JP3076832B2 - Engine fuel injection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for injecting fuel for each cylinder using an electromagnetic injection valve, and is mainly used for fuel supply of a gasoline engine for an automobile. You.

[Prior art] The fuel supply means of an engine that pressurizes fuel and directly injects it into a supply pipe is easier to control using electronic technology than a fuel supply means using a carburetor, and controls emissions such as emission control and output improvement. Many gasoline engines for automobiles use fuel injection systems based on the requirements. Among them, the multipoint injection system that injects each cylinder has a higher air-fuel ratio per cylinder than the single point injection system that injects into the intake manifold. Because of small variations, it is the mainstream in practical use.

Further, by detecting and electrically processing various engine conditions such as an intake pipe negative pressure, an intake air amount, a throttle valve opening, an engine rotation speed, an engine temperature, and using an electromagnetic injection valve for fuel injection, It is common to control the fuel injection amount by electrically controlling the valve opening time per operation based on various conditions, and furthermore, by pressurizing the fuel to a constant pressure. It is proportional to the opening time of the injection valve, that is, the energization time.

According to such a fuel injection system, the fuel is collectively injected into a part of the intake air of the air supply pipe, flows into the cylinder in a non-uniform mixing state, and mixes with the air by turbulence in the cylinder. This phenomenon is remarkable in a normal operation range, especially in a low-load low-speed motion range in which the air intake time per cylinder is long and the fuel injection time is short, and hardly mixes with the portion where the fuel is highly concentrated. Or into the cylinder in a mottled state consisting of air-only parts.

On the other hand, thinning the air-fuel mixture is a commonly used means for improving fuel economy, but in this case, if the air-fuel mixture in the cylinder immediately after ignition is rich or thin, it cannot be ignited by the spark of the spark plug Therefore, there is a limit to the dilution of the air-fuel mixture.

[Problem to be Solved by the Invention] The problem to be solved by the present invention is that if the air-fuel mixture is made thin for the main purpose of improving fuel economy, there may be cases where ignition cannot be performed in the cylinder.

That is, the present invention provides a fuel injection method for an engine in which an air-fuel mixture flowing into a cylinder is not a mottled state but a uniform mixing state, and a lean air-fuel mixture does not exist around a spark plug to prevent ignition. The purpose is to:

[Means for Solving the Problems] In order to solve the above-mentioned problems of the multipoint injection system for injecting fuel from the electromagnetic injection valve for each cylinder of the engine, the present invention takes the following measures.

That is, the opening time of the injection valve is determined so that the fuel injection time is proportional to the fresh air inflow time that changes in accordance with the change in the engine operating conditions, and a predetermined amount of fuel is injected during this valve opening time. The fuel pressure is adjusted so that the fuel is injected over the whole intake fresh air passing in front of the injection valve.

Injection valves are installed for each cylinder's air supply pipe, and injecting fuel in synchronism with the cylinder's intake stroke is the same as in a conventional multipoint injection system. The major feature is that the fuel is uniformly injected over the entire cylinder and a uniform combustible mixture is supplied to the cylinder.

For this reason, when the load of the engine is constant, first, the valve opening time (energization time or pulse width) of the injection valve is made inversely proportional to the rotation speed of the engine. That is, for all cylinders and their supply pipes, the fuel injection section indexed based on the crankshaft rotation angle is set to a constant value equal to the section occupied by the intake fresh air in one cylinder in the supply pipe. Set to inject fuel only to air. In this case, as the rotational speed rises from the idle speed, the time during which one intake fresh air passes in front of the injection valve becomes shorter, so the valve opening time is made shorter in inverse proportion to the rotational speed,
Fuel is injected only to the fresh intake air. The energization time or pulse width for determining the valve opening time can be easily obtained by detecting the rotation speed and calculating by a microcomputer mounted on the vehicle.

However, even in the region where the rotational speed is high, even if the air-fuel mixture has shading, the flow rate is large and the mixture is fairly evenly mixed, so that the valve opening time is kept constant (see FIG. 2).

Next, it is necessary to keep the fuel injection amount per injection valve constant and to always mix a constant amount of fuel with the intake fresh air. Therefore, the fuel pressure is adjusted according to the rotational speed. That is, if the fuel injection amount per injection is Q, the valve opening time is T, the rotation speed is N, and the fuel pressure is P, If P 燃料 N ² and the fuel pressure is proportional to the square of the rotation speed, a constant amount of fuel is always mixed even if the time during which the intake fresh air passes in front of the injection valve changes depending on the rotation speed. be able to. The fuel pressure can be adjusted by varying the discharge pressure of the fuel pump or varying the characteristics of the fuel pressure regulator based on the rotational speed. However, in a region where the rotation speed is high, the fuel pressure becomes extremely high and it is considered that it is technically difficult to put the fuel into practical use. Therefore, the fuel pressure is kept constant at a certain rotation speed or more as described above (see FIG. 3).

Therefore, it is sufficient to control the valve opening time of the injection valve and the fuel pressure by the engine speed in a normal range from an idle speed to a city speed, and the intake air flow rate in this speed range is sufficient. The advantage of adopting the present invention is relatively large because it is relatively low.

Further, at the same time as the opening of the intake valve of the cylinder, a part of the burned gas in the cylinder flows back to the air supply pipe in a negative pressure state, and the pressures in the cylinder and the air supply pipe are balanced. Combustion gas flows into the cylinder and then fresh air, but under the condition that the engine speed is constant, the ratio of backflow burned gas to fresh air in a single intake stroke is high due to the negative pressure in the intake pipe. The lower the load, the greater. Therefore, the time required for the intake fresh air to pass in front of the injection valve at one time differs depending on the load, even if the rotational speed is constant, so the valve opening time of the injection valve is corrected according to the change in the load, and the air-fuel ratio is kept constant. Mixture.

Further, it is necessary to determine the timing of the injection start so that the injection is started when the new intake air starts to pass in front of the injection valve. This is based on the three-dimensional schedule of the rotation speed, the load, and the injection start time. What is necessary is just to create in advance and to perform by map control. The load can be determined by at least two parameters among the throttle valve opening, the suction negative pressure, and the rotation speed.

FIG. 4 schematically shows a situation in which an air-fuel mixture is produced by the above-described means, in which one intake fresh air A exists upstream of the injection valve V of the air supply pipe P. At this time, the injection valve V is closed (FIG. 4A), and when the fresh intake air A starts to pass in front of the injection valve V, the injection of the fuel F is started (FIG. 4B). During the passage of the intake fresh air A, the fuel F is injected to form an air-fuel mixture M sequentially (FIG. 4C). When the air-fuel mixture has passed, the injection valve V is closed and the uniform air-fuel mixture M is supplied to the cylinder. (FIG. 4D).

Incidentally, the fuel injection amount per one time is the oxygen concentration in the exhaust gas,
It goes without saying that correction is appropriately made in accordance with operating conditions other than those directly required for the means of the present invention, such as intake air temperature and engine temperature.

[Operation] When the engine rotates and the intake valve of a certain cylinder is opened, a part of the burned gas flows back into the air supply pipe, and then flows into the cylinder, followed by fresh air. While the intake fresh air passes in front of the injection valve, the fuel whose injection time and pressure are controlled according to the operating conditions continues to be injected, and the air-fuel mixture in a uniform mixed state is supplied to the cylinder.

[Embodiment] FIG. 1 is a layout diagram showing an embodiment of the present invention, in which a supply pipe 4 is connected to a cylinder 2 of a multi-cylinder gasoline engine 1 for an automobile.
And the manifold branch of the exhaust pipe 6 is connected, and the operation of the piston 3, the intake valve 5, and the exhaust valve 7 in a four-cycle stroke is exactly the same as in the prior art.

Each branch of the air supply pipe 4 is provided with an electromagnetic injection valve 8. The fuel is pressurized by a fuel pump 10 from a fuel tank 9 and sent by a fuel pressure regulator 11 to inject fuel. The fuel pressure regulator 11 controls the fuel pressure of the engine 1
In order to make the rotation speed proportional to the square of the rotation speed, the conventional suction negative pressure
A stepping motor 12 was used instead of the diaphragm.

Reference numeral 13 denotes an electronic control unit including a microcomputer mounted on a vehicle, which includes a throttle valve opening signal 15, a suction negative pressure signal.
16, Intake air temperature signal 17, Intake air amount signal 18, Engine speed signal 19, Engine temperature signal 20, Oxygen concentration in exhaust gas signal 21, Crankshaft position signal 22, and other necessary signals are input. Then, the valve opening time and fuel pressure of the injection valve 8 are determined on the basis of the above, and a valve opening signal 23 and a drive signal 24 are output to the injection valve 8 and the stepping motor 12.

With this configuration, the injection valve 8 of the predetermined air supply pipe 4 opens in synchronization with the suction stroke of the cylinder 2, and the predetermined fuel is injected over the entire intake fresh air to produce a uniform mixture. .

[Effects of the Invention] According to the present invention, it is possible to inject fuel into the entire intake fresh air and to supply an air-fuel mixture in a uniform mixed state to the cylinder. Further, the ignition by the lean air-fuel mixture is ensured in the low-load low-speed motion range, and the fuel economy is sufficiently improved.

[Brief description of the drawings]

FIG. 1 is a layout diagram showing an embodiment of the present invention, FIG. 2 and FIG. 3 are basic characteristic diagrams of the present invention, and FIG. 4 is an explanatory diagram of a situation where fuel is injected and mixed into fresh intake air. 1 ... engine, 2 ... cylinder, 4 ... supply pipe, 8 ...
... Injection valve, 10 ... Fuel pump, 11 ... Fuel pressure regulator, 13 ...
... Electronic control device,

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02D 41/34

Claims (4)

(57) [Claims] When injecting fuel from an electromagnetic injection valve provided for each air supply pipe of each cylinder of an engine in synchronization with a suction stroke of the cylinder, fresh air inflow that changes according to a change in operating conditions of the engine. The valve opening time of the injection valve is determined so that the fuel injection time is proportional to the fuel injection time, and the fuel pressure is adjusted so that a predetermined amount of fuel is injected during the valve opening time. A method for injecting fuel into an engine, comprising injecting fuel over the entire air. 2. The fuel injection of an engine according to claim 1, wherein the valve opening time and fuel pressure of the injection valve are controlled in accordance with a change in operating conditions in a normal range of the engine and are kept constant in a higher rotation speed range. Method. 3. The fuel injection method for an engine according to claim 1, wherein the operating condition of the engine is a rotation speed, and the opening time of the injection valve and the fuel pressure are controlled in accordance with the change. 4. The engine according to claim 1, wherein the kinetic conditions of the engine are a rotational speed and a load, wherein the opening time of the injector is controlled in accordance with the change in the rotational speed and the load, and the fuel pressure is controlled in accordance with the change in the rotational speed. The fuel injection method for an engine according to any one of claims 1 and 2.