JP2023132420A - Spot-welding device and spot-welding method - Google Patents

Abstract

To be able to reduce poor welding in spot-welding.SOLUTION: A spot-welding device 1 comprises a spot-welding gun 10 which has electrodes 11 and 12 arranged oppositely to each other and an electrode driving motor 13 for driving the electrodes 11 and 12, and a control device 40 that controls the spot-welding gun 10. The control device 40 has a welding pressure control part 43 that controls welding pressure that is applied by the electrodes 11 and 12 to a member to be welded by activating the electrode driving motor 13, and a position control part 44 that holds positions of the electrodes 11 and 12 at certain positions, which in a state where the electrodes 11 and 12 are in contact with the member, makes welding pressure rise up to preset first welding pressure by welding pressure control by the welding pressure control part 43, then holds the positions of the electrodes 11 and 12 at certain positions by position control by the position control part 44 after the welding pressure is risen to start power distribution, starts cooling a welding spot and switches the position control to the welding pressure control, and retains the welding pressure at second welding pressure in a cooling period of time, after the power distribution is finished.SELECTED DRAWING: Figure 2

Description

This case relates to spot welding equipment and spot welding methods.

For example, in spot welding used in manufacturing vehicle bodies, the members to be welded are sandwiched between a pair of electrodes, and the electrodes are energized to melt the members to be welded. At this time, it is common practice to control the pressure force with which the member is sandwiched between the electrodes. Furthermore, techniques for controlling the position of electrodes when performing spot welding have also been developed.

For example, in Patent Document 1, at the start of spot welding control, a predetermined pressing force is applied to the member, and then the position of the pair of electrodes is maintained constant even after energization is started. , the pressure control is switched to the position control, the current is applied while controlling the position, and after the energization is finished, the workpiece is cooled while controlling the position.

Japanese Patent Application Publication No. 2018-034172

However, in the technique described in Patent Document 1, after the energization ends, the member is cooled while the electrode position is maintained constant, so there is a risk that the pressing force to sandwich the member to be welded is insufficient during cooling. Insufficient pressurizing force during cooling may lead to defective welding. This is due to the fact that gas is generated in the molten part during current application and heating in resistance spot welding. The gas generated in this molten part will be absorbed by the nugget and disappear if sufficient pressure is applied to the weld center from the start of cooling after the current is stopped to solidification, but if the applied pressure is If it is insufficient, gas will remain in the nugget after the molten part has solidified, and this gas will become a blowhole, which may cause internal defects (defects in welding) at the welding location.

The present invention was created to solve the above-mentioned problems, and one of the objects is to provide a spot welding device and a spot welding method that can reduce welding defects in spot welding. In addition, this purpose is not limited to this purpose, and it is also possible to achieve effects derived from each configuration shown in "Details for Carrying Out the Invention" that will be described later, which cannot be obtained with conventional techniques. It is a purpose.

The disclosed spot welding device and spot welding method can be realized as the embodiments or application examples disclosed below, and solve at least part of the above problems.
The disclosed spot welding apparatus includes a spot welding gun having a pair of electrodes arranged to face each other, an electrode drive motor that drives at least one of the pair of electrodes, and a control that controls the spot welding gun. A device. The control device includes a pressurizing force control unit that operates the electrode drive motor to control the pressurizing force that the pair of electrodes applies to the member to be welded, and a position control unit that maintains the position of the pair of electrodes at a constant position. and has. The control device increases the pressing force from a state in which the pair of electrodes are in contact with the member to a preset first pressing force by controlling the pressing force by the pressing force control unit, and increases the pressing force to a first pressing force that is set in advance. When a certain pressure is reached, the position of the pair of electrodes is held constant by the position control by the position control unit and energization is started, and the energization is stopped after a set time, and as cooling of the welding area starts, the pair of electrodes are held at the same position. The control is switched to the pressurizing force control, and the pressurizing force is maintained at a preset second pressurizing force during the cooling period.

The disclosed spot welding method controls a spot welding gun having a pair of electrodes arranged to face each other and an electrode drive motor that drives at least one of the pair of electrodes to weld a member to be welded. The spot welding method performs spot welding on the member, and in the pressurizing force control in which the electrode drive motor is operated from a state where the pair of electrodes are in contact with the member to control the pressurizing force applied to the member, the pressurizing force is is increased to a preset first pressing force, and when the pressing force reaches the first pressing force, the electrode drive motor is actuated to control the position of the one electrode. The energization is started while the position of the electrode is kept constant, the energization is ended after a set time from the start of the energization, and the position control is switched to the pressurizing force control at the same time as cooling of the welding area is started. During the cooling period, the pressurizing force is maintained at a preset second pressurizing force.

According to the disclosed spot welding device and spot welding method, when the pressing force of the pair of electrodes reaches the first pressing force, the position of the pair of electrodes is held constant and energization is carried out, so that the first pressing force is reduced. Even if it is not set high, the pressing force will increase as the welding object expands as the current passes. As a result, a necessary but not excessive pressing force can be obtained during energization, and neither insufficient nor excessive pressing force is likely to occur, and welding quality can be improved.
In addition, after energization ends, the control switches to pressure force control at the same time as cooling of the welding point begins, so even if the component shrinks due to cooling, pressure can be applied reliably to the component, and if pressure is insufficient during cooling. Welding defects caused by this can be suppressed.

FIG. 1 is a configuration diagram showing a spot welding device according to an embodiment. FIG. 2 is a block diagram showing a control system of the spot welding apparatus of FIG. 1. FIG. 2 is an example of a flowchart illustrating control of the spot welding apparatus of FIG. 1. FIG. FIG. 2 is a schematic cross-sectional view chronologically showing the relationship between a pair of electrodes of the spot welding device of FIG. 1 and a member to be welded. 2 is a time chart showing a pressurizing force state of an electrode and an energization state of the electrode for explaining control of the spot welding apparatus of FIG. 1. FIG. 2 is a time chart showing changes in plate thickness of members for explaining control of the spot welding apparatus of FIG. 1. FIG.

A spot welding device and a spot welding method as embodiments will be described with reference to the drawings. The embodiments shown below are merely illustrative, and there is no intention to exclude the application of various modifications and techniques not specified in the embodiments below. The configuration of each embodiment can be modified and implemented in various ways without departing from the spirit thereof. Further, they can be selected or combined as necessary.

[1. Device configuration]
The overall configuration of the spot welding device 1 of this embodiment will be explained.
As shown in FIGS. 1 and 2, the spot welding device 1 controls a spot welding gun 10, a robot 20 that operates the position and posture of the spot welding gun 10, and energization to the electrode 11 of the spot welding gun 10. It includes an energization control device 30 (also referred to as a "welding timer") and a control device 40 that controls the spot welding gun 10, the robot 20, and the energization control device 30.

Note that the spot welding device 1 is one of a plurality of manufacturing facilities installed in a manufacturing line for products that require spot welding, such as automobile bodies, and the control device 40 is a process control device that is a higher-level control device. It is connected to the control panel 50 by a signal line. The process control panel 50 sends information necessary for operation control and start-up command information to each manufacturing equipment (including the present spot welding apparatus 1) on the manufacturing line. Each manufacturing facility also sends its own operational information, such as process completion information.

The spot welding gun 10 includes a pair of electrodes 11 and 12, and an electrode drive motor 13 that drives at least one of the pair of electrodes 11 and 12 (here, referred to as electrode 11). By driving the electrodes 11 with the motor 13, one electrode 11 can be moved toward and away from the other electrode 12. In this embodiment, the electrode 11 is a movable electrode and the electrode 12 is a fixed electrode, but this may be reversed, or both the electrodes 11 and 12 may be movable electrodes.

An electrode drive circuit 13A is connected to the electrode drive motor 13. The electrode drive circuit 13A supplies the electrode drive motor 13 with a current according to a command signal from the control device 40. The electrode drive motor 13 drives the electrode 11 upon receiving the supplied current. When driving the electrode 11 toward the member 61 with the electrodes 11 and 12 sandwiching the two members 61 and 62 (workpieces) to be welded, a pressing force P is applied from the electrodes 11 and 12 to the members 61 and 62. Ru. This pressing force P can be increased or decreased by adjusting the magnitude of the current supplied to the electrode drive motor 13.

The spot welding gun 10 also includes an electrode position sensor 14 (position detection unit) that detects the position of the electrode 11 (relative position with respect to the electrode 12) driven by the electrode drive motor 13, and a pressurizing force P caused by the electrodes 11 and 12. A pressurizing force sensor 15 (pressing force detection section) for detecting the pressure is also attached.

Although not shown, a cooling liquid is supplied to the vicinity of the electrodes 11 and 12 of the spot welding gun 10 during welding, and a cooling liquid is supplied during and after the electrodes 11 and 12 are energized. A cooling liquid is supplied to the welding points 63 of the electrodes 11 and 12 and the members 61 and 62 to be welded. The cooling liquid suppresses excessive temperature rise at the welding points of the electrodes 11, 12 and the members 61, 62 while the electrodes 11, 12 are energized, and cools the electrodes 11, 12 and the members 61, 62 during the cooling period when the energization is stopped. Cool the welding points 61 and 62 to around room temperature.

The energization control device 30 controls the presence or absence of energization between the electrodes 11 and 12 of the spot welding gun 10, and the voltage at the time of energization, in response to a command signal from the control device 40. When energizing between the electrodes 11 and 12, it is necessary to properly manage the applied voltage value V (hereinafter referred to as "voltage V") and the energization time to ensure welding quality. For this reason, the energization control device 30 is provided with a timer 31, and the energization control device 30 performs energization at a timing based on information from the timer 31. A voltage supply circuit 30A is connected to the energization control device 30, and the voltage supply circuit 30A applies a voltage V between the electrodes 11 and 12 according to a command from the energization control device 30.

The robot 20 is an articulated robot having a plurality of joints, and is provided with a robot drive motor 21 that drives each joint.By operating each robot drive motor 21, the position and posture of the spot welding gun 10 can be adjusted. operate. A robot drive circuit 21A is connected to each robot drive motor 21, and the robot drive circuit 21A supplies the robot drive motor 21 with a current according to a command signal from the control device 40. Each robot drive motor 21 drives each joint with a driving force depending on the magnitude of the supplied current. Furthermore, each joint of the robot 20 is provided with a robot position sensor 22 (robot position detection unit) that detects the position and orientation of the joint.
Note that although the electrode drive circuit 13A, robot drive circuit 21A, and voltage supply circuit 30A are shown independently in FIG. It may be separate or separate.

The control device 40 includes a robot control section 40A (robot control device) that controls the robot 20, and a spot welding gun control section 40B (spot welding gun control device) that controls the spot welding gun 10. The control device 40 includes an electronic control unit including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like that are connected to each other via a bus.
In this embodiment, the control device 40, which is one piece of hardware, is equipped with a robot control section 40A and a spot welding gun control section 40B as software. may be equipped with separate hardware.

The spot welding gun control section 40B includes an electrode position control section 41 that controls the electrode drive motor 13, and an energization control section 42 that controls the energization state between the electrodes 11 and 12 of the spot welding gun 10 through the energization control device 30. ing.

In particular, the electrode position control section 41 controls the current supplied to the electrode drive motor 13, and at this time, the press force control section 43 controls the press force P applied by the electrodes 11 and 12 to the members 61 and 62 to a target state. and a position control unit 44 that controls the position of the electrode 11 (the relative position of the electrode 11 with respect to the electrode 12) to a target state.

The pressurizing force control unit 43 of this embodiment controls the pressurizing force P by operating the electrode drive motor 13 based on the pressurizing force P detected by the pressurizing force sensor 15 (detected pressurizing force). Further, the position control unit 44 of this embodiment operates the electrode drive motor 13 based on the position detected by the electrode position force sensor 14 (detected position) to maintain the position of the electrode 11 at a constant position. That is, the pressurizing force control unit 43 of this embodiment acquires the pressurizing force P detected by the pressurizing force sensor 15, and feeds back the current of the electrode drive motor 13 so that the detected pressurizing force P becomes the target state. Control. Further, the position control unit 44 of this embodiment acquires the position information of the electrode 11 detected by the electrode position sensor 14, and performs feedback control on the current of the electrode drive motor 13 so that the detected position is in the target state. do.

[2. Control configuration]
Next, control of spot welding by the spot welding device 1 will be explained.
When the spot welding device 1 receives startup command information from the process control panel 50, it operates the robot 20 based on the operation control information received from the process control panel 50 in advance to adjust the position and orientation of the spot welding gun 10 to a predetermined position. Set to state. As a result, the pair of electrodes 11 and 12 face each other at predetermined positions with the welding location 63 in between, while being separated from each other. At this point, the electrode drive motor 13 of the spot welding gun 10 is in a stopped state, and the electrodes 11 and 12 are also in a non-energized state. Thereafter, the spot welding gun control section 40B controls the spot welding gun 10.

The device and method of the present invention are characterized by the control of the spot welding gun 10 by the spot welding gun control section 40B. This control will be explained with reference to the flowchart of FIG. 3 and the time-series diagrams of FIGS. 4(a) to (j).
First, the electrodes 11 and 12 are in a state separated from the members 61 and 62, as shown in FIG. 4(a).

As shown in FIG. 3, first, as a preparation step, the electrodes 11 and 12 are driven until the electrodes 11 and 12 are in contact with the members 61 and 62 (see FIG. 4B) (step S10). . Note that the robot 20 is appropriately used to drive the electrode 12. For example, the robot 20 is actuated to bring the tip of the fixed electrode 12 into contact with the surface of the member 62, and at the same time (or subsequently) the electrode drive motor 13 is actuated to move the electrode 11. The tip is brought into contact with the surface of the member 61. To control the drive of the electrode 11 at this time, position control by the position control section 44 can be used. Note that when the electrodes 11 and 12 come into contact with the members 61 and 62, the pressurizing force sensor 15 reacts, so that contact can be determined based on the detection signal of the pressurizing force sensor 15.

When the electrodes 11 and 12 come into contact with the members 61 and 62, the position control by the position control unit 44 is switched to the pressure control by the pressure force control unit 43 (step S20). In this pressurizing force control, the pressurizing force P by the electrodes 11 and 12 is increased to a preset first pressurizing force P1 (step S30). Note that the first pressurizing force P1 is set in consideration of expansion of the members 61 and 62 due to energization. This will be discussed later.

When the pressurizing force P rises to the first pressurizing force P1, next, the pressurizing force control by the pressurizing force controller 43 is switched to the position control by the position controller 44 [step S40, see FIG. 4(c)]. In this position control, the positions of the electrodes 11 and 12 where the pressing force P becomes the first pressing force P1 are controlled so as to remain constant at that position (step S50).

After starting the position control, energization of the electrodes 11 and 12 is started [see FIG. 4(d)]. In this energization, a preset voltage V1 (target voltage) is applied between the electrodes 11 and 12, and continues to be applied for a preset predetermined time (set time) (step S60). By this energization, the welding point 63 transforms from solid to liquid, and expands to form a nugget 64 [see FIGS. 4(e) to 4(f)].

When the energization is finished, the position control by the position control section 44 is switched to the pressure control by the pressure control section 43 [step S70, see FIG. 4(g)]. In this pressurizing force control, the pressurizing force P by the electrodes 11 and 12 is adjusted to and held at a preset second pressurizing force P2 [see step S80, FIG. 4(h)]. When the energization of the electrodes 11 and 12 ends, the welding location 63 is cooled by the cooling liquid, but the control to maintain the pressurizing force P at the second pressurizing force P2 is continued until this cooling period ends. Note that the second pressing force P2 has a value different from the first pressing force P1, but may be equal to the first pressing force P1. However, it is preferable that the second pressing force P2 is greater than or equal to the first pressing force P1. This is to more reliably avoid insufficient pressurizing force that may occur due to contraction of the welding location 63 during the cooling period.

When the cooling period ends, the pressurizing force P is reduced from the second pressurizing force P2 to 0 by the pressurizing force control (see step S90, FIG. 4(i)).
When the pressing force P becomes 0, the electrode 11 and the electrode 12 are separated from the members 61 and 62 by position control as shown in FIG. 4(j) (step S100). Thereby, the robot 20 can evacuate the spot welding gun 10 or move it to another welding location.

Here, the control of the spot welding apparatus 1 will be further explained using the time series diagrams of FIGS. 4(a) to 4(j) and the time chart of FIG. 5. Note that the horizontal axis of the time chart in FIG. 5 is time, and the vertical axis is the pressing force P and voltage V by the apparatus and method of the present invention. Moreover, the solid line L1 shows the change in the pressing force P, and the broken line L2 shows the change in the voltage V.
First, at time T0, the pair of electrodes 11 and 12 face each other at a predetermined position with the welding location 63 in between and are spaced apart from each other [see FIG. 4(a)]. At this time, the pressing force P by the electrodes 11 and 12 is 0, and the voltage V between the electrodes 11 and 12 is also 0 (current is stopped).

As the pair of electrodes 11, 12 approaches the welding location 63, the electrodes 11, 12 come into contact with the welding location 63 at time Ts [see FIG. 4(b)]. Also at this time, the pressing force P by the electrodes 11 and 12 is 0, and the voltage V between the electrodes 11 and 12 is also 0 (current is stopped).

Thereafter, the pressurizing force P by the electrodes 11 and 12 is increased to the first pressurizing force P1, and at time T1, the pressurizing force P reaches the first pressurizing force P1 [see FIG. 4(c)]. With this pressing force P being the first pressing force P1, pressing force control is switched to position control, and the positions of the electrodes 11 and 12 are controlled (maintained) at a constant position. At time T2 after this position control is started, voltage application to the electrodes 11 and 12 is started. As a result, the voltage V of the electrodes 11 and 12 becomes the target voltage V1 [see FIG. 4(d)].

When a voltage is applied to the electrodes 11 and 12, the welding location 63 transforms from solid to liquid, and expands to form a nugget 64 [see FIGS. 4(e) to 4(f)]. Note that FIG. 4(e) shows a state in which ΔT1 hour has elapsed since the start of energization (voltage application) to the electrodes 11 and 12, and FIG. ΔT2>ΔT1) has elapsed. As shown in the figure, the formed nugget 64 gradually increases in size and welding progresses.

Since the positions of the electrodes 11 and 12 are controlled to be constant as shown in the curve of the pressurizing force P shown in FIG. 5, the pressurizing force P becomes higher than the first pressurizing force P1 according to the expansion of the welding location 63. However, this curve of the pressurizing force P is an example, and various forms may be assumed depending on the welding conditions, but it is considered that at least the pressurizing force P is higher than the first pressurizing force P1.

At time T3 when the electrodes 11 and 12 have been energized for a predetermined period of time, the energization of the electrodes 11 and 12 is terminated. At the same time, the electrodes 11 and 12 are switched from position control to pressure force control to adjust and hold the pressure P by the electrodes 11 and 12 at a preset second pressure P2 [see FIG. 4(g)] .

When the energization ends, the welding location 63 is cooled, so the welding location 63 contracts due to a decrease in temperature. At this time, since the pressure P adjusted to the second pressure P2 by the electrodes 11 and 12 is applied to the welding location 63, during the cooling period, the electrodes 11 and 12 are applied as the welding location 63 contracts. The distance between them becomes closer [see Figure 4(h)].

When the cooling period ends at time T4 [see FIG. 4(i)], the pressurizing force P is decreased from the second pressurizing force P2 to 0 by pressurizing force control, and when the pressurizing force P becomes 0 at time Te, the electrode 11 and the electrode 12 are separated from the members 61 and 62 [see FIG. 4(j)].
In addition, in FIG. 5, the period of increase in pressurizing force between time Ts and time T1, the period from the start of position control to the start of energization between time T1 and time T2, and the period between time T4 and time Te Although the periods during which the pressing force is reduced are shown in a large size for convenience, these periods are actually extremely small periods of time.

Next, with reference to the time chart of FIG. 6, the transition of the plate thickness t of the members 61 and 62 during welding will be described. The horizontal axis of the time chart in FIG. 6 is the time corresponding to the horizontal axis of the time chart in FIG. 5, and the vertical axis is the estimated thickness of the members 61 and 62 (the combined thickness of the members 61 and 62). This is a transition. Further, the solid line L3 shows the change in the plate thickness t according to the device and method of the present invention, and the broken line L4 shows the plate thickness t when the electrodes 11 and 12 are brought into contact with the members 61 and 62 without applying pressure P and energized. A dotted line L5 indicates a change in the plate thickness t when pressure control is performed to keep the pressure P constant during the period when the electrodes 11 and 12 are energized. In the pressurizing force control in this case, the target pressurizing force to be kept constant is set to be sufficiently larger than the first pressurizing force P1, so as not to cause insufficient pressurizing force.

As shown by the broken line L4, when the electrodes 11 and 12 are energized without applying pressure P to the electrodes 11 and 12, the members 61 and 62 are heated by the energization of the electrodes 11 and 12 (time T2 to T3). It expands and then contracts during the subsequent cooling period (times T3 to T4) to return to its original thickness.

On the other hand, as shown by the solid line L3, according to the apparatus and method of the present invention, during the energization period (time T2 to T3) of the electrodes 11 and 12, position control is performed to keep the distance between the electrodes 11 and 12 constant, and the subsequent cooling During the period (times T3 to T4), pressure control is performed to keep the pressure P exerted by the electrodes 11 and 12 constant. In this case, as shown by the solid line L3 in FIG. 6, the plate thickness t does not change during the energization period, but during the subsequent cooling period, the plate thickness t decreases as the members 61 and 62 contract.

Furthermore, as shown by the dotted line L5, when pressure control is performed to keep the pressure P constant during the energization period and the cooling period, the members 61 and 62 contract even during the energization period, and during the cooling period. The members 61 and 62 also shrink, and as a result, the plate thickness at the welding location 63 is greatly reduced.

[3. action, effect]
(1) In the spot welding device and spot welding method described above, the control device 40 has a pressurizing force control section 43 and a position control section 44, and from the state where the pair of electrodes 11 and 12 are in contact with the members 61 and 62, The pressurizing force P of the electrodes 11, 12 is increased to the first pressurizing force P1, and the pressurizing force P is switched to position control using the first pressurizing force P1 to maintain the position of the pair of electrodes 11, 12 constant. Therefore, even if the first pressurizing force P1 is not set large, a necessary pressurizing force P can be secured during energization, and insufficient pressurizing force is unlikely to occur during energizing.

For example, when controlling the pressurizing force to a constant value while energizing, the constant target pressurizing force must be set to a sufficiently large value so as not to cause insufficient pressurizing force. There is an increased risk that the plate thickness at the portion 63 will be reduced, and that spatter will occur due to excessive pressure. In this regard, according to the apparatus and method of the present invention, such reduction in plate thickness and occurrence of spatter can be suppressed.

Furthermore, during the cooling period of the welding point 63, the pressurizing force P is maintained at the second pressurizing force P2, so that insufficient pressurizing force that may occur due to contraction of the welding point 63 during the cooling period is avoided, and the welding quality is improved. Secured. In other words, in resistance spot welding, gas is generated in the molten part during energization and heating, and sufficient pressure is applied to the weld center from the start of cooling after energization to solidification. However, if the pressurizing force is insufficient, gas will remain in the nugget after the molten part solidifies, and this gas will form a blowhole, which can cause internal defects (defects in welding) at the welding location. There is a risk that In this regard, according to the apparatus and method of the present invention, insufficient pressurizing force during the cooling period is avoided, and the gas generated in the molten part is absorbed by the nugget 64 and disappears, so the occurrence of internal defects in the welding part 63 is suppressed. be done.

(2) Furthermore, the control device 40 of the present embodiment operates the electrode drive motor 13 to control the pressing force P based on the pressing force P detected by the pressing force sensor 15, and controls the pressing force P detected by the electrode position sensor 14. Since the position of the electrode 11 is controlled to be maintained at a constant position based on the detected position, the pressing force control and position control can be performed more accurately.

(3) Since the control device 40 brings the pair of electrodes 11 and 12 into contact with the members 61 and 62 using position control by the position control unit 44 in the preparation stage of pressurizing force control before the start of energization, the pair of electrodes 11 and 12 can be brought into proper contact with the members 61 and 62.
(4) Furthermore, by setting the second pressurizing force P2 to be larger than the first pressurizing force P1, it is possible to more reliably avoid a lack of pressurizing force that may occur due to contraction of the welding area 63 during the cooling period. This makes it possible to further suppress the occurrence of internal defects at the welding location 63 due to insufficient pressurizing force.

(5) When the cooling period ends, the control device 40 switches from pressure control to position control and separates the pair of electrodes 11 and 12 from the members 61 and 62, so that the spot welding completion process can be carried out smoothly. .
(6) Since the first pressurizing force P1 is set to be low considering the expansion of the members 61 and 62 due to energization, the generation of spatter can be suppressed and welding quality can be improved.

[4. Modified example]
The configuration of the spot welding device 1 and the spot welding method described above are merely examples, and are not limited to those described above. For example, in the embodiment, both the position control and the pressure control are performed by feedback control based on the position information and pressure information detected by the sensors 14 and 15, but they are not performed by feedback control but by open loop control. It's okay.

For example, regarding position control, if a locking mechanism is provided to fix the pair of electrodes 11, 12 in a predetermined state, the pair of electrodes 11, 12 can be controlled to a constant position. Furthermore, since the pressing force corresponds to the current supplied to the electrode drive motor 13, the current supplied to the electrode driving motor 13 may be controlled so that a predetermined pressing force P is obtained.

In the embodiment, an example will be described in which the spot welding device 1 is one of a plurality of spot welding devices installed in a product manufacturing line, and the control device 40 is connected to a process control panel 50, which is a higher-level control device, by a signal line. However, the spot welding device 1 may be configured to independently control welding without a higher-level control device.

1 Spot welding device 10 Spot welding gun 11, 12 Electrode 13 Electrode drive motor 13A Electrode drive circuit 14 Electrode position sensor (position detection section)
15 Pressure sensor (pressure force detection section)
40 Control device 43 Pressure force control section 44 Position control section 61, 62 Components to be welded 63 Welding location P Pressure force P1 First pressurization force P2 Second pressurization force

Claims (7)

a spot welding gun having a pair of electrodes arranged opposite to each other, and an electrode drive motor that drives at least one of the pair of electrodes;
A control device that controls the spot welding gun,
The control device includes:
a pressurizing force control unit that operates the electrode drive motor to control the pressurizing force that the pair of electrodes applies to the member to be welded;
a position control unit that maintains the position of the pair of electrodes at a constant position,
From the state in which the pair of electrodes are in contact with the member, the pressing force is increased to a preset first pressing force by the pressing force control by the pressing force control unit, and the pressing force reaches the first pressing force. Then, the positions of the pair of electrodes are kept constant by the position control by the position control unit, and energization is started, and the energization is stopped after a set time, and as cooling of the welding area starts, the pressure is increased by the position control. A spot welding apparatus, characterized in that the pressurizing force is maintained at a preset second pressurizing force during the cooling period by switching to control. The control device includes:
a pressurizing force detection section that detects the pressurizing force;
a position detection unit that detects the position of the one electrode,
The pressurizing force control unit controls the pressurizing force by operating the electrode drive motor based on the detected pressurizing force detected by the pressurizing force detecting unit,
The position control unit operates the electrode drive motor based on the detected position detected by the position detection unit to maintain the position of the one electrode at the constant position. Spot welding equipment as described. The control device is characterized in that the pair of electrodes are brought into contact with the member by position control by the position control unit in a preparatory stage of the pressurizing force control before the start of the energization. Spot welding equipment. The spot welding device according to any one of claims 1 to 3, wherein the second pressing force is larger than the first pressing force. Any one of claims 1 to 4, wherein the control device switches from the pressurizing force control to the position control to separate the pair of electrodes from the member when the cooling period ends. Spot welding equipment as described in Section. The spot welding device according to claim 1, wherein the first pressurizing force is set in consideration of expansion of the member due to the energization. Spot welding in which spot welding is performed on a member to be welded by controlling a spot welding gun that has a pair of electrodes arranged opposite to each other and an electrode drive motor that drives at least one of the pair of electrodes. A method,
In pressurizing force control in which the electrode drive motor is operated to control the pressurizing force applied to the member from a state in which the pair of electrodes are in contact with the member, the pressurizing force is increased to a preset first pressurizing force. ,
When the pressurizing force reaches the first pressurizing force, in position control that operates the electrode drive motor to control the position of the one electrode, the position of the pair of electrodes is held constant and energization is started. ,
The energization is ended after a set time has elapsed from the start of the energization, and at the same time as cooling of the welding area begins, the position control is switched to the pressure force control. A spot welding method characterized by holding at two pressures.

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