RU40112U1 - CONTROL WELD CONTROLLER - Google Patents

Abstract

1 area of use

The inventive device is used in resistance welding as a control device for a thyristor contactor in a resistance welding machine. In addition to the thyristor control function, the controller also has the function of controlling the quality parameters of welding. The controller is used in conjunction with a thyristor contactor (type KT-11UHL4, KT-12UHL4 or similar) and is installed in a spot welding machine (for example, MT-2202-2, etc.).

2. Description of the design

The resistance welding controller can be divided into 5 blocks (see Fig. 1). In the diagram:

1 - input cascades, 2 - alphanumeric indicator, 3 - microcontroller (single-chip micro-computer), 4 - keyboard, 5 - output cascades.

The input stages (1) receive signals from the welding machine: voltage from the electrodes, voltage from the current sensor. Block (1) performs the functions of adapting the input electrical signals for block (3). Also, a synchronizing voltage is supplied to block (1), which is simply an alternating voltage with a network frequency of 50 Hz. Block (1) is connected to the inputs of the ADC block (3).

The indicator (2) gives text messages and the values of the welding parameters received from the microcontroller (3). An 8-bit parallel data bus acts as a communication interface between (2) and (3). As an indicator, an alphanumeric indicator with a dimension of 2 lines of 16 characters is used.

The microcontroller (3) controls the operation of units (2), (4), (5).

Block (4) is a 16-key one. The keyboard is connected to the microcontroller (3) using the same 8-bit bus as the indicator (2).

The output stages (5) are amplification stages on powerful transistors and are connected to low-power outputs of the microcontroller (3). The signals from the output (5) are then sent to the actuator of the welding machine (pneumatic valve) and the pulse transformer of the thyristor contactor.

Blocks (1) - (3) - (5) form a feedback circuit for monitoring and regulating welding parameters.

The microcontroller unit (3) can also be decomposed, thus obtaining the following circuit (Fig. 2).

On the diagram: 6 - block ADC (analog-to-digital conversion) voltage from the electrodes; 7 - block ADC voltage from the current sensor; 8 - block ADC synchronization voltage; 9, 10, 11 - timers that provide time delay (compression, welding and crimping, respectively); 12 - unit for recording voltage values and calculating the control phase; 13 is a block for calculating the average current value; 14 - keyboard and pedal control unit; 15 - valve control system; 16 - thyristor phase control system; 17 - counter worked out by the device half-wave current and a device for supplying a measuring pulse; 18 is a display control unit.

It should be noted that the above circuit is located in the microcontroller and the communication between the blocks is implemented as an 8-bit microprocessor bus and registers.

Some of the blocks (6-18) are implemented in the controller in hardware in the form of input-output modules, ADC blocks, peripheral nodes, and some are implemented in the form of hardware and software.

3. The technical result of the utility model

Using the resistance welding controller, the dimensions of the cast core are stabilized during resistance welding of parts, and this result is also achieved for adjacent points, during welding of which a shunting current effect occurs, which previously entailed a reduction in the size of the core. In the inventive device, the stabilization of the size of the molten core is achieved by stabilizing the voltage on the electrodes. The second result is the product of a reliable weld point, even if for some reason (dirty electrodes or parts) a current has passed through the weld point, less than the critical minimum of the weld current. This is achieved due to the presence of an average current control device and re-welding. The third result is to provide the operator with complete information about the past welding. This is achieved due to the presence of an alphanumeric indicator as an information output device.

Description

1 area of use

The inventive device is used in resistance welding as a control device for a thyristor contactor in a resistance welding machine. In addition to the thyristor control function, the controller also has the function of controlling the quality parameters of welding. The controller is used in conjunction with a thyristor contactor (type KT-11UHL4, KT-12UHL4 or similar) and is installed in a spot welding machine (for example, MT-2202-2, etc.).

2. Technical solutions described in the literature (prior art)

Contact welding controllers performing similar control functions are already known in the art. An analogue of the claimed device can be considered a serial industrially produced by the Electric factory (St. Petersburg) resistance welding controller RVI-801.

Referring to the technical documentation [1] (technical documentation for the RVI-801 regulator) for the RVI-801 regulator, the following similarities with the claimed device can be distinguished. In both devices, there is a phase control unit for thyristor contactor with output amplifier stages. There are lamps indicating the progress of the welding cycle. There is a block for inputting welding parameters (however, it differs significantly from a similar block of the claimed device).

Referring to the technical documentation [1] (technical documentation for the RVI-801 regulator) for the RVI-801 regulator, the following disadvantages can be distinguished. RVI-801 does not provide control of welding quality parameters (average effective voltage and welding current). This leads to instability in the formation of the dimensions of the cast core. There are many elements of the input block for welding parameters and they are all located on the front panel of the device, which is somewhat inconvenient when entering parameters. There is no block output information about the past welding. The elemental base of RVI-801 is integrated circuits of a small degree of integration, which reduces the reliability of this device and increases the cost of its repair.

The prototype of the claimed device can be considered produced by the company 000 "Techservice" (Togliatti) welding cassette KTS-02T.

Referring to the official WEB site and documents of the technical data of the device [2] (official site 000 Techservice http://www.texs.ru/), we can distinguish the following similarities with the claimed device. Both devices have a phase block

control thyristor contactor with output amplifier stages. There is a block for inputting welding parameters (however, it differs significantly from a similar block of the claimed device). There is a block for outputting welding parameters (however, it differs significantly from a similar block of the claimed device). The elemental base of KTS-02T and the claimed device are single-chip micro-computers (however, of different brands).

Referring to the official WEB-site and documents of the technical data of the device [2] (official site 000 Techservice http://www.texs.ru/) the following disadvantages can be distinguished. Only one quality parameter is monitored - current. The measurement of the controlled parameter begins at the beginning of the welding time, and its result is calculated only at the end of the welding time. A current is used as a stabilized parameter of the quality of welding, therefore, when welding adjacent points, a shunt effect occurs. This leads to instability in the formation of the dimensions of the cast core. A 3-key keyboard of the “Parameter-More-Less” type is used: this is inconvenient when searching and setting the desired welding parameter. As an output device, a seven-segment LED indicator is used. This type of indicator can only display information in the form of numbers and dots, but cannot display text messages.

3. Description of the design

The resistance welding controller can be divided into 5 blocks (see Fig. 1). In the diagram:

1 - input cascades, 2 - alphanumeric indicator, 3 - microcontroller (single-chip micro-computer), 4 - keyboard, 5 - output cascades.

The input stages (1) receive signals from the welding machine: voltage from the electrodes, voltage from the current sensor. Block (1) performs the functions of adapting the input electrical signals for block (3). Also, a synchronizing voltage is supplied to block (1), which is simply an alternating voltage with a network frequency of 50 Hz. Block (1) is connected to the inputs of the ADC block (3).

The indicator (2) gives text messages and the values of the welding parameters received from the microcontroller (3). An 8-bit parallel data bus acts as a communication interface between (2) and (3). As an indicator, an alphanumeric indicator with a dimension of 2 lines of 16 characters is used.

The microcontroller (3) controls the operation of units (2), (4), (5).

Block (4) is a 16-key one. The keyboard is connected to the microcontroller (3) using the same 8-bit bus as the indicator (2).

The output stages (5) are amplification stages on powerful transistors and are connected to low-power outputs of the microcontroller (3). The signals from the output (5) are then sent to the actuator of the welding machine (pneumatic valve) and the pulse transformer of the thyristor contactor.

Blocks (1) - (3) - (5) form a feedback circuit for monitoring and regulating welding parameters.

The microcontroller unit (3) can also be decomposed, thus obtaining the following circuit (Fig. 2).

On the diagram: 6 - block ADC (analog-to-digital conversion) voltage from the electrodes; 7 - block ADC voltage from the current sensor; 8 - block ADC synchronization voltage; 9, 10, 11 - timers that provide time delay (compression, welding and crimping, respectively); 12 - unit for recording voltage values and calculating the control phase; 13 is a block for calculating the average current value; 14 - keyboard and pedal control unit; 15 - valve control system; 16 - thyristor phase control system; 17 - counter worked out by the device half-wave current and a device for supplying a measuring pulse; 18 is a display control unit.

It should be noted that the above circuit is located in the microcontroller and the communication between the blocks is implemented as an 8-bit microprocessor bus and registers.

Some of the blocks (6-18) are implemented in the controller in hardware in the form of input-output modules, ADC blocks, peripheral nodes, and some are implemented in the form of hardware and software.

4. The technical result of the utility model

Using the resistance welding controller, the dimensions of the cast core are stabilized during resistance welding of parts, and this result is also achieved for adjacent points, during welding of which a shunting current effect occurs, which previously entailed a reduction in the size of the core. In the inventive device, the stabilization of the size of the molten core is achieved by stabilizing the voltage on the electrodes. The second result is the product of a reliable weld point, even if for some reason (dirty electrodes or parts) a current has passed through the weld point, less than the critical minimum of the weld current. This is achieved due to the presence of an average current control device and re-welding. The third result is the provision

operator complete information about the past welding. This is achieved due to the presence of an alphanumeric indicator as an information output device.

5. Job Description

The main task, which is achieved by the technical result of the utility model, is to stabilize the voltage on the electrodes of the welding machine. The second task is to measure the welding current and compare it with the lower predetermined boundary, as a result of which a decision is made on re-welding. The third task is to display the most complete information about the welding performed in a convenient representation for the operator. The fourth task is to provide a convenient user interface when entering welding parameters.

To solve the main problem, a feedback circuit from blocks (1) - (3) - (5) is used (see the block diagram of the device). The voltage signals from the electrodes and the voltage from the current sensor are converted in block (1) and fed to the inputs of the analog-to-digital converters included in (3).

In the part of the construction description, block (3) was decomposed, therefore, its operation can be considered in more detail (see Fig. 2).

The input of the ADC unit (6) receives the converted voltage taken from the electrodes of the machine (19). The ADC block (6) converts the voltage into a number and transfers it further to the block (12). Block (7) works in a similar way, but its signal receives a signal (20) - a converted signal from a current sensor. The resulting digital equivalents are sent to block (13). The ADC (8) measures the level of the synchronization signal (21) and transmits digital values to the input of the counter of the half-wave current worked out by the device and controls the supply of the measuring pulse (17), the function of which is to determine the moment of voltage transition through 0 (search for the synchronization moment). The counter unit of the half-wave current spent by the device and the control of the supply of the measuring pulse (17) also serves as the counter of the half-wave spent by the device.

The keyboard control unit (14) controls the operation of the keyboard (22) and stores the welding parameters entered with its help in the form of a digital estimate of the values of time, voltage and current. The compression time values are entered from the keyboard - for the compression time timer block (9), the welding time - for the welding time timer block (10), the pressure testing time - for the pressure testing timer block (11), the set voltage - for the voltage value registration and calculation unit control phase (12), boundary current - for the unit for calculating the average current value (13). All these data are also sent to the display control unit (18) for their subsequent display. At the entrance

block (14) receives both signals from the keyboard (4) and the signal from the pedal of the welding machine (4), through which the entire system is launched. These signals are designated as (22). After depressing the pedal, the keyboard control unit by the pedal (14) sets the parameter and gives a command to the timer (9) to start the welding cycle. The difference of the claimed device from the prototype is that in the latter unit (14) is connected to the unit (4) via an external 8-bit data bus (25).

After receiving the start command and the holding time parameter, the compression time timer (9) starts to wait for the end of this time, and at the same time, when the start command is received, it sends a signal to the valve control system block (15) to turn on the valve (23). After the expiration of the time, a start signal for the welding time timer (10) is supplied in the compression time timer (9). From this moment begins the period of the welding cycle. It ends after the welding timer (10).

Blocks (6), (7), (12), (13), (16), (17) work during this welding period (the time until the timer for welding time (10) has worked). The obtained digital estimates of voltage and current from the ADC unit of the voltage of the electrodes (6) and the ADC unit of the voltage of the current sensor (7) are input to the units for recording voltage values and calculating the control phase (12) and the unit for calculating the average current value (13), respectively. The unit for recording voltage values and calculating the control phase (12) accumulates information in the memory of the voltage at the electrodes for the current half-wave. Then, when this half-wave ends, this block calculates the value of the control phase, using these accumulated data as the initial data. This calculated control phase is fed to the block of the thyristor phase control system (16). The difference between the claimed device from the prototype is that the latter has no blocks (6), (12), (17), and the block (13) is not connected to the block (9).

The unit for calculating the average current value (13) performs approximately the same function as the unit for recording voltage values and calculating the control phase (12), with the difference that its input receives digital current equivalents, and they do not accumulate for the current phase, and they are simply summed with each other to then calculate the average current for the entire welding cycle. In this block, a decision is made at the end of the welding cycle to re-conduct it.

The counter unit of the half-wave current spent by the device and the control of the supply of the measuring pulse (17) operates as a half-wave counter and performs the function of generating a command for the first measuring wave, i.e. gives a command about this to the block of the thyristor phase control system (16).

The block of the thyristor phase control system (16) is responsible for the generation of thyristor control pulses (24). On the first wave, the counter unit of the half-wave current worked out by the device and the control of the supply of the measuring pulse (17) gives a command about the low-power measuring wave, and in subsequent waves, the voltage registration unit and the calculation of the control phase (12) gives the thyristor phase control system block (16) indications of the angle of the opening phase of the thyristors.

After the end of the welding phase, the crimping phase begins (the shutter speed timer starts (11)). After the end of the holding time, the pressure test timer block (11) gives the command to the average current value calculation unit (13). The unit for calculating the average current value (13) compares the obtained current value with the boundary value, and if the current is less than the boundary value, the unit for calculating the average current value (13) instructs the compression timer (9) to re-weld (the whole algorithm is repeated again). If the unit for calculating the average current value (13) does not give a re-welding command, the valve control unit (15) turns off the valve, and the display control unit (18) displays the obtained values of current, voltage and time parameters (25). The difference between the claimed device and the prototype is that in the latter, the display control unit (18) is connected to the unit (2) via an external 8-bit data bus (25).

The fact that the main technical result is achieved through stabilization

voltage, it is said in [3] ("Automation and automation of the welding process" N.S. Lvov, E.A. Gladkov M .: "Mechanical Engineering" 1982 - pages 204-205). This source proves this statement as follows.

Schematically, the welding process can be represented as follows (see Fig. 3). In this case, during the welding of the second and subsequent points, the power will be

scatter at previous welded points (Fig. 4). So subsequent

adjacent points will boil slightly worse. In the diagram:

I _CB ⁼ I _CBl + ICB ₂

I _CBl - welding current flowing through the live parts of the machine;

icbi - welding current flowing at the current point;

1 _CB2 - welding current flowing at an adjacent point;

The scheme allows to ensure the constancy of the power allocated at each welding point (Fig. 5). Calculation is made according to Ohm's law for a chain section. In the diagram:

U _cv ⁼ const

I _CB2 <I _CBl

I _CBl = U _CB / R ₁ = const

U _{CB -} stabilized voltage at the electrodes;

R ₁ - resistance of the current welding point;

In the prototype of the claimed device, the welding current acts as a stabilized parameter, which leads to lack of penetration of an adjacent point (Fig. 4). Also, the prototype cannot stabilize the monitored parameter if, for example, during welding, the mains voltage drops sharply (which often happens at production sites). The prototype will not be able to evaluate this voltage drop during welding, since the decision to change the opening angle of the thyristors is made after the end of welding (the so-called stepwise current stabilization).

When solving the second problem, the value of the average effective current and the lower boundary current is used, which is entered before welding as one of the welding parameters. If the measured value falls below the boundary value in block (13), a decision is made to re-weld without expanding the electrodes. This decision is made after the initial welding. The prototype device does not have such a function. The result is achieved by solving this problem because if for some reason (the thickness of the part, characteristics of the welding transformer, voltage drop in the network) the controller cannot provide the welding current no less than the boundary current (the boundary current is established experimentally), repeated welding of the point can reduce the likelihood lack of penetration of the compound.

Unlike the prototype, the claimed device has a convenient system for inputting (4) and (14) and output (2) and (18) information (16 - a keypad and a Russified alphanumeric indicator). This allows you to enter parameters, check them, and also view the final parameters of the past welding in a mode convenient for the operator and the adjuster of the welding machine. The indicator also displays text messages informing the operator of his actions.

6. A brief description of the drawings. Figure 1 - Structural diagram of the resistance welding controller (I) and controlled by it.

welding machine (II). FIG. 2 - Decomposition of the microcontroller unit (3); FIG. 3 - Schematic representation of the welding process while stabilizing the welding current. FIG. 4 - Power loss when welding adjacent points. FIG. 5 - Voltage stabilization U _CB

7. Performance example

The resistance welding controller is implemented using the PIC16F877 microcontroller, the alphanumeric display BC 1602 and a 16-key keyboard with contacts of the "matrix" type SN-04. The device is located in the housing along with the power supply and connectors for connecting to the welding machine.

At the time of application, the inventive device was implemented and tested at a machine-building plant using a resistance welding machine MT-2202-1 and showed the following results.

After necessary adjustment of the controller and selection of the welding machine stage, about 10,000 welds were made in 2 days. When choosing 18 products from this batch, a cut of the welded parts was performed (2 points for each part), while the size of the cast core was 4.6-5.5 millimeters. Parts were selected in 2 pieces. for 1 work shift (at the beginning and in the middle of the shift). The permissible size of the cast core on the site was set by the design department of the enterprise before the start of testing and is 4-6 mm. This proves the practical applicability of the controller and the attainability with its help of the claimed technical result.

Claims (1)

Contact welding controller, consisting of input and output information blocks, input and output stages and an ADC block of electrode voltage, an average current counting unit, an input block control device, a valve control system, a thyristor phase control system, a compression time timer, a welding time timer, a timer pressure test time, the display control unit, where there is a communication line between the output of the compression time timer and the input of the welding time timer, between the output of the welding time timer and the input of the valve control system m, between the output of the welding time timer and the input of the pressure testing timer, between the output of the welding time timer and the input of the thyristor phase control system, between the output of the pressure testing timer and the input of the valve control system, the communication line between the ADC of the current sensor and the input of the average current value calculation unit, between the output of the keyboard control unit and the input of the compression time timer, between the output of the keyboard control unit and the input of the welding time timer, between the output of the keyboard control unit and the time timer input and crimping; between the output of the keyboard control unit and the input of the average current value calculation, between the output of the keyboard control unit and the input of the display control unit, between the output of the average current value calculation unit and the input of the display control unit, included in the microcontroller controlling them, characterized in that it additionally has The microcontroller contains in its composition an ADC block of voltage values, a unit for recording voltage values and calculating the control phase, the microcontroller block contains in its composition s between the counting unit and the average value of current timer time compression, the microcontroller unit contains in its composition ADC voltage synchronization and counter current half-waves of the exhaust device and the flow measuring device pulse input unit is configured as a 16-key keyboard; an alphanumeric indicator measuring two lines of sixteen characters each is used as an output block.