JP2018091260A - Cooling structure of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling structure of an internal combustion engine capable of efficiently cooling an exhaust port side of a cylinder head.SOLUTION: A water jacket 29 includes a head lower exhaust side jacket 52 formed at a cylinder block 7 side with respect to an exhaust port 19 of a cylinder head 8, and a head upper exhaust side jacket 53 formed at a head cover 11 side with respect to the exhaust port 19 of the cylinder head 8. An introduction hole 56 is formed on the cylinder head 8 in a manner that an introduction port 56a is opened on a second side face 8d at an exhaust port 19 side of the cylinder head 8, or on an end face 8a at a side opposite to the cylinder block 7, of the cylinder head 8, and reaches the head lower exhaust side jacket 52 through the head upper exhaust side jacket 53 while communicated with the head upper exhaust side jacket 53 from the introduction port 56a.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a cooling structure for an internal combustion engine.

  As a cooling device for an internal combustion engine, a cooling water passage for circulating cooling water to the cylinder head and the cylinder block is provided, and the cooling water passage is formed in the cooling water inlet portion provided in the upper portion of the exhaust manifold and the inside of the cylinder head. A head water jacket, a block water jacket formed around each cylinder, a communication path connecting the head water jacket and the block water jacket, and a cooling water outlet portion provided at a lower portion of the exhaust manifold, A cooling water inlet portion and a cooling water outlet portion are known to be arranged at the center in the direction in which the cylinders are arranged (Patent Document 1).

  In the cooling device described in Patent Document 1, the head water jacket is formed between the head water jacket main body formed around the combustion chamber and the like, the exhaust manifold, and the cooling water inlet, and passes through the cooling water guide path. An upper water jacket connected to the head water jacket main body, and a lower water jacket formed between the exhaust manifold and the cooling water outlet. The communication path includes an intake side communication path that connects the block water jacket and the head water jacket main body, and an exhaust side communication path that connects the block water jacket and the lower water jacket. Cooling water in order from the cooling water inlet, upper water jacket, cooling water guideway, head water jacket body, intake side communication path, block water jacket (from intake side to exhaust side), exhaust side communication path, lower water jacket It is discharged to the outside through the cooling water outlet.

JP 2009-216029 A

  However, in the cooling device described in Patent Document 1, the cooling water flowing in from the cooling water inlet directly flows into the upper water jacket, but the head water jacket main body and the block water jacket are circulated through the lower water jacket. Later warm water flows. Therefore, the exhaust port side of the cylinder head cannot be efficiently cooled.

  In view of such a background, an object of the present invention is to provide a cooling structure for an internal combustion engine that can efficiently cool the exhaust port side of a cylinder head.

  In order to solve such a problem, an embodiment of a cooling structure of an internal combustion engine (1) according to the present invention includes a cylinder block (7) that defines at least one cylinder (6), and the at least one cylinder At least one combustion chamber (14) is defined between at least one piston (13) slidably provided on the cylinder and one end of the cylinder block, and between the at least one piston; A cylinder head (8) defining an intake port (18) and an exhaust port (19) communicating with at least one combustion chamber, and an end face (8a) on the side opposite to the cylinder block of the cylinder head are coupled. A head cover (11), a water jacket (29) formed at least on the cylinder head, and the water jacket; An introduction hole (56) for introducing cooling water into the water jacket and at least one discharge hole (57, 59) for discharging cooling water from the water jacket, wherein the water jacket is connected to the exhaust port of the cylinder head. A head lower exhaust side jacket (52) formed on the cylinder block side and a head upper exhaust side jacket (53) formed on the head cover side with respect to the exhaust port of the cylinder head, and the introduction A hole is formed in the cylinder head so as to open an introduction port (56a) on a side surface (8d) of the cylinder head on the exhaust port side or the end surface (8a) of the cylinder head. Communicating with the upper exhaust side jacket and passing through the upper exhaust side jacket, the lower exhaust side of the head Leading to the jacket.

  According to this configuration, the cold cooling water introduced from the introduction hole flows directly to the head upper exhaust side jacket and the head lower exhaust side jacket. Therefore, the exhaust port side of the cylinder head is efficiently cooled.

  Preferably, in the above configuration, the at least one cylinder (6) includes two cylinders (6), and the water jacket (29) covers the combustion chamber (14) from the head cover (11) side. Further comprising a head main jacket (51) formed in the cylinder head (8) and communicating with the head lower exhaust side jacket (52) and the head upper exhaust side jacket (53), and the at least one discharge hole ( 57, 59) includes two head discharge holes (57) formed on the side of the intake port (18) of the cylinder head and at positions corresponding to the two cylinders so as to communicate with the head main jacket. .

  According to this configuration, the cooling water flowing through the head upper exhaust side jacket and the head lower exhaust side jacket flows into the head main jacket, and from the exhaust side to the intake side toward the two head discharge holes, It flows to both of the parts that cover the two combustion chambers. For this reason, both of the portions defining the combustion chamber of the cylinder head are cooled.

  Preferably, in the above configuration, the introduction hole (56) is disposed between the two cylinders (6) in the cylinder row direction.

  According to this configuration, the cooling water flows evenly through the portion of the head main jacket covering the two combustion chambers. Therefore, the part which defines the combustion chamber of a cylinder head is cooled equally, without varying between cylinders.

  Preferably, in the above-described configuration, the water jacket (29) is connected to the head main jacket (51) via a plurality of communication holes (58) formed at least on the exhaust port (19) side of the cylinder head (8). And a block water jacket (55) formed in the cylinder block (7) so as to communicate with the cylinder block (7), wherein the at least one discharge hole (57, 59) communicates with the block water jacket. The block further includes a block discharge hole (59) formed on the intake port (18) side of the block.

  According to this configuration, the cooling water flowing into the head main jacket from the introduction hole via the head upper exhaust side jacket or the head lower exhaust side jacket flows into the block water jacket from the exhaust port side toward the block discharge hole. Flows through the block water jacket to the intake side. Therefore, the cylinder block is also cooled.

  Preferably, in the configuration described above, a wall surface (8e) defining the head exhaust side jacket is formed in a communication portion between the head exhaust side jacket (53) and the introduction hole (56) of the cylinder head (8). ) Projecting from the head upper exhaust side jacket is provided so as to surround the introduction hole.

  According to this configuration, it is possible to suppress the cooling water flowing through the introduction hole from flowing more in the head exhaust side jacket near the introduction port than in the head lower exhaust side jacket. Thereby, both the cylinder block side and the head cover side can be efficiently cooled with respect to the exhaust port in the cylinder head.

  Preferably, in the above configuration, in the mounting posture on the vehicle, the cylinder block (7) has a cylinder axis (6X) such that the exhaust port (19) is on the lower side and the intake port (18) is on the upper side. ) Is extended almost horizontally.

  According to this configuration, the cooling water that has flowed into the head lower exhaust side jacket and the head upper exhaust side jacket disposed below the water jacket from the introduction hole absorbs heat and easily flows upward. Therefore, when the introduction of the cooling water into the water jacket continues, the circulation of the cooling water becomes smooth, and after the introduction of the cooling water into the water jacket is stopped, the cooling heated on the exhaust side of the cylinder head Cooling of the exhaust side of the cylinder head is continued by convection of water in the water jacket.

  Thus, according to the present invention, it is possible to provide a cooling structure for an internal combustion engine that can efficiently cool the exhaust port side of the cylinder head.

Schematic configuration diagram of an internal combustion engine according to an embodiment The perspective view which showed the water jacket of the internal combustion engine shown by FIG. 1 from diagonally upward. The perspective view which showed the water jacket of the internal combustion engine shown by FIG. 1 from diagonally downward. 3 is an enlarged cross-sectional view of the cylinder head taken along IV-IV in FIG. The perspective view of the water jacket corresponding to FIG. 2 which shows the flow of cooling water The perspective view of the water jacket corresponding to FIG. 3 which shows the flow of cooling water

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view of an internal combustion engine 1 according to the embodiment. As shown in FIG. 1, an internal combustion engine 1 includes an engine body 2 that is a reciprocating engine that uses gasoline as fuel, an intake system 3 that supplies intake air to the engine body 2, and exhaust that is discharged from the engine body 2 to the outside. And an exhaust system 4 for discharging.

  The engine body 2 includes a cylinder block 7 that defines a cylinder 6 and a cylinder head 8 that is coupled to one end of the cylinder block 7. In the present embodiment, the cylinder block 7 defines two cylinders 6. The two cylinders 6 are arranged in a direction orthogonal to the paper surface, and the direction orthogonal to the paper surface is the cylinder row direction. At the other end of the cylinder block 7, an upper case 9U (skirt portion) that forms the upper portion of the crankcase 9 is integrally formed. The crankcase 9 includes an upper case 9U and a lower case 9L coupled to an end of the upper case 9U opposite to the cylinder block 7, and defines a crank chamber 10 therein. A head cover 11 is coupled to an end surface 8 a of the cylinder head 8 on the side opposite to the cylinder block 7, and the valve head chamber 12 is defined in the cylinder head 8 and the head cover 11.

  A piston 13 is slidably provided in each cylinder 6, and a combustion chamber 14 is formed in a portion of the cylinder 6 between the piston 13 and the cylinder head 8. That is, the cylinder block 7 and the cylinder head 8 define a combustion chamber 14 in cooperation with the piston 13. The piston 13 is a concave type (concave type) in which the central portion of the top surface is concave, and a pent roof type combustion chamber concave portion 8 b is formed on the bottom surface of the cylinder head 8 on the cylinder 6 side. A small end portion of a connecting rod 15 is connected to the piston 13 via a piston pin. The large end of the connecting rod 15 is connected to the crankshaft 16 via a crankpin. The crankshaft 16 is rotatably supported by the crankcase 9 and is housed in the crank chamber 10 in such a manner that both ends protrude from the crankcase 9. Two balancer shafts 17 are rotatably accommodated in a portion of the crank chamber 10 on the side opposite to the piston 13 with respect to the crankshaft 16 in order to reduce vibration of the engine body 2.

  The cylinder head 8 has a first side surface 8c and a second side surface 8d extending in the cylinder axis 6X direction. A plurality (two in this embodiment) of intake ports 18 are opened on the first side face 8c, and a plurality (two in this embodiment) of exhaust ports 19 are opened on the second side face 8d. Each intake port 18 extends from the first side surface 8 c of the cylinder head 8 to the roof surface on the first side surface 8 c side of the corresponding combustion chamber recess 8 b and communicates with the combustion chamber 14. The exhaust port 19 extends from the second side surface 8 d of the cylinder head 8 to the roof surface on the second side surface 8 d side of the corresponding combustion chamber recess 8 b and communicates with the combustion chamber 14. The cylinder head 8 is slidably provided with a plurality of intake valves 20 and a plurality of exhaust valves 21 formed of poppet valves. The intake valve 20 opens and closes the end of the intake port 18 on the combustion chamber 14 side, and the exhaust valve 21 opens and closes the end of the exhaust port 19 on the combustion chamber 14 side. The intake valve 20 and the exhaust valve 21 are normally urged in the closing direction by a valve spring.

  The valve operating chamber 12 is provided with a valve operating mechanism 22 that drives the intake valve 20 and the exhaust valve 21. The valve mechanism 22 includes an intake camshaft 23 and an exhaust camshaft 24 that extend in the direction of the crank axis 16X. The intake camshaft 23 and the exhaust camshaft 24 are rotatably provided at the boundary between the cylinder head 8 and the head cover 11. The intake camshaft 23 opens and closes the intake valve 20 via a swing arm type intake rocker arm 25 that is swingably provided on the cylinder head 8. The exhaust camshaft 24 opens and closes the exhaust valve 21 via a swing arm type exhaust rocker arm 26 that is swingably provided on the cylinder head 8. That is, the internal combustion engine 1 includes a DOHC (Double Overhead Camshaft) type valve operating mechanism 22.

  Two fuel injection valves 28 are attached to the cylinder head 8 so that the nozzle faces the corresponding intake port 18, and two spark plugs are attached so that the electrode faces the corresponding combustion chamber 14. The engine body 2 is water-cooled, and a water jacket 29 through which cooling water flows is formed in a portion covering the combustion chamber 14 in the cylinder head 8 and a portion on the exhaust port 19 side and a portion surrounding the cylinder 6 in the cylinder block 7. Has been. The engine body 2 takes fuel and intake air from the intake port 18 into the combustion chamber 14, burns the fuel in the combustion chamber 14, and discharges the already burned gas (exhaust gas) from the exhaust port 19.

  The intake system 3 includes an intake passage member that defines an intake passage 30 that communicates with an intake port 18 from an air inlet located at an upstream end. The intake system 3 includes an air cleaner 31, an intake shut valve 32, an intake branch portion 33, a throttle valve 34, a supercharger 35 that is a supercharger, and an intake manifold 36 in order from the upstream side. The intake manifold 36 includes an intake chamber 36A on the upstream side and a plurality of (two in this embodiment) intake branch pipes 36B on the downstream side, and a water-cooled intercooler 37 is incorporated in the intake chamber 36A. Yes. A portion of the intake passage 30 passing through these intake passage members (31 to 37) is referred to as a main intake passage 30A, and a portion of the intake system 3 that defines the main intake passage 30A is referred to as an intake system main body portion 3A. .

  The intake system 3 has an intake bypass pipe portion 3B that defines a bypass passage 30B that bypasses the throttle valve 34 and the supercharger 35, in addition to the intake system main body portion 3A that defines the main intake passage 30A. The intake bypass pipe portion 3B is connected to a portion between the supercharger 35 and the intercooler 37 from the intake branch portion 33 in the main intake passage 30A. A bypass valve 38 is provided in the bypass passage 30B.

  The exhaust system 4 includes an exhaust passage member that communicates with the exhaust port 19 and defines an exhaust passage 40 that reaches a tail outlet located at the downstream end. The exhaust manifold 41, the catalytic converter 42, and the Has a silencer. The exhaust manifold 41 has a plurality (two in this embodiment) of exhaust branch pipes 41A on the upstream side and an exhaust collecting pipe 41B on the downstream side.

  Between the exhaust system 4 and the intake system 3, an EGR 45 (Exhaust Gas Recirculation), which is a device for returning the exhaust gas to the intake system 3 and recirculating it, is provided. The EGR 45 defines an EGR passage 46 connected from the downstream side of the catalytic converter 42 in the exhaust passage 40 to the intake branch portion 33 between the intake shut valve 32 and the throttle valve 34 in the intake passage 30. That is, the EGR 45 of the present embodiment is configured as a low pressure EGR that recirculates low pressure exhaust gas to negative pressure intake air. In the EGR passage 46, an EGR cooler 47 and an EGR valve 48 are provided in order from the upstream side.

  The engine body 2 is mounted on a vehicle such as an automobile on a flat floor surface in a posture in which the crank axis 16X is approximately horizontal and the cylinder axis 6X is approximately horizontal. Specifically, the engine body 2 is oriented such that the first side surface 8c where the intake port 18 opens is the upper surface and the second side surface 8d where the exhaust port 19 opens is the lower surface, and the cylinder head 8 side of the cylinder axis 6X is cranked. It is arranged below the rear seat with a slight inclination angle (5 ° in this embodiment, preferably 2 ° to 10 °) in a direction higher than the case 9 side.

  Hereinafter, the vertical direction is determined based on the mounting posture on the vehicle. The engine body 2 may be mounted with the cylinder head 8 facing forward, rearward, leftward, or rightward of the vehicle. In the following, for convenience of explanation, it is assumed that the engine body 2 is mounted on the vehicle with the cylinder head 8 facing the rear of the vehicle, and the front-rear and left-right directions based on the vehicle are used. Therefore, the end surface 8a to which the head cover 11 of the cylinder head 8 is fastened is the rear surface.

  In the lower part of the crankcase 9, an oil recovery portion 9 a that protrudes downward is formed in order to recover oil used for lubrication of each sliding portion of the engine body 2. The recovered oil is stored in an oil tank provided separately. An oil supply pipe connecting portion 9 b is formed at the front end of the crankcase 9 so as to supply oil sent from the oil tank to an oil pump provided in the crank chamber 10.

  An oil filter 49 is attached to the upper surfaces of the crankcase 9 and the cylinder block 7 so as to protrude upward. A cooling pipe connecting portion 7 a for discharging cooling water from the water jacket 29 is formed on the intake side wall (upper wall) of the cylinder block 7 so as to protrude upward.

  Next, the water jacket 29 of the internal combustion engine 1 having such a configuration will be described in detail.

  FIG. 2 is a perspective view showing the water jacket 29 formed as a cavity in the internal combustion engine 1 shown in FIG. 1 from the diagonally upper side, and FIG. 3 shows the water jacket 29 from the lower side. It is the perspective view shown in. It should be noted that in FIGS. 2 and 3, the water jacket 29 formed as a cavity is substantially shown. As shown in FIGS. 1 to 3, the water jacket 29 has a head water jacket 50 formed on the cylinder head 8 and a block water jacket 55 formed on the cylinder block 7 as main parts.

  The head water jacket 50 includes a head main jacket 51 formed so as to cover the combustion chamber recess 8b from the rear head cover 11 side, and a jacket portion formed on the front cylinder block 7 side (hereinafter referred to as the exhaust port 19). A head lower exhaust side jacket 52) and a jacket portion (hereinafter referred to as a head upper exhaust side jacket 53) formed on the rear head cover 11 side with respect to the exhaust port 19. The head main jacket 51 is formed in a shape corresponding to the two cylinders 6 when viewed from the cylinder axis 6X direction. The head lower exhaust side jacket 52 communicates with the front side (cylinder block 7 side) of the head main jacket 51. The head upper exhaust side jacket 53 communicates with the rear side (head cover 11 side) of the head main jacket 51.

  The block water jacket 55 is formed in one gourd-shaped cylindrical cavity that integrally surrounds the two cylinders 6. That is, the cylinder block 7 is a siamese type cylinder block that defines two cylinders 6 by connecting walls, and the block water jacket 55 is not formed between the two cylinders 6 adjacent to each other.

  In the cylinder head 8, an introduction hole 56 for introducing cooling water into the head water jacket 50 is formed in the lower part (exhaust side) of the cylinder head 8 and between the two cylinders 6 in the cylinder row direction. The introduction hole 56 opens an introduction port 56a serving as an inlet for cooling water on the rear surface of the cylinder head 8 (the end surface 8a on the head cover 11 side), and is straight forward from the introduction port 56a to the front substantially parallel to the cylinder axis 6X. It extends in a shape. The introduction hole 56 extends further forward beyond the head upper exhaust side jacket 53 while communicating with the head upper exhaust side jacket 53, reaches the head lower exhaust side jacket 52, and communicates with the head lower exhaust side jacket 52. .

  In the cylinder head 8, two head discharge holes 57 for discharging cooling water from the head water jacket 50 to the outside are formed in the upper part (intake side) of the cylinder head 8. The two head discharge holes 57 are formed at positions corresponding to the two cylinders 6 so as to communicate with the upper portion of the head main jacket 51. In the present embodiment, each of the two head discharge holes 57 is disposed at a position aligned with the cylinder axis 6X of the corresponding cylinder 6 in a top view.

  In the cylinder head 8, a plurality of communication holes 58 for flowing cooling water from the head water jacket 50 to the block water jacket 55 are formed in the rear portion (on the cylinder block 7 side) of the cylinder head 8. The plurality of communication holes 58 are formed at regular intervals along the circumferential direction of the block water jacket 55.

  A block discharge hole 59 for discharging cooling water from the block water jacket 55 to the outside is formed in the upper part (intake side) of the cylinder block 7. The block discharge hole 59 has a cross-sectional area larger than the total cross-sectional area of the two head discharge holes 57, extends upward from the block water jacket 55, and the upper surface of the cylinder block 7 (cooling pipe connection portion 7 a ) Is open. In the present embodiment, the block discharge hole 59 is disposed above the left cylinder 6 and at a position aligned with the cylinder axis 6X of the left cylinder 6 in a top view.

  As shown in FIG. 3, the lower end portion (exhaust side end portion) of the upper exhaust side jacket 53 and the lower head exhaust side jacket 52 that communicates with the introduction hole 56 is a plate-like shape that extends to the left and right with a substantially constant thickness. It is said that.

  4 is an enlarged cross-sectional view of the cylinder head 8 taken along line IV-IV in FIG. It should be noted that the water jacket 29 is shown as a cavity in FIG. In the cross-sectional view of FIG. 4, the introduction hole 56 is substantially orthogonal to the respective plate-like portions of the head upper exhaust side jacket 53 and the head lower exhaust side jacket 52. The thickness t1 of the plate-like portion of the head upper exhaust side jacket 53 and the thickness of the plate-like portion of the head lower exhaust side jacket 52 are substantially the same (t1≈t2).

  A projecting portion 60 that protrudes forward from a wall surface 8 e that defines the rear surface of the head exhaust side jacket 53 is provided at a communication portion between the head exhaust side jacket 53 and the introduction hole 56 of the cylinder head 8. Is provided in an arc shape so as to surround. As a result, the thickness t3 of the head upper exhaust side jacket 53 at the protrusion 60 is thinner than the thickness t2 of the plate-like portion of the head lower exhaust side jacket 52 (t3 <t2). The communication area between the head upper exhaust side jacket 53 and the introduction hole 56 is smaller than the communication area between the head lower exhaust side jacket 52 and the introduction hole 56.

  Next, the flow of cooling water in the water jacket 29 configured as described above will be described. FIG. 5 is a perspective view of the water jacket 29 corresponding to FIG. 2, in which the flow of cooling water is indicated by arrows, and FIG. 6 is a perspective view of the water jacket 29 corresponding to FIG. FIG.

  As shown in FIGS. 5 and 6, the cooling water flows from the inlet 56 a through the inlet hole 56 to the head upper exhaust side jacket 53 and the head lower exhaust side jacket 52. At this time, the cooling water has an inflow amount corresponding to the distance from the introduction port 56a, the communication area with the introduction hole 56, and the like of each of the head upper exhaust side jacket 53 and the head lower exhaust side jacket 52. 53 and the head lower exhaust side jacket 52. In the head upper exhaust side jacket 53 and the head lower exhaust side jacket 52, the cooling water flows upward while flowing left and right, and flows into the head main jacket 51. A part of the cooling water flowing into the head main jacket 51 flows upward through the head main jacket 51 and is discharged to the outside through the two head discharge holes 57. The remainder of the cooling water flowing into the head main jacket 51 flows into the block water jacket 55 mainly through the communication hole 58 disposed on the lower side (exhaust side), and moves upward so as to go around the block water jacket 55. The air is discharged from the block discharge hole 59 to the outside. The cooling water discharged from the two head discharge holes 57 and the block discharge holes 59 is sent to the radiator for cooling when the water temperature is equal to or higher than a predetermined value, and is returned to the water jacket 29 after cooling. On the other hand, when the water temperature is lower than the predetermined value, the cooling water is returned to the water jacket 29 without being sent to the radiator.

  Next, the operation and effect of the internal combustion engine 1 in which the water jacket 29 is configured in this manner will be described. As shown in FIGS. 1, 5, and 6, in the cooling structure of the internal combustion engine 1 according to the present embodiment, the water jacket 29 is formed on the cylinder block 7 side with respect to the exhaust port 19 of the cylinder head 8. A head lower exhaust side jacket 52 and a head upper exhaust side jacket 53 formed on the head cover 11 side with respect to the exhaust port 19 of the cylinder head 8 are included. The introduction hole 56 is formed in the cylinder head 8 so as to open the introduction port 56a in the end face 8a on the side opposite to the cylinder block 7 of the cylinder head 8, and communicates with the exhaust side jacket 53 on the head from the introduction port 56a. And passes through the head upper exhaust side jacket 53 and reaches the head lower exhaust side jacket 52. Therefore, the cold cooling water introduced from the introduction hole 56 flows directly to the head upper exhaust side jacket 53 and the head lower exhaust side jacket 52, and the exhaust port 19 side of the cylinder head 8 is efficiently cooled. Even if the introduction hole 56 is provided in the second side surface 8d of the cylinder head 8 on the exhaust port 19 side, the same effect can be obtained.

  The water jacket 29 further includes a head main jacket 51 that is formed in the cylinder head 8 so as to cover the combustion chamber 14 from the head cover 11 side and communicates with the head lower exhaust side jacket 52 and the head upper exhaust side jacket 53. . Two head discharge holes 57 are formed at positions corresponding to the two cylinders 6 on the side of the intake port 18 of the cylinder head 8 so as to communicate with the head main jacket 51. Therefore, the cooling water that has circulated through the head upper exhaust side jacket 53 and the head lower exhaust side jacket 52 flows into the head main jacket 51 and heads toward the two head discharge holes 57 from the exhaust side to the intake side. Therefore, both of the portions defining the combustion chamber 14 of the cylinder head 8 are cooled.

  Further, the introduction hole 56 is disposed between the two cylinders 6 in the cylinder row direction. Therefore, the cooling water flows evenly over the portion of the head main jacket 51 that covers the two combustion chambers 14, so that the portion that defines the combustion chamber 14 of the cylinder head 8 is evenly cooled without variation between the cylinders 6. The

  In the present embodiment, the water jacket 29 is a block formed in the cylinder block 7 so as to communicate with the head main jacket 51 via a plurality of communication holes 58 formed at least on the exhaust port 19 side of the cylinder head 8. A water jacket 55 is further included. A block discharge hole 59 is formed on the intake port 18 side of the cylinder block 7 so as to communicate with the block water jacket 55. Therefore, the cooling water flowing into the head main jacket 51 from the introduction hole 56 via the head upper exhaust side jacket 53 or the head lower exhaust side jacket 52 flows into the block water jacket 55 from the exhaust port side and enters the block discharge hole 59. Since the block water jacket 55 flows toward the intake side, the cylinder block 7 is also cooled.

  As shown in FIG. 4, the communicating portion between the head upper exhaust side jacket 53 and the introduction hole 56 of the cylinder head 8 projects from the wall surface 8 e defining the head upper exhaust side jacket 53 to the head upper exhaust side jacket 53. The protruding portion 60 is provided so as to surround the introduction hole 56. As a result, the cooling water flowing through the introduction hole 56 is suppressed from flowing more in the head upper exhaust side jacket 53 near the introduction port 56 a than in the head lower exhaust side jacket 52, and the exhaust port 19 in the cylinder head 8 is suppressed. Both the cylinder block 7 side and the head cover 11 side are efficiently cooled.

  As shown in FIG. 1, in this embodiment, in the mounting position on the vehicle, the cylinder block 7 has the cylinder axis 6 </ b> X approximately horizontally so that the exhaust port 19 is on the lower side and the intake port 18 is on the upper side. It is extended. As a result, the cooling water that has flowed into the head lower exhaust side jacket 52 and the head upper exhaust side jacket 53 disposed from the introduction hole 56 below the water jacket 29 absorbs heat and easily flows upward. Therefore, when the introduction of the cooling water into the water jacket 29 is continued due to the continued operation of the internal combustion engine 1, the circulation of the cooling water becomes smooth. On the other hand, after the introduction of the cooling water into the water jacket 29 is stopped by the operation of the internal combustion engine 1, the cooling water heated on the exhaust side of the cylinder head 8 is convected in the water jacket 29 to exhaust the cylinder head 8. Side cooling continues.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, the specific configuration, arrangement, quantity, angle, and the like of each member and part shown in the above embodiment can be changed as appropriate without departing from the spirit of the present invention. On the other hand, not all the constituent elements shown in the above embodiment are necessarily essential, and can be appropriately selected.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 6 Cylinder 6X Cylinder axis 7 Cylinder block 8 Cylinder head 8a End surface (end surface on the opposite side to a cylinder block)
8c 1st side (side of intake port side)
8d 2nd side (exhaust port side)
8e Wall surface 11 Head cover 13 Piston 14 Combustion chamber 18 Intake port 19 Exhaust port 29 Water jacket 50 Head water jacket 51 Head main jacket 52 Exhaust side jacket under head 53 Exhaust side jacket above head 55 Block water jacket 56 Introduction hole 56a Inlet 57 Head Discharge hole 58 Communication hole 59 Block discharge hole 60 Projection

Claims (6)

A cylinder block defining at least one cylinder;
At least one piston slidably provided on the at least one cylinder;
A cylinder head coupled to one end of the cylinder block, defining at least one combustion chamber with the at least one piston, and defining an intake port and an exhaust port communicating with the at least one combustion chamber; ,
A head cover coupled to an end surface of the cylinder head opposite to the cylinder block;
A water jacket formed on at least the cylinder head;
An introduction hole for introducing cooling water into the water jacket;
And at least one discharge hole for discharging cooling water from the water jacket,
The water jacket is
A head lower exhaust side jacket formed on the cylinder block side with respect to the exhaust port of the cylinder head;
An upper exhaust side jacket formed on the head cover side with respect to the exhaust port of the cylinder head,
The introduction hole is formed in the cylinder head so as to open an introduction port on a side surface on the exhaust port side of the cylinder head or the end surface of the cylinder head, and communicates from the introduction port to the exhaust side jacket on the head. And a cooling structure for an internal combustion engine, which passes through the exhaust gas jacket on the head and reaches the exhaust gas jacket on the bottom side of the head. The at least one cylinder has two cylinders;
The water jacket further includes a head main jacket that is formed on the cylinder head so as to cover the combustion chamber from the head cover side, and communicates with the head lower exhaust side jacket and the head upper exhaust side jacket,
The at least one discharge hole includes two head discharge holes formed on the intake port side of the cylinder head and at positions corresponding to the two cylinders so as to communicate with the head main jacket. The cooling structure for an internal combustion engine according to claim 1.   The cooling structure for an internal combustion engine according to claim 2, wherein the introduction hole is disposed between the two cylinders in a cylinder row direction. The water jacket further includes a block water jacket formed in the cylinder block so as to communicate with the head main jacket through a plurality of communication holes formed on at least the exhaust port side of the cylinder head,
The said at least 1 discharge hole further contains the block discharge hole formed in the said intake port side of the said cylinder block so that it may communicate with the said block water jacket, The Claim 2 or Claim 3 characterized by the above-mentioned. Internal combustion engine cooling structure.   A projecting portion projecting from the wall surface defining the exhaust gas jacket on the head to the exhaust gas jacket on the head is connected to the communication portion between the exhaust gas jacket on the head and the introduction hole of the cylinder head. The cooling structure for an internal combustion engine according to any one of claims 1 to 4, wherein the cooling structure is provided so as to surround the internal combustion engine.   The cylinder block has a cylinder axis extending substantially horizontally so that the exhaust port is on the lower side and the intake port is on the upper side when mounted on a vehicle. The cooling structure for an internal combustion engine according to claim 5.

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