JPH11320146A - Laser welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unevenness of penetration depth when welding is carried out while a work and a laser welding machine are relatively moved. SOLUTION: When a laser welding machine is moved to a work for carrying out laser welding along a circular weld line, the laser output is varied synchronizing with the moving speed at a portion where the delay of response for the moving speed command exists at the time of start of welding or completion of moving, so as to even the penetration depth of welding. Thereby, welding strength, durability and the like can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding method for welding a joint surface of a fitting to be fitted to a shaft, for example.

[0002]

2. Description of the Related Art Conventionally, for example, when a fitting having a circular fitting hole fitted into a shaft is welded to the shaft, the periphery of the hole is sometimes fixed by welding with a laser welding machine. . At this time, welding is performed by irradiating a laser beam with a predetermined output while moving the laser welding machine at a constant speed by, for example, NC control.

[0003]

However, in the above-described welding method, as shown in FIG. 5, after the movement command is issued to the laser welding machine by the NC control, the rising time until a predetermined feed speed is reached. Although there is a response delay between the time and the time from when the stop command is issued until the speed becomes zero, there is almost no response time of the beam irradiation to the laser beam output command, and therefore, FIG. As shown,
The penetration depth in laser welding has a problem that the welding start point and the welding end point become deeper. Particularly when welding a closed curve, as shown in FIG. Especially deep.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for welding a workpiece along a welding line while relatively moving the workpiece and a laser welding machine at a constant speed. In the method, when the relative movement speed between the laser welding machine and the workpiece changes, the laser output is changed in synchronization with the change in the movement speed, and the penetration depth of the welding line is controlled to be constant.

As described above, if the laser output is changed in accordance with the relative moving speed of the work and the laser welding machine, for example, if the relative moving speed is reduced, the laser output is reduced in accordance with the relative moving speed. The depth can be increased, and the welding strength, durability and the like can be improved.
Here, the relative movement between the work and the laser welding machine may be either when the position of the work is fixed and the laser welding machine is moved, or when the position of the laser welding machine is fixed and the work is moved. Further, the welding line may be either a straight line or a curved line. Further, when the relative moving speed changes, the relative moving speed is determined not only at the start and end of welding, but also at the corner of the welding line. It can be applied to the case where it changes.

The present invention is particularly effective when the welding line has a closed curve and the welding start position and the welding end position overlap. When making a welding line a closed curve in this way, a constant welding strength is often required in all circumferential directions, and if welding is performed at a uniform penetration depth from the welding start position to the welding end position, the load from which direction , It is possible to compete with more uniform strength and durability.

[0007]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an explanatory view of a welding method according to the present invention. The horizontal axis is time, the vertical axis is laser output and relative moving speed, FIG. 2 is an explanatory view of the penetration depth from the start to the end of welding, and FIG. Explanatory diagram in the case of a circle,
FIG. 4 is an explanatory diagram of the penetration depth when the welding start position and the end position of the circular welding line overlap.

In the laser welding method according to the present invention, when welding along a welding line while relatively moving a work and a laser welding machine, as shown in FIG. 1, the relative movement between the work and the laser welding machine is not constant. By changing the laser output in accordance with the relative movement speed in the response delay portion of the relative movement speed at the start of rising and the response delay portion of the relative movement speed at the time of the stop command of the welding end, as shown in FIG. The feature is that the penetration of laser welding from the start of welding to the end of welding is made constant.

That is, while the laser output of the laser welding machine has almost no delay with respect to the output command, for example, the motor rotation speed for driving the laser welding machine by NC control is as follows.
If there is a delay with respect to the command and the laser output command and the motor drive command are issued at the same time, the amount of laser irradiation increases at the start of welding, and the penetration becomes deep and non-uniform. When a laser output command is issued at the same time as the relative movement is stopped,
Even at the end of welding, the amount of laser irradiation increases, so that the penetration becomes deep and non-uniform. As a result, the penetration becomes uneven at the welding start position and the welding end position, and it becomes difficult to keep the laser welding penetration from the welding start to the welding end constant.

On the other hand, there is also a method in which a motor drive command is issued slightly earlier than the laser output command, a laser output command is issued from a state where the moving speed is stable, and a laser output stop command is issued simultaneously with the movement stop command. It is conceivable that in this case, the penetration depth can be kept constant, but unnecessarily moving time is generated before and after the start of welding, which is not preferable.

Therefore, in the present invention, the laser output is changed in synchronization with the number of rotations of the motor for driving the laser welding machine. It is suitable when the welding start position and the welding end position overlap with each other in a closed curve such as. In other words, in the case of such a circular welding line, the load is often evenly applied over the entire circumference, and in such a case, if the welding method of the present invention is applied, the welding start and the welding end overlap. The penetration depth of the portion and other portions can be made constant as shown in FIG.

In the above embodiment, the case where the moving speed at the start of welding and the moving speed at the end of welding are described as an example. In addition, the moving speed is changed when the welding line passes through a corner. It can be applied even when it changes. Also, the present invention can be applied to a case where the work does not move but the laser welding machine moves, and both cases may move.

The laser welding machine according to the present invention includes:
A gas laser welding machine such as a carbon dioxide laser or an argon laser may be used, or a solid laser such as a YAG laser or a ruby laser may be used.

[0014]

As described above, in the laser welding method according to the present invention, the relative movement speed between the laser welding machine and the workpiece is determined when the laser welding is performed along the welding line while the workpiece and the laser welding machine are relatively moved at a constant speed. When a change occurs in the welding speed, the laser output is changed in synchronization with the change in the moving speed, and the penetration depth of the welding line is controlled to be constant. , Durability and the like can be improved. Further, it is more effective if applied when the welding line is a closed curve and the welding start position and the welding end position overlap.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a welding method according to the present invention, wherein the horizontal axis represents time,
The vertical axis is the laser output and relative moving speed

FIG. 2 is an explanatory diagram of a penetration depth from the start to the end of welding.

FIG. 3 is an explanatory diagram when a welding line is circular.

FIG. 4 is an explanatory diagram of a penetration depth when a welding start position and an end position of a circular welding line overlap with each other.

FIG. 5 is an explanatory view of a conventional welding method, in which the horizontal axis represents time, and the vertical axis represents laser output and relative moving speed.

FIG. 6 is an explanatory view of a conventional penetration depth.

FIG. 7 is an explanatory diagram of a penetration depth when a conventional welding start position and an end position overlap each other.

Claims (2)

[Claims] 1. A welding method for performing laser welding along a welding line while relatively moving a work and a laser welding machine at a constant speed when welding the work, the relative movement between the laser welding machine and the work. A laser welding method characterized by changing a laser output in synchronism with a change in a moving speed at a time when a speed changes, thereby controlling a penetration depth of a welding line to be constant. 2. The laser welding method according to claim 1, wherein the welding line has a closed curve, and a welding start position and a welding end position overlap each other.