JP3775103B2 - Valve seat machining method for cylinder head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for processing a valve seat in a cylinder head for an internal combustion engine, and in particular, a dissimilar metal layer is formed in advance on the opening edge of an intake port or an exhaust port on the cylinder head side by a laser cladding method ( building up method). The present invention relates to a valve seat processing method in which a valve seat surface and a guide surface are formed by performing the following cutting process.
[0002]
[Prior art and problems to be solved by the invention]
As a processing method of the valve seat in the cylinder head, a concave groove is formed in advance on the opening edge on the intake or exhaust port side, and a different type of valve seat ring is press-fitted into the concave groove later, or a different metal is joined. In addition to the method, a method of forming a high-hardness built-up alloy layer (dissimilar metal layer) excellent in wear resistance by irradiating a high-density energy such as a laser beam while supplying a predetermined alloy powder to the concave groove It has been known.
[0003]
In this build-up method, in order to finish the valve seat surface that will be in direct contact with the counterpart valve with high accuracy, secondary finish cutting is indispensable. As shown in A) and (B), the port 2 of the cylinder head 1 is cut using a plurality of cutting tools 7, 8 and 9, and the dissimilar metal layer 3 is tapered in order from the back side of the port 2. The rear side guide surface 4, the valve seat surface 5, and the opening side guide surface 6 are each formed. The opening angle θ1 of the back side guide surface 4, the opening angle θ2 of the valve seat surface 5, and the opening angle θ3 of the valve seat surface 5 gradually increase toward the opening side of the port 2, and θ1 <θ2 < The relationship is θ3. The opening angle θ2 of the valve seat surface 5 is generally set to 90 degrees or 120 degrees.
[0004]
Here, in particular, when depositing the dissimilar metal layer 3 to be the valve seat, a high-hardness intermetallic compound is generated as the boundary layer 21 between the cylinder head 1 as a base material.
[0005]
Then, when the opening side guide surface 6 is processed by, for example, plunge cutting of the cutting tool 9 during the finishing cutting process, as shown in FIG. Is in contact with the boundary layer 21, and the local wear and chipping of the cutting edge is remarkably damaged, resulting in extremely shortened tool life and frequent tool changes. It is not preferable.
[0006]
On the other hand, in order to deal with the above-mentioned problem, as shown in FIG. 6, prior to the machining of the opening side guide surface 6 which is a finish cutting process, an opening angle θ4 (θ3 <θ4) is further formed on the outside as a roughing process. For example, Japanese Patent Application Laid-Open No. 8-218827 and Japanese Patent Application Laid-Open No. 8-218937 propose processing of the relief taper surface 10, but in this case, the cost increases due to an increase in the number of steps. become.
[0007]
The present invention has been made paying attention to the problems as described above, and solves the conventional problems without incurring an increase in cost. In particular, the present invention intends to provide a machining method capable of extending the tool life. Is.
[0008]
[Means for Solving the Problems]
The invention according to claim 1 is provided with a dissimilar metal layer functioning as a valve seat at the opening edge of the port opened and closed by the valve in the cylinder head, and the dissimilar metal layer from the back side to the opening edge side of the port. It is premised on that it is a valve seat processing method in which a tapered back side guide surface, a valve seat surface, and an opening side guide surface that gradually increase in opening angle are formed .
[0009]
On top of that, forming a groove in the portion to become the valve seat of the opening edge of the port, to form a surface corresponding to the opening-side guide surface in the opening edge of the port, of said groove Forming a chamfered corner portion by chamfering each corner edge portion on the back side and the opening edge side of the port, and depositing a dissimilar metal layer to be a valve seat in the concave groove including the chamfered corner portion And a taper that gradually increases the opening angle from the back side of the port to the opening edge side of the different metal layer while leaving the chamfered corner portion on the opening edge side of the port in the different metal layer. it is characterized in that it includes the step of forming Jo of the innermost side guide surface and the valve seat surface and the opening-side guide surface, respectively, the.
[0011]
Therefore, in the invention described in claim 1, since the opening side guide surface is formed on the cylinder head side which is the base material in advance before forming the dissimilar metal layer, when forming the dissimilar metal layer, The dissimilar metal layer is formed so as not to cover the opening side guide surface of the cylinder head as much as possible while filling the concave groove without excess or deficiency. In this way, when the opening side guide surface is formed in the dissimilar metal layer formed so as to fill the concave groove, the opening side guide surface on the dissimilar metal layer side is different from the opening side guide surface on the cylinder head side. The dissimilar metal layer is scraped off so as to be in a flush state, and as a result, the cutting allowance of the boundary layer generated at the boundary between the cylinder head and the dissimilar metal layer can be made substantially zero or minimal.
[0012]
In other words, by reducing the cutting allowance of the extremely hard boundary layer to the utmost limit, it is possible to reduce the burden on the tool for finishing the opening-side guide surface.
[0014]
The concave groove is usually formed by scraping the opening edge of the port in an annular shape, but the corner edge portion incidentally formed at the boundary with the opening edge as a result of forming the concave groove is left as it is. For example, if a dissimilar metal layer is formed by the overlaying method, the corner edge portion melts with the heat applied at the time of overlaying because its own heat capacity is small, and as a result, a cylinder head in which a part of the dissimilar metal layer is the base material The material will be diluted with the material. And if the dilution degree becomes large, it will become easy to invite the generation | occurrence | production of the crack by weakening of valve seat itself.
[0015]
Therefore, a chamfering process is performed in advance on the corner edge portion that is incidentally formed along with the formation of the concave groove as described above , and the chamfered corner portion is obtuse. By doing so, it is possible to avoid dilution due to melting at the corner chamfered portion when the dissimilar metal layer is formed by the overlaying method.
[0016]
【The invention's effect】
According to the first aspect of the present invention, in forming the opening side guide surface formed across the opening edge of the port and the dissimilar metal layer, the port opening edge of the cylinder head itself is formed before forming the dissimilar metal layer. Since the opening side guide surface to be formed in advance is formed in advance, the cylinder described above is used for processing the opening side guide surface on the side of the different metal layer which is formed for the first time by finishing cutting the different metal layer. The cutting allowance of the boundary layer formed at the boundary between the port opening edge on the head side and the dissimilar metal layer can be made substantially zero or minimal, so that the opening side can be reduced without increasing the number of machining steps. It is possible to extend the tool life by suppressing wear and chipping of the tool that controls the guide surface. In addition, by forming the opening side guide surface on the port opening edge side of the cylinder head itself as described above, the amount of build-up when forming the dissimilar metal layer by the build-up method can be reduced more than before, It can contribute to cost reduction.
[0017]
Also, more applying previously chamfering a corner edge portion of the recessed groove that will receive the different metal layer, corner chamfer for forming the different metal layer by the deposition method by heat at the time of the deposition It is difficult to melt and prevents dilution of the dissimilar metal layer with the base material, thereby contributing to improvement in quality.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
1 to 4 are views showing a preferred embodiment of a method for processing a valve seat according to the present invention. In particular, FIG. 1 shows an overall processing procedure, and FIGS. 2 to 4 are enlarged views of main parts of FIG. Each is shown. In addition, the same code | symbol is attached | subjected to the part which is common in FIG.
[0019]
As shown in FIG. 1, the valve seat processing procedure is largely divided into the groove processing step in FIG. 1A, the build-up step in FIG. 1B, and the finish cutting step in FIG. 1C. It consists of three steps.
[0020]
In the grooving step, as shown in FIG. 1A, the opening edge of the intake or exhaust port 2 formed in the cylinder head 1 made of aluminum alloy is cut into three parts in an annular shape. The groove 14 is cut using the cutting tools 11, 12, and 13. The machining here is plunge cut machining in which the cutting is performed by feeding only in the axial direction of the concave groove 14 in which each of the cutting tools 11, 12, 13 is to be formed, and the main shape of the concave groove 14 is cut by the cutting tool 11. At the same time, as shown in FIG. 2, an opening-side guide surface 15 having an opening angle θ 3 (see FIG. 5) similar to that of the conventional guide surface 6 is formed on the most opening edge side of the port 2 by the cutting tool 13. At the same time, the corner edge portion 16 on the back side and the corner edge portion 17 on the opening edge side that are incidentally formed by forming the concave groove 14 are chamfered by the cutting tool 12 to beveled corner portions 18 and 19. Form. The size of the chamfer here is, for example, about C0.1 to 0.5.
[0021]
In the build-up process subsequent to this groove processing process, as shown in FIG. 1B, for example, a predetermined alloy powder is supplied to the concave groove 14 while being melted by irradiation with a laser beam, followed by rapid cooling. The dissimilar metal layer 20 which is a build-up layer is formed as if the concave groove 14 is filled. At this time, as shown in FIG. 3, the edge portions on the back side and the opening edge side of the dissimilar metal layer 20 are stopped at the chamfered corner portions 18 and 19 formed earlier, and the dissimilar metal layer 20 is further connected to the port 2. Do not cover the general surface side.
[0022]
As described above, the chamfered corner portions 18 and 19 are formed in advance on the edge portion of the concave groove 14 to make the obtuse angle, so that even when high-density energy such as a laser beam is applied during the build-up processing, the chamfered corner is provided. The portions 18 and 19 are not easily melted, and the dissimilar metal layer 20 is not diluted by the melting of the aluminum alloy that is the base material of the cylinder head 1 as in the prior art. In addition, the amount of build-up of the dissimilar metal layer 20 can be smaller than before. However, the generation of the boundary layer 21 that is an intermetallic compound at the boundary between the cylinder head 1 that is the base material and the dissimilar metal layer 20 is unavoidable.
[0023]
In the finishing cutting process following the build-up process, as shown in FIG. 4 in addition to FIG. 1 (C), the dissimilar metal layer 20 previously formed using a plurality of cutting tools 7, 8, 9 is used as in the prior art. Cutting is performed to form the back side guide surface 4, the valve seat surface 5, and the opening side guide surface 25. Thereby, a valve seat having a shape substantially equivalent to that of the conventional one is formed. That is, the back side guide surface 4 is formed by plunge cutting with the cutting tool 7, while the valve seat surface 5 is formed by feeding the cutting tool 8 in an oblique direction, and the cylinder head 1 itself is formed by plunge cutting with the cutting tool 9. The opening side guide surface 25 on the different metal layer 20 side is formed so as to be flush with the opening side guide surface 15 on the port opening edge side.
[0024]
At this time, in the process of depositing the dissimilar metal layer 20 shown in FIG. 3, the dissimilar metal layer 20 side is strictly controlled by controlling the coating amount of the dissimilar metal layer 20 on the opening side guide surface 15. The cutting allowance t1 by the cutting tool 9 necessary for forming the opening side guide surface 25 can be significantly reduced to, for example, about 0 to 0.3 mm as compared with the conventional cutting allowance t2, resulting in higher hardness. The cutting allowance of the boundary layer 21 thus made can be minimized, and early wear and chipping of the cutting tool 9 can be suppressed. As a result of experiments conducted by the inventor, it has been confirmed that the life of the cutting tool 9 is extended to more than double the conventional life.
[Brief description of the drawings]
FIG. 1 is a process explanatory view showing a preferred embodiment of a valve seat processing method according to the present invention.
FIG. 2 is an enlarged explanatory view of a main part of FIG.
FIG. 3 is an enlarged explanatory view of a main part of FIG.
4 is an enlarged explanatory view of the main part of FIG.
FIG. 5A is an explanatory view showing an example of a conventional method for processing a valve seat, and FIG. 5B is an explanatory view of a main part of the valve seat after processing.
FIG. 6 is a main part explanatory view showing another example of a conventional valve seat processing method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Cylinder head 2 ... Port 4 ... Back side guide surface 5 ... Valve seat surface 14 ... Concave groove 15 ... Opening side guide surface (cylinder head side)
18, 19 ... Chamfered corner portion 20 ... Dissimilar metal layer (valve seat) as a build-up layer
21 ... Boundary layer 25 ... Opening side guide surface (different metal layer side)

Claims (1)

The cylinder head is provided with a dissimilar metal layer functioning as a valve seat at the opening edge of the port opened and closed by the valve, and the opening angle of the dissimilar metal layer gradually increases from the back of the port toward the opening edge. A processing method of a valve seat formed by forming a back side guide surface and a valve seat surface and an opening side guide surface, respectively,
Forming a groove in the portion to become the valve seat of the opening edge of said port,
A surface corresponding to an opening side guide surface is formed on the opening edge of the port, and a chamfered corner portion is formed by chamfering each corner edge portion on the back side and the opening edge side of the concave groove. Process,
Forming a dissimilar metal layer to be a valve seat in a concave groove including the chamfered corner portion by a build-up method ;
A tapered back-side guide whose opening angle gradually increases from the back side of the port toward the opening edge side of the dissimilar metal layer while leaving a chamfered corner portion on the opening edge side of the port in the dissimilar metal layer. Forming each of the surface, the valve seat surface and the opening side guide surface;
A method for processing a valve seat in a cylinder head , comprising :

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