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(11) | EP 3 361 065 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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| (54) |
WATER COOLED SOHC ENGINE WASSERGEKÜHLTER SOHC-MOTOR MOTEUR SOHC REFROIDI À L'EAU |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] The present invention relates to a water cooled SOHC (Single OverHead Camshaft) engine according to the preamble of independent claim 1. Such a water cooled Single OverHead Camshaft engine can be taken from the prior art document JP 4514637 B2.
[0002] JP 4514637 B2 discloses a water cooled-SOHC-V type-two cylinder engine. Two intake valves and two exhaust valves are provided in each cylinder. The intake valve and the exhaust valve corresponding to the same cylinder are opened and closed in accordance with the rotation of the same camshaft. As shown in FIG. 3 of JP 4514637 B2, a spark plug is inclined with respect to the center line of the cylinder. Each portion of the engine is cooled by a cooling liquid flowing through water jackets which are provided in a cylinder head and a cylinder body.
[0003] In a water cooled engine, each portion of the engine is cooled by a cooling liquid flowing through a water jacket provided in the engine. In an SOHC engine, a spark plug is obliquely disposed in some cases. Therefore, there is a case where restrictions are imposed on the shape and the size of the water jacket. In particular, as the number of intake valves and exhaust valves corresponding to the same cylinder is increased, restrictions imposed on the shape and the size of the water jacket become severe. It is thereby difficult to ensure high cooling performance in a water cooled SOHC engine.
[0004] Therefore, an object of the present invention is to provide a water cooled SOHC engine which can enhance the cooling performance. The present object is achieved by a water cooled SOHC engine according to Claim 1. Preferred embodiments are laid down in the dependent claims.
[0005] A preferred embodiment provides a water cooled SOHC engine including a cylinder body which includes a cylinder that has a center line extending in an up/down direction (first direction), a piston which reciprocates within the cylinder in the up/down direction, a cylinder head which on disposed in an upper (first) end portion of the cylinder body and which defines, together with the cylinder and the piston, a combustion chamber where an air-fuel mixture is burned, a spark plug which is attached to the cylinder head and which burns the air-fuel mixture within the combustion chamber, and a valve device which controls an intake gas to be supplied to the combustion chamber and an exhaust gas to be discharged from the combustion chamber.
[0006] The cylinder head includes an intake port which includes a plurality of intake outlets that are open at an inner surface of the combustion chamber, an exhaust port which includes a plurality of exhaust inlets that are open at the inner surface of the combustion chamber, a plug hole which includes a plug outlet that is open at the inner surface of the combustion chamber, and a head water jacket which guides a cooling liquid. The spark plug is inserted into the plug hole and is obliquely inclined with respect to the center line of the cylinder. The valve device includes a camshaft which rotates around a rotation axis extending in a left/right direction (second direction that is perpendicular with the first direction), a plurality of intake valves which respectively open and close the plurality of exhaust outlets according to a rotation of the camshaft, and a plurality of exhaust valves which respectively open and close the plurality of exhaust inlets according to the rotation of the camshaft.
[0007] The head water jacket includes a water supply inlet which is open at an outer surface of the cylinder head and into which the cooling liquid flows, a drain outlet which is open at the outer surface of the cylinder head and which discharges the cooling liquid that has flowed into the water supply inlet, an annular outer circumferential flow path which is disposed around the plurality of intake outlets and the plurality of exhaust inlets when viewed in the up/down direction and which guides the cooling liquid that has flowed into the water supply inlet toward the drain outlet, a center flow path which is disposed inside the outer circumferential flow path when viewed in the up/down direction and which overlaps the spark plug when viewed in the up/down direction, an upstream connection flow path which extends from the outer circumferential flow path to the center flow path and which guides the cooling liquid from the outer circumferential flow path to the center flow path, and a downstream connection flow path which extends from the center flow path to the outer circumferential flow path, which is separate from the upstream connection flow path and which guides the cooling liquid guided by the upstream connection flow path to the center flow path from the center flow path to the outer circumferential flow path. The water cooler SOHC engine of the preferred embodiment further comprises the features of the characterizing portion of claim 1, inter alia the feature that the sectional area of the upstream connection flow path is smaller than the sectional area of the downstream connection flow path.
[0008] With this arrangement, the cooling liquid which cools the engine enters the head water jacket from the water supply inlet of the head water jacket, and flows through the outer circumferential flow path of the head water jacket toward the drain outlet of the head water jacket. The cooling liquid flows, via the upstream connection flow path of the head water jacket, from the outer circumferential flow path to the center flow path of the head water jacket, and flows, via the downstream connection flow path of the head water jacket, from the center flow path to the outer circumferential flow path. In the meantime, each portion of the cylinder head, in particular, the exhaust port, the plug port, and portions in the vicinity thereof are cooled.
[0009] The center flow path of the head water jacket is disposed inside the outer circumferential flow path when viewed in the up/down direction parallel to the axial direction of the cylinder. The spark plug and the center flow path overlap each other when viewed in the up/down direction. Therefore, the center flow path is disposed near the tip end portion of the spark plug which makes a spark. Thereby, the tip end portion of the spark plug is mainly cooled by the cooling liquid which flows through the center flow path.
[0010] The sectional area of the upstream connection flow path is smaller than the sectional area of the downstream connection flow path. Since the sectional area of the upstream connection flow path is small, the cooling liquid flows swiftly through the upstream connection flow path. Since the cooling liquid whose flow velocity is high flows from the upstream connection flow path to the center flow path, the cooling liquid also flows swiftly through the center flow path. When the cooling liquid flows swiftly, heat is discharged efficiently. Therefore, it is possible to effectively lower the temperature of a portion around a plug, that is, a portion around the plug hole in the inner surface of the combustion chamber. In addition, it is possible to effectively lower the temperature of a portion between exhaust valve seats, that is, a portion between the exhaust inlets in the inner surface of the combustion chamber.
[0011] Furthermore, both the upstream connection flow path and the downstream connection flow path are not narrow, and only the upstream connection flow path is narrow. When the material of the cylinder head (the cylinder head before being subjected to machining such as cutting) is casted, the sand core which has the same shape as the head water jacket is used. When both the upstream connection flow path and the downstream connection flow path are narrow, the strength of the sand core is lowered. Therefore, only the upstream connection flow path is made narrow, and thus it is possible to enhance the cooling performance of the engine while suppressing a decrease in the strength of the sand core.
[0012] According to the invention, a maximum value of the width of the upstream connection flow path when viewed in the up/down direction is smaller than a maximum value of the width of the downstream connection flow path when viewed in the up/down direction. With this arrangement, since the width of the upstream connection flow path is smaller than the width of the downstream connection flow path, the sectional area of the upstream connection flow path is easily made smaller than the sectional area of the downstream connection flow path. Thereby, it is possible to increase the flow velocity of the cooling liquid in the center flow path, and thus it is possible to enhance the cooling performance of the engine.
[0013] According to the invention, a maximum value of the length of the upstream connection flow path in the up/down direction is smaller than a maximum value of the length of the downstream connection flow path in the up/down direction. With this arrangement, since the upstream connection flow path is shorter than the downstream connection flow path in the up/down direction, the sectional area of the upstream connection flow path is easily made smaller than the sectional area of the downstream connection flow path. Thereby, it is possible to increase the flow velocity of the cooling liquid in the center flow path, and thus it is possible to enhance the cooling performance of the engine.
[0014] In the present preferred embodiment, at least one of the following features may be added to the above water cooled SOHC engine.
[0015] The outer circumferential surface of the outer circumferential flow path includes an arc portion which has an arc-shaped configuration coaxial with the inner circumferential surface of the cylinder when viewed in the up/down direction and an inward convex portion which protrudes from the arc portion toward the center line of the cylinder when viewed in the up/down direction and which overlaps the spark plug when viewed in the up/down direction.
[0016] The center line of the head water jacket means a line which connects the barycenters of cross sections of the head water jacket which is orthogonal to the direction in which the cooling liquid flows. The "inward" means a direction which approaches the center line of the cylinder. The "outward" means a direction which separates from the center line of the cylinder.
[0017] With this arrangement, the inward convex portion which protrudes toward the center line of the head water jacket is provided in the outer circumferential surface of the outer circumferential flow path. The inward convex portion of the outer circumferential flow path protrudes from the arc portion coaxial with the inner circumferential surface of the cylinder toward the center line of the cylinder. In other words, as compared with a case where the inward convex portion is not provided, the sectional area of the outer circumferential flow path is reduced. Therefore, a swift flow of the cooling liquid is formed in the inward convex portion of the outer circumferential flow path. The inward convex portion of the outer circumferential flow path overlaps the spark plug when viewed in the up/down direction, and is disposed near the spark plug. Therefore, it is possible to efficiently cool the spark plug and a portion in the vicinity thereof.
[0018] The cylinder head further includes a gas vent which extends upward from the center flow path, the water cooled SOHC engine further includes a filling plug which closes the gas vent, and the distance from a center line of the gas vent to the center line of the cylinder is smaller than the diameter of the gas vent.
[0019] The center line of the gas vent may be a straight line which is parallel to the center line of the cylinder or may be a straight line which is inclined obliquely with respect to the center line of the cylinder. In the latter case, the "distance from the center line of the gas vent to the center line of the cylinder" means the shortest distance from the center line of the gas vent to the center line of the cylinder in a range from the upper end of the gas vent to the lower end of the gas vent.
[0020] With this arrangement, the gas vent which discharges the sand core that molds the head water jacket when the material of the cylinder head is casted is provided in the cylinder head, and is closed by the filling plug. The gas vent is disposed near the center line of the cylinder, and the distance from the center line of the gas vent to the center line of the cylinder is smaller than the diameter of the gas vent.
[0021] The gas vent extends upward from the center flow path which cools the spark plug and a portion in the vicinity thereof. A tip end surface of the center flow path is normally disposed near the spark plug. When the gas vent is far from the center line of the cylinder, the width of the center flow path is increased, and thus the flow velocity of the cooling liquid in the center flow path is lowered. By contrast, when the gas vent is brought close to the center line of the cylinder, the center flow path can be made narrow and it is possible to increase the flow velocity of the cooling liquid in the center flow path. Thereby, it is possible to efficiently cool the spark plug and a portion in the vicinity thereof.
[0022] The upstream connection flow path, the center flow path, and the downstream connection flow path define, between the upstream connection flow path and the downstream connection flow path, a mountain-shaped convex portion which extends toward the center flow path when viewed in the up/down direction, and the length of the center flow path in the left/right direction is smaller than the length of the center flow path in a front/rear direction which is orthogonal both to the up/down direction and the left/right direction (third direction which is orthogonal both to the first direction and the second direction).
[0023] With this arrangement, the mountain-shaped convex portion which extends toward the center flow path when viewed in the up/down direction is disposed between the upstream connection flow path and the downstream connection flow path. The tip end portion of the mountain-shaped convex portion is defined by the upstream connection flow path, the center flow path, and the downstream connection flow path. The tip end portion of the mountain-shaped convex portion enters the center flow path, and the center flow path is made narrow in the left/right direction. The length of the center flow path in the left/right direction is smaller than the length of the center flow path in the front/rear direction. As described above, since the center flow path is narrow in the left/right direction, it is possible to increase the flow velocity of the cooling liquid in the center flow path.
[0024] The length of the center flow path in the left/right direction is larger than the width of the upstream connection flow path when viewed in the up/down direction.
[0025] With this arrangement, the length of the center flow path in the left/right direction is not only smaller than the length of the center flow path in the front/rear direction, but also larger than the width of the upstream connection flow path when viewed in the up/down direction. When the center flow path is excessively narrow, the strength of the sand core that molds the head water jacket is lowered. Therefore, it is possible to enhance the cooling performance of the engine while suppressing a decrease in the strength of the sand core.
[0026] The center flow path includes a downward convex portion which protrudes downward (in first direction) from an upper (first) surface of the center flow path, and the downward convex portion includes a pair of side surfaces which are respectively disposed in an exhaust region and an intake region and a top surface which is disposed between the lower ends of the pair of side surfaces.
[0027] With this arrangement, the downward convex portion which protrudes toward the center line of the head water jacket is provided in the center flow path. The center flow path protrudes downward from the upper surface of the center flow path. Therefore, as compared with a case where the downward convex portion is not provided, the sectional area of the center flow path is reduced. Thereby, it is possible to increase the flow velocity of the cooling liquid in the center flow path, and thus it is possible to enhance the cooling performance.
[0028] Furthermore, the pair of side surfaces of the downward convex portion are respectively disposed in the exhaust region and the intake region. In this case, as compared with a case where the pair of side surfaces are not provided, that is, a case where the center flow path is simply reduced in thickness in the up/down direction, it is possible to reduce a decrease in a contact area between the head water jacket and portions in the vicinity of the exhaust port and the intake port and.
[0029] The above and other elements, features, steps, characteristics, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030]
FIG. 1 is a schematic view showing a vertical section of an engine according to a first preferred embodiment.
FIG. 2 is a sectional view showing a vertical section of a cylinder head and a cylinder body.
FIG. 3 is a diagram when the cylinder head is viewed from below in an upward direction.
FIG. 4 is a diagram when a head water jacket is viewed from above in a downward direction.
FIG. 5 is a diagram when the head water jacket is viewed from above in the downward direction.
FIG. 6 is a diagram when the head water jacket is viewed obliquely from below.
FIG. 7 is an enlarged view showing portion of the head water jacket when viewed in the direction of an arrow VII shown in FIG. 5.
FIG. 8 is a diagram when an upstream connection flow path, a center flow path, and a downstream connection flow path of the head water jacket are viewed from above in the downward direction.
FIG. 9 is a sectional view showing a vertical section taken along line IX-IX shown in FIG. 8.
FIG. 10 is a sectional view showing a vertical section taken along line X-X shown in FIG. 8.
FIG. 11 is a plan view when a head water jacket according to a second preferred embodiment is viewed from above in the downward direction.
FIG. 12 is a diagram when the center flow path of the head water jacket is viewed obliquely from above.
FIG. 13 is a sectional view showing a vertical section along a second imaginary plane.
FIG. 14 is a sectional view showing a vertical section taken along line XIV-XIV shown in FIG. 11.
FIG. 15 is a sectional view showing a vertical section taken along line XV-XV shown in FIG. 11.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0032] An up/down direction Dud is a direction parallel to the center line C1 of a cylinder 9. The upward direction is parallel to the center line C1 of the cylinder 9 and extends from a piston 2 toward a combustion chamber 15. The downward direction is parallel to the center line C1 of the cylinder 9 and extends from the combustion chamber 15 toward the piston 2.
[0033] A left/right direction Dlr is parallel to a first imaginary plane P1 (see FIG. 4) which is an imaginary plane including the center line C1 of the cylinder 9 and which partitions a space into, when viewed in the up/down direction Dud, an intake region where a plurality of intake outlets 14o are all disposed and an exhaust region where a plurality of exhaust inlets 16i are all disposed, and is orthogonal to the up/down direction Dud.
[0034] A front/rear direction Dfr is parallel to a second imaginary plane P2 (see FIG. 4) which is an imaginary plane including the center line C1 of the cylinder 9 and which is orthogonal to the first imaginary plane P1, and is orthogonal to the up/down direction Dud. The front/rear direction Dfr is orthogonal both to the up/down direction Dud and the left/right direction Dlr.
[0035] FIG. 1 is a schematic view showing a vertical section of an engine 1 according to a first preferred embodiment. FIG. 2 is a sectional view showing a vertical section of a cylinder head 6 and a cylinder body 8. FIG. 3 is a diagram when the cylinder head 6 is viewed from below in an upward direction.
[0036] As shown in FIG. 1, the engine 1 is a water cooled-SOHC-single cylinder engine. The engine 1 may be a multi-cylinder engine. The engine 1 may be mounted on a land or snow vehicle such as a straddled vehicle, may be mounted on a vessel propulsion apparatus such as an inboard motor, an outboard motor or an inboard/outboard motor or may be mounted on an aircraft such as a helicopter. The engine 1 may be mounted on a machine other than those described above.
[0037] The engine 1 includes a piston 2 which reciprocates within the cylinder 9 as a fuel-gas mixture is burned, a crankshaft 4 which converts the reciprocating movement of the piston 2 into rotation, and a connecting rod 3 which transmits the operation of the piston 2 to the crankshaft 4. The engine 1 further includes the cylinder body 8 which defines the cylinder 9, the cylinder head 6 which defines the combustion chamber 15 where the fuel-gas mixture is burned, a crankcase 10 which houses the crankshaft 4 together with the cylinder body 8, and a head cover 5 which is attached to the cylinder head 6.
[0038] The cylinder head 6 is disposed over the cylinder body 8. The head cover 5 is disposed over the cylinder head 6. The crankcase 10 is disposed below the cylinder body 8. The crankcase 10 may be integral with the cylinder body 8 or may be a separate member from the cylinder body 8 which is fixed to the cylinder body 8 with a bolt. The cylinder head 6 is fixed to the cylinder body 8 with a bolt. A gap between the cylinder body 8 and the cylinder head 6 is sealed by a gasket 7.
[0039] The cylinder head 6 includes an intake port 14 which supplies a gas to the combustion chamber 15 and an exhaust port 16 which discharges a gas such as exhaust gas from the combustion chamber 15. As shown in FIGS. 1 and 3, the intake port 14 includes one intake inlet 14i which is open at an outer surface 6a of the cylinder head 6 and two intake outlets 14o which are open at the inner surface of the combustion chamber 15. The exhaust port 16 includes two exhaust inlets 16i which are open at the inner surface of the combustion chamber 15 and one exhaust outlet 16o which is open at the outer surface 6a of the cylinder head 6. The valve device of the engine 1 includes two intake valves 18 which respectively open and close the two intake outlets 14o and two exhaust valves 19 which respectively open and close the two exhaust inlets 16i.
[0040] As shown in FIG. 2, the engine 1 includes a spark plug 24 which ignites the fuel-gas mixture within the combustion chamber 15. The spark plug 24 is inserted into a plug hole 25 provided in the cylinder head 6. The plug hole 25 includes one plug inlet 25i which is open at the outer surface 6a of the cylinder head 6 and one plug outlet 25o which is open at the inner surface of the combustion chamber 15. The spark plug 24 is inclined obliquely with respect to the center line C1 of the cylinder 9. A center electrode 24c and a side electrode 24b are provided at a tip end portion 24a of the spark plug 24.
[0041] As shown in FIG. 1, the engine 1 includes an intake pipe 11 which defines an intake passage that guides the gas to be supplied to the combustion chamber 15 via the intake port 14 and an exhaust pipe 17 which defines an exhaust passage that guides the gas discharged from the combustion chamber 15 via the exhaust port 16. The engine 1 further includes a throttle valve 12 which changes the flow rate of the gas to be supplied to the combustion chamber 15 and a fuel supply device 13 which supplies the fuel to the combustion chamber 15. The fuel supply device 13 may be either a carburetor or a fuel injector. Also, the fuel supply device 13 may supply the fuel via the intake passage to the combustion chamber 15 or may directly supply the fuel to the combustion chamber 15.
[0042] The valve device of the engine 1 includes a valve drive device 20 which moves the intake valves 18 and the exhaust valves 19. The valve drive device 20 includes a camshaft 21 which rotates around a rotation axis A2 parallel to a rotation axis A1 of the crankshaft 4, a drive gear which rotates in the same direction at the same speed as the crankshaft 4, a driven gear which rotates in the same direction at the same speed as the camshaft 21, and an endless chain which transmits the rotation of the drive gear to the driven gear. The rotation axis A1 of the crankshaft 4 and the rotation axis A2 of the camshaft 21 extend in the left/right direction Dlr.
[0043] The valve drive device 20 further includes an intake spring 23i which generates a force that moves the intake valves 18 toward a closed position, an exhaust spring 23e which generates a force that moves the exhaust valves 19 toward a closed position, an intake rocker arm 22i which pushes the intake valves 18 toward an open position, and an exhaust rocker arm 22e which pushes the exhaust valves 19 toward an open position. The valve drive device 20 may include a variable valve mechanism which changes the timing of the opening and closing of the intake valves 18 and the exhaust valves 19 and the lifted amounts thereof.
[0044] The camshaft 21, the intake rocker arm 22i, the exhaust rocker arm 22e, the intake spring 23i, and the exhaust spring 23e are disposed between the cylinder head 6 and the head cover 5. The camshaft 21 extends in a direction parallel to the rotation axis A1 of the crankshaft 4. The camshaft 21 is disposed between the intake valves 18 and the exhaust valves 19. The camshaft 21 is disposed below the intake rocker arm 22i and the exhaust rocker arm 22e.
[0045] Motive power generated by the burning of the fuel-gas mixture is transmitted from the crankshaft 4 to the camshaft 21 via the drive gear, the chain, and the driven gear. The camshaft 21 includes an intake cam 21i which moves the intake valves 18 toward the open position by transmitting, to the intake rocker arm 22i, the force transmitted to the camshaft 21. The camshaft 21 further includes an exhaust cam 21e which moves the exhaust valves 19 toward the open position by transmitting, to the exhaust rocker arm 22e, the force transmitted to the camshaft 21.
[0046] When the camshaft 21 rotates, the intake cam 21i is brought into contact with the intake rocker arm 22i, and thus the intake rocker arm 22i swings around a swing axis A3. Thereby, the intake valves 18 are pushed by the intake rocker arm 22i toward the open position, and thus the intake port 14 is opened. Thereafter, the intake cam 21i is separated from the intake rocker arm 22i, and thus the intake valves 18 return to the closed position by the force of the intake spring 23i. Thereby, the intake port 14 is closed.
[0047] Likewise, when the camshaft 21 rotates, the exhaust cam 21e is brought into contact with the exhaust rocker arm 22e, and thus the exhaust rocker arm 22e swings around a swing axis A4. Thereby, the exhaust valves 19 are pushed by the exhaust rocker arm 22e toward the open position, and thus the exhaust port 16 is opened. Thereafter, the exhaust cam 21e is separated from the exhaust rocker arm 22e, and thus the exhaust valves 19 return to the closed position by the force of the exhaust spring 23e. Thereby, the exhaust port 16 is closed.
[0049] As shown in FIG. 1, the engine 1 includes water jackets 29 and 30 which guide a cooling liquid that cools each portion of the engine 1 and a water pump 28 which feeds the cooling liquid to the water jackets 29 and 30. The water jackets 29 and 30 include a body water jacket 29 which is provided in the cylinder body 8 and a head water jacket 30 which is provided in the cylinder head 6.
[0050] The water pump 28 is driven by the motive force generated by the burning of the fuel-gas mixture. The water pump 28 includes an impeller which is rotated by the motive force generated by the burning of the fuel-gas mixture and a pump case which houses the impeller. The impeller is, for example, coaxial with the camshaft 21. The impeller rotates in the same direction at the same speed as the camshaft 21. The water pump 28 may be another type of pump such as a gear pump.
[0051] The body water jacket 29 is disposed around an inner circumferential surface 9a of the cylinder 9. The body water jacket 29 has a cylindrical configuration that is continuous over the entire circumference of the cylinder 9. The head water jacket 30 is disposed over the body water jacket 29. The head water jacket 30 includes a plurality of relay ports 44 which are open at the lower surface of the cylinder head 6 (see FIG. 3). The plurality of relay ports 44 are connected to the body water jacket 29 via a plurality of through holes 7a which penetrate the gasket 7.
[0052] The cooling liquid fed by the water pump 28 enters the head water jacket 30 through a water supply inlet 31 (see Fig. 4) of the head water jacket 30 and flows through the head water jacket 30. Thereafter, the cooling liquid is discharged from the head water jacket 30 through a drain outlet 42 (see FIG. 4) of the head water jacket 30. Some of the cooling liquid supplied to the head water jacket 30 is supplied to the body water jacket 29 via the plurality of relay ports 44, and returns to the head water jacket 30 via the plurality of relay ports 44.
[0053] In a case where the engine 1 is mounted on a motorcycle which is an example of a straddled vehicle, the cooling liquid discharged from the cylinder head 6 is supplied to a thermostat. In a case where the warm-up operation of the engine 1 is completed, the cooling liquid supplied to the thermostat is fed to a radiator and is cooled in the radiator. Thereafter, the cooled cooling liquid is supplied again to the water pump 28. In a case where the engine 1 is mounted on a vessel propulsion apparatus such as an outboard motor, water outside the vessel propulsion apparatus is taken into the vessel propulsion apparatus by the suction force of the water pump 28 and is fed to the head water jacket 30. Thereafter, the cooling liquid is discharged to the outside of the vessel propulsion apparatus.
[0055] FIGS. 4 and 5 are diagrams when the head water jacket 30 is viewed from above in a downward direction. FIG. 6 is a diagram when the head water jacket 30 is viewed obliquely from below. FIG. 7 is an enlarged view showing portion of the head water jacket 30 when viewed in a direction of an arrow VII shown in FIG. 5. In FIG. 4, the intake port 14, the exhaust port 16, and the spark plug 24 are represented by thick alternate long and two short dashed lines. In FIG. 5, the direction in which the cooling liquid flows is represented by thick arrows.
[0056] The head water jacket 30 includes a space through which the cooling liquid passes and an inner surface which defines this space. The space of the head water jacket 30 is a space within the cylinder head 6. The inner surface of the head water jacket 30 is the inner surface of the cylinder head 6, and is not seen from the outside of the engine 1. Therefore, in FIGS. 4 to 7, with the omission of portion of cylinder head 6, the appearance of the head water jacket 30 is shown. This is the same as in FIG. 8 and the like which will be described later.
[0057] The first imaginary plane P1 in the following description is an imaginary plane which partitions the space into, when viewed in the up/down direction Dud, the intake region where a plurality of intake outlets 14o are all disposed and the exhaust region where a plurality of exhaust inlets 16i are all disposed and which includes the center line C1 of the cylinder 9. The second imaginary plane P2 is an imaginary plane which is orthogonal to the first imaginary plane P1 and which includes the center line C1 of the cylinder 9. The second imaginary plane P2 partitions the space into an upstream region and a downstream region.
[0058] The first imaginary plane P1 and the second imaginary plane P2 partition the space into four regions. In the following description, a region which belongs both to the upstream region and the exhaust region is referred to as an "upstream exhaust region Rue," and a region which belongs both to the downstream region and the exhaust region is referred to as a "downstream exhaust region Rde." A region which belongs both to the upstream region and the intake region is referred to as an "upstream intake region Rui," and a region which belongs both to the downstream region and the intake region is referred to as a "downstream intake region Rdi."
[0059] As shown in FIG. 4, the head water jacket 30 includes the water supply inlet 31 through which the cooling liquid enters, the drain outlet 42 through which the cooling liquid is discharged, and a flow path 32 which extends from the water supply inlet 31 to the drain outlet 42. As shown in FIG. 6, the head water jacket 30 further includes the plurality of relay ports 44 through which the cooling liquid flowing between the body water jacket 29 (see FIG. 1) and the head water jacket 30 passes and a plurality of relay flow paths 43 which extend from the flow path 32 to the plurality of relay ports 44.
[0060] As shown in FIG. 4, the flow path 32 includes an annular outer circumferential flow path 34 which is disposed around the two intake outlets 14o and the two exhaust inlets 16i, a center flow path 39 which is disposed inside the outer circumferential flow path 34, an upstream connection flow path 38 which extends from the outer circumferential flow path 34 to the center flow path 39, and a downstream connection flow path 40 which extends from the center flow path 39 to the outer circumferential flow path 34. The flow path 32 further includes an upstream flow path 33 which extends from the water supply inlet 31 to the outer circumferential flow path 34 and a downstream flow path 41 which extends from the outer circumferential flow path 34 to the drain outlet 42.
[0061] As shown in FIG. 4, the water supply inlet 31 and the drain outlet 42 are disposed around the outer circumferential flow path 34. The water supply inlet 31 and the drain outlet 42 are open at the outer surface 6a of the cylinder head 6. The upstream flow path 33 extends from the water supply inlet 31 toward the center line C1 of the cylinder 9. The downstream flow path 41 extends from the drain outlet 42 toward the center line C1 of the cylinder 9. The water supply inlet 31 and the upstream flow path 33 are disposed in the upstream exhaust region Rue. The drain outlet 42 and the downstream flow path 41 are disposed in the downstream intake region Rdi.
[0062] As shown in FIG. 4, the downstream flow path 41 defines a through hole 41a which surrounds a bolt B1 that fixes the cylinder head 6 to the cylinder body 8. In other words, the bolt B1 penetrates the downstream flow path 41 in the up/down direction Dud. Therefore, as compared with a case where the bolt B1 does not penetrate the downstream flow path 41, the sectional area of the downstream flow path 41 is reduced. In a case where the bolt B1 does not penetrate the downstream flow path 41, such a through hole 41a is not needed. A bolt hole 45 into which the bolt B1 is inserted is open at the lower surface of the cylinder head 6 (see FIG. 3).
[0063] As shown in FIG. 4, the center flow path 39 is surrounded by the inner circumferential surface 9a of the cylinder 9. The center flow path 39 overlaps the center line C1 of the cylinder 9. Likewise, the tip end portion 24a of the spark plug 24 overlaps the center line C1 of the cylinder 9. The center flow path 39 is disposed over the tip end portion 24a of the spark plug 24, and overlaps the tip end portion 24a of the spark plug 24. The tip end portion 24a of the spark plug 24 is disposed between the intake port 14 and the exhaust port 16.
[0064] As shown in FIG. 4, the center flow path 39 is disposed over the two intake outlets 14o and the two exhaust inlets 16i, and overlaps the two intake outlets 14o and the two exhaust inlets 16i. At least portion of the upstream connection flow path 38 is disposed in the upstream exhaust region Rue, and at least portion of the downstream connection flow path 40 is disposed in the upstream intake region Rui. As shown in FIG. 4, the upstream connection flow path 38 is disposed over the exhaust inlets 16i disposed in the upstream exhaust region Rue, and overlaps the exhaust inlets 16i. As shown in FIG. 4, the downstream connection flow path 40 is disposed over the intake outlets 14o disposed in the upstream intake region Rui, and overlaps the intake outlets 14o.
[0065] As shown in FIG. 4, the outer circumferential flow path 34 is disposed over the body water jacket 29, and overlaps the body water jacket 29. The plurality of relay flow paths 43 extends from the outer circumferential flow path 34 toward the body water jacket 29. At least portion of the outer circumferential flow path 34 is disposed around the inner circumferential surface 9a of the cylinder 9. The entire outer circumferential flow path 34 may be disposed around the inner circumferential surface 9a of the cylinder 9 or only portion of the outer circumferential flow path 34 may be disposed around the inner circumferential surface 9a of the cylinder 9.
[0066] The outer circumferential flow path 34 includes an exhaust side flow path 35 which is disposed in the exhaust region, an intake side flow path 37 which is disposed in the intake region, and an intermediate flow path 36 which makes the exhaust side flow path 35 and the intake side flow path 37 connect to each other. The intermediate flow path 36 is disposed in the downstream region. As shown in FIG. 4, the intermediate flow path 36 is disposed below the spark plug 24, and overlaps the spark plug 24. As shown in FIG. 4, the exhaust side flow path 35 is disposed below the exhaust port 16, and overlaps the exhaust port 16. As shown in FIG. 4, the intake side flow path 37 is disposed below the intake port 14, and overlaps the intake port 14.
[0067] As shown in FIG. 5, an outer circumferential surface 35a of the exhaust side flow path 35 includes an arc portion 51 which is coaxial with the center line C1 of the cylinder 9. An outer circumferential surface 36a of the intermediate flow path 36 includes an inward convex portion 52 which protrudes from the arc portion 51 of the exhaust side flow path 35 toward the center line C1 of the cylinder 9. The inward convex portion 52 protrudes toward the center line of the head water jacket 30. As shown in FIG. 4, the inward convex portion 52 is disposed below the spark plug 24, and overlaps the spark plug 24. Since the inward convex portion 52 is provided, as compared with a case where the outer circumferential surface 36a of the intermediate flow path 36 is formed in the shape of an arc which is coaxial with the center line C1 of the cylinder 9, the sectional area of the intermediate flow path 36 is reduced.
[0068] As shown in FIG. 6, the exhaust side flow path 35 includes an upper convex portion 53 which protrudes upward from the lower surface of the exhaust side flow path 35. The upper convex portion 53 protrudes upward from the lower surface of the exhaust side flow path 35, and also protrudes from the outer circumferential surface 35a of the exhaust side flow path 35 toward the center line C1 of the cylinder 9. The upper convex portion 53 is disposed below the upper surface of the exhaust side flow path 35. As shown in FIG. 5, when the head water jacket 30 is viewed from above, the upper convex portion 53 is hidden by the upper surface of the exhaust side flow path 35.
[0069] As shown in FIG. 7, the upper convex portion 53 is disposed between the plurality of relay flow paths 43 in the circumferential direction (the left/right direction of FIG. 7) of the cylinder 9. The upper convex portion 53 guides the cooling liquid within the exhaust side flow path 35 toward the center line C1 of the cylinder 9 while guiding the cooling liquid upward. The flow of the cooling liquid flowing downstream toward the relay flow paths 43 is rectified to a direction which separates from the plurality of relay flow paths 43. Thereby, it is possible to reduce resistance applied to the cooling liquid, and thus it is possible to reduce a decrease in the flow velocity of the cooling liquid.
[0070] FIG. 8 is a diagram when the upstream connection flow path 38, the center flow path 39, and the downstream connection flow path 40 of the head water jacket 30 are viewed from above in the downward direction. FIG. 9 is a sectional view showing a vertical section taken along line IX-IX shown in FIG. 8. FIG. 10 is a sectional view showing a vertical section taken along line X-X shown in FIG. 8.
[0071] As shown in FIG. 8, the upstream connection flow path 38 and the downstream connection flow path 40 are separated from each other in the front/rear direction Dfr. The upstream connection flow path 38, the center flow path 39, and the downstream connection flow path 40 define a mountain-shaped convex portion 54 extending toward the center flow path 39 between the upstream connection flow path 38 and the downstream connection flow path 40. A width W1 of a tip end portion 54a of the mountain-shaped convex portion 54 in the front/rear direction Dfr is smaller than a width Wu of the upstream connection flow path 38 in the front/rear direction Dfr. A length Llr of the center flow path 39 in the left/right direction Dlr is smaller than a length Lfr of the center flow path 39 in the front/rear direction Dfr but larger than the width Wu of the upstream connection flow path 38 in the front/rear direction Dfr.
[0072] FIG. 9 shows a vertical section of the cylinder head 6 and the head water jacket 30. The material of the cylinder head 6, that is, the cylinder head 6 before being subjected to machining such as cutting is manufactured by, for example, casting. In this case, a sand core which has the same shape as the head water jacket 30 is disposed inside a casting mold, and thereafter a molten metal is poured into the casting mold. When the metal is solidified, and the material of the cylinder head 6 is molded, the collapsed sand core, that is, sand grains are removed from the material of the cylinder head 6. Thereby, a cavity which has the same shape as the head water jacket 30 is defined in the material of the cylinder head 6.
[0073] As shown in FIG. 9, the cylinder head 6 includes a gas vent 55 which discharges the sand grains within the head water jacket 30. The gas vent 55 extends upward from the center flow path 39. The gas vent 55 is open at the outer surface 6a of the cylinder head 6 and at the inner surface of the head water jacket 30. The gas vent 55 is closed by a cylindrical filling plug 56 which is attached to the cylinder head 6. The filling plug 56 is fixed to the cylinder head 6 with a male screw provided in the outer circumferential surface of the filling plug 56 and a female screw provided in the inner circumferential surface of the gas vent 55.
[0074] FIG. 9 shows an example where a circular bottom surface 56a of the filling plug 56 is disposed so as to be flush with the lower end of the gas vent 55. The bottom surface 56a of the filling plug 56 may be disposed at a different height from the lower end of the gas vent 55. In a case where the bottom surface 56a of the filling plug 56 protrudes downward from the lower end of the gas vent 55, the sectional area of the head water jacket 30 is reduced below the filling plug 56. Thereby, it is possible to increase the flow velocity of the cooling liquid or to divert portion of the cooling liquid flowing toward the filling plug 56 around the filling plug 56.
[0075] As shown in FIG. 8, the gas vent 55 overlaps the spark plug 24. A center line C2 of the gas vent 55 is parallel to the center line C1 of the cylinder 9. The shortest distance D2 from the center line C1 of the cylinder 9 to the center line C2 of the gas vent 55 is shorter than a diameter Φ2 of the gas vent 55. FIG. 8 shows an example where the center line C1 of the cylinder 9 does not overlap the gas vent 55 and is disposed around the gas vent 55. The center line C1 of the cylinder 9 may overlap the gas vent 55. That is, the distance D2 from the center line C1 of the cylinder 9 to the center line C2 of the gas vent 55 may be smaller than the radius of the gas vent 55.
[0076] FIG. 10 shows a vertical section of the upstream connection flow path 38 and the downstream connection flow path 40 along a cut plane parallel to the second imaginary plane P2. The width Wu of the upstream connection flow path 38 in the front/rear direction Dfr is increased continuously or stepwise from the lower end portion of the upstream connection flow path 38 to the upper end portion of the upstream connection flow path 38. Likewise, a width Wd of the downstream connection flow path 40 in the front/rear direction Dfr is increased continuously or stepwise from the lower end portion of the downstream connection flow path 40 to the upper end portion of the downstream connection flow path 40.
[0077] The maximum value of the width Wu of the upstream connection flow path 38 in the front/rear direction Dfr is smaller than the maximum value of the width Wd of the downstream connection flow path 40 in the front/rear direction Dfr. The maximum value of a length Lu (height) of the upstream connection flow path 38 in the up/down direction Dud is smaller than a length Ld of the downstream connection flow path 40 in the up/down direction Dud. The sectional area of the upstream connection flow path 38 is smaller than the sectional area of the downstream connection flow path 40. The cooling liquid flows from the upstream connection flow path 38 to the center flow path 39, and flows from the center flow path 39 to the downstream connection flow path 40. Since the sectional area of the upstream connection flow path 38 is small, a swift flow of the cooling liquid is formed in the upstream connection flow path 38. Therefore, the cooling liquid whose flow velocity is high flows from the upstream connection flow path 38 to the center flow path 39.
[0078] As described above, in the first preferred embodiment, the cooling liquid flowing through the head water jacket 30 cools the portions of the cylinder head 6, in particular, the exhaust port 16, the plug hole 25, and portions in the vicinity thereof. The center flow path 39 of the head water jacket 30 overlaps the spark plug 24 when viewed in the up/down direction Dud. Therefore, the center flow path 39 is disposed near the tip end portion 24a of the spark plug 24. Thereby, the tip end portion 24a of the spark plug 24 is mainly cooled by the cooling liquid flowing through the center flow path 39.
[0079] The sectional area of the upstream connection flow path 38 is smaller than the sectional area of the downstream connection flow path 40. Since the sectional area of the upstream connection flow path 38 is small, the cooling liquid flows swiftly through the upstream connection flow path 38. Since the cooling liquid whose flow velocity is high flows from the upstream connection flow path 38 to the center flow path 39, the cooling liquid also flows swiftly through the center flow path 39. When the cooling liquid flows swiftly, heat is discharged efficiently. Therefore, it is possible to effectively lower the temperature of a portion around a plug, that is, a portion around the plug hole 25 in the inner surface of the combustion chamber 15. In addition, it is possible to effectively lower the temperature of a portion between exhaust valve seats, that is, a portion between the exhaust inlets 16i in the inner surface of the combustion chamber 15.
[0080] Furthermore, both the upstream connection flow path 38 and the downstream connection flow path 40 are not narrow, and only the upstream connection flow path 38 is narrow. When the material of the cylinder head 6 is casted, the sand core which has the same shape as the head water jacket 30 is used. When both the upstream connection flow path 38 and the downstream connection flow path 40 are narrow, the strength of the sand core is lowered. Therefore, only the upstream connection flow path 38 is made narrow, and thus it is possible to enhance the cooling performance of the engine 1 while suppressing a decrease in the strength of the sand core.
[0081] In the first preferred embodiment, the inward convex portion 52 which protrudes toward the center line of the head water jacket 30 is provided in the outer circumferential surface of the outer circumferential flow path 34. The inward convex portion 52 of the outer circumferential flow path 34 protrudes from the arc portion 51 coaxial with the inner circumferential surface 9a of the cylinder 9 toward the center line C1 of the cylinder 9. In other words, as compared with a case where the inward convex portion 52 is not provided, the sectional area of the outer circumferential flow path 34 is reduced. Therefore, a swift flow of the cooling liquid is formed in the inward convex portion 52 of the outer circumferential flow path 34. The inward convex portion 52 of the outer circumferential flow path 34 overlaps the spark plug 24 when viewed in the up/down direction Dud, and is disposed near the spark plug 24. Therefore, it is possible to efficiently cool the spark plug 24 and a portion in the vicinity thereof.
[0082] In the first preferred embodiment, the gas vent 55 which discharges the sand core that molds the head water jacket 30 when the material of the cylinder head 6 is casted is provided in the cylinder head 6, and is closed by the filling plug 56. The gas vent 55 is disposed near the center line C1 of the cylinder 9, and the distance D2 from the center line C2 of the gas vent 55 to the center line C1 of the cylinder 9 is smaller than the diameter Φ2 of the gas vent 55.
[0083] The gas vent 55 extends upward from the center flow path 39 which cools the spark plug 24 and a portion in the vicinity thereof. A tip end surface 39a (see FIG. 4) of the center flow path 39 is normally disposed near the spark plug 24. When the gas vent 55 is far from the center line C1 of the cylinder 9, the width of the center flow path 39 is increased, and thus the flow velocity of the cooling liquid in the center flow path 39 is lowered. By contrast, when the gas vent 55 is brought close to the center line C1 of the cylinder 9, the center flow path 39 can be made narrow and it is possible to increase the flow velocity of the cooling liquid in the center flow path 39. Thereby, it is possible to efficiently cool the spark plug 24 and a portion in the vicinity thereof.
[0084] In the first preferred embodiment, the mountain-shaped convex portion 54 which extends toward the center flow path 39 when viewed in the up/down direction Dud is disposed between the upstream connection flow path 38 and the downstream connection flow path 40. The tip end portion 54a of the mountain-shaped convex portion 54 is defined by the upstream connection flow path 38, the center flow path 39, and the downstream connection flow path 40. The tip end portion 54a of the mountain-shaped convex portion 54 enters the center flow path 39, and the center flow path 39 is made narrow in the left/right direction Dlr. The length Llr of the center flow path 39 in the left/right direction Dlr is smaller than the length Lfr of the center flow path 39 in the front/rear direction Dfr. As described above, since the center flow path 39 is narrow in the left/right direction Dlr, it is possible to increase the flow velocity of the cooling liquid in the center flow path 39.
[0085] In the first preferred embodiment, the length Llr of the center flow path 39 in the left/right direction Dlr is not only smaller than the length Lfr of the center flow path 39 in the front/rear direction Dfr, but also larger than the width Wu of the upstream connection flow path 38 when viewed in the up/down direction Dud. When the center flow path 39 is excessively narrow, the strength of the sand core that molds the head water jacket 30 is lowered. Therefore, it is possible to enhance the cooling performance of the engine 1 while suppressing a decrease in the strength of the sand core.
Second preferred embodiment
[0086] In FIGS. 11 to 15 below, arrangements equivalent to those shown in FIGS. 1 to 10 are identified with the same reference signs as in FIG. 1 and the like, and the description thereof will be omitted.
[0087] FIG. 11 is a plan view when a head water jacket 30 according to a second preferred embodiment is viewed from above in the downward direction. FIG. 12 is a diagram when the center flow path 39 of the head water jacket 30 is viewed obliquely from above. FIG. 13 is a sectional view showing a vertical section along the second imaginary plane P2.
[0088] As shown in FIG. 12, the center flow path 39 includes a downward convex portion 61 which protrudes downward from the upper surface of the center flow path 39. As shown in FIG. 13, the downward convex portion 61 has a vertical section which is formed in the shape of the letter U that is open upward. The downward convex portion 61 includes a pair of side surfaces 61b which are respectively disposed in the exhaust region and the intake region and a top surface 61a which is disposed between the lower ends of the pair of side surfaces 61b. As shown in FIG. 12, the center flow path 39 includes the tip end surface 39a which is located close to the spark plug 24. The tip end surface 39a extends downward from the tip end edge (the edge located on the side of the spark plug 24) of the top surface 61a.
[0089] As shown in FIG. 11, the upstream connection flow path 38 and the downstream connection flow path 40 extend from the outer circumferential flow path 34 toward the center line C1 of the cylinder 9. A center line Cu of the upstream connection flow path 38 passes through the center line C1 of the cylinder 9. Likewise, a center line Cd of the downstream connection flow path 40 passes through the center line C1 of the cylinder 9. The center line Cu of the upstream connection flow path 38 and the center line Cd of the downstream connection flow path 40 are inclined in directions opposite to each other with respect to the first imaginary plane P1. The absolute value of an inclination angle θu at which the center line Cu of the upstream connection flow path 38 is inclined with respect to the first imaginary plane P1 is larger than the absolute value of an inclination angle θd at which the center line Cd of the downstream connection flow path 40 is inclined with respect to the first imaginary plane P1.
[0090] FIG. 14 is a sectional view showing a vertical section taken along line XIV-XIV shown in FIG. 11. FIG. 15 is a sectional view showing a vertical section taken along line XV-XV shown in FIG. 11. A distance from the center line C1 of the cylinder 9 to the cross section shown in FIG. 14 is equal to a distance from the center line C1 of the cylinder 9 to the cross section shown in FIG. 15. A scale on the cross section shown in FIG. 14 is equal to a scale on the cross section shown in FIG. 15. Therefore, the sectional area of the upstream connection flow path 38 is smaller than the sectional area of the downstream connection flow path 40. Thereby, it is possible to increase the flow velocity of the cooling liquid in the upstream connection flow path 38, and thus it is possible to feed the cooling liquid whose flow velocity is high from the upstream connection flow path 38 to the center flow path 39.
[0091] In addition to the actions and effects in the first preferred embodiment, the second preferred embodiment can exhibit actions and effects below. Specifically, in the second preferred embodiment, the downward convex portion 61 which protrudes toward the center line of the head water jacket 30 is provided in the center flow path 39. The center flow path 39 protrudes downward from the upper surface of the center flow path 39. Therefore, as compared with a case where the downward convex portion 61 is not provided, the sectional area of the center flow path 39 is reduced. Thereby, it is possible to increase the flow velocity of the cooling liquid in the center flow path 39, and thus it is possible to enhance the cooling performance.
[0092] Furthermore, the pair of side surfaces 61b of the downward convex portion 61 are respectively disposed in the exhaust region and the intake region. In this case, as compared with a case where the pair of side surfaces 61b are not provided, that is, a case where the center flow path 39 is simply reduced in thickness in the up/down direction Dud, it is possible to reduce a decrease in a contact area between the head water jacket 30 and portions in the vicinity of the exhaust port 16 and the intake port 14.
Other Preferred Embodiments
[0093] Although preferred embodiments have been described above, various modifications of the embodiments are possible.
[0094] For example, the number of intake valves 18 and exhaust valves 19 corresponding to the same cylinder 9 may be equal to or more than four. For example, three intake valves 18 and two exhaust valves 19 may be provided in the same cylinder 9.
[0095] Either of the intake rocker arm 22i and the exhaust rocker arm 22e may be omitted. In this case, it suffices to push the intake valves 18 or the exhaust valves 19 by the intake cam 21i or the exhaust cam 21e.
[0096] The water supply inlet 31 and the upstream flow path 33 may be omitted. Alternatively, the drain outlet 42 and the downstream flow path 41 may be omitted. In these cases, it suffices to make the plurality of relay ports 44 function as the water supply inlet 31 or the drain outlet 42. For example, the cooling liquid fed by the water pump 28 may be supplied, via the plurality of relay ports 44 serving as the water supply inlet 31, to the head water jacket 30.
[0097] The width Wu of the upstream connection flow path 38 may be constant from the upper end portion of the upstream connection flow path 38 to the lower end portion of the upstream connection flow path 38. The same is true for the downstream connection flow path 40.
[0098] An arrangement may be adopted in which the inward convex portion 52 is not provided in the intermediate flow path 36 of the outer circumferential flow path 34 and in which the outer circumferential surface 36a of the intermediate flow path 36 is formed in the shape of an arc coaxial with the center line C1 of the cylinder 9.
[0099] The distance D2 from the center line C2 of the gas vent 55 to the center line C1 of the cylinder 9 may be equal to the diameter Φ2 of the gas vent 55 or may be larger than the diameter Φ2 of the gas vent 55.
[0100] The length Llr of the center flow path 39 in the left/right direction Dlr may be equal to the length Lfr of the center flow path 39 in the front/rear direction Dfr or may be larger than the length Lfr of the center flow path 39 in the front/rear direction Dfr.
a cylinder body (8) which includes a cylinder (9) that has a center line (C1) extending in an first direction;
a piston (2) configured and arranged to reciprocate within the cylinder (9) in the first direction;
a cylinder head (6) which is disposed on an first end portion of the cylinder body (8) and which defines, together with the cylinder (9) and the piston (2), a combustion chamber (15) configured to burn an air-fuel mixture is burned;
a spark plug (24) which is attached to the cylinder head (6) and which is configured to ignite the air-fuel mixture within the combustion chamber (15) to burn the air-fuel mixture; and
a valve device configured to control an intake gas to be supplied to the combustion chamber (15) and an exhaust gas to be discharged from the combustion chamber (15), wherein the cylinder head (6) includes: an intake port (14) which includes a plurality of intake outlets (14o) that are open at an inner surface of the combustion chamber (15);
an exhaust port (16) which includes a plurality of exhaust inlets (16i) that are open at the inner surface of the combustion chamber (15); a plug hole (25) which includes a plug outlet (25o) that is open at the inner surface of the combustion chamber (15); and a head water jacket (30) which guides a cooling liquid,
the spark plug (24) is inserted into the plug hole (25) and is obliquely inclined with respect to the center line (C1) of the cylinder (9),
the valve device includes:
a camshaft (21) configured to rotate around a rotation axis (A2) extending in a second direction that is perpendicular with the first direction;
a plurality of intake valves (18) configured to respectively open and close the plurality of intake outlets (14o) according to a rotation of the camshaft (21); and
a plurality of exhaust valves (19) configured to respectively open and close the plurality of exhaust inlets (16i) according to the rotation of the camshaft (21),
the head water jacket (30) includes:
a water supply inlet (31) which is open at an outer surface (6a) of the cylinder head (6) and configured for the cooling liquid flow into;
a drain outlet (42) which is open at the outer surface (6a) of the cylinder head (6) and configured to discharge the cooling liquid that has flowed into the water supply inlet (31);
an annular outer circumferential flow path (34) which is disposed around the plurality of intake outlets (14o) and the plurality of exhaust inlets (16i) when viewed in the first direction and which is configured to guide the cooling liquid that has flowed into the water supply inlet (31) toward the drain outlet (42);
a center flow path (39) which is disposed inside the outer circumferential flow path (34) when viewed in the first direction and which overlaps the spark plug (24) when viewed in the first direction;
an upstream connection flow path (38) which extends from the outer circumferential flow path (34) to the center flow path (39) and which is configured to guide the cooling liquid from the outer circumferential flow path (34) to the center flow path (39); and
a downstream connection flow path (40) which extends from the center flow path (39) to the outer circumferential flow path (34), which is separate from the upstream connection flow path (38) and which is configured to guide the cooling liquid guided by the upstream connection flow path (38) to the center flow path (39) from the center flow path (39) to the outer circumferential flow path (34), characterized in that the upstream connection flow path (38) has a sectional area being smaller than a sectional area of the downstream connection flow path (40), wherein
a maximum value of a width (Wu) of the upstream connection flow path (38) when viewed in the first direction is smaller than a maximum value of a width (Wd) of the downstream connection flow path (40) when viewed in the first direction, and a maximum value of a length (Lu) of the upstream connection flow path (38) in the first direction is smaller than a maximum value of a length (Ld) of the downstream connection flow path (40) in the first direction.
characterized in that an outer circumferential surface of the outer circumferential flow path (34) includes: an arc portion (51) which has an arc-shaped configuration coaxial with an inner circumferential surface of the cylinder (9) when viewed in the first direction; and an inward convex portion (52) which protrudes from the arc portion (51) toward the center line (C1) of the cylinder (9) when viewed in the first direction and which overlaps the spark plug (24) when viewed in the first direction.
characterized in that the cylinder head (6) further includes a gas vent (55) which extends upward from the center flow path (39),
the water cooled Single OverHead Camshaft engine (1) further includes a filling plug (56) which closes the gas vent (55), and
a distance (D2) from a center line (C1) of the gas vent (55) to the center line (C1) of the cylinder (9) is smaller than a diameter (Φ2) of the gas vent (55).
a length (Llr) of the center flow path (39) in the second direction is smaller than a length (Lfr) of the center flow path (39) in a third direction which is orthogonal both to the first direction and the second direction.
characterized in that the length (Llr) of the center flow path (39) in the second direction is larger than the width (Wu) of the upstream connection flow path (38) when viewed in the first direction.
einen Zylinder-Körper (8), der einen Zylinder (9) beinhaltet, der eine Mittel-Linie (C1) hat, die sich in eine erste Richtung erstreckt;
einen Kolben (2), der konfiguriert und angeordnet ist, um in dem Zylinder (9) in der ersten Richtung hin und her zu gehen;
einen Zylinder-Kopf (6), der an einem ersten End-Abschnitt von dem Zylinder-Körper (8) positioniert ist und der, zusammen mit dem Zylinder (9) und dem Kolben (2), eine Verbrennungs-Kammer (15) definiert, die konfiguriert ist, um eine Luft-Kraftstoff-Mischung zu verbrennen;
eine Zündkerze (24), die an dem Zylinder-Kopf (6) angebracht ist und die konfiguriert ist, um die Luft-Kraftstoff-Mischung in der Verbrennungs-Kammer (15) zu entzünden, um die Luft-Kraftstoff-Mischung zu verbrennen; und
eine Ventil-Vorrichtung, die konfiguriert ist, um Einlass-Gas, das zu der Verbrennungs-Kammer (15) zuzuführen ist, und Auslass-Gas, das von der Verbrennungs-Kammer (15) abzugeben ist, zu steuern, wobei der Zylinder-Kopf (6) beinhaltet: einen Einlass-Anschluss (14), der eine Mehrzahl von Einlass-Auslässen (14o) beinhaltet, die zu einer Innen-Fläche von der Verbrennungs-Kammer (15) offen sind;
einen Auslass-Anschluss (16), der eine Mehrzahl von Auslass-Einlässen (16I) beinhaltet, die an der Innen-Fläche von der Verbrennungs-Kammer (15) offen sind;
ein Kerzen-Loch (25), das einen Kerzen-Auslass (25O) beinhaltet, der zu der Innen-Fläche von der Verbrennungs-Kammer (15) offen ist; und einen Kopf-Wasser-Mantel (30), der eine Kühl-Flüssigkeit führt,
die Zündkerze (24) ist in das Kerzen-Loch (25) eingesetzt, und schräg mit Bezug auf die Mittel-Linie (C1) von dem Zylinder (9) geneigt,
die Ventil-Vorrichtung beinhaltet:
eine Nocken-Welle (21), die konfiguriert ist, um um eine Dreh-Achse (A2) zu drehen, die sich in eine zweite Richtung, die senkrecht mit der ersten Richtung ist, erstreckt;
eine Mehrzahl von Einlass-Ventilen (18), die konfiguriert sind, um jeweils die Mehrzahl von Einlass-Auslässen (14o), gemäß zu einer Drehung von der Nocken-Welle (21), zu öffnen und zu schließen; und
eine Mehrzahl von Auslass-Ventilen (19), die konfiguriert sind, um die Mehrzahl von Auslass-Einlässen (16I), gemäß von der Drehung von der Nocken-Welle (21), zu öffnen und zu schließen,
der Kopf-Wasser-Mantel (30) beinhaltet:
einen Wasser-Zufuhr-Einlass (31), der an einer Außen-Fläche (6A) von dem Zylinder-Kopf (6) offen ist, und der für die Kühl-Flüssigkeit konfiguriert ist hineinströmt;
einen Ablass-Auslass (42), der an der Außen-Fläche (6A) von dem Zylinder-Kopf (6) offen ist, und konfiguriert ist, um die Kühl-Flüssigkeit, die in den Wasser-Zufuhr-Einlass (31) eingeströmt ist, abzugeben;
einen ringförmigen Außen-Umfangs-Strömungs-Pfad (34), der um die Mehrzahl von Einlass-Auslässen (14o) und die Mehrzahl von Auslass-Einlässen (16I) positioniert ist, wenn in der ersten Richtung betrachtet, und der konfiguriert ist, um die Kühl-Flüssigkeit, die in den Wasser-Zufuhr-Einlass (31) eingeströmt ist, zu dem Ablass-Auslass (42) zu führen;
einen Mitten-Strömungs-Pfad (39), der innerhalb des Außen-Umfangs-Strömungs-Pfads (34) positioniert ist, wenn in der ersten Richtung betrachtet, und der die Zündkerze (24) überlappt, wenn in der ersten Richtung betrachtet;
einen Stromauf-Verbindungs-Strömungs-Pfad (38), der sich von dem Außen-Umfangs-Strömungs-Pfad (34) zu dem Mitten-Strömungs-Pfad (39) erstreckt, und der konfiguriert ist, um die Kühl-Flüssigkeit von dem Außen-Umfangs-Strömungs-Pfad (34) zu dem Mitten-Strömungs-Pfad (39) zu führen; und
einen Stromab-Verbindungs-Strömungs-Pfad (40), der sich von dem Mitten-Strömungs-Pfad (39) zu dem Außen-Umfangs-Strömungs-Pfad (34) erstreckt, der von dem Stromauf-Verbindungs-Strömungs-Pfad (38) getrennt ist, und der konfiguriert ist, um die Kühl-Flüssigkeit, geführt durch den Stromauf-Verbindungs-Strömungs-Pfad (38), zu dem Mitten-Strömungs-Pfad (39), von dem Mitten-Strömungs-Pfad (39) zu dem Außen-Umfangs-Strömungs-Pfad (34) zu führen,
dadurch gekennzeichnet, dass der Stromauf-Verbindungs-Strömungs-Pfad (38) einen Querschnitts-Bereich hat, der kleiner ist als ein Querschnitts-Bereich von dem Stromab-Verbindungs-Strömungs-Pfad (40), wobei
ein Maximal-Wert einer Breite (Wu) von dem Stromauf-Verbindungs-Strömungs-Pfad (38), wenn betrachtet in der ersten Richtung, kleiner ist als ein Maximal-Wert von einer Breite (Wd) von dem Stromab-Verbindungs-Strömungs-Pfad (40), wenn betrachtet in der ersten Richtung, und ein Maximal-Wert von einer Länge (Lu) von dem Stromauf-Verbindungs-Strömungs-Pfad (38) in der ersten Richtung kleiner als ein Maximal-Wert von einer Länge (Ld) von dem Stromab-Verbindungs-Strömungs-Pfad (40) in der ersten Richtung ist.
und einen inwärtigen Konvex-Abschnitt (52), der von dem Bogen-Abschnitt (51) zu der Mittel-Linie (C1) von dem Zylinder (9) vorspringt, wenn in der ersten Richtung betrachtet, und der die Zündkerze (24) überlappt, wenn in der ersten Richtung betrachtet.
der wassergekühlte Motor (1) mit einzelner obenliegender Nocken-Welle beinhaltet weiter einen Füll-Stopfen (56), der die Gas-Ventilation (55) verschließt, und
ein Abstand (D2) von der Mittel-Linie (C1) von der Gas-Ventilation (55) zu der Mittel-Linie (C1) von dem Zylinder (9) ist kleiner als ein Durchmesser (Φ2) von der Gas-Ventilation (55).
un corps de cylindre (8) qui comporte un cylindre (9) possédant un axe (C1) qui s'étend dans une première direction ;
un piston (2) configuré et conçu pour effectuer un mouvement de va-et-vient à l'intérieur du cylindre (9) dans la première direction ;
une culasse (6) qui est disposée sur une première partie d'extrémité du corps de cylindre (8) et qui définit, avec le cylindre (9) et le piston (2), une chambre de combustion (15) configurée pour brûler un mélange air-carburant ;
une bougie d'allumage (24) qui est fixée sur la culasse (6) et qui est configurée pour allumer le mélange air-carburant à l'intérieur de la chambre de combustion (15) pour brûler le mélange air-carburant ; et
un dispositif formant soupape configuré pour commander un gaz d'admission devant être amené à la chambre de combustion (15) et un gaz d'échappement devant être déchargé de la chambre de combustion (15), dans lequel la culasse (6) comprend : un conduit d'admission (14) qui comporte une pluralité d'orifices de sortie côté admission (14o) qui s'ouvrent au niveau d'une surface interne de la chambre de combustion (15) ; un conduit d'échappement (16) qui comporte une pluralité d'orifices d'entrée côté échappement (16i) qui s'ouvrent au niveau de la surface interne de la chambre de combustion (15) ; un trou de bougie (25) qui comporte un orifice de sortie de bougie (25o) qui s'ouvre au niveau de la surface interne de la chambre de combustion (15) ; et une chemise d'eau de culasse (30) qui guide un liquide de refroidissement,
la bougie d'allumage (24) est insérée dans le trou de bougie (25) et est inclinée obliquement par rapport à l'axe (C1) du cylindre (9),
le dispositif formant soupape comprend :
un arbre à cames (21) configuré pour tourner autour d'un axe de rotation (A2) s'étendant dans une deuxième direction qui est perpendiculaire à la première direction ;
une pluralité de soupapes d'admission (18) configurées pour ouvrir et fermer, respectivement, la pluralité d'orifices de sortie côté admission (14o) en fonction d'une rotation de l'arbre à cames (21) ; et
une pluralité de soupapes d'échappement (19) configurées pour ouvrir et fermer, respectivement, la pluralité d'orifices d'entrée côté échappement (16i) en fonction de la rotation de l'arbre à cames (21),
la chemise d'eau de culasse (30) comprend :
une entrée d'alimentation d'eau (31) qui s'ouvre niveau d'une surface extérieure (6a) de la culasse (6) et est configurée pour l'introduction de l'écoulement de liquide de refroidissement ;
une sortie d'évacuation (42) qui s'ouvre niveau de la surface extérieure (6a) de la culasse (6) et est configurée pour décharger le liquide de refroidissement qui a été introduit dans l'entrée d'alimentation d'eau (31) ;
un chemin d'écoulement circonférentiel extérieur annulaire (34) qui entoure la pluralité d'orifices de sortie côté admission (14o) et la pluralité d'orifices d'entrée côté échappement (16i), en regardant dans la première direction, et qui est configuré pour guider l'écoulement de liquide de refroidissement introduit dans l'entrée d'alimentation d'eau (31) vers la sortie d'évacuation (42) ;
un chemin d'écoulement central (39) qui est disposé sur l'intérieur du chemin d'écoulement circonférentiel extérieur (34), en regardant dans la première direction, et qui chevauche la bougie d'allumage (24), en regardant dans la première direction ;
un chemin d'écoulement de connexion d'amont (38) qui s'étend du chemin d'écoulement circonférentiel extérieur (34) vers le chemin d'écoulement central (39) et qui est configuré pour guider le liquide de refroidissement du chemin d'écoulement circonférentiel extérieur (34) vers le chemin d'écoulement central (39) ; et
un chemin d'écoulement de connexion d'aval (40) qui s'étend du chemin d'écoulement central (39) vers le chemin d'écoulement circonférentiel extérieur (34), qui est séparé du chemin d'écoulement de connexion d'amont (38) et qui est configuré pour guider le liquide de refroidissement, guidé par le chemin d'écoulement de connexion d'amont (38) vers le chemin d'écoulement central (39), du chemin d'écoulement central (39) vers le chemin d'écoulement circonférentiel extérieur (34),
caractérisé en ce que le chemin d'écoulement de connexion d'amont (38) a une aire de section inférieure à une aire de section du chemin d'écoulement de connexion d'aval (40), dans lequel
une valeur maximale d'une largeur (Wu) du chemin d'écoulement de connexion d'amont (38), en regardant dans la première direction, est inférieure à une valeur maximale d'une largeur (Wd) du chemin d'écoulement de connexion d'aval (40), en regardant dans la première direction, et une valeur maximale d'une longueur (Lu) du chemin d'écoulement de connexion d'amont (38) dans la première direction est inférieure à une valeur maximale d'une longueur (Ld) du chemin d'écoulement de connexion d'aval (40) dans la première direction.
le moteur (1) à arbre à cames en tête simple refroidi à l'eau comprend en outre un bouchon de remplissage (56) qui ferme l'évent de gaz (55), et
une distance (D2) d'un axe (C1) de l'évent de gaz (55) à l'axe (C1) du cylindre (9) est inférieure à un diamètre (Φ2) de l'évent de gaz (55).
une longueur (Llr) du chemin d'écoulement central (39) dans la deuxième direction est inférieure à une longueur (Lfr) du chemin d'écoulement central (39) dans une troisième direction qui est orthogonale à la fois à la première direction et à la deuxième direction.
REFERENCES CITED IN THE DESCRIPTION
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Patent documents cited in the description