SU1505718A2 - Apparatus for controlling voltage in resistance welding - Google Patents

Abstract

The invention relates to mechanical engineering, in particular, to devices for the automation of resistance welding, and can be used, for example, in spot welding of winding wires to lamellae of a collector. The purpose of the invention is to improve the quality of the welded joint by stabilizing the level of energy released at the electrodes. A contact welding voltage control unit contains an actuator control command generation unit, a power supply unit, a summing meter unit and a phase control unit for welding current and stabilizing its effective value, a smooth control pulse setting unit and a welding transformer switching unit. A current transformer, a rectifying bridge, a multiplier unit, an integrator, a comparison unit, a welding energy reference value unit are inserted into the device. The device allows one to stabilize the level of energy released by the electrodes by comparing the measured energy with the reference one. Any required mode of the welding process and the possibility of setting the optimal technological mode of welding for various sizes of products are provided. 3 il.

Description

The invention relates to mechanical engineering, in particular for the automation of resistance welding, can be used in current control schemes of contact welding machines, mainly in spot welding of winding wires to the collector lamellas, and is an improvement of the device according to the author. St. No. 1252102.

The aim of the invention is to improve the quality of the welded joint by stabilizing the level of energy released by the electrodes.

FIG. 1 shows a functional block diagram of the device; in fig. 2 - block diagram of the reference values of the welding energy; in fig. 3 - time diagrams of voltages.

The device contains (Fig. 1) an actuator control command generation unit 1 and a power supply unit 2 providing alternating (24 V) and stabilized constant (15 V) voltage and connected to the summing meter unit 3 and the phase control unit 4 of the welding current and stabilization of its effective value. The latter is connected to the soft-rise unit 5 of the control pulse and the switching unit 6 of the welding transformer.

The unit 4 of phase control of the welding current and stabilization of its effective value includes a chain consisting of a trigger 7, a variable resistor 8, a capacitor 9 (RC circuit) and inverters 10 and 11, representing the time specifying the node for the duration of the welding process. Moreover, the inverter 11 is connected to the input "1 flip-flop 12, the counting input of which is connected to the diode 13 through

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I-NE logic element 14. A rectifying bridge with diodes 15-18 is connected to a sawtooth generator, consisting of a transistor 19, a capacitor 20 and resistors 21-24 and connected through resistors 25 and 26 to inputs of operational amplifiers 27 and 28, respectively working in comparator mode. The second inputs of the operational amplifiers 27 and 28 are connected via resistors 29 and 30 with variable resistors 31 and 32, which are connected respectively to variable resistors 33 and 34, capacitor 35, resistors 36 and 37, and zener diode 38. Comparators outputs 27 and 28 and trigger 39 are connected via logic elements 2I-HE 40 and 41 to logic element 2I-HE 42. Logic element 4I-HE 43, which is a modulator, is connected to trigger 12, logic element 2I-HE 42, and to the output of the combinator 44 of the block 5 of a smooth increase of the equalizing pulse.

The soft-rise control unit 5 of the pulse consists of a capacitor 45, charged 1 o to the voltage level determined by a chain consisting of an potentiometer 46, a resistor 47, a transistor 48 and a resistor 49. The lower limit of the capacitor discharge 45 is regulated by a chain consisting of a potentiometer 50, a resistor 51, a transistor 52, a diode 53 and a resistor 54. The capacitor 45 through the field-effect transistor 55 and the resistor 56 which stabilize the discharge current is connected to the input of the comparator 44, the second input of which is connected to the collector transistor 19 block 4.

Blocks 1 and 2 are connected to block 3. Block 1 is connected to block 4 via 6, b / w 2 - via diodes 13 and 15-18, and block 3 via trigger 39. Block 4 is connected by two outputs to block 5 via comparator 44, and through the output of element 4И-НЕ 43 - with the output of block 6.

The actuator control command generation unit 1 is a communication unit between the "Welding, Stop, Counting" switches and blocks 3 and 4, i.e. it generates signals and protects the control circuit from interference. Block 3 of the totalizer counts the number of points to be welded, and also determines the welding mode (i.e., welding the first three or four lamellae of the collector is increased by the current, since the electrodes are still cold and the rest are lowered, which improves the quality of the welding point) installation of a multi-position switch connected to the inputs of the RS-flip-flop 39. From the power supply 2 comes a stabilizing voltage (+ 15V) to the S-input of the meters CT of the power supply 3.

Voltage control during resistance welding from the output of element 4И-НЕ 43

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reduced to a change in the angle of unlocking of the simulator in block 6, switching the welding transformer. To the output of the switching unit 6 of the welding transformer, the primary winding of the welding transformer 57 is connected, in the secondary winding of which a current transformer 58 is connected. The secondary windings of the current transformer 58 are connected to a rectifying bridge 59, the negative terminal of which is grounded, and the positive terminal to the input of the multiplier unit 60. The output of multiplier unit 60 is connected to the input of integrator 61, made of potentiometer 62, connected to parallel connected capacitor 63 and operational amplifier 64, the output of which is the output of integrator 61 connected to one of the inputs of comparison unit 65, the second input of which is through the unit 66 reference values of the welding energy is connected to the output of the unit 1 for forming control commands by the executive mechanisms and to the input of the unit 3 for the summing counter. The output of the comparator unit 65 is connected to the input of the element 4I-HE 43, which is a modulator of the unit 4 for phase-control of the welding current and stabilization of its effective value.

The device works as follows.

During installation, the welding electrodes are lowered, at the end of which the end switches "Welding and" Counting, i.e. the signals from block 1 are sent to b; shki 3 and 4. The S input of the trigger 7 of block 4 receives a logic level of 1, it is transferred and a positive voltage level (+ 15V) appears at the forward output. This level through RC-chains S and 9, inverters 10 and 11, and trigger 12, goes to element 4И-НЕ 43, which ensures that welding takes place during the normalized time determined by the parameters of RC-chain 8 and 9.

When a sinusoidal voltage of a transformer with a ferromagnetic core is switched on, it is possible that the residual, remaining from the previous switching on and re-created by the transient current, the magnetic fluxes coincide in sign. To eliminate this, a synchronous contactor of the welding machine is used, which usually operates in such a way that the beginning of the welding occurs in a half period of one defined polarity, and the end in the period of reverse polarity. Therefore, the residual and newly created magnetic fluxes have opposite signs, which helps to reduce the maximum flux. ViarHHTHoro flux, with this, there are no aperiodic components of the primary current.

The synchronous contactor in the device is a triac in block 6. The start of welding is in the positive half-period,. and the end of the welding is negative. The passage of an even number of half-waves is provided by trigger 12, to the synchronization input of which synchronous pulses with a frequency of 50 Hz are supplied through diode 13 and the AND 14 element, and to the I and K inputs of the state, respectively, the logical "1 and logical “About from the outputs of the inverters 10 and And, and vice versa. For a voltage synchronous to the supply voltage network, a diode bridge 15-18, the minus of which is connected to the zero potential of the source, and a sawtooth generator, assembled on a transistor 19, a capacitor 20 and resistors, are intended. The sawtooth pulses at the generator output coincide in phase with the supply voltage, since a variable voltage (24 V) is supplied to the diode bridge.

The sawtooth voltage from the generator enters through resistors 25 and 26 to one of the driver inputs of operational amplifiers 27 and 28 operating in comparator mode, to the second input of which through resistors 29 and 30 receives a certain voltage level from variable resistors 31 and 32, which together with variable resistors 33 and 34, a capacitor 35, a zener diode 38 and resistors 36 and 37 form a welding current stabilization circuit. Therefore, at the inputs of the amplifiers 27 and 28, the voltage level changes with its sign. An increase in the network voltage, for example, from U to U., leads to an increase in the previously established phase shift from (% -ft) to (fo-fy) with respect to the network voltage, i.e. the angle of expansion of the simulator and, therefore, the reduction of the welding current, and vice versa, which ensures the maintenance of the welding current at a given level.

The welding current is controlled by varying the voltage at the driver input of the amplifiers 27 and 28 when a sawtooth voltage is applied to the second input. At the same time, as the voltage increases, the phase shift of the output pulse relative to the network voltage increases and vice versa. The value of the adjustable voltage is determined by changing the value of the variable resistors 31, 33, 32 and 34.

A trigger 39 is used to provide the welding mode with an increased current of three and four lamellas and the subsequent transition to the nominal welding mode, which is connected to the block 5 of the summing counter. At the beginning of welding, the signal from block 3 is fed to the direct input of the trigger 39.

The control pulse from the element 2I-NOT 41 is fed to one of the inputs of the logical

element 4I-NOT 43, which is a modulator. The other input of this element receives a signal from a smoothly rising control pulse unit 5, which

It works on the same principle as the welding current control assembly. A sawtooth voltage is applied to one driver input of the comparator 44, and a capacitor voltage 45 to the other input. At the initial instant, the capacitor 45 is charged, since a positive potential is applied to the base of transistor 48 from the potentiometer 46. In this case, the potentiometer can be connected with a variable adjustment resistor 8, the duration of the welding process in order to simultaneously change the charge level of the capacitor 45 and to obtain a smooth increase in current for any duration of the welding process when changing the duration of the welding process and.

0 In the block, the discharge current is stabilized, which leads to a straight-line voltage change when the capacitor 45 is discharged. The current is stabilized by a chain: field-effect transistor 55, the resistor 56. The presented circuit makes it possible to adjust the lower limit of the capacitor 45 through 50 , the resistor 51 and the transistor 52, i.e. to regulate the discharge time, and consequently, the time of the smooth rise of the welding current with the duration of the welding process in the range of 0.2-1.0 s. Diode 53 is necessary to protect the transistor 52 from breakdown in the voltage.

The modulation of signals by element 4И - NOT 43 is as follows.

When turning on the welding process, with inverse

The 5th output of trigger 12 enters a logic level “O. In this case, the transistor 48 is locked and the capacitor 45 begins to discharge, and consequently, at one of the master inputs of the comparator 44, a linear decrease in voltage occurs, while the second input receives a sawtooth voltage. At the output of the comparator, pulses appear with a constant decrease in the phase angle relative to the supply voltage of the network. Changing

5, the pulse is modulated in phase into the 4I-NO 43 element by the control pulse from element 42, which also enters this element (Fig. 3, C is the enable signal from trigger 12, U. - pulses with constant

 decreasing the phase shift angle from the comparator 44, Ui - the control pulse from element 42, and the inhibit signal from the comparison block 65).

At the end of the welding, the level of the logic "O" is removed from the base of the transistor 48, since the inverter outputs 10 and I change the signal to the opposite, which leads to the switching of the trigger 12 and

a screw output appears at a logistic level of "1. Transistor 48 is unlocked and the capacitor 45 is charged through resistor top 49. In this case, the charging time is less than or ({corresponds to the preparation time for the second | 1 cycle of welding.

Feedback works as follows.

When the welding current passes through the secondary winding of the welding transformer 57, the current transformer 58 produces a secondary voltage on the secondary winding, which is a projective welding current, which is supplied by the rectifier 59 and the voltage multiplier unit 60 is output, the voltage which is equal to the square of the input voltage, and is fed to the input of the integrator 6, whose voltage increases during each half-period in proportion to the square of the current. At the same time, this voltage is supplied to the comparison unit 65, where it is compared with the voltage coming from the unit 66 of the welding energy reference values. At this m. This block is assembled so that the welding energy of the first three to four lamellae is lower than the nominal one. With each pulse coming from the executive control command unit 1 corresponding to the first three to four lamellas, it stepwise reaches the reference value, the levels of these energy values being regulated (Fig. 2).

I When comparing the current voltage level with the set one, i.e. the current energy level and reference, comparison unit 65, sends a prohibition signal to the module 43 and |: the cooking is stopped (Fig. 3). I At each half-period, the output of the integrator 61 increases in proportion to the input-iiy voltage (and hence the square of the current) and | L is directly proportional to the constant integration RC. The larger the RC, the smaller the increase and, therefore, the longer the time required to achieve the voltage established by the unit 66. The integration constant is controlled by a capacitor 63 and a potentiometer 62. Moreover, the potentiometer can be connected to a variable resistor 8 for adjusting the duration of the welding process. Therefore, between the current

welding and the duration of the welding process are inversely proportional to dependence, and therefore the value of PRt remains constant.

By using the device, the level of energy released at the electrodes is achieved, which significantly improves the quality of the welding connection by introducing feedback, provides any desired mode of welding process and makes it possible to set the optimum welding process for various sizes of products.

Claims (1)

Invention Formula Voltage control device for resistance welding by aut. St. No. 1252102, characterized in that, in order to improve the quality of the welded joint by stabilizing the level of energy released by the electrodes, a block of reference values of the welding energy and a current transformer, a rectifying bridge, a multiplier unit, an integrator and a comparison unit, the output of which is connected to the input of the phase control unit of the welding current and stabilizing its effective value, are connected in series, the second input The comparator unit is connected via the welding energy reference unit with the output of the actuator control command generation unit, and the current transformer is connected to the secondary winding of the welding transformer. I  " "| With B-SC o- {in SG " R - See t,. "O" l t / ) VO Si "about "With l tl. h- "" a v CS NW NW SEG CJ b bw I "V4 f vj o "" / Oh Midrange | oS 5J u (/ 2 3 4 5