JPH07124754A - Projection welding method - Google Patents

Abstract

PURPOSE:To exactly detect the central position of projection of projection welding, to hold strength of projection welding and to speed up welding. CONSTITUTION:The distance of the recessed part surface from the specified position in the Z-axis direction vertical to the welding plate surface on the upper side of a recessed part 11 of the projection formed on plates to be welded is measured continuously in the X-axis direction of the welding plate surface. The central point X12 of a cross section side of 1 of the recessed part is detected from a value of the distance Z of this recessed part. In addition, the distance in the Z-axis direction is measured continuously in the Y-axis direction of the welding plate surface passing the central point X12 which is measured and a maximum depression point Z1 of the recessed part is retrieved from the obtained value of the distance Z of the recessed part and the center (X12, Y12) of a depressed part is detected. The central point obtained by detection is made to the central point Q of the recessed part of the projection and the center of an electrode is conformed to the central point to perform projection welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection welding method, and more specifically, the present invention relates to a method for detecting the center position of a projection for projection welding.

[0002]

2. Description of the Related Art Conventionally, in projection welding, for example, as shown in FIG. 2, a small projection is provided on one or both of the objects to be welded, and the materials 1 and 2 to be welded are pressed by electrodes 5 and 6, Welding is performed by concentrating the welding current and electrode pressure on the part.

The welding is performed by providing the protrusions by specifying the welded portions by providing the protrusions, contacting the laminated plate only between the identified welded portions, and applying the welding current intensively to the contact portions. This is because the flow current density is increased and a steep heat is generated in the welded portion to enable effective welding.

In the above arrangement, the center P of the two electrodes is aligned with the center Q of the protrusion, and a welding current is applied while applying a pressing force to the plate to be welded between the electrodes. Due to the momentary application of a large current, the current concentrates on the small contact parts of the protrusions formed on the work piece, high heat is generated due to the resistance of the contact parts, the periphery of the protrusions melts and fuses, and the parts to be welded are joined together. To be done. The ideal form of this welding is that the nugget formed in the weld is formed in a substantially perfect circle 8 centering on the protrusion before melting.

Details of the contents relating to projection welding are described in the following documents and the like.・ "Introduction to resistance welding course text for field engineers"
(Light Structure Bonding Research Committee, Japan Welding Society), "Resistance welding phenomenon and its application (1), spot welding
Top ”(Welding Society of Japan, Resistance Welding Research Committee, Welding Society of Japan, Technical Material No. 7, August 1982).

[0006]

However, in the above welding, when the electrode center P at the time of welding coincides with the projection center Q, the nugget formed by welding grows in a perfect circle, but the electrode center When P deviates from the projection center Q, the nugget does not grow in a perfect circle. In this case, for example, an elliptical shape as shown in FIG. This elliptical weld 81 lacks uniformity in the welded state, and may have a weaker strength than a perfect circle, especially with respect to a force perpendicular to the direction of the minor axis L2 of the nugget (direction of arrow in FIG. 4). Are known. To quickly and accurately detect the center of the protrusion, that is, the optimum electrode position,
This is an important issue in order to utilize high-speed welding, which is an advantage of projection welding, and to secure welding strength.

It is an object of the present invention to provide a projection welding method capable of accurately detecting the center position of a projection of projection welding, and maintaining the strength of the projection welding while enabling high-speed welding.

[0008]

In order to achieve the above object, the projection welding method of the present invention is such that a pair of objects to be welded, each having a plate-shaped portion, is provided on the back side of at least one plate-shaped portion with the other plate. A protrusion that abuts the back side surface of the plate-shaped portion is provided, and the recessed portion formed on the front side surface of the plate-shaped portion corresponding to the shape of the protrusion is aligned with the center of the pair of electrodes, and the pair of welding objects It is a projection welding method that sandwiches the contact parts from each front side, pressurizes and energizes to weld both plate-like parts, and recesses the distance from a predetermined position in the direction intersecting the front side surface of one plate-like part. From the first cross-sectional shape measuring step of continuously measuring in the first transverse direction across the portion and the distance obtained by the first cross-sectional shape measuring step, the start point and the end point of the depressed side of the depressed portion and this starting point And find the center point of the end point The recessed shape detection step and the distance from a predetermined position in the second transverse direction passing through the center point at a right angle to the first transverse direction and intersecting the surface of one plate-like portion with the recessed portion A second cross-sectional shape measuring step of continuously measuring in the second transverse direction that crosses, and a maximum depression point detecting step of detecting a maximum depression point from the distance of the depression portion obtained by the second transverse shape measuring step. It is characterized in that projection welding is performed by aligning the center lines of the pair of electrodes with the maximum depression point obtained by the maximum depression point detection step.

The starting point and the ending point of the depression side may be calculated from the amount of change in distance. In addition, the first cross-section shape measuring step is performed a plurality of times, and the result obtained by detecting the start point and the end point and the center point of the start point and the end point from the data of the plurality of distances obtained by the plurality of times of execution is good.

[0010]

According to the projection welding method of the present invention,
The distance from a predetermined position in the direction intersecting the front side of one plate-like part is continuously measured across the depression, and the starting and ending points and the center of the depression side of the depression are calculated from the distance obtained by this measurement. The point is detected, the distance from a predetermined position in the direction perpendicular to the above continuous measurement direction and passing through the center point is continuously measured, and the maximum depression point is determined from the distance of the depression obtained by this measurement. Detection is performed, and projection welding is performed by aligning the center line of the electrode with the maximum depression point. Therefore, the center of the electrode can be aligned with the contact portion between the protrusion forming the recess and the back side surface of the other plate-shaped portion.

[0011]

Embodiments of the projection welding method according to the present invention will now be described in detail with reference to the accompanying drawings. With reference to FIG. 1, in order to explain the procedure of the embodiment of the present invention, the shape of the projection of the plate to be welded is conceptually shown. Hereinafter, the configuration of the present invention will be described in detail with reference to FIG. 1 and related drawings after FIG.

The positional relationship between the electrodes 5 and 6 for projection welding and the plates 1 and 2 to be welded and the form of the nugget 8 formed at the weld are conceptually shown in FIG.
For example, a protrusion is formed on one plate 1 of the two plates to be welded 1 and 2. The protrusions of the protrusions are arranged in contact with the other plate 2. While the two electrodes 5 and 6 apply pressing force from both sides of the two plates to the center of the convex portion,
Weld by applying an instantaneous surge current. The nugget 8 formed by welding has a circular shape as shown in FIG. In order to obtain welding by forming such a circular nugget, it is an important condition that the center Q of the convex portion and the center P of the electrode coincide with each other as described above.

It is assumed that the shape of the convex portion formed on the upper side plate 5 of the plate to be welded is such that the edge of the deformation point viewed from the upper side is a substantially circular shape 11, and the side sectional shape is a substantially curved shape. An example will be described below based on this condition.

A distance sensor in the same direction as the upper electrode 5 is provided as a sensor for searching the center of the convex portion of the upper plate. That is, the surface shape of the upper plate is measured by measuring the surface of the upper plate as a distance from a predetermined reference position. The distance sensor used for this measurement is based on, for example, the principle of an optical three-point measuring method using a laser.
Further, although its structure is not shown, the sensor has a structure in which the distance measuring axis of the sensor is substantially perpendicular to the surface of the upper plate and the structure is movable in the direction parallel to the upper plate.

Based on the above conditions, the following procedure
The center position Q of the protrusion is measured. The procedure from the measurement of the center position to the start of welding will be described based on the flowchart of FIG.

In step S10, the distance sensor is moved in one X-axis direction of the top plate 1 to measure the planar shape of the top plate. A graph of the measurement results obtained in this measurement is shown in FIG. In step S12, a refraction point X1 on the surface of the first upper plate and a refraction point X2 on the surface of the second upper plate are detected from the ratio of the variation amount of the distance Z from the sensor.

In step S14, the center position X12 of the two refraction points X1 and X2 is calculated by the following equation (1).

X12 = X1 + (X2-X1) / 2 (1) In step S16, the surface distance of the upper surface plate in the Y direction, which is perpendicular to the X direction, is measured at the position X12. A conceptual diagram of the measurement result is shown in FIG. From this measurement result, in step S18, the first refraction point Y1 and the second refraction point Y2 are detected by the same method as the detection of the refraction points X1 and X2 on the X axis.

In step S20, the center position Y12 of the two refraction points Y1 and Y2 is calculated by the equation (2) below.

Y12 = Y2 + (Y1-Y2) / 2 (2) The intersection point (X12, Y12) of the two axial positions X12 and Y12 obtained above is obtained as the center Q of the protrusion. In step S22, the center P of the electrodes 5 and 6 is moved to the center position (X12, Y12), and welding is executed in step S24.

In measuring the center position Q of the above-mentioned protrusion,
The shape of the protrusion is assumed to be circular on the surface and curved on the side, but it is common to form a realistic protrusion by die processing such as pressing, and the above assumptions necessary for detection are substantially satisfied. Be done.

<Variation> The above-described measurement of the center position of the protrusion is a basic procedure, and various auxiliary procedures are added to the actual procedure in order to improve the reliability of the measurement.

For example, the measurement is performed a plurality of times. In the measurement of the center position in the X-axis direction, the average value of the measurement results X12 _{k obtained} by changing the position in the Y-axis direction, Xav = ΣX12 _k /
Let k, be the center point. Or the distance between measurement points | X2
-X1 | is less than the reference value L, | X2-X1 | ≤L, and the measurement is discarded.

As another method, it is checked whether the position Z1 of the position X12 in the Z-axis direction is the maximum depression point. The same method can be applied to the position Z2 in the Y-axis direction. According to this method of measuring the maximum depression point, the center position of the protrusion is directly searched, which is a more direct measurement method than the calculation of the center position from the depression shape that is the edge of the recess. .

As another method, there is also a method of detecting the point where the distance between the two bending points is maximum and finding the center axis position of the circle.

In each of the above-mentioned various methods, which is the main body and which is the assist for confirmation is determined by the accuracy of the actual measurement, the measurement speed, the required accuracy, and the like. It is of course effective to alternately combine these different methods.

It should be noted that the above-mentioned embodiment is an example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, the distance sensor may be of another type such as a radio wave type or a sound wave type.

[0028]

As is apparent from the above description, in the projection welding method of the present invention, the depth of the depressed portion is measured on one side, and from the distance obtained by this measurement, the starting point, the end point and the center point of the depressed side are measured. Then, the depth of the depression passing through this center point is measured in the direction perpendicular to the above-mentioned one side, and the center line of the electrode is aligned with the maximum depression point obtained by this measurement to perform projection welding. Therefore, the center of the electrode can be aligned with the contact portion between the protrusion and the back side surface of the other plate-like portion, and projection welding with a high welding effect can be performed.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a procedure of a projection welding method of the present invention, in which (A) is a hole viewed from above a protrusion, (B) is a measured distance graph in the X-axis direction, and (Y) is Y. It is a measurement distance graph of an axial direction.

FIG. 2 is a conceptual diagram of projection welding, (A)
Is an example of the relationship between the electrode and the axial position of the plate to be welded, and (B) is an example of the planar shape of the nugget.

FIG. 3 is a conceptual diagram of projection welding, (A)
Is an example of the relationship between the electrode and the axial position of the plate to be welded, and (B) is an example of the planar shape of the nugget.

FIG. 4 is a perspective view of a weld portion in which a nugget is formed in an elliptical shape.

5 is a flowchart showing a procedure for measuring the center position of a protrusion based on FIG.

[Explanation of symbols]

 11 Projection hole, X1, X2, Y1, Y2 Bending point of projection hole, Q Center point of bending hole. 1

Claims (3)

[Claims] 1. A projection that is in contact with the back side surface of the other plate-shaped portion is provided on the back side surface of at least one plate-shaped portion of the pair of objects to be welded, each of which has a plate-shaped portion, and corresponds to the shape of the projection. Then, the recessed portion formed on the front side surface of the plate-shaped portion and the center of the pair of electrodes are aligned, and the abutting portions of the pair of objects to be welded are sandwiched from the respective front sides, and both are pressed and energized. In a projection welding method for welding a plate-shaped portion, a distance from a predetermined position in a direction intersecting the front side surface of the one plate-shaped portion is continuously measured in a first transverse direction across the recessed portion. From the sectional shape measuring step 1 and the distance obtained by the first sectional shape measuring step,
A depression shape detecting step of detecting a start point and an end point of the depression side of the depression portion, and a center point of the start point and the end point; and a second step of passing through the center point at a right angle to the first transverse direction.
Second cross-sectional shape measuring step for continuously measuring a distance from a predetermined position in the direction transverse to the one plate-shaped portion and in a direction intersecting the surface of the one plate-shaped portion in a second transverse direction crossing the recess. And a maximum depression point detection step of detecting a maximum depression point from the distance of the depression portion obtained by the second transverse shape measuring step, wherein the maximum depression point obtained by the maximum depression point detection step is The projection welding method is characterized in that projection welding is performed by aligning the center lines of the pair of electrodes. 2. The projection welding method according to claim 1, wherein the starting point and the ending point of the depressed side are calculated from the amount of change in the distance. 3. The first cross-sectional shape measuring step is executed a plurality of times, and the start point and the end point and the center points of the start point and the end point are detected from data of a plurality of distances obtained by the plurality of executions. Claim 1 or claim 2 characterized in that
The described projection welding method.