JP2018172982A - Internal combustion engine - Google Patents

Abstract

An internal combustion engine capable of accurately detecting the occurrence of knocking by devising the arrangement of an in-cylinder pressure sensor is provided. A cam chain chamber (17c) for inserting a cam chain (36) for transmitting power of the internal combustion engine to a cam shaft (31) for driving an intake valve (46) and an exhaust valve (47) is provided in a cylinder head. A pressure sensing portion 51e of an in-cylinder pressure sensor 51, which is formed adjacent to the ceiling surface 41 on the ceiling surface 41 and detects the pressure in the combustion chamber 40, is located on the ceiling surface 41 with respect to the cylinder axis Lc, which is the central axis of the cylinder bore 16b. It is arranged facing the combustion chamber 40 on the opposite side of the chamber 17c. [Selection drawing] Fig. 4

Description

  The present invention relates to an internal combustion engine including an in-cylinder pressure sensor that detects a pressure in a combustion chamber.

In an internal combustion engine, a flame spreads in a combustion chamber after being ignited by a spark plug. However, before the flame reaches, so-called knocking may occur in which the compressed unburned mixture self-ignites.
An internal combustion engine having a knock sensor for detecting the occurrence of knocking in an engine body is well known (for example, see Patent Document 1).

JP 2008-51007 A

In Patent Document 1, the in-cylinder pressure sensor detects the pressure in the combustion chamber and controls the ozone supply means according to the detected pressure to avoid knocking. In addition to the in-cylinder pressure sensor, A knock sensor for detecting the occurrence of knocking is provided.
Referring to FIG. 2 of Patent Document 1, the in-cylinder pressure sensor is disposed on the cylinder head side and the knock sensor is disposed on the cylinder block side, but the exact position is not clear.

Since knocking is generated by self-ignition due to pressure rise before the flame generated by ignition with the spark plug propagates, the place where knocking occurs (knock generation point) is a position far from the spark plug.
The knock generation point is considered to be a place where the temperature is high.
That is, the knock generation point is a place where the temperature is far from the spark plug.

When detecting the occurrence of knocking by detecting the pressure in the combustion chamber with the in-cylinder pressure sensor, the pressure in the combustion chamber includes various pressure noises in addition to the pressure accompanying knocking, so only the pressure accompanying knocking is extracted and detected. There is a need to.
Therefore, since the pressure due to knocking tends to propagate more greatly as the position is farther from the knock generation point, it is desirable to provide the pressure sensor as far as possible from the knock generation point.

  In Patent Document 1, the position at which the knock sensor and the in-cylinder pressure sensor are provided is not clear, and a configuration for accurately detecting the pressure associated with knocking in consideration of pressure noise is not disclosed.

  The present invention has been made in view of the above points, and the object of the present invention is to provide an internal combustion engine capable of accurately detecting the occurrence of knocking by devising the arrangement of the in-cylinder pressure sensor.

In order to achieve the above object, an internal combustion engine according to the present invention comprises:
A combustion chamber is formed between the top surface of the piston that is slidably fitted in the cylinder bore of the cylinder block and the ceiling surface of the cylinder head that faces the same top surface,
On the ceiling surface, an intake valve port and an exhaust valve port that open and close respectively an intake valve and an exhaust valve are opened facing the combustion chamber,
In an internal combustion engine in which an electrode of a spark plug attached to the cylinder head faces the combustion chamber and is exposed on a ceiling surface,
A cam chain chamber for inserting a cam chain for transmitting the power of the internal combustion engine to the cam shaft for driving the intake valve and the exhaust valve is formed adjacent to the ceiling surface on the cylinder head,
A pressure-sensitive portion of an in-cylinder pressure sensor that detects a pressure in the combustion chamber is disposed facing the combustion chamber on the opposite side of the cam chain chamber with respect to a cylinder axis that is a central axis of the cylinder bore on the ceiling surface. And

With respect to the cylinder axis on the ceiling surface of the combustion chamber, the cam chain chamber side is a place (knock generation point) where knocking occurs because the temperature is kept low by the cam chain chamber and the temperature is unlikely to decrease and is likely to be higher than other portions.
Therefore, according to this configuration, the pressure-sensitive portion of the in-cylinder pressure sensor that detects the pressure in the combustion chamber is arranged facing the combustion chamber on the opposite side of the cam chain chamber with respect to the cylinder axis on the ceiling surface, so that the knock generation point By providing a pressure-sensitive part of the in-cylinder pressure sensor at a remote position where the pressure due to knocking on the opposite side of the cam chain chamber with respect to the cylinder axis on the ceiling surface of the combustion chamber Without detecting only the pressure associated with knocking, the occurrence of knocking can be detected with high accuracy.

In the above configuration,
The intake valve port and the exhaust valve port are formed on opposite sides with respect to the cylinder axis of the ceiling surface,
The pressure sensitive part of the in-cylinder pressure sensor may be arranged at a position closer to the exhaust valve port than the intake valve port.

  Since knocking tends to occur around the intake valve port where the pressure increases locally, according to this configuration, the pressure-sensitive portion of the in-cylinder pressure sensor is disposed closer to the exhaust valve port than the intake valve port. Thus, the occurrence of knocking can be detected with higher accuracy by disposing the pressure-sensitive portion of the in-cylinder pressure sensor as far as possible from the knocking occurrence point.

In the above configuration,
The pressure-sensitive portion of the in-cylinder pressure sensor may be disposed outside a virtual circle passing through the center of the spark plug electrode centered on the cylinder axis.

  According to this configuration, the pressure-sensitive portion of the in-cylinder pressure sensor is disposed outside the virtual circle passing through the center of the electrode of the spark plug centered on the cylinder axis, so that the pressure-sensitive portion of the in-cylinder pressure sensor is knocked It is possible to detect the occurrence of knocking with higher accuracy as far away as possible.

In the above configuration,
The electrode of the spark plug may be arranged on the opposite side of the cam chain chamber with respect to the cylinder axis.

  According to this structure, since the electrode of the spark plug is disposed on the opposite side of the cam chain chamber with respect to the cylinder axis, the position away from the spark plug where knocking is likely to occur is located on the cam chain with respect to the cylinder axis where knocking is likely to occur. By providing the pressure-sensitive portion of the in-cylinder pressure sensor away from a position on the chamber side that is extremely likely to cause knocking, the occurrence of knocking can be detected with higher accuracy.

In the above configuration,
There is one exhaust valve port on the ceiling surface,
The pressure sensing part of the in-cylinder pressure sensor includes the exhaust valve port sandwiched between a surface including the cylinder axis and the center of the exhaust valve port, and a surface including the cylinder axis and the center of the spark plug () electrode, You may make it arrange | position within the range which includes each part of each electrode of a spark plug ().

  According to this configuration, there is one exhaust valve port on the ceiling surface, and the pressure-sensitive portion of the in-cylinder pressure sensor includes the surface including the cylinder axis and the center of the exhaust valve port, the center of the cylinder axis and the electrode of the spark plug. Is located within the range including both the exhaust valve port and the spark plug electrode sandwiched by the surface including the cylinder, and as far as possible from the knocking occurrence point near the intake valve port on the cam chain chamber side. The pressure sensitive part of the internal pressure sensor can be arranged, and the occurrence of knocking can be detected more reliably.

In the above configuration,
There are two intake valve ports and two exhaust valve ports on the ceiling surface,
The pressure sensor of the in-cylinder pressure sensor is disposed on the opposite side of the cylinder axis with respect to a line connecting the centers of the intake valve port and the exhaust valve port located on the opposite side of the cam chain chamber with respect to the cylinder axis. You may make it do.

  According to this configuration, there are two intake valve ports and two exhaust valve ports on the ceiling surface, and the pressure-sensitive portion of the in-cylinder pressure sensor is connected to the intake valve port and the exhaust gas that are located on the opposite side of the cam chain chamber with respect to the cylinder axis. Since it is arranged on the opposite side of the cylinder axis with respect to the line connecting the centers of the valve ports, the pressure sensing part of the in-cylinder pressure sensor can be arranged as far as possible from the knocking occurrence point on the cam chain chamber side, The occurrence of knocking can be detected more reliably.

  In the present invention, the pressure sensing part of the in-cylinder pressure sensor for detecting the pressure in the combustion chamber is arranged facing the combustion chamber on the opposite side of the cam chain chamber with respect to the cylinder axis on the ceiling surface. By installing the pressure-sensitive part of the in-cylinder pressure sensor at a remote position where the pressure due to knocking on the opposite side of the cam chain chamber with respect to the cylinder axis on the ceiling surface of the cylinder is greatly propagated, knocking is not affected by pressure noise. By detecting only the accompanying pressure, it is possible to accurately detect the occurrence of knocking.

1 is a right sectional view of an internal combustion engine according to an embodiment of the present invention. 2 is a right side view of the cylinder head of the internal combustion engine and its vicinity. FIG. It is sectional drawing of the same internal combustion engine by the III-III arrow in FIG. It is a bottom view of a cylinder head. It is a bottom view of a cylinder head of an internal-combustion engine of another 2nd embodiment. It is a bottom view of a cylinder head of an internal-combustion engine of another 3rd embodiment.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
FIG. 1 is a right sectional view of an internal combustion engine according to an embodiment to which the present invention is applied.
In the description of the present specification, the front, rear, left, and right directions follow a normal standard in which a straight traveling direction of a motorcycle (not shown) on which the internal combustion engine according to the present embodiment is mounted is forward, , FR indicates the front, RR indicates the rear, LH indicates the left, and RH indicates the right.

The internal combustion engine 10 is an SOHC type two-valve single-cylinder four-stroke internal combustion engine, and is suspended in an upright posture with the crankshaft 12 oriented in the vehicle body width direction with respect to the vehicle body and the cylinder slightly tilted forward.
A crankcase 11 that rotatably supports a crankshaft 12 of an internal combustion engine 10 includes a transmission gear mechanism 15 between a main shaft 13 and a countershaft 14 disposed behind the crankshaft 12, and a counter The axis 14 is an output axis.

On the crankcase 11, a cylinder block 16 in which a cast iron cylinder liner 16L is cast, and a cylinder head 17 are stacked on the cylinder block 16 via a gasket, and are fastened together by a stud bolt. The cylinder head cover 18 covers the cylinder head 17 from above.
The cylinder block 16, the cylinder head 17, and the cylinder head cover 18 stacked on the crankcase 11 extend upward from the crankcase 11 in a slightly inclined posture.

  The crankcase 11 is divided into left and right parts, and the lower end portion of the cylinder liner 16L is fitted into the opening formed in the mating surface of the left and right crankcases, and the cylinder block 16 is slightly tilted forward and protrudes upward. A piston 25 is fitted in an internal cylinder bore 16b so as to be slidable back and forth, and a connecting rod 26 is connected between a piston pin 25p of the piston 25 and a crank pin 12p of the crankshaft 12 to constitute a crank mechanism.

A combustion chamber 40 is formed between the top surface 25t of the piston 25 sliding in the cylinder bore 16b of the cylinder block 16 and the ceiling surface 41 of the cylinder head 17 facing the same top surface 25t.
In the cylinder head 17, an intake valve port 42 and an exhaust valve port 43 are opened on the ceiling surface 41 at positions opposite to each other with respect to the cylinder axis C, which is the central axis of the cylinder bore 16b, facing the combustion chamber 40, and An intake port 44 and an exhaust port 45 are formed so as to extend from the valve port 42 and the exhaust valve port 43 while being curved away from each other.

  An intake valve 46 and an exhaust valve 47 that are slidably supported by valve guides 34i and 34e fitted integrally to the cylinder head 17 are driven by a valve mechanism 30 provided on the cylinder head 17, The intake valve port 42 of the intake port 44 and the exhaust valve port 43 of the exhaust port 45 are opened and closed in synchronization with the rotation of the crankshaft 12.

  1 and 2, a valve mechanism 30 is a valve mechanism of a SOHC type internal combustion engine in which a cam shaft 31 is pivotally supported on a cylinder head 17 in the left-right direction. The rocker arm shafts 32e and 32i are supported diagonally forward and backward of the cam shaft 31, the intake rocker arm 33i is pivotally supported by the rear rocker arm shaft 32i, and the exhaust rocker arm 33e is rockable by the front rocker arm shaft 32e. Is supported at the center.

  One end of the intake rocker arm 33i is in contact with the intake cam lobe of the cam shaft 31, the other end is in contact with the upper end of the valve stem 46s of the intake valve 46 biased by a spring via an adjusting screw, and one end of the exhaust rocker arm 33e is The shaft 31 is in contact with the exhaust cam lobe, the other end is in contact with the upper end of the valve stem 47s of the exhaust valve 47 biased by a spring via an adjusting screw, and the intake rocker arm 33i and the exhaust rocker arm 33e are swung by the rotation of the cam shaft 31. Then, the intake valve 46 and the exhaust valve 47 are opened and closed.

  The camshaft 31 protrudes to the left from the bearing, and a cam chain sprocket 35 is fixedly supported at the left end of the camshaft 31, and the cam chain 36 wound around the cam chain sprocket 35 faces the crankshaft 12 to the crankshaft 12. The camshaft 31 is wound around the fitted cam chain sprocket (not shown), and the camshaft 31 is synchronized with the crankshaft 12 and rotated in the same direction at half the number of rotations thereof.

Cam chain chambers 16c and 17c, which are rectangular holes through which the cam chain 36 is inserted, are formed on the left side of the cylinder bore 16b of the cylinder block 16 and the left side of the combustion chamber 40 of the cylinder head 17.
As shown in FIG. 3, a spark plug 50 is fitted into the right side wall of the cylinder head 17 toward the combustion chamber 40, and in-cylinder pressure sensor is substantially parallel to the front side of the spark plug 50. A certain finger pressure sensor 51 is fitted into the combustion chamber 40 and attached.

FIG. 4 is a bottom view of the cylinder head 17 superimposed on the cylinder block 16.
Referring to FIG. 4, on the mating surface 17f of the cylinder head 17 facing the mating surface of the cylinder block 16, a ceiling surface 41 of the combustion chamber 40 is formed to be recessed corresponding to the cylinder bore 16b, and the cam chain chamber A cam chain chamber 17c communicating with 16c is formed on the left side of the combustion chamber 40.

A circular opening edge 41s of the ceiling surface 41 of the combustion chamber 40 at the mating surface 17f of the cylinder head 17 coincides with the circular hole of the cylinder bore 16b.
A large-diameter intake valve port 42 opens behind the cylinder axis Lc of the ceiling surface 41, and an exhaust valve port 43 somewhat smaller in diameter than the intake valve port 42 opens ahead of the cylinder axis Lc of the ceiling surface 41. .

Further, on the right side of the cylinder axis Lc of the ceiling surface 41, a spark plug 50 is provided with a plug hole 48 through which the tip electrode 50e protrudes into the combustion chamber 40, and a finger pressure sensor 51 connects the tip pressure sensing portion 51e. A sensor hole 49 that faces the combustion chamber 40 is formed in front of the plug hole 48.
That is, the electrode 50e of the spark plug 50 on the right side of the cylinder axis Lc is disposed on the opposite side of the cam chain chamber 17c with respect to the cylinder axis Lc.

As shown in FIG. 4, the pressure-sensitive portion 51 e of the finger pressure sensor 51 is disposed facing the combustion chamber 40 on the opposite side of the cam chain chamber 17 c with respect to the cylinder axis Lc on the ceiling surface 41.
Further, the pressure-sensitive portion 51e of the finger pressure sensor 51 is disposed at a position closer to the exhaust valve port 43 than the intake valve port 42.
Furthermore, the pressure sensitive part 51e of the finger pressure sensor 51 is located outside a virtual circle Cv passing through the center of the electrode 50e of the spark plug 50 centered on the cylinder axis Lc.
The finger pressure sensor 51 detects the pressure of a space portion in contact with the pressure sensitive part 51e in the combustion chamber 40.

  Since knocking occurs by self-ignition due to a pressure increase before the flame generated by ignition by the pressure-sensitive part 51e of the spark plug 50 propagates, the place where knocking occurs (knock generation point) is the spark plug 50. It is a position far from.

In addition, knocking occurs in a place where the temperature at which self-ignition is easy is high.
On the side opposite to the cam chain chamber 17c with respect to the cylinder axis Lc on the ceiling surface 41 of the combustion chamber 40, heat easily escapes to the outside, whereas the temperature on the cam chain chamber 17c side is lowered by the temperature maintained by the cam chain chamber 17c. Since it is difficult and the temperature tends to be higher than other parts, knocking is likely to occur.
Further, since knocking tends to occur on the intake valve port side, it occurs at a location closer to the intake valve port 42 than the exhaust valve port 43.

That is, on the ceiling surface 41 of the combustion chamber 40, the knock generation point is a place far from the spark plug 50 and closer to the intake valve port 42 than the exhaust valve port 43 on the cam chain chamber 17c side with respect to the cylinder axis Lc. Corresponds to the point P indicated by ☆.
Since the pressure due to knocking tends to propagate more greatly as the position is farther from the knock generation point P, in order to detect only the pressure accompanying knocking without being affected by pressure noise, the pressure-sensitive portion 51e of the finger pressure sensor 51 is used. Must be provided as far as possible from the knock occurrence point P on the ceiling surface 41.

As shown in FIG. 4, the pressure sensitive part 51 e of the finger pressure sensor 51 is disposed away from the knock generation point P on the side opposite to the cam chain chamber 17 c with respect to the cylinder axis Lc on the ceiling surface 41.
Further, the pressure-sensitive part 51e of the finger pressure sensor 51 is disposed at a position closer to the exhaust valve port 43 than the intake valve port 42 and away from the knock occurrence point P.
Further, the pressure-sensitive portion 51e of the finger pressure sensor 51 is located away from the knock generation point P outside the virtual circle Cv passing through the center of the electrode 50e of the spark plug 50 centered on the cylinder axis Lc.

  That is, the pressure-sensitive part 51e of the acupressure sensor 51 is provided at a position as far as possible from the knock occurrence point P on the ceiling surface 41, detects only the pressure accompanying knocking without being affected by pressure noise, and The occurrence can be detected with high accuracy.

  The electrode 50e of the spark plug 50 on the right side of the cylinder axis Lc is disposed on the opposite side of the cam chain chamber 17c with respect to the cylinder axis Lc. Easy to detect the occurrence of knocking by providing the pressure sensing part 51e of the finger pressure sensor 51 away from the position where the possibility of knocking is very high (knock occurrence point P). Can do.

  As shown in FIG. 4, the pressure sensing part 51e of the finger pressure sensor 51 includes a cylinder axis Lc, a surface Fe including the center of the exhaust valve port 43, the cylinder axis (Lc), and the spark plug (50). The exhaust valve port 43 sandwiched by the surface Fp including the center of the electrode (50e) and the part 50 of the electrode 50e of the spark plug 50 are both disposed within a range S (range hatched in FIG. 4). .

Next, a second embodiment of a four-stroke internal combustion engine having two intake valves and one exhaust valve will be described with reference to FIG.
FIG. 5 is a bottom view of the cylinder head 70 corresponding to FIG. 4 described above.
Referring to FIG. 5, the mating surface 70 f of the cylinder head 70 with the cylinder block is formed to have a recessed ceiling surface 72 of the combustion chamber 71 corresponding to the cylinder bore, and the cam chain chamber 70 c is located on the left side of the combustion chamber 71. Has been drilled.

The circular opening edge 72s of the ceiling surface 72 of the combustion chamber 71 at the mating surface 70f of the cylinder head 70 coincides with the circular hole of the cylinder bore.
Two intake valve ports 73, 73 are opened side by side on the rear side of the cylinder axis Lc of the ceiling surface 72, and one exhaust valve port 74 is opened on the front side of the cylinder axis Lc of the ceiling surface 72.
The two intake valve ports 73 are positioned symmetrically on the left and right sides of the cylinder axis Lc, and the exhaust valve port 74 is positioned on the front side and on the left side of the cylinder axis Lc.

Further, a plug hole 76 for projecting the electrode 80e of the spark plug 80 into the combustion chamber 71 is opened on the front side and the right side of the cylinder axis Lc of the ceiling surface 72.
A sensor hole 77 is formed in front of the plug hole 76 so that the pressure sensitive part 81e of the finger pressure sensor 81 faces the combustion chamber 71.

The pressure sensor 81e of the finger pressure sensor 81 includes an exhaust valve port 43 sandwiched by a surface Fe including the cylinder axis Lc and the center of the exhaust valve port 74, and a surface Fp including the cylinder axis Lc and the center of the electrode 80e of the spark plug 50. The spark plug is disposed in a range S (a range in which lattice hatching is applied in FIG. 5) that includes each part of the electrode 80e of the spark plug.
Further, the pressure-sensitive part 81e of the finger pressure sensor 81 is located outside a virtual circle Cv passing through the center of the electrode 80e of the spark plug 80 centered on the cylinder axis Lc.

  Referring to FIG. 5, on the ceiling surface 72 of the combustion chamber 71, the knock generation point P is along the circular opening edge 72s closer to the intake valve port 73 than the exhaust valve port 74 on the cam chain chamber 70c side with respect to the cylinder axis Lc. It is a place.

  As shown in FIG. 5, the pressure sensor 81e of the finger pressure sensor includes a surface Fe including the cylinder axis Lc and the center of the exhaust valve port 74, and a surface Fp including the cylinder axis Lc and the center of the electrode 80e of the spark plug 50. Is located as far as possible from the knock generation point P within the range S including both the exhaust valve port 43 sandwiched by and the electrode 80e of the spark plug, so that the finger pressure sensor 81 is not affected by pressure noise. By detecting only the pressure accompanying knocking, the occurrence of knocking can be accurately detected.

  The pressure sensitive part 81e of the finger pressure sensor 81 is located outside the virtual circle Cv passing through the center of the electrode 80e of the spark plug centered on the cylinder axis Lc and further away from the knock occurrence point P. The occurrence of knocking can be detected with higher accuracy.

Next, a third embodiment of a four-valve four-stroke internal combustion engine having two intake valves and two exhaust valves will be described with reference to FIG.
FIG. 6 is a bottom view of the cylinder head 90 corresponding to FIGS. 4 and 5 described above.
Referring to FIG. 6, the mating surface 90 f of the cylinder head 90 with the cylinder block is formed with a recessed ceiling surface 92 of the combustion chamber 91 corresponding to the cylinder bore, and the cam chain chamber 90 c is on the left side of the combustion chamber 91. Has been drilled.

The opening edge 92s of the ceiling surface 72 of the combustion chamber 91 at the mating surface 90f of the cylinder head 90 coincides with the circular hole of the cylinder bore.
Two intake valve ports 93, 93 are opened side by side on the front side of the cylinder axis Lc of the ceiling surface 92, and two exhaust valve ports 94, 94 are opened on the rear side of the cylinder axis Lc of the ceiling surface 92. .
The two intake valve ports 93 and 93 are positioned symmetrically on the left and right sides of the cylinder axis Lc, and the two exhaust valve ports 94 and 94 are also positioned symmetrically on the left and right sides of the cylinder axis Lc. Yes.

A plug hole 96 for projecting the electrode 100e of the spark plug 100 into the combustion chamber 91 is opened at a position overlapping the cylinder axis Lc of the ceiling surface 92.
A sensor hole 97 is formed on the right side of the plug hole 76 in the vicinity of the opening edge 92s so that the pressure-sensitive portion 101e of the finger pressure sensor 101 faces the combustion chamber 91.

  The pressure-sensitive portion 101e of the finger pressure sensor 101 is disposed on the opposite side of the cylinder axis Lc with respect to a line Lr connecting the centers of the intake valve port 93 and the exhaust valve port 94 located on the opposite side of the cam chain chamber 90c with respect to the cylinder axis Lc. Has been.

  Referring to FIG. 6, on the ceiling surface 92 of the combustion chamber 91, the knock generation point P is along the circular opening edge 91s closer to the intake valve port 93 than the exhaust valve port 94 on the cam chain chamber 90c side with respect to the cylinder axis Lc. It is a place.

  As shown in FIG. 6, the pressure sensing part 101e of the finger pressure sensor 101 is a line Lr connecting the centers of the intake valve port 93 and the exhaust valve port 94 that are located on the opposite side of the cam chain chamber 90c with respect to the cylinder axis Lc. With respect to the cylinder axis Lc, on the side opposite to the intake valve port 93 and closer to the exhaust valve port 94, the finger pressure sensor 101 is knocked without being affected by pressure noise. By detecting only the accompanying pressure, it is possible to accurately detect the occurrence of knocking.

  As mentioned above, although the internal combustion engine which concerns on 1st, 2nd, 3rd embodiment which concerns on this invention was demonstrated, the aspect of this invention is not limited to the said embodiment, In the range of the summary of this invention, It includes what is implemented in various ways.

Lc: cylinder axis, P: knock generation point,
DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Crankcase, 12 ... Crankshaft, 13 ... Main shaft, 14 ... Countershaft, 16 ... Cylinder block, 16b ... Cylinder bore, 16c ... Cam chain chamber, 17 ... Cylinder head, 17c ... Cam chain chamber , 18 ... Cylinder head cover, 19 ... Connecting pipe,
20 ... Inlet pipe, 21 ... Throttle body, 22 ... Throttle valve, 23 ... Injector, 24 ... Air cleaner, 25 ... Piston, 26 ... Connecting rod,
30 ... Valve mechanism, 31 ... Cam shaft, 32e, 32i ... Rocker arm shaft, 33i ... Intake rocker arm, 33e ... Exhaust rocker arm, 34i, 34e ... Valve guide, 35 ... Cam chain sprocket, 36 ... Cam chain,
40 ... Combustion chamber, 41 ... Ceiling surface, 42 ... Intake valve port, 42a ... Projection part, 43 ... Exhaust valve port, 44 ... Intake port, 45 ... Exhaust port, 46 ... Intake valve, 46s ... Intake valve stem, 47 ... Exhaust valve, 48 ... plug hole, 49 ... sensor hole,
50 ... Spark plug, 50e ... Electrode, 51 ... Acupressure sensor, 51e ... Pressure sensitive part,
70 ... Cylinder head, 70f ... Mating surface, 70c ... Cam chain chamber, 71 ... Combustion chamber, 72 ... Ceiling surface, 72s ... Circular opening edge, 73 ... Intake valve port, 74 ... Exhaust valve port, 75 ..., 76 ... Plug Hole, 77 ... sensor hole, 80 ... spark plug, 80e ... electrode, 81 ... finger pressure sensor, 81e ... pressure sensitive part,
90 ... Cylinder head, 90f ... Mating surface, 90c ... Cam chain chamber, 91 ... Combustion chamber, 92 ... Ceiling surface, 92s ... Open edge, 93 ... Intake valve port, 94 ... Exhaust valve port, 96 ... Plug hole, 97 ... Sensor hole, 100 ... spark plug, 100e ... electrode, 101 ... acupressure sensor, 101e ... pressure sensitive part.

Claims (6)

Combustion between the top surface of the piston (25) slidably fitted in the cylinder bore (16b) of the cylinder block (16) and the ceiling surface (41) of the cylinder head (17) facing the top surface Chamber (40) is constructed,
On the ceiling surface (41), an intake valve port (42) and an exhaust valve port (43) for opening and closing an intake valve (46) and an exhaust valve (47), respectively, are opened facing the combustion chamber (40),
In the internal combustion engine in which the electrode (50e) of the spark plug (50) attached to the cylinder head (17) is exposed to the ceiling surface (41) facing the combustion chamber (40),
A cam chain chamber (17c) for inserting a cam chain (36) for transmitting power of an internal combustion engine to a cam shaft (31) for driving the intake valve (46) and the exhaust valve (47) includes the cylinder head. (17) is formed adjacent to the ceiling surface (41),
The pressure-sensitive portion (51e) of the in-cylinder pressure sensor (51) that detects the pressure in the combustion chamber (40) is the cylinder axis (Lc) that is the central axis of the cylinder bore (16b) on the ceiling surface (41). An internal combustion engine characterized by being disposed on the opposite side of the cam chain chamber (17c) from the combustion chamber (40). The intake valve port (42) and the exhaust valve port (43) are formed on opposite sides with respect to the cylinder axis of the ceiling surface (41),
The internal combustion engine according to claim 1, wherein the pressure-sensitive portion of the in-cylinder pressure sensor (51) is disposed at a position closer to the exhaust valve port (43) than the intake valve port (42).   The pressure-sensitive portion (51e) of the in-cylinder pressure sensor is disposed outside a virtual circle (Cv) passing through the center of the electrode (50e) of the spark plug (50) with the cylinder axis (Lc) as the center. The internal combustion engine according to claim 1 or 2, characterized in that.   The electrode (50e) of the spark plug (50) is disposed on the opposite side of the cam chain chamber (17c) with respect to the cylinder axis (Lc). The internal combustion engine according to item. There is one exhaust valve port (74) on the ceiling surface (72),
The pressure-sensitive portion (81e) of the in-cylinder pressure sensor (81) includes a surface (Fe) including the cylinder axis (Lc) and the center of the exhaust valve port (74), the cylinder axis (Lc), and the spark plug. Within the range (S) including both the exhaust valve port (74) and the electrode (80e) of the spark plug (80) sandwiched by the surface (Fp) including the center of the electrode (80e) of (80) The internal combustion engine according to any one of claims 1 to 4, wherein the internal combustion engine is disposed in the position. There are two intake valve ports (93) and two exhaust valve ports (94) on the ceiling surface (92),
The pressure sensing part 101e) of the in-cylinder pressure sensor (101) includes the intake valve port (93) and the exhaust valve port (94) located on the opposite side of the cam chain chamber (90c) with respect to the cylinder axis (Lc). The internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine is disposed on a side opposite to the cylinder axis (Lc) with respect to a line (Lr) connecting the centers of the cylinders.

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