Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L3/00—Lift-valve, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces; Parts or accessories thereof
  • F01L3/02—Selecting particular materials for valve-members or valve-seats; Valve-members or valve-seats composed of two or more materials
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L3/00—Lift-valve, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces; Parts or accessories thereof
  • F01L3/12—Cooling of valves
  • F01L3/14—Cooling of valves by means of a liquid or solid coolant, e.g. sodium, in a closed chamber in a valve

Definitions

• the present invention relates to a cylinder head of an internal combustion engine and an internal combustion engine having the cylinder head, and particularly relates to a cylinder head of an internal combustion engine and an internal combustion engine that use fossil fuel containing hydrogen.
• Patent Document 1 discloses an intake valve having a hollow part on the inside, and a refrigerant in the hollow part provided inside, and when the internal combustion engine is driven, the refrigerant absorbs heat on the umbrella side, which has a high temperature, and the shaft side, which has a low temperature.
• An internal combustion engine has been disclosed that has an exhaust valve in its cylinder head, which aims to reduce the temperature by repeatedly reciprocating between the cylinder head and the exhaust valve to transfer heat to the shaft side.
• the region near the front side of the exhaust valve cap (hereinafter simply referred to as the region near the cap surface) is maintained at a much higher temperature than the region near the cap surface of the intake valve.
• Such a temperature difference indoors in the area near the caps of both intake and exhaust valves is a problem in that it can generate hot spots in the area near the front side of the caps of the exhaust valves, making it more likely to cause knocking. becomes.
• the present invention reduces the temperature difference in the vicinity of the cap surfaces of both the intake valve and the exhaust valve in the combustion chamber of an internal combustion engine that uses decarbonized fuel containing hydrogen, thereby preventing knocking due to pre-ignition.
• a preventable cylinder head and internal combustion engine are provided.
• the inventors developed an automobile engine using a hollow valve (prior art) whose hollow part is filled with metallic sodium and a heat pipe cooled hollow valve whose hollow part is filled with water as a cooling medium.
• the inventors developed a heat pipe-cooled hollow valve whose hollow part is filled with water to be used as an exhaust valve in the cylinder head of an internal combustion engine that is equipped with an intake valve and an exhaust valve and uses decarbonized fuel containing hydrogen. We believe that by adopting this, the temperature on the exhaust valve cap surface can be significantly reduced, and the temperature difference in the vicinity of the caps of both the intake and exhaust valves in the combustion chamber can be reduced.
• a heat pipe-cooled hollow valve whose hollow part is filled with water is used as the exhaust valve, and an umbrella part of the intake valve composed of a solid body is used. It is possible to form unevenness uniformly on the entire bottom surface (umbrella surface) of the valve, or to form protrusions (concave lines) with a corrugated longitudinal section in concentric circles, or to change the thickness of the cap of the intake valve to the thickness of the exhaust valve.
• the thickness of the cap section of the intake valve is thinner than that of the conventional intake valve cap section (thickness of the cap section of the conventional intake valve)
• the temperature in the area near the cap sections of both intake and exhaust valves in the combustion chamber is reduced. The idea was to reduce the difference.
• the exhaust valve is configured as a refrigerant-filled hollow valve that has water as a refrigerant sealed in a hollow portion extending from the umbrella portion to the shaft end side.
• the intake valve is constituted by a solid valve having a protrusion portion formed in a lattice shape in plan view defined by a large number of intersecting grooves on the entire bottom surface of the umbrella portion.
• the exhaust valve is a heat pipe cooling type with excellent heat removal effect, which transfers heat from the umbrella side to the shaft side by changing the phase of the cooling medium (water) inside the hollow part between liquid and gas phases.
• the exhaust valve is composed of a hollow valve, and the heat transferred to the shaft side is further transferred (radiated) to the cylinder head, so the temperature rise on the exhaust valve head surface is suppressed.
• the heat pipe cooling type exhaust valve has a superior heat removal effect compared to the conventional hollow valve whose hollow part is filled with metallic sodium as a cooling medium, reducing the temperature at the top of the canopy. be done.
• the engine speed of a car driving in a city is in a low speed range
• the engine speed of a ship is also assumed to be operated in a low speed range
• internal combustion engines are When operating in a low rotation range (for example, 3000 rpm or less), the heat removal effect of the intake valve is much better with a water-filled heat pipe cooled hollow valve than with a metal sodium-filled hollow valve.
• the intake valve has a grid-like protrusion formed on the bottom surface of the umbrella portion, that is, the entire surface of the umbrella portion in a plan view, so that the surface area of the bottom surface of the umbrella portion (heat receiving area facing the combustion chamber) is expanded. becomes easily heated.
• the temperature in the region near the cap surface of the intake valve in the combustion chamber increases, the temperature in the region near the cap surface of the exhaust valve is sufficiently reduced, ensuring that the temperature difference between the regions near the cap surface of both intake and exhaust valves is maintained. reduced to
• a second aspect of the invention of a cylinder head for an internal combustion engine includes poppet-type intake valves and exhaust valves each having an umbrella portion formed on the shaft end side to open and close an intake port and an exhaust port opening into a combustion chamber.
• the exhaust valve is configured with a refrigerant-filled hollow valve in which water is sealed as a refrigerant in a hollow part extending from the umbrella part to the shaft end side, It is preferable that the intake valve is constituted by a solid valve having concentrically continuous convex ridges having a corrugated longitudinal section provided on the entire bottom surface of the umbrella part.
• the function of the exhaust valve is the same as the ⁇ exhaust valve function'' in the cylinder of the internal combustion engine according to the embodiment of the present invention described above, and a redundant explanation thereof will be omitted.
• conventional methods in which the bottom surface (umbrella surface) of the umbrella portion of an intake valve is formed as a flat surface by having concentrically continuous convex ridges with a wave-shaped longitudinal section throughout the intake valve. Compared to the intake valve of , the surface area of the bottom of the cap (heat receiving area facing the combustion chamber) is expanded, making it easier for the cap to heat up.
• a third aspect of the invention of a cylinder head for an internal combustion engine includes poppet-type intake valves and exhaust valves each having an umbrella portion formed on the shaft end side to open and close an intake port and an exhaust port opening into a combustion chamber.
• the exhaust valve is configured with a refrigerant-filled hollow valve in which water is sealed as a refrigerant in a hollow part extending from the umbrella part to the shaft end side, It is preferable that the intake valve is a solid valve having a cap portion thinner than a cap portion of the exhaust valve.
• the function of the exhaust valve is the same as the ⁇ exhaust valve function'' in the cylinder of the internal combustion engine according to the embodiment of the present invention described above, and a redundant explanation thereof will be omitted.
• the cap portion of the intake valve is thinner than the cap portions of conventional intake valves and exhaust valves.
• the intake valve cap has a smaller heat capacity compared to the conventional intake valve cap, which is formed to the same thickness as the exhaust valve cap. It gets hotter more easily than the head of the intake valve.
• a fourth aspect of the invention of the cylinder head for an internal combustion engine is a cylinder head according to the third aspect of the invention, in which a lattice-like shape in a plan view defined by a large number of intersecting grooves is provided on the entire bottom surface of the umbrella portion of the intake valve. It is desirable to provide a protrusion or a concentrically continuous convex ridge with a corrugated longitudinal section.
• the entire bottom surface of the umbrella portion of the intake valve is provided with protrusions that have a lattice shape in plan view defined by a large number of intersecting grooves or protrusions that are concentrically continuous and wave-shaped in longitudinal section.
• the bottom surface area of the cap of the intake valve increases, making the cap even more likely to heat up.
• the bottom surface of the umbrella portion of the exhaust valve is a mirror surface. It is desirable that it be configured.
• the bottom surface of the exhaust valve cap which is made of a mirror surface, reflects infrared rays and reduces radiant heat transmitted from the combustion chamber to the bottom surface of the cap, thereby suppressing temperature rise and cooling the exhaust valve cap further.
• the temperature in the area near the exhaust valve head inside the combustion chamber decreases.
• the internal combustion engine is a marine engine.
• the internal combustion engine includes a piston held in a cylinder so as to be able to reciprocate, a crankshaft that is rotatably held, and a crankshaft that is rotatably connected to both the piston and the crankshaft to control the reciprocating movement of the piston.
• a first embodiment of a cylinder head for an internal combustion engine which forms a combustion chamber between a cylinder block having a connecting rod inside the cylinder block and a connecting rod that is fixed to the cylinder block and inside the cylinder. It is desirable to have the aspect of the sixth invention.
• the surface area of the bottom surface of the intake valve cap is larger than that of the exhaust valve by the lattice-shaped, wave-shaped, etc. projections, or the intake valve cap is made thinner than the exhaust valve cap.
• the cap of the intake valve becomes more easily heated than the cap of a conventional intake valve due to the reduction in heat capacity, which reduces the temperature difference in the area near the cap of both the intake and exhaust valves in the combustion chamber.
• the water charged in the hollow part of the exhaust valve is a safer cooling medium compared to metallic sodium, and the fact that the fuel for internal combustion engines is a decarbonized fuel containing hydrogen is effective as a countermeasure against global warming. is also meaningful.
• the temperature of the exhaust valve cap is brought closer to the temperature of the intake valve cap, which is cooled by an intercooler, etc., thereby reducing the temperature difference in the area near the cap surface of both the intake and exhaust valves. Further, by reducing the occurrence of hot spots in the combustion chamber, knocking due to pre-ignition is reduced even when decarbonized fuel containing hydrogen is used.
• knocking due to pre-ignition is sufficiently reduced even when a decarbonized fuel containing hydrogen is used in a marine engine.
• this internal combustion engine improves torque based on ignition advance (slightly advancing the ignition timing from when the piston reaches top dead center). , fuel efficiency is improved.
• FIG. 1 is a vertical cross-sectional view showing an embodiment of an internal combustion engine having a cylinder head of the present application.
• FIG. 2 is an explanatory diagram of a valve mechanism including an exhaust valve of a marine internal combustion engine having the cylinder head of the present application.
• (a) A vertical cross-sectional view of an intake valve used in the cylinder head.
• (b) A vertical cross-sectional view of an exhaust valve used in the cylinder head.
• FIG. 3 is an enlarged view of the bottom surface of the umbrella portion of the intake valve, which is provided with a protrusion portion having a lattice shape when viewed from above, as viewed in the direction of arrow A in FIG. 2;
• FIG. 7 is an explanatory diagram showing a modification of the bottom surface of the umbrella portion of the intake valve, which is provided with a protrusion portion having a lattice shape in plan view.
• an internal combustion engine 1 includes a cylinder head 2 mounted on a cylinder block 3.
• the cylinder block 3 has a cylindrical cylinder 3a at the top and a crankshaft 3b at the bottom.
• a piston 3c is provided inside the cylinder 3a so as to be slidable back and forth.
• the connecting rod 3e is rotatably attached to both the cylinder 3a and the crankshaft 3b via a first connecting shaft 3f and a second connecting shaft 3g. As a result, the reciprocating motion of the cylinder 3a is converted into a rotational motion of the crankshaft 3b by the connecting rod 3e.
• the cylinder head 2 in FIG. 1 is connected and fixed to the cylinder block 3 at a position facing the cylinder 3a and piston 3c.
• a combustion chamber 4 is provided in the upper region of the upper surface of the cylinder 3a.
• the cylinder head 2 has an intake port 2a and an exhaust port 2b open toward the combustion chamber 4, and is provided with an ignition plug 2g that blows sparks into the combustion chamber.
• the spark plug 2g is provided in a gasoline internal combustion engine for an automobile, etc., but if the internal combustion engine 1 is a diesel internal combustion engine for a ship, the spark plug 2g is not provided.
• the intake port 2a communicates with an intake passage 2c
• the exhaust port 2b communicates with an exhaust passage 2d.
• the cylinder head 2 has an intake valve 5 and an exhaust valve 6.
• the intake valve 5 and the exhaust valve 6 are held by valve guides 2e and 2f attached to the cylinder head 2, respectively, so as to be able to reciprocate.
• the intake valve 5 and the exhaust valve 6 have shapes in which umbrella parts 5b and 6b whose diameters gradually increase are provided at one ends of shaft parts 5a and 6a, respectively.
• the shaft portions 5a and 6a sides of the intake valve 5 and exhaust valve 6 will be described as upper sides
• the umbrella portions 5b and 6b sides will be described as lower sides.
• the intake port 2a and the exhaust port 2b are opened and closed by umbrella portions 5b and 6b, respectively.
• the intake valve 5 and exhaust valve 6 shown in FIG. 1 have upper seats 5c and 6c attached to the base end portions of shaft portions 5a and 6a.
• the cylinder head 2 is provided with lower seats 5d, 6d at positions facing the upper seats 5c, 6c, and valve springs 5e, 6e, which are compression springs, are provided between the upper seats 5c, 6c and the lower seats 5d, 6d. , respectively.
• valve springs 5e, 6e which are compression springs
• the cylinder head 2 is provided with a fuel injection device (not shown), and this fuel injection device injects a mixture of atomized fuel into the combustion chamber 4 from the intake passage 2c at "intake” timing.
• this fuel injection device injects a mixture of atomized fuel into the combustion chamber 4 from the intake passage 2c at "intake” timing.
• the air-fuel mixture in the combustion chamber 4 is compressed, and the air-fuel mixture explodes due to the fire caused by the spark plug 301 (in a marine diesel internal combustion engine, due to spontaneous ignition due to the high temperature in the combustion chamber 4),
• the "combustion” process is executed, and in the exhaust stroke, exhaust gas is discharged from the exhaust passage 2d.
• FIG. 1A shows an exhaust valve operating mechanism 21 for a marine internal combustion engine, and the exhaust valve operating mechanism 21 includes a camshaft 22 having a cam 22a, a push rod 23, a rocker arm 24, a bridge arm 25, and a pair of exhaust valves. (26a, 26b), and a pair of compression coil springs (27a, 27b).
• An intake valve mechanism (not shown) is provided in the depth direction of the paper in FIG. 1A.
• the intake valve mechanism (not shown) includes a pair of intake valves instead of the pair of exhaust valves (26a, 26b), and the cam installation angle of the cam on the camshaft 22 is different from that of the cam 22a. have a common configuration.
• the exhaust valve mechanism 21 and the intake valve mechanism (not shown) shown in FIG. 1A are provided in a cylinder head 35, and the cylinder head 35 is mounted on a cylinder block (not shown) similarly to the internal combustion engine in FIG. , which constitutes a diesel internal combustion engine for ships. Similar to the internal combustion engine of FIG. 1, a cylinder block (not shown) is provided with a piston in a cylindrical cylinder that is connected to a connecting rod and slides back and forth as the crankshaft rotates.
• the cylinder head 35 has exhaust ports (28a, 28b) and an intake port (not shown) that open toward the combustion chamber 36.
• the exhaust ports (28a, 28b) have seat portions (29a, 29b) at the opening periphery and communicate with the exhaust passage 30, and the intake ports (not shown) communicate with the intake passage (not shown). .
• the rocker arm 24 is swingably attached around a rocker shaft 24a provided in the cylinder head 35.
• the rocker arm 24 swings around the rocker shaft 24a by connecting the pivot portion 24c of the base end 24b to the push rod 23 which moves up and down based on the rotation of the cam 22a of the camshaft 22.
• the tip portion 24d of the rocker arm 24 contacts a bridge arm 25 that is provided on the cylinder head 35 in a vertically movable manner.
• the bridge arm 25 is connected to the proximal ends (26a1, 26b1) of the exhaust valves (26a, 26b) on the left and right, and is biased toward the distal end 24d of the upper rocker arm 24 by compression coil springs (27a, 27b). Ru.
• the exhaust valves (26a, 26b) are held in a slidable state within the valve insertion tubes (31a, 31b) of the cylinder head 35.
• the exhaust valves (26a, 26b) open the exhaust ports (28a, 28b) when the distal end 24d of the rocker arm 24 descends based on the rotational mode of the cam 22a.
• the exhaust valve (26a, 26b) When the distal end portion 24d of the rocker arm 24 receives an upward biasing force from the bridge arm 25 by the compression coil spring (27a, 27b) based on the rotational mode of the cam 22a, the exhaust valve (26a, 26b) The exhaust ports (28a, 28b) are closed with the portions (26a2, 26b2) in contact with the seat portions (29a, 29b) of the cylinder head 35.
• the intake valve (not shown) is connected to the intake port at a different timing than the exhaust valves (26a, 26b) based on the rotational mode of an intake cam (not shown) which is installed at a different angle than the exhaust cam 22a of the camshaft 22. (not shown) opens and closes.
• FIGS. 2(a) and 2(b) the shaft portions 5a and 6a side will be referred to as the proximal end side, and the umbrella portions 5b and 6b side will be referred to as the distal end side.
• the exhaust valves (26a, 26b) in FIG. 1A and the intake valve not shown in FIG. 1A have substantially the same shape as the intake valve 5.
• FIG. 2(a) shows the intake valve 5 used in the cylinder head 2.
• the intake valve 5 is a solid internal combustion engine valve made of metal, and is formed by a shaft portion 5a having a constant outer diameter and an umbrella portion 5b integrally formed on the distal end side of the shaft portion 5a.
• the umbrella portion 5b is integrally formed with a neck portion 5b1 having a concave curved shape that increases in diameter toward the tip, and the tip of the neck portion, and when the valve is closed, comes into contact with the opening periphery of the intake port 2a shown in FIG. 1 and closes the intake port.
• It is configured to have a poppet shape by a notch-shaped face portion 5b2 that closes the face portion 2a and an umbrella outer portion 5b3 having a constant outer diameter and integrally formed at the tip of the face portion 5b2.
• FIG. 2(b) shows the exhaust valve 6 used in the cylinder head 2.
• the exhaust valve 6 is a hollow internal combustion engine valve made of metal with high heat resistance, and includes a shaft portion 6a having a constant outer diameter and an umbrella portion 6b integrally formed on the tip side of the shaft portion 6a. formed by.
• the shaft portion 6a includes a shaft tip portion six a1 having a hollow portion 9 extending in the axial direction at the center, and a shaft base end portion six a2 joined to a base end portion of the shaft tip portion six a1.
• the umbrella part 6b is integrally formed with a neck part 6b1 having a concave curved shape that increases in diameter toward the tip, and a neck part 6b1 which is integrally formed with the tip of the shaft tip part 6a1, and which is shown in FIG. 1 when the valve is closed.
• a poppet type is formed by a notch-shaped face portion 6b2 that contacts the opening periphery of the exhaust port 2b and closes the exhaust port 2b, and an umbrella outer portion 6b3 having a constant outer diameter and integrally formed at the tip of the face portion 6b2. is configured to have the following.
• the hollow portion 9 is formed to extend from the inside of the central portion of the shaft tip portion 6a1 of the shaft portion 6a to the vicinity of the base end portions of the neck portion 6b1 and the face portion 6b2.
• the shaft tip portion 6a1 is joined to the shaft base end portion 6a2 by friction welding or the like while water (purified water 10) as a refrigerant is charged into a partial region of the hollow portion 9.
• the exhaust valve 6 is a heat pipe cooled hollow valve, and when the valve 6 reciprocates in the axial direction in conjunction with the engine drive, the cooling medium (water) in the hollow part changes phase between the liquid phase and the gas phase. By doing so, the heat on the side of the umbrella part 6b can be transferred to the side of the shaft part 6a, that is, the high heat caused by the exhaust gas applied to the umbrella part 6b can be released to the shaft part 6a, which has a lower temperature.
• the inventors developed an automobile engine using a hollow valve (prior art) whose hollow part is filled with metallic sodium and a heat pipe cooled hollow valve whose hollow part is filled with water as a cooling medium.
• a dynamic heating test see Figure 2A
• the latter a heat pipe cooled hollow valve filled with water
• a heat pipe cooling type hollow valve filled with water 24% of the volume of the hollow part is purified water. Dynamic heating tests were conducted on various types of valves.
• a hollow part 9 is formed inside the shaft tip part 6a1 that is integrally formed with the neck part 6b1, and after charging water 10 as a refrigerant into the hollow part 9, the shaft base end part By joining 6a2, the hollow portion 9 is sealed (sealed).
• the shaft tip portion 6a1, the shaft base end portion 6a2, and the umbrella portion are integrally formed, and a hole (hollow portion) extending from the umbrella surface 6b4 side to the shaft end side is bored, and the refrigerant is injected into the exhaust valve.
• a cap may be welded to the opening of the hole (hollow portion) to seal the hole (hollow portion).
• the tip of the hollow part 9 shown in FIG. 2(b) may be an umbrella hollow part having a shape in which the inner diameter gradually increases toward the tip side inside the umbrella part 6b.
• the axial lengths of the intake valve 5 and the exhaust valve 6 (from the back surfaces Jr1, jr2 of each end to the umbrella parts (5, 6)
• the dimensions up to the umbrella surfaces 5b4 and 6b4, which are the bottom surfaces, are formed to be L1 and L1+ ⁇ .
• the outer diameters of the shaft portion 5a, neck portion 5b1, and face portion 5b2 of the intake valve 5 are formed to be the same as those of the shaft portion 6a, neck portion 6b1, and face portion 6b2 of the exhaust valve 6, and the outer diameters of the outer diameters of the canopy outer portions 5b3 and 6b3 are the same.
• the diameters are formed to have the same size d1.
• the temperature of the exhaust valve head surface can be significantly reduced. Since there is a limit to cooling (improving the heat removal effect), by using a structure that suppresses the drop in temperature of the intake valve (the umbrella surface) composed of a solid body, it is possible to reduce the temperature of both the intake and exhaust valves in the combustion chamber. This effectively reduces the temperature difference (prevents the occurrence of knocking) in the vicinity of the canopy.
• the outside portions (5b3, 6b3) of the intake valves (5, 6) shown in FIGS. 2(a) and (b) are exposed to the combustion chamber 4 when the valves are closed.
• the intake valve 5 in FIG. 2(a) has an outer cap 5b3 that is thinner in the axial direction than a conventional intake valve, and is also thinner than the outer cap 6b3 of the exhaust valve 6 in FIG. 2(b). , is formed thinner by an axial length ⁇ .
• the shapes (areas) of the face portions 5b2 and 6b2 do not change.
• the total length L1 of the intake valve 5 and the axial length J1 from the upper end of the face portion 5b2 to the umbrella surface 5b4 are the same as the total length L1+ ⁇ of the exhaust valve 6 and the axial length from the upper end of the face portion 6b2 to the umbrella surface 6b4. It is configured to be shorter than the length J2.
• the umbrella part 5b of the intake valve 5 has a thinner outer part 5b3 than the umbrella part 6b of the exhaust valve 6, so that the temperature of the umbrella table 5b4 is lowered by the smaller heat capacity than the conventional intake valve. encouraged to rise.
• the cap portion 5b of the intake valve 5 is more easily heated than the cap portion of a conventional intake valve, the temperature of the area near the cap surface 5b4 of the intake valve 5 increases in the combustion chamber 4, while By sufficiently reducing the temperature in the area near the umbrella face 6b4 of the exhaust valve 6, the temperature difference between the areas near the umbrella faces of both the intake valve 5 and the exhaust valve 6 is reduced.
• the cylinder head 2 of this embodiment even if it is adopted in an automobile engine or a marine engine that uses decarbonized fuel containing hydrogen, there will be a temperature difference in the combustion chamber 4 when operating at low rotation speed. By making large areas less likely to occur, knocking due to premature ignition can be prevented.
• the umbrella surface 6b4 of the exhaust valve 6 shown in FIG. 2(b) is subjected to mirror finishing, while the umbrella surface 5b4 which is the bottom surface of the intake valve 5 shown in FIG. 2(a) is A large number of minute protrusions 11 defined by a large number of intersecting grooves 12 and having a lattice shape in plan view are provided throughout the umbrella surface 5b4.
• the lattice-shaped protrusion 11 (white part) in FIG. 3 is a part surrounded by four intersecting grooves 12 formed in a concave shape at right angles to each other on the umbrella face 5b4. is formed.
• the umbrella surface 6b4 of the exhaust valve 6 configured with a mirror surface reflects infrared rays, thereby reducing the radiant heat transmitted from the combustion chamber 4 of FIG. 1 to the umbrella surface 6b4, thereby suppressing a temperature rise. Further, it is desirable that the number of protrusions 11 be increased by providing as many intersecting grooves 12 as possible.
• the umbrella portion of the intake valve 5 easily receives heat from the high-temperature exhaust gas within the combustion chamber 4. By doing so, the umbrella portion 5b of the intake valve 5 becomes more easily heated, so that the temperature difference in the vicinity of the umbrella surfaces 5b4 and 6b4 of both the intake valve 5 and the exhaust valve is reduced in the combustion chamber 4. Since hot spots are less likely to occur in the combustion chamber 4, knocking due to pre-ignition is reduced even when decarbonized fuel containing hydrogen is used.
• FIG. 4 shows a modification of the umbrella surface (bottom surface of the umbrella part) of the intake valve in which a large number of lattice-shaped minute protrusions 13 are provided.
• the umbrella surface of the intake valve has a plurality of concave cross grooves 14 intersecting at acute or obtuse angles, as shown in FIG.
• a plurality of diamond-shaped lattice-like protrusions 13 are provided. It is also desirable to form as many protrusions 13 as possible by providing as many intersecting grooves 14 as possible.
• the plurality of lattice-shaped protrusions formed on the umbrella surface of the intake valve are not limited to a rectangular shape or a diamond shape, as long as they are formed by a plurality of intersecting concave grooves.
• the umbrella surface of the intake valve 5 (bottom surface of the umbrella portion 5b) has first grooves formed in parallel at equal intervals and second grooves formed in parallel at equal intervals.
• Microprotrusions (lattice-like protrusions) extending to intersect with each other and having a rectangular shape in plan view defined by the first and second grooves are continuous along the grooves, and the microprotrusions are
• the grooves are uniformly distributed over the entire umbrella surface (bottom surface of the umbrella portion 5b) of the intake valve 5, the depth of the grooves, the width of the grooves, and the interval between the grooves (the pitch of the grooves) are limited. It's not something you can do.
• FIG. 5(a) and 5(b) show a lattice-shaped protrusion 11 formed from a plurality of intersecting grooves 12 on the umbrella surface 5b4 of the umbrella portion 5b of the intake valve 5 shown in FIG. 2(a).
• an intake valve 5' is shown in which a plurality of protrusions 37 having a wave-shaped longitudinal section are provided over the entire bottom surface.
• the axial length from the upper end of the face portion 5b2' of the umbrella portion 5b' to the lower end of the convex strip 37 is J1, which is the same as that of the intake valve 5.
• the convex portion 37 is composed of a plurality of annular convex portions provided concentrically.
• the umbrella surface 5b4' of the umbrella portion 5b' has a wavy shape in which curved convex portions and curved concave portions are alternately repeated in the longitudinal section. Similar to the umbrella surface 5b4, the umbrella surface 5b4' has an enlarged surface area and receives heat easily from the high-temperature exhaust gas, thereby reducing the temperature difference with the region near the umbrella portion of the exhaust valve.
• the umbrella surface 5b4 of the umbrella part 5b of the intake valve 5 is formed in a vertical cross-sectional wave shape in which annular irregularities are continuous in a concentric manner, and the depth of the curved concave part (curved convex part) (height) and the pitch of the curved concave portions (curved convex portions) are each set to predetermined values, and the surface area (heat receiving area) of the umbrella surface 5b4' is expanded, but the depth of the curved concave portions (curved convex portions) (height) and the pitch of the curved concave portions (curved convex portions) are not limited.
• the umbrella portion 5b is made thin as shown in FIG. ) has been established.
• the umbrella part 5b may be made thinner without providing the protrusion 11 (or the protruding strip 37) on the umbrella face 5b4, or the umbrella part 5b may not be made thinner but has a protrusion on the umbrella face 5b4.
• the portion 11 (or the protruding portion 37) may be provided.

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