阅读说明：本技术 电阻焊接的喷溅检测方法及其装置 (Splash detection method and device for resistance welding ) 是由 名和原彬 中崎大辅 于 2019-02-07 设计创作，主要内容包括：本发明提供一种电阻焊接的喷溅检测方法及其装置,所述装置具有：点焊装置(2),其在利用一对电极(33、34)对层叠多个金属板材而构成的工件W加压且维持规定压力的状态下,在对一对电极(33、34)间通电来焊接工件(W)；动作控制部(42),其以规定的时间间隔对一对电极(33、34)的电极间距离进行检测；运算部(51),其对所检测出的电极间距离的时间变化率进行检测；以及判断电路部(52),其在一对电极(33、34)的接近方向上的所检测出的变化率为规定阈值以上的情况下,判断为发生喷溅。(The invention provides a splash detection method and device for resistance welding, the device comprises: a spot welding device (2) which welds a workpiece (W) by applying current between a pair of electrodes (33, 34) while pressing the workpiece (W) formed by laminating a plurality of metal plate materials by the pair of electrodes (33, 34) and maintaining a predetermined pressure; an operation control unit (42) that detects the inter-electrode distance between the pair of electrodes (33, 34) at predetermined time intervals; a calculation unit (51) that detects the temporal rate of change of the detected inter-electrode distance; and a determination circuit unit (52) that determines that sputtering has occurred when the rate of change detected in the direction of approach of the pair of electrodes (33, 34) is greater than or equal to a predetermined threshold value.)

1. A spatter detection method for resistance welding in which a workpiece formed by stacking a plurality of metal plate materials is pressed by a pair of electrodes and a predetermined pressure is maintained, and a current is passed between the pair of electrodes to weld the workpiece, characterized in that:

the splash detection method for resistance welding comprises the following steps:

an inter-electrode distance detecting step of detecting an inter-electrode distance, which is a distance between the pair of electrodes, at predetermined time intervals;

a change rate detection step of detecting a time change rate of the detected inter-electrode distance; and

a determination step of determining that splash is occurring when the detected rate of change in the direction of approach of the pair of electrodes is greater than or equal to a predetermined threshold.

2. A spatter detecting method of resistance welding according to claim 1, wherein:

in the determining step, a rate of change in the inter-electrode distance detected during energization is determined.

3. The spatter detecting method for resistance welding according to claim 1 or 2, wherein:

the predetermined threshold value in the judging step is 0.3 mm/sec.

4. A spatter detecting method of resistance welding according to any one of claims 1 to 3, wherein:

in the determining step, it is determined that the splash phenomenon is more serious as the detected change rate is larger.

5. A spatter detecting method of resistance welding according to any one of claims 1 to 4, wherein:

in the inter-electrode distance detecting step, the inter-electrode distance is detected using a mechanism for driving a robot arm to which a welding gun including the pair of electrodes is attached at a tip end.

6. A spatter detection device for resistance welding in which a workpiece formed by stacking a plurality of metal plate materials is pressed by a pair of electrodes and a predetermined pressure is maintained, and a current is passed between the pair of electrodes to weld the workpiece, characterized in that:

this splash detection device of resistance welding includes:

an inter-electrode distance detection means for detecting an inter-electrode distance, which is a distance between the pair of electrodes, at predetermined time intervals;

a change rate detection unit that detects a time change rate of the detected inter-electrode distance; and

and a determination unit that determines occurrence of splash when the detected change rate in the direction of approach of the pair of electrodes is equal to or greater than a predetermined threshold value.

7. The splash detection device for resistance welding of claim 6, wherein:

the determination unit determines a rate of change of the inter-electrode distance detected during energization.

8. The splash detection device for resistance welding according to claim 6 or 7, characterized in that:

the prescribed threshold value of the judging unit is 0.3 mm/sec.

9. A splash detection device for resistance welding according to any of claims 6 to 8, characterized in that:

the judgment unit judges that the splash phenomenon is more serious as the detected change rate is larger.

10. A splash detection device for resistance welding according to any of claims 6 to 9, characterized in that:

the inter-electrode distance detection unit detects the inter-electrode distance using a mechanism for driving a robot arm having a welding gun including the pair of electrodes mounted on a tip end thereof.

Technical Field

The present invention relates to a spatter detection method and a spatter detection apparatus for resistance welding, in which a workpiece formed by stacking a plurality of metal plate materials is sandwiched between a pair of electrodes at a predetermined pressure, and the pressure is maintained, and a current is passed between the pair of electrodes to weld the plurality of metal plate materials.

Background

Conventionally, resistance welding apparatuses typified by spot welding have been used in many cases in vehicle body assembly factories and the like. The spot welding apparatus is configured to apply a current between a pair of electrodes while holding a workpiece formed by stacking a plurality of metal plate materials between the pair of electrodes and maintaining a predetermined pressure. Joule heat generated by the energization between the electrodes melts the welded portion of the work, and a nugget, which is a molten metal, is generated. Thereafter, the energization is stopped while maintaining a predetermined pressurized state, so that the nugget is cooled and solidified, and the welding of the workpiece made of the plurality of metal plate materials is completed.

On the other hand, the temperature of the welded portion is excessively increased due to the increase in the current density of the welded portion, and a phenomenon in which the melt of the welded portion is splashed out of the work, that is, a so-called splash phenomenon occurs. When the splash phenomenon occurs, the thickness of the welded portion is reduced by the splash of the melt, and therefore, the joint strength is reduced, and in the case where the splash adheres to the outer surface of the workpiece, it may be necessary to finish the coated surface. Therefore, a technique for preventing the occurrence of a splash phenomenon in which the melt splashes has been proposed.

The resistance welding apparatus of patent document 1 includes a pair of electrodes, a pressurizing device that applies pressure to an object to be welded from one electrode, and an energizing device that applies welding current to both electrodes, and performs welding by applying pressure to the object to be welded and energizing. The resistance welding device comprises: a sensor that detects a displacement amount of the electrode; and a current switching control device capable of switching the welding current according to the detected displacement amount, wherein the current switching control device switches the welding current to a higher current value than the previous welding current when the detected displacement amount exceeds a threshold value.

Patent document 1: japanese laid-open patent publication No. 2014-217854

Disclosure of Invention

Technical problems to be solved by the invention

The resistance welding apparatus in patent document 1 reduces the occurrence of spatter by increasing the welding current after increasing the contact area between the plate materials of the workpieces by melting the welded portion. However, when spatter occurs from the welded portion for some reason, it is necessary to detect the spattered workpiece from among a large number of workpieces conveyed on a production line and to perform trimming or the like. The resistance welding apparatus of patent document 1 attempts to suppress the occurrence of spatter by adjusting the welding current, but it is still necessary to rely on a confirmation operation based on visual observation by an operator to identify a workpiece actually having spatter on a production line, and it is not easy to detect a workpiece having spatter from among a plurality of workpieces.

Focusing attention on the phenomenon of the thickness of the welded portion becoming thin due to the spattering of the molten material, a method of detecting the occurrence of the spattering phenomenon based on the amount of change in the distance between the pair of electrodes is conceivable. However, depending on the welding conditions and the processing method such as the thickness of the workpiece, the welding current value, and the pressure, even if the spatter phenomenon does not occur, the workpiece (welded portion) may be severely crushed by the clamping operation of the pair of electrodes, and high detection accuracy may not be ensured only by the detection based on the change in the inter-electrode distance.

The purpose of the invention is that: a spatter detection method and a spatter detection device for resistance welding, which can quantitatively detect the occurrence of a spatter phenomenon without being restricted by welding conditions and the like.

Technical solution for solving technical problem

A spatter detection method for resistance welding according to claim 1 is a spatter detection method for resistance welding in which a workpiece formed by stacking a plurality of metal plate materials is pressed by a pair of electrodes and a predetermined pressure is maintained, and electricity is passed between the pair of electrodes to weld the workpiece, the spatter detection method comprising: an inter-electrode distance detecting step of detecting an inter-electrode distance, which is a distance between the pair of electrodes, at predetermined time intervals; a change rate detection step of detecting a time change rate of the detected inter-electrode distance; and a determination step of determining that splash is occurring when the detected rate of change in the direction of approach of the pair of electrodes is greater than or equal to a predetermined threshold value.

In the spatter detection method of resistance welding, since the inter-electrode distance detection step of detecting the inter-electrode distance at predetermined time intervals is provided, the inter-electrode distance can be detected in time series. Since the welding device has the change rate detection step of detecting the temporal change rate of the detected inter-electrode distance, the change in the state of the welded portion can be detected using the inter-electrode distance as a parameter.

Further, since the method includes the step of determining that the spatter is generated when the detected change rate in the direction of approach of the pair of electrodes is equal to or greater than the predetermined threshold value, it is possible to distinguish between a state in which the welded portion is crushed by the pinching operation of the electrodes and a state in which the spatter occurs by the change rate of the inter-electrode distance, and it is possible to quantitatively detect the occurrence of the spatter as a physical quantity.

The invention according to claim 1, the invention according to claim 2 is characterized in that: in the determining step, a rate of change in the inter-electrode distance detected during energization is determined. The interval excluding the determination can be set even during the energization in consideration of the influence of erroneous detection due to noise or the like.

According to this configuration, the change rate of the distance between the electrodes within the limited period can be determined, and the process can be simplified to eliminate the change in the state of the welded portion other than the occurrence of the spatter phenomenon.

The invention according to claim 1 or 2, the invention according to claim 3 is characterized in that: the predetermined threshold value in the judging step is 0.3 mm/sec. For new materials that do not fit the current predetermined threshold, the threshold can be set individually for each welding portion, and the predetermined threshold itself can be modified.

According to this configuration, the occurrence of the splash phenomenon can be quantitatively measured without being restricted by the thickness of the metal plate material.

The invention according to any one of claims 1 to 3, the invention of claim 4 is characterized in that: in the determining step, it is determined that the splash phenomenon is more serious as the detected change rate is larger.

According to this configuration, the magnitude of the splash phenomenon can be detected together with the occurrence of the splash phenomenon.

The invention according to any one of claims 1 to 4, the invention of claim 5 is characterized in that: in the inter-electrode distance detecting step, the inter-electrode distance is detected using a mechanism for driving a robot arm to which a welding gun including the pair of electrodes is attached at a tip end.

According to this configuration, the facility can be simplified by using an existing mechanism.

A spatter detecting device for resistance welding according to claim 6 is a spatter detecting device for resistance welding in which a workpiece formed by stacking a plurality of metal plate materials is pressed by a pair of electrodes and a predetermined pressure is maintained, and electricity is passed between the pair of electrodes to weld the workpiece, the spatter detecting device being characterized in that: comprising: an inter-electrode distance detection means for detecting an inter-electrode distance, which is a distance between the pair of electrodes, at predetermined time intervals; a change rate detection unit that detects a time change rate of the detected inter-electrode distance; and a determination unit that determines that splash has occurred when the detected rate of change in the direction of approach of the pair of electrodes is greater than or equal to a predetermined threshold.

In the spatter detecting device for resistance welding, since the electrode-to-electrode distance detecting means for detecting the electrode-to-electrode distance at predetermined time intervals is provided, the electrode-to-electrode distance can be detected in time series. Since the welding portion is provided with the change rate detection means for detecting the time change rate of the detected inter-electrode distance, the change in the state of the welding portion can be detected using the inter-electrode distance as a parameter.

Further, since the determination means is provided for determining that the spatter is generated when the detected change rate in the direction of approach of the pair of electrodes is equal to or greater than the predetermined threshold value, it is possible to distinguish between a state in which the welded portion is crushed by the sandwiching operation of the electrodes and a state in which the spatter occurs by using the change rate of the inter-electrode distance, and it is possible to quantitatively detect the occurrence of the spatter as a physical quantity.

According to the invention of claim 6, the invention of claim 7 is characterized in that: the determination unit determines a rate of change of the inter-electrode distance detected during energization. The interval excluding the determination can be set even during the energization in consideration of the influence of erroneous detection due to noise or the like.

According to this configuration, basically the same effect as that of claim 2 can be obtained.

According to the invention of claim 6 or 7, the invention of claim 8 is characterized in that: the predetermined threshold of the judging unit is 0.3 mm/sec. For new materials that do not fit the current predetermined threshold, the threshold can be set individually for each welding portion, and the predetermined threshold itself can be modified.

According to this configuration, basically the same effect as that of claim 3 can be obtained.

According to the invention of any one of claims 6 to 8, the invention of claim 9 is characterized in that: the judgment unit judges that the splash phenomenon is more serious as the detected change rate is larger.

According to this configuration, basically the same effect as that of claim 4 can be obtained.

The invention according to any one of claims 6 to 9, wherein the invention according to claim 10 is characterized in that the inter-electrode distance detecting means detects the inter-electrode distance using a mechanism for driving a robot arm to which a welding gun including the pair of electrodes is attached at a tip end.

According to this configuration, basically the same effect as that of claim 5 can be obtained.

Effects of the invention

The splash detection method and the device for resistance welding can quantitatively detect the splash phenomenon without being limited by welding conditions and the like.

Drawings

FIG. 1 is an overall schematic configuration diagram of a spatter detecting device in spot welding according to example 1;

FIG. 2 is a schematic view of a spot welding apparatus;

FIG. 3 is an enlarged schematic view of the weld gun of FIG. 2;

FIG. 4 is a graph of the position and rate of change of the upper electrode when no sputtering occurs;

FIG. 5 is a graph of the position and rate of change of the upper electrode when sputtering occurs;

FIG. 6 is a graph of the position and rate of change of the upper electrode when spatter occurs in a double thick plate weld;

FIG. 7 is a graph of the position and rate of change of the upper electrode when spatter occurs during double sheet welding;

FIG. 8 is a graph of the position and rate of change of the upper electrode when spatter occurs in a three-layer thick plate weld;

FIG. 9 is a graph of the position and rate of change of the upper electrode when spatter occurs in a three-layer sheet weld;

FIG. 10 is a graph of the position and rate of change of the upper electrode when spatter occurs in another three layer thick plate weld;

fig. 11 is a flowchart showing a welding process sequence;

FIG. 12 is a flowchart showing a splash detection processing sequence;

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The following description shows a case where the present invention is applied to a spatter detecting device for spot welding, and does not limit the present invention, its application, or its use.

The following description includes a description of a spatter detection method of spot welding.

(example 1)

Embodiment 1 of the present invention is described below with reference to fig. 1 to 12.

As shown in fig. 1, the splash detection device 1 for resistance welding of the present embodiment includes the following components as main components: a plurality of spot welding devices (resistance welding devices) 2 provided along the production line; a first server 3 for inputting data from the plurality of spot welding apparatuses 2; a second server 4 for inputting data from the first server 3; and a plurality of display units 5 capable of displaying the determination result determined by the second server 4.

First, the spot welding apparatus 2 will be explained. The plurality of spot welding apparatuses 2 are all configured to the same specification, and all of the spot welding apparatuses 2 are electrically connected in parallel to the first server 3. As shown in fig. 2, the spot welding apparatus 2 includes a spot welding robot (hereinafter, simply referred to as a robot) 11, a welding control apparatus 12, a robot controller 13, an electric spot welding gun (hereinafter, simply referred to as a welding gun) 14, and the like.

The robot 11 is an articulated robot having 6 joint axes J1 to J6. The robot 11 includes a base 21, a turning part 22, a lower arm 23, an upper arm 24, a first distal end 25, a second distal end 26, a distal end flange 27, and the like, which are configured to be rotatable with each other. The robot 11 is provided with a robot motor M1 (see fig. 1) capable of operating each member about each joint axis J1 to J6. These robot motors M1 are each constituted by a servo motor and are controlled by the robot controller 13.

As shown in fig. 1, encoders E1 are mounted to the robot motors M1,

the rotation amount and the rotation angle of each robot motor M1 are output to the robot controller 13. A welding gun 14 is attached to a tip of the robot arm, so-called tip flange 27, and the robot controller 13 controls the robot motor M1 to control the position, angle, orientation, and the like of the welding gun 14.

As shown in fig. 2 and 3, the welding gun 14 is a C-type spot welding gun, and includes a housing 31, a gun arm 32, an upper electrode 33 corresponding to a movable electrode, a lower electrode 34 corresponding to a fixed electrode, a gun motor M2, a ball screw mechanism 35, an encoder E2, a reducer 36, and the like. The gun motor M2, which is a servo motor, is controlled by the robot controller 13, and the rotation amount and the rotation angle are output to the robot controller 13 by the encoder E2. The ball screw mechanism 35 includes a screw shaft and a nut, and converts the rotational motion of the gun motor M2, which has been passed through the speed reducer 36, into a linear motion of the upper electrode 33. The spot welding gun is not limited to the C-type spot welding gun, and may be an X-type spot welding gun or an O-type spot welding gun.

As shown in fig. 1, the robot controller 13 includes: a main control unit 41 that collectively controls each component device of the robot controller; an operation control unit 42 that controls the operations of the robot 11 and the welding gun 14; an external interface unit 43 for receiving and transmitting signals to and from a welding control device or the like that controls the value of welding current flowing between the electrodes 33 and 34; and a storage unit 44 configured by a memory or the like. The main control unit 41 calls a teaching program registered in advance, and collectively controls each component device of the robot controller.

The operation controller 42 controls each of the robot motor M1 and the gun motor M2 based on the detection values of the encoder E1 and the encoder E2 so that the welding gun 14 moves to the welding portion (welding portion) of the workpiece W formed by stacking a plurality of metal plate materials. During welding, the driving current of the gun motor M2 is controlled so that the pressure applied to the workpiece W by the electrodes 33 and 34 reaches a predetermined pressure. Specifically, in order to set the pressure of the upper electrode 33 against the workpiece W to a predetermined pressure, a map in which a correspondence relationship is established between a pressurization command value corresponding to each welding specification (welding site, welding condition, etc.) and a current (torque) command value corresponding to the pressurization command values is set in advance by an experiment or the like, and control is performed based on a current command value corresponding to a pressurization command value of a welding site as a work target.

The external interface unit 43 is connected to the welding control device 12, and performs reception and transmission of signals such as a welding condition number, a welding command, and welding completion. Based on the welding condition number, the welding command, and the like received from the robot controller 13, the welding control device 12 applies a welding current between the electrodes 33, 34 in a state where the welded portion of the workpiece W is sandwiched between the upper electrode 33 and the lower electrode 34 at a predetermined pressure, performs spot welding, and transmits "welding completed" to the robot controller upon completion of the application of the welding current.

The storage unit 44 stores an inter-electrode distance, which is a distance between the electrodes 33 and 34 from a start time of a pressing operation for pressing the upper electrode 33 against the welded portion of the workpiece W to a time when the welding process of the welded portion is completed, at predetermined time intervals (for example, 100msec intervals). Specifically, the inter-electrode distance from the start time of the pressing operation to the end time of the welding process based on the detection value detected by the encoder E2 via the operation control unit 42 is stored.

Here, the operation control unit 42 corresponds to an inter-electrode distance detection means of the electrodes 33 and 34.

Next, the first server 3 is explained.

All the inter-electrode distances for each welding process (welded part) are inputted from the storage unit 44 of the spot welding apparatus 2 to the first server 3. For the purpose of efficiency of information processing, a collection device (for example, a collection PC (personal computer) or the like) that collects the inter-electrode distances of all the welding processes and converts the inter-electrode distances into data for accumulation may be provided between the plurality of spot welding apparatuses 2 and the first server 3.

Next, the second server 4 is explained.

The second server 4 extracts the inter-electrode distance of the welding process selected according to a predetermined selection condition (for example, production day) from the inter-electrode distances of all the welding processes accumulated in the first server 3, calculates the time change rate of the extracted inter-electrode distance of the welding process, determines whether spatter is generated, and accumulates the results. When the time rate of change of the inter-electrode distance can be acquired from the robot controller, the time rate of change can be collected and accumulated.

As shown in fig. 1, the second server 4 includes an arithmetic section 51 (change rate detection means) as welding process grasping means, a determination circuit section 52 (determination means), a processing result accumulation section 53, a display circuit section 54, and the like.

The calculation unit 51 extracts the inter-electrode distance currently being subjected to the welding process from the inter-electrode distance of the welding process input from the first server 3, and calculates a change rate of the inter-electrode distance, that is, a so-called moving speed of the upper electrode 33 toward the lower electrode 34, based on the extracted change rate, to grasp the welding process.

The processing result accumulation unit 53 stores the operation result of the operation unit 51, the determination result of the determination circuit unit 52, and the like, and the display circuit unit 54 converts the data such as the processing result accumulated in the processing result accumulation unit 53 into display data for display on the display unit 5.

The determination circuit unit 52 determines whether or not the spatter phenomenon is generated, using the change rate of the inter-electrode distance during the welding process, which is the calculation result of the calculation unit 51, and a predetermined determination threshold.

Here, the movement locus of the upper electrode 33 in the case where the splash phenomenon does not occur will be described.

As shown in fig. 4, in spot welding, at time a1, electrodes 33 and 34 start a pressing operation for pressing workpiece W. After the upper electrode 33 is rapidly lowered, the upper electrode is maintained at a position where a predetermined pressure acts on the welded portion after a rise (pressure overshoot) due to a control delay (time b 1). When the energization is started in a state where the predetermined pressure is applied to the welded portion (time c1), the welded portion expands and the upper electrode 33 rises as the temperature of the welded portion rises (time d 1). Thereafter, the position of the upper electrode 33 is stabilized (time e1), and welding is completed after the welded portion is gently lowered by the pinching operation after the nugget is formed (time f 1).

In fig. 4, the position (inter-electrode distance) of the upper electrode 33 is shown by a solid line, and the rate of change (velocity) of the position of the upper electrode 33 is shown by a broken line.

The splash phenomenon is one such phenomenon: the current density at the welded portion increases, so that the temperature at the welded portion excessively increases, and the melt at the welded portion splashes to the outside.

As shown in fig. 5, when the splash phenomenon occurs, the movement locus of the upper electrode 33 at the time a2 to the time e2 is substantially the same as the movement locus at the time a1 to the time e1 when the splash phenomenon does not occur.

However, since the molten material of the welded portion instantly splashes outward when the splash phenomenon occurs and the position of the upper electrode 33 rapidly lowers, when the downward movement is set to positive, the rate of change in position of the upper electrode 33 at time f2 in the main welding process is 0.916(mm/sec), which is significantly higher than the rate of change in position of the upper electrode 33 at time f1 of 0.153(mm/sec) when the splash phenomenon does not occur.

By judging the change rate of the distance between the electrodes, the splash phenomenon can be mechanically detected without observing the splash phenomenon by visual observation, so that the inventor of the application obtains the following conclusion through research: when the movement toward the lower electrode 34 is positive, 0.3mm/sec is suitable as a determination threshold for occurrence of the splash phenomenon.

Therefore, a verification experiment was performed for the above determination threshold.

Hereinafter, each verification experiment will be described based on fig. 6 to 10. In the drawings, A1a to A4 indicate the occurrence of splash.

FIG. 6 is a graph showing the position and the rate of change of the upper electrode 33 when spatter occurs in the double-layer thick-plate welding of the workpiece W having the welding plate thicknesses of 1.20mm and 0.60 mm.

The rate of change in the position of the upper electrode 33 of A1a when sputtering occurred was 3.66 (mm/sec).

The rate of change in the position of the upper electrode 33 of A1b when sputtering occurred was 0.92 (mm/sec).

FIG. 7 is a graph showing the position and the rate of change of the upper electrode 33 when spattering occurs in the double-layer thin-plate welding of a workpiece W having a weld plate thickness of 0.60mm and 0.65 mm.

The rate of change in the position of the upper electrode 33 of A2 when sputtering occurred was 7.78 (mm/sec).

FIG. 8 is a graph showing the position and the rate of change of the upper electrode 33 when spatter occurs in the welding of a three-layer thick plate of a workpiece W having a weld plate thickness of 1.20mm, 1.40mm and 1.60 mm.

The rate of change in the position of the upper electrode 33 of A3 when sputtering occurred was 4.73 (mm/sec).

FIG. 9 is a graph showing the position and the rate of change of the upper electrode 33 when spatter is generated in the three-layer thin plate welding of the workpiece W having a weld plate thickness of 0.65mm, 0.60mm and 0.60 mm.

The rate of change in the position of the upper electrode 33 of A4 when sputtering occurred was 9.61 (mm/sec).

FIG. 10 is a graph showing the position and the rate of change of the upper electrode 33 when spatter occurs in the welding of a three-layer thick plate of a workpiece W having a weld plate thickness of 1.00mm, 1.20mm and 1.00 mm.

The rate of change in the position of the upper electrode 33 of A5 when sputtering occurred was 0.31 (mm/sec).

According to the above verification experiment, the following results are obtained: when the rate of change in the position of the upper electrode 33 after the start of energization is equal to or greater than the determination threshold value 0.3, the splash phenomenon occurs regardless of the thickness of the plate material of the workpiece W or the number of plate materials, and when the rate of change in the position of the upper electrode 33 is less than the determination threshold value 0.3, the splash phenomenon does not occur.

The determination circuit unit 52 determines whether the change rate of the inter-electrode distance during the welding process, which is the calculation result of the calculation unit 51, is within a range of

Welding treatment (welding treatment in which spatter occurs) in which the determination threshold value after the start of energization is 0.3 or more, and

the welding process (welding process in which the spatter phenomenon is not generated) smaller than the determination threshold value of 0.3 is determined.

The greater the rate of change in the inter-electrode distance, the greater the spattering phenomenon can be determined.

The plurality of display units 5 are formed of a conventional PC or the like, and are configured to be able to input selection conditions (for example, production date or the like) for selecting the welding process extracted from the first server 3 to the second server 4. The display unit 5 is also configured to be able to display the processing result of the second server 4. Specifically, when a worker designates a specific production line, date and time, and welding process conditions (robot, welding condition number, etc.), a graph showing the distance between electrodes and the change rate during the welding process is displayed in a manner such that the occurrence of the spatter and the magnitude of the spatter can be recognized (see fig. 4 to 10).

Based on these pieces of information, the welding conditions of the next and subsequent welding can be corrected. For example, when spatter occurs in the first half of the welding process, it is conceivable to take a measure to reduce the welding current value, and when spatter occurs in the second half of the welding process, it is conceivable to take a measure to shorten the energization time, and the like, and thus an excessive temperature rise can be avoided. In addition, information unique to the produced workpiece is also given in the processing result. This allows the operator to confirm the workpiece W on which the spatter has occurred, and to perform confirmation of the bonding strength, appearance inspection, trimming, and the like.

Next, the welding process sequence will be described based on the flowchart of fig. 11.

Si (i ═ 1, 2 …) represents a procedure for performing each process. The welding position, the pressurization command value, the welding condition number, and the like are registered in the robot controller as teaching programs in advance according to the type of the workpiece and the work. Welding conditions such as welding current and energization time are registered as a condition map in the welding control device for each welding condition number.

As shown in fig. 11, at S1, the welding gun 14 is moved to the welding position of the workpiece W by driving the robot 11. In S2, the pressing operation for clamping the welded portion of the workpiece W by the electrodes 33, 34 is started.

The upper electrode 33 is pressurized toward the lower electrode 34 until the driving current (torque) of the gun motor M2 reaches a pressurization command value, and after the welding portion is clamped at a predetermined pressure (S3), a welding condition number and a welding command are transmitted to the welding control apparatus (S4). The welding control device reads the welding conditions from the condition map based on the received signal, and supplies the welding current to the electrodes 33, 34 (S5).

After the energization (including cooling) is completed, the welding control device transmits a welding completion signal to the robot controller (S6).

The robot controller receives the welding completion signal, ends the pressurizing operation, and releases the welding gun (S7).

Thereafter, the processing of S1 to S7 is repeated for the other welding sites registered in the teaching program, and the teaching program is executed until the teaching program is ended (S8 to S9).

Next, the spatter detection processing sequence will be described based on the flowchart of fig. 12.

The spatter detection process is performed by a start operation by an operator or an automatic start by a PC or the like, and is independent from the welding process shown in fig. 11.

As shown in fig. 12, in S11, data such as the inter-electrode distance detected by the robot controller, which is selected based on the selection condition (e.g., production date), is read from the first server 3.

Next, in S12, the time rate of change of the inter-electrode distance with time is calculated, the inter-electrode distance in the welding process is extracted, the point at which the upper electrode 33 descends from the raised position (hereinafter simply referred to as a descending point) is extracted, and the maximum rate of change of the inter-electrode distance at the descending point is calculated.

The processing result of S12 is stored and used for judgment of occurrence of splash and display of the processing result.

In S13, it is determined whether or not the change rate calculated in S12 is equal to or greater than a determination threshold (0.3 mm/sec). As a result of the determination at S13, when the change rate is equal to or greater than the determination threshold, it is determined that splash has occurred (S14), and the process proceeds to S16. As a result of the determination at S13, when the change rate is smaller than the determination threshold, it is determined that no splash has occurred (S15), and the process proceeds to S16.

In S16, the number of welding executions and the number of spatters generated for each welding process condition (each robot, each welding condition) corresponding to the selected condition are stored, and the process proceeds to S17. In S17, it is determined whether or not there is no undetermined data. If the result of the determination at S17 is that there is no undetermined data, the process ends; if there is any undetermined data, the process returns to S12 to continue the determination.

Next, the operation and effect of the spatter detecting device in the spot welding will be described.

According to the splash detection apparatus 1 of embodiment 1, since the operation control unit 42 that detects the inter-electrode distance between the pair of electrodes 33, 34 at predetermined time intervals is provided, the inter-electrode distance can be detected in time series. Since the calculation unit 51 is provided for extracting the inter-electrode distance during the welding process from the detected inter-electrode distance and calculating the maximum rate of change in the inter-electrode distance at the descending point based on the extracted inter-electrode distance, it is possible to detect a change in the state of the welded portion using the inter-electrode distance as a parameter.

Further, since the determination circuit unit 52 is provided to determine that spatter is generated when the maximum rate of change calculated by the calculation unit 51 is equal to or greater than the predetermined threshold value, the state in which the welded portion is crushed by the clamping operation of the electrodes 33 and 34 can be distinguished from the state in which spatter occurs by using the rate of change in the inter-electrode distance, and the occurrence of spatter can be quantitatively detected as a physical quantity.

Since the determination circuit unit 52 determines the maximum rate of change of the inter-electrode distance at the lowering point, it is only necessary to determine the rate of change of the inter-electrode distance within a predetermined period, and the process can be simplified and the state change of the welded portion other than the occurrence of the spatter phenomenon can be eliminated.

Since the determination threshold of the determination circuit unit 52 is 0.3mm/sec, the occurrence of the splash phenomenon can be quantitatively detected without being restricted by the thickness of the metal plate material or the like.

Further, since it is determined that the splash phenomenon is more serious as the detected change rate is larger, the magnitude of the splash phenomenon can be detected together with the occurrence of the splash phenomenon.

Since the motion control unit 42 detects the inter-electrode distance between the pair of electrodes 33, 34 by using a mechanism for driving the robot 11 having the welding gun 14 including the pair of electrodes 33, 34 attached to the tip thereof and the welding gun 14, the use of the conventional encoder E2 can simplify the apparatus.

In addition, since this splash detection method includes the inter-electrode distance detection step S11 for detecting the inter-electrode distance between the pair of electrodes 33 and 34 at predetermined time intervals, the inter-electrode distance can be detected in time series. Since the change rate detection step S12 for detecting the temporal change rate of the detected inter-electrode distance is provided, the change in the state of the welded portion can be detected using the inter-electrode distance as a parameter.

Further, since the determination step S13 is provided to determine that spatter is generated when the change rate of the detected distance in the direction of approach of the pair of electrodes 33 and 34 that has been grasped to be in the welding process is equal to or greater than the predetermined threshold value, the state in which the welded portion is crushed by the pinching operation of the electrodes 33 and 34 can be distinguished from the state in which the spatter occurs by using the change rate of the inter-electrode distance, and the occurrence of the spatter can be quantitatively detected as a physical quantity.

Next, a modification obtained by partially modifying the above embodiment will be described.

In the above embodiment, the example of application to spot welding has been described, but at least resistance welding is sufficient, and for example, projection welding or the like may be applied.

In the above embodiment, the example in which two servers, i.e., the first server and the second server, are provided has been described, but a single server in which both servers are shared may be used depending on the capacity of the servers, or the servers may be subdivided into 3 or more servers.

Furthermore, those skilled in the art can implement the above embodiments in various modifications or combinations thereof without departing from the spirit of the present invention, and the present invention also includes the above modifications.

-description of symbols-

1 splash detection device

2 Spot welding device

33 upper electrode

34 lower electrode

42 operation control part

51 arithmetic unit

52 judging circuit part

E2 encoder