JP2008223525A - Engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine capable of making the distribution amounts of intake air to a plurality of cylinders uniform. <P>SOLUTION: In the engine, a throttle valve 7 is arranged in a throttle intake passage 6, an intake amount is adjusted based on opening of the throttle valve, and a fuel in an amount corresponding to the intake amount is fed from a fuel feeding means 11 to the intake. A plurality of cylinders are provided, an intake distribution passage 2 is mounted to a cylinder head 1 and when a throttle intake passage 6 is arranged in an upstream of a distribution passage entrance part 4 of the intake distribution passage 2, a breather exit 51 is made facing to an area from the throttle intake passage 6 to the distribution passage entrance part 4 of the intake distribution passage 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine, and more particularly, to an engine that can equalize the distribution amount of intake air to a plurality of cylinders.

  As in the present invention, a throttle valve is arranged in the throttle intake passage as a conventional engine, the intake air amount is adjusted based on the opening of the throttle valve, and fuel corresponding to the intake air amount is taken from the fuel supply means. There is something to be supplied to.

  In the above prior art, a plurality of cylinders are provided, an intake distribution passage is attached to the cylinder head, and a throttle intake passage is arranged upstream of the distribution passage inlet of the intake distribution passage. There is an exit.

The above prior art has the following problems.
<Problem> The distribution amount of intake air to a plurality of cylinders cannot be equalized.
Because the breather outlet is provided downstream of the distribution passage inlet of the intake distribution passage, the air and blow-by gas in the crankcase sucked out from the breather outlet is distributed to some cylinders without being sufficiently mixed with the intake air. Is done. For this reason, the air-fuel ratio of the air-fuel mixture distributed to the plurality of cylinders cannot be equalized.

  An object of the present invention is to provide an engine that can solve the above-described problems, that is, an engine that can equalize the air-fuel ratio of an air-fuel mixture distributed to a plurality of cylinders.

Invention specific matters of the invention according to claim 1 are as follows.
As illustrated in FIG. 1A, a throttle valve (7) is disposed in the throttle intake passage (6), and the intake air amount is adjusted based on the opening of the throttle valve (7), and this intake air amount is accommodated. In an engine in which a specified amount of fuel is supplied to the intake air from the fuel supply means (11),
As illustrated in FIG. 3, a plurality of cylinders (3) are provided, an intake distribution passage (2) is attached to the cylinder head (1), and a throttle body ( 5) When installing,
As illustrated in FIG. 1 (A) or FIG. 2 (A), a breather outlet (51) is provided in a region from the throttle intake passage (6) to the distribution passage inlet (4) of the intake distribution passage (2). An engine characterized by that.

(Invention of Claim 1)
<Effect> It is possible to equalize the distribution amount of intake air to a plurality of cylinders.
As illustrated in FIG. 3, since the breather outlet (51) faces the region from the throttle intake passage (6) to the distribution passage inlet (4) of the intake distribution passage (2), the breather outlet (51 The air in the crankcase and the blow-by gas sucked out from the gas flow out into the intake distribution passage (2) while being mixed with the intake air in the above-mentioned region, and are evenly distributed to the plurality of cylinders (3). For this reason, the distribution amount of the intake air to the plurality of cylinders (3) can be equalized.

(Invention of Claim 2)
In addition to the effect of the invention according to claim 1, the following effect is achieved.
<Effect> It is possible to equalize the distribution amount of intake air to a plurality of cylinders.
As illustrated in FIG. 2 (A), the breather outlet (51) is disposed directly behind the valve shaft (12) when viewed in a direction parallel to the valve shaft (12) of the throttle valve (7). The air and blow-by gas in the crankcase sucked out from (51) is turbulent flow generated just behind the valve shaft (12), and is engulfed in the intake air and uniformly dispersed in the intake air. be introduced. For this reason, the distribution amount of the intake air to the plurality of cylinders (3) can be equalized.

(Invention of Claim 3)
In addition to the effect of the invention according to claim 1 or claim 2, the following effect is achieved.
<Effect> Increases exhaust gas performance and quiet operation.
As the cylinder (3) having a lower compression ratio is advanced in ignition timing, incomplete combustion is unlikely to occur, and the content of harmful components in the exhaust gas is reduced. Moreover, since the ignition timing is delayed as the cylinder (3) has a higher compression ratio, knocking is suppressed and combustion noise is reduced. For this reason, exhaust gas performance and quiet operation are enhanced.

(Invention of Claim 4)
In addition to the effect of the invention according to claim 3, the following effect is achieved.
<Effect> Fine control of the ignition timing for each cylinder can be performed.
Based on the different ignition timing control maps for each cylinder (3), the control means (17) controls the ignition timing for each cylinder (3), so fine control of the ignition timing for each cylinder (3) is possible. Can be implemented.

(Invention according to claim 5)
In addition to the effects of the invention according to any one of claims 1 to 4, the following effects are provided.
<Effect> The air-fuel ratio of the air-fuel mixture distributed to each cylinder can be equalized.
Since the fuel supply amount increases as the fuel supply to the cylinder (3) where the fuel concentration of the air-fuel mixture becomes lighter at the same fuel supply amount, the air-fuel ratio of the air-fuel mixture distributed to each cylinder (3) can be equalized. it can.

(Invention of Claim 6)
In addition to the effects of the invention according to any one of claims 1 to 5, the following effects are provided.
<Effect> The air-fuel ratio of the air-fuel mixture distributed to each cylinder can be equalized.
At the same fuel supply start time, the fuel supply start time is advanced as the fuel supply to the cylinder (3) where the fuel concentration of the air-fuel mixture becomes lighter. The problem of remaining in the passage (2) and being supplied to the other cylinder (3) can be prevented. For this reason, the air-fuel ratio of the air-fuel mixture distributed to each cylinder (3) can be equalized.

(Invention of Claim 7)
In addition to the effect of the invention according to claim 5 or claim 6, the following effect is produced.
<Effect> Finely controlled fuel supply for each cylinder can be performed.
Since the control means (17) controls the fuel supply to each cylinder (3) based on the different fuel supply control map for each cylinder (3), the fine fuel for each cylinder (3). Supply control can be implemented.

(Invention of Claim 8)
In addition to the effects of the invention according to any one of claims 1 to 7, the following effects are provided.
<Effect> The distribution amount of the intake air to each cylinder can be equalized.
As illustrated in FIG. 3, an intake distribution passage (2) that is straight and continuous in the longitudinal direction is formed in the box-type intake passage wall (2 a), and each cylinder (3) is held at a predetermined interval in the longitudinal direction. Since the intake port inlet (3a) of the cylinder faces the intake distribution passage (2), intake stagnation hardly occurs in the intake distribution passage (2), and the distribution amount of intake air to each cylinder (3) is equalized. can do.

(Invention according to claim 9)
In addition to the effects of the invention according to any one of claims 1 to 8, the following effects are provided.
<Effect> It is possible to prevent malfunction of the throttle valve.
As illustrated in FIG. 1A, an upstream breather outlet (52) is opened upstream of the throttle valve (7), and the upstream breather outlet (52) is connected to the breather chamber via the upstream breather passage (52a). When communicating with (56), the downstream breather outlet (53) is opened downstream of the throttle valve (7), and the downstream breather outlet (53) is connected to the breather chamber (56) via the downstream breather passage (53a). Therefore, the amount of blow-by gas sucked upstream of the throttle valve (7) can be reduced. For this reason, the engine oil contained in the blow-by gas adheres to the throttle valve (7), and the trouble that the carbide or the like adheres to the throttle valve (7) is suppressed, and the malfunction of the throttle valve (7) due to this is prevented. can do.

(Invention according to claim 10)
In addition to the effect of the invention according to claim 9, the following effect is obtained.
<Effect> It is possible to prevent malfunction of the throttle valve.
As illustrated in FIGS. 4A and 4B, the shared breather passage (54) is led out from the breather chamber (56), and the upstream breather passage (52a) and the downstream breather passage ( 53a), the engine oil flowing into the upstream breather passage (52a) can be sucked out into the downstream breather passage (53a) due to the pressure difference between the upstream side and the downstream side of the throttle valve (7). it can. For this reason, the engine oil contained in the blow-by gas adheres to the throttle valve (7), and the trouble that the carbide or the like adheres to the throttle valve (7) is suppressed, and the malfunction of the throttle valve (7) due to this is prevented. can do.

(Invention of Claim 11)
In addition to the effect of the invention according to claim 10, the following effect is achieved.
<Effect> It is possible to prevent malfunction of the throttle valve.
As illustrated in FIG. 5A, since the start end portion (52b) of the upstream breather passage (52a) protruding from the shared breather passage (54) is oriented upward, the upstream breather passage (52a) The inflowing engine oil is easily sucked into the downstream breather passage (53a). For this reason, the engine oil contained in the blow-by gas adheres to the throttle valve (7), and the trouble that the carbide or the like adheres to the throttle valve (7) is suppressed, and the malfunction of the throttle valve (7) due to this is prevented. can do.

(Invention of Claim 12)
In addition to the effect of the invention according to claim 10 or claim 11, the following effect is achieved.
<Effect> It is possible to prevent malfunction of the throttle valve.
As shown in FIG. 5B, since the downstream breather passage (53a) is directed downward from the shared breather passage (54) toward the downstream breather outlet (53), the downstream breather passage (53a) The engine oil that has flowed into the outlet immediately flows out from the downstream breather outlet (53), and the engine oil in the upstream breather passage (52a) is easily sucked into the downstream breather passage (53a). For this reason, the engine oil contained in the blow-by gas adheres to the throttle valve (7), and the trouble that the carbide or the like adheres to the throttle valve (7) is suppressed, and the malfunction of the throttle valve (7) due to this is prevented. can do.

(Invention of Claim 13)
In addition to the effects of any one of the ninth to twelfth inventions, the following effects are achieved.
<Effect> Excessive engine oil can be prevented from being sucked out of the breather chamber.
As illustrated in FIG. 1A, the passage cross-sectional area of the downstream breather passage (53a) is smaller than the passage cross-sectional area of the upstream breather passage (52a), so that the passage resistance of the downstream breather passage (53a) is reduced. Becomes larger. Therefore, as illustrated in FIG. 2A, the throttle valve (7) is in the fully closed position (7b) or the fully closed position (7c), and the intake pressure on the downstream side of the throttle valve (7) is considerably low. Even so, excessive suction of engine oil from the breather chamber (56) can be prevented.

(Invention according to Claim 14)
In addition to the effects of the invention according to any one of claims 9 to 13, the following effects are provided.
<Effect> Wasteful consumption of engine oil can be reduced.
As illustrated in FIG. 4C, the inlet (56b) of the breather chamber (56) is offset from directly above the rocker arm (55) and is lower than the bottom wall (56b) of the breather chamber (56). Therefore, it is difficult for engine oil to enter the breather chamber (56). For this reason, take-out of engine oil from the breather chamber (56) is suppressed, and useless consumption of engine oil can be reduced.

  Embodiments of the present invention will be described with reference to the drawings. FIGS. 1 to 10 are diagrams for explaining an engine according to an embodiment of the present invention. In this embodiment, a vertical water-cooled four-cycle in-line three-cylinder electronic fuel injection engine will be described.

The outline of the embodiment of the present invention is as follows.
As shown in FIG. 7, in this engine, the cylinder head (1) is assembled to the upper part of the cylinder block (24), the head cover (25) is assembled to the upper part of the cylinder head (1), and the lower part of the cylinder block (24) is assembled. An oil pan (26) is assembled, a gear case (27) is assembled at the front of the cylinder block (24), and a flywheel (28) is arranged at the rear of the cylinder block (24). An engine cooling fan (29) is disposed at the front of the gear case (27).

  As shown in FIG. 6, the intake air distribution passage (2) is attached to the cylinder head (1), and the air-fuel mixture is distributed to the plurality of cylinders (3) through the intake air distribution passage (2). A throttle body (5) is attached to the single distribution passage inlet (4), and a fuel supply means (11) is attached to the throttle body (5).

As shown in FIG. 3, the intake air distribution passage (2) is generally called an intake manifold, but since it has a box shape without a branch pipe, it is particularly called an intake air distribution passage (2). . The number of cylinders (3) is three, and these are referred to as the first cylinder, the second cylinder, and the third cylinder from the engine cooling fan (29) side. The single distribution passage inlet (4) is arranged at the end of the intake distribution passage (2) on the third cylinder side, and is viewed in a direction parallel to the cylinder center axis (30) as shown in FIG. With the flywheel (28) side as the rear, it is directed obliquely at an angle of 60 ° with respect to the crankshaft central axis (31). The liquid fuel supplied to the throttle body (5) is gasoline.
The ignition order is the order of the first cylinder, the second cylinder, and the third cylinder, and the ignition interval is approximately 240 ° (crank angle).

The outline of fuel supply is as follows.
As shown in FIG. 1A, a throttle intake passage (6) is provided in a throttle body (5), a butterfly throttle valve (7) is disposed in the throttle intake passage (6), and a throttle valve ( 7) is linked to the mechanical governor (42), the intake air amount is adjusted based on the opening of the throttle valve (7), and the fuel corresponding to the intake air amount is supplied to the intake air from the fuel supply means (11). Like to do. The mechanical governor (42) is interlocked with the governing lever (43).
In this engine, as shown in FIG. 2 (A), the governor force (42a) shown in FIG. 1 (A) is small during low-speed light load operation in which the throttle valve (7) is in the fully closed position (7c). The spring force (42c) of the governor spring (42b) that balances this is small, and the opening speed of the throttle valve (7) is slow even if the load increases.

The device of the throttle body is as follows.
As shown in FIG. 2A, of the inner peripheral surface of the throttle intake passage (6), an annular inner peripheral surface having a predetermined width around the throttle valve (7) is used as an inner peripheral surface (6d) around the valve. An annular inner peripheral surface adjacent to the inner peripheral surface (6d) is defined as an adjacent inner peripheral surface (6e), and a portion of the throttle valve (7) farthest from the valve shaft (12) is defined as a swing end portion (7a). The adjacent inner peripheral surface (6e) has a shape in which the passage cross-sectional area gradually increases as the distance from the end edge (6f) of the valve peripheral inner peripheral surface (6d) increases (inner diameter increases). The swing end (7a) of the throttle valve (7) in the closed position (7c) swings within the adjacent inner peripheral surface (6e).
With this configuration, even when the throttle valve (7) is open at a low speed and light load, the throttle valve (7) can be opened only slightly due to an increase in load, and the intake air can be increased quickly. A delay in fuel supply with respect to an increase in load can be suppressed.
In this engine, the fully closed posture (7b) is set to 0% opening, the fully opened posture (7d) is set to 100% opening, and the angle between them is equally divided into 100, and the ratio of the angle opened from the fully closed posture (7b) is determined. In the case of the opening, the fully closed posture (7c) refers to, for example, a range of opening 10 to 40%, 20 to 40%, 30 to 40%, and the like.

As shown in FIG. 2 (A), the adjacent inner peripheral surface (6e) has a gradually increasing passage sectional area (inner diameter) from the upstream end edge (6f) of the valve peripheral inner peripheral surface (6d) toward the upstream side. It has a tapered shape of a truncated cone.
With this configuration, the intake resistance of the throttle intake passage (6) is reduced.

The device of fuel supply control is as follows.
As shown in FIG. 1 (A), an intake pressure introduction passage (18) is formed in the throttle body (5), and a passage inlet (18a) of the intake pressure introduction passage (18) is formed in the throttle intake passage (6). The intake pressure of the throttle intake passage (6) is introduced to the intake pressure detection sensor (15) through the intake pressure introduction passage (18), and the intake pressure detection sensor (15) and the engine speed detection are opened. The sensor (16) is linked to the fuel supply means (11) via the control means (17), and based on the detection of the intake pressure of the throttle intake passage (6) and the engine speed, the control means (17) An amount of fuel corresponding to the amount of intake air is supplied from the fuel supply means (11) to the intake air.
With this configuration, the air-fuel ratio can be set accurately.
Specifically, the intake air amount is calculated based on the intake pressure, the engine speed, and the detection, the necessary fuel supply amount is calculated based on the intake air amount, and the determined amount of fuel is supplied to the intake air.
The intake pressure detection sensor (15) has a function of detecting the intake air temperature, and the control means (17) corrects the liquid fuel injection amount based on the intake air temperature. The control means (17) is a microcomputer.

As shown in FIG. 2 (B), the inner peripheral surface (6d) around the valve of the throttle intake passage (6) is a venturi portion (6i), and the inlet port of the intake pressure introduction passage (18) at this venturi portion (6i). (18a) is opened.
With this configuration, the change in the opening degree of the throttle valve (7) can be accurately detected based on the intake pressure as compared to the case where the inner diameter is constant, and the fuel supply can be finely adjusted according to the load. Control can be performed.
The reason is as follows.
When the passage inlet (18a) of the intake pressure introduction passage (18) is opened at the venturi section (6i), the throttle valve (7) is fully closed (when closed at the inner peripheral surface having a constant inner diameter). 7b) The intake pressure detected at the time drops considerably. The intake pressure detected in the fully open posture (7d) does not change much. For this reason, when the passage inlet (18a) of the intake pressure introduction passage (18) is opened at the venturi section (6i), the throttle valve (7) is fully opened (7d) as compared with the case where the inner diameter is constant. ) And the fully closed posture (7b), the difference in intake pressure increases, the detection range of the intake pressure widens, and the change in the opening of the throttle valve (7) can be accurately detected based on the intake pressure. It is.
The venturi section (6i) has a circular passage cross section, and the diameter of each section is reduced by 1 mm in order of the upstream end edge (6f), the downstream end edge (6g), and the center section.
As long as the venturi portion (6i) is an inner peripheral surface of the intake passage, the venturi portion (6i) may be provided at a location different from the valve peripheral inner peripheral surface (6d).

As shown in FIG. 2A, the radial direction of the throttle intake passage (6) orthogonal to the valve shaft (12) of the throttle valve (7) is defined as the left-right lateral direction, and the passage inlet ( 18a) is arranged on the inner circumferential surface of the throttle intake passage (6), the throttle valve (7) is divided into left and right with the valve shaft (12) as a boundary when the throttle valve (7) is in the fully closed position (7b). Of the left and right lateral halves of the valve, a portion directed to the downstream side of the valve shaft (12) of the throttle valve (7) when the throttle valve (7) is opened is defined as a downstream-oriented half (7e). A passage of the intake pressure introduction passage (18) is formed on the lateral inner peripheral surface (6j) opposite to the lateral inner peripheral surface of the throttle intake passage (6) to which the downstream directing half (7e) is directed during the valve opening of (7). An inlet (18a) is arranged.
With this configuration, the detection of the intake pressure is not disturbed by the intake flow guided by the downstream directing half (7a), and the intake pressure can be detected accurately.

The idea for evenly distributing the intake air to the cylinders is as follows.
As shown in FIG. 3, three cylinders (3) are provided, an intake distribution passage (2) is attached to the cylinder head (1), and a single distribution passage inlet (4) of the intake distribution passage (2) is provided. A single throttle body (5) is attached.
With this configuration, only one throttle body (5) is required for three cylinders (3), and the manufacturing cost of the engine can be reduced.

As shown in FIG. 1 (A) or FIG. 2 (A), the breather outlet (51) faces the distribution passage inlet (4).
With this configuration, air and blow-by gas in the crankcase sucked out from the breather outlet (51) flows out into the intake distribution passage (2) while being mixed with intake air in the distribution passage inlet (4), and each cylinder ( Evenly distributed to 3). For this reason, the distribution amount of the intake air to each cylinder (3) can be equalized.
In this engine, fuel has already been supplied to the intake air in the distribution passage inlet (4) and has already become an air-fuel mixture, so the air and blow-by gas in the crankcase sucked out from the breather outlet (51) In the distribution passage inlet (4), the mixture flows out into the intake distribution passage (2) while being mixed with the air-fuel mixture, and is equally distributed to each cylinder (3). For this reason, the air-fuel ratio of the air-fuel mixture to each cylinder (3) can be equalized.
The breather outlet (51) is not limited to the distribution passage inlet (4) of the intake distribution passage (2), but from the passage outlet (6h) of the throttle intake passage (6) to the distribution passage inlet (2) of the intake distribution passage (2). It is possible to face an appropriate place in the area up to 4).

As shown in FIG. 2A, the throttle valve (6) has a central axis (6a) in the front-rear direction and a downstream side of the throttle valve (7) from the valve shaft (12). The breather outlet (51) is arranged directly behind the valve shaft (12) when viewed in a direction parallel to the valve shaft (12) of 7).
With this configuration, air or blow-by gas in the crankcase sucked out from the breather outlet (51) is turbulent flow generated just behind the valve shaft (12), and is entrapped in the intake air and uniformly dispersed in the intake air. It is introduced into the distribution passage (2). For this reason, the distribution amount of the intake air to each cylinder (3) can be equalized.
In this engine, fuel is already supplied to the intake air passing through the vicinity of the breather outlet (51) to form an air-fuel mixture. Therefore, air and blow-by gas in the crankcase sucked out from the breather outlet (51) The turbulent flow generated immediately behind the shaft (12) is caught in the air-fuel mixture, is uniformly dispersed in the air-fuel mixture, and is introduced into the intake air distribution passage (2). For this reason, the air-fuel ratio of the air-fuel mixture distributed to each cylinder (3) can be equalized.
As shown in FIG. 2 (A), “behind the valve shaft (12)” refers to the central axis (6a) of the throttle intake passage (6) from the valve shaft (12) when viewed in a direction parallel to the valve shaft (12). ) Is the position moved back along.

As shown in FIG. 1A, each cylinder (3) is provided with an ignition plug (36), and an ignition circuit (37) of the ignition plug (36) is connected to a crankshaft phase detection sensor via a control means (17). Ignition timing control in which a spark is blown from the spark plug (36) at every predetermined timing of the combustion cycle of each cylinder (3) by the control means (17) based on the phase detection of the crankshaft (39) in cooperation with (38) In performing the above, the ignition timing is advanced as the cylinder (3) having a lower compression ratio.
With this configuration, the cylinder (3) with a lower compression ratio is advanced in ignition timing, so that incomplete combustion is less likely to occur and the content of harmful components in the exhaust gas is reduced. Moreover, since the ignition timing is delayed as the cylinder (3) has a higher compression ratio, knocking is suppressed and combustion noise is reduced. For this reason, exhaust gas performance and quiet operation are enhanced.
In this engine, the compression ratio of the cylinder (3) becomes lower as it moves away from the throttle body (5), the compression ratio of the first cylinder (3) is the lowest, the compression ratio of the third cylinder (3) is the highest, The compression ratio of the two cylinders (3) is an intermediate height between them.
In this engine, the ignition timing is set within a range of 30 ° to 15 ° (crank angle) before the top dead center of the compression stroke.
For example, at a predetermined rotation speed and a predetermined load, the first cylinder performs ignition at 23 ° before the top dead center of the compression stroke, the second cylinder at 21 °, and the third cylinder at 19 °.

The control method is as follows.
Based on the ignition timing control map, the control means (17) controls the ignition timing of each cylinder (3) by detecting the engine speed, the intake pressure of the throttle intake passage (6) and the phase of the crankshaft (39). .
Specifically, the control means (17) controls the ignition timing of each cylinder (3) based on a different ignition timing control map for each cylinder (3).
With this configuration, fine control of the ignition timing for each cylinder (3) can be performed.
In each ignition timing control map, the engine speed and the intake pressure of the throttle intake passage (6) are set as input values, and the optimal ignition for each cylinder (3) during a predetermined speed and a predetermined load operation corresponding to the input values. Data with time as an output value is stored.

The fuel supply devices are as follows.
A single fuel supply means (11) faces the throttle intake passage (6), and the single fuel supply means (11) is linked to the crankshaft phase detection sensor (38) via the control means (17). Based on the phase detection of the crankshaft (39), the control means (17) supplies the fuel supplied to each cylinder (3) as a single fuel at every predetermined timing of the combustion cycle of each cylinder (3). When performing fuel supply control for supplying the intake air from the means (11) to the throttle intake passage (6), the fuel supply amount is increased as the fuel is supplied to the cylinder (3) where the fuel concentration of the air-fuel mixture becomes lighter at the same fuel supply amount. Do more.
With this configuration, the air-fuel ratio of the air-fuel mixture distributed to each cylinder (3) can be equalized.
In this engine, at the same fuel supply amount, the fuel concentration of the air-fuel mixture supplied to the cylinder (3) becomes thinner as it goes away from the throttle body (5), and the fuel concentration of the first cylinder (3) is the lightest. The fuel concentration in the three cylinders (3) is the highest, and the fuel concentration in the second cylinder (3) is intermediate between them.
The fuel supply means (11) can face an appropriate place in the region from the throttle intake passage (6) to the distribution passage inlet (4) of the intake distribution passage (2).
In this engine, since the injector (8) is used as the fuel supply means (11), the fuel injection amount is increased as the fuel is injected into the cylinder (3) where the fuel concentration of the air-fuel mixture becomes thinner at the same fuel injection amount. become.

Further, the fuel supply start timing is advanced as the fuel is supplied to the cylinder (3) where the fuel concentration of the air-fuel mixture becomes lighter at the same fuel supply start timing.
With this configuration, it is possible to prevent a problem that the fuel to be supplied to the cylinder (3) whose fuel concentration tends to be thin remains in the intake distribution passage (2) and is supplied to the other cylinder (3). . For this reason, the air-fuel ratio of the air-fuel mixture distributed to each cylinder (3) can be equalized.
In this engine, since the injector (8) is used as the fuel supply means (11), the fuel injection start timing is advanced as the fuel is injected into the cylinder (3) where the fuel concentration of the air-fuel mixture decreases at the same fuel injection start timing. It will be.
In this engine, the fuel injection disclosure time is set within the range of 50 ° before top dead center to 50 ° (crank angle) after top dead center.
For example, at a predetermined rotation speed and a predetermined load, the fuel supply to the first cylinder is 10 ° before the top dead center of the intake stroke of the first cylinder, and the fuel supply to the second cylinder is the upper limit of the intake stroke of the second cylinder. At the dead point, the fuel supply to the third cylinder starts fuel injection at 10 ° after the top dead center of the intake stroke of the third cylinder.

The control method is as follows.
Based on the fuel supply control map, the control means (17) controls the fuel supply to each cylinder (3) by detecting the engine speed, the intake pressure of the throttle intake passage (6), and the phase of the crankshaft (39). .
Specifically, the fuel supply to each cylinder (3) is controlled by the control means (17) based on a different fuel supply control map for each cylinder (3).
With this configuration, fine fuel supply control can be performed for each cylinder (3).
In each fuel supply control map, the engine speed and the intake pressure of the throttle intake passage (6) are set as input values, and the fuel to each cylinder (3) optimal at the time of a predetermined speed and a predetermined load operation corresponding to the input values. Data having the supply start time and the fuel supply amount as output values is stored.
In this engine, since the injector (8) is used as the fuel supply means (11), the control means (17) controls the fuel injection of each cylinder (3) based on the fuel injection control map.

As shown in FIG. 3, a longitudinal box-type intake passage wall (2a) along the arrangement direction of a plurality of cylinders (3) is attached to the side surface of the cylinder head (1), and the inside of the box-type intake passage wall (2a) An intake distribution passage (2) that is continuous straight in the longitudinal direction is formed, and a predetermined interval is maintained in the longitudinal direction so that the intake port inlet (3a) of each cylinder (3) faces the intake distribution passage (2). I didn't.
With this configuration, intake air stagnation hardly occurs in the intake air distribution passage (2), and the distribution amount of the intake air to each cylinder (3) can be equalized.
In this engine, fuel is already supplied to the intake air that passes through the intake air distribution passage (2) to form an air-fuel mixture, so that the air-fuel mixture is less likely to stagnate in the intake air distribution passage (2). ) Can be equalized.
The cross-sectional area of the intake air distribution passage (2) is the largest at the portion close to the throttle body (5), the smallest at the far portion, and the intermediate portion has an intermediate size.

The device of the breather device is as follows.
As shown in FIG. 1A, when opening the upstream breather outlet (52) upstream of the throttle valve (7), the downstream breather outlet (53) is also opened downstream of the throttle valve (7). Yes.
With this configuration, the amount of blow-by gas sucked upstream of the throttle valve (7) can be reduced. For this reason, the engine oil contained in the blow-by gas adheres to the valve shaft (12) of the throttle valve (7), and the problem that the carbide or the like adheres to the valve shaft (12) is suppressed. ) Can be prevented.
The upstream breather outlet (52) is disposed upstream of the passage inlet (18a) of the intake pressure introduction passage (18), and the downstream breather outlet (53) is disposed at the passage inlet (18a) of the intake pressure introduction passage (18). The engine oil contained in the blow-by gas is less likely to clog the passage inlet (18a) of the intake pressure introduction passage (18).

As shown in FIGS. 4A and 4B, the shared breather passage (54) is led out from the breather chamber (56), and the upstream breather passage (52a) and the downstream breather passage (53a) are connected to the shared breather passage (54). ) And branched.
With this configuration, the engine oil accumulated in the upstream breather passage (52a) can be sucked into the downstream breather passage (53a) due to the pressure difference between the upstream side and the downstream side of the throttle valve (7). For this reason, the engine oil contained in the blow-by gas adheres to the throttle valve (7), and the trouble that the carbide or the like adheres to the throttle valve (7) (particularly, the valve shaft (12)) is suppressed. The malfunction of (7) can be prevented.

As shown in FIG. 5A, the start end portion (52b) of the upstream-side breather passage (52a) protruding from the shared breather passage (54) is directed upward.
With this configuration, engine oil in the upstream breather passage (52a) is easily sucked into the downstream breather passage (53a). For this reason, the engine oil contained in the blow-by gas adheres to the throttle valve (7), and the trouble that the carbide or the like adheres to the throttle valve (7) (particularly, the valve shaft (12)) is suppressed. The malfunction of (7) can be prevented.
The start end portion (52b) of the upstream breather passage (52a) is inclined upward and obliquely upward from the shared breather passage (54).

As shown in FIG. 5 (B), the downstream breather passage (53a) is directed downward from the leading end of the shared breather passage (54) toward the downstream breather outlet (53).
With this configuration, the engine oil flowing into the downstream breather passage (53a) quickly flows out from the downstream breather outlet (53), and the engine oil in the upstream breather passage (52a) enters the downstream breather passage (53a). Easy to be sucked out. For this reason, the engine oil contained in the blow-by gas adheres to the throttle valve (7), and the trouble that the carbide or the like adheres to the throttle valve (7) (particularly, the valve shaft (12)) is suppressed. The malfunction of (7) can be prevented.

As shown in FIG. 1 (A), the passage connecting the upstream breather outlet (52) to the breather chamber (56) is the upstream breather passage (52a), and the downstream breather outlet (53) is the breather chamber (56). The communicating passage is the downstream breather passage (53a), and the passage sectional area of the downstream breather passage (53a) is smaller than the passage sectional area of the upstream breather passage (52a).
With this configuration, the passage resistance of the downstream breather passage (53a) is increased. Therefore, as shown in FIG. 2 (A), the throttle valve (7) is in the fully closed position (7b) or the fully closed position (7c), and the intake pressure downstream of the throttle valve (7) becomes considerably low. However, excessive suction of engine oil from the breather chamber (56) can be prevented.

As shown in FIG. 4C, a head cover (25) is attached to the upper part of the cylinder head (1), the rocker arm (55) is covered with the head cover (25), and a breather chamber ( 56), the inlet (56a) of the breather chamber (56) is disposed at a position deviated from directly above the rocker arm (55) and lower than the bottom wall (56b) of the breather chamber (56). Yes.
With this configuration, it is difficult for engine oil to enter the breather chamber (56). For this reason, take-out of engine oil from the breather chamber (56) is suppressed, and useless consumption of engine oil can be reduced.

Other devices will be described.
As shown in FIG. 1 (A), the tip (9) of the injector (8) faces the throttle intake passage (6) downstream of the throttle valve (7), and as shown in FIG. 1 (B). The liquid fuel injection port (10) is opened at the tip (9) of the injector (8).
As shown in FIG. 1 (A), an intake pipe connection pipe (34) is attached to the intake passage inlet (6b) of the throttle intake passage (6), and the intake pipe connection pipe (34) is led out from an air cleaner (not shown). The outlet end of the intake pipe (35) is connected.

The relationship between the throttle valve and the injector is as follows.
As shown in FIG. 1 (A) and FIG. 2 (A), the tip (9) of the injector (8) faces the throttle intake passage (6) downstream of the throttle valve (7). The liquid fuel injection port (10) is opened at the tip (9) of 8).
With this configuration, fine oil droplets of the liquid fuel injected from the liquid fuel injection port (10) are entrained in the wake (turbulent flow) generated downstream of the throttle valve (7), and atomization of the liquid fuel is promoted. The air-fuel ratio of the air-fuel mixture distributed to each cylinder (3) can be equalized.

  As shown in FIGS. 2A and 2B, the direction of the central axis (6a) of the throttle intake passage (6) is the front-rear direction and the downstream side of the valve shaft (12) of the throttle valve (7) is the rear. The tip end portion (9) of the injector (8) is disposed directly behind the valve shaft (12) of the throttle valve (7), and the tip end portion (9) of the injector (8) from the central axis (8a) of the injector (8). And an extension axis (8b) of the injector (8) extended into the throttle intake passage (6) through the valve, and the extension axis (8b) of the injector (8) is the valve axis (12) of the throttle valve (7). The direction of the injector (8) is set so as to pass directly behind the. As shown in FIG. 2 (A), “behind the valve shaft (12)” refers to the central axis (6a) of the throttle intake passage (6) from the valve shaft (12) when viewed in a direction parallel to the valve shaft (12). ) Refers to the position moved backward along the line.

The configuration of the liquid fuel injection port is as follows.
As shown in FIG. 1 (B), four liquid fuel injection ports (10) are provided, and as shown in FIG. 1 (A) and FIG. 2 (A), each liquid fuel injection port (10) is connected to a throttle intake passage. (6) Assuming the injection axis (10a) of the liquid fuel injection port (10) extending inward, the injection axis (10a) of the liquid fuel injection port (10) with respect to the extension axis (8b) of the injector (8) The direction of the liquid fuel injection port (10) is set so that the angle formed by The liquid fuel injected from the liquid fuel injection port (10) passes directly behind or near the back of the valve shaft (12) of the throttle valve (7), making it less susceptible to direct high-speed intake, and spraying liquid fuel. From the viewpoint of preventing disturbance, the angle is desirably 30 ° or less, more desirably 25 ° or less, and most desirably 20 ° or less. Further, from the viewpoint of suppressing the overlapping of the sprays of the liquid fuel injected from the liquid fuel injection ports (10) and suppressing the oil droplets of the liquid fuel from becoming larger due to the coupling, the angle is desirably 5 ° or more. 7 ° or more is more desirable, and 10 ° or more is most desirable. Therefore, from both viewpoints, the angle is preferably 5 ° or more and 30 ° or less, more preferably 7 ° or more and 25 ° or less, and most preferably 10 ° or more and 20 ° or less. There may be a single liquid fuel injection port (10). In this case, the extension axis (8b) of the injector (8) may coincide with the injection axis (10a) of the liquid fuel injection port (10).

The structure related to the injection direction of the injector is as follows.
As shown in FIG. 1 (A), a cylindrical insulator (14) is interposed between the distribution passage inlet (4) of the intake distribution passage (2) and the intake passage outlet (6h) of the throttle intake passage (6). I am letting. The injector (8) is tilted so that the tip (9) of the injector (8) having the liquid fuel injection port (10) faces the downstream side of the throttle intake passage (6), and the extension axis of the injector (8) ( 8b) is directed toward the inner peripheral surface of the insulator (14), and the liquid fuel injected from the liquid fuel injection port (10) is in contact with the inner peripheral surface of the intake passage outlet (13) of the throttle intake passage (6) and the insulator (14). It collides with the inner peripheral surface of the.
Instead of this structure, the liquid fuel injected from the liquid fuel injection port (10) with the extension axis (8b) of the injector (8) directed toward the inner peripheral surface of the intake passage outlet (6h) of the throttle intake passage (6) May collide with the inner peripheral surface of the intake passage outlet (6h) of the throttle intake passage (6) and the inner peripheral surface of the insulator (14).

With this configuration, the following functions can be obtained.
During idling operation at a low intake speed or low speed light load operation, a part of the liquid fuel stays attached to the inner peripheral surface of the insulator (14), and before entering the intake distribution passage (2), the insulator (14). Is preliminarily vaporized, and the air-fuel mixture concentration in the intake air distribution passage (2) is made more uniform. In addition, during high load continuous operation at a high intake speed, part of the liquid fuel that collided with the inner peripheral surface of the insulator (14) flows into the intake distribution passage (2) by pushing in the intake air, and the temperature is increased by high load continuous operation. Is rapidly vaporized on the inner surface of the intake distribution passage (2), and the mixture concentration in the intake distribution passage (2) is made more uniform.
From the above, regardless of the operating state, the air-fuel mixture concentration in the intake air distribution passage (2) can be made more uniform, and the air-fuel ratio of the air-fuel mixture distributed to each cylinder (3) can be made more equal. high.

The structure related to the intake pressure detection sensor is as follows.
As shown in FIG. 1A, an intake pressure detection sensor (15) is attached to a throttle body (5) together with an injector (8). An intake pressure introduction passage (18) for introducing the intake pressure in the throttle intake passage (6) to the intake pressure detection sensor (15) is provided in the peripheral wall of the throttle intake passage (6) of the throttle body (5). A passage inlet (18a) of the intake pressure introduction passage (18) is arranged in the throttle intake passage (6) upstream of the injector (8) and downstream of the valve shaft (12) of the throttle valve (7). Opened to the peripheral surface.

With this configuration, the following functions can be obtained.
Since the passage inlet (18a) of the intake pressure introduction passage (18) is opened on the inner peripheral surface of the throttle intake passage (6) upstream of the injector (8), the liquid fuel injection port ( The liquid fuel injected from 10) is moved away from the passage inlet (18a) of the intake pressure introduction passage (18) by the flow of intake air, so that the liquid fuel does not easily enter the intake pressure introduction passage (18). For this reason, the detection of the intake pressure by the intake pressure detection sensor (15) is stabilized, there is no problem that the fuel injection amount from the injector (8) fluctuates unnecessarily, and the air-fuel mixture distributed to each cylinder (3) is empty. High function to equalize the fuel ratio.
As illustrated in FIG. 1A, since the intake pressure detection sensor (15) is attached to the throttle body (5) together with the injector (8), the fuel supply related parts are integrated into the throttle body (5) and the fuel is supplied. The supply device becomes compact.

The setting of the direction of the intake pressure introduction passage is as follows.
As shown in FIG. 9, a transverse line (19) that traverses the throttle intake passage (6) having a circular cross section in the radial direction and toward the passage inlet (18a) of the intake pressure introduction passage (18), and this transverse line ( 19), a transverse extension line (19a) extending outside the throttle intake passage (6) through the passage inlet (18a) of the intake pressure introduction passage (18) is assumed, and the transverse extension line (19a) The direction of the intake pressure introduction passage (18) to be drilled is set so that the angle formed by the intake pressure introduction passage (18) is 60 °. Even if the direction of the intake pressure introduction passage (18) is closer to the tangential direction than the radial direction of the throttle intake passage (6) and the passage cross-sectional area of the intake introduction passage (18) is reduced, the intake pressure introduction passage (18) From the viewpoint of making it possible to increase the opening area of the passage inlet (18a), the angle is preferably 45 ° or more, more preferably 50 ° or more, and 55 ° or more. Is more desirable. Further, there is no problem that the direction of the intake pressure introduction passage (18) is too close to the tangential direction of the inner peripheral surface of the throttle intake passage (6), and from the viewpoint of facilitating the machining of the intake pressure introduction passage (18), The angle is desirably 75 ° or less, more desirably 70 ° or less, and most desirably 65 ° or less. Therefore, from both viewpoints, the angle is preferably 45 ° or more and 75 ° or less, more preferably 50 ° or more and 70 ° or less, and 55 ° or more and 65 ° or less. Most desirable.

  As shown in FIG. 9, the angle (18α) formed by the intake pressure introduction passage (18) with respect to the transverse extension line (19a) on the projection orthogonal to the central axis (6a) of the throttle intake passage (6). The direction of the intake pressure introduction passage (18) is set so that is 60 °. The direction of the intake pressure introduction passage (18) is too close to the axial direction of the throttle intake passage (6) to avoid the problem that the intake pressure introduction passage (18) becomes unnecessarily long. From the viewpoint of facilitating processing, this angle (18α) is preferably 45 ° or more, more preferably 50 ° or more, and most preferably 55 ° or more. Further, there is no problem that the direction of the intake pressure introduction passage (18) is too close to the tangential direction of the inner peripheral surface of the throttle intake passage (6), and from the viewpoint of facilitating the machining of the intake pressure introduction passage (18), The angle (18α) is desirably 75 ° or less, more desirably 70 ° or less, and most desirably 65 ° or less. Therefore, from both viewpoints, the angle (18α) is preferably 45 ° or more and 75 ° or less, more preferably 50 ° or more and 70 ° or less, and 55 ° or more and 65 ° or less. It is most desirable to do.

As shown in FIG. 10 (B), the intake pressure introduction passage (18) is shown on a projection parallel to the central axis (6a) of the throttle intake passage (6) and the valve shaft (12) of the throttle valve (7). The passage inlet (18a) of the intake pressure introduction passage (18) is arranged so that the passage inlet (18a) of the intake air passage overlaps the central axis (6a) of the throttle intake passage (6).
Therefore, high-speed intake air that passes by the side of the throttle valve (6) passes by the side of the passage inlet (18a) of the intake pressure introduction passage (18) and enters the passage inlet (18a) of the intake pressure introduction passage (18). The clogged liquid fuel is sucked toward the throttle intake passage (18) by the negative pressure of the intake air, and the liquid fuel is less likely to clog the passage inlet (18a) of the intake pressure introduction passage (18).

  As shown in FIG. 10 (B), the intake pressure introduction passage (18) is inclined downward from the passage outlet (18b) toward the passage inlet (18b), and from the central axis (6a) of the throttle intake passage (6). Assuming an extension axis (6c) extending outside the throttle intake passage (6) through the passage inlet (6b) of the throttle intake passage (6), as shown in FIG. 10 (B), the throttle intake passage (6 ) On the projection parallel to the central axis (6a) of the throttle valve (7) and the valve shaft (12) of the throttle valve (7), the intake pressure introduction passage (18 The direction of the intake pressure introduction passage (18) is set so that the angle (18β) formed by) becomes 60 °.

  From the viewpoint of facilitating the flow of liquid fuel that has entered the intake pressure introduction passage (18) by its own weight, the angle (18β) is preferably 45 ° or more, more preferably 50 ° or more, and 55 °. The above is most desirable. The intake pressure introduction passage (18) is elongated in the axial direction of the throttle intake passage (6), and the opening of the passage inlet (18a) of the intake introduction passage (18) is larger than the passage sectional area of the intake introduction passage (18). From the viewpoint of increasing the area, the angle (18β) is desirably 75 ° or less, more desirably 70 ° or less, and most desirably 65 ° or less. From both viewpoints, the angle (18β) is preferably 45 ° or more and 75 ° or less, more preferably 50 ° or more and 70 ° or less, and 55 ° or more and 65 ° or less. Is most desirable.

The configuration of the mounting hole of the intake pressure detection sensor is as follows.
As shown in FIG. 10 (A), an attachment hole (20) for the intake pressure detection sensor (15) is formed in the throttle body (5), and an intake pressure introduction passage (18) is communicated with the attachment hole (20). Yes. An attachment hole (20) is formed downward, an intake pressure detection sensor (15) is attached to the attachment hole (20), a liquid fuel reservoir (21) is provided below the attachment hole (20), and the liquid fuel reservoir is provided. The passage outlet (18b) of the intake pressure introduction passage (18) is opened at the upper part of (21).

With this configuration, the following functions can be obtained.
The liquid fuel that has entered the intake pressure introduction passage (18) flows out from the passage inlet (18a) of the intake pressure introduction passage (18) to the throttle intake passage (6), and also the passage outlet of the intake pressure introduction passage (18) ( 18b) can also flow out into the liquid fuel reservoir (21), and clogging of the liquid fuel in the intake pressure introduction passage (18) hardly occurs. Further, since the liquid fuel or dust that has entered the intake pressure introduction passage (18) is accumulated in the liquid fuel reservoir (21) and does not contact the intake pressure detection sensor (15), the malfunction or sensitivity of the intake pressure detection sensor (15) is reduced. Decline can be prevented. For this reason, the detection of the intake pressure by the intake pressure detection sensor (15) is stabilized, there is no problem that the fuel injection amount from the injector (8) fluctuates unnecessarily, and the air-fuel ratio of the air-fuel mixture distributed to each cylinder (3) The function which can equalize is high.

The arrangement of parts to be attached to the throttle body is as follows.
As shown in FIG. 8 (A), the direction of the central axis (6a) of the throttle intake passage (6) is the front-rear direction, and the downstream side of the valve shaft (12) of the throttle valve (7) is the rear. 7), the injector (8) is disposed after the throttle input arm (22) with the direction orthogonal to the front-rear direction as the horizontal direction when viewed in a direction parallel to the valve shaft (12), and the throttle input arm (22) The boss (20a) of the mounting hole (20) of the intake pressure detection sensor (15) is arranged beside the pressure sensor.
For this reason, the rear space and the lateral space of the throttle input arm (22) can be effectively used as the placement space for the injector (8) and the boss (20a), respectively, and fuel supply related parts are concentrated in the throttle body (5). The fuel supply device becomes compact.

As shown in FIG. 8A, the boss (20a) of the mounting hole (20) of the intake pressure detection sensor (15) is also used as a swing stopper for the throttle input arm (22).
For this reason, it is not necessary to provide a swing stopper dedicated to the throttle input arm (22), and the number of parts can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a longitudinal side view of FIG. 1A and FIG. 1B is a view in which the tip of an injector is oriented parallel to the central axis of the injector according to an embodiment of the present invention. It is the figure seen in. 2A is a cross-sectional view taken along the line II-II in FIG. 1A, and FIG. 2B is an enlarged view of the vicinity of the inlet of the intake pressure introduction passage. It is a cross-sectional top view explaining the intake distribution channel of the engine which concerns on embodiment of this invention, and its peripheral part. FIG. 4A is a plan view, FIG. 4B is a bottom view, and FIG. 4C is a longitudinal side view, illustrating a head cover and peripheral components of an engine according to an embodiment of the present invention. FIG. 5A is a side view, and FIG. 5B is a rear view, illustrating a breather chamber of an engine and its peripheral components according to an embodiment of the present invention. 1 is a plan view of an engine according to an embodiment of the present invention. It is a side view of the engine of FIG. FIG. 8A is a plan view and FIG. 8B is a side view illustrating the throttle body of FIG. 1. It is an IX direction arrow directional view of Drawing 8 (B). FIG. 10A is a cross-sectional view taken along line XX of FIG. 8A, and FIG. 10B is a longitudinal side view of the throttle body.

Explanation of symbols

(1) Cylinder head
(2) Intake distribution passage
(2a) Box-type intake passage wall
(3) Cylinder
(3a) Inlet port inlet
(4) Distribution passage entrance
(5) Throttle body
(6) Throttle intake passage
(7) Throttle valve
(11) Fuel supply device
(12) Valve stem
(15) Intake pressure detection sensor
(16) Engine speed detection sensor
(17) Control means
(18) Intake pressure introduction passage
(18a) Passage entrance
(36) Spark plug
(37) Ignition circuit
(38) Crankshaft phase detection sensor
(39) Crankshaft
(51) Breeza exit
(52) Upstream breather exit
(52a) Upstream breather passage
(52b) Start end
(53) Downstream breather exit
(53a) Downstream breather passage
(54) Common breather passage
(55) Rocker arm
(56) Breezer room
(56a) Entrance
(56b) Bottom wall

Claims (14)

In an engine in which a throttle valve (7) is arranged in the throttle intake passage (6) and the intake air amount is adjusted based on the opening of the throttle valve (7).
A plurality of cylinders (3) are provided, an intake distribution passage (2) is attached to the cylinder head (1), and a throttle intake passage (6) is disposed upstream of the distribution passage inlet (4) of the intake distribution passage (2). Hitting
An engine characterized in that a breather outlet (51) is faced in a region from a throttle intake passage (6) to a distribution passage inlet (4) of the intake distribution passage (2). The engine according to claim 1,
The direction of the central axis (6a) of the throttle intake passage (6) is the front-rear direction, and the downstream side of the valve shaft (12) of the throttle valve (7) is the rear.
An engine characterized in that a breather outlet (51) is arranged directly behind the valve shaft (12) when viewed in a direction parallel to the valve shaft (12) of the throttle valve (7). The engine according to claim 1 or 2,
An ignition plug (36) is provided in each cylinder (3), and an ignition circuit (37) of the ignition plug (36) is linked to a crankshaft phase detection sensor (38) via a control means (17) to thereby provide a crankshaft ( 39) Based on the phase detection of 39), the control means (17) performs the ignition timing control in which a spark is blown from the spark plug (36) at every predetermined timing of the combustion cycle of each cylinder (3).
The engine characterized in that the ignition timing is advanced as the cylinder (3) having a lower compression ratio. The engine according to claim 3,
An engine characterized in that the ignition timing of each cylinder (3) is controlled by the control means (17) based on a different ignition timing control map for each cylinder (3). The engine according to any one of claims 1 to 4,
The fuel supply means (11) is exposed in the region from the throttle intake passage (6) to the distribution passage inlet (4) of the intake distribution passage (2), and the fuel supply means (11) is controlled by the control means (17). Are connected to the crankshaft phase detection sensor (38) via the control unit (17) based on the phase detection of the crankshaft (39) at each predetermined timing of the combustion cycle of each cylinder (3). In performing the fuel supply control for supplying the fuel to be supplied to (3) from the fuel supply means (11) to the intake air within the above region,
An engine characterized in that the fuel supply amount is increased as the fuel is supplied to the cylinder (3) in which the fuel concentration of the air-fuel mixture becomes thinner at the same fuel supply amount. The engine according to any one of claims 6 to 5,
The fuel supply means (11) is exposed in the region from the throttle intake passage (6) to the distribution passage inlet (4) of the intake distribution passage (2), and the fuel supply means (11) is controlled by the control means (17). Are connected to the crankshaft phase detection sensor (38) via the control unit (17) based on the phase detection of the crankshaft (39) at each predetermined timing of the combustion cycle of each cylinder (3). In performing the fuel supply control for supplying the fuel to be supplied to (3) from the fuel supply means (11) to the intake air within the above region,
An engine characterized in that the fuel supply start time is advanced as the fuel is supplied to the cylinder (3) in which the fuel concentration of the air-fuel mixture decreases at the same fuel supply start time. In the engine according to claim 5 or 6,
An engine characterized in that the control means (17) controls the fuel supply to each cylinder (3) based on a different fuel supply control map for each cylinder (3). The engine according to any one of claims 1 to 7,
A longitudinal box-shaped intake passage wall (2a) along the arrangement direction of a plurality of cylinders (3) is attached to the side surface of the cylinder head (1), and the box-shaped intake passage wall (2a) is continuous straight in the longitudinal direction. And the intake port inlet (3a) of each cylinder (3) faces the intake distribution passage (2) while maintaining a predetermined interval in the longitudinal direction. To engine. The engine according to any one of claims 1 to 8,
The upstream breather outlet (52) is opened upstream of the throttle valve (7), and the upstream breather outlet (52) is communicated with the breather chamber (56) via the upstream breather passage (52a).
A downstream breather outlet (53) is opened downstream of the throttle valve (7), and the downstream breather outlet (53) is communicated with the breather chamber (56) via the downstream breather passage (53a). Engine. The engine according to claim 9, wherein
An engine characterized in that a shared breather passage (54) is led out from a breather chamber (56), and an upstream breather passage (52a) and a downstream breather passage (53a) are branched from the shared breather passage (54). . The engine according to claim 10, wherein
An engine characterized in that the upstream end breather passage (52a) projecting from the common breather passage (54) is oriented upward. The engine according to claim 10 or claim 11,
An engine characterized in that the downstream breather passage (53a) is directed downward from the common breather passage (54) toward the downstream breather outlet (53). The engine according to any one of claims 9 to 12,
The engine characterized in that the passage cross-sectional area of the downstream breather passage (53a) is smaller than the passage cross-sectional area of the upstream breather passage (52a). The engine according to any one of claims 9 to 13,
When the head cover (25) is attached to the top of the cylinder head (1), the rocker arm (55) is covered with the head cover (25), and the breather chamber (56) is disposed on the ceiling of the head cover (25).
An engine characterized in that the inlet (56a) of the breather chamber (56) is disposed at a position offset from directly above the rocker arm (55) and at a position lower than the bottom wall (56b) of the breather chamber (56).

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