JP5702129B2 - Engine combustion chamber structure and cylinder head structure - Google Patents

Description

  The present invention relates to an engine combustion chamber structure and a cylinder head structure, and more particularly to a combustion chamber structure and a cylinder head structure having a pent roof type combustion chamber ceiling portion.

  2. Description of the Related Art Conventionally, an engine such as an automobile that requires high rotation and high output has a pent roof type in which a combustion chamber ceiling is provided with an intake side inclined surface provided with two intake valves and an exhaust side inclined surface provided with two exhaust valves. There is a method in which a tumble flow is generated in the combustion chamber by the intake air introduced into the combustion chamber from the opening end of the intake port that opens to the intake-side inclined surface of the combustion chamber ceiling portion, so that stable combustion is performed.

  This tumble flow is generated by introducing the intake air obliquely into the combustion chamber through the gap between the open intake valve and the intake port opening end when the piston descends from the top dead center position in the intake stroke. . Specifically, the intake air that is sucked into the combustion chamber as the piston descends flows into the combustion chamber obliquely with respect to the combustion chamber from the gap between each intake port opening end and the valve head of the intake valve, and is introduced as the piston further descends The intake air is directed downward along the inner peripheral surface of the cylinder bore on the exhaust side, and then bent toward the intake side along the top surface of the piston, and further flows upward and swirls vertically throughout the entire combustion chamber. It becomes a tumble style.

  Subsequently, when the piston moves up from the bottom dead center position by shifting to the compression stroke, the tumble flow becomes compact due to the decrease in the volume of the combustion chamber as the piston rises. Even after the middle stage of the compression stroke, the tumble flow is maintained without being collapsed until the middle stage of the compression stroke or later by the space between the ceiling portion of the pent roof type combustion chamber and the top surface of the piston. Then, when fuel is injected from the injector, it is carried to the vicinity of the spark plug by the flow of the tumble flow along the ceiling of the combustion chamber to form a combustible air-fuel mixture layer in an appropriate concentration state around the electrode.

  In addition, in a combustion chamber of an engine having a pent roof type combustion chamber ceiling portion, Patent Literature 1 proposes a combustion chamber in which a combustible air-fuel mixture is retained around an electrode of a spark plug to improve ignitability. The engine disclosed in Patent Document 1 will be described with reference to FIGS.

  5 is a cross-sectional view schematically showing the combustion chamber structure of the engine, FIG. 6 is a plan view schematically showing the cylinder head viewed from the cylinder block side, FIG. 7 is an enlarged view of the VII portion of FIG. 6, and FIG. It is a figure which shows typically the VIII-VIII line cross section of 6. FIG.

  As shown in FIG. 5, a cylinder bore 102 in which a piston 105 is reciprocally accommodated in a cylinder block 101 is formed, and an intake side inclined surface 117 and an exhaust gas that are inclined and extend downward from the top 116 to the cylinder head 110. A pent roof type combustion chamber ceiling portion 115 having a side inclined surface 118 is formed. A side wall portion 119 is formed from the lower edge of the intake side inclined surface 117 and the exhaust side inclined surface 118 to the lower end surface 111 of the cylinder head 110. A space surrounded by the intake side inclined surface 117, the exhaust side inclined surface 118, the side wall portion 119, and the top surface 106 of the piston 105 forming the cylinder bore 102 and the combustion chamber ceiling portion 115 becomes the combustion chamber 120.

  As shown in FIG. 6, the opening end 122 of the two intake ports 121 is formed along the apex 116 on the intake side inclined surface 117 of the combustion chamber ceiling 115, and the two exhaust ports are formed on the exhaust side inclined surface 118. Each open end 124 of 123 is formed. Each intake port open end 122 is opened and closed by an intake valve 131, and each exhaust port open end 124 is opened and closed by an exhaust valve 132. Each intake valve 131 is formed by a rod-shaped stem 131A and a valve head 131B provided at the end of the stem 131A on the combustion chamber 120 side. Each exhaust valve 132 is formed by a stem 132A and a valve head 132B provided at the end of the stem 132A on the combustion chamber 120 side.

  An airflow guide groove 125 that is recessed upward along the extending direction of the top portion 116 is formed at the top portion 116 of the combustion chamber ceiling portion 115. As shown in FIGS. 5 and 6, the airflow guide groove portion 125 has an ignition plug 133 with respect to the cylinder head 110 so that the electrode 133 a protrudes from the airflow guide groove 125 toward the combustion chamber 120 as shown in FIGS. 5 and 6. Attached.

  The airflow guide groove portion 125 is formed so as to gradually become deeper from the both end portions 125a toward the spark plug 133. Further, as shown in FIG. 7, the airflow guide groove 125 is formed by an intake side groove surface 127 and an exhaust side groove surface 128 which are continuous by the groove top portion 126, and the intake side groove surface 127 is located at the place where the spark plug 133 is disposed. The exhaust-side groove surface 128 is inclined with a predetermined angle with respect to the exhaust-side inclined surface 118, and is formed continuously with the intake-side inclined surface 117. Thus, it is continuously formed on the exhaust side inclined surface 118. On the other hand, where the intake valve 131 and the exhaust valve 132 are disposed, as shown in FIG. 8, the intake side inclined surface 117 is formed as one plane continuous to the intake side groove surface 127, and the exhaust side groove surface 128 is formed on the exhaust side. The inclined surface 118 is formed on a surface that is inclined at a predetermined angle. In addition, as shown in FIG. 6, an injector hole 129 into which an injector for injecting fuel (not shown) is inserted is formed in the base end portion 117 a of the intake side inclined surface 117.

  As a result, when the piston 105 rises, an airflow that flows along the intake-side inclined surface 117 and the exhaust-side inclined surface 118 in the combustion chamber 120 and an airflow that flows toward the ignition plug 133 along the airflow guide groove portion 125 are generated. While promoting the mixing of fuel and air in the combustion chamber 120, the combustible air-fuel mixture can be concentrated and retained around the electrode 133a of the spark plug 133, and an improvement in ignitability can be expected.

JP 2010-185457 A

  In the combustion chamber having the pent roof type combustion chamber ceiling portion, the intake air from the gap between the intake port opening end that opens to the intake side inclined surface by the lowering of the piston in the intake stroke and the valve head of the open intake valve Although a tumble flow is generated in the combustion chamber by the above, the intake port opening end opens close to the top of the combustion chamber ceiling, so that the piston descends to the combustion chamber through the gap between the intake port opening end and the intake valve. The flow of the intake air that flows in along the intake-side inclined surface and the exhaust-side inclined surface from the intake port opening end is weakened by the top portion extending across the flow direction and the exhaust-side inclined surface continuous to the top portion. Tumble flow generation in the combustion chamber is weakened. In addition, it affects the smooth suction of the intake air sucked from the opening end of the intake port, which increases the pressure loss of the intake passage in the intake port and the like and causes a decrease in charging efficiency.

  Also, when finishing the intake port opening edge, such as spot facing, a discontinuous portion is formed around the intake port opening end along with the machining, and the discontinuous portion also exhausts from the intake side inclined surface side. The flow of the intake air flowing toward the side inclined surface is weakened, and the generation of the tumble flow in the combustion chamber is weakened.

  On the other hand, according to Patent Document 1, an airflow guide groove 125 is formed along the top portion 116 of the pent roof type combustion chamber ceiling portion 115 so that the spark plug 133 side is deepened, whereby the combustible mixture in the combustion chamber 120 is ignited by the ignition plug 133. It is possible to expect improvement in ignitability by concentrating and staying with respect to the electrode 133a.

  However, the intake air that is introduced into the combustion chamber 120 through the gap between the intake port open end 124 and the valve head 131B of the open intake valve 131 and flows toward the exhaust side inclined surface 117 along the intake side inclined surface 116 is an airflow guide. The tidal flow is generated by weakening the intake flow that is guided to the spark plug 133 side by the groove portion 125 and stays in the portion, and flows along the intake side inclined surface side 116 and the exhaust side inclined surface 117 from the intake port opening end 122. Is weakened. In addition, the flow of intake air sucked from the intake port opening end 122 is weakened by the airflow guide groove portion 125 and stays there, affecting the smooth intake from the intake port opening end 122, and the intake air flow in the intake port 121 and the like. The pressure loss of the passage increases and causes a reduction in filling efficiency.

  Accordingly, an object of the present invention made in view of the above point is to provide an engine in which combustion stability of the engine and engine output are improved by improving tumble flow generation and filling efficiency in a combustion chamber having a pent roof type combustion chamber ceiling. An object of the present invention is to provide a combustion chamber structure and a cylinder head structure.

The combustion chamber structure for an engine according to the first aspect of the present invention that achieves the above object comprises a pent roof type combustion chamber ceiling having an intake-side inclined surface and an exhaust-side inclined surface extending inclined from the top to both sides. Two intake port opening ends opened and closed by an intake valve on the intake side inclined surface along the top, and two exhaust port opening ends opened and closed by the exhaust valve opposed to the intake port opening ends on the exhaust side inclined surface In the combustion chamber structure of the engine that generates a tumble flow in the fuel chamber by introducing the intake air through the gap between the open intake valve and the intake port opening end, the intake air portions facing each other are arranged on top of the combustion chamber ceiling portion. An imaginary line connecting the outer edge of the port opening end and the outer edge of the exhaust port opening end to the combustion chamber center side, and an imaginary line connecting the outer edge of the intake port opening end and the outer edge of the exhaust port opening end. Characterized in that a groove-like air flow guide socket to induce airflow to the exhaust side inclined surface side from the intake side inclined surface communicates with the intake port opening end side of the exhaust port opening end side of the each.

According to this, the intake air introduced obliquely to the combustion chamber through the gap between the intake valve in the open state and the intake port open end, the top of the combustion chamber ceiling, outer and exhaust port openings of the intake ports open end The combustion chamber is guided by an airflow induction recess that is recessed between an imaginary line connecting the combustion chamber center side of the outer edge of the end and an imaginary line connecting the outer edge of the intake port opening end and the outer edge of the exhaust port opening end. In addition, a strong tumble flow that flows along the ceiling of the combustion chamber from the intake-side inclined surface side to the exhaust-side inclined surface side is generated, which promotes airflow flow in the combustion chamber, and improves combustion stability and fuel efficiency even in lean regions. can get.

  Further, the flow of the intake air drawn from the intake port opening end is guided from the intake side inclined surface side to the exhaust side inclined surface side by the airflow induction recess and does not stay near the top of the combustion chamber ceiling portion, so that the intake port opening end Thus, fresh air is smoothly introduced into the combustion chamber, the pressure loss in the intake passage such as the intake port is reduced, and the charging efficiency is improved. The engine output is improved as the charging efficiency is improved.

According to a second aspect of the present invention, in the combustion chamber structure of the engine according to the first aspect , a flat portion that protrudes toward the combustion chamber along the top at the center of the top of the ceiling of the combustion chamber between the airflow guide recesses. And a spark plug mounting hole is formed in the flat portion.

  According to this, each intake port opening end and exhaust port opening end is provided by providing a flat portion protruding toward the combustion chamber along the top between each airflow guide recess, and forming a spark plug mounting hole in this flat portion. And a smooth combustion chamber ceiling is formed, and the spark plug can be attached while maintaining the tumble flow generation without affecting the air flow induced by each air flow guide recess.

According to a third aspect of the present invention, there is provided a cylinder head structure including a pent roof-type combustion chamber ceiling portion having an intake side inclined surface and an exhaust side inclined surface extending obliquely from the top to both sides, along the top portion. In a cylinder head structure having two intake port opening ends opened and closed by an intake valve on an intake side inclined surface and two exhaust port opening ends opened and closed by an exhaust valve on the exhaust side inclined surface opposite to each intake port opening end. An imaginary line connecting the outer edge of the intake port opening end and the outer edge of the exhaust port opening end facing each other on the top of the combustion chamber ceiling, and the outer edge of the intake port opening end and the outer edge of the exhaust port opening end. groove-shaped air flow induced concave to induce air flow into the exhaust-side inclined surface side with each of the intake ports opening end side exhaust port opening end side from the intake side inclined surface communicates between the imaginary line connecting the outer Characterized in that the formation of the

According to this, the intake air is introduced obliquely to the combustion chamber through the gap between the intake valve in the open state and the intake port opening end, on top of the combustion chamber ceiling, the outer edge and the intake ports open ends facing each other Induced by an airflow guide recess recessed between an imaginary line connecting the outer edge of the exhaust port opening end to the center of the combustion chamber and an imaginary line connecting the outer edge of the intake port opening end and the outer edge of the exhaust port opening end. A strong tumble flow is introduced along the combustion chamber ceiling from the intake side inclined surface side to the exhaust side inclined surface side and flows along the combustion chamber ceiling portion from the intake side inclined surface side to the exhaust side inclined surface side into the combustion chamber. Can be generated.

  Further, the flow of the intake air drawn from the intake port opening end is guided from the intake side inclined surface side to the exhaust side inclined surface side by the airflow induction recess and does not stay near the top of the combustion chamber ceiling portion, so that the intake port opening end Thus, fresh air is smoothly introduced into the combustion chamber, the pressure loss in the intake passage such as the intake port is reduced, and the charging efficiency is improved.

According to a fourth aspect of the present invention, in the cylinder head structure according to the third aspect , a flat portion that protrudes toward the combustion chamber along the top portion is provided at the center of the top portion of the combustion chamber ceiling portion between the airflow guide recesses. The spark plug mounting hole is formed in the flat portion.

  According to this, each intake port opening end and exhaust port opening end is provided by providing a flat portion protruding toward the combustion chamber along the top between each airflow guide recess, and forming a spark plug mounting hole in this flat portion. And a smooth combustion chamber ceiling is formed, and the spark plug can be attached while maintaining the tumble flow generation without affecting the air flow induced by each air flow guide recess.

According to a fifth aspect of the present invention, in the cylinder head structure according to the third or fourth aspect , each of the airflow guide recesses includes a bottom surface continuously extending from the intake port opening end side to the exhaust port opening end side, and the bottom surface And a groove shape having an inner surface and an outer surface continuous from the intake port opening end side to the exhaust port opening end side. Features.

  According to this, the air flow guide recesses continuously extend from the intake port opening end side to the exhaust port opening end side, and the planes or curved surfaces that are separated from each other as the distance from the bottom surface continues to each side edge of the bottom surface. In the shape of a groove having an inner surface and an outer surface continuous from the intake port opening end side to the exhaust port opening end side, intake air from the intake port opening end is efficiently guided to the exhaust side inclined surface side. A stronger tumble flow can be generated. Further, fresh air is smoothly introduced into the combustion chamber from the open end of the intake port, so that the charging efficiency is improved and the output of the engine is improved.

  According to the present invention, the intake air introduced obliquely into the combustion chamber from the gap between each open intake valve and the intake port opening end is guided to the airflow induction recess formed in the top of the combustion chamber ceiling. A strong tumble flow that flows along the combustion chamber ceiling from the intake-side inclined surface side to the exhaust-side inclined surface side is generated in the combustion chamber.

  Further, the flow of the intake air drawn from the intake port opening end is guided from the intake side inclined surface side to the exhaust side inclined surface side by the airflow induction recess and does not stay near the top of the combustion chamber ceiling portion, so that the intake port opening end Thus, fresh air is smoothly introduced into the combustion chamber, the pressure loss in the intake passage is reduced, and the charging efficiency is improved.

It is a top view which shows typically the cylinder head seen from the cylinder block side of the engine which concerns on embodiment. It is sectional drawing which shows the II-II line cross section of FIG. 1 typically. It is sectional drawing which shows the III-III line cross section of FIG. 1 typically. It is sectional drawing which shows the IV-IV line cross section of FIG. 1 typically. It is sectional drawing which shows typically the combustion chamber structure of the conventional engine. It is a top view which shows typically the cylinder head seen from the cylinder block side. It is an enlarged view which shows typically the VII part of FIG. It is sectional drawing which shows typically the VIII-VIII line cross section of FIG.

  Hereinafter, an embodiment of an engine combustion chamber and cylinder head structure according to the present invention will be described with reference to FIGS. 1 is a plan view schematically showing a cylinder head viewed from the cylinder block side of the engine, FIG. 2 is a sectional view schematically showing a section taken along line II-II in FIG. 1, and FIG. 3 is a line taken along line III-III in FIG. FIG. 4 is a cross-sectional view schematically showing a cross section taken along line IV-IV in FIG.

  As shown in FIGS. 1 and 2, the engine includes a cylinder block 10 and a cylinder head 20. The cylinder block 11 is formed with a cylinder bore 11 in which a piston (not shown) is reciprocally accommodated in the cylinder block 10, and the intake side inclined surface 24 and the exhaust side inclined surface 25 are inclined and extended from the top 23 toward both lower sides of the cylinder head 20. A pent roof-shaped combustion chamber ceiling portion 22 having the above is formed. Further, the side wall that becomes the inner peripheral portion of the combustion chamber 40 extends from the lower edge of the intake side inclined surface 24 and the exhaust side inclined surface 25 to the lower end surface 21 of the cylinder head 20 that contacts the cylinder block 10 with a gasket or the like interposed therebetween. A portion 26 is formed. A space surrounded by the intake side inclined surface 24, the exhaust side inclined surface 25, the side wall portion 26, and the top surface of the piston forming the cylinder bore 11 and the combustion chamber ceiling 22 is a combustion chamber 40.

  1, 2, and 3, the cylinder head 20 includes a pair of intake ports 41 </ b> A and 41 </ b> B that introduce intake fresh air into the combustion chamber 40 and a pair of exhaust ports 45 </ b> A and 45 </ b> B that discharge combustion exhaust gas. Is formed. Open ends 42A and 42B of the intake ports 41A and 41B are formed along the top portion 23 on the intake side inclined surface 24 of the combustion chamber ceiling portion 22, and fuel (not shown) is injected into the base end portion 24a of the intake side inclined surface 24. An injector hole 39 into which the tip of the injector to be inserted is inserted is formed.

  Annular valve seats 43A and 43B are provided at two intake port opening ends 42A and 42B formed on the intake side inclined surface 24, respectively. In addition, opening ends 46A and 46B of exhaust ports 45A and 45B having a smaller diameter than the suction port opening ends 42A and 42B are formed on the exhaust side inclined surface 25 along the top portion 23 so as to face the intake port opening ends 42A and 42B. Valve seats 47A and 47B are provided at two exhaust port opening ends 46A and 46B formed on the exhaust side inclined surface 25, respectively.

  As shown in FIG. 2, the intake port opening end 42A provided with the valve seat 43A is opened and closed by an intake valve 51A supported by a valve guide 44A attached to the intake port 41A. The intake valve 51A is formed by a rod-shaped stem 52A inserted in a liftable direction in the lift direction by a valve guide 44A and a valve head 53A provided at the end of the stem 52A on the combustion chamber 40 side, and in a closed state. The valve face of the valve head 53A is seated on the valve seat 43A, and the intake port opening end 42A is closed. In the open state, the valve head 53A is separated from the valve seat 43A and between the valve seat 43A and the valve head 53A. A gap is formed.

  The exhaust port open end 46A is opened and closed by an exhaust valve 55A supported by a valve guide 48A attached to the exhaust port 45A. The exhaust valve 55A is formed by a rod-shaped stem 56A inserted in a lift direction by a valve guide 48A and a valve head 57A provided at the end of the stem 56A on the combustion chamber 40 side. The valve face of the valve head 57A is seated on the valve seat 47A and closes the exhaust port opening end 46A. In the open state, the valve head 57A is separated from the valve seat 47A and between the valve seat 47A and the valve head 57A. A gap is formed.

  Further, as shown in FIG. 3, the intake port open end 42B provided with the valve seat 43B is defined by an intake valve 51B having a stem 51A and a valve head 51B supported by a valve guide 44B attached to the intake port 41B. In the closed state, the valve face of the valve head 53B is seated on the valve seat 43B to close the intake port open ends 42A and 42B. In the open state, the valve head 53B is separated from the valve seat 43B. Thus, a gap is formed between the valve seat 43B and the valve head 53B.

  The exhaust port open end 46B is opened and closed by an exhaust valve 55B having a stem 56B and a valve head 57B supported by a valve guide 48B mounted on the exhaust port 45A. In the closed state, the valve face of the valve head 57B is opened. The exhaust port opening end 46B is seated on the valve seat 47B, and in the open state, the valve head 57B is separated from the valve seat 47B, and a gap is formed between the valve seat 47B and the valve head 57B. The intake valves 51A and 51B and the exhaust valves 55A and 55B are opened and closed by a valve mechanism such as an intake cam and an exhaust cam (not shown) or a valve lift mechanism. These valve operating mechanisms are already known techniques and will not be described.

  As shown in the sectional view taken along the line III-III in FIG. 1 and FIG. A spark plug mounting hole 32 for mounting the spark plug 58 to the cylinder head 20 so as to project toward the combustion chamber 40 at the center is formed to project from the top 23 toward the combustion chamber 40, and from the spark plug mounting 32 to the top. A wing-like flat portion 31 is formed in which extending portions 33A and 33B extend in a direction away from each other along the extending direction of 23. The airfoil flat portion 31 protruding from the top 23 toward the combustion chamber 40 eliminates the step between the intake port opening ends 42A and 42B and the exhaust port opening ends 46A and 46B, and the intake side inclined surface 23 is inclined toward the exhaust side. A smooth combustion chamber ceiling 22 that is smoothly continuous with the surface 24 is formed.

  Continuing from the extending portion 33A of the flat portion 31, the intake port opening end 42A and the exhaust port opening 46A are recessed upward to communicate the intake port opening end 42A side and the exhaust port opening end 46A side. A groove-shaped airflow guiding recess 35A that is smoothly continuous with substantially the same cross-sectional shape is formed, and the intake port opening end 42B side is provided between the intake port opening end 42B and the exhaust port opening 46B continuously to the extending portion 33B. A groove-shaped airflow guide recess 35B that is recessed upward and communicates with the exhaust port opening end 46B side is formed.

  As shown in FIGS. 1, 2 and 4, the air flow guide recess 35A has an inner end 35Aa and an outer end 35Ab at the combustion chamber center side of the outer edge of the intake port opening end 42A and the outer edge of the exhaust port opening end 46A. An imaginary line La1 connecting the outer edge of the intake port opening end 42A and the outer edge of the exhaust port opening end 46A to the spark plug 58 side and a imaginary line La2 connecting the outside is formed, and from the intake port opening end 42A to the exhaust port opening end 46A. A bottom surface 36A that is substantially parallel to the cylinder head lower end surface 21 and a center side edge 36Aa of the bottom surface 36A, the outer end is continuous, and the inner end 35Aa is the outer end of the extending portion 33A of the flat portion 31. An inner surface 37A that is a continuous flat surface or curved surface and that continues from the intake port opening end 42A side to the exhaust port opening end 46A side, and an inner end that is continuous with an outer edge 36Ab of the bottom surface 36A. Ab is formed by an outer surface 38A continuous with the exhaust port opening end 46A side in a plan or curved surface shape continuous with the top portion 23 or the side wall portion 26.

  That is, the airflow guiding recess 35A is continuous with the extending portion 33A of the flat portion 31 to which the spark plug 58 is attached, between the imaginary lines La1 and La2, and from the intake port opening end 42A side of the top portion 23 to the exhaust port opening end. A combustion chamber is formed by a flat bottom surface 36A continuously extending to the 46A side, and an inner surface 37A and an outer surface 38A that are separated from each other as they move from the bottom surface 36A to the combustion chamber 40 side continuously to the inner edge 36Ab of the bottom surface 36A. The 40 side is formed in a wide groove shape. Further, the airflow guiding recess 35A can be formed in a relatively shallow chamfered shape of, for example, several millimeters.

  Similarly, as shown in FIGS. 1, 2 and 4, the air flow guide recess 35B has an inner end 35Ba and an outer end 35Bb at the center of the combustion chamber at the outer edge of the intake port opening end 42B and the outer edge of the exhaust port opening end 46B. Side, that is, between the imaginary line Lb1 connecting the spark plug 58 side and the imaginary line Lb2 connecting the outside, is substantially parallel to the cylinder head lower end surface 21 continuous from the intake port opening end 42B to the exhaust port opening end 46B side. Inlet port opening end 42B having a flat surface or curved surface in which the outer end is continuous to the bottom surface 36B and the center side edge 36Ba of the bottom surface 36B and the inner end 35Ba is continuous to the outer end of the extending portion 33B of the flat portion 31. An inner side surface 37B continuous from the side to the exhaust port open end 46B side, and a flat surface or curved surface in which the inner end is continuous to the outer edge 36Bb of the bottom surface 36B and the outer end 36Bb is continuous to the top 23 or the side wall portion 26. Formed by the outer surface 38B continuous to an exhaust port opening end 46B side from the intake port opening end 42B side Jo. That is, the airflow flow recess 35B is continuous from the extended portion 33B of the flat portion 31 and continuously from the intake port open end 42B side of the top 23 to the exhaust port open end 46B side between the virtual lines Lb1 and Lb2. A groove having a wide width on the combustion chamber 40 side by an extended flat bottom surface 36B and an inner side surface 37B and an outer surface 38B which are separated from each other as the transition from the bottom surface 36B to the combustion chamber 40 side continues to the inner edge 36Bb of the bottom surface 36B. It is formed in a shape. The airflow guiding recess 35B can be formed in a relatively shallow chamfered shape of, for example, several millimeters.

  Next, the operation of the combustion chamber and the cylinder head configured as described above will be described.

  In the engine thus configured, as the piston (not shown) descends from the top dead center position in the intake stroke, the valve head 53A and the intake port opening end 42A of the open intake valve 51A shown in FIGS. The intake air introduced obliquely with respect to the combustion chamber 40 through the gap with the valve seat 43A is a bottom surface 36A recessed in the top 23 of the combustion chamber ceiling 22 as shown by an arrow F1 in FIGS. The inner side 37A and the outer side 38A are guided by an airflow guide recess 35A formed in a groove shape that communicates the intake port open end 42A side and the exhaust port open end 46A side, and from the intake side inclined surface 24 side to the exhaust side inclined surface 25. It is introduced along the combustion chamber ceiling 22 to the side. Similarly, the intake air introduced obliquely into the combustion chamber 40 through the gap between the valve head 53B of the intake valve 51B in the open state and the valve seat 43B at the intake port opening end 42B is indicated by an arrow F2 in FIGS. As described above, the air flow induction formed in a groove shape communicating the intake port opening end 42B side and the exhaust port opening end 46B side by the bottom surface 36B, the inner side surface 37B, and the outer side surface 38B recessed in the top portion 23 of the combustion chamber ceiling portion 22 It is guided along the combustion chamber ceiling portion 22 from the intake side inclined surface 24 side to the exhaust side inclined surface 25 side by being guided by the recess 35B.

  As a result, the intake air sucked from the gap between the intake valve 51A and the valve seat 43A at the intake port opening end 42A and from the gap between the intake valve 51B and the valve seat 43B at the intake port opening end 43B flows in the flow direction. It is guided along the combustion chamber ceiling portion 22 from the intake side inclined surface 24 side to the exhaust side inclined surface 25 side without being weakened by the top portion 23 extending in the intersecting direction or the exhaust side inclined surface 25 continuing to the top portion 23. The

  As the piston is further lowered, the introduced intake air is directed downward along the inner peripheral surface of the exhaust-side cylinder bore 11, and then bent toward the intake side along the top surface of the piston. Further, the intake-side cylinder bore 11 is further bent. A tumble flow that flows toward the upper intake side inclined surface 24 along the inner peripheral surface of the combustion chamber 40 and swirls in the vertical direction over the entire combustion chamber 40 is generated.

  Here, in particular, each of the air flow guide recesses 35A is continuous with the inner edge 36Ab of the bottom surface 36A between the phantom lines La1 and La2, and the inner surface 37A and the outer surface 38A are separated from each other as they move from the bottom surface 36A to the combustion chamber 40 side. By forming the combustion chamber 40 side into a wide groove shape, the intake air from the intake port opening end 42A is efficiently guided to the exhaust side inclined surface 25 side along the combustion chamber ceiling 22 and airflow induction is performed. The width of the combustion chamber 40 side is increased by the inner side surface 37B and the outer side surface 38B which are spaced apart from each other as the recess 35B moves from the bottom surface 36B to the combustion chamber 40 side continuously from the inner edge 36Bb of the bottom surface 36B between the virtual lines Lb1 and Lb2. By forming a wide groove shape, the intake air from the intake port opening end 42B is efficiently guided to the exhaust side inclined surface 25 side along the combustion chamber ceiling portion 22. Strong tumble flow by these airflow can be generated.

  Subsequently, when the piston moves up from the bottom dead center position by shifting to the compression stroke, the tumble flow becomes compact due to the decrease in the volume of the combustion chamber 40 as the piston moves up. Even after the middle stage of the compression stroke, the airflow induction recesses 35A and 35B for guiding intake air from the space between the pent roof type combustion chamber ceiling portion 22 and the piston top surface and the intake side inclined surface 24 side to the exhaust side inclined surface 25 side. By this, the tumble flow is maintained without collapsing until the middle of the compression stroke. When the fuel is injected from the injector, the fuel flows along the combustion chamber ceiling 22 of the tumble flow to the vicinity of the spark plug 58 to form a combustible air-fuel mixture layer having an appropriate concentration around the electrode 58a.

  Thus, in the combustion chamber 40, along the combustion chamber ceiling portion 22 from the intake side inclined surface 24 side to the exhaust side inclined surface 25 side from the intake port open ends 42 </ b> A, 42 </ b> B toward the exhaust port open ends 46 </ b> A, 46 </ b> B. As a result, a strong tumble flow flowing in the combustion chamber 40 is generated, and the air flow in the combustion chamber 40 is promoted, and combustion stability and fuel efficiency are improved even in a lean region.

  Further, the flow of the intake air sucked from the intake port opening ends 42A and 42B is guided from the intake side inclined surface 24 side to the exhaust side inclined surface 25 side by the airflow induction recesses 35A and 35B and stays near the top of the combustion chamber ceiling. Therefore, fresh air is smoothly introduced into the combustion chamber from the intake port opening ends 42A and 42B, the pressure loss of the intake passages such as the intake ports 41A and 41B is reduced, and the charging efficiency is improved. Output improvement.

  Furthermore, each of the intake port opening ends 42 </ b> A is provided by providing a spark plug mounting hole 32 in the flat end portion 31 formed to protrude toward the combustion chamber 40 along the top portion 23 between the airflow guiding recess 35 </ b> A and the airflow guiding recess 35 </ b> B. 42B and the exhaust port opening ends 46A and 46B are eliminated, a smooth combustion chamber ceiling portion 22 is formed, and strong without affecting the air flow induced by the air flow guide recesses 35A and 35B. The spark plug 58 can be attached while maintaining tumble flow generation.

DESCRIPTION OF SYMBOLS 10 Cylinder block 11 Cylinder bore 20 Cylinder head 21 Lower end surface 22 Combustion chamber ceiling 23 Top 24 Intake side inclined surface 25 Exhaust side inclined surface 31 Flat part 32 Spark plug attachment hole 33A, 33B Extension part 35A, 35B Airflow guidance recessed part 35Aa , 35Ba Inner end 35Ab, 35Bb Outer end 36A, 36B Bottom surface 37A, 37B Inner side surface 38A, 38B Outer side surface 40 Combustion chamber 41A, 41B Intake port 42A, 42B Intake port open end 43A, 43B Valve seat 45A, 45B Exhaust port 46A, 46B Exhaust port opening end 47A, 47B Valve seat 51A, 51B Intake valve 53A, 53B Valve head 55A, 55B Exhaust valve 57A, 57B Valve head 58 Spark plug

Claims (5)

Two intakes that have a pent roof-type combustion chamber ceiling provided with an intake-side inclined surface and an exhaust-side inclined surface that are inclined and extended from the top to both sides, and that are opened and closed by an intake valve along the top of the intake-side inclined surface There are two exhaust port opening ends that are opened and closed by an exhaust valve opposite to each intake port opening end on the port opening end and the exhaust side inclined surface, and intake air from the gap between the opened intake valve and the intake port opening end In the combustion chamber structure of the engine that generates a tumble flow in the fuel chamber by introduction,
An imaginary line connecting the outer edge of the intake port opening end and the outer edge of the exhaust port opening end facing each other on the top of the combustion chamber ceiling, and the outer edge of the intake port opening end and the outer edge of the exhaust port opening end. A groove-like airflow guiding recess that communicates the intake port opening end side and the exhaust port opening end side with the imaginary line connecting the outside to guide the airflow from the intake side inclined surface side to the exhaust side inclined surface side. An engine combustion chamber structure characterized by being formed. A flat portion projecting toward the combustion chamber side along the top portion is provided at the center of the top portion of the combustion chamber ceiling portion between the airflow guide recesses, and a spark plug mounting hole is formed in the flat portion. Item 4. A combustion chamber structure of an engine according to Item 1 . Two intakes that have a pent roof-type combustion chamber ceiling provided with an intake-side inclined surface and an exhaust-side inclined surface that are inclined and extended from the top to both sides, and that are opened and closed by an intake valve along the top of the intake-side inclined surface In the cylinder head structure having two exhaust port opening ends opened and closed by an exhaust valve on the port opening end and the exhaust side inclined surface so as to face each intake port opening end,
An imaginary line connecting the outer edge of the intake port opening end and the outer edge of the exhaust port opening end facing each other on the top of the combustion chamber ceiling, and the outer edge of the intake port opening end and the outer edge of the exhaust port opening end. A groove-like airflow guide recess that guides airflow from the intake-side inclined surface side to the exhaust-side inclined surface side by communicating the intake port open end side and the exhaust port open end side between the imaginary lines connecting the outside A cylinder head structure characterized by that. A flat portion projecting toward the combustion chamber side along the top portion is provided at the center of the top portion of the combustion chamber ceiling portion between the airflow guide recesses, and a spark plug mounting hole is formed in the flat portion. Item 4. The cylinder head structure according to Item 3 . Each of the airflow guiding recesses has a bottom surface continuously extending from the intake port opening end side to the exhaust port opening end side;
A flat or curved surface that is continuous with each side edge of the bottom surface and is spaced apart from the bottom surface, and has a groove shape having an inner surface and an outer surface that are continuous from the intake port opening end side to the exhaust port opening end side. The cylinder head structure according to claim 3 or 4 , wherein

Images