JP2010209701A - Laser cladding method for forming valve seat and laser cladding device for forming valve seat - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of padding insufficiency at a padding end and inhibit occurrence of cracks due to dilution. <P>SOLUTION: A laser cladding method for forming a valve seat includes placing a metal powder ring 2 in a recessed groove 16 of a ring shape formed in a valve seat forming part of a cylinder head 1, and then forming the valve seat by emitting a laser beam hv to the metal powder ring 2, melting and solidifying it. The method includes, when the laser beam hv is emitted to the metal powder ring 2 sequentially in a circumferential direction from an emission start point and reaches an emission termination point, performing further padding by supplying metal powder 4 to the padding end 2A at the emission termination point and melting the metal powder 4 with the laser beam hv. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser cladding valve sheet forming method and a laser cladding valve sheet forming apparatus.

  For example, in an automobile engine, instead of a conventional method of driving a seat ring as a valve seat, a method of directly depositing a valve seat alloy on a cylinder head (laser cladding processing) has begun to be adopted. As described above, if the valve seat alloy is directly built on the cylinder head, the thermal conductivity can be greatly improved as compared with the seat ring driving method, and the cooling performance can be improved.

  Laser clad processing is a technique in which a metal powder (building material) is supplied to a valve seat forming portion of a cylinder head, and the metal powder is irradiated with a laser to be melted and solidified (for example, Patent Document 1). 2 etc.). Among them, a method of forming a ring-shaped valve seat by performing laser cladding on a valve seat forming portion of a cylinder head for an internal combustion engine is called laser cladding valve seat processing.

  In order to build up by irradiating a laser while supplying metal powder, tilt the cylinder head according to the angle of the valve so that the falling metal powder sits perpendicularly to the groove of the valve seat forming part, and the valve Processing is performed by irradiating a laser while rotating the cylinder head around the axis.

  However, if the cylinder head is rotated, the jig structure for that purpose becomes complicated and expensive, and only one valve can be built up. Therefore, a processing method is conceivable in which the cylinder head is fixed without rotating, and an annular metal powder ring body pressed in advance on the valve seat forming portion is placed and irradiated with laser to build up.

Japanese Patent Laid-Open No. 9-155583 JP 2003-275882 A

  However, in this processing method, when laser irradiation is performed, molten metal may be pulled at the processing end portion, resulting in insufficient overlay or cracking due to dilution. If the valve seat is thin or cracked, it is assumed that the airtightness in the cylinder cannot be maintained during the compression stroke of the air-fuel mixture.

  Therefore, the present invention provides a laser cladding valve sheet forming method and a laser cladding valve sheet forming apparatus capable of suppressing the occurrence of cracking due to dilution without causing an insufficient buildup at the buildup end portion.

  In the laser clad valve sheet forming method of the present invention, when the irradiation end point is reached by sequentially irradiating the ring-shaped metal material from the irradiation start point in the circumferential direction and reaching the irradiation end point, the build-up of this irradiation end point is performed. While the metal powder is supplied to the end portion, the metal powder is melted by a laser to further build up.

  The laser clad valve sheet forming apparatus of the present invention includes optical system means for irradiating a laser output from a laser oscillator along a circumferential direction to a ring-shaped metal material, and irradiation for irradiating the metal material with a laser. Metal powder supply means is provided for supplying metal powder to the end of the buildup at the irradiation end point when the irradiation end point is reached by sequentially irradiating in the circumferential direction from the start point.

  According to the laser clad valve sheet forming method of the present invention, when the laser is sequentially irradiated to the ring-shaped metal material from the irradiation start point in the circumferential direction to reach the irradiation end point, the molten metal is not irradiated at the irradiation end point. Pulling is likely to cause lack of build-up or dilution, but it is possible to build up by melting the metal powder with a laser while supplying the metal powder to the end of build-up at the end of irradiation. The shortage can be eliminated and the occurrence of dilution can be suppressed. Therefore, according to the method of the present invention, it is possible to produce a laser clad valve seat free from cracks.

  According to the laser clad valve sheet forming apparatus of the present invention, since the optical system means for irradiating the laser output from the laser oscillator to the ring-shaped metal material along the circumferential direction is provided, the cylinder head is rotated. Since it is not necessary to simplify the structure of the apparatus, the apparatus cost can be reduced. In addition, according to the apparatus of the present invention, since the metal powder supply means for supplying the metal powder to the buildup end portion at the laser irradiation end point is provided, the lack of buildup at the buildup end point can be solved.

FIG. 1 is a perspective view showing a laser cladding valve sheet forming apparatus. FIG. 2 is an enlarged perspective view of a main part showing a state before the metal powder ring body is arranged in the ring-shaped concave groove formed in the valve seat forming portion of the cylinder head shown in FIG. FIG. 3 is a view showing a state in which a laser is sequentially irradiated in the circumferential direction on the metal powder ring body. FIG. 4 is an enlarged perspective view of a main part showing the valve seat part after the build-up processing. FIG. 5 is a process diagram for further building up the buildup end portion. FIG. 6 is a process diagram showing a processing step when the build-up end portion is not further built up. FIG. 7 is a process diagram showing the processing method of the second embodiment. FIG. 8 is a process diagram showing the processing method of the third embodiment. FIG. 9 is a process diagram showing a processing method according to the fourth embodiment.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

“Embodiment 1”
First, the configuration of the laser cladding valve sheet forming apparatus will be described with reference to FIGS. 1 to 3.

  As shown in FIG. 1, the laser clad valve seat forming apparatus is a metal powder ring body (ring-shaped metal material) disposed in a ring-shaped concave groove formed in a valve seat forming portion of a cylinder head 1 such as an automobile engine. ) 2 is irradiated with a laser hv 3, and a powder supply device 5 that is a powder supply means for supplying the metal powder 4 to the build-up end portion of the metal powder ring body 2.

  The laser irradiation device 3 includes a laser oscillator 6 that oscillates a laser hv, a laser oscillator control unit 7 that controls the intensity of the laser hv oscillated by the laser oscillator 6, an NC control device 8, and a laser hv. And a condensing head 9 which is an optical means for irradiating the metal powder ring body 2 with light.

  The laser hv oscillated by the laser oscillator 6 is controlled by the laser oscillator control unit 7 and supplied to the condensing head 9. The condensing head 9 squeezes to a predetermined spot diameter and irradiates the metal powder ring body 2. The In the condensing head 9, the laser hv is directed in the circumferential direction (FIG. 3) with respect to the metal powder ring body 2 disposed in the ring-shaped concave groove 16 formed in the valve seat forming portion of FIG. A laser irradiation mirror 17 for sequentially irradiating in the direction of arrow A) is provided. The laser irradiation mirror 17 is driven to be rotatable so as to sequentially irradiate the laser hv oscillated from the laser oscillator 6 in the circumferential direction.

  The powder supply device 5 includes a nozzle 10 (not shown in FIG. 1 and shown in FIG. 5) for supplying the metal powder 4 to the build-up end portion of the metal powder ring body 2, and a hopper 11 for receiving and placing the metal powder 4. And a load meter 12 for measuring the amount of the metal powder 4, a feeder 13 for feeding the metal powder 4 from the hopper 11 to the nozzle 10, and a powder control unit 14 for controlling them.

  From the tip of the nozzle 10, the metal powder 4 accommodated in the hopper 11 is sent by the feeder 13, and is sprayed to the end portion of the metal powder ring body 2. As the metal powder 4, for example, a copper alloy having excellent thermal conductivity is used. The nozzle 10 is fixed, and the tip of the nozzle is directed toward the build-up end portion.

  In this laser clad valve seat forming apparatus, the laser oscillator 6, the laser oscillator control unit 7, the NC control device 8, and the powder supply control unit 14 are controlled by a computer 15, respectively. Further, in this laser clad valve sheet forming apparatus, the powder output is increased so that the laser output increases correspondingly when the supply amount of the metal powder 4 increases, and the laser output decreases correspondingly when the supply amount of the metal powder 4 decreases. The supply amount and laser output are linked.

  Next, a laser clad valve sheet forming method will be described. First, as shown in FIG. 2, for example, a metal powder, which is a ring-shaped metal material pressed into a valve seat shape in advance in a ring-shaped concave groove 16 formed in a valve seat forming portion of a cylinder head 1 made of an aluminum alloy, for example. The ring body 2 is arranged. In FIG. 2, since the engine structure has two intake and exhaust valves per cylinder, four laser clad valve seats are formed per cylinder. The cylinder head 1 is fixed to a jig so as not to rotate itself.

  Next, the laser oscillator 6 is driven to output the laser hv to the condensing head 9. The intensity of the output of the laser hv is controlled by the laser oscillator control unit 7. The outputted laser hv is focused to a predetermined beam spot diameter, and then irradiated onto the metal powder ring body 2 by the laser irradiation mirror 17. The laser irradiation mirror 17 is pivotally driven so as to sequentially irradiate the laser hv on the metal powder ring body 2 in the circumferential direction from the irradiation start point. When the metal powder ring body 2 is irradiated with the laser hv, the part is heated and the metal powder is melted.

  When the irradiation of the laser hv is sequentially performed in the circumferential direction from the irradiation start point and the irradiation end point is reached, the supply of the laser hv is stopped. In the buildup end portion 2A at this irradiation end point, as shown in FIG. 5 (A), the molten metal is pulled to cause a buildup shortage, resulting in a shortage. Therefore, as shown in FIG. 5B, the metal powder 4 is supplied from the nozzle 10 to the buildup end portion 2A, and the metal powder 4 is melted again by the irradiated laser hv to perform further buildup. The irradiation start point and the irradiation end point defined here are the same position or substantially the same position. When the metal powder 4 is supplied to the build-up end portion 2A, the additional build-up layer 18 is formed on the build-up end portion 2A that is recessed as shown in FIG. 5C. Is done.

  As shown in FIG. 5, when the processing is finished without supplying the metal powder 4 to the buildup end portion 2A, the molten metal is pulled as shown by the arrow B in FIG. As a result, a hollow portion 20 is formed which becomes a dent as shown in FIG. If the build-up is insufficient, the heat input to the base material 19 of the cylinder head 1 becomes too large and a dilution 22 is generated in which a part of the base material 19 is melted into the build-up layer 21 in which the metal powder ring body 2 is melted. After cooling, a crack 22 occurs in the buildup end portion 2A. However, in the present embodiment, since the metal powder 4 is melted by the laser hv while the metal powder 4 is supplied to the buildup end portion 2A, the buildup is further performed, so that occurrence of lacking and cracking is suppressed. be able to.

  When the build-up processing while supplying the metal powder 4 is finished, the supply of the laser hv and the metal powder 4 is stopped, and the build-up layer 21 is naturally cooled. The build-up layer 21 melted by natural cooling is solidified to become a cladding layer, that is, a laser cladding valve sheet.

  By repeating the above steps, a laser clad valve seat is formed by irradiating the laser hv to the metal powder ring bodies 2 disposed at all the valve seat forming portions formed on the cylinder head 1.

  According to the laser clad valve seat forming method of the present embodiment, when the metal powder ring body 2 pressed into a valve seat shape is sequentially irradiated with laser hv in the circumferential direction from the irradiation start point, the irradiation end point is reached. In this irradiation end point, the molten metal is pulled to cause overfilling or dilution easily. However, while supplying the metal powder 4 to the build-up end portion 2A at the irradiation end point, the metal powder 4 is lasered. By melting with hv and performing further overlaying, it is possible to eliminate the lack of overlaying and to reduce the heat input to the base material 19, thereby suppressing the occurrence of dilution. Therefore, according to the method of the present invention, it is possible to produce a laser clad valve seat free from cracks.

“Embodiment 2”
FIG. 7 is a process diagram showing the processing method of the second embodiment. In the second embodiment, the metal powder 4 is supplied to the melting portion 23 generated in the buildup end portion 2A at the irradiation end point of the laser hv, and the metal powder 4 is melted by the laser hv to perform further buildup.

  In the second embodiment, laser irradiation is not performed by supplying the metal powder 2 after stopping the irradiation of the laser hv at the irradiation end point as in the first embodiment, but performing the laser irradiation as shown in FIG. The metal powder 4 is supplied to the melting part (melting pool) 23 generated therein, and the metal powder 4 is melted by a laser hv to perform overlaying. The melting part 23 is a part where the metal powder is melted by irradiating the laser hv to the metal powder ring body 2 and heating it.

  By carrying out like this, the remelting part of the original build-up layer 21 can be reduced. That is, in the first embodiment, the supply of the laser hv is temporarily stopped at the irradiation end point, and then the laser hv is supplied again. Therefore, the build-up end portion 2A that has been cooled and solidified is melted again. However, in the second embodiment, even if the laser hv reaches the irradiation end point, the laser hv is continuously supplied as it is, and the metal powder 4 is supplied to the melting portion 23 heated by the irradiation of the laser hv, thereby increasing the build-up. As a result, the remelted portion is eliminated. In FIG. 5C, a boundary 24 as shown by a broken line is formed between the part that has been built up and the part that has not been built up, but such a boundary 24 is not formed in FIG. 7B.

  As described above, according to the laser clad valve sheet forming method of the second embodiment, the remelted portion of the original build-up layer 21 can be reduced, and the boundary 24 between the remelted portion and the other portion is suppressed. Generation of cracks can be further eliminated.

“Embodiment 3”
FIG. 8 is a process diagram showing the processing method of the third embodiment. In the third embodiment, in addition to the processing steps of the second embodiment, the metal powder 4 is also supplied from the irradiation end point to the overlap portion that overlaps the irradiation start point, and the metal powder 4 is melted with a laser hv to build up the metal. .

  In the second embodiment, it is possible to build up without the boundary 24, but there may be a slight dent 25 (see FIG. 7B) in the overlap region overlapping the irradiation start point. If the dent 25 is left as it is, it causes cracking due to stress concentration. Therefore, in the third embodiment, when the metal powder 4 is supplied to the melting part 23 in FIG. 8 (A) and the metal powder 4 is melted by the laser hv, the overfill is performed as shown in FIG. 8 (B). The metal powder 4 is also supplied to the lap portion, and overlaying is performed by laser hv irradiation. Then, the dent 25 slightly dented in the overlap portion is filled with the additional build-up layer 2B.

  The metal powder 4 supplied to the recess 25 in the overlap portion may be supplied from a dedicated nozzle 26 that supplies the metal powder 4 only to this portion. That is, the powder supply device 5 has a dedicated nozzle 10 for supplying the metal powder 4 to the buildup end portion 2A and a dedicated nozzle 26 for supplying the metal powder 4 to the recess 25 recessed in the overlap portion. The configuration. These two nozzles 10 and 26 are both in a fixed state.

  According to the laser clad valve sheet forming method of the third embodiment, the metal powder 4 is supplied to the overlap portion following the processing of the second embodiment to build up, so that a slight dent 25 can be eliminated, Generation of cracks can be further suppressed.

“Embodiment 4”
FIG. 9 is a process diagram showing a processing method according to the fourth embodiment. In the fourth embodiment, the supply amount of the metal powder 4 is changed in accordance with the moving position and output of the laser hv in the buildup end portion 2A.

  In any of the first to third embodiments, the nozzle 10 is fixed. In the fourth embodiment, the nozzle 10 is moved in synchronization with the laser hv, and the supply amount of the metal powder 4 is changed according to the output of the laser hv. Like that. Specifically, as shown in FIG. 9 (A), when the laser hv is moved in the circumferential direction with respect to the metal powder ring body 2, the laser hv is formed at the buildup end portion 2A where the lacking is most insufficient. When it reaches, the metal powder 4 is supplied from the nozzle 10. At that time, the supply amount of the metal powder 4 is changed according to the moving position and output of the laser hv. The intensity of the laser hv is controlled by the laser oscillator control unit 7. The supply amount of the metal powder 4 is controlled by the powder control unit 14.

  The overlaying end portion 2A is a concave recess. For this reason, the supply amount of the metal powder 4 is initially made small, and the supply amount of the metal powder 4 is gradually increased until the laser hv moves to the central position where the buildup end portion 2A is the largest recess. Similarly, the output of the laser hv is gradually increased, and the maximum output is obtained at the center position of the buildup end portion 2A where the supply amount of the metal powder 4 is the largest. At the center position of the build-up end portion 2A, the metal powder 4 is continuously supplied so as to be a substantially constant amount so as not to cause a lack of thickness. Thereafter, since the dent gradually decreases from the center position of the buildup end portion 2A, the supply amount of the metal powder 4 is decreased. Accordingly, the output of the laser hv is gradually reduced from the center position of the buildup end portion 2A.

  As described above, according to the laser cladding valve sheet forming method of the third embodiment, since the supply amount of the metal powder 4 is changed in accordance with the moving position and output of the laser hv at the buildup end portion 2A, this buildup is performed. It is possible to build up with the amount of metal powder, the amount of laser movement, and the amount of laser output corresponding to the shape of the dent of the end portion 2A, and it is possible to realize a smooth buildup with no dent as shown in FIG. it can. As a result, it is possible to suppress the occurrence of cracks due to stress concentration due to dilution, non-welding, and the presence of dents.

  The present invention can be used in a technique for directly depositing a valve seat alloy on a cylinder head.

1 ... Cylinder head 2 ... Metal powder ring body (ring-shaped metal material)
DESCRIPTION OF SYMBOLS 3 ... Laser irradiation apparatus 4 ... Metal powder 5 ... Powder supply apparatus 9 ... Condensing head (optical system means)
DESCRIPTION OF SYMBOLS 10,26 ... Nozzle 16 ... Ring-shaped concave groove 17 ... Laser irradiation mirror (optical system means)
18 ... Additional build-up layer 19 ... Base material 20 ... Missing portion 21 ... Build-up layer 22 ... Crack crack 23 ... Melting portion 24 ... Boundary 25 ... Depression

Claims (5)

Laser clad that forms a valve seat by placing a ring-shaped metal material in a ring-shaped groove formed in the valve seat formation part of the cylinder head, and then irradiating and melting the metal material to build up In the valve seat forming method,
When the laser beam is sequentially irradiated in the circumferential direction from the irradiation start point for irradiating the metal material to reach the irradiation end point, the metal powder is supplied to the buildup end portion of the irradiation end point while supplying the metal powder. A method for forming a laser clad valve sheet, comprising: melting the material with a laser to further build up. The laser cladding valve sheet forming method according to claim 1,
The method for forming a laser clad valve sheet, wherein the metal powder is supplied to a melted portion generated at a buildup end portion at the irradiation end point. A method for forming a laser clad valve sheet according to claim 2,
A method for forming a laser clad valve sheet, wherein the metal powder is further supplied from the irradiation end point to an overlap portion overlapping the irradiation start point. The laser cladding valve sheet forming method according to any one of claims 1 to 3,
The method for forming a laser-clad valve sheet, characterized in that the supply amount of the metal powder is changed in accordance with the moving position and output of the laser at the buildup end portion. A laser clad valve seat that forms a valve seat by placing a ring-shaped metal material in a ring-shaped concave groove formed in the valve seat formation portion of the cylinder head and then irradiating the metal material with a laser to melt and solidify it. In the forming device,
Optical system means for irradiating the metal material along the circumferential direction with the laser output from a laser oscillator;
A powder supply means for supplying metal powder to a buildup end portion of the irradiation end point when the laser beam is sequentially irradiated in the circumferential direction from the irradiation start point for irradiating the metal material and reaches the irradiation end point; A laser clad valve sheet forming apparatus comprising:

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