Hollow poppet valve
A hollow poppet valve ( 10 ) is provided with an additional flange shape cavity (S 1 a ), in addition to an ordinary valve head cavity (S 1 ) formed in the valve head ( 14 ) of the valve ( 10 ) in communication with a valve stem cavity (S 2 ) formed in a valve stem ( 12 ). A coolant ( 19 ) is loaded in the cavities to facilitate dissipation of heat out of the valve. This flange shape cavity (S 1 a ) extends radially outwardly round a bottom portion of the valve head cavity (S 1 ), extending close to a valve seat, thereby significantly facilitating heat transfer between the coolant ( 19 ) and the valve seat of the valve, yet, since the flange shape cavity (S 1 a ) does not influences the thickness of other regions of the valve, it does not degrade durability of the valve.
1. A hollow poppet valve the poppet valve comprising:
a valve head and a valve stem integral at one end thereof with the valve head, the poppet valve formed with an internal cavity that extends from within the valve head into the valve stem and is charged with a coolant together with an inert gas,
wherein the internal cavity has a diametrically large generally disk shaped cavity in the valve head and a diametrically small linear straight cavity in the valve stem in communication with the valve head cavity,
wherein only a bottom fringe portion of the valve head cavity is extended radially outwardly and circumferentially, forming a flange shape cavity at the bottom fringe portion of the valve head cavity, the flange shape cavity communicating with the valve head cavity,
wherein the valve head cavity is configured in the shape of a generally truncated circular cone whose longitudinal cross section is a substantial trapezoid and whose periphery is either an excurved skirt-like outer periphery or a tapered periphery parallel with the outer periphery of the valve head,
wherein a peripheral region of the valve head cavity around an open end of the valve stem cavity communicated with the valve head cavity is a flat plane perpendicular to the axis of the valve, and, serves as a ceiling of the valve head cavity,
wherein the coolant is charged in the valve head cavity and the valve stem cavity, and
wherein a vertical circulatory flow of coolant is generated in the coolant in the valve head cavity along the axis of the valve while a turbulent flow of coolant is generated in the coolant in the valve stem cavity, during a reciprocal motion of the valve.
2. The hollow poppet valve according to claim 1 ,
wherein a ceiling of the flange shape cavity is tapered so as to allow a part of the circulatory flows of coolant to be led into the flange shape cavity.
3. The hollow poppet valve according to claim 1 ,
wherein the valve head cavity has a stepped configuration in which the peripheral region around the open end of the valve head cavity is offset from a top end of the generally truncated circular cone by a predetermined distance towards the valve stem.
4. The hollow poppet valve according to claim 1 ,
wherein the valve stem cavity has a diametrically larger cavity in a stem end side of the valve stem and a diametrically smaller cavity in a valve head side of the valve stem;
wherein an annular step is provided at a predetermined axial position of the valve stem cavity; and
wherein the coolant is charged to a level exceeding the annular step, and
wherein the turbulent flow of coolant is generated in a downstream side of the annular step during the reciprocal motion of the valve.
5. The hollow poppet valve according to claim 4 ,
wherein the annular step in the valve stem cavity is located at an axial position not within an exhaust/intake port when the valve is installed in the exhaust/intake port of the engine.
6. The hollow poppet valve according to claim 2 ,
wherein the valve head cavity has a stepped configuration in which the peripheral region around the open end of the valve head cavity is offset from a top end of the generally truncated circular cone by a predetermined distance towards the valve stem.
7. The hollow poppet valve according to claim 2 ,
wherein the valve stem cavity has a diametrically larger cavity in a stem end side of the valve stem and a diametrically smaller cavity in a valve head side of the valve stem,
wherein an annular step is provided at a predetermined axial position of the valve stem cavity,
wherein the coolant is charged to a level exceeding the annular step, and
wherein the turbulent flow of coolant is generated in a downstream side of the annular step during the reciprocal motion of the valve.
8. The hollow poppet valve according to claim 3 ,
wherein the valve stem cavity has a diametrically larger cavity in a stem end side of the valve stem and a diametrically smaller cavity in a valve head side of the valve stem,
wherein an annular step is provided at a predetermined axial position of the valve stem cavity,
wherein the coolant is charged to a level exceeding the annular step, and
wherein the turbulent flow of coolant is generated in a downstream side of the annular step during the reciprocal motion of the valve.
9. The hollow poppet valve according to claim 6 ,
wherein the valve stem cavity has a diametrically larger cavity in a stem end side of the valve stem and a diametrically smaller cavity in a valve head side of the valve stem,
wherein an annular step is provided at a predetermined axial position of the valve stem cavity,
wherein the coolant is charged to a level exceeding the annular step, and
wherein the turbulent flow of coolant is generated in a downstream side of the annular step during the reciprocal motion of the valve.