Europaisches Patentamt J European Patent Office 00 Publication number: 0 353 989 Office europeen des brevets A2 EUROPEAN PATENT APPLICATION Application number: 89307802.2 lnt.CI.6: F 02 F 1/42 F 01 L 1/26, F 01 L 1/02 Date of filing: 01.08.89 Priority: 01.08.88 JP 192377/88 @ Applicant: HONDA GIKEN KOGYO KABUSHIKI KAISHA 1-1, Minami-Aoyama 2-chome Minato-ku Date of publication of application : Tokyo (JP) 07.02.90 Bulletin 90/06 @ Inventor: Niizato, Tomonori c/o K.K. Honda 4-1 Chuo 1-chome Designated Contracting States: DE FR GB IT Gijutsu Kenkyusho Wako-shi Saitama-ken (JP) Tsukimura, Kiyoshi c/o K.K. Honda Gijutsu Kenkyusho 4-1 Chuo 1-chome Wako-shi Saitama-ken (JP) Noguchi, Katsumi c/o K.K. Honda Gijutsu Kenkyusho 4-1 Chuo 1-chome Wako-shi Saitama-ken (JP) @ Representative: Piesold, Alexander J.etal Frank B. Dehn & Co. Imperial House 15-19 Kingsway London WC2B6UZ (GB) @ Cylinder head structure for plural cylinder engines. @ A cylinder head structure for a plural cylinder engine, Fig. 2 comprising, at least for each of its cylinders located at either longitudinal end of its cylinder bank: a combustion chamber (13) defined by the cylinder and a piston received therein; an intake passage (18) communicated with an intake manifold (20) -21b at its one end and with said combustion chamber (13) at its other end; an exhaust passage (19) communicated with an exhaust manifold (21) at its one end and with said combustion chamber (13) at its other end; at least one of said intake passage and said exhaust passage being curved toward a longitudinally central part of said cylinder bank as it extends from its other end to its one end. Hence, the size and weight of the intake manifold and/or the exhaust manifold can be 00 reduced. In particular, if the passage is communicated with the combustion chamber by a pair of ports controlled by valves and arranged along a longitudinal direction of the cylinder bank and different flow rates to these depending the s are assigned ports operating conditions of the engine, a significant improvement in CO the performance of the engine may be attained by symmetrically arranging these ports with respect to a longitudinal center of the cylinder bank. Q. LU Bundesdruckerei Berlin EP 0 353 989 A2 Description CYLINDER HEAD STRUCTURE FOR PLURAL CYLINDER ENGINES The present invention relates to a cylinder head exhaust manifold for mounting it on a cylinder head structure for plural cylinder engines which allows can be reduced in the dimension along the longitudi- more compact design of an engine than was 5 nal direction of the cylinder bank, and the overall size possible heretofore, and in particular to such a and weight of the engine can be reduced. Addition- cylinder head structure which can be . advant- ally, as the intake and/or exhaust passage can be ageously used in combination with an engine using a made shorter and smoother, the performance of the plurality of intake and/or exhaust valves having engine can be also improved. Further, as the part of different flow rate properties for each cylinder. 10 the flow passage directed to the port for a larger flow As it is preferred to increase the cross sectional rate is shorter and more linear than that for the other area of the passage leading to a combustion port for a smaller flow rate, an overall improvement in chamber in order to improve the volumetric effi- volumetric efficiency can be achieved. Additionally, ciency of the engine, it has become increasingly by appropriately selecting the configuration of the common to provide a plurality of intake valves and/or 15 overall intake and exhaust system, a favorable swirl exhaust valves for each cylinder with the aim of effect may be obtained and a favorable mixing of fuel maximizing the effective area of the valves in relation with air can be achieved. with the internal surface area of the combustion According to a preferred embodiment of the chamber. present invention, the curved passage consists of an Also is known the valve control technology known 20 exhaust passage, and an intake passage is com- as combination valve timing according to which a municated with the combustion chamber by at least swirl is produced in the mixture introduced into the two ports which are controlled by intake valves and combustion chamber by shifting the opening and arranged along a longitudinal direction of the closing timing of the plural valves (Japanese patent cylinder bank, one of the intake ports involving a laid-open publication No. 59-147822). 25 relatively smaller flow rate being disposed closer to a The temperature of combustion gas is extremely longitudinally central part of the cylinder bank than high and its flow speed may reach the sonic speed. It the other intake port involving a relatively larger flow is therefore desirable to minimize the flow resistance rate. According to this embodiment, a favorable of the exhaust passages to improve exhaust effi- scavenging effect can be obtained in addition to a ciency by taking advantage of the flow speed of 30 favorable volumetric efficiency. exhaust gas. According to a particularly preferred embodiment The exhaust manifold which merges the exhaust of the present invention, the exhaust and intake passages leading to the exhaust ports opening out valves are controlled by a valve actuating mechanism into the cylinder head is generally made of cast iron in such a manner that all the valves are fully opened because of the heat resisting property of the 35 in a high engine speed range, and one of the intake material, and the exhaust manifold is desired to be valves remote from a longitudinally central part of the made as small as possible to make room for cylinder bank and one of the exhaust valves close to mounting accessory equipment and to reduce the a longitudinally central part of the cylinder bank are overall weight of the engine. A similar consideration opened to intermediate extents while the other applies also to the intake system of the engine. 40 intake valve and the other exhaust valve are opened Viewed from one aspect the present invention to small extents in a low engine speed range. provides a cylinder head structure for a plural According to this embodiment, a favorable swirl cylinder engine, comprising, at least for each of its effect can be produced in the flow of air/fuel mixture, cylinders located at either longitudinal end of its and a favorable volumetric efficiency can be cylinder bank: a combustion chamber defined by the 45 achieved. cylinder and a piston received therein; an intake Alternatively, one of the intake ports involving a passage communicated with an intake manifold at its relatively larger flow rate may be disposed closer to a one end and with the combustion chamber at its longitudinally central part of the cylinder bank than other end; and an exhaust passage communicated the other intake port involving a relatively smaller with an exhaust manifold at its one end and with the 50 flow rate so that a favorable volumetric efficiency combustion chamber at its other end; at least one of may be obtained. the intake passage and the exhaust passage being Certain preferred embodiments of the invention curved toward a longitudinally central part of the will now be described by way of example and with cylinder bank as it extends from its other end to its reference to the accompanying drawings, in which: one end, the curved passage being communicated 55 Figure 1 is a schematic view of a part of an with the combustion chamber at its other end by at engine relevant to the present invention ; least two ports which are controlled by valves and Figure 2 is a horizontal sectional view of a arranged along a longitudinal direction of the cylinder head according to the present inven- cylinder bank, and one of the ports involving a tion; relatively larger flow rate being disposed closer to a 60 Figure 3 is a front view of an example of an longitudinally central part of the cylinder bank than exhaust manifold; the other port involving a relatively smaller flow rate. Figure 4 is a view as seen from arrow IV of Thus, the mounting surface of the intake and/or Figure 3; EP 0 353 989 A2 Figure 5 is a graph showing valve lift curves; of intake valves and a pair of exhaust valves. These Figure 6 is a schematic bottom view of a ports 14a, 14b, 15a and 15b are communicated with modified embodiment of the cylinder head intake openings 16 and exhaust openings 17 which according to the present invention; are provided on either side end of the cylinder head Figure 7 is a schematic plan view of a second 5 7, via intake passages 18 and exhaust passages 19 embodiment of the cylinder head according to provided in the cylinder head 7. the present invention; The intake openings 16 and the exhaust openings Figure 8 is a fragmentary plan view of a valve 17 are shifted towards a longitudinally central part of actuation mechanism; the cylinder bank in relation with the positions of the Figure 9 is a sectional view as seen from 10 corresponding combustion chambers, and, accord- arrow IX of Figure 8; ingly, the intake passages 18 and the exhaust Figure 10 is a sectional view taken along line passages 19 are slightly curved towards the center X-X of Figure 8; as they move away from the corresponding combus- Figure 1 1 is a sectional view taken along line tion chambers 13.