Patent Application
20210394297
The present invention relates to a resistance welding device for welding a workpiece by electrifying the workpiece via an electrode, relates to a hollow arm for holding an article, and relates to a method of manufacturing the hollow arm.
Japanese Laid-Open Patent Publication No. 2016-132031 discloses a welding gun (a resistance welding device) comprising a hollow arm that holds an electrode.
The hollow arm described in Japanese Laid-Open Patent Publication No. 2016-132031 includes: an arm main body having a recess that opens on one side; and a cover attached to an opening end surface of the arm main body so as to cover an opening of the recess.
The hollow arm described in Japanese Laid-Open Patent Publication No. 2016-132031 has suffered from a problem that, since the arm main body and the cover are fastened by a large number of fastening members (for example, bolts) in order to secure rigidity, there is a resulting increase in weight.
The present invention, which was made in view of such a problem, has an object of providing a hollow arm which is light-weight and of high rigidity, a resistance welding device comprising the hollow arm, and a method of manufacturing the hollow arm.
A first aspect of the present invention is a resistance welding device that welds a workpiece by electrifying the workpiece via an electrode, the resistance welding device comprising a hollow arm configured to hold the electrode, the hollow arm including: an arm main body including a cavity portion that opens at least on one side; and a cover attached to an opening end surface of the arm main body so as to cover an opening of the cavity portion, and the arm main body and the cover being fixed by a friction stir welding portion extending along a peripheral edge portion of the cover.
A second aspect of the present invention is a hollow arm that holds an article, the hollow arm comprising: an arm main body including a cavity portion that opens at least on one side; and a cover attached to an opening end surface of the arm main body so as to cover an opening of the cavity portion, the arm main body and the cover being fixed by a friction stir welding portion extending along a peripheral edge portion of the cover.
A third aspect of the present invention is a method of manufacturing a hollow arm that holds an article, the method comprising: a step of providing a main body member made of a metal and including a cavity portion that opens at least on one side, the main body member being an arm main body including the cavity portion or being a material prior to being molded in a shape of the arm main body; a step of providing a cover including a peripheral edge portion that follows an outer peripheral shape of the arm main body; a step of attaching the cover to the main body member in a manner that the cover covers an opening of the cavity portion; and a step of friction stir welding the main body member and the cover.
In the present invention, the arm main body and the cover are fixed by the friction stir welding portion extending along the peripheral edge portion of the cover. This makes it possible to provide a hollow arm which is light-weight and of high rigidity, a resistance welding device comprising the hollow arm, and a method of manufacturing the hollow arm.
A preferred embodiment of a resistance welding device, a hollow arm, and a method of manufacturing the hollow arm according to the present invention will be presented and described in detail below with reference to the accompanying drawings.
The welding gun 10 is employed in a welding robot, for example. That is, the welding gun 10 is gripped by the welding robot, for example. As shown in
As shown in
The electrode moving mechanism 18 has: a holding portion 41 that holds the movable electrode 14; and a moving mechanism portion 43 that moves the holding portion 41 in the X axis direction and includes, for example, a ball screw mechanism. The holding portion 41 holds the movable electrode 14 in such a manner that the movable electrode 14 faces the fixed electrode 12 in the X axis direction. The moving mechanism portion 43 is housed in the housing 24. The housing 24 functions also as a gripping portion to be gripped by the welding robot. The electrode moving mechanism 18 further has a motor 36 that drives the moving mechanism portion 43 to cause an advancing/retracting operation to be performed on the movable electrode 14.
The hollow arm 16 will be described in more detail below.
As shown in
The arm main body 17 has: a base plate portion 17c that configures a first side wall 16w1, which is one of the first side wall 16w1 and a second side wall 16w2 of the hollow arm 16 that face each other; and a peripheral wall plate portion 17d that projects in a thickness direction of the base plate portion 17c from a peripheral edge portion of the base plate portion 17c, and extends along the peripheral edge portion of the base plate portion 17c. That is, the arm main body 17 has a substantially U-like cross-sectional shape.
The cover 19 configures the second side wall 16w2 of the hollow arm 16. Describing this in detail, the cover 19 is configured from a plate-like member having a peripheral edge portion 19a that follows an outer peripheral shape of the arm main body 17 (refer to
A metal or the like may be cited as a material of the arm main body 17 and the cover 19. Here, the arm main body 17 and the cover 19 are configured made of aluminum, for example.
As shown in
Describing this in detail, as shown in
In more detail, the opening end surface 17b of the arm main body 17 and the peripheral edge portion 19a of the cover 19 are fixed by the friction stir welding portion 30 over an entire periphery. Note that the opening end surface 17b of the arm main body 17 and the peripheral edge portion 19a of the cover 19 may be partially fixed by the friction stir welding portion 30, without being limited to being fixed thereby over the entire periphery. Hence, for example, there may be a place in part of the entire periphery lying along the peripheral edge portion 19a of the cover 19 where the opening end surface 17b of the arm main body 17 and the peripheral edge portion 19a of the cover 19 are not fixed by the friction stir welding portion 30. Alternatively, the opening end surface 17b of the arm main body 17 and the peripheral edge portion 19a of the cover 19 may be fixed by the friction stir welding portion 30 at a plurality of places separated along the peripheral edge portion 19a of the cover 19. The percentage of an extension length of the friction stir welding portion 30 (in the case of there being a plurality of friction stir welding portions 30, a length totaling the plurality of their lengths) with respect to a length of the entire periphery lying along the peripheral edge portion 19a of the cover 19 is set to 60% or more, and is preferably set to 80% or more, for example.
Note that configurations of the arm main body 17 and the cover 19 are not limited to the above-described configurations, and may be appropriately altered. A cross-sectional shape of at least one of the arm main body 17 and the cover 19 may be configured to be substantially L-like, or the cross-sectional shape of the cover 19 may be configured to be substantially U-like, for example. Moreover, although the hollow arm 16 is configured to be substantially U-like in side view, it may be of another shape (for example, substantially L-like, linear, and so on, in side view).
Next, an example of the method of manufacturing the hollow arm 16 will be described using
First, as shown in
In
Next, as shown in
Next, the main body member 21 and the cover 19 are friction stir welded. Specifically, as shown in
Next, as shown in
By the above-described series of steps, the hollow arm 16, in which the arm main body 17 and the cover 19 are fixed over their entire periphery by the friction stir welding portion 30, is obtained as shown in
Note that although here, the material prior to being molded in the shape of the arm main body 17 has been employed as the main body member 21, the main body member 21 may be configured as the arm main body 17. That is, a configuration may be adopted whereby, for example, the first metal plate 32a is processed into the shape of the arm main body 17 to manufacture the arm main body 17, and the cover 19 is attached to the arm main body 17.
Next, operation of the welding gun 10 configured as above will be described.
The welding robot performs welding of the workpiece configured by the plurality of overlaid plate materials by gripping by a movable arm the housing 24 being the gripping portion of the welding gun 10. Specifically, the welding robot moves the welding gun 10 so that the workpiece is positioned between the movable electrode 14 and the fixed electrode 12 that have been separated from each other (in detail, so that the workpiece is positioned in a vicinity of the fixed electrode 12), by the movable arm. The welding robot drives the motor 36 to bring the movable electrode 14 close to the fixed electrode 12, and thereby sandwiches/pressurizes the workpiece by the fixed electrode 12 and the movable electrode 14. The welding robot performs spot joining of the workpiece by passing a welding current between the fixed electrode 12 and the movable electrode 14. In order that, when spot joining of one workpiece finishes, spot joining of another workpiece is performed, the welding robot moves the welding gun 10 similarly to as described above. That is, in order for the welding robot to sequentially weld a plurality of workpieces, it moves the welding gun 10 between the workpieces.
Next, advantages of the welding gun 10 configured as above will be described.
As shown in
Thus, the arm main body 17 and the cover 19 can be joined with high strength, without a fastening member such as a bolt being employed. As a result, the welding gun 10 comprising the light-weight and highly rigid hollow arm 16 can be realized.
In the case where an arm main body and a cover configuring a hollow arm of a welding gun are joined using a large number of fastening members, such as bolts, as in conventional technology (for example, Japanese Laid-Open Patent Publication No. 2016-132031), the welding gun itself ends up increasing in weight.
Since the hollow arm 16 is more light-weight compared to a conventional hollow arm, the welding gun 10 itself is made light-weight. In other words, the welding gun 10 excels in movement operability due to its inertial weight being small. In addition, since the hollow arm 16 of the welding gun 10 is of high rigidity, the welding gun 10 can stably hold the fixed electrode 12 so as to face (directly oppose) the movable electrode 14.
In conventional technology (for example, Japanese Laid-Open Patent Publication No. 2016-132031), fastening members are employed as mentioned above, hence a plurality of tap holes need to be formed in the arm main body, strength of the arm main body lowers, and it is difficult for the arm main body to be thinned (weight-lightened).
In the hollow arm 16, since there is not required a thickness for tap holes to be formed in a wall of the arm main body 17, the wall of the arm main body 17 can be made thinner, and even greater weight-lightening can be achieved, compared to in conventional technology (for example, Japanese Laid-Open Patent Publication No. 2016-132031) where fastening members are employed. That is, in the hollow arm 16, cutting processing can be performed along the cutting line CL shown in
In the welding gun 10, the hollow arm 16 does not need disposition of fastening members such as bolts to be considered, so degree-of-freedom of design of the hollow arm 16 is high, and since fastening members such as bolts are not employed, surface finish of the hollow arm 16 can be made beautiful.
In the welding gun 10, the hollow arm 16 has its arm main body 17 and cover 19 fixed by friction stir welding, hence initial deflection can be even further suppressed to a minimum, compared to when fixing is performed by welding joining. Thus, quality of the hollow arm 16 can be improved. As a result, the high quality hollow arm 16 can be realized, and the welding gun 10 comprising such a hollow arm 16 can be realized.
Friction stir welding is accomplished with less heat input compared to welding joining, hence is less prone to distortion due to molding, and is optimal for fixing of the arm main body 17 and cover 19 of the hollow arm 16 of the welding gun 10 where there are required shape accuracy for holding the electrodes and weight-lightening.
As shown in
As shown in
The opening end surface 17b of the arm main body 17 and the peripheral edge portion 19a of the cover 19 are fixed by the friction stir welding portion 30 over the entire periphery. Thus, the arm main body 17 and the cover 19 can be joined with even higher strength. That is, sufficient rigidity of the hollow arm 16 can be secured even without there being reinforcement of ribs or the like, or even with reinforcement of ribs or the like being reduced to the utmost. As a result, a welding gun 10 comprising an even more light-weight and even more highly rigid hollow arm 16 can be realized.
The welding gun 10 has the housing 24 as the gripping portion to be gripped by the welding robot. As a result, the movable arm of the welding robot does not require a large physical strength, so there is no need for a large-sized welding robot to be employed.
As shown in
As shown in
In the method of manufacturing the hollow arm 16, in the step of providing the main body member 21, the main body member 21 is the material prior to being molded in the shape of the arm main body 17, as shown in
In the step of providing the main body member 21, the main body member 21 is manufactured by forming the cavity portion 21a in the first metal plate 32a, as shown in
Configuration of the above-described welding gun 10 may be appropriately altered.
Although in the above-described embodiment, the fixed electrode 12 is employed as the article held by the hollow arm 16, the present invention is not limited to this. There may be adopted a configuration where the movable electrode 14 is held by the hollow arm, and the hollow arm is moved, for example. Moreover, an article such as a tool used in industry may be held by the hollow arm, for example.
Although in the above-described embodiment, the arm main body 17 of the hollow arm 16 opens on one side in the thickness direction of the hollow arm 16, the present invention is not limited to this.
For example, an arm main body 52 may open on both sides in the thickness direction of a hollow arm 50, as in modified example 1 shown in
For example, an arm main body 62 may open on one side in a direction orthogonal to the thickness direction of a hollow arm 60, as in modified example 2 shown in
For example, an arm main body 72 may open on both sides in a direction orthogonal to the thickness direction of a hollow arm 70, as in modified example 3 shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-181610 | Sep 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/036371 | 9/17/2019 | WO | 00 |
