JP2020176307A - Laser hardening device and laser hardening method - Google Patents

Abstract

To practice laser hardening at high efficiency and high precision.SOLUTION: A laser hardening device 19 comprises: a laser oscillator 21 emitting a laser beam LB; and an optical system 22 arranged in a space of the hardening object surface S (outer diameter surface (Wa) of a workpiece W. The optical system 22 includes a belt-like lens part 23 forming a circular beam spot BS elongating along a first direction A (the circumferential direction of the workpiece W) of the hardening object surface S, and, upon the injection of the laser beam LB, the workpiece W relatively moves to a second direction B (the axial direction of the workpiece W) of the hardening object surface S crossing (orthogonal to) the first direction A to the belt-like lens part 23.SELECTED DRAWING: Figure 3

Description

The present invention relates to a laser quenching apparatus and a laser quenching method.

In the manufacturing process of steel parts, it is common to perform quench hardening treatment on the base material (work) of steel parts to impart the required mechanical strength and hardness (wear resistance). The quench hardening treatment is roughly classified into whole quenching in which the entire work is quenched and partial quenching (surface quenching) in which the work is partially quenched, and is used properly according to required characteristics and the like. Surface hardening methods include induction hardening and laser hardening. Of these, in laser quenching, the work is self-cooled when the laser beam irradiation is stopped after heating the quenching target surface to the target temperature (quenching temperature) by irradiating the quenching target site (quenching target surface) with a laser beam. Can form a surface hardened layer. Therefore, there is an advantage that the device and process for forcibly cooling the work after heating, which is required in the case of induction hardening, can be omitted.

In the conventional laser quenching, for example, as described in Patent Documents 1 and 2 below, the laser beam focused on one point is applied to the quenching target surface of the work while the laser irradiation device and the work to be hardened are relatively moved. It is generally done by scanning along.

International Publication No. 02/090904 Japanese Patent No. 4431420

However, in the conventional laser quenching method disclosed in Patent Documents 1 and 2, since the area of the beam spot is small, there is a problem that quenching takes too much time when the area of the surface to be quenched is large. Further, when trying to quench the entire area of the quenching target surface evenly, it is necessary to accurately scan the laser beam (beam spot) along the quenching target surface, so that the operation of the laser irradiation device and / or the work is extremely high. It is necessary to control with precision. Therefore, when the area of the quenching target surface is large, it is difficult to accurately quench the entire area of the quenching target surface.

In view of the above circumstances, it is an object of the present invention to provide a technical means that enables efficient and accurate laser quenching even when the area of the work surface to be hardened is large.

The laser quenching device according to the present invention, which was devised to achieve the above object, is a laser quenching device that quenches the surface to be hardened by irradiating the surface to be hardened with a laser beam with the laser beam. In those comprising an emitting laser oscillator and an optical system arranged between the laser oscillator and the surface to be hardened, the optical system extends along the first direction of the surface to be hardened and has a dimension Z in the first direction. It has a band-shaped lens portion that forms a linear beam spot having the above longitudinal dimension L on the surface to be hardened, and when the laser beam is emitted, the work intersects the band-shaped lens portion in the first direction. It is characterized by relatively moving along the second direction of the surface to be hardened.

According to the laser quenching apparatus having the above configuration, if the beam intensity of the laser beam emitted from the laser oscillator and the relative moving speed of the work and the band-shaped lens portion are appropriately set, the laser beam can be emitted at the time of emission. The entire area of the quenching target surface can be laser-quenched evenly only by relatively moving the work and the band-shaped lens portion along the second direction of the quenching target surface intersecting (orthogonal) with the first direction of the quenching target surface. Therefore, even when the area of the quenching target surface of the work is large, laser quenching on the quenching target surface can be performed efficiently and accurately.

The optical system may be provided with a plurality of optical fibers arranged along the longitudinal direction of the band-shaped lens portion and having their respective outlet side ends facing the beam incident surface of the band-shaped lens portion. By doing so, the laser beam emitted from the laser oscillator can be branched and incident on each portion in the longitudinal direction of the band-shaped lens portion, so that the number of installed laser oscillators can be reduced.

At this time, it is preferable that the optical system is further provided with a collimated portion that makes the laser beam emitted from the laser oscillator parallel light so that the parallel light is incident on each optical fiber. As a result, the directivity of the laser beam can be improved, so that the beam intensity is attenuated until the laser beam is incident on the band-shaped lens portion (until the surface to be hardened is irradiated), resulting in poor quenching. It is advantageous in reducing the possibility of occurrence.

The band-shaped lens portion can be formed of, for example, a seamless band-shaped cylindrical lens, and a plurality of band-shaped cylindrical lenses having a longitudinal dimension La smaller than the longitudinal dimension L are connected along the first direction. It can also be formed by providing it. By doing so, it becomes easy to form an arbitrary shape along the longitudinal direction (first direction of the surface to be hardened) of the strip-shaped lens portion.

As the strip-shaped cylindrical lens, a lens having a constant focal length (cross-sectional shape) at each part in the longitudinal direction can be used, and a lens having different focal lengths at both ends and the center portion in the longitudinal direction (for example, in the longitudinal direction). The focal length is relatively long at both ends of the lens, and the focal length is relatively short at the center in the longitudinal direction).

In the above configuration, the surface to be quenched can be, for example, the outer diameter surface of a shaft-shaped (rod-shaped) work. That is, the laser quenching apparatus according to the present invention is preferably used when a tubular surface hardened layer is formed on the outer diameter side surface layer of the shaft work by irradiating the outer diameter surface of the shaft work with a laser beam. can do. At this time, if the first direction is the circumferential direction of the axial work, the second direction can be the axial direction (longitudinal direction) of the axial work.

Further, in the present invention, in order to achieve the above object, when the quenching target surface of the work is laser-quenched, it extends along the first direction of the quenching target surface and has a longitudinal dimension L equal to or larger than the dimension Z in the first direction. While irradiating the surface to be hardened with a laser beam transmitted through the band-shaped lens portion so that the linear beam spot having the beam spot is formed on the surface to be hardened, the workpiece intersects the first direction with respect to the band-shaped lens portion. Provided is a laser quenching method characterized in that the surface to be hardened is relatively moved in a second direction.

According to such a laser quenching method, it is possible to enjoy the same effects as when the laser quenching apparatus according to the present invention is adopted.

From the above, according to the present invention, even when the area of the quenching target surface of the work is large, it is possible to efficiently and accurately perform laser quenching of the quenching target surface.

It is a partial cross-sectional view of the drive shaft including the product to be processed by laser quenching. It is a figure which conceptually shows the whole structure of the laser quenching apparatus which concerns on one Embodiment of this invention. FIG. 5 is a perspective view schematically showing an example of an embodiment of laser quenching by the laser quenching apparatus shown in FIG. 2. FIG. 3 is a view when viewed from the direction of arrow X in the figure. (A) is a partial perspective view of a cylindrical lens, (b) is a view when (a) is viewed from the direction of arrow Y1, and (c) is a view of (a) when viewed from the direction of arrow Y2. It is a figure at the time. It is a developed view for demonstrating the dimensional relationship between the quenching target surface of a work, and the band-shaped lens part (beam spot). It is a partial front view of the laser quenching apparatus which concerns on other embodiment of this invention. (A) figure is a front view of the cylindrical lens used in laser hardening device shown in FIG. 7, (b) drawing, (a) view of the Y ₃ -Y ₃ a sectional view taken along a line, (c) drawing, ( it is Y ₄ -Y ₄ cross-sectional view taken along a line a) and FIG. It is a schematic diagram which shows the state which the work is laser-quenched by using the laser quenching apparatus which concerns on another Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an extraction of a part of a drive shaft 1 which is a kind of power transmission device. The drive shaft 1 is mounted on an automobile, for example, and transmits rotational power (torque) output from a rotational drive source such as an engine or an electric motor to drive wheels, and is inside the vehicle width direction (inboard side). Sliding constant velocity universal joint 2 arranged, fixed constant velocity universal joint (not shown) arranged outside in the vehicle width direction (outboard side), sliding constant velocity universal joint 2 and fixed constant velocity An intermediate shaft 10 for connecting the universal joint so as to be able to transmit torque is provided.

The sliding constant velocity universal joint 2 shown in FIG. 1 is a so-called tripod type, and is an outer joint member 3 having a cup portion 4 and a solid shaft portion 5, and an inner joint member housed in the inner circumference of the cup portion 4. A tripod member 7 as a torque transmission member and a roller 6 as a torque transmission member are provided. The tripod member 7 is provided with three leg shafts 8 extending in the radial direction at equal intervals in the circumferential direction, and one roller 6 is rotatably fitted to the outer periphery of each leg shaft 8.

Although not shown, guide grooves for guiding the rolling of the roller 6 are formed at three locations separated in the circumferential direction on the inner diameter surface of the cup portion 4 of the outer joint member 3. A spline 9 is formed on the outer diameter surface of the shaft portion 5 of the outer joint member 3 on the free end side to connect another member (for example, a side gear of a differential device) and the outer joint member 3 (for example, a side gear of a differential device) so as to be able to transmit torque. Has been done.

The cup portion 4 and the shaft portion 5 of the outer joint member 3 are made of a steel material having a carbon content of 0.20 to 0.45% by mass, such as carbon steel or alloy steel, and among them, high mechanical strength and The portion where hardness is required is hardened (surface quenching) to form a surface hardened layer Q. Specifically, as shown by cross-hatching in FIG. 1, a tubular (cylindrical) surface-hardened layer Q is formed on the surface layer portion on the free end side of the shaft portion 5. Although a surface-hardened layer is actually formed on the inner diameter surface of the cup portion 4, the illustration is omitted in FIG. The laser quenching apparatus (laser quenching method) according to the present invention can be preferably used, for example, when forming the surface-hardened layer Q to be provided on the shaft portion 5.

Hereinafter, the laser quenching apparatus according to the embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 conceptually shows the overall configuration of the laser quenching apparatus 19 according to the embodiment of the present invention. The laser quenching device 19 includes a laser irradiation device 20 and a drive mechanism (not shown) that moves the workpiece to be hardened relative to the laser irradiation device 20 (specifically, the band-shaped lens portion 23 described later). As shown in FIG. 3 and the like, the laser irradiation device 20 of the present embodiment irradiates the outer diameter surface Wa of the solid shaft-shaped work W with the laser beam LB to form a cylindrical surface on the surface layer of the work W. It is configured to form a hardened layer (for example, a surface hardened layer Q as shown in FIG. 1). Therefore, in the present embodiment, the outer diameter surface Wa of the work W is the quenching target surface S. Further, as the drive mechanism of the present embodiment, one that moves the work W along its longitudinal direction (the direction indicated by the arrow B in FIG. 3, which can also be said to be the axial direction of the work W) is adopted. Specifically, a conveyor or a linear drive device that linearly moves while holding the work W can be adopted.

The laser irradiation device 20 includes a laser oscillator 21 and an optical system 22 arranged on the traveling path of the laser beam LB emitted from the laser oscillator 21 (between the laser oscillator 21 and the outer diameter surface Wa of the work W). .. The optical system 22 includes a band-shaped lens portion 23, a plurality of optical fibers 25, and a collimating portion 26.

Any laser oscillator 21 can be used as long as it can emit a laser beam LB having a beam intensity capable of heating the outer diameter surface Wa of the work W to a target temperature (quenching temperature). That is, as the laser oscillator 21, an oscillator of various known lasers such as a carbon dioxide gas laser, a YAG laser, or a semiconductor laser can be used. However, if cost and compactness of the device are important, semiconductor lasers are preferable among the above-mentioned various lasers.

The band-shaped lens portion 23 extends along the first direction A of the outer diameter surface Wa of the work W, and has a linear beam spot BS (in the first direction A) having a longitudinal dimension L equal to or greater than the dimension Z of the first direction A. A continuous beam spot BS) is formed along the outer diameter surface Wa. In the present embodiment, as shown in FIGS. 3 and 4, the circumferential direction of the work W is the first direction A. Therefore, the dimension Z in the first direction A is the peripheral length of the outer diameter surface Wa of the work W. .. Therefore, in the present embodiment, the band-shaped lens portion 23 has an annular (round) shape as a whole, and the longitudinal dimension L is the same as the dimension Z in the first direction A of the outer diameter surface Wa. A band-shaped lens portion 23 capable of forming a (perfect circular) beam spot BS on the outer diameter surface Wa of the work W is used (see FIGS. 4 and 6).

As the band-shaped lens portion 23 for forming the beam spot BS as described above, a cylindrical lens having an annular (round) shape as a whole is used. In the present embodiment, as shown in FIGS. 4 and 6, a band-shaped (arc-shaped) cylindrical lens 24 capable of forming a linear beam spot BS whose longitudinal dimension La is smaller than the longitudinal dimension L is first. The band-shaped lens portion 23 is formed by providing a plurality of (here, a total of four cylindrical lenses 24A to 24D) in a row along the direction A. As shown in FIGS. 5A and 5B, each cylindrical lens 24 has a semicircular cross-sectional shape, and the flat surface serves as an incident surface (beam incident surface) 23a of the laser beam LB with respect to the band-shaped lens portion 23. Function. In this case, as shown in FIG. 5C, when the laser beam LB is incident on each portion of the beam incident surface 23a in the longitudinal direction, a linear beam spot BS is formed on the opposite side of the beam incident surface 23a.

As shown in FIGS. 2 to 4, a plurality (many) optical fibers 25 are arranged along the longitudinal direction of the strip-shaped lens portion 23, and the outlet side end portion 25a of each optical fiber 25 is a beam of the strip-shaped lens portion 23. It faces the incident surface 23a. By providing the optical fiber 25 in such an embodiment, the single laser beam LB emitted from the laser oscillator 21 is branched into a plurality of rows and then incident on each portion in the longitudinal direction of the strip-shaped lens portion 23. As a result, a linear (circular) beam spot BS can be formed on the outer diameter surface Wa of the work W without unnecessarily increasing the number of installed laser oscillators 21.

The collimating portion 26 shown in FIG. 2 is provided so that the laser beam LB emitted from the laser oscillator 21 is made into parallel light LB'and is incident on the inlet side end portion of each optical fiber 25. In this way, the directivity of the laser beam LB can be increased, so that the beam intensity is until the laser beam LB is incident on the band-shaped lens portion 23 (until the outer diameter surface Wa is irradiated). As a result, it is possible to prevent poor quenching from occurring as much as possible. In FIG. 2, the collimating portion 26 is composed of two lenses (concave lens and convex lens) arranged on the traveling path of the laser beam LB, but the configuration of the collimating portion 26 is not limited to this. That is, the collimating portion 26 can be configured by, for example, a combination of a lens and a mirror.

When laser quenching the quenching target surface S (outer diameter surface Wa) of the work W using the laser quenching apparatus 19 of the present embodiment having the above configuration, as shown in FIG. 3, the outer diameter of the work W The laser beam LB is directed toward the band-shaped lens portion 23 so that a circular beam spot BS extending in the circumferential direction of the surface Wa (first direction A of the surface S to be quenched) is formed on the outer diameter surface Wa of the work W. The work W is moved along its axial direction (second direction B of the quenching target surface S intersecting with the first direction A) while irradiating. At this time, the moving speed of the work W is set so that the forming portion of the circular beam spot BS (irradiated portion of the laser beam LB) of the outer diameter surface Wa of the work W is heated to the quenching temperature. As a result, as the work W moves, each axial portion of the outer diameter surface Wa of the work W is continuously heated and cooled and hardened. Therefore, when the axial movement of the work W is completed, the work W A tubular surface-hardened layer is formed on the surface layer portion.

According to the laser quenching apparatus 19 described above, when the laser beam LB is emitted from the laser oscillator 21, the work W is moved relative to the band-shaped lens portion 13 (here, the work W has an annular shape). The entire area of the quenching target surface S of the work W can be laser-quenched evenly only by passing the inside of the strip-shaped lens portion 13). For such an action effect, if the band-shaped lens portion 23 capable of forming the beam spot BS as described above is used, the beam intensity of the laser beam LB emitted from the laser oscillator 21 and the moving speed of the work W can be appropriately adjusted. Just by setting it, it can be enjoyed in the same way regardless of the size of the area S of the surface S to be hardened of the work W.

Therefore, according to the laser quenching apparatus 19 according to the present invention, even when the area of the quenching target surface S of the work W is large, the laser quenching of the quenching target surface S can be performed efficiently and accurately.

Although the laser quenching apparatus 19 and the laser quenching method according to the embodiment of the present invention have been described above, the embodiment of the present invention is not limited to this.

For example, in the embodiment described above, the strip-shaped lens portion 23 (cylindrical lens) having a perfect circular shape is used, but the strip-shaped lens portion 23 has a non-round shape as shown in FIG. Is also possible. That is, in the band-shaped lens portion 23 shown in FIG. 7, four cylindrical lenses 24 (24A to 24D) each having an arc shape are arranged in the circumferential direction of the work W (of the surface S to be hardened) as in the embodiment described above. It is formed by arranging the lenses along the first direction A), but by making the curvature (radius of curvature) of each cylindrical lens 24A to 24D different from that of the outer diameter surface Wa of the work W, it is a non-perfect circle. It is in the form.

In this case, in order to prevent the intensity of the linear (circular) beam spot BS formed on the outer diameter surface Wa of the work W from becoming non-uniform in the circumferential direction of the work W, each cylindrical lens 24 (24A to 24D) ) Have different focal lengths at both ends in the longitudinal direction and the central portion, more specifically, as shown in FIGS. 8A to 8C, from the central portion in the longitudinal direction to the longitudinal direction. I am using a lens whose focal length gradually increases toward the end. As a result, similarly to the embodiment described above, the outer diameter surface Wa of the work W can be laser-quenched efficiently and accurately, that is, a surface hardened layer having a uniform quenching depth (thickness) is formed on the work W. can do.

Further, in the embodiment described above, the work W is set to the driving side (the side that moves by receiving the driving force of the driving mechanism), and the band-shaped lens portion 23 (laser irradiation device 20) is set to the stationary side. On the contrary, the band-shaped lens portion 23 may be the driving side and the work W may be the stationary side.

Further, in the embodiment described above, the annular lens portion 23 is arranged so as to surround the outer diameter surface Wa of the axial work W, and the circular beam spot BS is placed on the outer diameter surface Wa of the work W. However, the band-shaped lens portion 23 may have a linear shape so as to form a linear beam spot BS extending in the axial direction of the work W (not shown). In this case, the "first direction A of the quenching target surface S" is the axial direction of the work W, and the "second direction B of the quenching target surface S intersecting (orthogonal) with the first direction A" is the circumferential direction of the work W. Is. In short, in this case, if the work W is relatively rotated around the axis of the linear band-shaped lens portion 23 extending in the axial direction of the work W, the surface layer of the work W is similar to the embodiment described above. A tubular surface-hardened layer can be efficiently and accurately formed on the portion. When adopting such a configuration, as the drive mechanism, one that rotates one of the work W and the band-shaped lens portion 23 relative to the other is used.

Further, in the above, the technical means according to the present invention was applied when laser quenching the outer diameter surface Wa of the work W (forming a tubular surface hardened layer on the work W). As schematically shown, it can also be applied when laser quenching is performed on the quenching target surface S having a flat surface shape.

FIG. 9 schematically shows an example in which laser quenching is performed on the upper surface of the flat work W, and the first direction A of the surface S to be hardened is defined as the width direction of the work W and the first direction A. The second direction B of the quenching target surfaces S that intersect (orthogonally) is the longitudinal direction of the work W. In this case, as the band-shaped lens portion 23, a linear (linear) beam spot BS having a longitudinal dimension L (L> Z in the illustrated example) equal to or greater than the dimension Z in the first direction A is quenched. A mechanism that can be formed above is used, and as a drive mechanism, a mechanism that moves the work W and the strip-shaped lens portion 23 relative to each other along the longitudinal direction of the work W is used.

The present invention is not limited to the above-described embodiments, and can be further implemented in various forms without departing from the gist of the present invention. That is, the scope of the present invention is indicated by the scope of claims, and further includes the equal meaning described in the scope of claims, and all modifications within the scope.

3 Outer joint member 5 Shaft 19 Laser quenching device 20 Laser irradiation device 21 Laser oscillator 22 Optical system 23 Band-shaped lens 23a Beam incident surface 24 Cylindrical lens 25 Optical fiber 25a Outlet side end 26 Collimating section A 1st direction B 2nd direction BS Beam Spot L Longitudinal Dimension La Longitudinal Dimension LB Laser Beam LB'Parallel Light Q Surface Hardened Layer S Hardened Surface W Work Wa Outer Diameter Surface

Claims (6)

A laser quenching device that quenches the quenching target surface by irradiating the quenching target surface of the work with a laser beam, and is arranged between the laser oscillator that emits the laser beam and the laser oscillator and the quenching target surface. In those equipped with an optical system
The optical system extends along the first direction of the quenching target surface, and forms a linear beam spot having a longitudinal dimension L equal to or larger than the first direction dimension Z on the quenching target surface. Have,
A laser quenching apparatus characterized in that when the laser beam is emitted, the work moves relative to the band-shaped lens portion along a second direction of the quenching target surface intersecting with the first direction. The optical system further includes a plurality of optical fibers arranged along the longitudinal direction of the band-shaped lens portion, and the outlet side end of each optical fiber faces the beam incident surface of the band-shaped lens portion. The laser quenching apparatus according to. The laser quenching apparatus according to claim 2, wherein the optical system further includes a collimating portion that makes the laser beam parallel light, and the parallel light is incident on the plurality of optical fibers. The band-shaped lens portion is formed by providing a plurality of band-shaped cylindrical lenses capable of forming a linear beam spot having a longitudinal dimension La smaller than the longitudinal dimension L in a row along the first direction. The laser quenching apparatus according to any one of claims 1 to 3. The laser quenching apparatus according to claim 4, wherein the cylindrical lens has different focal lengths at both ends and the center in the longitudinal direction. When laser quenching the surface to be hardened of the work,
The strip-shaped lens portion is formed so that a linear beam spot extending along the first direction of the quenching target surface and having a longitudinal dimension L equal to or larger than the dimension Z in the first direction is formed on the quenching target surface. While irradiating the quenching target surface with the transmitted laser beam, the work is relatively moved in the second direction of the quenching target surface intersecting the first direction with respect to the band-shaped lens portion. Laser quenching method.

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