An exhaust valve includes a stem extending to a valve end. The valve end includes a pressure relief apparatus. An engine assembly includes a casing defining a cylinder bore, a combustion chamber and an exhaust passage. The combustion chamber is disposed between the exhaust passage and the cylinder bore. The engine assembly also includes a piston movable in the cylinder bore. The engine assembly further includes an exhaust valve movable between a first position blocking fluid communication through the exhaust passage and a second position allowing fluid communication through the exhaust passage. The exhaust valve includes a pressure relief apparatus configured to allow fluid communication through the exhaust valve from the cylinder bore to the exhaust passage when the exhaust valve is in the first position and a predetermined pressure threshold occurs in the cylinder bore between the exhaust valve and the piston.

Provided are a cladding alloy powder that can increase the wear resistance of a cladding alloy to be deposited and a counterpart member adapted to contact the cladding alloy, and a method for producing an engine valve using the cladding alloy powder. The cladding alloy powder includes 0.2 to 0.5 mass % C, 30 to 45 mass % Mo, 15 to 35 mass % Ni, 0.5 to 2.0 mass % Zr, and a balance including Co with unavoidable impurities. The method for producing an engine valve includes melting the cladding alloy powder, and cladding a valve face portion of an engine valve adapted to contact a valve seat with the melted cladding alloy powder.

Provided are a cladding alloy powder that can increase the wear resistance of a cladding alloy to be deposited and a counterpart member adapted to contact the cladding alloy, and a method for producing an engine valve using the cladding alloy powder. The cladding alloy powder includes 0.2 to 0.5 mass % C, 30 to 45 mass % Mo, 15 to 35 mass % Ni, 0.5 to 2.0 mass % Zr, and a balance including Co with unavoidable impurities. The method for producing an engine valve includes melting the cladding alloy powder, and cladding a valve face portion of an engine valve adapted to contact a valve seat with the melted cladding alloy powder.

With a poppet valve using a coolant, maximum combustion efficiency is realized by adjusting relative values of a heat insulation effect and a heat dissipation effect. From the inside of a head portion (14) to a stem portion (12) of a hollow poppet valve (10) a heat insulating space (S1) and a cooling portion (S2) loaded with a coolant (19), separated from each other by a partition (15), are formed. By properly setting an installation position and a vertical length of the partition (15) according to a type of vehicle for which the valve is used, appropriate heat insulation effect and heat dissipation effect are obtained. Further, by the partition (15), mechanical or thermal strength of the poppet valve in which the heat insulating space (S1) and the cooling portion (S2) are formed is increased.

With a poppet valve using a coolant, maximum combustion efficiency is realized by adjusting relative values of a heat insulation effect and a heat dissipation effect. From the inside of a head portion (14) to a stem portion (12) of a hollow poppet valve (10) a heat insulating space (S1) and a cooling portion (S2) loaded with a coolant (19), separated from each other by a partition (15), are formed. By properly setting an installation position and a vertical length of the partition (15) according to a type of vehicle for which the valve is used, appropriate heat insulation effect and heat dissipation effect are obtained. Further, by the partition (15), mechanical or thermal strength of the poppet valve in which the heat insulating space (S1) and the cooling portion (S2) are formed is increased.

The object of the present invention is to provide a heat-resistant steel for exhaust valves, having relatively small Ni content, high mechanical characteristics (for example, tensile strength, fatigue strength, wear resistance and hardness) at high temperature, and excellent oxidation resistance. The present invention provides a heat-resistant steel for exhaust valves, which includes: 0.45≦C<0.60 mass %, 0.30<N<0.50 mass %, 19.0≦Cr<23.0 mass %, 5.0≦Ni<9.0 mass %, 8.5≦Mn<10.0 mass %, 2.5≦Mo<4.0 mass %, 0.01≦Si<0.50 mass %, and 0.01≦Nb<0.30 mass %, with the balance being Fe and unavoidable impurities, in which the steel satisfies 0.02≦Nb/C<0.70 and satisfies 4.5≦Mo/C<8.9.

An engine valve includes a stem, a head comprising an outer lip surface, a seating surface extending from the outer lip surface toward the stem, and a combustion surface extending from the outer lip surface on the opposite side of the head as compared to the seating surface. The combustion surface includes a first convex arcuate surface spaced away from the outer lip surface, at least partially forming a raised ring, and a first concave arcuate surface spaced away from the outer lip surface, at least partially forming a dimple.

An engine valve includes a stem, a head comprising an outer lip surface, a seating surface extending from the outer lip surface toward the stem, and a combustion surface extending from the outer lip surface on the opposite side of the head as compared to the seating surface. The combustion surface includes a first convex arcuate surface spaced away from the outer lip surface, at least partially forming a raised ring, and a first concave arcuate surface spaced away from the outer lip surface, at least partially forming a dimple.

A copper alloy for engine valve seats manufactured by laser cladding improves wear resistance of the copper alloy. The copper alloy includes 12 to 24 wt % of Ni, 2 to 4 wt % of Si, 4 to 12 wt % of Mo, 15 to 35 wt % of Fe, and the remaining wt % of Cu and impurities.

A copper alloy for engine valve seats manufactured by laser cladding improves wear resistance of the copper alloy. The copper alloy includes 12 to 24 wt % of Ni, 2 to 4 wt % of Si, 4 to 12 wt % of Mo, 15 to 35 wt % of Fe, and the remaining wt % of Cu and impurities.