JPH0468466B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fuel supply system for an internal combustion engine equipped with an intake system that improves torque and fuel efficiency.

<Prior Art> Conventionally, as shown in FIG. 6, each cylinder is provided with two intake valves 1A, 1B, and two intake ports 2A, which branch from an intake passage 2 and reach the intake valves 1A, 1B. 2B (intake port 2B) is provided with an on-off valve 3, and the on-off valve 3 is closed in the low speed range of the engine and opened in the high speed range (Reference document: JP-A-57-70914) ). Note that 4A and 4B are exhaust valves, and 5A and 5B are exhaust ports.

That is, in the low speed range where the on-off valve 3 closes, a strong swirl is generated in the combustion chamber by utilizing the intake air flowing in the direction connecting to the combustion chamber wall from only the intake port 2A, and the opening/closing timing of the intake valve 1A is determined based on the intake inertia. By setting it in conjunction with the low speed range where the engine speed is small, it improves combustibility and improves fuel efficiency, output, and exhaust characteristics.

In addition, in the high-speed range where the on-off valve 3 opens, the intake passage resistance is reduced by increasing the cross-sectional area of the intake passage, and the intake valve 1B, whose opening/closing timing is set according to the high-speed range with large intake inertia, is used in conjunction with the intake valve 1B to control the intake air. By doing so, we aim to improve the maximum output.

<Problems to be Solved by the Invention> Incidentally, in this conventional example, the fuel injection valve 6 is provided in the intake passage 2 upstream of the branch point of the intake ports 2A and 2B.

However, in the arrangement of the fuel injection valve 6,
Fuel injected from the fuel injection valve 6 in the low speed range when the on-off valve 3 is closed accumulates on the upstream side of the on-off valve 3, and intermittently flows in large quantities into the various intake ports 2A, creating an extremely rich air-fuel mixture. Since the gas is generated and supplied to the engine, problems arise such as deterioration of combustibility, lowering the stability of the engine, or having an adverse effect on the exhaust purification device installed in the exhaust passage.

On the other hand, in an engine equipped with two intake valves for each cylinder and an on-off valve at the intake port leading to one of the intake valves, the applicant proposed that when the on-off valve is closed, such as during idling, the intake port downstream of the on-off valve is We previously applied for an invention in which the blowback of exhaust gas when the intake valve is opened is suppressed by introducing fresh air close to atmospheric pressure to increase the pressure inside the intake port (Patent Application No. 59). No. 60918) discloses an embodiment in which a fuel injection valve is provided in the intake port on the side not provided with an on-off valve.

In this case, if the fuel injection speed is higher than when idling and the on-off valve is closed, etc.
The pressure difference before and after the on-off valve is reduced, and the time for introducing fresh air is shortened due to the increase in rotational speed.
There is a certain amount of exhaust blowing back, and this can be used to reduce NOx through residual exhaust, but when this blown back exhaust comes into contact with the on-off valve, the on-off valve and its surroundings are exposed to carbon and carbon in the exhaust. It is easily contaminated by tar-like polymers, which may adversely affect the operation of the on-off valve. Regarding this point, in the case of the known conventional example, the contaminated portion can be cleaned by the fuel supplied from the fuel injection valve provided upstream of the branch point of the two intake ports.

The present invention aims to prevent deterioration of fuel quality due to accumulation of fuel upstream of the above-mentioned on-off valve, resulting in a decrease in engine stability, contamination of the on-off valve and its surrounding areas due to blowback of exhaust gas, and even malfunction of the on-off valve. This was done to solve a problem.

<Means for solving the problem> For this reason, the present invention provides two intake valves for each cylinder,
In an internal combustion engine comprising two intake ports that branch from the middle of an intake passage and reach the two intake valves, and one of the intake ports has an on-off valve that is controlled to open and close according to engine operating conditions. A first fuel supply means is provided in the other intake port which is not equipped with the intake port, and a second fuel supply means is provided in the intake passage upstream of the two intake ports to supply fuel only when the on-off valve is in an open state. composition.

<Function> With this configuration, when the on-off valve is closed,
Fuel is supplied by the first fuel supply means provided at the intake port on the opposite side to the side where the on-off valve is installed, and fuel supply from the second fuel supply means upstream of the intake port is stopped. Therefore, it is possible to prevent fuel from accumulating upstream of the on-off valve, and on the other hand, when the on-off valve is open, the on-off valve and its surrounding area contaminated with exhaust gas can be cleaned by the fuel supplied from the second fuel supply means.

<Example> Hereinafter, an example of the present invention will be described based on the drawings.

However, in the following embodiment diagrams, the same components as those shown in FIG. 6 will be described with the same reference numerals.

1 and 2 show a first embodiment, in which each cylinder of an internal combustion engine is provided with a low-speed intake valve 1A and a high-speed intake valve 1B. Equipped with a low-speed intake port 2A and a high-speed intake port 2B leading to each intake valve 1A, 1B,
In addition, it is similar to the conventional example that the high-speed intake port 2B is provided with an on-off valve 3 that closes in the low speed range of the engine and opens in the high speed range.

The low-speed intake valve 1A is set to have a small operating angle (crank angle corresponding to the lift period) to shorten the overlap period with the exhaust valves 4A and 4B, and the high-speed intake valve 1B is set to a small operating angle (crank angle corresponding to the lift period). The operating angle is set to be large, the lift amount is large, and the overlap period with the exhaust valves 4A and 4B is set to be large.

As a configuration according to the present invention, a first fuel supply means is provided to the low-speed intake port 2A.
In addition, a fuel injection valve 11 as a second fuel supply means is installed in the intake passage 2 provided for each cylinder upstream from the branch point of the low-speed and high-speed intake ports 2A and 2B. 2 fuel injection valve 1
Attach 2.

Of these, the second fuel injection valve 12 is the on-off valve 3.
The first fuel injection valve 11 is controlled so that fuel is supplied only in a high speed range where the on-off valve 3 is opened, while the first fuel injection valve 11 is controlled so that fuel is supplied at all times or only in a low speed range where the on-off valve 3 is closed.

Here, the total fuel injection amount supplied to the engine by the two fuel injection valves 11 and 12 is equal to the intake air amount per engine rotation determined based on the detection signal of the intake air flow rate and the engine rotation speed. It is set by correcting the corresponding basic injection amount based on the cooling water temperature, etc.

Next, the action will be explained. In the low speed range of the engine, the on-off valve 3 is closed and intake is performed only through the low speed intake port 2A, and injection by the second fuel injection valve 12 is stopped and only from the first fuel injection valve 11. Fuel injection takes place.

In this case, the air-fuel mixture is inhaled along the inner wall of the combustion chamber to generate a strong swirl, improving the mixing property, and the low-speed intake valve 1A and exhaust valve 4A,
Since the overlap period with 4B is short, exhaust blowback is suppressed, and combustibility is improved due to the early closing timing of intake valve 1A and high actual compression ratio, resulting in improved fuel efficiency, output, and exhaust emissions in the low speed range. The ability to improve the characteristics is similar to the earlier conventional example and the earlier application example.

When the on-off valve 3 is closed in this way, fuel injection from the second fuel injection valve 12 is stopped, thereby preventing fuel from accumulating on the upstream side of the on-off valve 3. Accordingly, fluctuations in the mixture concentration due to intermittent fuel supply are prevented, stable combustibility can be ensured, and period stability can be improved.

On the other hand, in the high-speed range of the engine, the on-off valve 3 is opened, air is taken in from the high-speed intake valve 1B via the high-speed intake port 2B, and fuel is injected from the second fuel injection valve 12. Fuel injection valve 1 with first injection
As a result, the intake passage area is increased to reduce intake air circulation resistance, the closing timing of the intake valve 1B is delayed and the lift amount is increased to utilize inertial supercharging, and the swirl is reduced. Maximum output can be improved by reducing the amount. This point is similar to the conventional example and the prior application example.

When the on-off valve 3 is closed, fuel is injected from the second fuel injection valve 12, so the injected fuel causes the on-off valve 3 on the downstream side and its surrounding area to be blown back by exhaust gas. Adhering carbon, tar-like substances, etc. are washed away, and the operability of the on-off valve 3 can be maintained in good condition.

Note that FIG. 1 shows a state in which the on-off valve 3 is closed, and FIG. 2 shows a state in which the on-off valve 3 is open.

3 and 4 show a second embodiment of the present invention, in which a second fuel is supplied as a second fuel supply means to the intake passage 2 upstream of the low-speed and high-speed intake ports 2A and 2B. Only one injection valve 12 is provided.

In this case, the second fuel injection valve 12 may be provided upstream of the throttle valve 13 as shown in the figure, and
Although it may be provided on the downstream side, it is preferable to provide it on the upstream side of the passage that branches for each cylinder and at a position where the injected fuel is distributed as evenly as possible to each cylinder.
Further, when an exhaust turbo supercharger is installed, it may be arranged either upstream or downstream of the compressor of the supercharger.

The second fuel injection valve 1 arranged in this way
Similarly, the fuel injection valve 2 operates only when the on-off valve 3 is opened to inject fuel. The other configurations are the same as those of the first embodiment, and therefore the effects are also the same. Furthermore, since only one second fuel injection valve 12 needs to be provided, this embodiment can be implemented at a lower cost than the first embodiment.

3 shows a state in which the on-off valve 3 is closed in a low speed range, and FIG. 4 shows a state in which the on-off valve 3 is open in a high speed range.

FIG. 5 shows a third embodiment of the present invention, in which the carburetor 22 is connected to the intake passage upstream of the throttle valve 13 as a second fuel supply means in place of the second fuel injection valve in the second embodiment. 2.

In this case, almost no fuel is supplied to the carburetor 22 when the intake air flow rate of the engine is small, such as in a low speed range when the on-off valve 3 is closed, and when the intake air flow rate is low, such as in a high-speed range when the on-off valve 3 is open. Set it up so that fuel is supplied only when it grows.

With this fuel supply setting, the second
The same effects as in the embodiment can be obtained. In addition, since the carburetor 22 is used as the second fuel supply means, it can be implemented at a lower cost than the second embodiment.

<Effects of the Invention> As explained above, according to the present invention, the first fuel supply means is provided in one of the two intake ports provided for each cylinder, and the first fuel supply means is provided in the other intake port. The second fuel supply means, which supplies fuel only under operating conditions where the on-off valve is closed, is installed in the intake passage upstream of the branch point of the two intake ports, thereby preventing fuel from accumulating upstream of the on-off valve. In addition to maintaining stable fuel properties, the injected fuel cleans dirt such as carbon and tar that adheres to the on-off valve and its surrounding areas due to blowback of exhaust gas, and maintains good operability of the on-off valve. This has the effect of being able to.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing the structure of a first embodiment of the present invention, respectively. FIG. 1 shows the on-off valve in a closed state, and FIG. 2 shows the on-off valve in an open state. Figures 3 and 4
The figures are cross-sectional views showing the configuration of the second embodiment of the present invention, with FIG. 3 showing the on-off valve in a closed state, and FIG. 4 showing the on-off valve in an open state. FIG. 5 is a sectional view showing the configuration of a third embodiment of the present invention, and FIG. 6 is a sectional view showing a conventional example. 1A... Intake valve for low speed, 1B... Intake valve for high speed, 2A... Intake port for low speed, 2B... Intake port for high speed, 3... Open/close valve, 11... First
fuel injection valve (first fuel supply means), 12...
Second fuel injection valve (second fuel supply means), 22
...vaporizer.

Claims (1)

[Claims] Each cylinder has two intake valves and two intake ports that branch from the middle of the intake passage and reach the two intake valves, and one intake port has an opening/closing valve that is controlled to open and close according to engine operating conditions. In an internal combustion engine equipped with a valve, a first fuel supply means is provided at the other intake port not equipped with the on-off valve, and fuel is supplied to the intake passage upstream of the two intake ports only when the on-off valve is in an open state. 1. A fuel supply device for an internal combustion engine, characterized in that a second fuel supply means is provided.