JPH01306080A - Method and device for controlling electrification for resistance welding machine - Google Patents

Abstract

PURPOSE:To maintain a set current value by controlling an electrification current value of a second cycle so as to approach the set current value based on the measured data of a current value of test electrification of a first cycle and controlling successively an electrification current value of a third cycle. CONSTITUTION:A firing angle at the time of test electrification of the first cycle is preset in a ROM26 and a thyristor is ignited by said set firing angle and the test electrification is carried out. By this test electrification, an electrification current is measured and this current value is detected by a toroidal coil 21 and added to a CPU28 through a current detection circuit 22, an integration amplifier 23 and an A/D conversion circuit 24 and stored in a RAM27. Said electrification current value and the data on the firing angle against a relative welding current value characteristic stored in the ROM26 are calculated with the CPU28 and a % current effective value is calculated. Further, a maximum theoretical current value is calculated by calculating by the electrification current value and the % current effective value. With the second cycle, the calculated maximum theoretical current value and the set current value are subjected to proportional operation by the data to determine the firing angle.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to improving a method and device for controlling energization of a resistance welding machine used for spot welding and the like.

[Prior Art] Since the energization process of resistance welding is generally a transient phenomenon of several cycles of the power supply voltage, thyristors and control circuits used for control are required to have high-speed response characteristics.

In addition, the impedance of the welded object changes each cycle as welding progresses, so control is required for each cycle in order to keep the current value constant.

In other words, the 11# of the welding machine is generally R-
This is equivalent to the constant current control of an L direct gain circuit, and the effective value of the conducting current is uniquely determined by knowing the thyristor firing angle α, the current conduction angle β, and the power factor angle φ. Since the impedance of the workpiece is unknown before welding starts, and the control period is as short as several cycles of the power supply, it is extremely difficult to control the applied current to the set value.

For example, the welding conditions for corrosion-resistant galvanized steel sheets are different from those for mild steel sheets, and the range of appropriate current values for welding is narrow, and if this current value is exceeded, welding becomes impossible, so welding control is difficult. Very difficult.

In conventional welding machines, the mains voltage is applied to the welding transformer through anti-parallel connected thyristors, and the two
Welding current is applied to the workpiece from the next side, and joining is performed metallurgically using Joule heat. Constant current control is performed by controlling the firing angle of the thyristors connected in antiparallel in each power cycle. In this case, the energizing current value is detected on the primary side or secondary side of the welding transformer, and the firing angle of the cyrisk is controlled so that the energizing current value to the workpiece becomes the set current value.

However, in such devices, the energization in the first cycle is controlled at a pre-fixed firing angle, and the actual measured value of the energizing current is fed back to the control from the second cycle onwards. The applied current may deviate significantly from the set value. In this case, even if welding progresses and the welding current value is controlled to the set current value and stabilized in later cycles, if the welding current value deviates significantly in the first cycle, the welding quality will deteriorate. In other words, if the welding current value is too large, explosions will occur and dust will occur), and if it is too small, the welding condition will be upslope.

In order to perform welding with stable quality against such load fluctuations, it is necessary to
High-level control is required to bring the energization conditions of the next cycle closer to the set current 1 by measuring at least the energization conditions of the previous cycle and the actual energization current value.

If the impedance (power factor angle φ) of the welded object is known before welding starts, a characteristic diagram of firing angle α and relative welding current value ■ can be created in advance using the power factor as a parameter. Although it is easy to determine the firing angle based on the
It is necessary to find the firing angle from the data table every time the object to be welded changes.

Further, even if such a method is adopted, since the impedance of the welded object varies during welding, it is necessary to perform real-time control in accordance with the welding energization cycle, making control very difficult.

Conventional welding sequence control consisting of timers, relays, etc. cannot perform sufficient control because high-speed calculation processing is not possible.Welding sequence control that allows high-speed calculation processing using a CPU etc. development is desired.

[Problem H to be solved by the invention] The present invention is proposed to solve the above problems, and by improving the conventional control method for resistance welding machines, the initial stage of the energization process can be improved. The present invention provides a method for performing welding with stable quality by controlling the current to always maintain a set current from cycle to cycle.

Another object of the present invention, proposed at the same time, is to provide a welding current energization control device for effectively carrying out the above energization method.

[Means for Solving the Problems] The present invention proposed to achieve the above object is a method for resistance welding in which the conduction angle of a thyristor is controlled every time the thyristor is fired. The energization control device measures the test welding current that flows when the workpiece is energized with a constant power factor angle and ignition angle set in the first cycle of energization. Based on the welding current, the theoretical maximum current value is calculated from the firing angle versus relative welding current characteristic with the power factor angle created in advance as a parameter, and in the second cycle of energization, the theoretical maximum calculated above is used as the current value. Based on the ratio with the set current value, the firing angle corresponding to the set current value is calculated from the above firing angle vs. relative current value characteristics, and the thyristor is fired using the firing angle obtained. Furthermore, from the third cycle of energization onwards, the above point is determined based on the ratio of the q constant current (1σ and the energization current value measured in the immediately preceding energization cycle). The thyristor is fired at the firing angle obtained by calculating the firing angle corresponding to the set lt current value from the arc angle vs. relative welding current characteristic, and the current value at that time is measured.

Furthermore, the present invention proposed at the same time is a device for effectively implementing the above-mentioned energization control method, which includes a memory section in which a control program including an input setting routine program for setting a plurality of control elements is stored in advance; Information is processed based on the control program. It is configured to include a processing device, a data input section for inputting control elements according to the welding conditions to be set, and a display section capable of displaying characters for displaying the set welding conditions.

[Function] In the energization control method for a resistance welding machine of the present invention, in the first cycle of energization, a test energization of a low current is applied to the workpiece at a predetermined power factor angle and ignition angle.

Then, the applied current at that time is measured, and based on the measured test welding current, the theoretical maximum current value is calculated from the firing angle versus relative welding current characteristic using the power factor angle created in advance as a parameter.

In the second cycle of energization, based on the ratio between the calculated theoretical maximum current value and the set current value, the firing angle for energizing the set current value is calculated from the above firing angle vs. relative current value characteristic. do.

Then, the thyristor is fired at the obtained firing angle, and the energizing current (1α) at that time is measured.

Furthermore, after the third cycle of energization, ;☆ Based on the ratio of the constant current value and the energization current value determined by I11 in the immediately preceding energization cycle, the current value is set from the firing angle vs. relative welding current characteristic. Calculate the firing angle for energizing.

Then, energization control is performed by igniting the thyristor at the obtained ignition angle and measuring the energizing current value of the crest.

Thus, the test energization data of the first cycle allows the second
Welding energization after the cycle is set to 1! Control is performed to approach the flow value.

Furthermore, the energization control device of the present invention proposed at the same time effectively performs the energization method described above.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

Figure s1 is a block diagram schematically showing eleven components of the present invention.

The basic configuration of the device of the present invention includes a memory section l in which a control program including an input setting routine program for setting a plurality of control elements is stored in advance, and a processing device 2 that processes information based on the control program. , a data input section 3 for inputting control elements according to welding conditions to be set, and a display section 4 for sequentially displaying instruction messages necessary for inputting control elements and input control elements. , controls the resistance welding machine control device 5.

When setting welding conditions, instruction messages for input are sequentially displayed on the display section, thereby guiding data input to the control elements in an interactive manner.

FIG. 2 is a diagram showing a specific example of the configuration of the present invention using a microcomputer.

The microcomputer is CPU2B, ROM26, R
It has a basic configuration in which an AM27 is equipped with an I10 interface 25, and the current detected by the toroidal coil 21 provided on the primary or secondary side of the welding transformer 36 (performed by switching operation of a switch SW, etc.) is used as a current detection circuit. 22, taken out via the integrating amplifier 23, and further A
/D conversion circuit 'ta24 converts it into a digital signal,
It is taken in and processed by the CPU 2B, and welding current control is executed according to the control setting value calculated in advance.

A control signal is sent to the ignition control circuit 29 via the I10 interface 25.

In this embodiment, a phase control circuit 30 in which SCRs are connected in antiparallel is used to control the welding current, and a constant current control method is used in which the SCR is turned on by an ignition pulse sent from an ignition control circuit 29. It is being done. 33 is a common transformer for obtaining a synchronization signal corresponding to the voltage of the power supply 34, 31 is a voltage abnormality detection circuit for detecting an abnormality in the supply voltage, and 32 is a voltage feedback circuit.

35 is a transformer for stepping down the household power supply to obtain a stabilized power supply to be supplied to the microcomputer system.

Control box 1 for inputting further control elements
0 is connected to the I10 interface 25.

This control box 10, as shown in FIG.
It is large enough to allow key input operations while being held with one hand, and has a display section 71 in the center, a human key 72 and a mode changeover switch 73 below it. The display section 71 is a 16-digit liquid crystal display device, and is capable of displaying letters such as the alphabet and numbers. The input keys 72 include numeric keys 72n from 0 to 9, an increment key F that advances the setting program, a decrement key B that advances the setting program backwards, and a write key WR. The mode changeover switch 73 is a switch for switching the setting device to program input mode, monitor mode, and operation mode.

In the case of the welding apparatus of the present invention, the firing angle for the test energization of the first cycle is preset in the ROM 26, and the thyristor is fired at this set firing angle to perform the test energization.

By this test energization, the energizing current is measured, and this current value is detected by the toroidal coil 21, amplified to the CPU 2B through the current detection circuit 22, the integral amplifier 23, and the A/D conversion circuit 24, and stored in the RAM 27. At the same time, the CPU 2B calculates the % current effective value using this current value and the data of the firing angle vs. relative welding current value characteristics stored in the ROM 26, and further calculates the current value and the % current value.
The theoretical maximum current value is calculated by calculating the current effective value.

FIG. 4 is a diagram showing the characteristics of the firing angle and the relative welding current value using the power factor as a parameter.

In the second cycle, the firing angle is determined by proportionally calculating the theoretical maximum current value and the set current value obtained above based on the firing angle vs. relative welding current value characteristic data stored in the ROM 26.

Below, the details of the welding method of the present invention will be explained with reference to the firing angle versus relative welding current value characteristic shown in FIG. 5 and the flowchart shown in FIG. 6.

The power factor angle φ during general spot welding is usually 50° to 70°.
If the firing angle α is around 120°, the effective current value will be about 0%, although it depends on the load power factor.

Therefore, in the case of this example, the firing angle α=128° and the power factor angle φ
Depending on the workpiece, φ=50°, 60°, 70°
etc., and perform the first cycle test energization (6th cycle).
(See Figure 101).

Effective test current of the first cycle 111I1128
Find the % current effective value (ratio when fully energized is 100%) In128 for the first cycle, and find I128/In128.

This 1128/I n+28 is the theoretical maximum current when the firing angle α of the device being used is O'' (or when firing angle α≦power factor angle φ), so let the theoretical maximum current value be IM. (See Figure 6 102, 103).

That is, I M= l 128/ I n128
shall be.

In FIG. 5, when the characteristic curve is regarded as a substantially straight line, the firing angle at the intersection with the product axis is defined as A.

When the power factor angle φ is 60°, the energizing current becomes a substantially continuous wave by making the firing angle α match the power factor angle φ, and the energizing current reaches its maximum in this state. In other words, when the ignition angle is between 0° and 606° (H vs. melt 19 current (1 g is 1.0).

Let ka be the value obtained by subtracting 600 from the above, and let B be the value obtained by adding the firing angle αS for the set current IS from ζ and 8, and then the following relationship can be obtained from FIG.

is the theoretical maximum current 1+ff found in the first cycle
IM and the set current value Is, the first antecedent force in FIG. 5 is obtained. In other words, if the power factor angle φ is constant, ζ, firing angle α
By approximating the relationship between relative welding and current value I as a proportional relationship, energization control is performed to bring the firing angle α2 of the second cycle closer to the set current value as the value obtained by the formula (2). 6 (see Figures 104-106).

In the subsequent third cycle, from the firing angle pattern 1 phase pattern 1 welding current value characteristics in Fig. 5 and the actual measured value of the energizing current in the second cycle, at the firing angle α2 which is faster than the firing angle A by B. 1
Since the actual measured current value of 2 was obtained, if the firing angle for obtaining the set current value of IS is α3 and C=A−α3, then the relationship +2 Is is established.

However, in this case, the difference between α2 and a3 δ = α3 - α2 is B,
It is approximated as being smaller than C.

Therefore, the firing angle α3 of the third cycle is as follows, and the firing angle αn of energization in each cycle is updated by applying the actual 1jll value of the energization 71 of the previous cycle to the firing angle vs. relative welding current value characteristic. However, control is performed so that the applied current value approaches the set current value Is (see FIGS. 107 to 111).

In addition, although the above explanation shows the case where the measured value I2 of the energizing current in the second cycle is larger than the set current value Is, the same is true even if (2) is smaller than IS. .

When formula L is generally expressed for the firing angle αn of the n-th cycle, it becomes n-1, and the current is controlled so as to approach the set current value Is. In this embodiment, since digital control is performed by a microcomputer, numerical processing is performed by making the firing angle of 180° correspond to hexadecimal number 0999H. Therefore, if the firing angle vs. relative welding ti current value characteristic is regarded as a straight line, then (to 1 becomes approximately 1606 and 16
Since the base number is 0888H, the above equation can be expressed as follows.

The above explanation illustrates the principle of the method of the present invention.

Next, with reference to FIG. 7, an example of a welding sequence using the energization control method of the present invention will be described.

In the initial pressurization 300, an electrode pressurization valve (not shown) is operated, an electrode pressurization device (not shown) is driven, and the electrode 20
The part to be welded is pressurized. In the first energization 301, a current for preheating is applied to the welded part by the SCRs connected in antiparallel.

Throughout this first energization step and the second and third energization steps described below, the energization N and current value are controlled to set values by the energization method of the present invention described above.

In the first cooling 302, the power supply for preheating is stopped, and the welded part is temporarily cooled. Then, the second energization (main energization)
After the part to be welded is heated again by 303, the second cooling 3
The energization is stopped from 05, and finally, the third energization 306
After this, the heated part to be welded is pressurized by the holding pressure 307, and the series of welding steps is completed after a pause 30B. The method of the present invention described above is carried out by sequentially performing the first energization cycle, the second energization cycle, the third energization cycle, etc. for each energization step.

In this embodiment, so-called "pulsation" in which the main energization 303 is performed intermittently a predetermined number of times is possible.

In addition, in the above embodiment, an energization pattern is used three times: first energization, second energization, and third energization, but any energization pattern can be selected depending on the material to be welded and its thickness. Is possible.

Furthermore, in this embodiment, when performing revised current control (detecting the primary current of the welding transformer 36 and controlling the secondary welding current), the control elements shown in Table 1 are set as welding conditions. Yes, it is possible, and characters like a table will be displayed on the display of the control box. The numerical values in parentheses in the table are values of setting examples.

Furthermore, in this embodiment, an abnormality detection function is provided, and the abnormality detection function as shown in Table 2 is displayed on the display section of the control box.

Below is the blank space No. 1 The story of the Tanuki Hikan and the Hansara Kosatsu Akiden L Ri-i starting series PROGF? A.M.
1, 2, 3.4 (2) Pulsation PU
LSATE 01~09 (3) Number of initial pressurization times 5QUEE2E 00~9
9 (30) Eaves cycle first energization time WE
LDI 00~99 (2) ■Cru
.

First cooling time C00L+ 00~
99 (3) No. cycle 2nd energization time
WELD2 00~99 (20) Eaves cruise second cooling time C00L2 00~99
(9) Eaves cycle 3rd energization time IIE
L03 00~99 (10) F cycle holding pressure time HOLD 00~99
(8) Cycle rest time
OFF 00~99
(40) No. cycle 1st welding current
C-WELDl 030-399 (199)
X100A 2nd welding current C-11ELD
2 030-399 (150) XIQOA 3rd
Welding current C-WELD3 030~39
9 (120) X100A 1st step welding current C
-5TEP-5030~393 (Summer 20) X100
A final step welding current C-5TEP-E 0
30~39B (+99) X100A step number
5TEP-CNT 01~29 (phantom
Number of step welds WELD-CNT 0
1~99 (90) XIO turns transformer turns ratio
TURN-RATIOL-150 (48) Number of secondary circuits 2ND-CIRCUIT 1.2
('I) 2nd table temperature Ll LJm 1st welding current C-IFELDI 0
0~99% 2nd welding current C-WE
LD2 00~99% 3rd welding current
C-11ELD3 00-99
%1st step welding current C-5TEP-500~9
9% final step welding current C-5TEP-
E 00-99% Finally, the procedure for setting the welding conditions of this energization control device will be explained below. In this embodiment, welding conditions are set by operating a control box 10fe shown in FIG.

Further, the values of each control element can be set as shown in the setting examples in Table 1. In the following explanation, the message appearing on the display section 71 is shown in "rj" and the message from the input key 72 is shown in "".

(1) Set the mote selector switch 73 to "program".

If each series does not contain data, fPROcRAM J series 1,
If data is already contained in 3, fPROGRAM
J(2) Enter data into series 2.

"2" rPROGRA 1 2 Jr W RJ rPULsATE　　-2J (3) Set 3 pulsations.

"3j rPULsATE　　-23J W.R.J. rsQtJEEZE -2J (4) Set a pressurization period of 30 cycles.

"30" fsQUEEZE -230J W.R.J. rWELDl -21 (5) Set the first energization time to 2 cycles.

"2" rWELDl -22J rWR” rcOOLl -2J (6) Set the first cooling time to 3 cycles.

"3" rCOOLI -23J "WR" rWELD2 -2 j (7> Set the second energization time to 20 cycles.

"20" F W E L D 2 -2 20
:RrWR" fcOOL2 -2 J (8) Set the second cooling time to 9 cycles.

"9" fcOOL2 -2 9J (9) At this point @ If you do not operate the rWRJ key (the same applies in other cases), you can correct the input data, and the second cooling time of 9 cycles is incorrect, and the correct value is 6. If it is a cycle, correct it as follows.

"06" rcOOL2 -2 06JWRJ rWELD3 -2 J (10)
The third energization time is set to 10 cycles.

"l O" rWELD3 -2 10J1' W
RJ rHOLD -2J (11) Set the holding pressure time to 8 cycles.

"8" rHOLD -28J W.R.J. fOFF　　　　　　-2J (12) Set the pause time to 40 cycles.

"40" rOFF -240j WRj rC-WELD 1 -2 J(1
3) Set the first welding current to 199 (X 100A).

When the ``199J constant current-voltage auxiliary switch (not shown)'' is set to ``constant current,'' constant current control is performed, and the following is displayed.

rc-WELD 1-2
199J On the other hand, when the constant current-voltage auxiliary switch is set to "voltage auxiliary", voltage compensation control is performed, and the following is displayed, for example.

fC-WELD 1-2 99. ! "~
VRJ r C-W E L D 2-2
! (14) Second welding current 150 (X 100A)
Set to .

"150""C-~VELD2-2 150Jr
'vV RJ IC-WELD3 -3 J(1
5) Set the third welding current to 120 (X I 0QA)! :
All settings.

120J r(knee VilELD3-2 120J
r~VRJ ・When the S W C switch is OFF, the display section 71 shows r
TURN-RAT ICj and performs the following (16) to (17).

(16) is set to the numerical ratio of 48.

"7↓8 J 1'TURN-RAT 10
48JWRJ r2ND-CI RCU IT
J(17) Set the number of secondary circuits to 1.

“1” r2ND-CIRCUIT IJ “WR
” i'DATA COMPLETE This completes the program input mode and sets the mote selector switch 73 to monitor mode or operation mode.

・When the SWC switch is ON, the display section 71 shows H7.
i becomes rC-3TEP-3-2J, and the following settings are made.

(18) Set the step welding current to 120 (X100A).

120J rC-STEP-5-2120,! WRJ rC-5TEP-E-2J (19) Step final welding current 199 (X100A)
Set to .

199J (20) When the constant current-voltage auxiliary switch is set to "constant current", constant current control is performed and the following is displayed.

1'c-5TEP-E-2199J (21) When the constant current-voltage auxiliary switch is set to "voltage auxiliary", voltage compensation control is performed and the following is displayed.

? C-9TEP-E-299J (22) rWRJ rsTEP-CNT-2J (23) Set the number of steps to 9.

"9" f’5TEP-CNT-29J "W R" rt’,1ELD-CNT-2,1 (24) Set the number of welding times to 90.

"90" r 1. t/ELD-CNT
-290Jr W RJ The subsequent settings and display are the same as in (16) and (17) when the SWC switch is OFF.

As explained above, data can be easily input in an interactive format.

[Effects of the Invention] According to the energization control method of the present invention, in each energization process,
The current value of the test energization in the first cycle is controlled based on the actual measurement data so that the energization current value of the second cycle approaches the set current value, and the energization current value of the third cycle is controlled based on the measured value of the energization current of the second cycle. so that the value becomes the set current value.
Since the control is carried out sequentially, the set current value is always maintained even if the load impedance of the welded object fluctuates for each energization cycle, making it possible to perform welding with stable quality using a simple control method.

Further, by using the energization control device of the present invention, it becomes possible to effectively implement the energization control method of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of the present invention, FIG. 2 is a diagram of a specific example of the configuration of the present invention configured using a microcomputer, and FIG. 3 is an explanatory diagram of a control box.
Fig. 4 is a characteristic diagram of thyristor firing angle versus relative welding current value showing the power factor as a parameter, and Fig. 5 is a diagram illustrating the operating principle of the present invention using a characteristic diagram of thyristor firing angle versus relative welding current value. , FIG. 6 is a flowchart explaining the operating principle, and FIG. 7 is a flowchart explaining the welding process. [Explanation of symbols] I...Memory section 2...Processing device 3...Data input section/l...Display section 20...Workpiece 30...q Iristor Ml Fig. 7, ] No. Figure 3 Figure 7

Claims (2)

[Claims] (1) An energization control method in resistance welding in which the conduction angle of the thyristor is controlled each time the thyristor is fired, and current is passed through the workpiece to perform welding, and in the first cycle of energization, a constant power factor angle is applied. Measure the test welding current that flows when the workpiece is energized with the firing angle set to , and based on this measured test welding current,
The theoretical maximum current value is calculated from the firing angle vs. relative welding current characteristic with the power factor angle created in advance as a parameter, and in the second cycle of energization, the ratio of the theoretical maximum current value calculated above and the set current value is calculated. Based on the above firing angle vs. relative current value characteristics, calculate the firing angle corresponding to the set current value, fire the thyristor at the firing angle obtained, and measure the energizing current value at that time. Furthermore, after the third cycle of energization, the set current is determined based on the firing angle vs. relative welding current characteristic, based on the ratio of the set current value and the energized current value measured in the immediately previous energization cycle. A method for controlling energization of a resistance welding machine, characterized in that the thyristor is ignited at the ignition angle obtained by calculating the ignition angle corresponding to the value, and the energization current value at that time is measured. (2) a memory section in which a control program including an input setting routine program for setting a plurality of control elements is stored in advance; a processing device that processes information based on the control program; and control according to welding conditions to be set. The energization control device for a resistance welding machine according to claim 1, further comprising: a data input section for inputting elements; and a display section capable of displaying characters for displaying set welding conditions.