JPH0160668B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for a multi-cylinder engine that distributes intake air to branch intake pipes communicating with each cylinder via a surge tank.

(Prior Art) In general, in multi-cylinder engines, especially fuel-injected multi-cylinder engines, it is extremely important to distribute intake air evenly to each cylinder, and it is only through this equal distribution that the smooth output of the multi-cylinder engine can be achieved. can be guaranteed.

Conventionally, for example, Japanese Patent Application Laid-open No. 113919/1983 discloses an intake system for a multi-cylinder engine in which the passage lengths of branched intake pipes connecting a surge tank and each cylinder are made equal in order to evenly distribute intake air. There is.

However, even if the passage lengths of each branch intake pipe are set equal, the intake flow flows in with the dynamic pressure acting in the surge tank, so the pressure acting on the opening of each branch intake pipe that opens into the surge tank is equal. There is no guarantee that this will occur; if the dynamic pressures acting on the inflow openings of each branch intake pipe are different, even if the passage lengths are the same, the intake air will not be distributed equally to each cylinder.

(Object of the Invention) Accordingly, an object of the present invention is to provide an intake system for a multi-cylinder engine in which the distribution of intake air to each branch intake pipe can be almost completely equalized.

(Structure of the Invention) Therefore, the present invention provides an intake system for a multi-cylinder engine that distributes intake air to branch intake pipes communicating with each cylinder via a surge tank, and which includes An inlet for intake air to the surge tank is installed approximately at the center of one of the side walls, and an inlet pipe inlet opening for intake air to the intake branch pipe is arranged in a fan shape around this inlet opening. and a flow diversion surface that protrudes into the surge tank and divides the intake air to both sides in the longitudinal direction is formed in the center portion of the other side wall of the surge tank that faces the surge tank inflow opening, and an inner wall surface of the side wall that extends from the flow diversion surface in the longitudinal direction. provides an intake system for a multi-cylinder engine, characterized in that the intake pipe inflow openings are gradually inclined toward one side wall in accordance with the fan-shaped arrangement of the intake pipe inflow openings.

(Effects of the Invention) According to the present invention, the intake air flowing into the surge tank is first divided into left and right sides by the flow dividing surface, and
The intake air is guided smoothly along the fan-shaped side wall and flows into the inlet openings of each branch intake pipe arranged in a fan shape with almost equal dynamic pressure, ensuring reliable distribution of intake air to each cylinder. Since the output of each cylinder can be equalized, the performance of the multi-cylinder engine can be maintained well.

(Example) Examples of the present invention will be specifically described below.

As shown in Figures 1 and 2, downstream of a throttle valve 2 disposed in a horizontal throttle chamber 1 constituting a part of a common intake passage, there is a An inflow opening 3A provided in the center of one side wall along the longitudinal direction of the surge tank 3 having a sufficiently large cross-sectional area is connected horizontally. The surge tank 3 is formed in a closed cross-sectional shape that is symmetrical with respect to the center line of the inflow opening 3A of the surge tank 3 connected to the throttle chamber 1 and expands on both sides in the left-right direction.

As clearly shown in FIG. 1, branch intake pipes 4 to 7 that supply intake air to each cylinder (not shown) formed in the engine body E are opened at the bottom of the surge tank 3, respectively. The inflow openings 4a to 7a of each of the branch intake pipes 4 to 7 are arranged symmetrically along the longitudinal direction of the surge tank 3 (horizontal direction in the figure) with the inflow opening 3A of the surge tank 3 as the center. They are arranged in an almost fan shape.
In the case of the illustrated four-cylinder engine E, therefore,
With respect to the center line of inflow of intake air into the surge tank 3, there are a pair (5, 6) on both left and right sides thereof, and a pair (4, 7) on the outside thereof, a total of four inflow openings 4a to 4 of branch intake pipes 4 to 7. 7a are installed so as to form a fan shape. Further, the inner wall surface 3B of the other side wall facing the inflow opening 3A of the surge tank 3 is connected to the inflow opening 4.
Two branch intake pipes 5, which are gently inclined toward one side wall in the left-right direction according to the fan-shaped arrangement of a to 7a, and whose center portion in the left-right direction, that is, the part facing the inflow opening 3A, are inside. It is formed as a flow dividing surface 3C that is curved inward into a mountain shape so as to protrude between the inflow openings 5a and 6a of the flowchart 6.
This diversion surface 3C divides the intake air flowing into the surge tank 3 symmetrically to the left and right sides, and directs the divided intake air to the two outer branch intake pipes 4 along the slope of the inner wall surface 3B that continues to the diversion surface 3C. , 7 inlet opening 4
I will guide you towards a and 7a. The dynamic pressure of the intake air flowing in through the throttle valve 2 is approximately equal to the inflow openings 4a to 7a of the branch intake pipes 4 to 7 due to the above-mentioned fan-shaped arrangement and this inward diversion surface 3C. It becomes effective.

Further, as clearly shown in FIGS. 1 and 2, the inflow openings 5a and 6a of the two inner branch intake pipes 5 and 6
A projecting band 8 that slightly rises from the bottom wall surface of the surge tank 3 where the surge tank 3 is opened faces the diversion surface 3C of the surge tank 3 and connects the two inner inflow openings 5.
a, 6a, and each branch intake pipe 4 is formed slightly upstream of the protrusion band 8.
The upper surface wall portion 9 of the intake manifold 9 that constitutes ~7
A discharge port 11 of an EGR gas recirculation passage 10 penetrating through the interior of the chamber a is opened. This EGR discharge port 11 is
Therefore, the protruding band 8, which is located on the inflow center line of the intake air of the surge tank 3 and is formed to surround this slightly downstream, absorbs the inner two of the EGR gas discharged from the EGR outlet 11. Interfering with the EGR gas that is about to directly flow into the inflow openings 5a and 6a and restricting the direct inflow,
By guiding the projecting band 8 along both sides in the longitudinal direction, it has the role of distributing it to the inflow openings 4a and 7a of the two outer branch intake pipes 4 and 7. In other words, the protruding band 8 provided for the EGR discharge port 11 has the role of evenly distributing EGR gas to each of the branch intake pipes 4 to 7.

Although not specifically shown in FIGS. 1 and 2, mounting portions 9c, 9c, . . . for mounting injection valves are formed on the mounting bracket 9b of the intake manifold 9 mounted on the engine body E. A fuel injection valve (not shown) is provided in each mounting portion 9c. Furthermore, as shown in Figure 2,
The inclination of each branch intake pipe 4 to 7 is preferably set to a relatively large inclination angle so that air can flow straight into the combustion chamber of each cylinder. It is preferable to make the intake pipes 4 to 7 substantially equal in order to further improve uniform distribution of intake air.

As is clear from the above description, in this embodiment, the intake air flowing into the surge tank 3 from the horizontal direction is divided symmetrically by the dividing surface facing the inflow opening 3A, and is symmetrically divided with respect to the inflow opening 3A. Since the inflow openings 4a to 7a of the branch intake pipes 4 to 7 arranged along the longitudinal direction of the surge tank 3 act almost equally, in other words, the same dynamic pressure acts, the inflow into the surge tank 3 occurs. Intake air is distributed approximately equally to each branch intake pipe 4-7. At the same time, an opening was opened slightly downstream of the inflow opening 3A.
The EGR gas discharged upward from the EGR discharge port 11 is mixed with the intake air flow flowing in from the inflow opening 3A, and is evenly distributed to each of the branch intake pipes 4 to 7 according to the equal distribution of intake air. distributed. Therefore, with respect to the fuel equally supplied from the fuel injection valves, the set air-fuel ratio is correctly achieved for each cylinder, and each cylinder of the engine exhibits approximately equal output characteristics.
The operability, output performance, and emission performance of the engine are maintained well.

Note that the present invention applies not only to 4-cylinder engines but also to 6-cylinder engines.
Needless to say, the present invention can also be applied to cylinders, eight-cylinder engines, and the like.

[Brief explanation of drawings]

FIG. 1 is an explanatory horizontal cross-sectional view of a main part of an intake device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view along the - line in FIG. 1. 2...Throttle valve, 3...Surge tank, 3A...Inflow opening, 3C...Diversion surface, 4-7
... Branch intake pipe, 4a to 7a... Inflow opening of the branch intake pipe.

Claims (1)

[Scope of Claims] 1. An intake system for a multi-cylinder engine configured to distribute intake air to branch intake pipes communicating with each cylinder via a surge tank, comprising: one side wall along the longitudinal direction of the surge tank; An inflow port for intake air into the surge tank is installed approximately in the center, and an intake pipe inflow opening, which serves as an inflow port for intake air into the intake branch pipe, is arranged in a fan shape around this inflow opening, and the surge tank At the center of the other side wall of the surge tank facing the inflow opening, a flow dividing surface is formed that protrudes into the surge tank and divides the intake air to both sides in the longitudinal direction, while the inner wall surface of the side wall extending from the flow dividing surface in the longitudinal direction is connected to the intake pipe. An intake system for a multi-cylinder engine, characterized in that the inlet openings are gradually inclined toward one side wall in accordance with the fan-shaped arrangement of the inflow openings.