JPH0599601A - Method for inspecting welding whereby nugget diameter of spot-welding portion is measured - Google Patents

Abstract

PURPOSE:To reduce the weight of a non-destructive inspection device and achieve further miniaturization and cost reduction of the inspection device which measures the nugget diameter of a welding portion without destructing the nugget by means of insertion of an inspecting chisel between two spot- welded metal plates. CONSTITUTION:A chisel 1 having a V-groove at its end and a vibrator for vibrating the chisel 1 are provided, and the chisel is inserted between two spot- welded metal plates by means of vibration that the chisel receives from the vibrator, and a nugget is held in the V-groove. When the V-groove abuts on the nugget and the forward movement of the chisel 1 is stopped, the distance (c) from the apex B of the angle of the V-groove to the center O of the nugget is calculated according to the distance (b) from a predetermined reference line of the chisel 1 to the apex B of the angle of the V-groove and the amount (a) of movement obtained by measuring the distance from the apex B to the center O of the nugget, and the diameter of the nugget is measured from this (c) value and the angle theta of the v-groove.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nondestructive inspection method for spot welds which measures the size of the weld (nugget) without breaking the weld of the spot weld.

[0002]

2. Description of the Related Art In an automobile body assembly line, spot welding of several thousand points or more is performed by a multi-spot welding machine or a spot welding robot. When checking the spot-welded portion, generally, a U-shaped chisel or a V-shaped chisel is hammered between two metal plates,
An inspection method has been performed in which both sides of the nugget are pushed up by the force of the wedge to check whether or not the welded portion is completely attached, or to actually peel the nugget to check the size of the welded portion.

The above-mentioned method of inspecting a chisel requires not only breakage of the welded portion but also great labor. For this reason, recently, a pair of chisels were vibrated by a vibrator in the forward direction, inserted between two metal plates, and pushed into both sides of the welded part. Has been developed to measure the nugget diameter by moving the blades toward each other like a caliper measuring unit (“Nikkei Mechanical”, P.81-83, Nikkei BP, Inc. 1991-9).
-16).

It can be said that this inspector is excellent in that the diameter of the nugget can be automatically read without breaking the welded portion only by inserting the chisel between the two metal plates.

FIG. 1 illustrates the principle of the above-mentioned inspection device. To explain this measuring method, first, referring to FIG.
As shown in (A) and (a), a pair of two chisels are vibrated by a vibrator and the blade is pushed back and forth. Next, the chisel is inserted between two metal plates welded as shown in FIGS. 1B and 1B, and is deeply inserted so that the nugget can reach between the blades. Next, FIG.
As shown in (C) and (c), the powerful action of the air-hydraulic cylinder (not shown) moves the two chiseles toward each other, narrowing the blade spacing to the nugget width. .. Then read the scale as the nugget diameter at this time. After finishing the measurement, give the blade a vibration again and pull it out. The position where the chisel is inserted is slightly deformed, but it can be easily corrected by tapping from the top.

[0006]

However, in the conventional inspection method of this type, since the drive mechanism for moving the chisel in two directions and the device for switching the drive mechanism are built in, the machine body becomes large and heavy. It becomes a thing. Therefore, in order to make it practical as a nugget measuring instrument, it is necessary to further promote weight reduction, size reduction, and cost reduction, and a solution thereof has been desired.

[0007]

SUMMARY OF THE INVENTION The present invention provides a lightweight aircraft body,
In order to reduce the size, the following technical measures were taken.
That is, a chisel having a V-groove at its tip and a vibrator for vibrating the chisel are provided, and the chisel is spot-welded by the vibration received by the vibrator between two metal plates. Distance from the reference line of the predetermined chisel to the apex B of the corner of the V-groove when the V-groove hits the nugget and the forward movement of the chisel stops. The distance c from the apex B to the nugget center O is determined from b and the movement amount a measured from the reference line to the nugget center O, and the nugget diameter is measured from the value of this c and the angle θ of the V groove. It is characterized by doing so.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An application example for carrying out the method of the present invention will be described below with reference to the drawings. 2 (d) and 2 (e) are a side view and a plan view showing an example of the chisel structure according to the method of the present invention, and FIGS. 2 (a), 2 (b) and 2 (c) are insertion positions A of the chisel. −
It is sectional drawing of the welding part corresponding to A ^' , BB ^' , and CC ^' . Further, FIG. 3 shows a principle diagram of the measuring method of the present invention. Reference numeral 1 in the drawing indicates a chisel body having a V groove. 2 and 3 in FIG. 2 are welded metal plates. 4 and 5 are V-groove tapes
A pa-shaped blade is shown. Reference numeral 6 denotes a welded nugget.

When the nugget diameter is measured by the method of the present invention, the vibrating blade 1 of the V-groove is used as shown in FIG. 2 in the order of operation (a), (b), (c). It is vibrated by (omitted) and is inserted between the two metal plates 2 and 3 with the V groove welded while being pushed back and forth. That is, the nugget 6 is pushed so as to reach between the taper-shaped blades 4 and 5 of the V groove. As the nugget enters the V groove, the interval between the taper-shaped blades 4 and 5 becomes narrower and the blade tip contacts the nugget 6 so that the V groove completely sandwiches the circumference of the nugget. When the V groove sandwiches the nugget in this manner, the chisel 1 stops its forward movement.
When this is stopped, the radius x of the nugget 6 can be obtained from the following mathematical formula, as shown in the principle diagram of FIG.

That is, a line AB connecting the contact point of the circumference of the nugget from the apex of the V angle and the center of the nugget, that is, the center O of the circle.
Since the triangle OAB whose radius x is one side is a right triangle, sin θ = x / c from the theorem of the trigonometric function. Now, assume that the V groove is 30 °. That is, θ = 15 °
Then, x = 0.259 × c. However, a is the distance from the reference line Y to the center O of the circle, and b is the distance from the reference line Y to B. Therefore, the measured value (diameter) of the nugget can be detected by obtaining the values of a and b.

The embodiment of FIG. 4 is a schematic diagram showing an embodiment of a measuring instrument for carrying out the method of the present invention. in this case,
If a slide-type scale is pulled out from the inside of the measuring instrument and the tip of the scale is placed at the center of the nugget,
The values of b and c are measured, and the nugget diameter is calculated by this.
The measured value is displayed on the indicator.

The mechanism will be described below. As explained in the previous section, c = ab, and if the V groove is 30 °, the radius x of the nugget can be represented by 0.259 × c. The value of c always fluctuates. But b
This value is constant because it is the amount from the apex of the V groove provided on the chisel to the reference line. Therefore, slide-type scale
Value of b from the tip to the reference line on the
And The value between 0 and the reference line fluctuates, but this value is nothing but c. Since c × 0.259 is the radius of the nugget, when the V groove touches the nugget and stops, the numerical value displayed on the indicator is a converted value as shown in FIG.
The angle (θ × 2) of the V groove is set to 30 ° for convenience in the above description, but it is desirable to set the angle as small as possible in order to improve the measurement accuracy of the nugget diameter.

The following is a trial calculation of what kind of change the measured value has when the tip end of the slide type scale has the following variations. However,
The V groove is 30 ° and the exact value of c is 15 mm. The formula for determining the diameter R of the nugget at this time is R = c × 0.
Since it is 259 × 2, Becomes As described above, it can be seen that the error does not occur enough to cause a problem. Further, when the angle of the V groove is made small in order to improve the measurement accuracy, the value of sin θ becomes further smaller, so that the measurement error becomes smaller.

[0014]

As described above, when the chisel is conventionally moved from (a) to (c) in FIG. 1 without moving the chisel, the blade is directly translated from the left and right directions toward the nugget,
The pinching force at this time generates a large force of about 800 to 1000 kgf, but since the V-groove push-in method of the present invention uses the wedge action of the V angle, it is more than the direct pinching. Can be small. That is, for example, if the V angle is 30 °, it will be about 60%, and according to the vibrator or the air hammer, it depends on the striking force of the piston. Further, the conventional method requires the operation of switching the chisel in two directions, but the method of the present invention does not require this operation, has a simple structure, and can use a commercially available air-hammer, so that the cost is reduced. Furthermore, according to this method, the measured value (nugget diameter)
The display mechanism can be simplified and the weight and size of the nugget measuring device can be further reduced, and the cost can be further reduced, which is extremely practical.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the principle of a conventional method, in which (A)-
(C) is a plan view showing the insertion position of the chisel with respect to the nugget, and (a) to (c) are sectional views of the insertion position.

FIG. 2 is an explanatory view showing a chisel structure and a chisel insertion operation according to the method of the present invention, and FIGS. 2 (a) to 2 (c) are cross-sectional views of the chisel insertion position. (D) Side view of the chisel. (E) is a plan view of the chisel.

FIG. 3 is an explanatory diagram showing the principle of the measuring method of the present invention.

FIG. 4 is an explanatory diagram showing an example of an apparatus to which the principle of the present invention is applied.

FIG. 5 is an enlarged view of a slide type scale of the device of the present invention.

[Explanation of symbols]

 1 chisel having V groove 2 metal plate 3 metal plate 4 taper-shaped blade 5 taper-shaped blade 6 nugget

Claims (1)

[Claims] 1. A chisel having a V-shaped groove at its tip and a vibrator for vibrating the chisel, and the chisel being spot-welded by the vibration received by the vibrator. Inserted between a number of metal plates, sandwiching the nugget with the V groove, and when the V groove hits the nugget and the forward movement of the chisel stops, the apex of the corner of the V groove from the predetermined reference line of the chisel. From the distance b to B and the movement amount a measured from the reference line to the nugget center O, the vertex B
To the center O of the nugget, and the nugget diameter is measured from the value of this c and the angle θ of the V groove.