JPH01209103A - Manufacture of ceramic poppet valve - Google Patents

Abstract

PURPOSE:To economize material and the number of processes, to reduce production costs and realize mass production, by putting a rubber vessel in a high-pressure container, filling the vessel with ceramic powder material, molding it hydraulically with a dry-type rubber press, cold-processing the outer diameter, stem end etc., calcining them and finishing by grinding the stem and valve face. CONSTITUTION:A rubber vessel 5 has a hole of which dimension corresponds to the sum of the shape of a specified valve, its processing allowance and the compression allowance for molding. The rubber vessel 5 is put into a pressure vessel 8 of which inner diameter is the same as the outer diameter of a flange 5a, ceramic powder is fed from an opening, which is served to form a stem end, thereinto to fill the rubber vessel 5 in a uniform density and a plug 7 is fit into the opening. The pressure vessel 8 is supplied with hydraulic oil to press the rubber vessel 5 inward and pressed from the periphery to dry-mold to be a valve shape. After molding the hydraulic oil is discharged, and after the vessel 5 restores to its original state the molded valve is taken out. The back side of valve face 3a, the periphery of stem 2 and a cotter groove 2a are processed with a processing machine and cut to a specified length. It is calcined at a specified temperature, the periphery of stem and the valve face, also the outer side thereof if necessary, are finished by grinding.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing ceramic poppet valves for internal combustion engines.

BACKGROUND OF THE INVENTION In recent years, as the performance of internal combustion engines has improved, attempts have been made to use ceramics in valve train systems to take advantage of their light weight, reduce friction loss, and increase engine speed.

Of all valve train systems, valves have the greatest weight reduction effect and are heat resistant.

Various prototypes have been made using silicon nitride, which has well-balanced impact resistance.

Problems to be Solved by the Invention However, since the number of pieces to be manufactured is small at the trial production stage, a relatively large material is prepared as a rod-shaped or almost shaped molded object, and the whole surface is finished into a valve shape by raw machining, leaving a grinding allowance. After firing, the entire surface is polished to create the desired prototype shape.

For this reason, a lot of material is wasted during raw processing, and the purpose of raw processing is to provide a manufacturing method suitable for mass production.

Means to solve the problem: Close the bare side opening of the hole with the dimensions and shape of the valve plus the machining allowance and compression allowance during molding with a lid body that has a convex part at the center of the back of the umbrella that will serve as a reference concave part during machining. Place the rubber container in a high-pressure container, fill the hole with ceramic powder, close the opening on the stem side, and form it in a dry rubber press using hydraulic pressure, using the reference recess on the bare side of the molded valve body as a standard. The valve is attached to a processing machine, and the outer diameter, stem end, etc. are processed, then fired, and at least the stem and valve face are polished and finished.

A rubber container 5 having upper and lower flanges 5a with the operating lid 6 facing down at the center position is placed in a pressure container 8 having an inner diameter equal to the outer diameter of the flange 5a, the outer periphery of the rubber container is sealed, and the upper stem end is sealed. Ceramic powder blended to have properties required for a valve is poured into the opening, and if necessary, vibration is applied to fill the powder to an equal density. The stopper 7 is fitted in such a way that it does not come off. Pressure oil is supplied to the pressure vessel 8 to pressurize the rubber vessel 5 inwardly, and the rubber vessel 5 is compressed from the outer periphery and dry-molded into a valve shape. After molding, the pressure oil is discharged and the pressure is reduced, and after the rubber container 5 recovers due to elasticity and returns to its original state, the molded valve body is removed.

It is held between the center 9 which is tapered fitted into the reference recess 3b fitted on the main shaft side of a processing machine such as a copying lathe or an NC lathe, and the center 10 of the tailstock, and the cutting tool is used for copying cutting using a cutting tool or for cutting using N CIJ wB. The back surface of the valve face 3a, the outer periphery of the shaft of the stem 2, and the cock groove 2a are machined into a valve shape, leaving a grinding allowance, and the end of the stem is cut to a predetermined length. Next, it is placed in a firing furnace and fired at a predetermined temperature, and finished by polishing at least the outer periphery of the stem and the valve face using a centerless polisher or the like. Furthermore, the back of the umbrella may also be polished if necessary.

As shown in FIG. 1, the poppet valve 1 according to the embodiment has a cap 3 which serves as a head ζ valve portion of a stem 2, and a valve face 3a is formed on the back of the cap. A shallow tapered reference recess 3b is formed in the center of the back of the umbrella. In addition, the tip of the stem 2 has a groove 2a that prevents it from being removed after assembly.
is formed.

It is also possible to replace the reference recess 3b with a reference recess 3c formed as a part of a sphere as shown in FIG. At this time, center 9
A fitting spherical tip is used. By forming the reference recesses 3b and 3c in such a shape, it is possible to prevent concentration of stress or thermal stress during processing or use.

The rubber container 5 used in the rubber press has flange portions 5a at both ends, has a hole with a size and shape equal to the predetermined valve shape plus processing allowance and compression allowance during molding, and is made of an elastically deformable material, preferably rubber. It is made. The bare side opening is closed almost concentrically with a lid body 6 having a convex portion 6a at the center of the back of the bulb 1 and serving as a reference concave portion during processing. This lid body 6 is made of a material that does not deform due to molding pressure, such as metal, non-ferrous metal, synthetic resin, etc.

Effects As detailed above, the present invention, by manufacturing as claimed, can save more than 35% of materials and processing man-hours compared to conventional manufacturing, and can reduce manufacturing costs. This has the effect of realizing mass production.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing the poppet valve, Figures 3, 4, and 5 are diagrams showing the rubber press process, where Figure 3 is powder filling, Figure 4 is pressurization, Figure 5 is The figure shows reduced pressure, and FIG. 6 shows raw processing. 1... Valve 2... Stem 3a... Valve face 5... Rubber container 6... Lid body 7... Closing plug

Claims (1)

[Claims] (1) A rubber container in which the opening on the umbrella side of the hole, whose dimensions are the valve shape plus processing allowance and compression allowance during molding, is closed with a lid body that has a protrusion that serves as a reference recess during processing at the center of the umbrella surface. placed in a high-pressure container, filling the hole with ceramic powder material,
The opening on the stem side is closed, and the valve body is formed using a dry rubber press using hydraulic pressure.The valve body is mounted on a processing machine using the reference recess on the umbrella side of the molded valve body as a reference, and the outer diameter, stem end, etc. are green-processed, and then fired. A method for manufacturing a ceramic poppet valve, which comprises polishing at least a stem and a valve face.