JPH0774372B2 - Laser hardening method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser quenching method for quenching a workpiece such as a shaft or a tubular body in an annular shape by using a laser beam.

2. Description of the Related Art Conventionally, in the case of quenching a shaft or a cylindrical body using a laser beam in an annular shape, a laser beam b is applied to the quenching point of the work a while rotating the work a as shown in FIG. And a method of rotating the reflecting mirror c provided inside the work a as shown in FIG. 11 and quenching the work a while swinging the laser beam b along the inner peripheral surface of the work a. Generally adopted.

However, in any of the methods, a softening layer due to tempering is generated at the irradiation start point and the end point of the laser beam b and the hardening zone boundary portion adjacent to the irradiation point, and the wear resistance and the pitting fatigue limit of this portion are lowered. A problem occurs.

As a method for solving the above-mentioned inconvenience, a method for reflecting an annular laser beam b toward a work a using a Toric condensing mirror d as shown in FIG. 12 or a cone-shaped condensing mirror e as shown in FIG. Is also proposed.

Problems to be Solved by the Invention However, although the above method can prevent the generation of the softened layer due to tempering, only the unstable resonator can be used for generating the laser beam b, so that the use is restricted and each work is Toric condensing mirror d with different focal length etc.
A plurality of cone-shaped condensing mirrors e must be prepared in advance, and all of these mirrors having a concave spherical reflection surface are expensive.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a laser hardening method capable of uniformly hardening a workpiece without using an optical system such as an expensive Torrick condensing mirror. It is a thing.

Means and Actions for Solving the Problems In order to achieve the above-mentioned object, the present invention makes a laser beam generated by a laser generator inclined by a certain angle with respect to a plane perpendicular to the center of rotation and has a rotary drive source. By irradiating the reflection type polarizing means consisting of a concave mirror rotated at a high speed by irradiating the work annularly while oscillating the laser beam annularly by this polarizing means, the work is hardened in an annular shape. The work can be hardened without the need for an expensive optical system, and the adoption of a reflective polarization means allows the center of the polarization means to be supported for high-speed rotation, so there is no unevenness in baking due to uneven irradiation. Hard quenching becomes possible.

EXAMPLE An embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. In FIG. 1, reference numeral 1 denotes a cylindrical work in which a part of the inner surface is quenched into an annular shape. A cone-shaped mirror 2 having a cone-shaped upper part is installed in the. Above the cone-shaped mirror 2, a concave mirror 3 is provided on the axis of the work 1.

The concave mirror 3 is for deflecting a laser beam 4 generated by a laser generator (not shown) toward the cone-shaped mirror 2. The concave mirror 3 has a diameter which is at least twice the diameter of the laser beam 4 and is used on the reflecting surface 3a side. Is inclined by an angle θ with respect to the reference plane 3 ′ such that lθ = d.

In addition, l is the distance from the concave mirror 3 to the cone-shaped mirror 2, d
Is the annular beam diameter.

Further, a rotary drive source 5 such as an air motor having a rotary shaft 5a in a direction perpendicular to the reference plane 3'is connected to the back surface of the concave mirror 3 so that the concave mirror 3 can be rotated at a high speed of 6000 to 12000 rpm. ing.

Next, a method of quenching the work 1 will be described. The laser beam 4 generated by the laser generator is deflected to the cone-shaped mirror 2 side by the concave mirror 3 which is rotated at a high speed by the rotary drive source 5, and the cone-shaped mirror 2 is further rotated. Reflection surface 2a of the circular mirror 2
Is reflected by the inner peripheral surface of the work 1 and is irradiated onto the work 1.

Further, the irradiation point of the laser beam 4 rotates the inner peripheral surface of the work 1 at a high speed as the concave mirror 3 rotates, so that the next irradiation is performed before the temperature of the first irradiated portion decreases. It becomes possible to quench the inner circumference of the work 1 into an annular shape without generating a softened layer due to tempering.

The time from the first irradiation of the laser beam 4 to the irradiation of the next beam 4 is within 5 to 10 msec.
The hardening width D of the work 1 is determined in consideration of the hardness required for laser hardening and the hardenability of the work 1, but is usually about 0.5 to 5 mm.

On the other hand, FIG. 3 shows a quenching method in the case where the work 1 is an axis. In this case, two sets of annular plane mirrors 6 are arranged at appropriate intervals and the laser beam 4 reflected by the cone-shaped mirror 2 is applied to the work 1. It may be reflected toward the outer peripheral surface.

Further, FIGS. 4 and 5 show a reference example in which the converging lens 10 is rotated about a position eccentric from the optical axis 10 'as a rotation center to enable annular irradiation of the laser beam 4. The optical axis 10 'of the condenser lens 10 is eccentric from the center of rotation 13' of the lens holder 13 which is rotatably attached to the lens barrel 11 via a bearing 12 as shown in FIG. Installed in position. The lens holder 13 is connected to a rotary drive source (not shown) such as a motor which does not rotate by a power transmission means 14 such as a belt, and this rotary drive source allows a high speed of 100 rpm or more in the arrow direction (see FIG. 7). Lens holder
A cooling fin 15 is projectingly provided on the lower surface of 13 to prevent heat from distorting the condenser lens 10 and shortening the life of the condenser lens 10 by enhancing the heat dissipation effect.

Next, the laser quenching method by the quenching device will be described. The laser light having the intensity distribution as shown in 4'of FIG. Is polarized by and reaches the inner surface of the work 1 such as the injection nozzle shown in FIG. 8, and the irradiation point rotates along the inner surface of the work 1 to quench the work 1 in an annular shape. Also in this case, similarly to the above embodiment, the laser beam 4 is first introduced.
Since the next beam 4 arrives before the temperature of the part irradiated with is reduced, it is possible to prevent the softening layer from being generated by tempering, but when rotating the condenser lens 10, the outer peripheral portion of the condenser lens 10 is supported. Since the lens holder 13 must be rotated, the rotation mechanism becomes complicated and the lens holder 13
If the rotation accuracy of 13 is poor, uneven irradiation may occur on the work 1 and uniform quenching may not be possible.

Further, the valve seat 14a such as the relief valve 14 as shown in FIG. 9 can be quenched by the same method.

Effect of the Invention As described in detail above, according to the present invention, a laser beam generated by a laser generator is tilted at an angle with respect to a plane perpendicular to the center of rotation and is rotated at a high speed by a rotary drive source. By irradiating the reflection type polarizing means, the laser beam is circularly irradiated by the polarizing means and irradiated to the work annularly, so that the work is quenched in an annular shape, which is expensive like a toric condenser mirror. Quenching of a work is possible without using a special optical system, and since a softening layer due to tempering does not occur at the irradiation start point or end point and the hardening boundary adjacent to these, quenching quality is greatly improved.

Also, the laser beam reflected from the concave mirror reaches the work with a certain width, and the work can be continuously hardened with a constant width, so compared to the case where the work is linearly scanned and hardened. A wide range of quenching is possible in a short time, productivity is greatly improved, and since the quenching width can be arbitrarily selected by the inclination of the concave mirror, the hardening width can be set appropriately according to the work material and shape. is there.

Furthermore, by adopting a concave mirror, the concave mirror can be rotated at high speed while supporting the center of the concave mirror, which enables highly accurate rotation, which does not cause uneven irradiation on the workpiece, so that uniform quenching is possible. Will be possible.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a laser hardening apparatus used in the method of the present invention, FIG. 2 is an enlarged view within a circle II in FIG. 1, FIG. 3 is an explanatory view showing another embodiment, and FIG. 9 to 10 are explanatory views showing a reference example, and FIGS. 10 to 13 are conventional explanatory views. 1 is a work and 4 is a laser beam.

Claims (3)

[Claims] 1. A laser beam 4 generated by a laser generator is tilted at an angle with respect to a plane perpendicular to the center of rotation,
Further, the work 1 is annularly irradiated by irradiating the reflection type polarization means composed of the concave mirror 3 which is rotated at a high speed by the rotary drive source 5, and irradiating the work 1 annularly while oscillating the laser beam 4 annularly by the polarization means. A laser quenching method, characterized in that the laser quenching is performed. 2. A cone-shaped mirror 2 in which a laser beam 4 circularly oscillated by a polarizing means is positioned in a cylindrical work 1.
2. The laser hardening method according to claim 1, wherein the inner surface of the work 1 is annularly quenched by causing the inner surface of the work 1 to be annularly reflected with a constant width D. 3. An outer peripheral surface of a work 1 is hardened in an annular shape by causing a laser beam 4 oscillated in an annular shape by a polarizing means to be annularly reflected by the cone-shaped mirror 2 and a plurality of annular plane mirrors 6 to the outer peripheral surface of the work 1. The method of laser hardening according to claim 1, wherein