JP5989048B2 - Cylinder head of internal combustion engine - Google Patents

Description

  The present invention relates to a cylinder head of an internal combustion engine in which an exhaust collecting portion is formed.

  In a multi-cylinder engine, a plurality of intake ports and exhaust ports are formed inside a cylinder head, and an intake manifold that distributes intake air and an exhaust manifold that joins exhaust to the intake side surface and the exhaust side surface of the cylinder head, respectively. The form to join is common. In recent years, there is also a configuration in which an exhaust collecting portion for joining exhaust is formed inside a cylinder head, a single exhaust outlet is formed on the exhaust side surface of the cylinder head, and a single exhaust pipe is joined to the cylinder head. is there.

  A multi-cylinder engine with an exhaust collecting part formed in the cylinder head does not require a separate exhaust manifold, so the entire engine can be downsized and the amount of heat released from the exhaust gas can be reduced. The catalyst can be activated by raising the temperature of the catalyst early. Further, since the distance from the combustion chamber to the outlet of the exhaust collecting portion can be shortened, the responsiveness of the supercharger can be improved when a supercharger (turbocharger) that uses exhaust gas is provided.

  On the other hand, in the cylinder head in which the exhaust collecting portion is formed, the portion defining the exhaust outlet and the exhaust collecting portion in the vicinity thereof bulges laterally with respect to the cylinder block (joining surface with the cylinder block). Since it often has a shape, it is necessary to cool the bulging portion in order to prevent heat damage to the cylinder head body and the exhaust pipe due to excessive temperature rise. As a structure that effectively cools the periphery of the exhaust collecting portion formed in the cylinder head, the water jacket (coolant passage) in the cylinder head bulges so as to cover the exhaust collecting portion from the upper surface side and the lower surface side The structure extended to is known (for example, see Patent Document 1).

JP 2000-205042 A

  However, in the cylinder head having the exhaust collecting portion formed inside as described above, if the supercharger or the exhaust gas purification device catalyst is provided immediately downstream of the exhaust outlet, the supercharger or the exhaust gas purification device may become hot. As a result, when the heat load becomes high, the wall of the bulging portion is deformed. In particular, among the walls that define the water jacket, the inner wall located on the inner side defines the exhaust collecting part and is directly exposed to the exhaust gas, which is a heat source, so that it is hotter than the outer wall that is located outside and touches the outside air. Cheap. Thus, when a temperature difference arises between the inner wall and the outer wall, the inner wall is larger than the outer wall and thermally expands in the bulging direction, and stress is concentrated on the end portions on the exhaust outlet side of these walls. In addition, as shown in the cross-sectional view of FIG. 9, such thermal expansion causes deformation that impairs the flatness of the joint surface on which the exhaust outlet is formed, or deformation that deflects the outer wall closer to the inner wall. For this reason, the sealing performance between the cylinder head and the downstream exhaust passage member is lowered, and the cross-sectional area of the water jacket is reduced, which may reduce the cooling performance.

  In view of the problems included in the conventional technology, the present invention is configured such that even if the wall forming the exhaust collecting portion formed in the cylinder head bulges laterally with respect to the cylinder block. An internal combustion engine that can relieve stress concentration due to thermal expansion of the bulging portion, suppress deformation due to thermal expansion, and maintain the sealing performance between the cylinder head and its downstream exhaust passage member and the cooling performance around the exhaust collecting portion. An object is to provide a cylinder head.

  In order to solve such a problem, according to the present invention, a plurality of cylinders (1) are fastened to an upper portion of a cylinder block (2) formed in a row, and the top surface of a piston that slides in the cylinder is formed. A cylinder head (3) of an internal combustion engine (E) having a combustion chamber (6) formed therebetween and provided with an in-head coolant passage (30), the upstream end of which is located in the combustion chamber A plurality of exhaust ports (8a) that open to each other, and an exhaust collecting portion (8b) that joins the plurality of exhaust ports and opens an exhaust outlet (8c) at an intermediate position in the longitudinal direction on one side surface of the cylinder head. A portion (18) that is formed and delimits the exhaust outlet and the vicinity thereof form a bulging portion (19) that bulges laterally with respect to the cylinder block to form the exhaust collecting portion. Jacket A pair of exhaust-side coolant passages (32, 33) formed in the bulging portion so as to sandwich the exhaust collecting portion, and the bulging portion defines a pair of outer walls defining the exhaust-side coolant passage (41, 42) and a pair of inner walls (43, 44), and in a cross section perpendicular to the cylinder row direction and passing through the exhaust outlet, at least one inner surface (41i, 42i) of the pair of outer walls is A first curved region (61, 71) formed at an end on the exhaust outlet side and curved with a first radius of curvature (R1, R3) centered on the exhaust-side coolant passage; The first curved region is formed closer to the combustion chamber than the first curved region, and is curved with a second radius of curvature (R2, R4) larger than the first radius of curvature with the center of curvature located on the exhaust side coolant passage side. Two curved areas (62, 72) and front The second bending region is a structure including a first portion gradually increasing the height of the exhaust-side coolant passage toward the combustion chamber side from at least the exhaust outlet (66, 76).

  According to this configuration, when the inner surface of the outer wall includes the second curved region, the inner wall is heated by the exhaust gas so as to have a higher temperature than the outer wall, and when the thermal expansion is larger than the outer wall in the bulging direction, stress is applied to the outer wall. The stress concentration at the connection portion between the outer wall and the inner wall is alleviated. In addition, since the second curved region includes the first portion that gradually increases the height of the exhaust-side coolant passage, when the outer wall is deformed so as to approach the inner wall, the bulging direction of the outer wall becomes closer to the linear shape. Therefore, deformation that impairs the flatness of the joint surface on which the exhaust outlet is formed is suppressed. Therefore, the sealing performance between the cylinder head and the downstream exhaust passage member can be ensured. In addition, since the second curved region is formed so as to include the first portion that gradually increases the height of the exhaust-side coolant passage, even when the outer wall is deformed so as to approach the inner wall, the exhaust-side coolant passage The cooling performance around the exhaust collecting part can be maintained by securing the height.

  In the above invention, an inner surface (42i) of at least one of the pair of outer walls (42) is formed between the first curved region (71) and the second curved region (72), A third curve having a third radius of curvature (R5) that is larger than the first radius of curvature (R3) and smaller than the second radius of curvature (R4) with the center of curvature located on the exhaust side coolant passage side. It is preferable to further include a curved region (73), and the third curved region is smoothly connected to the first curved region and the second curved region.

  According to this configuration, since the third curved region having an intermediate radius of curvature is formed between the first curved region and the second curved region, the curvature change point during thermal expansion can be obtained. Stress concentration is suppressed, and the stress can be more reliably dispersed.

  In the above invention, the second curved region (62, 72) is continuous from the first portion (66, 76) to the combustion chamber (6) side, and from the exhaust outlet (8c) side. A configuration may further include a second portion (67, 77) for gradually decreasing the height of the exhaust-side coolant passage (32, 33) toward the combustion chamber.

  According to this configuration, since the second curved region having the second radius of curvature can be formed long in the bulging direction, the generated stress can be further dispersed on the outer wall. Further, since the dimension of the outer wall in the bulging direction when the outer wall is deformed so as to approach the inner wall becomes larger, deformation that impairs the flatness of the joint surface on which the exhaust outlet is formed is further suppressed.

  In the above invention, the most part of the outer wall (42) corresponding to the second curved region (72) preferably has a constant thickness (t1).

  According to this configuration, it is possible to eliminate wasteful meat while suppressing stress concentration, and to reduce the weight of the cylinder head.

  In the above invention, the inner surface (42i) of at least one of the pair of outer walls (42) is formed closer to the combustion chamber (6) than the second curved region (72), and the second A straight linear region (74) continuous to the curved region, and the outer wall includes a flat plate portion (42a) having a constant thickness at least at a portion of the linear region on the second curved region side. Then, the thickness (t2) of the portion corresponding to the linear region of the outer wall of the flat plate portion may be thicker than the average thickness (t1ave) of the portion corresponding to the second curved region.

  According to this configuration, if there is a flat plate-like portion continuously in the second curved region, stress tends to concentrate on this portion, but the thickness of the flat plate-like portion is the portion corresponding to the second curved region. By being thicker than the average thickness, it is possible to increase the rigidity of the portion where stress is easily concentrated and suppress deformation.

  In the above invention, the cylinder head (3) is disposed on the upper side in the vertical direction of the internal combustion engine (E), and the pair of outer walls are disposed on the upper outer wall (41) and the lower side. The upper outer wall is integrally formed with a side wall (3S) defining a valve operating chamber (11), and at least an inner surface (42i) of the lower outer wall is formed in the first curved region (42). 71) and the second curved region (72).

  According to this configuration, the upper outer wall has a relatively high rigidity because the side wall is integrally formed, and the moment generated by the load of the downstream exhaust passage member joined to the cylinder head acts as a tensile force. Therefore, although the stress generated at the time of thermal expansion is small, the first curved region and the second curved portion are not formed on the lower outer wall where the side wall is not integrally formed and the load of the downstream exhaust passage member acts as a compressive force. By forming the region, it is possible to effectively disperse the stress generated in the lower outer wall where a large compressive stress is likely to be generated.

  As described above, according to the present invention, the stress concentration due to the thermal expansion of the bulging portion that bulges laterally with respect to the cylinder block is alleviated, and the deformation due to the thermal expansion is suppressed, so that the cylinder head and its downstream exhaust It is possible to provide a cylinder head of an internal combustion engine that can maintain the sealing performance with the passage member and the cooling performance around the exhaust collecting portion.

Sectional drawing of the direction orthogonal to the cylinder row direction of the principal part of the engine which concerns on embodiment Perspective view of cylinder head as seen from below Sectional view of the cylinder head taken along line III-III in FIG. A perspective view of the coolant passage of the cylinder head extracted from an oblique upper side Perspective view of the cylinder head coolant passage extracted from diagonally below Enlarged view of VI in Fig. 1 Explanatory drawing of the principal part of the cylinder head shown in FIG. Sectional view of the main part of an engine according to the prior art Conceptual diagram showing deformation due to thermal expansion of an engine according to the prior art

  Hereinafter, an embodiment in which the present invention is applied to an internal combustion engine for automobiles (hereinafter simply referred to as engine E) will be described in detail with reference to the drawings. Below, it demonstrates according to the up-down direction shown in FIG. 1 on the basis of the state in which the engine E was mounted in the motor vehicle.

  As shown in FIGS. 1 and 2, the engine E is a SOHC 4-valve in-line four-cylinder gasoline engine. As shown in FIG. 1, an engine E includes a cylinder block 2 in which four cylinders 1 in which pistons are accommodated are formed in a row, a box-shaped cylinder head 3 fastened to the top of the cylinder block 2, and a cylinder head 3 and a head cover 4 fastened to the upper portion of the cylinder 3. The cylinder head 3 is mounted on the automobile in a posture in which the cylinder head 3 is arranged on the upper side in the vertical direction. The cylinder block 2 and the cylinder head 3 are cast from an aluminum alloy.

  The cylinders 1 extend in a substantially vertical direction, and are formed in the cylinder block 2 in parallel with each other. Hereinafter, the arrangement direction of the plurality of cylinders 1 arranged in a row is referred to as a cylinder row direction. Each cylinder 1 has an upper end opened to the upper end surface 2 a of the cylinder block 2, and a lower end opened to a crank chamber (not shown) formed in the lower part of the cylinder block 2. An in-block coolant passage 5 (in-block water jacket) is formed on the side of the cylinder 1 of the cylinder block 2 so as to integrally surround the side periphery of each cylinder 1. The in-block coolant passage 5 is curved so as to extend along the side periphery of each cylinder 1, and the upper end of the in-block coolant passage 5 is open to the upper end surface 2 a of the cylinder block 2. The in-block coolant passage 5 is formed as a cavity by a sand mold or the like when the cylinder block 2 is molded so as to circulate coolant such as coolant, oil or refrigerant.

  A combustion chamber recess 3b, which is a curved recess, is formed in a portion of the joint surface of the cylinder head 3 with the cylinder block 2 (hereinafter referred to as a pair-block joint surface 3a) facing each cylinder 1. Each combustion chamber recess 3 b defines a combustion chamber 6 together with a portion above the piston of each cylinder 1. That is, the cylinder head 3 defines the upper edge of the combustion chamber 6.

  Inside the cylinder head 3, the upstream end opens on one side surface (the left side surface in FIG. 1) along the cylinder row direction of the cylinder head 3, while the bifurcated downstream end is on the wall surface of each combustion chamber recess 3 b. Four intake ports 7 to be opened and two upstream ends open to the wall surface of each combustion chamber recess 3b, while the downstream end is on the other side surface (the right side surface in FIG. 1) along the cylinder row direction of the cylinder head 3. One exhaust collecting port 8 that is open is formed. That is, the exhaust collecting port 8 has a plurality (eight) of exhaust ports 8a opened in the respective combustion chamber recesses 3b and an exhaust collecting portion 8b for collecting all the exhaust ports 8a inside the cylinder head 3. The exhaust collecting portion 8 b forms a single exhaust outlet 8 c on the other side surface of the cylinder head 3. The side on which the intake port 7 is provided with reference to the combustion chamber recess 3b is the intake side, and the side on which the exhaust collection port 8 is provided is the exhaust side.

  In the cylinder head 3, an intake valve 9 for opening and closing each connection portion with the combustion chamber 6 of the intake port 7 and an exhaust valve 10 for opening and closing each connection portion with the combustion chamber 6 of the exhaust collecting port 8 are slidable. Is provided. A valve operating chamber 11 is defined between the cylinder head 3 and the head cover 4, and a valve operating mechanism 12 that opens and drives the intake valve 9 and the exhaust valve 10 is accommodated in the valve operating chamber 11. . The valve operating mechanism 12 includes a camshaft 13 rotatably attached to the cylinder head 3, a rocker shaft 14 disposed above the camshaft 13, an intake rocker arm 15 and an exhaust rocker arm 16 that are swingably supported by the rocker shaft 14. Etc. The camshaft 13 is formed with four valve cams 13 a that drive the pair of intake valves 9 and exhaust valves 10 for each cylinder 1.

  As shown in FIG. 2, the exhaust outlet 8 c is formed at an intermediate position in the longitudinal direction on the exhaust side surface 3 c of the cylinder head 3. Further, an ignition plug insertion hole 17 for inserting an ignition plug (not shown) passes through the upper surface of the cylinder head 3 in the center of the four intake ports 7 and the exhaust collecting port 8 on the wall surface of the combustion chamber recess 3b. Is formed.

  As shown in FIGS. 1 and 2, the exhaust collecting portion 8 b is formed on the exhaust side with respect to the pair-block joint surface 3 a of the cylinder head 3. More specifically, the exhaust outlet 8c is defined by a tubular exhaust outlet tubular portion 18 protruding from the exhaust side surface 3c of the cylinder head 3, and the exhaust outlet tubular portion 18 of the cylinder head 3 and the vicinity thereof are connected to the cylinder block 2. On the other hand, a bulging portion 19 is formed which bulges laterally to form an exhaust collecting portion 8b.

  The distal end surface of the exhaust outlet tubular portion 18 forms a joint surface 18a of a downstream exhaust passage member 20 such as a turbocharger (turbocharger) turbine or an exhaust purification device (not shown). A plurality of (four in the illustrated example) fastening bosses 21 for fastening the downstream exhaust passage member 20 with bolts are formed at the tip of the exhaust outlet tubular portion 18 so as to surround the exhaust outlet 8c. On the other hand, two ribs 22 are formed on the lower surface of the bulging portion 19 so as to reach the fastening boss 21 from the peripheral edge of the anti-block joint surface 3a. These ribs 22 extend in the front-rear direction, which is a direction in which they approach and separate from the cylinder row, and have a C-shape that opens from the fastening boss 21 toward the anti-block joint surface 3a.

  As described above, downstream exhaust passage members 20 such as a supercharger and an exhaust purification device are disposed in front of the cylinder block 2 and the cylinder head 3, and after the engine E is started, these become high temperatures. Therefore, the bulging portion 19 of the cylinder head 3 that bulges laterally with respect to the cylinder block 2 is easy to transfer heat from the supercharger or the exhaust purification device by heat conduction, radiation, and convection, and the lower surface is particularly hot. Prone. When the lower surface of the bulging portion 19 becomes high temperature, the sealing performance between the cylinder head 3 and the downstream side exhaust passage member 20 tends to deteriorate due to deformation accompanying thermal expansion. The ribs 22 extending in the direction approaching and separating from the cylinder row are formed, so that deformation of the bulging portion 19 is suppressed.

  As shown in FIGS. 1 and 3 to 5, in the cylinder head 3, a combustion chamber recess is provided in order to suppress a temperature rise due to heat propagation from the combustion gas in the combustion chamber 6 and the exhaust collecting port 8. 3 b, an in-head coolant passage 30 (31 to 39, an in-head water jacket) is formed around the intake port 7 and the exhaust collecting port 8. The in-head coolant passage 30 is also formed as a cavity by a sand mold or the like when the cylinder head 3 is molded so that coolant such as cooling water, oil, or refrigerant flows, but in FIG. 4 and FIG. The coolant liquid passage 30 in the head, which is a space portion, is actually shown through.

  The in-head coolant passage 30 includes a main coolant passage 31, an upper exhaust side coolant passage 32, a lower exhaust side coolant passage 33, an exhaust side connection passage 34, an intake side coolant passage 35, an intake side connection passage 36, and the like. As the main element. The main coolant passage 31 extends in the cylinder row direction (longitudinal direction) of the cylinder head 3 so as to pass near the upper portion of the plurality of combustion chamber recesses 3b. The upper exhaust side coolant passage 32 and the lower exhaust side coolant passage 33 are disposed so as to sandwich the exhaust collecting portion 8b from above and below, and each extend in the longitudinal direction of the cylinder head 3. The exhaust side connection passage 34 communicates the main coolant passage 31 with the upper exhaust side coolant passage 32 and the lower exhaust side coolant passage 33. The intake-side coolant passage 35 is disposed below the intake port 7 and extends in the longitudinal direction of the cylinder head 3. The intake side connection passage 36 communicates the main coolant passage 31 and the intake side coolant passage 35.

  A broken line in FIG. 2 indicates a portion where the upper end of the in-block coolant passage 5 contacts when the cylinder block 2 and the cylinder head 3 are fastened. In the in-block coolant passage 5, the coolant flows as indicated by the white arrows. At the end where the upper end of the in-block coolant passage 5 is in contact with the anti-block joint surface 3a at one end in the cylinder row direction, the cylinder head 3 extends upward from the anti-block joint surface 3a and communicates with the in-head coolant passage 30. Two coolant inflow passages 37 are formed. The two coolant inflow passages 37 communicate with the exhaust side connection passage 34 and the intake side connection passage 36 arranged on one end side in the cylinder row direction of the in-head coolant passage 30, respectively. Let the coolant flow in.

  Of the broken line portion where the upper end of the in-block cooling fluid passage 5 is in contact with the anti-block joint surface 3a, the other end side in the cylinder row direction from the anti-block fluid inflow passage 37 is located in the cylinder head 3 from the anti-block joint surface 3a. A bypass passage 38 that extends upward and communicates with the in-head coolant passage 30 is formed at an appropriate position. The bypass passage 38 communicates with the exhaust side connection passage 34, the lower exhaust side coolant passage 33, the intake side connection passage 36, or the intake side coolant passage 35 of the in-head coolant passage 30. Each bypass passage 38 is formed to have a smaller channel cross-sectional area than the coolant inflow passage 37.

  As shown in FIGS. 4 and 5, at the other end of the upper exhaust-side cooling fluid passage 32 in the cylinder row direction (the end different from the side where the cooling fluid inflow passage 37 is provided), the cooling fluid is supplied to the in-head cooling fluid. A coolant outflow passage 39 for discharging from the passage 30 is formed. The outer end of the coolant outflow passage 39 communicates with a radiator (not shown) through a pipe, a hose and the like. In the main coolant passage 31, the upper exhaust side coolant passage 32, the lower exhaust side coolant passage 33, and the intake side coolant passage 35, the coolant flows in the cylinder row direction as indicated by black arrows in FIG.

  As shown in FIG. 6, the upper exhaust side coolant passage 32 and the lower exhaust side coolant passage 33 are respectively formed inside the wall that forms the bulging portion 19. That is, in the cross section shown in FIG. 6 that is orthogonal to the cylinder row direction and passes through the exhaust outlet 8c, the bulging portion 19 is outside the upper exhaust side coolant passage 32 and the lower exhaust side coolant passage 33 (the exhaust collecting port 8 is connected). A pair of upper and lower upper outer walls 41 and lower outer walls 42 defining the contour of the outer side as a reference, and a pair of upper and lower upper inner walls 43 defining the inner contours of the upper exhaust side coolant passage 32 and the lower exhaust side coolant passage 33. And a lower inner wall 44. An upper exhaust-side coolant passage 32 is formed between an upper outer wall 41 and an upper inner wall 43 that are spaced apart from each other so as to form a cavity, and a lower outer wall that is spaced apart from each other so as to form a cavity. A lower exhaust-side coolant passage 33 is formed between 42 and the lower inner wall 44. As shown in FIG. 1, the upper outer wall 41 is integrally formed with a side wall 3 </ b> S of the cylinder head 3 that defines the valve operating chamber 11.

  In the cross section of FIG. 6, the exhaust collecting port 8 is formed in a substantially straight line shape. That is, in the same cross section, the inner surfaces 43i, 44i that define the exhaust collecting port 8 of the upper inner wall 43 and the lower inner wall 44 are substantially parallel and flat. On the other hand, as shown in FIGS. 6 and 7, the outer surfaces 43o, 44o defining the upper exhaust side coolant passage 32 and the lower exhaust side coolant passage 33 of the upper inner wall 43 and the lower inner wall 44 are on the combustion chamber 6 side (see FIG. 6). Linear straight regions 51, 52 extending from the inside (left side) to the exhaust outlet 8c (to the right side in the drawing) in parallel with the respective inner surfaces 43i, 44i and before the exhaust outlet 8c; A curved region 53 that is curved with a center of curvature on the exhaust side coolant passages 32 and 33 side (that is, outward with respect to the exhaust collecting port 8) continuously to the straight regions 51 and 52 in the vicinity of the exhaust outlet 8c. 54. That is, the upper inner wall 43 and the lower inner wall 44 have a substantially constant thickness in the straight regions 51 and 52 before the curved regions 53 and 54.

  On the other hand, the inner surface 41i that defines the upper exhaust side coolant passage 32 of the upper outer wall 41 is formed at the end on the exhaust outlet 8c side continuously to the curved region 53 of the outer surface 43o of the upper inner wall 43. A first curved region 61 that is curved with a first radius of curvature R1 with the center of curvature on the side of the passage 32 (that is, inward with respect to the exhaust collecting port 8), and a first curved region that is continuous with the first curved region 61. 61 is formed on the combustion chamber 6 side, and includes a second curved region 62 that is curved with a second curvature radius R2 larger than the first curvature radius R1 with the center of curvature on the upper exhaust side coolant passage 32 side. . The first curved region 61 and the second curved region 62 are smoothly connected. Here, “smoothly” means a state in which the inclination of the tangent line is continued without being bent in this specification. In the present embodiment, the first curvature radius R1 is 3 mm, and the second curvature radius R2 is 110 mm.

  The second curved region 62 is continuous from the exhaust outlet 8c side to the combustion chamber 6 side, the first portion 66 that gradually increases the height of the upper exhaust side coolant passage 32, and from the first portion 66 to the combustion chamber 6 side. And a second portion 67 for gradually reducing the height of the upper exhaust-side coolant passage 32 from the exhaust outlet 8c side toward the combustion chamber 6 side. The end portion of the second curved region 62 on the combustion chamber 6 side further continues to the combustion chamber 6 side via a curved connection portion 64 that curves with the center of curvature on the side opposite to the upper exhaust side coolant passage 32. The straight line region 65 is smoothly connected.

  On the other hand, the inner surface 42i that defines the lower exhaust side coolant passage 33 of the lower outer wall 42 is formed at the end on the exhaust outlet 8c side continuously to the curved region 54 of the outer surface 44o of the lower inner wall 44. A third curved region 71 having a curvature center on the side of the passage 33 and curved with a third radius of curvature R3 is formed on the combustion chamber 6 side with respect to the third curved region 71, and the curvature center on the lower exhaust side coolant passage 33 side. And a fourth curved region 72 that is curved with a fourth radius of curvature R4 that is larger than the third radius of curvature R3, and is formed between the third curved region 71 and the fourth curved region 72, and the lower exhaust side It includes a fifth curved region 73 that is curved with a fifth radius of curvature R5 that is larger than the third radius of curvature R3 and smaller than the fourth radius of curvature R4 with the center of curvature on the coolant passage 33 side. The third curved region 71 and the fifth curved region 73 and the fifth curved region 73 and the fourth curved region 72 are smoothly connected to each other. In the present embodiment, the third curvature radius R3 is 3 mm, the fourth curvature radius R4 is 110 mm, and the fifth curvature radius R5 is 15 mm.

  The fourth curved region 72 is continuous from the exhaust outlet 8c side to the combustion chamber 6 side, the first portion 76 that gradually increases the height of the lower exhaust side coolant passage 33, and the first portion 76 to the combustion chamber 6 side. And a second portion 77 that gradually decreases the height of the lower exhaust-side coolant passage 33 from the exhaust outlet 8c side toward the combustion chamber 6 side. A straight linear region 74 is smoothly connected to the end of the fourth curved region 72 on the combustion chamber 6 side, and the lower exhaust side coolant passage 33 is connected to the end of the linear region 74 on the combustion chamber 6 side. Are smoothly connected to a sixth curved region 75 that is curved with the center of curvature on the opposite side.

  The outer surface 42o of the lower outer wall 42 is continuous with the curved region 82 and a curved region 82 formed so that the thickness of the lower outer wall 42 is substantially constant at a portion corresponding to the fourth curved region 72 of the inner surface 42i. On the combustion chamber 6 side of the curved region 82, there is a straight linear region 84 formed in parallel with the linear region 74 of the inner surface 42i and shorter than the linear region 74. That is, a portion of the lower outer wall 42 corresponding to the straight region 84 of the outer surface 42o constitutes a flat plate portion 42a having a constant thickness. The end portion of the straight region 84 on the combustion chamber 6 side is smoothly connected to an outer curved portion 85 that is curved with the center of curvature on the side opposite to the lower exhaust side coolant passage 33, and the outer curved portion 85 is The connection is made in a bent state with the anti-block joint surface 3a.

  The portion of the lower outer wall 42 corresponding to the fourth curved region 72 is slightly increased in thickness at the end on the combustion chamber 6 side, and the entire length excluding this portion (the portion corresponding to the fourth curved region 72 in FIG. 6). It has a constant thickness t1 (FIG. 7) over the entire length in the left-right direction). The thickness t2 of the flat plate portion 42a of the lower outer wall 42 is constant at the same thickness as the end portion on the gradually increasing side of the portion corresponding to the fourth curved region 72. That is, the thickness t2 of the flat portion 42a of the lower outer wall 42 is thicker than the average thickness t1ave of the portion corresponding to the fourth curved region 72.

  According to the cylinder head 3 of the engine E configured as described above, the following operational effects can be obtained. That is, as shown in FIG. 8, in the conventional cylinder head 103 in which the inner surface 141i of the upper outer wall 141 and the inner surface 142i of the lower outer wall 142 are formed planarly, the inner walls 143 and 144 are heated by exhaust gas, and the outer walls 141 and 142 are heated. When the temperature is higher than that of the outer walls 141 and 142 and the thermal expansion is greater in the bulging direction, the outer walls 141 and 142 and the inner walls 143 and 144 are deformed as shown in FIG. Note that FIG. 9 is a diagram in which the amount of deformation is extremely larger than the actual one for easy understanding.

  That is, since the expansion of the upper inner wall 143 is suppressed by the upper outer wall 141 on the upper side of the bulging portion 19, a compressive stress is generated inside the upper inner wall 143, and distortion occurs so as to be crushed (shrink). On the other hand, at the connection portion between the upper inner wall 143 and the upper outer wall 141 on the exhaust outlet 8c side, compressive stress is generated on the upper inner wall 143 side, tensile stress is generated on the upper outer wall 141, and tensile stress is also generated on the upper outer wall 141. . However, in the illustrated example, since the upper outer wall 141 is formed several times thicker than the upper inner wall 143, the distortion of the upper outer wall 141 is larger on the lower side and smaller on the upper side, and the joint in which the exhaust outlet 8c is formed. The distortion of the surface 18a is relatively small.

  On the other hand, also on the lower side of the bulging portion 19, expansion of the lower inner wall 144 is suppressed by the lower outer wall 142, compressive stress is generated in the lower inner wall 144, and tensile stress is generated in the lower outer wall 142. Since the lower outer wall 142 is formed to have the same thickness as the lower outer wall 142 as in the embodiment, the bending force is exerted on the lower inner wall 144 and the lower outer wall 142 due to the distortion of the joint surface 18a on which the exhaust outlet 8c is formed. Join. In this example, stress concentrates on the end of the lower inner wall 144 on the exhaust outlet 8c side, and the lower inner wall 144 itself is deformed to bend downward (on the lower outer wall 142 side). On the other hand, the lower outer wall 142 is deformed so as to bend upward (on the lower inner wall 144 side) under the influence of the distortion of the joint surface 18a where the exhaust outlet 8c is formed.

  On the other hand, in the present embodiment, as shown in FIGS. 6 and 7, the inner surfaces 41 i, 42 i of the outer walls 41, 42 include the second curved region 62 and the fourth curved region 72, so that the inner wall 43, When 44 is heated by the exhaust gas and becomes hotter than the outer walls 41, 42 and is thermally expanded in the bulging direction larger than the outer walls 41, 42, the stress is distributed to the outer walls 41, 42, and the outer walls 41, 42 and the inner wall 43 , 44 is alleviated from stress concentration at the connecting portion.

  Further, as shown in FIGS. 6 and 7, the second curved region 62 and the fourth curved region 72 include first portions 66 and 76 that gradually increase the height of the exhaust-side coolant passages 32 and 33. When the outer walls 41 and 42 are thermally expanded in the bulging direction larger than the outer walls 41 and 42, the outer walls 41 and 42 are deformed so as to approach the inner walls 43 and 44, and the outer walls 41 and 42 bulge by approaching a linear shape. The direction dimension is increased, and deformation that impairs the flatness of the joint surface 18a on which the exhaust outlet 8c is formed is suppressed. Therefore, the sealing performance between the cylinder head 3 and the downstream side exhaust passage member 20 is ensured. Further, since the second curved region 62 and the fourth curved region 72 are formed so as to include the first portions 66 and 76 that gradually increase the height of the exhaust-side coolant passages 32 and 33, the outer walls 41 and 42 are the inner walls. The height of the exhaust-side coolant passages 32 and 33 is secured even when deformed to approach 43 and 44, and the cooling performance around the exhaust collecting portion 8b is maintained.

  Further, in the present embodiment, the second curved region 62 and the fourth curved region 72 are configured to gradually reduce the height of the exhaust-side coolant passages 32 and 33 continuously from the first portions 66 and 76 to the combustion chamber 6 side. 2 parts 67 and 77 are included. As a result, the second curved region 62 and the fourth curved region 72 having the second radius of curvature R2 and the fourth radius of curvature R4 are formed long in the bulging direction, and the stress is further dispersed in the outer walls 41 and 42. Further, since the dimensions of the outer walls 41 and 42 in the bulging direction when the outer walls 41 and 42 are deformed so as to approach the inner walls 43 and 44 become larger, the flatness of the joint surface 18a on which the exhaust outlet 8c is formed is impaired. Deformation is further suppressed.

  In the lower outer wall 42, a fifth curved region 73 having an intermediate radius of curvature is formed between the third curved region 71 and the fourth curved region 72. Therefore, stress concentration at the curvature change point during thermal expansion is suppressed, and the stress is more reliably dispersed.

  In the present embodiment, most of the portion corresponding to the fourth curved region 72 of the lower outer wall 42 has a constant thickness t1. Therefore, wasteful meat can be eliminated while suppressing the concentration of stress, and the cylinder head 3 is reduced in weight.

  On the other hand, if the flat plate portion 42a exists continuously from the fourth curved region 72 in the lower outer wall 42, stress tends to concentrate on the linear region 74 portion, but in this embodiment, the thickness t2 of the linear region 74 is the fourth. By being thicker than the average thickness t1ave of the portion corresponding to the curved region 72, the rigidity of the portion where stress is likely to concentrate increases, and deformation is suppressed.

  Further, in the present embodiment, the upper outer wall 41 has a relatively high rigidity because the side wall 3S of the cylinder head 3 is integrally formed, and a moment that generates a load on the downstream side exhaust passage member 20 joined to the cylinder head 3 is generated. Since it acts as a tensile force, the stress generated at the time of thermal expansion is small, but the side wall 3S is not integrally formed and the load on the downstream side exhaust passage member 20 acts as a compressive force on the lower outer wall 42. Due to the formation of the curved region 71, the fourth curved region 72, and the fifth curved region 73, the stress is effectively dispersed at the lower outer wall 42 where large compressive stress is likely to occur.

  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, in the above embodiment, the present invention is applied to a four-valve in-line four-cylinder gasoline engine for automobiles, but may be applied to a different type of internal combustion engine used for other purposes. In the above embodiment, only one exhaust outlet 8c is formed. However, two exhaust outlets 8c are formed for every two cylinders close to each other, and a plurality of exhaust collecting portions 8b are formed in the cylinder head 3. May be. In addition, the specific configuration, arrangement, quantity, angle, and the like of each member and part can be changed as appropriate without departing from the spirit of the present invention. On the other hand, all the components of the cylinder head 3 according to the present invention shown in the above embodiment are not necessarily essential, and may be appropriately selected.

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Cylinder block 3 Cylinder head 3S Side wall 6 Combustion chamber 8 Exhaust collecting port 8a Exhaust port 8b Exhaust collecting part 8c Exhaust outlet 11 Valve operating chamber 18 Exhaust outlet tubular part (part which defines exhaust outlet)
DESCRIPTION OF SYMBOLS 19 Swelling part 30 Head internal coolant passage 32 Upper exhaust side coolant passage 33 Lower exhaust side coolant passage 41 Upper outer wall 41i Inner surface 42 Lower outer wall 42a Flat plate portion 42i Inner surface 43 Upper inner wall 44 Lower inner wall 61 First curved region ( First curved region)
62 2nd bending area | region (2nd bending area | region)
66 1st part 67 2nd part 71 3rd curve area (1st curve area)
72 4th curved area (2nd curved area)
73 Fifth curved region (third curved region)
76 First part 77 Second part E Engine R1 First radius of curvature (first radius of curvature)
R2 second radius of curvature (second radius of curvature)
R3 3rd radius of curvature (first radius of curvature)
R4 Fourth radius of curvature (second radius of curvature)
R5 5th radius of curvature (3rd radius of curvature)
t1ave Average thickness of the portion corresponding to the fourth curved region 72 of the lower outer wall 42 t2 Thickness of the flat plate portion 42a

Claims (5)

A cylinder of an internal combustion engine, in which a plurality of cylinders are fastened to the upper part of a cylinder block formed in a line, a combustion chamber is formed between the top surface of a piston sliding in the cylinder, and an in-head coolant passage is provided Head,
Within the cylinder head, a plurality of exhaust ports with upstream ends open to the combustion chamber, is combined with a plurality of the exhaust ports, to open the exhaust outlet in the longitudinal direction of the intermediate position in the one side surface of the cylinder head exhaust A collective part is formed,
The portion defining the exhaust outlet and the vicinity thereof form a bulging portion that bulges laterally with respect to the cylinder block to form the exhaust collecting portion,
The in-head cooling fluid passage includes a pair of exhaust-side cooling fluid passages formed in the bulging portion so as to sandwich the exhaust collecting portion,
The bulging portion has a pair of outer walls and a pair of inner walls that define the exhaust-side coolant passage,
In cross-section through the orthogonal and the exhaust outlet to the cylinder row direction, at least one of the inner surfaces of the pair of the outer wall is formed in an end portion of the side of the exhaust outlet, the center of curvature on the side of the exhaust-side coolant passage the first curved region is curved with a first radius of curvature at the than the first turn region is formed on a side of the combustion chamber, wherein at the center of curvature on the side of the exhaust-side coolant passage first A second curved region that curves with a second radius of curvature greater than the radius of curvature of 1;
The second bending region is, viewed contains a first portion gradually increasing the height of the exhaust-side coolant passage toward at least the side of the exhaust outlet side of the combustion chamber,
A cylinder head for an internal combustion engine, characterized in that most of a part of the pair of outer walls corresponding to at least one of the second curved regions has a constant thickness . At least the one of the inner surfaces of the pair of the outer wall, than the second curved region are formed on a side of the combustion chamber further comprises a straight linear region continuous with the second bent region,
On at least said pair of said outer wall, said at least a side portion of the second curved region of the linear region has a flat portion having a constant thickness, the flat-plate-like portion of the thickness second The cylinder head of the internal combustion engine according to claim 1 , wherein the cylinder head is thicker than an average thickness of a portion corresponding to the curved region. At least the one of the inner surfaces of the pair of the outer wall, wherein the first turn region is formed between the second bending region, wherein the first at the center of curvature on the side of the exhaust-side coolant passage A third curved region that curves with a third radius of curvature that is greater than the radius of curvature and less than the second radius of curvature;
Internal combustion according to claim 1 or claim 2, wherein the third bending regions are connected so as to continuously said first curved region and the second bending region and mutual tangent slope Engine cylinder head. The second bending region is continuous from the first portion to the side of the combustion chamber, second gradually decreasing the height of the exhaust-side coolant passage toward the side of the combustion chamber from the side of the exhaust outlet The cylinder head of the internal combustion engine according to any one of claims 1 to 3 , further comprising a portion. The cylinder head is disposed above the vertical direction in the internal combustion engine;
A pair of the outer walls comprises an upper outer wall disposed on the upper side and a lower outer wall disposed on the lower side,
The upper outer wall is integrally formed with a side wall defining a valve operating chamber,
The cylinder head for an internal combustion engine according to any one of claims 1 to 4 , wherein at least an inner surface of the lower outer wall includes the first curved region and the second curved region.

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