JPH1119778A - Resistance welding method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely demonstrate an excellent welding quality while superior stability is secured for the control. SOLUTION: A work W is held in flotation by a floating air cylinder 9 of a holding device 2. The welding equipment also employes an upper pressurizing air cylinder 17 which energizes an upper roller electrode 24 so as to impart an upper pressurizing force to the work W from above and a lower pressurizing air cylinder 14 which energizes a lower roller electrode 25 so as to impart a lower pressurizing force to the work W from below. Then, with an inter- electrode pressure difference measured between the upper and lower pressurizing forces, the floating air cylinder 9 is feedback controlled so that the difference is approximated to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a resistance welding method and a resistance welding apparatus.

[0002]

2. Description of the Related Art In a general resistance welding method, for example, a seam welding method, a lower roller electrode is rotatably fixed, is paired with a lower roller electrode, and is covered by an upper roller electrode urged by an upper cylinder. Continuous welding of the workpiece is performed by applying a pressing force to the workpiece from above, sandwiching the workpiece, and rotating the two roller electrodes while applying a welding current between the two roller electrodes. At this time, the work fixing table for fixing the workpiece is used in combination with a pin-cam type holding means that moves by the driving force of the two roller electrodes, or the hand that holds the workpiece in a floating state moves according to the teaching, and Can be used together with a robot-type holding means that moves by the driving force of the hand and the driving force of both roller electrodes.

In the former general seam welding method using the pin cam type holding means, the upper roller electrode is urged by the upper cylinder and the lower roller electrode is urged by the lower cylinder. There is also known a seam welding apparatus in which an upper pressure and a lower pressure are equally applied to a workpiece by feedback control (Japanese Utility Model Publication No. 63-2322).

[0004]

However, in the above-described general resistance welding method, there are problems such as waving or misalignment caused by press-forming of a workpiece, and a workpiece caused by a driving force for driving the workpiece. There is a case where the upper pressure and the lower pressure are different due to the distortion and the residual stress. In this case, as shown in FIG. 16, the center of the nugget 10 formed on the workpiece W is displaced up and down.

That is, taking the seam welding method as an example,
When the upper pressing force Fu acting on the workpiece W from the upper roller electrode 11 is larger than the lower pressing force Fd acting on the workpiece W from the lower roller electrode 12, the equilibrium point between the upper pressing force Fu and the lower pressing force Fd is obtained. Are shifted downward, so that the nugget 10 is formed from below. On the other hand, when the upper pressing force Fu is smaller than the lower pressing force Fd, the equilibrium point between the upper pressing force Fu and the lower pressing force Fd is shifted upward, so that the nugget 10 is formed from above.
According to the test results of the present inventors, if the center of the nugget 10 is excessively displaced from between the plates, the nugget 10 may be cracked, resulting in poor welding quality.

[0006] In particular, due to recent needs and diversification of seeds, for example, the melting point of metals such as plated steel sheets, particularly metals having relatively higher heat transfer coefficients than steel materials such as aluminum alloys and titanium alloys, and lead alloys. These tendencies are large when a steel sheet or the like plated with a metal having a low hardness is used as a welding wire. In this respect, in the seam welding apparatus described in Japanese Utility Model Publication No. 63-2322, both the upper roller electrode and the lower roller electrode are in a floating state, and the upper pressure and the lower pressure are equally applied to the workpiece. Therefore, it is possible to prevent the center displacement of the nugget and exhibit excellent welding quality.

However, in such a seam welding apparatus, large upper and lower cylinders are required because the upper and lower roller electrodes sandwich the workpiece with a large force and perform welding. Further, the work to be welded is fixedly held, and the feedback control is performed as pressure correction of the upper cylinder and the lower cylinder. For this reason, the pressure to be corrected by the upper cylinder or the lower cylinder also acts on the workpiece to be fixed, so that it is not necessary to employ a large cylinder capable of generating a large pressure as both the upper cylinder and the lower cylinder. Do not act equally on the work to be welded, which rather impairs control stability.

The present invention has been made in view of the above-mentioned conventional situation, and provides a resistance welding method and a resistance welding apparatus capable of reliably exhibiting excellent welding quality while ensuring excellent control stability. Is the task to be solved.

[0009]

[Means for Solving the Problems]

(1) In the resistance welding method according to the first aspect, the object to be welded is held by a holding means, and a pressure is applied to the object to be welded by a pair of electrodes urged by a pressurizing means. In a resistance welding method of welding the workpiece by sandwiching and applying a welding current between the two electrodes, the holding unit floats and holds the workpiece, and the pressing unit includes A first pressing means for urging the electrode to apply a first pressing force to the workpiece from one side, and a second pressing force from the other to energizing the other electrode to the workpiece. And a second pressurizing means for applying the pressure. The difference between the first pressurizing force and the second pressurizing force is measured, and the holding means is feedback-controlled so that the difference approaches zero.

In the resistance welding method according to the first aspect, the one electrode and the other electrode are both in a floating state, and the difference between the first pressing force and the second pressing force is measured, so that the difference approaches zero. Since the holding means is feedback-controlled, the pressing force acts equally on the workpiece, so that the center displacement of the nugget is prevented, and excellent welding quality can be exhibited. At this time, the holding means floats and holds the workpiece, and the feedback control is performed on the holding means. For this reason, since the holding means changes the position of the work to be welded, even if the large first pressurizing means and the second pressurizing means which can generate both large pressures are not employed, the welding force is equal and the welding force is not changed. Will act on things. Therefore, high control stability can be ensured.

Therefore, according to the resistance welding method of the first aspect, excellent welding quality can be reliably exhibited while ensuring excellent control stability. (2) In the resistance welding method according to the second aspect, in the resistance welding method according to the first aspect, the holding means includes a floating cylinder that holds the workpiece to be floated from below, and the workpiece that faces the floating cylinder. And a clamp cylinder having a clamp cylinder that floats from above, and the feedback control is performed as pressure correction of the floating cylinder.

In the resistance welding method according to the second aspect, the means according to the first aspect is embodied in a case where a pin cam type holding means is used. (3) In the resistance welding method according to the third aspect, in the resistance welding method according to the first aspect, the holding means moves a hand for floatingly holding the workpiece to be taught, and the driving force of the hand is applied to the workpiece. And a robot type moving by the driving force of both roller electrodes, wherein the feedback control is performed as the teaching correction.

[0013] The resistance welding method according to a third aspect of the present invention embodies the means of the first aspect in the case where a robot-type holding means is used. (4) The resistance welding method according to the fourth aspect is the first, second, or third aspect.
In the resistance welding method described above, the resistance welding method is a seam welding method for performing continuous welding of a workpiece while rotating both roller electrodes, which are both electrodes. The difference between the actual welding speed and the actual welding speed, which is the actual welding speed of the workpiece, is measured, and the actual welding speed is feedback-controlled so that the difference approaches zero.

In the case where the resistance welding method according to the first, second or third aspect is a seam welding method, the assumed welding speed and the actual welding speed may be different. in this case,
The roller electrode has caused a slip with the work to be welded, so that a nugget with a desired nugget thickness cannot be formed,
The nugget may be cracked or the nugget wrap may be absent, resulting in poor welding quality.

In this respect, according to the resistance welding method of the present invention, when the assumed welding speed and the actual welding speed are different, the difference between the assumed welding speed and the actual welding speed is measured. That is, it is determined whether or not a slip has occurred with the object. Then, since the actual welding speed is feedback-controlled so that the difference approaches zero, the slip is reliably suppressed.

Therefore, according to the resistance welding method of the present invention, since a nugget having a desired nugget thickness can be formed on an object to be welded, cracking does not occur and excellent welding quality with a nugget wrap is exhibited. be able to. (5) The resistance welding apparatus according to claim 5, wherein the holding means floats and holds the workpiece, and the first pressing force detecting means detects a first urging force for urging the first electrode by the first pressing means. , Second
First pressing force detecting means for detecting a second urging force for urging the second electrode by the pressurizing means; calculating means for calculating a difference between the first pressing force and the second pressing force; Control means for performing feedback control of the holding means so as to approach zero.

According to a fifth aspect of the present invention, there is provided a resistance welding apparatus in which the method of the first aspect is conceived. (6) The resistance welding apparatus according to a sixth aspect of the present invention is the resistance welding apparatus according to the fifth aspect, wherein the holding means includes a floating cylinder that holds the workpiece to be floated from below, and the workpiece that faces the floating cylinder. And a clamp cylinder having a clamp cylinder that floats from above, and the feedback control is performed as pressure correction of the floating cylinder.

The resistance welding apparatus according to claim 6 is based on the concept of the method according to claim 2. (7) In the resistance welding apparatus according to the seventh aspect, in the resistance welding apparatus according to the fifth aspect, the holding means is configured such that a hand for holding the workpiece in a floating state is moved by teaching, and the workpiece is driven by the driving force of the hand. And a robot type moving by the driving force of both roller electrodes, wherein the feedback control is performed as the teaching correction.

A resistance welding apparatus according to a seventh aspect of the present invention envisions the method according to the third aspect as an apparatus. (8) The resistance welding apparatus according to claim 8 is the same as in claim 5, 6, or 7.
In the resistance welding apparatus described above, a driving unit that drives the workpiece, an assumed welding speed detecting unit that detects an assumed welding speed at which the driving unit is supposed to weld the workpiece, and the driving unit that drives the workpiece. Actual welding speed detecting means for detecting an actual welding speed at which the welded article is actually welded, wherein the calculating means calculates a difference between the assumed welding speed and the actual welding speed,
The control means performs feedback control of the driving means so that the calculation result approaches zero.

[0020] The resistance welding apparatus according to claim 8 is conceived of the method according to claim 4 as an apparatus.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 3 which embody the invention of each claim will be described below with reference to the drawings. (Embodiment 1) The seam welding apparatus of Embodiment 1 embodies claims 1, 2, 4, 5, 6, and 8. In this seam welding apparatus, as shown in FIG. 1, a pin cam type holding device 2 as a holding means on a base 1, a welding machine main body 3,
The iron man jig 4 is fixed.

In the holding device 2, an arm 6 is provided on a bracket 5 erected on the base 1 so as to be able to swing horizontally via a vertical axis, and a hand 7 is also provided on the arm 6 via a vertical axis. It is provided so as to be able to swing horizontally. A work fixing base 8 is fixed to the lower claw portion of the hand 7 with the upper surface horizontal, and a floating air cylinder 9 capable of extending a rod upward is fixed to the work fixing base 8. A guide pin 8a is protrudingly provided on the back surface of the work fixing stand 8,
Thereby, the work fixing base 8 defines the welding line WL of the workpiece W together with the iron man jig 4 as shown in FIG.
In addition, an optical sensor 40 facing the work fixing table 8 is provided on the base 1, and the optical sensor 40 constitutes actual welding speed detecting means. As shown in FIG. 1, a lower work fixing plate 10 having a horizontal upper surface is attached to the upper end of the rod of the floating air cylinder 9.

On the other hand, a clamp air cylinder 11 capable of extending a rod downward is fixed to the upper claw portion of the hand 7, and an upper work fixing plate 12 having a horizontal lower surface is provided at the lower end of the rod of the clamp air cylinder 11. Installed. The clamp air cylinder 11 and the floating air cylinder 9 are respectively provided with control valves 45 and 46 shown in FIG.
Through an air pump (not shown).

Further, as shown in FIG. 1, in the welding machine main body 3, a frame 13 having upper and lower flanges is fixed on the base 1. A lower pressurizing air cylinder 14 capable of extending a rod upward is fixed to the lower flange, and a lower load cell 1 is attached to a rod of the lower pressurizing air cylinder 14.
5, a lower electrode gear box 16 is attached. A pressurizing upper air cylinder 17 capable of extending a rod downward is fixed to the upper flange, and an upper load cell 1 is attached to a rod of the pressurizing upper air cylinder 17.
The gear box 19 for the upper electrode is attached with the electrode box 8 interposed therebetween. Here, the pressurizing upper air cylinder 17 is
The pressurizing means is constituted, and the lower pressurizing air cylinder 14 constitutes the second pressurizing means. Also, the upper load cell 18
Constitute first pressure detecting means, and the lower load cell 15 constitutes second pressure detecting means.

An AC three-pole servo motor 20 is fixed to the back of the frame 13.
Are connected to two swingable drive shafts 22 and 23 via a gear box 21. The drive shafts 22 and 23 are connected to an upper electrode gear box 19 and a lower electrode gear box 16, respectively. Have been. The upper electrode gear box 19 and the lower electrode gear box 16 are provided with an upper roller electrode 24 and a lower roller electrode 25 so as to be driven by drive shafts 22 and 23, respectively. Here, the upper roller electrode 24 constitutes a first roller electrode, the lower roller electrode 25 constitutes a second roller electrode, and the upper roller electrode 24 and the lower roller electrode 25 directly constitute drive means. Further, rotors 26 and 27 having slits (not shown) are fixed to the drive shafts 22 and 23 shown in FIG. 1, and the rotors 26 and 27 face optical sensors 41 and 42 also shown in FIG. Here, the optical sensors 41 and 42 constitute an assumed welding speed detecting means.

The upper roller electrode 24 and the lower roller electrode 25 are mainly composed of Cu, and as shown in FIG.
Is adopted. Although not shown in FIG. 1, the forming member 32 shown in FIG. 5 is movably opposed to the upper roller electrode 24 and the lower roller electrode 25, respectively. The upper roller electrode 24 and the lower roller electrode 25 are connected to a welding power source (not shown) via a controller 49 shown in FIG.

Further, as shown in FIGS. 1 and 2, in the iron man jig 4, an inertia 28 is provided on the frame 13 of the welding machine main body 3 so as to be able to swing horizontally, and the inertia 28 has a guide on the upper surface. A guide rail 29 having a groove is provided so as to be horizontally swingable. The guide groove of the guide rail 29 guides the guide pin 8a of the work fixing stand 8 of the holding device 2 in a detachable manner. A rod of a balance air cylinder 30 fixed to the base 1 is swingably fixed to the inertia 28, and a guide rail 29
Also, a rod of a damper air cylinder 31 fixed to the base 1 is swingably fixed. Here, the balance air cylinder 30 constitutes auxiliary driving means. The balance air cylinder 30 and the damper air cylinder 31 are connected to an air pump (not shown) via control valves 47 and 48 shown in FIG. 3, respectively.

The control valves 45, 46, 47, 48,
Upper and lower load cells 18, 15 and optical sensor 40,
41 and 42 are the computer 5 via the controller 49
0 is connected. In addition, the welding power source is also a computer 5
0 is connected. Here, the computer 50 calculates the welding speed difference S between the assumed welding speed Vi and the actual welding speed Vr, and also calculates the inter-electrode pressure difference F between the upper pressing force Fu and the lower pressing force Fd. Result S, F
Constitutes a control means for performing feedback control of the control valve 47 and the control valves 45 and 46 such that the value approaches zero.

With the seam welding apparatus configured as described above, seam welding along the welding line WL shown in FIG. 6 is performed on the workpiece W made of two aluminum-plated steel sheets. From the point O, the welding line WL is straight line portion 1S, curved portion 1
C, straight section 2S, curved section 2C, straight section 3S, curved section 3
C, straight section 4S, curved section 4C, straight section 5S, curved section 5C
And the straight portion 6S in this order. At this time, the computer 50 performs the processing shown in FIG.

First, in step 100, the moving speed of the work fixing base 8 detected by the optical sensor 40 is input as the actual welding speed Vr. Further, the peripheral velocity Vu of the upper roller electrode 24 detected by the optical sensor 41, the peripheral velocity Vd of the lower roller electrode 25 detected by the optical sensor 42, and the upper load of the upper roller electrode 24 detected by the upper load cell 18. The pressure Fu and the lower pressure Fd of the lower roller electrode 25 detected by the lower load cell 15 are input.

Next, in step 101, (Vu
An assumed welding speed Vi at which the workpiece W is assumed to move is calculated from an arithmetic expression of + Vd) / 2. Then, in step 102, the assumed welding speed Vi and the actual welding speed V
The welding speed difference S from r is calculated. After this, step 10
In 3, it is determined whether or not the welding speed difference S is smaller than -ΔS. Here, ΔS is the balance air cylinder 30
Is a preset value close to 0 in order not to operate too sensitively. If YES in step 103, it can be determined that the upper roller electrode 24 and the lower roller electrode 25 are slipping with the workpiece W and the actual welding speed Vr is higher than the assumed welding speed Vi.
Proceed to step 104. In step 104, the balance air cylinder 30 separates the inertia 28 to reduce the actual welding speed Vr by the counterbalance.
An UP signal is sent to the control valve 47. Thereafter, the process returns to step 107 described later.

If NO in step 103, the process proceeds to step 105, where it is determined whether or not the welding speed difference S is larger than ΔS. If YES in step 105, the upper roller electrode 24 and the lower roller electrode 25 are slipping with the workpiece W, and the actual welding speed Vr
Can be determined to be smaller than the assumed welding speed Vi. In step 106, the balance air cylinder 30 attracts the inertia 28, and increases the actual welding speed Vr by the counter balance.
A DOWN signal is sent to the control valve 47. Thereafter, the process returns to step 107 described later.

If NO in step 105, the upper roller electrode 24 and the lower roller electrode 25
It can be determined that there is no slippage that may cause a problem between the process and the process. Step 107
Then, the inter-electrode pressure difference F between the upper pressing force Fu and the lower pressing force Fd is calculated. Thereafter, in step 108, it is determined whether or not the inter-electrode pressure difference F is smaller than -ΔF. Here, ΔF is a value set in advance to a value close to 0 in order to prevent the floating air cylinder 9 from operating excessively. If YES in step 108,
Since it can be determined that the upper pressing force Fu acting on the workpiece W from the upper roller electrode 24 is smaller than the lower pressing force Fd acting on the workpiece W from the lower roller electrode 25, the process proceeds to step 109. In step 109, the control valve 46 is adjusted so that the floating air cylinder 9 pushes up the lower work fixing plate 10 to correct the lower pressing force Fd to a small value.
To send an UP signal. Thereafter, the process returns to step 100.

If NO in step 108, the process proceeds to step 110, where it is determined whether or not the inter-electrode pressure difference F is larger than ΔF. If YES in step 110, it can be determined that the upper pressing force Fu acting on the workpiece W from the upper roller electrode 24 is greater than the lower pressing force Fd acting on the workpiece W from the lower roller electrode 25. Go to 111. In step 111, a DOWN signal is sent to the control valve 46 so that the floating air cylinder 9 pushes down the lower work fixing plate 10 to greatly correct the lower pressing force Fd. Thereafter, the process returns to step 100.

If NO in step 110, the upper pressing force Fu acting on the workpiece W from the upper roller electrode 24 and the lower pressing force Fd acting on the workpiece W from the lower roller electrode 25 will cause a problem. Since it can be determined that there is no significant difference, the process returns to step 100. Thus, a fuel tank made of an aluminum-plated steel sheet is obtained.

The actual welding speed Vr after the control in the first embodiment.
FIG. 8 shows (m / min). On the other hand, the actual welding speed Vr (m / m
In), the result is as shown in FIG. 8 and 9, in the first embodiment, the bending portions 1C, 2C, 3C, 4
Even when the assumed welding speed Vi and the actual welding speed Vr are different in C and 5C, the upper and lower roller electrodes 24 and 25 surely suppress the slip generated between the upper and lower roller electrodes 24 and 25 and the workpiece W as compared with the comparative example. You can see that it is. This is because in the first embodiment, the difference S between the assumed welding speed Vi and the actual welding speed Vr is measured to determine whether or not a slip actually occurs, and the actual welding is performed so that the difference S approaches zero. This is because the speed Vr is feedback controlled.

FIG. 10 shows the pressure difference F (kg) between the electrodes after control in the first embodiment.
The variation in the first embodiment is 22 kg. On the other hand, in the case of the comparative example, the pressing force (kg) by the upper pressing force Fu and the lower pressing force Fd is as shown in FIG. 11A, and the pressure difference F (kg) between the electrodes is as shown in FIG. And the pressing force average (kg) was as shown in FIG. 11 (C). The variation amount in the comparative form is 60 kg.

As shown in FIGS. 10 and 11, in the first embodiment,
It can be seen that the pressing force acts equally on the workpiece W as compared with the comparative example. This is because, in the first embodiment, both the upper and lower roller electrodes 24 and 25 are in a floating state, and the inter-electrode pressure difference F between the upper pressing force Fu and the lower pressing force Fd is measured. This is because feedback control of the floating air cylinder 9 is performed based on this.

FIG. 12 shows the relationship between the nugget offset amount (mm) and the pressure difference F (kg) between the electrodes. It can be seen from FIG. 12 that if the pressure difference F between the electrodes is large, the nugget offset amount increases. For this reason, it is understood that in Embodiment 1, the center displacement of the nugget can be prevented. In particular, the floating air cylinder 9 holds the workpiece W in a floating state, and the feedback control is performed on the floating air cylinder 9. For this reason, the floating air cylinder 9 is
, The pressing force is equally applied to the workpiece W without using the large pressurizing upper air cylinder 17 and the pressurizing lower air cylinder 14 that can generate a large pressure. Become. Therefore, high control stability can be ensured.

Furthermore, the embodiment 1 and the comparative embodiment were evaluated for nugget failure, cracking or goodness. FIG. 13 shows the results. From FIG. 13, it is understood that excellent welding quality can be reliably exhibited in the first embodiment. It should be noted that, as shown in FIG. 8, the reason why no crack is generated is that the mechanical characteristics of the holding device 2 and the Ironman jig 4
This is because the actual welding speed Vr drops at a peak in the curved portion 1C and the like.

Therefore, in the first embodiment, excellent stability of control can be ensured, and a nugget having a desired nugget thickness can be formed on the workpiece W. It turns out that a certain excellent welding quality can be surely exhibited. In the first embodiment, the protrusions 24a of the upper roller electrode 24 and the lower roller electrode 25,
An Al-Cu compound is generated at the tip of 25a. The Al-Cu compound is formed by alloying Al of the aluminum-plated steel sheet constituting the workpiece W with Cu constituting the upper roller electrode 24 and the lower roller electrode 25 during resistance welding. is there. Since such an Al-Cu compound has a large electric resistance value, a large amount of heat is required for desired welding, which greatly affects the weldability. For this reason, if a roller electrode having a general shape is employed, it is necessary to cut the entire outer peripheral surface or to cool the roller electrode at the expense of great cost. If the thickness of the roller electrode is reduced to avoid this, the rigidity is reduced and the heat capacity is reduced, so that the roller electrode is easily worn. In this regard,
In the first embodiment, the upper roller electrode 24 and the lower roller electrode 25 having the protrusions 24a and 25a are employed, and the forming member 32 shown in FIG. 5 is sometimes brought into contact with the upper roller electrode 24 and the lower roller electrode 25. Therefore, the protrusions 24a and 25a in a narrow range may be cut, and the Al-Cu compound can be easily removed. In the first embodiment, the cooling cost is reduced without impairing the rigidity and the abrasion. According to the test results of the inventor, it is preferable that the protrusions 24a and 25a have a height of 1 to 3 mm and a width of about 2/3 of the width of the upper and lower roller electrodes 24 and 25. (Second Embodiment) A seam welding apparatus according to a second embodiment also embodies claims 1, 2, 4, 5, 6, and 8. In this seam welding apparatus, as shown in FIG. 14, a slider 34 is provided on a frame 33 so as to be vertically slidable, and the slider 34 is connected to an AC three-pole servo motor 36 via a ball screw 35. The slider 34 has upper and lower flanges, and the lower electrode gear box 16 similar to that of the first embodiment is attached to the lower flange with the lower load cell 37 interposed therebetween. Other configurations are the same as in the first embodiment.

In the second embodiment, if it is determined that the upper pressing force Fu is smaller than the lower pressing force Fd, the slider 34
To increase the upper pressure Fu. On the other hand, if it is determined that the upper pressure Fu is larger than the lower pressure Fd, the slider 34 is raised to increase the lower pressure Fd. Other operations are the same as those of the first embodiment. Therefore, also in the second embodiment, the same effect as in the first embodiment can be exhibited. (Third Embodiment) A seam welding apparatus according to a third embodiment is embodied in claims 1, 3, 4, 5, 7, and 8. In this seam welding apparatus, as shown in FIG. 15, a robot-type holding device 60 as a holding means is fixed on the base 1, and the iron man jig 4 of the first embodiment is not used.

In the holding device 60, a robot body 51 is erected on the base 1, and a hand 53 is provided on an arm 52 provided movably in three axes from the robot body 51. ing. A first air cylinder 54 capable of extending a rod upward is provided on a lower claw portion of the hand 53.
Is fixed, and a first work fixing plate 5 is attached to the end of the rod.
5 is attached. On the other hand, a second air cylinder 5 capable of extending a rod downward is provided on the upper claw portion of the hand 53.
The second work fixing plate 57 is attached to the end of the rod. The robot main body 51 is instructed in advance so that the hand 53 moves along the welding line WL of the workpiece W, and the hand 53 constitutes a driving means together with the upper and lower roller electrodes 24 and 25. An optical sensor 58 facing the workpiece W is provided on the front surface of the frame 13, and the optical sensor 58 constitutes actual welding speed detecting means. Other configurations are the same as in the first embodiment.

In the third embodiment, the teaching speed to the hand 53 is the assumed welding speed Vi, and the moving speed of the workpiece W detected by the optical sensor 58 is the actual welding speed Vr.
Therefore, the upper roller electrode 24 and the lower roller electrode 25
Is slipping with the workpiece W, and it is determined that the actual welding speed Vr is higher than the assumed welding speed Vi,
The actual welding speed Vr is reduced by delaying the peripheral speed of the servomotor 20 by teaching correction. On the other hand, the upper roller electrode 24
And the lower roller electrode 25 is slipping with the workpiece W, and if it is determined that the actual welding speed Vr is lower than the assumed welding speed Vi, the servo motor 2 is corrected by teaching correction.
The peripheral speed of 0 is increased to increase the actual welding speed Vr.
Other operations are the same as those of the first embodiment.

Therefore, also in the third embodiment, the same effect as in the first embodiment can be exhibited.

[Brief description of the drawings]

FIG. 1 is a front view of a partial cross section of a seam welding apparatus according to a first embodiment.

FIG. 2 is a plan view of the Iron Man jig according to the first embodiment.

FIG. 3 is a block diagram of a control unit and the like according to the first embodiment.

FIG. 4 is a partial axial sectional view of an upper or lower roller electrode according to the first embodiment.

FIG. 5 is a partial cross-sectional view in the axial direction of a forming member according to the first embodiment.

FIG. 6 is a plan view showing a welding line of an object to be welded according to the first embodiment.

FIG. 7 is a flowchart illustrating a part of processing of a computer according to the first embodiment.

FIG. 8 is a graph showing a relationship between time and an actual welding speed according to the first embodiment.

FIG. 9 is a graph showing a relationship between time and actual welding speed according to a comparative example.

FIG. 10 is a graph showing a relationship between time and a pressure difference between electrodes according to the first embodiment.

11A and 11B are graphs showing a relationship between time and pressure, FIG. 11B is a graph showing a relationship between time and pressure difference between electrodes, and FIG. 11C is a graph showing time and pressure average. 6 is a graph showing a relationship with the graph.

FIG. 12 is a graph showing a relationship between a pressure difference between electrodes and a deviation amount of a nugget according to the first embodiment and a comparative example.

FIG. 13 is a graph showing welding quality according to the first embodiment and a comparative example.

FIG. 14 is a partial front view of the seam welding apparatus according to the second embodiment.

FIG. 15 is a front view of a partial section of the seam welding apparatus according to the third embodiment.

FIG. 16 is a schematic cross-sectional view illustrating a relationship between an upper pressing force, a lower pressing force, and a nugget.

[Explanation of symbols]

2, 60 ... holding device (2 ... pin cam type holding means, 60 ...
9: Floating air cylinder (floating cylinder) 11 Clamp air cylinder (clamp cylinder) W: Workpiece 17: Upper air cylinder for pressurization (first pressurizing means) 14: Lower air cylinder for pressurization (No. 1) 2 pressing means) 24 upper roller electrode (first roller electrode, driving means) 25 ... lower roller electrode (second roller electrode, driving means) Vi: assumed welding speed Vr: actual welding speed S: welding speed difference Fu ... Upper pressing force Fd Lower pressing force F ... Pressure difference between electrodes 8 ... Work fixing table 53 ... Hand (driving means) 41, 42 ... Optical sensor (estimated welding speed detecting means) 40 ... Optical sensor (actual welding speed detecting means) Reference numeral 50: Computer (arithmetic means) 18: Upper load cell (first pressing force detecting means) 15: Lower load cell (second pressing force detecting means)

Claims (8)

[Claims] An object to be welded is held by a holding means, and a pressure is applied to the object by a pair of electrodes urged by a pressurizing means to sandwich the object. In the resistance welding method of welding the workpiece by applying a welding current to the workpiece, the holding unit floats and holds the workpiece, and the pressurizing unit biases one of the electrodes. A first pressing means for applying a first pressing force to the workpiece from one side, and a second pressing means for applying a second pressing force to the workpiece from the other by energizing the other electrode A resistance welding method comprising: measuring a difference between the first pressure and the second pressure; and feedback-controlling the holding means so that the difference approaches zero. The holding means is of a pin-cam type having a floating cylinder for floatingly holding an object to be welded from below and a clamp cylinder opposed to the floating cylinder for floatingly holding the object to be welded from above. 2. The resistance welding method according to claim 1, wherein the feedback control is performed as a pressure correction of the floating cylinder. 3. The holding means is of a robot type in which a hand for floatingly holding the workpiece moves by teaching, and the workpiece moves by a driving force of the hand and a driving force of both roller electrodes. 2. The resistance welding method according to claim 1, wherein the feedback control is performed as the teaching correction. The resistance welding method is a seam welding method for performing continuous welding of an object to be welded while rotating both roller electrodes, ie, both electrodes. And measuring a difference from an actual welding speed, which is an actual welding speed of the workpiece, and performing feedback control on the actual welding speed so that the difference approaches zero. The resistance welding method described. 5. A holding means for floatingly holding an object to be welded,
A first pressing force detecting means for detecting a first urging force for urging the first electrode by the pressing means;
First pressing force detecting means for detecting a second urging force for urging the electrode; calculating means for calculating a difference between the first pressing force and the second pressing force; and a calculating means for calculating a difference between the first pressing force and the second pressing force. And a control means for performing feedback control of the holding means. 6. A pin cam type holding means having a floating cylinder for floatingly holding an object to be welded from below, and a clamp cylinder opposed to the floating cylinder and floatingly holding the object to be welded from above. 6. The resistance welding apparatus according to claim 5, wherein the feedback control is performed as a pressure correction of the floating cylinder. 7. The holding means is of a robot type in which a hand for floatingly holding the workpiece moves by teaching, and the workpiece moves by the driving force of the hand and the driving forces of both roller electrodes. The resistance welding apparatus according to claim 5, wherein the feedback control is performed as the teaching correction. 8. A driving means for driving an object to be welded, an assumed welding speed detecting means for detecting an assumed welding speed at which the driving means is supposed to weld the object to be welded, and the object to be welded by the driving means. Actual welding speed detecting means for detecting an actual welding speed at which welding is actually performed. The calculating means calculates a difference between the assumed welding speed and the welding dynamic speed, and the control means makes the calculation result approach zero. Wherein the driving means is feedback-controlled.
The resistance welding apparatus according to 6 or 7.