JPH0621295B2 - Laser quenching method for inner surface of cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a method of quenching an inner surface of a cylinder by a laser beam.

<Prior art> Conventionally, for example, cast iron is generally used for engine cylinder blocks (crankcases), and the inner surface of the cylinder hole is made of high phosphorus cast iron or the like to improve wear resistance and prevent seizure. The sleeve that became was inserted. However, the sleeve is not only expensive, but also has the drawback of increasing the weight. Therefore, the present inventors have developed a laser quenching method for the inner peripheral surface of the cylinder that does not require the use of a sleeve by directly quenching the inner peripheral surface of the cylinder hole with a laser beam.

<Problems to be Solved by the Invention> In this laser quenching method for the inner peripheral surface of the cylinder, various portions such as a checkerboard pattern and a spiral pattern are provided on the inner peripheral surface of the cylinder by providing a portion for irradiating the laser beam and a portion for not irradiating the laser beam. A hardened pattern can be formed. In this quenching pattern, as shown in FIG. 5, when quenching is performed in a checkerboard pattern in which rectangular quenching portions 26 and unquenched portions 27 are alternately arranged, for example, when applied to a cylinder hole of an engine, At the initial stage of engine start, the unquenched portion 27 is worn and becomes an oil reservoir, so that a good sliding surface can be obtained.

In order to carry out quenching in a checkerboard pattern, for example, a method of moving the laser beam irradiation position in the cylinder circumferential direction while intermittently oscillating the laser oscillation by pulse oscillation and gradually shifting it in the axial direction is conceivable. However, in this method, if the relationship between the laser oscillation pulse time and the moving speed of the laser beam is changed a little, not only the positions of the hardened portion 26 and the unquenched portion 27 are displaced as shown in FIG. There is a problem that it is difficult to obtain an accurate rectangular checkerboard pattern because the quenching start end and the end end are rounded.

The present invention solves such a problem, and an object of the present invention is to provide a laser quenching method for the inner peripheral surface of a cylinder, which is capable of performing accurate checkerboard-like quenching.

<Means for Solving the Problems> A laser quenching method for a cylinder inner peripheral surface according to the present invention to achieve this object has a structure in which a plurality of rod-shaped shielding materials that reflect a laser beam are reflected on the cylinder inner peripheral surface. The cylinder inner peripheral surface is arranged at predetermined pitch intervals in the circumferential direction along the axial direction, and the cylinder inner peripheral surface exposed between the shields by irradiating a laser beam from the central portion toward the cylinder inner peripheral surface is predetermined. In the step of quenching over the axial quenching width of, and in a state where the arrangement position of the shielding material is shifted with respect to the step, the center portion is also directed toward the inner peripheral surface of the cylinder at an axial position different from the step. And irradiating a laser beam to quench the inner peripheral surface of the cylinder exposed between the shields over a predetermined quenching width in the axial direction.

<Operation> By irradiating the laser beam with the shielding material, the inner peripheral surface of the cylinder, which is the shadow of the shielding material, is not quenched, only the exposed portion between the shielding materials is quenched, and as a result The rectangular hardened portions having the axial hardened width are formed side by side in the circumferential direction at intervals. By shifting the position of the shielding material in the circumferential direction and displacing the laser beam irradiation position in the axial direction, it is possible to perform hardening in a checkered pattern in which rectangular hardened portions and non-hardened portions are arranged alternately.

<Example> An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an essential part of an embodiment of the present invention, and FIG.
II-II sectional view of the figure, FIG. 3 is a schematic configuration diagram of a laser hardening apparatus, and FIG. 4 is a sectional view of an engine cylinder block which is an example of an application target of the present invention.

In the cylinder inner peripheral surface quenching apparatus used in this embodiment, the third
As shown in the figure, a laser beam 11 emitted from a laser oscillator (not shown) is redirected by a bend mirror 12 toward a condenser lens 13, and after passing through the condenser lens 13, is further orthogonalized by a copper mirror 14. The direction is changed and it is irradiated. The copper mirror 14 is supported by a holder 15, and the holder 15 is supported by a support frame 16 so as to be rotatable around the optical axis of the condenser lens 13. On the other hand, a circumferential driving motor 17 is mounted on the support frame 16, and the motor 17 and the holder 15 are connected via a timing belt 18. The support frame 16 is slidably supported by a base 20 via a slider 19 in a direction parallel to the optical axis, and the axial drive motor 2 mounted on the base 20 is also supported.
The ball screw 22 which is connected to 1 is screwed. Therefore, insert the tip of the holder 15 into the center of the cylinder 23,
By operating the circumferential drive motor 17, the holder 15
To rotate the laser beam 11 so that the inner peripheral surface 2 of the cylinder 23 is rotated.
It is possible to move the laser beam 11 in the axial direction of the cylinder 23 by moving the support frame 16 by operating the axial drive motor 21.

In carrying out the method of the present invention, first, a Si heat-resistant paint is applied to the surface of the inner peripheral surface 23a of the cylinder 23 as a treatment for absorbing the laser beam 11. Then, as shown in FIGS. 1 and 2, a plurality of rod-shaped shielding members 24 for reflecting the laser beam 11 are arranged in the vicinity of the inner peripheral surface of the cylinder 23 along the axial direction thereof so as to have a predetermined pitch in the peripheral direction. Place an interval. That is, the upper ends of the shielding members 24 are fixed to the disc 25 at predetermined pitch intervals, and the shielding members 24 are suspended in the cylinder 23 by placing the discs 25 on the upper end surface of the cylinder 23. , Is positioned at the required position. The relation between the circumferential width of the cylinder 23 of the shielding material 24 and the pitch between the arranged pitches is such that when light is emitted from the center of the cylinder 23 and projected onto the inner peripheral surface of the cylinder 23, the light is projected on the inner peripheral surface. The lengths in the inner circumferential direction of the portion to be irradiated with and the shadowed portion of the shielding material 24 are made substantially equal.

Then, the laser beam is oscillated to irradiate the laser beam 11 from the center of the cylinder 23 toward the upper end of the inner peripheral surface 23a to start laser hardening, while the laser beam 11
The irradiation position of is moved in the circumferential direction by the circumferential drive motor 17 and is moved downward in the axial direction by the axial drive motor 21. The feed amount in the axial direction is set to be twice the quenching width in the axial direction (irradiation diameter of the laser beam 11) every time the laser beam 11 makes one revolution in the circumferential direction.
By irradiating the laser beam 11 using the shielding material 24 in this way, the inner peripheral surface 23a of the cylinder 23, which is a shadow of the shielding material 24, is not quenched, and only the portion exposed between the shielding materials 24 is quenched. To be done. Then, after moving the laser beam 11 to the required axial length, the laser oscillation and both motors 17 and 21 are stopped once. In this state, rectangular hardened portions having an axial hardened width corresponding to the irradiation diameter of the laser beam 11 are formed on the inner peripheral surface 23a of the cylinder 23 with a space therebetween and are arranged side by side in the circumferential direction. The directional interval is opened by the above-mentioned axial quenching width.

Next, by holding the disc 25 and shifting the shielding member 24 in the circumferential direction of the cylinder 23 by 1/2 of the pitch of the arrangement, a portion of the shielding member 24 which has been shaded until now is placed between the shielding members 24. Expose. Subsequently, the axial drive motor 21 is operated to raise the irradiation position of the laser beam 11 in the axial direction by the axial hardening width, and then laser oscillation is started and both motors 17 and 21 are moved in the opposite direction to the above process. The laser beam 11 is driven to rotate the irradiation position of the laser beam 11 in the circumferential direction and is raised in the axial direction, and the laser beam 11 is moved along a path which the laser beam 11 did not pass through in the above-mentioned step.
In this process, as in the previous step, the inner peripheral surface 23 of the cylinder 23 is
The portion exposed from between the shielding members 24 of a is hardened, and it is displaced from the hardened portion in the above step in the circumferential direction and the axial direction. As a result, the rectangular hardened portion 26 and the unquenched portion 27 are staggered. Hardened in a checkered pattern arranged in. Then, the laser beam 11 is applied to the cylinder 2
When reaching the upper end of 3, laser oscillation and both motors 1
Quenching work is completed by stopping 7 and 21.

As an example, a copper rod having a metallic luster is used as the shielding member 24, the diameter of the rod is set to 10 mm, and the arrangement interval thereof is set to 10 mm on the inner peripheral surface 23a of the cylinder 23, and the laser beam 11 is irradiated. The diameter is 5 mmφ, the laser wavelength is 10.6 μm, and the laser output is 1.0 kw continuous oscillation. The circumferential movement speed of the irradiation position of the laser beam 11 is 1.7 m / min on the circumferential surface, and the irradiation position of the laser beam 11 is Axial movement speed is 10 mm per revolution in the circumferential direction (axial hardening width 5 mm
5 times), a hardened portion 26 and a non-hardened portion 27 having the same length and a rectangular hardened portion 26 as shown in FIG. 5 were obtained. Further, the hardened portion 26 and the non-quenched portion 27 could be formed in a checkered pattern in which the vertical and horizontal directions are well ordered. The hardness of the hardened part 26 is 750 in Vickers hardness.
.About.800, the unquenched portion 27 was 200 to 250. As a result of assembling the cylinder 23 into an engine and testing the wear resistance, the unhardened portion 27 is slightly worn, and that portion serves as an oil reservoir to contribute to the formation of an oil film, thereby significantly improving the wear resistance. It was confirmed.

Although the irradiation position of the laser beam 11 is moved in the circumferential direction at the same time as it is moved in the axial direction in the above-described embodiment, in addition to this, for example, only the circumferential direction is moved to perform quenching, and then laser oscillation is performed. May be stopped and moved in the axial direction, and in this case, quenching can be performed sequentially from the end by switching the circumferential position of the shielding material 24 for each revolution.

Further, by changing the circumferential width of the shielding material 24, the pitch between the arranged pitches, or the axial length of the irradiation of the laser beam 11, it is possible to form quenching patterns of various sizes.

<Effects of the Invention> As described above in detail with reference to the embodiments, according to the present invention, it is possible to perform accurate checkerboard-like quenching on the inner peripheral surface of the cylinder. If it is applied to the quenching of the sliding surface such as the inner peripheral surface of the cylinder, good wear resistance performance can be imparted.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an embodiment of the present invention, and FIG.
II-II sectional view of the figure, FIG. 3 is a schematic configuration diagram of a laser hardening device, FIG. 4 is a sectional view of an engine cylinder block which is an example of an application target of the present invention, and FIG. 5 is an accurate checkerboard pattern FIG. 6 is an explanatory diagram of the hardened pattern of FIG. In the drawings, 11 is a laser beam, 23 is a cylinder, 23a is a cylinder inner peripheral surface 24 is a shielding material, 26 is a quenched portion, and 27 is an unquenched portion.

Claims (1)

[Claims] 1. A cylinder-shaped inner peripheral surface is provided with a plurality of rod-shaped shielding members which reflect a laser beam along the axial direction thereof at predetermined pitch intervals in the peripheral direction, and is directed from the central portion toward the cylinder inner peripheral surface. Of irradiating a laser beam on the cylinder inner peripheral surface exposed between the shielding materials over a predetermined axial quenching width, and a state in which the arrangement position of the shielding material is shifted with respect to the step. In the same manner, the cylinder inner peripheral surface exposed between the shielding members by irradiating the inner peripheral surface of the cylinder in the axial direction different from the step of the step to a predetermined axial quenching width. And a step of quenching continuously, a laser quenching method for an inner circumferential surface of a cylinder.