JP5825665B2 - Resistance welding control device - Google Patents

Description

  The present invention relates to a resistance welding control apparatus for performing welding by supplying electric power between an upper electrode and a table electrode serving as a lower electrode.

  Conventionally, in spot welding, in order to optimize the nugget diameter and prevent the occurrence of scattering, adaptive control has been performed to optimize the temperature change during spot welding according to the material of the base material, the plate thickness, etc. ing. In this adaptive control, the temperature change of the weld is calculated in real time to obtain the estimated temperature of the weld. In order to calculate the temperature change of the welded portion, the temperature of the welded portion is estimated from the welding current value, the welding voltage value, the resistance value of the electrode and the base material, and the like. (For example, refer to Patent Document 1).

  In a standard resistance welding control device in which both the upper electrode and the lower electrode are formed of rod-shaped electrodes and the base material is sandwiched from above and below, the resistance value is calculated from the current value and the voltage value detected by energizing between the electrodes. In the case where the base material is not provided between the electrodes, the inter-electrode resistance value in the no-load state in which the electrodes are short-circuited is calculated if the electrode shape is the same, and this resistance value is used. Thus, the temperature of the weld is estimated.

Japanese Patent No. 3212296

  Aside from the standard resistance welding control device described above, of the pair of electrodes sandwiching the base material from above and below, the upper electrode is a rod-shaped electrode, and a resistance using a table electrode in which the lower electrode is formed in a plate shape is used. There is a welding control device. This is to place the base material on the table electrode and move only the upper electrode to the welding location to perform welding. Any part of the surface of the table electrode can serve as the lower electrode. There is an advantage that it is not necessary to move.

  However, in the resistance welding control apparatus using the table electrode, a voltage detection line is connected to one end of the table electrode, and the voltage detection line connection portion to which the voltage detection line is connected and the upper electrode of the table electrode are in contact with each other. In order to calculate the resistance value between the voltage detection line and the welding point, even if the electrode shape is the same, the distance from the voltage detection line connection to the welding point changes. There was a problem that the resistance value between the electrodes changed. Therefore, the resistance value of the base material cannot be accurately calculated.

  The present invention relates to a resistance welding control device that uses a table electrode, and can accurately calculate the resistance value of the base material even if the distance from the voltage detection line connecting portion of the table electrode to the welding location changes. The purpose is to provide.

In order to solve the above-described problems, the invention of claim 1
A welding power source for supplying power between the upper electrode and the table electrode serving as the lower electrode;
A control unit for controlling the output of the welding power source,
The control unit detects the current and the voltage between the electrode reference electrodes when the upper electrode is moved to the voltage detection line connecting portion of the table electrode and is energized before welding, and from these detected values. When the electrode reference resistance value is calculated and welding is performed, a base material is installed between the upper electrode and the table electrode, and the upper electrode is moved to the welding position of the table electrode and brought into contact with the table. The distance from the voltage detection line connection part of the table electrode to the welding location is inputted in a state where the electrode is pressurized, and the electrode is calculated from the function of the distance from the voltage detection line connection part of the table electrode and the resistance value. Calculate the correction resistance value,
Electric power is supplied between the upper electrode and the table electrode by the welding power source to start welding, a welding current and an inter-electrode voltage are detected during welding, and an inter-electrode resistance value is calculated from these detected values. , (Base material resistance value) = (resistance value between the electrodes) − (electrode reference resistance value) − (the electrode correction resistance value).

The invention of claim 2
The control unit calculates the electrode reference resistance value, and then contacts the upper electrode with a predetermined distance from the voltage detection line connection part of the table electrode and supplies a current and a no-load inter-electrode voltage. Is calculated from the detected values, and the function is calculated as {(the no-load inter-electrode resistance value) − (the electrode reference resistance value)} / (the predetermined value). The resistance welding control device according to claim 1, wherein the resistance welding control device is set from a distance).

  The resistance welding control device of the present invention includes a welding power source that supplies power between an upper electrode and a table electrode that functions as a lower electrode, and a control unit that controls the output of the welding power source. Even if the distance to the location changes, the resistance value of the base material can be accurately calculated.

It is a block diagram of resistance welding control device 1 of the present invention. It is a figure which shows the function of distance L [mm] from the voltage detection line connection part 16a of the table electrode 16 of the resistance welding control apparatus 1, and resistance value R [(ohm)]. It is a figure for demonstrating operation | movement of the resistance welding control apparatus 1 of this invention.

[Embodiment 1]
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on examples with reference to the drawings. FIG. 1 is a block diagram of a resistance welding control apparatus 1 according to the present invention. FIG. 2 is a diagram illustrating a distance L [mm] and a resistance value R [Ω] from the voltage detection line connection portion 16 a of the table electrode 16 of the resistance welding control apparatus 1. ] FIG. 3 is a diagram for explaining the operation of the resistance welding control apparatus 1 of the present invention. In FIG. 1, in the resistance welding control device 1, commercial power AC power generated by an AC power source PS is rectified by a rectifier circuit RE. The DC power output from the rectifier circuit RE is input to the inverter circuit INV. The inverter circuit INV is composed of a bridge circuit composed of a plurality of switching elements (not shown), and the input DC power is converted into pulsed high-frequency AC power by a high-frequency switching operation. The switching operation of the inverter circuit INV is controlled by a control signal from an inverter drive circuit DR described later.

The welding transformer T includes a primary coil 7, a secondary coil 8, and a core 9. The primary coil 7 is connected to the output side of the inverter circuit INV, and the output terminal of the secondary coil 8 is the first rectifying element D1 and the second coil. The center tap 14 of the secondary coil 8 is connected to the lower arm 13 while being connected to the upper arm 12 via the rectifying elements D2. An upper electrode 15 and a table electrode 16 are attached to the distal ends of the upper arm 12 and the lower arm 13, respectively. The upper electrode 15 is attached to, for example, the tip of a welding robot.

The high-frequency AC power output from the inverter circuit INV is applied to the primary coil 7 of the welding transformer T, and a high-frequency high-frequency AC power with a reduced voltage is generated in the secondary coil 8 of the welding transformer T. The high-frequency AC power generated in the secondary coil 8 is alternately rectified every half cycle by the first rectifier element D1 and the second rectifier element D2, and DC power is supplied between the upper arm 12 and the lower arm 13. . A plurality of base materials W are pressed by the upper arm 12 and the lower arm 13, a direct current flows, and the welded portion is metallurgically joined by Joule heat.

The secondary current detector ID detects a welding current which is a current on the secondary side of the welding transformer T. The secondary current setter IR is set with a secondary current, and the current error amplifier circuit EI receives the detection signal of the secondary current detector ID and the output signal of the secondary current setter IR and amplifies these errors. To do. The welding time setter TMR sets the welding time per time. The welding start circuit ST outputs a signal that becomes a high level when welding is started. The start-up circuit ON receives the output signal of the welding time setter TMR and the output signal of the welding start circuit ST, and only the time set by the welding time setter TMR after the output signal of the welding start circuit ST becomes high level. A signal that is at a high level is output.

  The interelectrode voltage detector VD detects an interelectrode voltage between the upper electrode 15 and the voltage detection line connection portion 16 a of the table electrode 16. The resistance value calculation circuit 17 calculates the resistance value between the electrodes by using the detection values of the secondary current detector ID and the interelectrode voltage detector VD as inputs. In the distance setting device 18, the distance from the voltage detection line connecting portion 16a of the table electrode 16 to the welding location is set by a control signal from a robot control device (not shown), for example. The correction resistance value calculation circuit 19 inputs the distance setting value from the distance setting device 18 and the electrode correction resistance corresponding to the distance setting value from the function of the distance from the voltage detection line connection portion 16a of the table electrode 16 and the resistance value. The value Ra is calculated. The correction resistance value calculation circuit 19 stores a function of the distance L [mm] from the voltage detection line connecting portion 16a of the table electrode 16 and the resistance value R [Ω] shown in FIG. This function is determined by measuring the resistance value R [Ω] when the material of the table electrode 16 is specified and the distance L [mm] is changed.

Alternatively, the current when the upper electrode 15 is brought into contact with the predetermined distance from the voltage detection line connection portion 16a of the table electrode 16 and the voltage between the electrodes when no load is detected are detected, and the no-load electrode is detected from these detected values. The inter-resistance value may be calculated, and the function may be set from {(no-load inter-electrode resistance value) − (electrode reference resistance value R1)} / (predetermined distance).

As will be described later, the base material resistance value calculation circuit 21 inputs the interelectrode resistance value R2 from the resistance value calculation circuit 17, and (base material resistance value Rw) = (interelectrode resistance value R2) − (electrode reference resistance value). R1) − (electrode correction resistance value Ra) is calculated. The welding condition correction circuit 22 inputs the output signal of the current error amplifier circuit EI and the base material resistance value Rw from the base material resistance value calculation circuit 21, and further inputs other welding conditions not shown in the figure. A temperature change of the weld is calculated using a simulation using conduction calculation to obtain an estimated temperature of the weld. A control signal is output to the inverter drive circuit DR so as to obtain a desired welding quality by correcting the welding conditions corresponding to the estimated temperature value.

The welding power source 10 includes an AC power source PS, a rectifier circuit RE, an inverter circuit INV, a welding transformer T, a first rectifier element D1, and a second rectifier element D2. The control unit 11 includes a secondary current detector ID, a secondary current setter IR, a current error amplifier circuit EI, a welding time setter TMR, a welding start circuit ST, a start circuit ON, an interelectrode voltage detector VD, and a resistance value. The calculation circuit 17, the distance setting device 18, the correction resistance value calculation circuit 19, the base material resistance value calculation circuit 21, and the inverter drive circuit DR.

The operation will be described below.
(1) As shown in FIG. 3, the upper electrode 15 is moved to the voltage detection line connecting portion 16 a of the table electrode 16 and brought into contact with a welding robot (not shown) before welding.
(2) The electrode reference current I1 is set in the secondary current setting device IR, and the welding power source 10 supplies power between the upper electrode 15 and the table electrode 16. At this time, the secondary current detector ID detects the current, and the interelectrode voltage detector VD detects the electrode reference electrode voltage V1 between the upper electrode 15 and the voltage detection line connection portion 16a of the table electrode 16. .
(3) The resistance value calculation circuit 17 calculates the electrode reference resistance value R1 using the detection values of the secondary current detector ID and the interelectrode voltage detector VD as inputs.

(4) When welding is performed, the base material W is installed between the upper electrode 15 and the table electrode 16, and the upper electrode 15 is moved to the welding position of the table electrode 16 by a welding robot (not shown). The upper electrode 15 is pressed against the table electrode 16 by contact.
(5) A distance L2 from the voltage detection line connecting portion 16a of the table electrode 16 to the welding location is set in the distance setting device 18 by a control signal from a robot control device (not shown).
(6) The correction resistance value calculation circuit 19 inputs the distance setting value from the distance setting device 18, and the electrode correction corresponding to the distance L2 from the function of the distance from the voltage detection line connection portion 16a of the table electrode 16 and the resistance value. The resistance value Ra is calculated.

(7) The welding current I2 is set in the secondary current setting device IR, and the welding power source 10 supplies electric power between the upper electrode 15 and the voltage detection line connecting portion 16a of the table electrode 16. At this time, the secondary current detector ID detects the welding current during welding, and the interelectrode voltage detector VD detects the interelectrode voltage V2 between the upper electrode 15 and the voltage detection line connecting portion 16a of the table electrode 16. To detect.
(8) The resistance value calculation circuit 17 receives the detection values of the secondary current detector ID and the interelectrode voltage detector VD and calculates the interelectrode resistance value R2.

(9) The base material resistance value calculation circuit 21 inputs the interelectrode resistance value R2 from the resistance value calculation circuit 17, and (base material resistance value Rw) = (interelectrode resistance value R2) − (electrode reference resistance value R1) −. (Electrode correction resistance value Ra) is calculated.
(10) The welding condition correction circuit 22 inputs the output signal of the current error amplifier circuit EI and the base material resistance value Rw from the base material resistance value calculation circuit 21, and further inputs other welding conditions not shown. Then, a temperature change of the weld is calculated using a simulation using heat conduction calculation to obtain an estimated temperature of the weld. The inverter drive circuit DR is controlled so that the welding condition is corrected corresponding to the estimated temperature value to obtain a desired welding quality.

As a result, the resistance welding control device 1 of the present invention can accurately calculate the resistance value Rw of the base material even if the distance from the voltage detection line connecting portion 16a of the table electrode 16 to the welding location changes. Using the measured resistance value Rw, the adaptive control and monitoring of the heat input state of the welded portion can be appropriately performed.

DESCRIPTION OF SYMBOLS 1 Resistance welding control apparatus 7 Primary coil 8 Secondary coil 9 Core 10 Welding power supply 11 Control part 12 Upper arm 13 Lower arm 14 Center tap 15 Upper electrode 16 Table electrode 16a Voltage detection line connection part 17 Resistance value calculation circuit 18 Distance setting device 19 Correction resistance value calculation circuit 21 Base material resistance value calculation circuit 22 Welding condition correction circuit D1 First rectifier element D2 Second rectifier element DR Inverter drive circuit EI Current error amplifier circuit I1 Electrode reference current I2 Welding current ID Secondary current detector INV Inverter circuit IR Secondary current setter L Distance L2 Distance ON Start circuit PS AC power supply R Resistance value R1 Electrode reference resistance value R2 Interelectrode resistance value Ra Electrode correction resistance value RE Rectifier circuit Rw Base material resistance value ST Welding start circuit T Welding transformer TMR Welding time setting device V1 Voltage between electrode reference electrodes V2 Voltage between electrodes VD Electrode Voltage detector W base material

Claims (2)

A welding power source for supplying power between the upper electrode and the table electrode serving as the lower electrode;
A control unit for controlling the output of the welding power source,
The control unit detects the current and the voltage between the electrode reference electrodes when the upper electrode is moved to the voltage detection line connecting portion of the table electrode and is energized before welding, and from these detected values. When the electrode reference resistance value is calculated and welding is performed, a base material is installed between the upper electrode and the table electrode, and the upper electrode is moved to the welding position of the table electrode and brought into contact with the table. The distance from the voltage detection line connection part of the table electrode to the welding location is inputted in a state where the electrode is pressurized, and the electrode is calculated from the function of the distance from the voltage detection line connection part of the table electrode and the resistance value. Calculate the correction resistance value,
Electric power is supplied between the upper electrode and the table electrode by the welding power source to start welding, a welding current and an inter-electrode voltage are detected during welding, and an inter-electrode resistance value is calculated from these detected values. , (Base material resistance value) = (resistance value between the electrodes) − (electrode reference resistance value) − (the electrode correction resistance value).   The control unit calculates the electrode reference resistance value, and then contacts the upper electrode with a predetermined distance from the voltage detection line connection part of the table electrode and supplies a current and a no-load inter-electrode voltage. Is calculated from the detected values, and the function is calculated as {(the no-load inter-electrode resistance value) − (the electrode reference resistance value)} / (the predetermined value). The resistance welding control device according to claim 1, wherein the resistance welding control device is set from a distance).

Images