JP4209441B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine having an intake / exhaust port and two plugs in a cylinder head.

Some conventional internal combustion engines for vehicles are provided with an exhaust gas sensor (oxygen concentration sensor) in a cylinder head in order to set a target air-fuel ratio of intake air based on the oxygen concentration of the exhaust gas (for example, see Patent Document 1 below). ).
JP 2004-316430 A

By the way, in the above-mentioned internal combustion engine, when twin-plugging is performed in order to improve combustion performance and improve output and reduce fuel consumption, each plug and exhaust gas sensor are efficiently laid out in consideration of cooling efficiency around each plug hole. There is a demand for such a configuration.
The present invention has been made in view of the above circumstances, and an object of the present invention is to efficiently lay out each plug and an exhaust gas sensor in an internal combustion engine having a cylinder head provided with an intake / exhaust port and two plugs.

In order to solve the above problems, the present invention employs the following means.
That is, the first internal combustion engine of the present invention has a cylinder head (for example, the cylinder head 24 of the embodiment) provided with an intake port (for example, the intake port 49 of the embodiment) and an exhaust port (for example, the exhaust port 50 of the embodiment). 124) and two plugs (for example, the respective plugs 64, 65 of the embodiment) attached to the cylinder head, the internal combustion engine (for example, the engine 20, 120 of the embodiment) sandwiching the exhaust port One of the plugs is disposed on one side, and an exhaust gas sensor (for example, the exhaust gas sensor 68 of the embodiment) is disposed on the other side.

  In the first internal combustion engine, the other of the plugs is disposed on the same side as the exhaust gas sensor in the cylinder head; and the plug hole of each plug (for example, each plug hole in the embodiment) is disposed in the cylinder head. 66, 67) An air jacket (for example, the air jacket 69 in the embodiment) for cooling the periphery may be provided.

  Further, the second internal combustion engine of the present invention has a cylinder head (for example, the cylinder head 24 of the embodiment) provided with an intake port (for example, the intake port 49 of the embodiment) and an exhaust port (for example, the exhaust port 50 of the embodiment). 124) and two plugs (for example, the respective plugs 64, 65 of the embodiment) attached to the cylinder head, the internal combustion engine (for example, the engine 20, 120 of the embodiment) sandwiching the exhaust port A traveling wind inlet (for example, the traveling wind inlet 75 of the embodiment) of an air jacket (for example, the air jacket 69 of the embodiment) provided in the cylinder head is disposed on one side, and an exhaust gas sensor (for example, the embodiment) is disposed on the other side. An example exhaust gas sensor 68) is arranged.

  In the first and second internal combustion engines, the two plugs may be arranged in a single air jacket provided in the cylinder head. The first and second internal combustion engines have cylinder portions (for example, the cylinder portions 22 and 122 of the embodiment) arranged so that the axis (for example, the axis C of the embodiment) is substantially horizontal with respect to the ground. You may have.

  According to the first internal combustion engine, the two plugs and the exhaust gas sensor can be efficiently laid out in a single cylinder head. Further, the exhaust gas sensor is easily activated, and an accurate gas concentration can be detected from the warm-up operation.

  In addition, when the other of the plugs is disposed on the same side of the cylinder head as the exhaust gas sensor; and the cylinder head is provided with an air jacket for cooling around the plug hole of each plug, The two plugs can be efficiently laid out while avoiding the exhaust gas sensor, and the flow of traveling air in the air jacket can be improved to improve the cooling efficiency around each plug hole and the outer wall of the combustion chamber.

  According to the second internal combustion engine, the flow of the traveling air introduced into the air jacket is not obstructed by the exhaust gas sensor, and the flow of the traveling air in the air jacket is made good so that each plug hole and the outer wall of the combustion chamber Cooling efficiency can be improved.

  In the first and second internal combustion engines, when two plugs are arranged in a single air jacket provided in the cylinder head, the two plug seats and the cylinder head are separated by the single air jacket. Can be cooled.

  When the first and second internal combustion engines are provided with a cylinder portion arranged so that the axis thereof is substantially horizontal with respect to the ground, a sufficient amount of traveling wind is taken into the air jacket of the horizontally-placed air-cooled internal combustion engine. Thus, the cooling efficiency can be improved.

1 is a left side view of a motorcycle according to Embodiment 1 of the present invention. Fig. 3 is a top view showing the arrangement of the engine, the exhaust pipe and the like of the motorcycle. It is a right view of the same engine and an exhaust pipe. It is sectional drawing of the same engine. It is sectional drawing in the cross section orthogonal to the axis line of a cylinder main body of the same engine. It is sectional drawing in the cross section orthogonal to the axis line of a cylinder head of the same engine. It is a figure which shows arrangement | positioning of the ignition plug of the same engine, Comprising: It is a right view equivalent to FIG. It is explanatory drawing which looked at the cylinder part of the same engine from the left side. It is the figure which looked at the cylinder head of the engine from the front side. FIG. 7 is a cross-sectional view corresponding to FIG. 6, illustrating Example 2 of the present invention. It is a figure which shows the engine of the Example, Comprising: It is a right view equivalent to FIG.

Explanation of symbols

1 Motorcycle (vehicle)
20,120 engine (internal combustion engine)
22, 122 Cylinder portion 24, 124 Cylinder head 49 Intake port 50 Exhaust port 64 First plug (plug)
65 Second plug (plug)
66 First plug hole (plug hole)
67 Second plug hole (plug hole)
68 Exhaust gas sensor 69 Air jacket 75 Running wind inlet C axis

  Embodiments of the present invention will be described below with reference to the drawings. Note that the front / rear / left / right orientations in the following description are the same as the front / rear / left / right orientations of the vehicle unless otherwise specified. In the drawing, an arrow FR indicates the front of the vehicle, an arrow LH indicates the left side of the vehicle, and an arrow UP indicates the upper side of the vehicle.

  In the motorcycle (vehicle) 1 shown in FIG. 1, left and right front forks 5 that pivotally support the front wheels 4 are pivoted to a head pipe 3 positioned at the front end portion of the vehicle body frame 2 via a steering stem 6. Be supported. A bar handle 7 for turning is attached to the upper portion of the steering stem 6.

  The vehicle body frame 2 is a so-called backbone type in which one main tube 8 is extended obliquely downward and rearward from the head pipe 3 and the stride between the head pipe 3 and the occupant seat 9 is lowered to improve the ease of straddling. . Left and right pivot plates 10 are joined to the rear end portion of the main tube 8, and the front end portion of a swing arm 12 that pivotally supports the rear wheel 11 is pivotally supported on the left and right pivot plates 10.

  The front ends of the left and right seat frames 13 extending obliquely upward and rearward are joined to the rear portion of the main tube 8, and between the front and rear intermediate portions of the left and right seat frames 13 and the rear left and right arms of the swing arm 12, Left and right rear cushions 14 are respectively disposed. Above the left and right seat frames 13, the seat 9 having seat surfaces for the driver and the rear passenger on the front and rear is arranged. Reference numeral 15 in the figure denotes a driver step, and reference numeral 16 denotes a rear passenger step.

  An engine (internal combustion engine) 20, which is a prime mover of the motorcycle 1, is disposed inside the center lower part of the body frame 2 (inside the lower part). The engine 20 is an air-cooled single-cylinder engine whose crank rotation axis is along the vehicle width direction (left-right direction), and has a basic configuration in which a cylinder portion 22 protrudes from the front end portion of the crankcase 21 toward the front of the vehicle. . The engine 20 is supported by the left and right pivot plates 10 at the rear upper and lower portions of the crankcase 21, and the upper portion of the crankcase 21 is supported by the front and rear intermediate portions of the main tube 8 via the engine hanger 8a. It is mounted on.

  The cylinder head 24 on the front end side (front end side) of the cylinder portion 22 is connected to the downstream side of the throttle body 26 from above and to the base end side of the exhaust pipe 27 from below. An air cleaner case 26 a supported on the lower front side of the main tube 8 is connected to the upstream side of the throttle body 26.

  This will be described with reference to FIG. The exhaust pipe 27 bends and extends forward at one end below the cylinder head 24, folds back to the left and slightly forward from the front end of the cylinder portion 22, and the diagonally lower left side of the cylinder portion 22 is substantially parallel to the rear. Is then bent to the approximate center in the vehicle width direction below the crankcase 21 and connected to the front end (base end) of the silencer 27a located behind the engine 20. A catalytic converter (hereinafter sometimes simply referred to as a catalyst) 28 for purifying exhaust gas is provided in a portion of the exhaust pipe 27 located obliquely below and to the left of the cylinder portion 22 (see FIG. 5). Silencer 27a extends from the base end portion located between the rear end of engine 20 and the front end of rear wheel 11 to the right of rear wheel 11, and from this extended portion to the front portion of rear wheel 11 and the side surface. By extending backward so as to overlap when viewed, it is formed in a substantially L shape in a top view.

  Rotational power from the engine 20 is output to a drive sprocket 32 on the left side of the rear of the crankcase 21 via clutches and transmissions 31 (see FIG. 4), which will be described later, housed in the crankcase 21, and this drive sprocket. 32 is transmitted to the driven sprocket 34 on the left side of the rear wheel 11 through the drive chain 33.

  The front portion of the body frame 2, the cylinder portion 22 of the engine 20, the throttle body 26, the air cleaner case 26a, and the like are covered with a front body cover 35 made of synthetic resin. The front body cover 35 also serves as a leg shield that protects the driver's legs from wind pressure from the front. The rear portion of the vehicle body frame 2 is covered with a rear vehicle body cover 36 that is also made of synthetic resin. The rear body cover 36 supports the seat 9 together with the left and right seat frames 13. An article storage box 37 located below the seat 9 is disposed in the rear body frame 2. A fuel tank 38 supported by the front portions of the left and right seat frames 13 is disposed below the front portion of the article storage box 37.

  As shown in FIG. 3, the cylinder portion 22 of the engine 20 is forward (in the vehicle traveling direction) from the front end portion of the crankcase 21 so that the axis C thereof is substantially horizontal (in detail, slightly upward). Protruding. The cylinder portion 22 includes a cylinder body 23 attached to the front end portion of the crankcase 21, the cylinder head 24 attached to the front end portion of the cylinder body 23, and a head cover 25 attached to the front end portion of the cylinder head 24. Is the main component. Hereinafter, in the cylinder portion 22, the front-rear direction parallel to the axis C (cylinder axis) may be referred to as the cylinder front-rear direction, and the vertical direction orthogonal to the axis C may be referred to as the cylinder vertical direction.

  This will be described with reference to FIG. The cylinder body 23 is formed therein with a cylinder bore 39 along the axis C, and a piston 40 is fitted in the cylinder bore 39 so as to be able to reciprocate. A small end portion of a connecting rod 41 is swingably connected to the piston 40 via a piston pin extending in the left-right direction. The large end portion of the connecting rod 41 is connected to the crankshaft 42 via a crank pin extending in the left-right direction. It is connected rotatably. The crankshaft 42 supports a crankpin via left and right crank webs between left and right shaft portions along the left and right direction.

  A centrifugal clutch 29 is coaxially arranged at the right end portion of the crankshaft 42, and the rotational power of the crankshaft 42 is transmitted to the primary drive gear 43 via the centrifugal clutch 29 according to the rotational speed. The primary drive gear 43 is coaxially arranged on the right shaft portion of the crankshaft 42, and the primary drive gear 43 meshes with a primary driven gear 44 coaxially arranged on the right side portion of the main shaft 45 behind the crankshaft 42. . The main shaft 45 is disposed behind the crankshaft 42 in parallel with the left and right shaft portions, and a multi-plate clutch 30 capable of intermittently transmitting and receiving power by the operation of the driver is coaxially disposed at the right end portion. The rotational power input to the primary driven gear 44 is transmitted to the main shaft 45 via the clutch 30.

  The main shaft 45 supports a transmission gear group 47 (only one set of transmission gear pairs fitted to each other is shown in FIG. 4) together with a countershaft 46 arranged in parallel behind the main shaft 45. The main shaft 45, the countershaft 46, and the transmission gear group 47 mainly constitute the transmission 31, and the reduction ratio of the transmission gear group 47 is multistaged by a driver's operation through a change mechanism (not shown). Change. The left end portion of the counter shaft 46 projects out of the crankcase 21, and the drive sprocket 32 is attached to the left end portion.

  The cylinder head 24 closes the front end opening of the cylinder bore 39 and forms a so-called pent roof type combustion chamber together with the piston 40 at the top dead center. The engine 20 in this embodiment is an OHC two valve, and a single combustion chamber side opening in the intake port 49 or the exhaust port 50 is formed on two inclined upper surfaces in the roof forming portion 48 of the combustion chamber, respectively. The combustion chamber side opening is opened and closed by an intake valve 51 or an exhaust valve 52, respectively.

  Each intake port 49 and exhaust port 50 is a flow passage that communicates the combustion chamber with the throttle body attachment portion 53 at the upper part of the cylinder head 24 or the exhaust pipe attachment portion 54 at the lower part of the cylinder head 24, and from the combustion chamber side opening. After extending obliquely forward so as to be substantially orthogonal to the inclined upper surface, it curves upward or downward to reach the throttle body attachment portion 53 or the exhaust pipe attachment portion 54. The throttle body attaching portion 53 and the exhaust pipe attaching portion 54 form a plane that is substantially orthogonal to the cylinder vertical direction, and the insulator of the throttle body 26 or the coupling flange of the exhaust pipe 27 is brought into contact with these planes to be fastened.

  The stems of the valves 51 and 52 extend obliquely forward so as to be substantially orthogonal to the inclined upper surface and pass through the inner walls of the intake and exhaust ports 49 and 50, respectively, and then the intake side or exhaust side rocker arm 55 and The front-end | tip part of 56 is engaged. The other end portions of the rocker arms 55 and 56 are in sliding contact with two cam peaks formed on the single cam shaft 57, and the valves 51 and 52 reciprocate along the stem by driving the cam shaft 57. It moves and opens and closes the combustion chamber side opening of each port 49,50. The stems of the valves 51 and 52, the rocker arms 55 and 56, the camshaft 57 and the like are supported inside the front portion of the cylinder head 24. These are the front portion of the cylinder head 24 and the cup-shaped head cover 25 that closes the cylinder head 24. It is accommodated in the valve train chamber to be formed.

  A driven sprocket 58 is coaxially fixed to the left end portion of the camshaft 57, and an endless cam chain 60 is wound around the driven sprocket 58 and a drive sprocket 59 coaxially fixed to the left end portion of the crankshaft 42. . As a result, the camshaft 57 is linked to the crankshaft 42 to open and close the valves 51 and 52. A generator (not shown) is coaxially arranged at the left end of the crankshaft 42.

  This will be described with reference to FIG. A large number of cooling fins 61 a and 61 b are integrally formed on the outer periphery of the cylinder portion 22. Specifically, a plurality of side cooling fins 61 a are formed on the right side of the cylinder body 23 and the cylinder head 24 so as to be substantially orthogonal to the cylinder axis C, and above and below the cylinder body 23, approximately the cylinder axis C. A plurality of upper and lower cooling fins 61b are formed in parallel.

  A cam chain chamber 62 for accommodating the cam chain 60 is formed in the left side portion of the cylinder portion 22. The cam chain chamber 62 also functions as a return path for the engine oil fed into the cylinder head 24 into the crankcase 21, and the engine oil temperature is adjusted so that the detection unit faces the cam chain chamber 62. An oil temperature sensor 63 for detection is provided. The oil temperature sensor 63 is located on the lower left side of the cylinder body 23 and in the vicinity of the crankcase 21 (see FIG. 8), and is attached to the cylinder body 23 so as to be inserted from the left side. Reference numeral 60a in the figure denotes a cam chain tensioner that applies a predetermined tension to the cam chain 60. Further, the catalyst 28 is located below the cam chain chamber 62 (slightly lower left of the cylinder portion 22).

  This will be described with reference to FIG. The cam chain chamber 62 forms a flat space with a reduced left-right width in the left side portions of the cylinder body 23 and the cylinder head 24. The outside is surrounded by an outer wall 62b having a U-shaped cross section. Since heat generated by combustion in the cylinder bore 39 is not directly transmitted to the outer wall portion 62b of the cam chain chamber 62, no cooling fin is formed on the outer wall portion 62b (the left side portion of the cylinder portion 22).

  As shown in FIGS. 6 and 7, the engine 20 is twin-plugged in order to improve combustion performance to improve output and reduce fuel consumption. A spark plug 64 is attached, and a second spark plug 65 is attached to the left side of the cylinder head 24 from the diagonally right front side. First and second plug holes 66 and 67 for allowing the plugs 64 and 65 to reach the roof forming portion 48 inside the cylinder head 24 are formed in the lower part and the left part of the cylinder head 24, respectively. Each plug 64, 65 is screwed into a female screw hole formed in the roof forming portion 48 through the corresponding plug hole 66, 67, and is fixed to the cylinder head 24 with its tip electrode portion facing the combustion chamber. ing.

  The first plug 64 is inclined with respect to the cylinder vertical direction in a plane substantially orthogonal to the left-right direction, and its central axis is viewed in a line of sight along the cylinder axis (viewed along the cylinder axis C). In this case, the intake and exhaust ports 49 and 50 are arranged so as to be substantially parallel to the extending direction (so as to be substantially parallel to the vertical direction). On the other hand, the second plug 65 is inclined with respect to the left-right direction in a plane substantially perpendicular to the cylinder vertical direction, and the central axis thereof is substantially orthogonal to the extending direction of the intake / exhaust ports 49, 50 as viewed in the cylinder axial direction. (So as to be substantially parallel to the left-right direction). In other words, the plugs 64 and 65 are arranged so as to be substantially L-shaped when viewed in the cylinder axial direction. The first plug 64 is provided with an offset so that its center axis is located on the left side of the cylinder axis C, and the second plug 65 is offset so that its center axis is located above the cylinder axis C. Is provided.

  The intake port 49 has an opening on the combustion chamber side located above the roof forming portion 48 and on the left side of the cylinder axis C, and is directed generally upward from the opening on the combustion chamber side (in detail, slightly inclined to the right). It extends to the throttle body mounting portion 53 that is positioned almost immediately above the cylinder axis C. On the other hand, the exhaust port 50 has an opening on the combustion chamber side located below the roof forming portion 48 and on the right side of the cylinder axis C, and is directed generally downward from the opening on the combustion chamber side. E) to the exhaust pipe attachment 54 located on the right side of the cylinder axis C. Since the exhaust pipe attaching portion 54 is offset to the right side, a work space for attaching and detaching the first plug 64 is secured.

  The exhaust port 50 is provided with an exhaust gas sensor (oxygen concentration sensor) 68 so that the target air-fuel ratio of the intake air based on the oxygen concentration of the exhaust gas can be set. The exhaust gas sensor 68 uses a gate (catalyst) such as platinum, and the exhaust gas sensor 68 is arranged so that the detection portion faces the exhaust port 50 of the cylinder head 24, so that the gate has a predetermined operating temperature. The detection sensitivity during warm-up operation (during cold operation) increases.

  The exhaust gas sensor 68 is attached to the lower right side of the cylinder head 24 (the right side of the exhaust port 50) so as to be inserted from the right side. The first plug 64 is located on the opposite side (left side) of the exhaust gas sensor 68 across the exhaust port 50 in the cylinder head 24, and the second plug 65 is located on the same side (right side) as the exhaust gas sensor 68. Further, the exhaust gas sensor 68 is disposed so as to be spaced below the cylinder axis C and the center axis thereof is substantially parallel to the left-right direction. That is, the exhaust gas sensor 68 is disposed so as to be substantially orthogonal to the first plug 64 and substantially parallel to the second plug 65 when viewed in the cylinder axial direction.

  The engine 20 is an air jacket that distributes cooling air (running air) in the rear part of the cylinder head 24 in order to effectively cool the cylinder head 24 (especially around the plug holes 66 and 67) having a particularly large thermal load. (Cooling airflow passage) 69 is provided. The air jacket 69 is a space formed between the roof forming portion 48 at the rear portion of the cylinder head 24 and the bottom portion 70 of the valve operating chamber so as to allow the plug holes 66 and 67 to communicate with each other. 71, 72, the upper inner wall portion 73 of the cam chain chamber 62, the fastening bolt insertion portion 74 between the cylinder body 23 and the crankcase 21, and the like. The air jacket 69 allows the cooling air (running air) to flow well around the plug holes 66 and 67 and introduces the cooling air (running air) to the inside of the cylinder head 24. Cooling efficiency is improved.

  The air jacket 69 has a traveling air inlet 75 around the first plug hole 66 that opens downward in the lower part of the cylinder head 24 by the action of two air guide plates 78 and 79, which will be described in detail later. The second plug hole 67 that opens to the right side is configured to have a traveling wind outlet (hereinafter referred to as a main outlet) 76. In other words, the air jacket 69 bends in a substantially L shape when the main path of the traveling wind from the traveling wind introduction port 75 to the main exhaust port 76 is viewed from the line of sight along the cylinder axial direction. Is formed. In addition, on both sides of the intake port forming portion 71 in the upper part of the cylinder head 24, there are provided auxiliary exhaust ports 76a for discharging part of the traveling air introduced into the air jacket 69 from the traveling air inlet 75. The flow of the traveling wind in the air jacket 69 is indicated by a chain line arrow in FIG.

  The traveling wind inlet 75 (first plug hole 66) is formed between the exhaust port forming portion 72 and the lower left fastening bolt insertion portion 74, and the main exhaust port 76 (second plug hole 67) is located at the upper right and right. It is formed between the lower fastening bolt insertion part 74. The traveling wind introduction port 75 has a narrower width in the cylinder axial direction view than the main exhaust port 76, and the first plug 64 is disposed so as to be sandwiched between the exhaust port forming portion 72 and the fastening bolt insertion portion 74. . The exhaust port forming portion 72 (exhaust port 50), the traveling wind introduction port 75, and the first plug 64 are arranged so as to be lined up substantially on the left and right. The exhaust gas sensor 68 is arranged on the opposite side of the cylinder head 24 from the first plug 64 and the traveling air inlet 75 with the exhaust port forming portion 72 (exhaust port 50) interposed therebetween.

  In the air jacket 69, there is provided a center fin 77 that crosses the vicinity of the cylinder axis C to the left and right when viewed with a line of sight along the cylinder axis direction. The center fin 77 is plate-shaped across the upper and lower walls of the air jacket 69, and is positioned between the intake / exhaust port forming portions 71, 72 in the L-shaped intermediate portion of the air jacket 69, and the left end portion is downward (running wind It is inclined toward the introduction port 75 side). The center fin 77 smoothly guides the traveling wind introduced into the air jacket 69 from the traveling wind introduction port 75 toward the main exhaust port 76, increases the contact area of the traveling wind, and reduces the traveling wind. By branching to pass through the vicinity of the plugs 64 and 65, the cooling efficiency of the cylinder head 24 is improved.

  As shown in FIGS. 8 and 9, the traveling wind (indicated by a chain line arrow in FIG. 8) is directed toward the traveling wind inlet 75 (first plug hole 66) of the air jacket 69 at the lower part (road surface side) of the cylinder head 24. ) Is provided. The first air guide plate 78 has a flat plate-like air guide plate main body 78a that is substantially parallel to the left-right direction spaced downward from the traveling air introduction port 75, and a pair of legs that support both left and right ends of the air guide plate main body 78a. And a traveling airflow passage that penetrates forward and backward in a substantially U shape that opens upward when viewed in a line of sight along the cylinder axial direction. The wind guide plate main body 78a is inclined rearward and guides a part of the traveling wind flowing through the traveling wind flow path toward the traveling wind introduction port 75 above. Such a first air guide plate 78 is integrally formed under the cylinder head 24 by aluminum die casting or the like.

  The oil temperature sensor 63 is located behind (on the downstream side) the first air guide plate 78, and immediately before the oil temperature sensor 63, a stopper wall 80 is provided to suppress the air contact with the oil temperature sensor 63. Is erected downward. The stopper wall 80 has a plate-like shape substantially orthogonal to the axis C, and is integrally formed at the lower part of the cylinder head 24 by aluminum die casting or the like to reduce the contact of obstacles from the road surface to the oil temperature sensor 63.

  A second air guide plate 79 that guides the traveling wind toward the inside of the first air guide plate 78 is provided at a lower portion (road surface side) of the head cover 25. The second air guide plate 79 includes a flat air guide plate main body 79a that is substantially parallel to the left-right direction spaced downward from the lower portion of the head cover 25, and a pair of leg portions 79b that support both left and right ends of the air guide plate main body 79a. When viewed in a line of sight along the cylinder axial direction, a traveling airflow passage that penetrates forward and backward is formed in a substantially U shape that opens upward. The front end of the second air guide plate 79 is located in the vicinity of the front end of the head cover 25, takes in the traveling air just after hitting the front end of the head cover 25, flows this rearward, and guides it into the first air guide plate 78. Such a second air guide plate 79 is integrally formed under the head cover 25 by aluminum die casting or the like.

  As shown in FIGS. 3 and 5, the catalytic converter 28 accommodates, for example, a honeycomb structure (monolith) to which a catalyst such as platinum is attached in a cylindrical case having a diameter larger than that of the exhaust pipe 27. An engine that is provided substantially coaxially with the exhaust pipe 27 at a position offset obliquely to the lower left of the cylinder portion 22 and passes through the catalyst 28 while being heated to a predetermined reaction promoting temperature. The exhaust gas from 20 is appropriately purified. The catalyst 28 is located obliquely below the left side of the cylinder portion 22, that is, below the cam chain chamber 62, so that the heat of the catalyst 28 in a heated state is not directly transmitted to the cylinder inner wall. Further, the catalyst 28 is disposed offset to the left side from the traveling air inlet 75 of the air jacket 69, so that the heat of the catalyst 28 is difficult to enter the air jacket 69.

  As described above, the engine 20 of the present embodiment includes the cylinder head 24 provided with the intake and exhaust ports 49 and 50, and the first and second plugs 64 and 65 attached to the cylinder head 24. The first plug 64 is disposed on one side of the exhaust port 50 and the exhaust gas sensor 68 is disposed on the other side.

  According to this configuration, the two plugs 64 and 65 and the exhaust gas sensor 68 can be efficiently laid out for the single cylinder head 24. Further, the exhaust gas sensor 68 is easily activated, and an accurate gas concentration can be detected from the warm-up operation.

  Further, according to the engine 20, the second plug 65 is disposed on the same side of the cylinder head 24 as the exhaust gas sensor 68, and the cylinder head 24 has plug holes 66, 66 of the plugs 64, 65. By providing an air jacket 69 that cools around 67, the two plugs 64 and 65 can be efficiently laid out while avoiding the exhaust gas sensor 68, and the flow of the running air in the air jacket 69 is made good, so that each plug The cooling efficiency around the holes 66 and 67 and the outer wall of the combustion chamber can be improved.

  Furthermore, according to the engine 20, the running air introduction port 75 of the air jacket 69 is disposed on one side of the exhaust port 50, and the exhaust gas sensor 68 is disposed on the other side. It is possible to improve the cooling efficiency of the surroundings of the plug holes 66 and 67 and the outer wall of the combustion chamber by improving the flow of the traveling wind in the air jacket 69 without being obstructed by the exhaust gas sensor 68. it can.

Next, a second embodiment of the present invention will be described with reference to FIGS.
The engine (internal combustion engine) 120 in the present embodiment has an exhaust port 50 extending obliquely upward and to the right when viewed in a line of sight along the cylinder axial direction as compared to the first embodiment. Are mainly different from each other, and the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  In the cylinder head 124 of the cylinder portion 122, the exhaust port 50 has an opening on the combustion chamber side located below the roof forming portion 48 and on the right side of the cylinder axis C, and is inclined downward to the right from the combustion chamber side opening. It extends to the exhaust pipe attachment portion 54 that opens obliquely downward to the right on the right side of the cylinder axis C. As a result, the lateral width of the traveling wind introduction port 75, which is also the work space for attaching and detaching the first plug 64, is ensured to be relatively large. .

  The exhaust gas sensor 68 is attached to the right side of the exhaust port 50 so as to be inserted from the upper right side so as to be substantially orthogonal to the extending direction of the exhaust port 50 when viewed in a line of sight along the cylinder axial direction, for example. It has been. As in the first embodiment, the exhaust gas sensor 68 may be mounted so that its central axis is substantially parallel to the left-right direction. In this case, the exhaust gas sensor 68 is mounted directly beside the cylinder portion 22. The mounting workability is relatively improved.

The present invention is not limited to the above-described embodiments. For example, a DOHC engine having two camshafts for intake and exhaust in a cylinder head, a direct push that directly drives a valve with a camshaft without using a rocker arm. The present invention can also be applied to a type engine, an engine having a plurality of at least one of intake and exhaust valves, a multi-cylinder engine, and a water-cooled engine.
The configurations described in the above embodiments are examples of the present invention, and can be applied to various vehicles such as a scooter type vehicle, and various modifications can be made without departing from the scope of the present invention. Is possible.

  According to the present invention, two plugs and an exhaust gas sensor can be efficiently laid out on a single cylinder head. Further, the exhaust gas sensor is easily activated, and an accurate gas concentration can be detected from the warm-up operation.

Claims (6)

An internal combustion engine comprising a cylinder head provided with an intake port and an exhaust port, and two plugs attached to the cylinder head,
A first plug, which is one of the plugs, is disposed on one side of the exhaust port, and an exhaust gas sensor is disposed on the other side. The first plug is substantially orthogonal to the exhaust gas sensor when viewed in the cylinder axial direction. And the first plug is disposed so as to be substantially parallel to the extending direction of the intake / exhaust port,
A second plug, which is the other of the plugs, is disposed on the same side of the cylinder head as the exhaust gas sensor so that the second plug is substantially orthogonal to the extending direction of the intake / exhaust port when viewed in the cylinder axial direction. And the second plug is arranged so as to be substantially parallel to the exhaust gas sensor . The internal combustion engine according to claim 1,
The cylinder head is provided with an air jacket for cooling around the plug hole of each plug. The internal combustion engine according to claim 1 or 2,
Wherein on one side across the exhaust port, wherein is arranged running wind introducing port of the air jacket provided in the cylinder head, and the exhaust gas sensor is disposed on the other side. The internal combustion engine according to any one of claims 1 to 3,
The two plugs are arranged in a single air jacket provided in the cylinder head. The internal combustion engine according to any one of claims 1 to 4,
The cylinder part arrange | positioned so that an axis line may become substantially horizontal with respect to the ground is provided. An internal combustion engine according to any one of claims 1 to 5,
A cam chain chamber is disposed on the opposite side of the exhaust port and the first plug, and on the opposite side of the second plug and the cylinder axis when viewed in the cylinder axis direction.

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