JP2023012059A - Laser beam machining apparatus - Google Patents

Abstract

To provide a laser beam machining apparatus which performs groove machining onto a steel plate.SOLUTION: A laser beam machining apparatus 1 which scans the surface of a steel plate ES with laser beam LB and, thereby, forms a line-shaped groove part or a line-shaped strain part on the steel plate ES includes a laser beam emission part, a scanning mirror Mp, minor axis condensing mirror ML which condenses beam in the direction of a first axis corresponding to short axis of a beam spot and a focus position adjusting mirror Ms which radiates onto the surface of the steel plate ES. Therein, the scanning mirror Mp scans the surface of the steel plate ES with laser beam LB and the focus position adjusting mirror Ms has a curvature which condenses the laser beam LB to a point on the surface of the steel plate at which a condensed light focal distance that is a distance provided by subtracting a distance between a point at which the laser beam LB is reflected on the minor axis condensing mirror ML and a point at which the laser beam LB is reflected on the focus position adjusting mirror Ms from the focal distance of the minor condensing mirror ML is equal to a distance from a point at which the laser beam LB is reflected on the focus position adjusting mirror Ms.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laser processing apparatus.

An electromagnetic steel sheet, which is a type of steel sheet, is passed along a conveying line at high speed, and a high-power laser beam is irradiated onto the surface of the electromagnetic steel sheet to scan it linearly in a direction almost perpendicular to the sheet threading direction. Therefore, a so-called magnetic domain control process has been put into practical use, in which linear grooves and strains are formed at regular intervals to reduce the core loss of the electrical steel sheet.
Magnetic steel sheets that have undergone the magnetic domain control process are used as materials for iron cores of transformers, etc., and contribute to the improvement of power loss. In particular, the magnetic domain control material in which linear grooves are formed by laser has the characteristic that the magnetic domain control effect is maintained even after the heat treatment in the wound core manufacturing process.
However, since the magnetic steel sheet is bent in the manufacturing process of the wound iron core, if the direction of the bending line during bending matches the direction of the linear grooves, the stress concentrates on the linear grooves. , the electromagnetic steel sheet may break.
The direction of the bending line when bending the electromagnetic steel sheet, that is, the bending direction is generally the width direction of the electromagnetic steel sheet. Adjustment is desirable. For example, it is considered desirable to incline the direction of the linear grooves by about 10° from the sheet width direction.

For example, in Patent Documents 1, 3, and 4 below, when a steel plate is transported along the peripheral surface of a steel plate support roll and irradiated with a laser beam, the irradiation position of the laser beam at the vertex of the steel plate support roll in contact with the steel plate is a reference point, and a laser beam is irradiated in a range separated from this reference point along the outer peripheral surface of the steel sheet support roll by 3 to 7 degrees in the sheet passing direction. In addition, the techniques described in these patent documents employ a method in which the scanning direction of the laser beam is tilted by about 4° from the plate width direction at a position moved 3 to 7° in the rotational direction from the vertex of the steel plate support roll. .
Further, in Patent Document 2, when conveying a steel plate along the peripheral surface of a steel plate support roll and irradiating a laser beam along the width direction of the steel plate, the change in the focal length of the laser beam along the width direction of the steel plate A technique for changing the inclination of the steel plate support roll is disclosed.

Japanese Patent No. 6826603 Japanese Patent No. 6826604 Japanese Patent No. 6826605 Japanese Patent No. 6826606

If the steel plate support roll is tilted as described in Patent Document 2, the balance of tension in the width direction of the plate is lost, so the steel plate tends to meander, and in the worst case, the steel plate may break. Further, the steel plate support roll is a heavy object, and there is a problem that a large and highly accurate actuator is required to precisely control the inclination of the steel plate support roll.

By the way, high-speed grooving on a steel plate surface using a laser beam requires a high laser power density. It is necessary to irradiate the surface of the steel plate and scan it. In general, an f-theta lens or a parabolic mirror is used as a laser focusing element, but when a high-output laser is applied to a lens that is a transmission element, even a small amount of heat generated by absorption or contamination of the lens causes changes in the refractive index and thermal expansion. occurs, resulting in a problem of degraded light-gathering performance. It is said that the deterioration of the light-gathering performance of the lens is due to the thermal lens effect. There's a problem.
On the other hand, the collecting mirror can be easily cooled by using a metal element, and the deterioration of the light collecting property is small, which is convenient for the above purpose. In addition, to meet the demand for condensing light into a small beam spot diameter, it is necessary to use a condensing element with a short focal length. On the other hand, the allowable fluctuation width may be ±0.5 mm or less.

In the steel sheet manufacturing process, the steel sheet is threaded at high speed, in which case the steel sheet is threaded over a plurality of rotating support rolls. At this time, the steel plate vibrates between the support rolls due to factors such as changes in the tension of the steel plate and changes in the strength of the steel plate. occurs, resulting in deterioration of workability.
Methods for suppressing the vibration of the steel plate include, for example, adjusting the parallelism of the support rolls, the spacing, the tension between the rolls, etc. By using such methods, it is possible to suppress the vibration to some extent. However, it is difficult to sufficiently adjust all of these, and there is a limit to suppressing vibration.

Another method of suppressing vibration is to force the steel plate through the support rolls (that is, to apply tension to the steel plate so that the steel plate is pressed against the support roll so as to be in close contact with the apex of the support roll. A method of irradiating the steel sheet with a laser beam at a position where the steel sheet passes over the support rolls is conceivable. In this method, since the steel plate follows the curved surface of the apex portion of the roll surface, the steel plate hardly vibrates. However, since the rotation axis direction of the support rolls coincides with the width direction of the steel sheet, it is necessary to set a constant angle between the scanning direction of the laser beam and the width direction of the steel sheet, as described above. In this case, due to the influence of the curved surface of the support roll, the distance from the condensing element to the steel plate changes from the center position on the scanning path toward the end position on the scanning path. Even if the laser beam is focused at the position, there is a problem that the defocus of the laser beam becomes large on the end side of the laser beam scanning line, degrading the workability.

The present invention has been devised in view of the above-mentioned problems. An object of the present invention is to provide a laser processing apparatus capable of forming a linear groove portion or a linear distorted portion having a stable width and depth in a steel plate while suppressing defocus as much as possible.

In order to solve the above problems, according to one aspect of the present invention, the surface of a steel sheet that is passed while being biased by support rolls is scanned with a laser beam having a circular or elliptical beam spot diameter. A laser processing apparatus for forming a linear groove portion or a linear distorted portion in the steel plate, comprising a laser beam emitting portion for emitting a laser beam, a scanning mirror for reflecting the laser beam, and the scanning mirror a short-axis condensing mirror that reflects the reflected laser beam and converges in a direction of a first axis corresponding to the minor axis of the beam spot diameter; and a focus position adjusting mirror for irradiating the surface of the steel plate, wherein the scanning mirror changes the direction in which the laser beam is reflected, and changes the position at which the laser beam is irradiated on the surface of the steel plate. Thus, the surface of the steel plate is scanned with the laser beam, and the focal position adjusting mirror shifts the laser beam from the focal length of the short-axis condensing mirror so that the laser beam is reflected by the short-axis condensing mirror. The focal length, which is the distance obtained by subtracting the distance between the point where the laser beam is reflected by the focus adjustment mirror and the point where the laser beam is reflected by the focus adjustment mirror, and the distance from the point where the laser beam is reflected by the focus adjustment mirror A laser processing apparatus is provided that has a curvature that focuses light to a point on the surface of the steel sheet that is equal to the distance.

Further, in the laser processing apparatus, a long-axis condensing mirror (Mc) that reflects the laser beam emitted from the laser beam emitting unit and converges the light in a direction of a second axis corresponding to the long axis of the beam spot. , and the scanning mirror (Mp) can adopt a configuration in which the laser beam reflected by the long-axis collecting mirror (Mc) is reflected.

Further, in the laser processing apparatus, the focusing position adjusting mirror (Ms ) can adopt the configuration represented by the following equations (1) to (3).
(S ₂ , Z ₂ ) are the coordinates on the plane (SZ plane) perpendicular to the first axis of the point (A2′) where the laser beam is reflected by the focus position adjusting mirror (Ms). can be,
(S ₄ , Z ₄ ) is the surface of the steel plate where the condensing focal length (G3′) is equal to the distance from the point (A2′) where the laser beam is reflected by the focus position adjusting mirror (Ms). coordinates of a point on a plane perpendicular to the first axis;
α1 is an angle of incidence when the laser beam is incident on the focus position adjusting mirror (Ms) on a plane perpendicular to the first axis;
β is an angle of incidence when the laser beam is incident on the focus position adjusting mirror (Ms) on a plane perpendicular to the second axis;
θso is a reflection angle when the laser beam is reflected by a plane mirror (M0) having no curvature at the position of the focus position adjusting mirror (Ms) on a plane perpendicular to the first axis,
θ's is a reflection angle when the laser beam is reflected by the focus position adjusting mirror (Ms) on a plane perpendicular to the first axis.

Moreover, in the laser processing apparatus, it is preferable that the reflection surface of the short-axis condensing mirror (ML) is a linear paraboloid.
Moreover, in the laser processing apparatus, the scanning mirror (Mp) is preferably a rotating polygon mirror or a galvanomirror.

According to the present invention, it is possible to form a linear groove portion or a linear distorted portion by scanning a steel sheet that is forced by a support roll while being focused with a laser beam, thereby stably forming the linear groove portion or the linear distorted portion. It is possible to form linear grooves or linear distorted portions.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the processing system provided with the laser processing apparatus which concerns on embodiment of this invention. It shows the irradiation position relationship of the support roll and the laser beam provided in the processing system shown in FIG. 1, FIG. FIG. 2(C) is a side view showing the relationship between the side surface and the irradiation position, and FIG. 2(C) is an enlarged view of the laser beam irradiation portion near the top of the support roll. The relationship between the steel plate surface position and the laser beam irradiation position in the processing system of the reference example is shown. FIG. FIG. 3(B) is an enlarged view of the laser beam irradiated portion of the steel plate near the top of the support roll. FIG. 4A shows the relationship between the steel plate surface position and the laser beam irradiation position in the processing system according to the first embodiment of the present invention. FIG. 4B is an enlarged view of a laser beam irradiated portion of the steel plate near the top of the support roll. When the angle of reflection (θs) of the laser beam irradiated by the polygon mirror of the first embodiment is 10°, the coordinates of the intersection of the focal position of the laser beam and the surface of the steel sheet on the coordinate plane including the scanning direction of the laser beam are It is a graph which shows the calculated|required result. FIG. 6A shows the angle of reflection on the second mirror, and FIG. 6A is an explanatory diagram showing the case of changing the virtual angle of reflection _θs0 to the effective angle of reflection θs′ on the special reflection curved surface of the second mirror, and FIG. is an explanatory diagram showing a case where the virtual angle of reflection θs ₀ is changed to the effective angle of reflection θs′ in the optical path of the laser beam from the second mirror to the surface of the steel plate on the support roll. Under the conditions shown in Table 1, when the virtual reflection angle θs ₀ on the special reflection curved surface of the second mirror is changed from 0 to 20°, the inclination angle α ₁ of the normal to the special reflection curved surface with respect to the Z axis and the It is a graph which shows the relationship with a position. FIG. 5 is an explanatory diagram showing the reflection angle of a laser beam reflected from a second mirror when a laser beam with an incident angle β is incident on the second mirror from the first mirror; FIG. 4 is a perspective view showing an example of a galvanomirror applicable as a scanning mirror;

Preferred embodiments of the present invention will be described below with reference to the drawings.
In the drawings used in the following description, in order to make the features easier to understand, there are cases where the features are emphasized, such as by enlarging them for the sake of convenience.

First, an outline of a grain-oriented electrical steel sheet, which is an object to be processed in this embodiment, will be described.
<Overview of grain-oriented electrical steel sheet>
A typical grain oriented electrical steel sheet is an electrical steel sheet in which the axis of easy magnetization (the <100> direction of a body-centered cubic crystal) of the grains of the steel sheet is substantially aligned in the rolling direction of the steel sheet. A grain-oriented electrical steel sheet has a structure in which a plurality of magnetic domains having magnetic poles oriented in the rolling direction are arranged with domain walls interposed therebetween. Since such a grain-oriented electrical steel sheet is easily magnetized in the rolling direction, it is suitable as a material for the iron core of a transformer in which the magnetic lines of force flow in a substantially constant direction.

Transformers are generally classified into stacked transformers and wound transformers. The grain-oriented electrical steel sheet is suitable as a material for the iron core of a wound transformer manufactured by winding steel sheets in multiple layers and then forming the iron core into a shape (for example, a quadrangular prism shape having a hollow portion). used.
A grain-oriented electrical steel sheet has, for example, a steel sheet body (base iron), glass coatings formed on both front and back surfaces of the steel sheet body, and insulating coatings formed on the glass coating. The steel plate body is made of, for example, an iron alloy containing Si.

In grain-oriented electrical steel sheets, in order to reduce iron loss (that is, for magnetic domain control), the surface of the steel sheet is irradiated with a laser beam, and the rolling direction of the steel sheet (that is, the conveying direction during manufacture, the length of the steel sheet, By scanning in the direction intersecting the rolling direction of the steel sheet, linear grooves or linear distorted portions extending in the direction intersecting with the rolling direction of the steel sheet are formed. A plurality of these grooves or distorted portions are formed on the surface of the grain-oriented electrical steel sheet at predetermined intervals in the rolling direction.
In this embodiment, in order to control the magnetic domain of the grain-oriented electrical steel sheet, the surface of the grain-oriented electrical steel sheet is linearly scanned and irradiated with a laser beam to form linear grooves or linear strained portions at regular intervals. will be explained. In the following description, the grain-oriented electrical steel sheet may be simply described as a steel sheet.

FIG. 1 is a schematic diagram of a processing system provided with a laser processing device 1 according to one embodiment of the present invention.
In this embodiment, the laser processing apparatus 1 has a laser beam emitting part LL, a long-axis collecting mirror Mc, a plane mirror MF, a scanning mirror Mp, a short-axis collecting mirror ML, and a focus position adjusting mirror Ms.
The laser processing apparatus 1 scans the surface of the steel sheet ES, which is passed while being biased by support rolls, with a laser beam LB having a circular or elliptical beam spot diameter, thereby forming linear grooves in the steel sheet ES. Alternatively, it is a device for forming a linear distorted portion.
That is, the laser processing apparatus 1 irradiates the surface of the electromagnetic steel sheet with a laser beam LB and scans the surface of the electromagnetic steel sheet with the laser beam LB in a direction that intersects the rolling direction of the electromagnetic steel sheet, for example, in order to control the magnetic domain of the electromagnetic steel sheet. , a linear groove can be formed on the surface of the electromagnetic steel sheet, or a linear strained portion can be formed on the surface of the electromagnetic steel sheet.
The laser beam emitting unit LL includes a known laser light source LM, a transmission fiber 4, and an emitter 7. The laser light source LM oscillates and outputs a laser beam LB, and the output laser beam LB is , and transmitted through a transmission fiber 4 composed of an optical fiber or the like, and emitted from an emitter 7 into the atmosphere. The laser beam LB emitted from the laser emitting portion LL is irradiated toward a long-axis condensing mirror Mc, which will be described later.

For the laser light source LM, it is preferable to use a fiber laser or a disk laser excellent in fine light-gathering characteristics from the viewpoint of forming a narrow groove. can be selected, and for example, a continuous wave laser or a pulse laser may be used. The wavelength of the fiber laser or disk laser is in the near-ultraviolet region to the near-infrared region (for example, 1 μm band), and the laser beam LB can be transmitted with high efficiency through an optical fiber. 4, the laser processing apparatus 1 can be realized with a relatively compact configuration.

The laser beam LB has high energy, and by irradiating the steel plate, it can scatter the steel plate to form a groove portion or apply thermal strain to the steel plate to form a distorted portion. The laser beam LB already has a circular or elliptical beam spot at the time it is emitted from the emitter 7 into the atmosphere, and has various mirrors (long-axis condensing mirror Mc, plane mirror, etc.) described later. MF, scanning mirror Mp, short-axis condensing mirror ML, focus position adjusting mirror Ms, etc.), the light is irradiated onto the steel plate ES. It has a perfect circular or elliptical beam spot, although the size and shape are often different from those at the point in time.
Therefore, when the shape of the beam spot just before hitting the steel plate ES is elliptical, the directions of the minor axis and the major axis that intersect perpendicularly through the center can be defined. Then, the laser processing apparatus 1 in the present embodiment scans the laser beam LB in the direction of the long axis of the shape of the beam spot just before the laser beam LB hits the steel plate ES.

On the other hand, when the shape of the beam spot just before hitting the steel plate ES is a perfect circle, there is no distinction between short and long for each axis. be able to. Then, the laser processing apparatus 1 in the present embodiment scans the laser beam LB in the direction of the long axis of the shape of the beam spot just before the laser beam LB hits the steel plate ES.

Thus, the direction in which the laser processing apparatus 1 scans the laser beam LB is the direction corresponding to the major axis direction of the beam spot (irrespective of whether the beam spot is circular or elliptical). The direction corresponding to the long axis direction of the beam spot is called the second axis, and the direction corresponding to the short axis direction of the beam spot orthogonal to the second axis is called the first axis.
A direction parallel to the second axis is referred to as the S direction, and a straight line passing through the surface of the steel plate ES at the top portion of the support roll SR and parallel to the second axis (that is, parallel to the S direction) is referred to as the S axis.
The laser processing apparatus 1 can be set so that the scanning direction of the laser beam LB is the S direction by a rotation adjustment device (not shown).

The steel sheet ES is an electromagnetic steel sheet to be axially controlled, is cold-rolled into a belt shape, and is passed while being biased by the support rolls SR constituting a part of the conveying device. That is, the steel plate ES receives tension from the conveying device, and is pressed so as to be in close contact with the upper surface of the support roll SR in the vicinity of the vertex of the curved surface formed by the support roll SR. It is bent in a mountain shape and threaded. Therefore, since the steel plate ES is restrained near the vertex of the support roll SR, the steel plate ES is less likely to vibrate.

As an example, FIG. 1 depicts a state in which a steel plate ES is being passed along the upper surface side of a support roll SR while being curved into a mountain shape having a gentle slope.
In this embodiment, the surface of the steel plate ES near the vertex of the support roll SR is irradiated with a laser beam LB through various mirrors while being focused to a minute elliptical beam spot BS of several tens of μm level. By scanning the LB in the direction of the second axis, linear grooves or linear strained portions are formed on the surface of the steel plate ES. Although the beam spot diameter is about several tens of μm, the beam spot BS is enlarged and displayed in FIG. 1 for illustration.

In the embodiment shown in FIG. 1, the support rolls SR are installed so that their rotation axes are horizontal, and the strip-shaped steel sheet ES is threaded with its rolling direction perpendicular to the direction of the rotation axes of the support rolls SR. be done. The steel plate ES is threaded with its width direction aligned with the direction of the rotation axis of the support roll SR.
As shown in FIG. 1, in the present invention, for the sake of convenience, the width direction of the steel sheet ES positioned at the vertex of the support roll SR is defined as the X direction. The direction along the longitudinal direction is defined as the Y direction. Further, the direction of a straight line perpendicular to the X direction and the Y direction and connecting the center of the reflection position of the focus position adjusting mirror Ms, which will be described later, and the steel plate ES positioned at the vertex of the support roll SR is defined as the Z direction. Therefore, when the support roll SR is arranged so that the rotation axis is horizontal, and the laser beam LB is vertically irradiated from the focal position adjusting mirror Ms toward the steel plate ES, the Z direction is high. It means the horizontal direction (vertical direction).

The long-axis condensing mirror Mc reflects the laser beam LB emitted from the laser beam emitting part LL, and condenses the light in the direction of the second axis corresponding to the long axis of the beam spot immediately before the steel plate ES is irradiated. is. Thus, the component of the laser beam LB in the direction of the second axis is focused at a point equidistant from the long axis collector mirror Mc (regardless of the presence of mirrors in the optical path). The laser beam LB reflected by the long-axis condensing mirror Mc travels toward a plane mirror MF, which will be described later.
The plane mirror MF is a mirror that reflects the laser beam LB reflected by the long-axis focusing mirror Mc and changes the traveling direction of the laser beam LB. The plane mirror MF may not have the function of condensing the laser beam LB. The laser beam LB reflected by the plane mirror MF travels toward a scanning mirror Mp, which will be described later.

The scanning mirror Mp is a mirror that reflects the laser beam LB reflected by the plane mirror MF. But also. The scanning mirror Mp has the function of scanning the surface of the steel plate with the laser beam LB by changing the direction of reflection of the laser beam LB and changing the position at which the surface of the steel plate ES is irradiated with the laser beam LB. ing.
Therefore, more specifically, the scanning mirror Mp is realized by a polygon mirror, a galvanometer mirror, or the like, and the polygon mirror is rotated or the angle of the galvanometer mirror is changed moment by moment in accordance with the irradiation of the laser beam LB. , the direction in which the laser beam LB is irradiated is changed. The laser beam LB reflected by the scanning mirror Mp travels to a short-axis collecting mirror ML, which will be described later.

The short-axis condensing mirror ML is a mirror that reflects the laser beam LB reflected by the scanning mirror Mp and converges the light in the direction of the first axis corresponding to the short axis of the beam spot immediately before the steel plate ES is irradiated. Thus, the component of the laser beam LB in the direction of the first axis is focused at a point equidistant from the short axis collector mirror ML (regardless of the presence of mirrors in the optical path). The laser beam LB reflected by the short-axis condensing mirror ML travels toward a focal position adjusting mirror Ms, which will be described later.
The focus position adjusting mirror Ms is a mirror that reflects the laser beam LB reflected by the short-axis condensing mirror ML and irradiates the surface of the steel plate ES. The direction in which the laser beam LB is reflected by the scanning mirror Mp changes with time, and the focus position adjusting mirror Ms reflects the laser beam LB, whose incident position has changed, toward the steel plate ES. , the position of the surface of the steel plate ES irradiated with the laser beam LB changes with time. As a result, the surface of the steel plate ES can be scanned with the laser beam LB.

The focal position adjusting mirror Ms adjusts the focal position of the laser beam LB from the focal length F_0 of the short-axis condensing mirror ML to the point (A1′) where the laser beam LB is reflected by the short-axis condensing mirror ML. The focal length (G3'), which is the distance obtained by subtracting the distance between the point (A2') reflected by the mirror Ms, and the point (A2') where the laser beam LB is reflected by the focus position adjustment mirror Ms. ) has a curvature that focuses the light to a point on the surface of the steel plate that is equal to the distance from (see FIG. 4).

When the laser beam LB is used to form a linear groove portion or a linear distorted portion, it is necessary to condense the laser beam LB in order to increase the energy density of the laser beam LB. Affects the workability of grooves or linear strained parts.
Therefore, on the surface of the steel plate ES, it is necessary to condense the light in the first axis direction. The light is condensed at a point on the projection line of the linear groove or linear strained portion (support roll SR point on the S-axis passing through the surface of the steel plate ES located at the vertex of ), and is out of the surface of the steel plate ES conveyed in a curved manner, and cannot be focused on the surface of the steel plate ES.
Therefore, by using the focus position adjusting mirror Ms, the direction of the laser beam LB can be changed to match the focal point, which is off the surface of the steel plate ES, with the position on the steel plate. As a result, it becomes possible to stably form a linear groove portion or a linear distorted portion.

Next, with reference to FIG. 1, the relationship between the components of the laser processing apparatus 1 in this embodiment, the movement of the laser beam LB, and the like will be described.
In the embodiment shown in FIG. 1, a case is shown in which a polygon mirror is used as an example of the scanning mirror Mp. placed above the department.
As shown in FIG. 1, the polygon mirror is in the shape of a flat, regular polygonal prism which is a regular polygonal shape when viewed from the direction of the rotating shaft 2 . The polygon mirror has a horizontally extending rotation axis 2 and rotates around the rotation axis 2 .
The outer peripheral surface of the polygon mirror is formed by a plurality of rectangular reflecting surfaces 3 (each forming a regular polygonal surface of the polygon mirror) and corners 5 formed by these reflecting surfaces 3 . Each reflecting surface 3 is a planar surface with a mirror attached. Assuming that the number of reflecting surfaces 3 (the number of corners 5) is N, the polygon mirror has a regular N prism shape. In the embodiment shown in FIG. 1, the polygon mirror has a regular dodecagonal prism shape, and N (the number of reflecting surfaces 3) is twelve.
By rotating the polygon mirror around the rotation axis 2, a specific reflecting surface 3 out of the 12 reflecting surfaces 3 can be made to face the plane mirror MF and the short-axis collecting mirror ML in order.

In this embodiment, a long-axis condensing mirror Mc and a plane mirror MF are installed so as to be vertically positioned on the left front side (-X direction side) of the polygon mirror shown in FIG. The long-axis condensing mirror Mc is arranged obliquely downward with its reflecting surface 6 facing the polygon mirror, and the plane mirror MF is arranged obliquely upward with its reflecting surface 8 facing the side surface of the polygon mirror. .

As shown in FIG. 1, the emitter 7 of the laser beam emitting part LL is arranged laterally on the front side with respect to the reflecting surface 6 of the long axis condenser mirror Mc.

The laser beam LB is emitted from the emitter 7 of the laser beam emitting portion LL and reflected by the reflecting surface 6 of the long-axis collecting mirror Mc. The laser beam LB reflected downward by the reflecting surface 6 of the long-axis focusing mirror Mc is incident on the reflecting surface 8 of the lower plane mirror MF. The laser beam LB incident on the reflecting surface 8 of the plane mirror MF is reflected again and is incident on one of the twelve reflecting surfaces 3 of the polygon mirror Mp.
The arrangement of the long-axis light-collecting mirror Mc and the plane mirror MF is not limited to the example shown in FIG. can be For example, the long-axis focusing mirror Mc and the plane mirror MF may be arranged in the left-right direction, or may be arranged in the oblique up-down direction or in the oblique left-right direction.

When the reflecting surface 3 of the polygon mirror receives the laser beam LB, it reflects the laser beam LB toward the reflecting surface 9 of the short-axis collecting mirror ML installed obliquely below the polygon mirror.
As shown in FIG. 1, the focal position adjusting mirror Ms is installed near and to the left of the short-axis light collecting mirror ML, and the reflecting surface 9 of the short-axis light collecting mirror ML is located leftward in FIG. The laser beam LB is reflected toward the special reflecting curved surface 10 of the focus position adjusting mirror Ms located at . Upon receiving the laser beam LB, the special reflecting curved surface 10 of the focus position adjusting mirror Ms reflects the laser beam LB toward the surface of the steel plate ES positioned at the vertex of the support roll SR.

In this embodiment, as shown in FIG. 1, the laser beam LB is focused so as to form a perfect circular or elliptical laser spot BS on the surface of the steel plate ES. Then, the laser beam LB linearly scans the steel plate ES in the S direction, which is inclined at a scanning angle (θc) of about 10° with respect to the X direction, and linearly scans the surface of the steel plate ES along the S direction. Form grooves or distortions.
The reason why the grooves or distorted parts are formed in the steel plate ES at a scanning angle of about 10° is that, as described above, when the steel plate ES is used to manufacture the iron core of the wound transformer, the directionality is improved by forming the grooves. This is to prevent breakage of the steel sheet ES while improving the magnetic properties of the electrical steel sheet. The scanning angle may be smaller than 10°, but if the scanning angle is close to 0°, it may cause breakage during the manufacture of the iron core, so an angle close to 0° should be avoided. desirable.

The diameter of the beam spot just before the steel plate ES is irradiated is about several tens of micrometers, but FIG. 1 shows the beam spot BS in an enlarged manner. The laser beam LB is scanned along the second axis of the beam spot BS (that is, along the S direction).
When the laser beam LB is scanned in the direction of the second axis of the beam spot BS, the width of the groove or distorted portion formed on the surface of the steel plate ES is determined by accurately focusing the first axis of the laser beam LB. can be processed accurately.
Condensing of the laser spot BS in the first axis direction can be performed by the short axis condensing mirror ML, and condensing of the laser spot BS in the second axis direction can be performed by the long axis condensing mirror Mc. Even if there are some fluctuations in the condensing of the laser spot BS in the major axis direction, there is little effect on the accuracy of the grooves or distorted parts formed in the steel plate ES.

For example, in the beam spot BS, the focused diameter in the second axis direction is larger than the focused diameter in the first axis direction. It may be about 5 to 10 times the diameter. Therefore, the condensing focal length of the focus position adjusting mirror Ms is 5 to 10 times the condensing focal length of the short-axis condensing mirror ML, and the workable focal depth is similarly long. Therefore, even if some defocusing occurs on the major axis side of the laser spot BS, the influence on workability is reduced.

The short-axis focusing mirror ML is formed in a pentahedron-shaped main body 11 elongated in the direction parallel to the S direction, and this main body 11 has five side surfaces 11a and two end faces 11b. The body portion 11 is arranged so that its length direction is parallel to the S direction, and two end faces 11b are directed parallel to the S direction.
Of the five side surfaces 11a of the body portion 11, one side surface 11a is formed with a reflecting surface 9 formed of a short-axis linear paraboloid. As shown in FIG. 1, the reflecting surface 9 is inclined so as to face both the polygon mirror installed obliquely above the reflecting surface 9 and the focus position adjusting mirror Ms located on the left side of the reflecting surface 9. It is a reflective surface. In addition, the reflective surface 9 is a reflective surface that has a parabolic outline when viewed in a cross section of the main body 11 , and reflects light from one end side to the other end side along the length direction of the main body 11 . The surface 9 maintains the same contour shape. That is, the reflective surface 9 is formed in a linear paraboloid having the same shape from one longitudinal end side to the other longitudinal end side of the body portion 11 .
Also, the reflecting surface 9 is formed of a linear paraboloid that converges the direction of the first axis of the incident laser beam LB.

The focus position adjusting mirror Ms has a rectangular prism-shaped main body 12 elongated in the direction parallel to the S direction, and this main body 12 has four side surfaces 12a and two end surfaces 12b. The body portion 12 is arranged so that its length direction is directed parallel to the S direction, and two end faces 12b are directed to one side and the other side of the direction parallel to the S direction. Of the four side surfaces 12a of the body portion 12, one side surface 12a is formed with a special reflecting curved surface 10 made of a special curved surface.
As shown in FIG. 1, the special reflection curved surface 10 is composed of a short-axis condenser mirror ML installed on the right side (Y direction) of the special reflection curved surface 10 and a support roll SR arranged below the special reflection curved surface 10. It is a reflective surface having an inclination facing both sides.
As will be described later, the special reflecting curved surface 10 is a reflecting surface whose curvature gradually changes along the length direction of the body portion 12. The detailed shape of the special reflecting curved surface 10 will be described later.
Side surfaces 12a, 12a of the main body 12 are arranged on both sides of the special reflection curved surface 10 in the vertical direction. formed in the shape of That is, the curvature of the special reflection curved surface 10 changes along the length direction of the main body 12 (that is, the direction corresponding to the second axis), but the curvature changes in the width direction (that is, the direction corresponding to the first axis). The reflecting surface is flat and has no curvature.

The laser beam LB reflected by the polygon mirror can be scanned within a predetermined range by rotating the polygon mirror around the rotation axis 2 while the laser beam LB is being irradiated onto the reflecting surface 3 of the polygon mirror. .
In FIG. 1, the half angle of the reflection angle range when the laser beam LB is reflected by the rotation of the polygon mirror is indicated as the reflection angle (reflection angle half angle) θs.

As shown by the solid line in FIG. 1, the scanned laser beam LB is incident on the special reflecting curved surface 10 of the focal position adjusting mirror Ms from the short-axis collecting mirror ML, and is reflected by the special reflecting curved surface 10. By irradiating along the direction and scanning in that state, a linear groove portion or a linear distorted portion 15 can be formed.

Next, the special reflecting curved surface 10 of the focus position adjusting mirror Ms will be described in detail.
As a premise for the explanation, it is assumed that the scanning center of the laser beam LB is positioned on the surface of the steel plate ES at the vertex portion of the support roll SR. Here, the width direction of the steel plate ES or the rotation axis direction of the support roll SR is the X direction, the threading direction is the Y direction, and the normal direction of the XY plane is the center of the reflection position of the focus position adjustment mirror Ms and the support roll SR. can be defined as the Z direction, and the scanning direction (that is, the direction of the second axis) as the S direction. The XYZ directions are orthogonal to each other, and the angle formed by the S direction and the X direction can be defined as the scanning angle θc. A reflection angle (reflection angle half angle) of the laser beam LB scanned by the scanning mirror Mp on a plane perpendicular to the first axis is defined as θs.

In this embodiment, a mirror that does not produce a thermal lens effect even when a high-power laser is used is used as the condensing optical element. The condensing shape of the laser beam LB (the shape of the beam spot BS) is a fine circular or elliptical shape having the second axis in the direction coinciding with the scanning direction and the first axis in the vertical direction. . The reason why the elliptical shape is used is that the workability is superior to that of a perfectly circular condensing shape. In addition, it is the convergence in the short axis direction of the elliptical shape that particularly affects the workability. It is desirable to perform laser processing. However, it is possible to implement the present embodiment even if the shape is a perfect circle instead of the elliptical shape.

In order to collect light in this manner, a major axis condensing mirror Mc and a minor axis condensing mirror ML are used, and the second axis and the first axis corresponding to the major axis direction and the minor axis direction of the elliptical converging light are aligned. , are collected by independent linear parabolic mirrors.
A linear parabolic mirror is a paraboloid in one direction that reflects and converges a beam in a direction determined by the shape of the paraboloid. A mirror that reflects a laser beam with a symmetrical angle of incidence and does not have a focusing function. A linear curved mirror has a specific curved surface in one direction, reflects and condenses the laser beam in a direction determined by the curved surface of the mirror at the incident position, and is flat in the orthogonal direction and symmetrical to the normal to the flat surface. It can be explained that it is a mirror that reflects a laser beam at an incident reflection angle and does not have a focusing function.

Next, the focal position where light is condensed by the laser processing device will be described with reference to FIG.
FIG. 3 shows a laser beam of a reference example in which the laser processing apparatus 1 shown in FIG. A processing device 20 is shown.
In the laser processing apparatus 20 shown in FIG. 3, the plane mirror M0 is located at the position of the focus position adjusting mirror Ms in FIG. The arrangement of the axis collecting mirror Mc, the plane mirror MF, the scanning mirror Mp, and the short axis collecting mirror ML and the relative positional relationship between them are the same as in FIG.

FIG. 3 shows an SZ plan view of the trajectory of the laser beam LB scanned by the scanning mirror Mp. The steel plate ES extends along the curved surface of the top portion of the support roll SR, and FIG. 3 simply shows the surface of the support roll SR as the steel plate surface.
This SZ plan view is a plane formed by the S-direction axis and the Z-direction axis passing through the surface of the steel plate ES positioned at the vertex portion of the support roll SR, that is, the steel plate positioned at the vertex portion of the support roll SR. A plane perpendicular to the first axis through the surface of ES. A point on the surface of the steel plate ES located at the vertex portion of the support roll SR is set as the origin, and the origin is arranged at the center of the scanning direction of the laser beam LB.

Although the laser beam LB is actually reflected in three-dimensional directions as shown in FIG. 1, in FIG. to the steel plate ES are shown in a linear arrangement relationship. Therefore, it can be said that FIG. 3 is a diagram obtained by projecting the trajectory of the laser beam LB passing through the scanning mirror Mp, the short-axis collecting mirror ML, and the plane mirror M0 onto the SZ plane.
Let A0 be the reflection point on the reflecting surface 3 of the scanning mirror Mp, A1 be the reflection point of the laser beam LB on the short-axis collecting mirror ML on the scanning center optical axis (θs=0), and A1 be the reflection point on the plane mirror M0. Let the point be A2. Also, let A3 be the point where the laser beam LB is focused on the surface of the steel plate ES, G1 be the distance between the reflection point A0 and the reflection point A1, G2 be the distance between the reflection point A1 and the virtual reflection point A2, and the virtual reflection point A2. ∼ G3 is the distance between reaching points A3.
In this case, assuming that the focal length of the short-axis collecting mirror ML is F_0, the relationship of distance G2+distance G3=F_0 holds.

On the optical axis where the laser beam LB is reflected at an arbitrary reflection angle (virtual reflection angle) θs ₀ from the reflection point A0, an arbitrary reflection point of the laser beam LB on the short-axis condensing mirror ML is A1′, and the virtual reflection on the plane mirror M0 is Let the point be A2'. Further, a point where the laser beam LB is focused on the way to the surface of the steel plate ES is defined as A3′, and a reflection point A0 to a reflection point A1′, a reflection point A1′ to a virtual reflection point A2′, and a virtual reflection point A2′ to the laser Let the distances between the focal positions A3' of the beam LB be G1', G2', and G3', respectively.
In this case, the focal position A3′ is the focal point of the short-axis light collecting mirror ML at the reflection angle (virtual reflection angle) _θs0 as described above, but the focus of the short-axis light collecting mirror ML at an arbitrary reflection angle θs is , on the S axis (Z=0). This is derived from the following calculations.

Condensing focal length of the short-axis light collecting mirror ML when the laser beam LB is incident at a predetermined incident angle θs in a direction (plane perpendicular to the first axis) perpendicular to the parabolic curve of the short-axis light collecting mirror ML : F(θs) can be expressed by the following equation (4).

In equation (4), F ₀ indicates the focal length of the short-axis collecting mirror ML, which coincides with the focal length at the scanning center "θs=0". Therefore, the focal length of the short-axis collecting mirror ML increases as the angle of reflection θs increases. On the other hand, the propagation distance (G2'+G3') from the short-axis focusing mirror ML to the steel plate ES also depends on the reflection angle .theta.s and can be expressed by the following equation (5).

Therefore, since the focal length and the propagation distance change at the same ratio depending on the angle of reflection θs, the focal position is positioned on the S axis (Z=0) over the entire width of the scanning line. For reference, the diameter _d0 of the focused beam can be expressed by the following equation (6).

In equation (6), Const is a laser-specific constant determined by the quality of the laser beam LB, D is the diameter of the laser beam incident on the short-axis focusing mirror ML in the first axis direction, and λ is the laser wavelength.
From the equation (6), F(θs) increases depending on the increase in the reflection angle θs. Therefore, as the reflection angle θs increases, the diameter of the laser beam at the focal point increases. is 20 degrees, the beam diameter expansion ratio at the scanning end is about 6% of the scanning center, and it is considered that there is almost no deterioration in workability.

FIG. 2(A) is a developed view of the upper surface side of the support roll SR viewed from the XY plane, FIG. 2(B) is a developed view of the side surface side of the support roll SR viewed from the YZ plane, and FIG. It is the figure which expanded the top area|region of support roll SR in FIG.2(B).
From the XY plan view shown in FIG. 2(A), when the laser beam LB is scanned in the S direction at the scanning angle θc with the X direction, the point at which the laser beam LB reaches the surface of the steel plate ES is the support roll SR The separation distance Wy in the Y direction from the X axis (Y=0) forming the ridgeline of the top can be expressed as a function of S by the following equation (7).

From the YZ plan views shown in FIGS. 2(B) and 2(C), the distance h(s) between the tangent line at the vertex of the support roll SR and the surface of the support roll SR is a function of S as shown in the following (8) (10) is derived.

Here, R is the radius of the support roll SR, and φ is the center angle of the support roll SR at the intersection B of the straight line S=Wy and the surface of the support roll SR (approximation of the surface of the steel plate ES) (Fig. 2 (B), Fig. 2 ( C)).
Therefore, when the scanning angle θc>0°, h(s) increases as S increases, that is, as the distance S from the scanning center increases. Therefore, when performing laser scanning irradiation at the vertex portion of the support roll SR, the focal point of the laser beam LB to be scanned is the tangential line of the vertex of the support roll SR. It will be done.

In addition, in the focused shape of the laser beam, the focused diameter of the beam spot BS in the direction of the second axis (direction C) is larger than that in the direction of the first axis (direction L) of the beam spot BS. In grooving, the diameter dL of the second shaft is five to ten times as large as the diameter dc of the first shaft. Therefore, the condensing focal length of the long-axis condensing mirror Mc is 5 to 10 times longer than that of the short-axis condensing mirror ML, and the depth of focus that can be processed is approximately the same. does not affect gender.

In this embodiment, a certain specific A focus position adjusting mirror Ms having a special reflecting curved surface 10 is installed. This makes it possible to match the focal position with the curved surface of the support roll ES.
The function of the focus position adjusting mirror Ms and the method of setting the curved surface will be described in detail below.

FIG. 4 shows an SZ plan view of the trajectory of the laser beam LB scanned by the scanning mirror Mp (for example, a polygon mirror) in the laser processing apparatus 1 of this embodiment shown in FIGS.
The steel plate ES extends along the curved surface of the top portion of the support roll SR, and the surface of the support roll SR is simply illustrated as the steel plate surface. The laser beam LB is actually three-dimensionally reflected as shown in FIG. 1, but for the sake of simplification, in FIG. is shown by a straight line. Therefore, it can be said that FIG. 4 is a diagram in which the trajectory of the laser beam LB passing through the scanning mirror Mp, the short-axis collecting mirror ML, and the focus position adjusting mirror Ms is projected onto the SZ plane.

The focus position adjusting mirror Ms has curvature only in the direction parallel to the S direction, and is flat in the orthogonal direction. Therefore, it does not affect the condensing characteristics of the short-axis condensing mirror ML. That is, the point where the laser beam LB is reflected by the short-axis condensing mirror ML from the condensing focal length G3′ from the short-axis condensing mirror ML shown in FIG. A1′) and the point (A2′) where the laser beam LB is reflected by the focus position adjustment mirror Ms) is subtracted to obtain F(θs)=G3′, which does not change even in FIG. .
Therefore, from an arbitrary virtual reflection point A2' on the focus position adjusting mirror Ms to the surface point A4 shown in FIG. A special reflecting curved surface 10 of the focus position adjusting mirror Ms is provided with a curved surface that changes the angle of reflection so that . Any virtual reflection point A2' shown in FIG. 3 and any virtual reflection point A2' shown in FIG. Show equivalence position.

Due to the presence of the special reflecting curved surface 10, it becomes possible to focus the short-axis collecting mirror ML on the surface of the support roll SR along the scanning direction S. The surface point A4 shown in FIG. 4B is the intersection point of h(S) of the functional expression shown in the above equation (10) and the circle f(S, Z) of radius G3' centered on the virtual reflection point A2'. is.
Here, f(S, Z) can be expressed by the following equations (11) and (12) with the coordinates of the virtual reflection point A2′ as (S ₂ , Z ₂ ).

From the equations (11) and (12), the intersection coordinates A4 (S ₄ , Z ₄ ) on the SZ plane can be obtained for any virtual reflection angle θs ₀ .
As an example, h(s) and f(S, Z) are plotted on the SZ plane (SZ coordinate plane) when the virtual reflection angle θs = 10° under the setting conditions shown in Table 1 below. FIG. 5 shows the result of obtaining the intersection coordinate A4.
As shown in FIG. 5, intersection coordinates A4 are obtained as (42.45, -0.27).

Next, the effective angle of reflection θs′ after change is obtained. The effective angle of reflection θs′ after change can be calculated from the coordinates A2′ (S ₂ , Z ₂ ) and A4 (S ₄ , Z ₄ ) by the following equation (13).

Here, Z ₂ =G3, and since S4 and Z4 are determined as intersections of equations (11) and (12) as described above, the effective angle of reflection θs′ after change is given by equation (13) is a function of _S2 .
That is, the design value of the curved surface at an arbitrary S-direction position of the effective reflection angle θs' of the focus position adjusting mirror Ms can be obtained.
The curved surface of the special reflecting curved surface 10 provided on the focus position adjusting mirror Ms can be defined by its normal angle.
As shown in FIG. 6, in order to change the virtual angle of reflection at the focal position adjusting mirror Ms from _θs0 to the effective angle of reflection θs′, the normal to the special reflection curved surface 10 is tilted by an angle of α1 with respect to the Z axis. Then, α1 can be represented by the following equation (14). That is, α1 is the incident angle when the laser beam is incident on the focus position adjusting mirror Ms on a plane perpendicular to the first axis.

Since the changed effective angle of reflection θs′ is a function of S as described above, it is possible to determine the normal angle at each position in the S direction on the special reflecting curved surface 10 of the focus position adjusting mirror Ms.
FIG. 7 shows the relationship between the position in the S direction and α1 when the virtual reflection angle θs0 is changed from ₀ to 20° under the conditions in Table ₁ , which is the specific example. As shown in FIG. 7, the relationship between the S _- direction position and α1 was almost proportional.

The normal angle distribution α1 that defines the S-direction curved surface of the special reflection curved surface ₁₀ of the focus position adjustment mirror Ms obtained as described above is the laser beam incident on the special reflection curved surface 10 of the focus position adjustment mirror Ms. This is the value when LB is specularly reflected in the direction of the short-axis condensing mirror ML.

However, in an actual mirror arrangement, as shown in FIG. 8, the focus position adjusting mirror Ms reflects the incident laser beam LB from the short-axis collecting mirror ML substantially vertically downward along the Z axis. Therefore, it is necessary to consider the incident reflection angle in the reflecting surface design (curved surface design) of the focal position adjusting mirror Ms to be manufactured.

FIG. 8 illustrates a case where the incident/reflection angle from the short-axis collecting mirror ML to the focus position adjusting mirror Ms is β on a plane perpendicular to the second axis.
When the laser beam LB is incident and reflected in the direction shown in FIG. 8 to the focus position adjusting mirror Ms having a radius of curvature in the S direction, the reflected beam has a radius of curvature obtained by multiplying the radius of curvature in the S direction by 1/cos β. reflected. Therefore, when the curved surface distribution of α1 shown in the above equation ( ₁₄ ) is realized at the incident reflection angle β, the actual normal angle design value α2 of the focus position adjustment mirror Ms is given by the following equation ₍ 15) can be displayed with

Since the special reflecting curved surface 10 of the focus position adjusting mirror Ms has a curvature distribution in the scanning direction (S direction) of the laser beam, the major axis direction of the elliptical condensing shape of the laser beam LB changes simultaneously with the change in the virtual angle of reflection _θs of light condensing properties. However, since the curvature change is very small as shown in FIG. 7, the effect of the laser beam LB on the long axis direction of the elliptical condensing shape is small.

From the above explanation, it was possible to obtain the actual normal angle design value _α2 of the focus position adjusting mirror Ms. If the curvature along the line is obtained and the special reflecting curved surface 10 is manufactured based on this curvature, the desired focus position adjusting mirror Ms can be manufactured.
By applying this focus position adjusting mirror Ms as shown in FIGS. 1 and 4, it is possible to accurately form linear grooves or linear distorted portions along the intended scanning direction on the steel plate ES. That is, since the focal position can be accurately positioned on the surface of the steel plate ES from one end to the other end in the scanning direction S, linear grooves or linear distorted portions can be formed without defocusing.

When scanning the surface of the steel plate ES with the laser beam LB, the laser beam LB may be scanned so as to form a definite groove shape, or the distorted portion may be formed although the groove is not a definite groove in terms of shape. The laser beam LB may be scanned to configure. The target magnetic domain control may be performed as a grain-oriented electrical steel sheet by providing a distorted portion.
In the above description, the laser processing apparatus 1 includes the long-axis condensing mirror Mc and the plane mirror MF. The laser processing apparatus 1 can be configured without the long-axis condensing mirror Mc and the plane mirror MF.

Also, in the explanation using FIG. 1, the laser beam LB is assumed to be a fiber laser or a disk laser, but it is not limited to these. For example, it may be a _CO2 laser.
Also, the rotating polygon mirror used as the scanning mirror Mp in the previous embodiment may be replaced with a galvanomirror 30 configured as shown in FIG.
A galvanomirror 30 shown in FIG. 9 is rotationally driven in the direction of the arrow in FIG. 9 by a drive motor 31 . The reflection direction of the laser beam LB can be changed according to the rotation angle of the galvanomirror 30, and the laser beam LB can be scanned.

DESCRIPTION OF SYMBOLS 1... Laser processing apparatus, 3... Reflective surface, 6... Reflective surface, 8... Reflective surface, 9... Reflective surface, 10... Special reflective curved surface, 11... Main body part, 11a... Side surface, 12... Main body part, 12a... Side surface, 30 Galvanomirror BS Beam spot ES Grain-oriented electromagnetic steel sheet (steel plate) LB Laser beam Mc Major axis condenser mirror MF Plane mirror ML Short axis condenser mirror Mp Scanning mirror , Ms... Focus position adjustment mirror, SR... Support roll, ?c... Scanning angle, ?s... Reflection angle (reflection angle half angle), ? _s0 ... Virtual reflection angle, ?s'... Effective reflection angle, S... Scanning direction, G1, G2 , G3...distance, G1', G2'...distance, focusing focal length...G3', A0, A1...reflection point, A2...virtual reflection point, A1'...reflection point, A2'...virtual reflection point, A3, A3 '…Focus position.

Claims (5)

By scanning the surface of a steel sheet that is passed through a support roll with a laser beam having a circular or elliptical beam spot, linear grooves or linear distorted portions are formed in the steel sheet. A laser processing device,
a laser beam emitting unit that emits a laser beam;
a scanning mirror that reflects the laser beam;
a short-axis collecting mirror that reflects the laser beam reflected by the scanning mirror and collects the light in a direction of a first axis corresponding to a short axis of the beam spot;
a focus position adjusting mirror that reflects the laser beam reflected by the short-axis focusing mirror and irradiates the surface of the steel plate;
has
The scanning mirror changes the direction in which the laser beam is reflected and changes the position at which the laser beam is irradiated on the surface of the steel sheet, thereby scanning the surface of the steel sheet with the laser beam,
The focus position adjustment mirror directs the laser beam to
The distance obtained by subtracting the distance between the point where the laser beam is reflected by the short-axis focusing mirror and the point where the laser beam is reflected by the focal position adjusting mirror from the focal length of the short-axis focusing mirror. and the distance from the point where the laser beam is reflected by the focal position adjusting mirror are equal to each other, and has a curvature for converging the laser beam at a point on the surface of the steel plate. a long-axis collecting mirror that reflects the laser beam emitted from the laser beam emitting unit and collects the light in a second axis direction corresponding to the long axis of the beam spot;
2. The laser processing apparatus according to claim 1, wherein said scanning mirror reflects said laser beam reflected by said long-axis collecting mirror. The curvature α2 of the focusing position adjustment mirror, which is defined by the angle of incidence of the laser beam on the focusing position mirror viewed from the direction of the first axis, is defined by the following (1) to (3) ).
(S ₂ , Z ₂ ) are coordinates on a plane perpendicular to the first axis of the point at which the laser beam is reflected by the focus adjustment mirror;
(S ₄ , Z ₄ ) is perpendicular to the first axis of a point on the surface of the steel plate where the focal length and the distance from the point where the laser beam is reflected by the focus positioning mirror are equal; are the coordinates on the plane,
α1 is an angle of incidence when the laser beam is incident on the focus position adjusting mirror on a plane perpendicular to the first axis;
β is an angle of incidence when the laser beam is incident on the focus adjustment mirror in a plane perpendicular to the second axis;
θso is a reflection angle when the laser beam is reflected by a flat mirror having no curvature at the position of the focus position adjustment mirror on a plane perpendicular to the first axis;
θ's is a reflection angle when the laser beam is reflected by the focus position adjustment mirror on a plane perpendicular to the first axis.

4. The laser processing apparatus according to any one of claims 1 to 3, wherein the reflection surface of said short-axis condensing mirror is a linear paraboloid. 5. The laser processing apparatus according to claim 1, wherein said scanning mirror is a rotating polygon mirror or a galvanomirror.

Images