JPS6341677B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention enables complete spot welding by automatically controlling the energization time while continuously monitoring changes in the voltage (or resistance) between electrode tips that changes moment by moment during weld nugget generation. This paper relates to the improvement of an adaptive control system for ensuring the quality of Nuggets.
Further, to explain the present invention in detail, even if the actual energization time exceeds the energization time corresponding to the so-called required welding quality (hereinafter referred to as standard energization time) that can obtain the most appropriate welding strength, In addition, if the weld nugget generation state is not perfect, weld nugget growth is actively promoted by switching and circulating a welding current larger than the current value during the actual energization period at a predetermined time,
The object of the present invention is to provide a spot welding control method and a welding timer device that aim to shorten the overcurrent energization time, prevent the actual work takt time from being exceeded, and stabilize and secure the work rhythm.

Currently, adaptive control devices for lap resistance welding include those that detect the interelectrode voltage or interelectrode resistance as changes associated with the generation of weld nuggets, those that detect the amount of electrode expansion, and those that detect the amount of electrode expansion. Various methods have been studied, such as methods that detect temperature rise or ultrasonic transmittance between electrodes, but most of them detect a predetermined intensity by adjusting the flow time of the welding current. This is a method to obtain weld nuggets.

In an adaptive control device that adjusts the energization time, the amount of heat input to the welding part is generally adjusted by changing the length of the energization time, and the welding current is generally kept constant. However, with this type of method, for example, if the tip of the electrode tip is crushed and its area increases, the energization time will naturally be extended and adaptive control will be carried out, but this does not mean that the time for one spot welding becomes longer. In automatic welding lines, this results in exceeding the work tact, and in manual welding, it unnecessarily disrupts the rhythm of repetitive work.
This is undesirable from the industrial standpoint of suitability for efficient continuous production systems. In addition, among the types that detect the resistance between the welding electrodes, the resistance between the welding electrodes is monitored, and the minimum resistance (Rmin) between the welding electrodes and the subsequent increase rate of the ladder value during the heating stage between the welding electrodes are used. (dr/dt) and compare the effective values of both with the target values of Rmin and dr/dt,
JP-A-56-158286 discloses a technique in which the welding current is fluidly corrected in accordance with the comparison during the heating step between the welding electrodes.

This is carried out at the time when the welding current is corrected according to the deviation between the actual measured value and the target value of the Rmin value that occurs at the very beginning of the welding energization time and the dr/dt value that occurs immediately after that. Therefore, efforts are made to achieve the generation of weld nuggets within a certain target value (time), and in this sense, the present invention prevents the phenomenon of substantially exceeding the work takt until the generation of weld nuggets. At first glance, the technical purpose is similar to that of .

However, since the target welding time in this case is always constant, if the welding nugget is still incomplete at the time when the target welding time has elapsed despite the fluid correction of the welding current, it is no longer necessary to use this. This poses problems such as lowering the manufacturing yield rate on the continuous production line without an opportunity to compensate, and also producing defective products that are difficult to visually detect, damaging the credibility of the company.

The present invention completely eliminates the incompleteness of weld nugget generation after the target welding time has elapsed, and also limits the extension of the actual energization time as much as possible. The idea is to increase the welding current by a predetermined amount at the point when the standard energization time corresponding to the above period has been exceeded, thereby solving the above-mentioned drawbacks.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Figure 1 is an explanatory diagram showing the operating principle of the present invention, and Figure A is an operational model of the control relationship between standard welding current and standard energization time to ensure the most appropriate welding nugget in terms of welding quality. shows. In this case, if standard welding control is performed, a weld nugget will be generated within the standard energization time setting value.

That is, in the state shown in FIG. 1A, the welding current is not increased and the welding current is stopped because the energization stop signal is sent from the adaptive control device before the output from the standard energization time setting device, which will be described later.

On the other hand, Figure 1B shows a control operation model when the standard energization time is exceeded;
A signal for increasing the welding current is given to an ignition phase controller, which will be described later, based on the output of the standard energization time setting device set in . As a result, the current increases to promote nugget generation, and nugget generation is completed. From this point on, the energization time is automatically interrupted by the output of the same process as in Figure A.

Next, an example of a specific electrical structure using the invention will be explained with reference to FIG. The electrical block diagram enclosed in squares in the figure shows the main parts of the present invention.

The welding detector 1 is capable of electrically detecting changes in the voltage between electrode tips, electrode expansion, temperature at the tip of the electrode, ultrasonic transmittance between the electrodes, etc. due to the generation of weld nuggets. Anything is fine.

The adaptive control device 2 continuously monitors the transition of the amount of change and changes the energization time moment by moment in order to generate appropriate weld nuggets.

When performing spot welding by flowing a welding current under a predetermined electrode pressure, the welding current is set by a standard welding current setting device 7, fed back by a current detector 12, and stabilized by an ignition phase controller 9. controlled. The above-mentioned adaptive control device 2 sends a energization stop signal at the same time as the welding nugget is completed,
This signal passes through the energization time controller 3, locks the ignition signal transmitter 10, shuts off the alternating current electronic switch circuit 11, such as a thyristor or stack, and stops the welding energization.

The comparator 5 determines the value of the actual energization time by the adaptive control device 2, which is set by the standard energization time setting device 4 (set approximately 2 cycles longer than the normal standard energization time), and indicates a good welding result. As a result, it is detected that the actual energization time has been exceeded and a signal is sent to the current setting device 6.

When the current setting switch 6 receives this signal, the current setting switch 6 switches to a larger welding current by adding the increased current by the excess current setting device 8 to the current value for standard welding based on the standard welding current setting device 7. It will be done. This current switching is performed when the actual energization time exceeds the standard energization time.

Now, when both the welding machine and the workpiece are in an appropriate welding quality state, the standard energization time is 1 to 2 cycles longer than the normal energization time that can yield good welding results, for example, 12 cycles. If selected, for the standard energization time setting value,
Considering the normal case in which the actual energization time is extended to, for example, 25 cycles due to condition fluctuation factors such as changes in plate thickness, in the present invention, the number of cycles after exceeding the above set value is By switching to a welding current larger than the standard current value and flowing it, the cycle can be shortened to, for example, 15 cycles.

As described above, according to the present invention, when the welding nugget generation state is still insufficient even after the normal standard energization time has been reached, by increasing the welding current at a predetermined time and circulating it, the welding current can be increased until the nugget generation is completed. This reduces the extension time and ensures proper nugget generation in a cycle as close to the standard energization time as possible, which not only prevents nugget generation failures but also prevents variations in work tact and maintains a stable work rhythm. It is possible to achieve spot welding quality assurance that contributes to the development of an efficient production system.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the operating principle of the present invention;
The figure is an electrical block diagram showing one embodiment of the present invention. [Explanation of symbols], 1... Welding detector, 2... Adaptive control device, 3... Energization time controller, 4... Standard energization time setting device, 5... Comparator, 6... Current setting switcher , 7...Standard welding current setting device, 8...Excess current setting device, 9...Ignition phase controller, 10...
Ignition signal transmitter, 11...AC electronic switch, 1
2... Current detector.

Claims (1)

[Scope of Claims] 1. In the case of forming a weld nugget with appropriate welding strength by adjusting the flow time of welding current during the weld nugget generation process, a preset standard necessary for the above-mentioned nugget formation is provided. The energizing time is compared with the actual energizing time during actual welding, and when the actual energizing time exceeds the above set time, the welding current is substantially increased from then on and the above welding is performed. A spot welding control method characterized by regulating the extension of energization time until nugget generation. 2. Adaptive control means that has the function of constantly changing the energization time based on the amount of change in the voltage (or resistance) between the electrode tips and the amount of expansion associated with the generation of welding nuggets, and an adaptive control means that corresponds to the required welding quality in advance. A standard energization time setting device that sets the standard energization time,
A comparator that compares the value of the actual energizing time required for actual welding with the set value of the standard energizing time, and when the value of the actual energizing time exceeds the above set value, the signal from the comparator From the welding current when energized,
A spot welding control device consisting of a current setting switcher that switches to a larger welding current.