JP2013169590A - One side spot welding equipment and one side spot welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide one side spot welding equipment and a one side spot welding method, by which a workpiece is welded satisfactorily even when eccentricity is generated in a contact pressure between the workpiece and a welding electrode.SOLUTION: In one side spot welding equipment 1, welding is performed by making an electrode abut only from upper surface side of a workpiece W against a welding region P of the workpiece W which is constituted by superposing a flange part 111 and a panel 120. The one side spot welding equipment 1 includes: a welding electrode 11 which abuts on the workpiece W from one side; a ground electrode 12 which abuts on the workpiece W from one side; and a ground electrode position-adjusting means for adjusting the position of the ground electrode 12 so that an energizing route A1 formed between the welding electrode 11 and the ground electrode 12 may be eccentric on the front side where the contact pressure between the welding region P and the welding electrode 11 is lower centering around the welding electrode 11.

Description

  The present invention relates to a one-side spot welding apparatus and a one-side spot welding method for welding by applying an electrode only from one side of a workpiece.

  As a method of joining workpieces made by stacking a plurality of metal welded members, spot welding is performed by energizing the workpiece while abutting the electrode with a predetermined pressure and melting the metal with resistance heat generated by the energization. It has been known. Spot welding is broadly classified into two-side spot welding in which a workpiece is sandwiched between a welding electrode and a ground electrode, and one-side spot welding in which a welding electrode and a ground electrode are brought into contact with only one side of the workpiece (see Patent Document 1).

  The welding quality (welding strength, etc.) in such spot welding is related to the shape / position, etc., of the nugget (joining part) formed at the boundary portion of the plurality of members to be welded. For example, in one-side spot welding, it is preferable that a nugget that is elliptical in a side view and circular in a plan view is formed almost directly below a welding electrode.

Japanese Patent Application Laid-Open No. 2011-3271

  By the way, as a welding part by one-side spot welding, for example, a welding part for welding panels (outer panel, inner panel, etc.) constituting a vehicle body, and a panel and a pillar (center pillar, front pillar, etc.) are welded. There is a welding site to do. Specifically, a welded portion is configured by overlapping a flange portion formed on the outer peripheral edge of the panel and a mating member (a flange portion or the like of another panel).

  On the other hand, as a means of promoting weight reduction and cost reduction of the vehicle, the above-described flange portion tends to be short, that is, the width of the flange portion tends to be small. Thereby, the case where a welding electrode etc. contact | abut to the welding site | part which comprises a short flange part is increasing.

  Then, as shown in FIG. 5, the panel main body 112 rising from the flange portion 111 exists in the vicinity of the welded part P that contacts the welding electrode 11, and therefore, the surface direction of the welded part P (perpendicular to the welded electrode 11). ), The reaction force (flexibility) is different. As a result, the contact pressure between the welding electrode 11 and the welded part P has a distribution that is high inside the flange portion 111 (the rear side in FIG. 5) and low outside the flange portion 111 (the front side in FIG. 5). That is, since the panel body 112 is present inside the flange portion 111 and the rigidity is high and it is difficult to bend, the contact pressure is high. On the other hand, the outside of the flange portion 111 is easy to bend and the contact pressure is low.

  And in this state where the contact pressure centered on the welding electrode 11 is biased, the ground electrodes 12 and 12 are arranged on both sides of the welding electrode 11 in parallel with the end face of the flange portion 111, and normally energized. As the melting of the side with higher contact pressure proceeds, the nugget Q does not have a circular shape in a plan view (viewed in the axial direction of the welding electrode 11), but becomes a shape closer to the side with the higher contact pressure. Etc.) may decrease (see FIG. 5B).

  Therefore, an object of the present invention is to provide a one-side spot welding apparatus and a one-side spot welding method that can weld a workpiece satisfactorily even when the contact pressure between the workpiece and the welding electrode is uneven.

  As a means for solving the above-mentioned problems, the present invention is a one-side spot welding apparatus that welds a workpiece by welding an electrode only from one side of the workpiece to a welding portion of a workpiece in which a plurality of members to be welded are stacked. A welding electrode that comes into contact with the workpiece from one side, a ground electrode that comes into contact with the workpiece from one side, and an energization path formed between the welding electrode and the ground electrode, A one-side spot welding apparatus comprising: an earth electrode position adjusting unit that adjusts a position of the earth electrode so as to be eccentric to a side where a contact pressure between a welding site and the welding electrode is low.

  As means for solving the above-mentioned problems, the present invention provides a one-side spot for welding by welding a welding electrode and a ground electrode only from one side of the workpiece to a welding portion of a workpiece formed by stacking a plurality of members to be welded. In the welding method, the position of the ground electrode is adjusted so that a current-carrying path formed between the weld electrode and the ground electrode is eccentric to a side where the contact pressure between the welded part and the weld electrode is low This is a one-side spot welding method characterized by:

  According to such a configuration, the energization path formed between the welding electrode and the ground electrode by the ground electrode position adjusting means is on the side where the contact pressure between the welding site and the welding electrode is low, centering on the welding electrode. Adjust the position of the ground electrode so that it is eccentric. When energized in the state adjusted in this way, the energization path formed between the welding electrode and the ground electrode is eccentric to the side where the contact pressure between the welding site and the welding electrode is low with the welding electrode as the center. It becomes easy to energize the side where the contact pressure is low.

  Then, (1) the amount of heat generated on the side with a high contact pressure mainly due to the high contact pressure, and (2) the amount of heat generated on the side with a low contact pressure mainly due to the eccentricity of the energization path, It becomes easy to become equal, and it becomes easy to form a circular nugget in a plan view in a welding part. Thereby, a workpiece | work can be welded favorable.

  ADVANTAGE OF THE INVENTION According to this invention, even if the contact pressure of a workpiece | work and a welding electrode has biased, the one side spot welding apparatus and the one side spot welding method which can weld a workpiece | work favorably can be provided.

It is a front view of the one side spot welding apparatus which concerns on this embodiment. It is a side view of the earth electrode concerning this embodiment. It is a perspective view of the welding electrode and ground electrode which concern on this embodiment. It is a top view explaining the one-side spot welding method which concerns on this embodiment, (a) is energizing (under welding), (b) shows after welding. It is a top view explaining the one-side spot welding method which concerns on a comparative example, (a) is energizing (under welding), (b) shows after welding. It is a top view explaining the one-side spot welding method which concerns on a modification.

  An embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, a one-side spot welding apparatus 1 includes a flange portion 111 (see FIG. 3) of a panel 110 (member to be welded) such as an inner panel constituting a vehicle body, and a plate-like panel 120 (welded to be welded). This is a spot welding apparatus in which the welding electrode 11 is brought into contact with only the upper surface side (one side) of the workpiece W on the welding portion P of the workpiece W formed by superimposing the member).

≪Configuration of one-side spot welding equipment≫
The one-side spot welding apparatus 1 includes a welding gun 10, a servo motor 21 (pressurizing mechanism), a power supply circuit 31, an input device 41, and a control device 50. Such a one-side spot welding apparatus 1 is incorporated, for example, at the tip of an arm of a welding robot.

<Welding gun>
The welding gun 10 includes a welding electrode 11 on the + (plus) pole side, two ground electrodes 12 on the-(minus) pole side, and a welding electrode holding portion 13 that holds the welding electrode 11.

<Welding gun-welding electrode>
The welding electrode 11 has a round bar shape, and its tip (lower end in FIG. 1) is brought into contact with the upper surface of the welded part P of the workpiece W. A proximal end portion (upper end portion in FIG. 1) of the welding electrode 11 is inserted into and fixed to the welding electrode holding portion 13. That is, the welding electrode holding part 13 holds the welding electrode 11, and the welding electrode 11 and the welding electrode holding part 13 are integral.

<Welding gun-ground electrode>
The ground electrode 12 is parallel to the welding electrode 11 in the initial state, and is arranged with the welding electrode 11 as the center of symmetry with a distance L between the left and right sides of the welding electrode 11.

  As shown in FIG. 2, the base end portion 12a of the ground electrode 12 is detachably attached to the adapter 14 by bolts 17a and nuts 17b. Specifically, a bolt 17a is inserted into the base end portion 12a, and a long hole 12b extending in the front-rear direction is formed. Thereby, the earth electrode 12 can slide with respect to the adapter 14 in the front-rear direction, and the relative position of the earth electrode 12 with respect to the adapter 14 can be adjusted.

  That is, the energization path A <b> 1 (see FIG. 4A) formed between the welding electrode 11 and the ground electrode 12 is a contact between the welding site P and the welding electrode 11 with the welding electrode 11 as the center in plan view. The earth electrode position adjusting means for adjusting the position of the earth electrode 12 so as to be eccentric (to be deviated) toward the low pressure side (front side) includes a long hole 12b, a bolt 17a and a nut 17b. Yes.

  The adapter 14 has a shaft 14 a at the upper part thereof, the shaft 14 a is inserted into the insertion hole 13 a of the welding electrode holding part 13, and the shaft 14 a (earth electrode 12) can be moved up and down with respect to the welding electrode holding part 13. ing. A flange 14b is formed at the upper end of the shaft 14a to prevent the shaft 14a from falling off the welding electrode holding portion 13.

  A compression coil spring 15 is interposed between the welding electrode holding part 13 and the adapter 14. The compression coil spring 15 biases the ground electrode 12 toward the workpiece W, and causes the ground electrode 12 to be in good contact with the workpiece W during welding (energization). However, the spring force of the compression coil spring 15 is such that welding proceeds and the welding electrode 11 sinks with respect to the workpiece W after the welding electrode 11 contacts the workpiece W. Even if it is displaced, the compression coil spring 15 is degenerated and the ground electrode 12 is set to a weak spring force that does not displace relative to the workpiece W.

<Servo motor>
The servo motor 21 moves the welding gun 10 (welding electrode holding portion 13) in the vertical direction of FIG. 1 according to a command from the control device 50, and pressurizes the welding part P of the workpiece W with the welding electrode 11. It is. The voltage sensor 22 detects the voltage applied to the servo motor 21 and outputs it to the control device 50. Therefore, when the welding electrode 11 comes into contact with the workpiece W, the voltage detected by the voltage sensor 22 increases, so that the control device 50 detects when the welding electrode 11 is in contact. Further, the amount of sinking of the welding electrode 11 (the amount of displacement after contact with the workpiece W) is detected by the amount of rotation of the servo motor 21. However, it is good also as a structure which attaches a displacement sensor and detects the displacement amount (sinking amount) of the welding electrode 11. FIG.

<Power supply circuit>
The power supply circuit 31 is a circuit for applying a current for spot welding so as to pass through the welding electrode 11 and the ground electrode 12 in accordance with a command from the control device 50. The + terminal of the power circuit 31 is connected to the welding electrode 11, and the − terminal of the power circuit 31 is connected to the ground electrode 12. Such a power supply circuit 31 includes an AC power supply, an inverter, a switching circuit, and the like.

<Input device>
The input device 41 is a device in which an operator inputs a contact pressure of the welding electrode 11, a welding current value, a welding time (energization time), and the like, and includes a keyboard and the like. Then, the input device 41 outputs the input information to the control device 50.

<Control device>
The control device 50 is a control device that electronically controls the one-side spot welding device 1 and includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like, and according to programs stored therein, The device is controlled to execute various processes.

≪Operation of single-side spot welding equipment, single-side spot welding method≫
Next, the operation of the one-side spot welding apparatus 1 and the one-side spot welding method will be described with reference to FIGS.

<Welding site>
Here, the welding part P is demonstrated.
The welding part P is a part where the nugget Q for joining the flange portion 111 and the panel 120 is to be formed, and has a circular shape in plan view. And the welding electrode 11 is contact | abutted on the upper surface of the welding site | part P, and after welding, the nugget Q which is circular in a plan view and elliptical in a side view is formed.

  Further, the width (length in the front-rear direction in FIG. 3) of the flange portion 111 constituting the welded portion P is small, and a panel body 112 that rises upward from the rear end portion of the flange portion 111 is formed behind the welded portion P. Has been. Thereby, in the width direction (front-rear direction) of the flange portion 111, the reaction force (rigidity) of the welded portion P increases toward the rear panel body 112 and toward the front end surface of the front flange portion 111). Get smaller. That is, the welded part P is less likely to bend toward the panel body 112 and is more likely to bend toward the front end surface of the flange portion 111.

  Therefore, when the axial direction of the welding electrode 11 is perpendicular to the welding part P (flange 111), the welding electrode 11 and the welding part P when the welding electrode 11 is brought into contact with the welding part P at a predetermined pressure are used. In plan view, the contact pressure increases from the center of the welding electrode 11 toward the panel body 112 (rear) and decreases toward the front end surface (front) of the flange portion 111.

In the one-side spot welding method, the energization path A1 formed between the welding electrode 11 and the ground electrode 12 is decentered to the front side where the contact pressure between the welding site P and the welding electrode 11 is low with the welding electrode 11 as the rotation center. In this manner (see FIG. 4A), the position of the ground electrode 12 is adjusted, that is, the ground electrode 12 is slid forward (to the end face side of the flange portion 111) with respect to the welding electrode 11.
When there is no bias in the contact pressure, that is, when two flat plates are welded, for example, one welding electrode 11 and two ground electrodes 12 are arranged in a straight line.

  Here, the degree of eccentricity of the energization path A1, that is, the degree of sliding of the ground electrode 12, is, for example, pressure-sensitive paper by the pressure applied during energization (welding) by the welding electrode 11 and the welded part P (flange 111). As the difference in contact pressure in the front-rear direction (contact pressure distribution) increases, the amount of eccentricity (the amount of slide of the ground electrode 12) may increase. Then, according to the slide amount calculated in this way, the ground electrode 12 is slid to the front side (the side with low contact pressure) (see FIG. 2).

  In addition, as (1) the workpiece W (especially the flange portion 111 on the welding electrode 11 side) becomes thicker, (2) the eccentricity increases as the melting point of the workpiece W (especially the flange portion 111 on the welding electrode 11 side) becomes higher. It is good also as a structure corrected so that it may become.

  Also, welding conditions (outer diameter of welding electrode 11, welding current value, applied pressure, etc.) and specifications of welded part P (workpiece W material / thickness, position of welded part P (distance from panel body 112, etc.)) ) And the amount of eccentricity are stored in advance in the control device 50, and the control device 50 stores the current welding conditions and the specifications of the welding part P input by the operator using the input device 41. It is good also as a structure which calculates the amount of eccentricity based on the database which has. An actuator that slides the ground electrode 12 in the front-rear direction may be provided, and the actuator may be driven based on the amount of eccentricity calculated by the control device 50.

  Next, the control device 50 drives the servo motor 21 to lower the welding electrode 11 and the ground electrode 12.

  Then, the control device 50 detects that the welding electrode 11 has come into contact with the flange portion 111 due to an increase in the voltage detected via the voltage sensor 22, and then causes the servomotor 21 to have a predetermined applied pressure. While controlling the voltage applied to the power supply, the power supply circuit 31 is controlled to apply a welding current.

  Then, as shown in FIG. 4 (a), when the ground electrode 12 is slid forward, the energization path A1 formed between the welding electrode 11 and the ground electrode 12 is centered on the welding electrode 11. It becomes a state eccentric to the front side.

  As a result, in the front-rear direction, (1) the amount of heat generated on the side with the high contact pressure (rear side) mainly due to the high contact pressure, and (2) the contact mainly due to the eccentricity of the energization path A1. The amount of heat generated on the low pressure side (front side) is likely to be equal, and a circular nugget Q is easily formed in the welded part P in plan view (see FIG. 4B). That is, the deviation of the heat generation amount due to the bias of the applied pressure immediately below the welding electrode 11 is alleviated by the deviation of the heat generation amount due to the bias of the energization path A1.

  For example, after a predetermined time has elapsed, the control device 50 controls the power supply circuit 31 to turn the welding current OFF (0 A), and then controls the servo motor 21 to control the welding gun 10 (welding electrode 11, The ground electrode 12) is raised and the one-side spot welding is finished.

≪Effect of one-side spot welding equipment (welding method) ≫
According to such a one-side spot welding apparatus 1, the following effects are obtained.
By decentering the energization path A1 formed between the welding electrode 11 and the ground electrode 12 on the front side where the contact pressure of the welding electrode 11 is low, (1) the contact pressure mainly resulting from the high contact pressure. The heat generation amount on the higher side (rear side) and (2) the heat generation amount on the lower contact pressure side (front side) mainly due to the eccentricity of the energizing path A1 are likely to be equal, A circular nugget Q is easily formed in a plan view (see FIG. 4B). Thereby, the flange part 111 and the panel 120 can be favorably welded.

≪Modification≫
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, For example, it can change as follows.

In the above-described embodiment, the configuration in which the ground electrode 12 slides in the front-rear direction is illustrated. However, for example, the ground electrode 12 may be configured to rotate in an arc shape without changing the distance L from the welding electrode 11. .
In addition, for example, as illustrated in FIG. 6, a configuration in which the ground electrode 12 is moved to the front side while being away from the welding electrode 11, that is, a configuration in which the distance L between the ground electrode 12 and the welding electrode 11 is variable may be employed. With this configuration, the angle θ between the reference line and the imaginary line passing through the welding electrode 11 and the ground electrode 12 is smaller than the configuration in which the ground electrode 12 is slid only on the front side (see FIG. 4). Become. The reference line is a virtual line passing through the welding electrode 11 and the ground electrodes 12 and 12 arranged in a line on the straight line (see FIG. 5A).

  In the above-described embodiment, as shown in FIG. 3, the configuration in which the welding electrode 11 and the like are in direct contact with the upper surface of the flange portion 111 having different reaction forces is exemplified. The structure which contact | abuts to the lower surface of the panel 120 may be sufficient.

  In the above-described embodiment, the form in which the reaction force of the flange part 111 (welded part P) is different depending on the panel body 112 rising from the vicinity of the flange part 111 is exemplified, but other forms may be used. For example, a configuration in which a welded portion of a middle thickness portion of a flat plate whose thickness is gradually different from large, medium, and small may be used.

DESCRIPTION OF SYMBOLS 1 One side spot welding apparatus 11 Welding electrode 12 Ground electrode 12b Long hole (Earth electrode position adjustment means)
13 Welding electrode holding part 13a Insertion hole 50 Control device 110, 120 Panel 111 Flange part A1 Current path P Welding part Q Nugget

Claims (2)

A one-side spot welding apparatus for welding by welding an electrode only from one side of the workpiece to a welding portion of a workpiece formed by stacking a plurality of members to be welded,
A welding electrode that contacts the workpiece from one side;
A ground electrode that contacts the workpiece from one side;
The position of the ground electrode is such that a current-carrying path formed between the weld electrode and the ground electrode is eccentric to the side where the contact pressure between the weld site and the weld electrode is low with the weld electrode as the center. Earth electrode position adjusting means for adjusting
A one-side spot welding apparatus comprising: It is a one-side spot welding method in which a welding electrode and a ground electrode are brought into contact with and welded only from one side of the workpiece to a welding portion of a workpiece formed by stacking a plurality of members to be welded,
The position of the ground electrode is such that a current-carrying path formed between the weld electrode and the ground electrode is eccentric to the side where the contact pressure between the weld site and the weld electrode is low with the weld electrode as the center. The one-side spot welding method characterized by adjusting the above.

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