JPH08218827A - Machining method for valve seat part of cylinder head - Google Patents

Abstract

PURPOSE: To prevent breakage of a padded layer, or pitching of a cutting tool by adding a pre-stage cutting process for forming a flank work surface of a larger diameter than a guide surface of an applicable diameter to a cutting tool for a flank taper surface of a larger opening angle than a guide taper surface. CONSTITUTION: In machining of a valve seat part T of a cylinder head 1, in a pre-stage of a cutting process, a flank work surface a' of a larger diameter than a guide work surface (a) applicable to a rotation diameter of a cutting tool for a guide taper surface T3 and a flank taper surface T4 of a larger opening angle than an opening angle of the guide taper surface T3 is formed on the side of a suction air valve aperture 2 and a lower mating face 1a of an exhaust valve aperture 3. Breakage or generation of cracks at the time of cutting work to a padded layer 7 are thus prevented, and generating of pitching of the cutting itself can be prevented. Yield of products can thus be improved, and life of the cutting tool can be elongated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head in which a build-up layer is formed on the periphery of a valve opening of a cylinder head by, for example, a laser cladding method, and a tapered valve seat surface is machined on the build-up layer. The present invention relates to a method for processing a valve seat portion.

[0002]

2. Description of the Related Art In recent years, a valve seat portion of a cylinder head has been proposed which is formed by a laser clad method (see, for example, JP-A-62-150014 and JP-A-4-123885). . As shown in FIG. 10, this laser clad method uses a cylinder head 5
An annular groove 53 is formed in the valve opening 52 of No. 1, and while supplying metal powder into the groove 53, the metal powder is irradiated with high-density energy by a laser or the like to be melted, It is cooled by the self-cooling ability to form a build-up layer (different metal layer) 54.
The valve seat portion T is formed by cutting the above.

In forming the valve seat portion T, a second opening angle of 90 degrees with respect to the axis C of the intake and exhaust valves is provided so that intake and exhaust gases can smoothly flow in and out during valve lift. Generally, the first tapered surface T1 having an opening angle of 30 degrees is formed on the upstream side and the downstream side of the tapered surface (valve seat surface) T2, and the third tapered surface T3 having an opening angle of 120 degrees is formed on the downstream side. is there. The sealing surface of the valve is in airtight contact with the second tapered surface T2.

Such first to third tapered surfaces T1 to T3
Conventionally, when cutting, the tool holder has 30
Degrees, 90 degrees and 120 degrees bite are mounted on the concentric circles, and first, the 30 degree bite and 120 degree bite are advanced to perform plunge cutting, thereby forming the first and third tapered surfaces T1 and T3 at the same time. After this, both the above-mentioned cutting tools are 0.2-1mm
The tool is retracted about a degree, and in this state, the 90 degree bite is advanced to traverse cut, thereby forming the second tapered surface T2.

[0005]

However, in the above-mentioned conventional processing method, as shown in FIG.
There is a problem that the hard particles 54a constituting the overlay layer 54 are apt to be chipped or cracked when the traverse is cut, and the product may be defective in some cases. In addition, there is a problem that the above-mentioned cutting tool itself may be pitched, resulting in a short cutting tool life.

The present invention has been made in view of the above-mentioned conventional situation. A cylinder capable of extending the life of the cutting tool while preventing chipping of the overlay layer (different metal layer) and pitching of the cutting tool to reduce product defects. It is an object of the present invention to provide a valve seat processing method for a head.

[0007]

The inventor of the present application has investigated the cause of the chipping and cracking of the hard particles, and when cutting with a 90-degree cutting tool, the 120-degree cutting tool has a third tapered surface a It was found that the above problem can be solved by avoiding the contact of the 120-degree bite, and the present invention has been achieved. Is.

According to a first aspect of the present invention, there is provided a different metal layer forming step of forming a different metal layer made of a material having higher wear resistance and higher heat resistance than the cylinder head material on the periphery of the valve opening of the cylinder head, and the different metal layer. A tapered valve seat surface having a first opening angle, and a guide taper surface having a second opening angle larger than the first opening angle closer to the cylinder block mating surface than the valve seat surface,
In a method of processing a valve seat portion of a cylinder head, which comprises a cutting step of cutting a guide surface having a diameter corresponding to the guide taper surface cutting tool, prior to the cutting step, the cylinder is further cut from the guide tapered surface. It is characterized in that a pre-stage cutting step of cutting a flank taper surface having an opening angle larger than the second opening angle and a flank surface having a diameter larger than that of the guide surface is added near the block mating surface.

Here, as shown in FIG. 10, the material of the cylinder head 51 and the overlay layer 54 are formed on the third taper surface T3.
There is a case where a boundary portion 56 is located and there is a fine cavity in the boundary portion 56. Such a boundary 56
When machining a tool with a high wear resistance, the tool itself may be chipped because intermittent cutting is performed under the same cutting conditions at portions with extremely different hardness.

Therefore, the invention of claim 2 is characterized in that the boundary portion between the material of the cylinder head and the different metal layer is located within the relief taper surface.

According to a third aspect of the present invention, in the different metal forming step, an annular groove is formed in the peripheral edge of the valve opening, the different metal powder is filled in the groove, and the different metal powder has a high density. It is characterized in that a different metal layer is formed by irradiating energy.

[0012]

According to the method of machining the valve seat portion of the cylinder head according to the invention of claim 1, it corresponds to the relief taper surface and the guide taper surface cutting tool having a larger opening angle than the guide taper surface in the preceding step of the cutting process. Since a pre-cutting process that forms a relief surface with a larger diameter than the guide surface with a diameter that is larger than that of the guide surface, the relief taper surface and the relief surface become relief when machining the valve seat surface This can be avoided, and vibration of the cutting tool for valve seat surface processing can be prevented. As a result, the motion of the valve seat surface processing tool becomes smooth, chipping of the hard particles and occurrence of pitching of the tool itself can be prevented, the product yield can be improved, and the tool life can be extended.

According to the second aspect of the invention, since the boundary between the cylinder head material and the different metal layer is set in the escape taper surface, the entire guide taper surface is located in the different metal layer. Intermittent cutting due to cavities at the boundary can be avoided, chipping when using a high wear resistant bite can be prevented, and from this point the tool life can be extended.

According to the third aspect of the invention, the different metal powder is melted by high density energy and rapidly cooled by the self-cooling ability of the cylinder head material to form the different metal layer.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 9 are views for explaining a method of processing a valve seat portion of a cylinder head according to an embodiment of the invention of claim 1, and FIG. 1 shows a valve seat portion formed by the method of this embodiment. Sectional views shown in FIGS. 2 to 4 are process drawings for explaining the method of the above embodiment, and FIGS.
(C) is a view showing a cutting tool holder adopted in the method of the above embodiment, FIGS. 6 and 7 are sectional views for explaining the build-up process of the above embodiment, and FIGS. 8 and 9 are the methods of this embodiment. 3A and 3B are a sectional view and a bottom view of a cylinder head to which is applied.

In FIGS. 8 and 9, 1 is a cylinder head made of aluminum die cast having a valve seat portion formed by the method of this embodiment, and a cylinder block (not shown) is provided on the lower mating surface 1a of the cylinder head 1. A head cover is connected to the upper mating surface 1b. A combustion recess 1c forming a combustion chamber is recessed in the lower mating surface 1a of the cylinder head 1, and three intake valve openings 2 and two exhaust valve openings 3 are formed in the recess 1c. The intake valve opening 2 is led out to one side wall of the cylinder head 1 by the intake port 4, and the exhaust valve opening 3 is led out to the other side wall by the exhaust port 5.

A valve seat portion T is formed in the intake valve opening 2 and the exhaust valve opening 3 by a processing method described later. The valve seat portion T includes a first taper surface (upstream guide taper surface) T1 having an opening angle of 30 degrees with respect to the shaft center (valve shaft core) C of the openings 2 and 3 and a second taper surface (valve seat) having an opening angle of 90 degrees. Surface) T2, a third taper surface (downstream guide taper surface) T3 of 120 degrees, and the sealing surfaces of the intake and exhaust valves (not shown) come into airtight contact with the second taper surface T2. There is.

The valve seat portion T is composed of a built-up layer 7 and a cylinder head material. The overlay layer 7 is made of, for example, a copper alloy, a molybdenum alloy, a tungsten alloy, or the like, and is overlay-molded by a laser clad method described later.

Here, the second taper surface T2 is entirely constructed by the overlay layer 7, while most of the first and third taper surfaces T1 and T3 are overlay. Layer 7, the rest being composed of cylinder head material. In other words, the first and third inner peripheral areas occupied by the overlay layer 7 on the first tapered surface T1 and the third tapered surface T3 are
Ratio A to the inner peripheral area of the entire third tapered surface T1, T3
1 / A and A1 '/ A' are 50% or more. By setting the area of the overlay layer 7 to be 50% or more of the total area of the tapered surface in this way, it becomes possible to optimally set the processing conditions of the cutting tool in the cutting process, and the processing accuracy and the cutting tool life can be improved accordingly. .

The ratio A2 / A, A2 '/ A' of the inner peripheral area of the cylinder head material to the total inner peripheral area is 5
The above processing can be stabilized by setting it to 0% or more, that is, setting the area of either one to 50% or more, but it is more desirable to increase the area occupied by the hardfacing layer 7 having high hardness. On the other hand, when using the engine,
The area occupied by the overlay layer 7 is reduced, that is, A1 / A,
It is desirable to reduce the ratio of A1 '/ A'. With such a structure, peeling of the overlay layer 7 can be prevented. It is considered that this is because the build-up layer 7 has a smaller linear expansion coefficient than that of the cylinder head material, and thus the larger the A1 / A and A1 ′ / A ′, the greater the stress generated in the boundary layer portion.

A fourth taper surface (escape taper surface) T4 having an opening angle larger than the opening angle of the third taper surface T3 is provided near the lower mating surface 1a side of the intake valve opening 2 and the exhaust valve opening 3.
Further, a relief processing surface a'having a larger diameter than the guide processing surface a corresponding to the rotation diameter of the third taper surface T3 bite is formed. Specifically, the opening angle of T4 is 140 degrees, and the processing surface a'is set to be larger than the diameter of the processing surface a for 120 degrees by about 0.6 mm (see FIG. 1). In this way, the fourth taper surface (escape taper surface) T4 and the relief surface a
By forming ′ ′, it is possible to prevent the occurrence of chips and cracks during the cutting process of the overlay layer 7, and it is possible to smoothly perform the inflow of the intake air and the outflow of the exhaust gas, thereby improving the gas exchange efficiency. be able to.

Next, a method of forming the valve seat portion, which is a feature of this embodiment, will be described. The method of this embodiment comprises a build-up process, a pre-stage cutting process, and a cutting process, and each process will be described below in order.

1. Overlaying process First, the cylinder head material 1'manufactured by the aluminum die casting method in the shape shown by the chain double-dashed line in FIG. 6 is subjected to the cutting process shown by the solid line in the figure to form the annular recessed groove 10.
In this case, it is desirable that the top portion 10a of the recessed groove 10 be as thick as possible within a range that can be removed by post-processing. If the top portion 10a is thinned, the aluminum of the material 1'may be melted during the laser processing to cause a pinhole. Further, it is desirable to set the tapered surface in the concave groove 10 as little as possible so that the cutting tool will not chatter during the above processing.

Next, while supplying the copper alloy powder into the groove 10 with a nozzle (not shown) with the top 10a facing upward, the alloy powder is irradiated with a laser to be melted. The melted alloy is rapidly cooled by the self-cooling ability of the cylinder head material 1 ', whereby the buildup layer 7 is formed. The two-dot chain line shown in FIG. 7 is a finish processing line in the cutting step described later.

2. Pre-stage cutting process This pre-stage cutting process is performed by the end mill 1 as shown in FIG.
1 is used to cut the valve seat portion of the cylinder head material 1 ′, and the relief processing surface is about 0.6 mm larger than the diameter of the fourth taper surface 4 having an opening angle of 140 degrees and the processing surface a for 120 degrees. a'is formed. In this case, the intake and exhaust openings 2 and 3 can be continuously processed by the end mill 11.

3. Cutting process The cutting tool holder 15 used in this cutting process is shown in FIG.
As shown in (c) to (c), the main shaft device (not shown) is supported so as to be movable back and forth, and is rotationally driven by a motor. The blade holder 15 has a predetermined angle of 30
A degree machining bit 16, a 120 degree machining bit 17, and a 90 degree machining bit 18 are mounted, and the 90 degree bite 18 is arranged on a feed member 19 that moves relative to the cutting tool holder 15 in the axial direction. It is set up. Here, a CBN bite is adopted for each of the above-mentioned bits in order to improve wear resistance.

Then, with the feed member 19 retracted, the blade holder 15 is inserted into the opening 2 of the cylinder head blank 1 '.
No. 3 insert, first 30 degree bit 16 and 120 degree bit 17 are advanced to make plunge work.
The tapered surface T1 and the third tapered surface T3 are simultaneously formed. After this plunge processing, both cutting tools 16 and 17 are retracted by about 0.2 mm (see FIG. 3).

Then, the feeding member 19 is advanced to move to 9
A traverse process is performed by the 0 degree cutting tool 18 to form the second tapered surface T2. In this case, 0.3 mm is provided between the turning diameter of the 120-degree machining tool and the relief machining surface a '.
Since a certain degree of clearance is secured, the 120-degree cutting tool 17 does not come into contact with the 90-degree cutting tool 18, and the movement of the 90-degree cutting tool 18 can be performed smoothly. In this way, the valve seat portion T of the cylinder head 1 described above is formed (see FIG. 1).
reference).

As described above, according to the method of this embodiment, in the pre-cutting step of the cutting step, the fourth taper surface T4 having an opening angle of 140 degrees and the relief surface a'having a diameter larger than the rotation diameter of the 120-degree cutting tool. Since it was formed, 120 degree byte 1
The vibration due to the contact of 7 with the processed surface is not transmitted to the 90-degree cutting tool 18. As a result, it is possible to prevent the hard particles of the build-up layer 7 from being chipped, and to prevent pitting from occurring in the cutting tool itself, thereby improving the product yield and
The tool life can be extended.

Next, an embodiment of the invention of claim 2 will be described. In this embodiment, as shown in FIG. 1, a boundary portion 9'between the material of the cylinder head 1 and the overlay layer 7'is located on the fourth tapered surface T4. This makes the third
The entire tapered surface T3 is located in the overlay layer 7 '.

As described above, in this embodiment, the build-up layer 7'is extended so that the boundary portion 9 between the aluminum material of the cylinder head 1 and the build-up layer 7'is located within the fourth tapered surface T4. , CBN tool can prevent chipping when processing the third tapered surface T3, and extend the tool life. here,
Since the fourth tapered surface T4 is processed by the end mill 11, the problem of chipping does not occur so much.

In the above embodiment, the case where the different metal layer is formed by the laser clad method has been described, but the different metal layer of the present invention can be formed by various methods such as press fitting and joining of a seat ring. .

[0033]

As described above, according to the method of machining the valve seat portion of the cylinder head according to the invention of claim 1, as a pre-stage of the cutting process, the relief taper surface and the guide taper having an opening angle larger than that of the guide taper surface. Since a pre-stage cutting process that cuts a relief surface with a larger diameter than the guide surface corresponding to the surface tool is added, it is possible to prevent chipping during the cutting process and pitching of the cutting tool itself, which can improve the product yield accordingly. At the same time, it has the effect of extending the tool life.

According to the second aspect of the present invention, since the boundary between the material of the cylinder head and the different metal layer is located in the relief taper surface, chipping of the cutting tool due to intermittent cutting can be prevented, and the tool life can be extended. According to the invention of claim 3, the formation of the different metal layer is easy and reliable.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a method of processing a valve seat portion of a cylinder head according to an embodiment of the present invention.

FIG. 2 is a diagram showing a pre-stage cutting step of the method of the embodiment.

FIG. 3 is a diagram showing a cutting process using a 30-degree and 120-degree cutting tool in the method of the embodiment.

FIG. 4 is a view showing a cutting process using a 90-degree cutting tool in the method of the above embodiment.

FIG. 5 is a view showing a cutting tool holder used in the cutting process.

FIG. 6 is a diagram showing a build-up process of the above-described method of the embodiment.

FIG. 7 is a diagram showing a build-up process of the method of the above-mentioned embodiment.

FIG. 8 is a cross-sectional view of a cylinder head to which the method of the above embodiment is applied.

FIG. 9 is a bottom view of a cylinder head to which the method of the above embodiment is applied.

FIG. 10 is a diagram showing a conventional processing method.

FIG. 11 is a diagram showing a problem with the conventional method.

[Explanation of symbols]

 1 Cylinder head 7,7 'Overlay layer (different metal layer) a Guide processing surface a'Escape processing surface T Valve seat part T2 2nd taper surface (valve seat surface) T3 3rd taper surface (guide taper surface) T4 4 taper surface (escape taper surface)

Claims (3)

[Claims] 1. A different metal layer forming step of forming a different metal layer made of a material having higher wear resistance and heat resistance than a cylinder head material on the periphery of a valve opening of the cylinder head, and a first opening angle for the different metal layer. And a guide taper surface having a second opening angle larger than the first opening angle, which is closer to the cylinder block mating surface than the valve seat surface, and a cutting tool for the guide taper surface. In a method of processing a valve seat portion of a cylinder head, which comprises a cutting step of cutting a guide surface having a diameter corresponding to the above, prior to the cutting step, the first portion is provided closer to the cylinder block mating surface than the guide taper surface. 2 A pre-cutting step was added to cut the relief taper with an opening angle larger than the opening angle and the relief surface with a larger diameter than the guide surface. A method of processing a valve seat portion of a cylinder head, which is characterized in that 2. The method of processing a valve seat portion of a cylinder head according to claim 1, wherein a boundary portion between the material of the cylinder head and the different metal layer is located within the relief taper surface. 3. The method according to claim 1 or 2, wherein the different metal forming step forms an annular groove on the periphery of the valve opening,
A method for processing a valve seat portion of a cylinder head, comprising: filling a different metal powder into the groove and irradiating the different metal powder with high density energy to form a different metal layer.