JPH0357564A - Dc resistance welding equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC resistance welding device in which suitable current control is performed based on the resistance value of a member to be welded between welding tips during pressurization.

[Prior Art] Recently, in DC resistance welding, welding that occurs due to fluctuations in the pressure applied to the workpiece held by the welding gun, such as changes in compressed air pressure and fluctuations in the pressing force of the pressurizing cylinder, etc. In order to prevent quality deterioration, etc., the voltage generated by the resistance between the welding tips is detected. Next, a resistance welding device has been proposed that identifies the state of the pressurizing force based on the voltage value and controls energization (see Japanese Patent Publication No. 552,595).

Furthermore, a spot welding method has been proposed in which current flow is controlled by directly measuring the resistance value of the welded member between the welding tips (see Japanese Patent Laid-Open No. 150786/1986).
.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, in the above example, a large current, for example, tens of thousands of amperes, is applied to the switch that is opened during measurement. Therefore, a large switch is required, which is inconvenient when installed in industrial robots, etc., which are required to be miniaturized these days. Furthermore, the welding time is delayed due to the ○N/○FF operation during measurement/energization.

In the example below, the resistance value of the welded member between the welding tips is relatively small, and therefore changes in resistance value due to changes in pressure during measurement cannot be accurately detected. It has its drawbacks.

The present invention has been made in view of the above points, and has a relatively small and simple structure, in which the voltage related to the resistance value in the normal pressurized state of the welded member between the welding tips, that is, in the normal pressurized state. detection is carried out reliably and as soon as possible.
Another object of the present invention is to provide a DC resistance welding device that enables effective energization control and effectively prevents damage to the welding tip due to the energization of a large current.

[Means for Solving the Problems 1] In order to solve the above-mentioned problems, the DC resistance welding device of the present invention has the following features: A DC resistance welding device comprising a detection means for generating a detection signal based on a resistance value, and a control means for energizing the welding tip based on the detection signal, wherein a positive voltage is applied to one of the welding tips. One electrode that is blocked from passing is connected, the positive end of the power supply unit is connected to the other electrode that allows positive voltage to pass, and the negative end of the power supply unit is connected to the other welding tip, so that the workpiece is welded. The semiconductor device is configured to include: a semiconductor element that becomes conductive at a predetermined resistance value when pressurizing the conductive state; and a detection signal generating means that generates a detection signal based on the current related to the conductive state.

[Function] In the above structure, the semiconductor element employs, for example, a photocoupler, and the resistance value between the welding tips with the workpiece to be welded sandwiched therein decreases due to the pressure applied, and then, at a predetermined value, the resistance value between the welding tips decreases. conducts. In this case, at the voltage at the start of energization, the electrical connection of the semiconductor element is in the opposite direction and becomes non-conductive.

The detection signal generating means is, for example, a switching element section of the photocoupler, and the switching element section becomes conductive when the detection element section conducts and emits light. It is derived as a detection signal indicating that the pressing force is normal.

[Example 7] Next, an example of the DC resistance welding apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows the structure of the embodiment, and FIG. 2 is a timing chart. Furthermore, FIG. 3 is a flowchart relating to the control program of the system controller.

The example shown in FIG. 1 has a general structure including a welding power supply section 10, a welding section 20, a detection circuit 30 for detecting a normal pressurized state in the welding section 20, and a system controller 40 for controlling the welding sequence. ing.

First, the welding power source section 10 will be explained. The welding power supply section
0, the diode of converter section 1l? el, D8■
, De3, D84, D85, De6, etc., are converted into direct current (rectified voltage). continue,
The rectified voltage is supplied to the inverter 12 and converted into a pulsed high frequency (high frequency voltage) in the switching transistors Trl, Tr2, Tr3, Tr4, etc.

In this case, switching transistors Tri, Tr2,
A base drive circuit 14 is connected to the bases of Tr3 and Tr4, and the pulsed high frequency is generated from the welding power source 10 by switching operation based on a control signal from an inverter control circuit 16 for performing PWM control. be done. Next, in the welding transformer To, in order to convert the high frequency to low voltage, that is, to obtain a large current, for example,
0V conversion is performed, followed by double-wave rectification by rectifiers Da and Db, and a DC voltage V is derived.

Next, in the welding section 20, the double-wave rectified DC voltage V1 is applied to the welding gun 21.

The member to be welded 22 is held between the welding tips 21a and 2lb that make up the welding gun 21. in this case,
A predetermined portion of the member to be welded 22 is held and pressurized in the P direction shown in the drawing by a pressure driving means (not shown).

Further, the detection circuit 30 includes the welding tips 21a and 2.
lb, that is, the normal pressurized state of the welded member 22, the detection circuit 30 first detects that one side of the voltage of the variable DC power supply E, for example 9V, is the welding tip 21. a, and further connected to the anode of the light emitting portion of the photocoupler 32 via a resistor R1. Next, the cathode of the light emitting section is connected to the welding tip 2lb, and an external voltage Vcc is applied to the collector of the detection section via a resistor R2. In the detection circuit 30 having such a structure, when the pressure applied to the welded member 22 is normal, for example, when 9V is applied and the resistance value between the welding tips 21a and 2lb is 30 to 300 μohm, the photocoupler 32 becomes conductive. (○N) state, and becomes non-conductive (OFF) when the resistance value is higher than the above, and as a result, an ON/OFF voltage is generated at the collector, and the detection signal S,
is derived. Furthermore, as can be easily understood from the figure,
The DC voltage V1 derived from the rectifier DaSDb becomes a reverse voltage at the light emitting part of the photocoupler 32, and does not flow and does not cause any adverse electrical effects when energized during welding.

Note that the photocoupler 32 detects that the noise signal is the detection signal S1.
It is adopted to effectively prevent the superimposition of

Next, the system controller 40 to which the detection signal S1 is supplied includes a ■/○ interface 42 (or A/D converter), a CPU 44, a ROM 46, and a RAM 48, and is, for example, an FMS computer that performs full-closed NC control. Deriving a control signal S2 connected to the setting means/centralized control device and for driving the inverter section 12, as well as controlling the cooperation of the interlocking device with other pressurizing cylinders (solenoids), conveying means, etc.; So-called welding sequence control is performed.

Welding sequence control of the system controller 9 and roller 40 based on the detection signal S1 and the program stored in the ROM 46 will be described below (see FIGS. 2 and 3).

■ In step 101, after the start of the overall operation, a signal C of a welding start command is sent from the setting means/central control device.
1 is taken in (see FIG. 3a).

■ In step 102, a control signal C2 is sent to a pressure cylinder, conveyance means, etc. (not shown) in order to clamp and pressurize the workpiece 22 between the welding tips 21a and 2lb.
The transmission instruction is processed.

Note that the period between the front and rear edges of the control signal C2 is one welding process period (see FIG. 3b).

■ In step 103, a signal C l indicating completion of clamping of the workpiece 22 to be welded, that is, completion of the process of the conveyance means.
The process of taking in a is performed (the state of the pressing force is shown in FIG. 2C).

(2) In step 104, processing related to determining whether the process of the conveying means has been completed is performed based on the signal CIM.

If NO, return to step 103; if YES, proceed to the next step.

10. In step 105, a process of capturing the detection signal S1 is performed (see FIG. 3d).

(2) In step 106, the state of pressurization is determined based on the detection signal S. That is, processing is performed to determine whether the value of the detection signal S1 is a predetermined value.

If NO, return to step 105; if YES, proceed to the next step.

■ After the pressurization is performed in the step 107,
The delay time t until the pressing force reaches the maximum is counted.

(2) In step 108, a control signal S2 is sent to turn on the inverter section 12 after a delay time t1, and an energizing current S5 (time t4) shown in FIG. 3e flows through the welded member 22.

In step 109, after the holding time t2, the control signal C2 is turned green, that is, the signal S6 instructing to release the pressurizing cylinder after the elapse of the time t5 is sent, and the workpiece 22 to be welded is welded. The program related to this ends.

In this way, the resistance value of the welded member 22 held between the welding tips 21a and 2lb is reduced by pressurization, and at a predetermined value, that is, in a predetermined normal pressurized state, the resistance value of the welded member 22 is lowered by the detection circuit 30. A detection signal S1 is derived.

When the energization is controlled based on the detection signal S1, the normal pressurized state of the welded member 22 is determined as soon as possible, and the point at which the energization starts is clarified. Conventionally, the squeeze time t3 shown in Figure 2e is
For example, the time is shorter than the expected time when the pressurizing force reaches its maximum. In such a case, the overall welding time is reduced.

In addition, although the said Example demonstrated using the photocoupler 32, it is not limited to this. For example, the voltage generated between the resistors in a series circuit of a diode and a resistor can be used as the detection signal S1, or the voltage caused by the N/O FF of the contact can be used as the detection signal S1 using a series circuit of a diode and a relay. The present invention also includes using a diode and a transistor to drive the base to construct a switching circuit similar to the photocoupler 32, and using a comparator or the like to obtain similar effects. It will be done.

[Effects of the Invention] As described above, according to the DC resistance welding apparatus of the present invention, detection is performed based on the resistance value of the welded member held between one and the other welding chimps to which positive and negative voltages are respectively applied. A DC resistance welding device comprising a detection means for generating a signal and a control means for energizing the welding tip based on the detection signal, wherein the one welding tip is prevented from passing a positive voltage; The positive end of the power supply section is connected to the other electrode through which a positive voltage is passed, and the negative end of the power supply section is connected to the other welding tip, so that a predetermined voltage is applied when pressurizing the workpiece to be welded. 13. A semiconductor element that becomes conductive at a resistance value of , and a detection signal generating means that generates a detection signal based on the current associated with the conduction state, whereby, in a relatively small and simple structure, Voltage detection related to the normal pressurized state of the welded member between the welding tips, that is, the resistance value during normal pressurization, is performed reliably, making it possible to control current flow as quickly and effectively as possible, and to prevent large currents. This has the effect of effectively preventing damage to the welding tip due to energization.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the DC resistance welding device of the present invention, FIG. 2 is a timing chart related to signal processing and pressurization state used to explain the operation of FIG. 1, and FIG. The figure is a flowchart related to the program of the system controller of the embodiment. 12... Inverter section 16... Inverter control circuit 21... Welding gun 21. a, 2lb...
・Welding tip 1 4 22... Workpiece to be welded 32... Photo coupler 40... System controller 46 = -ROM Da, Db... Rectifier E
...Variable DC power supply R2...Resistance SI...Detection signal V1...DC voltage 30...Detection circuit l5

Claims (1)

[Scope of Claims] 2. Scope of Patent (1) Detection means for generating a detection signal based on the resistance value of a welded member held between one and the other welding tips to which positive and negative voltages are respectively applied. and a control means for energizing the welding tip based on the detection signal, wherein one electrode that prevents passage of positive voltage is connected to the one welding tip; The positive end of the power supply part is connected to the other electrode through which the voltage passes, and the negative end of the power supply part and the other welding tip are connected, and a conductive state is established at a predetermined resistance value when pressurizing the workpiece to be welded. A DC resistance welding device comprising: a semiconductor element; and a detection signal generating means for generating a detection signal based on the current related to the conduction state. (2) The DC resistance welding apparatus according to claim 1, wherein the semiconductor element and the detection signal generating means are a circuit using a photocoupler.