JPH057555B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for a four-stroke internal combustion engine that has three intake valves adjacent to each other for one cylinder and injects fuel into an intake passage.

There are four-stroke internal combustion engines in which three adjacent intake valves are provided for one cylinder. When one fuel injection valve is used for one cylinder in this type of engine, the mounting position of the injection valve has a large effect on combustion. For example, it is conceivable to connect the downstream side of one intake passage to three intake valves and inject fuel into this intake passage. However, in this case, the cross-sectional area of the intake passage becomes large and the intake flow velocity becomes small during low-load, low-speed operation, so fuel tends to adhere to the inner wall of the intake passage and form a wall flow, causing a problem that fuel atomization deteriorates.

Therefore, it is conceivable to provide three intake passages independently for each intake valve, and to open and close some of the intake passages according to operating conditions such as operating load and speed. However, in this case, if fuel is to be supplied from one fuel injection valve, fuel will be injected only into one intake passage for low load and low speed. For this reason, if all the intake passages are opened at high speeds, the fuel will be distributed non-uniformly within the combustion chamber, resulting in a problem that combustion will deteriorate.

The present invention has been made in view of these circumstances, and has an object to improve fuel atomization in all operating ranges, improve and stabilize combustion even though a single fuel injector is used. An object of the present invention is to provide an intake system for a four-stroke internal combustion engine that is capable of

According to the present invention, this object is achieved in a four-stroke internal combustion engine having three intake valves adjacent to each other for one cylinder, with a plurality of intake passages communicating with the intake valve, and each intake air passage in the vicinity of the intake valve. It includes a communication chamber that communicates the passages with each other, and a fuel injection valve that injects fuel into the communication chamber toward the intake passage at the center in a plan view, and at least one intake passage on the upstream side of the communication chamber has an operating condition. The present invention is constituted by an intake system for a four-stroke internal combustion engine, which is characterized by being provided with a control valve that opens and closes depending on the timing. The present invention will be explained in detail below based on the illustrated embodiments.

FIG. 1 is a partially sectional plan view of a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line 2, and FIG. 3 is a torque characteristic diagram. Number 10 in Figures 1 and 2
is the cylinder body, 12 is the cylinder head, 14
is a piston, and a combustion chamber 16 is formed by these pistons. The cylinder head 12 has two exhaust valves 18, 18a, 18b per cylinder and three mutually adjacent intake valves 20, 20a, 20b, 20.
c is provided. These exhaust/intake valves 18,
20 is opened and closed by a known double overhead camshaft type valve operating mechanism comprising overhead camshafts 22, 24, rocker arms 26, 28, etc., respectively. 30 is a cylinder head cover, 32 is an exhaust passage communicating with the exhaust valve 18, and 34 in FIG. 1 is a spark plug.

36 is a surge tank, and 38 is an intake pipe that connects the surge tank 36 and the cylinder head 12 for each cylinder. Inside the intake pipe 38, a first intake passage 40 is provided.
a, a second intake passage 40b is formed. 1st
The intake passage 40a and the second intake passage 40b have approximately the same diameter, and a butterfly-shaped control valve 44 that opens and closes the second intake passage 40b is attached to a valve shaft 42 that passes through these passages 40a and 40b. There is. This control valve 44 is controlled to open and close in response to operating conditions, such as increases and decreases in operating load and engine speed.

The downstream side of the intake passage 40 is connected to a communication chamber 46 provided in the cylinder head 12, and this communication chamber 46 communicates with the three intake valves 20.

48 is an electromagnetic fuel injection valve. This injection valve 4
As shown in FIG. 2, 8 is located between the distribution pipe 50 disposed at the upper part of the intake pipe 38 and the upper part of the communication chamber 46 of the cylinder head 12, and its injection port is directed toward the central intake valve 20b. do. The injection valve 48 opens at a predetermined timing in response to an electric signal output by a controller (not shown), and intermittently injects fuel in the distribution pipe 50 pressurized to a predetermined pressure into the communication chamber 46. .

The operation of this first embodiment is as follows. During low load/low speed operation, the control valve 44 is closed and intake air is guided from the first intake passage 40a to the communication chamber 46.
During low-speed operation, the pulsation of the intake air is large, and since the first intake passage 40a has a small diameter, the intake inertia is also large. Therefore, when the intake valve 20 is closed, the intake air enters the communication chamber 46 from the first intake passage 40a, creating a strong turbulent flow. The fuel injected intermittently into the communication chamber 4 is quickly and well atomized by the turbulent flow of intake air.
The mixture becomes homogenized and flows into the combustion chamber 16 as the intake valve 20 opens. At this time, the turbulent flow within the communication chamber 46 also strengthens the swirl, and combustion can be stabilized.

During high load/high speed operation, the control valve 44 opens and intake air enters the communication chamber 46 from the first and second intake passages 40a, 40b. The fuel injected from the injection valve 48 not only has a certain degree of spread, but also spreads over a long distance within the relatively wide communication chamber 46 without hitting the inner wall. This reduces the amount of fuel adhering to the inner wall and promotes atomization of the fuel.

In FIG. 3, the solid line A represents the torque characteristic when the control valve 44 is kept open, and shows that the torque decreases significantly due to the decrease in the intake inertia effect at medium and low speeds. The dashed line B in the figure is the torque characteristic when the control valve 44 is closed. By opening and closing the control valve 44 in the medium speed range, these two characteristics A and B can be combined to improve the torque characteristics.

FIG. 4 is a partially sectional plan view of the second embodiment. This embodiment is based on the first embodiment in the first embodiment.
The intake passage 40a is formed to have a smaller diameter than the second intake passage 40b. According to this embodiment, the injection port of the injection valve 48 is connected to the first and second intake passages 40a, 40.
It is deviated toward the second intake passage 40b side from the wall between b. As a result, when the control valve 44 opens under high load and high speed, the intake air flowing into the communication chamber 46 from the second intake passage 40b hits the fuel injected from the injection valve 48 more effectively than in the first embodiment, and Atomization is further promoted. Furthermore, since the second intake passage 40b has a small diameter, it is possible to increase the torque due to intake inertia from a lower speed than in the first embodiment. Furthermore, since the amount of deviation of the first intake passage 40a with respect to the communication chamber 46 is larger than that in the first embodiment, the vortex generated in the communication chamber 46 at low speeds when the control valve 44 is closed becomes even stronger, and the intake air When the valve 20 is opened, an even stronger swirl (suction vortex) is generated within the combustion chamber 16 due to this vortex. Therefore, combustion at low speeds is stabilized, and the effect of smoothing low speed operation becomes even more pronounced.

FIG. 5 is a partially sectional plan view of the third embodiment, in which the first intake passage 40a is arranged in the center, while the second intake passage 40b is divided into two.
Control valves 44, 44 are provided respectively.

According to this embodiment, the intake air passing through the first intake passage when the control valve 44 is closed at low load and low speed hits the fuel injected from the injection valve 48 well, and the atomization is particularly good at low load and low speed. This is further improved compared to the first and second embodiments.

FIG. 6 is a partially sectional plan view of the fourth embodiment, which shows the first, second, and third intake passages 40.
a, 40b, 40c, the first intake passage 40a
The second and third intake passages 40b and 40c sandwiching the
Control valves 44a and 44b are provided which open and close at different times.

According to this embodiment, like the third embodiment (FIG. 5), not only atomization at low speeds is promoted, but also torque characteristics can be improved at the same time. That is, FIG. 7 is a torque characteristic diagram of this fourth embodiment. In this figure, the solid line A indicates the characteristic when the control valves 44a, 44b are kept open, and the broken line B indicates the characteristic when the control valves 44a, 44b are kept open in the low speed range.
The chain line C shows the characteristic when only the control valve 44b is opened in the medium speed range.
By opening and closing the control valves 44a and 44b at different operating speeds and combining these characteristics A, B, and C, it is possible to improve the torque in the medium speed range compared to the first to third embodiments.

FIG. 8 is a partially sectional plan view of the fifth embodiment, and this embodiment is obtained by swapping the positions of the first intake passage 40a and the second intake passage 40b in the fourth embodiment (FIG. 6). It is.

According to this embodiment, the fourth embodiment (FIG. 6)
Similarly, not only can the torque be increased in the medium speed range, but also the swirl can be strengthened in the low speed range as in the second embodiment (Fig. 4), making rotation even smoother during low speed operation. .

In addition, in FIGS. 4, 5, 6, and 8, the same parts as in FIG. 1 are given the same reference numerals, so the description thereof will not be repeated.

As described above, the present invention allows a plurality of intake passages to communicate with each other in a communication chamber provided near three intake valves,
While fuel is injected into the communication chamber toward the central intake passage, at least one intake passage upstream of the communication chamber is provided with a control valve, and this control valve is opened and closed according to increases and decreases in operating load and operating speed. It was configured as follows. Therefore, when the load is low and the engine speed is low, the control valve closes and the intake air passes through only a portion of the intake passage, making it possible to effectively utilize intake inertia to improve air supply efficiency and increase output. At this time, a strong turbulent flow is generated in the communication chamber due to the intake pulsation, and the fuel injected into the communication chamber is mixed well with the intake air due to this turbulence, and atomization of the fuel is promoted. This improves combustion and improves fuel efficiency. Note that the turbulent flow in the communication chamber also strengthens the turbulence (swirl) of the intake air flowing into the combustion chamber, reducing fluctuations in combustion from cycle to cycle and smoothing the operation.

On the other hand, since the fuel is injected into the communication chamber, the injected fuel can spread over a relatively long distance without hitting the inner wall, improving fuel atomization under all operating conditions, improving combustion, and fuel efficiency. It is possible to improve the

[Brief explanation of the drawing]

FIG. 1 is a partially sectional plan view of the first embodiment;
Fig. 2 is a sectional view taken along the - line, Fig. 3 is a torque characteristic diagram, Figs. 4, 5, and 6 are partially sectional plan views of the second, third, and fourth embodiments, respectively, and Fig. The torque characteristic diagram of the fourth embodiment, and FIG. 8 is a partially sectional plan view of the fifth embodiment. 20...Intake valve, 40...Intake passage, 44...Control valve, 46...Communication chamber, 48...Fuel injection valve.

Claims (1)

[Scope of Claims] 1. In a four-stroke internal combustion engine having three intake valves adjacent to each other for one cylinder, a plurality of intake passages communicate with the intake valve, and each intake passage is connected near the intake valve. It includes communication chambers that communicate with each other, and a fuel injection valve that injects fuel into the communication chamber toward an intake passage at the center in a plan view, and at least one intake passage on the upstream side of the communication chamber is provided with a fuel injection valve according to operating conditions. An intake system for a four-stroke internal combustion engine, characterized in that it is provided with a control valve that opens and closes at the same time.