JP6971724B2 - One-sided spot welding equipment and one-sided spot welding method - Google Patents

Description

The present invention relates to a one-sided spot welding apparatus and a one-sided spot welding method.

Conventionally, direct spot welding is known in which a work composed of a plurality of laminated metal plates is sandwiched between a pair of electrodes at a welding point position, and a current is passed from one electrode to the other electrode to join the laminated metal plates. Has been done. Further, in the manufacturing process of a vehicle such as an automobile, when the work cannot be sandwiched between the electrodes from both sides, the weld electrode is pressed against the welding spot position and the ground electrode is pressed against the welding spot position, which is different from the facing position. One-sided spot welding is used, in which welding is performed by energizing between the electrodes of.

In one-sided spot welding, electricity is applied to only one side of the work at the welding point position with a pressure applied by the welding electrode. Therefore, compared to direct spot welding in which the work is sandwiched from both sides by the welding electrode, the work is placed at the welding point position. The contact surface between the metal plates constituting the above tends to be unstable. In particular, if there is a gap between the metal plates at the welding spot position during welding, a hole is opened in the welded portion, resulting in poor welding or spattering. When a welding defect occurs, the subsequent reworking work is required, which increases the man-hours and leads to a decrease in production efficiency.

On the other hand, if the pressure applied by the weld electrode is increased in one-sided spot welding in order to eliminate such a gap between the metal plates, the work may be deformed, the contact area between the plates may increase, and the calorific value may decrease. Will be difficult to form, which will affect the welding quality and assembly accuracy.

In one-sided spot welding, as a method of suppressing the formation of gaps between metal plates without increasing the pressing force of the weld electrode, Patent Document 1 describes a tubular pressure around the weld electrode that surrounds the weld electrode. A one-sided spot welder with a guide is described. In this one-sided spot welding device, before pressing the welding electrode, a pressing force is applied to the work around the welding spot position to eliminate the gap between the metal plates, and in this state, the welding electrode and the ground electrode are held together. It is in contact with the work and energized.

Japanese Unexamined Patent Publication No. 8-168886

However, even in a state where pressure is applied by the pressing guide, the gap may not be sufficiently eliminated due to dust being sandwiched between the metal plates and the like. In the conventional one-sided spot welding apparatus, welding is performed even in such a state, which leads to a decrease in quality and an increase in manufacturing cost due to the occurrence of reworking work.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a one-sided spot welding apparatus and a one-sided spot welding method capable of ensuring welding quality and reducing manufacturing costs in a mass production process. ..

In order to achieve the above object, the one-sided spot welding apparatus according to claim 1 is applied to the first metal plate with respect to a work having a first metal plate and a second metal plate superposed on the first metal plate. A welding electrode that abuts, an earth electrode that abuts on the second metal plate, and a pressing means that is arranged in the vicinity of the welding electrode and presses the first metal plate toward the second metal plate. In a one-sided spot welding apparatus that welds the first metal plate and the second metal plate by energizing between the welding electrode and the ground electrode, the first metal plate and the first metal plate at the welding position are provided. Based on the detection means for detecting the state of the gap between the two metal plates and the state of the gap detected by the detection means when a predetermined pressing force is applied to the work by the pressing means or the welding electrode. The detection means includes the first metal plate and the first metal plate based on the reaction force received from the work by the pressing means or the welding electrode. It is characterized in that the state of the gap between the two metal plates is detected.
Further, the one-sided spot welding apparatus according to claim 2 has a welding electrode that abuts on the first metal plate with respect to a work having a first metal plate and a second metal plate superposed on the first metal plate. The weld electrode and the welding electrode are provided with a ground electrode that abuts on the second metal plate and a pressing means that is arranged in the vicinity of the weld electrode and presses the first metal plate toward the second metal plate. In a one-sided spot welding device that energizes between the ground electrodes to weld the first metal plate and the second metal plate, the first metal plate and the second metal plate at the welding position are Spot welding is executed based on the detection means for detecting the state of the gap between the gaps and the state of the gap detected by the detection means when a predetermined pressing force is applied to the work by the pressing means or the welding electrode. A control unit for determining whether or not the welding means is provided, and the control unit includes the first metal plate and the first metal plate in a state where the pressing means and the welding electrode are separated from the work based on the detection result of the detection means. When it is determined that there is no gap between the pressing means and the second metal plate, spot welding is performed with the pressing means separated from the first metal plate, and the pressing means and the welding electrode are removed from the work. When there is a gap between the first metal plate and the second metal plate in a separated state, and when the pressing means or the welding electrode abuts and the predetermined pressing force is applied to the work. When it is determined that the state of the gap is within a predetermined range set in advance, spot welding is executed in a state where a pressing force is applied to the first metal plate by the pressing means, and the pressing means and the welding are performed. With the electrode separated from the work, there is a gap between the first metal plate and the second metal plate, and the pressing means or the welded electrode abuts on the work to apply the predetermined force. It is characterized in that when it is determined that the state of the gap is out of the specified range when pressure is applied, the execution of spot welding is prohibited .

According to this configuration, spot welding is performed based on the state of the gap between the first metal plate and the second metal plate detected by the detecting means when a predetermined pressing force is applied by the pressing means or the welding electrode. Since it is determined whether or not to execute, when there is a possibility that welding failure may occur due to the state of the gap between the first metal plate and the second metal plate under the pressure applied, the spot Welding can be prohibited. As a result, it is possible to reduce the reworking work due to welding defects and reduce the manufacturing cost.

Further, according to the configuration of claim 1, the reaction force received from the work by the pressing means or the welding electrode changes in the process of applying the pressing force by the pressing means or the welding electrode, so that the first metal plate and the first metal plate can be used. Since the state of the gap between the metal plates of 2 can be detected, the state of the gap can be detected using an existing relatively inexpensive device such as a load cell capable of measuring the reaction force, and the manufacturing cost can be reduced. It can be suppressed.

Further, according to the configuration of claim 2 , when there is no gap between the first metal plate and the second metal plate in a state where no pressing force is applied by the pressing means and the welding electrode, the pressing means. Spot welding can be performed while releasing the pressure applied by the metal plates to prevent the contact area between the metal plates from becoming too large. In addition, when there is a gap and the state of the gap is within the specified range by applying a predetermined pressing force, spot welding is performed with the pressing force applied by the pressing means to perform spot welding, thereby forming a metal plate. Good spot welding can be applied to workpieces with gaps between them. Further, when there is a gap and the state of the gap is out of the specified range even if a predetermined pressing force is applied, it is possible to prevent the occurrence of welding defects by prohibiting the execution of spot welding. ..

Further, in order to achieve the above object, the one-sided spot welding method according to claim 3 uses the welding electrode for a work having a first metal plate and a second metal plate superposed on the first metal plate. The first metal plate and the second metal plate are brought into contact with each other by contacting the ground electrode with the second metal plate and energizing between the welded electrode and the ground electrode. In the one-sided spot welding method for welding, a predetermined pressing force is applied to the work by a pressing means arranged in the vicinity of the welding electrode and pressing the first metal plate toward the second metal plate side or the welding electrode. Based on the gap detection step in which the detection means detects the state of the gap between the first metal plate and the second metal plate at the welding position, and the state of the gap detected by the detection means. Te, seen including a determination step of determining whether or not to perform the spot welding, the in the gap detection step, said detection means, said pressing means or the welding electrode on the basis of the reaction force received from the workpiece It is characterized in that the state of the gap between the first metal plate and the second metal plate is detected.
Further, in the one-sided spot welding method according to claim 4, the welding electrode is brought into contact with the first metal plate with respect to the work having the first metal plate and the second metal plate superposed on the first metal plate. In the one-sided spot welding method in which the ground electrode is brought into contact with the second metal plate and the welding electrode and the ground electrode are energized to weld the first metal plate and the second metal plate. A predetermined pressing force is applied to the work by a pressing means arranged in the vicinity of the welding electrode and pressing the first metal plate toward the second metal plate side or the welding electrode, and welding is performed by the detecting means. Whether to perform spot welding based on the gap detection step of detecting the state of the gap between the first metal plate and the second metal plate at the position and the state of the gap detected by the detection means. In the welding step, the pressing means and the welding electrode are separated from the work. When it is determined that there is no gap between the first metal plate and the second metal plate in this state, spot welding is executed with the pressing means separated from the first metal plate. There is a gap between the first metal plate and the second metal plate in a state where the pressing means and the welding electrode are separated from the work, and the pressing means or the welding electrode is in contact with the pressing means or the welding electrode. When the state of the gap is determined to be within a preset predetermined range when the predetermined pressing force is applied to the work, the pressing means applies the pressing force to the first metal plate. In a state where the pressing means and the welding electrode are separated from the work, there is a gap between the first metal plate and the second metal plate, and further, the pressing means or the above. It is characterized in that when it is determined that the state of the gap is out of the specified range when the welding electrode abuts and the predetermined pressing force is applied to the work, the execution of spot welding is prohibited.

According to this configuration, whether or not spot welding is performed based on the state of the gap between the first metal plate and the second metal plate when a predetermined pressing force is applied by the pressing means or the welding electrode. Therefore, when there is a possibility that welding defects may occur due to the state of the gap between the first metal plate and the second metal plate when the pressing force is applied, the execution of spot welding is prohibited. be able to. As a result, it is possible to reduce the reworking work due to welding defects and reduce the manufacturing cost.

According to the one-sided spot welding apparatus and the one-sided spot welding method according to the present invention, welding quality can be ensured and the manufacturing cost can be reduced in the mass production process.

The block diagram of the one-sided spot welding apparatus which is an embodiment of this invention. The schematic diagram explaining the outline of the 1st pattern of one-sided spot welding. The schematic diagram explaining the outline of the 2nd pattern of one-sided spot welding. The schematic diagram explaining the outline of the 4th pattern of one-sided spot welding. It is a graph which shows the time change of the reaction force which a pressing member receives from a work, (a) is a graph explaining a 1st pattern, (b) is a graph explaining a 2nd pattern and a 3rd pattern, (c). ) Is a graph explaining the fourth pattern. Flow chart showing the operation of the control unit A table showing the change in nugget diameter when the current value of spot welding is changed. An enlarged perspective view of a main part showing a modified example of a one-sided spot welder. An enlarged perspective view of a main part showing another modification of a one-sided spot welder.

FIG. 1 is a side view showing a one-sided spot welding apparatus 10 according to an embodiment of the present invention. The one-side spot welding device 10 is used, for example, in a manufacturing process of a vehicle such as an automobile (for example, joining an outer panel and a reinforcement), and is a work (covered) composed of a plurality of metal plates 51 and 52 having at least a part overlapped with each other. The welding electrode 13 and the ground electrode 15 are brought into contact with the welding member) 50, and the metal plates 51 and 52 are joined by energizing between them.

In the present embodiment, as an example of the work 50, two metal plates 51 and 52 are laminated, but the number of metal plates is not limited to two and may be three or more. In the following description, when the work 50 is set on the one-side spot welding device 10, the metal plate with which the welding electrode 13 abuts is referred to as the first metal plate 51, and the metal plate with which the earth electrode 15 abuts is referred to as the second metal plate. It is a metal plate. In the present embodiment, the plate thickness of the first metal plate 51 is thinner than that of the second metal plate 52. The first metal plate 51 and the second metal plate 52 may each be composed of a plurality of welded metal plates.

The one-side spot welding device 10 has a support bracket 3 attached to the robot arm 2 of the welding robot, and has a first pressurizing mechanism 11 and a second pressurizing mechanism 12 fixed to the support bracket 3, and a first pressurizing mechanism 12. The welding electrode 13 connected to the pressurizing mechanism 11, the pressing member (pressing means) 14 connected to the second pressurizing mechanism 12, the ground electrode 15, the welding transformer 16, the detecting means 17, and the control unit 18. And an alarm device 19.

The first pressurizing mechanism 11 includes a first actuator 21 and a rod 22 connected to the first actuator 21 and extending in the vertical direction. The second pressurizing mechanism 12 includes a second actuator 25 and a rod 26 that is connected to the second actuator 25 and extends in the vertical direction.

The first actuator 21 and the second actuator 25 are fixed to the lower surface of the base portion 3a located at the lower part of the support bracket 3, respectively, and may be configured by, for example, an air cylinder, a servo cylinder, a servo motor, or the like. can. The rods 22 and 26 extend in parallel with each other, and move back and forth in the vertical direction in the axial direction by the driving forces of the first actuator 21 and the second actuator 25, respectively.

A welding electrode 13 is provided at the tip of the rod 22 of the first pressurizing mechanism 11 via the shank 23. The welding electrode 13 moves upward and abuts on the surface of the first metal plate 51 of the work 50 by the operation of the first pressurizing mechanism 11 and moves downward, and the first metal plate 13 is brought into contact with the surface of the first metal plate 51 of the work 50. It moves between the pressure welding position and the pressure welding position that applies pressure to 51.

A pressing member 14 is provided at the tip of the rod 26 of the second pressurizing mechanism 12. The pressing member 14 has a flat plate-shaped base portion 31 whose upper surface is connected to the rod 26 and extends toward the welding electrode 13, and a pressing portion 32 protruding downward from the lower surface of the base portion 31. At least a part of the pressing member 14 is formed of an insulating material so that the pressure portions 32a and 32b and the detecting means 17 are insulated from each other. As shown in FIG. 1, an insulating member 34 may be interposed between the detection means 17 and the pressing member 14 in order to secure the insulating property of the pressing member 14. In this case, the pressurization may be performed. The material of the parts 32a and 32b can be selected from any material in consideration of the wear and heat resistance of the pressure parts 32a and 32b when the work is pressurized.

The pressurizing portion 32 is a portion that abuts on the first metal plate 51 of the work 50 and presses the first metal plate 51 toward the second metal plate 52. As shown, a pair of pressurizing portions 32a and 32b are arranged in the vicinity of the welding electrode 13 so as to be able to press the first metal plate 51 on both sides of the welding electrode 13 at a position near the welding electrode 13. Has been done.

The pressing member 14 moves upward and abuts on the surface of the first metal plate 51 of the work 50 by the operation of the second pressurizing mechanism 12, and moves downward to the first metal plate. It moves between the pressurizing position that applies the pressurizing force to 51.

The welding transformer 16 is a welding power source for passing an electric current between the welding electrode 13 and the ground electrode 15, and the welding electrode 13 is electrically connected to the output terminal of the welding transformer 16 via the shank 23 and the cable 41. The ground electrode 15 is electrically connected to the ground terminal of the welding transformer 16 via the cable 42. The ground electrode 15 in the illustrated example is attached to the tip of the rod 44 of the third pressurizing mechanism 43 provided with the actuator, and the rod 44 moves back and forth to move the rod 44 to the second position of the set work 50. It is configured to be in contact with and separated from the metal plate 52.

The detecting means 17 detects the state of the gap between the first metal plate 51 and the second metal plate 52 at the welding position. Here, the welding position means a welding spot position where the welding electrode 13 abuts and / or a position in the vicinity thereof. Further, the state of the gap means the presence or absence of the gap, the size of the gap, and information on the gap in which these can be estimated. In the present embodiment, a load cell is used as an example of the detection means 17, and the load cell is attached to the upper surface of the pressing member 14, and the pressing portions 32a and 32b of the pressing member 14 come into contact with the first metal plate 51. When a predetermined pressing force is applied, the reaction force received from the first metal plate 51 is detected, and based on this detection result, the presence / absence of a gap between the metal plates 51 and 52, the size of the gap, and the like are determined. Estimate and detect the state of the gap. In this embodiment, since the load cell is used as the detection means 17 to measure the reaction force from the work 50, the work shape is different, the first metal plate 51 and the second metal are notched or the like. Measurement is possible regardless of the case where the plates 52 are arranged so as to be offset. Further, the detection means 17 is not limited to the load cell, and when the work shape as described above is different, the first metal plate 51 and the second metal plate 52 are misaligned due to a notch or the like, for example, A dial gauge, a laser sensor, a camera, or the like may be appropriately installed to detect the presence or absence of a gap and the size of the gap.

The control unit 18 includes, for example, an information processing unit such as a CPU, a storage unit such as a RAM or ROM, an input / output interface, and the like, and includes a first pressurizing mechanism 11, a second pressurizing mechanism 12, a welding transformer 16, and the like. It is connected to the detection means 17 and the alarm device 19. The control unit 18 is based on a program stored in the storage unit (for example, the vertical position and pressing force of the welding electrode 13 and the pressing member 14 at each timing, the energization current of the welding electrode 13 at each timing, etc.). The pressure mechanism 11 and the second pressurizing mechanism 12 control the advancing / retreating movement of the welding electrode 13 and the pressing member 14, the pressing force on the work 50, and the current value of the welding current supplied to the welding electrode 13 by the welding transformer 16. Further, in the storage unit, one or more for determining the state of the gap between the first metal plate 51 and the second metal plate 52, which is used for determining whether or not spot welding is executed. A threshold value (predetermined value) is set. In the present embodiment, pre-setting the reaction force value N _th the welding process can be performed properly in the case of using the target work _(may be one having a predetermined range) as a threshold value.

Further, the control unit 18 spots based on the state of the gap between the first and second metal plates 51 and 52 detected by the detecting means 17 in a state where a predetermined pressing force is applied by the pressing member 14. It has a determination unit for determining whether or not to execute welding. In the present embodiment, the work 50 is set in the spot welding device 10 on one side, the welding electrode 13 is separated from the work 50, and the pressing member 14 is moved from the retracted position to the pressurized position at a predetermined speed to move the work. A predetermined pressing force is applied to 50, and the reaction force received by the pressing member 14 from the first metal plate 51 and the second metal plate 52 at this time is measured by the detecting means 17. The control unit 18 has, for example, the relationship between a predetermined pressing force by the pressing member 14 and the detected reaction force, and the reference reaction force waveform data and the detected reaction force waveform data stored in advance in the storage unit. The state of the gap between the first and second metal plates 51 and 52 is classified into the first to fourth patterns by comparison with the first and second metal plates 51 and 52.

Specifically, as shown in FIGS. 2A and 2B, in a state where the welding electrode 13 and the pressing member 14 are separated from the work 50 and in a state where a predetermined pressing force is applied to the work 50 by the pressing member 14. When it is determined that there is no gap between the first metal plate 51 and the second metal plate 52, the pattern is classified into the first pattern. In FIGS. 2 to 4, the alternate long and short dash line B indicates the vertical reference position of the work 50 in a state where the work 50 is set (a state in which no pressure is applied to the work 50). In the present embodiment, at the welding position of the work 50, an installation table for supporting the second metal plate 52 is not arranged on the lower surface side of the second metal plate 52, and the work 50 is applied with a pressing force from the reference position B. It sinks slightly downward.

Further, as shown in FIGS. 3A and 3B, the determination unit includes the first metal plate 51 and the second metal plate 52 with the welding electrode 13 and the pressing means 14 separated from the work 50. It determines that the gap d is present between the further, when the pressing means 14 is imparted with a predetermined pressure to the workpiece 50 in contact, the reaction force from the the workpiece 50 detected is equal to or smaller than the threshold n _th a predetermined condition If it is determined to be, it is classified into the second pattern. In the second pattern, the gap d is crushed to a predetermined range by applying the pressing force, and it is determined that the state of the gap d is within the preset specified range.

Further, as shown in FIGS. 4A and 4B, the determination unit determines that there is a gap d when the welding electrode 13 and the pressing means 14 are separated from the work 50, and the pressing means 14 is further applied. upon applying a predetermined pressure to the workpiece 50 in contact, the reaction force detected by the predetermined conditions exceeds the threshold value n _th, or be given a pressure when the gap d is not collapse until the predetermined range When it is determined, it is classified into a third or fourth pattern. In the third and fourth patterns, it is determined that the state of the gap d is out of the preset specified range.

FIG. 5 is a graph showing the time change of the reaction force that the pressing member 14 receives from the work 50. In the first pattern, as shown in FIG. 5A, when the pressing member 14 is moved from the retracted position to the pressing position, the pressing member 14 does not come into contact with the work 50 until the _{time threshold Tth.} The reaction force value (unit: N) is zero (or a value close to zero). Here, the threshold value _Th may have a predetermined range. At the time threshold T _th , the reaction force is linearly increased at a substantially constant inclination angle θ1 by receiving the reaction force by the first and second metal plates 51 and 52. Here, "linearly" means that, for example, _{a change point such as a point X 2} and a point X ₄ in FIG. 5 in which the tendency of the reaction force value changes significantly with respect to the time axis does not occur. Although linearly shown before and after in FIG. 5 (a) ~ (c) the convenience change point _{X 2, X 4, X 5} , X 7, X 8, necessarily linear in actual measurement value It is not always the case. A pressure of the pressing member 14 sinks workpiece 50 downwardly reaches a predetermined value (Fig. 5 points X ₂ in _(a)), receives a substantially constant reaction force equivalent to this.

In the second pattern, as shown in FIG. 5B, the pressing member 14 comes into contact with the first metal plate 51 until the _{time threshold Tth, and the reaction force of the first metal plate 51 is applied.} receive. Until the time threshold T _th , the reaction force increases linearly at a substantially constant tilt angle θ2. Here, the magnitude of the inclination angle is θ1> θ2. At the time threshold T _th , the inclination angle θ3 becomes large due to the reaction forces of the first and second metal plates 51 and 52. A pressure of the pressing member 14 reaches a predetermined value (point X ₅ in FIG. 5 _(b)), receives a substantially constant reaction force. In particular, in the second pattern, the change point X ₄ in which inclination angle is changed from θ2 to .theta.3, the reaction force value is less than a reaction force threshold n _th. Work 50 having such a reactive force data, preset pressure by the pressing member 14 (i.e., equal to the threshold value n _th pressure n _th) that is applied, the gap d is within a predetermined range (i.e., It is estimated that the gap d ≦ the threshold value _dth ), and it is determined that the state of the gap d is within the preset predetermined range.

On the other hand, if the reaction force value at the change point X ₄ exceeds the threshold value n _th (when in range of the third pattern of FIG. 5 (b)), the gap also by the pressing member 14 to impart pressure n _th d Is out of the predetermined range (that is, gap d> threshold value _dth ), or even if the gap d ≦ threshold value _dth , it is presumed that the contact area at the time of welding is insufficient. Such work 50 having a reaction force data, since the pressure required to the gap d within a predetermined range exceeds a pressure n _th, it is determined that outside the scope of the state of the clearance d is set in advance, It is classified into the third pattern.

In the fourth pattern, as shown in FIG. 5C, first, the pressing member 14 receives the reaction force of the first metal plate 51, and the reaction force is substantially constant at an inclination angle θ4 (θ4 <θ1). increases linearly, before the time reaches the threshold value _{T th} (change point _X 7), the inclination angle .theta.5 receives a reaction force of the first and second metal plates 51,52 (θ5> θ4) linearly in The reaction force increases. Pressure of the pressing member 14 and reaches a predetermined value (point X _8), receives a substantially constant reaction force. In the work 50 having such reaction force data, the gap d cannot be crushed even if a predetermined pressing force is applied due to the presence of foreign matter between the metal plates 51 and 52 (that is, the gap d> the threshold value _dth). ), And it is determined that the state of the gap d is out of the preset specified range.

In this way, from the reaction force waveform data, it is possible to detect the timing at which the first metal plate 51 abuts, the timing at which a change point at which the inclination angle θ and the inclination angle θ change occurs, the reaction force value at the change point, and the like. Then, the state of the gap d can be detected, and the work 50 can be classified into the first to fourth patterns. In the present embodiment, the third pattern and the fourth pattern are outside the preset specified range, but only the fourth pattern may be outside the preset specified range.

In the case of the first pattern, the control unit 18 controls to release the pressure applied by the pressing member 14 to perform spot welding as shown in FIG. 2 (c). Further, in the case of the second pattern, as shown in FIG. 3C, control is performed to execute spot welding in a state where a predetermined pressing force is applied by the pressing member 14. Further, in the case of the third and fourth patterns, control is performed to prohibit the execution of spot welding.

The alarm device 19 operates based on an instruction signal from the control unit 18 to generate a visual alarm (for example, lighting of a lamp) and / or an auditory alarm (for example, a buzzer sound).

The robot arm 2 of the one-side spot welding device 10 is operated by operation control of a robot control unit (not shown) and can move in a three-dimensional direction. As the robot arm 2 moves, the welding electrode 13 and the pressing member 14 are dimensioned. Move in the direction. The robot control unit stores data such as an operation program for sequentially spot welding the welding spot positions of the work 50.

Next, a welding method using the one-side spot welding apparatus 10 will be described.

First, as shown in FIG. 1, the robot arm 2 of the one-side spot welding device 10 is moved to a welding position, the work 50 is set on an installation table (not shown), and the ground electrode 14 is applied to the second metal plate 52. Contact (work installation process). In the work installation process, the welding electrode 13 and the pressing member 14 are in the retracted position.

Next, the second pressurizing mechanism 12 is operated to move the pressing member 14 from the retracted position to the pressurizing position. At this time, the detecting means 17 detects the reaction force that the pressing member 14 receives from the work 50, and based on this detection result, the control unit 18 has a gap between the first metal plate 51 and the second metal plate 52. The state of d is detected (gap detection step). In the present embodiment, the work 50 is classified into any of the first to fourth patterns based on the state of the gap before and after the pressing force is applied by the pressing member 14.

The control unit 18 determines whether or not to execute spot welding based on the waveform data (see FIG. 5) due to the reaction force of the gap detected by the detection means 17 (determination step), and spots based on the determination result. Perform or prohibit welding (welding process).

FIG. 6 is a flowchart showing an operation when the control unit 18 divides the work 50 into the first to fourth patterns and executes or prohibits spot welding in the above-mentioned gap detection step, determination step, and welding step. Is.

When the work 50 is set, the control unit 18 moves the pressing member 14 to the pressurizing position, applies a predetermined pressing force to the work 50 (step S1), and acquires the detection result from the detecting means 17 (step S1). Step S2). Based on the acquired detection result (that is, the reaction force received from the work 50), the determination unit of the control unit 18 is in a state before applying a pressing force to the work 50, and the first and second metal plates 51 at the welding position. It is determined whether or not there is a gap d between, and 52 (step S3).

In step S3, when it is determined that there is no gap d (that is, the gap d is substantially 0) based on the waveform data of the reaction force at the time of pressing by the detection means 17 (step S3: Yes), the work 50 is the first pattern. (See FIGS. 2 (a) and 2 (b)). When classified into the first pattern, as shown in FIGS. 2 (b) and 2 (c), the control unit 18 moves the pressing member 14 from the pressing position to the retracting position to release the pressing force (step). S4). After that, the welding electrode 13 is moved to the pressure welding position, electricity is applied between the welding electrode 13 and the ground electrode 15, and spot welding is performed (step S5).

When it is determined in step S3 that there is a gap d (that is, a value where the gap d is larger than substantially 0) (step S3: No), the determination unit of the control unit 18 determines the detection result acquired from the detection means 17. Based on this, it is determined whether or not the gap d can be crushed when a predetermined pressing force is applied by the pressing member 14 (step S6). Gap d is collapsible (i.e., out of the waveform data to FIG. 5 (c)) If (step S6: Yes), the change point _{X 4,} which occurs at time threshold _{T th,} the reaction force value n is the threshold value _{n th} received from the workpiece 50 It is determined whether or not it is as follows (step S7).

In step S7, when it is determined that the reaction force value n is equal to or less than the threshold value _{n th} (Step S7: Yes), dividing the workpiece 50 to the second pattern (FIG. 3 (a), reference (b)). When classified into the second pattern, as shown in FIG. 3C, the control unit 18 maintains the pressing member 14 in the pressurizing position and applies a predetermined pressing force to the work 50 while applying a predetermined pressing force to the welding electrode. 13 is moved to the pressure welding position, an electric current is applied between the welding electrode 13 and the ground electrode 15, and spot welding is performed (step S5).

In step S7, when it is determined that the reaction force value n exceeds the threshold value _{n th} (step S7: No), dividing the workpiece 50 to the third pattern. When classified into the third pattern, the control unit 18 controls to prohibit the execution of spot welding. In the present embodiment, the pressing member 14 is separated from the work 50, the welding electrode 13 and the pressing member 14 are set to the retracted positions, and the alarm device 19 is operated to generate an alarm (step S8).

If it is determined in step S6 that the gap d is not crushed (step S6: No), the work 50 is classified into a fourth pattern (see FIGS. 4A and 4B), and then to step S8. Control is performed to prohibit the execution of spot welding by shifting.

In the one-sided spot welding method described above, the ground electrode 15 may be brought into contact with the work 50 after the determination to perform spot welding is made. Further, the predetermined pressing force when detecting the reaction force and the predetermined pressing force applied by the pressing member 14 when performing spot welding in the second pattern may be the same value or different. It may be a value.

According to the one-sided spot welding method using the one-sided spot welding apparatus 10 described above, when there is a gap d between the first and second metal plates 51 and 52, a pressing force is applied by the pressing member 14 to apply a gap. Since spot welding can be performed by applying pressure to the welding electrode 13 with d crushed within a predetermined range, quality is stabilized by welding in consideration of the influence of gaps between plates generated in mass production. Can be planned. In addition, if the gap d is not crushed due to the presence of foreign matter while pressure is applied, there is a high probability that welding defects will occur. Can be reduced. Further, when the reaction force value n exceeds the threshold value n _th at step S7, the weld quality be imparted to pressure by the pressing member 14 by prohibiting the spot welding as possibly not stable, more reliable It is possible to suppress the occurrence of welding defects.

Further, when there is substantially no gap d in the state where the pressing force is not applied, the pressing force by the pressing member 14 is released and spot welding is performed, so that the first and second metal plates are placed at the welding position. Spot welding can be performed without increasing the contact area between 51 and 52. If the contact area is large, the starting point of heat generation disappears and it becomes difficult to form a nugget at the welding point position. However, by releasing the pressing member 14 to prevent an excessive contact area, a good spot welded portion can be obtained. can.

Further, by using or not using the pressing member 14 depending on the presence or absence of the gap d, it is possible to secure a wide current value range of the one-side spot welding apparatus 10 in the mass production process. FIG. 7 is a table showing changes in the nugget diameter when the current value of spot welding is changed, and the work 50 having no gap classified into the first pattern and the first metal plate 51 pressing force required to the second metal plate 52 are in contact (i.e., threshold n _th) was set to 60N, shown by comparing the workpiece 50 "with gap" which is divided into a second pattern It is a thing. 7 (a) shows the case where the pressing member 14 is not used, FIG. 7 (b) shows the case where a pressing force of 60 N is applied by the pressing member 14, and FIG. 7 (c) shows the case of (a). "No gap" and "with gap" in (b) are arranged side by side. It is preferable that the spot welding is in a state where the specified nugget diameter is satisfied and dust is not generated (that is, the range shown by the dots in FIG. 7 in which the specified nugget diameter is secured and dust is generated).

When the pressing member 14 of FIG. 7 (a) is not used, there is no appropriate current value range for ensuring welding quality for both the “no gap” and “with gap” workpieces 50, and FIG. 7 (b) When a pressing force of 60 N is applied, 8.5 to 9.5 kA is an appropriate current value range. When the use and non-use of the pressing member 14 are combined with the first pattern of "no gap" and the second pattern of "with gap" as in the present embodiment, FIG. 7C is shown. As shown in the above, an appropriate current value range is 8 to 9.5 kA, and a wide current value range can be secured to improve quality stability.

(Modification example)
FIG. 8 is an enlarged perspective view of a main part showing a modified example of the one-sided spot welding device 10. In FIGS. 8 and 9, the positions where the pressure portions 32a and 32b of the pressing member 14 abut on the first metal plate 51 are indicated by dots. The one-side spot welding device 10 may perform spot welding by arranging the welding electrode 13 and the ground electrode 15 on the upper surface side of the work 50, and the welding electrode 13 and the ground electrode 15 are attached to one gun. It may be a twin gun system that can be individually moved forward and backward (moving up and down).

FIG. 9 is an enlarged perspective view of a main part showing another modification of the one-sided spot welding apparatus 10. In this modification, the second metal plate 52 of the work 50 is composed of two metal plates 52a and 52b to which the second metal plate 52 is welded. The two metal plates 52a and 52b form a closed cross section, and the ground electrode 15 abuts on the metal plate 52a in contact with the lower surface of the first metal plate 51 from above as shown by a solid line. Instead of this arrangement, the ground electrode 15 may come into contact with the laminated portion of the metal plate 52a and the metal plate 52b or the metal plate 52b as shown by a virtual line.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention. For example, in the above-described embodiment, the pair of pressurizing portions 32a and 32b of the pressing member 14 pressurize two points around the welding electrode 13, but the pressing member 14 presses a plurality of points in the vicinity of the welding electrode 13. Alternatively, it may be configured to pressurize at least one point, and the pressurizing portion of the pressing member 14 may be formed in a tubular shape to pressurize the entire circumference of the weld electrode 13.

Further, the present invention is not limited to the embodiment in which the detection means 17 is provided on the pressing member 14 side, for example, the detection means 17 is provided on the welding electrode 13 side, a predetermined pressing force is applied by the welding electrode 13, and welding is performed. The state of the gap may be detected from the reaction force received by the electrode 13.

10 One-sided spot welding device 11 1st pressurizing mechanism 12 2nd pressurizing mechanism 13 Welding electrode 14 Pressing member 15 Earth electrode 16 Welding transformer 17 Detection means 18 Control unit 19 Alarm device

Claims (4)

For a work having a first metal plate and a second metal plate superposed on the first metal plate, a welding electrode that abuts on the first metal plate, an earth electrode that abuts on the second metal plate, and the above. It is provided with a pressing means arranged in the vicinity of the welding electrode and pressing the first metal plate toward the second metal plate, and the first metal is energized between the welding electrode and the ground electrode. In a one-sided spot welding device for welding a plate and the second metal plate,
A detection means for detecting the state of the gap between the first metal plate and the second metal plate at the welding position, and
A control unit for determining whether or not spot welding is performed based on the state of the gap detected by the detecting means when a predetermined pressing force is applied to the work by the pressing means or the welding electrode is provided. ,
The detecting means is characterized in that the state of the gap between the first metal plate and the second metal plate is detected based on the reaction force that the pressing means or the welding electrode receives from the work. One-sided spot welder. For a work having a first metal plate and a second metal plate superposed on the first metal plate, a welding electrode that abuts on the first metal plate, an earth electrode that abuts on the second metal plate, and the above. It is provided with a pressing means arranged in the vicinity of the welding electrode and pressing the first metal plate toward the second metal plate, and the first metal is energized between the welding electrode and the ground electrode. In a one-sided spot welding device for welding a plate and the second metal plate,
A detection means for detecting the state of the gap between the first metal plate and the second metal plate at the welding position, and
A control unit for determining whether or not spot welding is performed based on the state of the gap detected by the detecting means when a predetermined pressing force is applied to the work by the pressing means or the welding electrode is provided. ,
The control unit is based on the detection result of the detection means.
When it is determined that there is no gap between the first metal plate and the second metal plate in a state where the pressing means and the welding electrode are separated from the work, the pressing means is used as the first metal. Perform spot welding away from the plate,
There is a gap between the first metal plate and the second metal plate in a state where the pressing means and the welding electrode are separated from the work, and further, the pressing means or the welding electrode comes into contact with the pressing means or the welding electrode. When it is determined that the state of the gap is within the predetermined range when the predetermined pressing force is applied to the work, the spot is in a state where the pressing force is applied to the first metal plate by the pressing means. Perform welding,
With the pressing means and the welding electrode separated from the work, there is a gap between the first metal plate and the second metal plate, and the pressing means or the welding electrode comes into contact with the pressing means or the welding electrode. A one-sided spot welding apparatus comprising prohibiting execution of spot welding when it is determined that the state of the gap is out of the specified range when the predetermined pressing force is applied to the work. With respect to the work having the first metal plate and the second metal plate superposed on the first metal plate, the weld electrode is brought into contact with the first metal plate and the ground electrode is brought into contact with the second metal plate. In the one-sided spot welding method in which the first metal plate and the second metal plate are welded by energizing between the welding electrode and the ground electrode.
A predetermined pressing force is applied to the work by a pressing means arranged in the vicinity of the welding electrode and pressing the first metal plate toward the second metal plate side or the welding electrode, and welding is performed by the detecting means. A gap detection step for detecting the state of the gap between the first metal plate and the second metal plate at the position, and a gap detection step.
Based on the state of the gap detected by said detecting means, seen including a determination step of determining whether to execute a spot welding, a,
In the gap detecting step, the detecting means detects the state of the gap between the first metal plate and the second metal plate based on the reaction force received by the pressing means or the welding electrode from the work. One- sided spot welding method characterized by With respect to the work having the first metal plate and the second metal plate superposed on the first metal plate, the weld electrode is brought into contact with the first metal plate and the ground electrode is brought into contact with the second metal plate. In the one-sided spot welding method in which the first metal plate and the second metal plate are welded by energizing between the welding electrode and the ground electrode.
A predetermined pressing force is applied to the work by a pressing means arranged in the vicinity of the welding electrode and pressing the first metal plate toward the second metal plate side or the welding electrode, and welding is performed by the detecting means. A gap detection step for detecting the state of the gap between the first metal plate and the second metal plate at the position, and a gap detection step.
A determination step for determining whether or not spot welding is to be performed based on the state of the gap detected by the detection means, and
A welding step in which spot welding is executed or prohibited based on the determination result of the determination step is included.
In the welding process,
When it is determined that there is no gap between the first metal plate and the second metal plate while the pressing means and the welding electrode are separated from the work, the pressing means is used as the first metal plate. Perform spot welding away from the metal plate and
There is a gap between the first metal plate and the second metal plate in a state where the pressing means and the welding electrode are separated from the work, and further, the pressing means or the welding electrode comes into contact with the pressing means or the welding electrode. When it is determined that the state of the gap is within the predetermined range when the predetermined pressing force is applied to the work, the pressing means applies the pressing force to the first metal plate. Perform spot welding,
With the pressing means and the welding electrode separated from the work, there is a gap between the first metal plate and the second metal plate, and the pressing means or the welding electrode comes into contact with the pressing means or the welding electrode. A one-sided spot welding method comprising prohibiting execution of spot welding when it is determined that the state of the gap is out of the specified range when the predetermined pressing force is applied to the work.

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