JPH0780057B2 - DC resistance welding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a plurality of inverters that are operated in parallel, and it is preferable to control the operation stop of all the inverters when the output of one of the inverters decreases or when an overcurrent occurs. The present invention relates to a direct current resistance welding device.

[Prior Art] A DC resistance welding apparatus using an inverter requires a current of tens of thousands of amperes when welding a member to be welded, for example, aluminum. For this reason, the present inventor has proposed that a plurality of power supply units each including a converter, an inverter, a welding transformer, and a rectifier are provided, and a DC output from the rectifier is combined to obtain a large current.

In such a device, the switching transistors of the inverters operating in parallel are driven on the same time axis and pulse width by the control adopting the base drive means such as the PWM method which constitutes the inverter, and the constant current is controlled by the feedback amount. Control, etc. are being performed.

In such a case, abnormality processing corresponding to each power supply unit using detection signals corresponding to abnormality of each power supply unit, for example, external cable damage (ground fault) and leakage, temperature rise of switching transistor and welding transformer, etc. Generally, such control means is formed, for example, when the power is turned off.

[Problems to be Solved by the Invention] However, in the above-described conventional technique, the control means relating to the abnormality processing is formed in each power supply unit. For this reason, for example, when the switching transistor of a certain inverter is damaged due to demagnetization or the like, and output reduction, stop, etc. occur, other inverters are added to the member to be welded as a load,
That is, since the welding current is supplied from the normal inverter, the output current of each inverter increases to a predetermined value or more, which is so-called overcurrent. Therefore, there is a risk that the switching transistor may be damaged, and it is difficult to identify the inverter that has caused an abnormality such as output reduction or stop.

The present invention has been made in view of the above point, and in a relatively simple configuration, abnormality of inverters performing parallel operation, that is, output reduction or overcurrent is individually detected, and all of the abnormality is detected. It is an object of the present invention to provide a DC resistance welding device in which quick stoppage control of an inverter is suitably performed.

[Means for Solving the Problems] In order to solve the above problems, the DC resistance welding apparatus of the present invention, as shown in the basic principle diagram of FIG. 1, includes at least a converter, an inverter (A), and a welding transformer. In a DC resistance welding device in which a plurality of power supply units each including a rectifier are provided and which derives a combined substantial DC, the current related to the connection line between the converter and the inverter (A) or the output path of the inverter (A) is detecting and, a detection means for delivering a detection signal (S _i) (B), and compares the value with a predetermined value of said detection signal (S _i), the determination signal when the difference is yielded (S _m) Comparing means (C) for sending out, and control means (D) for sending the drive signal (S _o ) for stopping the operation to the inverter (A) when the judgment signal (S _m ) is supplied. It is equipped and configured.

[Operation] In the above-mentioned configuration, the detection means (B) is, for example, a toroidal coil detector, and is provided in the connection line between the converter and the inverter (A) or the output path of the inverter (A). ,
A detection signal (S _i ) related to the current is derived.

A comparator or the like is adopted as the comparing means (C), for example, the normal time of the current is set as a predetermined value (reference value), and the detection signal (S _i ) is supplied, and then the respective comparison is made to detect the detection signal. When the (S _i ) is larger or smaller than the predetermined value, the determination signal (S _m ) is sent.

When the control means (D) confirms the determination signal (S _m ), it sends a drive signal (S _o ) to all the inverters (A), for example, to instruct the base drive unit to stop the operation of the inverter (A). Stop the operation of the inverter.

[Embodiment] Next, an embodiment of the DC resistance welding apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 shows the structure of the embodiment, and FIG. 3 shows the structure of the abnormal current detector. Furthermore, FIG. 4 shows the state of DC output,
Further, FIG. 5 shows a flowchart relating to the program of the system controller.

In FIG. 2, reference numeral 10 is a three-phase 400V ON / OFF section (including ELB and the like), and A, B, C, and D are power supply sections that perform parallel operation. A converter is provided in each of the power supply units A to D.
12a to 12d, inverters 14a to 14d, welding transformer 16a
To 16d and rectifiers 18a to 18d, and the rectifiers 18a to 18d
The direct current E ₁ synthesized at the output end of 18d is applied to the welding gun 20. Further, a member (work) 22 to be welded is sandwiched between the welding tips 20a and 20b of the welding gun 20.

Reference numerals 26a to 26d denote switching transistors T _r1 , T _r2 , T _r3 , and T _r4 connected to the inverters 14 a to 14 d, respectively.
It is a base drive circuit that performs base drive of (full bridge circuit), ON / O with the switching frequency fixed.
A so-called fixed frequency pulse modulation method (PWM) that changes the FF time ratio is used.

Reference numeral 30 is a one-chip microprocessor (welding timer) equipped with a CPU, RAM, ROM, I / O, etc., and is connected to, for example, a setting means / centralized control device such as a computer for FMS that performs full-closed NC control. The so-called system controller is provided with a so-called welding sequence control and a PWM circuit and the like.

In such a configuration, three-phase 400V converters 12a through 1
It is rectified by 2d and then converted into pulsed high frequency waves (hereinafter, referred to as alternating current as necessary) by the inverters 14a to 14d. Further, the alternating current is supplied to the welding transformers 16a to 16d and converted into a relatively low voltage of 10V and a large current. Subsequently, the double-wave rectification is performed by the rectifiers 18a to 18d and combined to obtain the direct current E ₁ .

Furthermore, the system controller 30 is connected to a bus fuse disconnection, a primary cable leakage, an abnormality detection means (not shown),
Switching transistors T _{r1 to} T _r4 / Welding transformer 16
A detection signal relating to the temperature of a to 16d is supplied, and predetermined control, for example, operation stop of the corresponding converters 12a to 12d and inverters 14a to 14d or interruption of three-phase 400V (ON / OFF)
A sequence control signal for performing the section 10) and the like is derived.

The above-described configuration for performing such an operation is a well-known inverter control power source used for a so-called welding robot or the like.

Next, current detectors 32a to 32d and 34a to 34d such as toroidal coils are arranged on the connecting lines of the converters 12a to 12d of the power supply units A to D and the inverters 14a to 14d. Then, the currents I _a1 , I _b1 , I _c1 , I _d1 and I _a2 , I _b2 , I _b2 , the polarity of which is reversed due to the switching operation of the inverters 14a to 14d,
A signal having a value corresponding to I _c2 and I _d2 is derived, and the current determination unit 3
It is supplied to 6a, 36b, 36c and 36d.

Here, an example of the current determination unit 36a will be briefly described. In this case, the configurations of the other current determination units 36b to 36d are also the same.

The current determination unit 36a has two systems of signal processing units connected to the current detectors 32a and 34a, but each has the same configuration.

In FIG. 3, the signals from the current detectors 32a and 34a are supplied to the comparators 50 and 52, respectively. A predetermined value (reference value) is set in the comparators 50 and 52, for example, a variable resistor VR that is set to use a value obtained by the current detectors 32a and 34a as a reference during normal operation of the inverters 14a to 14d. ₁ and VR ₂ are installed. Then, the isolation circuit 56 for separating the noise signal, which is derived from the comparators 50 and 52, that is, the signal from the current detectors 32a and 34a is superposed on the derived signal with a predetermined value or more, 58 are provided. Further, latch circuits (JK / FF) 62 and 64 for timing the control operation of the system controller 30 and a negative theoretical AND circuit 6
The determination signals S _1a and S _1b are derived via 6 and 68.

In the current determination units 36a to 36d, first, the currents I _{a1 to} I _d1 and I _{a2 to} I _d2 derived by inverting the polarity on the time axis are constant (see FIGS. 4 (a) to (d)), That is, the operation of the power supply units A to D is normal, and thereafter, FIG.
As shown in FIG. 4, when the power supply unit A causes a decrease / stop of the output (after the point t shown in the figure), the outputs of the power supply units B to D become overcurrent (FIGS. 4 (f) to (h)). After the indicated t point). In this case, the currents I _b1 to I _d1 and I _{b2 to} I _d2 increase, and the determination signals S _2a , S _{2b to} S _4a , and S _4b from the current determination units 36b to 36d are transmitted to the system controller.
30 are supplied respectively. And the system controller 30
Then, the presence / absence of the determination signals S _1a and S _{1b to} S _{4a to} S _4b is sequentially determined. First, the determination signal S _2a determines the overcurrent in the outputs of the inverters 14a to 14d. Here, the base driving of the switching transistors T _{r1 to} T _r4 respectively arranged in the inverters 14a to 14d is stopped, that is, sent to the base driving circuits 26a to 26d via the signal distributor 32 to stop the switching operation. Drive signal
Transmission of C ₃ (timing gate signal) is stopped. Therefore, for example, the switching transistor T
_{In the} state where the output of the other inverters 14b to 14d is overcurrent due to the damage or the like of _r1 , which causes the output to decrease or stop, the operation of the inverters 14a to 14d is stopped, except for the switching transistor T _r1. Will be prevented from being damaged.

In addition, the inverters 14a to 14a that have caused output drop, stop, etc.
By performing a visual display of 4d, for example, an LED display (not shown), the abnormal portion in the inverters 14a to 14d, that is, the inverter 14a in the above example, can be confirmed as soon as possible.

Below, drive signal C based on the program stored in ROM
The sequence control of the system controller 30 relating to the derivation of ₃ will be described (see FIG. 5).

After the operation of the whole program is started, its execution is started based on the welding start command from the setting means / centralized control device.

In step 101, a process of instructing to take in the determination signals S _1a and S _1b is performed.

In step 102, the process of determining the presence / absence of the determination signals S _1a and S _1b is performed. If NO, proceed to the next step 103. If YES, the process proceeds to step 109.

In step 103, processing for instructing the fetching of the determination signals S _2a and S _2b is performed.

In step 104, the process of determining the presence / absence of the determination signals S _2a and S _2b is performed. If NO, go to the next step 105.
If YES, the process proceeds to step 109.

In step 105, the processing of the instruction to take in the determination signals S _3a and S _3b is performed.

In step 106, the process of determining the presence / absence of the determination signals S _3a and S _3b is performed. If NO, go to the next step 107.
If YES, the process proceeds to step 109.

In step 107, processing for instructing to take in the determination signals S _4a and S _4b is performed.

In step 108, the process of determining the presence / absence of the determination signals S _4a and S _4b is performed. If NO, the program ends and this program ends. If YES, the process proceeds to step 109.

In step 109, after the processing of the drive signal C ₃ transmission stop command is performed, the present program ends.

Then, similarly to the end of the program in step 108, the execution of the program is subsequently restarted. The execution of such a program is repeated while the system controller 30 is operating.

In the above embodiment, the overcurrent in the converters 12a to 12d is detected, and then the operation of the inverters 14a to 14d is stopped. However, the present invention is not limited to this, and the current determination units 36a to 3d.
A value smaller than a predetermined value (reference value) at 6d, that is, the output is reduced or one of the inverters 14a to 14d that is stopped is detected,
Subsequently, the operation of the inverters 14a to 14d is stopped to obtain the same action and effect as described above, and the current detectors 32a to 32d and 34a to 34d are connected to the inverters 14a to 14d and the welding transformers 16a to 16d. It is also included in the present invention.

[Advantages of the Invention] As described above, according to the DC resistance welding apparatus of the present invention, the output sides of the n power supply units including the converter, the inverter, the welding transformer, and the rectifier are connected to each other, and the combined output of these outputs is used. A direct current that is configured to weld a welded object and that detects an abnormality in each inverter by detecting the current value on the input side or output side of each inverter and comparing each with a normal range value In the resistance welding device, so that the combined value of the detected current value of each of the inverters is a constant value, while feedback-controlling the current value flowing in each of the inverters to a value of 1 / n of the constant value, and of each of the inverters. A drive signal that stops operation when it is detected from the comparison result that the detected current value of any one of the inverters is out of the normal range value. Control means for sending the signal to all of the inverters.

With this, in a relatively simple configuration, abnormality of inverters performing parallel operation, that is, output reduction or overcurrent can be individually detected, and quick detection control of all inverters can be suitably performed in detecting such abnormality. Thus, the switching transistor and the like are effectively protected.

[Brief description of drawings]

FIG. 1 is a basic principle diagram corresponding to the claims of the DC resistance welding apparatus of the present invention, FIG. 2 is a configuration diagram showing an entire embodiment of the DC resistance welding apparatus of the present invention, and FIG. 3 is FIG. FIG. 4 is a block diagram showing the configuration of the abnormal current detector of the embodiment shown in FIG. 4, FIG. 4 is a diagram showing a direct current deriving state used in the explanation of the operation in FIG. 2, and FIG. 5 is a diagram showing the embodiment in FIG. It is a flow chart which concerns on a program of a system controller. 14a to 14d ...... Inverter 26a to 26d ...... Base drive circuit 30 ...... System controller 32a to 32d, 34a to 34d ...... Current detector 36a to 36d ...... Current judging unit A to D ...... Power supply unit T _{r1 to} T _r4 …… Switching transistor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidenori Koga 1-10-1 Shin-Sayama, Sayama City, Saitama Prefecture Honda Engineering Co., Ltd. (72) Inventor Makoto Suzuki 1-10-1 Shin-Sayama, Sayama City, Saitama Prefecture Within Engineering Co., Ltd. (56) Bibliographic Development Flat 1-333387 (JP, U) Real Development Sho 59-124672 (JP, U)

Claims (1)

[Claims] 1. A converter, an inverter, a welding transformer,
The output sides of the n (n ≧ 2) power supply sections made up of rectifiers are connected to each other, and the combined output of these is configured to weld an object to be welded, and the current on the input side or the output side of each inverter. In a DC resistance welding device that is configured to detect an abnormality in each inverter by detecting a value and comparing each with a normal range value, so that the combined value of the detected current values of each inverter is a constant value, The value of the current flowing through each of the inverters is feedback-controlled to a value of 1 / n of the constant value, and the fact that the detected current value of any one of the inverters is out of the normal range is described. A DC resistance welding apparatus, comprising a control means for sending a drive signal for stopping the operation to all of the inverters when detected by the comparison result.