JPH07241684A - Method and equipment for seam welding of fuel tank - Google Patents

Abstract

PURPOSE:To provide a method and equipment for the seam welding of a fuel tank capable of dispensing with complicate jigs, easily coping with the change in the shape of the fuel tank, and automatically following and correcting to the wear of a lower electrode ring. CONSTITUTION:A flange part (c) for joining the periphery of the divided surfaces of a fuel tank (d) is located between upper and lower electrode rings 3, 4 of a seam welding machine 2 positioned by supporting the fuel tank (d) by a multiaxis robot 5, and the periphery o the flange part (c) for joining is successively and sequentially seam-welded by turning the fuel tank (d).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seam welding method and apparatus for a fuel tank for an automobile.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, a fuel tank for automobiles is formed by sheet metal press molding in a state of being divided into an upper member (a) and a lower member (b), and a joining flange portion around the divided surface. (C) is temporarily fixed beforehand by spot welding of 4 to several points, set on the lower jig (1) shown in FIG. 4, and then the seam welding machine (2).
The upper electrode wheel (3) is pressed against the lower electrode wheel (4) to pressurize the joining flange portion (c) temporarily fixed, and a welding current is passed between the upper and lower electrode wheels (3) and (4). The fuel tank (d) is manufactured by airtightly joining the surroundings. In this case, the lower jig (1) has a structure controlled by a copying jig (not shown) so that the seam welding locus is stable.

[0003]

According to the above-mentioned conventional method, it is necessary to manufacture the lower jig (1) and the copying jig each time the shape of the fuel tank (d) is different. There is a problem in that the production of the ingredients requires a large production cost and production period. Further, the seam height was lowered due to the abrasion of the lower electrode wheel (4), which required the height adjustment.

The present invention has been proposed in view of these problems, and its object is to eliminate the need for complicated jigs and to easily cope with changes in the shape of the fuel tank. It is possible to provide a seam welding method and apparatus for a fuel tank, which is capable of automatically tracking and correcting wear of the lower electrode wheel.

[0005]

In order to achieve the above-mentioned object, the method of the present invention comprises a fuel tank which is divided into upper and lower parts,
At the tip of the arm of the multi-axis robot, it is rotatably supported around an axis that is orthogonal to the dividing surface and passes through the center of the dividing surface.In this state, the joint flange around the dividing surface of the fuel tank is fixed. Between the upper and lower electrode wheels of the seam welding machine, the divided surface is supplied horizontally, and the upper and lower electrode wheels are rotated while pressing the joining flange portion with the upper and lower electrode wheels. While rotating around, the rotation angle is detected, and based on this rotation angle and the peripheral shape of the fuel tank set in advance, the change in the radius of rotation from the center of rotation of the fuel tank to the welding position of the joining flange is referred to as the rotation. Calculated as a function of angle, the position of the shaft that serves as the center of rotation of the fuel tank so that the welding position of the joint flange around the dividing surface of the fuel tank is always located between the upper and lower electrode wheels of the fixed seam welder. It is intended to automatically controlled via the multi-axis robot.

Further, in the method of the present invention, a plurality of peripheral portions of the joining flange portion of the fuel tank, which are divided into upper and lower parts, are spot-welded in advance to make a first temporary fixing, and the first electrode is attached to the upper and lower electrodes of the seam welding machine. It is supplied between the wheels via a multi-axis robot,
By changing the pressing force of the upper and lower electrode wheels on the joining flange part alternately, the second temporary fixing is performed around the joining flange part at the time of strong pressure, and then the pressing force of the upper and lower electrode wheels is made constant. The main welding is continuously performed around the joining flange portion.

The apparatus of the present invention comprises a fuel tank gripping means for vertically supporting a fuel tank formed by splitting into upper and lower portions, which is rotatable about an axis which is orthogonal to the dividing surface and passes through the center of the dividing surface, and upper and lower electrode wheels. The seam welder, which is rotatable and supported so that it can approach and separate from each other, is fixed, the rotation angle detector of the fuel tank, and the fuel tank gripping means are attached to the tip of the arm,
Based on the rotation angle detected by the rotation angle detector and the preset peripheral shape of the fuel tank, the change in the radius of rotation from the center of rotation of the fuel tank to the welding position of the joining flange is calculated as a function of the rotation angle. The position of the shaft, which is the center of rotation of the fuel tank, is controlled via the control device so that the welding position of the joining flange portion around the split surface of the fuel tank is always located between the upper and lower electrode wheels of the seam welder that is fixed. It is provided with a multi-axis robot which is automatically controlled.

Further, in the apparatus of the present invention, the seam welding machine is provided with a function of alternately changing the pressing force between the upper and lower electrode wheels.

Further, the apparatus of the present invention detects the pressing force between the flange portion of the fuel tank and the lower electrode wheel of the seam welding machine during the welding operation, and when the pressing force falls below a predetermined value,
A pressing force detector is provided to send a signal to the control device of the multi-axis robot to move the fuel tank gripping means downward to increase the pressing force to a predetermined value.

[0010]

According to the present invention, the joint flange around the dividing surface of the fuel tank is positioned between the upper and lower electrode wheels of the seam welding machine, which is fixedly supported by the multi-axis robot, and the fuel tank is rotated. By doing so, the periphery of the joining flange portion is sequentially and continuously seam welded. Due to this rotation of the fuel tank, the radius of gyration from the center of rotation of the fuel tank to the welding position of the joining flange is changed. In response to this change, the position of the center of rotation of the fuel tank should be controlled by the multi-axis robot. To change. The control of the multi-axis robot detects the rotation angle of the fuel tank, and based on this rotation angle and the preset peripheral shape of the fuel tank, determines the rotation radius from the rotation center of the fuel tank to the welding position of the joining flange portion. The change is calculated as a function of the rotation angle, and the position of the rotation center of the fuel tank is set so that the welding position of the joining flange portion around the dividing surface of the fuel tank is always located between the upper and lower electrode wheels of the fixed seam welder. This is done by controlling through a multi-axis robot. Thereby, a complicated jig can be omitted, and even if the shape of the fuel tank is changed, it can be easily dealt with.

Further, according to the present invention, a plurality of peripheral portions of the joining flange portion of the fuel tank, which are formed separately in the upper and lower parts, are spot-welded in advance to perform the first temporary fixing, and this is fixed between the upper and lower electrode wheels of the seam welding machine. To be supplied via a multi-axis robot, the pressing force of the upper and lower electrode wheels on the joining flange portion is alternately changed, and the second temporary fixing is performed around the joining flange portion at the time of strong pressure. Since a constant strong pressure is applied to the electrode wheel to continuously perform the main welding around the joining flange portion, the periphery of the joining flange portion of the fuel tank is intermittently welded during the second temporary fixing. As a result, welding distortion is reduced by that amount, and the welding trajectory is stabilized. Moreover, the second temporary fixing enhances the rigidity of the fuel tank and can increase the pressing force at the time of main welding, prevents the upper and lower electrode wheels from coming off, stabilizes the welding trajectory, and ensures good seam welding. The welding distortion can be reduced and corrected.

Further, the present invention detects the pressing force between the flange portion of the fuel tank and the lower electrode wheel of the seam welding machine during the welding operation, and when the pressing force falls below a predetermined value, the fuel tank gripping means is operated. By providing a pressing force detector that sends a signal to the control device of the multi-axis robot so as to increase the pressing force to a predetermined value by moving it downwards, the multi-axis robot's fuel tank The support position can be automatically tracked and corrected.

[0013]

FIG. 1 is a side view showing a schematic structure of an apparatus according to an embodiment of the present invention. (2) is a seam welder, (3) is an upper electrode wheel, (4) is a lower electrode wheel, and (5) ) Is at least 3
Multi-axis robot with multiple axes, preferably 6 or 7 axes,
(6) is a fuel tank gripping means, (7) is a rotation imparting means such as an electric motor and a fluid pressure motor, (8) is a rotation angle detecting means such as a rotary encoder, (9) is a pressing force detecting means, and (10). Shows a control device by a computer.

The seam welder (2) vertically opposes a rotatable upper electrode wheel (3) movably supported and a fixed lower electrode wheel (4) rotatably supported. And is installed on a base (not shown).
Further, the upper electrode wheel (3) is provided with a means (not shown) capable of approaching and separating toward the lower electrode wheel (4) and applying a pressing force, and the pressing force is alternately changed to be applied. A control means (not shown) is also provided. Of course, a welding current supply control means (not shown) is also provided.

The multi-axis robot (5) includes a control device (10).
Thus, each axis can be independently controlled and the fuel tank gripping means (6) is attached to the tip of the arm (5a).

The fuel tank gripping means (6) is installed with the tank retainer (6b) and the tank receiver (6c) facing each other above and below the substantially C-shaped frame (6a), and the tank retainer (6b) is moved up and down ( 6d), fixed tank receiver (6c)
With respect to the fuel tank (d), the fuel tank (d) is rotatably gripped around an axis (0) which is orthogonal to the dividing surface and passes through the center of the dividing surface, and is releasable.

The rotation imparting means (7) crosses the fuel tank (d) at right angles to the dividing surface through the tank retainer (6b) and the tank receiver (6c) of the fuel tank gripping means (6). It is for rotating about an axis (0) passing through the center, and is a substantially C-shaped frame (6) of the fuel tank gripping means (6).
It is installed in a).

The rotation angle detector (8) detects the rotation angle (θ) when the rotation imparting means (7) imparts rotation to the fuel tank (d) and sends it to the control device (10). .

The pressing force detector (9) detects the pressing force between the joining flange portion (c) of the fuel tank (d) and the lower electrode wheel (4) during the welding operation, and this pressing force is a predetermined value. When the temperature falls below the range, a signal is issued to the control device (10) of the multi-axis robot (5) to move the gripping means (6) of the fuel tank (d) downward to increase the pressing force to a predetermined value. is there.

The control device (10) is a multi-axis robot (5).
For independently controlling each axis of the fuel tank (d), the peripheral shape of the fuel tank (d), in particular, the flange portion (c) for joining.
The shape of the fuel tank (d) is preset and registered, and the fuel tank (d) is gripped at a predetermined position, the positioning movement to the seam welding position,
The carrying-out operation to a predetermined position after seam welding is registered as a handling program, and the multi-axis robot (5) is controlled based on this.

The apparatus according to the present invention has the above-mentioned structure, and the seam welding machine (2) is arranged so that the fuel tank (d) is supported by the multi-axis robot (5) through the fuel tank holding means (6). Between the upper and lower electrode wheels (3) and (4) of the fuel tank (d)
By arranging the joining flange portion (c) around the dividing surface and rotating the fuel tank (d), the periphery of the joining flange portion (c) is sequentially and continuously seam welded. By the rotation of the fuel tank (d), (B) of FIG.
As shown in Fig. 4, the radius of gyration (R) from the rotation center (0 ') of the fuel tank (d) to the welding position of the joining flange portion (c) changes. ) Position of the rotation center (0 ') of the multi-axis robot (5)
Change by controlling. Multi-axis robot (5)
Is controlled by detecting the rotation angle (θ) of the fuel tank (d) and determining the rotation angle (θ) and the preset peripheral shape of the fuel tank (d), that is, the shape of the joining flange portion (c). Based on the above, the change of the radius of gyration (R) from the center of rotation (0 ′) of the fuel tank (d) to the welding position of the joining flange portion (c) is expressed as a function of the rotation angle (θ) R = f.
Between the upper and lower electrode wheels (3) and (4) of the seam welder (2) in which the welding position of the joining flange portion (c) around the divided surface of the fuel tank (d) is always fixed. This is done by controlling the position of the rotation center (0 ') of the fuel tank (d) so that it is positioned through the multi-axis robot (5).
The fuel tank (d) naturally rotates around the shaft (0) by the rotation of the upper and lower electrode wheels (3) and (4), so that the seam welding is not necessary even if the rotation imparting means (7) is not provided. It is possible. That is, the rotation imparting means (7) is useful when positioning the seam welding start position, but is not necessary once seam welding has started.

Further, according to the present invention, as shown in FIG. 2 (A), spot welding (m) is performed in advance at a plurality of locations around the joining flange portion (c) of the fuel tank (d) which is divided into upper and lower parts. Then, the first temporary fixing is performed, and this is supplied between the upper and lower electrode wheels (3) and (4) of the seam welder (2) through the multi-axis robot (5), and the upper and lower electrode wheels (3) ( The pressing force of the joining flange portion (c) by 4) is alternately changed between strong and weak, and intermittent welding (n) in the shape of a broken line is applied to the periphery of the joining flange portion (c) at the time of strong pressure for second temporary fixing. In the above, in the second round, the pressing force of the upper and lower electrode wheels (3) and (4) is set to a constant high pressure, and the periphery of the joining flange portion (c) is continuously main welded. The higher pressure applied to the upper and lower electrode wheels (3) and (4) at the time of the second temporary fixing is set to such a high pressure that a weld lump (nugget) cannot be formed, and there is little welding distortion, and the upper and lower electrode wheels (3) ( 4)
The trajectory of is stable. In this way, by performing the second temporary fixing, the rigidity of the fuel tank (d) is significantly increased, and even if the pressing force of the upper and lower electrode wheels (3) and (4) is increased in the main welding, the flange portion for joining is joined. Since the shape of (c) is stable, the trajectory of the main welding will not be distorted at all. Spot welding (m)
Is carried out by a spot welder (not shown) in the previous step, and the multi-axis robot (2) carries in the fuel tank (d) from the previous step to the seam welder (2) of the present invention. Can be done.

The present invention is suitable for application to seam welding of fuel tanks for automobiles, but it can also be applied to other similar air-tight or liquid-tight container seam welding to obtain similar operational effects. .

[0024]

EFFECTS OF THE INVENTION According to the present invention, complicated jigs are unnecessary, and even if the shape of the fuel tank changes, it is possible to easily cope with the change in the shape of the fuel tank. (EN) A fuel tank seam welding method and apparatus capable of shortening a fuel tank manufacturing period and capable of automatically following and correcting wear of a lower electrode wheel only by controlling a multi-axis robot. .

[Brief description of drawings]

FIG. 1 is a side view showing a schematic configuration of an apparatus according to an embodiment of the present invention.

FIG. 2A is an explanatory view of a temporary fixing method according to the present invention,
(B) is an explanatory view of a method for automatically controlling a welding position according to the present invention.

FIG. 3 is an explanatory view of a fuel tank.

FIG. 4 is a schematic perspective view of a conventional device.

[Explanation of symbols]

 d Fuel tank 2 Seam welding machine 3 Upper electrode wheel 4 Lower electrode wheel 5 Multi-axis robot 6 Fuel tank gripping means 7 Rotation imparting means 8 Rotation angle detector 9 Contact detector 10 Control device

Claims (5)

[Claims] 1. A vertically divided fuel tank is supported at the tip of an arm of a multi-axis robot so as to be rotatable about an axis that is orthogonal to the dividing surface and passes through the center of the dividing surface. The joining flange portion around the dividing surface of the fuel tank is supplied between the upper and lower electrode wheels of the fixed seam welding machine while the dividing surface is horizontal, and the upper and lower electrode wheels press the joining flange portion. The upper and lower electrode wheels are rotated, and together with this, the rotation angle of the fuel tank is detected while rotating the fuel tank around the axis, and the fuel tank is joined from the center of rotation of the fuel tank based on this rotation angle and the preset peripheral shape of the fuel tank. The change in the radius of gyration of the welding flange up to the welding position is calculated as a function of the rotation angle, and the welding position of the joining flange around the dividing surface of the fuel tank is always fixed between the upper and lower electrode wheels of the seam welder. position A method for seam welding a fuel tank, wherein the position of the axis that is the center of rotation of the fuel tank is automatically controlled via a multi-axis robot. 2. A multi-axis robot which is spot-welded in advance at a plurality of locations around a joint flange portion of a fuel tank which is divided into upper and lower parts to perform first temporary fixing, and which is provided between upper and lower electrode wheels of a seam welding machine. The pressure of the upper and lower electrode wheels is changed alternately by changing the pressing force of the upper and lower electrode wheels. 2. The seam welding method for a fuel tank according to claim 1, wherein a constant strong pressure is applied to continuously perform main welding around the joining flange portion. 3. A fuel tank gripping means for rotatably supporting an upper and lower split fuel tanks rotatably around an axis that is orthogonal to the split surface and passes through the center of the split surface, and upper and lower electrode wheels are rotatable. A seam welder, which is supported so as to be able to approach and separate from each other, and is fixed, a rotation angle detector for the fuel tank, and the rotation angle detector detects the rotation angle by attaching the fuel tank gripping means to the tip of the arm. Based on the preset peripheral shape of the fuel tank, the change in the radius of gyration from the center of rotation of the fuel tank to the welding position of the welding flange is calculated as a function of the rotation angle, and used for joining around the dividing surface of the fuel tank. And a multi-axis robot in which the position of the shaft, which is the center of rotation of the fuel tank, is automatically controlled through a controller so that the welding position of the flange is always located between the upper and lower electrode wheels of the seam welder. A seam welding device for a fuel tank, which is characterized in that 4. The seam welding apparatus for a fuel tank according to claim 3, wherein the seam welding machine is provided with a function of alternately changing the pressing force between the upper and lower electrode wheels. 5. When the pressing force between the flange portion of the fuel tank and the lower electrode wheel of the seam welding machine is detected during the welding operation, and the pressing force is below a predetermined value, the fuel tank gripping means is moved downward. The fuel tank seam welding apparatus according to claim 3 or 4, further comprising a pressing force detector for outputting a signal to a control device of the multi-axis robot so as to increase the pressing force to a predetermined value.