JP7313048B2 - CONTROL DEVICE FOR RESISTANCE WELDER, CONTROL METHOD THEREOF, AND CONTROL PROGRAM - Google Patents

Description

The present invention relates to a resistance welder control device, its control method, and a control program.

2. Description of the Related Art In a resistance welder that welds a work by resistance heat generated by bringing an electrode into contact with a welding portion of the work and passing an electric current through the work, welding failure may occur when the electrode in contact with the work wears out.

For this reason, conventionally, the shape of the electrode is maintained by polishing the electrode after welding is performed a predetermined number of times in resistance welding or periodically (see, for example, Patent Document 1).

Also, there is a device for measuring the shape of an electrode by moving the electrode to a device for detecting the degree of wear of the electrode of a resistance welder (see, for example, Patent Document 2).

JP 2008-254069 A JP-A-08-224671

However, in the prior art, the electrodes were polished after a predetermined number of welding times or periodically. Therefore, if the amount of wear of the electrodes was less than expected, the electrodes that did not need to be polished were polished, resulting in unnecessary costs. In addition, if the amount of wear of the electrode is greater than expected, welding defects may occur in the welding before polishing, and the entire line including the welding machine may stop, resulting in a decrease in productivity.

In addition, in order to measure the shape of the electrode in the shape measuring device, the cost of the device increases as the shape measuring device is added, and it takes time to move the electrode to the measuring device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control device for a resistance welder, a method for controlling the same, and a control program, which are capable of grasping the correct polishing timing of the electrode of the resistance welder at low cost and improving the productivity of the welder.

(1) In order to solve the above problems, a control device for a resistance welder is a control device for a resistance welder that moves an electrode to a welded portion of a workpiece, brings the electrode into contact with the workpiece and pressurizes the workpiece, and performs welding of the welded portion by resistance heat generated by applying current from the electrode. and a providing unit.

(2) In the resistance welder control device of the embodiment, the measurement unit may measure the amount of physical expansion by measuring the amount of movement of the electrode.

(3) In the control device for a resistance welder according to the embodiment, the measurement unit may measure the amount of displacement of the gun yoke that holds the electrode when the electrode presses the workpiece, and convert the amount of strain into the amount of movement of the electrode.

(4) In the control device for a resistance welder according to the embodiment, the determination unit may determine the state of wear of the electrode based on the amount of physical expansion at the start of energization.

(5) Further, in the resistance welder control device of the embodiment, the determination unit may determine the wear state of the electrode based on the presence or absence of a saturation point of the amount of physical expansion.

(6) In the resistance welder control device of the embodiment, the determination unit may determine the wear state of the electrode based on the behavior of the physical expansion amount after the physical expansion amount is saturated.

(7) Further, the control device for the resistance welder of the embodiment may further include a storage unit for pre-storing a reference value of the amount of physical expansion, and the judgment unit may judge the state of wear of the electrode by comparing the amount of physical expansion measured by the measurement unit with the reference value stored in the storage unit.

(8) Further, the control device for the resistance welder of the embodiment may further include a recording unit that records the amount of physical expansion in time series, and the judgment unit may judge the state of wear of the electrode by comparing the amount of physical expansion measured in the measurement unit with the amount of physical expansion recorded in time series in the recording unit.

(9) In the resistance welder control device of the embodiment, the measurement unit may measure the amount of physical expansion by measuring the amount of rotation of a ball screw for linearly moving the electrode.

(10) In order to solve the above problems, a control method for a resistance welder is a method for controlling a resistance welder in which an electrode is moved to a welded portion of a workpiece, the electrode is brought into contact with the workpiece and pressurized, and the welded portion is welded by resistance heat generated by applying current from the electrode. and a providing step of providing.

(11) In order to solve the above problems, the control program for the resistance welder is a control program for a resistance welder that moves an electrode to a welded portion of a work, brings the electrode into contact with the work, pressurizes the work, and performs welding of the welded portion by resistance heat generated by the application of current from the electrode. and a provision function that provides the information of

According to one embodiment of the present invention, the amount of physical expansion of the workpiece is measured during welding, the state of wear of the electrode is determined based on the measured amount of physical expansion, and information on the determined state of wear is provided. This makes it possible to accurately determine when to grind the electrodes of a resistance welder at low cost and to improve the productivity of the welder.

It is a block diagram showing an example of the software configuration of the control device of the resistance welder in the embodiment. It is a figure showing the 1st example of composition of the resistance welder in an embodiment. It is a figure showing the 2nd example of composition of the resistance welder in an embodiment. 4 is a flow chart showing an example of the operation of the control device of the resistance welder in the embodiment; It is a figure which shows an example of the 1st measurement result of the physical expansion of the electrode in embodiment. It is a figure which shows an example of the 2nd measurement result of the physical expansion of the electrode in embodiment. It is a block diagram showing an example of hardware constitutions of a control device of a resistance welding machine in an embodiment.

Hereinafter, a resistance welder control device, a resistance welder control method, and a resistance welder control program according to an embodiment of the present invention will be described in detail with reference to the drawings.

First, with reference to FIG. 1, the function of the resistance welder control device will be described. FIG. 1 is a block diagram showing an example of a software configuration of a control device for a resistance welder according to an embodiment.

In FIG. 1, a control device 1 is a device for controlling a resistance welder (not shown). The control device 1 is communicably connected to the wear monitoring device 2 via a network 9, for example. The wear monitoring device 2 is a device for notifying the wear of the electrode of the resistance welder to a maintenance person or the like who maintains the electrode of the resistance welder. Although FIG. 1 illustrates a system configuration in which one control device 1 and one wear monitoring device 2 are connected by the network 9, the system configuration is not limited to this. For example, a plurality of control devices 1 may be connected to one wear monitoring device 2 to configure a system in which one wear monitoring device 2 monitors a plurality of resistance welders. The network 9 is a wired or wireless communication path, and any communication means such as a communication protocol can be used.

A control device 1 for a resistance welder includes functional units including a measurement unit 11 , an input/output unit 12 , a storage unit 13 , a recording unit 14 , a determination unit 15 , a supply unit 16 , a drive unit 17 and a current control unit 18 . The functional units of the control device 1 according to the present embodiment will be described as functional modules realized by the control program (software) of the resistance welder according to the present embodiment.

The measurement unit 11 measures the amount of physical expansion of the work during welding. In this embodiment, a case where the physical expansion amount of the work is measured using the measured values of the angular position sensor 111, the strain sensor 112, or the displacement sensor 113 will be described as an example (described later).

Here, the wear of the electrode and the amount of physical expansion of the workpiece will be explained. An electrode (electrode tip) in resistance welding (resistance spot welding) wears due to contact with a workpiece at a welding point and application of pressure to the workpiece. The amount of wear of the electrode varies depending on various factors such as the number of times of welding, workpiece (material, surface condition, thickness, etc.), amount of energized current, and strength of pressure. Therefore, for example, it may be difficult to estimate the actual amount of wear based only on the number of welding times. Further, when the electrode wears, the contact area with the work increases, so the current path widens, the resistance value between the work and the electrode decreases, and the amount of Joule heat generated decreases. Further, when the contact area with the work increases, the heat of the work is easily conducted to the electrode, and the temperature rise at the welded portion of the work becomes smaller. This property of reducing the temperature rise of the welded portion is sometimes called "cooling capacity". That is, as the contact area between the work and the electrode increases, the cooling capacity improves and the temperature rise at the welded portion decreases. Therefore, when the wear amount of the electrode increases, the temperature rise at the welded portion is insufficient due to the two effects of a decrease in Joule heat (first effect) and an improvement in cooling capacity (second effect), and welding defects may occur.

On the other hand, the workpiece physically expands (physical expansion) as the temperature rises. The workpiece undergoes physical expansion according to the original shape of the electrode as the temperature rises from the start of welding. For example, when the electrode is new, as described above, the contact area is small and the cooling capacity is small, so the temperature of the workpiece tends to rise, and the amount of physical expansion tends to increase. On the other hand, when the electrode is worn, the temperature rise is insufficient due to the cooling effect, and the amount of physical expansion of the work becomes small. Therefore, if it is possible to measure the amount of physical expansion of the workpiece from the start of current application, it will be possible to measure the state of wear of the electrode. Measurement unit 11 measures the amount of physical expansion of the workpiece by using the measurements of angular position sensor 111, strain sensor 112, or displacement sensor 113 during welding. The measurement unit 11 can measure the physical expansion amount of the workpiece based on the measurement values of the angular position sensor 111, the strain sensor 112, or the displacement sensor 113, thereby measuring the measurement value for determining the consumption state of the electrode.

The input/output unit 12 acquires a reference value of the physical expansion amount for comparison with the physical expansion amount measured by the measurement unit 11 . For example, the reference value is a predetermined threshold value, and the input/output unit 12 acquires the reference value by manual input by a maintenance person or the like via an I/O device such as a keyboard (not shown). The input/output unit 12 may acquire the reference value from an external device such as the wear monitoring device 2 .

The storage unit 13 stores in advance the reference value of the physical expansion amount acquired via the input/output unit 12 . The storage unit 13 may store a plurality of reference values according to welding conditions. For example, the storage unit 13 may store different reference values depending on the type of workpiece to be welded, the number of welding times after electrode polishing, the temperature, the number of welding times per unit time, or the like.

The recording unit 14 records the time-series physical expansion amounts measured by the measurement unit 11 . For example, the recording unit 14 may chronologically record physical expansion amounts for the past thousand times. The amount of physical expansion measured by the measuring unit 11 may contain measurement errors (variation) for each welding operation. By recording the amount of physical expansion in time series, the recording unit 14 can calculate, for example, the average value of the measured values, and can calculate the trend of the measured values in which the errors of the measured values are leveled. This makes it possible to obtain temporal changes in the amount of physical expansion that gradually change over time.

The determination unit 15 determines the state of wear of the electrode based on the amount of physical expansion measured by the measurement unit 11 . For example, the determination unit 15 compares the physical expansion amount measured by the measurement unit 11 with the reference value stored in the storage unit 13 to determine the wear state of the electrode. Further, the determination unit 15 may determine the wear state of the electrode by comparing the physical expansion amount measured by the measurement unit 11 and the physical expansion amount recorded in the recording unit 14 in time series. For example, the judgment unit 15 judges the state of wear in two stages of "OK to use" or "NG to use". In addition, the determination unit 15 may determine a numerical value of "100%" to "0%" when the wear state after polishing is "100%" and the wear state of use NG is "0%", or the degree of wear may be determined as a plurality of ranks. A specific example of determination by the determination unit 15 will be described later.

The providing unit 16 provides information on the wear state determined by the determining unit 15 . For example, the providing unit 16 provides the wear state to the wear monitoring device 2 . Further, the providing unit 16 may provide information for stopping the resistance welder, information for adjusting the amount of energized current, or the like, according to the state of wear.

The driving unit 17 controls driving of an actuator that moves the electrode to contact and press the electrode against the workpiece to be welded.

The current control section 18 controls the energizing current in the electrodes. For example, the current control section 18 controls the waveform of the energized current. The waveform of the energized current determines the temporal change in the amount of current from the start of the energization to the end of the energization.

It should be noted that the above-described functional units of the control device 1 of the resistance welder 3 are examples of the functional units of the control device 1, and the functions of the control device 1 are not limited. For example, the control device 1 does not need to have all the functional units described above, and may have some of the functional units. Also, the control device 1 may have functions other than those described above. For example, the control device 1 may have an input function for inputting information and an output function for notifying the operating state of the device using an LED lamp or the like.

Moreover, as described above, each functional unit of the control device 1 has been described as being realized by software. However, at least one or more of the functional units included in the control device 1 may be realized by hardware.

Further, one of the functional units included in the control device 1 may be implemented by dividing one functional unit into a plurality of functional units. Moreover, any two or more of the above-described functional units included in the control device 1 may be integrated into one functional unit and implemented. That is, FIG. 1 expresses the functions of the control device 1 by functional blocks, and does not indicate that each functional unit is configured by a separate program file or the like, for example.

Further, the control device 1 may be a device realized by one housing, or a system realized by a plurality of devices connected via a network or the like. For example, the control device 1 may realize part or all of its functions by another virtual device such as a cloud service provided by a cloud computing system. That is, the control device 1 may implement at least one or more of the above functional units in another device. Further, the control device 1 may be a general-purpose computer such as a desktop PC, or may be a dedicated device with limited functions.

For example, the wear monitoring device 2 may have the function of determining the wear state of the electrode based on the physical expansion amount measured by the measuring unit 11 from the control device 1, or the function of providing information on the determined wear state. Also, the functions of the control device 1 may be implemented integrally as a resistance welder. That is, the control device 1 may be implemented as a resistance welder.

Next, the configuration of the resistance welder will be described with reference to FIGS. 2 and 3. FIG. FIG. 2 is a diagram showing a first configuration example of a resistance welder according to the embodiment. FIG. 3 is a diagram showing a second configuration example of the resistance welder according to the embodiment. A resistance welder 3 a shown in FIG. 2 is a first configuration example of the resistance welder 3 , and a resistance welder 3 b shown in FIG. 3 is a second configuration example of the resistance welder 3 .

2, the resistance welder 3a includes a motor 31, a gear (pulley) 32, a ball screw 33, an electrode 34, a gun yoke 35, an angular position sensor 111 and a strain sensor 112. FIG. The resistance welder 3a, which is the first configuration example, measures the amount of physical expansion of the electrode 34 using the angular position sensor 111 and the strain sensor 112. FIG.

A motor 31 rotates a ball screw 33 via a gear (pulley) 32 . The rotation of the motor 31 is controlled by the drive unit 17 . The rotation of the motor 31 is decelerated by the gear (pulley) 32 and transmitted to the ball screw 33 . For example, when the welding gun of the resistance welder 3a is a C-type welding gun that moves the electrode linearly, the rotational motion of the ball screw 33 is converted into vertical motion (linear motion) via a spline (not shown), thereby linearly moving the upper electrode 34 shown in the figure, which moves up and down together with the spline. That is, the work is pressed by the electrode 34 by rotating the motor 31 . In the present embodiment, the term "electrode movement amount" means the movement amount in linear motion in the direction in which the electrode 34 presses the workpiece. In the illustrated resistance welder 3a, the amount of movement of the electrode is the amount of movement in the vertical direction. For example, when the direction of pressure is the horizontal direction, the amount of movement of the electrode is the horizontal direction. Further, for example, when the welding gun of the resistance welder 3a is an X-type welding gun in which the electrode rotates about the fulcrum, the movement of the spline rotates the electrode. That is, in the present embodiment, the term "electrode movement amount" means the movement amount in the rotational movement in the direction in which the electrode 34 presses the workpiece.

An angular position sensor 111 is attached to the rotating shaft of the motor 31 . The angular position sensor 111 is a sensor that detects the angular position of the motor 31, and can be implemented by, for example, a rotary encoder or resolver. In the following description, angular position sensor 111 is described as being a rotary encoder. The rotary encoder can measure the amount of rotation of the motor 31 as pulses. That is, the range of motion 36 in linear motion of the electrode 34 is measured as the number of pulses of the angular position sensor 111 .

If the angular position sensor 111 is a 2048 pulses/revolution rotary encoder, the angular position sensor 111 measures one revolution of the motor as 2048 pulses. That is, one pulse detected by the angular position sensor 111 indicates 1/2048 rotation of the motor 31 . When the gear damping ratio of the gear (pulley) 32 is 2:1 and the pitch of the ball screw 33 is 20 mm, one rotation of the motor results in a linear momentum of the electrode of 10 mm. That is, one pulse detected by the angular position sensor 111 is 10 mm/2048 pulses≈0.00488, and the linear motion of the electrode 34 is measured as 4.88 μm/pulse (Formula 1).

The strain sensor 112 is a sensor that measures the amount of strain that occurs in the gun yoke 35 when the electrode 34 presses the workpiece. The strain sensor 112 can measure, as a strain amount, an increase in applied pressure that occurs when the workpiece physically expands during welding. The amount of strain ε of the gun yoke 35 and the amount of rotation of the motor 31 measured by the angular position sensor 111 can be measured in advance, for example, by blank firing before welding. For example, when the linear distance of the electrode from the starting pressure (e.g., 1 kN) when the electrode starts pressurizing the work to reaching the ultimate pressure (e.g., 5 kN), which is the pressure required for welding, is measured as 1600 pulses as the pulse amount of the angular position sensor 111, the number of pulses per unit applied pressure is 1600 pulses / (5-1) kN = 400 pulses / kN. Further, when the strain amount of the gun yoke 35 from the starting pressure to the ultimate pressure is 400 με, the strain amount per unit pressure is 400 με/(5−1) kN=100 με/kN. That is, the number of pulses per strain amount is 400 pulses/100 με=4 pulses/με. Here, since the movement amount of the electrode per pulse is 4.88 μm/pulse as described above, the movement amount of the electrode per strain amount is 4.88 μm/(1/4 με)=19.52 μm/με (equation 2). That is, the strain sensor 112 can measure the amount of physical expansion as the amount of movement of the electrode from the amount of strain generated in the gun yoke 35 .

<Measurement of Physical Expansion of Electrodes (1)>
Next, a method of measuring physical expansion in the resistance welder 3a, which is the first configuration example, will be described. The workpiece expands as a physical expansion amount 37 in the movement direction of the electrode 34 by the ball screw 33 due to Joule heat generated by the energization. The amount of physical expansion 37 increases the pressure applied between the electrode 34 and the workpiece and is measured as the amount of strain on the gun yoke 35 . For example, when the strain amount measured by the strain sensor 112 during welding (during current application) is 5 με, the physical expansion amount 37 is measured as 5*19.52 μm/με=97.6 μm (measurement result 1).

When the ball screw 33 rotates in the opposite direction (rotation in the direction opposite to the pressing direction) due to thermal expansion of the work, the amount of rotation of the ball screw 33 is measured as the number of pulses of the angular position sensor 111 . For example, if 10 pulses are measured at the angular position sensor 111 due to reverse rotation of the ball screw 33, then according to Equation 1, it will be measured as 10*4.88 μm/pulse=48.8 μm (measurement result 2). In this case, the sum of the measurement result 1, that is, 97.6+48.8=146.0 μm is measured as the physical expansion amount 37.

Here, specific examples (judgment methods indicated by A to E) for judging the state of wear of the electrode 34 using the value of the physical expansion amount 37 in the judging section 15 will be described. The wear state refers to the state of wear in the physical shape, and is the degree of shape change in which the tip of the electrode 34 (the portion that contacts the work first) is gradually worn away. At least one of the determination methods described below is implemented. Also, two or more determination methods may be combined for implementation.

<Judgment method A: Judgment based on the amount of physical expansion at the start of energization>
The determination unit 15 determines the wear state of the electrode 34 based on the physical expansion amount 37 at the start of energization. The physical expansion amount 37 at the start of energization is, for example, the magnitude of the physical expansion amount 37 after a predetermined time has elapsed since the start of energization, and is the amount of change in the physical expansion amount 37 per unit time. When the amount of wear of the electrode 34 is small, the amount of change in the amount of physical expansion 37 per unit time is large due to the small cooling capacity. On the other hand, when the amount of wear of the electrode 34 is large, the amount of change in the amount of physical expansion 37 per unit time is small because the cooling capacity is large. The amount of change in the amount of physical expansion 37 per unit time accurately corresponds to the cooling capacity according to the state of wear of the electrode 34 . Therefore, by measuring the amount of change in the amount of physical expansion 37 per unit time, it is possible to accurately determine the state of wear of the electrode 34 .

For example, the amount of change in the amount of physical expansion 37 per unit time is expressed as the slope of the graph in which the horizontal axis indicates the elapsed time from the start of energization and the vertical axis indicates the amount of physical expansion. Assuming that the physical expansion amount 37 after 25 mS from the start of energization is 100 μm, the slope of the graph is measured as 100 μm/25 mS=4 μm/mS. For example, when the inclination is 1 μm/mS or more, the determination unit 15 determines that the wear state is OK, and when it is less than 1 μm/mS, the wear state is determined to be NG. The determining unit 15 determines level 1 wear when the slope is 4 µm/mS or more, level 2 wear when the slope is 3 µm/mS or more and less than 4 µm/mS, level 3 wear when the slope is 2 µm/mS or more and less than 3 µm/mS, level 4 wear when the slope is 1 µm/mS or more and less than 2 µm/mS, and level 5 wear when the slope is less than 1 µm/mS. You may do so.

<Judgment Method B: Judgment Based on Presence or Absence of Saturation Point of Physical Expansion Amount>
The determination unit 15 determines the state of wear of the electrode 34 based on the presence or absence of the saturation point of the physical expansion amount 37 . The presence or absence of the saturation point of the physical expansion amount 37 is whether or not there appears a point (saturation point) where the physical expansion amount 37 is saturated and no longer increases within a predetermined time from the start of energization. As described above, when the amount of wear of the electrode 34 is small, the amount of change in the amount of physical expansion 37 per unit time is large due to the small cooling capacity. Therefore, the temperature of the electrode 34 rises to a predetermined temperature within a predetermined time (for example, until the end of energization) from the start of energization, and the saturation point of the amount of physical expansion 37 appears. On the other hand, when the amount of wear of the electrode 34 is large, the amount of change in the amount of physical expansion 37 per unit time is small because the cooling capacity is large. For this reason, the temperature of the electrode 34 does not reach a predetermined temperature even after a predetermined time has elapsed since the start of energization, and the saturation point of the physical expansion amount 37 does not appear. As mentioned above, the amount of change in physical expansion 37 per unit time corresponds exactly to the cooling capacity. Therefore, it is possible to accurately determine the state of wear of the electrode 34 by determining whether or not there is a saturation point of the physical expansion amount 37 .

For example, if the determination unit 15 determines that the saturation point of the physical expansion amount 37 exists within a predetermined time, it determines that the wear state is OK, and if it determines that the saturation point does not exist, it determines that the wear state is NG. Whether or not there is a saturation point can be determined by, for example, when the amount of change per unit time in the amount of physical expansion 37 is less than or equal to a predetermined amount, or when the amount of change in the amount of physical expansion 37 reaches a predetermined value.

Further, the determination unit 15 may determine the state of wear of the electrode 34 based on the time from the start of energization until the amount of change in the amount of physical expansion 37 reaches the saturation point. For example, it may be determined that level 1 wear occurs when the wear occurs within 25 ms after the start of energization, level 2 wear occurs when the wear occurs between 25 and 50 ms, level 3 wear occurs when the wear occurs between 50 and 100 ms, level 4 wear occurs when the wear occurs between 100 and the end of energization, and level 5 wear occurs when the wear does not occur between 100 and the end of energization.

<Judgment Method C: Judgment Based on Behavior of Physical Expansion Amount After Saturation of Physical Expansion Amount>
The determination unit 15 determines the wear state of the electrode 34 based on the behavior of the physical expansion amount 37 after saturation of the physical expansion amount 37 . The behavior of the physical expansion amount 37 after saturation is an increase or decrease in the value of the physical expansion amount 37 after saturation. Saturation of the physical expansion amount 37 can be determined by, for example, when the amount of change in the physical expansion amount 37 reaches a predetermined value as described above. However, since the change in the physical expansion amount 37 becomes gradual as the electrode 34 wears, it may become difficult to detect saturation. Therefore, even when it is determined that the physical expansion amount 37 is saturated, it is possible to determine the saturation of the physical expansion amount 37 more accurately by determining the behavior of the physical expansion amount 37 after saturation.

For example, if the physical expansion amount 37 further increases after it is determined that the physical expansion amount 37 is saturated, the determination unit 15 may determine the wear state based on the newly increased physical expansion amount 37. Further, when the physical expansion amount 37 once decreases after it is determined that the physical expansion amount 37 is saturated, the determination unit 15 may confirm the determined saturation.

Incidentally, in the determination methods A to C, the wear state can be determined based on the reference values stored in the storage unit 13 . For example, the judgment unit 15 judges the wear state by comparing the physical expansion amount 37 measured by the judgment methods A to C with the reference value stored in the storage unit 13 . Since a predetermined numerical value can be stored in the storage unit 13 as the reference value, the reference value stored according to the welding conditions (for example, the type of workpiece, the amount of current applied, or the waveform pattern of the current, etc.) can be read out and used to determine the state of wear.

Further, in determination methods A to C, the wear state can be determined based on the physical expansion amount 37 recorded in the recording unit 14 in chronological order. For example, the determination unit 15 stores the physical expansion amount 37 measured by the determination methods A to C in the recording unit 14, and compares the measured physical expansion amount 37 with the recorded chronological records to determine the wear state. The amount of physical expansion 37 may be erroneously measured as the welding is performed. By recording the physical expansion amounts 37 in time series, for example, the physical expansion amounts 37 can be averaged to cancel errors. By comparing the physical expansion amount 37 with the error canceled, it becomes possible to accurately determine the state of wear. Also, by recording the physical expansion amount 37 in chronological order, the change (trend) of the physical expansion amount 37 over time can be recorded. Since the wear state gradually changes according to the number of welding times, errors can be canceled by correcting the physical expansion amount 37 with the trend, and the wear state can be accurately determined.

Since the resistance welder 3a, which is the first configuration example, uses the value of the physical expansion amount 37 during welding, in-line measurement of the resistance welder 3a is possible, and there is no need to increase the number of processes for detecting wear of the electrode 34. Therefore, the state of the electrode can be grasped at low cost, and the productivity of the welder can be improved.

3, the resistance welder 3b includes a motor 31, a gear (pulley) 32, a ball screw 33, an electrode 34, a gun yoke 35 and a displacement sensor 113. FIG. A resistance welder 3b, which is a second configuration example, measures the physical expansion amount 37 of the electrode 34 using the displacement sensor 113. FIG. In addition, the same configurations as those in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

<Measurement of Physical Expansion of Electrode (2)>
The displacement sensor 113 is a sensor that directly measures the change in the distance between the electrodes (the distance between the upper electrode and the lower electrode) that occurs when the workpiece expands, and can use, for example, a laser displacement meter. For example, the distance between the electrodes can be measured by attaching a laser-type displacement sensor 113 to a position that moves together with the upper electrode 34 and attaching a reflecting plate that reflects the laser to a position that is fixed to the gun yoke 35 together with the lower electrode 34. The change in the distance between the electrodes is caused by the strain that occurs in the gun yoke 35 due to the expansion of the work or the reverse rotation of the ball screw 33 . The displacement sensor 113 can directly measure the physical expansion amount 37 by measuring the change in the distance between the electrodes.

Like the resistance welder 3a of the first configuration example, the resistance welder 3b of the second configuration example uses the value of the physical expansion amount 37 during welding energization. Therefore, the state of the electrode can be grasped at low cost, and the productivity of the welder can be improved.

Next, the operation of the control device 1 will be described with reference to FIG. FIG. 4 is a flow chart showing an example of the operation of the control device 1 of the resistance welder 3 in the embodiment. Note that the operations described here are performed mainly by the control device 1, but may be realized by each function of the control device 1 described with reference to FIG.

In FIG. 4, the control device 1 determines whether or not the pressure applied by the electrodes has reached the pressure required for welding (step S11). Whether or not the pressure required for welding has been reached can be determined, for example, from the number of pulses of the angular position sensor 111 . Note that, if the electrode pressurization is performed under the control of a robot controller, for example, the control device 1 may acquire information as to whether or not the pressurization force required for welding has been reached from the robot controller. When determining that the pressure required for welding has not been reached (step S11: NO), the control device 1 repeats the operation of step S11 and waits for the pressure to reach.

On the other hand, when determining that the pressure required for welding has been reached (step S11: YES), the control device 1 starts energization from the electrode 34 (step S12). The energization from the electrodes 34 is performed, for example, by a current having a predetermined pulse waveform.

After the process of step S12 is executed, the control device 1 starts measuring the physical expansion amount 37 (step S13). The physical expansion amount 37 can be measured by at least one of the above-described "work physical expansion measurement (1)" and "work physical expansion measurement (2)".

After the process of step S13 is executed, the control device 1 terminates the energization from the electrodes 34 (step S14). The energization from the electrodes 34 is terminated, for example, by energizing the current having a predetermined pulse waveform (eg, rectangular pulse waveform) a predetermined number of times (eg, once).

After the process of step S14 is executed, the control device 1 determines the worn state of the electrode 34 (step S15). Determination of the state of wear can be performed by the determination section 15 using the determination methods A to C described above. The wear state is determined, for example, depending on whether the electrode 34 is usable (wear state OK) or unusable (wear state NG).

When it is determined that the wear state is NG in the process of step S15 (step S16: YES), the control device 1 provides the wear state (step S17). The controller 1 provides the wear status, for example to the wear monitor 2, as described above. When it is determined that the wear condition is OK in the process of step S15 (step S16: NO), or after the process of step S17 is executed, the control device 1 ends the process shown in the flowchart.

Next, measurement results of the physical expansion amount 37 of the workpiece will be described with reference to FIGS. 5 and 6. FIG. FIG. 5 is a diagram showing an example of a first measurement result of the physical expansion amount 37 of the work according to the embodiment. FIG. 6 is a diagram showing an example of a second measurement result of the physical expansion amount 37 of the work in the embodiment. FIG. 5 shows the measurement results when the electrode 34 is new or polished. FIG. 6 shows the measurement results when the wear of the electrodes has progressed.

In FIG. 5, the x-axis indicates the passage of time from the start of energization (x-axis: 0 mS). A current waveform 41 indicated by a thick line indicates changes over time in the current supplied from the electrode 34 . In this embodiment, the current waveform 41 is a rectangular pulse wave. The current waveform 41 is a current value of 8000A from 0 to 150mS.

In FIG. 5, the solid line indicates the measured value 42 of the physical expansion amount 37 when the electrode 34 is new, and the dotted line indicates the measured value 43 of the resistance value between the electrodes. The measured value 42 reaches saturation at about 25 mS, maintains about 100 μm thereafter, and gradually decreases from 150 mS at the end of energization. In the judgment method A, since it becomes 100 μm after 25 mS from the start of energization, the slope of the graph is measured as 100 μm/25 mS=4 μm/mS. The determination unit 15 determines that the electrode is not worn from the measurement result. Further, in the determination method B, since saturation is reached at about 25 ms, the determination unit 15 determines that there is no wear of the electrode from this measurement result. Furthermore, in determination method C, since the thickness is maintained at about 100 μm after reaching saturation, the determination unit 15 determines that there is no wear of the electrode from the measurement result.

The amount of heat generated in resistance welding is calculated as r* ^I2 from the resistance value r and the current I. Here, in the rectangular pulse, since the current is constant, the measurement result of the measured value 43 is proportional to the amount of heat generated per unit time. The measured value 43 shows a high resistance value of 300 μΩ at the start of energization, and the amount of heat generated increases in proportion to this. Since the measured value 43 gradually decreases with physical expansion, the measured value 42 can also be maintained at 100 μm. Since the cooling capacity increases as the temperature difference increases, the cooling capacity decreases as the amount of heat generated decreases due to the decrease in the resistance value. Therefore, it can be inferred that the measured value 42 maintains a constant value because the calorific value and the cooling capacity are well balanced.

In FIG. 6, a current waveform 51 indicated by a thick line is the same as in FIG. The solid line shows the measured value 52 of the physical expansion amount 37 when the electrode 34 is worn, and the dotted line shows the measured value 53 of the resistance value between the electrodes. The measured value 52 reaches about 25 μm at about 25 mS from the start of energization, and then gradually increases until the end of energization without saturating. In the judgment method A, since it becomes 25 μm after 25 mS from the start of energization, the slope of the graph is measured as 25 μm/25 mS=1 μm/mS. The determination unit 15 determines that the electrode is worn out from the measurement result. Further, in the judgment method B, since the saturation is not reached from the start to the end of the energization, the judgment unit 15 judges that the electrode is worn from the measurement result. Furthermore, in judgment method C, since saturation has not been reached, the judgment unit 15 judges that the electrode is worn out from this measurement result.

Measured value 53 is about 250 μΩ at the start of energization, but thereafter decreases to about 150 μΩ, which is lower than measured value 43 in FIG. 5 . This is because the contact area with the work increases due to wear of the electrode 34, indicating that the electrode 34 cannot generate a sufficient amount of heat compared to when it is new.
Next, the hardware configuration of the control device 1 will be described with reference to FIG. FIG. 7 is a block diagram showing an example of the hardware configuration of the control device 1 according to the embodiment.

The control device 1 has a CPU (Central Processing Unit) 101 , a RAM (Random Access Memory) 102 , a ROM (Read Only Memory) 103 , an I/O device 104 and a communication I/F (Interface) 105 . The control device 1 is a device that executes the control program of the control device 1 described with reference to FIG.

The CPU 101 controls the user terminal by executing an information processing program stored in the RAM 102 or ROM 103 . The information processing program is acquired, for example, from a recording medium recording the program or from a program distribution server via a network, installed in ROM 103, read out by CPU 101, and executed.

The I/O device 104 has an operation input function and a display function (operation display function). The I/O device 104 is, for example, a touch panel. The touch panel enables the user of the control device 1 to perform operation input using a fingertip, a touch pen, or the like. The I/O device 104 in this embodiment uses a touch panel having an operation display function, but the I/O device 104 may have a display device having a display function and an operation input device having an operation input function separately. In that case, the display screen of the touch panel can be implemented as the display screen of the display device, and the operation of the touch panel can be implemented as the operation of the operation input device. Note that the I/O device 104 may be implemented in various forms such as a head-mounted type, glasses type, wristwatch type display, and the like.

Communication I/F 105 is an I/F for communication. The communication I/F 105 executes short-range wireless communication such as wireless LAN, wired LAN, and infrared. Although the figure shows only the communication I/F 105 as a communication I/F, the control device 1 may have respective communication I/Fs in a plurality of communication methods.

It should be noted that the above-described various processes of the present embodiment may be performed by recording a program for realizing the functions constituting the apparatus described in the present embodiment in a computer-readable recording medium, and causing the computer system to read and execute the program recorded in the recording medium. Note that the “computer system” referred to here may include hardware such as an OS and peripheral devices. The "computer system" also includes the home page providing environment (or display environment) if the WWW system is used. In addition, "computer-readable recording medium" refers to a storage device such as a flexible disk, a magneto-optical disk, a ROM, a writable non-volatile memory such as a flash memory, a portable medium such as a CD-ROM, and a hard disk built into a computer system.

Furthermore, the term "computer-readable recording medium" includes volatile memory (e.g., DRAM (Dynamic Random Access Memory)) inside a computer system that acts as a server or client when the program is transmitted via a network such as the Internet or a communication line such as a telephone line, and includes those that hold the program for a certain period of time. Further, the above program may be transmitted from a computer system storing this program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in a transmission medium. Here, the "transmission medium" for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. Further, the program may be for realizing part of the functions described above. Furthermore, a so-called difference file (difference program), which realizes the functions described above in combination with a program already recorded in the computer system, may be used.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and various modifications are included without departing from the scope of the present invention.

Reference Signs List 1 control device 11 measurement unit 111 angular position sensor 112 strain sensor 113 displacement sensor 12 input/output unit 13 storage unit 14 recording unit 15 determination unit 16 supply unit 17 drive unit 18 current control unit 2 wear monitoring device 3 (3a, 3b) resistance welder 31 motor 32 gear (pulley)
33 ball screw 34 electrode 35 gun yoke 36 range of motion 37 physical expansion 41, 51 current waveform 42, 52 measured value 43, 53 measured value 9 network 101 CPU
102 RAMs
103 ROMs
104 I/O device 105 Communication I/F

Claims (12)

A control device for a resistance welder that moves an electrode to a welded portion of a work, presses the electrode by contacting the work, and welds the welded portion by resistance heat generated by applying current from the electrode,
a measuring unit that measures the amount of physical expansion of the workpiece during welding;
a determination unit that determines the state of wear of the electrode based on the amount of physical expansion measured by the measurement unit;
a providing unit that provides information on the state of wear determined by the determining unit ;
A control device for a resistance welder , wherein the judgment unit judges the state of wear of the electrode based on the presence or absence of a saturation point of the amount of physical expansion . A control device for a resistance welder that moves an electrode to a welded portion of a work, presses the electrode by contacting the work, and welds the welded portion by resistance heat generated by applying current from the electrode,
a measuring unit that measures the amount of physical expansion of the workpiece during welding;
a determination unit that determines the state of wear of the electrode based on the amount of physical expansion measured by the measurement unit;
a providing unit that provides information on the state of wear determined by the determining unit;
with
The control device for a resistance welder, wherein the judgment unit judges the state of wear of the electrode based on the behavior of the amount of physical expansion after the amount of physical expansion is saturated. 3. The control device for a resistance welder according to claim 1 , wherein said measuring unit measures said amount of physical expansion by measuring the amount of movement of said electrode. 4. The control device for a resistance welder according to claim 3 , wherein the measurement unit measures the amount of displacement of a gun yoke holding the electrode when the electrode presses the workpiece, and converts the amount of strain into the amount of displacement of the electrode. The control device for a resistance welder according to any one of claims 1 to 4 , wherein said judgment unit judges the state of wear of said electrode based on said amount of physical expansion at the start of energization. Further comprising a storage unit that stores in advance a reference value of the physical expansion amount,
6. The control device for a resistance welder according to claim 1 , wherein the judgment unit judges the state of wear of the electrode by comparing the physical expansion amount measured by the measurement unit with the reference value stored in the storage unit. Further comprising a recording unit for recording the amount of physical expansion in time series,
The resistance welder control device according to any one of claims 1 to 6 , wherein the judgment unit judges the state of wear of the electrode by comparing the amount of physical expansion measured by the measurement unit and the amount of physical expansion recorded in the recording unit in time series. The resistance welder control device according to any one of claims 1 to 7 , wherein the measurement unit measures the amount of physical expansion by measuring the amount of rotation of a ball screw for linearly moving the electrode. A control method for a resistance welder that performs welding at a welding point by moving an electrode to a welding point on a workpiece, bringing the electrode into contact with the workpiece and pressurizing it, and performing resistance heating generated by applying current from the electrode, wherein
a measuring step of measuring the amount of physical expansion of the workpiece during welding;
a determination step of determining the state of wear of the electrode based on the amount of physical expansion measured in the measurement step;
a providing step of providing the wear state information determined in the determining step ;
A method of controlling a resistance welder , wherein in the determination step, the state of wear of the electrode is determined based on the presence or absence of a saturation point of the amount of physical expansion. A control method for a resistance welder that performs welding at a welding point by moving an electrode to a welding point on a workpiece, bringing the electrode into contact with the workpiece and pressurizing it, and performing resistance heating generated by applying current from the electrode, wherein
a measuring step of measuring the amount of physical expansion of the workpiece during welding;
a determination step of determining the state of wear of the electrode based on the amount of physical expansion measured in the measurement step;
a providing step of providing information on the wear state determined in the determining step;
including
A method of controlling a resistance welder, wherein, in the determination step, the state of wear of the electrode is determined based on the behavior of the amount of physical expansion after the amount of physical expansion is saturated. A control program for a resistance welder that moves an electrode to a welded portion of a work, presses the electrode by contacting the work, and welds the welded portion by resistance heat generated by applying current from the electrode,
to the computer,
a measurement function that measures the amount of physical expansion of the workpiece during welding;
a judgment function for judging the state of wear of the electrode based on the amount of physical expansion measured by the measurement function;
a providing function for providing information on the state of wear determined by the determining function ;
A control program for a resistance welder for judging the state of wear of the electrode based on the presence or absence of the saturation point of the amount of physical expansion in the judging function. A control program for a resistance welder that moves an electrode to a welded portion of a work, presses the electrode by contacting the work, and welds the welded portion by resistance heat generated by applying current from the electrode,
to the computer,
a measurement function that measures the amount of physical expansion of the workpiece during welding;
a judgment function for judging the state of wear of the electrode based on the amount of physical expansion measured by the measurement function;
a providing function for providing information on the state of wear determined by the determining function;
to realize
A control program for a resistance welder for determining, in the determination function, the state of wear of the electrode based on the behavior of the amount of physical expansion after saturation of the amount of physical expansion.

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