JPH0313429B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for a fuel-injected engine that is equipped with a high-load intake passage that supplies intake air only during high loads in addition to a low-load intake passage. It is related to.

(Prior art) In recent years, lean operation (operation with a large air-fuel ratio) has become more common in order to improve fuel efficiency.
For this reason, as shown in Japanese Patent Laid-Open No. 56-148636, for example, efforts have been made to obtain stratified combustion by injecting fuel in time with the intake stroke of each cylinder.

Incidentally, an engine intake system is equipped with a low-load intake passage and a high-load intake passage for each cylinder, and controls the opening and closing of a shutter valve disposed in the high-load intake passage. At times, high-flowing intake air was supplied only from the low-load intake passage to improve driveability, while at high loads, intake air was also supplied from the high-load intake passage to improve charging efficiency. be. In the intake system of such an engine, while it is possible to supply fuel to each cylinder using only one fuel injector, in order to promote atomization (vaporization) of the fuel, the fuel injector is placed downstream of the shutter valve. It has been considered to arrange the fuel injection valve in the high-load intake passage on the side, and to direct the injection port of the fuel injection valve toward the downstream opening of the low-load intake passage. In other words, even when the load is high, fuel atomization can be promoted by injecting fuel so that it flows through the high-load intake passage, rather than simply supplying air from the high-load intake passage. The idea is to make it possible to do so.

(Problems to be Solved by the Invention) However, in the case where fuel is distributed and supplied from one fuel injection valve to the low-load intake passage and the high-load intake passage as described above, especially The promotion of fuel atomization at low loads, where lean operation is required, is not always satisfactory, and this poses a problem in promoting lean operation.

The present invention was made in consideration of the above-mentioned circumstances, and includes a low-load intake passage and a high-load intake passage in which a shutter valve is disposed, and the high-load intake passage downstream of the shutter valve. The fuel injection type is equipped with a fuel injection valve whose nozzle part is oriented toward the downstream opening of the low-load intake passage, which enables better atomization of fuel during low-load conditions. The purpose is to provide an intake system for an engine.

(Means for solving the problem) In the present invention, the atomization effect of the fuel injected from the fuel injection valve is promoted even before it reaches the downstream opening of the low-load intake passage. Therefore, the intake air of the shutter valve upstream valve is led out from the upstream side of the fuel injection valve nozzle portion in the intake air flow direction. Specifically, a low-load intake passage, a high-load intake passage provided with a shutter valve that is closed during low load, and a high-load intake passage provided downstream of the shutter valve, a fuel injection valve whose nozzle port is directed toward the downstream opening of the low-load intake passage; and when the shutter valve is closed, the intake air on the upstream side of the shutter valve is directed toward the nozzle port of the fuel injection valve. and a partial flow passage which is led out from the right upstream side in the direction of the intake passage.

(Function) With this configuration, when the load is low, intake air from the partial flow passage is supplied to the collected liquid fuel immediately after being injected from the nozzle of the fuel injection valve. The collected liquid fuel is mixed with the intake air from the partial flow passage even before reaching the downstream opening of the low-load intake passage, and its atomization is promoted.

(Example) Examples of the present invention will be described below based on the attached drawings.

1 and 2 show a first embodiment of the present invention. In these figures, 1 is an engine body, which is composed of a cylinder block 2, a cylinder head 3, a cylinder head cover 4, etc., and each cylinder 5 of this engine body 1 is equipped with a piston 6. A combustion chamber 7 is formed above the piston 6. Two intake ports 8 and 9, a first and a second intake port, and an exhaust port 10 are opened in the combustion chamber 7. Both intake ports 8 and 9 are each equipped with an intake valve 11 (the intake valve on the second intake port side is not shown), and the exhaust port 10 is equipped with an exhaust valve 12, and these valves are operated. It is operated by a valve mechanism 13 to open and close each port 8, 9, 10 at a predetermined timing. The combustion chamber 7 is also equipped with a spark plug 14 .

Further, 16 is a surge tank, and 17 is an intake pipe for each cylinder connected to the surge tank 16. Outside air is introduced into the surge tank 16 via an air cleaner 18, an air flow meter 15, and a throttle valve 19. It's getting old. Above intake pipe 1
7 is connected to the cylinder head 3, and this intake pipe 1
7 and a predetermined internal area of the cylinder head 3, a common intake passage 21 is formed, and within the cylinder head 3, the common intake passage 21 is branched from the downstream end side to become a high-load intake passage. The first and second branch intake passages 22 and 23 are
It communicates with both the intake ports 8 and 9. A shutter valve 24 for opening and closing the common intake passage 21 is provided at a predetermined position of the common intake passage 21, and the shutter valve 24 is closed in a low-load operating range below a predetermined load by an actuator (not shown). In other words, it is fully closed or closed to a small opening,
On the contrary, it is opened in high-load operation areas. Further, a third branch intake passage 25 as a low-load intake passage branches off from a predetermined location of the common intake passage 21 upstream of the shutter valve 24. This third branch intake passage 25 is formed with a relatively small passage cross-sectional area, and is provided along the downstream side of the common intake passage 21, and the inlet portion 25 on the upstream side
a opens at a predetermined location in the common intake passage 21, while an outlet portion 25b on the downstream end side merges with an outlet portion on the downstream side of the first branch intake passage 22 near the first intake port 8. The outlet portion 25b is opened toward the circumferential direction of the combustion chamber 7, that is, it is opened to form a swirl of intake air within the combustion chamber 7.

Common intake passage 2 downstream from the shutter valve 24
1 is equipped with one fuel injection valve 26, and fuel is supplied from this fuel injection valve 26 through the common intake passage 21 into the first and second branch intake passages 22, 23. . When the shutter valve 24 is opened and intake air is sent from the common intake passage 21 to each intake port 8, 9, the first
The intake air flowing into the second branch intake passage 22, the intake air flowing into the second branch intake passage 23, and the third
The position, injection direction, etc. of the fuel injection valve 26 are set in advance so that the fuel is distributed and supplied in as equal a ratio as possible to the intake air that joins the branch intake passage 25 at the outlet portion 25b.

In particular, the fuel injection valve 26 is oriented so that its injection port 26a is oriented so that fuel is supplied to the outlet portion 25b of the third branch intake passage 25, which serves as a low-load intake passage, in consideration of its injection angle. .

The shutter valve 24 is a disc-shaped butterfly valve, and rotates clockwise in FIGS. 2 and 3 from its closed position shown in FIGS. 1, 2, 3, and 4. However, when the valve is closed, there is a notch 24a as a partial flow passage located in the vicinity (directly upstream) of the nozzle part 26a of the fuel injection valve 26.
is formed. That is, the fuel injection valve 26
As shown in FIG. 1, the notch 24a is located at the center in the width direction of the common intake passage 24, and therefore the notch 24a is formed at the top of the shutter valve 24 when the valve is closed. .

In the above configuration, when the load is low, the shutter valve 24 is closed, thereby preventing or suppressing the intake air from flowing into the first and second branch intake passages 22 and 23, which serve as intake passages for high loads. Intake air mainly passes through the branch intake passage 25 as a low-load intake passage, and is sent into the combustion chamber 7 from its outlet portion 25b via the downstream end of the first branch intake passage 22 and the first intake port 8. As a result, the intake air flow rate is increased, and the combustion chamber 7
Swirl is generated in the engine, providing intake conditions that are advantageous for improving combustibility at low loads. Particularly, during this low load, the intake air is drawn from the notch 24a of the shutter valve 24 in the closed state, that is, directly upstream of the nozzle part 26a of the fuel injection valve 26, to the upstream side of the shutter valve 24 with respect to the nozzle part 26a. The intake air in the passage is supplied, and therefore the nozzle part 26a
The fuel injected from the third branch intake passage 25
It is sufficiently mixed with air before reaching the outlet portion 25b, and its atomization is promoted. As a result, the leanness can be further improved compared to the case where the notch 25a is not provided.

In addition, when the load is high, the shutter valve 24 is opened, so that each branch intake passage 22, 23, 25
Intake air is sent from the intake ports 8 and 9 to the intake ports 8 and 9,
The filling effect will be enhanced.

Here, the fuel injection timing from the fuel injection valve 26 may be either simultaneous injection in which the fuel is injected into each cylinder 5 at the same time, or synchronous injection (independent injection) in which the fuel is injected in accordance with the intake stroke of each cylinder 5. It may be. However, synchronous injection allows fuel to be more effectively added to the swirl and flow velocity of the intake air, which is more preferable in terms of lean engine combustion.

FIG. 5 shows another embodiment of the present invention, and the same components as those in the previous embodiment are given the same reference numerals and their explanations are omitted (this also applies to other embodiments below). ).

In this figure 5, the fuel injection valve 26
is offset to the lower side in FIG. 1, that is, to the side of the intake port 8 where the outlet portion 25b of the third branch intake passage 25 as the low-load intake passage is located, and accordingly, the shutter valve 24 is The position of the formed notch 24a is different from that in FIG. 4. In the case of this embodiment, more fuel is supplied to the intake port 8 on the third branch intake passage 25 side, which further improves the flow velocity of the intake air and makes it leaner using swirl. obtain.

FIG. 6 shows still another embodiment of the present invention, in which only one intake port 8 is provided for each cylinder 5.
It is assumed that one is provided. That is, compared to the embodiment shown in FIG. 1, the intake port 9 is eliminated, and the second branch intake passage 23 is also eliminated, thereby simplifying the mechanism.

In the above embodiment, the notch 24 of the shutter valve 24
Although a case has been described in which the partial flow passage is constituted by a, the partial flow passage may also be constituted by a bypass passage with a small effective opening area that bypasses the shutter valve 24. In this case, this bypass passage The downstream end opening of the shutter valve 2, which is located when the valve is closed,
4 on the downstream side and the nozzle part 26a of the fuel injection valve 24
It may be opened directly upstream.

(Effects of the Invention) As is clear from the above, the present invention has the following advantages:
The fuel is better atomized at low loads, which is extremely effective in ensuring combustion stability and achieving lean.

[Brief explanation of drawings]

FIG. 1 is a plan view showing one embodiment of the present invention. Second
The figure is a sectional view taken along the - line in FIG. 1. FIG. 3 is an enlarged sectional view of the main part of FIG. 2. FIG. 4 is a view of the fuel injection valve seen from the downstream side of the shutter valve in FIG. FIG. 5 shows another embodiment of the present invention and corresponds to FIG. 4. FIG. 6 shows still another embodiment of the present invention, and corresponds to FIG. 1. 1: Engine body, 5: Cylinder, 7: Combustion chamber,
8, 9: Intake port, 21: Common intake passage, 2
2, 23: Branch intake passage (high load intake passage),
24: Shutter valve, 24a: Notch (partial flow passage), 25: Branch intake passage (low load intake passage),
26: Fuel injection valve, 26a: Nozzle part.

Claims (1)

[Scope of Claims] 1. A low-load intake passage; a high-load intake passage in which a shutter valve that is closed at low load is disposed; and a shutter valve disposed in the high-load intake passage on the downstream side of the shutter valve. a fuel injection valve whose injection port is directed toward the downstream opening of the low-load intake passage; and when the shutter valve is closed, the intake air on the upstream side of the shutter valve is directed to the injection port of the fuel injection valve. An intake device for a fuel-injected engine, comprising: a partial flow passage that leads out from immediately upstream in the direction of the intake passage.