Laser welding device and laser welding method

1. A laser welding device for welding a weld part with a laser light, the laser welding device comprising:

an irradiator configured to overlap the laser light and a measurement light coaxially with each other and apply the laser light and the measurement light to the weld part, a wavelength of the measurement light being different from a wavelength of the laser light;

a measuring instrument configured to repeatedly measure a weld penetration depth of the weld part based on the measurement light that is emitted from the irradiator and reflected on the weld part so as to generate a plurality of measured values;

a determiner configured to determine the weld penetration depth of the weld part based on: (i) one or more of the plurality of measured values; or (ii) an average value of the one or more of the plurality of measured values, the one or more of the plurality of measured values being included within a predetermined range with reference to a greatest side measured value of the plurality of measured values; and

an irradiation position changer configured to change: (i) an irradiation position of the measurement light such that the irradiation position of the measurement light moves on a predetermined welding path; and (ii) an opticla axis position as the irradiation position of the measurement light such that the optical axis position moves within a region of the weld part having a radius of rotation that is smaller than half of a spot diameter of the laser light,

wherein the measuring instrument is configured to generate the plurality of measured values while the measurement light is being moved.

2. The laser welding device according to claim 1 , wherein:

the irradiation position changer is configured to change the irradiation position of the measurement light such that the irradiation position of the measurement light moves orbitally around a center of rotation that moves on the predetermined welding path; and

the determiner is configured to determine the weld penetration depth of the weld part based on the one or more of the plurality of measured values obtained at a position rearward in a welding direction relative to an irradiation position of the laser light while the measurement light is being moved orbitally.

3. The laser welding device according to claim 1 , wherein the measuring instrument is configured to: (i) set a measurement interval to be a predetermined fixed time period; (ii) maintain the measurement interval when performing multiple measurements, and (iii) generate the plurality of measured values while shifting a measurement starting point of the measurement interval such that the measurement intervals overlap with each other.

4. The laser welding device according to claim 1 , wherein the measuring instrument is configured to: (i) set a measurement interval to be a predetermined fixed time period; and (ii) generate the plurality of measured values within the measurement interval.

5. The laser welding device according to claim 3 , wherein the predetermined range is from equal to or greater than an eightieth percentile of the greatest side measured value to equal to or less than a ninety-ninth percentile of the greatest side measured value.

6. The laser welding device according to claim 4 , wherein the predetermined range is from equal to or greater than an eightieth percentile of the greatest side measured value to equal to or less than a ninety-ninth percentile of the greatest side measured value.

7. The laser welding device according to claim 3 , wherein the predetermined range is from equal to or greater than a ninety-third percentile of the greatest side measured value to equal to or less than a ninety-seventh percentile of the greatest side measured value.

8. The laser welding device according to claim 4 , wherein the predetermined range is from equal to or greater than a ninety-third percentile of the greatest side measured value to equal to or less than a ninety-seventh percentile of the greatest side measured value.