US20090020082A1 - Hollow valve for internal combustion engine, and internal combustion engine having the hollow valve - Google Patents
Hollow valve for internal combustion engine, and internal combustion engine having the hollow valve Download PDFInfo
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- US20090020082A1 US20090020082A1 US12/216,304 US21630408A US2009020082A1 US 20090020082 A1 US20090020082 A1 US 20090020082A1 US 21630408 A US21630408 A US 21630408A US 2009020082 A1 US2009020082 A1 US 2009020082A1
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- thermal
- valve
- cavity
- heat
- conductivity
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- 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
- This invention relates to a hollow valve for an internal combustion engine for use in an intake/exhaust valve actuating mechanism of the internal combustion engine, and also relates to an internal combustion engine in which the hollow valve or valves is/are mounted.
- a valve is provided for permitting or interrupting communication between an intake port and the combustion chamber or between an exhaust port and the combustion chamber.
- the valve is roughly divided into an umbrella portion and a stem portion, and the stem portion is adapted to reciprocate in its axial direction, so as to create a condition where the intake port and the combustion chamber, or the exhaust port and the combustion chamber, communicate with each other, or a condition where communication between the intake port or exhaust port and the combustion chamber is interrupted.
- the umbrella portion of the valve in particular, a portion of the umbrella portion that forms a part of the wall of the combustion chamber, is exposed to combustion gas present in the combustion chamber, and therefore, heat generated through combustion is likely to be transferred to that portion of the umbrella portion.
- the amount of heat generated in the combustion chamber has a tendency of increasing, due to its combustion modes for reducing the fuel consumption and pollutants (such as hydrocarbon) contained in exhaust gas, while achieving high power or output of the engine. As a result, the heat transferred to the umbrella portion is increased.
- JP-A-5-113113 Japanese Patent Application Publication No. 5-113113
- JP-A-5-113113 Japanese Patent Application Publication No. 5-113113
- a gastight cavity that extends from an umbrella portion to a stem portion is formed, and a green compact serving as a heat transfer medium is contained in the cavity, so that heat transferred to the umbrella portion is likely to be dissipated.
- the heat transfer medium is shaken in the cavity under the reciprocating motion of the valve, to flow between the umbrella portion and the stem portion. In this manner, the heat transfer medium can transfer the heat of the umbrella portion received from the combustion chamber, to the stem portion, for dissipation of the heat, thereby to suppress or avoid an excessive temperature rise in the umbrella portion.
- Japanese Patent Application Publication No. 2003-188324 is concerned with a heat sinking or radiating substrate of a semiconductor device, which is not related to the hollow valve for the internal combustion engine.
- rods formed of at least one of a carbon-fiber reinforced composite material, a carbon-based metal composite material, a high-thermal-conductivity metallic material, etc.
- a base material having a higher thermal conductivity than a base material are embedded in the base material in the vertical direction, so as to achieve good heat transfer characteristics.
- the axial directions of hollow valves for engines do not coincide with the direction of gravity (i.e., the vertical direction) in most of the types of the engines. Therefore, the heat transfer medium (coolant) does not necessarily contact uniformly with the respective walls of the umbrella portion and stem portion in the cavity, and the umbrella portion and the stem portion may not be cooled uniformly.
- a so-called in-line engine is normally inclined and installed on the vehicle, and thus the axial directions of the hollow engine valves are less likely or unlikely to coincide with the direction of gravity.
- a so-called V-type engine (including a horizontal opposed engine) has banks forming a certain bank angle, and thus the axial directions of the hollow engine valves are less likely or unlikely to coincide with the direction of gravity. Furthermore, since the hollow engine valves are generally inclined and installed on the engines, the axial directions of the valves do not coincide with the direction of gravity.
- the heat transfer medium in the hollow engine valve of the related art, even if heat is transferred to the heat transfer medium in a certain portion of the umbrella portion in the cavity, so that the heat can be dissipated to an object, such as a stem portion, to which heat is to be transferred, the heat transfer medium may not be able to contact a wall of the cavity in another portion of the umbrella portion, and thus cannot take heat from this portion.
- the cooling effect may vary from portion to portion in the umbrella portion for which cooling is particularly needed.
- the amount of the heat transfer medium (generally, metallic sodium) may be increased so as to solve this problem
- most of the heat transfer medium moves in a direction opposite to that of movements of the valve, and the inertial force of the valve may increase as the amount of the heat transfer medium contained increases.
- the thus increased inertial force of the valve may become an impediment to smooth reciprocating movements of the hollow engine valve.
- the present invention provides a hollow valve for an internal combustion engine, which has a good cooling capability, and an internal combustion engine in which such hollow valves are mounted.
- a first aspect of the invention relates to a hollow valve for an internal combustion engine, which includes: a stem portion, an umbrella portion provided at one end of the stem portion, the stem portion and the umbrella portion cooperating with each other to form a gastight cavity that communicates an interior of the stem portion with an interior of the umbrella portion, and a coolant contained in the cavity.
- the umbrella portion has a wall portion having a combustion-chamber-side wall that forms a part of a wall of a combustion chamber of the internal combustion engine, and a cavity-side wall that forms a part of a wall of the cavity, and at least one high-thermal-conductivity member is provided on the cavity-side wall, for conduction of heat between the wall portion of the umbrella portion and one of at least the coolant and the stem portion as a heat-conduction medium.
- heat of the wall portion is taken or absorbed by the high-thermal-conductivity member(s), so that the wall portion is cooled.
- the heat taken by the high-thermal-conductivity member(s) is transferred to a heat-conduction medium, such as a coolant, and is finally transferred from the heat-conduction medium to a cylinder head.
- a heat-conduction medium such as a coolant
- the above-indicated at least one high-thermal-conductivity member may have a directional characteristic in heat conduction between one end thereof that is in contact with the cavity-side wall and the other end that is in contact with the heat-conduction medium.
- the high-thermal-conductivity member of this type may be formed of a carbon-fiber reinforced metal.
- the heat of the wall portion can be surely transferred to a desired heat-conduction medium.
- the above-indicated at least one high-thermal-conductivity member may include a plurality of high-thermal-conductivity members that form a convex portion that protrudes in substantially the same direction as an axial direction of the stem portion, so as to transfer heat of the wall portion to the coolant.
- the hollow engine valve provides a high cooling effect, in particular, a high effect of cooling the umbrella portion.
- the above-indicated at least one high-thermal-conductivity member may be placed in position so as to transfer heat between the cavity-side wall and a wall close to one end of the stem portion remote from the umbrella portion.
- the heat of the wall portion is transferred, without fail, directly to the wall closed to the end of the stem portion remote from the umbrella portion, so that the wall portion can be surely cooled, irrespective of whether the hollow valve itself is mounted in the engine with its axis inclined relative to the vertical direction, or even if the valve lift is small and the coolant does not rise to a high level.
- the above-indicated at least one high-thermal-conductivity member may include a first high-thermal-conductivity member placed in position so as to transfer heat between a central portion of the cavity-side wall and the heat-conduction medium, and a second high-thermal-conductivity member placed in position so as to transfer heat between a peripheral portion of the cavity-side wall and a wall of the cavity which is close to a valve seat of the umbrella portion.
- the heat of the wall portion is transferred to a portion of the umbrella portion that is close to the valve seat, as well as the heat-conduction medium (the coolant or stem portion). Accordingly, when it is not desired to raise the temperature of the stem portion, which would result in an increase in the temperature of intake air, the high-thermal-conductivity member are placed in position so that a relatively large amount of heat is dissipated to the portion close to the valve seat, thereby to suppress or prevent a temperature rise of the intake air.
- the high-thermal-conductivity members have a high capability of dissipating heat, and heat is transferred from the high-thermal-conductivity members to the heat-conduction medium, so that the umbrella portion, in particular, can be favorably cooled.
- An internal combustion engine includes an intake valve having a structure of the hollow valve for the internal combustion engine according, to the first aspect of the invention, and an exhaust valve having a structure of the hollow valve for the internal combustion engine according to the first aspect of the invention.
- the umbrella portions of the intake valve and exhaust valve are cooled with improved efficiency, so that the engine is less likely to suffer from knocking. Owing to the effect of suppressing or preventing knocking, the ignition timing can be advanced as needed, thus assuring improved output performance of the engine.
- the number of the high-thermal-conductivity members provided in the exhaust valve may be made larger than the number of the high-thermal-conductivity members provided in the intake valve.
- the larger number of high-thermal-conductivity members are provided in the exhaust valve on the exhaust side where the valve is more likely to be exposed to hot gas, than that provided in the intake valve on the air intake or induction side, thus assuring a sufficient cooling effect. Since the intake/exhaust valves used in the engine according to the second aspect of the invention can change the degree of cooling simply by adjusting the number of the high-thermal-conductivity members provided in the valve, all of the components can be shared between the exhaust valve and the intake valve, and the internal combustion engine can be manufactured at reduced cost.
- FIG. 1 is a cross-sectional view showing the construction of a hollow valve for an internal combustion engine according to a first embodiment of the invention
- FIG. 2 is a perspective view showing the shape and arrangement of high-thermal-conductivity members of the hollow engine valve of the first embodiment
- FIG. 3 is a cross-sectional view showing the construction of a hollow valve for an internal combustion engine according to a second embodiment of the invention
- FIG. 4 is a cross-sectional view showing the construction of a hollow valve for an internal combustion engine according to a third embodiment of the invention.
- FIG. 5 is a cross-sectional view showing the construction of a hollow valve for an internal combustion engine according to a fourth embodiment of the invention.
- FIG. 6 is a top view as seen from the inside of a cavity of the hollow valve of the fourth embodiment, showing the arrangement of high-thermal-conductivity members;
- FIG. 7 is a cross-sectional view showing the construction of a hollow valve for an internal combustion engine according to a fifth embodiment of the invention.
- FIG. 8 is a cross-sectional view taken along line X-X in FIG. 7 , showing the arrangement of high-thermal-conductivity members of the fifth embodiment.
- a hollow valve for an internal combustion engine according to a first embodiment of the invention will be described with reference to FIG. 1 and FIG. 2 .
- reference numeral 10 A denotes the hollow engine valve of the first embodiment.
- the hollow engine valve 10 A of the first embodiment may be used in an intake or exhaust valve actuating mechanism (a mechanism including, for example, a valve lifter 101 ) of the internal combustion engine, which is not illustrated in the drawings.
- the hollow engine valve 10 A reciprocates in the axial direction so as to communicate a combustion chamber CC of the engine and an intake port P (or the combustion chamber CC and an exhaust port P) with each other or interrupt communication between the combustion chamber CC and the intake or exhaust port P.
- the hollow engine valve 10 A of the first embodiment is divided roughly into a stem portion (so-called valve stem) Vs and an umbrella portion Vh provided at one end of the stem portion Vs.
- the hollow valve 10 A having the stem and umbrella portions Vs, Vh is constituted by a cylindrical valve body 1 having opposite open ends, a first closure member (which will be called “upper cap”) 2 that closes one of the open ends of the valve body 1 , and a second closure member (which will be called “lower cap”) 3 that closes the other open end of the valve body 1 .
- the valve body 1 has a cylindrical portion 1 a having opposite open ends, and a truncated cone portion 1 b formed generally in the shape of a truncated cone, which has an inner space that connects the upper opening with the lower opening thereof.
- the cylindrical portion 1 a is connected at one of the opposite open ends to the upper open end of the truncated cone portion 1 b , to form the valve body 1 as an integral body.
- the inner space of the truncated cone portion 1 b is shaped like a truncated cone that is substantially the same as the outer shape or outline of the truncated cone portion 1 b .
- the valve body 1 has a cavity 4 formed by connecting the columnar space of the cylindrical portion 1 a with the generally truncated-cone-shaped space of the truncated cone portion 1 b .
- the cavity 4 of the valve body 1 is formed in substantially the same shape as the outline of the valve body 1 .
- the cylindrical portion 1 a forms a main part of the stem portion Vs
- the upper cap 2 is provided at the remaining open end (i.e., the open end remote from the truncated cone portion 1 b ) of the cylindrical portion 1 a .
- the stem portion Vs of the hollow engine valve 10 A illustrated herein consists of the cylindrical portion 1 a of the valve body 1 and the upper cap 2 .
- the upper cap 2 is joined integrally to the cylindrical portion 1 a by welding, or the like, thereby to close the above-indicated open end of the cylindrical portion 1 a of the valve body 1 .
- the truncated cone portion 1 b forms a main part of the umbrella portion Vh
- the lower cap 3 is provided at the remaining open end (i.e., the open end at the bottom) of the truncated cone portion 1 b
- the umbrella portion Vh of the hollow engine valve 10 A illustrated herein consists of the truncated cone portion 1 b of the valve body 1 and the lower cap 3 .
- the lower cap 3 provides a wall portion having a combustion-chamber-side wall 3 a as shown in FIG.
- combustion-chamber-side wall 3 a and the cavity-side wall 3 b face in the opposite directions, namely, provide the opposite surfaces of the lower cap 3 , or wall portion.
- the lower cap 3 is joined integrally to the truncated cone portion 1 b by welding, or the like, with the cavity-side wall 3 b facing inwards, so that the lower cap 3 closes the above-indicated open end of the truncated cone portion 1 b of the valve body 1 .
- the hollow engine valve 10 A formed as described above reciprocates in the axial direction of the stem portion Vs under the action of the valve actuating mechanism.
- the hollow engine valve 10 A is pushed down by the action of a cam or rocker arm (not shown) via a valve lifter 101 .
- the inclined face of the umbrella portion Vh of the hollow engine valve 10 A moves away from an interface (i.e., an annular valve seat 102 as shown in FIG. 1 ) between the port (intake port or exhaust port) P and the combustion chamber CC, for communication between the port P and the combustion chamber CC.
- an elastic member (coil spring) 104 is compressed between an annular retainer 103 fixed to the upper cap 2 and a cylinder head 105 for example. Accordingly, the spring force of the elastic member 104 acts on the hollow engine valve 10 A via the retainer 103 , according to the operation of the cam, or the like. As a result, the hollow engine valve 10 A is moved in a direction opposite to that of the push-down action, so that the inclined face of the umbrella portion Vh abuts on the valve seat 102 , thereby to interrupt communication between the port P and the combustion chamber CC.
- the stem portion Vs of the hollow engine valve 10 A is surrounded by a cylindrical valve stem guide 106 , and is smoothly guided by the valve stem guide 106 while the valve 10 A is reciprocating.
- the hollow engine valve 10 A is provided with a cooling means for dissipating heat (in particular, heat of a portion, such as the lower cap 3 , that is exposed to combustion gas) transferred from the combustion chamber CC.
- a coolant 5 such as metallic sodium, which serves as the cooling means is contained in the cavity 4 .
- the coolant 5 if it is metallic sodium, is heated to a temperature exceeding the fusing point thereof, and is brought into a liquid state.
- the coolant 5 is shaken in accordance with the reciprocating motion of the hollow engine valve 10 A, and is thus caused to flow in the cavity 4 .
- the coolant 5 takes heat away from a wall of the cavity 4 having a temperature higher than that of the coolant 5 when it contacts the wall, and further flows in the cavity 4 each time the valve 10 A repeats the reciprocating motion, so as to transfer the heat to a wall of the cavity 4 having a temperature lower than that of the coolant 5 when it contacts the wall.
- the coolant 5 receives heat of the umbrella portion Vh that is most likely to be heated to a high temperature, and moves to the stem portion Vs under the reciprocating motion of the hollow engine valve 10 A, so that the heat received from the umbrella portion Vh is transferred from the coolant 5 to the stem portion Vs, to thus effect cooling of the umbrella portion Vh.
- At least one high-thermal-conductivity member 6 A having high thermal conductivity and a particular directional characteristic of heat conduction is provided as another cooling means on the cavity-side wall 3 b of the lower cap 3 .
- CFRRM carbon-fiber reinforced metals
- the carbon-fiber reinforced metal uses metal as a base material, and uses carbon fibers as a reinforcing material.
- the metal as the base material is exposed at the opposite ends of the high-thermal-conductivity member 6 A, so that the member 6 A can transfer heat from the metal exposed face of one end thereof on the high-temperature side, to the metal exposed face of the other end on the low-temperature side.
- the high-thermal-conductivity members 6 A have substantially the same length and a small diameter (of, for example, about 10 ⁇ m), and are formed straight like rods. While clearances are apparently provided between the adjacent high-thermal-conductivity members 6 in FIG. 2 , these clearances are illustrated for the sake of convenience.
- Each of the high-thermal-conductivity members 6 A is bonded at one end to the cavity-side wall 3 b by a method, such as metal plating, so that the efficiency of heat transfer between the high-thermal-conductivity member 6 A and the lower cap 3 is not reduced.
- the high-thermal-conductivity members 6 A are formed upright over the entire area of the cavity-side wall 3 b of the lower cap 3 , so that the heat of the lower cap 3 is taken or absorbed by all of the high-thermal-conductivity members 6 A, and the lower cap 3 can be thus cooled. Also, in the hollow engine valve 10 A, the heat is transferred to the coolant 5 that is in contact with free ends (i.e., the ends remote from the cavity-side wall 3 b ) of the respective high-thermal-conductivity members 6 A.
- the high-thermal-conductivity members 6 A raise the level of the coolant 5 as a heat-conduction medium.
- the coolant 5 reaches the upper portion (close to the valve lifter 101 ) of the stem portion Vs with higher reliability, under the reciprocating motion of the hollow valve 10 A, even if the hollow engine valve 10 A is mounted in the engine with its axis inclined relative to the vertical direction.
- the hollow engine valve 10 A of the first embodiment permits highly efficient cooling of the lower cap 3 ; therefore, temperature rises of the valve seat 102 and the valve face of the umbrella portion Vh that abuts on the valve seat 102 are effectively suppressed or prevented, and the valve seat 102 and the valve face are less likely to wear, thus assuring improved durability and improved gas tightness of the combustion chamber CC.
- the hollow engine valve having no high-thermal-conductivity members 6 A provides a sufficient cooling effect
- the high-thermal-conductivity members 6 A provided in the hollow engine valve 10 A of the first embodiment serve to reduce the amount of the coolant 5 contained in the cavity 4 , and reduce the inertial mass of the valve 10 A when reciprocating.
- the hollow engine valve 10 A of the first embodiment can reciprocate with increased agility and good responsiveness, thus assuring improved accuracy in the valve-opening timing and valve-closing timing.
- the hollow engine valve 10 A of the first embodiment permits effective cooling of the umbrella portion Vh that is most likely to be heated to a high temperature, thus assuring improvements in the durability of the valve 10 A itself, durability of the valve seat 102 , gas-tightness of the combustion chamber CC, and the accuracy in the valve-opening timing and valve-closing timing. Therefore, the hollow engine valve 10 A achieves improved accuracy of its movements in response to a command value of the excess air ratio (i.e., the air-fuel ratio, in particular, the stoichiometric air-fuel ratio) of the combustion chamber CC, and an increased pressure in the cylinder, which lead to increased engine power and reduced fuel consumption.
- the excess air ratio i.e., the air-fuel ratio, in particular, the stoichiometric air-fuel ratio
- the hollow engine valve 10 A of this embodiment ensures sufficient heat resistance and durability even if the valve 10 A and the valve seat 102 are formed of low-cost materials having lower heat resistance and durability than those of the related art.
- the hollow valve 10 A and its peripheral components are available at reduced cost.
- the hollow engine valve 10 A of this embodiment allows the umbrella portion Vh (in particular, the combustion-chamber-side wall 3 a of the lower cap 3 that forms a part of the wall of the combustion chamber CC) to be cooled by a greater degree than that of the related art, the engine is less likely to suffer from knocking, as compared with the engine of the related art.
- the hollow engine valve 10 A having an effect of suppressing or preventing knocking, the ignition timing can be advanced as needed, thus assuring improved output performance.
- the degree of cooling of the umbrella portion Vh can be adjusted as desired by increasing or reducing the number of the high-thermal-conductivity members 6 A provided in the valve 10 A. Accordingly, when the hollow engine valve 10 A is used at the exhaust side (as an exhaust valve) that is more likely to be exposed to a high temperature, the larger number of the high-thermal-conductivity members 6 A than that in the case where the valve 10 A is used at the intake side (as an intake valve) may be provided in the valve 10 A, so as to ensure a sufficient cooling effect.
- the hollow engine valve 10 A of the first embodiment can change the degree of cooling simply by adjusting the number of the high-thermal-conductivity members 6 A, as described above, all of the components can be shared between the exhaust side and the intake side, and exhaust valves and intake valves can be manufactured at reduced cost.
- FIG. 3 is a cross-sectional view taken along the center axis of the valve body 1 , and the hollow engine valve assumes the same shape or configuration as that shown in FIG. 3 , when viewed in each section cut along the center axis at any angle across 360 degrees.
- reference numeral 10 B denotes the hollow engine valve of the second embodiment.
- the hollow engine valve 10 B of the second embodiment is provided by replacing the high-thermal-conductivity members 6 A used in the hollow engine valve 10 A of the above-described first embodiment, with a plurality of high-thermal-conductivity members 6 B as shown in FIG. 3 .
- the high-thermal-conductivity members 6 B of the second embodiment are different from the high-thermal-conductivity members 6 A of the first embodiment in that the high-thermal-conductivity members 6 B on a central portion of the cavity-side wall 3 b of the lower cap 3 protrude inwardly of the cavity 4 .
- a plurality of rod-like, high-thermal-conductivity members 6 B having substantially the same length and diameter as those of the first embodiment are placed on an annular, peripheral portion of the cavity-side wall 3 b of the lower cap 3 , and a plurality of high-thermal-conductivity members 6 B that are longer than those in the peripheral portion are placed on a radially inner portion of the cavity-side wall 3 b , so that a convex portion 7 is formed inside the peripheral portion.
- the high-thermal-conductivity members 6 B are formed with a length that gradually increases from the periphery of the convex portion 7 , so that the height of the high-thermal-conductivity members 6 B gradually increases toward the center axis of the hollow engine valve 10 B.
- a cluster of high-thermal-conductivity members 6 B on the central portion of the cavity-side wall 3 b is shaped like a mound or mountain, in other words, the high-thermal-conductivity members 6 B on the central portion are formed with lengths greater than that of the members 6 B on the peripheral portion so as to conform to the space shaped like a truncated cone.
- heat is more likely to be transferred from the lower cap 3 to the high-thermal-conductivity members 6 B, particularly in the convex portion 7 , as compared with the first embodiment.
- the level of the coolant 5 as a heat-conduction medium that is in contact with the convex portion 7 can be raised to a higher level than that of the first embodiment, so that the coolant 5 reaches the upper portion (close to the valve lifter 101 ) of the stem portion Vs with increased reliability.
- the hollow engine valve 10 B of this embodiment exhibits a higher cooling effect than the hollow engine valve 10 A of the first embodiment.
- the provision of the convex portion 7 as in the second embodiment permits reduction of the amount of the coolant 5 contained in the cavity 4 .
- the inertial mass of the hollow valve 10 B when reciprocating can be reduced to be smaller than that of the first embodiment.
- the hollow engine valve 10 B of the second embodiment permits effective cooling of the umbrella portion Vh that is most likely to be heated to a high temperature, thus assuring further improvements in the durability of the valve 10 B itself, durability of the valve seat 102 , gas-tightness of the combustion chamber CC, and the accuracy in the valve-opening timing and valve-closing timing. Therefore, the hollow engine valve 10 B achieves further improved accuracy of its movements in response to a command value of the excess air ratio (i.e., the air-fuel ratio, in particular, the stoichiometric air-fuel ratio) of the combustion chamber CC, and a further increased pressure in the cylinder, to more effectively increase the engine power and reduce the fuel consumption.
- the excess air ratio i.e., the air-fuel ratio, in particular, the stoichiometric air-fuel ratio
- the hollow engine valve 10 B of this embodiment ensures sufficient heat resistance and durability even if the valve 10 B and the valve seat 102 are formed of low-cost materials having lower heat resistance and durability than those of the related art.
- the hollow valve 10 B and its peripheral components are available at reduced cost.
- the hollow engine valve 10 B of this embodiment allows the umbrella portion Vh (in particular, the combustion-chamber-side wall 3 a of the lower cap 3 that forms a part of the wall of the combustion chamber CC) to be cooled by a greater degree than that of the related art, as in the first embodiment, the engine is less likely to suffer from knocking, as compared with the related art.
- the hollow engine valve 10 B having an effect of suppressing or preventing knocking, the ignition timing can be advanced as needed, thus assuring improved output performance.
- the degree of cooling of the umbrella portion Vh can be adjusted as desired by increasing or reducing the number of the high-thermal-conductivity members 6 B provided in the valve 10 B, as in the first embodiment. Accordingly, when the hollow engine valve 10 B is used at the exhaust side (as an exhaust valve) that is more likely to be exposed to a high temperature, the larger number of the high-thermal-conductivity members 6 A than that in the case where the valve 10 B is used at the intake side (as an intake valve) may be provided in the valve 10 B, so as to ensure a sufficient cooling effect.
- the hollow engine valve 10 B of the second embodiment can change the degree of cooling simply by adjusting the number of the high-thermal-conductivity members 6 B, as described above, all of the components can be shared between the exhaust side and the intake side, and exhaust valves and intake valves can be manufactured at reduced cost.
- the hollow engine valve 10 B of the second embodiment can provide a sufficient cooling effect, the high-thermal-conductivity members 6 B disposed on the peripheral portion of the cavity-side wall 3 b may be removed, and the high-thermal-conductivity members 6 B may be disposed only on the central portion of the wall 3 b (or in the convex portion 7 ), to provide a similar cooling effect.
- the hollow engine valve 10 B in which the high-thermal-conductivity members 6 B are placed over the entire area of the cavity-side wall 3 b , which provides a relatively high effect of cooling the umbrella portion Vh, may be manufactured as an exhaust valve
- the hollow engine valve 10 B in which the high-thermal-conductivity members 6 B are placed only on the central portion, which provides a relatively low effect of cooling the umbrella portion Vh may be manufactured as an intake valve.
- FIG. 4 is a cross-sectional view taken along the center axis of the valve body 1 , and the hollow engine valve assumes the same shape or configuration as that shown in FIG. 4 , when viewed in each section cut along the center axis at any angle across 360 degrees.
- reference numeral 10 C denotes the hollow engine valve of the third embodiment.
- the hollow engine valve 10 C of the third embodiment is provided by replacing the high-thermal-conductivity members 6 A used in the hollow engine valve 10 A of the above-described first embodiment, with a plurality of high-thermal-conductivity members 6 C as shown in FIG. 4 .
- the high-thermal-conductivity members 6 C of the third embodiment are different from the high-thermal-conductivity members 6 A of the first embodiment in that the high-thermal-conductivity members 6 C disposed on a central portion of the cavity-side wall 3 b of the lower cap 3 are extended up to the upper cap 2 .
- the high-thermal-conductivity members 6 B disposed in a central portion of the convex portion 7 in the second embodiment are extended up to the upper cap 2 , to provide the high-thermal-conductivity members 6 C of the third embodiment.
- a plurality of rod-like high-thermal-conductivity members 6 C having substantially the same length and diameter as those of the first embodiment are placed on an annular, peripheral portion of the cavity-side wall 3 b of the lower cap 3 , and a plurality of high-thermal-conductivity members 6 C each having one end that contacts the lower face of the upper cap 2 (namely, the face that forms a part of the wall of the cavity 4 ) are placed on a radially inner portion of the cavity-side wall 3 b that is located inside the peripheral portion.
- the high-thermal-conductivity members 6 C are bonded to the upper cap 2 by a method, such as metal plating, as is the case with bonding between the members 6 C and the lower cap 3 .
- the cavity-side wall 3 b of the lower cap 3 and the lower face of the upper cap 2 are connected to the opposite ends of the high-thermal-conductivity members 6 C on the central portion, so that heat taken from the lower cap 3 can be surely transferred directly to the lower face of the upper cap 2 as a heat-conduction medium, and the heat thus transferred can be dissipated to the cylinder head 105 via the valve lifter 101 , valve stem guide 106 and other components.
- the high-thermal-conductivity members 6 C disposed on the central portion of the cavity-side wall 3 b have an increased length, and thus provide a high heat-dissipating effect.
- the coolant 5 as a heat-conduction medium to which heat is transferred from the high-thermal-conductivity members 6 C on the peripheral portion of the cavity-side wall 3 b reaches the stem portion Vs under the reciprocating motion of the valve 10 C.
- the heat of the lower cap 3 is transferred to the upper portion of the stem portion Vs (i.e., the lower face of the upper cap 2 ) without fail, to surely effect cooling of the lower cap 3 , irrespective of whether the valve 10 c is mounted in the engine with its axis inclined, or even if the level of the coolant 5 is not raised largely because of a small valve lift.
- the hollow engine valve 10 C of the third embodiment permits effective cooling of the umbrella portion Vh that is most likely to be heated to a high temperature, thus assuring further improvements in the durability of the valve 10 C itself, durability of the valve seat 102 , gas-tightness of the combustion chamber CC, and the accuracy in the valve-opening timing and valve-closing timing. Therefore, the hollow engine valve 10 C achieves further improved accuracy of its movements in response to a command value of the excess air ratio (i.e., the air-fuel ratio, in particular, the stoichiometric air-fuel ratio) of the combustion chamber CC, and a further increased pressure in the cylinder, to more effectively increase the engine power and reduce the fuel consumption.
- the excess air ratio i.e., the air-fuel ratio, in particular, the stoichiometric air-fuel ratio
- the hollow engine valve 10 C of this embodiment ensures sufficient heat resistance and durability even if the valve 10 C and the valve seat 102 are formed of low-cost materials having lower heat resistance and durability than those of the related art.
- the hollow engine valve 10 C and its peripheral components are available at reduced cost.
- the hollow engine valve 10 C of this embodiment allows the umbrella portion Vh (in particular, the combustion-chamber-side wall 3 a of the lower cap 3 that forms a part of the wall of the combustion chamber CC) to be cooled by a greater degree than that of the related art, as in the first embodiment, the engine is less likely to suffer from knocking, as compared with the engine of the related art.
- the hollow engine valve 10 C having an effect of suppressing or preventing knocking, the ignition timing can be advanced as needed, thus assuring improved output performance.
- the degree of cooling of the umbrella portion Vh can be adjusted as desired by increasing or reducing the number of the high-thermal-conductivity members 6 C provided in the valve 10 C, as is the case with the first embodiment. Accordingly, when the hollow engine valve 10 C is used at the exhaust side (as an exhaust valve) that is more likely to be exposed to a high temperature, the larger number of the high-thermal-conductivity members 6 C than that in the case where the valve 10 C is used at the intake side (as an intake valve) may be provided in the valve 10 C, so as to ensure a sufficient cooling effect.
- the hollow engine valve 10 C of the third embodiment can change the degree of cooling simply by adjusting the number of the high-thermal-conductivity members 6 C, as described above, all of the components can be shared between the exhaust side and the intake side, and exhaust valves and intake valves can be manufactured at reduced cost.
- the hollow engine valve 10 C of the third embodiment as described above can provide a sufficient cooling effect, the high-thermal-conductivity members 6 C disposed on the peripheral portion of the cavity-side wall 3 b may be removed, and the high-thermal-conductivity members 6 C (that connect the cavity-side wall 3 b of the lower cap 3 with the lower face of the upper cap 2 ) may be disposed only on the central portion of the wall 3 b , to provide a similar cooling effect.
- the coolant 5 is not necessarily contained in the cavity 4 provided that a desired cooling effect can be obtained. If the coolant 5 is not contained, the inertial mass is further reduced, and the hollow engine valve 10 C can reciprocate with increased agility and good responsiveness.
- the hollow valve 10 C in which the high-thermal-conductivity members 6 C are placed over the entire area of the cavity-side wall 3 b , which provides a relatively high effect of cooling the umbrella portion Vh may be manufactured as an exhaust valve
- the hollow valve 10 C in which the high-thermal-conductivity members 6 C are placed only on the central portion, which provides a relatively low effect of cooling the umbrella portion Vh may be manufactured as an intake valve
- the hollow valve 10 C in which the coolant 5 is contained may be manufactured as an exhaust valve
- the hollow valve 10 C having no coolant 5 may be manufactured as an intake valve.
- reference numeral 10 D denotes the hollow engine valve of the fourth embodiment.
- the hollow engine valve 10 D of the fourth embodiment is provided by replacing the high-thermal-conductivity members 6 A used in the hollow engine valve 10 A of the above-described first embodiment with a plurality of high-thermal-conductivity members 6 D 1 , 6 D 2 as shown in FIG. 5 and FIG. 6 .
- the high-thermal-conductivity members 6 A of the first embodiment disposed on a peripheral portion of the cavity-side wall 3 b are modified such that the free ends of the members 6 A are in contact with a wall of the cavity 4 that is close to the valve face of the umbrella portion Vh.
- a plurality of rod-like, high-thermal-conductivity members 6 D 1 having substantially the same length and diameter as those of the first embodiment are placed on a circular, central portion of the cavity-side wall 3 b of the lower cap 3 , and a plurality of high-thermal-conductivity members 6 D 2 are placed on a peripheral portion of the cavity-side wall 3 b , to extend in radial directions, such that the high-thermal-conductivity members 6 D 2 connect the cavity-side wall 3 b with the wall close to the valve face at the opposite ends thereof, as shown in FIG. 6 . While clearances are apparently provided between the adjacent high-thermal-conductivity members 6 D 1 , 6 D 2 in FIG.
- the high-thermal-conductivity members 6 D 2 are bonded to the wall close to the valve face by a suitable method, such as metal plating, that is also used for bonding the members 6 D 2 to the lower cap 3 .
- the peripheral portion of the cavity-side wall 3 b of the lower cap 3 and the wall close to the valve face are connected to each other at the opposite ends of the high-thermal-conductivity members 6 D 2 .
- heat taken from the lower cap 3 can be dissipated from the wall close to the valve face as a heat-conduction medium, to the cylinder head 105 , via the valve seat 102 .
- the coolant 5 as a heat-conduction medium to which heat is transferred from the high-thermal-conductivity members 6 D 1 disposed on the central portion of the cavity-side wall 3 b reaches the upper portion of the stem portion Vs under the reciprocating movements of the valve 10 D.
- the heat of the lower cap 3 is separately directed to the stem portion Vs and to the valve seat 102 , for dissipation.
- the hollow engine valve 10 D of the fourth embodiment can surely effect cooling of the lower cap 3 , as in the first embodiment.
- the valve 10 D In the case where the hollow engine valve 10 D is used at the exhaust side (as an exhaust valve), the valve 10 D needs to provide a greater cooling effect than that in the case where the valve 10 D is used at the intake side (as an intake valve) since the whole valve is sometimes exposed to high-temperature exhaust gas, for example, on the exhaust stroke.
- the hollow engine valve 10 D In the case where the hollow engine valve 10 D is used at the intake side (as an intake valve), on the other hand, if a large amount of heat is dissipated to the stem portion Vs that is constantly in contact with intake air, the temperature of the intake air is increased, and the volumetric efficiency in the combustion chamber CC deteriorates, which may result in a reduction of the thermal efficiency.
- the number of the high-thermal-conductivity members 6 D 2 disposed on the peripheral portion and the number of the high-thermal-conductivity members 6 D 1 disposed on the central portion are determined so that the larger amount of heat is dissipated to the wall close to the valve face, rather than to the stem portion Vs.
- the valve face directly contacts the valve seat 102 fitted in the cylinder head 105 for conduction of heat, the heat is transferred with higher efficiency to the cylinder head 105 if the heat is dissipated to the wall close to the valve face, rather than to the stem portion Vs.
- the cooling capability of the hollow engine valve 10 D is enhanced by increasing the amount of heat dissipated to the wall close to the valve face.
- the hollow engine valve 10 D when the hollow engine valve 10 D is used at the intake side where a cooling capability suitably controlled not to deteriorate the volumetric efficiency is required of the valve 10 D, the number of the high-thermal-conductivity members 6 D 2 disposed on the peripheral portion and the number of the high-thermal-conductivity members 6 D 1 disposed on the central portion are determined so that the amount of heat dissipated to the stem portion Vs is reduced. In this manner, it is possible to avoid a situation where the intake air is warmed by the heat of the stem portion Vs, resulting in deterioration of the volumetric efficiency. Thus, the hollow engine valve 10 D can prevent a reduction of the thermal efficiency of the engine while avoiding wasteful, excessive cooling.
- the hollow engine valve 10 D of the fourth embodiment can change the degree of cooling simply by adjusting the numbers of the high-thermal-conductivity members 6 D 1 , 6 D 2 provided in the valve 10 D. Therefore, all of the components can be shared between the exhaust side and the intake side, and exhaust valves and intake valves can be manufactured at reduced cost.
- the high-thermal-conductivity members 6 D 2 of the fourth embodiment can almost uniformly distribute heat in the vicinity of a welded portion 8 as shown in FIG. 5 at which the valve body 1 and the lower cap 3 are welded to each other, and thus serve as a means for reinforcing the welded portion 8 . Furthermore, the high-thermal-conductivity members 6 D 2 are arranged to cover the welded portion 8 , and, for this reason, too, serve as a means for reinforcing the welded portion 8 . Namely, since the carbon-fiber reinforced metal of which the high-thermal-conductivity members 6 D 2 are formed possesses high stiffness, the members 6 D 2 can suppress or prevent warpage and distortion of the welded portion 8 . Thus, the hollow engine valve 10 D of the fourth embodiment can prevent cracks, or the like, from being formed in the welded portion 8 and its neighborhood.
- the high-thermal-conductivity members 6 D 1 disposed on the central portion may be replaced with the high-thermal-conductivity members 6 B that provide the convex portion 7 in the above-described second embodiment, or may be replaced with the high-thermal-conductivity members 6 C that connect the cavity-side wall 3 b of the lower cap 3 with the lower face of the upper cap 2 in the above-described third embodiment.
- reference numeral 10 E denotes the hollow engine valve of the fifth embodiment.
- the hollow engine valve 10 E of the fifth embodiment is provided by replacing the high-thermal-conductivity members 6 A used in the hollow engine valve 10 A of the above-described first embodiment, with a plurality of high-thermal-conductivity members 6 E as shown in FIG. 7 and FIG. 8 .
- each of the high-thermal-conductivity members 6 E of the fifth embodiment connects a peripheral portion of the cavity-side wall 3 b of the lower cap 3 with a wall of the cavity 4 that is close to the valve stem guide 106 at the opposite ends thereof.
- the high-thermal-conductivity members 6 E are arranged in radial directions as shown in FIG. 8 , to radiate out from the center axis of the hollow engine valve 10 E. While clearances are apparently provided between the adjacent high-thermal-conductivity members 6 E in FIG. 8 , these clearances are illustrated for the sake of convenience.
- the high-thermal-conductivity members 6 E are bonded to the wall close to the valve stem guide 106 by a suitable method, such as metal plating, that is also used for bonding the members GE to the lower cap 3 .
- the peripheral portion of the cavity-side wall 3 b of the lower cap 3 and the wall close to the valve stem guide 106 are connected to the opposite ends of the high-thermal-conductivity members 6 E, to be thus connected to each other.
- heat taken from the lower cap 3 can be surely transferred directly to the wall close to the valve stem guide 106 as a heat-conduction medium, and the heat thus transferred can be dissipated to the cylinder head 105 via the valve stem guide 106 .
- the high-thermal-conductivity members 6 E of the hollow engine valve 10 E have a relatively long length, and thus provide a high heat-dissipating effect.
- the coolant 5 that takes heat from the central portion of the cavity-side wall 3 b reaches the stem portion Vs under the reciprocating movements of the valve 10 E. Accordingly, in the hollow engine valve 10 E of the fifth embodiment, the heat of the lower cap 3 is transferred to the wall close to the valve stem guide 106 without fail, irrespective of whether the valve 10 E is mounted in the engine with its axis inclined, or even if the level of the coolant 5 is not raised to a sufficiently high level because of a small valve lift. Thus, the lower cap 3 is cooled with high reliability.
- the high-thermal-conductivity members 6 E may be formed with a relatively large cross-sectional area (i.e., the cross-sectional area of metal as a base material), which leads to an increase in the amount of heat dissipated from the members 6 E.
- the hollow engine valve according to the present invention is useful or advantageous in terms of the cooling capability, in particular, the capability of cooling the umbrella portion.
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- Engineering & Computer Science (AREA)
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Abstract
Description
- The disclosure of Japanese Patent Application No. 2007-178867 filed on Jul. 6, 2007, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
- 1. Field of the Invention
- This invention relates to a hollow valve for an internal combustion engine for use in an intake/exhaust valve actuating mechanism of the internal combustion engine, and also relates to an internal combustion engine in which the hollow valve or valves is/are mounted.
- 2. Description of the Related Art
- In an intake/exhaust valve actuating mechanism of an internal combustion engine, a valve is provided for permitting or interrupting communication between an intake port and the combustion chamber or between an exhaust port and the combustion chamber. Generally, the valve is roughly divided into an umbrella portion and a stem portion, and the stem portion is adapted to reciprocate in its axial direction, so as to create a condition where the intake port and the combustion chamber, or the exhaust port and the combustion chamber, communicate with each other, or a condition where communication between the intake port or exhaust port and the combustion chamber is interrupted.
- Here, the umbrella portion of the valve, in particular, a portion of the umbrella portion that forms a part of the wall of the combustion chamber, is exposed to combustion gas present in the combustion chamber, and therefore, heat generated through combustion is likely to be transferred to that portion of the umbrella portion. Especially in recent years, the amount of heat generated in the combustion chamber has a tendency of increasing, due to its combustion modes for reducing the fuel consumption and pollutants (such as hydrocarbon) contained in exhaust gas, while achieving high power or output of the engine. As a result, the heat transferred to the umbrella portion is increased.
- Under the circumstances as described above, a hollow valve for an internal combustion engine is disclosed in, for example, Japanese Patent Application Publication No. 5-113113 (JP-A-5-113113), in which a gastight cavity that extends from an umbrella portion to a stem portion is formed, and a green compact serving as a heat transfer medium is contained in the cavity, so that heat transferred to the umbrella portion is likely to be dissipated. In the hollow engine valve in which the cavity is not filled with the heat transfer medium, the heat transfer medium is shaken in the cavity under the reciprocating motion of the valve, to flow between the umbrella portion and the stem portion. In this manner, the heat transfer medium can transfer the heat of the umbrella portion received from the combustion chamber, to the stem portion, for dissipation of the heat, thereby to suppress or avoid an excessive temperature rise in the umbrella portion.
- In the meantime, Japanese Patent Application Publication No. 2003-188324 is concerned with a heat sinking or radiating substrate of a semiconductor device, which is not related to the hollow valve for the internal combustion engine. To provide the heat sinking substrate disclosed in this publication, rods (formed of at least one of a carbon-fiber reinforced composite material, a carbon-based metal composite material, a high-thermal-conductivity metallic material, etc.) having a higher thermal conductivity than a base material are embedded in the base material in the vertical direction, so as to achieve good heat transfer characteristics.
- Although a wide variety of types of internal combustion engines are available, the axial directions of hollow valves for engines do not coincide with the direction of gravity (i.e., the vertical direction) in most of the types of the engines. Therefore, the heat transfer medium (coolant) does not necessarily contact uniformly with the respective walls of the umbrella portion and stem portion in the cavity, and the umbrella portion and the stem portion may not be cooled uniformly. For example, a so-called in-line engine is normally inclined and installed on the vehicle, and thus the axial directions of the hollow engine valves are less likely or unlikely to coincide with the direction of gravity. Also, a so-called V-type engine (including a horizontal opposed engine) has banks forming a certain bank angle, and thus the axial directions of the hollow engine valves are less likely or unlikely to coincide with the direction of gravity. Furthermore, since the hollow engine valves are generally inclined and installed on the engines, the axial directions of the valves do not coincide with the direction of gravity.
- Namely, in the hollow engine valve of the related art, even if heat is transferred to the heat transfer medium in a certain portion of the umbrella portion in the cavity, so that the heat can be dissipated to an object, such as a stem portion, to which heat is to be transferred, the heat transfer medium may not be able to contact a wall of the cavity in another portion of the umbrella portion, and thus cannot take heat from this portion. As a result, the cooling effect may vary from portion to portion in the umbrella portion for which cooling is particularly needed. While the amount of the heat transfer medium (generally, metallic sodium) may be increased so as to solve this problem, most of the heat transfer medium moves in a direction opposite to that of movements of the valve, and the inertial force of the valve may increase as the amount of the heat transfer medium contained increases. The thus increased inertial force of the valve may become an impediment to smooth reciprocating movements of the hollow engine valve.
- The present invention provides a hollow valve for an internal combustion engine, which has a good cooling capability, and an internal combustion engine in which such hollow valves are mounted.
- A first aspect of the invention relates to a hollow valve for an internal combustion engine, which includes: a stem portion, an umbrella portion provided at one end of the stem portion, the stem portion and the umbrella portion cooperating with each other to form a gastight cavity that communicates an interior of the stem portion with an interior of the umbrella portion, and a coolant contained in the cavity. In the hollow engine valve, the umbrella portion has a wall portion having a combustion-chamber-side wall that forms a part of a wall of a combustion chamber of the internal combustion engine, and a cavity-side wall that forms a part of a wall of the cavity, and at least one high-thermal-conductivity member is provided on the cavity-side wall, for conduction of heat between the wall portion of the umbrella portion and one of at least the coolant and the stem portion as a heat-conduction medium.
- In the hollow valve for the internal combustion engine according to the first aspect of the invention, heat of the wall portion is taken or absorbed by the high-thermal-conductivity member(s), so that the wall portion is cooled. The heat taken by the high-thermal-conductivity member(s) is transferred to a heat-conduction medium, such as a coolant, and is finally transferred from the heat-conduction medium to a cylinder head. Thus, the hollow engine valve permits highly efficient cooling of the umbrella portion that is most likely to be heated to a high temperature.
- The above-indicated at least one high-thermal-conductivity member may have a directional characteristic in heat conduction between one end thereof that is in contact with the cavity-side wall and the other end that is in contact with the heat-conduction medium. For example, the high-thermal-conductivity member of this type may be formed of a carbon-fiber reinforced metal.
- In the above case, the heat of the wall portion can be surely transferred to a desired heat-conduction medium.
- The above-indicated at least one high-thermal-conductivity member may include a plurality of high-thermal-conductivity members that form a convex portion that protrudes in substantially the same direction as an axial direction of the stem portion, so as to transfer heat of the wall portion to the coolant.
- With the above arrangement, the coolant the level of which is raised by the convex portion under the reciprocating motion of the valve reaches the upper side of the stem portion, so that the heat which the coolant takes from the high-thermal-conductivity members is transferred to the upper side of the stem portion. Thus, the hollow engine valve provides a high cooling effect, in particular, a high effect of cooling the umbrella portion.
- The above-indicated at least one high-thermal-conductivity member may be placed in position so as to transfer heat between the cavity-side wall and a wall close to one end of the stem portion remote from the umbrella portion.
- With the above arrangement the heat of the wall portion is transferred, without fail, directly to the wall closed to the end of the stem portion remote from the umbrella portion, so that the wall portion can be surely cooled, irrespective of whether the hollow valve itself is mounted in the engine with its axis inclined relative to the vertical direction, or even if the valve lift is small and the coolant does not rise to a high level.
- The above-indicated at least one high-thermal-conductivity member may include a first high-thermal-conductivity member placed in position so as to transfer heat between a central portion of the cavity-side wall and the heat-conduction medium, and a second high-thermal-conductivity member placed in position so as to transfer heat between a peripheral portion of the cavity-side wall and a wall of the cavity which is close to a valve seat of the umbrella portion.
- With the above arrangement, the heat of the wall portion is transferred to a portion of the umbrella portion that is close to the valve seat, as well as the heat-conduction medium (the coolant or stem portion). Accordingly, when it is not desired to raise the temperature of the stem portion, which would result in an increase in the temperature of intake air, the high-thermal-conductivity member are placed in position so that a relatively large amount of heat is dissipated to the portion close to the valve seat, thereby to suppress or prevent a temperature rise of the intake air.
- In the hollow valve for the internal combustion engine according to the invention, the high-thermal-conductivity members have a high capability of dissipating heat, and heat is transferred from the high-thermal-conductivity members to the heat-conduction medium, so that the umbrella portion, in particular, can be favorably cooled.
- An internal combustion engine according to a second aspect of the invention includes an intake valve having a structure of the hollow valve for the internal combustion engine according, to the first aspect of the invention, and an exhaust valve having a structure of the hollow valve for the internal combustion engine according to the first aspect of the invention.
- In the internal combustion engine according to the second aspect of the invention, the umbrella portions of the intake valve and exhaust valve are cooled with improved efficiency, so that the engine is less likely to suffer from knocking. Owing to the effect of suppressing or preventing knocking, the ignition timing can be advanced as needed, thus assuring improved output performance of the engine.
- The number of the high-thermal-conductivity members provided in the exhaust valve may be made larger than the number of the high-thermal-conductivity members provided in the intake valve.
- In the above case, the larger number of high-thermal-conductivity members are provided in the exhaust valve on the exhaust side where the valve is more likely to be exposed to hot gas, than that provided in the intake valve on the air intake or induction side, thus assuring a sufficient cooling effect. Since the intake/exhaust valves used in the engine according to the second aspect of the invention can change the degree of cooling simply by adjusting the number of the high-thermal-conductivity members provided in the valve, all of the components can be shared between the exhaust valve and the intake valve, and the internal combustion engine can be manufactured at reduced cost.
- The foregoing and further features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements, and wherein:
-
FIG. 1 is a cross-sectional view showing the construction of a hollow valve for an internal combustion engine according to a first embodiment of the invention; -
FIG. 2 is a perspective view showing the shape and arrangement of high-thermal-conductivity members of the hollow engine valve of the first embodiment; -
FIG. 3 is a cross-sectional view showing the construction of a hollow valve for an internal combustion engine according to a second embodiment of the invention; -
FIG. 4 is a cross-sectional view showing the construction of a hollow valve for an internal combustion engine according to a third embodiment of the invention; -
FIG. 5 is a cross-sectional view showing the construction of a hollow valve for an internal combustion engine according to a fourth embodiment of the invention; -
FIG. 6 is a top view as seen from the inside of a cavity of the hollow valve of the fourth embodiment, showing the arrangement of high-thermal-conductivity members; -
FIG. 7 is a cross-sectional view showing the construction of a hollow valve for an internal combustion engine according to a fifth embodiment of the invention; and -
FIG. 8 is a cross-sectional view taken along line X-X inFIG. 7 , showing the arrangement of high-thermal-conductivity members of the fifth embodiment. - In the following, some embodiments of hollow valves for internal combustion engines according to the invention will be described in detail with reference to the drawings. It is to be understood that this invention is not limited to these embodiments.
- A hollow valve for an internal combustion engine according to a first embodiment of the invention will be described with reference to
FIG. 1 andFIG. 2 . - In
FIG. 1 ,reference numeral 10A denotes the hollow engine valve of the first embodiment. Thehollow engine valve 10A of the first embodiment may be used in an intake or exhaust valve actuating mechanism (a mechanism including, for example, a valve lifter 101) of the internal combustion engine, which is not illustrated in the drawings. In operation, thehollow engine valve 10A reciprocates in the axial direction so as to communicate a combustion chamber CC of the engine and an intake port P (or the combustion chamber CC and an exhaust port P) with each other or interrupt communication between the combustion chamber CC and the intake or exhaust port P. - The
hollow engine valve 10A of the first embodiment is divided roughly into a stem portion (so-called valve stem) Vs and an umbrella portion Vh provided at one end of the stem portion Vs. Thehollow valve 10A having the stem and umbrella portions Vs, Vh is constituted by acylindrical valve body 1 having opposite open ends, a first closure member (which will be called “upper cap”) 2 that closes one of the open ends of thevalve body 1, and a second closure member (which will be called “lower cap”) 3 that closes the other open end of thevalve body 1. - The
valve body 1 has acylindrical portion 1 a having opposite open ends, and atruncated cone portion 1 b formed generally in the shape of a truncated cone, which has an inner space that connects the upper opening with the lower opening thereof. Thecylindrical portion 1 a is connected at one of the opposite open ends to the upper open end of thetruncated cone portion 1 b, to form thevalve body 1 as an integral body. The inner space of thetruncated cone portion 1 b is shaped like a truncated cone that is substantially the same as the outer shape or outline of thetruncated cone portion 1 b. Thus, thevalve body 1 has acavity 4 formed by connecting the columnar space of thecylindrical portion 1 a with the generally truncated-cone-shaped space of thetruncated cone portion 1 b. Namely, thecavity 4 of thevalve body 1 is formed in substantially the same shape as the outline of thevalve body 1. - In the
valve body 1, thecylindrical portion 1 a forms a main part of the stem portion Vs, and theupper cap 2 is provided at the remaining open end (i.e., the open end remote from thetruncated cone portion 1 b) of thecylindrical portion 1 a. Namely, the stem portion Vs of thehollow engine valve 10A illustrated herein consists of thecylindrical portion 1 a of thevalve body 1 and theupper cap 2. For example, theupper cap 2 is joined integrally to thecylindrical portion 1 a by welding, or the like, thereby to close the above-indicated open end of thecylindrical portion 1 a of thevalve body 1. - In the
valve body 1, thetruncated cone portion 1 b forms a main part of the umbrella portion Vh, and thelower cap 3 is provided at the remaining open end (i.e., the open end at the bottom) of thetruncated cone portion 1 b. Namely, the umbrella portion Vh of thehollow engine valve 10A illustrated herein consists of thetruncated cone portion 1 b of thevalve body 1 and thelower cap 3. For example, thelower cap 3 provides a wall portion having a combustion-chamber-side wall 3 a as shown inFIG. 1 , which forms a part of the wall of the combustion chamber CC when the port (intake port or exhaust port) P and the combustion chamber CC are not in communication with each other, and a cavity-side wall 3 b as shown inFIG. 2 , which forms a-part of the wall of thecavity 4. The combustion-chamber-side wall 3 a and the cavity-side wall 3 b face in the opposite directions, namely, provide the opposite surfaces of thelower cap 3, or wall portion. Thelower cap 3 is joined integrally to thetruncated cone portion 1 b by welding, or the like, with the cavity-side wall 3 b facing inwards, so that thelower cap 3 closes the above-indicated open end of thetruncated cone portion 1 b of thevalve body 1. - The
hollow engine valve 10A formed as described above reciprocates in the axial direction of the stem portion Vs under the action of the valve actuating mechanism. For example, thehollow engine valve 10A is pushed down by the action of a cam or rocker arm (not shown) via avalve lifter 101. As a result, the inclined face of the umbrella portion Vh of thehollow engine valve 10A moves away from an interface (i.e., anannular valve seat 102 as shown inFIG. 1 ) between the port (intake port or exhaust port) P and the combustion chamber CC, for communication between the port P and the combustion chamber CC. - As the
hollow engine valve 10A is pushed down, an elastic member (coil spring) 104 is compressed between anannular retainer 103 fixed to theupper cap 2 and acylinder head 105 for example. Accordingly, the spring force of theelastic member 104 acts on thehollow engine valve 10A via theretainer 103, according to the operation of the cam, or the like. As a result, thehollow engine valve 10A is moved in a direction opposite to that of the push-down action, so that the inclined face of the umbrella portion Vh abuts on thevalve seat 102, thereby to interrupt communication between the port P and the combustion chamber CC. - The stem portion Vs of the
hollow engine valve 10A is surrounded by a cylindrical valve stemguide 106, and is smoothly guided by thevalve stem guide 106 while thevalve 10A is reciprocating. - Furthermore, the
hollow engine valve 10A is provided with a cooling means for dissipating heat (in particular, heat of a portion, such as thelower cap 3, that is exposed to combustion gas) transferred from the combustion chamber CC. - In the first embodiment, a
coolant 5, such as metallic sodium, which serves as the cooling means is contained in thecavity 4. At least during operation of the engine, thecoolant 5, if it is metallic sodium, is heated to a temperature exceeding the fusing point thereof, and is brought into a liquid state. Thecoolant 5 is shaken in accordance with the reciprocating motion of thehollow engine valve 10A, and is thus caused to flow in thecavity 4. Then, thecoolant 5 takes heat away from a wall of thecavity 4 having a temperature higher than that of thecoolant 5 when it contacts the wall, and further flows in thecavity 4 each time thevalve 10A repeats the reciprocating motion, so as to transfer the heat to a wall of thecavity 4 having a temperature lower than that of thecoolant 5 when it contacts the wall. In thehollow engine valve 10A of this embodiment, for example, thecoolant 5 receives heat of the umbrella portion Vh that is most likely to be heated to a high temperature, and moves to the stem portion Vs under the reciprocating motion of thehollow engine valve 10A, so that the heat received from the umbrella portion Vh is transferred from thecoolant 5 to the stem portion Vs, to thus effect cooling of the umbrella portion Vh. - In the first embodiment, at least one high-thermal-
conductivity member 6A having high thermal conductivity and a particular directional characteristic of heat conduction is provided as another cooling means on the cavity-side wall 3 b of thelower cap 3. For example, carbon-fiber reinforced metals (CFRM) may be used for this type of high-thermal-conductivity member 6A. The carbon-fiber reinforced metal uses metal as a base material, and uses carbon fibers as a reinforcing material. The metal as the base material is exposed at the opposite ends of the high-thermal-conductivity member 6A, so that themember 6A can transfer heat from the metal exposed face of one end thereof on the high-temperature side, to the metal exposed face of the other end on the low-temperature side. - In the first embodiment, a plurality of high-thermal-conductivity members Blare disposed on the circular cavity-
side wall 3 b so as to cover the entire area of thewall 3 b, as shown inFIG. 1 andFIG. 2 . The high-thermal-conductivity members 6A have substantially the same length and a small diameter (of, for example, about 10 μm), and are formed straight like rods. While clearances are apparently provided between the adjacent high-thermal-conductivity members 6 inFIG. 2 , these clearances are illustrated for the sake of convenience. Each of the high-thermal-conductivity members 6A is bonded at one end to the cavity-side wall 3 b by a method, such as metal plating, so that the efficiency of heat transfer between the high-thermal-conductivity member 6A and thelower cap 3 is not reduced. - Thus, in the
hollow engine valve 10A of the first embodiment, the high-thermal-conductivity members 6A are formed upright over the entire area of the cavity-side wall 3 b of thelower cap 3, so that the heat of thelower cap 3 is taken or absorbed by all of the high-thermal-conductivity members 6A, and thelower cap 3 can be thus cooled. Also, in thehollow engine valve 10A, the heat is transferred to thecoolant 5 that is in contact with free ends (i.e., the ends remote from the cavity-side wall 3 b) of the respective high-thermal-conductivity members 6A. - In the
hollow engine valve 10A, the high-thermal-conductivity members 6A raise the level of thecoolant 5 as a heat-conduction medium. Thus, if the same amount of thecoolant 5 as that of a hollow engine valve having no high-thermal-conductivity members 6A is contained in thecavity 4, thecoolant 5 reaches the upper portion (close to the valve lifter 101) of the stem portion Vs with higher reliability, under the reciprocating motion of thehollow valve 10A, even if thehollow engine valve 10A is mounted in the engine with its axis inclined relative to the vertical direction. Therefore, most of the heat which thecoolant 5 receives from the high-thermal-conductivity members 6A (namely, the heat of the lower cap 3) is transferred to the stem portion Vs (thecylindrical portion 1 a of thevalve body 1 and the lower face of theupper cap 2, which provide walls of the cavity 4), and is dissipated from the stem portion Vs to thecylinder head 105 via thevalve stem guide 106,valve lifter 101, cam, and other components, Thus, thehollow engine valve 10A of the first embodiment permits highly efficient cooling of thelower cap 3; therefore, temperature rises of thevalve seat 102 and the valve face of the umbrella portion Vh that abuts on thevalve seat 102 are effectively suppressed or prevented, and thevalve seat 102 and the valve face are less likely to wear, thus assuring improved durability and improved gas tightness of the combustion chamber CC. - On the other hand, where the hollow engine valve having no high-thermal-
conductivity members 6A provides a sufficient cooling effect, the high-thermal-conductivity members 6A provided in thehollow engine valve 10A of the first embodiment serve to reduce the amount of thecoolant 5 contained in thecavity 4, and reduce the inertial mass of thevalve 10A when reciprocating. In this case, thehollow engine valve 10A of the first embodiment can reciprocate with increased agility and good responsiveness, thus assuring improved accuracy in the valve-opening timing and valve-closing timing. - As described above, the
hollow engine valve 10A of the first embodiment permits effective cooling of the umbrella portion Vh that is most likely to be heated to a high temperature, thus assuring improvements in the durability of thevalve 10A itself, durability of thevalve seat 102, gas-tightness of the combustion chamber CC, and the accuracy in the valve-opening timing and valve-closing timing. Therefore, thehollow engine valve 10A achieves improved accuracy of its movements in response to a command value of the excess air ratio (i.e., the air-fuel ratio, in particular, the stoichiometric air-fuel ratio) of the combustion chamber CC, and an increased pressure in the cylinder, which lead to increased engine power and reduced fuel consumption. Also, thehollow engine valve 10A of this embodiment ensures sufficient heat resistance and durability even if thevalve 10A and thevalve seat 102 are formed of low-cost materials having lower heat resistance and durability than those of the related art. Thus, thehollow valve 10A and its peripheral components are available at reduced cost. In addition, since thehollow engine valve 10A of this embodiment allows the umbrella portion Vh (in particular, the combustion-chamber-side wall 3 a of thelower cap 3 that forms a part of the wall of the combustion chamber CC) to be cooled by a greater degree than that of the related art, the engine is less likely to suffer from knocking, as compared with the engine of the related art. With thehollow engine valve 10A having an effect of suppressing or preventing knocking, the ignition timing can be advanced as needed, thus assuring improved output performance. - In the
hollow engine valve 10A of the first embodiment, the degree of cooling of the umbrella portion Vh can be adjusted as desired by increasing or reducing the number of the high-thermal-conductivity members 6A provided in thevalve 10A. Accordingly, when thehollow engine valve 10A is used at the exhaust side (as an exhaust valve) that is more likely to be exposed to a high temperature, the larger number of the high-thermal-conductivity members 6A than that in the case where thevalve 10A is used at the intake side (as an intake valve) may be provided in thevalve 10A, so as to ensure a sufficient cooling effect. Since thehollow engine valve 10A of the first embodiment can change the degree of cooling simply by adjusting the number of the high-thermal-conductivity members 6A, as described above, all of the components can be shared between the exhaust side and the intake side, and exhaust valves and intake valves can be manufactured at reduced cost. - Next, a hollow valve for an internal combustion engine according to a second embodiment of the invention will be described with reference to
FIG. 3 .FIG. 3 is a cross-sectional view taken along the center axis of thevalve body 1, and the hollow engine valve assumes the same shape or configuration as that shown inFIG. 3 , when viewed in each section cut along the center axis at any angle across 360 degrees. - In
FIG. 3 ,reference numeral 10B denotes the hollow engine valve of the second embodiment. Thehollow engine valve 10B of the second embodiment is provided by replacing the high-thermal-conductivity members 6A used in thehollow engine valve 10A of the above-described first embodiment, with a plurality of high-thermal-conductivity members 6B as shown inFIG. 3 . - More specifically, the high-thermal-
conductivity members 6B of the second embodiment are different from the high-thermal-conductivity members 6A of the first embodiment in that the high-thermal-conductivity members 6B on a central portion of the cavity-side wall 3 b of thelower cap 3 protrude inwardly of thecavity 4. In the second embodiment, for example, a plurality of rod-like, high-thermal-conductivity members 6B having substantially the same length and diameter as those of the first embodiment are placed on an annular, peripheral portion of the cavity-side wall 3 b of thelower cap 3, and a plurality of high-thermal-conductivity members 6B that are longer than those in the peripheral portion are placed on a radially inner portion of the cavity-side wall 3 b, so that aconvex portion 7 is formed inside the peripheral portion. - In the
convex portion 7 of the second embodiment, the high-thermal-conductivity members 6B are formed with a length that gradually increases from the periphery of theconvex portion 7, so that the height of the high-thermal-conductivity members 6B gradually increases toward the center axis of thehollow engine valve 10B. - Thus, in the
hollow engine valve 10B the second embodiment, a cluster of high-thermal-conductivity members 6B on the central portion of the cavity-side wall 3 b is shaped like a mound or mountain, in other words, the high-thermal-conductivity members 6B on the central portion are formed with lengths greater than that of themembers 6B on the peripheral portion so as to conform to the space shaped like a truncated cone. With this arrangement, heat is more likely to be transferred from thelower cap 3 to the high-thermal-conductivity members 6B, particularly in theconvex portion 7, as compared with the first embodiment. Also, during reciprocating movements of thehollow engine valve 10B, the level of thecoolant 5 as a heat-conduction medium that is in contact with theconvex portion 7 can be raised to a higher level than that of the first embodiment, so that thecoolant 5 reaches the upper portion (close to the valve lifter 101) of the stem portion Vs with increased reliability. Thus, thehollow engine valve 10B of this embodiment exhibits a higher cooling effect than thehollow engine valve 10A of the first embodiment. - In the case where the
hollow engine valve 10A of the first embodiment provides a sufficient cooling effect, the provision of theconvex portion 7 as in the second embodiment permits reduction of the amount of thecoolant 5 contained in thecavity 4. In this case, the inertial mass of thehollow valve 10B when reciprocating can be reduced to be smaller than that of the first embodiment. - As described above, the
hollow engine valve 10B of the second embodiment permits effective cooling of the umbrella portion Vh that is most likely to be heated to a high temperature, thus assuring further improvements in the durability of thevalve 10B itself, durability of thevalve seat 102, gas-tightness of the combustion chamber CC, and the accuracy in the valve-opening timing and valve-closing timing. Therefore, thehollow engine valve 10B achieves further improved accuracy of its movements in response to a command value of the excess air ratio (i.e., the air-fuel ratio, in particular, the stoichiometric air-fuel ratio) of the combustion chamber CC, and a further increased pressure in the cylinder, to more effectively increase the engine power and reduce the fuel consumption. Also, like thehollow engine valve 10A of the first embodiment, thehollow engine valve 10B of this embodiment ensures sufficient heat resistance and durability even if thevalve 10B and thevalve seat 102 are formed of low-cost materials having lower heat resistance and durability than those of the related art. Thus, thehollow valve 10B and its peripheral components are available at reduced cost. In addition, since thehollow engine valve 10B of this embodiment allows the umbrella portion Vh (in particular, the combustion-chamber-side wall 3 a of thelower cap 3 that forms a part of the wall of the combustion chamber CC) to be cooled by a greater degree than that of the related art, as in the first embodiment, the engine is less likely to suffer from knocking, as compared with the related art. With thehollow engine valve 10B having an effect of suppressing or preventing knocking, the ignition timing can be advanced as needed, thus assuring improved output performance. - In the
hollow engine valve 10B of the second embodiment, the degree of cooling of the umbrella portion Vh can be adjusted as desired by increasing or reducing the number of the high-thermal-conductivity members 6B provided in thevalve 10B, as in the first embodiment. Accordingly, when thehollow engine valve 10B is used at the exhaust side (as an exhaust valve) that is more likely to be exposed to a high temperature, the larger number of the high-thermal-conductivity members 6A than that in the case where thevalve 10B is used at the intake side (as an intake valve) may be provided in thevalve 10B, so as to ensure a sufficient cooling effect. Since thehollow engine valve 10B of the second embodiment can change the degree of cooling simply by adjusting the number of the high-thermal-conductivity members 6B, as described above, all of the components can be shared between the exhaust side and the intake side, and exhaust valves and intake valves can be manufactured at reduced cost. - If the
hollow engine valve 10B of the second embodiment can provide a sufficient cooling effect, the high-thermal-conductivity members 6B disposed on the peripheral portion of the cavity-side wall 3 b may be removed, and the high-thermal-conductivity members 6B may be disposed only on the central portion of thewall 3 b (or in the convex portion 7), to provide a similar cooling effect. In this case, thehollow engine valve 10B in which the high-thermal-conductivity members 6B are placed over the entire area of the cavity-side wall 3 b, which provides a relatively high effect of cooling the umbrella portion Vh, may be manufactured as an exhaust valve, and thehollow engine valve 10B in which the high-thermal-conductivity members 6B are placed only on the central portion, which provides a relatively low effect of cooling the umbrella portion Vh, may be manufactured as an intake valve. - Next, a hollow valve for an internal combustion engine according to a third embodiment of the invention will be described with reference to
FIG. 4 .FIG. 4 is a cross-sectional view taken along the center axis of thevalve body 1, and the hollow engine valve assumes the same shape or configuration as that shown inFIG. 4 , when viewed in each section cut along the center axis at any angle across 360 degrees. - In
FIG. 4 ,reference numeral 10C denotes the hollow engine valve of the third embodiment. Thehollow engine valve 10C of the third embodiment is provided by replacing the high-thermal-conductivity members 6A used in thehollow engine valve 10A of the above-described first embodiment, with a plurality of high-thermal-conductivity members 6C as shown inFIG. 4 . - More specifically, the high-thermal-
conductivity members 6C of the third embodiment are different from the high-thermal-conductivity members 6A of the first embodiment in that the high-thermal-conductivity members 6C disposed on a central portion of the cavity-side wall 3 b of thelower cap 3 are extended up to theupper cap 2. In other words, the high-thermal-conductivity members 6B disposed in a central portion of theconvex portion 7 in the second embodiment are extended up to theupper cap 2, to provide the high-thermal-conductivity members 6C of the third embodiment. In the third embodiment, for example, a plurality of rod-like high-thermal-conductivity members 6C having substantially the same length and diameter as those of the first embodiment are placed on an annular, peripheral portion of the cavity-side wall 3 b of thelower cap 3, and a plurality of high-thermal-conductivity members 6C each having one end that contacts the lower face of the upper cap 2 (namely, the face that forms a part of the wall of the cavity 4) are placed on a radially inner portion of the cavity-side wall 3 b that is located inside the peripheral portion. The high-thermal-conductivity members 6C are bonded to theupper cap 2 by a method, such as metal plating, as is the case with bonding between themembers 6C and thelower cap 3. - Thus, in the
hollow engine valve 10C of the third embodiment, the cavity-side wall 3 b of thelower cap 3 and the lower face of theupper cap 2 are connected to the opposite ends of the high-thermal-conductivity members 6C on the central portion, so that heat taken from thelower cap 3 can be surely transferred directly to the lower face of theupper cap 2 as a heat-conduction medium, and the heat thus transferred can be dissipated to thecylinder head 105 via thevalve lifter 101, valve stemguide 106 and other components. Also, in thehollow engine valve 10C, the high-thermal-conductivity members 6C disposed on the central portion of the cavity-side wall 3 b have an increased length, and thus provide a high heat-dissipating effect. In thehollow engine valve 10C illustrated herein, thecoolant 5 as a heat-conduction medium to which heat is transferred from the high-thermal-conductivity members 6C on the peripheral portion of the cavity-side wall 3 b reaches the stem portion Vs under the reciprocating motion of thevalve 10C. Thus, in thehollow engine valve 10C of the third embodiment, the heat of thelower cap 3 is transferred to the upper portion of the stem portion Vs (i.e., the lower face of the upper cap 2) without fail, to surely effect cooling of thelower cap 3, irrespective of whether the valve 10 c is mounted in the engine with its axis inclined, or even if the level of thecoolant 5 is not raised largely because of a small valve lift. - As described above, the
hollow engine valve 10C of the third embodiment permits effective cooling of the umbrella portion Vh that is most likely to be heated to a high temperature, thus assuring further improvements in the durability of thevalve 10C itself, durability of thevalve seat 102, gas-tightness of the combustion chamber CC, and the accuracy in the valve-opening timing and valve-closing timing. Therefore, thehollow engine valve 10C achieves further improved accuracy of its movements in response to a command value of the excess air ratio (i.e., the air-fuel ratio, in particular, the stoichiometric air-fuel ratio) of the combustion chamber CC, and a further increased pressure in the cylinder, to more effectively increase the engine power and reduce the fuel consumption. Also, like thehollow engine valve 10A of the first embodiment, thehollow engine valve 10C of this embodiment ensures sufficient heat resistance and durability even if thevalve 10C and thevalve seat 102 are formed of low-cost materials having lower heat resistance and durability than those of the related art. Thus, thehollow engine valve 10C and its peripheral components are available at reduced cost. In addition, since thehollow engine valve 10C of this embodiment allows the umbrella portion Vh (in particular, the combustion-chamber-side wall 3 a of thelower cap 3 that forms a part of the wall of the combustion chamber CC) to be cooled by a greater degree than that of the related art, as in the first embodiment, the engine is less likely to suffer from knocking, as compared with the engine of the related art. With thehollow engine valve 10C having an effect of suppressing or preventing knocking, the ignition timing can be advanced as needed, thus assuring improved output performance. - In the
hollow engine valve 10C of the third embodiment, the degree of cooling of the umbrella portion Vh can be adjusted as desired by increasing or reducing the number of the high-thermal-conductivity members 6C provided in thevalve 10C, as is the case with the first embodiment. Accordingly, when thehollow engine valve 10C is used at the exhaust side (as an exhaust valve) that is more likely to be exposed to a high temperature, the larger number of the high-thermal-conductivity members 6C than that in the case where thevalve 10C is used at the intake side (as an intake valve) may be provided in thevalve 10C, so as to ensure a sufficient cooling effect. Since thehollow engine valve 10C of the third embodiment can change the degree of cooling simply by adjusting the number of the high-thermal-conductivity members 6C, as described above, all of the components can be shared between the exhaust side and the intake side, and exhaust valves and intake valves can be manufactured at reduced cost. - If the
hollow engine valve 10C of the third embodiment as described above can provide a sufficient cooling effect, the high-thermal-conductivity members 6C disposed on the peripheral portion of the cavity-side wall 3 b may be removed, and the high-thermal-conductivity members 6C (that connect the cavity-side wall 3 b of thelower cap 3 with the lower face of the upper cap 2) may be disposed only on the central portion of thewall 3 b, to provide a similar cooling effect. In this case, thecoolant 5 is not necessarily contained in thecavity 4 provided that a desired cooling effect can be obtained. If thecoolant 5 is not contained, the inertial mass is further reduced, and thehollow engine valve 10C can reciprocate with increased agility and good responsiveness. In this case, for example, thehollow valve 10C in which the high-thermal-conductivity members 6C are placed over the entire area of the cavity-side wall 3 b, which provides a relatively high effect of cooling the umbrella portion Vh, may be manufactured as an exhaust valve, and thehollow valve 10C in which the high-thermal-conductivity members 6C are placed only on the central portion, which provides a relatively low effect of cooling the umbrella portion Vh, may be manufactured as an intake valve. Also, thehollow valve 10C in which thecoolant 5 is contained may be manufactured as an exhaust valve, and thehollow valve 10C having nocoolant 5 may be manufactured as an intake valve. - Next, a hollow valve for an internal combustion engine according to a fourth embodiment of the invention will be described with reference to
FIG. 5 andFIG. 6 . - In
FIG. 5 ,reference numeral 10D denotes the hollow engine valve of the fourth embodiment. Thehollow engine valve 10D of the fourth embodiment is provided by replacing the high-thermal-conductivity members 6A used in thehollow engine valve 10A of the above-described first embodiment with a plurality of high-thermal-conductivity members 6D1, 6D2 as shown inFIG. 5 andFIG. 6 . - More specifically, in the fourth embodiment, the high-thermal-
conductivity members 6A of the first embodiment disposed on a peripheral portion of the cavity-side wall 3 b are modified such that the free ends of themembers 6A are in contact with a wall of thecavity 4 that is close to the valve face of the umbrella portion Vh. Namely, in the fourth embodiment, a plurality of rod-like, high-thermal-conductivity members 6D1 having substantially the same length and diameter as those of the first embodiment are placed on a circular, central portion of the cavity-side wall 3 b of thelower cap 3, and a plurality of high-thermal-conductivity members 6D2 are placed on a peripheral portion of the cavity-side wall 3 b, to extend in radial directions, such that the high-thermal-conductivity members 6D2 connect the cavity-side wall 3 b with the wall close to the valve face at the opposite ends thereof, as shown inFIG. 6 . While clearances are apparently provided between the adjacent high-thermal-conductivity members 6D1, 6D2 inFIG. 6 , these clearances are illustrated for the sake of convenience. The high-thermal-conductivity members 6D2 are bonded to the wall close to the valve face by a suitable method, such as metal plating, that is also used for bonding the members 6D2 to thelower cap 3. - In the
hollow engine valve 10D of the fourth embodiment, the peripheral portion of the cavity-side wall 3 b of thelower cap 3 and the wall close to the valve face are connected to each other at the opposite ends of the high-thermal-conductivity members 6D2. With this arrangement, heat taken from thelower cap 3 can be dissipated from the wall close to the valve face as a heat-conduction medium, to thecylinder head 105, via thevalve seat 102. In thehollow engine valve 10D illustrated herein, thecoolant 5 as a heat-conduction medium to which heat is transferred from the high-thermal-conductivity members 6D1 disposed on the central portion of the cavity-side wall 3 b reaches the upper portion of the stem portion Vs under the reciprocating movements of thevalve 10D. Namely, in thehollow engine valve 10D of the fourth embodiment, the heat of thelower cap 3 is separately directed to the stem portion Vs and to thevalve seat 102, for dissipation. With this arrangement, thehollow engine valve 10D of the fourth embodiment can surely effect cooling of thelower cap 3, as in the first embodiment. - In the case where the
hollow engine valve 10D is used at the exhaust side (as an exhaust valve), thevalve 10D needs to provide a greater cooling effect than that in the case where thevalve 10D is used at the intake side (as an intake valve) since the whole valve is sometimes exposed to high-temperature exhaust gas, for example, on the exhaust stroke. In the case where thehollow engine valve 10D is used at the intake side (as an intake valve), on the other hand, if a large amount of heat is dissipated to the stem portion Vs that is constantly in contact with intake air, the temperature of the intake air is increased, and the volumetric efficiency in the combustion chamber CC deteriorates, which may result in a reduction of the thermal efficiency. - Accordingly, when the
hollow engine valve 10D is used at the exhaust side where a high cooling capability is required of thevalve 10D, the number of the high-thermal-conductivity members 6D2 disposed on the peripheral portion and the number of the high-thermal-conductivity members 6D1 disposed on the central portion are determined so that the larger amount of heat is dissipated to the wall close to the valve face, rather than to the stem portion Vs. Namely, since the valve face directly contacts thevalve seat 102 fitted in thecylinder head 105 for conduction of heat, the heat is transferred with higher efficiency to thecylinder head 105 if the heat is dissipated to the wall close to the valve face, rather than to the stem portion Vs. Thus, the cooling capability of thehollow engine valve 10D is enhanced by increasing the amount of heat dissipated to the wall close to the valve face. - On the other hand, when the
hollow engine valve 10D is used at the intake side where a cooling capability suitably controlled not to deteriorate the volumetric efficiency is required of thevalve 10D, the number of the high-thermal-conductivity members 6D2 disposed on the peripheral portion and the number of the high-thermal-conductivity members 6D1 disposed on the central portion are determined so that the amount of heat dissipated to the stem portion Vs is reduced. In this manner, it is possible to avoid a situation where the intake air is warmed by the heat of the stem portion Vs, resulting in deterioration of the volumetric efficiency. Thus, thehollow engine valve 10D can prevent a reduction of the thermal efficiency of the engine while avoiding wasteful, excessive cooling. - Thus, the
hollow engine valve 10D of the fourth embodiment can change the degree of cooling simply by adjusting the numbers of the high-thermal-conductivity members 6D1, 6D2 provided in thevalve 10D. Therefore, all of the components can be shared between the exhaust side and the intake side, and exhaust valves and intake valves can be manufactured at reduced cost. - Also, the high-thermal-conductivity members 6D2 of the fourth embodiment can almost uniformly distribute heat in the vicinity of a welded
portion 8 as shown inFIG. 5 at which thevalve body 1 and thelower cap 3 are welded to each other, and thus serve as a means for reinforcing the weldedportion 8. Furthermore, the high-thermal-conductivity members 6D2 are arranged to cover the weldedportion 8, and, for this reason, too, serve as a means for reinforcing the weldedportion 8. Namely, since the carbon-fiber reinforced metal of which the high-thermal-conductivity members 6D2 are formed possesses high stiffness, the members 6D2 can suppress or prevent warpage and distortion of the weldedportion 8. Thus, thehollow engine valve 10D of the fourth embodiment can prevent cracks, or the like, from being formed in the weldedportion 8 and its neighborhood. - The high-thermal-conductivity members 6D1 disposed on the central portion may be replaced with the high-thermal-
conductivity members 6B that provide theconvex portion 7 in the above-described second embodiment, or may be replaced with the high-thermal-conductivity members 6C that connect the cavity-side wall 3 b of thelower cap 3 with the lower face of theupper cap 2 in the above-described third embodiment. - Next, a hollow valve for an internal combustion engine according to a fifth embodiment of the invention will be described with reference to
FIG. 7 andFIG. 8 . - In
FIG. 7 ,reference numeral 10E denotes the hollow engine valve of the fifth embodiment. Thehollow engine valve 10E of the fifth embodiment is provided by replacing the high-thermal-conductivity members 6A used in thehollow engine valve 10A of the above-described first embodiment, with a plurality of high-thermal-conductivity members 6E as shown inFIG. 7 andFIG. 8 . - More specifically, each of the high-thermal-
conductivity members 6E of the fifth embodiment connects a peripheral portion of the cavity-side wall 3 b of thelower cap 3 with a wall of thecavity 4 that is close to thevalve stem guide 106 at the opposite ends thereof. The high-thermal-conductivity members 6E are arranged in radial directions as shown inFIG. 8 , to radiate out from the center axis of thehollow engine valve 10E. While clearances are apparently provided between the adjacent high-thermal-conductivity members 6E inFIG. 8 , these clearances are illustrated for the sake of convenience. The high-thermal-conductivity members 6E are bonded to the wall close to thevalve stem guide 106 by a suitable method, such as metal plating, that is also used for bonding the members GE to thelower cap 3. - Thus, in the
hollow engine valve 10E of the fifth embodiment, the peripheral portion of the cavity-side wall 3 b of thelower cap 3 and the wall close to thevalve stem guide 106 are connected to the opposite ends of the high-thermal-conductivity members 6E, to be thus connected to each other. With this arrangement, heat taken from thelower cap 3 can be surely transferred directly to the wall close to thevalve stem guide 106 as a heat-conduction medium, and the heat thus transferred can be dissipated to thecylinder head 105 via thevalve stem guide 106. Also, the high-thermal-conductivity members 6E of thehollow engine valve 10E have a relatively long length, and thus provide a high heat-dissipating effect. In thehollow engine valve 10E illustrated herein, thecoolant 5 that takes heat from the central portion of the cavity-side wall 3 b reaches the stem portion Vs under the reciprocating movements of thevalve 10E. Accordingly, in thehollow engine valve 10E of the fifth embodiment, the heat of thelower cap 3 is transferred to the wall close to thevalve stem guide 106 without fail, irrespective of whether thevalve 10E is mounted in the engine with its axis inclined, or even if the level of thecoolant 5 is not raised to a sufficiently high level because of a small valve lift. Thus, thelower cap 3 is cooled with high reliability. - While a large number of high-thermal-conductivity members are arranged at a high density in the first through fourth embodiments, a relatively small number of high-thermal-
conductivity members 6E are provided in the fifth embodiment; therefore, the high-thermal-conductivity members 6E may be formed with a relatively large cross-sectional area (i.e., the cross-sectional area of metal as a base material), which leads to an increase in the amount of heat dissipated from themembers 6E. - As described above, the hollow engine valve according to the present invention is useful or advantageous in terms of the cooling capability, in particular, the capability of cooling the umbrella portion.
- While the invention has been described with reference to example embodiments thereof, it is to be understood that the invention is not limited to the described embodiments or constructions. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the example embodiments are shown in various combinations and configurations, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention.
Claims (11)
Applications Claiming Priority (2)
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JP2007-178867 | 2007-07-06 | ||
JP2007178867A JP2009013935A (en) | 2007-07-06 | 2007-07-06 | Hollow valve for internal combustion engine |
Publications (1)
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US20090020082A1 true US20090020082A1 (en) | 2009-01-22 |
Family
ID=40263827
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US12/216,304 Abandoned US20090020082A1 (en) | 2007-07-06 | 2008-07-02 | Hollow valve for internal combustion engine, and internal combustion engine having the hollow valve |
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US (1) | US20090020082A1 (en) |
JP (1) | JP2009013935A (en) |
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DE102019106222A1 (en) * | 2019-03-12 | 2020-09-17 | Federal-Mogul Valvetrain Gmbh | Process for the production of a hollow valve for internal combustion engines |
WO2020182387A1 (en) | 2019-03-12 | 2020-09-17 | Federal-Mogul Valvetrain Gmbh | Method for producing a hollow valve for internal combustion engines |
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DE102013203443A1 (en) * | 2013-02-28 | 2014-08-28 | Mahle International Gmbh | Metallic hollow valve |
US9255559B2 (en) | 2013-02-28 | 2016-02-09 | Mahle International Gmbh | Metallic hollow valve |
US20150354727A1 (en) * | 2013-03-14 | 2015-12-10 | Nittan Valve Co., Ltd. | Hollow poppet valve |
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US20180274401A1 (en) * | 2015-09-22 | 2018-09-27 | Federal-Mogul Valvetrain Gmbh | Valve for internal combustion engines having a guide vane for coolant |
US11441454B2 (en) * | 2015-09-22 | 2022-09-13 | Federal-Mogul Valvetrain Gmbh | Valve for internal combustion engines having a guide vane for coolant |
US11143063B2 (en) * | 2016-09-02 | 2021-10-12 | Nittan Valve Co., Ltd. | Cylinder head and engine |
US11300018B2 (en) | 2018-03-20 | 2022-04-12 | Nittan Valve Co., Ltd. | Hollow exhaust poppet valve |
US11951561B2 (en) * | 2018-09-13 | 2024-04-09 | Federal-Mogul Valvetrain Gmbh | Method for producing a welded cavity valve |
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DE102019106214A1 (en) * | 2019-03-12 | 2020-09-17 | Federal-Mogul Valvetrain Gmbh | Process for the production of a hollow valve for internal combustion engines |
WO2020182365A1 (en) | 2019-03-12 | 2020-09-17 | Federal-Mogul Valvetrain Gmbh | Method for producing a hollow valve for internal combustion engines |
WO2020182387A1 (en) | 2019-03-12 | 2020-09-17 | Federal-Mogul Valvetrain Gmbh | Method for producing a hollow valve for internal combustion engines |
DE102019106222A1 (en) * | 2019-03-12 | 2020-09-17 | Federal-Mogul Valvetrain Gmbh | Process for the production of a hollow valve for internal combustion engines |
US11524330B2 (en) | 2019-03-12 | 2022-12-13 | Federal-Mogul Valvetrain Gmbh | Method for producing a hollow valve for internal combustion engines |
US11813658B2 (en) | 2019-03-12 | 2023-11-14 | Federal-Mogul Valvetrain Gmbh | Method for producing a hollow valve for internal combustion engines |
US11850690B2 (en) | 2020-03-30 | 2023-12-26 | Nittan Corporation | Method for manufacturing engine poppet valve |
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