JPH0651234B2 - Resistance welding control device - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a resistance welding control device, and more particularly to a resistance welding control device for controlling various welding conditions (welding current, energizing time, welding tip pressure, etc.) in resistance welding.

[Prior art]

In resistance welding, the tip of the welding tip wears out after each welding,
The diameter gradually increases. For this reason, there is a possibility that the current density is lowered and the welding strength is lowered. In order to prevent this, conventionally, the tip of the welding tip is polished for every fixed number of welding points. Further, so-called step-up control is added to increase the current at a predetermined rate for each predetermined number of welding spots so that the number of times of polishing can be minimized.

[Problems to be Solved by the Invention]

By the way, the rate of increase of the current in the step-up control is experimentally and empirically determined. Therefore, the difference in the characteristics of each welding machine, the variation of the plate pressure of the work (workpiece),
It is difficult to accurately respond to variations in the surface condition. Further, it is difficult to confirm whether the welding is good or bad, particularly whether or not the welding strength is sufficient at the production site for the actual product. For this reason, many sites use the presence or absence of splash as a guide for setting welding conditions. In this case, if there is no splash, it is indistinguishable from the case of non-energization or insufficient melting. In addition, the splash may not be generated due to the variation or inaccuracy in setting the step-up rate. For this reason, the worker tends to inevitably set the energizing current and energizing time to be large. Such condition setting, together with the inadequacy of the step-up rate setting described above, causes a strong splash. A strong splash causes a decrease in welding strength. It also shortens the life of the welding tip. Furthermore, the degree of danger to the worker is increased. It also promotes deterioration and insulation deterioration of cables, hoses, welder bodies, control equipment, and the like.

[Means for Solving the Problems]

Therefore, in the present invention, a detecting means for detecting the occurrence of splash, a continuity detecting means for detecting continuous occurrence or non-occurrence of splash, and a control means for controlling a predetermined welding condition so that the continuous occurrence or non-continuous occurrence does not occur. To solve the above problems.

[Action]

If welding conditions are set so that splashes occur moderately, the occurrence state becomes random to some extent. It is most preferable to maintain such a state when controlling the welding conditions using the splash as a guide. In order to do so, in the present invention, it is first checked by the detection means whether or not splash occurs during energization. Then, the continuity detection means detects whether the welding spots that have generated a splash are continuous for a predetermined number or whether the welding spots that do not generate a splash are continuous for a predetermined number, and when this is detected, they are detected by the control means. Welding conditions such as welding current and energizing time are controlled in a direction that does not occur.

【Example】

Hereinafter, the details of the present invention will be described based on illustrated embodiments. First
In the figure, reference numeral 1 is a rectifying circuit, which rectifies a three-phase alternating current 3φ to generate a direct current voltage DC. Reference numeral 2 is a choke coil, and 3 is an electrolytic capacitor, which smoothes the DC voltage DC.
Reference numeral 4 denotes an inverter, which generates an AC AF of about 1000 Hz whose duty ratio changes according to the control signal CS. A transformer 5 steps down the AC AF supplied from the inverter 4 to generate a low voltage LV. Reference numerals 6 and 7 are diodes for full-wave rectifying the low voltage LV. Reference numerals 8 and 9 denote welding tips, which are supported by a resistance welding machine main body (not shown), and are brought into close contact with the work 10 by a pressing force, and a welding current I is supplied thereto. Reference numeral 11 denotes a current detection coil, which generates a minute current i corresponding to a change amount (differential value) of the welding current I. An integrating circuit 12 integrates the minute current i to generate a digital value DI. This value DI corresponds to the welding current I. Reference numeral 13 is a differentiating circuit, which generates a pulse DP in response to the fall of the welding tip voltage VC. Reference numeral 14 is a gate circuit, and the input terminal IN and the output terminal OUT are electrically connected while the gate signal G is supplied. A flip-flop 15 is set by the output of the gate circuit 14 and reset by the signal R. When set, its output Q becomes "1". Reference numeral 16 is a central processing unit (CPU) so-called microcomputer including an integrated circuit, which uses a random access memory (RAM) 17 and a read-only memory (R).
The following processing is executed according to the program of the OM) 18.
A so-called RAM card 19 is used to store data and programs. Reference numeral 20 is a printing device and 21 is a display device.
The control data (welding current change time, welding spot number at that time, device operating status, etc.) supplied from 6 are printed out or displayed. 22 is a keyboard, CPU16
Used to input data to. Reference numeral 23 denotes an input / output port, which is used for data between the above-described circuits and the like and the CPU 16, between the resistance welding machine control circuit (not shown) and the CPU 16, and between the external computer and the like (not shown) and the CPU 16. To deliver. Next, a splash detection method in this embodiment will be described with reference to FIG. In FIG. 2, FIG. 2A shows an example of the welding current I, in which constant current control is performed from the energization start time t0 to the end time t1. The magnitude of the current I is increased / decreased by the CPU 16 (described later). (B) and (C) in the figure show the welding tip voltage VC at this time.
An example of change of is shown. (B) VC in the same figure shows an example in which energization ends without generating splash, and (C) VC2 in the figure shows an example in which splash occurs during energization. In this example, a splash occurs at time t2 in the middle. As a result, the welding tip voltage VC2 drops sharply. In this embodiment, the occurrence of splash is detected by utilizing such characteristics. Specifically, the differentiating circuit 13, the gate circuit 14, and the flip-flop 15 are used. That is, the differentiating circuit 13 generates the pulse DP when the welding tip voltage VC falls as described above (FIG. 2 (D)). Therefore, the flip-flop 15 is reset to t0 at the start of energization, and the gate signal G is supplied to the gate circuit 14 from an appropriate time t3 when the welding tip voltage VC stabilizes to a time t4 immediately before the end of energization (see FIG. 2). (E)).
By doing so, the pulse D generated at the time t1 at the end of energization
P2 is blocked by the gate circuit 14, and only the pulse generated during that period, for example, the pulse DP1 is supplied to the flip-flop 15 (FIG. 2 (F)). As a result, the output Q of the flip-flop 15 is "0" when there is no splash and "1" when there is splash.
Then (the same applies when the number of times is two or more), the presence or absence of splash can be detected. The operation of the first embodiment will be described with reference to FIG. First, when the workpiece 10 is positioned on the main body of the welder by the robot or the like, the control circuit of the main body of the welder supplies a work start command JS to the CPU 16. In response to this, the CPU 16 starts this processing routine, and first sets the target value MI of the energizing current to the initial value M0 (step S1). The initial value M0 is roughly set to a value at which a splash is moderately produced according to the characteristics of the work and the welding machine. Next, the leading sample flag S and the consecutive number C are set to "0" (step S2) (the usage of these will be described later). Next, it waits for the energization command ST to arrive from the welding machine body control circuit (step S3). Energization command ST is welding tip 8,
When a predetermined time (squeeze time) elapses after 9 is brought into contact with a predetermined welding point, it is sent from the welding machine main body control circuit. When the energization command ST arrives, the CPU 16 supplies the reset signal R to the flip-flop 15 (step S
4). As a result, the output Q of the flip-flop 15 becomes "0". Then switch signal SW to the inverter 4
To supply the welding current I (step S
5, FIG. 2 t0). The magnitude of the welding current I is the digital value D
Represented by I. Based on this digital value DI, the CPU 16 controls the control signal CS so that the welding current I becomes the target value MI.
Controls the duty ratio of AC AF. Next, the process proceeds to step S6, and waits for elapse of a predetermined time T1 from the time point t0 at which power is supplied. Generally, welding tip voltage VC
1 and VC2 change as shown in FIGS. 2B and 2C at the start of energization. Therefore, in the present embodiment, the gate circuit 14 is not energized immediately after the energization is started, but is delayed by the time T1 to make the gate circuit 14 conductive. In this way, even if the pulse DP is generated due to the voltage drop at the beginning of energization, it will not be erroneously detected as a splash. It should be noted that this time T1 is preferably changeable so as to be compatible with the shape and material of the work. When the time T1 has elapsed, the gate signal G is supplied to the gate circuit 14 (step S7). Next, the process proceeds to S8 and waits for the predetermined time T2 to elapse (FIG. 2 (E)). This time T2 is slightly shorter than the difference between the predetermined energization time T3 (FIG. 2 (A)) and the time T1. If a splash occurs within this time T2, the output of the gate circuit 14 (OU
The pulse DP1 appears at (T) (FIG. 2 (F)) and the flip-flop 15 is set. When the predetermined time T2 has elapsed, the supply of the gate signal G is stopped (step S9). Next, in step S10, the supply of the switch signal SW to the inverter 4 is stopped and the energization ends. Then, the energization completion signal E is sent to the welding machine control circuit (step S11). In response to this signal E, the welding machine body control circuit moves the welding tips 8 and 9 to the next welding position. Next, the processing proceeds to step S12, and the CPU 16 checks whether or not the leading sample flag S at this time is "0". The present invention, when a predetermined number of splashes occur continuously,
Alternatively, when a predetermined number of consecutive non-occurrences have occurred, a predetermined welding condition is controlled in a direction in which such a phenomenon does not occur. Therefore, immediately after the start of the welding operation or for the first welding spot after the adjustment of the welding conditions, only the occurrence of splash at the welding spot is recorded, and the welding conditions are not adjusted. The leading sample flag S is a flag used to determine whether or not the welding spot is the first one, and is set to "0" in step S2. Therefore, the answer here is "yes", and the CPU 16 proceeds to step S13.
Here, after setting the leading sample flag S to "1", the value of Q indicating the splash occurrence state at this time is loaded into the variable F in the next step S14. This variable F is used as data indicating the occurrence state of the splash at the previous welding spot when processing the next welding spot. Next, the CPU 16 proceeds to step S15 and sets the variable C to "1". This variable C is used as a counter for counting the number of consecutive splash points or non-splash points. After this, the CPU 16 returns to step S3. When the welding tips 8 and 9 are abutted and pressed against the next welding spot in response to the energization completion signal E in step S11, the welding machine body control circuit supplies the energization command ST to the CPU 16. In response to this, the CPU 16 executes steps S4 to S11 for the next welding spot, and proceeds to step S12. In step S13, the leading sample flag S is set to "1". So this time the answer to this step is no
Becomes Therefore, the CPU 16 proceeds to step S16, and a variable F representing the presence / absence of a splash of the welding spot before and a flip-flop 15 representing the situation of the welding spot at this time.
The difference D between the output Q and the output Q is obtained, and the process proceeds to step S17. When the difference D is not “0”, that is, the answer here is “No”
If, the occurrence status of the splash at the last welding point and the current welding point is different (when F = 1 and Q = 0, D =
1, D = 1 when F = 0 and Q = 1. ). In this case, the CPU 16 proceeds to step S14, fetches the contents of the new Q at this time into F, proceeds to the next step S15, resets the side continuous number C to "1", and then returns to step S3. When the difference D is "0", that is, when the answer is "yes" in step S17, the splash situation of the previous welding spot and the welding spot of this time are the same (F = 0, Q = 0, or F =). 1
Therefore, when Q = 1, D = 0. ). In this case, the CPU 16 proceeds to step S18 and adds "1" to the continuous number C. Then, the process proceeds to step S19, and it is determined whether or not the continuous number C has reached "5". When the continuous number C does not reach "5", the welding conditions are not changed in this embodiment. The answer is "No" because the second welding point is still assumed here. So CPU16
Returns to step S3 and repeats the same processing for the third and subsequent welding points. As described above, if the welding conditions are properly set, for example, if a splash occurs at a certain welding spot, no splash occurs at the subsequent two welding spots, and 1 after that.
Occurrences are random, such as splashing again at one welding spot. Therefore, if the welding conditions are set appropriately and the welding tip is in good condition, there are many situations of splashing the welding spot and the splash of the welding spot before the welding spot while executing welding for several welding spots. In case of
The answer is "No" in step S17, and step S
It is repeated that C = 1 at 15 and the continuous number becomes a break. Moreover, as described above, the welding conditions for the work 10 are not always adapted to that state, and the condition of the welding tip also changes as the number of execution points increases. For this reason, while the number of run points increases, finally the number of consecutive C
It happens that the value of reaches "5". In this case, the answer in step S19 is "yes" and the CPU
16 proceeds to step S20. Then, the contents of Q at that time are inspected. If the answer in this step is "yes", that is, Q is "1", it means that five welding spots "with splash" including the welding spot are continuous. Therefore, the CPU 16 subtracts the predetermined adjustment value MA from the target value MI in the next step S21, returns to step S2, sets the continuous number C and the leading sample flag S to "0", and then proceeds to step S3 again. If the answer in step S20 is "no", it means that five welding points without splash occur in a row. Therefore, the CPU 16 proceeds to step S22 and sets the target value M.
A predetermined adjustment value MA is added to I. If the welding current I is too large, the nugget may be defective. In addition, the current supply capacity is naturally limited. Therefore, in this embodiment, in step S22, the target value M
When I is increased, it is checked in the next step S23 whether it exceeds the upper limit value MM. When the target value MI exceeds the upper limit value MM, step S2
In step 4, the maximum current arrival signal M is supplied to the welding machine main body control circuit, and this routine is once ended. When the increased MI does not exceed the upper limit MM, the process returns to step S2. The adjustment value MA is determined in accordance with the characteristics of the work and the welding machine, following the example of the conventional manual adjustment. Next, the operation of the second embodiment will be described with reference to FIG. In this example, when the welding spots that generated splashes were continuous, it reached 3 dots, and when the welding spots without splashes were continuous, it was 6 dots, the target. The value MI is changed (steps S31 to S33). 1st about other flow
The embodiment is the same as that of the first embodiment, and the same step numbers are attached. As described above, when welding conditions are appropriate, splashes occur randomly to some extent. Therefore, as in the first embodiment, the continuous number C of splash-occurring welding spots and the continuous number C of non-splash-occurring welding spots are not discriminated and are judged based on the same criterion (= 5) (step S19) and maintained. When the welding conditions are controlled as described above, the number of welding spots at which a splash occurs and the number of welding spots at which a splash does not occur are roughly 5 minutes and 5 minutes. On the other hand, in the second embodiment, the continuous number of the welding spots with splash and the continuous number of welding spots without splash are different values (C ≧ 3 in step S32, step S32).
In 33, C ≧ 6) is determined. For this reason, in this embodiment, approximately one welding spot with splash generation and one welding spot without splash generation, that is, one for three welding spots do not generate splash.
Welding spots with splash appear at one rate. When it is desired to adjust the splash occurrence state, different judgment criteria are set for the continuous number C of occurrence and the continuous number C of non-occurrence as in the second embodiment. The third embodiment will be described with reference to FIG. In this embodiment, the process of calculating the ratio of the number of spots for splash generation to the number of spots for welding and adjusting the target value MI based on the result is added to the first embodiment (steps S42 to S49). ). The same steps as those in the first embodiment are designated by the same step numbers. When the welding conditions are controlled with a predetermined number of splash generation welding spots or a predetermined number of non-splash generation welding spots, it is possible to quickly respond to a change in the situation of the work 10, the welding tips 8, 9 and the like. This is a great advantage of the present invention. On the other hand, the process added here is a control based on the splash generation state of many welding spots, and therefore, there is an advantage that welding conditions more suited to the states of the work 10 and the welding tips 8 and 9 are created. . The third embodiment aims at a synergistic effect of these two advantages. That is, in the third embodiment, in the step S41 in place of the step S2 of the first embodiment, the CPU 16 adds the same variables S and C as those of the first embodiment and a variable indicating the number of welding execution points. A variable Y indicating the cumulative number of P and splash points at which a splash has occurred is set to "0", respectively. In step S42 following step S15, the CPU 1
6 inspects whether the value of Q at this time is "1". If the answer is "yes", then "1" is added to the sprache generation welding point cumulative number Y (step S43). When the answer is "no", this step S43 is bypassed and the process proceeds to step S44. Here, 1 is added to the number of welding points P. Then, in the next step S45, it is inspected whether or not the number of welding spots P has reached 100. In the third embodiment, for every 100 welding execution points, the number of splash generation points generated during that time is integrated, and the splash generation ratio is calculated based on this. When the welding execution spot P does not reach 100, the answer here is "No". In this case, the CPU 16 returns to step S3 and repeats the same processing. When the addition of the number of splash generation spots for 100 welding spots is completed, the answer in step S45 is "Yes". As a result, the CPU 16 proceeds to step S46. In this embodiment, the number of welded spots is 100, the splashed spot number is "30" as the center value, and "33" is the control upper limit,
The control lower limit is “27”. Steps S46 and S47 judge these. When the management upper limit is exceeded, the answer in step S46 is "Yes", and the CPU 16 subtracts the predetermined adjustment value MB from the target value MI (step S47). It returns to step S41. If it is within the control limit, the answer in steps S46 and S48 is "No", and the CPU 16 returns to step S41 without changing the target value MI. If the control lower limit is exceeded, the answer in step S46 is "No", the answer in step S48 is "Yes", and the process proceeds to step S49 where the CPU 16 adds the predetermined adjustment value MB to the target value MI. . When the target value MI is increased, that is, this step S49
If is executed, the process proceeds to step S23 as in the first embodiment to check whether the target value MI has reached the upper limit value MM. The adjustment value MB is smaller than the adjustment value MA. In this way, the adjustment value MA corresponds to a large fluctuation, and the adjustment value MB
With this, it becomes a form corresponding to small fluctuations and more detailed control is possible.

[Other Examples]

Although the welding current is controlled in this embodiment, other welding conditions such as welding time may be controlled. Also, two or more welding conditions may be controlled simultaneously. Further, it is advisable to devise the method of taking samples, the number thereof, the method of obtaining the ratio, the control limit, etc. in accordance with the characteristics of the work and the welding machine. Further, regarding the detection of splash, for example, the light-receiving element detects the occurrence thereof, the pressure sensor detects the fluctuation of the pressing force, the position sensor detects the welding tip movement, and A-D.
A method other than the embodiment may be used, such as using a converter and a CPU or detecting the resistance change by dividing the integrated value of the welding current I by the integrated value of the welding tip voltage VC for one AC cycle. Furthermore, although the present invention is applied to the inverter system in this embodiment, the present invention can be applied to other systems such as an AC system and a capacitor system.

【The invention's effect】

As described above, in the present invention, the splash generation impact point,
Welding conditions were controlled so that the number of spots without splashes would not continue for more than a specified number. Therefore, even if there is a variation in the state of each work, for example, the plate thickness or the surface state, it can be promptly dealt with, and the welding condition can be maintained at an appropriate value. Further, even with respect to a phenomenon in which the tip of the welding tip gradually becomes thicker, the change is reflected in the occurrence state of splash, so in the present invention, if the welding conditions are controlled, it is possible to quickly increase the diameter of the welding tip. It corresponds accurately, and the conventional step-up control becomes unnecessary. Further, under the welding conditions in which a splash is moderately generated in this way, the splash becomes far weaker than the conventional one. Therefore, the degree of danger to the operator, the degree of wear of the equipment, and the degree of wear of the welding tip can be further reduced. Furthermore, since the splashes are moderately present, it is possible to improve the welding quality and make the welding quality uniform without setting the welding condition to an excessive value such that the splashes occur every time. If control is performed so that the ratio of the number of spots for splash generation to the number of spots for welding performed within a predetermined range is added (third embodiment), more detailed control of welding conditions can be performed.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a block diagram showing a circuit configuration, FIG. 2 is a waveform diagram showing each signal, and FIGS. 3 to 5 are first to third embodiments, respectively. 6 is a flowchart showing the processing procedure of FIG. 13-15 ... Detecting means, 16-19, 23 ... Continuity detecting means, 4, 11, 12, 16-19, 23 ... Control means.

Claims (3)

[Claims] 1. A detection means for detecting the occurrence of splash,
A resistance welding control device comprising a continuity detecting means for detecting continuous generation or non-generation of splash and a control means for controlling welding conditions so that the continuous generation or non-generation of splash does not occur. 2. The resistance welding according to claim 1, wherein the predetermined number when the continuous generation is made and the predetermined number when the continuous non-generation is made are different numerical values. Control device. 3. The control means sets a ratio of the number of splash-occurring dots to the predetermined number of welding-executable dots to a predetermined value in a state where the splash is continuously generated or not continuously generated for the predetermined number of welding-executable dots. The resistance welding control device according to claim 1, wherein the welding condition is controlled so as to fall within the range.