JP2794751B2 - Intake system for fuel injection type multi-cylinder engine - Google Patents

Description

The present invention relates to an intake system for a fuel injection type multi-cylinder engine, and more particularly to an intake system for a fuel injection type multi-cylinder engine with an improved surge tank. .

(Prior Art) An engine mounted on an outboard motor generally requires compactness. Therefore, the length of the intake passage or the volume of the surge tank may not be sufficient.

(Problems to be Solved by the Invention) In particular, in the case of a fuel injection type multi-cylinder engine, if the volume of the surge tank is insufficient as described above, pulsation occurs in the intake passage. In the intake passage, a fuel mixture is generated for each cylinder by the fuel injector. Therefore, if pulsation occurs in each intake passage, the air-fuel ratio of the mixture generated for each cylinder may vary. There is.

The present invention has been made in view of the above circumstances, and provides an intake device for a fuel injection type multi-cylinder engine capable of reducing variation in air-fuel ratio of an air-fuel mixture between cylinders even in a compact engine. The purpose is to:

[Configuration of the invention]

(Means for Solving the Problems) An intake device for a fuel injection type multi-cylinder engine according to the present invention provides a reed valve in which a reed valve is provided in a crankcase of a multi-cylinder two-cycle engine in order to solve the above-mentioned problems. An inlet manifold is joined via a holder, the inlet manifold is provided with a main surge tank and each intake pipe to the multi-cylinder two-stroke engine, and a fuel injector is installed in each intake pipe, and each of the intake pipes is provided with a fuel injector. In the intake system of a fuel injection type multi-cylinder engine in which an air-fuel mixture is generated, a recess is formed between each intake pipe of the intake manifold, and the recess is formed inside the sub-surge tank by the reed valve holder serving as a lid. The sub-surge tank and the main surge tank are communicated with each other through a communication hole. A surge tank is constituted by a sub surge tank and a main surge tank.

(Operation) Therefore, according to the intake device for a fuel injection type multi-cylinder engine according to the present invention, the surge tank is constituted by the main surge tank and the subsurge tank, and the surge tank volume is increased. The pulsation of the intake air can be significantly reduced. As a result, the pressure in each intake pipe is stabilized, and a fuel-air mixture is generated in each intake pipe by the fuel sprayed from the fuel injector. However, the air-fuel ratio of this air-fuel mixture has little variation among the cylinders.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a fuel injection type two-cycle three-cylinder engine to which an embodiment of a fuel injection type multi-cylinder engine intake device according to the present invention is applied, and FIG. 2 is a II-II of FIG.
FIG. 3 is a side view showing an outboard motor on which the engine shown in FIG. 1 is mounted.

As shown in FIG. 3, in an outboard motor, an engine 2 is generally mounted on an upper portion of a drive shaft housing 1, and the engine 2 is covered with an engine cover 3. A gear case 4 is connected to a lower portion of the drive shaft housing 1, and a propeller shaft (not shown) is connected to the gear case 4.
, The propeller 5 is fixed. The rotational force of the engine 2 is controlled by the drive shaft housing 1 and the gear case 4.
The power is transmitted to a propeller shaft through a power transmission mechanism in the inside, and the propeller 5 is driven to propel the hull. Reference numeral 6 denotes a clamp bracket for mounting the outboard motor.

The engine 2 is a two-cycle multi-cylinder vertical crank engine as shown in FIG. 1, and a fuel injection engine in which a fuel injector 8 is installed in an intake pipe as shown in FIG.

That is, as shown in FIG. 1, three cylinders (cylinders) 10 are horizontally arranged in the cylinder block 9, and each cylinder
A piston 11 is disposed at 10 so as to be able to reciprocate. A cylinder sleeve 12 is adhered to the inner surface of the cylinder 10, so that wear of the cylinder 10 and the piston 11 is reduced. A cylinder head 13 is joined to the cylinder block 9 to form a combustion chamber 14 with each piston 11. The cylinder head 13 is provided with an ignition plug 15.

The piston 11 is connected to a crankshaft 17 by a connecting rod 16. This crankshaft 17
Is rotatably supported by a cylinder block 9 and a crankcase 18 via a crankshaft bearing 19. The small end of the connecting rod 16 is pivotally supported by the piston 11 by the piston pin 20, and the large end of the connecting rod 16 is pivotally supported by the crankshaft 17 by the crankpin 21. This connecting rod 16
Thereby, the reciprocating linear motion of the piston 11 is converted into the rotational motion of the crankshaft 17.

The crankshaft 17 is disposed vertically and each cylinder 10
Each cylinder is sealed by a crankshaft seal 22 installed for each cylinder. Therefore, the above crankcase
The crank chambers 23A, 23B, and 23C are formed for each cylinder by the cylinder block 18, the cylinder block 9, and the crankshaft seal 22. Each crankcase 23A,
A reed valve 24 is provided in each intake passage communicating with B and C. The reed valve 24 is assembled in a reed valve holder 25 and then housed in each intake passage of the crankcase 18.

An inlet manifold 26 is joined to each intake passage of the crankcase 18 in which the reed valve 24 is installed. In this inlet manifold 26, three intake pipes 27 and one main surge tank 28 are integrally formed.

Each intake pipe 27 is joined to each intake passage of the crankcase 18. A throttle body 29 is joined to the main surge tank 28 as shown in FIG. A throttle valve 30 is rotatably supported in the throttle body 29.
Therefore, the intake air is sucked by the negative pressure generated by the reciprocating motion of the piston 11, and the flow thereof is controlled by the throttle valve 30, and flows into the surge tank. The pulsation of this intake air is reduced in the surge tank 28, and is guided to each intake pipe 27.

Each intake pipe 27 is provided with a fuel injector 8. A delivery pipe 31 is connected to each of the fuel injectors 8. The delivery pipe 31 distributes the fuel, the pressure of which has been increased by a fuel pump (not shown), to each fuel injector 8. The fuel is sprayed into the intake pipe 27 by the fuel injector 8 to generate an air-fuel mixture.

As shown in FIG. 1, the generated air-fuel mixture
From 27, it is led into the respective crank chambers 23A, 23B, 23C of the crankcase 18 via the reed valve 24. In the cylinder block 9 joined to the crankcase 18, scavenging passages 32A, 32B, 32C are formed for each cylinder 10. The scavenging passages 32A, B, C are provided so as to communicate with the crank chambers 23A, B, C and the cylinders 10.
Therefore, the air-fuel mixture introduced into the crank chambers 23A, B, C is introduced into each cylinder 10 through the scavenging passages 32A, B, C.

The crankshaft 17 has a flyhole magnet 33 at one end and a drive shaft 34 at the other end. An exhaust passage 40 is formed in the cylinder block 9 as shown in FIG.

A recess 35 is formed between the intake pipes 27 of the inlet manifold 26. The sub-surge tank 36 is closed by covering the recess 35 with the reed valve holder 25.
Is formed. The sub surge tank 36 is communicated with the main surge tank 28 by a communication hole 37 formed in the bottom surface of the recess 35.

As described above, in the two-stroke engine, since the scavenging passages 32A, 32B, and 32C are provided between the cylinders 10 of the cylinder block 9, the layout pitch of the cylinders 10 cannot be made too small. Therefore, the inlet manifold 26
, The layout pitch of each intake pipe 27 is also sufficiently large, and the subsurge tank 36 is configured to have a large volume. The sub surge tank 36 and the main surge tank 28 constitute a surge tank.

According to the above embodiment, the surge tank is constituted by the main surge tank 28 and the sub surge tank 36,
When the fuel injection control method is set to D-Jetronic (a method of controlling by the rotation speed-suction pipe negative pressure) because the surge tank volume has increased, the volume of the surge tank is increased to increase the volume of each surge pipe 27. The fluctuation of the negative pressure is reduced, and the pulsation of the intake air can be significantly reduced. As a result, the pressure in each intake pipe 27 is stabilized, and the air-fuel ratio of the air-fuel mixture generated in each intake pipe 27 becomes substantially uniform for each cylinder 10. That is, even in a small multi-cylinder engine, it is possible to reduce the variation in the air-fuel ratio of the air-fuel mixture between the cylinders 10. Therefore, the multi-cylinder simultaneous injection system can be adopted by the fuel injector 8.

If the distance between the front surface 38 of the inlet manifold 26 and the crankshaft 17 is restricted due to layout constraints, the presence of the subsurge tank 36 causes the rear surface 39 of the inlet manifold 26 to approach the front surface 38, and the main surge tank 28 And the intake pipe 27 can be set long. In general, if the intake pipe 27 is short, a spray phenomenon occurs in which the spray fuel injected upstream of the reed valve 24 flows into the intake pipe 27 of another cylinder 10 due to the pulsation of the intake air.
Every time, the air-fuel ratio varies. However, since the length of the intake pipe 27 can be increased, it is possible to prevent the air-fuel ratio of the air-fuel mixture from fluctuating due to the blowback.

Further, the sub-surge tank 36 functions as a resonance chamber regardless of whether the fuel injection control method is the D-Jetronic method or the α-N method (a method in which control is performed only by the throttle angle and the rotation speed). Therefore, the intake noise can be reduced. In reducing the intake noise, the size of the communication hole 37 and the volume of the subsurge tank 36 may be selected according to the frequency of the intake noise.

Further, since the pressure in the intake pipe 27 is stabilized by the subsurge tank 36, the fuel control by the fuel injector 8 can be performed with high accuracy.

Further, since the subsurge tank 36 is formed only by using the recess 35 between the intake pipes 27 in the inlet manifold 26, the structure is easy and the cost does not increase.

Although the sub surge tank 36 is formed using the reed valve holder 25, it may be formed by the crankcase 18 instead of the reed valve holder 25. further,
In the above embodiment, the case of a two-cycle engine has been described. However, the intake device of the present invention may be applied to an intake pipe and a surge tank of a four-cycle engine.

〔The invention's effect〕

As described above, in the intake device for a fuel injection type multi-cylinder engine according to the present invention, a recess is formed between the intake pipes of the intake manifold, and the recess is formed by the reed valve holder serving as a lid. The sub-surge tank and the main surge tank communicate with each other through the communication hole, while the surge tank is formed by the sub-surge tank and the main surge tank. The pulsation of the engine intake can be significantly reduced, the pressure in each intake pipe is stabilized, and high-precision fuel control is enabled by the fuel sprayed from the fuel injector, and a stable air-fuel mixture is generated in each intake pipe. , The variation in the air-fuel ratio of the air-fuel mixture can be reduced, and the intake noise can be reduced.

The subsurge tank can be formed by sealing the recess formed between the intake pipes of the inlet manifold with a reed valve holder, and the existing reed valve holder that supports the reed valve is used as a common lid for each recess. The closed space of the sub-surge tank can be formed by using it effectively, and no separate new parts are required to form the closed space of the sub-surge tank. While the holder can have a reed valve support function and a subsurge tank forming function, the subsurge tank can form a resonance chamber to reduce intake noise.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fuel injection type two-cycle 3 to which an embodiment of an intake device for a fuel injection type multi-cylinder engine according to the present invention is applied.
FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a side view showing an outboard motor on which the engine of FIG. 1 is mounted. 2 ... Engine, 8 ... Fuel injector, 10 ... Cylinder, 11 ... Piston, 17 ... Crankshaft, 18 ...
… Crankcase, 25 …… Reed valve holder, 26 ……
Inlet manifold, 27 ... Intake pipe, 28 ... Main surge tank, 35 ... Recess, 36 ... Sub surge tank,
37 …… Communication hole.

Claims (1)

(57) [Claims] An inlet manifold is joined to a crankcase of a multi-cylinder two-cycle engine via a reed valve holder provided with a reed valve. Each of the inlet manifold is connected to a main surge tank and each of the multi-cylinder two-cycle engine. An intake pipe, a fuel injector is provided in each of the intake pipes, and an air-fuel mixture is generated in each of the intake pipes. A concave portion is formed in the concave portion, and the concave portion forms a sub-surge tank with the reed valve holder serving as a lid. The sub-surge tank communicates with the main surge tank through a communication hole. A fuel injection type fuel tank characterized in that a surge tank is constituted by a main surge tank. Intake system of the cylinder engine.