JP6286384B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine mounted on a vehicle, and more particularly to an internal combustion engine capable of effectively generating intake and exhaust flows in a combustion chamber and improving combustion efficiency.

  In order to increase the combustion efficiency of an internal combustion engine and reduce fuel consumption, a method of stabilizing the combustion by generating a tumble flow in the intake air sucked in the combustion chamber and sending the fuel around the spark plug at the top of the combustion chamber is there.

  In order to promote the tumble flow of the internal combustion engine in this way, in the internal combustion engine in which the intake port and the exhaust port are arranged on both sides in the radial direction on the ceiling surface of the combustion chamber of the cylinder head, the ceiling surface of the combustion chamber in a bottom view There is an internal combustion engine in which a pair of crescent-shaped squish surfaces are formed so as to connect an intake port and an exhaust port (for example, Patent Document 1).

JP 2013-227966 A

  In an internal combustion engine in which the crescent-shaped squish surface is provided on the ceiling of the combustion chamber, the intake air that is blocked from intake from the outer edge of the intake valve port is the surface on the intake port side of the umbrella portion of the intake valve Are guided by crescent-shaped squish surfaces on both sides and rectified toward the exhaust valve port side to promote tumble, thereby generating strong vortex tumble and improving combustion efficiency.

  However, the piston top surface of this internal combustion engine is formed in a substantially flat shape with a shallow center and recessed, and when the tumble flow reaches the flat piston top surface, the flow of the tumble flow vortex is disturbed, When the air temperature rises to the top dead center, a gap remains between the top surface of the piston and the crescent-shaped squish surface provided on the ceiling of the combustion chamber, and the flow of the tumble flow generated in the combustion chamber is separated from the squish surface. In some cases, it is disturbed in the gap with the top surface of the piston, preventing improvement in combustion efficiency.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an internal combustion engine capable of improving the combustion efficiency by improving the flow of the tumble flow in the combustion chamber of the internal combustion engine. That is.

In the internal combustion engine of the present invention, a combustion chamber is configured between a piston top surface of a piston that is slidably fitted in a cylinder bore of a cylinder block, and a ceiling surface of a cylinder head that the piston top surface opposes.
On the ceiling surface of the cylinder head, an intake valve port and an exhaust valve port are opened to face the combustion chamber one by one at positions opposite to each other with respect to a cylinder axis that is a central axis of the cylinder bore,
In the cylinder head, an intake port and an exhaust port are formed to extend away from each other from the intake valve port and the exhaust valve port, respectively.
The ceiling surface of the cylinder head is provided with a pair of crescent squish surfaces on the outside in the inner diameter direction,
In the internal combustion engine provided with a dome-shaped recess having an elliptical cross section at a position where the intake valve port and the exhaust valve port are surrounded on both sides in the radial direction by the pair of crescent squish surfaces on the ceiling surface,
On the top surface of the piston, a crescent-shaped projecting portion projecting from the top surface of the piston toward the cylinder head is provided at a position facing the crescent-shaped squish surface,
A squish area is constituted by the crescent-shaped squish surface and the crescent-shaped protrusion ,
The peripheral edge of the piston top surface is provided with peripheral protrusions connecting both ends of the crescent-shaped protrusion, respectively, and the curvature of the inner edge constituting the combustion chamber of the crescent-shaped protrusion and the peripheral protrusion The curvature of the internal combustion which comprises the said combustion chamber of a part differs, It is characterized by the above-mentioned.
In the internal combustion engine of the present invention, a combustion chamber is formed between a piston top surface of a piston slidably fitted in a cylinder bore of a cylinder block and a ceiling surface of a cylinder head opposed to the piston top surface. ,
On the ceiling surface of the cylinder head, an intake valve port and an exhaust valve port are opened to face the combustion chamber one by one at positions opposite to each other with respect to a cylinder axis that is a central axis of the cylinder bore,
In the cylinder head, an intake port and an exhaust port are formed to extend away from each other from the intake valve port and the exhaust valve port, respectively.
The ceiling surface of the cylinder head is provided with a pair of crescent squish surfaces on the outside in the inner diameter direction,
In the internal combustion engine provided with a dome-shaped recess having an elliptical cross section at a position where the intake valve port and the exhaust valve port are surrounded on both sides in the radial direction by the pair of crescent squish surfaces on the ceiling surface,
On the top surface of the piston, a crescent-shaped projecting portion projecting from the top surface of the piston to the cylinder head side is provided at a position facing the crescent-shaped squish surface,
A squish area is constituted by the crescent-shaped squish surface and the crescent-shaped protrusion,
The crescent-shaped protrusion is linearly inclined upward as it goes toward the piston axial center,
The crescent-shaped squish surface of the cylinder head is characterized in that an inclined surface corresponding to the inclination of the crescent-shaped projecting portion is formed.

  Since the present invention is configured as described above, the tumble flow rectified by the pair of crescent squish surfaces provided on the cylinder head can be further guided by the crescent protrusion of the piston top, and the piston top On the surface, a crescent-shaped projecting portion facing the crescent-shaped squish surface is provided, and the squish area is constituted by the crescent-shaped squish surface and the crescent-shaped projecting portion. The gap between the protrusions is reduced, the tumble flow vortex flow in the combustion chamber is not disturbed, the tumble flow can be improved, and the combustion efficiency of the internal combustion engine can be improved.

On the top surface of the piston, an elliptical recess is formed in top view,
A step is provided between the dent and the crescent protrusion.
The step portion and the dent portion may be formed by a continuous curved surface.

  According to the above configuration, the tumble flow is received by the indented portion formed on the top surface of the piston, and the tumble flow can be guided at the step portion between the indented portion and the crescent-shaped protruding portion. The flow can be improved. Furthermore, by configuring the dent and stepped parts with a continuous curved surface, the tumble flow guided from the cylinder head from above can be smoothly guided to the dent by the curved surface, disturbing the tumble flow vortex. The flow can be further improved.

The squish area is, in a top view of the piston, perpendicular to a straight line connecting the intake valve port center and the exhaust valve port center, and a straight line passing through the piston axial center of the range on the intake valve port side. An intake valve port side squish area and an exhaust valve port side squish area in the range of the exhaust valve port side;
The area of the intake valve port side squish area may be configured to be smaller than the area of the exhaust valve port side squish area.

  According to the above configuration, by making the intake valve port side squish area smaller than the exhaust valve port side squish area, it becomes easier to increase the outer diameter of the intake valve than the exhaust valve, and more air is put into the combustion chamber. It becomes easy to guide.

  A peripheral protrusion that connects the crescent-shaped protrusions may be provided on the peripheral edge of the piston top surface.

  According to the said structure, the tumble flow which flows from the cylinder head side or the tumble flow to the cylinder head side can be guided by providing a peripheral protrusion part. Furthermore, it becomes easy to rectify the air in the peripheral portion toward the center of the combustion chamber, and the combustion efficiency is improved.

  On the upper surface of the piston, the peripheral edge of the combustion chamber may be formed by a curved line that is composed of the crescent-shaped protrusion and the peripheral protrusion and smoothly continues in a circumferential shape.

  According to the above configuration, the peripheral edge of the combustion chamber is formed by a curved line that smoothly and continuously forms a crescent-shaped protrusion and the peripheral protrusion, so that the intake air taken into the combustion chamber is surrounded and centered. It can be collected efficiently and the combustion efficiency can be improved. Furthermore, since the periphery of the combustion chamber is configured with a smooth continuous curve, the flow of air in the combustion chamber is not hindered.

  The crescent-shaped protrusion may be inclined upward as it goes toward the piston axial center, and the crescent-shaped squish surface of the cylinder head may be formed on an inclined surface corresponding to the inclination of the crescent-shaped protrusion.

  According to the above configuration, the crescent-shaped projecting portion is inclined upward as it goes toward the piston axial center, and an inclination corresponding to the crescent-shaped squish surface of the cylinder head is formed, so that the piston performs a compression stroke. When heading to the dead center, the intake air taken into the squish area can be pushed out without leaking into the cylinder, and since the inclination is formed, the intake air can be easily guided to the center in the vertical direction of the combustion chamber.

On the top surface of the piston, in the top view of the piston, a valve escape portion is formed close to the cylinder axial direction of the peripheral protrusion connecting the crescent-shaped protrusions,
The curvature of the inner edge constituting the combustion chamber of the crescent-shaped protrusion and the curvature of the inner edge constituting the combustion chamber of the peripheral protrusion may be larger than the curvature of the peripheral protrusion.

  According to the said structure, since it can suppress that a squish area goes into a cylinder axial direction by enlarging the curvature of a peripheral protrusion part, the distance with a valve | bulb can be taken.

  According to the present invention, the tumble flow rectified by the pair of crescent squish surfaces provided on the cylinder head can be further guided by the crescent-shaped protrusion at the top of the piston, and at the top dead center of the piston, The clearance between the squish surface and the crescent-shaped protrusion can be reduced, the tumble flow vortex flow in the combustion chamber is prevented from being disturbed, the tumble flow flow is improved, and the combustion efficiency of the internal combustion engine Can be improved.

1 is a right side view of a motorcycle on which an internal combustion engine according to an embodiment of the present invention is mounted. It is a right side sectional view of the internal combustion engine. It is a bottom view of a cylinder head. It is the longitudinal cross-sectional view which cut | disconnected the internal combustion engine of the state which lowered | hung the piston in the straight line L which passes along the cylinder axis | shaft CL. It is the longitudinal cross-sectional view which cut | disconnected the internal combustion engine in the state in which the piston was located in the top dead center in the straight line L which passes along the cylinder axis CL. It is a top view of a piston. It is the longitudinal cross-sectional view which expanded the principal part of the piston.

  An embodiment of an internal combustion engine of the present invention will be described with reference to FIGS. FIG. 1 is an overall side view of a motorcycle 1 equipped with an intake structure for an internal combustion engine E according to the present embodiment. In the present specification, the forward and backward directions of the motorcycle 1 are set to the front, and the front, rear, left and right are defined based on the posture facing the front.

  The body frame 2 of the motorcycle 1 is as follows. The main frame 2b fixed to the head pipe 2a extends downward on the vehicle body center line so as to surround the cylinder head 12 of the internal combustion engine E of the motorcycle 1, and then bent downward. A down frame 2c extends downward from the head pipe 2a at an acute angle.

  From the upper rear side of the main frame 2b, a pair of left and right seat rails 2d extend rearward while opening left and right, and a pair of back stays 2e connecting the central portion of the seat rail 2d and the main frame 2b are a pair of seat rails. 2d is supported.

  In such a vehicle body frame 2, a front fork 3 is pivotally supported on the head pipe 2a, a handle 3a extending left and right is attached to the upper end of the front fork 3, and a front wheel 4 is rotatably supported at the lower end. A rear fork 5 pivotally supported at the front end by a pivot plate 2f provided at the lower part of the frame 2b extends rearward, and a rear wheel 6 is pivotally supported at the rear end. The rear fork 5 and the center portion of the seat rail 2d A rear cushion 7 is interposed therebetween. A fuel tank 8 is installed on the main frame 2b, and a seat 9 is supported behind the fuel tank 8 by a seat rail 2d.

  The internal combustion engine E mounted on the vehicle body frame 2 is an SOHC type two-valve single-cylinder four-stroke internal combustion engine. The crankshaft 15 is directed in the vehicle body width direction with respect to the vehicle body, and the internal combustion engine E is directed rearward from above. The cylinder is mounted slightly tilted forward so that it is surrounded by the main frame 2b and surrounded by the down frame 2c from the front to the bottom.

  As shown in FIG. 2, in the internal combustion engine E, a cylinder block 11 and a cylinder head 12 are sequentially stacked on a crankcase 10 and fastened together by bolts (not shown). The upper part of the cylinder head 12 is covered with a head cover 13.

  The crankcase 10 that supports the crankshaft 15 of the internal combustion engine E has a left-right split crankcase structure, and the crankshaft 15 is rotatably supported in the crankcase 10. A transmission gear mechanism 18 is formed between the main shaft 16 and the counter shaft 17 disposed on the rear side, and the counter shaft 17 is an output shaft, and between the counter shaft 17 and the rotation shaft of the rear wheel 6. A chain (not shown) is stretched over and the power of the crankshaft 15 is transmitted to the rear wheel 6.

  A cast iron cylinder liner 11c is cast into the cylinder block 11, and a cylinder bore 11a penetrating vertically is formed in the cylinder liner 11c. A piston 30 is slidably fitted in the cylinder bore 11a, and a crank pin 15p of the crankshaft 15 is connected to the piston 30 via a connecting rod 19.

  As shown in FIG. 4, the lower surface 12 a of the cylinder head 12 is attached to the upper surface 11 b of the cylinder block 11, and the piston top surface 31 of the piston 30 is attached to the lower surface 12 a of the cylinder head 12. A concave ceiling surface 20 that is recessed from the lower surface 12a of the cylinder head 12 is formed so as to face the cylinder head 12, and a combustion chamber 40 is formed between the piston top surface 31 and the ceiling surface 20 of the cylinder head 12. . As shown in FIG. 2, the combustion energy in the combustion chamber 40 of the internal combustion engine E is converted into kinetic energy of the piston 30, whereby the piston 30 is moved up and down, and the crankshaft 15 is rotationally driven via the connecting rod 19. It has come to be.

  FIG. 3 shows a bottom view of the cylinder head 12. 2 and 3, the surface of the lower surface 12a of the cylinder head 12 that faces the piston top surface 31 is the ceiling surface 20 of the combustion chamber 40 as described above. A peripheral edge 20 a of the ceiling surface 20 is formed in a circular shape having substantially the same diameter as the inner diameter of the cylinder bore 11 a provided in the cylinder block 11. On the ceiling surface 20, an intake valve port 21 and an exhaust valve port 22 are opened to the combustion chamber 40, one at opposite positions with respect to the cylinder axis CL, which is the central axis of the cylinder bore 11 a, in the cylinder head 12. Is formed. The inner diameter of the intake valve port 21 is larger than the inner diameter of the exhaust valve port 22. Furthermore, the spark plug hole 23 into which the spark plug 41 is inserted is opened on the ceiling surface 20 so as to be positioned at the center of the intake valve port 21 and the exhaust valve port 22 in the front-rear direction and to the right of the ceiling surface 20. Is provided.

  Further, as shown in FIG. 3, the cylinder head 12 has an intake port 26 communicating with the intake valve port 21 and an exhaust port 27 communicating with the exhaust valve port 22 in directions away from each other across the cylinder shaft CL. It is formed to extend. The intake port 26 is formed to be gently curved rightward from the intake valve port 21 toward the inlet 26a of the intake port 26. The exhaust port 27 is directed from the exhaust valve port 22 to the outlet 27a of the exhaust port 27. And is curved to the right.

  As shown in FIG. 2, the internal combustion engine E has a single intake valve 60 that opens and closes the flow of intake air from the intake port 26 into the combustion chamber 40, and the flow of exhaust gas from the combustion chamber 40 to the exhaust port 27. A single exhaust valve 61 that opens and closes is provided. The intake valve port 21 is provided with an intake valve 60 for opening and closing the intake valve port 21, and the exhaust valve port 22 is provided with an exhaust valve 61 for opening and closing the exhaust valve port 22. The intake valve 60 and the exhaust valve 61 are always urged in the valve closing direction by the coiled valve spring 62. A rocker arm type SOHC type valve operating device 65 for opening and closing the intake valve 60 and the exhaust valve 61 is provided in the head cover 13, and the valve operating device 65 allows the intake valve port 21 and the exhaust valve port 22 to be opened and closed. Are opened and closed at a predetermined timing.

  Further, as shown in FIG. 1, an intake pipe 70, a throttle body 71, a connecting tube 72, and an air cleaner 73 are sequentially connected to the internal combustion engine E to the intake port 26 of the cylinder head 12. The outside air is sent to the connecting tube 72, the throttle body 71, and the intake pipe 70 in this order, and the fuel spray injected from the fuel injection valve 74 inserted into the intake pipe 70 is mixed to become an air-fuel mixture. To be sent to the combustion chamber 40.

  As shown in FIG. 3, the ceiling surface 20 provided on the lower surface 12 a of the cylinder head 12 constituting the combustion chamber 40 of the internal combustion engine E has a ceiling surface so as to surround the intake valve port 21 and the exhaust valve port 22. A pair of crescent-shaped squish surfaces 24 formed in a crescent-shaped plane are provided on the inner side along the inner diameter of 20 on the left and right sides of the cylinder axis CL. In the present invention, the crescent shape is a shape surrounded by an outer edge that bulges outward and an inner edge that is recessed inward, and the outer edge consists of a single curve with one curvature. The inner edge means a shape composed of at least one curve having a different curvature from the outer edge.

  As shown in FIG. 3, the crescent-shaped squish surface 24 includes an outer edge 24a located on the outer side and an inner edge 24b. The outer edge 24 a of the crescent-shaped squish surface 24 is composed of a single curve with the same curvature as the peripheral edge 20 a of the ceiling surface 20. The inner edge 24b is formed so that one end thereof is along the outer diameter of the exhaust valve port 22, and the other end is formed so as to follow the shape of the outer diameter of the intake valve port 21 while maintaining a certain distance from the intake valve port 21. In the meantime, a smooth curve having a smaller curvature than the curvature of the outer edge 24a is connected between them. As shown in FIG. 4, the outer edge 24a is flush with the lower surface 12a of the cylinder head 12, and upwards from the outer edge 24a of the crescent-shaped squish surface 24 toward the inner inner edge 24b. It is formed on an inclined surface 24c.

  Further, as shown in FIG. 3, the range in which the intake valve port 21 and the exhaust valve port 22 are surrounded on both sides in the radial direction by a pair of crescent squish surfaces 24 is elliptical on the ceiling surface 20 of the cylinder head 12. A dome-shaped recess 25 is formed, and the cross-sectional shape of the dome-shaped recess 25 is formed to be a dome shape recessed upward as shown in FIG.

  As shown in FIG. 4, a piston top surface 31 of a piston 30 slidably fitted in a cylinder bore 11 a penetrating in the vertical direction of the cylinder block 11 is a ceiling surface provided on the cylinder head 12. Opposed to 20.

As shown in FIGS. 3, 5, and 6, the piston top surface 31 has a pair of corresponding shapes at positions facing the pair of crescent squish surfaces 24 provided on the ceiling surface 20 of the cylinder head 12. The crescent shaped protrusion 33 is provided. As shown in FIG. 6, a peripheral protrusion 31 is provided on the peripheral edge 31 a of the piston top surface 31 so as to connect and connect the pair of crescent-shaped protrusions 33. The pair of crescent-shaped protrusions 33 and the pair of peripheral protrusions 34 form a protrusion 32 that surrounds the peripheral edge 31a of the piston top surface 31 and protrudes. An inner edge 32a of the protrusion 32 is composed of an inner edge 33a of the crescent-shaped protrusion 33 and an inner edge 34a of the peripheral protrusion 34, and the curvature χ ₁ of the inner edge 33a constituting the combustion chamber 40 of the crescent-shaped protrusion 33 is The curvature χ ₂ of the inner edge 34a constituting the combustion chamber 40 of the peripheral protrusion 34 is larger than the curvature χ ₂ of the inner edge 34a of the peripheral protrusion 34. The inner edge 33a of the crescent-shaped protrusion 33 and the inner edge 34a of the peripheral protrusion 34 are formed by a continuous curve, and the inner edge 32a of the protrusion 32 serving as the peripheral edge 40a on the piston side of the combustion chamber 40 is all smooth. It consists of a continuous curve.

  As shown in FIG. 4, the crescent-shaped protrusion 33 is formed on an inclined surface 24c inclined upward as it goes toward the piston axial center 30C. As shown in FIG. It is formed on an inclined surface 33b corresponding to the inclination of the crescent-shaped squish surface 24 of the cylinder head 12 in a state of being positioned at a point.

  As shown in FIGS. 4 and 6, the inside of the protruding portion 32 of the piston top surface 31 is an indented portion 35 that is recessed in an elliptical shape when viewed from above, and between the protruding portion 32 and the recessed portion 35, A step 36 is formed. As shown in FIG. 7, the cross-sectional shape of the step portion 36 includes a straight portion 36 a and a curved portion 36 b, and the straight portion 36 a is formed at an angle close to a right angle with respect to the top surface of the protruding portion 32. The straight portion 36a and the dent portion 35 are formed by a curved surface that is continuous by the curved portion 36b, and the step portion 36 and the dent portion 35 are connected smoothly and continuously.

  As described above, the inclined surface 33b of the crescent-shaped protrusion 33 of the piston top surface 31 is formed so as to correspond to the inclined surface 24c of the crescent-shaped squish surface 24 of the cylinder head 12, and is provided on the cylinder head 12. The squirrel-shaped squish surface 24 and the crescent-shaped protrusion 33 provided on the piston top surface 31 constitute a squish area 50. As shown in FIG. 5, when the piston 30 rises, the combustion gas in the combustion chamber 40 is pushed and collected toward the center of the combustion chamber 40 by the squish area 50, and the combustion efficiency of the internal combustion engine E can be improved. It is like that. As shown in FIG. 6, the squish area 50 is the same area as the protrusion 32 in the top view of the piston 30. The combustion chamber 40 of the internal combustion engine E includes a dome-shaped recess 25 in the ceiling surface 20 of the cylinder head 12 and a recess 35 in the piston top surface 31 when the piston 30 is located at the top dead center.

  FIG. 3 shows a straight line LB connecting the center 21C of the intake valve port 21 and the center 22C of the exhaust valve port 22, and a straight line L orthogonal to the straight line LB and passing through the piston axial center 30C is shown. Has been. As shown in FIG. 6, in the top view of the piston, the protrusion 32 of the piston 30 corresponding to the squish area 50 is partitioned by a straight line L, and the intake valve port side squish area 50a in the intake valve port side range; It is divided into an exhaust valve port side squish area 50b in the range on the exhaust valve port side. The area of the intake valve port side squish area 50a is formed to be smaller than the area of the exhaust valve port side squish area 50b.

  A valve escape portion 37 is formed on the piston top surface 31 so that the intake valve 60 and the exhaust valve 61 can be avoided when the piston 30 rises to the cylinder head 12 side. When viewed from the top of the piston 30, the intake valve escape portion 37 a is arranged along the peripheral protrusion 34 on the intake valve port 21 side in close proximity to the curved surface on the inner cylinder shaft side, and the peripheral protrusion on the exhaust valve port 22 side. Exhaust valve relief portions 37b are provided so as to be recessed from the piston top surface 31 so as to be close to the curved surface on the inner cylinder shaft side. Since the diameter of the umbrella portion 60a of the intake valve 60 is larger than the diameter of the umbrella portion 61a of the exhaust valve 61, the intake valve escape portion 37a is formed to have a larger area than the exhaust valve escape portion 37b.

  As described above, the internal combustion engine E of the present embodiment includes the piston top surface 31 of the piston 30 slidably fitted in the cylinder bore 11a of the cylinder block 11, and the cylinder head 12 opposed to the piston top surface 31. A combustion chamber 40 is formed between the cylinder head 12 and the ceiling surface 20, and an intake valve port 21 and an exhaust valve port are provided on the ceiling surface 20 of the cylinder head 12 one at a position opposite to each other with respect to the cylinder axis CL that is the central axis of the cylinder bore 11 a 22 is opened facing the combustion chamber 40, and the cylinder head 12 is formed with an intake port 26 and an exhaust port 27 respectively extending from the intake valve port 21 and the exhaust valve port 22 so as to extend away from each other. The ceiling surface 20 is provided with a pair of crescent squish surfaces 24 on the outer side in the inner diameter direction, and the intake valve port 21 and the exhaust valve port 22 are radially formed on the ceiling surface 20 by the pair of crescent squish surfaces 24. Position surrounded by both sides In addition, a dome-shaped recess 25 having an elliptical cross-sectional shape is provided, and a crescent-shaped projecting portion projecting from the piston top surface 31 to the cylinder head 12 side at a position facing the crescent-shaped squish surface 24 on the piston top surface 31 33 is provided, and the squish area 50 is constituted by the crescent-shaped squish surface 24 and the crescent-shaped projecting portion 33.

  Since the internal combustion engine E of the present embodiment is configured as described above, the tumble flow rectified by the pair of crescent squish surfaces 24 provided on the cylinder head 12 is further projected into a crescent shape on the piston top surface 31. Since the squish area 50 is constituted by the crescent squish surface 24 and the crescent-shaped protrusion 33, the crescent squish surface 24 and the crescent-shaped protrusion are formed at the top dead center of the piston 30. It is possible to reduce the gap between the portion 33 and the tumble flow in the combustion chamber 40 without disturbing the tumble flow, and the combustion efficiency of the internal combustion engine E can be improved. Can be improved.

  Further, the piston top surface 31 is formed with an elliptical recess 35 in a top view, and a step 36 is provided between the recess 35 and the crescent-shaped projection 33, and the step 36 and the recess are formed. 35 is formed by a continuous curved surface, so that the tumble flow is received by the indented portion 35 formed on the piston top surface 31, and at the stepped portion 36 between the indented portion 35 and the crescent-shaped protruding portion 33, Since the flow can be guided, the flow of the tumble flow can be further improved.

  The cross-sectional shape of the stepped portion 36 includes a straight portion 36a and a curved portion 36b. The straight portion 36a is formed at an angle close to a right angle with respect to the top surface of the protruding portion 32. 36a and the dent portion 35 are formed by a curved surface that is continuous by a curved portion 36b, and the step portion 36 and the dent portion 35 are connected smoothly and continuously, so that the tumble flow from above guided by the cylinder head 12 is achieved. Can be smoothly guided to the recessed portion 35 by a curved surface formed by the curved portion 36b, and the flow can be further improved without disturbing the vortex flow of the tumble flow.

  Furthermore, the squish area 50 is defined by a straight line L orthogonal to a straight line LB connecting the center 21C of the intake valve port 21 and the center 22C of the exhaust valve port 22 in the top view of the piston 30 and passing through the piston axial center 30C. The intake valve port side squish area 50a in the range on the intake valve port side and the exhaust valve port side squish area 50b in the range on the exhaust valve port side are divided into the exhaust valve side squish area 50a. Since it is configured to be smaller than the area of the mouth-side squish area 50 b, it becomes easier to increase the outer diameter of the intake valve port 21 than the exhaust valve port 22, and more air is put into the combustion chamber 40. It becomes easy to guide.

  Further, since the peripheral protrusion 31 connecting the crescent-shaped protrusions 33 is provided on the peripheral edge 31a of the piston top surface 31, it is possible to guide the tumble flow flowing from the cylinder head 12 side or the cylinder head side. . Furthermore, it becomes easy to rectify the air in the peripheral portion toward the center of the combustion chamber, and the combustion efficiency can be improved.

  On the piston top surface 31, the inner edge 32 a of the protrusion 32, which is the peripheral edge 40 a of the piston-side combustion chamber 40, smoothly continues in a circumferential shape composed of the inner edge 33 a of the crescent-shaped protrusion 33 and the inner edge 34 a of the peripheral protrusion 34. Since the peripheral edge 40a of the combustion chamber 40 is formed by a continuous curve, the intake air taken into the combustion chamber 40 can be efficiently collected around the center, and the combustion of the internal combustion engine E can be performed. Efficiency can be improved. Furthermore, since the peripheral edge 40a of the combustion chamber 40 is configured by a curve, the flow of air in the combustion chamber 40 is not hindered.

  The crescent-shaped protrusion 33 is formed so as to be inclined upwardly toward the piston axial center 30C, and the crescent-shaped squish surface 24 of the cylinder head 12 is formed on an inclined surface corresponding to the inclination of the crescent-shaped protrusion 33. Therefore, when the piston 30 goes to the top dead center to perform the compression stroke, the intake air taken into the squish area 50 can be pushed out without leaking into the cylinder, and the inclination is formed so that the intake air is injected into the combustion chamber 40. It becomes easy to guide to the center part of the up and down direction.

A valve escape portion 37 is formed on the piston top surface 31 in the cylinder axial direction of the peripheral projection 34 connecting the crescent-shaped projections 33 in the top view of the piston 30, and the combustion chamber 40 of the crescent-shaped projection 33 is defined. Since the curvature χ ₁ of the inner edge 33 a and the curvature χ ₂ of the inner edge 34 a constituting the combustion chamber 40 of the peripheral protrusion 34 are larger than the curvature χ ₂ of the peripheral protrusion 34, the peripheral protrusion 34 Since the squish area 50 is prevented from entering the cylinder axis CL direction by increasing the curvature χ ₂ , the distance between the intake valve 60 and the exhaust valve 61 can be increased.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various other modifications are possible. The internal combustion engine E of the present invention is not limited to the motorcycle 1 and can be widely applied to other types of saddle-type vehicles.

E: Internal combustion engine, CL: Cylinder shaft, LB: Straight line, L ... Straight line, χ ₁ ... Curvature, χ ₂ ... Curvature,
DESCRIPTION OF SYMBOLS 1 ... Motorcycle, 11 ... Cylinder block, 11a ... Cylinder bore, 12 ... Cylinder head, 20 ... Ceiling surface, 21 ... Intake valve port, 21C ... Center, 22 ... Exhaust valve port, 22C ... Center, 24 ... Crescent squish surface 24c ... Inclined surface, 25 ... Dome-shaped recess, 26 ... Intake port, 27 ... Exhaust port, 30 ... Piston, 30C ... Piston axial center, 31 ... Piston top surface, 31a ... Periphery, 32 ... Projection, 33 ... Crescent projection, 33a ... inner edge, 34 ... periphery protrusion, 34a ... inner edge, 35 ... recessed part, 36 ... stepped part, 37 ... valve relief part, 40 ... combustion chamber, 40a ... periphery, 50 ... squish area, 50a ... intake valve side squish area, 50b ... exhaust valve side squish area.

Claims (12)

The piston top surface (31) of the piston (30) slidably fitted in the cylinder bore (11a) of the cylinder block (11) and the ceiling of the cylinder head (12) opposed to the piston top surface (31) Combustion chamber (40) is formed between the surface (20) and
On the ceiling surface (20) of the cylinder head (12), an intake valve port (21) and an exhaust valve port (one) are respectively placed at positions opposite to each other with respect to the cylinder axis (CL) which is the central axis of the cylinder bore (11a). 22) is opened facing the combustion chamber (40),
In the cylinder head (12), an intake port (26) and an exhaust port (27) are respectively formed to extend away from the intake valve port (21) and the exhaust valve port (22),
The ceiling surface (20) of the cylinder head (12) is provided with a pair of crescent squish surfaces (24) on the outer side in the inner diameter direction,
On the ceiling surface (20), the intake valve port (21) and the exhaust valve port (22) are oval in cross-sectional shape at a position surrounded by a pair of crescent-shaped squish surfaces (24) on both sides in the radial direction. In the internal combustion engine (E) provided with a dome-shaped recess (25) of
On the piston top surface (31), a crescent-shaped projecting portion (33) projecting from the piston top surface (31) to the cylinder head side is provided at a position facing the crescent-shaped squish surface (24),
The crescent-shaped squish surface (24) and the crescent-shaped protrusion and by (33), the squish area (50) is configured Rutotomoni,
The peripheral edge (31a) of the piston top surface (31) is provided with a peripheral protrusion (34) connecting both ends of the crescent-shaped protrusion (33), respectively.
The curvature (χ ₁ ) of the inner edge (33a) constituting the combustion chamber (40) of the crescent-shaped protrusion (33) and the inner edge of the peripheral protrusion (34) constituting the combustion chamber (40) ( An internal combustion engine characterized in that the curvature (χ ₂ ) of 34a) is different . The piston top surface (31) is formed with an elliptical recess (35) in a top view,
A step portion (36) is provided between the dent portion (35) and the crescent-shaped projection portion (33),
The internal combustion engine according to claim 1, wherein the step portion (36) and the dent portion (35) are formed by a continuous curved surface. The squish area (50) is a straight line (LB) connecting the center (21C) of the intake valve port (21) and the center (22C) of the exhaust valve port (22) in a top view of the piston (30). ) And a straight line (L) passing through the piston axial center (30C), the intake valve port side squish area (50a) in the range on the intake valve port (21) side, and the exhaust valve port (22) Is divided into the exhaust valve side squish area (50b)
The internal combustion engine according to claim 1 or 2, wherein an area of the intake valve port side squish area (50a) is smaller than an area of the exhaust valve port side squish area (50b). On the upper surface of the piston (30),
A peripheral edge (40a) of the combustion chamber (40) is formed by a curved line that is formed of the crescent-shaped protrusion (33) and the peripheral protrusion (34) and smoothly continues in a circumferential shape. The internal combustion engine according to claim 3 . The crescent-shaped protrusion (33) is inclined upward as it goes toward the piston axial center (30C),
Crescent-shaped squish surface of the cylinder head (12) (24) according to claim 1 to claim 4, characterized in that the inclined and the inclined surface corresponding crescent shaped protrusion (33) (24c) is formed An internal combustion engine according to any one of the above. In the piston top surface (31), in the top view of the piston (30), a valve escape portion (close to the cylinder axial direction of the peripheral protrusion (34) connecting the crescent-shaped protrusions (33) to each other ( 37) is formed,
The curvature (χ ₁ ) of the inner edge (33a) constituting the combustion chamber (40) of the crescent-shaped protrusion (33) and the inner edge (34a) of the peripheral protrusion (34) constituting the combustion chamber (40) curvature) (chi ₂₎ is an internal combustion engine according to claim 5, wherein the direction of curvature of the inner edge (34b) of the peripheral protrusion ₍₃₄₎ (χ ₂₎ is large. The piston top surface (31) of the piston (30) slidably fitted in the cylinder bore (11a) of the cylinder block (11) and the ceiling of the cylinder head (12) opposed to the piston top surface (31) Combustion chamber (40) is formed between the surface (20) and
On the ceiling surface (20) of the cylinder head (12), an intake valve port (21) and an exhaust valve port (one) are respectively placed at positions opposite to each other with respect to the cylinder axis (CL) which is the central axis of the cylinder bore (11a). 22) is opened facing the combustion chamber (40),
In the cylinder head 12, an intake port (26) and an exhaust port (27) are respectively formed extending from the intake valve port (21) and the exhaust valve port (22) in directions away from each other,
The ceiling surface (20) of the cylinder head (12) is provided with a pair of crescent squish surfaces (24) on the outer side in the inner diameter direction,
On the ceiling surface (20), the intake valve port (21) and the exhaust valve port (22) are oval in cross-sectional shape at a position surrounded by a pair of crescent-shaped squish surfaces (24) on both sides in the radial direction. In the internal combustion engine (E) provided with a dome-shaped recess (25) of
On the piston top surface (31), a crescent-shaped projecting portion (33) projecting from the piston top surface (31) to the cylinder head side is provided at a position facing the crescent-shaped squish surface (24),
The crescent-shaped squish surface (24) and the crescent-shaped projecting portion (33) constitute a squish area (50),
The crescent-shaped protrusion (33) is inclined linearly upward as it goes toward the piston axial center (30C),
The internal combustion engine , wherein the crescent-shaped squish surface (24) of the cylinder head (12) is formed with an inclined surface (24c) corresponding to the inclination of the crescent-shaped projecting portion (33) . The piston top surface (31) is formed with an elliptical recess (35) in a top view,
A step portion (36) is provided between the dent portion (35) and the crescent-shaped projection portion (33),
The internal combustion engine according to claim 7, wherein the step portion (36) and the dent portion (35) are formed by a continuous curved surface. The squish area (50) is a straight line (LB) connecting the center (21C) of the intake valve port (21) and the center (22C) of the exhaust valve port (22) in a top view of the piston (30). ) And a straight line (L) passing through the piston axial center (30C), the intake valve port side squish area (50a) in the range on the intake valve port (21) side, and the exhaust valve port (22) Is divided into the exhaust valve side squish area (50b)
The internal combustion engine according to claim 7 or 8, wherein an area of the intake valve port side squish area (50a) is smaller than an area of the exhaust valve port side squish area (50b). The peripheral edge (31a) of the piston top surface (31) is provided with a peripheral protrusion (34) connecting the crescent-shaped protrusions (33) to each other. An internal combustion engine according to any one of the above. On the upper surface of the piston (30),
A peripheral edge (40a) of the combustion chamber (40) is formed by a curved line that is formed of the crescent-shaped protrusion (33) and the peripheral protrusion (34) and smoothly continues in a circumferential shape. The internal combustion engine according to claim 10. In the piston top surface (31), in the top view of the piston (30), a valve escape portion (close to the cylinder axial direction of the peripheral protrusion (34) connecting the crescent-shaped protrusions (33) to each other ( 37) is formed,
The curvature (χ of the inner edge (33a) constituting the combustion chamber (40) of the crescent-shaped protrusion (33) ₁ ) And the curvature (χ of the inner edge (34a) constituting the combustion chamber (40) of the peripheral protrusion (34) ₂ ) Is the curvature (χ of the inner edge (34b) of the peripheral protrusion (34). ₂ The internal combustion engine according to claim 11, wherein:

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