Abstract: An engine valve, formed of a titanium alloy, enables improvement of reliability and productivity while improving creep resistance and fatigue strength at a high temperature. The engine valve, including a stem section and a bevel section provided at one end of the stem section, is integrally formed of the titanium alloy. A portion of the valve, extending from the bevel section to a medial portion of the valve stem, is formed mainly of a needle-like crystallographic texture. Another portion of the valve, extending from the medial section to the other end of the stem section, is formed of a material having a substantially equiaxed crystallographic texture. A boundary between the needle-like texture and the equiaxed texture is provided in a range of sliding movement of the valve relative to a valve guide that slidably guides the stem section within the cylinder head.

Abstract: An engine valve, formed of a titanium alloy, enables improvement of reliability and productivity while improving creep resistance and fatigue strength at a high temperature. The engine valve, including a stem section and a bevel section provided at one end of the stem section, is integrally formed of the titanium alloy. A portion of the valve, extending from the bevel section to a medial portion of the valve stem, is formed mainly of a needle-like crystallographic texture. Another portion of the valve, extending from the medial section to the other end of the stem section, is formed of a material having a substantially equiaxed crystallographic texture. A boundary between the needle-like texture and the equiaxed texture is provided in a range of sliding movement of the valve relative to a valve guide that slidably guides the stem section within the cylinder head.

Abstract: An assist gas fuel injection mechanism for a 2-cycle internal combustion engine includes a chamber communicated to a combustion chamber through a communicating passage. A rotary valve is provided in the communicating passage for controlling the opening and closing of the communicating passage. A fuel injection device is provided in the communicating passage between the rotary valve and the chamber. With this configuration, a highly compressed gas from the chamber, and fuel from the fuel injection device, are mixed with each other, and a concentrated mixture gas is supplied to the combustion chamber through the communicating passage. A protective layer is provided on the outside surface of the valve body of the rotary valve by using a material which is softer than the valve body of the rotary valve and the housing of the rotary valve and which is susceptible to plastic deformation.

Abstract: To provide an aluminum alloy member having a high machinability while keeping a sufficient mechanical strength and a sufficient wear resistance, and a method of producing the aluminum alloy member. In an aluminum alloy member formed from an aluminum-silicon alloy by casting, eutectic silicon grains are exposed from at least part of an exposed plane of the aluminum alloy member. A coating layer having a thickness nearly equal to or thinner than a diameter of each of the eutectic silicon grains is formed on the exposed plane from which the eutectic silicon grains are exposed.

Abstract: An assist gas fuel injection mechanism for a 2-cycle internal combustion engine includes a chamber communicated to a combustion chamber through a communicating passage. A rotary valve is provided in the communicating passage for controlling the opening and closing of the communicating passage. A fuel injection device is provided in the communicating passage between the rotary valve and the chamber. With this configuration, a highly compressed gas from the chamber, and fuel from the fuel injection device, are mixed with each other, and a concentrated mixture gas is supplied to the combustion chamber through the communicating passage. It is desirable to minimize the clearance between a valve body and a housing of the rotary valve, to reduce leakage of the assist gas for injection, and to reduce the size of the assist gas fuel injection mechanism.

Abstract: To provide an aluminum alloy member having a high machinability while keeping a sufficient mechanical strength and a sufficient wear resistance, and a method of producing the aluminum alloy member. In an aluminum alloy member formed from an aluminum-silicon alloy by casting, eutectic silicon grains are exposed from at least part of an exposed plane of the aluminum alloy member. A coating layer having a thickness nearly equal to or thinner than a diameter of each of the eutectic silicon grains is formed on the exposed plane from which the eutectic silicon grains are exposed.