JPH04158986A - Resistance welding controller - Google Patents

Abstract

PURPOSE:To surely prevent defective welding quality by detecting actual pressurizing force impressed on a work and judging timing of welding current energizing. CONSTITUTION:Work start instructions JS are supplied to a CPU 21. Welding chips 8 and 9 are abutted on welding spots. A specified pressure command value VP1 is then supplied to an air pressure servo circuit 13 so that the first stage pressurizing force FP is applied to the work 10. The first stage pressurizing force FP is maintained for a specified time TP. A VP2 is then supplied so that the second stage pressurizing force is applied to the work. When the specified time TH elapses after the energizing finishing time E is attained, the cylinder pressure P1 is made in a released state and the cylinder pressure P2 is regulated to a specified value and the welding chips 8 and 9 are separated from the welding spots and these are shifted to next welding spots and the same processing is repeated. The time TH is holding time.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a resistance welding control device, and particularly to a resistance welding control device suitable for use in projection welding.

[Conventional technology]

When changing welding conditions in response to changes in pressurizing force in resistance welding, the timing (synchronization) must be well matched. For example, welding quality will deteriorate unless energization is started after sufficient pressure has been applied to the workpiece. In addition, the welding tip wears out quickly. On the other hand, work efficiency will decrease unless the current is started promptly after a sufficient pressure is applied. Furthermore, in projection welding that requires two-stage pressurization, good welding cannot be expected unless the welding current is increased in time with the transition to the second-stage pressurization force. For this reason, conventionally, for example, the timing at which welding starts is determined by adjusting the squeeze time. In addition, in the case of projection welding, the timing is adjusted by adjusting the waiting time from when the pneumatic servo circuit is commanded to increase the pressure to when the welding current control circuit is commanded to increase the current. .

[Problem to be solved by the invention]

By the way, the movement of the piston of the urging means for urging the welding tip, especially the commonly used pneumatic (pneumatic) cylinder, becomes faster or slower depending on the season, air temperature, machine temperature, etc. Furthermore, even if the cylinders are of the same type, the speed of movement differs depending on the welding machine. For this reason, it is necessary to frequently check and adjust the squeeze time and the waiting time after the pressure increase command, which is complicated. Furthermore, there was no easy way to check whether these synchronizations were good or bad on site, and adjustments required intuition and experience.

[Means to solve the problem]

Therefore, the present invention includes a pressurizing force detecting means that is arranged between a welding tip and a biasing means that biases the welding tip and detects the pressurizing force of the part, and a pressurizing force detecting means that changes the welding conditions in response to the output of the detecting means. We aim to solve the above problem by using a welding condition control means that allows the welding conditions to be controlled.

[Effect]

That is, in the resistance welding control device of the present invention, the pressing force detection means is disposed between the welding tip and the urging means for urging the welding tip. In this way, the force acting on the portion also acts directly on this pressurizing force detection means. Therefore, the pressing force applied to the welding tip, that is, the pressing force actually applied to the workpiece is detected by this pressing force detection means. By using this output, it is possible to change the welding conditions in exact timing with the change in the pressurizing force.

【Example】

The details of the present invention will be explained below based on illustrated embodiments. 1st
In the figure, 1 is a rectifier circuit that rectifies three-phase AC 3φ to generate DC voltage DC. 2 is a choke coil, 3 is an electrolytic capacitor, and these smooth the DC voltage DC. 4 is an inverter that generates AC AF of 1000 Hz with a pulse width corresponding to the designated pulse width value WP. A transformer 5 steps down the AC AF supplied from the inverter 4 to generate low voltage LV. 6.7 is a diode that performs full-wave rectification of the low voltage LV. A welding tip 8.9 is supported by the welding machine main body (not shown), is brought into close contact with the workpiece 10 by a pressing force F, and supplies a welding current I to it. Reference numeral 11 denotes a current detection coil that generates a minute current i corresponding to a change (differential value) of the welding current I. 12 is an integrating circuit that integrates the minute current i;
Generates digital value D1. This value DI corresponds to the welding current I. Reference numeral 13 denotes a pneumatic servo circuit, which controls each pressure P1, P2 in the pneumatic cylinder 14 according to a specified pressure value supplied from a welding machine main body control circuit (main body control circuit) (not shown). 1
Reference numeral 5 denotes a strain resistor serving as a pressurizing force detection means, which is attached to a connecting rod 17 that connects the piston 16 and the welding tip 8, and its resistance value changes depending on the pressurizing force F (strain) of the portion. A constant current circuit 18 supplies a constant current CI to the distortion resistor 15. 19 is an analog-to-digital converter (A/D converter)
Then, the terminal voltage VR of the distortion resistor 15 is converted into a digital value DP. This digital value DP represents the pressing force F. 20
is a time counting circuit which, when supplied with the reset signal R, executes time counting from "0". 21 is a central processing unit (CPU) so-called microcomputer consisting of an integrated circuit, and a random access memory (RA).
Read only memory (ROM) while using M) 22
The processing described below is executed according to the program No. 23. 24 is a so-called RAM cart, which is used to store data and programs. 25 is a printing device, 26 is a display device, and each CPU 2
The control status data (welding current, welding point number, operation status of each part, etc.) supplied from 1 is printed out or displayed. 27 is a keyboard, which is used for inputting data to the CPU 21; 28 is an input/output port, which is connected between each of the above-mentioned circuits and the CPU 21, between the main body control circuit and the CPU 21, and between an external computer, etc. (not shown) and the CPIJ2.
Data is transferred to and from 1. The operation of this embodiment will be explained with reference to FIG. First, when the workpiece 10 is positioned on the welding machine main body by a robot or the like, the main body control circuit executes the following processing. First, a work start command JS is supplied to the CPU 21. Then, the welding tip 8.9 is brought into contact with the first welding point. Next, an energization command ST is supplied to the CPU 21. Subsequently, a predetermined pressure specification value vP1 is supplied to the pneumatic servo circuit 13 so that the first stage pressurizing force FP is applied to the workpiece 10. Wait until a predetermined time TP has elapsed. This time TP is the time for maintaining the first stage pressurizing force FP. After the predetermined time TP has elapsed, the second stage pressure FS is applied to the workpiece 10.
A predetermined pressure specified value V is applied to the pneumatic servo circuit 13 so that
Supply P2. Thereafter, wait for the arrival of the energization end signal E from the CPU 21, and when a predetermined time TH has elapsed since the arrival of the signal, the cylinder pressure P1 is set to an open state, and the cylinder pressure P2 is set to a predetermined value, and the welding tip 8°9 is turned off. They are moved away from the welding point and transferred to the next welding point, and the same process is repeated. Time TH is a hold time. In response to these processes of the main body control circuit, the CPU 21 executes the following processes. First, in response to the work start command ST, the CPU 21 enters the control main routine shown in FIG. Then, in steps S1 and S2, it waits for the return command RT or the energization command ST to arrive. When the energization command ST arrives and the answer in step S2 becomes "yes," the CPU 21 proceeds to step S3, where the output DP of the A/D converter 19 (pressure force F
) until it reaches a predetermined value PMI. The predetermined value PMI is
90 of the digital value DP1 corresponding to the first stage pressurizing force FP
It may be a value of around %. The answer in step S3 is "yes", that is, work 10
When 90% of the first stage pressure FP is actually applied to
The CPU 21 proceeds to steps S4 and S5, where it sets the control target value MI of the welding current I to the target value Mll when applying the first stage pressurizing force FP, and sets the current control pulse width specified value WP to this target value M11. Set to the corresponding initial value WPI. Next, the process proceeds to step S6, and the switch signal SW is sent to the inverter 4.
and start it. Next, the CPU 20 proceeds to step S7 and executes the current I control subroutine (FIG. 4). In this subroutine, the CPU 21 first calculates the difference between the digital value DI indicating the welding current (■) at that time and the target value MI (step 5
71). In this embodiment, when the absolute value of this difference is smaller than the predetermined value DS, the pulse width adjustment value WA is set to "0" (step S
72→S74→576). If the absolute value of this difference is larger than the predetermined value DS but not as large as the even larger predetermined value DL, the pulse width adjustment value WA is set to a small predetermined value WS (step S72→574). -S75
). When the absolute value of the difference exceeds the larger predetermined value DL, the pulse width adjustment value WA is set to the larger predetermined value WL (step S72→573). Next, the CPU 21 executes the above step S73. S75, S7
6, the process proceeds to step S77, and the polarity of the difference is determined. When the difference is positive, the digital value DT corresponding to the welding current I at that time is larger than the target value MI, so in order to reduce this, the CPU 21 changes the pulse width adjustment value WA from the pulse width specified value WP at that time. is subtracted, and this is set as a new pulse width designated value WP (step 578). If the difference is negative, perform the opposite process (step 579).
. Note that if the difference is "0", processing is performed in step S78. The CPU 21 then proceeds to step S80, supplies a new designated pulse width value WP to the inverter 4, and returns to the main routine of FIG. 3. In the next step S8, the CPU 21 determines that the digital value DP indicating the pressing force is equal to the digital value DPI when the first stage pressing force FP is applied.
It is checked whether a larger predetermined value PM2 has been reached. This predetermined value PM2 is determined by adjusting the welding current I as the pressurizing force F increases.
In this embodiment, the value is set to be an intermediate value between the first stage pressurizing force FP and the second stage pressurizing force FS, and the corresponding digital value is set as this predetermined value PM.
Set it to 2. When the pressurizing force F exceeds this digital value PM2, the answer in step S8 is "yes". Therefore, the CPU 21 proceeds to step S9 and supplies the reset signal R to the clock circuit 20. In response to this, the clock circuit 20 starts clocking from "0". Next, the target value Ml of the welding current I is set to the value MI2 for applying the second stage pressurizing force FS, and correspondingly, the pulse width specified value WP is also set to the initial value WP2 corresponding to this target value MI2. (Step 5IO1S11). Next, the process advances to step S13, and the current I control subroutine shown in FIG. 4 is executed. The process of maintaining the value of welding current I at target value MI2 is continued until output T of clock circuit 20 reaches predetermined value TM (step 514). The output of the clock circuit 20 reaches TM, that is, the target value MT2
When the energization is maintained for the time TM, step S14
The answer is "yes." Therefore, the CPU 21 proceeds to step S15, cuts off the switch signal SW being supplied to the inverter 4, and stops its operation. Next, a signal E indicating that energization has ended is supplied to the main body control circuit. The time TM is determined according to the characteristics of the workpiece 10. When the main body control circuit receives this signal E, it waits for the hold time TH to elapse from that point, as described above. This time TH is also determined according to the characteristics of the workpiece 10. After this time TH has elapsed, the main body control circuit separates the welding tips 8 and 9 from the workpiece IO and moves the welding tips 8 and 9 to the next welding point, as described above. When such processing is executed up to the last welding point and the CPU 21 supplies the energization end signal E to the main body control circuit for the welding point, the circuit supplies the return command RT to the CPU 21. When the CPU 21 receives this command RT, the CPU 21 moves from step S1 to an upper level routine (not shown), and ends the process shown in FIG. 3.

[Other Examples]

Note that the present invention can be used to determine the timing for interrupting or terminating energization. It can also be used to determine the timing of starting, interrupting, and ending energization in normal resistance welding without changing the applied force. Furthermore, it can also be applied to other welding conditions, such as controlling the voltage between welding tips. It can also be used for control such as changing two or more welding conditions simultaneously or sequentially. It can also be applied to AC, capacitor, and other resistance welding methods. Furthermore, the present invention can be applied to other systems such as an AC system and a capacitor system.

【Effect of the invention】

As explained above, in the present invention, a pressurizing force detection means is disposed between a welding tip and a biasing means for biasing the welding tip, and the pressurizing force at that part, that is, the actual pressure applied to the workpiece is measured. We decided to use this to detect the pressurizing force and use this detection output to determine the timing of welding current application, etc. Therefore, energization may start before sufficient pressure is applied to the welding tip, or conversely, energization may not start even though sufficient pressure is applied, or the timing of transition to the second stage pressure may be incorrect. It is possible to reliably prevent poor welding quality, wear and tear on the welding tip, decrease in work efficiency, etc. caused by the timing of increasing the welding current not being right, especially when two-stage pressure is required. It is suitable for use in such projection welding. Furthermore, the present invention can also be applied to other types of resistance welding that require two-step pressurization, such as resistance welding of sintered metals, aluminum, and the like.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a block diagram showing the circuit configuration, Fig. 2 is a waveform chart showing changes in pressurizing force and welding current, Fig. 3 is a flowchart showing the control main routine, and Fig. 3 is a flowchart showing the control main routine. FIG. 4 is a flowchart showing the current 1 control subroutine. 8.9... Welding tip, 13.14... Urging means,
15.18.19... Pressure force detection means, 11.12.
21-23... Control means. Patent applicant Akira Matsui, Patent attorney representing Myachi Technos Co., Ltd. - Figure 2 Pressure force, welding current transition time t □ Figure 3 Control main routine

Claims (1)

[Claims] (1) Welding force detection means that is arranged between a welding tip and a biasing means that biases the welding tip and detects the pressure force on the part, and that changes welding conditions in response to the output of the detection means. A resistance welding control device characterized by comprising condition control means.