Cylinder head cooling arrangement for a four-cycle internal combustion engine

Abstract: The present invention relates to a cylinder head cooling arrangement for a four-cycle internal combustion engine (1), specifically adapted for a five valve engine comprising three intake valves (14) and is devoted to improve the cooling efficiency of a cooling jacket (31) arrangement of the cylinder head (4). According to the present invention communicating vent holes (31e) are provided to connect the top portions of a central cooling jacket (31) and another cooling jacket disposed at the intake or exhaust sides of the cylinder head structure in order to remove air which may collect at the top portion of the central jacket (31c) effecting the cooling efficiency of the cooling arrangement. Preferably, the vent holes (31e) penetrate an integral wall section between the left and right intake passages and neighbouring bolt holes (10c) of the cylinder head bolts.

Description: The present invention relates to a cylinder head cooling arrangement for a four cycle internal combustion engine comprising more than two intake valves and a plurality of exhaust valves for each of its cylinders and a coolant jacket structure including a central jacket disposed along an area between the intake and exhaust valves as well as side jackets on the intake and exhaust valve sides of the cylinder head, wherein the central jacket is connected with at least one of the intake or exhaust side jackets via a venting structure. In order to acquire appropriate cooling of a four-cycle internal combustion engine usually the cylinder block comprises a cooling jacket and also the cylinder head comprises a cooling jacket structure through which cooling water from the cylinder block cooling jacket is circulated. Conventionally, a cooling jacket is formed in the cylinder head above the combustion chamber of each cylinder and such a cylinder head cooling jacket is composed of a central jacket formed between the intake passages and the exhaust passages lengthening the intake valve opening and the exhaust valve openings, respectively and outer wall of the cylinder head whereas an intake side cooling jacket is formed between a lateral outer wall of the cylinder head and the intake passages. Correspondingly, an exhaust side cooling jacket is formed between the opposite outer wall of the cylinder head and the exhaust passages. With such a cooling structure the cooling water flows from the cooling jacket of the cylinder block into the exhaust side jacket of the cylinder head, then through the central jacket and into the intake side cooling jacket from which it will be drained off through the drain outlet. Nowadays, in order to increase the performance of the engine more than two intake valves, specifically five valve engines are used comprising three intake valves and two exhaust valves for each cylinder thus improving the charging efficiency of the engine. In order to assure a sufficient cross-section of the intake passages of such an engine said intake passages occupy increased space resulting in difficulties to provide the space required for providing a communicating passage between the central jacket and the cooling jacket at the intake side. Depending on the shape of the central jacket, the intake side cooling jacket and the intake passages, it becomes particularly difficult to communicate the upper portions of both jackets with each other so that air can be entrapped in the upper portion of the central jacket which can effect the cooling efficiency of said cooling jacket structure. A cylinder head cooling arrangement of the type indicated at the beginning is known from EP-A-0 282 808. This known cooling arrangement, however, does not provide a satisfactory venting structure, so that the cooling efficiency of the cooling arrangement may be reduced. Accordingly, it is an objective of the present invention to provide an improved cylinder head cooling arrangement which enables air to be easily removed from each cooling jacket of the cylinder head cooling arrangement but also provides sufficient space in order to assure the necessary cross-sectional areas of the intake passages of a plurality of more than two intake valves, specifically for a five valve engine, in order to obtain both high cooling efficiency by preventing air from being entrapped in the cooling jacket of the cylinder head and a high charging efficiency. According to the present invention the afore-noted objective is performed by a cylinder head cooling arrangement according to claim 1. According to a preferred embodiment of the present invention the intake side cooling jacket which is substantially defined between an outer wall of the cylinder head and the intake passages for the intake valves and, moreover, which is continuous with the central cooling jacket at a bottom area of both jackets adjacent to the combustion chamber but which is separated from said central jacket at a top end portion through an inner wall portion of the cylinder head, is communicated with the central cooling jacket and that top area by venting connection holes penetrating said inner wall portion of the cylinder head and communicating both the intake side and central cooling jackets with each other in order to establish a fluid communication therebetween which enables air to be removed from the cooling jacket arrangement of the cylinder head. As the venting holes which communicate the intake side cooling jacket and the central cooling jacket of the cylinder head cooling arrangement with each other are disposed to establish a fluid connection of the top areas of both jackets any air which may have entrapped in the central jacket will be pured and removed out of the central cooling jacket towards to the intake side cooling jacket and discharged therefrom. Consequently, also the central cooling jacket will completely be filled with the coolant, staying of air bubbles is eliminated and the cooling efficiency of the cylinder head cooling structure is improved. According to yet another preferred embodiment of the present invention, the same or a similar venting structure comprising at least one, preferably a pair of venting holes, is provided between the central jacket and the exhaust side cooling jacket. Thus, generally the disposal and layout of the venting structure to be disposed in between the central jacket and one of the intake or exhaust side jackets depends on the inclination of the cylinder head and the height level of the portion of one or the other side jackets. Preferably, the intake or exhaust side cooling jacket which is positioned higher than the other one is communicated with the central jacket by at least one venting hole. Generally, that side cooling jacket which is disposed on the same side as the majority of valves is disposed at a higher level than the other one. Preferably the venting holes are drilled through the cylinder head outer wall at both sides of the left and right intake passages at the positions for connecting the top portions of the intake side cooling jacket and the central cooling jacket. It is possible to design the diameters of said venting holes to be desirably small in order to design the intake passages larger ensuring sufficient cross-sections of the intake passages and, simultaneously, reliably puring air out of the cooling system to improve the cooling efficiency. Further advantageous embodiments of the present invention are laid down in the further subclaims. In the following the invention is explained in greater detail pointing to an embodiment thereof in conjunction with the accompanying drawings, wherein Figure 1 is a diagrammatic front view of a V-type engine to which the present invention is applied, Figure 2 is a sectional front view of a cylinder head portion of the right cylinder bank as shown in Figure 1, Figure 3 is a plane view of the cylinder head portion according to Figure 2, Figure 4 is a sectional view taken along line IV-IV in Figure 2, Figure 5 is a sectional view taken along the line V-V in Figure 2, Figure 6 is a sectional view taken along the line VI-VI in Figures 2, Figure 7 is a sectional view taken along the line VII-VII of Figure 3. In the following a V-type four-cycle internal combustion engine comprising five valves for each cylinder, specifically the cylinder head portion thereof to which an embodiment of the present invention is applied, is explained referring to the accompanying drawings. In the following the basic structure of the engine is explained referring to Figure 1. In Figure 1, showing schematically a front view of the engine 1 a cylinder block 2 is shown connected to a crankcase 3 at its lower end face and comprising a pair of left and right cylinder heads 4 having head covers 5 stuck and fastened on its upper face. The cylinder block 2 defines a plurality of cylinders or liners 6 arranged in V-shape as seen in the crankshaft direction shown in Figure 1. A piston is inserted in each cylinder 6 and is connected through a connecting rod 8 with the crankshaft 9 as usual. The cylinder head 4 of each clyinder bank of the V-type engine is of a V-sectional structure composed of an upper head 11 and a lower head 10, respectively (see Figure 7). The lower head 10 defines combustion cavities 12 which, in turn, form a combustion chamber for each cylinder 6 defined by the top face of the respective piston 7 slidably received therein. As shown in Figure 2 the combustion cavity 12 of the respective cylinder 6 comprises three intake openings 12a, 12b and 12c as well as two exhaust openings 12d and 12e arranged along the periphery of the combustion cavity 12 whereas its centre portion is formed with an inserting hole 12i adapted to accommodate a usual ignition plug therein. The exhaust openings 12d and 12e are lead out to the outside wall 10b of the cylinder head 4 extending along the side periphery of the V-shaped cylinder bank by means of exhaust passages 13d and 13e. The intake openings 12a, 12b and 12c are lead out to a wall 10a of the cylinder head 4 located at the inner side of the V-shaped cylinder bank by means of intake passages 13a, 13b and 13c which joint with one another through an extension portion 11c extending through and upward of the upper head 11. The junction area 13f is shaped to be elliptical with its major diameter oriented in parallel to the crankshaft axis. A mounting hole 11d for receiving a fuel injection valve 13 is provided to extend through a portion of the central intake passage 13b. A slide valve 39 for opening and closing the junction portion 13f is disposed in the extension portion 11c of the intake passages and an air horn 40 is connected to that extension portion 11c. In order to prevent dust or the like from entering into the air horn 40 a cover 41 is provided. The intake and exhaust valves 14, 15 each comprising valve stems 14b, 15b with valve plates 14a, 15a at their lower end portion adapted to open or close the intake openings 12a, 12b, 12c and exhaust openings 12d and 12e, respectively. The upper end portion of the valve stems 14b, 15b of the intake and exhaust valves 14, 15 is disposed in guide holes 11a, 11b, defined in the upper head 11. These guide holes 11a and 11b as shown in greater detail in Figure 3 are formed in a unitary structure respectively establishing a radially connected double structure (exhaust side) or triple structure (intake side). Accordingly, the diameters of said guide holes 11a, 11b are sufficiently large to eliminate any boundary wall portion between adjacent guide holes 11a, 11b at the intake or exhaust sides. Moreover, cast intake and exhaust inserts 16, 17 form liners for said guide holes 11a, 11b as a reinforcement structure. In this way said intake and exhaust inserts 16 and 17 form slide holes to slidably receive intake and exhaust lifters 18, 19, respectively which are of a bottomed cylinder shape wherein the upper end of each valve stem 14b, 15b is engaged with the respective inside bottom portion of the intake and exhaust lifters 18, 19 through a pad, respectively. Near to the upper end of each valve stem 14b and 15b is installed a spring retainer 20, 21 adapted to retain the urging springs 22, 23 of the intake and exhaust valves 14, 15, respectively. Both valve urging springs 22 and 23 of the intake and exhaust valves 14, 15, respectively, are of a concentric double structure and extend between the retainers 20 and 21 and the associated valve seats 12g and 12h, formed on the lower head 10 of the cylinder head 4, respectively. By means of said valve springs 22 and 23 the intake and exhaust valves 14, 15 are kept urged in a direction for closing the intake and exhaust openings. The intake valves 14 and the exhaust valves 15 of each row of the V-type engine are operated by an intake camshaft 24 and an exhaust camshaft 25, respectively, which establish rotating contact with each intake lifter 18 and each exhaust lifter 19. Bearing portions, formed on the upper head 11 and cam caps 32 fastened through bolts 32a, as shown in Figure 7, form bearings for both camshafts 24, 25. The intake valve 14 and exhaust valve 15 are moved downwardly by pushing down the intake lifter 18 and exhaust lifter 19 through the related cam lobes of the cam shafts 24 and 25, respectively. While the afore-going description refers to the conventional structure of such a five valve engine the specific design in compliance with the embodiment of the present invention is explained in the following with reference to Figures 2 to 7, respectively. As indicated in Figure 2 a coolant jacket for circulating cooling water from the cylinder block through the cylinder head is shown to be provided in the lower head 10. The cooling water jacket and internal structure of the cylinder head is designed to cover the combustion cavity 12. This cooling water jacket is composed of a water jacket 31a at the intake side ranging from the portion of the intake passages 13a, 13b and 13c to the side of the inside wall 10a of the lower head 10, another cooling jacket 31b disposed at the exhaust side ranging from the portion of the exhaust passages 13d and 13e to the outer side wall 10b of the lower head 10, and of a central cooling jacket 31c substantially extending between the intake passages 13a, 13b, 13c and the exhaust passgages 13d and 13e. The design and disposal of the different sections 31a, 31b, 31c of the water jacket arrangement are clearly shown in Figures 2 to 7, specifically in Figures 1, 2, 4, 5 and 7. Figures 2 shows the right hand portion of the cylinder row of the V-bank in view of its cylinder head portion of the engine. The position the engine is accommodated in an engine compartment, said mounting position is reflected in Figures 1 and 2, lead to an increasing positional height of the different sections or jackets 31b, 31c, 31a of the water jacket cooling arrangement, i.e. the central jacket 31c is positioned higher than the exhaust side jacket 31b and the intake side jacket 31a is positioned higher than the central jacket 31c. The coolant (cooling water) flows from a cooling water jacket of the cylinder block 2 (not shown in the drawings) into the side jacket 31b of the exhaust side, then through the central jacket 31c and from that portion through the intake side jacket 31a from which it is drained out and recirculated through a drain outlet 31d. Depending on the general layout of the cooling system of the engine the flow direction of the cooling water can be inverse to the afore-noted flow direction. As is apparent from Figures 4 and 5 the exhaust side jacket 31b and the central cooling jacket 31c are integrally provided and define a continuous space as a whole. On the other hand, the central cooling jacket 31c and the intake side cooling jacket 31a are also integral with each other along a relatively large area at their bottom portions near the combustion cavity 12 as shown in Figure 5, but some portions along the top portion facing to the upper head 11 are not communicated to each other but separated through an inner cylinder head wall portion defining the bolt holes for the cylinder head bolts as shown on the left side of Figures 4 and 7, respectively. For that reason it may occur that a certain amount of air remains entrapped in the upper portion of the central water cooling jacket 31c which might effect the cooling efficiency of the cooling structure due to the heat insulating effects of the air reducing the heat transfer between the circulated coolant and the hot cylinder head portions. In order to overcome this problem the present invention contemplates to provide communicating or venting holes 31e to be drilled between the top portions of the central cooling jacket 31c and the cooling jacket 31a on the intake side in. order to communicate these water jackets 31a, 31c at the head portions thereof. these communicating holes or venting holes are formed by drilling through the cylinder head wall 10a at the inside of the V-bank structure outside of the left and right intake passages 13a and 13c at the positions for connecting the highest portions of the central jacket 31c and the intake side cooling jacket 31a as shown in Figures 2, 4, 6 and 7 while the waste holes created through the drilling process between the cylinder head wall 10a (outer side wall extending along the inner side of the V-bank) are plugged, using respective plugs 31f as shown in Figure 4. As already indicated above, the communicating vent holes 31e, in this embodiment, penetrate an integral inner wall of the cylinder head defining the intake passages 13a, 13b, 13c and the bolt holes lOc for the cylinder head bolts as shown in Figures 4 and 7. Figure 7 elucidates the construction of the cylinder head 4 comprising the upper head 11 and the lower head 10 bolted to each other by cylinder head bolts 32a. According to this structure of the cylinder head cooling arrangement according to the present embodiment there is a circulation of the cooling water from the cylinder blocks coolant jacket (not shown) to the cooling jacket 31b at the exhaust side of the lower head 10 of the cylinder head 4. Then the cooling water flows from the outside of the exhaust passages 13b, 13e and between them into the central cooling jacket 31c. From there the cooling water continues to flow along the outside of the intake passages 13a and 13c into the cooling jacket 31a at the intake side of the cylinder head and then discharged through a drain outlet 31d. Accordingly, any air that may have remained in the top area of the central cooling jacket 31c is poured out with the coolant into the intake side cooling jacket 31a through the communicating vent holes 31e and then is discharged through the drain outlet 31d together with the coolant flow. After the discharge of air from the central cooling jacket 31a is completed a part of the circulated cooling water will also flow from the central cooling jacket 31c towards the intake side cooling jacket 31a through the communicating holes 31e. Accordingly, the central and intake side jackets 31c and 31a communicating vent holes 31e serve to improve the cooling efficiency of the engine as they reliably prevent heat insulating air to occupy some space at the top of the central cooling jacket 31c when the coolant is circulated. Moreover, as according to a specifically preferred embodiment of the present invention, the holes 31e are formed by drilling through an inner wall portion integrally defining the bolts holes 10c for the cylinder head bolts and left and right intake passages 13a and 13c only small space is required for disposing the communicating vent holes 31e. Therefore, the cross-section of the intake passages 13a, 13b and 13c can be increased, so as to obtain high charging efficiency of the engine. The present invention, of course is not limited to be applied to five valve engines or those of a V-type arrangement but may be applied to other types as well. Moreover, the communicating vent holes can also be provided to connect the top portions of the central and exhaust side jackets, respectively, specifically in case the number of exhaust valves exceeds those of the intake valves.

Claims: A cylinder head cooling arrangement for a four cycle internal combustion engine comprising more than two intake valves (14) and a plurality of exhaust valves (15) for each of its cylinders and a coolant jacket structure including a central jacket (31c) disposed along an area between the intake and exhaust valves (14,15) as well as side jackets (31a, 31b) on the intake and exhaust valve sides of the cylinder head (4), wherein the central jacket (31c) is connected with at least one of the intake or exhaust side jackets (31a, 31b) via a venting structure, characterised in that, said venting structure comprises venting holes (31e) communicating a top portion of the central jacket (31c) with a top portion of the relevant side jacket (31a, 31b) penetrating an inner wall (10a) of the cylinder head (4), said inner wall (10a) defining bolt holes (10c) of the cylinder head bolt (32a), and that said head bolt holes (10c) are disposed such that a plane containing their axes crosses the vent holes (31e) which are disposed between the relevant head bolt hole (l0c) and the adjacent part of the intake or exhaust passages (13a, 13b, 13c; 13d, 13e). A cylinder head cooling arrangement for a five valve engine comprising three intake valves and two exhaust valves for each cylinder, as claimed in claim 1, characterised in that the intake side jacket (31a) substantially defined between an outer wall (10a) of the cylinder head (10, 11) and the intake passages (13a to 13c) of the intake valves (14) which is continuous with the central jacket (31c) at a combustion chamber side bottom area of both jackets (31a, 31c) but is separated from the central jacket (31c) at a top end portion thereof through an inner cylinder head wall portion is communicated with the central jacket (31c) at that top area by venting holes (31e) penetrating said inner cylinder head wall portion to establish fluid communication between the intake side jacket (31a) and the central jacket (31c). A cylinder head cooling arrangement as claimed in the preceding claims 1 or 2, characterised in that the venting holes (31e) are provided by drilling through the cylinder head wall (10a) laterally of the left and right intake passages (13a, 13c) at the positions for connecting the highest portions of the intake side jacket (31a) and the central jacket (31c), waste hole sections in the cylinder head outer wall (10a) being closed with plugs (31f). A cylinder head cooling arrangement as claimed in at least one of the preceding claims 1 to 3, characterised in that the exhaust side jacket (31a) is provided between an exhaust side outer wall (10b) of the cylinder head (4) and the exhaust passages (13d, 13e) of the exhaust valves (15), with the exhaust side jacket (31b) being formed integral with the central jacket (31c). A cylinder head cooling arrangement as claimed in at least one of the preceding claims 1 to 4, characterised in that the cylinder head comprises three intake passages (13a, 13b, 13c) joining to a common extension portion (llc) and two exhaust passages (13e, 13d). A cylinder head cooling arrangement as claimed in at least one of the preceding claims 1 to 5, characterised in that the venting structure (31e) communicating the top portion of the central jacket (31c) to one of the intake and exhaust side jackets (31a, 31b), extends to that side of the intake or exhaust sides where the number of valves is greater. A cylinder head cooling arrangement as claimed in at least one of the preceding claims 1 to 6, characterised in that the central jacket (31c) is communicated to the top portion of the exhaust side jacket (31b) and the number of exhaust valves per cylinder exceeds those of the intake valves. A cylinder head cooling arrangement as claimed in at least one of the preceding claims 1 to 7, characterised in that the cylinder head (4) is inclined with respect to the vertical in such a manner that the intake or exhaust side jacket (31a, 31b) which is communicated to the central jacket (31c) through at least one venting hole (31e) preferably a pair thereof, is disposed at a level higher than the other opposite exhaust or intake side jacket (31b, 31a). A cylinder head cooling arrangement as claimed in at least one of the preceding claims 1 to 8, characterised in that the position at which the venting holes open into the cooling jacket (31c, 31a, 31b) substantially corresponds to the upper top end portion of the cooling jacket (31c, 31a, 31b) to communicate the central jacket (31c) to the intake side or exhaust side jackets (31a, 31b) at the highest portions thereof. A cylinder head cooling arrangement as claimed in at least one of the preceding claims 1 to 9, characterised in that the coolant is adapted to flow from the intake or exhaust side jackets (31a, 31b) to the opposite exhaust or intake side jacket (31b, 31a), the latter being in fluid communication with the central jacket (31c) at least through the venting hole arrangement (31e).

Inventors: OYAIZU TAKAESHI, OYAIZU, TAKAESHI
Applicants: YAMAHA MOTOR CO LTD, YAMAHA HATSUDOKI KABUSHIKI KAISHA
Application year: 1991
Main classification: F02F1
IPC codes: F02B1, F02B75, F02F1, F01P11, F01P3, F02B3