JPS62107024A - Method for laser quenching inner circumferential surface of cylinder - Google Patents

Abstract

PURPOSE:To quench an inner circumferential surface of a cylinder in chequered state in which rectangular quenched parts and unquenched parts are alternately arranged, by irradiating a laser beam to cylinder inner circumferential surface to which bar shaped interruption materials are arranged in shaft direction, from the center part and sliding the interruption material in circumferential direction. CONSTITUTION:Laser is oscillated to irradiate the laser beam 11 from center of the cylinder 23 to upper end part of the inner circumferential surface 23a and laser quenching is started. Simultaneously with this, irradiation position of the beam 11 is moved in circumferential and shaft directions. As the result, only the part exposed between the bar shaped interruption materials 24 is quenched. The beam 11 is moved to a required length in shaft direction, then laser oscillation is once stopped. Next, the material 24 is slidden by 1/2 of the arranged pitch in circumferential direction of the cylinder 23. Successively irradiating position of the beam 11 is raised in shaft direction by the quenching width in shaft direction, then irradiating position of the beam 11 is raised in shaft direction while being similarly revolved in circumferential direction to quench the surface 23a in the aimed chequered state.

Description

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

<Conventional technology> Conventionally, for example, cast iron has been generally used for cylinder blocks (crankcases) for engines, and the inner surface of the cylinder hole is coated with cast iron or the like to improve wear resistance and prevent seizure. A sleeve of more than 100 mm was inserted. However, the sleeve is not only expensive, but also has the drawback of increasing the amount of molded soil. Therefore, the present inventors have developed a method for laser hardening the inner circumferential surface of a cylinder, in which the inner circumferential surface of the cylinder hole is directly hardened using a laser beam, thereby eliminating the need for a sleeve.

<Problems to be Solved by the Invention> In this method of laser hardening the inner circumferential surface of a cylinder, by providing a portion that is irradiated with a laser beam and a portion that is not irradiated with a laser beam, each of the inner circumferential surfaces of the cylinder is formed into a checkerboard pattern, a spiral pattern, etc. A hardened pattern can be formed. In this hardening pattern, when hardening is performed in a checkerboard pattern in which rectangular hardened parts 26 and unhardened parts 27 are alternately arranged as shown in FIG. 5, for example, when applied to the cylinder hole of an engine, At the initial stage of starting the engine, the unhardened portion 27 wears out and becomes an oil reservoir, so that a good sliding surface can be obtained.

To harden in a checkered pattern, for example, while intermittent laser oscillation by pulse oscillation, the laser beam irradiation position I
A possible method is to move t in the circumferential direction of the cylinder and to gradually shift it in the axial direction. However, in this method, if the relationship between the laser oscillation noise time and the moving speed of the laser beam is even slightly out of order, not only will the positions of the hardened part 26 and the unhardened part 27 shift, as shown in FIG. The quenching start end and end end had a rounded shape, making it difficult to obtain an accurate rectangular checkered pattern.

The present invention is intended to solve these problems, and aims to provide a method for laser hardening the inner circumferential surface of a cylinder, which can perform hardening in an accurate checkered pattern.

Measures to Solve the Problems The method of laser hardening the inner circumferential surface of a cylinder according to the present invention to achieve this objective has a structure in which a plurality of rod-shaped shielding members that reflect a laser beam on the inner circumferential surface of the cylinder are used. are arranged along the axial direction at predetermined pitch intervals in the circumferential direction, and a laser beam is irradiated from the center toward the inner circumferential surface of the cylinder to expose the inner circumferential surface between the shielding materials. quenching over a predetermined axial quenching width, and in a state where the placement position of the shielding material is shifted with respect to the step, the inner circumferential surface of the cylinder at a different axial position from the center from the same step. A step of hardening the inner circumferential surface of the cylinder exposed between the shielding materials over a predetermined axial hardening width by irradiating a laser beam toward the shielding material. By using a shielding material and irradiating it with a laser beam, the inner peripheral surface of the cylinder that is in the shadow of the shielding material is not hardened, but only the portion exposed between the shielding materials is hardened, and as a result, the specified axis Rectangular hardened portions shouldering the directional hardening width are formed side by side in the circumferential direction at intervals. By shifting the position of this shielding material in the circumferential direction and displacing the laser beam irradiation position in the axial direction, hardening can be performed in a checkerboard pattern in which rectangular hardened parts and unhardened parts are arranged alternately.

Practical example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of essential parts of one embodiment of the present invention, and FIG.
■-■ cross-sectional view in the figure, Figure 3 is a schematic diagram of the laser hardening equipment
A JR diagram and FIG. 4 are Ifr side views of an engine cylinder block, which is an example of an object to which the present invention is applied.

In the cylinder inner peripheral surface hardening device used in this example, the third
As shown in the figure, a laser beam 11 emitted from a laser oscillator (not shown) is directed toward a condensing lens 13 by a pend mirror 12, and after passing through the condensing lens 13, it is further directed at right angles by a steel mirror 14. It is irradiated by changing the This steel 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, the support frame 16
A circumferential drive motor 17 is mounted thereon, and the motor 17 and the holder 15 are connected via a timing belt 18. The support frame 16 is slidably supported on a base 20 via a slider 19 in a direction parallel to the optical axis, and is connected to a drive motor 21 mounted on the base 20 in the axial direction. ? - The screws 22 are screwed together. Therefore, by inserting the tip of the holder 15 into the center of the cylinder 23 and operating the drive motor 17 in the circumferential direction, the holder 15 is rotated and the laser beam 11 is moved in the circumferential direction of the inner peripheral surface 23a of the cylinder 23. It is also 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-based heat-resistant paint is applied to the inner circumferential surface 23a of the cylinder 23 as a coating for absorbing the laser beam 11. As shown in FIGS. 1 and 2, a plurality of bar-shaped shielding materials 24 that reflect the laser beam 11 are placed close to the inner circumferential surface of the cylinder 23 along its axial direction at a predetermined pitch in the circumferential direction. Place at intervals. That is, each of the shielding materials 24 has its upper end fixed to a disc 25 at a predetermined pitch interval, and by placing the disc 25 on the upper end surface of the cylinder 23, the shielding material 24 is attached to the cylinder 23.
suspended inside and positioned at the desired position. The relationship between the width of the shielding material 24 in the circumferential direction of the cylinder 23 and its arrangement pitch is such that when light is irradiated from the center of the cylinder 23 and projected onto the inner peripheral surface of the cylinder 23, The length in the circumferential direction of the portion irradiated with light and the portion shaded by the shielding material 24 are made to be approximately equal.

Then, the laser 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.
The irradiation position is moved in the circumferential direction by the circumferential direction 1 m drive motor 17 and moved axially downward by the axial direction 1 drive motor 21. This axial feed amount is set so that it becomes twice the axial hardening width (irradiation diameter of the laser beam 11) every time the laser beam 11 makes one rotation in the circumferential direction. In this way, using the shielding material 24, the laser beam 11
By irradiating the cylinder 23, which becomes a shadow of the shielding material 24,
The inner circumferential surface 233 of the shield member 23 is not hardened, but only the portion extending between the shielding members 24 is hardened. After the laser beam 11 is moved to the required axial length, the laser oscillation and both motors 17 and 21 are temporarily stopped. 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 circumferential surface 23a of the cylinder 23 so as to be lined up in the circumferential direction at intervals,
The axial distance is the same as the axial hardening width.

Next, by holding the disk 25 and shifting the shielding material 24 in the circumferential direction of the cylinder 23 by the arrangement pitch b, the entire portion of the shielding material 24 that has been in the shadow of the shielding material 24 until now is exposed between the spaces. . Next, 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 irradiation position of the laser beam 11 is rotated in the circumferential direction and raised in the axial direction, and the laser beam 11 is moved along the MfJ path. In this process, as in the previous process, cylinder 2
The portion exposed between the shielding materials 24 on the inner circumferential surface 23a of No. 3 is hardened, and since it is shifted in the circumferential and axial directions from the hardened portion in the previous step, as a result, a rectangular hardened portion 26 and an unhardened portion are formed. The hardening is performed in a checkerboard pattern in which the portions 27 are arranged alternately. And laser beam 1
1 reaches the upper end of the cylinder 23, the laser oscillation and both motors 17 and 21 are stopped to complete the hardening work.

As an example, a round bar made of copper with metallic luster is used as the shielding material 24, the diameter of the round bar is set to 10, and the interval is 10 on the inner peripheral surface 23a of the cylinder 23, and the laser beam 11 is used as the shielding material 24. The irradiation diameter is 5 orchid φ, the laser wavelength is 10.6 μm, the laser output is 1.0 kW continuous oscillation, and the circumferential movement speed of the irradiation position of the laser beam 11 is increased to 1.7″/, l, Opening of laser beam 11 A17
When the illumination direction IW was set at 10 mrx for every 10% direction rotation (twice the axial hardening width of 5 mm), the hardened part 26 and the unhardened part were formed as shown in Fig. 5. A hardened portion 26 having the same length and a rectangular shape was obtained. Further, the hardened portions 26 and the unhardened portions 27 could be formed into an orderly checkered pattern vertically and horizontally. The hardness of the hardened portion 26 was 750 to 800 in terms of Vickers hardness, and the hardness of the unhardened portion 27 was 200 to 250. This cylinder 2
3 was assembled into an engine and tested for wear resistance, it was found that the unhardened part 27 was slightly worn, and that part became an oil pool and contributed to the formation of an oil film, significantly improving the wear resistance. confirmed.

In the above embodiment, the irradiation position of the laser beam 11 is moved in the circumferential direction and also in the axial direction, but in addition to this, for example, the irradiation position of the laser beam 11 is moved only in the circumferential direction to perform hardening, and then laser oscillation is performed. The shielding material 24 may be stopped and moved in the axial direction, and in this case, by switching the circumferential position of the shielding material 24 every round, it is also possible to perform hardening sequentially from the end.

Further, by changing the circumferential width of the shielding material 240, the arrangement pitch thereof, or the axial length of the laser beam 11 irradiation, it is possible to form hardened patterns of various sizes.

<Effects of the Invention> As described above in detail with reference to one embodiment, according to the present invention, the inner circumferential surface of the cylinder can be hardened in an accurate checkered pattern, and this can be applied to the cylinder block of the engine. By hardening the sliding surface such as the inner peripheral surface of the cylinder, good wear resistance can be imparted.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of essential parts of one embodiment of the present invention, and 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 the application of the present invention, and FIG. 5 is a precise checkered pattern. FIG. 6 is an explanatory diagram of an inaccurate checkered pattern. In the drawing, 11 is a laser beam, 23 is a cylinder, 23a is an inner peripheral surface of the cylinder, 24 is B paper material, 26 is a hardened portion, and 27 is an unhardened portion.

Claims (1)

[Claims] A plurality of rod-shaped shielding materials that reflect laser beams are arranged along the axial direction of the cylinder at predetermined pitch intervals in the circumferential direction, and the laser beam is irradiated from the center toward the cylinder inner peripheral surface. and hardening the inner circumferential surface of the cylinder exposed between the shielding materials over a predetermined axial hardening width; irradiating the inner circumferential surface of the cylinder at an axial position different from the step in the step of hardening the inner circumferential surface of the cylinder exposed between the shielding materials over a predetermined axial hardening width; A method for laser hardening an inner circumferential surface of a cylinder, comprising the steps of: