JP2013071165A - Method and device for welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding method that sets the optimal welding current corresponding to a gap between plate materials which configure a workpiece by easily calculating the gap without increasing working hours.SOLUTION: The welding method is to weld a workpiece W formed by joining a plurality of plate materials W1 and W2 on top of each other by flowing electric current under the condition of the workpiece W being held by a movable electrode 21 and a static electrode 22. This welding method includes: a process to measure the pressurization start-up time (t-t) from the start of pressurizing the workpiece W to the time of reaching a predetermined pressurization force; a process to calculate the gap amount between the joined plate materials W1 and W2 before the start of pressurization based on the measured pressurization start-up time; and a process to select setting of the welding current flowed to the pressurization part of the workpiece W based on the calculated gap amount.

Description

  The present invention relates to a welding method and an apparatus therefor. Specifically, the present invention relates to a welding method and apparatus for selecting a setting of a welding current based on a gap amount between stacked plate members.

  Conventionally, spot welding is used for welding a workpiece in which a plurality of plate materials are overlapped. In this spot welding, a work is sandwiched between a pair of electrode tips and pressurized, and electricity is applied between the electrodes in this state. Then, the work material is melted by Joule heat generated by energization, and a nugget that is a melt of the work material is generated inside the work between the electrodes. Then, by stopping energization while maintaining the pressurized state, the nugget is cooled and solidified, and the workpiece is welded.

  By the way, when spot-welding a workpiece in which a plurality of plate materials are overlapped, a gap is generated between the plate materials due to factors such as the pressing state of each plate material. In addition, the gap varies between the workpieces. In such a state, when the workpiece is pressurized under certain conditions, the contact conditions (pressing force, contact diameter between the plate materials) vary, so even if the same current is passed through the workpiece between the electrodes, The growth state cannot be kept constant.

  Therefore, in order to keep the growth state of the nugget constant, it is necessary to appropriately set welding conditions such as a welding current flowing between the electrodes. For this purpose, a technique for measuring the gap between the plate members is known (for example, see Patent Document 1).

JP 2009-85856 A

  However, in the technique of Patent Document 1, there are many parameters to be measured, and there is a problem that processing for measuring a gap between each plate material constituting the workpiece becomes complicated.

  The present invention has been made in view of the above, and an object of the present invention is to easily calculate the gap between the plate members constituting the workpiece, thereby setting an optimum welding current according to the gap without increasing the number of man-hours. It is in providing the welding method which performs.

In order to achieve the above object, the present invention provides a work (for example, a work W described later) in which a plurality of plate materials (for example, plate materials W1 and W2 described later) are laminated to a pair of electrodes (for example, a movable electrode 21 and a fixed electrode described later). 22) A welding method is provided in which a current is applied in a state of being sandwiched by step 22).
The welding method according to the present invention includes a step of measuring a pressurization rising time (for example, t ₂ -t ₁ described later) from the start of pressurization of the workpiece by the pair of electrodes until reaching a predetermined applied pressure (for example, t ₂ -t ₁ described later) A step of measuring a pressure rising time by a strain gauge 17 to be described later), and a step of calculating a gap amount before the start of pressurization between the laminated plate materials based on the measured pressure rising time (for example, A step of calculating a gap amount by a control device 100 described later) and a step of selecting a setting of a welding current to be passed through the pressurizing portion of the workpiece based on the calculated gap amount (for example, the control device 100 described later includes And a step of selecting the setting of the welding current).

According to the present invention, the pressurization rise time from the start of pressurization of the workpiece until the predetermined pressurization force is measured, and based on the measured pressurization rise time, the gap between the stacked plate materials before the start of pressurization Calculate the amount. Therefore, the gap amount between the plate materials can be easily calculated by measuring the pressure rising time.
Moreover, according to this invention, the setting of the welding current sent through the pressurization part of a workpiece | work is selected based on the calculated gap amount. Therefore, since the current value of the welding current is determined according to the gap amount, it is possible to appropriately set the welding conditions and keep the nugget growth state constant.
As described above, according to the present invention, the gap amount can be calculated during the welding operation for one cycle, and the setting of the welding current can be selected. Therefore, the optimum welding corresponding to the gap amount can be performed without increasing the number of man-hours. Work can be done.

Further, a welding device (for example, a spot welding device 1 described later) for welding a workpiece (for example, a workpiece W described later) in which a plurality of plate materials (for example, plate materials W1, W2 described later) are stacked is provided.
This welding apparatus is disposed opposite to each other, and a pair of electrodes (for example, a movable electrode 21 and a fixed electrode 22 to be described later) that are approached or separated by an advancing and retreating mechanism, and a current source that flows current between the pair of electrodes (for example, A current source (not shown), a pressure detection means (for example, a strain gauge 17 described later) for detecting a pressure when the work is sandwiched between the pair of electrodes and pressed, and the pressure detection A pressurization rise time measuring means (for example, strain gauge 17 described later) for measuring a pressurization rise time from when the means starts to detect the pressurization force of the workpiece until the predetermined pressurization pressure is detected; and the pressurization rise time Based on the pressurization rise time measured by the measurement unit, a gap amount calculation unit (for example, a control device 10 described later) that calculates the gap amount before the pressurization between the stacked plate materials is performed. ) And current setting selection means (for example, a control device 100 described later) for selecting setting of a welding current to be passed through the pressurizing portion of the workpiece based on the gap amount calculated by the gap amount calculation means. It is characterized by that.

  According to this invention, there exists an effect similar to invention of said welding method.

  ADVANTAGE OF THE INVENTION According to this invention, the welding method which sets the optimal welding current according to a gap can be provided, without increasing a man-hour by calculating easily the gap between each board | plate material which comprises a workpiece | work.

It is a side view which shows the structure of the spot welding apparatus which concerns on one Embodiment of this invention. It is a schematic diagram showing the state of the current density which flows into the workpiece | work which concerns on the said embodiment, and the shape of the nugget produced | generated. It is a schematic diagram showing the state of the current density which flows into the workpiece | work which concerns on the said embodiment, and the shape of the nugget produced | generated. It is a schematic diagram showing the state of the current density which flows into the workpiece | work which concerns on the said embodiment, and the shape of the nugget produced | generated. It is a graph showing the relationship between the welding current which concerns on the said embodiment, and a nugget diameter. It is a graph showing the relationship between the welding current which concerns on the said embodiment, and a nugget diameter. It is a graph showing the relationship between the welding current which concerns on the said embodiment, and a nugget diameter. It is a graph showing the relationship between the welding current which concerns on the said embodiment, and a nugget diameter. It is a graph showing the relationship between the gap amount which concerns on the said embodiment, and pressurization rise time. It is a figure showing the relationship between the welding current which concerns on the said embodiment, and the applied pressure to a workpiece | work.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing a configuration of a spot welding apparatus according to an embodiment of the present invention. The spot welding apparatus 1 according to the present embodiment is an electric spot welding apparatus attached to the tip of a robot arm 80.
The spot welding apparatus 1 welds the workpiece W by pressing a workpiece W obtained by superimposing a plurality of plate materials W1 and W2 between a plurality of electrodes, which will be described later, and energizing the electrodes in this state.

  The spot welding apparatus 1 includes a spot welding gun 10 supported by a support portion 90 provided at the tip of a robot arm 80 and a control device 100 that controls the spot welding gun 10.

  The support part 90 includes a support bracket 91. The support bracket 91 includes an upper plate 91a and a lower plate 91b parallel to the upper plate 91a. A guide bar 92 is bridged between the upper plate 91a and the lower plate 91b.

  A support plate 93 slidable in the axial direction is attached to the guide bar 92. The support plate 93 extends in parallel to the upper plate 91a and the lower plate 91b from the robot arm 80 side, and supports the spot welding gun 10 on the tip side. A casing-like support body 94 is provided on the upper surface on the base end side of the support plate 93. A first coil spring 95 wound around the guide bar 92 is interposed between the upper plate 91a and the support 94. Similarly, a second coil spring 96 wound around the guide bar 92 is interposed between the lower plate 91 b and the support plate 93.

The spot welding gun 10 can be moved up and down relative to the support portion 90 by being supported by the support plate 93. The spot welding gun 10 includes a welding gun main body 11, an electrode portion 15 provided at the tip of the welding gun main body 11, and a current source (not shown).
The welding gun body 11 includes a servo motor 16 provided on the upper portion thereof, and a feed screw mechanism (not shown) connected to the servo motor 16.
The electrode unit 15 includes a movable electrode 21 and a fixed electrode 22.

The movable electrode 21 protrudes downward from the tip of the welding gun body 11 and is supported by the tip of the rod 12 connected to the feed screw mechanism. The movable electrode 21 can be moved back and forth with respect to the fixed electrode 22 described later by moving the rod 12 up and down (moving in the A2 direction or A1 direction in FIG. 1) via the feed screw mechanism by the servo motor 16. .
The fixed electrode 22 is supported at the tip of a C-shaped yoke 13 that extends downward from a connecting portion 14 connected to the tip of the welding gun body 11.
The movable electrode 21 and the fixed electrode 22 are disposed to face each other with the workpiece W interposed therebetween.

  The C-shaped yoke 13 is attached with a strain gauge 17 for detecting the pressure applied to the work W by the movable electrode 21 and the fixed electrode 22. The strain gauge 17 measures the pressurization rising time from the start of detecting the applied pressure until the predetermined applied pressure is detected. The strain gauge 17 is electrically connected to the control device 100 via a cable (not shown).

The control device 100 includes a gap amount calculation unit, a current setting selection unit, and a welding current energization unit (all not shown). Further, the control device 100 controls the servo motor 16 and a current source (not shown). Further, the gap amount calculation unit of the control device 100 receives the pressurization rising time from the strain gauge 17, calculates the gap amount between the plate materials W1, W2, and the current setting selection unit is based on the calculated gap amount. The setting of the welding current is selected, and the welding current energization unit energizes the workpiece W with the welding current by controlling a current source (not shown).
Although details will be described later with reference to FIGS. 5 to 8, the control device 100 sets the welding current lower as the calculated gap amount increases.

Next, operation | movement of the spot welding apparatus 1 which concerns on this embodiment is demonstrated.
First, in a state where the movable electrode 21 is separated from the fixed electrode 22, the spot welding gun 10 is moved to the welding portion of the workpiece W by the operation of the robot arm 80 and the support portion 90.
At this time, the lower surface of the workpiece W comes into contact with the front end surface of the fixed electrode 22.

  Next, the servo motor 16 is controlled by the control device 100, and the movable electrode 21 is advanced with respect to the workpiece W by the action of the feed screw mechanism. Then, the tip surface of the movable electrode 21 comes into contact with the upper surface of the workpiece W.

  Next, while maintaining pressurization by the movable electrode 21 and the fixed electrode 22, a current source (not shown) is controlled by the control device 100 to supply a welding current. As a result, melting of the work material is promoted between the movable electrode 21 and the fixed electrode 22 of the work W, and the nugget 23 is generated.

  Thereafter, the control device 100 controls a current source (not shown) to stop the supply of the welding current. Next, the servo motor 16 is controlled by the control device 100, and the movable electrode 21 is moved backward with respect to the workpiece W by the action of the feed screw mechanism. Thereby, the nugget 23 is cooled and solidified, and the workpiece W is welded.

  Next, the current density flowing through the workpiece W between the movable electrode 21 and the fixed electrode 22 and the generated nugget 23 will be described with reference to FIGS.

  FIG. 2 is a schematic diagram showing the state of the current density flowing through the workpiece W between the movable electrode 21 and the fixed electrode 22 and the shape of the generated nugget 23 when there is no gap between the plate material W1 and the plate material W2. 2A shows the state of current density, and FIG. 2B shows the shape of the nugget 23.

  According to FIG. 2, since the plate material W1 and the plate material W2 are in contact with each other over the entire surface, a current flows evenly through the workpiece W between the movable electrode 21 and the fixed electrode 22, and the current density becomes substantially constant (FIG. 2). (A)). Therefore, a nugget 23 having a diameter that can provide an appropriate bonding strength is generated (FIG. 2B).

  FIG. 3 shows the state of the current density flowing in the work W between the movable electrode 21 and the fixed electrode 22 and the generated nugget 23 when the pressure on the work W rises when there is a gap between the plate material W1 and the plate material W2. It is a schematic diagram showing the shape. 3A shows the state of current density, and FIG. 3B shows the shape of the nugget 23.

According to FIG. 3, the plate material W <b> 1 and the plate material W <b> 2 having a gap are pressed by the movable electrode 21 and the fixed electrode 22 and are in contact with each other near the center of the workpiece W. Therefore, since the current flows concentrated on the contact portion, the current density is biased compared to the case where there is no gap (see FIG. 2) (FIG. 3A).
As a result, the heat generation efficiency of the contact portion is increased, and the nugget 23 centered on the contact portion is generated faster than the case where there is no gap (see FIG. 2). However, since the diameter of the nugget 23 is smaller than that when there is no gap (see FIG. 2), an appropriate bonding strength cannot be obtained.

  Therefore, even when there is a gap, in order to increase the diameter of the nugget 23 and obtain an appropriate joint strength, it is necessary to reduce the deviation of the current density flowing through the workpiece W as much as possible. For this purpose, it is necessary to reduce the current flowing between the movable electrode 21 and the fixed electrode 22 as compared with the case where there is no gap (see FIG. 2). This case will be described with reference to FIG.

  FIG. 4 shows the state of the current density flowing through the workpiece W and the generated nugget 23 between the movable electrode 21 and the fixed electrode 22 after the pressurization to the workpiece W rises when there is a gap between the plate material W1 and the plate material W2. It is a schematic diagram showing the shape. 4A shows the state of current density, and FIG. 4B shows the shape of the nugget 23.

  According to FIG. 4, as in FIG. 3, the plate material W <b> 1 having a gap and the plate material W <b> 2 are pressed by the movable electrode 21 and the fixed electrode 22 and are in contact with each other near the center of the workpiece W. However, since the current flowing between the movable electrode 21 and the fixed electrode 22 is reduced as compared with the case of FIG. 3, the current density is less biased (FIG. 4A). Therefore, compared with the case of FIG. 3, since the heat generation efficiency of the contact portion is reduced and the nugget generation is made uniform, the diameter of the nugget 23 is increased without spattering (FIG. 4B).

  Next, with reference to FIG. 5 thru | or FIG. 8, the welding current set according to the gap amount of the board | plate material W1 and the board | plate material W2 is demonstrated.

FIG. 5 is a graph showing the relationship between the welding current flowing between the movable electrode 21 and the fixed electrode 22 and the nugget diameter when the gap amount between the plate material W1 and the plate material W2 is 0 mm.
According to FIG. 5, a nugget having a diameter exceeding a nugget diameter (hereinafter referred to as “required nugget diameter”) necessary for the plate material W1 and the plate material W2 in the present embodiment to have appropriate joint strength is generated. The minimum welding current required for this is 8.5 KA. Therefore, the appropriate current value when the gap amount is 0 mm is 8.5 KA.

FIG. 6 is a graph showing the relationship between the welding current flowing between the movable electrode 21 and the fixed electrode 22 and the nugget diameter when the gap amount between the plate material W1 and the plate material W2 is 1 mm.
According to FIG. 6, the minimum value of the welding current necessary for generating a nugget having a diameter exceeding the necessary nugget diameter is 8.0 KA. At this time, the current density is the same as in the case where there is no gap, and the diameter of the nugget becomes larger than the necessary nugget diameter without spattering. Therefore, the appropriate current value when the gap amount is 1 mm is 8.0 KA.

FIG. 7 is a graph showing the relationship between the welding current flowing between the movable electrode 21 and the fixed electrode 22 and the nugget diameter when the gap amount between the plate material W1 and the plate material W2 is 2 mm.
According to FIG. 7, the minimum value of the welding current required for producing a nugget having a diameter exceeding the necessary nugget diameter is 7.5 KA. At this time, the current density is the same as in the case where there is no gap, and the diameter of the nugget becomes larger than the necessary nugget diameter without spattering. Therefore, the appropriate current value when the gap amount is 2 mm is 7.5 KA.

FIG. 8 is a graph showing the relationship between the welding current flowing between the movable electrode 21 and the fixed electrode 22 and the nugget diameter when the gap amount between the plate material W1 and the plate material W2 is 3 mm.
According to FIG. 8, the minimum value of the welding current required for producing a nugget having a diameter exceeding the necessary nugget diameter is 7.0 KA. At this time, the current density is the same as in the case where there is no gap, and the diameter of the nugget becomes larger than the necessary nugget diameter without spattering. Therefore, the appropriate current value when the gap amount is 3 mm is 7.0 KA.

  According to the description of FIGS. 5 to 8, a nugget having an appropriate nugget diameter can be generated by lowering the welding current as the gap amount is larger.

  FIG. 9 shows the relationship between the gap amount between the plate material W1 and the plate material W2 and the pressurization rise time from when the pressurization of the workpiece W by the movable electrode 21 and the fixed electrode 22 is started until the predetermined pressurization force is reached. It is a graph.

  FIG. 9 shows the pressure rise time when the gap amount is 0 mm, 1 mm, 2 mm, and 3 mm. Further, the gap amount and the pressurization rise time are substantially proportional, and the pressurization rise time is longer as the gap amount is larger. This is because the time for closing the gap increases as the gap amount increases.

  FIG. 10 is a diagram illustrating the relationship between the welding current flowing between the movable electrode 21 and the fixed electrode 22 and the pressure applied to the workpiece W by the movable electrode 21 and the fixed electrode 22.

With reference to FIG. 10, changes in pressure and welding current with time will be described. Between times t ₀ ~t ₁ is before the start pressurization to the work W, pressure and welding current are both zero. During this time, the control device 100 controls the servo motor 16 to bring the tip surface of the movable electrode 21 into contact with the upper surface of the workpiece W.

Then, the pressure rises in the pressurization starts from time t ₁ t _2. The pressurization rise time (t ₂ −t ₁ ) is measured by the strain gauge 17 (the strain gauge 17 measures the time from the start of detecting the applied pressure until the predetermined applied pressure is detected), and the control device 100. The pressurization rise time changes according to the gap amount between the plate material W1 and the plate material W2 (see FIG. 9). The control device 100 calculates the gap amount from the received pressurization rise time based on the relationship of FIG.
Note that the applied pressure in the pressure rising state is constant regardless of the gap amount.

Next, the period from time t ₂ to t ₃ is a time (about 100 ms) for stabilizing the applied pressure, and the welding current is changed at time t ₃ after the elapse of this time. The welding current has an appropriate value determined according to the gap amount. As described with reference to FIGS. 5 to 8, the appropriate current value when the gap amount is 0 mm, 1 mm, 2 mm, or 3 mm, 8.5KA, 8.0KA, 7.5KA or 7.0KA. That is, there is a relationship that the appropriate current value decreases as the gap amount increases. Based on this relationship, control device 100 selects a welding current setting from the calculated gap amount.

Next, the control device 100 controls the current source (not shown) at time t ₃ to change the welding current is energized until the time t _4. By this energization, a nugget 23 having an appropriate nugget diameter corresponding to the gap amount is generated. The energization time is constant regardless of the gap amount.
At time t _4, the control device 100 stops the supply of the welding current, the movable electrode 21 is retracted relative to the workpiece W at time t _5. Thereby, the nugget 23 is cooled and solidified, and the workpiece W is welded with an appropriate joint strength.

According to the present embodiment, the pressurization rise time from the start of pressurization of the workpiece W to a predetermined applied pressure is measured, and between the stacked plate members W1 and W2 based on the measured pressurization rise time. The gap amount before the start of pressurization is calculated. Therefore, the gap amount between the plate material W1 and the plate material W2 can be easily calculated by measuring the pressure rising time.
Moreover, according to this embodiment, the setting of the welding current sent through the pressurization part of the workpiece | work W is selected based on the calculated gap amount. Therefore, since the current value of the welding current is determined according to the gap amount, the welding condition is appropriately set, and the growth state of the nugget 23 can be kept constant.
As described above, according to the present embodiment, the gap amount can be calculated during the welding operation for one cycle, and the setting of the welding current can be selected. Therefore, the optimum amount corresponding to the gap amount can be obtained without increasing the number of man-hours. Welding work can be performed.

In addition, according to the present embodiment, the welding pressure and energization time of the welding conditions are the same regardless of the gap amount, and the welding current is reduced in accordance with the gap amount to reduce the welding current density flowing between the plate material W1 and the plate material W2. The bias was reduced to the same level as when there was no gap. Therefore, compared with the case where the welding current is large, the heat generation efficiency of the contact portion between the plate material W1 and the plate material W2 is reduced, and the nugget 23 is not generated concentrated on the contact portion. The nugget 23 which becomes large and has appropriate joint strength can be generated.
In addition, according to the present embodiment, the energization time does not extend because the welding current is only changed according to the gap amount. Therefore, production efficiency does not deteriorate.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

DESCRIPTION OF SYMBOLS 1 ... Spot welding apparatus 10 ... Spot welding gun 21 ... Movable electrode 22 ... Fixed electrode 23 ... Nugget W ... Workpiece | work W1, W2 ... Plate material

Claims (2)

A welding method in which a current is passed and welded in a state where a workpiece in which a plurality of plate materials are stacked is sandwiched between a pair of electrodes,
Measuring a pressurization rise time from the start of pressurization of the workpiece by the pair of electrodes until reaching a predetermined applied pressure;
Based on the measured pressure rise time, calculating a gap amount before the start of pressurization between the laminated plate materials,
And a step of selecting a setting of a welding current to be passed through the pressurizing portion of the workpiece based on the calculated gap amount. A welding device for welding a workpiece in which a plurality of plate materials are laminated,
A pair of electrodes arranged opposite to each other and approaching or separating by an advancing and retreating mechanism;
A current source for passing a current between the pair of electrodes;
A pressure detection means for detecting a pressure when the work is sandwiched between the pair of electrodes and pressurized;
A pressurization rise time measuring means for measuring a pressurization rise time from when the pressurization detection means starts to detect the pressurization force of the workpiece until a predetermined pressurization force is detected;
Based on the pressurization rise time measured by the pressurization rise time measurement means, a gap amount calculation means for calculating a gap amount before the pressurization between the laminated plate members,
A welding apparatus comprising: current setting selection means for selecting a setting of a welding current to be passed through the pressurizing portion of the workpiece based on the gap amount calculated by the gap amount calculation means.

Images