material.

  In the invention of the item (3), in the invention described in the item (1), by calculating the input energy obtained by time integration of the current and the voltage from the start of energization, the timing for starting the melting of the welded material can be easily and It can be detected accurately.

  (4) The detected start timing of melting of the welded material and the predetermined start timing of melting of the welded material are such that an alternating current is passed from the electrode to the welded material and the number of cycles since the start of energization. And comparing both timings according to the number of cycles, the resistance welding evaluation method according to any one of (1) to (3).

  In the invention described in item (4), both timings in the invention described in any one of items (1) to (3) can be easily quantified and compared. Note that a direct current may be applied from the electrode, and in this case, both timings can be compared using the energization time from the start of energization.

  (5) As a predetermined timing for starting the melting of the welded material, a melting start timing at the time of occurrence of dust when the dust is generated is set in advance. The method for evaluating resistance welding according to any one of (1) to (4), wherein the occurrence of dust is predicted when it is earlier than the melting start timing at the time of occurrence.

  In the invention described in item (5), in the invention described in any one of items (1) to (4), the detected melting start timing of the welded material is a predetermined start of melting when dust occurs. When it is earlier than the timing, it is possible to easily and reliably predict that the current density is increased due to disturbance such as a gap and the molten metal is scattered from between the materials to be welded to generate dust.

  (6) As a predetermined timing for starting the melting of the welded material, a melting start timing at the time of occurrence of a joint failure when a joint failure occurs is set in advance, and the detected timing for starting the melting of the welded material is 6. The resistance welding evaluation method according to any one of (1) to (5), wherein occurrence of a bonding failure is predicted when it is later than a melting start timing when the bonding failure occurs.

  In the invention described in item (6), in the invention described in any one of items (1) to (5), the detected melting start timing of the welded material is a predetermined melting at the occurrence of a bonding failure. When it is later than the start timing, current density becomes small due to disturbances such as electrode wear and improper shaping, so that the formation of a melted part is delayed and a nugget of sufficient diameter is not formed, resulting in poor bonding. Therefore, it is possible to predict reliably and reliably.

(Claim 2)
(7) In a resistance welding machine that melts and joins the welded material by applying Joule heating by pressing and applying current to the welded material with an electrode, it is a method for controlling the welded material to be satisfactorily joined. And
Detecting the start of melting of the workpiece,
A step of comparing the detected start timing of melting of the welded material with a predetermined start timing of melting of the welded material;
Determining the quality of the joining state of the workpieces based on whether the difference between the two timings is within a preset range; and
And a step of changing welding conditions when the joining state is not good in the determination.

  In the invention described in item (7), a current is supplied to the workpiece to be welded that has been pressurized by the electrode, and the timing of the start of melting of the workpiece is detected. Then, the timing of the start of melting of the welded material detected is compared with the predetermined timing of the start of melting of the welded material, and whether or not the difference between both timings is within a preset range. If the difference between both timings is within a preset range, the welding condition of the welded material is good, and if the difference between both timings is not within the preset range, the welded material Is determined to be defective. Since the quality of the welding condition of the welded material is determined based on the start of melting of the welded material, it is possible to easily and accurately evaluate the bonded condition of the welded material without being affected by disturbance during welding. can do. And when it is determined by this evaluation that the joining state is not good, the welding conditions are changed until the welding is completed, and when the welding is completed, the joining state is judged to be good. it can.

  (8) The ultrasonic wave is transmitted between the electrodes of the material to be welded, and the timing of the melting start of the material to be welded is detected by detecting the change of the ultrasonic wave. Control method for resistance welding machine.

  In the invention described in item (8), in the invention described in item (7), an ultrasonic wave is transmitted between the electrodes of the material to be welded, and a reflected wave or a transmitted wave of the transmitted ultrasonic wave is received. By detecting the change, the timing of the melting start of the welded material is accurately detected, and as a result, the joining state of the welded material is easily and accurately evaluated, and it is determined by this evaluation that the joining state is not good. In such a case, it is possible to change the welding conditions until the welding is completed, and to determine that the joining state is good when the welding is completed. In order to detect a change in the received ultrasonic wave, specifically, energy (intensity), transmittance or reflectance, spectral intensity, amplitude, and the like can be measured.

  (9) The resistance welding machine control method according to (7), wherein the timing of melting start of the welded material is detected by calculating energy input between the electrodes of the welded material.

  In the invention of the item (9), in the invention of the item (7), by calculating the input energy obtained by time integration of the current and the voltage from the start of energization, the timing for starting the melting of the welded material can be easily and As a result, the welding condition is easily and accurately evaluated, and if it is determined that the bonding condition is not good in this evaluation, the welding condition is changed until the welding is completed. Thus, when welding is completed, it can be determined that the joining state is good.

  (10) The detected start timing of melting of the welded material and the predetermined start timing of melting of the welded material are such that an alternating current is passed from the electrode to the welded material and the number of cycles since the start of energization. The control method for a resistance welder according to any one of (7) to (9), wherein both timings are compared according to the number of cycles.

  In the invention described in item (10), in the invention described in any one of items (7) to (9), both timings can be easily quantified and compared. Note that a direct current may be applied from the electrode, and in this case, both timings can be compared using the energization time from the start of energization.

  (11) As a predetermined timing for starting the melting of the welded material, a melting start timing at the time of occurrence of dust when the dust is generated is set in advance, and the detected timing for starting the melting of the welded material is the aforementioned dust The method for controlling a resistance welder according to any one of (7) to (10), wherein the occurrence of dust is predicted when it is earlier than the melting start timing at the time of occurrence.

  In the invention described in item (11), in the invention described in any one of items (7) to (10), the detected melting start timing of the welded material is a predetermined melting start time when dust occurs. When it is earlier than the timing, it is possible to easily and reliably predict that the current density is increased due to disturbance such as a gap and the molten metal is scattered from between the materials to be welded to generate dust. Then, when it is predicted that the dust will occur, the welding conditions are changed so that the dust can be prevented before the welding is completed, and it is determined that the joining state is good when the welding is completed. Can be. In addition, the change of this welding condition can reduce the electric current value which supplies with electricity to a to-be-welded material via an electrode, or can increase the applied pressure of the to-be-welded material by an electrode.

  (12) As a predetermined timing for starting the melting of the welded material, a melting start timing at the time of occurrence of a joint failure when a joint failure occurs is set in advance, and the detected timing for starting the melting of the welded material is The control method for a resistance welder according to any one of (7) to (11), wherein occurrence of a joint failure is predicted when the time is later than a melting start timing when the joint failure occurs.

  In the invention described in item (12), in the invention described in any one of items (7) to (11), the detected start timing of melting of the welded material is a predetermined melting at the occurrence of bonding failure. When it is later than the start timing, current density becomes small due to disturbances such as electrode wear and improper shaping, so that the formation of a melted part is delayed and a nugget of sufficient diameter is not formed, resulting in poor bonding. Therefore, it is possible to predict reliably and reliably. And when it is predicted that this joint failure will occur, the welding conditions are changed so that the occurrence of the joint failure can be prevented before the welding is completed. It can be determined. In addition, the change of this welding condition can increase the electric current value which energizes to-be-welded material via an electrode, or can extend energization time.

(13) In a resistance welding machine that melts and joins the welded material by applying Joule heating by applying pressure to the welded material with an electrode and energizing, a control device for controlling the welded material to be joined well. There,
Means for detecting the timing of the start of melting of the material to be welded;
The detected start timing of melting of the welded material is compared with a predetermined start timing of melting of the welded material, and based on whether the difference between the two timings is within a preset range. Means for judging the quality of the joined state of the workpieces;
A resistance welding machine control device comprising: means for changing a welding condition when the joining state is not good in the determination.

  In the invention described in item (13), an electric current is supplied to the material to be welded that has been pressurized by the electrodes, and the timing of the start of melting of the material to be welded is detected. Then, the timing of the start of melting of the welded material detected is compared with the predetermined timing of the start of melting of the welded material, and whether or not the difference between both timings is within a preset range. If the difference between both timings is within a preset range, the welding condition of the welded material is good, and if the difference between both timings is not within the preset range, the welded material Is determined to be defective. Since the quality of the welding condition of the welded material is determined based on the start of melting of the welded material, it is possible to easily and accurately evaluate the bonded condition of the welded material without being affected by disturbance during welding. can do. Then, when it is determined that the joining state is not good in this evaluation, the welding condition is changed until the welding is completed, and the resistance welding machine is configured so that the joining state is determined to be good when the welding is completed. Can be controlled.

  (14) The means for detecting the timing of the start of melting of the welded material transmits ultrasonic waves between the electrodes of the welded material, and detects changes in the ultrasonic waves (13) Control device for resistance welding machine according to item.

  In the invention described in item (14), in the invention described in item (13), an ultrasonic wave is transmitted between the electrodes of the material to be welded, and a reflected wave or a transmitted wave of the transmitted ultrasonic wave is received. Detect changes. Therefore, when the welding start timing of the welded material is accurately detected, and as a result, the joining state of the welded material is easily and accurately evaluated, and it is determined in this evaluation that the joining state is not good. The welding conditions can be changed until the welding is completed, and the welding state can be determined to be good when the welding is completed. In order to detect a change in received ultrasonic waves, specifically, energy (intensity), transmittance or reflectance, spectrum intensity, amplitude, and the like can be measured.

  (15) The resistance welding machine according to (13), wherein the means for detecting the melting start timing of the welded material calculates energy input between the electrodes of the welded material. Control device.

  In the invention of the item (15), in the invention described in the item (13), the means for detecting the start timing of melting of the welded material calculates the input energy obtained by time-integrating the current and voltage from the start of energization. Therefore, it is possible to easily and accurately detect the start timing of melting of the welded material, and as a result, the joining state of the welded material is easily and accurately evaluated, and it is determined in this evaluation that the joining state is not good. In some cases, it is possible to change the welding conditions until the welding is completed and to determine that the joining state is good when the welding is completed.

(16) The current passed from the electrode to the work piece is an alternating current,
The means for detecting the melting start timing of the welded material is for detecting the number of cycles from the start of energization to the start of melting of the welded material,
The means for determining whether or not the joining state of the welded material is good is based on a comparison between the detected number of cycles for starting the melting of the welded material and a predetermined number of cycles for starting the melting of the welded material. The control device for a resistance welder according to any one of (13) to (15), wherein the quality of the joined state of the welded material is determined.

  In the invention described in item (16), in the invention described in any one of items (13) to (15), the means for quantifying both timings and determining the quality of the joined state of the welded material is easy. Can be compared. Note that a direct current may be applied from the electrode, and in this case, both timings can be compared using the energization time from the start of energization.

  (17) The means for determining whether the joining state of the welded material is good or not is preset as a melting start timing at the time of dust generation when dust is generated as a predetermined timing for starting the melting of the welded material. Any one of (13) to (16), wherein the occurrence of dust is predicted when the detected melting start timing of the welded material is earlier than the melting start timing at the time of dust generation. Control device for resistance welding machine according to item.

  In the invention described in item (17), in the invention described in any one of items (13) to (16), the means for determining the quality of the joining state of the welded material is the detected material to be welded. When the melting start timing is earlier than the predetermined start timing of the occurrence of dust, the current density increases due to a disturbance such as a gap, and the molten metal scatters from the material to be welded to generate dust. Predict easily and reliably what to do. And when it is predicted that the dust will occur, the means for changing the welding condition changes the welding condition so as to prevent the dust from being generated before the welding is completed. It can be determined to be good. Note that the means for changing the welding conditions can reduce the value of the current applied to the material to be welded via the electrode or increase the pressure of the material to be welded by the electrode.

  (18) The means for determining whether or not the welding condition of the welded material is predetermined as a predetermined timing for starting the melting of the welded material is a preset melting start timing when a bonding failure occurs when a bonding failure occurs. Any of (13) to (17) is characterized in that the occurrence of bonding failure is predicted when the detected melting start timing of the welded material is later than the melting start timing when the bonding failure occurs. The resistance welding machine control device according to claim 1.

  In the invention described in item (18), in the invention described in any one of items (13) to (17), the means for determining the quality of the joined state of the welded material is the melting of the detected welded material. When the start timing is later than the predetermined melting start timing when a defective joint occurs, the current density becomes small due to disturbances such as electrode wear and inappropriate shaping, and the formation of the melted part is delayed, resulting in a sufficient diameter. It can be easily and reliably predicted that no nugget will be formed and a bonding failure will occur. Then, when the occurrence of this bonding failure is predicted, the welding condition is changed so that the occurrence of the bonding failure can be prevented before the welding is completed, and it is determined that the bonding state is good when the welding is completed. You can make it. The means for changing the welding conditions can increase the value of current to be applied to the material to be welded via the electrode or extend the energization time.

(Claim 4)
(19) An electrode for pressurizing the material to be welded and means for supplying an electric current to the electrode are provided, and the material to be welded is melted by Joule heating by pressurizing the material to be welded with an electrode and energizing it. A resistance welding machine for joining,
(13)-(18) The resistance welding machine provided with the control device given in any 1 paragraph.

  In the invention of item (19), by providing the control device according to any one of items (13) to (18), the welding material is pressurized by the electrode, and the current is supplied to the electrode by means of supplying current. Supply. At this time, the control device detects the timing of the melting start of the welded material, compares the detected timing of the melting start of the welded material with the predetermined timing of the melting start of the welded material, It is determined whether or not the difference between both timings is within a preset range, and if the difference between both timings is within a preset range, the joining state of the welded material is good and both If the difference in timing is not within a preset range, it is determined that the joining state of the workpieces is poor. Since the quality of the welding condition of the welded material is determined based on the start of melting of the welded material, it is possible to easily and accurately evaluate the bonded condition of the welded material without being affected by disturbance during welding. can do. Then, when it is determined that the joining state is not good in this evaluation, the welding condition is changed until the welding is completed, and the resistance welding machine is configured so that the joining state is determined to be good when the welding is completed. Can be controlled.

It is the conceptual diagram shown in order to demonstrate one Embodiment of the resistance welding machine provided with the control apparatus of this invention. It is the flowchart shown in order to demonstrate one Embodiment of the evaluation method of resistance welding of this invention. FIG. 3 is a graph showing an example of a waveform of an ultrasonic wave that detects the timing of the start of melting when there is a possibility of occurrence of dust shown in FIG. 2. It is the flowchart shown in order to demonstrate one Embodiment of the control method of the resistance welder of this invention. FIG. 5 is a graph showing an example of an ultrasonic waveform when the current value is lowered due to the possibility of dust generation shown in FIG. 4. FIG. It is the flowchart shown in order to demonstrate 2nd Embodiment of the evaluation method of resistance welding of this invention. It is the graph which showed an example of the waveform of an ultrasonic wave at the time of evaluating that the good nugget diameter shown in Drawing 6 was formed. It is a microscope picture of the cross section of the junction part in the case of being shown in FIG. It is the graph which showed an example of the waveform of an ultrasonic wave in case the welding start timing shown in FIG. 6 is later than the fusion start timing at the time of joining defect generation. FIG. 10 is a photomicrograph of a cross section of the joint in the case shown in FIG. 9. It is the flowchart shown in order to demonstrate 2nd Embodiment of the control method of the resistance welder of this invention. 12 is a graph showing an example of an ultrasonic waveform when the energization time is extended because the welding start timing shown in FIG. 11 is later than the melting start timing when a joining failure occurs. It is a microscope picture of the cross section of the junction part in the case of being shown in FIG. It is explanatory drawing which compared the state from the energization start to the middle period of electricity supply, when there is no disturbance (A) and when there is a gap as an example of disturbance (B).

First, an embodiment of a resistance welder and its control device according to the present invention will be described with reference to FIG.
The resistance welding machine of the present invention has good electrodes 1 and 2 for pressurizing a material W to be welded consisting of a plurality of W1 and W2, means 3 for supplying current to the electrodes 1 and 2, and materials to be welded W1 and W2. And a control device 4 for controlling the welded materials W1 and W2 to be welded by pressurizing the welded materials W1 and W2 with the electrodes 1 and 2 to energize them to melt the welded materials W1 and W2. The control device 4 detects the start timing of melting of the workpiece W, the detected timing of starting melting of the workpiece W, and a predetermined workpiece W to be welded. Means for determining the quality of the joining state of the welded materials W1, W2 based on whether the difference between the two timings is within a preset range or not (described later), And the determination of the joining state of the workpieces W1 and W2 If state and a timer 6 which constitutes the means (to be described later) to change the welding conditions when no good.

  In this embodiment, the material to be welded W is a plate having a predetermined thickness. In this embodiment, the case where two materials to be welded W1 and W2 are lap welded will be described. However, the present invention is not limited to this embodiment, and can be applied to, for example, the case where three plate-like workpieces W are lap welded. Moreover, the material of each to-be-welded material W is not specifically limited, The material may be same or different from each other, and the surface may be plated.

  The electrodes in this embodiment are composed of a pair 1 and 2, each formed in a rod shape, arranged so that the tips are opposed to each other, at least one of them is close to and far from the other 2 The workpiece W can be pressurized with a predetermined force by being relatively close to each other. The tips of the electrodes 1 and 2 are shaped so as to be in contact with each other with a predetermined area when the workpieces W1 and W2 are pressed with a predetermined force.

  The electrodes 1 and 2 are connected to a means 3 for supplying current (hereinafter referred to as a power supply device) 3. The power supply device 3 in this embodiment can supply a single-phase or three-phase alternating current to the electrodes 1 and 2 at a desired current value. However, the present invention is not limited to this embodiment, and may be a power supply device that supplies a direct current. The power supply device 3 is connected to the timer 6 of the control device 4 and is controlled so that a predetermined current value can be supplied between the electrodes 1 and 2 in a predetermined energization time. The details of the control by the control device 4 will be described in detail in an evaluation method or a control method described later.

  The means 5 for detecting the melting start timing of the workpiece W in this embodiment includes an ultrasonic transmission element 51, an ultrasonic reception element 52, and an amplifier that amplifies the ultrasonic waveform received by the ultrasonic reception element 52. 53, a pulser / receiver 54 for transmitting ultrasonic waves to the ultrasonic transmitting element 51 at a predetermined frequency and receiving an ultrasonic waveform amplified through the amplifier 53, and an instruction to transmit ultrasonic waves to the pulser / receiver 54 And a computer 55 for storing the result of the evaluation of the joint output from the timer 6.

Further, in this embodiment, means 56 and 57 for detecting the current value and the voltage value supplied to the electrodes 1 and 2 are provided. The means 56 and 57 for detecting the current value and the voltage value are connected to the timer 6. The timer 6 is also configured to function as an input energy calculation unit that calculates input energy that is a time integration of a current value and a voltage value input to the workpiece W through the electrodes.

Next, the resistance welding evaluation method of the present invention will be described in detail with reference to FIGS. 2 to 5 together with the operation of the control device 4 depending on the case of using the resistance welding machine having the control device 4 described above.
The evaluation method of resistance welding according to the present invention is generally joined by heating a material W consisting of a plurality of W1 and W2 with electrodes 1 and 2 and applying Joule heating to energize the materials W1 and W2. In the resistance welding to be performed, for the purpose of evaluating the joining state of the workpieces W1 and W2, step S2 for detecting the start timing of melting of the workpiece W and the melting of the detected workpiece W Step S3 (first embodiment) or S20 (second embodiment) for comparing the start timing with a predetermined timing for starting the melting of the workpiece W, and the difference between the two timings is determined in advance. Steps S5, S7 (first embodiment) or S21, S23, S24 (second embodiment) for determining whether or not the joining state of the workpieces W is within the set range. Form) There.

  A first embodiment relating to the resistance welding evaluation method of the present invention will be described. When performing resistance welding, first, the workpieces W1 and W2 are overlapped with each other, placed between the electrodes 1 and 2, the electrodes 1 and 2 are held close to each other, and applied with a predetermined force. Press. In this state, when supply of current is started from the power supply device 3 to the electrodes 1 and 2 at a normal value set in advance, that is, welding is started (S1 in FIG. 2), the joined portions of the welded materials W1 and W2 are As shown in FIG. 14A, the joule is heated and is softened and pressed between the workpieces W1 and W2 without first being melted until the workpieces W1 and W2 are melted. The pressure contact portion is formed, and the melted portion is formed by further Joule heating the inside of the pressure contact portion while the pressure contact portion expands.

  At this time, a step (S2 in FIG. 2) of detecting the start timing of melting of the workpiece W is performed. In this embodiment, an instruction signal for ultrasonic transmission is output from the computer 55 to the pulsar / receiver 54, and the pulsar / receiver 54 transmits ultrasonic waves from the ultrasonic transmission element 51 provided on one electrode 1, In this embodiment, the ultrasonic wave transmitted through the workpieces W1 and W2 is received by the ultrasonic wave receiving element 52 provided on the other electrode 2, and the amplitude of the received ultrasonic wave is amplified by the amplifier 53 and amplified. The ultrasonic wave amplitude is sent from the pulser / receiver 54 to the timer 6. The timer 6 creates a waveform that changes with time of the amplitude of the ultrasonic wave sent from the pulser / receiver 54.

  Here, FIG. 3 is a graph showing a waveform of the current supplied to the electrodes 1 and 2 and the amplitude of the received and amplified ultrasonic waves over time. Although the time in the graph is expressed in seconds (s), in this embodiment, the current supplied to the electrodes 1 and 2 is alternating current, and the timing such as the start of melting of the workpiece W is alternating current. In other words, for example, in the case of an alternating current of 60 Hertz, 1/60 seconds = 1 cycle.

  It is known that the amplitude of the received ultrasonic wave decreases when the workpiece W starts to melt by Joule heating as welding starts (= energization starts). In the graph of FIG. 3, for example, the amplitude of the ultrasonic wave rapidly decreases in two cycles. As shown in the dashed ellipse in FIG. 3, dust actually occurred in the subsequent 5.6 cycles. The cause of the generation of dust is that, as shown in FIG. 14B, due to the presence of a gap, the current-carrying area of the material W to be welded is reduced and the current density supplied from the electrodes 1 and 2 is increased. There is.

  Therefore, in this embodiment of the present invention, in the example of this embodiment, the timing immediately before the occurrence of dust is defined as the melting start timing at the time of dust generation, which is a threshold value for determining the occurrence of dust. It is preset to 5 cycles.

  Referring again to FIG. 2, in S3, the detected melting start timing of the workpiece W is compared with the melting start timing at the occurrence of dust, and the difference between both timings is within a preset range. In this case, in this embodiment, the detected melting start timing of the workpiece W is slower than the five cycles set as the melting start timing at the occurrence of dust (that is, the number of cycles of the detected melting start timing ≧ chili In the case of (the number of cycles of melting start timing at the time of occurrence) (in the case of YES in S3 in FIG. 2), it is predicted that there is no possibility of dust generation (S4 in FIG. 2), and the nugget diameter is normally formed. Judgment is made (S5 in FIG. 2), and the resistance welding evaluation is finished (S9 in FIG. 2).

  On the other hand, when the detected melting start timing of the workpiece W is earlier than 5 cycles (that is, the detected melting start timing cycle number <the number of melting start timing cycle times when dust occurs) (S3 in FIG. 2). In the case of NO), it is predicted that dust may occur (S6 in FIG. 2), and it is determined that the nugget diameter may be insufficient (S7 in FIG. 2). A ladle inspection is performed to check the presence of peeling by driving around the joint of the material W (S8 in FIG. 2), and the resistance welding evaluation is completed (S9 in FIG. 2).

In the evaluation method according to this embodiment, the gap or excess of the gap is detected at an early timing (before 5 cycles in the above example) from the start of energization to the end of energization (for example, 10 to 30 cycles). It is possible to predict the possibility of dust generation due to electric current.

  Next, an embodiment of the resistance welding machine control method of the present invention is based on the case of using a resistance welding machine configured as shown in FIG. This will be described in detail. In addition, about the part similar or equivalent to the evaluation method of the resistance welding machine demonstrated based on FIG. 2, FIG. 3, the same code | symbol is attached | subjected and the description is abbreviate | omitted, and only a different part will be demonstrated here. .

  The control method of the resistance welder of the present invention is roughly a resistance welder that pressurizes the materials to be welded W1 and W2 with the electrodes 1 and 2 and applies Joule heating to melt and join the materials to be welded W1 and W2. In the above, a method for controlling the materials to be welded W1 and W2 to be satisfactorily joined, the above-described resistance welding evaluation method is performed, and the joining state of the materials to be welded W is determined to be poor. In this case, step S12 (first embodiment) or S25 and S27 (second embodiment) for changing the welding conditions is further included.

  1st Embodiment regarding the control method of the resistance welder of this invention is described. When resistance welding is performed, the workpieces W1 and W2 are overlapped with each other, placed between the electrodes 1 and 2, the electrodes 1 and 2 are held close to each other, and pressed with a predetermined force. Then, supply of current from the power supply device 3 to the electrodes 1 and 2 is started at a normal value set in advance (S1 in FIG. 4), and the joint portion of the workpiece W is Joule-heated. The melting start timing is detected (S2 in FIG. 4), and the detected melting start timing of the workpiece W is compared with a preset melting start timing at the occurrence of dust (S3 in FIG. 4). If the detected melting start timing of the workpiece W is later than the melting start timing when dust occurs (YES in S3 in FIG. 4), it is predicted that there is no possibility of dust generation (S4 in FIG. 4). ), And the timing of the start of melting of the detected workpiece W As described above with reference to FIG. 2, it is predicted that there is a possibility of dust generation (S6 in FIG. 4) when the dust is earlier than the melting start timing at the time of dust generation (in the case of NO in S3 of FIG. 4). This is the same as the resistance welding evaluation method.

  In the control method in this embodiment, when it is predicted that dust may occur (S6 in FIG. 4), as a specific example of the welding conditions to be changed, as shown in FIGS. The value is decreased (S12).

  As shown in FIG. 5, it is detected that the material to be welded W has started melting in 2 cycles, and there is a possibility of occurrence of dust because it is earlier than 5 cycles which is the preset melting start timing at the time of dust generation. When predicted, the current value is reduced (suppressed) at a timing earlier than 5 cycles, which is the melting start timing when dust occurs. In this embodiment, the current value is set to be reduced at the time of 4 cycles as the timing earlier than 5 cycles that is the melting start timing when dust occurs. Thereby, when the gap is generated and the current-carrying area of the workpiece W is small, the current density supplied from the electrodes 1 and 2 can be suppressed. As can be seen, a rapid increase in the amplitude of the ultrasonic waves can be suppressed, and the generation of dust can be prevented (less dust is caused).

  The welding conditions to be changed in the embodiment for preventing the generation of dust are not limited to the decrease in the current value (S12), and the pressure applied to the electrodes 1 and 2 with respect to the materials to be welded W1 and W2. May be increased to eliminate the gap itself.

Thereafter, when it is predicted that dust does not occur in S4 of FIG. 4, in any case where the current value is reduced in S12, the input energy after the start of melting (time integration of current and voltage from the start of energization) is It is determined whether the predetermined value has been reached (S10 in FIG. 4). The detection of the input energy can be calculated by integrating the current value and voltage value of the electrodes 1 and 2 detected by the means 56 and 57 shown in FIG. If the input energy does not reach the predetermined value (NO in S10), energization is continued until the predetermined value is reached, and if the input energy reaches the predetermined value (YES in S10), It is determined that a nugget having a good diameter has been formed (S11 in FIG. 4), and the control for preventing the generation of dust in the resistance welder is terminated (S13 in FIG. 4). At this time, the timer 6 informs the computer 55 of data such as the current values and voltage values of the electrodes 1 and 2 detected by the means 56 and 57, the calculated input energy, and the result of the quality determination of the joining state of the welded material. Output and store.

Next, a second embodiment of the resistance welding evaluation method of the present invention will be described in detail with reference to FIGS. Note that portions that are the same as or correspond to those in the above-described embodiment are denoted by the same reference numerals, description thereof is omitted, and only portions that are different from the above-described embodiment are described.
In the first embodiment described above, the occurrence of dust due to the occurrence of a plate gap is predicted as a disturbance of resistance welding, whereas in the second embodiment, the electrodes 1 and 2 are disturbed as a disturbance of resistance welding. Due to wear or improper shaping, the contact area (energization area) when the workpieces W1 and W2 are pressed with a predetermined force is expanded and the current density is reduced, so that the pressure contact portion and the molten portion due to Joule heating are reduced. Therefore, it is evaluated whether the nugget cannot be formed with a sufficient diameter between the materials to be welded due to a delay in the formation of the material and insufficient bonding strength or so-called peeling has occurred.

  When resistance welding is performed, the workpieces W1 and W2 are overlapped with each other, placed between the electrodes 1 and 2, the electrodes 1 and 2 are held close to each other, and pressed with a predetermined force. Then, supply of current from the power supply device 3 to the electrodes 1 and 2 is started at a normal value set in advance (S1 in FIG. 6), and the joint portion of the workpiece W is Joule-heated. It is the same as that of embodiment mentioned above to detect the timing of the melting start of (S2 of FIG. 6).

  Here, FIG. 7 shows the current and the received ultrasonic wave when the welding material W is welded in a state where the electrodes 1 and 2 are normal (for example, the diameter of the electrode contacting the welding material is 6 mm). It is the graph which showed the waveform with time passage with the amplitude of. In the graph shown in FIG. 7, the amplitude of the ultrasonic wave received in five cycles from the start of welding (= energization start) decreases, that is, melting has started. The nugget in this case is formed with a diameter of a predetermined size (for example, nugget diameter = 7.7 mm) as shown in a micrograph of its cross section in FIG.

  On the other hand, FIG. 9 shows a material to be welded in a state where the electrodes 1 and 2 do not have a predetermined shape due to wear or the like (for example, the diameter of the electrode in contact with the material to be welded is increased to 7 mm). It is the graph which showed the waveform with time passage of the electric current at the time of welding W, and the amplitude of the received ultrasonic wave. In the graph shown in FIG. 9, the amplitude of the ultrasonic wave received in 11 cycles from the start of welding (= start of energization) decreases, that is, melting has started. This is considered to be because the current density of the electrodes 1 and 2 is reduced as compared with the case where resistance welding is performed in a state where the electrodes 1 and 2 are normal. As a result, the nugget in this case has a diameter (for example, nugget diameter) smaller than a predetermined size (in the example of FIG. 8, nugget diameter = 7.7 mm), as shown in a micrograph in FIG. = 4.8 mm). In the case where the nugget is not formed with a sufficiently large diameter as described above, the joining strength is insufficient, or the welded material W is not joined and so-called peeling occurs.

  Therefore, in the present invention, the timing of the start of melting at which the nugget cannot be formed with a predetermined diameter is set as the melting start timing at the time of occurrence of bonding failure, which is a threshold value for determining the bonding failure, as shown in FIG. The timing is set in advance to the 11 cycles shown (8 cycles in the example of this embodiment).

  Referring again to FIG. 6, the melting start timing is detected (S <b> 2), and then the detected melting start timing of the welded material W and the preset melting start timing when a joining failure occurs are set. In comparison (S20 in FIG. 6), if the detected melting start timing of the workpiece W is earlier than the melting start timing at the occurrence of a bonding failure (YES in S20 in FIG. 6), a good nugget diameter Is determined (S21 in FIG. 6), and it is predicted that there is no possibility of occurrence of poor bonding, and the resistance welding evaluation is terminated (S9 in FIG. 6). On the other hand, when the detected melting start timing of the workpiece W is later than the melting start timing at the occurrence of bonding failure (NO in S20 of FIG. 6), the energization from the start of energization to the end of energization is continued. It is determined whether or not there is a melting start within the time (S22 in FIG. 6). If there is a melting start within the energization time (YES in S22 in FIG. 6), it is determined that there is a possibility of insufficient bonding strength. (S23 in FIG. 6) If there is no melting start within the energization time (NO in S22 in FIG. 6), it is determined that there is a possibility of peeling (S24 in FIG. 6), and resistance welding is evaluated. The process ends (S9 in FIG. 6). At this time, the timer 6 informs the computer 55 of data such as the current values and voltage values of the electrodes 1 and 2 detected by the means 56 and 57, the calculated input energy, and the result of the quality determination of the joining state of the welded material. Output and store.

In the evaluation method according to the second embodiment, the electrode is used at an early timing (before 8 cycles in the above example) between the start of energization and the end of energization (for example, 10 to 30 cycles). It is possible to predict the possibility of joint failure due to wear of 1 and 2. In addition, the present invention is set in combination with the evaluation method in the first embodiment described above, that is, the melting start timing when dust occurs (for example, 5 cycles) and the melting start timing when bonding failure occurs (for example, 8 cycles). In addition, it can be determined that a good nugget diameter is formed when the detected melting start timing is later than the melting start timing when dust occurs and earlier than the melting start timing when bonding failure occurs. Then, if the detected melting start timing is earlier than the melting start timing at the time of occurrence of dust or later than the melting start timing at the time of occurrence of bonding failure, it is collectively determined that a good nugget diameter is not formed. You can also.

  Next, the second embodiment of the resistance welding machine control method of the present invention is mainly shown in FIGS. 11 to 13 together with its operation depending on the case of using the resistance welding machine configured as shown in FIG. This will be described in detail. In addition, about the part which is the same as that of the 1st Embodiment mentioned above and the evaluation method of resistance welding demonstrated based on FIGS. 6-10, or the part corresponded, the same code | symbol is attached | subjected and the description is abbreviate | omitted here. Only the different parts will be described.

  In the first embodiment described above, the occurrence of dust due to the occurrence of a gap is predicted as a disturbance of resistance welding, and control is performed to prevent the occurrence of dust by reducing the current value as a welding condition to be changed. On the other hand, in the second embodiment, due to the resistance welding resistance, the electrodes 1 and 2 are worn or improperly shaped, and the formation of the pressure contact portion and the molten portion due to Joule heating is delayed, Control is performed so as not to cause insufficient bonding strength or so-called peeling caused by the inability to form a nugget with a sufficient diameter during W2.

  When resistance welding is performed, the workpieces W1 and W2 are overlapped with each other, placed between the electrodes 1 and 2, the electrodes 1 and 2 are held close to each other, and pressed with a predetermined force. Then, supply of current from the power supply device 3 to the electrodes 1 and 2 is started at a normal value set in advance (S1 in FIG. 11), and the joint portion of the workpiece W is Joule-heated. At this time, the workpiece W The melting start timing is detected (S2 in FIG. 11), and the detected melting start timing of the workpiece W is compared with a preset melting start timing when a joining failure occurs (S20 in FIG. 11). If the detected melting start timing of the welded material W is earlier than the melting start timing at the occurrence of a joint failure (YES in S20 of FIG. 11), it is predicted that a good nugget diameter will be formed. (S21 in FIG. 11), bonding failure Predicting that there is no possibility of the raw is similar to the second embodiment of the evaluation method described above (Figure 6). In addition, when it is predicted that a good nugget diameter is formed (S21 in FIG. 11), it is determined whether the input energy after the start of melting is equal to or higher than various positions (S10 in FIG. 11). The control method is the same as that of the first embodiment (FIG. 4). Further, when the detected melting start timing of the workpiece W is later than the melting start timing at the occurrence of a joint failure (NO in S20 of FIG. 11), within the energization time from the energization start to the energization end. It is determined whether or not there is a melting start (S22 in FIG. 11), and if there is a melting start within the energization time (YES in S22 in FIG. 11), it is predicted that the bonding strength may be insufficient (FIG. 11). S23), if melting does not start within the energization time (NO in S22 of FIG. 11), it is predicted that there is a possibility of occurrence of peeling (S24 of FIG. 11). This is the same as the second embodiment (FIG. 6).

  In FIG. 11, when the melting start timing is later than the melting start timing at the time of occurrence of a bonding failure (NO in S20) and the melting does not start within the energization time (NO in S22), the current value is increased. (S25) It is determined whether or not melting has started (S26), and if melting is not started (NO in S26), it is output that the joining quality of the workpiece W is poor if necessary. Then, the cause of the bonding failure is investigated, and the control of the resistance welder is finished (S29). On the other hand, when the current value is increased (S25) and melting is started (YES in S26), the energization time is extended so that the input energy after melting becomes a predetermined value or more (S27).

  In addition, when melting is started within the energization time (YES in S22) and it is predicted that there is a possibility of insufficient bonding strength (S23), energization is performed so that the input energy after melting becomes a predetermined value or more after that. The time is extended (S27).

  Here, FIG. 12 is a graph showing that the energization time has been extended by detecting that melting has started in 11 cycles slower than 8 cycles from the start of energization set in advance as the melting start timing at the occurrence of bonding failure. . As a result, the nugget is formed with a diameter of a predetermined size (for example, nugget diameter = 6.6 mm) as shown in a micrograph of its cross section in FIG.

  In any case where melting is started, it is determined whether the input energy after the start of melting is equal to or greater than a predetermined value, as in the first embodiment (FIG. 4) of the control method described above (FIG. 11). S10), resistance welding control is terminated (S29).

  In the control method of the present invention, the electrodes 1 and 2 are worn at an early timing (before 8 cycles in the above example) from the start of energization to the end of energization (for example, 10 to 30 cycles). The possibility of occurrence of bonding failure due to the above or the like can be predicted, and measures against the bonding failure can be taken before the welding of the workpiece W is completed. Note that the present invention is combined with the control method in the first embodiment described above, that is, the melting start timing at the occurrence of dust (for example, 5 cycles) and the melting start timing at the occurrence of bonding failure (for example, 8 cycles) are set. In addition, it can be determined that a good nugget diameter is formed when the detected melting start timing is later than the melting start timing when dust occurs and earlier than the melting start timing when bonding failure occurs. If the detected melting start timing is earlier than the melting start timing at the time of occurrence of dust, the current value is decreased or the pressurizing force is increased as a change in welding conditions, and the melting start timing is delayed after the occurrence of defective bonding. In this case, the current value can be increased or the energization time can be extended as a change in the welding conditions.

  The present invention is not limited to the above-described embodiment, and includes a case in which detection of melting start is performed by a method other than the calculation of ultrasonic waves or energy input between electrodes. Further, various time points from the start of energization can be specified by absolute time without depending on the number of cycles of alternating current. In addition, the numerical value shown by embodiment mentioned above was shown in illustration in describing this invention, and changes according to welding conditions, such as the thickness of a to-be-welded material, an electric current value, and a voltage value. Can do.

  W: material to be welded, W1: first material to be welded, W2: second material to be welded, 1, 2: electrode, 3: power supply device (means for supplying current to electrode), 4: control device 5: Means for detecting the melting start timing of the welded material 6: Timer (comparing the detected timing for starting the melting of the welded material with a predetermined timing for starting the melting of the welded material) , Means for determining whether the welding condition of the welded material is good based on whether or not the timing difference is within a preset range, and when the bonding condition is not good in the determination of the welding condition of the welded material To change the welding conditions)

Claims (4)

In resistance welding in which a welded material is melted and joined by applying Joule heating by energizing the welded material with an electrode, a method for evaluating the joining state of the welded material,
Detecting the start of melting of the workpiece,
A step of comparing the detected start timing of melting of the welded material with a predetermined start timing of melting of the welded material;
And a step of judging whether or not the joining state of the workpieces is good based on whether or not the difference between the two timings is within a preset range. In a resistance welding machine that melts and joins a welded material by applying Joule heating by pressing and applying current to the welded material with an electrode, a method for controlling the welded material to be joined well,
Detecting the start of melting of the workpiece,
A step of comparing the detected start timing of melting of the welded material with a predetermined start timing of melting of the welded material;
Determining the quality of the joining state of the workpieces based on whether the difference between the two timings is within a preset range; and
And a step of changing welding conditions when the joining state is not good in the determination. In a resistance welding machine that melts and joins the welded material by applying Joule heating by pressing and applying current to the welded material with an electrode, a control device for controlling the welded material satisfactorily,
Means for detecting the timing of the start of melting of the material to be welded;
The detected start timing of melting of the welded material is compared with a predetermined start timing of melting of the welded material, and based on whether the difference between the two timings is within a preset range. Means for judging the quality of the joined state of the workpieces;
A resistance welding machine control device comprising: means for changing a welding condition when the joining state is not good in the determination. An electrode for pressurizing the material to be welded, and means for supplying a current to the electrode, a resistance for melting and joining the material to be welded by applying Joule heating by pressing the material to be welded with an electrode A welding machine,
A resistance welding machine comprising the control device according to claim 3.