JPH0326831A - Intake system structure of engine - Google Patents

Abstract

PURPOSE:To improve the deceleration transient characteristics by arranging a fuel feeding device at a position separated from the collection part of the upstream part in an intake passage leading to the collection part of an intake manifold and arranging a throttle valve at a position close to the collection part in the downstream part in the intake passage. CONSTITUTION:The fuel jetted from a fuel feeding device SPI (single point injection) 2 is mixed with the air supplied from an air cleaner 1 and atomized, and a supercharger 3 agitates air and accelerates the atomization of fuel, and the fuel is sufficiently atomized up to the flow to a intake manifold collection part 5a. Further, though the capacity from the SPI 2 to the combustion chamber of an engine body 6 is large, and the adhesion quantity of the jetted fuel onto the inner wall of an intake passage 4 for the jetted fuel becomes large, the fuel adhering onto the downstream side part of a throttle valve 4 which is given with the influence of the negative pressure is little, even if the downstream side of the throttle valve 4 is put into negative pressure state, since the throttle valve 4 is arranged at the position close to the collection part 5a. Therefore, only this slight quantity of fuel is introduced into the combustion chamber, and the generation of overrich state is prevented.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to the structure of an intake system for a multi-cylinder engine.

[Prior Art] Generally, in the intake system of a multi-cylinder engine, a throttle valve is provided in the intake passage leading to the intake manifold gathering part.
For example, single point injection (SP
A fuel supply device such as a fuel pump (referred to as I) or a carburetor is usually arranged upstream of the throttle valve. In particular, fuel O
(The feeding device is installed in the upstream part near the throttle valve, and by injecting fuel toward the throttle valve,
It is designed to promote atomization of fuel.

In such a conventional engine intake system structure, for example, when a supercharger is installed in the intake system,
A fuel supply device such as an SPI or a carburetor and a throttle valve are arranged upstream of the supercharger.

[Problems to be Solved by the Invention] However, if the fuel supply device and throttle valve are placed upstream of the supercharger as in the conventional engine intake system structure described above, the fuel supply device and throttle valve The volume from the combustion chamber to the combustion chamber increases,
The amount of injected fuel adhering to the inner wall of the intake passage increases. Therefore, there is a large amount of injected fuel adhering to the inner wall of the intake passage downstream of the throttle valve, and when the downstream side of the throttle valve becomes negative pressure during deceleration, the adhering fuel in this area is sucked into the combustion chamber, causing overflow in the combustion chamber. Become rich,
There is a problem in that deceleration transient characteristics deteriorate due to misfire or the like.

Note that FIGS. 2(a) to (e) are graphs showing examples of experimental results of various characteristics (time changes) during such deceleration, and FIG. 2(a) shows the supercharger output pressure ( S/C (ILIT P) .Figure 2 (b) shows the air-fuel ratio (A/F) .Figure 2 (c) shows the output torque (TOR
QU [mi], Figure 2 (d) shows the Karman vortex generation frequency (KARMAN) as an intake flow rate parameter, Figure 2 (e
) is the throttle opening (rps), and the unmeasurable region in Fig. 2(b) is the part where the fuel was extremely overrich and could not be measured.
- It can be seen that when the valve opening is reduced, the intake flow velocity (flow rate) and supercharger output pressure (intake pressure) decrease, leading to an overrich air-fuel ratio and a large deceleration shock (sudden decrease in torque).

Also, even if a supercharger is not installed, increasing the distance between the fuel supply system and the combustion chamber, for example to improve the distribution of fuel to each cylinder or due to layout constraints, can increase the fuel consumption. supply'! The volume from the A position to the combustion chamber becomes large, making it easy for two series of problems to occur.

The present invention was devised in view of these problems.
It is an object of the present invention to provide an intake system structure for an engine that allows good deceleration transient characteristics to be achieved even in an intake system with a large volume from a fuel supply device to a combustion chamber.

[Means for Solving the Problems] Therefore, in the intake system structure of the engine of the present invention, in the intake system of a multi-cylinder engine, the upstream portion of the intake passage leading to the gathering portion of the intake manifold is spaced Im apart from the gathering portion. The present invention is characterized in that a fuel supply device is disposed at a position in the downstream portion of the intake passage, and a throttle valve is disposed at a position close to or within the convergence portion in the downstream portion of the intake passage.

[Function] In the intake system structure of the engine of the present invention described above, since the fuel supply device is disposed in the second-flow part of the intake passage one space apart from the gathering part of the intake manifold, the fuel is supplied to the intake passage. The fuel is evenly mixed while flowing through the cylinders, and the distribution of fuel to each cylinder is improved. In this method, the volume from the fuel feeder to the combustion chamber becomes larger, so the amount of injected fuel that adheres to the inner wall of the intake passage increases; Since a 1-throttle valve is installed, it is necessary to install the throttle valve downstream of the throttle valve.
The amount of fuel deposited becomes small, and even if the downstream side of the throttle valve becomes negative pressure during deceleration, only this small amount of deposited fuel will be sucked into the combustion chamber, causing over-richness in the combustion chamber. is prevented.

[Embodiment] Hereinafter, the structure of an engine intake system as an embodiment of the present invention will be explained with reference to the drawings. FIG. 1 is a schematic diagram of the structure.

This intake system structure is installed in a multi-cylinder engine and is equipped with a supercharger.

As shown in FIG. 1, this intake system structure includes an air cleaner 1, a single point 1 as a fuel supply device, an injection passage 14, and an air cleaner 1, a single point 1 as a fuel supply system, (SPI) 2, supercharger 3, and throttle valve 4 are arranged in this order.

In other words, the SPI 2 is provided at a position upstream of the supercharger 3 in the intake passage 14 and away from the intake manifold gathering portion 5a.

Further, the throttle valve 4 is provided in the intake passage 14 at a position downstream of the supercharger 3 and closer to the intake manifold gathering portion 5a.

The reference numeral 6 is the engine body, 7 is the IJIE air manifold, 8 is a bypass passage provided in parallel with the supercharger 3, and 9 is a bypass valve that is opened when the supercharger 3 is stopped.

The structure of the intake system of an engine according to an embodiment of the present invention is constructed as described above. When fuel is injected from SI1I2, this fuel is mixed with the air supplied through the air cleaner 1 and atomized. Here, since the throttle valve 4 is not near the spout of the SPI 2, we cannot expect the throttle valve 4 to promote atomization, but the supercharger 3, which performs supercharging in the intake passage 14, Since the fuel is agitated to promote atomization of the fuel, the fuel is sufficiently atomized in the intake passage 14 from the SPI 2 to the intake manifold gathering part 5a, and the fuel is thoroughly atomized in the intake manifold 5 of each air in the engine 6. This ensures good transient characteristics, for example during acceleration.

In addition, since the SPI 2 is provided upstream and the supercharger 3 is provided in the middle of the intake passage 14, the volume from the SPI 2 to the combustion chamber of the engine body 6 becomes large, and the injected fuel flows to the inner wall of the intake passage 14. However, since the throttle valve 4 is located close to the intake manifold gathering portion 5a, even if the downstream side of the throttle valve 4 becomes negative pressure during deceleration, this negative pressure will be removed. Only a small amount of fuel adheres to the affected downstream portion of the throttle valve 4, and only this small amount of adhered fuel is sucked into the combustion chamber.

Therefore, over-richness in the combustion chamber is prevented and the deceleration transient characteristics are improved.

In this embodiment, a single point injection (SPI) 2 is provided as the twisting material supply device, but a carburetor may be used as the fuel supply device.

Further, the throttle valve 4 may be provided at an artificial part within the gathering portion 5a.

Furthermore, although the intake system of this embodiment is equipped with a supercharger 3, even if a supercharger is not installed, a fuel supply system may be installed to improve fuel distribution to each cylinder or for layout reasons. (For example, S
When the distance between the PI) and the combustion chamber is set to be long, the throttle valve 4 may be provided at a position close to the intake manifold collecting part 5a or within the collecting part 5a.
Similarly to the above, the deceleration transient characteristics are improved.

[Effects of the Invention] As detailed above, according to the engine intake system structure of the present invention, in the intake system of a multi-cylinder engine, the air flow from the upstream portion of the intake passage leading to the gathering portion of the intake manifold. A fuel supply device is disposed at a separate position, and a throttle valve is disposed at a position close to the gathering portion in the downstream portion of the intake passage or within the gathering portion. Even in an intake system with a large volume, it is difficult to achieve good deceleration transient characteristics.
When the intake system is equipped with a supercharger, the deceleration transient characteristics are significantly improved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing the structure of an intake system of an engine as an embodiment of the present invention, and FIG. 2(a) to (8.
) are graphs showing the problems of the conventional intake system structure, respectively. Fig. 2 (a) is a graph of supercharger output pressure characteristics, Fig. 2 (b) is a graph of air-fuel ratio characteristics, and Fig. 2 (
c) is a graph of output 1/lux characteristics, FIG. 2(d) is a graph of intake flow rate characteristics, and FIG. 2(e) is a graph of throttle opening characteristics. 1.12 Acleaner, 2.1 Single Point Injection (SPI) as a fuel supply system. 3.1.
Supercharger, 4.1. Throttle valve, 5. Intake manifold, 5a--Intake manifold gathering part,
6-Engine body, 7.. Exhaust manifold, 8.. Bypass passage-L-.. Bypass valve, 14.. Intake flow path.

Claims (1)

[Claims] In an intake system of a multi-cylinder engine, a fuel supply device is disposed at a position in an upstream portion of an intake passage leading to a gathering portion of an intake manifold at a position separated from the gathering portion, and a fuel supply device is provided at a position separated from the gathering portion in a downstream portion of the intake passage. An intake system structure for an engine, characterized in that a throttle valve is disposed in a close position or in the gathering part.