JPH05200560A - Method and equipment for resistance welding - Google Patents

Abstract

PURPOSE:To prevent spatters and burrs from being drawn into a part inside diameter side by forming energizing paths on the inside diameters of parts having holes, carrying an electric current in the opposite direction to a welding current simultaneously with welding energizing and forming a magnetic field to negate the electromagnetic force. CONSTITUTION:Two parts 5 and 6 having holes to be welded are pressurized between an upper electrode 3 and a lower electrode 4 and the current required for welding is applied from a welding transformer 10. At the same time, the current in the opposite direction to the welding current is carried to an electromagnetic balance electrode 8 from a transformer 13 for a reverse current. Since the current flows through the energizing paths passing through the inside diameters of the parts 5 and 6 to be welded from the lower part to the upper part and anticlockwise magnetic flux is generated, this is balanced with magnetic flux remaining on the outside and welding is performed without drawing the spatters and burrs into the inside of the parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applicable to welding a part having a hole penetrating the center of a part to be welded (a part having a hole).
A projection is formed on one of the surfaces to be welded of the two perforated parts to be welded, and the projection and the other perforated part are brought into contact with each other, and the contact portion is pressed between welding electrodes to conduct electricity. The present invention relates to a resistance welding method and apparatus for fusion-bonding contact portions. More specifically, when the welding current is applied, the electromagnetic forces of the welding current that simultaneously flow through the multiple protrusions act on each other to lose the force that magnetically attracts spatter and burrs to the inside of the weld, causing spatter to occur during welding. TECHNICAL FIELD The present invention relates to a resistance welding method and apparatus in consideration of preventing burrs from adhering to the inner diameter of a perforated component.

[0003]

2. Description of the Related Art In resistance welding, it is well known that spatters and burrs generated during welding are pulled by an electromagnetic force generated by a welding current. The resistance welding device that welds by applying a magnetic field that cancels the electromagnetic force generated by the welding current flowing from the welding transformer to the electrode is
For example, Japanese Patent Laid-Open No. 58-53385 and Japanese Patent Publication No. 2-61876 have been proposed.

That is, in the former welding method, a welding transformer for supplying a welding current to the object to be welded is arranged on the left and right sides of the electrode holding the object to be welded through a conductor, and the welding current from the welding transformer causes the welding transformer. The conductors are arranged so that the spatter is scattered in the direction away from the workpiece by the electromagnetic force.

On the other hand, in the latter welding method, a magnetic material is placed in a high density portion of the magnetic field generated around the projection when the welding current is applied, and the magnetic field is canceled in the direction of canceling the magnetic field generated around the projection when the welding current is applied. Welding is performed by generating a magnetic field in the body.

However, in the former case, when welding a part having a hole penetrating in the center (a part having a hole), particularly when projection welding a plurality of annular projections arranged around the penetrating hole. The electromagnetic force acting in the central direction cannot be canceled due to the interaction of the magnetic field generated by the welding current flowing through each protrusion, and spatter and burrs are likely to occur inside the through hole.

That is, for example, when currents are simultaneously applied to the four protrusions from the top to the bottom as shown in FIG. 2, the inner magnetic fluxes cancel each other out, and the outer magnetic fluxes remain. A force in the central direction (F) acts on the point,
Spatter adheres to the inside when welded normally.

In such a case, spatter and burrs are likely to adhere to the inside of the through hole, particularly in welding of a gas for a fuel injection pump and a fly weight, which are made of sintered metal as the object to be welded. It takes a lot of time to strictly inspect and remove it in a separate process. If spatters or burrs remain inside the holes, they become harmful substances that enter the engine together with the fuel and cause engine troubles.
Therefore, it is absolutely necessary to avoid attaching spatter and burrs to the inner diameter of the component.

On the other hand, in the latter method, in the case of welding with an alternating current, the magnetic body for canceling the magnetic field must also generate an alternating magnetic field, which is impossible with a permanent magnet. In addition, the coil has a complicated shape and the number of protrusions must be arranged, which is troublesome and impractical. The present invention was developed in view of such problems.

[0010]

The problem to be solved by the present invention is to weld a perforated part having a plurality of projections formed around the through hole and a perforated part which is superposed in contact with the projection. Conventionally, when welding current flows through multiple protrusions at the same time during energization, the electromagnetic forces generated by the welding currents flowing through each protrusion act on each other to generate a force that pulls spatter, etc. toward the center of the component, causing spatter. The point is that it was not possible to completely remove harmful substances such as burrs and burrs. In addition, the complexity of arranging the magnetic body around the protrusion is unavoidable.

[0011]

According to the method of the present invention, one perforated part having a plurality of projections formed on the surface to be welded and the other perforated part in contact with the plurality of projections of the perforated part. In a resistance welding method in which a holed part and a pair of welding electrodes are energized under pressure to join the two parts together, an energization path is formed in the inner diameter of the perforated parts that are overlapped, and the welding current is defined in this energization path. The main feature is that a current in the opposite direction is applied at the same time as welding current is applied to form a magnetic field around the projection to be welded to cancel the electromagnetic force generated by the welding current. The present invention is particularly effective for projection welding in which the perforated part to be welded is made of sintered metal. Further, the present invention is extremely effective for projection welding of one of the perforated parts, which is a gear of a fuel pump having a plurality of projections, and the other perforated part, which is a fly weight holder.

Next, as a device for carrying out the method of the present invention, a device for projection welding two perforated parts in which a plurality of projections are provided on one surface to be welded and which are superposed, A pair of welding electrodes that apply welding force and welding current to two perforated parts to be welded, and the inner diameter of the perforated parts are inserted, and at the same time as welding energization, a current in the opposite direction to the welding current is passed to perform welding. The main features are that it includes an electromagnetic force balance electrode forming an energization path for generating a magnetic flux in a direction of canceling an electromagnetic force generated by an electric current, a welding power source and a reverse current power source.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of an apparatus for carrying out the method of the invention. In the figure, 1 is an upper platen, and a pressure cylinder (not shown)
It is supported by the upper arm to move up and down. The lower platen 2 is supported by the lower arm. An upper electrode 3 is supported by the upper platen. A lower electrode 4 is supported by the lower platen. Reference numerals 5 and 6 are perforated parts to be welded, for example, having through holes 0 located concentrically at the centers of sintered metal parts such as a fly weight holder and a gear of a fuel pump. On one of the perforated parts 5 which is in contact with the pressing surface of the upper electrode 3, a plurality of protrusions P are formed along the annular shape around the inner diameter thereof. On the other perforated part 6 that contacts the pressing surface of the lower electrode 4, a guide 7 that is fitted into the inner diameter of the perforated part 5 and positioned, and a guide 7 that is fitted and positioned in the groove of the lower electrode.
^' Is provided. Reference numeral 8 denotes an electromagnetic force balance electrode, which vertically moves through holes of the upper and lower electrodes on the same axis (aa) and is insulated from the lower electrode 4 by an insulating material 14. This electrode forms a current-carrying path in the inner diameter of the object to be welded as a means to prevent spatter and burrs.A current in the direction opposite to the welding current flows when the welding current is applied and is generated in the inner diameter direction of the part by the welding current. A magnetic field is generated to cancel the electromagnetic force that occurs. Reference numeral 9 is a cylinder for driving the electromagnetic force balance electrode. Reference numeral 10 is a welding transformer, in which the upper platen 1 is connected to the positive side of the output terminal, and the lower platen 2 is connected to the negative side via conductors 11 and 12. A reverse current transformer 13 is arranged at a position symmetrical to the welding transformer 13 and each output terminal is connected to the electromagnetic force balance electrode 8 so that the current flows in the direction opposite to the direction of the current flowing from the welding transformer. On the conductor 1
The transformer for welding 10 is connected to the welding transformer 10 via 5 and 16 with the polarities being positive and negative.

Next, the operation will be described. After the upper platen 1 is lifted by the pressurizing cylinder and the upper electrode 3 is opened, two perforated parts to be welded are combined and the electromagnetic force balance electrode 8 is inserted into the inside diameter of the part and positioned to position the electrode surface of the lower electrode 4. Set to. When the setting is completed, the pressurizing cylinder is operated to pressurize the combined parts between the upper electrode 3 and the lower electrode 4, and the upper and lower electrodes are supplied with a current required for welding from the welding transformer 10 and, at the same time, a reverse current is applied. A current in the direction opposite to the welding current is passed from the working transformer 13 to the electromagnetic balance electrode 8. The current flows through a current-carrying path that passes through the inner diameter of the part to be welded from bottom to top. As described above, when a current in the direction opposite to the welding current is passed through the center of the perforated component at the same time when the welding current is applied, a counterclockwise magnetic flux is generated as shown in FIG. Also, welding can be performed without pulling the burr inward. Therefore, it is possible to prevent spatter and burrs adhering to the inner diameter of the component, and improve the welding quality. In this case, the current in the opposite direction to the welding current may be small.

In the embodiment of the method of the present invention, the welding transformer and the reverse current transformer are arranged symmetrically. However, the present invention is not limited to this embodiment. For example, the influence of the magnetic field of the welding transformer causes welding. If burr is generated on the outside of the projection on the side opposite to the work transformer, it is necessary to install another welding transformer to cancel this electromagnetic force. In this case, two reverse current transformers are required. It is desirable to use. Also, the secondary side of the welding transformer is 2 coils 4
In the case of a terminal, the same operation can be obtained even if one coil is used for welding and the other coil is used for the reverse direction by using one welding transformer as a reverse current transformer.

[0016]

As described above, according to the method of the present invention, when a plurality of protrusions are arranged and welded around the hole of a perforated part, the periphery of each protrusion is affected by the welding current flowing through the plurality of protrusions. The force that pushes in the direction of the center of the part due to the combined magnetic flux generated in the part is canceled by applying a reverse current to the center of the part to be welded, and the electromagnetic force generated by the welding current is balanced, and spatter and burrs are drawn to the inside diameter of the part. Can be welded without.

Further, according to the apparatus of the present invention, one welding transformer can be used together for reverse current. Also, the reverse current transformer can be symmetrically arranged on the existing welding transformer, and since only the electromagnetic balance electrode is added for positioning the work, the structure is simple and the spatter scattering is easily prevented. As a result, it is possible to realize a welding device having a simple structure and a low cost, which can save the post-process equipment effective for removing spatter and burrs as in the conventional case.

[Brief description of drawings]

1 is a cross-sectional view showing in principle one example of an apparatus for carrying out the method of the present invention.

FIG. 2 is a magnetic flux distribution diagram showing a principle of canceling out inner magnetic fluxes when currents are simultaneously applied to four protrusions from top to bottom.

FIG. 3 is a magnetic flux distribution diagram showing the principle in the case where a force in the central direction (F) acts on each protrusion due to the combined magnetic flux remaining on the outside and the spatter adheres to the inside.

FIG. 4 is a magnetic flux distribution diagram for explaining the principle of the present invention.

[Explanation of symbols] 1 upper platen 2 lower platen 3 upper electrode 4 lower electrode 5 perforated part 6 perforated part 7 guide 8 electromagnetic force balance electrode 9 cylinder 10 welding transformer 11 conductor 12 conductor 13 reverse current transformer

Claims (5)

[Claims] 1. A welding electrode forming a pair of one perforated component having a plurality of protrusions formed on the surface to be welded and the other perforated component superposed in contact with the plurality of protrusions of the perforated component. In the resistance welding method in which pressure is applied between the two parts to join them together, a current-carrying path is formed in the inner diameter of the overlapped perforated parts, and a current in the direction opposite to the welding current is passed through this current-carrying path simultaneously with welding current-carrying. A resistance welding method characterized in that a magnetic field for canceling an electromagnetic force generated by a welding current is formed around a projection to be welded. 2. The resistance welding method according to claim 1, wherein the perforated part to be welded is made of sintered metal. 3. The resistance according to claim 1, wherein one of the perforated parts to be welded is a gear of a fuel pump having a plurality of projections, and the other of the perforated parts is a fly weight holder. Welding method. 4. A device for performing projection welding of two perforated parts, wherein one surface to be welded is provided with a plurality of projections and is overlapped, wherein the two perforated parts to be welded have a necessary welding force. A pair of welding electrodes that give pressure and welding current,
An electromagnetic force balance electrode that is inserted into the inner diameter of the perforated part, and that flows a current in the direction opposite to the welding current at the same time as welding current is applied to form a current passage for generating a magnetic flux in a direction that cancels the electromagnetic force generated by the welding current. , A resistance welding apparatus including a welding power source and a reverse current power source. 5. The resistance welding apparatus according to claim 5, wherein the current value in the opposite direction is smaller than the welding current value.