JPS6213115B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for controlling the output of a resistance welding machine, and is intended to grasp the welding quality during welding and to control the welding quality so that the quality is appropriate.

Conventionally, welding quality during resistance welding (tensile shear stress,
It is extremely difficult to grasp the appearance of nuggets, etc. during welding and to control the welding quality to achieve appropriate welding quality, and this has only been known through welding quality tests after welding.

That is, the appropriate values for the welding quality of resistance welding (particularly spot welding) have been determined by conducting preliminary experiments in advance and determining the appropriate values for the three major welding conditions: welding current, total energization cycle, and pressurizing force.

Recently, among these three major conditions, by measuring the effective value of welding current and the actual energization cycle during welding, the deviation from each value from the preset value is found and indirect judgment of welding quality has been made. It was on.
However, since component factors that have a primary relationship with welding quality are detected and optimization control is not performed during welding, it is necessary to correct the three major conditions each time for chip wear and the like. Furthermore, when there was a sudden change in the conditions, it was necessary to perform welding again.

In order to overcome these conventional problems, the present invention attempts to perform appropriate control during welding and to homogenize welding quality.

First, the principle of the present invention will be explained.

First, perform model welding (standard welding), and memorize the welding current (current that actually flowed) and chip-to-chip voltage (first integral value of chip-to-chip voltage or second integral value of chip-to-chip voltage). , calculate the heat input for each energization cycle at this time, and control the firing angle of the control rectifier from the second time onward to achieve this heat input,
Controls heat input to welding material. In other words, if the experimental heat input is as per the model welding, the strength will be constant (unchanged)
It has been concluded that welding is possible.

Note that the first function in this specification is based on the above principle, and the following constant K ₁ is calculated (first function K ₁ =I _e ×V _t
( _Ie and _Vt are known from the model welding, and _K1 can be found). Next, the proportionality constant K ₂ of the second function is determined by model welding.

That is, the second function Therefore, _Ie is known, θ is θ at the time of model welding, and K ₂
is found.

The first function and second function are determined by the above, and 2
For subsequent welding, welding with constant heat input is performed.

An embodiment of the present invention is shown in FIG. 1 below. In the figure, 1 is a control rectifier such as a bidirectional three-terminal control rectifier, 2 is a welding transformer, 3 and 3' are electrode chips, 4 and 4' are inter-chip voltage detection lines; One end is connected to the P ₁ and P ₂ points above. Reference numeral 5 indicates the welding work material, and 6 indicates a first integration circuit, the input side of which is connected to the detection lines 4 and 4'.This circuit 6 detects the chips for each cycle from the 1st cycle to the arbitrarily set energization cycle set in advance. Integrate the voltage across half a cycle. This integral value for each cycle is called a first integral value. Then this first
The integral value is input to the second integral circuit 7 in the next stage, and the first integral value is integrated from the first cycle to the arbitrarily set energization cycle, that is, the entire first integral value is integrated, and this value is called the second integral value. . Next, this second integral value is input to the first function circuit 8 installed at the next stage, and this circuit 8 inputs the second integral value (this value is set as V _t ) and the desired welding effective current value (this value is set as I _The circuit has a circuit configuration that calculates the first functional expression shown in the relationship between
The desired welding effective current value I _e is determined by: If we now introduce a first functional expression I _e = K ₁ = V _t , the first functional constant is K ₁ . Also the first
The first function circuit 8 may be installed at the next stage of the integration circuit 6, and the second integration circuit 7 may be deleted. At this time,
The first function circuit 8 is the first integrated value group of the first integral value group of the first integral circuit 6.
The integrated value (particularly referred to as V _o ) is received, a desired welding effective current value I _e is calculated using the first functional equation, and the welding effective current value I _e is outputted from the output end of the first functional circuit 8 . The first functional expression at this time is I _e =K ₁ /V _o . Further, a second function circuit 9 is installed next to the first function circuit 8, and the welding effective current value I is connected to the input terminal of the second function circuit 9.
Enter _e . The second function circuit 9 is composed of an arithmetic circuit expressed by a relational expression (referred to as a second function expression) between the welding effective current value I _e and the firing angle signal of the control rectifying element 1. If the effective welding current value _Ie is input to the second function circuit 9, a desired firing angle signal is generated from the output terminal of the second function circuit 9. Now, if the desired firing angle is θ, and the instantaneous value of welding current (i
), it is expressed as i=K ₂ sin θ, and the effective current value I _e at this time is expressed by the following second functional expression. That is, It is. K ₂ is called the second function constant. That is,
A control signal representing the desired firing angle θ (this signal is referred to as V〓) is generated from the output terminal of the second function circuit 9. Further, an ignition circuit 10 is provided at the next stage of the second function circuit 9.
The ignition circuit 10 receives the control signal V and converts it into a signal sufficient to drive the control rectifier 1. Now, if the firing angle of the control rectifying element 1 set before the start of the main welding is θ ₀ , it is converted to the desired firing angle θ by driving the main control circuit configuration. The entire remaining energization cycle is then sustained at θ. Incidentally, the signal indicating the arbitrarily set energization cycle is indicated by the output from the counting circuit 11. That is, the counting circuit 11 detects the welding current with a current detection device (current transformer or shunt) 12, counts the number of energization cycles based on the detected current, and when the preset arbitrary energization cycle is reached, the cycle is stopped. The counter circuit 11 generates a signal shown in FIG. The signal output is inputted to the circuits 6, 7, 8, and 9, and the circuits 6, 7, 8, and 9 perform the desired function based on the input. Note that the output of the circuit 11 is not necessarily the output of the circuit 6,
It is not necessary to input to all circuits 7, 8, and 9, and it is possible to input only to circuits 7 and 8. The waveforms of each part of the above circuit configuration are shown in FIGS. 2 and 3. Figure 2A shows the welding current waveform i with respect to time t, Figure 2B shows the inter-chip voltage waveform v at the detection end points P ₁ and P ₂ , and Figure 2C shows each voltage waveform integrated by the first integrating circuit 6. FIG. 3 is a diagram showing an integral value V during a positive half cycle for each energization cycle. Note that integration between negative half cycles may also be used. for example
V ₁ , V ₂ , and V ₃ are the integral values. Now, in the first integration circuit 6, the integral values V ₁ , V ₂ , V ₃ for each positive half cycle
... is taken as the first integral value. Also, the first integral value of each cycle is reset to zero. Incidentally, t ₁ , t ₂ . . . t ₁₀ indicate time, and the correspondence between the respective waveform positions is indicated by t ₁ , t ₂ , . . . t ₁₀ . The chip-to-chip voltage e is expressed as e=iR+Ldi/dt, where i is the welding current, R is the DC resistance, and L is the inductance.The first integrating circuit 6 determines the chip-to-chip voltage for each cycle. If we integrate for half a cycle in the direction, we get V
=∫edt=∫i・Rdt, which is a true value proportional to the heat generation of the welding part. That is, the first integral values of the first integrating circuit 6 indicate V ₁ , V ₂ . . . . If these _V1 , _V2 , . The total energization cycle of the α waveform in Figure 3 is 10.
The cycle is shown from V ₁ to V ₁₀ .
Further, in the β waveform obtained in the same manner, the first integral value (this is referred to as V ₅ ') decreases significantly at the fifth cycle. This is probably due to dust generated during welding. Now, if the fifth cycle is the arbitrarily set energization cycle, the value _V5 of the α waveform at that time becomes the Vn shown above. If V ₅ ' of the β waveform is extracted as _Vo , this value will not be truly proportional to the heat generation, and must be taken into consideration in the control circuit as will be shown later. Note that the second integral value V _t is V _t =V ₁ +V ₂ +V ₃ +V ₄
+ _V5 .

Next, the control method of the present invention will be explained.

First, as a first step, standard welding is performed and the inter-chip voltage of standard welding is determined. For example, α in Figure 3
The waveform corresponds to this.

The value obtained here is defined as the first integral value or the second integral value. Let these values be _VN .

As the second step, the effective current I during standard welding is
Find _e and set the firing angle at that time to θ. Then, temporarily store I _e .

As the third step, from the above V _N and I _e , the first function
Find K ₁ and the second function K ₂ .

In the fourth step, arbitrary welding is performed and the voltage between the chips is determined. For example, the β waveform in FIG. 3 corresponds to this.

In addition, the first and second functional expressions are determined so that the β waveform asymptotically approaches the α waveform during the arbitrary welding, θ is determined from these functions, and the firing angle θ is increased or decreased for each cycle. do.

By the way, it is necessary to determine the effective current value I _e and the first function value V _o in a preliminary experiment. Therefore, _Ie is detected by the current detection device 12 shown in FIG. 1, the detected current is converted into an effective current by the welding effective current conversion circuit 13, and the output is received by the circuit 8 to achieve the above purpose. It is possible to do so. It is assumed that the circuit 13 also calculates and outputs the phase angle θ of the current waveform. However, if _Ie is determined by another device during a preliminary experiment, it may be sufficient to store this in advance in the circuit 8 using another method, and the circuit 13 is not necessarily required.

Next, FIGS. 4 and 5 show an example of the concept of the second function formula built in the second function circuit 9. Now, as shown in Figure 4, the current waveform is i=
Assume that K ₂ sin θ and the conduction angle is π from θ and 2π from (π+θ).

The effective current value at that time is determined from the γ waveform in FIG. In other words, the γ waveform is It is.

By the way, the method for finding K ₂ is to calculate the effective current value I _e
Although it is possible to always correct K ₂ during actual welding by detecting θ and θ, there is no need to receive the output from the circuit 13 if the value of K ₂ is known in advance from a preliminary experiment. Furthermore, another second function may be obtained using another method. This must be taken into consideration especially when using an inductance load.

Next, if dust occurs like the β waveform in FIG. 3, the following operation may be considered. An example of the circuit is shown in FIG. 14 is an abnormality detection discrimination circuit, 15 is a timer circuit, and circuits 6,
The configurations 14, 15, and 10 allow the following operations. First, the output of the circuit 6 is detected by the abnormality detection discrimination circuit 14.
The circuit 14 generates envelopes such as the α and β waveforms shown in FIG. and temporarily memorize it. Furthermore, as shown in the β waveform, within the arbitrarily set energization cycle,
When there is an abnormal voltage drop such as V ₅ ', a discrimination output indicating that there is an abnormal voltage drop is generated (when there is no abnormal voltage drop, no discrimination output is generated). Then, the timer circuit 15 is activated to change only the initial setting energization cycle while keeping the ignition circuit 10 fixed at the initial setting current.

That is, when the output of the timer circuit 15 is present, the output of the circuit 9 is cut off, and the firing angle θ that determines the welding current is determined by changing θ determined before welding to the circuit 1.
It lasts for a timer period determined by the output of step 5.

In this way, malfunctions will not occur even when dust is generated.

In FIG. 1, what is shown by a solid line is the basic circuit of the present invention, and what is shown by a broken line is an auxiliary circuit. In addition, the optional setting energization cycle is
As can be seen from FIG. 3, it is better to decide in advance within the positive differential coefficients of the α and β waveforms, that is, around 3, 4, and 5 cycles.

According to the output control method and device according to the present invention as described above, the following effects can be achieved.

(1) The welding quality can be controlled to be constant (homogenized) during welding.

(2) Since the first functional equation is adopted, the desired welding current can be easily determined.

(3) Unlike conventional methods, there is no need to check the welding quality after welding, contributing to labor and manpower savings in factories.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of the output control device of a resistance welding machine according to the present invention, Fig. 2 A, B, and C are diagrams showing various waveforms during resistance welding, and Fig. 3 shows the energization cycle and the first
FIG. 4 is a diagram showing the relationship with the integral value, FIG. 4 is a diagram showing the welding current waveform, and FIG. 5 is a diagram showing the relationship between the firing angle and the welding effective current value. 1... Control rectifying element, 2... Welding transformer, 3,
3'... Electrode chip, 4, 4'... Inter-chip voltage detection line, 5... Welding work material (base material), 6... First integral circuit, 7... Second integral circuit, 8... First function circuit, 9...
Second function circuit, 10... Ignition circuit, 11... Counting circuit, 12... Current detection device, 13... Welding effective current conversion circuit, 14... Abnormality detection discrimination circuit, 15... Timer circuit.

Claims (1)

[Claims] 1. Detects the voltage between electrode tips during welding of a resistance welding machine with a built-in control rectifying element for controlling welding output, and detects the voltage between the electrode tips during welding, up to an arbitrarily set energization cycle arbitrarily set in advance during the entire energization cycle. The integral value of the inter-electrode chip voltage during each half cycle for each cycle is determined and these values are used as the first integral value, or further, the first integral value for each cycle is determined from the first cycle to the arbitrary setting. The value accumulated up to the energization cycle is defined as the second integral value, and the first integral value for each cycle or the overall second integral value in the arbitrarily set energizing cycle is the sum of each integral value and the desired welding effective current value. The desired welding effective current value is determined by substituting it into the first functional formula determined in advance according to the relationship, and the first
The first function constant of the function formula is determined by measuring the first integral value or second integral value and the corresponding welding effective current value during the arbitrarily set energization cycle in a preliminary experiment before starting the actual welding, and then formulating the first function constant in the first function formula. The desired welding effective current value is further determined by substituting the desired welding effective current value into a second functional equation previously determined based on the relationship between the welding effective current value and the desired firing angle of the control rectifying element. The firing angle is determined, and the second function constant of the second function formula can be determined by measuring the relationship between the welding effective current value and its conduction angle in advance in the preliminary experiment and substituting it into the second function formula, or during actual welding. The resistance welding machine is characterized in that the output of the resistance welding machine is controlled by converting the firing angle, which is obtained by performing the above operation and is set before the start of main welding, into the desired firing angle. output control method. 2. The first functional expression represents the first integral value during the arbitrarily set energization cycle as _Vo , the second integral value of the electrode tip voltage as _Vt , the desired welding effective current value _{as Ie} , and the first functional constant as K. ₁ , I _e = K ₁ /V _o or I _e =
The output control method for a resistance welding machine according to claim 1, characterized in that the output is expressed as K ₁ /V _t . 3 When the second functional formula assumes that the welding effective current value is I _e , the firing angle of the control rectifying element is θ, and the second function constant is K ₂ , An output control method for a resistance welding machine according to claim 1, characterized in that: 4. The output control method for a resistance welding machine according to claim 1, wherein the arbitrarily set energization cycle is preset within a positive differential coefficient on the envelope of the first integral value. 5 In a resistance welding machine with a built-in control rectifying element for controlling welding output, the voltage between the electrode tips is used as an input signal, and the voltage between the electrode tips is integrated for half a cycle from the first cycle to the arbitrarily set energization cycle. a first integral circuit that outputs a first integral value, and a second integral circuit that integrates the first integral value directly or outputs a second integral value on the output side of the first integral circuit.
Selectively receives the first integral value only during the arbitrarily set energization cycle connected via the integral circuit, or receives the second integral value and calculates the desired welding value according to the first function equation determined in advance. a first function circuit that outputs an effective current value; and a second function equation determined in advance connected to the output side of the first function circuit that calculates and outputs a desired firing angle signal of the control rectifier. a second function circuit; and an ignition circuit connected to the output side of the second function circuit that converts the ignition angle of the control rectifier into the desired ignition angle, and displays the arbitrarily set energization cycle. A resistor characterized in that a signal is inputted from the output side of a separately installed counting circuit to the first integrating circuit, the second integrating circuit, the first function circuit, and the second function circuit installed at the next stage to perform the control respectively. Welding machine output control device.