WO2020189111A1

WO2020189111A1 - Resistance welding method and welding device

Info

Publication number: WO2020189111A1
Application number: PCT/JP2020/005630
Authority: WO
Inventors: 周一庄内
Original assignee: 株式会社ダイセル
Priority date: 2019-03-15
Filing date: 2020-02-13
Publication date: 2020-09-24
Also published as: JP2020146742A

Abstract

This resistance welding method includes a step for preparing a sensor-retaining base. This resistance welding method also includes: a step for placing a first to-be-welded object and a second to-be-welded object on the sensor-retaining base so that, when the sensor-retaining base is viewed from above, joining surfaces of the first to-be-welded object and the second to-be-welded object are positioned in a sensor installation region, and the outer edge of a bottom surface positioned on the side of the second to-be-welded object opposite from the joining surface overlaps the sensor installation region, the second to-be-welded object being disposed below the first to-be-welded object; a step for confirming that a load on a plurality of load sensors is equally applied in a state in which a load is applied to the joining surfaces; and a step for conducting a current to the first to-be-welded object and the second to-be-welded object in a state in which the load is applied toward the joining surfaces.

Description

Resistance welding method and welding equipment

The present disclosure relates to a resistance welding method and a welding apparatus used therein.

Resistance welding is known in which each joint of these objects to be welded is melted and joined by the resistance heat generated by passing an electric current through the two objects to be welded. For example, Patent Document 1 describes that a tubular member is joined to the end of a bottle used in an airbag device by resistance welding. Patent Document 2 describes a resistance welding method in which aluminum-based materials are superposed and joined by resistance welding.

Japanese Unexamined Patent Publication No. 2008-229630 Japanese Unexamined Patent Publication No. 5-185246

In resistance welding, when an electric current is passed through two objects to be welded, a load is applied to the joints with the joints of the two objects in contact with each other. At this time, if the load applied to the joints is uneven, the joints cannot be joined evenly, and the joint strength becomes uneven.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a technique capable of suppressing unevenness in joint strength in resistance welding.

In order to solve the above problems, the present disclosure is a resistance welding method for joining a first object to be welded and a second object to be welded, and the load is applied to a plurality of load sensors with a load applied to the joint surface. It includes a step of confirming that is applied evenly and a step of passing an electric current through the first object to be welded and the second object to be welded with a load applied to the joint surface.

Specifically, the present disclosure is a resistance welding method, which is a sensor holding portion for holding a load sensor, and defines a sensor installation area in which the centers of a plurality of load sensors are arranged in an annular shape. A plurality of sensor holding portions that hold each load sensor so that the surfaces of the plurality of load sensors are arranged on the same plane as each other, and the plurality of load sensors held by each of the plurality of sensor holding portions. And the step of preparing the sensor holding table having the above, and when the sensor holding table is viewed from above, the joint surfaces of the first welded object and the second welded object are located on the sensor installation area. The first work piece and the first work piece and the first work piece to be welded so that the outer edge of the bottom surface of the second work piece to be welded, which is located on the opposite side of the joint surface, overlaps the sensor installation area. The step of placing the second object to be welded on the sensor holding table, the step of confirming whether the load is evenly applied to the plurality of load sensors with the load applied to each of the joint surfaces, and the above-mentioned step. It includes a step of passing a current through the first object to be welded and the second object to be welded with a load applied to each joint surface.

In the above resistance welding method, by passing an electric current through the first object to be welded and the second object to be welded, the joint surfaces of the first object to be welded and the second object to be welded are melted and the joint surfaces are joined to each other. The first and second welded objects are joined by joining or by melting one of the joined surfaces and fixing it to the remaining surface. Further, in the above resistance welding method, before joining the first object to be welded and the second object to be welded, the load is evenly applied to a plurality of load sensors in a state where a load is applied toward each joint surface. Check if it is. In the above resistance welding method, the first object to be welded and the second object to be welded are joined after confirming that the load applied to each joint surface is not uneven, so that the first object to be welded and the second object to be welded are joined. It is possible to suppress the occurrence of unevenness in the welding strength of the joint portion for joining the welded objects.

Here, the plurality of sensor holding portions are arranged in an annular shape, and the sensor installation area may be defined in an annular shape by the plurality of sensor holding portions. Further, the plurality of sensor holding portions are arranged in an elliptical or polygonal ring shape, and the sensor installation area may be defined by the plurality of sensor holding portions in an elliptical shape or a polygonal shape. The sensor installation area may be defined so as to overlap the outer edge of the bottom surface of the second workpiece when the sensor holding table is viewed from above.

Further, if the load applied to the circumferential region of each joint surface is the load sensed by the load sensor arranged on the bottom surface side of the second welded object corresponding to the region, the first welded object and the first welded object and the load are detected. When each load sensor shows an equal value when a current is passed through the second welded object, the load applied to each joint surface is equal, and each joint surface of the first welded object and the second welded object has an equal value. It is uniformly joined in the circumferential direction. Therefore, in the above resistance welding method, in the step of passing an electric current through the first object to be welded and the second object to be welded, a load is applied to each of the joint surfaces and the load is evenly distributed to the plurality of load sensors. It may be determined that the first welded object and the second welded object are uniformly joined in the circumferential direction by confirming that the first object to be welded and the second object to be welded are uniformly joined. As a result, the joint surfaces of the first object to be welded and the second object to be welded are uniformly bonded to each other in the circumferential direction, so that it is possible to suppress the occurrence of unevenness in the joint strength of the joint portion.

In the above resistance welding method, the step of preparing a cover arranged on the sensor holding table so as to cover the surfaces of the plurality of load sensors is further included, and the first object to be welded and the second object to be welded are formed. In the step of mounting on the sensor holding table, the second work piece may be placed on the cover so that the outer edge of the bottom surface of the second work piece overlaps with the sensor installation area. By preparing the above cover, a flat mounting surface can be formed on a plurality of load sensors. As a result, the load uniformly applied in the circumferential direction of each joint surface of the first object to be welded and the second object to be welded can be uniformly applied to each load sensor. By confirming that the load is evenly applied to each load sensor, it is possible to confirm that the load is evenly applied in the circumferential direction of each joint surface. Therefore, according to the above-mentioned resistance welding method, each joint surface of the first object to be welded and the second object to be welded can be uniformly joined in the circumferential direction, so that the welding strength of the joint portion is uneven. Can be suppressed.

In the above resistance welding method, in the step of placing the first object to be welded and the second object to be welded on the sensor holding table, the outer edge of the bottom surface of the second object to be welded is the plurality of load sensors. The first object to be welded and the second object to be welded may be placed on the sensor holding table so as to overlap with an annular virtual curve connecting the centers of the above. As a result, when a load is applied to the joint surface, it is possible to more accurately measure whether or not the load is evenly applied to the joint surface by a plurality of load sensors.

Here, the present disclosure can be grasped from the side surface of the welding apparatus. That is, the present disclosure is a welding device, a sensor holding portion for holding a load sensor, and defines a sensor installation area in which the centers of the plurality of load sensors are arranged in an annular shape, and the plurality of loads. A sensor holding having a plurality of sensor holding portions holding each load sensor so that the surfaces of the sensors are arranged on the same plane as each other, and the plurality of load sensors held by each of the plurality of sensor holding portions. When the table and the sensor holding table are viewed from above, the joint surfaces of the first object to be welded and the second object to be welded are located on the sensor installation area, and the first object to be welded. The sensor is placed on the first and second workpieces so that the outer edge of the bottom surface of the second workpiece located on the lower side opposite to the joint surface overlaps the sensor installation area. It is provided with a pressurizing device for applying a load to each joint surface in a state of being placed on a holding table, and an electrode portion for passing a current through the first object to be welded and the second object to be welded. The welding device can join the first object to be welded and the second object to be welded after confirming that the load applied to each joint surface is not uneven, and thus the first object to be welded. It is possible to suppress the occurrence of unevenness in the welding strength of the joint portion for joining the second object to be welded.

According to the present disclosure, it is possible to suppress the occurrence of unevenness in the joint strength in resistance welding.

FIG. 1 is an external view of a welding apparatus used for resistance welding. FIG. 2A is an external perspective view of the sensor holding table of the welding apparatus. FIG. 2B is a plan view of the sensor holding table. FIG. 3 is a plan view of the sensor holding table. FIG. 4 is a flowchart of a resistance welding method. FIG. 5 is an external view of a welding apparatus used for resistance welding. FIG. 6 is a flowchart of a resistance welding method.

The resistance welding method and the welding apparatus used for the resistance welding method according to the embodiment of the present disclosure will be described below with reference to the drawings. It should be noted that each configuration and a combination thereof in each embodiment is an example, and the configuration can be added, omitted, replaced, and other changes as appropriate without departing from the gist of the present invention. The present disclosure is not limited by embodiments, but only by the claims.

<Example 1>
FIG. 1 is an external view of the welding apparatus used in the resistance welding method according to the first embodiment of the present embodiment when viewed from the side. The welding device 1 includes a sensor holding base 2, load sensors 3a to 3d (load sensors 3d are not shown in FIG. 1),

electrode units

5 and 6, pressurizing device 7, power supply unit 8 and

wirings

9a and 9b. The welding device 1 is used to join two conductive objects to be welded (in this embodiment, the first object to be welded 11 and the second object to be welded 12) by resistance welding.

First, the sensor holding table 2 of the welding device 1 will be described with reference to FIGS. 2 and 3. FIG. 2A is an external perspective view of the sensor holding table 2, and FIG. 2B is a plan view of the sensor holding table 2 as viewed from the upper surface portion 2a side. As shown in FIG. 2A, the sensor holding base 2 has a cylindrical shape. In the installed state of the sensor holding base 2, a plurality of sensor holding portions 21a to 21d are formed on the columnar upper surface portion 2a. The sensor holding portions 21a to 21d are provided to hold the load sensor. Note that in FIGS. 2A and 2B, the load sensor is not shown for the purpose of explaining the shapes of the sensor holding portions 21a to 21d.

As shown in FIGS. 2A and 2B, the sensor holding portions 21a to 21d are formed on the upper surface portion 2a so as to be adjusted to the shape and size of the load sensor and fixed by fitting the load sensor. .. In this embodiment, the load sensor has a cylindrical shape, and the sensor holding portions 21a to 21d are formed in a cylindrical concave shape so that the load sensor is fitted. Further, the sensor holding portions 21a to 21d are arranged in an annular shape on the upper surface portion 2a. In this embodiment, the sensor holding portions 21a to 21d are arranged side by side on the upper surface portion 2a in a circumferential shape. In a plan view, the upper surface portion 2a is circular, and the circular virtual curve c1 connecting the centers of the sensor holding portions 21a to 21d and the circular contour line of the upper surface portion 2a are concentric circles. In a plan view, the upper surface portion 2a may have an elliptical shape or a polygonal shape, and the virtual curve c1 connecting the centers of the sensor holding portions 21a to 21d may have an elliptical shape or a polygonal shape.

Further, on the upper surface portion 2a, each load sensor installed on the sensor holding portions 21a to 21d and a display device (for example, a voltmeter) installed outside the sensor holding base 2 and displaying the output signal of each load sensor are provided. Wiring grooves 22a to 22d through which the wiring to be connected is passed are formed. The wiring grooves 22a to 22d are formed in a rectangular concave shape that is connected to the sensor holding portions 21a to 21d and extends to the side surface of the sensor holding base 2. The upper surface portion 2a is formed in a flat shape except for the formation regions of the sensor holding portions 21a to 21d and the wiring grooves 22a to 22d.

FIG. 3 is a plan view of the sensor holding base 2 similar to FIG. 2B, and shows a state in which load sensors 3a to 3d are installed on the sensor holding portions 21a to 21d. A load sensor 3a is installed in the sensor holding unit 21a, a load sensor 3b is installed in the sensor holding unit 21b, a load sensor 3c is installed in the sensor holding unit 21c, and a load sensor 3d is installed in the sensor holding unit 21d. Has been done. In this way, one load sensor is installed in each sensor holding portion. The load sensors 3a to 3d may be any one that can output a signal corresponding to the load, and for example, well-known ones such as a strain gauge type sensor and a piezo type sensor can be used.

In a state where the load sensors 3a to 3d are installed on the sensor holding portions 21a to 21d, a sensor installation area 20 in which the centers of the load sensors 3a to 3d are arranged in an annular shape is defined. In FIG. 3, the sensor installation area 20 is an area indicated by hatching that rises to the right. In this embodiment, the sensor installation area 20 is an area surrounded by a circular virtual curve c2 that is in contact with the load sensors 3a to 3d on the outside and a circular virtual curve c3 that is in contact with the load sensors 3a to 3d on the inside. In this embodiment, the sensor holding portions 21a to 21d define the annular sensor installation area 20. Further, each center of the load sensors 3a to 3d is arranged on the virtual curve c1. As described above, the sensor holding portions 21a to 21d define the sensor installation area 20 in which the centers of the load sensors 3a to 3d are arranged in an annular shape. Further, the load sensors installed on the sensor holding base 2 are preferably two or more, and more preferably three or more. When three or more load sensors are installed on the sensor holding base 2, each sensor holding portion is arranged so that each center of the plurality of load sensors is arranged at each vertex of the polygonal shape on the upper surface portion 2a. An annular sensor installation area 20 may be defined by each sensor holding portion. In this case, the sensor holding portions 21a to 21d are formed on the upper surface portion 2a so that each center coincides with each vertex of the polygonal shape. The sensor installation area 20 may be defined so as to overlap the outer edge of the bottom surface (bottom surface 12b shown in FIG. 1) of the second object to be welded 12 when the sensor holding table 2 is viewed from above.

Further, wirings 4a to 4d are connected to the load sensors 3a to 3d, respectively. The wirings 4a to 4d are connected to a display device installed outside the sensor holding base 2 through the wiring grooves 22a to 22d and displaying the output signals of each load sensor.

Further, in the state where the load sensors 3a to 3d are installed in the sensor holding portions 21a to 21d, the upper surfaces are arranged on the same plane as each other. The welding device 1 confirms by the load sensors 3a to 3d whether or not the load applied to the objects to be welded placed above the load sensors 3a to 3d is evenly applied to each joint surface of the objects to be welded. be able to.

As described above, the sensor holding base 2 of the welding device 1 defines the sensor installation area 20 in which the centers of the plurality of load sensors 3a to 3d are arranged in an annular shape, and the surfaces of the plurality of load sensors 3a to 3d are covered. A plurality of sensor holding portions 21a to 21d for holding the load sensors 3a to 3d are provided so as to be arranged on the same plane as each other.

Next, returning to FIG. 1, the configuration of the welding apparatus 1 will be further described. The welding device 1 includes a pair of

electrode portions

5 and 6. The electrode portion 5 is arranged on the upper side of the welding device 1, and the electrode portion 6 is arranged on the lower side of the welding device 1.

At the time of resistance welding, the welding device 1 passes an electric current through the

electrode portions

5 and 6 to the first object to be welded 11 and the second object to be welded 12. The first object to be welded 11 and the second object to be welded 12 have, for example, a cylindrical shape having a diameter of about 20 to 25 mm. The first object to be welded 11 and the second object to be welded 12 having such a shape and size are, for example, a bottle of a gas generator that activates an airbag for protecting an occupant in the event of a side collision of an automobile. Is. The first object to be welded 11 includes a bottom surface 11b located on the opposite side of the joint surface 11a and the joint surface 11a. Similarly, the second object to be welded 12 includes a joint surface 12a and a bottom surface 12b located on the opposite side of the joint surface 12a. The first object to be welded 11 is placed on the second object to be welded 12 in a state where these

joint surfaces

11a and 12a are aligned with each other. The welding device 1 is used to join the

joint surfaces

11a and 12a of the first object to be welded 11 and the second object to be welded 12 by resistance welding. The shape of the first object to be welded 11 and the second object to be welded 12 is not limited to the cylindrical shape, and may be a cylindrical shape, a polygonal cylinder shape, a polygonal shape, a truncated cone, a truncated cone, or the like. Further, on at least one of the

joint surfaces

11a and 12a, when an electric current is passed through the first object to be welded 11 and the second object to be welded 12, the electrical resistance is relatively increased so that high-temperature resistance heat is generated. A small protrusion may be provided on the joint surface, or a member that increases the electrical resistance between the

joint surfaces

11a and 12a may be inserted between the

joint surfaces

11a and 12a.

The electrode portion 6 includes a flat upper surface portion 6a and a lower surface portion 6b, and is arranged so as to overlap the sensor installation area 20 when the sensor holding base 2 is viewed from above (vertically above). At the time of resistance welding, the second object to be welded 12 is placed on the upper surface portion 6a of the electrode portion 6. Further, the electrode portion 5 includes a flat upper surface portion 5a and a lower surface portion 5b, and the lower surface portion 5b is in contact with the first object to be welded 11. In the

electrode portions

5 and 6, the lower surface portion 5b and the upper surface portion 6a, which are the current-carrying surfaces, are arranged so as to face each other. 12 is sandwiched from the vertical direction.

Further, when the sensor holding base 2 is viewed from above, the

joint surfaces

11a and 12a of the first object to be welded 11 and the second object to be welded 12 are located on the sensor installation area 20 and the second The first object to be welded 11 and the second object to be welded 12 are placed on the sensor holding table 2 so that the outer edge of the bottom surface 12b located on the opposite side of the joint surface 12a of the object to be welded 12 overlaps the sensor installation area 20. Weld.

Further, the welding device 1 includes a pressurizing device 7 for applying a load toward the

joint surfaces

11a and 12a in a state where the first object to be welded 11 and the second object to be welded 12 are placed on the sensor holding table 2. .. The pressurizing device 7 includes a main body portion 7a and a connecting portion 7b that connects to the upper surface portion 5a of the electrode portion 5. The pressurizing device 7 applies a pressing force generated by the main body portion 7a to the first object to be welded 11 via the connecting portion 7b and the electrode portion 5. The pressurizing device 7 is connected to a drive mechanism (not shown) and can be raised and lowered in the vertical direction by an operator's operation. Since the sensor holding base 2 is fixed, according to the law of action and reaction, the load applied to the first work piece 11 also acts on the second work piece 12, and the second work piece 12 Also acts on the first object to be welded. Therefore, a load is applied to the welded

surfaces

11a and 12a. By lowering the pressurizing device 7 and the electrode portion 5, the first workpiece 11 and the second workpiece 12 are sandwiched between the

power supply portions

5 and 6. The main body 7a is fixed, and the connecting portion 7b and the electrode portion 5 may be moved up and down by a drive mechanism.

As described above, in the pressurizing device 7 according to the present embodiment, the first object to be welded 11 and the second object to be welded 12 to be welded are sandwiched between the

electrode portions

5 and 6, and the joint surface 11a is held by the pressurizing device 7. , 12a is loaded with an electric current through the first object to be welded 11 and the second object to be welded 12. In this embodiment, the diameters of the

electrode portions

5 and 6 are larger than the diameters of the first work piece 11 and the second work piece 12. The

electrode portions

5 and 6 for passing an electric current through the first object to be welded 11 and the second object to be welded 12 are different from the portions sandwiching the first object to be welded 11 and the second object to be welded 12. May be good.

Further, the welding device 1 includes a power supply unit 8. The power supply unit 8 is connected to the

electrode units

5 and 6 by

wirings

9a and 9b, and supplies a current to the

electrode units

5 and 6. The power supply unit 8 supplies the

electrodes

5 and 6 with a current normally used for resistance welding, such as a direct current, a single-phase alternating current, or a three-phase alternating current. The power supply unit 8 may be provided outside the welding device 1.

Next, the resistance welding method according to this embodiment will be described with reference to FIG. FIG. 4 is a flowchart relating to the resistance welding method according to this embodiment. First, in the resistance welding method according to this embodiment, the sensor holding base 2 shown in FIGS. 2 and 3 is prepared (step S101).

In step S102 following step S101, the first object to be welded 11 and the second object to be welded 12 are placed on the sensor holding table 2. At this time, when the sensor holding table 2 is viewed from above, the

joint surfaces

11a and 12a of the first object to be welded 11 and the second object to be welded 12 are located on the sensor installation area 20 shown in FIG. In addition, the outer edge of the bottom surface 12b of the second object to be welded 12 arranged below the first object to be welded 11 overlaps with the sensor installation area 20.

In step S102, the first object to be welded so that the outer edge of the bottom surface 12b of the second object to be welded 12 overlaps with the annular virtual curve c1 (see FIG. 3) connecting the centers of the plurality of load sensors 3a to 3d. The 11 and the second object to be welded 12 may be placed on the sensor holding table 2. As a result, when a load is applied to the

joint surfaces

11a and 12a, it is possible to more accurately measure whether the load is evenly applied to the joint surfaces 12a by the load sensors 3a to 3d.

In step S103 following step S102, it is confirmed by the load sensors 3a to 3d that the load is evenly applied in the circumferential direction of the

joint surfaces

11a and 12a while the load is applied to the

joint surfaces

11a and 12a. In this embodiment, the

joint surfaces

11a and 12a can be uniformly joined to each other by applying a load evenly in the circumferential direction of the

joint surfaces

11a and 12a.

In step S104, which is next to step S103, an electric current is passed through the first object to be welded 11 and the second object to be welded 12 with a load applied to the

joint surfaces

11a and 12a. The

joint surfaces

11a and 12a are melted by the heat resistance generated by this, and the first object to be welded 11 and the second object to be welded 12 are joined at the

joint surfaces

11a and 12a. According to the resistance welding method according to this embodiment and the welding apparatus 1 used therefor, the

joint surfaces

11a and 12a can be joined evenly. As a result, according to the resistance welding method and the welding apparatus 1 according to the present embodiment, it is possible to suppress the occurrence of unevenness in the joint strength in the circumferential direction at the joint portion in the resistance welding.

When a current is passed through the first object to be welded 11 and the second object to be welded 12, if the values of the loads sensed by the load sensor are substantially the same, the loads applied to the

joint surfaces

11a and 12a are even in the circumferential direction. The

joint surfaces

11a and 12a of the first object to be welded 11 and the second object to be welded 12 are uniformly joined in the circumferential direction. The load applied to the circumferential region of each of the

joint surfaces

11a and 12a is the load sensed by the load sensor arranged on the bottom surface 12b side of the second welded object 12 corresponding to that region (overlapping when viewed in the vertical direction). If there is, if the load sensors 3a to 3d show equal values when a current is passed through the first welded object 11 and the second welded object 12, the loads applied to the

joint surfaces

11a and 12a are equal. This is because the

joint surfaces

11a and 12a of the first object to be welded 11 and the second object to be welded 12 are uniformly joined in the circumferential direction. Therefore, in step S104, when a load is applied to the first object to be welded 11, it may be confirmed that the load is evenly applied to the plurality of load sensors 3a to 3d. As a result, it is determined that the

joint surfaces

11a and 12a of the first object to be welded 11 and the second object to be welded 12 are uniformly joined in the circumferential direction. As a result, it is possible to suppress the occurrence of unevenness in the welding strength of the joint portion that joins the first object to be welded 11 and the second object to be welded 12.

By the way, although the above-mentioned Patent Document 1 describes that a bottle to which an ignition device is attached and a tubular member are joined by resistance welding, there is no description about a specific method of resistance welding. .. In a gas generator used for an airbag device or the like, if the members are joined by resistance welding and the load applied to the joint surfaces of the members is uneven, the members are not evenly joined over the entire joint surface. Spots occur in the joint strength. If the joint strength between the members of the gas generator is uneven, the gas generator will break from the portion where the joint strength is relatively weak when the gas generator is operated, and the output characteristics as designed cannot be obtained. However, it is difficult to confirm the joint strength by non-destructive inspection after joining the members by resistance welding. In a gas generator, if the joint strength becomes uneven, the output characteristics as designed cannot be obtained.

On the other hand, according to the resistance welding method and the welding apparatus 1 according to the present embodiment, there is no unevenness in the load applied to the joint surface 12a when the first object to be welded 11 and the second object to be welded 12 are joined (load distribution). After confirming that the first object to be welded 11 and the second object to be welded 12 are uniform, resistance welding is performed. As a result, the

joint surfaces

11a and 12a of the first object to be welded 11 and the second object to be welded 12 are evenly bonded to each other over the entire surface, and it is possible to suppress the occurrence of unevenness in the bonding strength. Therefore, in the gas generator manufactured by the resistance welding method and the welding apparatus 1 according to the present embodiment, it is possible to suppress unevenness in the joint strength between the members due to resistance welding, and the joint strength is confirmed after the members are joined to each other. It is not necessary to do so, and the output characteristics as designed can be obtained.

Further, in the resistance welding method for aluminum-based materials described in Patent Document 2, the diameter of the insert member inserted between the workpieces to increase the electrical resistance between the workpieces and the pressure applied to the workpieces. The diameters of the electrodes through which the current flows are similar, and it is easy to apply even pressure to the welded area, and it seems that even bonding of the workpiece to be welded can be expected. However, the diameters of these electrodes and insert members are relatively sufficiently small as compared with the bottle of the airbag device described in Patent Document 1. When the diameter is relatively large (for example, about 20 mm) like the bottle of the airbag device, the load applied in the circumferential direction of the joint surface when a load is applied toward the joint surface of the bottle during resistance welding. As a result, unevenness is likely to occur in the welding strength. It is difficult to confirm that the welding strength of joints by resistance welding is uniform by non-destructive inspection such as visual inspection.

On the other hand, according to the resistance welding method and the welding apparatus 1 according to the present embodiment, there is no unevenness in the load applied to the

joint surfaces

11a and 12a when the first object to be welded 11 and the second object to be welded 12 are joined ( After confirming that the load distribution is uniform), the first workpiece 11 and the second workpiece 12 are joined. As a result, according to the resistance welding method and the welding apparatus 1 according to the present embodiment, it is possible to suppress the occurrence of unevenness in the welding strength of the joint portion.

<Example 2>
Next, the resistance welding method according to the second embodiment of the present embodiment and the welding apparatus 1 used therefor will be described with reference to FIGS. 5 and 6. In this embodiment, a cover 10 arranged on the sensor holding base 2 is prepared so as to cover the surfaces of the plurality of load sensors 3a to 3d.

FIG. 5 is an external view of the welding apparatus used in the resistance welding method according to the second embodiment of the present embodiment when viewed from the side. The welding apparatus 1 according to the present embodiment has the same configuration as the welding apparatus 1 according to the first embodiment shown in FIG. 1 except that the cover 10 is provided. Therefore, the same components as the components of the welding apparatus 1 according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The cover 10 includes an upper surface portion 10a covering the surfaces of the load sensors 3a to 3d and a side surface portion 10b covering the side surface portion of the sensor holding base 2, and the upper surface portion 10a and the side surface portion 10b are integrally formed to form the cover 10 as a whole. It has a cup shape. The upper surface portion 10a of the cover 10 is formed in a flat shape. The cover 10 is made of a hard material (for example, metal) in order to prevent the cover 10 from being damaged when it receives a load applied by the pressurizing device 7. Further, since the upper surface portion 10a of the cover 10 receives the load applied by the pressurizing device 7, if it is too thin, it is easily cracked, but if it is too thick, the measurement sensitivity of the load by the load sensors 3a to 3d is lowered. Based on these viewpoints, it has been found that the thickness of the upper surface portion 10a of the cover 10 is preferably about 3 mm.

Also, the clearance between the side surface portion 10b of the cover 10 and the side surface portion of the sensor holding base 2 is set as small as possible. As a result, the cover 10 is prevented from being displaced in the radial direction of the upper surface portion 10a and the cover 10 from rattling with respect to the sensor holding base 2.

Next, the resistance welding method according to this embodiment will be described. FIG. 6 is a flowchart relating to the resistance welding method according to this embodiment. Since the steps S201, S204, and S205 in the flowchart of FIG. 6 are the same as the steps of steps S101, S103, and S104 in the flowchart of FIG. 4, their description will be omitted.

In step S202 in the resistance welding method according to this embodiment, the cover 10 shown in FIG. 5 is prepared. In step S203 following step S202, when the first object to be welded 11 and the second object to be welded 12 are placed on the sensor holding table 2, the second object to be welded 11 is placed on the cover 10 and the outer edge of the bottom surface 12b. Is placed so as to overlap the sensor installation area 20 shown in FIG.

In this embodiment, by arranging the cover 10 between the load sensors 3a to 3d and the electrode portion 6, a flat mounting surface is formed on the load sensors 3a to 3d. As a result, the load uniformly applied to the

joint surfaces

11a and 12a in the circumferential direction can be evenly applied to the load sensors 3a to 3d, so that it is confirmed that the load is evenly applied to the load sensors 3a to 3d. As a result, it can be confirmed that the load is uniformly applied in the circumferential direction of the

joint surfaces

11a and 12a. Therefore, according to the resistance welding method and the welding apparatus 1 according to the present embodiment, the

joint surfaces

11a and 12a can be uniformly joined in the circumferential direction, so that uneven welding strength of the joints is suppressed. it can.

In the resistance welding method and the welding apparatus 1 according to the above embodiment, when it is determined that the load sensors 3a to 3d are not evenly loaded when the load is applied toward the

joint surfaces

11a and 12a. , The

electrode portions

5 and 6 may be driven by a driving device to adjust so that the load is evenly applied to the load sensors 3a to 3d. In this case, the welding device 1 may include a control unit that executes control related to the adjustment.

In the first and second embodiments, a load is applied to the

joint surfaces

11a and 12a, and after confirming that the load sensors 3a to 3d are evenly loaded, the first welded object 11 and the second welded object 11 and the second object are covered. An electric current is passed through the welded object 12 to join the first object to be welded 11 and the second object to be welded 12. In the present disclosure, the present invention is not limited to this, and a load is applied to the first object to be welded 11 while passing a weak electric current, and after confirming that the load sensors 3a to 3d are evenly loaded, the first object to be welded is applied. The first object to be welded 11 and the second object to be welded 12 may be joined by passing a current of a magnitude required for resistance welding through the 11 and the second object to be welded 12. Further, in the welding device 1, the electrode portion 5 is fixed, and the pressurizing device 7 may be arranged on the sensor holding base 2 side.
Each aspect disclosed herein can be combined with any other feature disclosed herein.

1 Welding device 2 Sensor holding base

3a Load sensor

3b Load sensor 3c Load sensor 3d Load sensor 5 Electrode part 6 Electrode part 7 Pressurizing device 8 Power supply part 20 Sensor installation area 21a Sensor holding part 21b Sensor holding part 21c Sensor holding part 21d Sensor Holding part c1 Virtual curve

Claims

A sensor holding unit that holds a load sensor, which defines a sensor installation area in which the centers of the plurality of load sensors are arranged in an annular shape, and the surfaces of the plurality of load sensors are arranged on the same plane as each other. A step of preparing a sensor holding base having a plurality of sensor holding portions for holding each load sensor and the plurality of load sensors held by the plurality of sensor holding portions, respectively.
When the sensor holding table is viewed from above, the joint surfaces of the first object to be welded and the second object to be welded are located on the sensor installation area, and the lower side of the first object to be welded. The first object to be welded and the second object to be welded are placed on the sensor holding table so that the outer edge of the bottom surface located on the opposite side of the joint surface of the second object to be welded is overlapped with the sensor installation area. And the steps to put on
A step of confirming whether the load is evenly applied to the plurality of load sensors with the load applied to each of the joint surfaces, and a step of confirming that the load is evenly applied to the plurality of load sensors.
A step of passing an electric current through the first object to be welded and the second object to be welded with a load applied to each of the joint surfaces.
Including resistance welding methods.
In the step of passing an electric current through the first object to be welded and the second object to be welded, a load is applied to each of the joint surfaces and it is confirmed that the load is evenly applied to the plurality of load sensors. It is determined that the joint surfaces of the first work piece and the second work piece are uniformly joined in the circumferential direction.
The resistance welding method according to claim 1.
Further including the step of preparing a cover arranged on the sensor holding table so as to cover the surface of the plurality of load sensors.
In the step of placing the first work piece and the second work piece on the sensor holding table, the second work piece is on the cover and the outer edge of the bottom surface of the second work piece is said. Placed so that it overlaps the sensor installation area,
The resistance welding method according to claim 1 or 2.
In the step of placing the first work piece and the second work piece on the sensor holding table, the outer edge of the bottom surface of the second work piece is an annular shape connecting the centers of the plurality of load sensors. The first object to be welded and the second object to be welded are placed on the sensor holding table so as to overlap the virtual curve of.
The resistance welding method according to any one of claims 1 to 3.
A sensor holding unit that holds a load sensor, which defines a sensor installation area in which the centers of the plurality of load sensors are arranged in an annular shape, and the surfaces of the plurality of load sensors are arranged on the same plane as each other. A sensor holding base having a plurality of sensor holding portions for holding each load sensor and the plurality of load sensors held by the plurality of sensor holding portions, respectively.
When the sensor holding table is viewed from above, the joint surfaces of the first object to be welded and the second object to be welded are located on the sensor installation area, and the lower side of the first object to be welded. The first object to be welded and the second object to be welded are placed on the sensor holding table so that the outer edge of the bottom surface located on the opposite side of the joint surface of the second object to be welded is overlapped with the sensor installation area. A pressurizing device that applies a load to each joint surface in the state of being placed on the
An electrode portion for passing an electric current through the first object to be welded and the second object to be welded,
A welding device.