JP2008183617A - Flat coil for electromagnetic seam welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat one-turn coil for electromagnetic welding which improves defects that a large power supply energy is needed in a conventional flat coil when welding an aluminum alloy thin plate to be hardly welded with respect to the flat one-turn coil for electromagnetic welding for electromagnetically welding a metal thin plate by solving. <P>SOLUTION: The flat one-turn coil 3 is connected to a power source 1 and a switch 2. A large pulse current runs in the coil by closing the switch 2. Since the spacing between wide peripheral parts 4B, 4C is partially changed, aluminum alloy thin plates 5A, 5B can be welded in an excellent energy efficiency. Since the narrow width of a current concentration part 4A is constant, the part is hardly deformed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coil for electromagnetic seam welding used in the field of assembling automobile parts, electronic parts and the like that require welding of thin metal plates such as aluminum alloys and copper.

Technical background

As a method for easily seam welding a thin metal plate such as an aluminum alloy or copper, which is said to be difficult to weld, there is an electromagnetic welding method considered by the present inventor (Patent Document 1). This electromagnetic welding method is an electromagnetic welding apparatus for seam welding a thin metal plate, for example, using a flat one-turn coil in which two grooves are added to a single metal plate material to form an E shape, and the width of the plate material is narrow. The narrow central part is used for the forward current, the wide peripheral part on both sides is used for the return current, the pulse current is reciprocated from the power source, and the narrow, narrow central part is used as the current concentration part. This is a method of seam welding a thin metal plate by heat generated by eddy current generated in the thin metal plate placed on and pressed by electromagnetic force. The present inventor has also filed a patent application for the invention of the coil improved with respect to the coil used in the electromagnetic welding method (Patent Document 2) and (Patent Document 3).
Japanese Patent No. 3751153 (FIG. 4) JP 2004-342535 A Japanese Patent Application No. 2006-263529

  The flat one-turn coil has the following excellent features. Unlike a planar coil around which an electric wire is wound, the inductance as a coil is small, and a large current is likely to flow. Due to the single plate shape, it is not easily damaged even if a large pulse current of 100 kA or more flows. The electromagnetic coupling between the coil (plate shape) and the material to be welded (metal thin plate) is strong. A thin metal sheet placed on one side (top) of the coil can be welded.

  Generally, a capacitor power source is used as a power source for the electromagnetic welding apparatus. The capacity of the capacitor power supply is 50 to 400 μF, and the charging energy is several kJ. A large pulse current of 100 kA or more flows through the coil for a short time of several 100 μs or less. The thickness of the metal thin plate (material to be welded) is 1 mm or less, and the length of the welded portion is 200 mm or less. When welding is performed by providing a gap of about 1 mm between stacked metal sheets, seam welding can be performed with energy efficiency due to the effect of collision of the two metal sheets at high speed (Patent Document 2). Further, when the collision is performed at a high speed, seam welding can be performed more efficiently when the collision is performed at an inclined angle (Patent Document 3).

  An outline of a flat one-turn coil that has been filed earlier and an electromagnetic seam welding apparatus that uses this coil to cause an oblique collision at high speed will be described (Patent Document 3). Next, problems of this flat plate one-turn coil will be described.

  FIG. 7 shows a schematic diagram of a typical flat one-turn coil used for the slant collision. (A) is a coil plan view and a discharge circuit, and (B) is a cross-sectional example perpendicular to the current direction of the coil central portion 4A. The flat plate-shaped one-turn coil 3 is composed of a single flat plate that is electrically insulated. The coil 3 is composed of a narrow and narrow central part 4A (current forward path), wide peripheral parts 4B and 4C (current return path) on both sides thereof, and a part 4D connecting these at one end side. . The width of the coil central portion 4A continuously decreases from the end in the longitudinal direction to the center in the longitudinal direction along the direction of current flow, and continuously increases from the center in the longitudinal direction. The coil material is chrome copper, and the plate thickness is 4 mm. The central portion 4A has a length of about 100 mm, a width of a maximum of 4 mm, and a minimum of 2 mm. This width is a minimum of 2 mm at the longitudinal center of the coil central portion 4A.

  FIG. 8 shows an outline of an electromagnetic seam welding apparatus using the flat plate-shaped one-turn coil 3 shown in FIG. FIG. 3A is a plan view and a discharge circuit, and FIG. 2B is a cross-sectional example of a BB portion in FIG. When the switch 2 is closed and a current is suddenly passed through the flat plate-shaped one-turn coil 3, the center portion 4A of the coil 3 has a narrow width at the center in the longitudinal direction. When the magnetic flux 7 intersects the aluminum alloy thin plates 5A and 5B which are overlapped with a gap, an eddy current flows through the lower alloy thin plate 5A by the electromagnetic induction action, and is heated. Further, since electromagnetic force acts on the eddy current, the lower alloy thin plate 5A is accelerated upward.

  At the center in the longitudinal direction of the central portion 4A of the coil 3 where the high magnetic flux density B is generated, the acceleration acting on the lower aluminum alloy thin plate 5A is large, and the alloy thin plates 5A and 5B in this portion are earlier in time than the other portions. collide. As a result, each part of the stacked aluminum alloy thin plates collides with a time difference. The colliding part moves at high speed. Further, the stacked alloy thin plates collide in an inclined state, not parallel to each other. Such a collision is called an inclined collision.

When the stacked aluminum alloy thin plates collide at a high speed as described above, a metal jet is generated. The metal jet has a strong force for cleaning the surface of the alloy thin plate. If such a metal jet function is added, seam welding can be efficiently performed with low power source energy (Non-Patent Document 1).
Edited by Japan Society for Technology of Plasticity "High Energy Speed Machining", Corona (April 1993) Page 183

  For example, when the aluminum alloy A5182 thin plate (thickness 1 mm) is overlapped with a gap of 1 mm, and collided with an inclination, and the energy of the power source required for seam welding over a length of 100 mm is about 2.5 kJ, It can be welded with about 20% lower power energy.

  Next, problems of the flat plate-shaped one-turn coil 3 will be described. In the flat plate-shaped one-turn coil 3 shown in FIG. 7, a narrow (2 mm) portion exists in the central portion of the coil. For this reason, after about 100 experiments, deformation was observed in the cross section of this narrow portion. If the experiment is continued thereafter, the deformation progresses and the electromagnetic coupling between the coil and the material to be welded (aluminum alloy thin plate) deteriorates, so that seam welding cannot be performed at a power source energy of about 2.5 kJ. At present, there is a problem in narrowing the width of the central portion of the coil because no coil material that can solve this deformation is found.

  Further, the width of the seam welded portion is not uniform. This width is narrow at the coil center and wide at the coil end. In a wide portion, the bonding strength may be extremely weak. The width of the seam welded portion is desired to be as uniform as possible from the appearance.

  As another coil structure that causes an oblique collision, there is a method in which the thickness of the coil central portion is changed instead of narrowing the width of the coil central portion (Patent Document 3). However, the current flowing through the coil often changes at a high frequency, and the current tends to flow concentrated on the coil surface. For this reason, the effect of changing the thickness of the coil central portion to cause an oblique collision is less likely to appear.

  Means for performing seam welding with high energy efficiency by making the welded material collide at a high speed without partially reducing the width of the central part of the flat one-turn coil or reducing the thickness of the coil in the following order. . The width of the seam welded portion is also relatively uniform.

(1) First, a flat one-turn coil 3 in which the width and thickness of the coil central portion 4A are constant and the widths of the wide peripheral portions 4B and 4C on both sides thereof are partially changed in three stages (FIG. 1). think of. The space between the coil central portion 4A and the peripheral portions 4B and 4C will be referred to as “cut” for simplicity. This cut width changes in three stages. As a numerical example, the width of the central portion 4A is 5 mm, the length is 150 mm, the widths of three stages of cuts are 3, 5, 7 mm, and the length is 50 mm.

(2) When a current is supplied to the coil 3, a reciprocating current is present in a relatively close portion where the cut width is narrow (3 mm). Therefore, in this portion, the magnetic flux density generated in the upper portion of the coil central portion 4A. Becomes smaller. On the contrary, the magnetic flux density generated in the upper part of the coil central portion 4A is increased in the portion having a large cut width (7 mm).

(3) Next, consider the flat plate-shaped one-turn coil 3 (FIG. 2) in which the cutting width is continuously changed. The magnetic flux density generated at the longitudinal end of the coil central portion 4A with a narrow cut width is small, and conversely, the magnetic flux density generated at the central portion with a wide cut width is large. As a result, when an aluminum alloy thin plate placed on top of this coil is placed and a large pulse current is rapidly applied to the coil, the alloy thin plate collides at a high speed and can be seam welded with high energy efficiency.

  As described above, the present invention provides a flat plate-shaped one-turn coil capable of causing energy-efficient electromagnetic seam welding by causing sloping collision of stacked metal thin plates at high speed without partially reducing the width of the coil central portion.

  Even when the flat one-turn coil according to the first and second aspects of the invention is used in place of the flat one-turn coil 3 of FIG. 8, electromagnetic seam welding can be similarly performed on a thin metal plate such as an aluminum alloy provided with a gap. At this time, in these flat plate-shaped one-turn coils, the magnitude of the magnetic flux density generated on the coil central portion 4A (current concentration portion) changes along the direction in which the current flows. As a result, the stacked metal sheets collide with each other with a slight time difference along the coil central portion 4A and are welded with high energy efficiency.

  If the flat plate-shaped one-turn coil according to the second aspect of the present invention is used, the width of the seam welded portion becomes substantially constant. The joint strength of the welded part does not become extremely weak in part. In addition, since the width of the coil central portion 4A (current concentration portion) is not partially reduced, deformation of this portion is relatively reduced.

  When this type of flat plate-shaped one-turn coil is used, it is possible to seam weld thin metal plates stacked with a gap in a liquid such as water. By causing the abrupt inclined collision, the water in the welded portion is pushed out from the welded portion to the outside one after another, and the portion where the water disappears is continuously welded (seam welding).

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 2 shows the width of the space between the coil central portion 4A and the peripheral portions 4B and 4C (referred to as “cut” for simplicity) along the direction of current flow from the longitudinal end of the coil central portion. The schematic diagram of the flat plate-shaped one-turn coil which is continuously increased and continuously decreased from the longitudinal center is shown together with the discharge circuit. Examples of coil materials and dimensions are shown below. The material is chrome copper and the plate thickness is 3 mm. The central portion 4A has a length of about 130 mm and a width of 5 mm. The cut width is a maximum of 7 mm and a minimum of 3 mm, and changes continuously.

  FIG. 3 shows an outline of an electromagnetic seam welding apparatus using the flat plate-shaped one-turn coil 3 shown in FIG. 3A is a plan view and a discharge circuit, and FIG. 3B is a cross-sectional example of the BB portion of FIG. When the switch 2 is closed and a current is rapidly passed through the flat plate-shaped one-turn coil 3, a magnetic flux 7 having a magnetic flux density B larger than the others is generated at the center in the longitudinal direction of the central portion 4A of the coil 3. In this portion, the electromagnetic force acting on the aluminum alloy thin plates 5A stacked with a gap is strong, and the alloy thin plates 5A and 5B in this portion collide with each other earlier in time than the other portions. As a result, the alloy thin plates 5A and 5B collide at high speed and are welded with high energy efficiency.

For example, two aluminum alloy A5182 thin plates (thickness 1 mm) with a gap of 1 mm are stacked and collided at an angle, and the energy of the power source required for seam welding over a length of 100 mm is approximately 2.7 kJ, and no collision occurs at an angle. Welding was possible with power source energy about 10% lower than the case. After the experiment about 100 times, a slight deformation was observed at the coil cutting tip. This deformation is solved by changing the tip of the cut portion as shown in FIG. 4 (Patent Document 4).
Japanese Patent Application No. 2006-285506

  FIG. 5 shows a schematic diagram of a flat plate-shaped one-turn coil in which the cut width is partially changed along the longitudinal direction of the central portion of the coil together with the discharge circuit. Examples of coil materials and dimensions are shown below. The material is chrome copper and the plate thickness is 3 mm. The central portion 4A has a length of about 130 mm and a width of 5 mm. Although most of the cut widths are 3 mm, they are partially changed to 4, 5, and 7 mm at five locations on one side. Even if such a coil is used, it is possible to make a collision at high speed and to perform energy efficient welding.

  FIG. 6 shows a plan view and a discharge circuit of a flat plate-shaped one-turn coil in the case of seam welding in a square shape. A portion of the coil central portion 4A where the current concentrates is divided into two at an angle of about 90 ° from the middle, and merges again to form a rectangular portion 8. The coil plate thickness is 3 mm, the width of the square-shaped portion 8 is 5 mm, and the length of one side of the square is about 30 mm. Since the interval between the quadrangular portion 8 and the peripheral portions 4B and 4C is changed, it is possible to make a seam weld in a quadrangular shape efficiently by colliding with each other in the same manner as a coil for seam welding in a straight line.

  It is a top view of the flat plate-shaped one-turn coil and discharge circuit used as the basis of this invention.   It is a top view of the flat plate-shaped one-turn coil and discharge circuit which show Example 1 of this invention.   It is the schematic of the electromagnetic welding apparatus which seam welds an aluminum alloy thin plate using the flat plate-shaped one-turn coil which shows Example 1 of this invention. (A) is a coil plan view and a discharge circuit, and (B) is a cross-sectional view perpendicular to the current direction of the central portion.   It is the top view which improved a part of flat plate-shaped one-turn coil which shows Example 1 of this invention.   It is a top view of the flat plate one-turn coil and discharge circuit which show Example 2 of the present invention.   It is a top view of the flat plate one-turn coil and discharge circuit which show Example 3 of the present invention.   1 is a schematic view of a typical electromagnetic welding apparatus using a flat one-turn coil. (A) is a plan view and (B) is a cross-sectional view.   It is the schematic which shows the method of arrange | positioning an aluminum alloy thin plate and a fixing tool to the coil upper part shown in FIG. 7, and performing electromagnetic welding. (A) is a plan view and (B) is a cross-sectional view.

Explanation of symbols

1 Power supply or capacitor power supply 2 Switch 3 Flat one-turn coil 4A Central part of flat one-turn coil (current concentration part)
4B, 4C Peripheral part of flat plate one-turn coil 4D Part 5A connecting the central part and peripheral part of flat plate one-turn coil Aluminum alloy thin plate (lower side)
5B Aluminum alloy sheet (upper)
6 Fixing tool 7 Magnetic flux 8 A rectangular part of a flat plate one-turn coil that is seam welded in a rectangular shape

Claims (2)

An electrically conductive metal plate is processed to provide a narrow current concentrator for flowing current from the power source, and a wide portion for supplying return current is provided in the remaining peripheral part. An electromagnetic welding apparatus that places a thin metal plate on a flat plate-shaped one-turn coil composed of a single insulated plate, energizes the coil from a power source to generate electromagnetic force, and welds the thin metal plate by this electromagnetic force. In
A flat one-turn coil in which the current is concentrated between a narrow width and a wide peripheral area.   2. The flat plate one-turn coil according to claim 1, wherein a width of the narrow current-concentrating portion is constant in the flat plate one-turn coil.

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