JPH05288095A - Fuel injection timing controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent adhesion on the wall face of an intake passage, of fuel injected to the straight port side of an internal combustion engine which includes an intake control valve which generates an intake swirl and allows fuel injection to a swirl port and the straight port. CONSTITUTION:Fuel injection is applied to a swirl port 12a and a straight port 12b from a fuel injection valve 26. A communication passage 27 which allows communication between both ports 12a,12b is provided on a partitioning wall 28 located downstream of the fuel injection valve 26, so that the fuel injection to the straight port side when an intake control valve 32 is closed is atomized by airstream which flows from the swirl port side to the straight port side through the communication passage 27. The fuel injection must be finished before air flow speed becomes excessively large for the purpose of preventing the fuel from adhering on the wall face, but the air flow speed is varied depending on an air leaking quantity at the time of closing the intake control valve 32. Accordingly, the air leaking quantity is determined by a control circuit (ECU) 50 on the basis of the opening of a throttle valve 22, engine speed, an intake air quantity and the like, and a fuel injection timing is adjusted so as to prevent the adhesion of fuel on the wall face.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection timing control system for a fuel injection type internal combustion engine having a swirl intake port, a straight intake port and an intake control valve.

[0002]

2. Description of the Related 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. This intake control valve is provided for the purpose of operating the engine by switching between a lean air-fuel ratio and a rich air-fuel ratio according to the load condition.For example, when the engine has a low load and a low rotation speed, the intake control valve is closed and intake air on the straight port side is closed. The lean air-fuel ratio operation is performed by closing the passage and switching the fuel injection amount and the ignition timing.

By closing the intake control valve to allow most of the fresh air to flow into the cylinder from the swirl port and to generate a strong swirl of the air-fuel mixture in the combustion chamber, stable combustion is achieved even at a lean air-fuel ratio. Fuel consumption can be reduced. On the other hand, when the engine is under high load and high rotation, the intake control valve is opened to increase the intake air amount to the cylinder, and the fuel injection amount and the ignition timing are set to the rich air-fuel ratio (or theoretical) according to the opening operation of the intake control valve. It is possible to secure high output of the engine by switching to the (air-fuel ratio) side.

In an engine equipped with an intake control valve, various considerations have been given to the arrangement of fuel injection valves and the fuel injection method. It is generally effective to inject fuel into both the swirl port and the straight port in synchronization with the intake valve opening timing in order to expand the lean side limit of the air-fuel ratio of the air-fuel mixture and improve the response during transition. As an engine of this type, there is an engine disclosed in Japanese Utility Model Publication No. 61-147336. In the engine described in the publication, a fuel injection valve having two injection ports that open toward both ports is arranged in a partition wall that divides the intake passage into a straight port side and a swirl port side, and a single fuel is provided. By injecting fuel to both ports with the injection valve, the same effect as that of providing a fuel injection valve for each port is obtained.

When fuel is injected into both the swirl port and the straight port as in the device of Japanese Utility Model Laid-Open No. 61-147336, a partition wall immediately downstream of the fuel injection valve connects the intake passages of both ports. It has been found that the provision of passages is necessary to improve fuel atomization. That is, the fuel injected from the fuel injection valve in synchronism with the intake valve opening timing is normally atomized by the intake flow flowing through the intake passage and flows into the combustion chamber. Intake flow through the passage is low. For this reason, the fuel injected to the straight port side while the intake control valve is closed flows into the combustion chamber without being atomized, and NOx in the exhaust gas increases. Therefore, the communication passage is provided, and when the intake control valve is closed, an air flow that flows from the swirl port side into the low pressure straight port through the communication passage is generated, and this air flow atomizes the fuel injected to the straight port side. It is necessary to do so. However, if the airflow velocity through this communication passage is too high, the fuel injected into the straight port side will flow into the airflow through the communication passage without being sufficiently atomized, and the wall surface facing the communication passage of the straight port side intake passage will Crash into,
It causes a sticking problem. This deposited fuel flows down the wall surface and flows into the combustion chamber in a liquid state.
The amount of x will increase.

In order to prevent this problem, the intake control valve is usually made so as to cause some leakage even when the valve is closed. Even when the intake control valve is closed, the air flow flowing through the intake control valve to the straight port side is prevented. It can be secured. This prevents a large negative pressure in the intake passage on the downstream side of the intake control valve, and reduces the pressure difference between the intake passage and the intake passage on the swirl port side, which reduces the air flow velocity through the communication passage and prevents fuel from adhering to the wall surface. To be prevented.

Further, in the previous application, the applicant of the present application has already proposed to reduce the fuel adhesion on the wall surface by setting the fuel injection end timing to 40 degrees before the top dead center of the intake stroke (Japanese Patent Application No. Hei 10-135242). 2-157702). The airflow velocity flowing from the swirl port side to the straight port side through the communication passage increases as the intake stroke progresses after the intake valve opens.
It has been experimentally confirmed that the flow velocity rapidly increases near 40 degrees after the top dead center of the intake stroke (see Fig. 2). Therefore, fuel injection of each cylinder should be completed before 40 degrees after top dead center. As a result, it is possible to minimize the adhesion of the injected fuel on the wall surface due to the air flow passing through the communication passage.

[0008]

As described above, the velocity of the airflow flowing from the swirl port side to the straight port side through the communication passage changes depending on the amount of leaked air when the intake control valve is closed. However, the amount of leaked air from the intake control valve may change over time and is not constant. For example, when the blow-by gas is recirculated by PCV or EGR (exhaust gas recirculation) for reducing exhaust emission is performed, dirt components in the exhaust gas adhere to the intake control valve body to reduce the clearance. The amount of leaked air may decrease.

Therefore, even if the communication passage airflow velocity is appropriately set at the start of use, if the communication passage airflow velocity increases thereafter due to a decrease in the leakage air amount of the intake control valve, fuel may adhere to the wall surface. The above-mentioned Japanese Patent Application No. 2-1577
Even if the fuel injection is terminated before the airflow passing through the communication passage reaches the maximum flow velocity, as in the device No. 02, if the amount of leaked air decreases, the flow velocity of the airflow passing through the communication passage generally increases. Therefore, even if the maximum flow velocity is not reached, the injected fuel may adhere to the wall surface.

In view of the above problems, the present invention detects the amount of leaked air from the intake control valve and controls the fuel injection timing according to this amount of leaked air to prevent fuel from adhering to the wall surface without being affected by aging. It is an object of the present invention to provide a fuel injection timing control device for an internal combustion engine that can be effectively prevented.

[0011]

Means for solving the above problems are shown in FIG. In FIG. 1, an intake control valve B is provided in the intake passage that follows the straight port of the internal combustion engine A. Further, the leak air amount detecting means D detects the leak air amount flowing into the internal combustion engine A through the intake control valve B when the intake control valve B is closed, and the injection timing setting means E responds to the detected leak air amount. To set the fuel injection end timing.

The control means F determines the fuel injection amount based on the load condition of the internal combustion engine and controls the fuel injection valve C to end the fuel injection at the fuel injection end timing set by the injection timing setting means E. ..

[0013]

The operation of the present invention will be described with reference to FIG. Figure 2
Shows the change of the air velocity flowing from the swirl port side to the straight port side with respect to the crankshaft rotation angle through the partition passage when the intake control valve is closed. As shown in the figure, the airflow velocity rapidly increases around 40 degrees after the top dead center of the intake stroke of the crankshaft rotation angle.

Therefore, in order to prevent the fuel from adhering to the wall surface, it is necessary to finish the initial setting of the fuel injection timing before the communication passage airflow velocity reaches the maximum velocity, as shown by the section A in FIG. However, when the leakage air amount of the intake control valve changes, the communication passage airflow velocity changes according to the leakage air amount. For example, when the amount of leaked air is reduced, the communication passage airflow velocity is generally higher than the flow velocity I at the initial setting as shown by the dotted line II in FIG. 2, so the fuel injection timing at the initial setting (FIG. 2, section If the condition of A) is maintained, the airflow velocity of the communicating passage at the time of fuel injection becomes excessively high and the injected fuel adheres to the wall surface.

On the other hand, when the amount of leaked air increases, on the other hand, the airflow velocity of the communication passage decreases overall as shown by the dotted line III in FIG. Atomization of the injected fuel becomes insufficient due to the decrease in the passage airflow velocity. In the present invention, the injection timing setting means E changes the fuel injection end timing according to the leak air amount detected by the leak air amount detecting means D. That is, the amount of leaked air is small,
When the communication passage airflow velocity is high (dotted line II), the fuel injection timing is advanced from the initial setting (section A), and the fuel injection is terminated before the communication passage airflow velocity becomes excessive (section B in FIG. 2).
This prevents the fuel from adhering to the wall surface. Also, if there is a large amount of leaked air and the airflow velocity in the communication passage is low (dotted line II
Conversely, the fuel injection timing is set to be delayed in (I) (section C in FIG. 2). As a result, fuel injection is performed at a time when the communication passage airflow velocity is relatively high, and atomization of the injected fuel is improved by the airflow passing through the communication passage.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 3 is a schematic diagram showing the structure of an internal combustion engine that employs the fuel injection timing control device of the present invention. In the figure, 10 is a cylinder block, 12 is a combustion chamber, 14 is a spark plug, 12a and 12b are intake ports, and two intake valves 16a and 16 are provided for each intake port and exhaust port.
b, a so-called four-valve configuration in which two exhaust valves 18a and 18b are provided is shown. The first intake port 12a is of a helical type and has a shape that is convenient for forming an intake swirl. The second intake port 12b is a straight type.

An intake control valve 32 as a butterfly valve is provided in the intake passage following the straight intake port 12b. When the intake control valve 32 is closed, the intake control valve 32 is provided in the intake passage on the straight port 12b side. Air is introduced only through the gap between the periphery of the valve 32 and the wall surface of the intake passage. When the intake control valve 32 is closed, most of the intake air flows into the engine cylinder from the helical port 12a, and a powerful swirl (swirl flow) of the intake air is generated in the cylinder, so that stable lean mixture combustion is possible. Become. Intake control valve 32
Is opened, air is introduced from both intake ports 12a and 12b, and the intake amount increases. A lever 34 is attached to the 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 is composed of a diaphragm 40 and a spring 41. When the negative pressure is not applied to the diaphragm 40, the spring 41
The diaphragm 40 is pushed to the left in the figure, and the intake control valve 32 takes the open position. When a negative pressure is applied to the diaphragm 40, the diaphragm 40 moves to the spring 41.
The intake control valve 32 is in a position to close the intake port 12b by being pulled rightward against the.

The diaphragm 40 is connected to a negative pressure tank 45 via an electromagnetic three-way switching valve 44. Further, the negative pressure tank 45 is connected via a check valve to the negative pressure extraction port 24 provided on the downstream side of the throttle valve 22 of the intake pipe 20. The check valve 46 holds the negative pressure applied to the diaphragm 40. The switching valve 44 has three ports 44
a, 44b, 44c are provided, and port 4 is used for static elimination
The diaphragm 40 is communicated with the negative pressure port 24 by communicating with 4a and 44b, the ports 44a and 44c are communicated with each other when energized, and the diaphragm 40 is communicated with the atmosphere.

A fuel injection valve 26 is arranged on a partition wall 28 which separates the helical intake port 12a from the straight intake port 12b. The fuel injection valve 26 has two injection ports 26a and 26b in one body.
a and 26b are the intake valve 16a of the helical intake port 12a and the intake valve 1 of the straight intake port 12b, respectively.
It is provided so as to face the back surface of the umbrella portion 6b. Therefore, the fuel injected at the time of opening the intake valves 16a and 16b collides with the back surface of the intake valve umbrella portion, scatters, is atomized into the cylinders, and a uniform air-fuel mixture is formed in the combustion chamber.

A communication passage 27 that connects the helical port 12a and the straight port 12b is provided in a partition wall 28 immediately downstream of the injection ports 26a and 26b of the fuel injection valve 26. 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. The control circuit (ECU) 50 is configured as, for example, a microcomputer system, and the solenoid valve 4 is formed by a known method.
In addition to controlling the switching timing of No. 4 and the injection time (injection amount) of the fuel injection valve 26, the fuel injection timing of the fuel injection valve 26 is controlled as described later. For this purpose the control circuit (EC
U) 50 receives pulses G1 and NE representing crankshaft rotation angles, respectively, from crank angle sensors 54 and 56 provided in the engine distributor. The pulse G1 transmitted from the first crank angle sensor 54 is for detecting the reference position, and for example, the crankshaft rotation 720 is performed every time the first cylinder of the engine reaches the exhaust bottom dead center.
It is sent once every time. In addition, the second crank angle sensor 5
6 emits a pulse NE every 30 degrees of crankshaft rotation.
The ECU 50 calculates the engine speed by counting the number of pulses NE per unit time, and the reference pulse G
The phase of each cylinder stroke can be detected by counting the number of pulses NE after one input.

Further, in this embodiment, the throttle valve 22 of the engine intake pipe is provided with a throttle opening sensor 58 for inputting a signal corresponding to the throttle valve opening TA to the ECU 50, and also upstream of the throttle valve 22. An air flow meter 60 is provided in the side intake pipe and a cooling water temperature sensor 62 is provided in the engine cooling water passage.
And a signal corresponding to the engine cooling water temperature THW
You have entered 0.

In the present embodiment, the ECU 50 controls the fuel injection timing to a predetermined set timing according to the operating conditions, and adjusts the above set timings according to the leakage air amount of the intake control valve 32 as described above. is doing. FIG. 4 shows the relationship between the fuel injection timing and the change in the airflow velocity through the communication passage in this embodiment.

The horizontal axis of FIG. 4 shows the crankshaft rotation angle with reference to the intake top dead center, and the curve V on the upper part of the horizontal axis shows the change of the communication passage airflow velocity with respect to the crank rotation angle. Further, a symbol IO on the lower side of the horizontal axis indicates a period during which the intake valve is open. In this embodiment, as the fuel injection timing when the intake control valve is closed, the sections indicated by A1 and A2 in the figure are selected according to the engine operating conditions.

That is, when the engine is cold, the section A1 in FIG. 4 is selected, and the fuel injection is finished at the beginning of the intake stroke (FIG. 4, a1). As a result, even when the intake control valve is closed, fuel injection is finished at a time when the communication passage airflow velocity is low, and fuel is prevented from adhering to the wall surface. The blowback can be used to accelerate the vaporization of the fuel.

When the intake control valve is closed after the engine has been warmed up, the section A2 in FIG. 4 is selected, and the fuel injection is slightly earlier than the top dead center of 40 degrees at which the communication passage airflow velocity becomes maximum (FIG. 4, a2) The process is completed. This makes it possible to atomize the fuel by using the air flow passing through the communication passage while preventing the injected fuel from adhering to the wall surface. Although not shown, during the valve opening operation of the intake control valve after warm-up is completed (high load operation), fuel injection is performed over the entire intake valve opening period. In this state, there is no air flow through the communication passage, but since the intake control valve is open, an intake air flow is also generated in the straight port side intake passage, and the fuel injected into the straight port side is atomized by this air flow. Is sucked into the cylinder. Therefore, the intake air cooling effect due to the vaporization of the fuel can be obtained throughout the intake stroke, and the intake volume efficiency can be improved and knocking can be prevented.

Further, in the present embodiment, the above-mentioned fuel injection end timings a1 and a2 are adjusted according to the change of the leak air amount of the intake control valve. FIG. 5 shows an example of a flow chart of the above-mentioned fuel injection end timing setting operation. This routine is executed by the ECU 50 at every constant crank rotation angle (for example, every 180 degrees).

When the routine starts in FIG. 5, in step 500, the engine cooling water temperature THW is read from the cooling water temperature sensor 62, the intake air amount Q is read from the air flow meter 58, and the engine speed N is read from the crank rotation angle sensor 56. Be done. Next, at step 502, it is judged from the cooling water temperature THW whether the engine is warmed up. In the present embodiment, if THW <40 ° C., it is determined that the engine is in a cold state, and the routine proceeds to step 504, where the fuel injection end timing AINJEND is the cold set value indicated by a1 in FIG. It is given as the sum of the correction value KINJEND due to the leaked air amount of the control valve. As a result, the fuel injection timing is set to the section A1 in FIG.

If THW ≧ 40 ° C. in step 504, it is determined that the engine is warmed up, and step 5
06 is executed. Step 506 is a determination of the engine load condition, and it is determined whether or not the intake air amount Q / N per engine revolution is smaller than a predetermined value K as a parameter representing the engine load. Here, the value of K is taken as the load at which the intake control valve opens. Q / N <in step 506
If it is K, that is, because the intake control valve closing operation is completed after warm-up is completed, the routine proceeds to step 508, and the fuel injection end timing AINJEND is the sum of the set value a2 after warm-up and the correction value KINJEND due to the amount of leak air Given as. As a result, the fuel injection timing is set to the section A2 in FIG.
Further, if Q / N ≧ K in step 506, it means that the intake control valve opening operation is performed after the warm-up is completed, and thus AINJEND.
Is set to a predetermined set value a3, and the correction based on the leaked air amount is not performed (step 510).

When the fuel injection end timing AINJEND is set by the routine of FIG. 5, the ECU 50 controls the fuel injection valve so that the fuel injection is ended at the set injection end timing AINJEND. That is, the ECU 50 obtains the crank angle at which fuel injection should be started from the set injection end timing AINJEND, the engine speed N, and the fuel injection amount (injection time) TI, and starts the injection from the stroke reference point (exhaust bottom dead center). The required time TS up to the crank angle is calculated based on the engine speed N.

Next, when it is detected from the outputs G1 and NE of the crank angle sensors 54 and 56 that the cylinder has reached the stroke reference point, the fuel injection of the cylinder is started after the time TS from that time and the injection is continued for the time TI. .. As a result, the fuel injection of each cylinder ends at the set timing AINJEND. Next, the determination of the correction value KINJEND of the fuel injection end timing according to the leaked air amount of the present embodiment will be described. As described above, the smaller the leaked air amount is, the higher the velocity of the airflow passing through the communication passage becomes.

In this embodiment, as shown in FIG. 6, KINJEND is changed substantially linearly with respect to the leak air amount Qm of the intake control valve. In addition, what is shown by Qmo in FIG. 6 is the initial (reference) leakage air amount at the time of starting the use of the engine. As shown in FIG. 6, KINJEND is set to a large negative value as the leak air amount decreases, so the value of AINJEND is set smaller as the leak air amount decreases, and the fuel injection end timing is earlier. Become.

Next, a method of calculating the leak air amount Qm from the intake control valve will be described. In this embodiment, the leak air amount Qm is calculated using the engine speed N, the throttle opening TA, and the intake air amount Q / N per engine revolution. There is a correlation between these parameters and the leak air amount Qm. For example, even if the throttle opening TA is the same, the larger the leak amount Qm, the smaller the resistance of the intake system, so the intake air amount increases.
Therefore, when the rotational speed N and the intake air amount (load) Q / N are held constant, the larger the Qm, the smaller the throttle opening TA. Similarly, the rotation speed N and the throttle opening TA
When Q and H are held constant, the intake air amount Q / N increases as Qm increases. Therefore, in the initial state of the engine, the leakage amount Qm is variously changed to measure the relationship between the engine speed N, the throttle opening TA, and the intake air amount Q / N to calculate the secular change of Qm from these parameters. can do.

FIG. 7 shows a routine for calculating the correction amount KINJEND as described above. This routine is executed by the ECU 5
The value 0 is executed at every constant rotation angle of the crankshaft. When the routine starts in FIG. 7, in step 700, the engine speed N, the throttle opening TA, and the intake air amount Q are input from the crank rotation angle sensor 56, the throttle sensor 60, and the air flow meter 58, respectively.
Next, at step 702, the leak air amount Qm of the intake control valve is calculated from the engine speed N, the throttle opening TA, and the intake air amount Q / N per engine revolution.

The relationship between Qm and N, TA, Q / N is previously obtained by actual measurement and is stored in the ECU 50 in the form of a map. Next, at step 704, the leakage air amount Qm calculated above and the reference leakage air amount Qmo are used to calculate the amount shown in FIG.
From this, the correction amount KINJEND of the fuel injection end timing is obtained.

As a result, the fuel injection timing is always set to an optimum value according to the leak air amount Qm of the intake control valve.

[0036]

As described above, according to the present invention, the amount of leaked air when the intake control valve is closed is detected and the fuel injection timing is adjusted according to the detected amount of leaked air. Therefore, the optimum fuel injection timing can always be set, and it is possible to prevent the injected fuel from adhering to the wall surface and improve atomization.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a diagram for explaining the operation of the present invention.

FIG. 3 is a schematic configuration diagram of an embodiment of an engine to which the fuel injection timing control device of the present invention is applied.

FIG. 4 is a diagram showing an example of fuel injection timing setting in the embodiment of FIG.

FIG. 5 is a flowchart showing a fuel injection timing setting operation.

FIG. 6 is a diagram showing a relationship between a leaked air amount and a fuel injection end timing correction amount.

FIG. 7 is a flowchart showing a correction operation of a fuel injection end timing based on a leak air amount.

[Explanation of Codes] 12a ... Swirl port 12b ... Straight port 16a, 16b ... Intake valve 22 ... Throttle valve 26 ... Fuel injection valve 27 ... Communication passage 28 ... Partition wall 32 ... Intake control valve 50 ... ECU 54, 56 ... Crank rotation angle Sensor 58 ... Air flow meter 60 ... Throttle sensor 62 ... Cooling water temperature sensor

Claims (1)

[Claims] 1. A swirl port and a straight port,
An intake control valve that closes the intake passage that follows the straight port when the engine load is low, and is provided at a position downstream of the intake control valve of a partition that separates the intake passage that follows the swirl port and the intake passage that follows the straight port, A fuel injection valve that injects fuel in two directions toward the swirl port and the straight port, and a communication passage that is provided in a partition wall on the downstream side of the fuel injection valve and that communicates with the intake passages that follow the ports. In a fuel injection timing control device for an internal combustion engine, comprising: a leakage air amount detection means for detecting an amount of leakage air from the intake control valve when the intake control valve is closed; and the fuel injection according to the leakage air amount. A fuel injector for an internal combustion engine, comprising: an injection timing setting means for setting a fuel injection end timing from the valve; and a control means for injecting fuel at the set timing. Charge injection timing control device.