JP6592391B2 - Air-cooled internal combustion engine - Google Patents

Description

  The present invention relates to a crankcase that rotatably supports a crankshaft, a cylinder block that has a cylinder bore that slidably fits a piston and is coupled to the crankcase, and a combustion chamber that faces the top of the piston And a cylinder head that is coupled to the cylinder block and is disposed so that the exhaust valve can be opened and closed, and a part of a valve mechanism that opens and closes the exhaust valve is provided. A camshaft having an axis along a plane perpendicular to the axis of the cylinder bore is rotatably supported by the cylinder head, and a part of an exhaust port in which exhaust from the combustion chamber is controlled by the exhaust valve And first and second fastening bosses for connecting an exhaust pipe communicating with the exhaust port to the exhaust pipe connection pipe part. Is formed integrally with the cylinder head, a cooling air passage for cooling the periphery of the combustion chamber is formed in the cylinder head, and the exhaust gas is disposed at a position adjacent to the first fastening boss among the first and second fastening bosses. The present invention relates to an air-cooled internal combustion engine in which a sensor mounting boss for mounting an oxygen sensor is integrally projected on a pipe connecting pipe portion.

  Such an air-cooled internal combustion engine is known from Patent Document 1.

JP 2013-72383 A

  However, in the one disclosed in the above-mentioned Patent Document 1, on a projection view on a plane including the axis of the cylinder bore and the axis of the camshaft, on one side of an imaginary line connecting the centers of the tip ends of the pair of fastening bosses, The oxygen sensor and the one end opening of the cooling air passage are disposed, and the oxygen sensor and the fastening boss tend to hinder the flow of the cooling air flowing through the cooling air passage. In order to protect the area around the oxygen sensor from thermal damage, it is desirable to improve the cooling performance around the oxygen sensor. However, the fastening boss disposed near the oxygen sensor out of the pair of fastening bosses circulates around the oxygen sensor. This tends to hinder the flow of cooling air. Therefore, it is desired to further facilitate the circulation of the cooling air around the cooling air passage and the oxygen sensor.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an air-cooled internal combustion engine that can more smoothly distribute the cooling air around the cooling air passage and the oxygen sensor.

  In order to achieve the above object, the present invention provides a crankcase for rotatably supporting a crankshaft, a cylinder block having a cylinder bore for slidably fitting a piston, and a cylinder block coupled to the crankcase, Combustion chamber facing the top of the piston is formed between the cylinder block and coupled to the cylinder block, and the exhaust valve is arranged to be openable and closable, and the exhaust valve is driven to open and close A camshaft that constitutes a part of the valve mechanism that has an axis along a plane orthogonal to the axis of the cylinder bore is rotatably supported by the cylinder head, and exhaust from the combustion chamber is controlled by the exhaust valve. An exhaust pipe connecting pipe part that forms a part of the exhaust port inside, and an exhaust pipe that communicates with the exhaust port are connected to the exhaust pipe connecting pipe part. The first and second fastening bosses project integrally with the cylinder head, and a cooling air passage for cooling the periphery of the combustion chamber is formed in the cylinder head. The first of the first and second fastening bosses In an air-cooled internal combustion engine in which a sensor mounting boss for mounting an oxygen sensor is integrally projected from the exhaust pipe connecting pipe portion at a position adjacent to a fastening boss, the axis of the cylinder bore and the axis of the camshaft are parallel to each other. The sensor mounting boss and one end opening of the cooling air passage are arranged on one side of an imaginary line passing through the center of the tip of the first and second fastening bosses on the first projection onto the plane. A screw which the first fastening boss has at least a part of the communication passage formed in the cylinder head so as to cross the above, on a second projection view on a plane perpendicular to the axis of the cylinder bore And the first being disposed between the exhaust port.

  According to the present invention, in addition to the configuration of the first feature, at least a part of a portion of the communication path disposed between the screw hole and the exhaust port is a through hole on the second projection view. The second feature is that it is formed as follows.

  In the present invention, in addition to the configuration of the second feature, on the second projection view, the opening end of the through hole on the one side of the imaginary line is more than the first fastening boss. The third feature is that the first end is disposed near the one end opening.

  In the present invention, in addition to the configuration of the second feature, on the second projection view, the opening end of the through hole on the one side of the imaginary line has the cooling air passage more than the sensor mounting boss. It is the 4th characteristic to arrange near the above-mentioned one end opening.

  According to the present invention, in addition to the configuration of the second feature, a concave passage that opens the cylinder block side so as to form the communication passage together with the through hole is provided on a surface of the cylinder head that faces the cylinder block. A fifth feature is that a part of the concave passage is arranged so as to overlap the sensor mounting boss on the second projection.

  Furthermore, in addition to the configuration of the first feature, the present invention provides that the one end opening of the cooling air passage is part of the oxygen sensor attached to the sensor attachment boss on the first projection view. It is the sixth feature that they are arranged at overlapping positions.

  According to the first aspect of the present invention, one of the imaginary lines passing through the centers of the tip ends of the first and second fastening bosses on the first projection onto the plane parallel to the axis of the cylinder bore and the axis of the camshaft. The sensor mounting boss and the one end opening of the cooling air passage are arranged on the side, but the communication passage formed in the cylinder head crosses the imaginary line, thereby Cooling air can be smoothly circulated, and at least a part of the communication path is disposed between the screw hole of the first fastening boss and the exhaust port on a second projection view on a plane orthogonal to the axis of the cylinder bore. Therefore, the cooling air can be circulated also around the oxygen sensor, and the area around the oxygen sensor can be cooled.

  According to the second feature of the present invention, at least a part of a portion of the communication path disposed between the screw hole and the exhaust port on the second projection view is a through-hole. Of these, by surrounding at least a part of the cylinder head with the meat of the cylinder head, the rigidity of the first fastening boss can be secured, and the support rigidity of the exhaust pipe at the first fastening boss can also be increased.

  According to the third feature of the present invention, since the through hole is opened at a position closer to the one end opening of the cooling air passage than the first fastening boss, the first fastening boss is located near the one end opening of the cooling air passage. Even if it exists, it can distribute | circulate cooling air more efficiently around the one end opening part of a cooling air channel | path.

  According to the fourth aspect of the present invention, since the through hole opens at a position closer to the one end opening of the cooling air passage than the sensor mounting boss, the sensor mounting boss is located near the one end opening of the cooling air passage. In addition, the cooling air can be distributed more efficiently around the one end opening of the cooling air passage.

  According to the fifth feature of the present invention, the concave passage provided on the surface of the cylinder head facing the cylinder block constitutes a communication passage together with the through hole, and a part of the concave passage is formed on the second projection view. Since it overlaps the sensor mounting boss, the cooling air flowing through the concave passage can be efficiently cooled around the sensor mounting boss, and the cooling air can be distributed more efficiently around the one end opening of the cooling air passage. it can.

  Further, according to the sixth aspect of the present invention, since the one end opening of the cooling air passage overlaps with a part of the oxygen sensor on the first projection view, the periphery of the oxygen sensor is cooled by the cooling air flowing through the communication passage. In addition, the oxygen sensor can be cooled with cooling air flowing around the oxygen sensor.

1 is a left side view of a motorcycle. FIG. 2 is a sectional view taken along line 2-2 in FIG. FIG. 3 is a partial cross-sectional view of the engine body taken along line 3-3 in FIG. 2. It is the front view which looked at the cylinder head from the 4 arrow direction of FIG. FIG. 5 is a view taken along line 5-5 in FIG. 3. FIG. 6 is a sectional view taken along line 6-6 of FIG. FIG. 7 is a cross-sectional view taken along line 7-7 in FIG. 5. FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 5. FIG. 9 is a sectional view taken along line 9-9 in FIG. 5.

  Embodiments of the present invention will be described with reference to FIGS. 1 to 8 attached hereto. In the following description, front and rear, left and right, and top and bottom refer to directions as viewed from a rider riding a motorcycle.

  First, in FIG. 1, a front fork 12 and a bar-shaped steering handle 13 that pivotally support a front wheel WF are supported by a head pipe 11 at the front end of the body frame F of the motorcycle so as to be steerable. A down frame 14 constituting a part of F is disposed behind the front wheel WF so as to extend rearwardly downward from the head pipe 11. Further, a rear wheel WR is pivotally supported on the rear portion of the swing arm 15 supported so as to be swingable up and down at an intermediate portion in the front-rear direction of the body frame F.

  An engine body 16 of an air-cooled internal combustion engine E that exerts power for driving the rear wheel WR is supported by the vehicle body frame F so as to be disposed between the down frame 14 and the rear wheel WR. A mount member 17 that supports the front portion of the crankcase 21 included in the engine body 16 is fixed to the lower portion of the down frame 14. A fuel tank 18 disposed above the engine body 16 is supported by the front portion of the vehicle body frame F, and a riding seat 19 disposed behind the fuel tank 18 is supported by the rear portion of the vehicle body frame F. The

  2 and 3 together, the engine main body 16 includes a crankcase 21 that rotatably supports a crankshaft 20 (see FIG. 1) extending in the vehicle width direction, and a slightly forward tilted posture. A cylinder block 22 that is coupled to the front upper part of the crankcase 21 and rises upward, a cylinder head 23 that is coupled to the upper part of the cylinder block 22, and a head cover 24 that is coupled to the cylinder head 23 from above. The cylinder block 22 is integrally provided with a plurality of cooling fins 22a that are spaced apart in the vertical direction, and also cools at a plurality of locations spaced in the vertical direction of the cylinder head 23. The fins 23a are integrally projected.

  A piston 26 connected to the crankshaft 20 is slidably fitted in a cylinder bore 25 of the cylinder block 22, and a combustion chamber 27 that faces the top of the piston 26 includes the cylinder block 22 and the cylinder block 22. It is formed between the cylinder heads 23.

  On the rear side wall of the cylinder head 23, an intake pipe connecting pipe portion 30 that forms an intake port 29 for taking air into the combustion chamber 27 is integrally projected so as to protrude rearward. An intake pipe 32 constituting a part of an intake device 31 extending rearward from the cylinder head 23 is connected to the pipe connection pipe portion 30.

  4 to 6, an exhaust pipe connecting pipe portion 34 that forms a part of an exhaust port 33 that discharges combustion gas from the combustion chamber 27 is formed on the right side wall of the cylinder head 23. An exhaust pipe 36 that is part of an exhaust device 35 is connected to the exhaust pipe connecting pipe portion 34 so as to project obliquely forward, and the exhaust pipe 36 is shown in FIG. Thus, it extends rearward through the lower part of the engine body 16.

  A flange 37 on the exhaust pipe 36 side is fastened to the front side wall of the cylinder head 23 with bolts 38 and 39 in order to connect the exhaust pipe 36 to the exhaust pipe connecting pipe portion 34. The second fastening bosses 40 and 41 are integrally protruded, and the first fastening boss 40 is disposed at a position continuous to the lower left portion of the exhaust pipe connecting pipe portion 34, whereas the second fastening boss 40 41 is arranged at a position continuous with the middle portion on the right side of the exhaust pipe connecting pipe section 34 on the right side.

  Referring to FIG. 3, an intake valve 43 that controls intake air from the exhaust port 29 to the combustion chamber 27 is arranged in the cylinder head 23 so that it can be opened and closed while being urged by a valve spring 45 in the valve closing direction. An exhaust valve 44 that controls exhaust from the combustion chamber 27 to the exhaust port 33 is disposed so as to be opened and closed while being urged by a valve spring 46 in the valve closing direction. A valve operating mechanism 48 for opening and closing the intake valve 43 and the exhaust valve 44 is accommodated in a valve operating chamber 47 formed between the head covers 24.

  The valve mechanism 48 is linked to and coupled to the crankshaft 20 via a timing transmission mechanism (not shown), and is rotatably supported by the cylinder head 23. The camshaft 49 and the intake valve And an exhaust side rocker arm 51 interposed between the camshaft 49 and the exhaust valve 44. The camshaft 49 has an axis C2 parallel to the axis of the crankshaft 20 and orthogonal to the axis of the cylinder bore 25, that is, the cylinder axis C1, and the cylinder head has an axis parallel to the camshaft 49. The intake-side and exhaust-side rocker arms 50 and 51 are swingably supported by a rocker shaft 52 supported by 23.

  The cylinder head 23 is provided with a plug mounting seat 54 having a plug mounting hole 53 that opens on the right side wall thereof, and an ignition plug 55 that faces the tip of the combustion chamber 27 is mounted on the plug mounting seat 54. It is done.

  An oxygen sensor 57 for detecting oxygen components in the combustion gas flowing through the exhaust port 33 is attached to the exhaust pipe connecting pipe portion 34, and a mounting hole which is a screw hole for attaching the oxygen sensor 57 A sensor mounting boss 59 having 58 is located on the left side of the exhaust pipe connecting pipe portion 34 at a position adjacent to the first fastening boss 40 of the first and second fastening bosses 40, 41, that is, a position near the first fastening boss 40. Projected integrally with the wall.

  By the way, stud bolt holes for inserting stud bolts (not shown) for connecting the cylinder head 23 and the cylinder block 22 to the crankcase 21 are inserted into the cylinder head 23 at four locations around the combustion chamber 27. Mounting bosses 65, 66, 67, 68 having 61, 62, 63, 64 are integrally provided.

  7 and 8 together, the cylinder head 23 is provided with a cooling air passage 69 for cooling the periphery of the combustion chamber 27 in a range surrounded by the mounting bosses 65-68. One end opening 69 a of the cooling air passage 69 is formed between the attachment boss 65 to 68 and the left front mounting boss 65 and the exhaust pipe connecting pipe portion 34. The end opening 69b is disposed between the two right mounting bosses 67 and 68, and is formed to be bifurcated so that the cooling air flows through both sides of the spark plug 55 attached to the plug mounting seat 54.

  Further, on the left side of the exhaust pipe connecting pipe portion 34 on the front side wall of the cylinder head 23, a recess 70 for guiding traveling air from the front of the motorcycle to the cooling air passage 69 is provided at the one end of the cooling air passage 60. It is formed so as to be continuous with the opening 69 a, and the cooling air from the other end opening 69 b of the cooling air passage 69 flows on the right side wall of the cylinder head 23 to the right side of the cylinder head 23. A recess 71 is formed which is continuous with the other end opening 69b.

  As shown in FIG. 4, on the first projection view onto the plane parallel to the cylinder axis C1 and the axis C2 of the camshaft 49, the tip end centers 40a, 41a of the first and second fastening bosses 40, 41 are shown. The sensor mounting boss 59 and the one end opening 69a of the cooling air passage 69 are disposed on one side of the imaginary line L passing through.

  On the first projection (corresponding to FIG. 4), a communication path 72 that crosses the virtual line L is formed in the cylinder head 23, and at least a part of the communication path 72 is formed by the first fastening boss 40. 9 corresponding to the projected view in the direction along the axis of the bottomed screw hole 73 and the second projected view on the plane perpendicular to the cylinder axis C1, as shown in FIG. It is disposed between the screw hole 73 and the exhaust port 33.

  Moreover, at least a part of the communication path 72 disposed between the screw hole 73 and the exhaust port 33 on the second projection view (the figure corresponding to FIGS. 6 and 9) (one in this embodiment) Part) is formed by a through hole 74.

  Moreover, the opening end of the through hole 74 on the one side of the imaginary line L is more than the first fastening boss 40 and the sensor mounting boss 59 on the second projection view, as shown in FIG. The cooling air passage 69 is disposed near the one end opening 69a.

  By the way, the surface of the cylinder head 23 facing the cylinder block 22 is provided with a concave passage 75 that opens the cylinder block 22 side so as to form the communication passage 72 together with the through-hole 74. As shown in FIG. 5, a part of is arranged so as to overlap the sensor mounting boss 59 on the second projection view.

  Further, the one end opening 69a of the cooling air passage 69 overlaps with a part of the oxygen sensor 57 attached to the sensor attachment boss 59 on the first projection view as shown in FIG. Be placed.

  Next, the operation of this embodiment will be described. First and second fastening bosses 40 and 41 are connected to the cylinder head 23 of the air-cooled internal combustion engine E in order to connect the exhaust pipe 36 to the exhaust pipe connecting pipe portion 34. Are projected integrally, and on the first projection view onto a plane parallel to the cylinder axis C1 and the axis C of the camshaft 49, the distal ends 40a, 41a of the first and second fastening bosses 40, 41 are shown. A sensor mounting boss 59 and one end opening 69a of the cooling air passage 69 are disposed on one side of the virtual line L passing through the heart. The sensor mounting boss 59 and one end opening 69a of the cooling air passage 69 are disposed across the virtual line L. Since the passage 72 is formed, the cooling air can be smoothly circulated around the one end opening 69 a of the cooling air passage 69. In addition, since at least a part of the communication path 72 is disposed between the screw hole 73 and the exhaust port 33 of the first fastening boss 40 on the second projection view onto the plane orthogonal to the cylinder axis C1, oxygen Cooling air can also be circulated around the sensor 57, and the area around the oxygen sensor 57 can be cooled.

  Further, at least a part of the portion of the communication path 72 disposed between the screw hole 73 and the exhaust port 33 on the second projection view (the figure corresponding to FIGS. 6 and 9) is a through hole 74. Therefore, the rigidity of the first fastening boss 40 is secured by surrounding at least a part of the communication path 72 with the flesh of the cylinder head 23, and the exhaust pipe 36 at the first fastening boss 40 is secured. The support rigidity of can also be increased.

  In the second projection view, as shown in FIG. 6, the opening end of the through hole 74 on the one side of the imaginary line L is more cooled than the first fastening boss 40 and the sensor mounting boss 59. Since it is disposed near the one end opening 69 a of the air passage 69, even if the first fastening boss 40 and the sensor mounting boss 59 are in the vicinity of the one end opening 69 a of the cooling air passage 69, the one end opening of the cooling air passage 69 is provided. Cooling air can be circulated more efficiently around 69a.

  A concave passage 75 is provided on the surface of the cylinder head 23 facing the cylinder block 22 so as to form the communication passage 72 together with the through hole 74, and a part of the concave passage 75 is opened. Is arranged so as to overlap the sensor mounting boss 59 on the second projection (corresponding to FIG. 5), the cooling air flowing through the concave passage 75 efficiently cools the periphery of the sensor mounting boss 59. In addition, the cooling air can be distributed more efficiently around the one end opening 69a of the cooling air passage 69.

  Further, the one end opening 69a of the cooling air passage 69 is arranged at a position overlapping with a part of the oxygen sensor 57 attached to the sensor attachment boss 59 on the first projection view as shown in FIG. Therefore, in addition to cooling the surroundings of the oxygen sensor 57 with the cooling air flowing through the communication passage 72, the oxygen sensor 57 can be cooled with the cooling air flowing around the oxygen sensor 57.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. Is possible.

  For example, in the above-described embodiment, the cylinder block 22 is a type in which the cylinder block 22 is tilted slightly forward from the crankcase 21 and stands upright, and the single cylinder is configured such that cooling air enters the cooling air passage 69 from the exhaust port 33 side. Although the air-cooled internal combustion engine E has been described, the present invention can also be applied to a forced air-cooled internal combustion engine used in a scooter type motorcycle, in which case the flow direction of the cooling air is reversed.

20 ... crankshaft 21 ... crankcase 22 ... cylinder block 23 ... cylinder head 25 ... cylinder bore 26 ... piston 27 ... combustion chamber 33 ... exhaust port 34 ... Exhaust pipe connecting pipe portion 36 ... exhaust pipe 40 ... first fastening boss 40a ... first fastening boss tip center 41 ... second fastening boss 41a ... second fastening boss tip Center 44 ... Exhaust valve 48 ... Valve mechanism 49 ... Cam shaft 57 ... Oxygen sensor 59 ... Sensor mounting boss 69 ... Cooling air passage 69a ... One end opening of cooling air passage Portion 72 ... Communication passage 73 ... Screw hole 74 ... Through hole 75 ... Concave passage C1 ... Cylinder bore axis C2 ... Camshaft axis E ... Internal combustion engine L ... Virtual line

Claims (6)

  A cylinder block coupled to the crankcase (21) having a crankcase (21) for rotatably supporting the crankshaft (20) and a cylinder bore (25) for slidably fitting the piston (26). (22) and a combustion chamber (27) facing the top of the piston (26) is formed between the cylinder block (22) and coupled to the cylinder block (22), and an exhaust valve (44) And a cylinder head (23) disposed so as to be openable and closable, and constitutes a part of a valve operating mechanism (48) for driving the exhaust valve (44) to open and close to form an axis (C1) of the cylinder bore (25) ), A camshaft (49) having an axis (C2) along a plane orthogonal to the cylinder head (23) is rotatably supported by the exhaust valve (44) and the combustion chamber (27). An exhaust pipe connection pipe part (34) that internally forms a part of the exhaust port (33) for controlling the exhaust gas, and an exhaust pipe (36) communicating with the exhaust port (33) are connected to the exhaust pipe connection pipe part. The first and second fastening bosses (40, 41) for connecting to (34) project integrally with the cylinder head (23), and cool air passages for cooling the periphery of the combustion chamber (27) ( 69) is formed on the cylinder head (23), and the exhaust pipe connecting pipe portion (34) is located at a position adjacent to the first fastening boss (40) of the first and second fastening bosses (40, 41). In the air-cooled internal combustion engine in which the sensor mounting boss (59) for mounting the oxygen sensor (57) is integrally projected, the axis (C1) of the cylinder bore (25) and the axis (C2) of the camshaft (49) First to a plane parallel to On the projection view, the sensor mounting boss (59) and the cooling are arranged on one side of an imaginary line (L) passing through the front end centers (40a, 41a) of the first and second fastening bosses (40, 41). One end opening (69a) of the air passage (69) is disposed, and at least a part of the communication passage (72) formed in the cylinder head (23) so as to cross the virtual line (L) Arranged between the screw hole (73) of the first fastening boss (40) and the exhaust port (33) on the second projection onto the plane orthogonal to the axis (C1) of the cylinder bore (25). An air-cooled internal combustion engine.   On the second projection view, at least a part of a portion of the communication path (72) disposed between the screw hole (73) and the exhaust port (33) is formed by a through hole (74). The air-cooled internal combustion engine according to claim 1.   On the second projection view, the opening end of the through hole (74) on the one side of the imaginary line (L) is more in the cooling air passage (69) than the first fastening boss (40). The air-cooled internal combustion engine according to claim 2, wherein the air-cooled internal combustion engine is arranged near the one end opening (69).   On the second projection view, the opening end of the through hole (74) on the one side of the imaginary line (L) is more than the sensor mounting boss (59) in the cooling air passage (69). The air-cooled internal combustion engine according to claim 2, wherein the air-cooled internal combustion engine is disposed closer to the one end opening (69a).   On the surface of the cylinder head (23) facing the cylinder block (22), a concave passage (opening the cylinder block (22) side so as to constitute the communication passage (72) together with the through hole (74) ( 75), and a part of the concave passage (75) is arranged on the second projection so as to overlap the sensor mounting boss (59). Air-cooled internal combustion engine.   On the first projection, the one end opening (69a) of the cooling air passage (69) overlaps with a part of the oxygen sensor (57) attached to the sensor attachment boss (59). The air-cooled internal combustion engine according to claim 1, wherein the air-cooled internal combustion engine is arranged.

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