Laser beam hardening method and apparatus

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Field of application to which the invention belongs]

The present invention relates to a laser quenching method and apparatus for quenching the surface of a gear using laser light.

【0002】

[Conventional technology]

As a gear quenching method, a laser quenching method using a very high-energy laser has the following advantages because rapid heating is possible and only the polar surface layer needs to be heated.

【0003】

In other words, because it utilizes the self-cooling action due to the large temperature difference between the inside of the gear and the surface, it has the advantage that no coolant is required, and because it heats only the polar surface layer, there is little overall distortion due to heating. There are advantages.

【0004】

By the way, a molded part having a complicated shape such as a gear has a problem that the state of heat diffusion to the inside at the time of heating and the state of heat conduction from the inside at the time of cooling are not constant.

【0005】

Further, as shown in FIG. 9, the angle of incidence of the laser beam 4 on the gear 2 is θ2 at the tooth bottom due to its complicated surface shape, whereas it is θ1 smaller than θ2 at the tooth surface. And it will not be constant. Therefore, even if the energy density distribution of the laser beam 4 is uniform as shown in FIG. 9 (a), when the gear 2 is irradiated, the irradiation is performed as shown in FIG. 9 (b). The energy has a problem that the tooth bottom becomes larger than the tooth surface, and it is difficult to evenly apply heat to every place.

【0006】

Regarding the correction of the amount of heat input due to the difference in the incident angle of the laser beam 4 to the gear 2, as described above, the absorbent is applied only to the tooth surface where the incident angle tends to be small to increase the absorption rate of the laser and the amount of heat input. There is a method of irradiating the laser beam so that the energy density of the tooth surface becomes larger than the energy density of the tooth bottom by correcting the laser energy density distribution as shown in FIG.

【0007】

Further, as shown in FIG. 10, a laser beam is incident on the tooth surface and the tooth bottom at an angle with respect to the tooth bottom so that the angle of incidence on the tooth surface is large, and the tooth surfaces facing each other are arranged. There is also a method of irradiating each tooth surface with laser beams 4a and 4b so that the incident angles are the same.

【0008】

[Problems to be Solved by the Invention]

In general, the performance required for a surface-hardened gear is the tooth root bending strength and slippage against a load during use, or the tooth surface strength during rolling or rolling, which are the hardening depth, hardness, and residual stress after quenching. Is influential.

【0009】

The curing depth and hardness can be adjusted by the incident laser energy, irradiation time, irradiation speed, etc., but it is difficult to adjust the residual stress by the quenching process alone, so after the quenching process, residual stress improvement treatment such as shot peening is performed. It had to be improved by giving.

【0010】

Therefore, in order to harden the surface of the gear and impart a higher residual stress, a residual stress improving treatment step is required after the laser quenching step, and an apparatus for this is also required.

【0011】

Therefore, in the laser quenching method for gears in the prior art, it is difficult to shorten the processing time and it is also difficult to reduce the manufacturing cost.

【0012】

An object of the present invention is to realize a laser quenching method and apparatus capable of performing residual stress improving treatment during a laser quenching step and omitting another step.

【0013】

[Means for solving problems]

In order to achieve the above object, the present invention is configured as follows. (1) In the laser quenching method of irradiating the tooth profile surface of a member having a tooth profile with a laser, the tooth bottom portion and the tooth root portion of the member having the tooth profile are irradiated with a laser, and the tooth bottom portion and the tooth root portion are irradiated with the laser. Subsequently, the tooth surface portion of the member is irradiated with a laser.

【0014】

(2) Preferably, in the above (1), the laser is line-shaped, and the line-shaped laser is irradiated so as to be located on a straight line connecting the teeth adjacent to each other of the member. The optical axis of the laser irradiates the tooth bottom portion in an inclined manner, and following the irradiation of the tooth bottom portion and the tooth root portion with the laser, the tooth surface portion of the member is irradiated with the laser.

【0015】

(3) Preferably, in the above (2), the member is a gear, and the line-shaped laser is radiated parallel to the circumferential direction of the gear and toward the central axis of the gear.

【0016】

(4) In the laser quenching method of irradiating the tooth profile surface of a gear member having a tooth profile with a laser, two line-shaped lasers are provided, and these two lasers are crossed at a predetermined position so that the lines overlap each other. The entire tooth muscle is irradiated so that the laser line is parallel to the central axis of the gear, the tooth bottom of the gear is hardened at the intersection position of the two lasers, and the gear and the intersection position are formed. Separated from each other, the above two lasers burn the two adjacent tooth roots and tooth surfaces at the same time in the order of tooth root, tooth surface, and tooth tip.

【0017】

(5) Preferably, in the above (4), the linear laser is irradiated from the optical system lens to the gear, and after the irradiation of the tooth bottom with the laser, the position of the optical system lens is moved. By separating the optical system lens and the gear from each other, the above two lasers simultaneously burn the two tooth roots and the tooth surface adjacent to each other in the order of the tooth root, the tooth surface, and the tooth tip.

【0018】

(6) In a laser quenching device that irradiates the tooth profile surface of a member having a tooth profile with a laser, a laser oscillator that generates a laser and a laser generated from the laser oscillator are formed into a line shape, and the line-shaped laser is used as the member. The optical system that irradiates the laser so that it is located on a straight line connecting the adjacent teeth and the laser optical axis tilts with respect to the tooth bottom, and the tooth bottom and the tooth root. Following the laser irradiation, the laser irradiation position moving means for irradiating the tooth surface portion of the member with the laser is provided.

【0019】

(7) In a laser quenching device that irradiates the tooth profile surface of a gear member having a tooth profile with a laser, the laser oscillator that generates the laser and the laser generated from the laser oscillator are designated as two line-shaped lasers, and these two lasers are used. The distance between the optical system and the gear so that the line and the line intersect each other at a predetermined position so that the laser line is parallel to the central axis of the gear and irradiate the gear. The two lasers are applied to the entire tooth muscle of the gear, the bottom of the gear is hardened at the intersection of the two lasers, and the gear and the intersection are separated from each other. It is provided with a laser irradiation position moving means for simultaneously quenching the two lasers adjacent to each other in the order of the tooth root, the tooth surface, and the tooth tip.

【0020】

A line-shaped laser is used to specify the irradiation site and change the irradiation order, and a high residual stress is applied to the specific site by the balance between the thermal stress and the transformation stress generated during cooling. When applying a high compressive residual stress to the tooth root portion, the laser is first applied to the tooth bottom and the tooth root portion to harden the tooth base, and then irradiated to the tooth surface and the tooth tip to harden the tooth base.

【0021】

As a result, the thermal stress and transformation stress of the tooth surface hardened later are applied to the tooth roots on the tooth bottom and the tooth root portion that have been hardened first.

【0022】

In general, transformation due to rapid heating and rapid cooling causes volume expansion, the tooth surface expands, the tooth root is compressed, and the tooth root remains a residual stress with a higher compression tendency than during quenching and hardening. ..

【0023】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, using an external gear having a tooth profile on the outside of the member as an example. FIG. 1 is an overall schematic configuration diagram of a laser quenching apparatus that implements the laser quenching method according to the first embodiment of the present invention.

【0024】

In FIG. 1, the laser light emitted from the laser oscillator 6 is reflected by the cylindrical reflecting lenses 5c and 5b and converted into parallel light having a different aspect ratio. Then, the distance between the gear 2 and the focusing lens 5a is adjusted so as to focus the laser beam that has become parallel light at the irradiation position of the gear 2 which is the member 1 to be processed by the focusing lens 5a. As an example of an actual device, the distance between the gear 2 and the focusing lens 5a may be long, but in this case, the focal length of the laser from the focusing lens 5a is also large. Therefore, in this case, the focal position of the laser from the focusing lens 5a is adjusted so that the tooth bottom 2a and the tooth surface 2b are within the depth of focus.

【0025】

As shown in FIGS. 2 and 3, the member 1 to be laser-quenched has a cylindrical surface processed so that the tooth bottom and the tooth portion are alternately formed. Then, as shown in FIG. 1, the member 1 to be processed is fixed on the rotary table 3 at the time of quenching.

【0026】

Further, the gear 2 to be processed, the focusing lens 5a, and the like are arranged so that the optical axis of the laser beam 4 is connected to the rotation center axis of the member 1 to be processed.

【0027】

The laser beam 4 oscillated from the laser oscillator 6 passes through the lenses 5c, 5b, and 5a, and is adjusted to be a line-shaped beam 4 at a position where the gear 2 is irradiated.

【0028】

As shown in FIG. 1, the optical axis of the laser beam 4 focused in a line by the optical system lens 5a is irradiated with an inclination of a predetermined angle θ with respect to the axial direction of the member 1. Alternatively, the optical axis of the laser beam 4 is inclined with respect to the tooth bottom portion 2a and irradiated.

【0029】

Further, as shown in FIG. 2, the irradiated beam 4 is a line-shaped beam extending from the tooth tip to the adjacent tooth tip centering on the tooth bottom 2a.

【0030】

That is, the line of the linear beam is located on a straight line connecting the teeth adjacent to each other and is irradiated so as to be parallel to the circumferential direction of the gear 2.

【0031】

The state of the irradiated portion of the laser beam 4 on the member 1 to be processed is as shown in FIG. That is, when viewed in the arrangement shown in FIG. 3, the laser irradiation position of the tooth bottom 2a is located below the tooth surface 2b in the drawing, and is located above the tooth surface 2b from the tooth surface 2b toward the tooth tip. ing.

【0032】

In this beam irradiation state, the laser beam 4 is scanned to the lower position in FIG. 3 with respect to the member 1 to be machined by the laser irradiation position moving means such as a motor, or the member 1 is moved upward with respect to the laser beam 4. By moving, the tooth bottom 2a is hardened first, followed by the tooth surface 2b.

【0033】

That is, according to the first embodiment of the present invention, the linear laser beam 4 is used to change the order of irradiating the laser irradiation site on the member 1 to be processed, and the thermal stress and transformation stress generated during cooling A high residual stress is applied to a specific part by the balance.

【0034】

When applying a high compressive residual stress to a specific part, the laser beam 4 is first irradiated to the tooth bottom 2a and the tooth root to be cured, and then irradiated from the tooth surface 2b toward the tooth tip to be cured.

【0035】

The thermal stress and transformation stress of the tooth surface 2b hardened later are applied to the tooth base 2a and the tooth base that have been hardened first. In general, rapid heating and rapid cooling cause volume expansion due to transformation stress, so the tooth surface 2b expands, which compresses the tooth root and the tooth root tends to compress more than during quench hardening. Residual stress will remain.

【0036】

Therefore, according to the first embodiment of the present invention, it is possible to realize a laser quenching method and an apparatus capable of performing residual stress improving treatment during the laser quenching step and omitting another step.

【0037】

In the above example, as shown in FIG. 3, the laser beam 4 is moved from the top to the bottom of the figure to quench the gear 2, but the tooth bottom 2a and the tooth surface 2b It is also possible to invert the optical systems 5a to 5c and move the laser beam from the lower part to the upper part in FIG. 3 to perform quenching processing.

【0038】

In this case as well, it goes without saying that the tooth bottom 2a is irradiated with the laser beam in advance of the tooth surface 2b.

【0039】

Next, a second embodiment of the present invention will be described with reference to FIGS. 4, 5, and 6. FIG. 4 is an overall schematic configuration diagram of a laser quenching apparatus that implements the laser quenching method according to the second embodiment of the present invention.

【0040】

In FIG. 4, the laser beam emitted from the laser oscillator 6 is converted into parallel light having a different aspect ratio by the cylindrical lens 5f, focused by the focusing lens 5e, and then passed through the focusing lens 5d at a position farther than the focal position. By doing so, it is converted into parallel light.

【0041】

Finally, the laser beam 4 is adjusted to be a parallel linear laser beam 4 at the irradiation position of the gear 2.

【0042】

At this time, it is necessary to irradiate the laser beam 4 over the entire tooth muscle. For this purpose, by moving the position of the focusing lens 5d, the distance between the lenses 5d and 5e is changed, and the width of the line-shaped beam 4 is adjusted. The position of the focusing lens 5d can be moved by using a linear stage or the like.

【0043】

In this second embodiment, as shown in FIG. 4, a linear laser beam is formed along the axial direction of the gear 2. Although not shown in FIG. 4, the laser beam 4 has two optical axes, and as shown in FIG. 5, the line beams 4a and 4b can intersect each other (the lines can intersect each other so as to overlap each other). It is composed.

【0044】

As described in the first embodiment of the present invention, since it is necessary to cure the tooth bottom 2a prior to the tooth surface 2b, the laser is applied to the tooth bottom 2a at the intersection of the laser beams 4a and 4b. The positions of the laser beams 4a and 4b and the member 1 to be machined are adjusted so that the beams 4a and 4b are irradiated. That is, the adjustment is made so that the positional relationship is as shown in (a) of FIG.

【0045】

Then, when the laser beam 4 is irradiated at the position shown in FIG. 6A, the cured portion is partially formed as shown by hatching in the figure. Subsequently, as shown in FIG. 6B, the gear 2 is gradually moved by a laser irradiation position moving means such as a motor so as to move away from the intersection position of the laser beams 4a and 4b and the lens 5d.

【0046】

In other words, when defocused, the position of the tooth bottom 2a moves away from the intersection of the laser beams 4a and 4b, and after the two line-shaped beams 4a and 4b intersect, the two teeth facing each other from the left and right tooth roots. Each moves to the surface 2b, and the cured portion extends to the tooth surface 2b as shown in the figure.

【0047】

Further, when defocusing is performed, as shown in FIG. 6 (c), the laser beams 4a and 4b are finally irradiated to the tooth tips and cured. At this time, the same effect can be obtained by moving the laser optical system with respect to the gear 2 instead of moving the member 1 for defocusing.

【0048】

In this case, the tooth bottom 2a to be hardened first is hardened and the volume expansion due to transformation is superior, so that the compressive residual stress remains, and then the tooth surface 2b is hardened, so that the volume expansion due to the hardening of the tooth surface causes. A higher compressive residual stress will be applied to the tooth bottom 2a.

【0049】

In the second embodiment of the present invention, the same effect as that of the first embodiment can be obtained.

【0050】

In the second embodiment described above, two optical systems are provided, but one laser beam may be divided into two laser beams 4a and 4b by one optical system. it can.

【0051】

FIG. 7 shows an example of a configuration in which one laser beam is divided into two laser beams 4a and 4b by the above-mentioned one system of optical systems. In FIG. 7, the laser from the laser oscillator 6 irradiates the beam splitter (half mirror) 5g through the lenses 5f, 5e, and 5d. With this half mirror 5g, the laser beam is divided into two, one laser beam irradiates the gear 2 and the other laser beam irradiates the mirror 5h. Then, the laser beam reflected by the mirror 5h is applied to the gear 2.

【0052】

To move these two laser beams from the bottom of the gear to the tooth surface, the half mirror 5g and the mirror 5h are placed with respect to the gear 2 as shown in FIGS. 7A to 7B. Move the gear 2 upward (arrow u) and rotate the gear 2 to the left (arrow R).

【0053】

With the configuration as shown in the example shown in FIG. 7, one laser beam can be divided into two laser beams 4a and 4b.

【0054】

FIG. 8 shows another example of a configuration in which one laser beam is divided into two laser beams 4a and 4b by the above-mentioned one system of optical systems. In FIG. 8, the laser from the laser oscillator 6 irradiates the beam splitter 5i through the lenses 5f, 5e, and 5d. In this beam splitter 5i, the laser beam is split into two, one laser beam is radiated to the mirror 5j, and the other laser beam is radiated to the mirror 5k. Then, the two laser beams reflected by the mirrors 5j and 5k are applied to the gear 2.

【0055】

To move these two laser beams from the bottom of the gear to the tooth surface, move the beam splitter 5i, mirror 5j, and 5k to the gear 2 as shown in FIGS. 8 (a) to 8 (b). , Move up the figure.

【0056】

Even with the configuration as shown in the example shown in FIG. 8, one laser beam can be divided into two laser beams 4a and 4b.

【0057】

Although the above-described embodiment describes the external gear, the present invention can be similarly applied to the internal gear and the like.

【0058】

[Effect of the invention]

According to the present invention, it is possible to realize a laser quenching method and an apparatus capable of performing a residual efficacy improving treatment during a laser quenching step and omitting another step.

【0059】

That is, by controlling the quenching order, it is possible to increase the residual stress at the desired portion to the compression side, perform the residual stress improvement treatment during the laser quenching process, and provide a gear having high mechanical properties. It becomes.

[Simple explanation of drawings]

[Figure 1]

It is an overall schematic block diagram of the laser quenching apparatus which carries out the laser quenching method which is 1st Embodiment of this invention.

[Figure 2]

It is operation explanatory drawing of the 1st Embodiment of this invention.

[Fig. 3]

It is operation explanatory drawing of the 1st Embodiment of this invention.

[Fig. 4]

It is an overall schematic block diagram of the laser quenching apparatus which carries out the laser quenching method which is 2nd Embodiment of this invention.

[Fig. 5]

It is operation explanatory drawing of the 2nd Embodiment of this invention.

[Fig. 6]

It is operation explanatory drawing of the 2nd Embodiment of this invention.

[Fig. 7]

It is explanatory drawing of one modification of the 2nd Embodiment of this invention.

[Fig. 8]

It is explanatory drawing of another modification of the 2nd Embodiment of this invention.

[Fig. 9]

It is explanatory drawing of an example of the laser processing method in the prior art.

[Fig. 10]

It is explanatory drawing of another example of a laser processing method in a prior art.

[Explanation of symbols]

1 Material to be processed 2 gears 2a tooth bottom 2b tooth surface 3 rotating stages 4 laser beam 5a, 5d, 5e focused lens 5b, 5c reflective lens 5f Cylindrical lens 5g, 5i beam splitter 5h, 5j, 5k mirror 6 laser oscillator