JP2000218378A - Good/bad conditions judging method in projection welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge quality in real time and also judge good/bad conditions without a breakage test by providing a step for detecting a variable pressurizing force and a step for judging good/bad conditions of welding by means of a computer from variation of the detected pressutizing force. SOLUTION: One pair of electrodes 5, 6 nipping a projection 1 of first and second members 3, 4 are pressurized by pressurizing devices 9, 10. A switch/ control mechanism 13 is connected to the pressurizing device 9, and passages of an operational fluid source 11 and a drain 12 are switched so as to control the pressurizing force of the electrode 5. Pressurizing force detection sensors 17, 18 are installed to pressurizing rods of the pressurizing devices 9, 10, and an electric output is inputted into a computer 21 so as to judge good/bad conditions of welding. It is preferable that good/bad conditions of projection welding are judged based on whether or not a projection crashing time Tt from starting deterioration of the pressurizing force from a target pressurizing force till the force becomes the target pressurizing force again is in a given time range, or whether or not a pressurization time Tm from the start of pressurization till the start of crashing the protrusion is in within a given time range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for judging the quality of projection welding.

[0002]

2. Description of the Related Art Conventionally, the quality of projection welding is determined by cutting and polishing the projection welding portion and visually judging the joining state, or by cutting out a portion of the work including the projection welding portion and performing a tensile strength test. This is done by determining whether or not the sheet has a predetermined tensile strength. Note that Japanese Patent Application Laid-Open No. 8-902
No. 51 discloses a technique for judging a welding defect by monitoring a pressurized state. However, this is a technique for confirming a setting defect of a work in advance and cannot judge the quality of welding. .

[0003]

There are the following problems in the quality judgment of the conventional projection welding. Since a test piece is created and determined by a testing machine different from the welding machine, real-time determination cannot be performed. Also,
The test is time-consuming and expensive. The workpiece is subjected to a destructive test, and the tested workpiece cannot be used. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for judging the quality of projection welding, in which quality can be judged in real time and quality can be judged without performing a destructive test.

[0004]

The present invention to achieve the above object is as follows. (1) A method for judging the quality of projection welding, comprising: a step of detecting a changing pressing force; and a step of determining the quality of the projection welding by a computer from the detected change in the pressing force. (2) Whether the projection welding is good or not is determined based on whether or not the projection crushing time _Tt from when the pressing force starts decreasing from the target pressing force and rises to reach the target pressing force again within the predetermined time range (1). 4) The method for judging the quality of the projection welding described in the above. (3) pressing time T _m of a to start collapse projecting from the starting pressure
(1) The quality judgment of the projection welding according to (1), wherein the quality of the projection welding is judged by whether or not is within a predetermined time range. (4) The projection crushing time _{Tt from} when the pressure starts to decrease from the target pressure and rises to reach the target pressure again is within a predetermined time range. Depending on whether the pressurization time _Tm is within a predetermined time range,
The method for judging the quality of projection welding according to (1), wherein the quality of projection welding is judged. (5) The method for judging pass / fail of the projection welding according to any one of (2) to (4), wherein the predetermined time range is determined according to the type of the material to be welded. (6) The method according to any one of (1) to (5), wherein the projection welding is performed between the member having the ring-shaped protrusion and the plated steel sheet.

[0005] Judgment of the quality of the projection welding of the present invention
In the method, at least one of the upper and lower electrodes or its driving
Force detection for dynamic system (cylinder or servo motor)
Attach a sensor (for example, a load cell) and
Change in pressure during projection welding is detected moment by moment,
Is input to the computer. Force vs. time graph
Pressure is applied simultaneously with the contact of the electrode with the workpiece.
Turns on and increases with time, almost reaching the target pressure
At this time, but at this time, a little
The welding current is turned on and the current increases, heating the protrusion
When the projections reach the melting temperature and begin to melt and collapse,
The pressure is partially released and drops once from the target pressure,
The pressure rises again to reach the target pressure, and the target pressure is applied until the pressurization is completed
Power continues. In this case, from the pressing ON to the start of protrusion collapse
Time T_mAnd the pressure once dropped from the start of the projection collapse
Time to reach the target pressure again
Time T_t) Can be related to the quality of the welding, the inventor
Was found by: Specifically, the protrusion crushing time T_tIs prescribed
If it is longer than the time range, ring projection
Slanted on the hand member and pressed to crush the protrusion all around
It takes a long time, and the pressing force is weak
The part has large resistance and large heat generation, causing dust, leakage, etc.
No welding defect has occurred. Protrusion crushing time T_tAt a given time
If it is shorter than the range, the projection
Melts, dust is generated around the entire circumference,
Such as welding defects. Also, from the pressing force ON
Time T until the start of protrusion collapse_mIs longer than the specified time range
If the force is too large, the protrusion will bite into the mating member.
Becomes too large, the electric resistance decreases and the heat generation becomes small, and welding is performed.
When it is no longer possible, and there is a bonding failure
It is. Also, the time T_mIs shorter than the specified time range
Is too small and the contact area is too small
This is the case where the resistance increases and the heat generation is large. The above (1)
The method for determining the quality of ring projection welding in
From the change in pressure, the protrusion crushing time T_tAnd from pressure ON
Time T to start collapse_mAnd at least one of
A method for judging the quality of projection welding
Can be detected during welding from a load cell, etc.
Enter it into the computer and check if it is within the predetermined time range.
By making a judgment, the quality of welding can be determined in real time during welding.
Judgment can be made and judgment can be made without destroying the work
You. Judgment of ring projection welding of (2) above
In the standard method, it falls once from the start of protrusion collapse and rises again
Until the target pressure is reached (projection crushing time T _t)
Is within the specified time range by projection welding
Is judged in real time.
Pass / fail can be judged, and judgment can be made without destroying the work
Wear. Quality of ring projection welding of (3) above
In the judgment method, when the pressure is
Interval T_mIs within the specified time range.
The quality of welding is judged in real time during welding.
Can judge the quality of welding and without destroying the work
Can be determined. Ring projection welding of (4) above
In the pass / fail judgment method, the protrusion crushing time T_tIs within the specified time range
Is good or bad for projection welding
And the pressurizing time T from the start of pressurization to the start of protrusion collapse_m
Is within the specified time range by projection welding
Is judged in real time.
Pass / fail can be judged, and judgment can be made without destroying the work
Wear. Pass / fail of the ring projection welding of (5) above
In the determination method, T_t, T_mTime range for
It is determined by the type of contact material. For example, 1ms <T_t<5ms For aluminized steel sheet 2ms <T_t<10ms Lead-plated steel sheet 32ms <T_m<48ms For aluminized steel sheet 48ms <T_m<60 ms. Good for ring projection welding of (6) above
The method of determining rejection is based on a member having a ring-shaped protrusion and a mating member.
It can be applied to welding between plated steel sheets.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an apparatus for carrying out a method for judging the quality of ring projection welding according to an embodiment of the present invention, and FIG. 2 shows a control for carrying out a method for judging quality of ring projection welding according to an embodiment of the present invention. FIG. 3 shows a program, and FIG. 3 shows a change in the pressing force and a change in the welding current in the method for judging the quality of the ring projection welding according to the embodiment of the present invention.

First, an apparatus for carrying out the method for judging the quality of ring projection welding according to an embodiment of the present invention is shown in FIGS.
With reference to FIG. Ring projection welding according to the embodiment of the present invention is projection welding performed between a first member 3 having a ring-shaped projection 1 (ring projection) and a second member 4. The projection 1 is formed on the flange 2 of the first member 3 so as to project from the flange surface. The cross-sectional shape of the projection 1 is usually a tapered triangle, but may be another shape, for example, a semicircle. The second member 4 is a flat plate portion such as a container.

The ring projection welding is applied, for example, to a fuel inlet of an automobile fuel tank. In this case, the first member 3 is an inlet member of a cylindrical member with a flange, and the second member 4 is a half member. This is the tank body at the split stage. In the case of a fuel tank for an automobile, the projection welded portion must be full-circle welded, have no leakage, and have a certain or more tensile strength. Therefore, welding dust must not be generated over the entire circumference of the projection welded portion, and the pressing force must be appropriate over the entire circumference. For this purpose, the first member 3 has to be pressed against the second member 4 with its axis perpendicular to (not inclined to) the second member 4. If the pressing force is too large, the projection 1
If the contact area becomes too large, the contact area becomes too large, the electric resistance becomes small, the heat generation becomes small and welding cannot be performed, and if the pressing force is too small, the protrusion 1 does not bite into the second member 4 and the contact area becomes small. It becomes too small, the electric resistance becomes large,
Heat generation becomes too large, and welding dust is generated instantaneously over the entire circumference. Further, when the first member 3 is inclined and pressed against the second member 4, a portion where the pressing force is large and a portion where the pressing force is small occur in the circumferential direction, and welding dust occurs in the small portion.

In FIG. 1, works 3 and 4 have a projection 1 sandwiched between a pair of electrodes 5 and 6, and a pair of electrodes 5 and 6 are pressed with pressure devices 9 and 10 (for example, cylinders, The pressure may be driven by a pressure device that changes the rotation into a linear motion. In the example shown, both electrodes 5, 6
Although the case where the pressurizing devices 9 and 10 are connected to each other is shown, the pressurizing device may be connected to only one of the electrodes. A switching control mechanism 13 for the working fluid is connected to the pressurizing device 9, and switches the flow path between the working fluid source 11 and the drain 12 to control the pressing force of the electrode 5. Similarly, when the electrode 6 is provided with the pressurizing device 10, a switching control mechanism 16 for the working fluid is connected to the pressurizing device 10 to switch the flow path between the working fluid source 14 and the drain 15 to switch the electrode 6. To control the applied pressure. The switching control is performed by a command signal (output signal) from the computer 21.

Then, the pressure rods of the pressure devices 9 and 10
A pressure detection sensor that can detect the pressure every moment
(For example, load cells) 17 and 18 are provided. This
The pressure detection sensor of this type detects the collapse of the protrusion described later with high accuracy.
Milliseconds (10 ^-3sec) or
Pressurization following a change in pressure in a shorter time
It is possible to use one that can detect force (available on the market)
desirable. When the pressure device 10 is not provided on the electrode 6
Also, the pressure detection sensor 18 is provided on the device supporting the electrode 6.
Be killed. Pressure detection sensor (for example, load cell)
The electric outputs of the amplifiers 17 and 18 are amplifiers (amplifiers) 19 and 20
The data is input to the computer 21 through the like.

A welding current from a welding current power supply 7 is applied to the electrodes 5 and 6 via a welding current control device 8. The start of welding current application by the welding current controller 8 and the timing thereof are performed by a command signal (output signal) from the computer 21.

Next, a projection welding method will be described with reference to FIG. The pressurizing devices 9 and 10 (at least one of them) are actuated to relatively approach the electrodes 5 and 6,
At the same time as the workpiece is brought into contact with and clamped by the workpiece, the pressurization is turned on and the pressure increases from 0, and becomes constant when the pressure reaches almost the target pressure. Slightly after pressing ON (for example, 0.02
(With a delay of about 0.04 sec), the welding current is turned on (start of energization), and the welding current rises from 0. When the welding current becomes almost the target welding current, the protrusion 1 melts due to resistance heat and starts to be crushed, and the pressure is increased. Cannot follow the pressure release due to the melting of the protrusion 1, the pressing force starts to decrease once from the target pressing force, the electrode moves by the amount of the melting of the protrusion 1, and the pressure is applied again.
The pressing force increases again to the target pressing force, and thereafter, the state where the target pressing force is constant continues. The time from pressurization ON to the start of the crushing of the protrusion 1 is defined as _Tm, and the time from when the protrusion 1 starts to crush and the pressing force starts to decrease until the pressing force increases and reaches the target pressing force again is crushed. Time _Tt . _Tm is about 0.06 sec and _Tt is about 0.02 sec.

The computer 21 stores a program for judging the quality of the projection welding shown in FIG.
In FIG. 2, in step 101, a pressure value corresponding to an input signal from a pressure detection sensor is read. Next, at step 102, _Tm is calculated as the time from the pressure ON to the start of the collapse of the projection 1. Next, at step 103, it is determined whether or not _Tm is within a predetermined time range. Here, the predetermined time range varies depending on the type of the second member 4 (or the first member 3 and the second member 4), and in the case of a lead-plated steel sheet, 32 ms <T _m <48 ms in the case of an aluminum-plated steel sheet, 48 ms < T _m <60 ms. If _Tm is not within the predetermined time range, step 10
The process proceeds to step 4 to issue a warning. If _Tm is within the predetermined time range, the process proceeds to step 105. Next, at step 105, the protrusion crushing time _Tt is calculated, and the routine proceeds to step 106. In step 106, it is determined whether or not the protrusion crushing time _Tt is within a predetermined time range. Here, the predetermined time range differs depending on the type of the second member 4 (or the first member 3 and the second member 4), and is 1 ms <T _t <5 ms for a lead-plated steel sheet and 2 ms <for an aluminum-plated steel sheet. T _t <10 ms. If T _t is not within the predetermined time range, step 10
The process proceeds to step 7 and a warning is issued. If _Tt is within the predetermined time range, the process ends.

In the method for judging the quality of the projection welding according to the embodiment of the present invention, it is determined whether or not the projection welding has a joining defect and dust (which leads to generation of a leaked portion) as follows. The judgment of the quality of the projection welding according to the embodiment of the present invention includes the steps of detecting a change in the pressing force by the pressing force detecting sensors 17 and 18 (for example, load cells), and inputting the detected pressing force to the computer 21 and Determining the quality of the projection welding.

In the pass / fail judgment step, the quality of the projection welding is determined based on whether or not the projection crushing time _Tt from when the pressing force starts decreasing from the target pressing force and rises to reach the target pressing force again is within a predetermined time range. Is determined. This is performed by steps 105 and 106 in FIG. When the protrusion crushing time _Tt is longer than the predetermined time range, it takes a long time for the ring-shaped protrusion 1 to be inclined and pressed against the partner member and to crush the protrusion 1 all around. The weak portion has large resistance and large heat generation, causing dust, and causing welding defects such as leakage. When the protrusion crushing time _Tt is shorter than the predetermined time range, the protrusions are not melted over the entire circumference instantaneously, dust is generated over the entire circumference, and welding defects such as leakage occur.

[0016] In quality determination step determines the quality of projection welding pressing time T _m of a to start collapse protrusion from the start pressurization on whether within a predetermined time range. This is performed by steps 102 and 103 in FIG. If time T _m of a to start collapse projecting from pressure ON is longer than a predetermined time range, the amount of bite of the mating member of the pressurizing pressure is too large projection is too large next electrical resistance becomes decreased heating small welding This is the case where it is no longer possible, and a bonding failure has occurred. When the time _Tm is shorter than the predetermined time range, the pressing force is too small, the contact area becomes too small, the electric resistance increases, and the heat generation increases.

In the pass / fail judgment step, the protrusion crushing time _Tt from when the pressing force starts to decrease from the target pressing force and rises to reach the target pressing force again is within a predetermined time range. pressing time T _m of a to start collapse projections at both whether within a predetermined time range, may determine the quality of projection welding. This corresponds to step 10 in FIG.
2, 103 and steps 105, 106.

In the above, the predetermined time range varies depending on the type of the member to be welded (the second member 4, or the first member 3 and the second member 4). The projection welding may be performed between the member 3 having the ring-shaped protrusion 1 and the plated steel plate 4. That is, the second member 4, or the first member 3 and the second member 4 may be plated steel sheets. The steel material is generally steel, and the plating metal is lead, aluminum, zinc, tin, zinc / tin, etc., and these plating metals may be pure metals or alloys containing other elements. For example, aluminum is about 10% by weight of silicon
Aluminum may be included.

The operation of the method for judging the quality of the projection welding is as follows. It is found that there is a relationship between the change in the pressing force and the quality judgment of the welding, and the quality of the welding is determined from the change in the pressing force. A change in the pressing force can be detected from time to time in real time by the pressing force detection sensors 17 and 18 (for example, load cells), and the output thereof is input to a computer to judge the quality of welding in real time.

Since it is not a destructive inspection, the work judged to be good or bad in welding is used as a product as it is. Since it is not a destructive inspection, it is possible to judge the quality of welding of all products. Further, by storing the determination result of the computer on a disk or the like and storing it, it is possible to manage welding of all products. Further, by learning the welding quality judgment result and feeding it back to the next welding, it is possible to learn the optimum pressing force. In addition, by making the pressurizing system a system that can be controlled momentarily using a servomotor, when welding is likely to occur, the pressing force is increased to suppress the generation of dust. When welding is likely to occur, welding control, such as reducing the pressing force, becomes possible.

[0021]

According to the method for determining the quality of the ring projection welding according to the first aspect of the invention, the welding force is detected during the welding, and is input to the computer, and the quality of the welding is determined from the change in the welding force every moment. Thus, the determination can be made in real time during welding, and the determination can be made without breaking the work. According to the method for determining the quality of the ring projection welding according to the second aspect, the quality of the projection welding is determined based on whether or not the protrusion crushing time _Tt is within a predetermined time range. Judgment can be made, and judgment can be made without destroying the work. According to quality determination method of the ring projection welding according to claim 3, the pressing time T _m of a to start collapse protrusion from the start pressurization whether within a predetermined time range, to determine the quality of projection welding, The quality of welding can be determined in real time during welding, and can be determined without breaking the work. According to the method for determining the quality of the ring projection welding according to claim 4, the quality of the projection welding is determined based on whether the projection crushing time _Tt is within a predetermined time range,
And since pressing time T _m of a to start collapse projecting from the pressure starts to determine the quality of projection welding at whether within a predetermined time range, can determine the quality of the welding in real time during welding and the workpiece Can be determined without breaking. According to the method for determining the quality of the ring projection welding according to the fifth aspect, the predetermined time range for T _t and T _m is determined by the type of the material to be welded, and the quality of the projection welding according to the type of the material to be welded can be determined. . According to the method for judging the quality of ring projection welding according to claim 6, the method can be applied to welding between a member having a ring-shaped projection and a plated steel plate as a mating member.

[Brief description of the drawings]

FIG. 1 is a system diagram of an apparatus (system) for implementing a method for determining the quality of ring projection welding according to an embodiment of the present invention.

FIG. 2 is a flowchart of an execution means (program) for executing a method for determining the quality of ring projection welding according to the embodiment of the present invention.

FIG. 3 is a graph showing a change over time of a pressing force and a welding current during execution of a method for determining the quality of ring projection welding according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Projection 2 Flange 3 1st member 4 2nd member 5, 6 electrode 7 Welding current power supply 9, 10 Pressurizing device (cylinder or servomotor) 17, 18 Pressurized force detection sensor (for example, load cell) 21 Computer

Claims (6)

[Claims] 1. A method for judging the quality of projection welding, comprising: a step of detecting a changing pressing force; and a step of determining the quality of the projection welding by a computer based on the detected change in the pressing force. 2. The quality of the projection welding is determined based on whether or not the projection crushing time _Tt from when the pressing force starts decreasing from the target pressing force and rises to reach the target pressing force again is within a predetermined time range. The method for judging the quality of projection welding according to claim 1. 3. A pressing time T _m is quality determination method of projection welding according to claim 1, wherein determining the quality of projection welding at whether within a predetermined time range to the start of collapse projecting from the starting pressure. 4. A projection crushing time _{Tt from} when the pressure starts to decrease from the target pressure and rises to reach the target pressure again is within a predetermined time range. The quality of the projection welding is determined based on whether the pressurizing time _{Tm up} to the predetermined time is within a predetermined time range.
The method for judging the quality of the projection welding described in the above. 5. The method according to claim 2, wherein the predetermined time range is determined according to a type of a material to be welded. 6. The method according to claim 1, wherein the projection welding is performed between the member having the ring-shaped protrusion and the plated steel sheet.
5. The method for judging the quality of projection welding according to 5.