JP2591261B2 - Fuel supply method for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an internal combustion engine provided with an intake control valve.

[Conventional technology]

BACKGROUND ART There is known an engine in which a swirl port and a straight port are provided in an intake valve of each cylinder, and an intake control valve opens and closes a straight port side intake passage according to an engine load.

The intake control valve is provided for the purpose of operating the internal combustion engine by switching between a lean air-fuel ratio and a rich air-fuel ratio in accordance with a load state. The lean air-fuel ratio operation is performed by switching the fuel injection amount and the ignition timing while closing the passage.

By closing the intake control valve and letting the entire intake air flow into the cylinder from the swirl port, a strong swirl of the air-fuel mixture is generated in the combustion chamber, thereby achieving stable combustion even at a lean air-fuel ratio and reducing fuel consumption. be able to. on the other hand,
When the engine is under high load and high speed, the intake control valve is opened to increase the amount of intake air to the cylinder, and the fuel injection amount and the ignition timing are set to a rich air-fuel ratio (or stoichiometric air-fuel ratio) according to the opening operation of the intake control valve. By switching to the side, it is possible to secure a high output of the engine.

In an engine having an intake control valve, various considerations have been given to the arrangement of the fuel injection valve and the fuel injection method. In general, it is effective to inject fuel into both the swirl port and the straight port in order to increase the air-fuel ratio lean limit of the air-fuel mixture and improve the responsiveness during a transition.

As an engine of this type, the present applicant has published
There is one disclosed in Japanese Patent No. 147336. In the engine described in the publication, a fuel injection valve having two injection ports opened to both ports is disposed on a partition partitioning an intake passage into a straight port side and a swirl port side, and a single fuel injection valve is provided. Injecting fuel into both ports with the injection valve has the same effect as providing individual fuel injection valves at each port.

[Problems to be solved by the invention]

The engine described in Japanese Utility Model Laid-Open Publication No. 61-147336 has a configuration in which fuel is injected from two injection ports provided in a single fuel injection valve to ports on both sides. Therefore, the second
As shown in the figure, it is inevitable that a portion (FIG. 2a) in which the swirl port side communicates with the straight port side is formed on the partition wall near the injection port opening.

In the above configuration, when the intake control valve is open, there is no problem that the communication portion between the swirl port and the straight port exists.

However, when the intake control valve is closed, the intake pipe on the straight port side is closed by the intake control valve, so that when the intake valve of the cylinder is opened, a negative pressure state similar to that in the cylinder is generated. .

For this reason, an airflow from the swirl port side to the straight port side is generated in a portion connecting the two ports of the partition wall. In addition, since the speed of this air flow increases as the intake stroke progresses, a phenomenon occurs in which the fuel injected from the fuel injection valve is deflected by the air flow after a certain point in the intake stroke. When the injected fuel is deflected, the injected fuel collides with and adheres to the inner wall of the intake pipe, flows along the wall surface and flows into the cylinder. Therefore, the fuel is not atomized and a uniform mixture is not generated in the cylinder. For this reason, the fuel condition at the time of the lean air-fuel ratio is deteriorated, and sufficient performance cannot be obtained, thereby causing a problem such as an increase in the NO _X amount of the exhaust gas.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to eliminate the deflection of injected fuel by performing fuel injection at an appropriate timing and improve the performance during lean combustion.

[Means for Solving the Problems] The present invention provides a fuel injection method that completes fuel injection before a strong airflow is formed by increasing the speed of the flow through the communicating portion of the partition when the intake control valve is closed. Is prevented from being deflected.

That is, according to the present invention, each intake passage leading to the intake port of the internal combustion engine is divided into two by a partition extending in the intake flow direction, and one of the divided intake passages generates a swirl in the combustion chamber by the intake flow. An intake control valve that guides the swirl port of the shape and guides the other intake passage to a straight port of a straight shape, and closes the intake port when the engine is under a light load operation to close the straight port side intake path; In an internal combustion engine provided with a fuel injection valve having two injection ports which are opened at a downstream portion of the intake control valve and inject fuel with both the swirl port and the straight port directed to both, at least the intake control valve is closed. An internal combustion engine wherein fuel injection from the fuel injection valve is completed at the latest at least 40 degrees after the top dead center of the intake stroke at the time of valve opening. The method of the fuel supply is provided.

(Operation)

When the intake control valve is closed, the airflow passing from the swirl port side to the straight port side through the communicating portion of the partition wall,
The speed is low near the top dead center of the intake stroke of the cylinder and gradually increases with the progress of the intake stroke, and the flow velocity rapidly increases from about 40 degrees after the top dead center of the intake stroke. Accordingly, by completing the fuel injection of each cylinder before 40 degrees after the top dead center, it is possible to prevent the communication part from deflecting the injected fuel due to the airflow.

〔Example〕

 Hereinafter, the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an example of an apparatus for carrying out a fuel supply method according to the present invention.

In the figure, 10 is a cylinder block, 12 is a combustion chamber, 14
Indicates a so-called four-valve configuration in which a spark plug and 12a and 12b are intake ports, and two intake valves 16a and 16b and two exhaust valves 18a and 18b are provided at each intake port and exhaust port. The first intake port 12a is a helical type, and is formed in a shape that is convenient for forming an intake swirl. The second intake port 12b is of a straight type.

The straight type intake port 12b is provided with an intake control valve 32 as a butterfly valve, and when the intake control valve 32 is closed, intake air is introduced only from the helical type intake port 12a, and the intake Since a strong swirl (swirl flow) of intake air is generated, stable combustion of a lean air-fuel mixture becomes possible. When the intake control valve 32 is opened, air is introduced from both the intake ports 12a and 12b, and the intake amount increases. A lever 34 is attached to a valve shaft of the intake control valve 32 of each cylinder, and the lever 34 is connected to a negative pressure actuator 38 via a rod 36. The negative pressure actuator 38 includes a diaphragm 40 and a spring 41. When no negative pressure is applied to the diaphragm 40, the spring
By the action of 41, the diaphragm 40 is pushed to the left in the figure, and the intake control valve 32 assumes the open position. When a negative pressure is applied to the diaphragm 40, the diaphragm 40 is pulled right against the spring 41, and the intake control valve 32 takes a position to close the intake port 12b.

The diaphragm 40 is connected to a negative pressure tank 45 via an electromagnetic three-way switching valve 44. The negative pressure tank 45 is connected to a negative pressure outlet port 24 provided on the downstream side of the slot valve 22 of the intake pipe 20 via a check valve.

The check valve 46 holds a negative pressure applied to the diaphragm 40. The switching valve 44 has three ports 44a, 44b, and 44c. When electricity is removed, the ports 44a and 44b communicate with each other. The diaphragm 40 communicates with the negative pressure port 24.When electricity is supplied, the ports 44a and 44c communicate with each other. The diaphragm 40 is in communication with the atmosphere.

In addition, a fuel injection valve 26 is arranged on a partition wall 28 that partitions the helical intake port 12a and the straight intake port 12b.

FIGS. 2A and 2B are views showing details of a portion of the partition wall 28 where the fuel injection valve 26 is mounted. The fuel injection valve 26 has two injection ports 26a and 26b in one main body, and the injection ports 26a and 26b are respectively connected to the intake valve 16a of the helical intake port 12a and the straight intake port 12a.
The intake valve 16b of b is provided so as to face the umbrella rear surface. Therefore, the fuel injected when the intake valves 16a and 16b are opened collides with the back surface of the intake valve head, scatters, is atomized, and is sucked into the cylinder, so that a uniform mixture is formed in the combustion chamber. Further, the partition 28 at the position facing the injection ports 26a, 26b is provided with the notch 28b so that the fuel injection from the injection ports 26a, 26b of the fuel injection valve 26 does not interfere with the partition 28, so that the notch 28b
A communication part 28a is formed at the tip of the helical type port 12a and the straight type port 12b. (Fig. 2A,
The switching valve 44 of the intake control valve 32 and the fuel injection valve 26 are driven by a control circuit 50 of the engine. Control circuit (EC
U) 50 is configured as a microcomputer system, for example, and controls the switching timing of the solenoid valve 44 and the injection time (injection amount) of the fuel injection valve 26 by a known method, and also controls the fuel injection of the fuel injection valve 26 as described later. The injection timing is controlled. For this purpose, pulses G1 and NE representing the crankshaft rotation angle are input to the control circuit (ECU) 50 from crank angle sensors 54 and 56 provided in the distributor of the engine. The pulse G1 transmitted from the first crank angle sensor 54 is for detecting a reference position. For example, every time the engine first cylinder reaches the exhaust bottom dead center, the crankshaft rotation 72
Sent once at 0 degrees. Also, the second crank angle sensor 5
6 transmits a pulse NE every 30 degrees of crankshaft rotation. ECU 5
0 is to calculate the engine speed by counting the number of pulses NE per unit time and to detect the phase of each cylinder stroke by counting the number of pulses NE after the reference pulse G1 is input.

Next, the timing of fuel injection in the present invention will be described. As described above, the injection ports 26a and 26b of the fuel injection valve 26 inject fuel toward the back of the head of the intake valves 16a and 16b, respectively, and the injected fuel is atomized by the collision with the head of the intake valve. Promoted.

However, when the intake control valve 32 is closed, there is an airflow that flows from the helical port side to the straight port side through the communication portion 28a of the partition wall 28. , 26b are deflected and deviate from the heads of the intake valves 16a, 16b and adhere to the inner wall of the intake port.

FIG. 3 shows an example of actually measured values of a change in the speed of the airflow passing through the communication portion 28a with respect to the crank angle. According to the research of the present applicant, the velocity of the air flow passing through the communication portion 28a shows a change with respect to the crank angle as shown in FIG. 3 regardless of the displacement and the number of revolutions of the engine. It is almost zero, and then gradually increases in speed, showing a sharp increase from around 40 degrees after top dead center. Therefore, when the fuel injection is continued until 40 degrees after the top dead center of the intake air, the air flow causes the deflection of the injected fuel. FIG. 4 shows the measurement results of the NO _X amount in the exhaust gas when the fuel injection amount is kept constant and the injection end timing is changed. The NO _X amount shows a change similar to that shown in FIG. 3, and increases sharply when the fuel injection end timing is about 40 degrees or later, indicating that the influence of the deflection of the injected fuel by the air flow passing through the communication portion 28a is large. Is shown. From the above, it can be seen that the fuel injection needs to be completed at the latest up to 40 degrees after the intake top dead center, preferably before 30 degrees.

In normal fuel injection control, fuel injection is started at a constant crank angle after top dead center, and the injection completion timing is not constant because the crank angle at which injection is completed is determined by the fuel injection amount (injection time). However, in this embodiment, the fuel injection start timing is adjusted in accordance with the fuel injection amount (time), and the airflow passing through the communication portion is fixed in each cylinder so that the fuel injection completion timing is fixed at 30 degrees after the intake top dead center. The effect of is prevented. As a method of controlling the fuel injection completion crank angle to be constant as described above, there is a method proposed by the present applicant in Japanese Patent Application Laid-Open No. 56-148636. In the present embodiment, the following control is performed by a method similar to this method. It is. That is, in this embodiment, the ECU
The 50 has a built-in free-running counter, which keeps a reference time during operation. The control of the fuel injection timing is performed based on the time from the stroke reference point of each cylinder by the above timing. Now, for example, if the bottom dead center of the exhaust stroke of each cylinder is set as the reference point, the point 30 degrees after the top dead center of the intake stroke at which fuel injection is completed is equivalent to a crank rotation angle of 210 degrees from the reference point (bottom dead center of the exhaust stroke). I do. The time Tc (millisecond) required for this rotation is Tc = 6000 × 210/360 × 1 / N, where N is the number of rotations. Further, assuming that the fuel injection time of each fuel injection valve is t _i ,
The time Ts (millisecond) from the reference point to the start of fuel injection is Ts =
The Tc-t _i. Therefore, the fuel injection of each cylinder is started at the elapse of Ts milliseconds after reaching the stroke reference point of each cylinder, and the fuel injection can always be completed at 30 degrees after the top dead center of the intake stroke if performed only for t _i milliseconds. .

In the above calculation, the engine speed N is a crank angle sensor
It is calculated by counting the pulses NE transmitted at every crank rotation angle of 30 degrees from 56, and the reference point (exhaust bottom dead center) of each cylinder is detected by the number of pulses NE after the input of the reference pulse G1. That is, when the pulse G1 is input, it indicates that the first cylinder has reached the reference point. Hereinafter, in the case of a four-cylinder engine, when the pulse NE number input simultaneously with the pulse G1 is counted as 1, the seventh, thirteenth, and nineteenth cylinders are counted. Are detected as the reference points of the third, fourth, and second cylinders, respectively.

FIG. 5 is a flowchart showing the fuel injection timing control operation of the ECU 50. This control routine is executed, for example, every 180 degrees of the crank rotation angle, but may be executed as a part of the main routine.

In the figure, when the routine starts in step 500, in step 510, the engine speed N and the intake air flow rate Q are read. Here, the engine speed N is obtained from the above-mentioned pulse NE, and the intake air amount Q is obtained from the output of an air flow meter (not shown) provided in the intake pipe.

Basic value t _p of the next step 520 the fuel injection amount is set. The fuel injection amount is expressed as a fuel injection time (millisecond), and in this embodiment, is read from a map stored in the ECU 50 using the intake air amount Q / N per one revolution of the engine. Then the cooling water temperature t _p set in step 510 In step 530, is determined from the operating conditions such as load conditions by multiplying the correction coefficient α fuel injection time t _i is calculated. Then step 540
Time required from the stroke reference point (exhaust bottom dead center) at the engine speed N to the completion of fuel injection (30 degrees after intake top dead center)
The time Ts from the stroke reference point to the point at which fuel injection should be started is calculated from Tc and T _i from Tc and t _i , and Ts and t _i are output to the output port in step 560, and the routine ends.

Fuel injection valves 26 of each cylinder based on the measurement of the aforementioned free-running counter, the fuel injection start after reaching after Ts msec stroke reference point of each cylinder is driven to perform a t _i milliseconds injection , Fuel injection completion time is always after intake top dead center
Keep at 30 degrees.

In the present embodiment, the bottom dead center of the exhaust stroke is taken as the stroke reference point of each cylinder, but, for example, the intake top dead center or the like may be set as the reference point. Further, in the present embodiment, the ratio between the intake air amount Q and the engine speed N is used for setting the fuel injection time t _i , but the present invention is also applicable when the injection time is set by another appropriate method. It is possible.

〔The invention's effect〕

The present invention reduces the fuel injection of each cylinder at least 40
The combustion state is controlled by controlling the injection start timing according to the fuel injection amount so as to be completed later, thereby preventing the influence of the air flow generated in the partition wall communication portion when the intake control valve is closed on the injected fuel. improved, it is made possible to achieve improved and NO _X reduction in the exhaust gas of the engine performance in a lean air-fuel ratio at the same time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating the configuration of an embodiment of the present invention, and FIG.
Fig. A is a view showing details of a fuel injection valve mounting portion and a communicating portion of an intake pipe partition, Fig. 2B is a cross-sectional view taken along line BB of Fig. 2A, and Fig. 3 is a diagram passing through a partition communicating portion. FIG. 4 is a diagram showing the relationship between the fuel injection completion timing and the NO _X amount in the exhaust gas, and FIG. 5 is a flowchart showing the control operation of the fuel injection timing. 12a ... Helical intake port, 12b ... Straight intake port, 16a, 16b ... Intake valve, 26 ... Fuel injection valve, 26a, 26b ... Injection port, 28 ... Partition wall, 28a ... Communication part, 32 ... ... intake control valve 40 ... diaphragm, 44 ... electromagnetic three-way switching valve, 50 ... control circuit (ECU).

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location F02D 43/00 301 F02D 43/00 301U 301J (56) References JP-A-1-182540 (JP, A) JP-A-64-66434 (JP, A) JP-A-61-261638 (JP, A) JP-A-59-77045 (JP, A) Fully open Showa 61-147336 (JP, U) Really open Showa 62 -12771 (JP, U) Fully open 1986-186725 (JP, U)

Claims (1)

(57) [Claims] An intake passage communicating with an intake port of an internal combustion engine is divided into two by a partition extending in an intake flow direction, and one of the divided intake passages has a helical shape for generating a swirl in a combustion chamber by an intake flow. Introducing the swirl port and guiding the other intake passage to a straight port of a straight shape, and providing an intake control valve to close the straight port side intake passage by closing the intake passage at the time of engine light load operation,
An internal combustion engine provided with a fuel injection valve having two injection ports opened to a downstream portion of an intake control valve of the partition and injecting fuel toward both the swirl port and the straight port, at least the intake control A fuel supply method for an internal combustion engine, wherein the fuel injection from the fuel injection valve is completed at least 40 degrees after the top dead center of the intake stroke when the valve is closed.