JPS62192276A - Method and device for resistance welding of damping steel plate - Google Patents

Abstract

PURPOSE:To obtain the stabilized welding quality equivalent to an ordinary steel plate by supervising the prescribed physical quantity relating to the 1st current passing a short circuit conductor part and by passing the prescribed 2nd current between a pair of electrode chips by shifting to the preset welding conditions based on the result thereof. CONSTITUTION:A small welding current (i) is passed on the shunt path of a short circuit lead wire 18 when the 1st electrification mode is started with the prescribed pressure force being impressed between electrode chips 10, 12 by the signal transmitted from a sequence control part 50. The 1st electrification mode is forcibly stopped by transmitting a shifting instruction signal QS from a comparison part 48 in case of the current (i) exceeding the reference level, when the welding current (i) is abruptly increased with the direct short circuit of the steel plate part of steel plates 14, 16 by the pressure force between this welding current (i) and chips 10, 12. The 2nd electrification mode is then started and the resistance welding equivalent to the ordinary steel plate is performed under the welding conditions as scheduled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to resistance welding of damping steel plates, and is particularly designed to provide stable welding quality equivalent to ordinary steel plates.

(Prior art) A damping steel plate is a sandwich-like steel plate with an insulator such as a resin layer interposed between (two) steel plates, and has the effect of damping vibrations with the insulator. Applications are expanding for various structures such as automobile exterior panels.

Resistance welding of such damping steel plates is generally performed by a split flow preheating method as shown in FIGS. 3 and 4. In these figures, between the electrode tips 10 and 12,
A welding current is applied for a predetermined period of time without applying a predetermined pressing force in the direction of arrows Fl and F2. Material to be welded 14.1
6 are resin composite type (laminate type) vibration damping steel plates, and two steel plates 14a, 14a (16a, 16
A viscoelastic material 14b (16b) such as organic resin is placed between a)
is inserted. A shorting conductor 8 is attached to short-circuit both outer surfaces of the damping steel plates 14 and 18 as shown, and provides a short-circuiting conductor for the first welding point.

Now, in the initial stage of energization in FIG. 3, current flows between the electrode tips 10 and 12 through the branch path as indicated by the arrow. Then, the side in contact with the current chip 10.12 (
Joule heat is generated in the outer steel plates 14a, 16a, and the organic resins 14b, 16b are softened by the heat, and further crushed by the electrode pressure and expelled to the surroundings. As a result, the fourth
The steel plate portion 14 between the electrode tips 10 and 12 as shown in the figure
a, 14a, , tea, and IC3a are directly short-circuited, so that the current flows along this main path W, and the original resistance welding is performed.

FIG. 5 shows the change in current during resistance welding of damping steel plates such as "double series". Period TC is a preset energization period, period TA is a period during which current flows through the branch path (L), and period TB is a period during which current flows through the main path (W). The current in period TA is smaller than the current in period TB because the resistance of the shunt path (L) is large. Furthermore, as can be understood from FIGS. 3 and 4, it is the current during period TB that contributes to nugget formation (metallic bonding), and the current during period TA hardly contributes.

FIG. 6 shows an example of the distribution of welding points Pi. First welding point Pa
In this case, the short-circuit conductor 18 provides a short-circuit conductor portion as described in -1-, but in welding after the second black eye PI, adjacent already welded points provide a short-circuit conductor portion.

(Problem to be solved by the invention) By the way, in conventional resistance welding of damping steel plates, current is applied for a preset time Tc by timer control as in the case of ordinary steel plates, but stable welding cannot be achieved. I couldn't get the quality. In other words, in the case of damping steel plates, there are many unknown points regarding the types of condition factors used to find the appropriate welding conditions and their effects (particularly problematic is the distribution of current, and the Because the distance (Di) of the diversion path varies, and furthermore, the softening and crushing time of the resin layer varies, it is impossible to accurately predict the diversion energization period TA, and therefore the main energization also varies. This results in unstable welding results.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method that enables stable welding quality equivalent to that of ordinary steel plates in resistance welding of damping steel plates.

Another object of the invention is to provide a device suitable for carrying out the above method.

(Means for Solving the Problems) The method of the present invention for achieving the above-mentioned first object uses a pair of electrodes in resistance welding where at least one of the materials to be welded is a damping steel plate with an insulator interposed between the steel plates. passing a first current between the pair of electrode tips through a short-circuited conductor portion adjacent to the tips; monitoring a predetermined physical quantity related to the first welding current, and detecting the timing when the physical quantity reaches a preset value; and a step of switching to preset welding conditions based on the detected timing and flowing a predetermined second current between the pair of electrode tips.

Moreover, the structure of the present invention to achieve the above-mentioned other object is that at least one of the steel plates is a vibration damping steel plate with an insulator interposed between the steel plates.
In a device that performs resistance welding by placing a pair of electrode tips in contact with both sides of two materials to be welded and applying pressure between the electrode tips while passing a current, there is a a shorting conductor connected to selectively provide a shorting conductor portion; current measuring means for measuring a predetermined physical quantity related to the current and generating a measured value signal representative of its level; providing a preset value of the current; means; comparing the measured value signal with a preset value during a first energization mode in which a first current is passed between the electrode tips through a short-circuited conductor portion adjacent to the electrode tips; and when the measured value signal is higher than the latter; a comparison means for generating a switching instruction signal; forcibly stopping the first energization mode in response to the switching instruction signal;
The present invention is characterized by comprising a sequence control means for switching to the energization mode.

(Function) When the first current flows through the short-circuited conductor, Joule heat is generated in the steel plate portion of the shunt path, the insulator is softened by the heat, and further crushed by the pressing force and removed to the surrounding area. In this case, the steel plate portion between the electrode tips is directly short-circuited, and the current increases rapidly.

According to the present invention, the timing at which the current suddenly changes is detected and the welding conditions are switched to the preset welding conditions. Since the welding current (current) is carried out according to the settings, uniform and stable welding results can be obtained.

Furthermore, in the device according to the present invention, when the above-mentioned timing is detected, the first energization mode (separate energization) is forcibly stopped and switched to the second energization mode (main energization). Even if the energization period changes, the second energization mode is not affected.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2. In this embodiment, the electrode tip 10,1
2. The materials to be welded 14, 18 and the shorting conductor 18 correspond to those shown in FIGS. 3 and 4.

An alternating current voltage Eo is applied between the input terminals 20 and 22, and this alternating voltage EO is supplied to the welding transformer 28 via a contactor consisting of a thyristor 24 and 26, and a welding current i is applied from the secondary coil of the welding transformer 28. Electrode tip 10
．． 12. Furthermore, the AC voltage Eo is also applied to a synchronization signal generation circuit 30, and the synchronization signal generation circuit 30 detects the zero-crossing point of the AC voltage Eo to generate a synchronization signal SY1. SY2 are respectively connected to voltage-phase converters 32.
A cycle counter 38 is supplied.

The voltage one-phase conversion section 32 adjusts the points of the thyristors 24 and 26 so that the error voltage between the current value display voltage MV from the effective value calculation section 42 and the set reference voltage Sv from the reference voltage generation section 44, which will be described later, becomes zero. It controls the firing angle, for example, an analog circuit configuration that controls the firing angle at the timing when a comparison reference voltage that changes according to the error voltage intersects with a fixed harmonic voltage, or corresponds to the error voltage. A microcomputer function may be used to obtain the firing angle from memory.

The cycle counter 38 provides time information to the sequence control unit 50 by counting the synchronization signal SY2. The sequence control section 50 sends a control signal GSj to each section based on the time information from the cycle counter 38 so that each welding step is executed sequentially according to the set time, but according to this embodiment, the control signal GSj is as described below. When receiving the switching instruction signal QS from the comparator 48, the first energization mode (separate energization) is forcibly terminated and switched to the second energization mode (main energization). The welding conditions in this second energization mode (one welding current energization time, pressing force, etc.) are the vibration damping steel plate 14. It is selected to be approximately the same as the appropriate welding strip I/1 for a translucent steel plate with a thickness equivalent to IF5.

The toroidal coil 36 is attached to the secondary circuit of the welding transformer 28, and generates a current detection signal Di corresponding to the differential waveform of the welding current i when it flows. This current detection signal Di is converted into a voltage signal Fv having a waveform corresponding to the welding current i by a waveform restoration circuit 40 consisting of an integrating circuit. Then, the effective value calculation unit 42 calculates the effective value of the welding current i for one cycle or 1/2 based on the voltage signal Fv.
The measurement is performed for each cycle, and a voltage signal MV representing the effective value thereof is sequentially provided to the voltage-phase converter 32 and the comparator 48.

On the other hand, the reference voltage generation section 44 generates a reference voltage Sv corresponding to the reference current level IS set by a setting switch 46 consisting of a digital switch etc., and this reference voltage S■ is generated by the voltage-phase conversion section 32 and the comparison section. 48. The reference current level IS is used to detect the timing at which the welding current i suddenly increases when shifting from the branch current to the main current, and is set to a value close to the current level I of the main current.

The comparison unit 48 compares the levels of the current display voltage signal SV and the reference voltage SV, and generates an output signal of "1" as the switching instruction signal QS when the former exceeds the latter. As described above, when this switching instruction signal QS is generated, the sequence control unit 5o forcibly shifts from the first energization mode to the second energization mode.

Next, the operation of this embodiment will be explained with reference to the timing diagram of FIG.

First, at time to, the sequence control unit 5o starts pressurizing means (
A pressurization/ON signal GS3 is sent to the terminal (not shown), thereby applying a predetermined pressurizing force between the electrode tips 10 and 12 (FIG. 2g).

Then, when the second time TH has elapsed, an energization/ON signal GSI is sent from the sequence control section 50 to the ignition pulse generation circuit 34 at time tl, thereby causing the thyristor 2
At 4.26, gate drive signals Ga and Gb are supplied, respectively, and the first energization mode starts (FIG. 2b).

The sequence control section 50 operates to continue the first energization mode for a set time TK until it receives the switching instruction signal QS from the comparison section 48.

In this first energization mode, as shown in FIG. 3, a small welding current i flows through a branch path (L) of large resistance over a relatively long distance (FIG. 2e). Therefore, the voltage MV from the effective value calculation section 42 representing the effective value of the welding current i is lower than the reference voltage SV from the reference voltage generation section 44 (Fig. 2g).
, the output voltage of the comparator 48 is "0".

However, when the organic resins 14b and IEtb are crushed by the Joule heat generated in the steel plates 14a and 16a on the side (outside) in contact with the current chips 10 and 12 and the electrode pressurizing force and are removed to the surroundings, as shown in FIG. Electrode tip 10.
Steel plate parts 14a, 14a, 16a+16a between 12
is directly short-circuited, and as a result, the current i increases rapidly (Fig. 2e), and its effective value also increases rapidly.

As a result, the current value display voltage MV exceeds the reference voltage S■, and the comparison section 48 generates the switching instruction signal QS. As a result, at time t2, the sequence control unit 50 cuts off the energization/ON signal GSI to the ignition pulse generation circuit 34 and forcibly stops the first energization mode (FIG. 2, e). Then, after a predetermined cooling period TR, the sequence control unit 48 energizes the ignition pulse generation circuit 34 again at time t3.
The ON signal GSI is applied to start the second energization mode (Fig. 2 d, f).

The welding conditions in this second energization mode (welding current 5 energization time, pressing force, etc.) are as described above for the damping steel plate 14.1.
The welding conditions were selected to be approximately the same as the appropriate welding conditions for a normal steel plate with a thickness equivalent to 6.

In this embodiment, constant current control is performed by the voltage-phase converter 32, and the thyristor firing angle is controlled so that the welding current i is maintained at the set value ID.

Then, at time t4 when the preset energization time Tb has elapsed, the sequence control unit 50 cuts off the energization/ON signal GSI to the ignition pulse generation circuit 34 and stops the second energization mode (
Figure 2 d, f). Although the pressing force is shown as being constant in FIG. 2(a), it is changed to a set value as necessary in the second energization mode. Also, cooling (Fig. 2C)
may also be omitted if necessary.

As described above, in this embodiment, the welding current i is measured in the first energization mode (divided energization) and compared with the reference level, and when the welding current i suddenly increases and exceeds the reference level, The timing is detected and the first energization mode is forcibly stopped.

In the second energization mode, resistance welding equivalent to that of ordinary steel sheets is performed under the set welding conditions.

Therefore, changes in the distance (D+) of the diversion path for each welding point PI as shown in FIG. 6 (that is, changes in the resistance value of the diversion path), softening of the resin layers 14b and 16b, variations in crushing time, etc. Even if the distribution current period A changes due to
Main energization is always carried out according to preset welding conditions, and a stable and desired welding result can be obtained.

In this embodiment, the materials to be welded 14 and 16 are both damping steel plates, but one of them may be a normal steel plate or other metal material. Furthermore, in this embodiment, the current i is monitored to detect the timing at which the level changes suddenly, or the voltage level or resistance value between the electrode tips 10 and 12 may be monitored. Since the voltage level (or resistance value) rapidly decreases when switching from branch energization to main energization, the timing when the voltage level falls below the set level is detected and the mode is switched to the second energization mode. In addition to the voltage-phase conversion section 32, the ignition pulse generation circuit 34. Waveform restoration circuit 40, effective value calculation section 42.
Reference voltage generation section 44° comparison section 48. It is also possible to configure the sequence control section 50 and the like with microcomputer functions. It is also possible to indirectly measure the current i by attaching the toroidal coil 36 to the primary circuit of the welding transformer 28.

(Effects of the Invention) As described above, according to the present invention, the timing of transition from branch energization to main energization is properly detected and the switch is made to main energization according to preset welding conditions. Even if there are variations in the distribution current due to factors such as the softening and crushing characteristics of the insulator, stable resistance welding can be performed and a constant welding quality equivalent to that of ordinary steel plates can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a welding resistance device according to an embodiment of the present invention, FIG. 2 is a timing diagram for explaining the operation of the welding resistance device, and FIGS. 3 and 4 are: FIG. 5 is a cross-sectional perspective view showing resistance welding of vibration damping steel plates by the shunt preheating method, and FIG. It is a top view which shows the example of arrangement|positioning of the welding point in resistance welding of a shaken steel plate. 10.12... Electrode tip, 14. IF5...
... Material to be welded, 18 ... Short circuit conductor, 24.2
6... Thyristor, 28... Welding transformer,
30... Synchronization signal generation circuit, 32... Voltage-phase conversion section, 34... Firing pulse generation section, 3
6 (36')...Toroidal coil, 38
... Cycle counter, 40 ... Waveform restoration circuit, 42 ... Effective value calculation section, 44 ... Reference voltage generation section, 46 ... Setting switch, 48 ...
... Comparison section, 50... Sequence control section. Patent applicant Miyaji Denshi Co., Ltd. Company agent
Patent Attorney Takashi Sasaki (Figure 3, Figure 5, Figure 6, Figure 5, c, Figure 6, 1 (11)) Procedural Amendment (Spontaneous) April 9, 1985 1, Case Description 1985 Patent Application No. 32258 2. Name of the invention Method and device for resistance welding of damping steel plates 3. Relationship with the case of the person making the amendment Patent applicant address: 3 names, 95 Nitzuka, Noda City, Chiba Prefecture (
Name) Miyaji Electronics Co., Ltd. Representative Keiji Nishizawa 4, Agent address 2-11-16 Kanda Surugadai, Chiyoda-ku, Tokyo 101
Corrected to Surugadai Saikachizaka Building No. 302. (2) Correct rsVJ on page 12, line 5 of the specification to rMVJ. (3) "48" on page 14, line 8 of the specification is corrected to "50". (4) Correct rIDJ on page 14, line 17 of the specification to rls J. (5) Print the drawing as shown on the attached sheet (no changes to the content). - Above Figure 3 Figure 4 JP-A-62-19227G (11) Figure 5 Figure 6 +4 (IG)

Claims (5)

[Claims] (1) In resistance welding where at least one of the materials to be welded is a damping steel plate with an insulator interposed between the steel plates, a first current is applied between the pair of electrode tips through a short-circuit conductor portion adjacent to the pair of electrode tips. monitoring a predetermined physical quantity related to the first current and detecting the timing when the physical quantity reaches a preset value; and adjusting the welding conditions to the preset welding condition based on the detected timing. A method for resistance welding vibration-damping steel plates, comprising: flowing a predetermined switching current between the pair of electrode tips. (2) The resistance welding method according to claim 1, wherein the predetermined physical quantity is the level of the first current. (3) The resistance welding method according to claim 1, wherein the predetermined physical quantity is a voltage level between the pair of electrode tips. (4) The resistance welding method according to claim 1, wherein the predetermined physical quantity is a resistance value between the pair of electrode tips. (5) A pair of electrode tips are brought into contact with both sides of two materials to be welded, at least one of which is a damping steel plate with an insulator interposed between the steel plates, and a current is applied while applying pressure between the electrode tips. A device for performing resistance welding, comprising: a shorting conductor connected between a joint surface and an opposing outer surface of the welded material to selectively provide a shorting conductor; and a shorting conductor that measures a predetermined physical quantity related to the electric current and current measuring means for generating a measured value signal representing a level; means for providing a preset value of the physical quantity; Comparing means for comparing the measured value signal and the preset value during the energization mode of No. 1 and generating a switching instruction signal when the former becomes higher than the latter; A resistance welding apparatus for vibration-damping steel plates, comprising: sequence control means for stopping the first energization mode and switching to a second energization mode according to preset welding conditions.