KR100660227B1 - Friction stir spot-welding apparatus - Google Patents

Abstract

A friction stir spot-welding equipment which can weld plural sheets to an accurate depth and improves bonding strength accordingly by measuring displacement of a frame of the spot-welding equipment, thereby constantly controlling an inserting depth of a welding pin is provided. A friction stir spot-welding equipment(100) comprises: a frame(102) having a support(116) mounted on a lower portion(104b) thereof such that sheets(160) to be welded are placed on the support; a rotation mechanism(108) of which an end is connected to an upper portion(104a) of the frame such that a welding pin(114) is mounted on the end of the rotation mechanism; a drive part(112) for rotating the rotation mechanism; a displacement measuring instrument for measuring displacement of the frame; and a transfer part(110) for correcting position of the rotation mechanism according to the displacement of the frame. The friction stir spot-welding equipment further comprises: a calculation part(140) for calculating a displacement measured in the displacement measuring instrument; a transfer control part(130) for controlling the transfer part according to displacement calculation of the calculation part; and a control part(150) for controlling the entire operation including welding operation.

Description

Friction Stir Spot Welding Device {FRICTION STIR SPOT-WELDING APPARATUS}

1 is a block diagram of a rotating stirring spot welding apparatus according to the prior art.

FIG. 2 is a view for explaining spot welding using the apparatus of FIG. 1.

3 is a cross-sectional view of a pair of sheet materials spot welded with the apparatus of FIG. 1.

Figure 4 is a schematic diagram of a rotary stirring spot welding apparatus according to the present invention.

5 is a graph showing the relationship between the insertion depth of the pin and the weld strength in the rotary stirring spot welding apparatus.

Figure 6 is a flow chart showing the operation of the rotary stirring spot welding apparatus according to the present invention.

7 is a cross-sectional view of a pair of plate welded by a rotary stirring welding device according to the present invention.

8 is a graph comparing the performance of the spot welding operation according to the prior art and the present invention.

<Explanation of symbols of main parts in drawings>

100: spot welding device 102: frame

108: rotating mechanism 110: transfer unit

112: drive unit 114: rotary mechanism pin

116: support 118: displacement measuring unit

120: drive control unit 130: transfer control unit

140: calculator 150: control unit

The present invention relates to a friction stir spot welding device that overlaps and welds a plurality of sheets using frictional heat. More specifically, it is possible to weld to a precise depth by measuring the displacement of the frame of the spot welding apparatus of the present invention to control the insertion depth of the welding pins constantly.

Spot welding is a welding technique that does not require airtight or watertight welding of two or more overlapping sheets in the form of spots. The most common form of spot welding is electric resistance spot welding. This technique joins the plate by using Joule heat generated by applying a current between two electrodes to flow a current while the plate is fixed. This technology is mainly used for joining plates of 3mm or less in automobiles and home appliances.

However, as the demand for lightweighting has recently increased, the demand for welding of nonferrous metals such as aluminum and magnesium has increased. In general, lightweight nonferrous metals have low electrical resistance and large thermal conductivity. This property causes the electric resistance welding to be difficult.

Electric resistance welding, which is mainly used in industry, uses AC power. This technology is suitable for welding steel with high resistance and low thermal conductivity, but it is difficult to weld due to reactive power at the point where the direction of energization changes in light weight material. .

To remedy this problem, welding with direct current power or three-phase low frequency power is used. However, these technologies are limited in their use because of the high cost of the device and the high consumption of electrical energy.

Therefore, a friction stir spot welding technique has been proposed as an alternative. Friction stir spot welding is a technique that performs welding with heat generated by rubbing a pin attached to the tip of a rotary tool with a material to be joined. Further, in order to avoid interference with the material to be welded, the friction stir spot welding device is made of a C-shaped frame.

Conventional friction stir spot welding devices are provided as part of a system such as a robot. The conventional spot welding apparatus has a structure in which the driver moves up and down with the rotary tool, so that the volume of the apparatus is increased and the load weight is also increased. Therefore, Japanese Patent Laid-Open Publication No. 2002-137067 as shown in Figs. 1 and 2 has been proposed to solve such a problem.

According to the above document as shown in Figs. 1 and 2, the friction stir spot welding device 20 generally consists of a frame 21 of C shape (mirror shape C shape in the drawing). Rotation transmission means 30 for transmitting the driving force of the motor 25 to the rotating shaft 26 is installed on the upper side of the frame, and the head 40 with the rotor 22 is installed at the tip of the rotating shaft 26. . On the lower end of the frame 21 opposite the rotor 22, a support 23 for supporting the welding plate materials P1 and P2 is provided.

Accordingly, when the pair of plates P1 and P2 to be welded are placed on the support 23 and the rotating shaft 26 is rotated, the plate 51 is formed by the pressure and heat applied by the pin 51 of the rotor 22 through friction stir. , P2) is welded to each other in the form as shown in FIG.

However, the friction stir spot welding device 20 according to the related art is generated according to the pressure applied to the support 23 through the pin 51 of the rotor 22 and the rotation of the rotary shaft 26 to generate frictional force. There is a problem that the frame 21 is bent by a force such as torsion. In this case, since the insertion depth of the pin 51 is shallow, the stirring action of the material is not sufficient, and the bonding between the upper and lower plate materials P1 and P2 is not properly performed. In order to solve this problem, there is a method of increasing the rigidity of the frame 21. However, this causes an increase in weight and an increase in frame size, which is not preferable.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, the object of the present invention is to measure the displacement of the frame in a rotary stir spot welding device to weld to a precise depth by constantly controlling the insertion depth of the welding pin Accordingly, the bonding strength is improved.

In order to achieve the above object of the present invention, the present invention includes a frame mounted on the bottom support for mounting the plate to be welded; A rotary mechanism equipped with a welding pin at an end connected to an upper side of the frame; A driving unit for rotating the rotating mechanism; A displacement measuring device measuring a displacement of the frame; And it characterized in that it provides a friction stir spot welding device comprising a transfer unit for correcting the position of the rotating mechanism according to the displacement of the frame.

Spot welding apparatus of the present invention includes a calculation unit for calculating the displacement measured by the displacement measuring device; The apparatus may further include a transfer control unit controlling the transfer unit according to the displacement calculation of the calculation unit.

The spot welding apparatus of the present invention may further include a controller for controlling the entire operation, and the controller is preferably mounted on the frame or the system in which the spot welding apparatus is mounted.

In the spot welding apparatus of this invention, the said displacement measuring device is a strain gauge, It is characterized by the above-mentioned.

In the spot welding apparatus of the present invention, the displacement measuring device measures a distance of at least two points of the frame.

In the spot welding apparatus of this invention, the said displacement measuring device is a laser displacement sensor, It is characterized by the above-mentioned.

In addition, the spot welding apparatus of the present invention is configured to measure the displacement occurring in the frame during the welding operation and to control the position of the rotary mechanism based on this value to maintain a constant insertion depth of the rotary mechanism pin. .

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

Figure 4 is a schematic diagram of a rotary stirring spot welding apparatus according to the present invention.

The rotary stirring spot welding apparatus 100 according to the present invention is mounted as part of an entire system (not shown), such as a robot. In addition, the spot welding apparatus 100 is rotatably mounted in the C-shaped frame 102, the main shaft 106 connected to the upper end 104a of the frame 102 and extended downward, and the main shaft 106. The rotating mechanism 108, the transfer unit 110 connecting the main shaft 106 to the frame 102 so that the position can be adjusted, and the driving unit 112 mounted above the transfer unit 110 to rotate the rotating mechanism 108. Include. A pin 114 for spot welding is mounted at the end of the rotary mechanism 108, and a pair of plate 160 to be welded with a support 116 is installed at the lower end 104b of the frame 102 opposite thereto. ). Of course, the plate 160 may be three or more.

On the other hand, the displacement measuring instrument 118 is mounted to the frame 102 to measure the displacement of the frame 102. In addition, the spot welding apparatus 100 of the present invention is the frame 102 measured by the drive control unit 120 for controlling the drive unit 112, the transfer control unit 130 for controlling the transfer unit 110, the displacement measuring unit 118. It further includes a calculator 140 for calculating the displacement of the) and a controller 150 for controlling the overall operation, including the welding operation. Here, the driving controller 120, the transfer control unit 130, the calculator 140, and the controller 150 may be mounted on the frame 102 of the spot welding apparatus 100. Alternatively, it may be mounted on a system such as a robot (not shown) to control the spot welding apparatus 100 of the present invention. In addition, the driving controller 120, the transfer controller 130, and the calculator 140 may be implemented as part of the controller 150.

Displacement meter 118 may be implemented by, for example, a strain gauge. The strain gauge is attached to the frame 102 so that its length changes when displacement of the frame 102 occurs. Changing the length of the strain gauge causes a change in resistance, so a voltage change is detected when a current flows through the strain gauge. The detected value is transferred to the calculator 140, and the calculator 140 calculates the value to measure the displacement of the frame 102. In this case, the transfer control unit 130 controls the transfer unit 110 to control the position of the rotary mechanism 108.

Alternatively, the displacement meter 118 may be implemented as a laser displacement sensor.

Hereinafter, the reason for controlling the position of the rotating mechanism 108 will be described with reference to FIG. 5. 5 is a graph showing the relationship between the insertion depth of the pin and the weld strength in the rotary stirring spot welding apparatus.

As shown in Figure 5, the strength of the weld portion increases with the insertion depth of the pin, but rather decreases when it is above a certain depth. In other words, when the insertion depth of the pin is insufficient, the weld strength is low because the interface between the plates is not formed, but sufficient weld strength is obtained when the insertion depth of the pin is appropriate. On the other hand, when the insertion depth is too deep, the weld strength is rather reduced.

Therefore, the optimum insertion depth is determined according to the type, thickness, etc. of the plate, and the pin 114 of the rotary mechanism 108 is inserted into the plate 160 in accordance with the insertion depth.

However, even if the optimal insertion depth is determined in this way, if the frame 102 bends due to a torsion or the like during the rotation of the rotary mechanism 108, the pin 114 of the rotary mechanism 108 has a predetermined insertion depth. It will not be inserted into 160. That is, even if the pin 114 of the rotation mechanism 108 is lowered according to the insertion depth, the position of the actual plate 160 is changed by the twisting of the frame 102.

Therefore, in the present invention, the displacement measurer 118 and the calculator 140 are used as described above to prevent this.

The displacement measuring instrument 118 may use a strain gauge or the like as described above, and preferably the displacement of the frame 102 may be known by measuring two points of the frame 102. In detail, the position of any two points of the frame 102 is measured while the load welding device 100 is not loaded, and the output of the displacement measuring instrument 118 according to the load is measured in the state where the load is applied. You can measure and calculate the change in position of any two points based on this data. More preferably, calculating the displacement of three or more points of the frame 102 can perform more precise correction.

In this way, the displacement measuring unit 118 and the calculator 140 measure the displacement of the frame 102 due to the torsion, etc., and transmit the displacement to the control unit 150. The control unit 150 controls the transfer control unit 130 based on the data. Control the transfer unit 110 through. As a result, the transfer unit 110 corrects the position of the rotary mechanism 108 based on the control signal, thereby allowing the pin 114 of the rotary mechanism 108 to be inserted into the plate 160 with an optimal insertion depth.

Next, the operation of the rotary stir spot welding apparatus according to the present invention will be described with reference to the flowchart of FIG. 6.

First, the specimen, that is, the plate 160 is mounted on the support 116 and the working conditions are set (S102), and then the operation is started (S104).

When the driving unit 112 is operated by the control of the driving control unit 120, the rotating mechanism 108 is lowered (S106) to start the welding operation (S108).

The displacement measuring unit 140 and the calculator 140 measure the displacement of the frame 102 and determine whether the displacement is greater than the set value (S110).

If the frame displacement is larger than the set value, the transfer control unit 130 controls the transfer unit 110 to correct the position of the rotary mechanism 108 (S122), and continues the welding operation.

If the frame displacement does not exceed the set value, the welding operation is continued, and then the welding is properly performed (S112).

If the welding was not performed properly, go back to S110 to perform the previous operation. If the welding is properly performed, the welding is terminated (S114).

Then, the rotating mechanism 106 is raised (S116) and the entire operation is finished (S120).

In this way, if a displacement occurs in the frame 102 during the welding operation, precise welding operation can be performed by correcting the position of the rotating mechanism 104 by this displacement.

Thus, the cross section of a pair of plate welded using the rotary stirring spot welding apparatus of the present invention will be described with reference to FIG.

As shown in FIG. 7, it can be seen that the plastic flow of the material occurs at the interface between the upper plate and the lower plate, so that bonding is normally performed. In particular, it can be seen that the width W2 of the junction is greater when compared to that of the prior art of FIG. 3.

Then compare the performance of the spot welding operation according to the prior art and the present invention with reference to the graph of FIG.

As can be seen in Figure 8, the bonding strength of the present invention is higher than that of the prior art. In addition, in the prior art, the deviation between the upper limit and the lower limit is large around the average value M2, whereas the present invention shows a small deviation around the average value M2. This high and stable bond strength is achieved by measuring the displacement of the frame as described above and thus correcting the position of the rotating mechanism 106.

As described above, the rotary stir spot welding apparatus of the present invention can measure the displacement of the frame and constantly control the insertion depth of the welding pin to weld to a precise depth, thereby improving the bonding strength.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be understood that modifications and variations can be made.

Claims (7)

A frame mounted at a lower end of the support for mounting the plate to be welded; A rotary mechanism equipped with a welding pin at an end connected to an upper side of the frame; A driving unit for rotating the rotating mechanism; A displacement measuring device measuring a displacement of the frame; And Friction stir spot welding device comprising a transfer unit for correcting the position of the rotating mechanism in accordance with the displacement of the frame. The method of claim 1, A calculation unit calculating a displacement measured by the displacement meter; Friction stir spot welding apparatus further comprises a transfer control unit for controlling the transfer unit in accordance with the displacement calculation of the calculation unit. The friction stir spot welding device according to claim 1 or 2, further comprising a control unit for controlling the overall operation, wherein the control unit is mounted to the frame or the system in which the spot welding device is mounted. 3. The friction stir spot welding device according to claim 1 or 2, wherein the displacement measuring device is a strain gauge. 3. The friction stir spot welding device according to claim 1 or 2, wherein the displacement measuring device measures a distance of at least two points of the frame. The friction stir spot welding device according to claim 1 or 2, wherein the displacement measuring device is a laser displacement sensor. 3. The method according to claim 1 or 2, characterized in that it is configured to measure the displacement occurring in the frame during the welding operation and to control the position of the rotating mechanism based on this value to keep the insertion depth of the rotating mechanism pin constant. Friction stir spot welding device.

Images