JPS6352776A - Resistance welding machine - Google Patents

Abstract

PURPOSE:To stabilize the welding and to reduce a maximum electrification current value by giving a, drooping characteristic to an electric power control means based on the setting of a drooping characteristic setting means in case a detected value is larger than a set value in a comparison means. CONSTITUTION:A specific control point is set on an outside characteristic line by a means 11 to set the control point and an electric current to be supplied to a welding transformer 4 which is detected by an electric current detection means 8 is compared with the electric current corresponding to the control point. On the other hand, the drooping characteristic is set with a proper incline with the control point a boundary on the outside characteristic line by the drooping characteristic setting means 15. Then, in the comparison means 14, in case the detected value by the electric current detection means 8 is smaller than the set value, a control means 17 is operated so that the electric power control means 3 controls the electric power along the outside characteristic line of the titled welding machine. Furthermore, in the comparison means 14, in case the detected value by the electric current detection means 8 is larger than the set value, the control means 17 is operated by a means 16 to give the drooping characteristic so that the electric power control means 3 controls the electric power based on the set drooping characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a rectifier type DC resistance welding machine that can adjust external characteristics determined by the relationship between electrode tip voltage and welding current of each machine.

(b) Conventional technology resistance welding machines have electrical external characteristics unique to the equipment. For example, as shown in Figure 6, the welding object is inserted between the external characteristic line AB and the electrode tip. Load characteristic line X when
The welding current (IM) is applied at the intersection point M (operating point). In this case, due to fluctuations in the power supply voltage, etc., the external characteristic line A
As B changes by IMvc, the operating point changes to V, resulting in a large change in welding current (IM-+IM'), and the welding result becomes unstable.

In particular, as shown in Figure 7, the rectifier DC resistance welding machine has external characteristics closer to constant voltage characteristics than the commonly used single-phase AC resistance welding machine.
The slope is small δh). This has the following problems. In other words, a large maximum current value (IDS) that is not used in actual bath welding is likely to cause excessive changes in welding current in response to changes in load characteristics, causing dust to occur during welding energization and poor nugget formation due to insufficient current. For example, it is uneconomical to produce equipment that can be flushed.

``Furthermore, conventionally, in order to eliminate such adverse effects, the external characteristics are represented by the A, P Q v diagram shown in Figure 6, and the welding current (IN) is determined at the intersection point N with the load characteristic line X. Constant current, commonly referred to as constant current fGI
All the characteristics of J-type have been used.

However, in this constant current control, the current remains constant even when the slope of the load characteristic X fluctuates, and for this reason, 'tL may be a problem and welding may become unstable. r In other words, during the welding energization process such as glossejection welding, the energized road surface f
If * changes significantly, the change in current density will increase, resulting in a current shortage just before the end of welding, which may result in poor welding.

(c) Problems to be Solved by the Invention The present invention solves the above-mentioned conventional problems.Until the welding current reaches the control point, it is assumed to be an external characteristic unique to the welding machine, and beyond the control point, it is determined as appropriate. Welding stability can be obtained by obtaining external characteristics with a steep slope and suppressing fluctuations in bath welding current to a small extent in response to fluctuations in load characteristics, and the maximum current value can be suppressed even more. By making it possible to manufacture welding equipment economically, and by making it possible to appropriately adjust the welding current to variations in load characteristics,
For example, it is an object of the present invention to provide an entire welding machine that can solve the drawbacks of constant current control as in the case of the above-mentioned grosgeection welding.

B) Means for Solving the Problems Means for achieving the above object will be explained based on FIGS. 1 to 4, which correspond to embodiments.

First, the first invention includes a rectifier 5 in the secondary circuit of the welding transformer, power control means 3, 3' in the primary circuit, and a current detection means 8 that detects the entire current supplied to the welding transformer 4. In a rectifying DC resistance welding machine in which the control angle of the power control means 3 and 3' is controlled by the control means 17 and 17' based on this detected value, it is determined by the relationship between the voltage between the electrode tips of the welding machine and the welding current. Means 11 for setting a specific control point P on the external characteristic line AB and determining the welding current value corresponding to f'L
, means 14 for comparing the detection value of the current detection means 8 and the welding current value setting means 11, and means 15 for setting the drooping characteristic at an appropriate slope with respect to the control point P on the external characteristic line AB. and when the detected value by the comparison means 14 is larger than the set value, the control means 17 and 17' of the power control means 3, 3' are operated to give a drooping characteristic based on the setting of the drooping characteristic setting means 15. The device is characterized in that a means 16 is provided.

Further, the second invention provides a rectifier 5 in the secondary circuit of the welding transformer.
The primary circuit is equipped with power control means 3, 3' and 14
A rectifying DC resistance welding machine in which the current supplied to the welding transformer 4 is detected by the tMt detection stage 8, and the control angle of the power control means 3, 3' is controlled by the control means 17, 17' based on this detected value. Accordingly, a specific control point P is set on the external characteristic line A B determined by the relationship between the electrode tip 1IJj* pressure of the welding machine and the welding current, and the welding current value corresponding to this is determined. means 11; means 14 for comparing the detected value of the current detection means 8 with the current value of the control point setting means 11; and means 14 for setting the drooping characteristic at an appropriate slope with the control point on the external characteristic line as the border. means 15, and control means 17, 17' of the power control means 3, 3' based on the setting of the drooping characteristic setting means 15 when the detected value by the comparison means 14 is larger than the set value.
A means 16 that acts to impart a droop characteristic to the welding transformer, a means 20 for detecting the voltage of the primary circuit of the welding transformer, and a comparison of the outputs of the voltage detecting means 20 and the means 16 for imparting the droop characteristic to determine the power supply voltage. The invention is characterized in that means 22 are provided for adjusting the control means of the power control means so as to compensate for fluctuations in the power control means.

(E) Effect In the bath water heater of the first invention having the above configuration, the control point setting means 11 sets a specific control point P on the external characteristic line AB.
is set, and the current supplied to the welding transformer 4 detected by the current detection means 8 and the current corresponding to the control point P are compared. On the other hand, means 15 for setting drooping characteristics on the external characteristic line AB
Set the drooping characteristic at an appropriate slope with the control point P as the boundary.

Then, the comparison means 14 determines that if the detected value by the current detection means 8 is smaller than the set value, the power control means 3.3' controls the power along the external characteristic line AB of the welding machine. 17, 17', and comparison means 1
4, if the detected value by the current detection means 8 is thicker than the set value, the power control means 3
, 3' are the means 16 for imparting drooping characteristics to control the power and actuate the control means 17, 17'.

In this way, in the present invention, until the welding current reaches the control point, it is set as an external characteristic unique to the machine, and above the control point, an external characteristic with an appropriate slope is obtained, so that the load characteristics can be adjusted. It is possible to suppress fluctuations in welding current to a small level and to provide appropriate fluctuations.

However, the welding machine of the invention of i42 having the above-mentioned configuration has, in addition to the configuration of the welding machine of the first invention, a means 20 for detecting the voltage of the primary circuit of the welding transformer 4, and this voltage detection means 20. and the means 16 for imparting drooping characteristics to compensate for fluctuations in power supply voltage.
By providing the means 22 for adjusting the control means 17 of the welding machine, it is possible to compensate for fluctuations in the power supply voltage of the welding machine. The same effect as in invention 1 can be obtained.

(f) Example Embodiments of the present invention will be described below with reference to the drawings.

1FgJ is a block circuit diagram of an inverter-controlled rectifying DC resistance welding machine according to an embodiment of the present invention.

In the figure, 1 is a rectifier circuit that rectifies a three-phase AC welding power source, 2 is a smoothing capacitor, 3 is an inverter device (power control means) that replaces the DC current with a high-frequency light current, and 4 is a rectifier circuit that rectifies a three-phase AC welding power source. The welding transformer, 5, 5 is a rectifier provided in the secondary circuit of the welding transformer 4, 6, 6 is a T-pole tip, and 7, 7 is a workpiece.

Further, 8 is a current transformer 9 coupled to the primary circuit of the welding transformer 4.
and a current output circuit *10 that outputs the primary current (I) detected by the current transformer 9 as a DC voltage (Ex) proportional to it.
11 is the external characteristic line AB of the welding machine.
This is a means of setting a control point P on the top, as shown in Figure 2.
A control point P is arbitrarily set on the unique external characteristic line AB of No. 7 # coal bales. The control point setting means 11 outputs the welding current corresponding to the control point P and the corresponding DC voltage (Ep) from the control point setting circuit 13 based on the reference power source 12. This control point setting circuit 13 is provided with an adjustment mechanism so that the control point P can be arbitrarily determined on the external characteristic line AB.

Reference numeral 14 denotes a comparison means, which compares the outputs of the current detection means 8 and the control point setting means 11, and Er-Ep.
Outputs the subtraction result.

fc15 is a means for setting the drooping characteristic (drooping degree setting circuit), and it sets the drooping characteristic at an appropriate slope (fo to f illusion) with *1+point P on the Q1 external characteristic line AB as the boundary, 16 is the comparison means 14, and when El is larger than EP,
This is a means that works to cause the control means 17 of the power control means 3 to have a drooping characteristic based on the settings of the drooping characteristic setting means 15. In this means 16 for imparting all the drooping characteristics, Ex is Ep
For a smaller field @-, without operating to adjust the degree of droop, a signal is sent to the pulse width modulation circuit 18 of the control means 17 so that the inverter device 3 operates at the maximum arc control angle, and the comparison means 14 A command is issued to the pulse width modulation circuit 18 so that the inverter device 3 operates at the set degree of droop only when the result is Er)Ep.

That is, in the means 16 for imparting drooping characteristics, the output EI -Ep of the comparing means 14 is converted to α(EI-Ep) by an amplification circuit.
EP), but this amplification circuit does not operate when the input voltage is negative, and outputs only after receiving a positive input signal.

In addition, when the output of the amplification circuit is received by the next 'jf control circuit and the slope f due to the droop degree setting is fixed, the droop degree control circuit outputs the droop degree control voltage corresponding to α(EI-Ep). E
Output f. Then, this output E/ is subtracted from the set voltage Ec of the power supply voltage setting circuit by a subtraction circuit, and a signal of Ec-Bf is inputted to the pulse width modulation circuit 18. As a result, the control APf shown in FIG. 2 is performed.

18 is a pulse width modulation circuit (PWM) of the inverter unit ft3.
19 is a drive circuit for driving the semiconductor elements of the inverter device 1t3 based on the variable circuit 18 No. 46, and these are the control means 17 of the power control means (inverter device f3).

Although the embodiment described above is an inva one-type resistance welding machine, the same applies to a single-phase rectifier type DC resistance welding machine in which a single-phase power source is controlled by a power control means 3' (thyristor) shown in Fig. 3. I can say that.

In the figure, 17' is a control means, 20 is a firing angle control circuit in the control means, and 21 is a firing circuit.

Next, what is shown in FIG. 4 is the above-mentioned invention with an added function of compensating for T'L when the power supply voltage fluctuates. Specifically, the primary circuit of the welding transformer 4 is The control means 17 of the power control means 3 is adjusted to compensate for fluctuations in the power supply voltage by comparing the outputs of the voltage detection means 20 and the means 16 for imparting drooping characteristics. 2.

That is, the voltage of the primary circuit is detected by the transformer 21 21'
Correctly, the injected voltage Vo proportional to this n'2 voltage detection circuit t
'ft: Output and input to the subtraction circuit 22. Subtraction circuit 2
2, the human power Ec-E from the means 16 for imparting drooping characteristics
Vo'fc is subtracted from f and the result of 7 is outputted to the pulse width modulation circuit 18. The pulse width modulation circuit 18 operates to increase the inverter output with a positive input and decrease the inverter output with a negative input. Tsu1su, Ec
This feed puncture circuit operates so that -E f -Vo = 0.

FIG. 5 shows the relationship between the primary voltage of the welding transformer 4 and the primary voltage v11 when the device shown in FIG. 4 is operated fc. In this figure, when the primary current of the bath transformer 4 is between 0 and Ip, the welding transformer input voltage Vc is constant regardless of the direct current, and even if fluctuations in the human power source occur during this period, it is compensated. n value. 'Also, in the current region above IP, it shows the voltage V on PflliA due to the Vcli lower level setting f, and this voltage is always fed back to the subtraction circuit 22 as VO, so that even if the voltage on the Pf line is reached, the power supply Voltage compensation will be provided.

Note that the second invention h can also be applied to a system in which a single-phase AC input power source is controlled by a thyristor, as described in the first invention.

(G) Effects of the Invention As described above, the resistance welding machine of the present invention can reduce fluctuations in welding current in response to fluctuations in load characteristics, resulting in stable welding and maximum current flow. Since the value can be made small, welding equipment can be manufactured economically.

In addition, by providing a drooping characteristic of an appropriate slope, the welding current can be made to have appropriate fluctuations in response to load fluctuations, which solves the drawbacks of glossejection welding using constant current control, and allows the welding current to be adjusted to an appropriate level. It is possible to eliminate the occurrence of welding defects by energizing the bath at a high density.

[Brief Description of the Drawings] Fig. 1 is a block circuit diagram of a rectifying DC resistance welding machine according to an embodiment of the present invention, and Fig. 2 shows the voltage between the electrode tips and the melting W! An explanatory diagram of external characteristic lines, control points, and drooping characteristics that are determined by the relationship with current, FIG. 3 is a block circuit diagram of another embodiment of the present invention, and FIG. 4 is a diagram of another embodiment of the invention. Block circuit diagram, 5th
Figure 4 shows the relationship between the input voltage and input current of the welding transformer in the device shown in Figure 4. Figure 6 is an explanatory diagram of external characteristics, load characteristics, and constant current control. A picture of a late elbow;
FIG. 7 is an explanatory diagram of external characteristics of a single-phase AC resistance welding machine and a rectifying DC resistance welding machine. 3.3' ~ Power control means 4 ~ Welding transformer 5 ~ Rectifier 8 ~ Current detection means 11 ~ Control point setting means 14 ~ Comparison means 15 ~ Drooping characteristic setting means 16 ~ Means working to impart drooping characteristics to the control means 17.17' ~ Control means 20 of power control means
~1! L pressure detection means 22 ~ means AB for adjusting the control means ~ external characteristic line P ~ control point

Claims (2)

[Claims] (1) The secondary circuit of the welding transformer is equipped with a rectifier, the primary circuit is equipped with a power control means, the current detection means detects the current supplied to the welding transformer, and the control means controls the power based on this detected value. In a rectifying DC resistance welding machine that controls the control angle of the means, a specific control point is set on an external characteristic line determined by the relationship between the electrode tip voltage and the welding current of the welding machine,
means for determining a corresponding welding current value; means for comparing the detected value of the current detection means with the current value of the control point setting means; means for setting a drooping characteristic; and means for causing the control means of the power control means to apply the drooping characteristic based on the setting of the drooping characteristic setting means when the detected value by the comparing means is larger than the set value. A resistance welding machine characterized by: (2) The secondary circuit of the welding transformer is equipped with a rectifier, the primary circuit is equipped with a power control means, the current detection means detects the current supplied to the welding transformer, and the control means controls the power based on this detected value. In a rectifying DC resistance welding machine that controls the control angle of the means, a specific control point is set on an external characteristic line determined by the relationship between the electrode tip voltage and the welding current of the welding machine,
means for determining a corresponding welding current value; means for comparing the detected value of the current detection means with the current value of the control point setting means; Welding means for detecting the voltage of the primary circuit of the transformer; and control means for the power control means so as to compensate for fluctuations in power supply voltage by comparing the outputs of the voltage detection means and the means for imparting drooping characteristics. A resistance welding machine characterized by having a means for adjusting.