JPH09192851A - Device for judging appropriateness of welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an appropriate nugget diameter by judging that the welding is inappropriate when the actual nugget forming starting time is longer than the nugget forming starting time of the target estimated nugget diameter in the delay standard. SOLUTION: The corresponding table is read from a nugget diameter forming starting time storage device, and an appropriate nugget forming starting time is set as the comparison reference based on the target estimated nugget diameter. The voltage, the current, etc., are measured by a detection part 10 when electrodes 1, 2 are energized, and the energization time is compared with the nugget forming starting time. When the energization time is within the nugget forming starting time of the target estimated nugget diameter, a monitor 8 displays that the welding is appropriate, the monitor 8 displays that the welding is inappropriate when long time. Acceptance/rejection of the welding can be judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding adequacy determining device capable of appropriately determining whether or not welding is properly performed in a welding device.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Application Laid-Open No. 6-170552 has been disclosed as a welding quality monitoring device for resistance welding for making a proper judgment of a welding portion in electric welding.

This welding quality monitoring device estimates and calculates the temperature distribution and the estimated nugget diameter of the material to be welded by the heat conduction model by using the inter-chip voltage and the welding current detected by the toroidal coil and the integrator. The input means for inputting the shape and material of the material to be welded, the means for detecting the welding current and the voltage between tips, and the temperature of the material to be welded are calculated from the detected values based on the heat conduction model. A means for estimating the estimated nugget diameter based on the distribution, a means for inputting the reference nugget diameter necessary to secure the welding strength of the workpiece, a comparison of the estimated nugget diameter and the reference nugget diameter, and output of the comparison result It is equipped with a means to do.

[0004]

The conventional welding adequacy determining device can obtain good accuracy with respect to changes in welding conditions such as crushing of chips that occur in the welding process, and perform welding experiments at the welding site for each material to be welded. It is not necessary to obtain the relationship between welding quality and discrimination criteria in advance. There is an advantage that the suitability of welding can be determined by comparing the estimated nugget diameter with the reference nugget diameter by inputting data.

By the way, in general, the nugget formation start time after which the nugget starts to be formed after energization is delayed due to the difference in the plate thickness of the material to be welded and the increase in the estimated nugget diameter. Since the nugget formation start time is uniformly set based on the specific estimated nugget diameter, it is judged that the nugget was formed while the nugget formation was not sufficient, or when the nugget diameter was small enough There is a problem in that the energization is performed and the energization time does not correspond to the nugget diameter.

The present invention focuses on such a problem, and provides a welding adequacy determination device which can set a nugget formation start time corresponding to the size of the estimated nugget diameter and perform more appropriate determination. With the goal.

[0007]

In order to solve the above-mentioned problems, a welding adequacy determining apparatus according to claim 1 of the present invention comprises a specific resistance, a specific temperature coefficient, and a plate of a material to be welded located between welding electrodes. An appropriate resistivity is calculated from the thickness, the voltage and current between the welding electrodes sandwiching the material to be welded are detected, and the amount of heat generated is calculated from the calculated resistivity and the voltage and current, and the diffusion model of heat conduction is calculated. Based on the temperature distribution in the welded material based on the above, the diameter of the molten portion of the welded material is used as the estimated nugget diameter, and the generation time of this estimated nugget diameter is used as the nugget formation time, and the nugget formation of the desired nugget diameter is made. In the welding adequacy determination device that determines adequacy of the welding when the actual energization time at the welding electrode is longer than the time, the estimated nugget formation start time by energization When the nugget formation start time by actual energization is shorter than the nugget formation start time of the target estimated nugget diameter based on this delay criterion In addition, it is determined that the welding is appropriate, and when the start time of the nugget formation by the actual energization is longer than the start time of the nugget formation of the target estimated nugget diameter in the delay standard, the welding unsuitability is determined.

Further, in the welding adequacy determining device according to a second aspect of the present invention, in the welding adequacy determining device according to the first aspect, the estimated nugget diameter and the nugget formation start time are set to a constant interval region depending on the size of the estimated nugget diameter. The nugget formation start timing is set stepwise with respect to the estimated nugget diameter.

[0009]

According to the welding adequacy determining device of the first aspect of the present invention, the nugget formation start time is set corresponding to the size of the estimated nugget diameter, so the estimated nugget diameter becomes large and the nugget formation start timing is delayed. Even when the welding is performed, the suitability of welding can be determined by determining the energization time according to the delayed nugget formation start timing. Therefore, it is possible to obtain an appropriate nugget diameter by controlling the appropriate energization time of the electrode based on the determined energization time.

According to the welding adequacy determining apparatus of the second aspect of the present invention, the size of the estimated nugget diameter is set within a certain range, and the nugget formation start timing is set stepwise correspondingly. Therefore, the judgment is easy and does not take much time.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a welding suitability determining device according to a preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block circuit diagram of a welding adequacy determining apparatus according to an embodiment of the present invention, in which 1 and 2 are welding electrodes, 3 is a galvanized steel plate as a material to be welded, and 4 is electrodes 1 and 2. A power source, 5 is a computer for processing data and program control, and 6 is an input device for controlling the computer 5 and inputting data. Reference numeral 7 is a calculation program storage unit for storing a welding suitability determination program for activating the computer 5, 8 is a monitor as a display for displaying the determination result of the computer 5, and 9 is a printer for outputting the determination result of the computer 5 and the like. is there. Reference numeral 10 is a detection unit that detects a displacement between the electrodes 3 and 3, that is, a plate thickness, and also detects a welding current, a welding voltage, and an energization time. , 12 are storage devices for storing a correspondence table of the estimated nugget diameter and the nugget formation start time according to the present invention.

The computer 5 is constituted by a so-called personal computer or a board computer, is activated by turning on the power of the computer itself, and reads the welding adequacy determination program from the arithmetic program storage unit 7 by an operation from the input device 6.

The input device 6 consisting of a keyboard inputs control commands of a program and various data to the computer 5, and outputs data of the plate thickness of the galvanized steel plates 3 and 3 (depending on the displacement amount of the electrodes 1 and 2). From the input device 6, the specific resistance value of the galvanized steel sheet, the temperature coefficient of the specific resistance value that changes with temperature changes, the melting temperature of the galvanized steel sheet 3, and the like are input.

The calculation program storage unit 7 includes electrodes 1, 2
A welding adequacy determination program for determining adequacy of welding of the material to be welded by is stored. This welding adequacy determination program uses the data of the thickness of the galvanized steel sheets 3 and 3 (electrode 1,
2), the specific resistance value of the galvanized steel sheet from the input device 6 and the temperature coefficient of the specific resistance value that changes with the temperature change, the melting temperature of the galvanized steel sheet 3, and the welding between the electrodes 1 and 2. Current and welding voltage, galvanized steel sheets 3 and 3 based on these voltages / correction resistance values / currents / energization times and heat conduction diffusion model data of the storage device 11.
The diameter of the molten portion is calculated as the estimated nugget diameter based on the temperature distribution between the two.

That is, the specific resistance values of the galvanized steel sheets 3 and 3 change as the temperature rises.
Since the specific resistance value further changes depending on the plate thickness of No. 3, this is corrected, and the amount of heat generated is calculated from this corrected resistance value, energizing voltage, welding current, and energizing time. By applying this amount of heat by a heat conduction diffusion model to obtain a two-dimensional or three-dimensional temperature distribution and comparing this distributed temperature with the melting temperature of the galvanized steel sheets 3 and 3, the estimated nugget diameter can be calculated. As the arithmetic expression itself, a well-known model published in a paper or the like regarding welding technology may be used.

The heat conduction / diffusion model storage device 11 stores the temperature distribution of the welding material obtained by reproducing the simulation model using heat conduction by sequential calculation as a data of the heat conduction / diffusion model.

In the welding adequacy determination program, after the computer is started up, the welding adequacy determination program is read out, and at the same time, the correspondence table of the estimated nugget diameter and nugget formation start time is called from the nugget diameter / formation start time storage device 12, An appropriate nugget formation start time is set as a comparison reference based on the target estimated nugget diameter. The voltage, current, plate thickness, and energization time are measured by the detection unit 10 as the electrodes 1 and 2 are energized. The energization time on the electrodes 1 and 2 is compared with the nugget formation start time. In this comparison, when the energization time is within the nugget formation start time of the target estimated nugget diameter, the adequacy of welding is displayed on the monitor 8 and the energization time is longer than the target nugget formation start time of the estimated nugget diameter. At the same time, the improper welding is displayed on the monitor 8.

Nugget diameter / nugget start time storage device 1
In Table 2, the delay criteria of the nugget formation start time with the increase of the estimated nugget diameter are stored as a table. In this embodiment, the discriminating means is composed of a nugget diameter / nugget start time delay reference held in the storage device 12 and an arithmetic expression for making a comparison determination with the actual electrode energization time based on this delay reference. . In this embodiment, an arithmetic expression is included in the welding adequacy judgment program as an expression for controlling the computer, but of course a comparison circuit may be constituted as a judgment means by a logic circuit.

FIG. 2 shows a table of delay criteria. In this table,
As the estimated nugget diameter increases, the nugget formation start time gradually increases, and as the estimated nugget diameter increases,
The nugget formation start time is set to be long. Using the estimated nugget diameter in this table as a comparison reference, the energization time during actual welding is calculated. If the energization time is within the range of the nugget formation start time of the estimated nugget diameter, it is connected to the computer 5 that welding is appropriate. The monitor 8 and the printer 9 are output.

When the actual energization time during welding is longer than the nugget formation start time of the target estimated nugget diameter, it is judged that the welding is unsuitable and is output to the monitor 8 and the printer 9 via the computer 5. .

According to this embodiment, when the estimated nugget diameter is large or when the plate thickness is large and the current density related to welding is low, the energization time must be set long, but the nugget formation start time is delayed. Since it is set long, it can be welded sufficiently. Further, when the estimated nugget diameter is small or the plate thickness is small, the current density is high and the energization time is short, but the nugget formation start time is set accordingly short, so that welding can be sufficiently performed in a short time.

In the above embodiment, the welding suitability judging means is used as a single body, but it is also possible to perform welding control by incorporating it into the welding control means.

[0024]

According to the welding adequacy determining apparatus of the first aspect of the present invention, the nugget formation start time is set corresponding to the size of the estimated nugget diameter, so the estimated nugget diameter becomes large and the nugget formation start timing is increased. Even when the welding is delayed, the suitability of welding can be determined by determining the energization time according to the delayed start time of the nugget formation. Therefore, it is possible to obtain an appropriate nugget diameter by controlling the appropriate energization time of the electrode based on the determined energization time.

According to the welding adequacy determining device of the second aspect of the present invention, the size of the estimated nugget diameter is set within a certain range, and the nugget formation start timing is set stepwise correspondingly. Therefore, the judgment is easy, the accuracy is improved, and it does not take time.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of a welding adequacy determining device according to an embodiment of the present invention.

FIG. 2 is an estimated nugget diameter of the welding adequacy determination device of the present invention.
Correspondence table with nugget formation start time

[Explanation of symbols]

 1, 2 Welding electrode 3 Galvanized steel plate (material to be welded) 5 Computer 6 Input device 7 Calculation program storage unit 8 Monitor 9 Printer 10 Detection unit 11 Thermal conduction diffusion model storage device 12 Nugget diameter / nugget formation start time storage device

Claims (2)

[Claims] 1. An appropriate resistivity is calculated from the intrinsic resistivity, intrinsic temperature coefficient and plate thickness of the material to be welded located between the welding electrodes,
The voltage and current between the welding electrodes sandwiching the material to be welded are detected, the amount of heat generated is calculated from the calculated resistivity and the voltage and current, and the temperature distribution in the material to be welded is based on a diffusion model of heat conduction. Thus, the diameter of the molten portion of the material to be welded is used as the estimated nugget diameter, and the generation time of this estimated nugget diameter is used as the nugget formation time. The nugget formation time of the desired nugget diameter and the actual energization time of the welding electrode are determined. In the welding adequacy determining device that determines the adequacy of welding based on the above, the nugget formation start time by energization has a delay reference indicating that the nugget formation start time is delayed corresponding to the increase in the estimated nugget diameter. Based on this, it was determined that welding was appropriate when the nugget formation start time due to actual energization was shorter than the target estimated nugget diameter start time. And the actual nugget formation start time by energization, when longer than the nugget formation start time of the estimated nugget diameter for a target in the delay reference, welding proper determination apparatus characterized by determining the improper welding. 2. The welding adequacy determining device according to claim 1, wherein the estimated nugget diameter and the nugget formation start time are:
A welding adequacy determining device characterized in that a certain interval region is set for the estimated nugget diameter and the nugget formation start timing is set stepwise with respect to the estimated nugget diameter.