JP7158145B2 - welding equipment - Google Patents

Description

The present invention relates to a welding device for welding materials to be welded.

When joining objects to be welded in which a plurality of plate materials or other materials to be welded are piled up, they may be joined by spot welding. Spot welding is a type of resistance welding method that uses resistance heating to join metals. In indirect welding, which is a type of spot welding, the welding target is pressed with an electrode while the materials to be welded are placed on top of each other, and current is passed from the electrode to the ground through the welding target to heat the welded part by resistance heat generation. to locally melt the object to be welded, thereby metallurgically joining the object to be welded. In spot welding, the melted and solidified portion is called a "nugget", and the object to be welded is joined at the nugget.

A welding apparatus used for indirect welding includes an electrode, a ground connected to an object to be welded, a transformer for applying current to the electrode, and a robot for moving the electrode. The electrode is arranged so as to be in contact with the surface of the object to be welded, and is configured to pressurize the object to be welded. Moreover, the electrode is configured to be able to apply an arbitrary current to the object to be welded under pressure. A ground is connected to the back side to the surface of the object to be welded on which the electrode is placed. An electrode or ground is connected to each of the front and back surfaces of the object to be welded, and by applying a current to the electrode, the current flows from the electrode to the ground through the object to be welded. Then, by applying an electric current to the objects to be welded, the welded portion is heated and melted to join the objects to be welded.

In this way, in conventional indirect welding, an electrode and a ground are connected to an object to be welded, which is made up of a plurality of superimposed materials to be welded. , to fuse and join the materials to be welded.

JP 2013-158776 A

However, in the conventional indirect welding, the current density of the current flowing during welding varies depending on the presence or absence of a gap between the welded materials to be joined and the contact area between the welded materials. Due to differences in contact areas and current densities, the quality of welding between materials to be welded may not be stable. In addition, due to unstable welding quality, if the welding is performed with excessive strength, the strength of the welded product may vary and the appearance of the product may be defective. sometimes occurred.

For example, when the materials to be welded are warped or the joint surfaces of the materials to be welded have low flatness, a gap is generated between the materials to be welded at the welded portion. Moreover, when welding is performed at a plurality of locations on the object to be welded, gaps may occur between the materials to be welded due to the influence of previous welding. When indirect welding is performed on one part of the object to be welded, welding is performed while the electrode presses the object to be welded, so that the periphery of the material to be welded to which the electrode is pressed may warp. Therefore, a gap is generated between the materials to be welded around the previously welded portion.

As described above, depending on the presence or absence of gaps between the materials to be welded, the contact area between the materials to be welded may not be constant, and the welding quality may not be stable.

An object of the welding apparatus of the present invention is to stabilize welding quality in order to solve the above problems.

Here, the inventors of the present invention conducted extensive studies and found that by focusing on the resistance value of the energization path through which the current flows through the object to be welded, the contact state between the objects to be welded, such as the size of the contact area between the objects to be welded, can be determined. Inferred, it was found that it can contribute to the improvement of welding quality. However, as a result of further intensive studies, although it may be a rare case, in cases such as the case where the welding target materials to be welded are in contact with each other at a place other than the planned welding place, the contact area at the joint has not reached the planned area, only the resistance value may be reduced to a predetermined value or less. Therefore, as the start conditions for starting welding, in addition to the conditions related to the resistance value described above, the welding start conditions that take into consideration the phenomenon of the decrease in resistance value due to the contact between the welded materials at places other than the intended welding location. If we also consider this, it will be possible to more accurately estimate whether or not the contact area at the joint has reached the planned area before welding, which in turn contributes to the further improvement of welding quality. Got an insight.

Based on these considerations, further investigations were carried out. As a result of further investigation, in addition to the conditions regarding the resistance value of the current flow path through which the current flows through the object to be welded, the conditions for starting welding were as follows: We have come to the conclusion that it is better to add a starting condition based on the amount of electrode displacement. Specifically, when the materials to be welded come into contact with each other with a sufficient contact area at the planned welding location, the electrode is displaced by a predetermined amount or more while the welding target is being pressurized in preparation for welding. On the other hand, it has been found that in the case where the welded materials to be welded are in contact with each other at a location other than the intended welding location, the displacement of the electrode is less likely to change as described above. Therefore, if the starting condition for welding is to satisfy at least both the starting condition for the resistance value of the current-carrying path through which the current flows through the object to be welded and the starting condition for the amount of displacement of the electrode, the contact area at the joint can be more reliably achieved. It is considered possible to provide a welding apparatus capable of starting welding in a state in which a predetermined area has been reached, thereby obtaining good welding quality.

A welding apparatus of the present invention provided based on such knowledge includes an electrode that pressurizes an object to be welded and applies current to the object to be welded, a driving device that drives the electrode, and a power supply that applies the current to the electrode. A device, a resistance measuring device for measuring the resistance value of the energized path in the object to be welded, and a displacement for measuring the amount of displacement that the electrode moves in the plate thickness direction of the object to be welded when the electrode presses the object to be welded. and a control device for controlling the operation of the drive device and the power supply device, wherein the control device controls the resistance value to be below a certain value and the displacement amount to be above a certain value. It is characterized by controlling the operation of the power supply device so as to perform welding after the welding is completed.

According to such a configuration, it is possible to provide a welding apparatus that can start welding in a state where the contact area at the joint reaches a predetermined area without fail, and obtain good welding quality.

Further, in the welding device of the present invention, it is preferable that the control device controls the application time of the current during the welding.

In this way, when the electrode moves by a certain amount or more and the resistance value of the energization path becomes equal to or less than a predetermined value, the amount of current applied from the electrode and the time for applying the current are optimally adjusted. A controller controls the power supply. As a result, it is possible to apply the current at the optimum current density for the optimum time according to the contact area of the material to be welded, and to stabilize the welding quality.

Further, the welding apparatus of the present invention measures the resistance value while a current of a first current value is applied from the electrode, and the displacement amount of the electrode is equal to or greater than a certain value, and the resistance of the energization path is The control device may control the power supply device so as to apply a current having a second current value different from the first current value for a predetermined time after the value becomes equal to or less than a predetermined value.

According to this configuration, full-scale welding work can be performed after the contact area between the materials to be welded reaches a predetermined area. As a result, welding can be performed under appropriate current application conditions, so that welding quality can be stabilized.

Further, the welding apparatus of the present invention applies a current of a predetermined current value from the electrode, measures the resistance value when the displacement amount becomes a constant value, and applies the current under the application condition according to the measured value. The controller may control the power supply to apply current.

Thus, first, a current of a predetermined current value is applied, and the resistance value is measured when the amount of displacement reaches a predetermined value. After that, a current is applied under an application condition corresponding to the measured resistance value. As a result, the welding operation can be performed under the optimum current application conditions according to the contact area between the welded materials while the contact area between the welded materials is close to the area suitable for welding. As a result, welding can be performed under appropriate current application conditions, so that welding quality can be stabilized.

As described above, according to the present invention, welding defects caused by the presence or absence of gaps between the materials to be welded and the state of contact between the materials to be welded can be minimized, and welding can be performed with high quality and stable welding quality. We can provide welding equipment.

1 is a diagram illustrating a schematic configuration of a welding device of the present invention; FIG. FIG. 4 is a diagram for explaining the configuration of the electrode portion and the displacement of the electrode in the welding device of the present invention; Sectional view illustrating the configuration of the object to be welded Diagram explaining the relationship between the presence or absence of gaps between welded materials and the contact area Schematic diagram showing current path and change in resistance value when welding is performed multiple times Schematic diagram showing in detail the energization path and changes in resistance when welding is performed multiple times 4 is a diagram showing the relationship between changes in resistance during welding and current application conditions in Example 1. FIG. FIG. 2 is a flowchart showing steps of the welding method in Example 1. FIG. FIG. 7 is a diagram showing the relationship between changes in resistance during welding and current application conditions in Example 2; Flow chart showing the steps of the welding method in Example 2

First, a configuration example of a welding apparatus according to the present invention will be described with reference to FIGS. 1 and 3. FIG.

FIG. 1 is a diagram illustrating the schematic configuration of the welding apparatus of the present invention, and FIG. 3 is a diagram illustrating the configuration of the electrode portion and displacement of the electrodes in the welding apparatus of the present invention.

As illustrated in FIG. 1, a welding apparatus 1 of the present invention includes an electrode 4, a ground 6 paired with the electrode 4, a robot 8 having a robot arm 20 capable of holding and moving the electrode 4; and ground 6, a timer 12 for controlling the current supplied to the transformer 10, a resistance measuring device 14 for measuring the resistance of the current flowing through the object 18 to be welded, and the electrode 4 having a predetermined A displacement amount measuring device 15 for measuring a displacement amount, which is a distance moved in the plate thickness direction of the object to be welded 18 from a position, and a control device 16 for controlling the operation of the timer 12 and the robot 8 are provided.

In the welding device 1 , the electrode 4 presses the object to be welded 18 and applies a predetermined current to the object to be welded 18 , thereby causing the current to flow from the electrode 4 through the object to be welded 18 to the ground 6 . The object to be welded 18 is formed by stacking a plurality of materials to be welded (a detailed configuration example will be described later). In the object to be welded 18, adjacent welded materials are joined by welding. The electrode 4 applies pressure to the object 18 to be welded and applies a predetermined current to the object 18 to be welded, thereby heating and melting the object 18 between the electrode 4 and the ground 6 to weld the object 18 to be welded. The current value of the current applied to the electrode 4 can be determined according to the thickness of the object 18 to be welded, the thickness of each material to be welded, the required welding strength, etc., and is adjusted by the transformer 10 .

The transformer 10 converts the current supplied via the timer 12 into a predetermined current value and applies the converted current to the electrodes 4 . For example, a current of 400 V and several A supplied via the timer 12 is converted into a current of 15000 A at 3 to 5 V and applied to the electrode 4 . A timer 12 controls the timing of supplying current to the electrodes 4 via the transformer 10 . Transformer 10 is controlled by controller 16 , which may also control transformer 10 via timer 12 .

The robot 8 comprises an electrode 4 and a robot arm 20 . The robot 8 is configured to be able to move the electrode 4 to any position within a predetermined range by the robot arm 20, and moves the electrode 4 to a predetermined welding position.

The robot 8 is aware of certain spatial coordinates and is programmed to move the electrodes 4 to previously taught coordinates. For example, when starting welding, the tip of the electrode 4 is set to the coordinates at which the tip of the electrode 4 is separated from the welding location of the welding target 18 by a certain distance, or the coordinate at which the tip of the electrode 4 is expected to come into contact with the welding location of the welding target 18, and the like. Taught as coordinates. As the coordinates to be taught next, the main welding start coordinates are taught that are assumed to bring the materials to be welded into contact with each other with an appropriate contact area at the welding location. Then, the robot 8 moves the electrodes 4 to the taught coordinates in this order.

The displacement amount measuring device 15 measures the amount of displacement of the electrode 4 while the object 18 to be welded is being pressed after the electrode 4 has moved to the temporary welding start coordinates.

Here, the configuration around the electrode 4 and the displacement of the electrode when the object 18 to be welded is pressurized will be described with reference to FIG.

First, the electrode 4 is connected to the robot arm 20 via the cylinder 21, as shown in FIG. 2(a). The cylinder 21 is composed of a cylinder body 17 and a cylinder head 19 . A cylinder body 17 is fixed to a robot arm 20 and an electrode 4 is fixed to a cylinder head 19 . The cylinder head 19 has a telescopic structure, and the distance from the cylinder body 17 is variable. With such a configuration, the electrode 4 can be moved away from the cylinder body 17 and in a direction toward the cylinder body 17 . When pressurizing the object 18 to be welded, the object 18 to be welded is pressurized by movement of the electrode 4 by the robot arm 20, expansion and contraction of the cylinder 21, or both. Further, the pressure applied by the electrode 4 to the object 18 to be welded is adjusted by the cylinder 21 .

Also, as described above, the robot 8 moves the electrode 4 to coordinates taught in advance. During welding, first, the electrode 4 is moved to the temporary welding start coordinates. As shown in FIG. 2B, the temporary welding start coordinates are coordinates 23 assumed to be at a certain distance from the material 22 to be welded of the object 18 to be welded, and coordinates 23 assumed to be in contact with the material 22 to be welded at the welding location. is coordinate 25. From this temporary welding start coordinate, the electrode 4 starts pressurizing the object 18 to be welded.

Next, as shown in FIGS. 2(c) and 2(d), the electrode 4 is moved from the temporary welding start coordinates to the final welding start coordinates, or the cylinder 21 is extended from the temporary welding start coordinates, or both. , the electrode 4 presses the material to be welded 22, and the material to be welded 22 and the material to be welded 24 are brought into contact with each other with an appropriate contact area.

At this time, the displacement measuring device 15 measures the amount of displacement of the electrode 4 in the plate thickness direction of the object 18 to be welded after the start of pressurization of the object 18 to be welded. In this way, when the electrode 4 moves by a displacement amount Δx from the coordinates 23 or 25, which are the temporary welding start coordinates, it is assumed that the contact area between the weld material 22 and the weld material 24 becomes an area suitable for welding. .

The control device 16 in the welding apparatus 1 having such a robot 8 controls the operation of the robot 8 and the operation of the timer 12 at the same time. The control device 16 receives the measured resistance value from the resistance measuring device 14 and the displacement amount from the displacement measuring device 15 . The control device 16 then controls the timer 12 according to the received resistance value and displacement amount. The timer 12 controls the transformer 10 so as to control the current applied from the electrode 4 to the object 18 to be welded according to instructions from the control device 16 .

Here, a detailed explanation will be given later, but in resistance welding, if there is a gap or the like between the materials to be welded, the contact state such as the contact area between the materials to be welded changes during welding, and stable joining is performed. can't break For example, if the contact area between the materials to be welded is large, the current density will be small, the welded portion will not be heated sufficiently, and nugget formation will be hindered. If the nugget does not grow to a sufficient size, the welding strength will be insufficient, resulting in poor welding. Furthermore, due to contact conditions such as gaps between the materials to be welded and the contact area between the materials to be welded, the contact area at the welding location may not be the specified area, or at an unplanned location other than the welding location. The materials to be welded may come into contact with each other, and the current density of the current flowing through the welded portion of the object to be welded 18 may not be a constant value. When the current density is high, the amount of heat generated at the welded portion increases and fusion bonding is promoted, and when the current density is low, the amount of heat generated at the welded portion decreases and fusion bonding is reduced. Therefore, if the current density is too high, the bonding strength will be excessive compared to the assumed current density, and if the current density is too low, the bonding strength will be insufficient and the bonding quality will be unstable. Further, the current density of the current flowing through the object to be welded 18 is proportional to the resistance value of the energization path.

Therefore, in the welding apparatus 1 of the present invention, the resistance value of the current path is measured by the resistance measuring device 14 as temporary welding, and the contact state between the welded materials (hereinafter, in this embodiment, the contact area is taken as an example) is measured from the resistance value. explain). At the same time, the displacement measuring device 15 measures the amount of displacement of the electrode 4 during pressurization of the object 18 to be welded. Then, the controller 16 controls the contact area between the materials to be welded to be equal to or larger than the minimum necessary displacement amount for the contact area to be suitable for welding, and to correspond to the contact area between the materials to be welded having an appropriate resistance value. When it becomes less than or equal to the value that In the main welding, the application conditions such as the current value of the current applied from the electrode 4 to the welding object 18 and the current application time are controlled via the timer 12 and the transformer 10 so as to be the optimum conditions for welding.

As described above, in the welding apparatus 1 of the present invention, the resistance value of the energization path of the object 18 to be welded is measured and the amount of movement of the electrode 4 is measured in the temporary welding. Then, when the resistance value becomes equal to or less than a predetermined value and the amount of displacement becomes equal to or more than a predetermined value, the contact area at the welded portion becomes an appropriate contact area for welding, and main welding is started. Therefore, after the contact area between the materials to be welded becomes suitable for welding, welding can be performed under the optimum current application conditions corresponding to the contact area, and welding can be performed with stable welding quality. can be done.

In addition, it is preferable that the welding device 1 further includes a cooling device. The cooling device is a device that cools the electrode 4 and cools the electrode 4 when current is applied from the electrode 4 to the object 18 to be welded. During welding, an electric current flows through the electrode 4, so that the electrode 4 is heated and softened. At this time, since the electrode 4 presses the object 18 to be welded, the softened electrode 4 receives force from the object 18 to be welded. Therefore, the tip of the electrode 4 is deformed or damaged by repeated welding. The shape of the tip of the electrode 4 affects the current density of the current supplied to the object 18 to be welded and the pressure applied to the object 18 to be welded, depending on the area in contact with the object 18 to be welded. Since current density and applied pressure affect welding accuracy, the electrode 4 is cooled during welding. Cooling can be performed, for example, by circulating cooling water through the electrode 4 .

Further, in FIG. 1, the timer 12 related to the current supply to the electrode 4, the control device 16, and the like are illustrated as being configured to supply power from separate power sources, but power is supplied from a common power source. Alternatively, each device may be supplied with power from another power source as needed.

Further, the electrode 4 is driven by the robot 8 functioning as a driving device in response to instructions from the control device 16 .

Also, the timer 12 and the transformer 10 function as a power supply device that supplies current to the electrodes 4 . The power supply device may have other configurations as long as it can supply current to the electrode 4 under predetermined application conditions. Alternatively, the control device 16 may be provided with the function of the timer 12 so that the timer 12 is not provided.

Next, an example of the configuration of objects to be welded by the welding apparatus of the present invention will be described with reference to FIG.

FIG. 3 is a cross-sectional view illustrating the configuration of objects to be welded.

As described above, the object to be welded 18 is a stack of a plurality of welded materials. In the example shown in FIG. 3 , the object to be welded 18 is composed of a material to be welded 22 and a material to be welded 24 , and the material to be welded 22 and the material to be welded 24 are joined by welding at a welding point 26 . For example, the material to be welded 22 is a flat plate. The material 24 to be welded is three-dimensionally formed, and one surface of the material 28 to be welded, which is also three-dimensionally formed, is joined to the interior of the open space. At the welding point 26 , the back surface of the material to be welded 24 that is in contact with the material to be welded 22 is closed in a space formed by the material to be welded 28 and the material to be welded 24 . Since the electrode 4 cannot be placed in the space formed by the material to be welded 28 and the material to be welded 24 during welding, the material to be welded 22 and the material to be welded 24 are joined by indirect welding. In indirect welding, the electrode 4 is arranged on the back side of the surface of the material to be welded 22 that contacts the material to be welded 24 at the welding point 26 , and the ground 6 is arranged so as to be electrically connected to the material to be welded 24 . . Then, a predetermined current is applied from the electrode 4, and the current flows through the energization path 30 leading to the ground 6 via the materials 22 and 24 to be welded. The current that flows joins the material to be welded 22 and the material to be welded 24 at the welding point 26 .

Next, with reference to FIGS. 4 to 6, a description will be given of the joining area between the materials to be welded during welding and the change in the resistance value in the path of the current flowing between the materials to be welded.

4A and 4B are diagrams for explaining the relationship between the presence or absence of a gap between the materials to be welded and the contact area. ) indicates the case where an unplanned contact point is included. 5A and 5B are schematic diagrams showing current paths and changes in resistance values when welding is performed multiple times, and FIG. FIG. 5(b) is a diagram showing a change in resistance value at that time, and FIG. 5(c) is a diagram showing an energization path including an unexpected contact point. FIG. 6 is a schematic diagram showing in detail the energization path and changes in the resistance value when welding is performed a plurality of times. It is a figure which shows a change over time.

As shown in FIG. 4( a ), when there is no gap between the material to be welded 22 and the material to be welded 24 , when the electrode 4 is pressed against the object to be welded 18 during welding, current flows through the material to be welded 22 . and the contact surface 32 with the material to be welded 24 is appropriate, and the current density is appropriate. When a current is passed from the electrode 4 to the ground 6 in this state, the materials 22 and 24 to be welded in the vicinity of the contact surface 32 are melted, and a sufficiently large nugget 34 grows around the contact surface 32 . For example, if the contact area of the contact surface 32 is 1000 mm 2 and a current of 1000 A is applied from the electrode 4 for a predetermined time, the current density of the current flowing through the contact surface 32 is 1.0 A/mm 2 . Under such conditions, it is assumed that the nugget 34 grows appropriately and the weld material 22 and the weld material 24 are optimally joined.

On the other hand, as shown in FIG. 4B, when there is a gap t between the material to be welded 22 and the material to be welded 24, the electrode 4 is pressed against the object to be welded 18 during welding. The material to be welded 22 and the material to be welded 24 come into contact with each other only when the material 22 is bent. Since the pressure applied by the electrode 4 is constant, the contact surface 38 between the material to be welded 22 and the material to be welded 24 through which the current flows is narrower than the contact surface 32 when there is no gap. If a current is passed from the electrode 4 to the ground 6 in this state, the contact surface 38 becomes narrower than the contact surface 32 in the case of no gap, resulting in an excessive current density. As a result, the nugget 40 becomes too large, and the welded portion may melt down or crack, resulting in poor welding. For example, if the contact area of the contact surface 38 is 100 mm 2 and a current of 1000 A is applied from the electrode 4 for a predetermined time, the current density of the current flowing through the contact surface 38 is 10 A/mm 2 . In the case of such conditions, the contact area of the contact surface 38 is smaller than the assumed contact area, so the current density becomes higher than expected, the nugget 40 becomes too large, and the welded portion burns down or cracks. Poor welding. Moreover, when the contact area of the contact surface 38 becomes larger than the assumed area, the current density of the current flowing through the contact surface 38 becomes smaller than expected. In this case, if the material to be welded 22 or the material to be welded 24 is a thin plate, the nugget 40 may not reach the material to be welded 22 or the material to be welded 24, resulting in insufficient joint strength and poor welding.

Furthermore, as shown in FIG. 4(c), although the contact area of the contact surface 38 at the welding location is not an appropriate area, the materials to be welded come into contact with each other at an unexpected location and the contact surface 39 is broken. may be formed. At this time, since the contact area of the contact surface 38 at the welding location is not sufficient, the joint area between the materials to be welded may be insufficient, resulting in poor welding. In addition, the current may be dispersed in unplanned energization paths, resulting in excess or deficiency in the current density at the welding location, resulting in inadequate welding.

As described above, in the conventional welding apparatus, on the premise that there is no gap between the materials to be welded, the voltage applied to the electrode 4 is such that optimum welding is performed when the materials to be welded are in proper contact with each other. The application condition of the current to be applied is determined in advance. Note that the predetermined application conditions will be described in detail later. Here, the presence or absence of a gap between the materials to be welded affects the contact area, and the current density of the flowing current changes in proportion to the contact area. The current density of the current is proportional to the resistance value in the conducting path when the current value of the applied current is constant. In response to this, first, the welding apparatus 1 (see FIG. 1) of the present invention measures the resistance value of the energization path, and from the measured resistance value, the contact area between the materials to be welded becomes the appropriate contact area. Confirm that Even in this case, as described above, even though the contact area at the welding point is not the appropriate area, the welded materials come into contact with each other at an unplanned point, and current also flows through that part. , the resistance may decrease. Therefore, the welding apparatus 1 (see FIG. 1) of the present invention further confirms, based on the amount of displacement of the electrode 4, that pressure is being applied to ensure a sufficient contact area at the welding location. Then, only when the resistance value becomes equal to or less than an appropriate value in a state where the amount of displacement becomes equal to or greater than an appropriate value, final welding is performed. In this manner, by performing welding after the contact state between the materials to be welded becomes appropriate, it is possible to perform welding with stable welding quality.

Further, as shown in FIG. 5A, when welding is performed at a plurality of locations on the object 18 to be welded, the material 22 to be welded is bent by the previous welding, and a gap is formed between the material 22 to be welded and the material 24 to be welded. It is formed. Therefore, in the initial stage of welding, the materials to be welded 22 and the materials to be welded 24 do not come into contact in the vicinity of the welding location where the electrode 4 is arranged. When the current is applied from the electrode 4 while the material to be welded 22 and the material to be welded 24 are not in contact with each other, the current flowing through the object to be welded 18 is mainly formed by the electrode 4, the material to be welded 22, and the previous welding. The electric current flows through the welding portion 42 , the material to be welded 24 and the ground 6 in this order. After that, as the electrode 4 presses the material to be welded 22 , the material to be welded 22 bends and comes into contact with the material to be welded 24 . Due to the contact between the materials to be welded 22 and the materials to be welded 24, the current flowing through the object to be welded 18 passes from the electrode 4 through the contact points between the materials to be welded 22 and the materials to be welded 24 in addition to the current path A. Then, it flows straight through the material to be welded 22 and the material to be welded 24 and flows through the current path B to the ground 6 . In this way, since the current flows through the conducting path B in addition to the conducting path A, the resistance value of the conducting path through which the current flows from the electrode 4 to the ground 6 is as shown in FIG. It will be smaller than in the early stages of the weld flowing through A only.

Again, the case of welding at a plurality of locations will be described in detail with reference to FIG.

As described above, in the object to be welded 18 , the material to be welded 22 warps due to previous welding, and a gap is formed between the material to be welded 22 and the material to be welded 24 . When welding is started in this state, the material to be welded 22 and the material to be welded 24 are not in contact with each other at the placement position of the electrode 4, which is the welded portion. Therefore, the current path from the electrode 4 to the ground 6 is only the current path A. At this time, the resistance value of the energization path through which the current flows through the object to be welded 18 is in a relatively high state (state I in FIG. 6).

Next, as the electrode 4 presses the material 22 to be welded, the material 22 to be welded bends, and the material 22 to be welded and the material 24 to be welded come into contact with each other. Due to the contact between the materials to be welded 22 and the materials to be welded 24, the current flowing through the object to be welded 18 passes from the electrode 4 through the contact points between the materials to be welded 22 and the materials to be welded 24 in addition to the current path A. Then, directly below the electrode 4 , the current flows straight through the materials to be welded 22 and 24 to reach the ground 6 . At the moment when the material to be welded 22 and the material to be welded 24 contact each other, the contact area of the contact surface 32 between the material to be welded 22 and the material to be welded 24 is relatively small. Since the contact surface 32 is narrow, the resistance value at the contact surface 32 is high, and the current-carrying path A is dominant. After that, as the electrode 4 presses the material to be welded 22 further, the contact surface 38 between the material to be welded 22 and the material to be welded 24 becomes larger than the contact surface 32 . As the area of the contact surface 38 increases, the current flowing through the energization path B increases, and the resistance value of the energization path through which the current flows through the welding target 18 decreases by combining the energization path A and the energization path B (Fig. 6 II condition).

When the area of the contact surface 38 is sufficiently large, the currents flowing through the energization paths A and B are made uniform, and the resistance value of the energization path through which the current flows through the object to be welded 18 becomes constant (see III in FIG. 6). state).

Further, as shown in FIG. 5(c), by pressurizing the material to be welded 22 by the electrode 4, the material to be welded 22 is brought into contact with the material to be welded 24, and in addition, the material to be welded 22 and the material to be welded are also in contact with each other. contact with the welding material 24 may occur. In this case, the current flowing through the object to be welded 18 flows through the energization path C in addition to the energization path A and the energization path B. In such a situation, although the contact area between the material to be welded 22 and the material to be welded 24 is not an appropriate contact area at the welding point, the current flows through the current paths A, B, and C. may reduce the applied resistance.

As described above, the resistance value of the energization path through which the current flows varies depending on the presence or absence of gaps between the welded materials and the contact area between the welded materials. A change in the resistance value depends on the current density of the current flowing through the conducting path. The current density affects the welding quality such as the strength of welding, the welding range, and the surface condition of the material 22 to be welded or the material 24 to be welded. Current application conditions are set in advance according to the assumed contact state between the materials to be welded and the required welding quality. Therefore, in the event of unexpected conditions such as an unexpected gap between the welded materials or insufficient contact between the welded materials at the welding point, the welding quality may not be ensured. be. Therefore, the welding apparatus 1 (see FIG. 1) of the present invention measures the resistance value of the current-carrying path through which the current flows, and detects contact between the materials to be welded from the measured resistance value. Furthermore, as shown in Fig. 5(c), even though the contact area of the welded portion is insufficient, the state where the resistance value falls below a predetermined value due to contact between the welded materials at other locations is eliminated. Therefore, the amount of displacement of the electrode 4 is measured. Even if the resistance value becomes equal to or less than the predetermined value, if the displacement amount of the electrode 4 does not reach the predetermined value, the contact area of the welded portion does not reach an appropriate area, and the main welding is not started. . Only when the resistance value becomes equal to or less than a predetermined value and the amount of displacement of the electrode 4 becomes equal to or more than a predetermined value, final welding is started under appropriate current application conditions. In this way, it is judged that the contact area between the materials to be welded at the welding point has become an appropriate area based on the resistance value of the energization path and the amount of displacement of the electrode 4, and the main welding is performed under the optimum current application conditions. By starting, welding with stable welding quality can be performed. Note that the optimum current application condition is achieved by optimizing, for example, the current value of the current, the conduction time of the current, or both of them. Also, the current value of the current may be changed in multiple steps.

Specific examples of the welding apparatus of the present invention will be described below.

(Example 1)
Welding operation of the welding apparatus according to the first embodiment will be described with reference to FIGS. 1, 7, and 8. FIG.

7A and 7B are graphs showing the relationship between changes in resistance value during welding and current application conditions in Example 1, FIG. ) and (c) are graphs showing current application conditions according to gaps. FIG. 8 is a flowchart showing steps of the welding method in Example 1. FIG.

In the welding operation of the welding apparatus in Example 1, first, as temporary welding, a current of a constant current value I0 is applied from the electrode 4 to the object 18 to be welded. Measure the resistance of At the same time, the amount of displacement of the electrode 4 is measured. Then, the current of the current value I0 is applied until it is detected that the displacement of the electrode 4 is equal to or greater than a predetermined value Δx and the resistance value is equal to or less than R0. The resistance value R0 is a resistance value assumed when the materials to be welded come into contact with each other and the contact area of the contact surfaces becomes a predetermined area. Further, the predetermined displacement amount Δx is the displacement amount of the electrode 4 that is assumed to have a predetermined contact area of the contact surface. Temporary welding is performed by applying a current value I0 that is lower than the current value of the main welding that actually joins the welded materials, and it is detected that the contact area between the welded materials reaches a predetermined area. It is done in order to

For example, when there is no gap between the materials to be welded, as shown in the resistance change 44 in FIG. . Further, when there is a gap between the materials to be welded, as shown in the resistance change 46 in FIG. The rate of decrease in resistance value is slower than when there is no gap between weld metals. Therefore, the resistance value becomes R0 at the energization time T2, which is later than T1. This is because the resistance value is constant while there is a gap between the welded materials, and even if the welded materials are in contact with each other, the welding target 18 is pressed by the electrode 4 and the contact area between the welded materials is kept constant. This is because it takes time to reach the area. At the same time, by confirming the amount of displacement of the electrode 4, it is possible to eliminate the situation where only the resistance value is reduced due to the contact between the welded materials at an unexpected point, and the contact area between the welded materials is more reliably increased. A predetermined area can be detected.

Next, when the resistance value reaches R0, main welding is performed. In the main welding, current is applied from the electrode 4 to the welding target 18 under predetermined application conditions so that appropriate welding is performed when the materials to be welded are in contact with each other over the above-mentioned predetermined area. be done.

For example, when there is no gap between the materials to be welded, as shown in FIG. A current is applied from the electrode 4 to the object to be welded 18 under predetermined application conditions from the current application time T1, which is the time point when the electrodes 4 come into contact with each other. Further, when there is a gap between the materials to be welded, as shown in FIG. The application of the current at the current value I0 is continued until the energization time T2 when the electrodes are in contact with each other, and from the energization time T2, the current is applied from the electrode 4 to the object to be welded 18 under predetermined application conditions.

Next, the operation flow of the welding device in Example 1 will be organized.

First, as temporary welding, the electrode 4 starts to apply a current value I0 to the object 18 to be welded while pressing the object 18 to be welded with a predetermined force (step 1 in FIG. 8). Next, while the current of the current value I0 is being applied, the displacement measuring device 15 measures the displacement of the electrode 4 from the temporary welding start coordinates (step 2 in FIG. 8).

Next, the control device 16 confirms the measured displacement amount and determines whether or not the displacement amount is equal to or greater than a predetermined Δx (step 3 in FIG. 8). If the displacement is Δx or more, the process proceeds to step 4. If the displacement is not Δx or more, the determination of whether the displacement is Δx or more is repeated until the displacement is Δx or more.

Next, while the current of current value I0 is being applied, the resistance value of the energization path through which the current flows through the object 18 to be welded is measured by the resistance measuring device 14 (step 4 in FIG. 8). Then, the control device 16 confirms the measured resistance value and determines whether the resistance value is equal to or less than R0 (step 5 in FIG. 8). If the resistance value is R0 or less, the process proceeds to step 6. If the resistance value is not R0 or less, the resistance is measured and whether the resistance value is R0 or less is checked until the resistance value becomes R0 or less. Repeat judgment. It is preferable to control the pressure applied from the electrode 4 and keep the pressure applied from the electrode 4 to the object to be welded 18 constant when the resistance value becomes equal to or less than R0. As a result, it is possible to suppress the subsequent change in the contact area between the materials to be welded.

Next, main welding is performed when the resistance value becomes R0 or less. The control device 16 controls the timer 12 to apply current from the electrode 4 to the object to be welded 18 under predetermined application conditions. Specifically, the control device 16 applies the current of the current value I1 for the time Ta from the energization time T1 (step 6 in FIG. 8). After that, the control device 16 applies the current of the current value I2 for the time Tb (step 7 in FIG. 8).

As described above, in the welding apparatus according to the first embodiment, the current application condition is determined in advance when the contact area between the materials to be welded is a predetermined area. Also, a resistance value is obtained in the case where a predetermined constant current value flows through the object 18 to be welded in a predetermined contact area. Furthermore, the amount of displacement of the electrode 4 necessary for the contact area between the welded materials to reach a predetermined area is assumed in advance. Then, a current of a constant current value is passed through temporary welding, and the energization time during which the displacement of the electrode 4 becomes equal to or greater than a predetermined value and the resistance value becomes equal to or less than a predetermined resistance value is detected. Assume that the contact area between the materials has reached a predetermined area. After this time, a current is applied from the electrode 4 to the object 18 to be welded under predetermined current application conditions. As a result, it is detected that the contact area between the materials to be welded has reached a predetermined area, and welding is performed by applying a current under suitable conditions for this contact area. can be performed, and the welding quality can be stabilized.

In the description of Example 1, it was confirmed that the displacement of the electrode 4 was equal to or greater than a predetermined value, and then that the resistance was equal to or less than a predetermined value. can be measured in any order. Further, the main welding was performed in two stages by applying a current of current value I1 for time Ta and applying a current of current value I2 for time Tb. is. For example, a current with a constant current value may be applied for a certain period of time, or multi-stage welding such as three or seven stages may be performed intermittently, or welding may be performed by continuously changing the current value. may be performed.
(Example 2)

Welding operation of the welding apparatus according to the second embodiment will be described with reference to FIGS. 1, 9, and 10. FIG.

9A and 9B are graphs showing the relationship between changes in resistance value during welding and current application conditions in Example 2. FIG. 9A is a graph showing changes in resistance value according to the gap. ) and (c) are graphs showing current application conditions according to gaps. FIG. 10 is a flowchart showing a welding method in Example 2. FIG.

In the welding operation of the welding apparatus in Example 2, first, as temporary welding, the amount of displacement of the electrode 4 is measured while applying a constant current value I0 from the electrode 4 to the object 18 to be welded. Then, when the amount of displacement reaches a predetermined amount of displacement Δx, the resistance value of the energization path through which the current flows through the object 18 to be welded is measured by the resistance measuring device 14 . The energization time at which the displacement amount Δx is reached is assumed to be T0. Here, when the current value of the current is constant, the resistance value of the energization path in the object to be welded 18 is proportional to the current density of the current, and the current density is proportional to the contact area of the contact surface between the welded materials. Therefore, by obtaining the relationship between the resistance value of the energization path and the contact area of the contact surface between the welded materials in advance, the resistance value at the energization time T0 can be obtained, and the contact between the welded materials at that time can be calculated. The contact area of the faces can be calculated. The amount of displacement Δx is the amount of displacement of the electrode 4 that is assumed to provide the optimum contact area for welding by contact between the materials to be welded. Temporary welding is performed by applying a current value I0 that is lower than the current value for actually joining the materials to be welded. It is done in order to seek.

For example, when there is no gap between the materials to be welded, the resistance value decreases immediately after the current is applied, as shown by the resistance change 44 in FIG. 9(a). Further, when there is a gap between the materials to be welded, as shown in the resistance change 46 in FIG. The rate of decrease in resistance value is slower than when there is no gap between weld metals. Therefore, at the energization time T0, the resistance value is higher when there is a gap between the welded materials than when there is a gap between the welded materials. This is because the resistance value is constant while there is a gap between the materials to be welded, and even if the materials to be welded come into contact with each other, the electrode 4 presses the object 18 to be welded and the contact area between the materials to be welded increases. This is because it takes time to

Next, final welding is performed according to the contact area between the welded materials obtained from the measured resistance value. In the main welding, the optimum current application conditions are defined in advance according to the contact area between the materials to be welded. Then, an optimum current application condition is selected according to the measured resistance value, and the current is applied from the electrode 4 to the welding target 18 under the selected application condition.

For example, when there is no gap between the materials to be welded, as shown in FIG. 9B, the resistance value is R1 at the energization time T0. A current is applied from 4 to the object to be welded 18 . Specifically, a current of current value I3 is applied from energization time T3 to energization time T4, and a current of current value I4 is applied from energization time T4 to energization time T5. When there is a gap between the materials to be welded, as shown in FIG. 9(c), the resistance value is R2 at the current application time T0. A current is applied from 4 to the object to be welded 18 . Specifically, a current of current value I5 is applied from the energization time T6 to the energization time T7, and a current of the current value I6 is applied from the energization time T7 to the energization time T8.

Next, the operation flow of the welding device in Example 2 will be organized.

First, as temporary welding, the electrode 4 applies a current value I0 to the object 18 to be welded while pressurizing the object 18 to be welded with a predetermined force (step 1 in FIG. 10). Next, while the current of the current value I0 is being applied, the displacement measuring device 15 measures the displacement of the electrode 4 from the temporary welding start coordinates (step 2 in FIG. 10).

Next, the control device 16 confirms the measured displacement amount and determines whether or not the displacement amount is a predetermined Δx (step 3 in FIG. 10). If the displacement is .DELTA.x, the process proceeds to step 4, and if the displacement is not .DELTA.x, the determination of whether the displacement is .DELTA.x is repeated until the displacement is .DELTA.x. Here, the energization time at which the displacement amount becomes Δx is defined as the energization time T0.

Next, the control device 16 confirms the resistance value measured by the resistance measuring device 14 (step 4 in FIG. 10), and selects the optimum current application condition according to the measured resistance value ( step 5). The controller 16 selects the optimum application condition for the measured resistance value from a plurality of predetermined application conditions. It is preferable to control the pressurization from the electrode 4 and keep the pressure applied from the electrode 4 to the object to be welded 18 constant at the time when the energization time T0 is reached. As a result, it is possible to suppress the subsequent change in the contact area between the materials to be welded.

Next, final welding is performed under the selected current application conditions. The control device 16 controls the timer 12 to apply current from the electrode 4 to the object 18 to be welded under the selected application conditions (step 6 in FIG. 10).

As described above, in the welding apparatus according to the second embodiment, the optimum current application conditions corresponding to the respective contact areas between the plurality of welded materials are determined in advance in association with the measured resistance values. Furthermore, the amount of displacement of the electrode 4 necessary for the contact area between the welded materials to reach a predetermined area is assumed in advance. Then, in temporary welding, a current of a constant current value is passed through, the resistance value is measured at the time when the displacement amount of the electrode 4 reaches a constant value, and the current application condition corresponding to the measured resistance value is determined. select. After that, a current is applied from the electrode 4 to the object 18 to be welded under the selected current application conditions. As a result, the displacement of the electrode 4 becomes a predetermined value, and the resistance value of the energization path is measured in a state where the contact area between the welded materials is close to the area suitable for welding. Since welding is performed by applying current under the optimum application conditions for the contact area between them, welding can always be performed under appropriate current application conditions, and welding quality can be stabilized.

In the description of the second embodiment, a plurality of resistance values are assumed, and the current application conditions corresponding to the respective resistance values are determined in advance. A configuration may be adopted in which the current application condition is automatically designed on a case-by-case basis. For example, the control device 16 may be provided with a program for designing optimum current application conditions according to the measured resistance value. By automatically designing the optimum current application condition according to the measured resistance value each time, welding can be performed under the more optimum current application condition according to the measured resistance value. Therefore, it is possible to perform welding with more stable welding quality.

In addition, two-step welding was performed as the main welding, but the current application conditions for the main welding are arbitrary. For example, a constant current value may be applied for a certain period of time, or multi-stage welding may be performed by providing a plurality of combinations of application time and current value, such as 3 stages or 7 stages.
In the above description, indirect welding has been described as an example, but other resistance welding such as direct welding and series welding can also be implemented.

1 welding device 4 electrode 6 ground 14 resistance measuring device 15 displacement measuring device 16 control device 17 cylinder body 19 cylinder head 21 cylinder 22 material to be welded 23 coordinates 24 material to be welded 25 coordinates 26 welding point 28 material to be welded 39 contact surface

Claims (1)

an electrode that pressurizes the object to be welded and applies a current to the object to be welded;
a driving device for driving the electrodes;
a power supply device that applies current to the electrodes;
a resistance measuring instrument for measuring the resistance value of the current path in the object to be welded;
a displacement measuring device that measures the amount of displacement that the electrode moves in the plate thickness direction of the object to be welded when the electrode presses the object to be welded;
a control device for controlling the operation of the driving device and the power supply device;
The control device applies a current under an application condition corresponding to the measured resistance value, and measures the resistance value and the displacement amount while applying a current of a first current value from the electrodes. Temporary welding is performed by performing temporary welding, and after the resistance value becomes a certain value or less by the temporary welding, and the displacement amount becomes a certain value or more, the optimum current according to the measured resistance value The operation of the power supply device is controlled so as to perform a welding operation for performing final welding by applying a current of a second current value different from the first current value for a predetermined time according to the application condition of
A welding device , wherein the final welding is performed continuously with the temporary welding .

Images