| 摘要 |
PURPOSE:To reduce the ground area of a valve without reducing its strength and improve the productivity thereof by grinding around the central axis of an umbrella part, the nearly intermediate part of a slant surface of the umbrella part reaching from the connecting part of a stem to the contact part with a valve seat. CONSTITUTION:A valve made of ceramics which is an intake/exhaust valve of an internal combustion engine is composed of an umbrella part 1 in a conical shape and a columnar stem 2 connected to the top of the umbrella part 1. In this case, the nearly intermediate part of a slant surface of the umbrella part 1 reaching from the connecting part of the stem 2 to the contact part 10 with the valve seat is ground in a ring shape around the central axis of the umbrella part 1. The part 11 ground in a ring shape is formed in a ring band which has its center on the central axis of the umbrella 1, includes a circle whose circumference coincides with the locus of the intermediate point of a generatrix reaching from the connecting part of the stem 2 to the contact part of the valve seat and the width on the generatrix is 1/3-1/2 of the length of the generatrix. Thus, the ground area can be reduced without reducing its strength and the productivity of the valve can be raised up. |
