Cooling system for multi-cylinder engine

Abstract: In a cooling system for a multi-cylinder engine, a main gallery is provided around outer peripheral portions of the plurality of cylinder bores upstream of a block-side coolant jacket to commonly surround the cylinder bores, and an upstream coolant gallery is provided between the block-side coolant jacket and the main coolant gallery to separately surround each of the outer peripheries of the cylinder bores. The upstream coolant gallery and the main coolant gallery are in communication with each other through a constriction communication passage provided around the outer periphery of each of the cylinder bores, and the upstream coolant gallery is further in communication with an upstream end of the block-side coolant jacket. The cooling system further includes a block-side and flange-surrounding coolant gallery provided in the cylinder block to surround an outer periphery of the outward flange of a cylinder liner, and a plurality of dispensing passages permitting communication between said block-side coolant jacket and said flange-surrounding coolant gallery. Further, a jacket sidewall is disposed in the cylinder head inside at least one of opposite outside walls in an axial direction of at crank shaft to define a head-side coolant jacket. This makes it possible to uniformly and efficiently cool heated portions of the cylinder block in the multi-cylinder engine and an outward flange at an upper end of the cylinder liner inserted in the cylinder. In addition, the head-side coolant jacket is provided only in a relately narrow section required to be cooled, so that the flow speed of a coolant in the head-side coolant jacket can be increased to a relatively fast level to improve the cooling efficiency for the cylinder head.

Description: The field of the present invention is cooling systems using a coolant for multi-cylinder engines. Such cooling systems are well known which comprise a common coolant jacket defined around a plurality of cylinder bores in a cylinder block of a multi-cylinder engine, so that cooling water is permitted to flow through the coolant jacket to cool the periphery of the plurality of cylinder bores (see "Automobile Engineering Handbook, No. 10, Electric Equipments, Vehicle Body Maintenance Articles, Engine Parts" issued by Sankaido, Chapter 4, Engine Parts). In the above prior art cooling systems, however, the following problems are encountered: The cylinder bores are surrounded, over a region from their upper portions to their lower portions, by a common coolant jacket and hence a cylinder located away from a coolant inlet may be cooled by the coolant which has been warmed by another cylinder located in the vicinity of the inlet, and hence the respective cylinders tend to be cooled unevenly. In addition, due to variation and unevenness in flow area of a coolant passage, not only the flow resistance of the coolant may be increased, but also the coolant may be apt to stagnate at parts of the passage, and consequently the total cooling efficiency is not high. FR-A-553461 discloses a cooling system for a cylinder of an internal combustion engine, comprising a coolant jacket between a wet liner and the cylinder block, which coolant jacket is formed to define one or more helical coolant flow paths leading upwardly around the wet liner. According to the present invention there is provided a cooling system of a multi-cylinder engine having a plurality of cylinder liners fitted in a row in a cylinder block, said system comprising a block-side coolant jacket which surrounds the outer peripheral portions of the said cylinder liners so that a coolant can flow through said jacket from the lower end to the upper end of the cylinder liners, characterised by further comprising an upstream coolant gallery located upstream of said block-side coolant jacket and surrounding each of the outer peripheries of the cylinder liners, and a main coolant gallery having an inlet port connected to a cooling circuit and being located upstream of said upstream coolant gallery, at the lower end of the cylinder liners, and commonly surrounding the cylinder liners, the said main coolant gallery communicating with the said upstream coolant gallery through constricted communication passage means provided therebetween and around the outer periphery of each of the cylinder liners. With such an arrangement, a coolant having an increased flow speed can be uniformly distributed to the block-side coolant jacket which surrounds the plurality of cylinder liners in the cylinder block, thereby efficiently cooling the heated portions of the cylinder block. In a preferred form of the invention the said block-side coolant jacket includes a plurality of coolant passages defined around each of the cylinder liners and extending parallel to the axis of the cylinder liner. With such an arrangement the cooling surface area of the block-side coolant jacket can be increased, which makes it possible to further efficiently cool the heated portions of the cylinder block. Further, there is known a multi-cylinder engine comprising an engine block which includes a cylinder block having a block-side coolant jacket surrounding cylinder bores each having a piston received therein, and a cylinder head having a head-side coolant jacket which surrounds combustion chambers defined above the pistons and communicates with the block-side coolant jacket, with opposite outside walls of the cylinder head extending in the axial direction of the crank shaft being substantially aligned with opposite outside walls of the cylinder block (for example, see Japanese Patent Application Laid-open No. 81451/85). In this multi-cylinder engine the head-side coolant jacket is provided over substantially the entire surface of the cylinder head. In some cases, the cylinder block may be constructed to have its outside wall spaced outwardly from a portion defining the block-side coolant jacket, in order to improve the rigidity and strength of the cylinder block. In such cases, if the head-side coolant jacket is provided over substantially the entire surface of the cylinder head as described above, coolant is caused to flow over a wide area including portions other than that portion of the cylinder head which is heated to the highest temperature and which corresponds to the combustion chamber. Consequently, a problem arises that the flow speed of a coolant within the head-side coolant jacket is reduced, resulting in an inferior cooling efficiency in the cylinder head. Thus in a further preferred form of the invention the engine further includes a cylinder head connected to the cylinder block and having a head-side coolant jacket which surrounds a plurality of combustion chambers defined above the pistons, the head-side coolant jacket communicating with the block-side coolant jacket, outside walls of said cylinder head being located on opposite sides of the axis of a crank shaft which is substantially aligned with opposite outside walls of said cylinder block, said cylinder head having a jacket sidewall disposed inside at least one of its said opposite outside walls in the axial direction of the crank shaft for defining the head-side coolant jacket. With such an arrangement the head-side coolant jacket is provided only in a relatively narrow section required to be cooled and hence it is possible to increase the flow speed of coolant in the head-side coolant jacket, thereby improving the cooling efficiency for the cylinder head. Some embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figs. 1 to 10 illustrate a first embodiment of the present invention, wherein Fig. 1 is a plan view of a cylinder block with cylinder liners inserted in cylinders, taken along a line I-I in Fig.4; Fig.2 is a plan view of the cylinder block with the cylinder liners removed from the cylinders; Fig.3 is a longitudinal sectional view of the cylinder block, taken along a line III-III in Fig.1; Fig.4 is a longitudinal sectional view of the cylinder block and a cylinder head, taken along a line IV-IV in Fig.3; Fig.5 is a longitudinal sectional view of the cylinder block and a cylinder head, taken along a line V-V in Fig.3; Fig.6 is a cross-sectional view of the cylinder block, taken along a line VI-VI in Fig.3; Fig.7 is a cross-sectional view of the cylinder block, taken along a line VII-VII in Fig.3; Fig.8 is a perspective view of a portion of the cylinder block; Fig.9 is a bottom view of a portion of the cylinder head, taken along a line IX-IX in Fig.4; and Fig.10 is a partially longitudinal sectional view of the cylinder block and the cylinder head, taken along a line X-X in Fig.4; Fig.11 is a partially longitudinal sectional view illustrating a modification of the first embodiment similar to Fig.10; Figs.12 to 14 illustrate a second embodiment of the present invention, wherein Fig.12 is a plan view of a portion of a cylinder block with cylinder liners inserted therein; Fig.13 is a longitudinal sectional view of the cylinder block and a cylinder head, taken along a line XIII-XIII in Fig.12; and Fig.14 is a perspective view of a portion of the cylinder block; Fig.15 is a perspective view of a portion of a cylinder block in a third embodiment of the present invention; Figs.16 to 22 illustrate a fourth embodiment of the present invention, wherein Fig.16 is a front view in longitudinal section of a multi-cylinder engine provided with a system of the present invention, illustrating a cylinder block and cylinder head in a longitudinal sectional view taken along a line XVI-XVI In Fig.17: Fig.17 is a longitudinal sectional view of the cylinder block and the cylinder head, taken along a line XVII-XVII in Fig.16; Fig.18 is a view taken along a line XVIII-XVIII in Fig.17; Fig.19 is a cross-sectional view of a portion of the cylinder head, taken along a line XIX-XIX in Fig.17; Fig.20 is a bottom view of a portion of the cylinder head, taken along a line XX-XX in Fig.17; Fig.21 is a longitudinal sectional view of a portion of the cylinder head, taken along a line XXI-XXI in Fig.19; and Fig.22 is a longitudinal sectional view of a portion of the cylinder head, taken along a line XXII-XXII in Fig.19; Fig.23 is a longitudinal sectional front view similar to Fig.16, but illustrating a fifth embodiment of the present invention. The present invention will now be described by way of embodiments in which a system according to the present invention is applied in a serial or in-line type four-cylinder engine, with reference to the accompanying drawings. As shown in Figs. 3 and 4, a body E of the engine comprises a cylinder block 1 and a cylinder head 2 joined to a deck surface 1a of the cylinder block 1 through a gasket G as in a conventional case. A first embodiment of the cooling system of the present invention will now be described below with reference to Figs. 1 to 10. Four cylinders 3 --- are arranged in series in the cylinder block 1, and each has a wet liner 5 inserted therein as a hollow cylindrical cylinder liner having an outward flange portion 5a formed at its upper end. The wet liner 5 may be fitted into the cylinder block 1 by a press-fitting or the like, or integrally cast into the cylinder block 1 during casting. The outward flange portion 5a is supported in the cylinder block 1 by placement onto an annular bearing surface 1b formed on an upper end of the cylinder block 1. A piston which is not shown is slidably received in a cylinder bore 4 in the wet liner 5. As shown in Figs. 3, 7 and 8, a plurality of cooling fins 5b are mounted at circumferentially spaced locations on the entire outer peripheral surface of a body of the wet liner 5 to extend in parallel to each other in the direction of a cylinder axis ℓ₁-ℓ₁. When the wet liner 5 has been fitted in the cylinder 3, outer surfaces of the plurality of cooling fins 5b are placed into close contact with an inner peripheral surface of a cylinder wall 1e of the cylinder block 1 to define a plurality of rectilinear parallel cooling passages 6 extending in the direction of the cylinder axis ℓ₁-ℓ₁ between the individual adjacent cooling fins 5b, thereby forming a block-side cooling jacket J B . A lower side of the block-side cooling jacket J B , i.e., a side of the cylinder block 1 closer to a crank case 1c, is an upstream side, and a side thereof closer to the deck surface 1a is a downstream side. As shown in Figs. 2 and 7, the block 1 includes a wall 1d between the adjacent wet liners 5, 5 which is cut away at a portion astride a crank axis ℓ₂-ℓ₂ to leave a space over opposite sides thereof as a band-like notch 7 having a predetermined width. At the notch 7, the outer peripheral surfaces of the adjacent wet liners 5, 5 are opposed to each other at a slight distance, and some cooling fins 5b on the opposed outer peripheral surfaces are aligned in phase with each other to define therebetween coolant passages 6₁ common to the adjacent cylinders 3, 3 and having a large passage sectional area. Adjoining portions of the adjacent wet liners 5, 5 will be heated to a highest temperature, but the common coolant passages 6₁ in the adjoining portions can have an increased cooling efficiency, because they have a large passage sectional area. As shown in Figs. 3, 4 and 6, a main coolant gallery 8 having a relatively large capacity is defined between lower portions of the plurality of wet liners 5 and corresponding cylinder wall 1e of the cylinder block 1, the gallery 8 commonly surrounding the outer peripheries of the plurality of wet liners 5 and being provided at its one end with an inlet port 9 which is connected to a pump 10 connected to a cooling circuit which is not shown. As shown in Fig.4, directly below the block-side coolant jacket J B comprising the plurality of coolant passages 6, an annular upstream coolant gallery 11 is defined around the outer periphery of the individual wet liner 5 by the outer peripheral surface of that wet liner 5 and an inner peripheral surface of the cylinder wall 1e of the cylinder block 1, so that it is in direct communication with a lower end, i.e., the upstream end of the block-side coolant jacket J B . As shown in Fig.3, an annular partition wall 5c is integrally formed in a fillet-like configuration on the outer periphery of each wet liner 5 so as to partition the main coolant gallery 8 and the upstream coolant gallery 11, with an outer periphery of the partition wall 5c being in close contact with the inner surface of the cylinder wall 1e. A plurality of constriction communication passages 12 are defined in each of the partition walls 5c at circumferentially spaced apart locations, so that the main coolant gallery 8 is connected with the upstream coolant gallery 11 through these constriction communication passages 12. Thus, a coolant such as water flowing through the main coolant gallery 8 is passed through the plurality of constriction communication passages 12 into the upstream coolant gallery 11 from which it further flows into the block-side coolant jacket J B . Further, directly above the block-side coolant jacket J B , an annular downstream coolant gallery 13 is defined around the outer periphery of each of the wet liners 5 by the outer peripheral surface of that wet liner 5 and the inner peripheral surface of the cylinder wall 1e of the cylinder block 1, and is in direct communication with the upper end, i.e., the downstream end, of the block-side coolant jacket J B . As shown in Figs. 4 and 10, a plurality of U-shaped dispensing passages 15 --- are defined at circumferentially spaced locations at an upper end of the inner peripheral wall of each cylinder 3. They are in direct communication with the downstream coolant gallery 13 and have upper ends opened to the upper surface of the cylinder 3. As clearly shown in Fig. 1, an endless block-side flange-surrounding coolant gallery 16 is also defined between outer peripheral surfaces of the outward flange portions 5a of the wet liners 5 and upper ends of the inner peripheral surfaces of the cylinders 3 so as to commonly surround the outer peripheral surfaces of the outward flange portions 5a. The block-side flange-surrounding coolant gallery 16 communicates with the plurality of dispensing passages 15 --- and is opened to the deck surface 1a of the cylinder block 1a. Thus, the coolant entering the downstream coolant gallery 13 flows into the plurality of dispensing passages 15 --- from which it flows into the block-side flange-surrounding coolant gallery 16. As clearly shown in Figs. 1 and 8, the adjoining portions of the outward flange portions 5a, 5a of the adjacent wet liners 5, 5 are chamfered as substantially flat chamfered portions f and f which are in contact with each other. As shown in Figs. 5 and 8, a rectilinear inter-flange coolant passage 17 is defined between lower halves at the contacted surfaces of the chamfered portions, with its opposite ends communicating with the block-side flange-surrounding coolant gallery 16 and with its lower surface opened into the downstream coolant gallery 13. Thus, the coolant within the downstream coolant gallery 13 flows into the inter-flange coolant passage 17 and further from opposite ends of the latter into the block-side flange-surrounding coolant gallery 16 as shown in Fig. 8. Longitudinal passages 18, 18 are provided at the opposite ends of the inter-flange coolant passage 17 to permit the direct communication between the downstream coolant gallery 13 and the block-side flange-surrounding coolant gallery 16, so that part of the coolant within the downstream coolant gallery 13 flows through the longitudinal passages 18, 18 directly into a head-side coolant jacket J M which will be described hereinbelow. As clearly shown in Fig. 9, on the other hand, a lower surface of the cylinder head 2 joined to the deck surface 1a of the cylinder block 1 through the gasket G is provided with a head-side flange-surrounding coolant gallery 20 of an inverted U-shaped cross section, opposed to the block-side flange-surrounding coolant gallery 16 through the gasket G. Both coolant galleries 16 and 20 are connected to each other through a plurality of water holes 21 made in the gasket G, as shown in Fig. 10. The flange-surrounding coolant galleries 16 and 20 co-operate to form a flange-surrounding combined coolant gallery GR through which the coolant within the block-side coolant jacket J B flows into the head-side coolant jacket J H . As shown in Figs.4 and 9, the head-side flange-surrounding coolant gallery 20 is connected to the head-side coolant jacket J H through a large number of communication holes 22 --- made in a bottom wall of the cylinder head 2. Head-side longitudinal passages 23, 23 having a diameter larger than that of the communication hole 22 are also provided in the bottom wall of the cylinder head 2 to directly communicate with the block-side longitudinal passages 18, 18, so that the coolant within the downstream coolant gallery 13, as shown by an arrow in Fig.5, can be passed through the block-side longitudinal passages 18, 18, the water holes 21, 21 in the gasket G and the head-side longitudinal passages 23, 23 directly into the head-side coolant jacket J H to cool the heated portions between the adjacent cylinders 3, 3. As shown in Fig.10, the plurality of block-side dispensing passages 15, 15 ---, the plurality of water holes 21, 21 --- provided in the gasket G, and the plurality of head-side communication holes 22, 22 --- are misaligned in phase from each other circumferentially of the cylinder 3, so that the coolant flows therethrough in a zigzag and diverted manner as shown by arrows in Fig.10, wherein it flows uniformly within the flange-surrounding combined coolant gallery G R comprised of the block-side and head-side flange-surrounding coolant galleries 16 and 20. A modification of the portion shown in Fig.10 is shown in Fig.11, wherein circumferential phases of block-side dispensing passages 15, 15 --- and water holes 21 --- in the gasket 21 --- are aligned with each other. In Figs.4, 5 and 9, the reference character V₁ is an intake valve; V E is an exhaust valve; P G is a spark plug; C C is a combustion chamber; and B O is a bolt connecting the cylinder block 1 with the cylinder head 2. The operation of the first embodiment of the present invention shown in Figs.1 to 10 will be described below. The coolant such as water flows into the main coolant gallery 8 driven by the pump 10 connected to the cooling circuit. When the main coolant gallery 8 has been filled up with the coolant, the latter is passed through the plurality of constriction communication passages 12 to increase its flow speed and then flows uniformly within the upstream coolant gallery 11 from which it is supplied into the block-side coolant jacket J B comprising the plurality of coolant passages 6 ---. The coolant entering the coolant passages 6 - -- of the block-side coolant jacket J B flows along the cylinder axis ℓ₁-ℓ₁ and then into the downstream coolant gallery 13, while cooling the outer periphery of the heated body of each wet liner 5 in the cylinder block 1. In this way, the coolant flows from the main gallery 8 via the plurality of constriction communication passages 12 and through the upstream coolant gallery 11 into the block-side coolant jacket J B and hence, the coolant increased in flow speed can be uniformly distributed into the block-side coolant jacket J B and moreover the block-side coolant jacket J B has its cooling surface area substantially increased by the presence of the large number of cooling fins 5b. In addition, because of an enlarged flow sectional area of the common coolant passages 6₁ at the boundary portion between the adjacent wet liners 5, much coolant can be passed through the boundary portion which is usually heated to the highest temperature to effectively cool the boundary portion. The coolant which has entered the downstream coolant gallery 13 flows through the plurality of dispensing passages 15 --- into the block-side flange-surrounding coolant gallery 16 as shown in Fig.10 or 11 and further from the latter through the communication holes 21 --- in the gasket G into the head-side flange-surrounding coolant gallery 20. During this time, the highly heated portions such as the outer periphery of the outward flange portion 5a of the wet liner 5 and the joined surfaces of the cylinder block 1 and the cylinder head 2 can be uniformly and effectively cooled by the coolant. Then, the coolant in the head-side flange-surrounding coolant jacket 20 flows through the plurality of communication holes 22 --- into the head-side coolant jacket J H to cool the cylinder head 2. A portion of the coolant within the upstream coolant gallery 11 flows into the rectilinear inter-flange coolant passage 17 and further from the latter through the relatively large diameter longitudinal passages 18 --- and 23 --- at opposite ends of the passage 17 directly into the head-side coolant jacket J H to intensively cool the adjoining boundary portions of the outward flanges 5a, 5a of the adjacent wet liners 5, 5. A second embodiment of a system according to the invention is shown in Figs.12 to 14, wherein the same parts as those in the previously-described first embodiment are designated by the same reference characters. In the second embodiment, a plurality of cooling fins 30 --- are provided on the lower half of the chamfered portion f of the outward flange 5a of the wet liner 5 to extend in the direction of the cylinder axis ℓ₁-ℓ₁, and a plurality of short coolant passages 31 --- are defined between the cooling fins 30 ---, so that the downstream coolant gallery 13 is permitted to communicate with the inter-flange coolant passage 17 through the short passages 31. Thus, the coolant within the downstream coolant gallery 13, as shown by arrows in Fig.13, can be passed through the short passages 31 --- between the plurality of the cooling fins 30 --- into the inter-flange coolant passage 17 to efficiently cool the adjoining portions of the outward flanges 5a, 5a of the adjacent wet liners 5, 5. A third embodiment of the present invention is shown in Fig.15, wherein the same parts as in the previous first embodiment are designated by the same reference characters. In the third embodiment, a plurality of cooling fins 32 ---are provided on each of the mutually-contacting flat chamfered portions f of the outward flanges 5a of the adjacent cylinder liners 5 to extend along the cylinder axis ℓ₁-ℓ₁, and a plurality of coolant passages 33 --- are defined between the cooling fins 32 --- and opened into the upper and lower surfaces of the outward flange 5a to communicate with the downstream coolant gallery 13 and the head-side coolant jacket J H . Thus, the coolant within the downstream coolant gallery 13 can be passed through the plurality of coolant passages 33 -- into the head-side coolant jacket J H to efficiently cool the adjoining portions of the outward flanges 5a, 5a of the adjacent wet liners 5, 5. A fourth embodiment of the present invention will be described below with reference to Figs.16 to 22. In the following description, the same parts as in the previous first embodiment are denoted by the same reference characters. Referring to Figs.16 to 18, a body E' of an engine is comprised of a cylinder block 101 including four cylinder bores 4 having the same structure as in the previous first embodiment and arranged on a straight line, a cylinder head 102 joined to a deck surface 101a of the cylinder block 101 through a gasket G, and a crank case 103 coupled to a lower surface of the cylinder block 101. A head cover 105 is attached to an upper surface of the cylinder head 102 through a cam case 104, and an oil pan 106 is joined to a lower surface of the crank case 103. A crank shaft 107 is rotatably carried on mated surfaces of the cylinder block 101 and the crank case 103, and pistons 108 --- are slidably received in the corresponding cylinder bores 4 --- in the cylinder block 101 and connected to the crank shaft 107 through connecting rods 109 ---. The cylinder block 101 except a rigid membrane member 110 is integrally formed from Fe or a light alloy material such as Al and Mg alloys by casting, and the entire cylinder block 101 is rectangular. More specifically, the cylinder block 101 is constructed by three parts integrally formed: a cylinder barrel-combined block 111, a framework 112 and a rigid membrane member 110, so as to have a light weight, a high strength and a high rigidity. The cylinder barrel-combined block 111 forms a kernel portion as a main strength member for the cylinder block 101, and is constructed as a unit which comprises four cylinders 3 --- arranged in a row with their adjoining boundary portions in communication with one another. A wet liner 5 having an outward flange 5a at its upper end is inserted into each of the cylinders 3, thereby defining cylinder bores 4 --- each having a vertically extending axis. The framework 112, which is a strength member for the cylinder block 101, is integrally formed into a three-dimensional lattice by casting from the same material as the combined block 111 so as to surround an outer periphery of the cylinder barrel-combined block 111, and is comprised of the following components integrally coupled: a plurality of transverse beams 113 --- projecting from the cylinder barrel-combined block 111 in a lateral direction substantially perpendicular to the crank axis, longitudinal beams 114 --- having a square cross-section and connected to outer ends of the transverse beams 113 ---, and pillars 115. The plurality of the longitudinal beams 114 are provided at substantially uniform distances, spaced apart vertically of the cylinder barrel-combined block 111, so as to extend in parallel to one another and longitudinally of the combined block 111, while the plurality of pillars 115 are provided at substantially uniform distances, spaced apart longitudinally of the cylinder barrel-combined block 111, so as to extend in parallel to one another and vertically of the combined block 111. The construction of such framework 112 by framing the transverse beams 113 ---, the longitudinal beams 114 --- and the pillars 115 into a three dimensional lattice ensures that the framework has high bending and torsional strength while being lightweight. The rigid membrane member 110, 110 comprising either a single metal sheet such as steel or aluminum sheet, or a single reinforced synthetic resin sheet such as FRP or FRM, is bonded with an adhesive directly to each of those rectilinear left and right outer side faces of the framework 112 which extend vertically along the axes of the cylinder bores 4. Such adhesive used may be, for example, FM-300 (made by American Cyanamid Corp.) comprising essentially a heat-resistant epoxy-based resin. The formation of the left and right outer side faces of the framework 112 into a vertically straight surface ensures that the rigid membrane member 110, 110 can be also formed from a sheet material having vertically straight faces, and the fabrication thereof into a high rigidity member or a vibration damper is facilitated. The rigid membrane member 110 is capable of receiving a flexing action on the cylinder block 101 and a torsional vibration about the crank shaft 107 mainly as thrust stresses, because of its rectilinear form substantially parallel to the axes of the cylinder bores 4 ---. In such cylinder block 101, as shown in Figs.16 and 18, a block-side coolant jacket J B or the like is defined between each of the wet liners 5 --- and each of the cylinders 3 ---, and a rectilinear inter-flange coolant passage 17 is defined between the outward flange portions 5a, 5a of the adjacent wet liners 5, 5. The construction of them is completely the same as in the previous first embodiment, and the description thereof is omitted herein. The crank case 103 is formed so that its planar shape may be substantially identical to the planar shape of the cylinder block 101. Accordingly, as shown in Figs.16 and 17, the assembly of the cylinder block 101 coupled with the crank case 103 is constructed into a rectangular structure where all of front and rear end faces and left and right side faces of the engine body E' are vertically straight. The cylinder head 102 coupled to the cylinder block 101 forms combustion chambers C C --- above the pistons 108 in sections corresponding to the cylinder bores 4 ---, and a pair of exhaust valves V E and a pair of intake valves V I are openably and closably disposed in the cylinder head 102 in association with each of the combustion chambers C C ---. More specifically, in order to construct a so-called cross-flow type intake and exhaust system, exhaust ports 116 are opened in a side face of the cylinder head 102 at one of lateral sides (right side as viewed in Fig.16) of the direction X of arrangement of the combustion chambers C C ---, i.e., in the axial direction of the crank shaft 107 (see Fig.19) so as to correspond to the combustion chambers C C ---, respectively, and intake ports 117 are opened in a side face of the cylinder head 102 at the lateral other side (left side as viewed in Fig. 16) to correspond to the combustion chambers C C ---. At opposed places in a ceiling surface of the combustion chamber C C , there are a pair of exhaust openings 118 leading to the exhaust ports 116, and a pair of intake openings 119 leading to the intake ports 117, and there are exhaust valves V E arranged to open the exhaust openings 118 and intake valves V I arranged to open and close the intake openings 119, respectively. Each exhaust valve V E and each intake valve V I is biased in a closing direction by valve springs 120 and 121, and the cam case 104 carries essential parts of an exhaust-side valve operating device for opening and closing the exhaust valves V E as well as essential parts of an intake-side valve operating device for opening and closing the intake valves V I . At a place corresponding to a central portion of each of the combustion chambers C C ---, the cylinder head 102 is integrally provided with a cylindrical central block 124 extending upwardly in order to permit a spark plug P G to project into each of the combustion chambers C C ---. It is to be noted that the cylinder head 102 is coupled to the cylinder block 101, with outer surfaces of outside walls 125 and 126 of the head, located at laterally opposite sides in the direction X of arrangement of the combustion chambers C C ---, being substantially aligned with laterally opposite side faces of the cylinder block 101. Specifically, in the cylinder block 101, the rigid membrane members 110 are each disposed as an outside wall at an outer location spaced apart from the cylinder barrel-combined block 111 which provides walls defining the block-side coolant jacket J B and the like, and the cylinder head 102 is coupled to the cylinder block 101 so that the outside walls 125 and 126 thereof are substantially continuous to the rigid membrane members 110, respectively. Moreover, a jacket sidewall 127 is provided in the cylinder head 102 inside the outside wall 126 provided with the intake port 117, in order to define a head-side coolant jacket J H communicating with the block-side coolant jacket J B . Thus, the head-side coolant jacket J H is defined between the jacket sidewall 127 and the outside wall 125 at the laterally one side. Referring also to Figs. 19, 20, 21 and 22, the head-side coolant jacket J H comprises a gallery portion 128 extending in the direction X of arrangement of the combustion chambers C C --- at laterally one side in that direction X, i.e. on that side of the outside wall 125 in which the exhaust ports 116 are disposed, a plurality of, i.e. four in this embodiment, first branch passages 129 disposed above the respective combustion chambers C C --- so as to surround the central block 124, a plurality of, i.e. three in this embodiment, second branch passages 130 disposed each between the adjacent combustion chambers C C , and two third branch passages 131 disposed outside of the first branch passages 129 at the opposite ends in the direction X of arrangement of the combustion chambers C C ---. In order to provide a dominant flow of the coolant within the head-side coolant jacket J H from the laterally other side to the one side in the direction X of arrangement of the combustion chambers C C --- (from the left side to the right side as viewed in Fig. 16, and from the upper side to the lower side as viewed in Fig. 19), the branch passages 129, 130 and 131 are commonly in communication with the gallery portion 128 and also with the block-side coolant jacket J B . As in the previous first embodiment, on a lower joined surface 132 of the cylinder head 102 coupled to the deck surface 101a of the cylinder block 101 through the gasket G, there is provided a head-side flange-surrounding coolant gallery 20 which communicates with a block-side flange-surrounding coolant gallery 16 (see Figs. 3, 4 and 16) of the block-side coolant jacket L B through holes made in the gasket G and which has a shape corresponding to that of the gallery 16. Further, as in the previous first embodiment, the cylinder head 102 is provided with a plurality of communication holes 22 and longitudinal passages 23 connecting the coolant gallery 20 and the head-side coolant jacket J H . Specifically, the communication holes 22 are arranged at uniform spacings while communicating with the head-side flange-surrounding coolant gallery 20 formed along a phantom circle corresponding to the block-side and flange-surrounding coolant gallery 16 of the block-side coolant jacket J B and while communicating with the first and third branch passages 129 and 131. The longitudinal passages 23 communicate the head-side flange-surrounding coolant gallery 20 with the second branch passages 130 and are disposed each in a pair corresponding to each of the second branch passages 130. Moreover, each of the communication holes 22 and each of the longitudinal passages 23 are made so that they are inclined upwardly toward the spark plug P G . At places corresponding to the cylinder bores 4 ---outside the head-side flange-surrounding coolant gallery 20, the cylinder head 102 is provided with vertically extending cylindrical bolt-insertion portions 136 and 137 each in a pair, into which bolts (not shown) are inserted for coupling the cylinder head 102 and the cylinder block 101 to each other. The cylindrical bolt-insertion portions 137 are integrally provided on the jacket sidewall 127. The first and second branch passages 129 and 130 are divided by a fin 138 mounted in a projecting manner on a lower wall surface of the head-side coolant jacket J H and curved toward the first branch passage 129. The fin 138 is disposed between the cylindrical insertion portions 136 and 137 so that its opposite ends are spaced apart from these portions, respectively. Therefore, the first and second branch passages 129 and 130 are capable of communicating with each other, but the degree of communication between the passages is set so that the direction of the dominant coolant flow in each of the branch passages 129 and 130 is not obstructed. Furthermore, auxiliary fins 139 are mounted in a projecting manner on the lower wall surface of the head-side coolant jacket J H in correspondence to the second branch passage 130 in order to insure the direction of the dominant coolant flow in the second branch passage 130. The first and third branch passages 129 and 131 are also divided by a fin 140 which is mounted in a projecting manner on the lower wall surface of the head-side coolant jacket J H and curved toward the first branch passage 128. The fin 140 is disposed between the cylindrical insertion portions 136 and 137 so that its opposite ends are spaced apart from these portions, respectively. Therefore, the first and third branch passages 129 and 131 are capable of communicating with each other, but the degree of communication between the passages 129 and 131 may be set so that the direction of the dominant coolant flow in each of the branch passages 129 and 131 is not obstructed. Furthermore, an auxiliary fin 141 is mounted in a projecting manner on the lower wall surface of the head-side coolant jacket J H in correspondence to the third branch passage 131 in order to insure the direction of the dominant coolant flow in the third branch passage 131. In this manner, not only the central block 124, the pair of exhaust openings 118, and the pair of intake openings 119 but also the first branch passage 129 surrounding guide portions 142 for the exhaust valves V E are defined between the second branch passages 130, 130 on the opposite sides, or between the second and third branch passages 130 and 131. Moreover, in view of the fact that the lower wall surface of the head-side coolant jacket J H is raised upwardly at places corresponding to the combustion chambers C C ---, the upper wall surface of the head-side coolant jacket J H is formed so that its portion corresponding to the first branch passage 129 may be at a level higher than portions corresponding to the second and third branch passages 130 and 131 on the opposite sides thereof, thereby avoiding that the flow speed of the coolant in the first branch passage 129 is too fast. At a portion corresponding to the second branch passage 130, the upper wall surface of the head-side coolant jacket J H is sloped so that it may be gradually raised toward the gallery 128. This has the effect that the closer to the gallery 128, the larger the amount of the coolant flowing in the second branch passage 130, because the pair of longitudinal passages 23, 23 are disposed at starting and terminating ends of the second branch passage 130 in the direction of flow of the coolant. Further, the first branch passage 129 and the gallery 128 are divided by a fin 143 which is mounted in a projecting manner on the lower wall surface of the head-side coolant jacket J H between the adjacent cylindrical bolt-insertion portions 136, 136 in the direction X of arrangement of the combustion chambers. Moreover, the fin 143 is formed in a curved manner toward the gallery 128 between the bolt-insertion portions 136, 136 so that its opposite ends are spaced apart from these portions 136, respectively. Thus, the coolant passing through the first, second and third branch passages 129, 130 and 131 flows through between the fin 143 and the bolt-insertion portions 136, 136 into the gallery 128. The operation of the fourth embodiment will be described below. The coolant which has cooled the cylinder block 101 in the block-side coolant jacket J B and the like enters the head-side coolant jacket J H to cool the cylinder head 102 and is then discharged. The head-side coolant jacket J H is formed with its flow area relatively decreased by the jacket side wall 127 disposed inside the outside wall 126, in spite of the cylinder head 102 being formed widely in correspondence to a wide formation of the cylinder block 101 in order to insure a high rigidity and a high strength. Therefore, the speed of the coolant flowing in the head-side coolant jacket J H can be increased to a relatively high level and hence, it is possible to efficiently cool the cylinder head 102, except for portions not required to be cooled. Furthermore, the head-side coolant jacket J H is divided into the gallery 128, the first branch passage 129, the second branch passage 130 and the third branch passage 131, so that the coolant entering the individual branch passages 129, 130, 131 flows with its dominant flow direction toward the gallery 128. Therefore, it is possible to permit the coolant to flow at respective suitable speeds in the branch passages 129, 130, 131, to improve the cooling efficiency and moreover to eliminate the influences of the adjacent cylinders on each other. That portion of the cylinder head 102 which is heated to the highest temperature is a portion corresponding to the combustion chamber C C , i.e., a portion corresponding to the first branch passage 129, while that portion of the cylinder block 101 which is heated to the highest temperature is a portion corresponding to a section located between the adjacent cylinder bores. The coolant passed between the adjacent cylinder bores 4 in the block-side coolant jacket J B flows from the block-side longitudinal passage 18 through the head-side longitudinal passages 23 into the second branch passage 130, and cannot basically enter the first branch passage 129. Thus, it is possible to guide the coolant having a relatively low temperature into the first branch passage 129, thereby efficiently cooling the highly heated portion corresponding to the combustion chamber C C . Fig. 23 illustrates a fifth embodiment, wherein the same parts as in the above fourth embodiment are designated by the same reference characters. In the fifth embodiment, a head-side coolant jacket J H ' is defined between jacket sidewalls 127 and 144 which are disposed inside the opposite outside walls 125 and 126 of the cylinder head 102, respectively. Also in this embodiment, it is possible to increase the flow speed of coolant in the head-side coolant jacket J H ' to a relatively fast level, thereby improving the cooling efficiency. Although the above embodiments of the present invention have been described as applied to a four-cylinder engine, it will be understood that the present invention is applicable to other types of multi-cylinder engines, and also that an oil or another liquid may be used as a coolant instead of water. It will thus be seen that the present invention, at least in its preferred forms, provides a cooling system for a multi-cylinder engine, which is designed to ensure a uniform flow of a coolant and to provide an increase in cooling area and in flow speed of the coolant, thereby substantially improving the total cooling efficiency; and furthermore provides a cooling system for a multi-cylinder engine, in which a coolant is allowed to flow uniformly directly along an outer periphery of an outward flange of each of a plurality of cylinder liners and particularly, even when adjacent ones of such flanges have portions contacted with each other, the coolant is allowed to flow between such contacted portions, and as a result it is possible to uniformly and efficiently cool the outward flange of a cylinder liner heated to a relatively high temperature; and furthermore provides a cooling system for a multi-cylinder engine, which is designed to prevent the flow speed of a coolant in a head-side coolant jacket from being reduced.

Claims: A cooling system of a multi-cylinder engine having a plurality of cylinder liners (5) fitted in a row in a cylinder block (1), said system comprising a block-side coolant jacket (J B ) which surrounds the outer peripheral portions of the said cylinder liners so that a coolant can flow through said jacket from the lower end to the upper end of the cylinder liners, characterised by further comprising an upstream coolant gallery (11) located upstream of said block-side coolant jacket and surrounding each of the outer peripheries of the cylinder liners, and a main coolant gallery (8) having an inlet port (9) connected to a cooling circuit and being located upstream of said upstream coolant gallery, at the lower end of the cylinder liners, and commonly surrounding the cylinder liners, the said main coolant gallery communicating with the said upstream coolant gallery through constricted communication passage means (12) provided therebetween and around the outer periphery of each of the cylinder liners. A cooling system according to claim 1, wherein said constricted communication passage means comprises a plurality of communication passages (12) provided for each cylinder liner (5) at circumferentially spaced locations around the outer periphery of the cylinder liner. A cooling system according to claim 1 or 2, wherein said block-side coolant jacket (J B ) includes a plurality of coolant passages (6,6₁) defined around each of the cylinder liners (5) and extending parallel to the axis of the cylinder liner. A cooling system according to any of claims 1 to 3, further including a downstream coolant gallery (13) provided around the outer periphery of each of the cylinder liners (5) downstream of said block-side coolant jacket (J B ), said downstream coolant gallery being in communication with a downstream end of said block-side coolant jacket. A cooling system according to claim 4, wherein said main coolant gallery (8), said upstream coolant gallery (11), said block-side coolant jacket (J B ) and said downstream coolant gallery (13) are defined in a sequentially layered relation along the axes (ℓ₁-ℓ₁) of the cylinder liners (5) from the lower ends toward the upper ends of the same. A cooling system according to any preceding claim, wherein said block-side coolant jacket (J B ) is directly defined between said cylinder liners and a cylinder wall of said cylinder block (1). A cooling system according to any preceding claim, wherein the engine further includes a cylinder head (2,102) connected to the cylinder block (1,101) and having a head-side coolant jacket (J H ,J H ') which surrounds a plurality of combustion chambers (C C ) defined above the pistons (108), the head-side coolant jacket communicating with the block-side coolant jacket (J B ), outside walls (125,126) of said cylinder head being located on opposite sides of the axis (ℓ₂-ℓ₂) of a crank shaft (107) which is substantially aligned with opposite outside walls of said cylinder block, said cylinder head having a jacket sidewall (127) disposed inside at least one (126) of its said opposite outside walls in the axial direction (ℓ₂-ℓ₂) of the crank shaft for defining the head-side coolant jacket. A cooling system according to claim 7, wherein the engine further includes an exhaust port (116) provided in one of the opposite outside walls (125) of said cylinder head (102) in the axial direction of the crank shaft (107) and an intake port (117) provided in the other outside wall (126), said jacket sidewall (127) being disposed inside said outside wall (126) having said intake port provided therein, said head-side coolant jacket (J H ,J H ') being defined between said jacket sidewall and said outside wall (125) having said exhaust port provided therein. A cooling system according to claim 8, wherein said head-side coolant jacket (J H ,J H ') comprises a plurality of passages (129,130,131) divided from one another to independently cool the plurality of combustion chambers (C C ), and a coolant gallery portion (128) provided in the outside wall (125) having the exhaust port (116) provided therein and extending in the direction of arrangement of the combustion chambers so as to commonly communicate with the said plurality of passages. A cooling system according to any of claims 7 to 9, wherein said cylinder block (1,101) includes an outside wall portion at a location spaced outwardly from the wall defining the block-side coolant jacket (J B ), said opposite outside walls (125,126) of the cylinder head (102) in the axial direction of the crank shaft (107) being disposed in an aligned relation to said outside wall portion of the cylinder block.

Inventors: INOUE KAZUO C O KABUSHIKI KAIS, KISHI NORIYUKI C O KABUSHIKI K, KONNO TSUNEO C O KABUSHIKI KAI, MIYAO MASAKATSU C O KABUSHIKI, NAKAMURA KATSUNORI C O KABUSHI, SHIMADA HIROO C O KABUSHIKI KA, TAKETOMI HARUMI C O KABUSHIKI, INOUE, KAZUO C/O KABUSHIKI KAISHA, KISHI, NORIYUKI C/O KABUSHIKI KAISHA, KONNO, TSUNEO C/O KABUSHIKI KAISHA, MIYAO, MASAKATSU C/O KABUSHIKI KAISHA, NAKAMURA, KATSUNORI C/O KABUSHIKI KAISHA, SHIMADA, HIROO C/O KABUSHIKI KAISHA, TAKETOMI, HARUMI C/O KABUSHIKI KAISHA
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1989
Main classification: F02F7
IPC codes: F02F1, F02B1, F01P3, F02B75, F02F7