Patent Description:
Known in the art is a technique for welding objects by a laser beam. For example, Patent Literature <NUM> describes a laser welding apparatus for welding a lid body to a case body.

Patent Literature <NUM>: <CIT>
<CIT> discloses a handy laser head for YAG laser, and forms the basis for the preamble of claim <NUM>.

<CIT> discloses a YAG laser beam machining head.

<CIT> discloses a manually operated laser beam welding head.

As a result of manufacturing errors, fixing errors, and a temperature errors, errors in sizes of objects to be welded may occur. In particular, when a plurality of objects that are each of the same size are welded for manufacture, variations may occur between sizes of the objects. When such objects are welded by use of a laser beam in sequence, even if positioning of the laser beam is carried out relative to one object to be welded, the laser beam may shift upon replacing with a next object to be welded. To correct such a shift in positioning, there is conceived repositioning of the laser beam for each of the objects to be welded; however, such an approach is time consuming and imposes a burden on a welder.

An object of the present invention is to correct a shift in position of a laser beam used for welding objects without need for intervention by a welder.

In the present invention, there is provided a laser welding system according to claim <NUM>.

For the case where the junction is welded from the inside of the corner, the nozzle may have a shape that fits inside the corner.

The laser welding unit may further eject shielding gas from the nozzle to the junction, and the shape may be a tapered shape.

The laser welding system may further include, for the case where the object to be welded are a first plate-shaped member and a second plate-shaped member that are joined by a butt joint, a jig that is provided on the first plate-shaped member and forms the corner with at least one of the first plate-shaped member and the second plate-shaped member.

For the case where the welding part is welded from the outside of the corner, the nozzle may have a shape that fits outside the corner.

The laser welding system may further include; a recognizing unit configured to recognize a shape of the corner; a selecting unit configured to select a nozzle having a shape corresponding to the recognized shape from a plurality of nozzles whose shapes are different to each other; and an attaching unit configured to attach the selected nozzle to the laser welding unit.

According to the present invention, it is possible to correct a shift in position of a laser beam used for welding objects without need for intervention by a welder.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. Note that, in the drawings, in order to facilitate understanding of the invention, the sizes, shapes, and ratios of constituent elements may be different from those of actual ones. An X-axis direction, a Y-axis direction, and a Z-axis direction shown in the drawings are directions that are perpendicular to each other. A -X-axis direction, a -Y-axis direction, and a -Z-axis direction are respectively directions opposite to the X-axis direction, the Y-axis direction, and the Z-axis direction. The vertical direction may be the -Z-axis direction.

<FIG> is a diagram illustrating an example of the configuration of laser welding system <NUM> according to an embodiment. Laser welding system <NUM> welds objects to be welded <NUM> by a laser beam. In laser welding system <NUM>, welding progresses without an operator performing continuous operations. Laser welding system <NUM> includes laser welding machine <NUM>, arm apparatus <NUM> (an example of a holding unit), turntable <NUM> (an example of a moving apparatus), and control apparatus <NUM>.

Objects to be welded <NUM> are hollow tubular member <NUM> and disk-shaped flange <NUM>, for example. Flange <NUM> is joined to one end of tubular member <NUM> so as to protrude in a radial direction. The outer peripheral face of tubular member <NUM> and the surface of flange <NUM> form an L-shaped cross-sectional face. The inside corner of L is junction <NUM> (an example of welding part) between tubular member <NUM> and flange <NUM>. This junction <NUM> is formed by fillet welding along the circumference direction of tubular member <NUM>.

Laser welding machine <NUM> welds objects to be welded <NUM> by a laser beam. Laser welding machine <NUM> includes oscillator <NUM> and irradiator <NUM> (an example of a laser welding unit). Oscillator <NUM> and irradiator <NUM> are connected through cable <NUM>. Oscillator <NUM> generates a laser beam. The laser beam generated by oscillator <NUM> is supplied to irradiator <NUM> through cable <NUM>. Irradiator <NUM> irradiates junction <NUM> with the laser beam for welding. Here, the laser beam is condensed and emitted by an optical system. Nozzle <NUM> is attached to a leading end of irradiator <NUM>. The laser beam is emitted to junction <NUM> from nozzle <NUM>. Also, irradiator <NUM> ejects shielding gas from nozzle <NUM> to junction <NUM> in order to prevent oxidization of junction <NUM>. Argon, helium, or nitrogen may be used as the shielding gas, for example.

As shown in <FIG>, nozzle <NUM> is shaped to be fitted in the corner formed at junction <NUM> of objects to be welded <NUM>. Here, "shaped to be fitted in" means a shape with which at least a portion of nozzle <NUM> comes into contact with the corner and nozzle <NUM> stops. The shape of nozzle <NUM> and the shape of the corner need only partially match and need not completely match. When junction <NUM> of objects to be welded <NUM> is formed by welding from the inside of the corner, nozzle <NUM> is shaped to be fitted in the inside of the corner. Also, in order to sufficiently supply the shielding gas to junction <NUM>, nozzle <NUM> preferably has a tapered shape. For example, the nozzle <NUM> may have a shape obtained by obliquely cutting a hollow tube relative to the bottom face.

Arm apparatus <NUM> holds irradiator <NUM> such that nozzle <NUM> can move to a position at which nozzle <NUM> is fitted in the corner of junction <NUM>, using an elastic force of coil spring <NUM> (an example of an elastic member). Arm apparatus <NUM> includes fixing unit <NUM>, arm <NUM>, and holder <NUM>. Fixing unit <NUM> is fixed to oscillator <NUM>. A clamp may be used as fixing unit <NUM>, for example. Arm <NUM> is for changing the position and angle of holder <NUM>. One end of arm <NUM> is connected to fixing unit <NUM>. The other end of arm <NUM> is connected to holder <NUM>. Arm <NUM> includes a plurality of joints that can rotate or move. The position or angle of holder <NUM> is changed by rotating or moving the joints of arm <NUM>. When the joints of arm <NUM> are fixed, the position or angle of holder <NUM> is maintained.

<FIG> is an enlarged view of irradiator <NUM> and arm apparatus <NUM>. <FIG> is an I-I cross-sectional view of arm apparatus <NUM> shown in <FIG> viewed in the direction indicated by the arrow in <FIG>. Holder <NUM> supports irradiator <NUM>, at a central portion thereof, so as to be movable in the Z-axis direction from the -Z-axis direction. Holder <NUM> includes plate-shaped base portion <NUM> and support member <NUM>. Base portion <NUM> extends in the -Z-axis direction viewed from irradiator <NUM>. As shown in <FIG>, support member <NUM> includes first portion 25A, second portion 25B, and third portion 25C. First portion 25A extends in the Z-axis direction. Second portion 25B extends in the -X-axis direction. Third portion 25C extends in the Z-axis direction. The end of first portion 25A in the Z-axis direction substantially perpendicularly meets the end of second portion 25B in the X-axis direction. The end of second portion 25B in the -X-axis direction substantially perpendicularly meets the end of third portion 25C in the -Z-axis direction. First portion 25A is fixed to an end portion of base portion <NUM> in the -Z-axis direction. Second portion 25B and third portion 25C forms an L shape. A space for housing the central portion of irradiator <NUM> is formed between base portion <NUM>, second portion 25B, and third portion 25C. This space is open in the Z-axis direction.

Also, holder <NUM> rotatably supports a rear end portion of irradiator <NUM>. As shown in <FIG>, in irradiator <NUM>, fixing member <NUM> that protrudes in the -Z-axis direction is fixed at a position between the position supported by support member <NUM> and a rear end. The protruding portion of fixing member <NUM> is rotatably attached to an end portion of base portion <NUM> in the -Z-axis direction by supporting point member <NUM>. That is, base portion <NUM> rotatably holds fixing member <NUM> by supporting point member <NUM>. A supporting point stepped screw may be used as supporting point member <NUM>, for example.

Furthermore, holder <NUM> and a leading end portion of irradiator <NUM> are connected via coil spring <NUM>. In irradiator <NUM>, fixing member <NUM> protruding in the -Z-axis direction is fixed at a position between the position supported by support member <NUM> and the leading end. The protruding portion of fixing member <NUM> and base portion <NUM> is connected by coil spring <NUM>. A biasing force acting toward junction <NUM> is applied to nozzle <NUM> by this coil spring <NUM>.

Returning to <FIG>, turntable <NUM> is for rotating objects to be welded <NUM> placed thereon. For example, when the welding direction is counterclockwise, turntable <NUM> rotates objects to be welded <NUM> in a clockwise direction.

Control apparatus <NUM> controls operations of laser welding machine <NUM> and turntable <NUM>. Control apparatus <NUM> is connected to laser welding machine <NUM> and turntable <NUM> through communication lines <NUM>. Foot pedal <NUM> is connected to control apparatus <NUM>. Foot pedal <NUM> is used to perform an operation to control the operations of laser welding machine <NUM> and turntable <NUM>. For example, when a worker steps on foot pedal <NUM>, control apparatus <NUM> causes turntable <NUM> to rotate, and causes irradiator <NUM> to emit laser beams. When the worker leaves the foot from foot pedal <NUM>, control apparatus <NUM> stops rotation of turntable <NUM>, and stops emission of laser beams. Starting or stopping emission of laser beams may be respectively performed in synchronization with starting or stopping of rotation of turntable <NUM>. These control may be realized by transmitting control signals, for example.

<FIG> is a flowchart illustrating an example of operations of laser welding system <NUM>. Here, an example in which objects to be welded 60A to 60C that are manufactured in the same size are successively welded will be described. In step S1, a worker places objects to be welded 60A on turntable <NUM>. In step S2, the positioning of the laser beam with respect to objects to be welded 60Ais performed. The positioning is performed using a known method such as a method of using a laser beam that is weaker than a normal laser beam, or a method of using a camera, for example. Upon completing the positioning of the laser beam, the worker changes the position and angle of irradiator <NUM> by moving arm <NUM> of arm apparatus <NUM>, for example, such that the laser beam is incident on junction <NUM>, and thereafter arm <NUM> is fixed. Accordingly, irradiator <NUM> is held at a position from which the laser beam is incident on junction <NUM>. Also, the position at which irradiator <NUM> is held is a position at which nozzle <NUM> comes into contact with junction 63A of objects to be welded 60A, and a position at which a biasing force toward junction 63A is applied to nozzle <NUM>. In step S3, when the worker steps on foot pedal <NUM>, turntable <NUM> rotates, and the laser beam is emitted from irradiator <NUM>. Accordingly, junction <NUM> of objects to be welded 60A is irradiated with the laser beam along a welding direction, and welding of junction <NUM> is started. In step S4, when turntable <NUM> has rotated once, the entire junction 63A of objects to be welded 60A in the circumferential direction has been irradiated with the laser beam along the welding direction, and the welding is ended. Upon ending the welding, the worker removes their foot from foot pedal <NUM>. Accordingly, turntable <NUM> is stopped and emission of the laser beam is also stopped. If next objects to be welded 60B are present (determination in step S5 is YES), in step S6, the worker places next objects to be welded 60B on turntable <NUM>.

<FIG> and <FIG> are diagrams illustrating an example of operations of arm apparatus <NUM>. As described above, there are cases where, although objects to be welded 60A and objects to be welded 60B are manufactured in the same size, an error occurs in the size due to causes such as a manufacturing error. In particular, because the laser beam is narrow, if there is an error in size between objects to be welded 60A and objects to be welded 60B, the position on which the laser beam is incident is shifted from junction <NUM>. If welding is performed without correcting the positional shift of the laser beam, junction <NUM> may not be sufficiently welded. In order to prevent such a welding failure, nozzle <NUM> of irradiator <NUM> moves according to the error between objects to be welded 60A and objects to be welded 60B.

In the example shown in <FIG>, the length in the Z-axis direction of flange 62B of objects to be welded 60B is larger than that of flange 62A of objects to be welded 60A. In this case, when objects to be welded 60A are replaced with objects to be welded 60B, nozzle <NUM> of irradiator <NUM> is brought upward in the Z-axis direction by the surface of flange 62B of objects to be welded 60B. Then, coil spring <NUM> extends and irradiator <NUM> rotates in the clockwise direction about supporting point member <NUM>, as shown in <FIG>. Accordingly, nozzle <NUM> of irradiator <NUM> moves in the Z-axis direction. Also, as described above, nozzle <NUM> of irradiator <NUM> is shaped so as to be fitted inside the corner formed at junction <NUM> of objects to be welded <NUM>. Therefore, when objects to be welded 60A are replaced with objects to be welded 60B, nozzle <NUM> of irradiator <NUM> stops at a position at which nozzle <NUM> is fitted inside the corner of junction 63B, as shown in <FIG>. The position at which nozzle <NUM> is fitted inside the corner of junction 63B is preset to the position at which the center of the laser beam is incident on junction <NUM>.

Returning to <FIG>, after step S6, the above-described operations in step S3 and onward are performed. Here, the above-described positioning of laser beam in step S2 may not be performed. After welding of objects to be welded 60B is ended in this way, if next objects to be welded 60C are present (determination in step S5 is YES), in step S6, the worker places next objects to be welded 60C on turntable <NUM>.

In the example shown in <FIG>, the length in the Z-axis direction of flange 62C of objects to be welded 60C is smaller than that of flange 62B of objects to be welded 60B. In this case, when objects to be welded 60B are replaced with objects to be welded 60C, the force to bring nozzle <NUM> of irradiator <NUM> upward in the Z-axis direction is lost. Then, as shown in <FIG>, coil spring <NUM> contracts, and irradiator <NUM> rotates in the counterclockwise directions about supporting point member <NUM>. Accordingly, nozzle <NUM> of irradiator <NUM> moves in the -Z-axis direction. Also, as described above, nozzle <NUM> of irradiator <NUM> is shaped so as to be fitted inside the corner formed at junction <NUM> of objects to be welded <NUM>. Therefore, when objects to be welded 60B are replaced with objects to be welded 60C, nozzle <NUM> of irradiator <NUM> stops at a position at which nozzle <NUM> is fitted inside the corner of junction 63C, as shown in <FIG>. The position at which nozzle <NUM> is fitted inside the corner of junction 63C is preset to the position at which the center of the laser beam is incident on junction <NUM>.

Also, when an error is present in the size of objects to be welded <NUM>, there are cases where the position of junction <NUM> shifts in the Z-axis direction or in the -Z-axis direction. For example, when there is an error in the length of flange <NUM> in the Z-axis direction, and the surface of flange <NUM> is not flat, the position of junction <NUM> shifts in the Z-axis direction or in the -Z-axis direction. In such a case as well, similarly to the case where objects to be welded <NUM> are replaced, nozzle <NUM> of irradiator <NUM> moves according to the error in size in objects to be welded <NUM>, and therefore the shift in position of the laser beam can be prevented in a period from when welding of objects to be welded <NUM> is started until the welding is ended.

According to the embodiment described above, even if an error in size is present in a plurality of objects to be welded <NUM> that are manufactured in the same size, when objects to be welded <NUM> are replaced, nozzle <NUM> of irradiator <NUM> moves to the position at which nozzle <NUM> is fitted inside the corner of junction <NUM> of objects to be welded <NUM>. Therefore, the shift in position of the laser beam relative to the junction <NUM> can be corrected without worker intervention. Also, positioning of the laser beam need not be performed with respect to individual objects to be welded <NUM>, and therefore the time and effort required of a worker are reduced, and the time it takes for the work is reduced. Also, a complex configuration is not needed, and therefore the shift in position of the laser beam relative to junction <NUM> can be corrected with a simple configuration. Furthermore, since nozzle <NUM> has a tapered shape, the shielding gas can be sufficiently supplied to junction <NUM>, and the oxidization of junction <NUM> can be prevented.

The present invention is not limited to the embodiment described above. Also, the embodiment described above may be implemented while incorporating modifications described in the following examples. Here, two or more modifications described below may be used in combination.

In the embodiment described above, objects to be welded <NUM> are not limited to tubular member <NUM> and flange <NUM> that are shown in <FIG>. Objects to be welded <NUM> may be members having any shapes. For example, objects to be welded <NUM> may also be two plate-shaped members. Also, when these plate-shaped members are welded along a straight line, a moving apparatus that moves objects to be welded <NUM> along the straight line may be used in place of turntable <NUM>. Furthermore, when first plate-shaped member <NUM> and second plate-shaped member <NUM> are joined by a butt joint, as shown in <FIG>, jig <NUM> may be provided on first plate-shaped member <NUM>. Jig <NUM> has a predetermined height and extends in a welding direction, for example. The side face of jig <NUM> and the surfaces of first plate-shaped member <NUM> and second plate-shaped member <NUM> form an L-shaped cross-sectional face. This L-shaped corner is formed in the vicinity of junction <NUM> between first plate-shaped member <NUM> and second plate-shaped member <NUM>. That is, this corner is formed at a position corresponding to junction <NUM>. The position at which nozzle <NUM> is fitted inside the corner corresponding to junction <NUM> is preset to the position at which the center of the laser beam is incident on junction <NUM>. According to this configuration, even in a case where first plate-shaped member <NUM> and second plate-shaped member <NUM> are joined by a butt joint, the shift in position of the laser beam can be corrected without worker intervention.

In the embodiment described above, the shape of nozzle <NUM> is not limited to the example described in the embodiment. The shape of nozzle <NUM> may be any shape as long as nozzle <NUM> can be fitted in the corner formed in junction <NUM> of objects to be welded <NUM>. For example, the shape of nozzle <NUM> may be a pointed shape, or may also be a round point shape. Also, when junction <NUM> is welded from the outside of the corner, the shape of nozzle <NUM> may be a shape such that nozzle <NUM> is fitted outside this corner. As shown in <FIG>, for example, when objects to be welded <NUM> are two plate-shaped members <NUM> that are joined by corner assembly, and fillet welding is performed from the outside of the corner formed at a position in the vicinity of junction <NUM>, that is, a position corresponding to junction <NUM>, the shape of nozzle 14A may be a shape having a cutout whose shape corresponds to the corner. The position at which nozzle <NUM> is fitted outside the corner corresponding to junction <NUM> is preset to the position at which the center of the laser beam is incident on junction <NUM>.

In the embodiment described above, objects to be welded <NUM> may be moved, arm apparatus <NUM> may be moved, or objects to be welded <NUM> and arm apparatus <NUM> may both be moved. That is, objects to be welded <NUM> and nozzle <NUM> for emitting a laser beam need only be moved relatively. When objects to be welded <NUM> are moved, the moving apparatus moves objects to be welded <NUM> in a direction opposite to the welding direction. On the other hand, when arm apparatus <NUM> is moved, the moving apparatus moves arm apparatus <NUM> in the welding direction. In short, the configuration need only be such that welding is performed along the welding part of objects to be welded <NUM> by relatively moving objects to be welded <NUM> and nozzle <NUM> for emitting a laser beam.

In the embodiment described above, an apparatus or a person that moves arm apparatus <NUM> is not limited to a worker. A robot may move arm apparatus <NUM> in place of a worker. In this case, the robot includes a processor, a memory, and a driving unit. A program is stored in the memory. The robot changes the position and angle of nozzle <NUM> of irradiator <NUM> by the driving unit moving arm apparatus <NUM> such that junction <NUM> is irradiated with a laser beam, where these hardware constituent elements and software constituent elements function together.

In the embodiment described above, nozzle <NUM> may be replaced according to the shape of the corner formed in junction <NUM> of objects to be welded <NUM>. In this case, a plurality of nozzles <NUM> whose shapes are different to each other are prepared in advance, and a worker may select nozzle <NUM> having a shape corresponding to the shape of the corner formed in junction <NUM> of objects to be welded <NUM> from these nozzles <NUM>, and attach nozzle <NUM> that has been selected to irradiator <NUM>. Also, a robot may perform this task in place of the worker. In this case, the robot includes a camera, a processor, a memory, and a driving unit. A program is stored in the memory. The robot may realize functional units such as a recognizing unit, a selecting unit, and an attaching unit by causing these hardware constituent elements and software constituent elements to function together. Specifically, the robot captures an image of junction <NUM> of objects to be welded <NUM> using the camera. The recognizing unit recognizes the shape of the corner formed in junction <NUM> from the captured image using an image recognition technique. The selecting unit selects nozzle <NUM> having a shape corresponding to the recognized shape. The attaching unit attaches nozzle <NUM> that has been selected to irradiator <NUM> by causing the driving unit to move arm apparatus <NUM>. According to this configuration, nozzle <NUM> suitable for welding of objects to be welded <NUM> can be attached to irradiator <NUM> without worker intervention.

In the embodiment described above, a means for applying a biasing force to nozzle <NUM> is not limited to coil spring <NUM>. A pressing means such as a spring other than coil spring <NUM>, a rubber, and an actuator, an electromagnetic means, a means using a pneumatic pressure, or a means utilizing dead weight may also be used as the means.

In the embodiment described above, the moving direction of nozzle <NUM> is not limited to the Z-axis direction. The moving direction of nozzle <NUM> may also be the X-axis direction or the Y-axis direction. That is, arm apparatus <NUM> may hold irradiator <NUM> such that nozzle <NUM> can move in at least one direction among the X-axis direction, the Y-axis direction, and the Z-axis direction. Accordingly, even if an error in the size of objects to be welded <NUM> occurs in any of the X-axis direction, the Y-axis direction, and the Z-axis direction, nozzle <NUM> moves according to the error.

Claim 1:
A laser welding system (<NUM>) comprising:
a laser welding unit (<NUM>) comprising a nozzle (<NUM>) for emitting a laser beam and configured to perform welding along a junction (<NUM>, <NUM>, <NUM>) of objects (<NUM>) to be welded, said junction (<NUM>, <NUM>, <NUM>) forming a corner, by relatively moving the objects (<NUM>) to be welded and the nozzle (<NUM>); and
a holding unit (<NUM>) configured to movably hold the nozzle (<NUM>) while applying a biasing force to the nozzle (<NUM>) in a direction toward the junction (<NUM>, <NUM>, <NUM>) such that the nozzle (<NUM>) comes into contact with the objects (<NUM>) to be welded to irradiate the junction (<NUM>, <NUM>, <NUM>) with the laser beam,
characterized in that the holding unit (<NUM>) rotatably holds a rear end portion of the laser welding unit (<NUM>), and a leading end portion of the laser welding unit (<NUM>) is connected to the holding unit (<NUM>) via an elastic member (<NUM>) that provides the biasing force to the nozzle (<NUM>).