JP7258427B2 - spot welding method - Google Patents

Description

The present invention relates to a spot welding method.

In spot welding, two or more metal plates (steel plates) are sandwiched between a pair of electrodes and pressurized, and a high current is applied between the pair of electrodes to partially melt the metal plates due to resistance heat generation. , to form a nugget of the required size (see, for example, Patent Document 1).

For example, as shown in FIG. 7, when a plate assembly composed of two metal plates 101 and 102 is sandwiched and pressed between a pair of electrodes 103 and 104, as shown in FIG. Recesses 101a and 102a are formed in plates 101 and 102, respectively. In this case, the areas around the recesses 101a and 102a are lifted, forming a gap G between the metal plates 101 and 102 (sheet separation).

JP 2013-173155 A

For example, if a gap is formed between metal plates in a part that constitutes the vehicle body of an automobile, there is a risk of affecting steering stability, NV, and the like. Therefore, it is desirable to make the gap formed between the metal plates as small as possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a technical object of the present invention is to reduce gaps between metal plates that occur when a plurality of metal plates are joined by spot welding.

The present invention is intended to solve the above problems, and in a spot welding method in which a plurality of metal plates are sandwiched between a pair of electrodes and welded, in a state in which the plurality of metal plates are sandwiched and pressed by a pressing member, the pair of metal plates is pressed. Welding is performed using electrodes of

According to such a configuration, by sandwiching and pressing the plurality of metal plates by the pressing member together with the pair of electrodes, it is possible to suppress deformation of each metal plate due to the pressure of the electrodes. This makes it possible to minimize the gap formed between the metal plates during spot welding.

ADVANTAGE OF THE INVENTION According to this invention, the clearance gap between metal plates which arises when spot-welding a several metal plate can be made small.

It is a side view of a welding device. FIG. 3 is a partial cross-sectional view showing the main part of the welding device; FIG. 2 is a cross-sectional view along the line III-III in FIG. 1; It is a side view which shows 1 process of a spot-welding method. It is a side view which shows 1 process of a spot-welding method. It is a side view which shows 1 process of a spot-welding method. It is a side view showing a conventional spot welding method. FIG. 10 is an enlarged side view showing a main part of a conventional spot welding method;

EMBODIMENT OF THE INVENTION Hereinafter, it demonstrates, referring drawings for the form for implementing this invention. 1 to 6 show an embodiment of the spot welding method and welding apparatus according to the present invention.

As shown in FIG. 1, in this embodiment, as the members W to be welded, a first metal plate 1 and a second metal plate 2 are exemplified. Each of the metal plates 1 and 2 is elongated along the direction orthogonal to the plane of FIG. The first metal plate 1 has a hat-shaped cross section, and includes a flange portion 3 that overlaps a part of the second metal plate 2 and a vertical wall portion 4 that is inclined from the flange portion 3. , and a top plate portion 5 connected to the vertical wall portion 4 . The second metal plate 2 is configured in a flat plate shape. In this embodiment, the case where the overlapping portion of the flange portion 3 of the first metal plate 1 and the second metal plate 2 is welded will be exemplified.

As shown in FIG. 1, the welding device includes a welding gun 6. As shown in FIG. The welding gun 6 is supported by a robot arm and is capable of three-dimensional movement and attitude change including swing motion.

The welding gun 6 includes a main body 7, a movable electrode 8 and a fixed electrode 9 as a pair of electrodes, a driving section 10 for driving the movable electrode 8, pressing mechanisms 11a and 11b for pressing the workpiece W, and a welding transformer. 12 are mainly provided.

The main body 7 is made of metal having rigidity and supports the fixed electrode 9 , the driving section 10 and the welding transformer 12 . The body 7 has a support arm 13 that supports the fixed electrode 9 . Further, the main body 7 is internally provided with a cable for supplying power to the electrodes 8 and 9 and a water supply pipe for supplying cooling water for cooling the electrodes 8 and 9 (not shown).

The movable electrode 8 and the fixed electrode 9 are provided with tips 14a, 14b that contact the member W to be welded, and shanks 15a, 15b that support the tips 14a, 14b. The tips 14a, 14b are exchangeably attached to the shanks 15a, 15b. A shank 15 a of the movable electrode 8 is supported by a portion of the drive section 10 . A shank 15 b of the fixed electrode 9 is supported by the support arm 13 of the main body 7 .

The drive unit 10 includes a servomotor 16 , a motion conversion unit 17 and a movable arm 18 . The servomotor 16 is supported by the main body 7 with its rotating shaft directed downward. The motion converter 17 is connected to the rotating shaft of the servomotor 16 and converts the rotating motion of the rotating shaft into vertical motion. The movable arm 18 is connected to the motion conversion section 17 and configured to be linearly movable by the motion conversion section 17 . The movable arm 18 supports the shank 15 a of the movable electrode 8 and can move the movable electrode 8 toward or away from the fixed electrode 9 .

As shown in FIG. 1, the pressing mechanisms 11a and 11b include a first pressing mechanism 11a that presses the first metal plate 1 together with the movable electrode 8, and a second pressing mechanism 11a that presses the second metal plate 2 together with the fixed electrode 9. mechanism 11b. The first pressing mechanism 11a and the second pressing mechanism 11b have the same structure. In this embodiment, two first pressing mechanisms 11a are provided corresponding to the movable electrode 8, and two second pressing mechanisms 11b are provided corresponding to the fixed electrode 9. Each pressing mechanism 11a , 11b is not limited to this embodiment.

The first pressing mechanism 11a is fixed at a position near the movable electrode 8 via a first mounting member 19a. The second pressing mechanism 11b is fixed at a position near the fixed electrode 9 via a second mounting member 19b.

The first mounting member 19a and the second mounting member 19b have the same structure. As shown in FIG. 2, each mounting member 19a, 19b includes a mounting portion 20 attached to the shank 15a, 15b of each electrode 8, 9, and a support portion 21 for supporting each pressing mechanism 11a, 11b. The mounting portion 20 is formed in an annular shape and is fixed while being inserted into the shanks 15a and 15b. The support portion 21 has a plate shape and is integrally formed with the mounting portion 20 . The support portion 21 of the first mounting member 19a supports the two first pressing mechanisms 11a with a space therebetween. A movable electrode 8 is positioned between the two spaced apart first pressing mechanisms 11a. Similarly, the support portion 21 of the second mounting member 19b supports the two second pressing mechanisms 11b with a space therebetween. A fixed electrode 9 is positioned between the two spaced apart second pressing mechanisms 11b.

As shown in FIG. 2, each of the pressing mechanisms 11a and 11b includes a pressing member 22 that presses the members W to be welded (the first metal plate 1 and the second metal plate 2) and an urging member 22 that presses the pressing member 22. A biasing member 23 and a case 24 that houses a part of the biasing member 23 and the pressing member 22 are provided.

The pressing member 22 is made of an insulating member and has a rod-like or plate-like shape, and is configured to be movable relative to the electrodes 8 and 9 along a direction parallel to the shanks 15a and 15b of the electrodes 8 and 9. be done. The pressing member 22 is not limited to the above configuration, and may be a metal rod-shaped member or plate-shaped member coated with an insulating material.

The pressing member 22 includes a pressing portion 25 that contacts the member W to be welded, an engaging portion 26 that engages with the biasing member 23 , and a stopper 27 that regulates the position of the pressing member 22 .

The pressing portion 25 is a bar-shaped or plate-shaped portion protruding from a portion of the stopper 27 . As shown in FIG. 2, the pressing portion 25 protrudes at a distance D from the tips 14a and 14b of the electrodes 8 and 9 when not in contact with the member W to be welded. As a result, when the electrodes 8 and 9 are brought into contact with the members W to be welded, the pressing portion 25 contacts the members W to be welded earlier than the electrodes 8 and 9 .

The pressing portion 25 has a pressing surface 28 that contacts the member W to be welded at its tip. As shown in FIG. 3, the pressing surface 28 is configured in a rectangular shape, and has a first edge 28a parallel to the longitudinal direction of the hat shape of the first metal plate 1 (the direction indicated by symbol L in FIG. 3). and a second edge 28b, a third edge 28c facing the electrodes 8 and 9, a fourth edge 28d connecting the first edge 28a and the second edge 28b, and the first edge 28a A fifth edge portion 28e connected to the third edge portion 28c is provided.

The first edge 28a and the second edge 28b are configured linearly. The length dimension of the first edge portion 28a is set larger than the length dimension of the other edge portions 28b to 28e. The third edge portion 28c is formed in an arc shape corresponding to the curved surface shape (circular shape) of the tips 14a, 14b of the electrodes 8, 9. As shown in FIG. The fourth edge portion 28d and the fifth edge portion 28e are linear portions extending in a direction orthogonal to the first edge portion 28a and the second edge portion 28b.

In FIG. 3, the desirable range of the positional relationship between the electrodes 8, 9 and the pressing surface 28 is indicated by chain double-dashed lines N1, N2. Each two-dot chain line N1, N2 is a straight line passing through the center O of each electrode 8,9. The two-dot chain lines N1 and N2 are formed at predetermined angles θ1 and It is tilted at θ2. The angles θ1 and θ2 are approximately 45°, but are not limited to this. It is desirable that the pair of pressing surfaces 28 be positioned at least inside the two-dot chain lines N1 and N2 (within the angles θ1 and θ2). The pressing surface 28 according to the present embodiment is positioned within the range of the angles θ1 and θ2 related to the two-dot chain lines N1 and N2, and is configured in an elongated shape extending beyond this range.

The engaging portion 26 is configured in a columnar shape and protrudes from a portion of the stopper 27 in the direction opposite to the pressing member 22 .

The stopper 27 is housed inside the case 24 and configured as a plate-like body projecting outward from the outer surface of the pressing portion 25 . The stopper 27 restricts the position of the pressing member 22 by contacting the inner surface of the case 24 due to the biasing force of the biasing member 23 .

The biasing member 23 is composed of an elastic member such as a compression coil spring. An engaging portion 26 of the pressing member 22 is inserted through one end portion of the biasing member 23 . The other end of the biasing member 23 is supported by the case 24 . The biasing member 23 biases the pressing member 22 with an elastic force generated by compression.

The case 24 may be made of an insulating member or metal. The case 24 is supported by the support portions 21 of the mounting members 19a and 19b. The case 24 includes an opening 29 through which the pressing portion 25 of the pressing member 22 is inserted, and a support protrusion 30 that supports the biasing member 23 . The opening 29 has an opening area through which the pressing portion 25 can be inserted and which is smaller than the stopper 27 . With this configuration, the opening 29 functions as a guide portion that guides the pressing member 22 to move along its longitudinal direction. The support protrusion 30 is configured in a cylindrical shape and protrudes from the inner surface of the case 24 so as to face the engaging portion 26 of the pressing member 22 . An end portion of the biasing member 23 is inserted through the support protrusion 30 .

The welding transformer 12 is connected to a power source (not shown) and generates current necessary for welding. Welding transformer 12 is connected to electrodes 8 and 9 via a power cable to supply necessary current to electrodes 8 and 9 .

A method (direct spot welding method) of welding the first metal plate 1 and the second metal plate 2 using the welding apparatus (welding gun 6) having the above configuration will be described below.

In this method, first, the temporarily assembled first metal plate 1 and the second metal plate 2 are arranged between the fixed electrode 9 and the movable electrode 8, as shown in FIG. After that, as shown in FIG. 4, the welding gun 6 is moved to weld the portion to be joined P set between the first metal plate 1 and the second metal plate 2, and the fixed electrode 9 is moved. It is brought into contact with the second metal plate 2 . At this time, the pressing member 22 (pressing surface 28) of the second pressing mechanism 11b contacts the second metal plate 2 before the fixed electrode 9 does. When the fixed electrode 9 is brought into contact with the second metal plate 2 from this state, the pressing member 22 moves so as to retreat relative to the fixed electrode 9 . As a result, the biasing member 23 (coil spring) that biases the pressing member 22 is further compressed. Due to this compression, the biasing member 23 increases the force (elastic restoring force) that biases the pressing member 22 .

After that, the driving section 10 rotates the rotating shaft of the servomotor 16 to operate the movable arm 18 via the motion converting section 17 . The movable arm 18 brings the movable electrode 8 and the first pressing mechanism 11a closer to the part P to be joined. At this time, as shown in FIG. 5, the pressing member 22 (pressing surface 28) of the first pressing mechanism 11a contacts the flange portion 3 of the first metal plate 1 before the movable electrode 8 does. As shown in FIG. 6, the movable arm 18 further moves the movable electrode 8 to contact the first metal plate 1 (flange portion 3). The pressing member 22 moves so as to retreat relative to the movable electrode 8 . As a result, the biasing member 23 (coil spring) that biases the pressing member 22 is further compressed. Due to this compression, the biasing member 23 increases the force (elastic restoring force) that biases the pressing member 22 .

When the movable electrode 8 comes into contact with the first metal plate 1 , the portion to be joined P is sandwiched between the movable electrode 8 and the fixed electrode 9 . By the operation of the movable arm 18, the movable electrode 8 and the fixed electrode 9 apply pressure to the portion to be welded P with a predetermined pressure.

The pressing member 22 of the first pressing mechanism 11a and the pressing member 22 of the second pressing mechanism 11b press the first metal plate 1 and the second metal plate 2 at positions apart from the movable electrode 8 and the fixed electrode 9. It becomes a sandwiched state. The pressing forces of the pressing mechanisms 11 a and 11 b against the metal plates 1 and 2 are due to the elastic force (elastic restoring force) of the biasing member 23 . This pressing force is set to be smaller than the force with which the movable electrode 8 and the fixed electrode 9 press the portion P to be welded. In addition, the pressure force with which the movable electrode 8 and the fixed electrode 9 press the portion P to be welded is set in consideration of the reaction force generated by this pressing force.

After that, a suitable current is supplied from the welding transformer 12 to the electrodes 8 and 9, and the current is applied to the welded member W at the same time as the pressure is applied. As a result, a nugget N is formed in the portion to be joined P, and the nugget N is cooled, so that the first metal plate 1 and the second metal plate 2 are joined. The welding gun 6 repeats the above operation while changing the welding position, thereby welding the first metal plate 1 and the second metal plate 2 at a plurality of locations.

According to the present embodiment described above, the metal plates 1 and 2 tend to be deformed by the pressure applied by the electrodes 8 and 9, but the metal plates 1 and 2 are pressed by the pressing member 22 and thus deformed. , the deformation is suppressed. This makes it possible to make the gap between the first metal plate 1 and the second metal plate 2 as small as possible. Therefore, the automobile component manufactured by this method can contribute to the improvement of steering stability and NV.

In this embodiment, two pressing mechanisms 11a and 11b are arranged for each of the electrodes 8 and 9, and a pressing member 22 having a rectangular pressing surface 28 is arranged along the longitudinal direction L of each of the metal plates 1 and 2. Due to the arrangement, it is possible to press the pressing member 22 over a wide range in the longitudinal direction of the metal plates 1 and 2 . In addition, by pressing the flange portion 3 at a position near the vertical wall portion 4 of the first metal plate 1 with each pressing member 22, the end portion of the flange portion 3 on the side of the vertical wall portion 4 of the first metal plate 1 and the second metal plate 2 can be made as small as possible.

In addition, the present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. Various modifications can be made to the present invention without departing from the gist of the present invention.

In the above-described embodiment, an elastic body (compression coil spring) was exemplified as the biasing member 23 of the pressing mechanisms 11a and 11b, but the present invention is not limited to this configuration. The biasing member 23 may be composed of, for example, a fluid pressure cylinder or other various actuators.

In the above embodiment, the case where two metal plates 1 and 2 are joined by spot welding was illustrated, but the present invention is not limited to this aspect, and can be used when joining three or more metal plates.

In the above embodiment, the mounting members 19a and 19b are fixed to the shanks 15a and 15b of the electrodes 8 and 9, and the mounting members 19a and 19b support the pressing mechanisms 11a and 11b. It is not limited to this configuration. For example, the pressing mechanisms 11a and 11b have the mounting portions 20 of the mounting members 19a and 19b slidably attached to the shanks 15a and 15b of the electrodes 8 and 9, and the compression coil springs as the biasing members 23 are attached to the respective shanks. 15a and 15b, and a configuration in which the mounting members 19a and 19b are biased by the compression coil spring can be adopted. By fixing the pressing member 22 to the mounting members 19a and 19b and biasing the mounting members 19a and 19b and the pressing member 22 with the biasing member 23, the member to be welded W can be pressed. In this example, the mounting portion 20 slides along the shanks 11a and 11b, thereby functioning as a guide portion that guides the pressing members 19a and 19b along the longitudinal direction of the shanks 11a and 11b. With the above configuration, it is possible to reduce the size and simplification of the pressing mechanisms 11a and 11b.

REFERENCE SIGNS LIST 1 first metal plate 2 second metal plate 8 movable electrode 9 fixed electrode 22 pressing member

Claims (1)

In a spot welding method in which a plurality of metal plates are sandwiched between a pair of electrodes and welded,
A step of performing welding with the pair of electrodes in a state in which the plurality of metal plates are sandwiched and pressed by pressing members,
The metal plate includes a first metal plate and a second metal plate,
The first metal plate has a flange portion superimposed on the second metal plate, and an elongated vertical wall portion erected from the flange portion,
The pressing member has a pressing surface that presses the flange portion of the first metal plate,
The spot welding, wherein the pressing surface has a linear edge that contacts the flange of the first metal plate along the longitudinal direction of the vertical wall of the first metal plate. Method.

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