JPH0742512A - Intake valve and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the weight of an intake valve, and extend its endurance time during high load opperation of an engine. CONSTITUTION:An intake valve 1 is formed of an aluminum complex matrial 2 including SiC whiskers short fiber 3. Its umbrella shaped surface is cut by means of mechanical work, aluminum alloy 4 is dissolved by means of acid picking, and the SiC whiskers short fibers 3 are exposed. On the surface thereof, partial stabilizing zirconiz ZrO2-8%Y2O3 is flame sprayed at a speed of acoustic velocity orr more so as to form a ceramic flame spray coat film 5 whose film thickness is 0.6 to 2mm and porosity is 5 to 40%. Heat input from the umbrella shaped surface is suppressed by the ceramic flame spray coat film 5. Sine transmission of heat is excellent in an aluminum alloy base material, any temperature rise in the valve umbrella part is suppressed. It is thus possible to prevent deposits from sticking on an umbrella back part, and also to thin the concentration of Hc in exhaust gas. And also the weight of a valve itself is, small to contribute to reduction of fuel consumption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake valve for an internal combustion engine and a method for manufacturing the intake valve.

[0002]

2. Description of the Related Art In order to improve fuel economy, weight reduction of intake engine valves has been studied, and an intake valve made of aluminum composite material containing fibers for improving strength or hard particles for improving wear resistance is disclosed. Has been done. For example, the intake valve described in Japanese Patent Laid-Open No. 61-143535 is manufactured by press-casting powdery needle crystals (whiskers) made of silicon carbide, which is one of the components having heat resistance and wear resistance. After molding the valve substrate that forms the shape of the valve,
An aluminum alloy, which is lightweight and has a good heat dissipation property, is filled in at least the gap between the needle crystal and the surface of the valve base after the molding. The volume ratio of the silicon carbide needle crystal (whisker) to the valve is 15
The amount of aluminum alloy is set to 35%, and the volume ratio of the aluminum alloy to the valve is set to 85 to 65%.

[0003]

In the above-mentioned conventional technique, the wear resistance of the sliding portion can be secured by adding fibers or hard particles, but the heat resistance strength of the umbrella portion of the intake valve is the heat resistance strength of the aluminum alloy material. Be restricted by. Therefore, during high-load continuous operation of the engine, the temperature of the umbrella portion rises, causing a decrease in strength, causing deformation such as cupping, and deteriorating the sealing performance between the valve face and the seat, resulting in deterioration of engine performance. There was a point. The deformation of the umbrella part occurs because the heat input during explosion / combustion of the air-fuel mixture from the surface of the umbrella (the surface exposed in the cylinder) is larger than the heat radiation from the valve face and the shaft part. This is because the temperature rises.

In order to suppress heat input from the umbrella portion, the inventor of the present application has proposed so-called ceramic adiabatic spraying in which a ceramic sprayed coating is formed on the umbrella surface of the intake valve (Japanese Patent Laid-Open No. Hei 4).
-311611). This ceramic adiabatic thermal spray is
Perform shot blasting as a pretreatment, thermal spraying of Ni-C _r, etc. as surface treatment for increasing the adhesion of the ceramic, because they were sprayed ceramic such as Z _r O ₂ thereon, the processing cost significantly more expensive to It could not be put to practical use.
Therefore, the present invention provides an intake valve that can solve the above-mentioned problems by performing ceramic adiabatic thermal spraying to prevent heat input to the umbrella surface of the intake valve formed of an aluminum composite material, and to provide a practical manufacturing method. To aim.

[0005]

In order to achieve the above object, the intake valve of the present invention comprises an aluminum composite material containing fibers for improving strength and wear resistance or hard particles for improving wear resistance. The ceramic sprayed coating (5) having a porosity of 5% or more and 40% or less and a film thickness of 0.6 mm or more and 2 mm or less is formed on the umbrella surface of the molded product having a valve shape.

[0006] The manufacturing method is such that an aluminum composite material containing fibers or hard particles is molded into the shape of an intake valve, and at least the umbrella portion including at least the umbrella surface of the molded body is degreased and then cutting oil is not used. The surface of the umbrella is machined by turning or grinding to have a surface roughness of 12.5 μm Rz to 70 μm Rz, and the machined surface is pickled with hydrochloric acid or the like to dissolve the aluminum alloy of the matrix and Hard particles to 0.
It is characterized in that it is exposed for 5 μm or more, and a ceramic film is formed thereon at a spraying speed higher than the speed of sound.

In the manufacturing method, the acid pickling step may be omitted and the other steps ,, and may be used.

[0008]

[Function] The ceramic sprayed coating suppresses heat input from the umbrella surface,
The aluminum alloy that is the matrix in the aluminum composite material improves heat dissipation, and the fibers or hard particles help improve strength and wear resistance. Before ceramic spraying, a surface is machined to a predetermined surface roughness, and a ceramic coating is formed on this surface at a spraying speed higher than the sonic speed, so that a sprayed film having an excellent anchoring effect can be formed. Also, by exposing the fibers or hard particles from the aluminum alloy of the matrix in the step of pickling, the anchoring effect can be further improved.

[0009]

1 is an embodiment of an intake valve according to the present invention, in which 1 is an intake valve, 2 is an aluminum composite material, which contains short SiC whiskers, and a matrix is formed of an aluminum alloy A2024. This intake valve 1 has a displacement of 200
It is used for a 0cc internal combustion engine, and most of the surface of the umbrella (excluding the area within 5mm from the outer diameter of the umbrella) is machined into a concave shape, pickled to dissolve the aluminum alloy of the matrix, and then SiC. Ceramic adiabatic spraying was performed on the exposed whisker short fibers. Ceramic thermal spray material is Z _r O
And ₂ -8% Y ₂ O _3, an embodiment of the present invention as shown in Table 1 No. In addition to Nos. 8-12, No. 1-7
Was also manufactured under various conditions and tested for durability. Figure 1
Reference numeral 3 is a short SiC whisker fiber, 4 is an aluminum alloy as a matrix, and 5 is a ceramic film, and the short SiC whisker fiber 3 projects downward from the aluminum alloy 4 by 0.5 μm or more.

The steps of the manufacturing method of the embodiment of the present invention are shown in FIG.
Table 1 shows the umbrella surface roughness (ten-point average roughness R _z ), the ceramic sprayed coating, the spraying rate, the porosity of the ceramic sprayed coating, and the like after machining during the process in Table 1, together with the conditions of the comparative product.
The comparative product No. In No. 1, as in the prior art, Ni--C _r undercoat was sprayed to a film thickness of 0.1 mm. As the thermal spraying machine used, SG-100 manufactured by Mirror Corp. was used and the plasma thermal spraying method was used, but high speed flame thermal spraying may also be used.

[0011]

[Table 1] Comparative product No. 1 to 7 and Example No. 1 of the present invention. 8 ~
FIG. 3 shows the results of durability test of No. 12 mounted on the engine by high-load continuous operation.

Comparative product No. Since Nos. 1, 2 and 3 had a low thermal spraying rate, the anchoring effect was inferior, and the ceramic coating peeled off early and the umbrella portion was deformed. Comparative product No. In No. 4, since the ceramic coating was thin, the heat insulating effect was small and the umbrella portion was thermally deformed early.

Comparative product No. In No. 5, the ceramic coating was thick and cracks were generated at an early stage, resulting in peeling and deformation of the umbrella portion. Comparative product N
o. Since No. 6 had a small porosity, the heat insulating effect was small and the umbrella portion was thermally deformed early.

Example No. 1 of the present invention. All of 8 to 12 achieved the target of 200 hours and remained more durable than that. In Table 1, it has been the ceramic thermal barrier coating by spraying the partially stabilized zirconia _{Z r O 2 -8% Y 2} O 3,
Stabilized zirconia _{Z r O 2 -20% Y 2} O 3 or, what may be used as long as it has a low ceramic thermal conductivity such as alumina Al ₂ O _3. Also, the porosity of the ceramic coating is 5
If it is less than%, the heat insulating effect is not good, and if the porosity exceeds 40%, the strength of the film is remarkably reduced. Furthermore, if the thickness of the ceramic coating is less than 0.6 mm, there is almost no heat insulating effect, and if it exceeds 2 mm, the elastic deformation of the umbrella portion cannot be followed and peeling occurs.

The pickling step of claim 2 is to secure the adhesion force by entangling the ceramic sprayed particles on the fibers or hard particles, and it is sufficient if the particles are exposed by 0.5 μm or more. If the adhesive force can be secured without the need, the pickling step can be omitted as in claim 3.

[0016]

As described above, the intake valve of the present invention has the following features.
Aluminum composite material intake valve that can be used even under high load continuous operation because a ceramic thermal spray coating was formed on the surface of the intake valve made of aluminum composite material that was impossible to use due to deformation of the umbrella part during high load operation. Valves can be provided to reduce engine friction loss and improve fuel efficiency. Also, heat input from the surface of the umbrella is suppressed by the ceramic thermal spray coating, and since the base material is an aluminum alloy and heat conduction is good, the umbrella part, especially the umbrella back part, is significantly cooled by intake air and fuel, and The temperature of the deposit is lower than the temperature at which the deposit is generated, and the deposit on the back of the umbrella is reduced. Therefore, it is possible to prevent the HC concentration in the exhaust gas from deviating from the regulation value and the drivability from being deteriorated due to deposits.

[0017] Furthermore, in the manufacturing method, shot blasting and as a pretreatment, for Ni-C _r, etc. of the spray process of the surface treatment becomes unnecessary, inexpensive aluminum composite obtained by forming the ceramic thermal sprayed coating on the head front A material intake valve can be provided.

[Brief description of drawings]

1 is an embodiment of an intake valve of the present invention, (a) is a front view in which a part of the intake valve is shown in section, (b) is a view (a)
FIG.

FIG. 2 is a schematic view showing steps of the manufacturing method of the present invention.

FIG. 3 is a view showing a result of a durability test.

[Explanation of symbols]

1 ... Intake valve, 2 ... Aluminum composite material, 3 ... SiC whisker short fiber, 4 ... Aluminum alloy, 5 ... Ceramic film.

Claims (3)

[Claims] 1. A valve-shaped aluminum composite material containing fibers for improving strength and wear resistance or hard particles for improving wear resistance has a porosity of 5% on its umbrella surface.
An intake valve, wherein a ceramic sprayed coating having a film thickness of 0.6 mm or more and 2 mm or less is formed at 40% or less and 40% or less. 2. An aluminum composite material containing fibers or hard particles is molded into the shape of an intake valve, and after degreasing the umbrella portion including at least the umbrella surface of the molded body, it is turned or cut without using cutting oil. By machining by grinding, the umbrella surface is processed so that the surface roughness becomes 12.5 μm Rz to 70 μm Rz, and the processed surface is pickled with hydrochloric acid or the like to dissolve the aluminum alloy of the matrix, and the fibers or hard particles contained 0.
A method for manufacturing an intake valve, which comprises exposing the surface of the insulating film to a thickness of 5 μm or more and forming a ceramic film thereon at a thermal spraying speed of sonic speed or higher. 3. A method of manufacturing an intake valve, wherein the step of pickling in the step of claim 2 is omitted and the steps of other steps, and are included.