JP2014173577A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device of an internal combustion engine capable of preventing reduction in output of an engine and deterioration of an exhaust gas purifying performance due to blow-back of an air-fuel mixture blown to an intake pipe from a combustion chamber, to the intake pipe, in the internal combustion engine including a fuel injection valve injecting a fuel into the intake pipe.SOLUTION: A fuel injection control device of an internal combustion engine including a fuel injection valve injecting a fuel into an intake pipe, includes control means executing avoidance fuel injection by injecting fuel while avoiding a blow-back generation timing when a blow-back of a gas in a combustion chamber to the intake pipe side occurs, immediately after start of valve opening of an intake valve.

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine capable of improving the fuel consumption of the internal combustion engine.

In a conventional fuel injection control device for an internal combustion engine, there is an apparatus having a variable valve timing mechanism that can arbitrarily change the opening timing and period of an intake valve or an exhaust valve for the purpose of improving fuel consumption and output of the internal combustion engine. It is used.
In addition, low penetration type fuel injection valves have been used due to the recent urgency in improving fuel efficiency.
This low-penetration type fuel injection valve is a fuel injection valve having a feature that atomized fuel is made finer by reducing the injection strength at the time of fuel injection compared to the conventional fuel injection valve.
As a result, it is possible to reduce the amount of fuel adhering to the intake pipe and the inner wall of the combustion chamber and to improve the mixing efficiency with air to improve the homogenization with air.

Japanese Patent No. 4916544

However, in an internal combustion engine having both the variable valve timing mechanism and the low-penetration type fuel injection valve, the overlap period in which the intake valve and the exhaust valve are opened simultaneously is prolonged, and the fuel injection is performed during the overlap period. If it is performed, and if the engine speed is low and fuel injection is performed during the overlap period, the momentum of the injected fuel droplets is small and the state of low penetration In some cases, the air is blown back to the upstream side of the intake pipe (also referred to as “blow back”).
In this case, there is a problem that necessary fuel is not introduced into the combustion chamber of the internal combustion engine, and sufficient output and fuel consumption performance cannot be obtained.
In addition, the fuel blown back to the upstream side of the intake pipe adheres to the intake pipe wall, which causes a disadvantage of deteriorating exhaust gas purification performance.

As a prior art regarding the fuel injection control device of the internal combustion engine, there is one disclosed in Patent Document 1.
The one disclosed in Patent Document 1 performs fuel injection a plurality of times for each cylinder in one cycle, and one of these injections is made into the intake passage while the intake valve is open. This is performed in accordance with a period in which the gas in the cylinder is blown back.
Thus, fuel evaporation and air mixing can be promoted, and fuel consumption and exhaust gas cleanliness can be improved.
However, in the above low penetration type fuel injection valve, since the injection strength is weaker than before, the fuel injected by blowing back the gas in the cylinder is not introduced into the combustion chamber, leading to a decrease in engine output, There is an inconvenience that the fuel consumption is deteriorated due to the fuel increase injection due to the engine output reduction.
Further, exhaust gas deviates from a predetermined air-fuel ratio, exhaust gas purification by the catalyst is not performed, and exhaust gas purification performance deteriorates.

  The present invention relates to an internal combustion engine having a fuel injection valve that injects fuel into an intake pipe, in which an air-fuel mixture from a combustion chamber to the intake pipe blows back into the intake pipe, thereby reducing output of the internal combustion engine and deterioration of exhaust gas purification performance. An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can be prevented.

  Accordingly, in order to eliminate the above-described disadvantages, the present invention provides a fuel injection control device for an internal combustion engine that includes a fuel injection valve that injects fuel into the intake pipe, to the intake pipe side immediately after the start of opening of the intake valve. Control means for performing avoidance fuel injection for performing fuel injection while avoiding a blowback generation period in which gas blowback in the combustion chamber occurs is provided.

  According to the present invention, a required amount of fuel injected by blowing back the gas injected into the intake pipe is not introduced into the combustion chamber, reducing the output of the internal combustion engine, the fuel consumption performance, and the exhaust gas purification performance. Invitation can be prevented.

FIG. 1 is a control flowchart of a fuel injection control device for an internal combustion engine. (Example) FIG. 2 is a schematic system diagram of a fuel injection control device for an internal combustion engine. (Example) FIG. 3 is a view showing the movement of the exhaust valve / intake valve. (Example)

  Embodiments of the present invention will be described below in detail with reference to the drawings.

1 to 3 show an embodiment of the present invention.
In FIG. 2, reference numeral 1 denotes a fuel injection control device.
The fuel injection control apparatus 1 includes an internal combustion engine 2, an intake pipe 4 whose downstream end communicates with a combustion chamber 3 of the internal combustion engine 2, an intake passage 5 formed in the intake pipe 4, and the intake air A fuel injection valve 6 that injects fuel into the passage 5, an intake valve 7 that opens and closes a downstream end of the intake passage 5, an exhaust pipe 8 whose upstream end communicates with the combustion chamber 3, and this exhaust An exhaust passage 9 formed in the pipe 8 and an exhaust valve 10 for opening and closing the upstream end portion of the exhaust passage 9 are provided.
A throttle body 12 having a throttle valve 11 is disposed in the intake passage 5 upstream of the fuel injection valve 6.
Further, in the intake passage 5, a load sensor (also referred to as “air flow sensor”) 13 for detecting an engine load is provided between the throttle body 12 and the fuel injection valve 6.
The internal combustion engine 2 is provided with a rotation speed sensor 14 for detecting the engine rotation speed.

Further, in the fuel injection control device 1 of the internal combustion engine 2, avoid the blow-back generation period in which the gas in the combustion chamber 3 is blown back to the intake pipe 4 side immediately after the intake valve 7 starts to open. The control means 15 which performs the avoidance fuel injection which performs fuel injection is provided.
More specifically, as shown in FIG. 2, the control means 15 includes a valve overlap calculation unit 16, an engine speed determination unit 17, an injection mode determination unit 18, a split injection instruction unit 19, and a single injection instruction. On the other hand, a control signal for changing the valve opening timing is output to the variable valve timing mechanism 21.
That is, the valve overlap calculator 16 calculates the overlap state between the intake valve 7 and the exhaust valve 10.
The engine speed determination unit 17 receives a detection signal from the speed sensor 14 and performs a comparison determination with a predetermined speed set in advance.
Further, the injection mode determination unit 18 sets the control content by the control means 15 of the fuel injection control device 1, that is, the injection mode from the fuel injection valve 6.
The divided injection instruction unit 19 outputs a control signal to the fuel injection valve 6 to instruct divided injection control when the injection form by the injection form determination unit 18 is divided injection.
The single-stage injection instruction unit (also referred to as “single injection instruction unit”) 20 outputs a control signal to the fuel injection valve 6 when the injection mode determined by the injection mode determination unit 18 is single injection. The single injection control is instructed.
The variable valve timing mechanism 21 changes the valve opening timing of the intake valve 7 and the exhaust valve 10 so that when the control signal from the control means 15 is input, the valve opening timing according to the control signal is reached. To do.
As a result, the required amount of fuel injected by blowing back the gas injected into the intake pipe 4 is not introduced into the combustion chamber 3, and the output of the internal combustion engine 2 and the fuel consumption performance are reduced. It can prevent the purification performance from deteriorating.

The fuel injection control device 1 includes the variable valve timing mechanism 21 that changes the valve opening timing of at least one of the exhaust valve 10 and the intake valve 7, and the rotation speed sensor 14 that detects the engine speed. It has.
The fuel injection control device 1 avoids fuel injection when the overlap amount that both the exhaust valve 10 and the intake valve 7 are opened is equal to or greater than a predetermined value and the engine speed is smaller than the predetermined speed. The structure which performs is provided.
That is, the control means 15 of the fuel injection control device 1 determines whether or not the overlap amount calculated by the valve overlap calculation unit 16 is greater than or equal to a predetermined value, and the engine speed determination unit 17 A comparison determination result between the actual engine speed from the speed sensor 14 and a predetermined speed set in advance is input.
The control means 15 controls to perform avoidance fuel injection when the overlap amount is not less than a predetermined value and the engine speed is smaller than the predetermined speed.
Thereby, it is possible to determine whether or not the avoidance fuel injection is necessary from the overlap amount and the engine speed.

Further, the fuel injection control device 1 includes the split injection instructing unit 19 that performs fuel injection during an exhaust stroke when the exhaust valve 10 is opened and during an intake stroke when the intake valve 7 is opened, and detects an engine load. The load sensor 13 is provided.
The fuel injection control device 1 is configured to increase the fuel injection amount during the intake stroke with respect to the fuel injection amount during the exhaust stroke as the engine load increases.
In other words, the control means 15 of the fuel injection control device 1 inputs a detection signal from the load sensor 13, and when the engine load increases, the fuel during the intake stroke increases with the engine load. The injection amount is increased with respect to the fuel injection amount during the exhaust stroke.
Thus, while performing the avoidance fuel injection, the fuel injection amount during the intake stroke is increased with respect to the fuel injection amount during the exhaust stroke in accordance with the engine load, thereby reducing the temperature in the combustion chamber 3 in an early stage. Generation of ignition and the like can be prevented.

In addition, as shown in FIG. 3, when the exhaust valve 10 starts to open from the EVO position, the piston (not shown) of the internal combustion engine 2 becomes the bottom dead center BDC position.
When the exhaust valve 10 is further opened, it operates in the closing direction from the maximum opening.
During the closing operation of the exhaust valve 10, the intake valve 7 starts to open from the IVO position, and the piston reaches the top dead center TDC position.
Thereafter, the exhaust valve 10 is fully closed at the EVC position.
Further, when the intake valve 7 is further opened, the intake valve 7 operates in the closing direction from the maximum opening degree, and after passing through the bottom dead center BDC position of the piston, is fully closed at the IVC position.
At this time, the overlap between the intake valve 7 and the exhaust valve 10 occurs between the IVO position where the intake valve 7 starts to open and the EVC position where the exhaust valve 10 is fully closed.

  Next, the operation will be described along the control flowchart of the fuel injection control device 1 of the internal combustion engine 2 shown in FIG.

When the control program of the fuel injection control device 1 of the internal combustion engine 2 is started (101), the process proceeds to valve overlap amount calculation, engine speed detection, and engine load detection processing (102).
That is, in this process (102), the valve overlap calculation unit 16 of the control means 15 calculates the overlap amount between the intake valve 7 and the exhaust valve 10, and the control means 15 rotates the rotation. The engine speed detection signal from the number sensor 14 and the engine load detection signal from the load sensor 13 are input.
After this process (102), the overlap amount is a predetermined value or more, that is,
The overlap amount ≧ predetermined value and the engine speed is smaller than the predetermined speed, that is,
The process proceeds to a determination (103) as to whether or not the engine rotational speed <the predetermined rotational speed.
In this determination (103), a predetermined value and a predetermined number of revolutions are set in advance and stored in map data or the like, and the overlap amount calculated by the valve overlap calculating unit 16 by the control means 15 is set to a predetermined value. It is determined whether or not the engine speed is greater than or equal to a value, and it is determined whether or not the actual engine speed from the engine speed sensor 14 by the engine speed determination unit 17 is smaller than a predetermined engine speed.
If the determination (103) is YES in the determination (103), the process proceeds to the avoidance fuel injection execution / divided injection processing (104).
That is, in this process (104), it is determined that the influence of the blow-back is large, and the avoidance fuel injection and the split injection are performed. The larger the engine load, the larger the fuel injection amount during the intake stroke. .
If it adds, in this process (104), it will control by the said control means 15 to implement avoidance fuel injection.
Further, the control means 15 increases the fuel injection amount during the intake stroke with respect to the fuel injection amount during the exhaust stroke as the engine load increases.
The above overlap amount is a predetermined value or more, that is,
The overlap amount ≧ predetermined value and the engine speed is smaller than the predetermined speed, that is,
If the determination (103) is NO in the determination (103) as to whether or not the engine speed is less than the predetermined speed, the process proceeds to the avoidance fuel injection prohibition / single-stage injection process (105).
That is, in this process (105), it is determined that the influence of the blowback is small, the avoidance fuel injection is prohibited, and the single-stage injection is performed without performing the split injection.
After the avoidance fuel injection execution / divided injection processing (104) and the avoidance fuel injection prohibition / single stage injection processing (105), the control program for the fuel injection control device 1 of the internal combustion engine 2 is executed. To the end (106).

  The present invention is not limited to the above-described embodiments, and various application modifications can be made.

For example, in the embodiment of the present invention, the number of fuel injection valves that perform split injection is not limited, and the operation is described as one fuel injection valve. However, two or more fuel injection valves are provided in one combustion chamber. It is also possible to have a special configuration of an internal combustion engine having
That is, for example, when two fuel injection valves are provided in one combustion chamber of an internal combustion engine, two fuel injections differing between the first fuel injection and the second fuel injection in divided injection. It is set as the structure performed by a valve alternately.
Then, since fuel injection is performed from each fuel injection valve, more accurate fuel injection can be performed than when split injection is performed by one fuel injection valve.
Specifically, even if the fuel injection interval between the first time and the second time is short and the second fuel injection cannot be sufficiently performed after the first fuel injection, two fuels Since the injection valves are provided and operated alternately, fuel injection can be reliably performed.

DESCRIPTION OF SYMBOLS 1 Fuel-injection control apparatus 2 Internal combustion engine 3 Combustion chamber 4 Intake pipe 5 Intake passage 6 Fuel injection valve 7 Intake valve 8 Exhaust pipe 9 Exhaust passage 10 Exhaust valve 11 Throttle valve 12 Throttle body 13 Load sensor (It is also called an "air flow sensor." )
DESCRIPTION OF SYMBOLS 14 Rotational speed sensor 15 Control means 16 Valve overlap calculation part 17 Engine rotational speed determination part 18 Injection form determination part 19 Split injection instruction | indication part 20 Single stage injection instruction | indication part 21 Variable valve timing mechanism

Claims (3)

  In a fuel injection control device for an internal combustion engine having a fuel injection valve for injecting fuel into an intake pipe, a blow-back occurrence period in which gas in the combustion chamber is blown back to the intake pipe immediately after the intake valve is opened A fuel injection control device for an internal combustion engine, comprising control means for performing fuel injection while avoiding fuel injection.   A variable valve timing mechanism that changes the valve opening timing of at least one of the exhaust valve and the intake valve, and a rotation speed sensor that detects the engine rotation speed, and the exhaust valve and the intake valve are both opened. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the avoidance fuel injection is performed when the lap amount is a predetermined value or more and the engine speed is smaller than the predetermined speed.   In addition to a split injection instruction unit that performs fuel injection during an exhaust stroke when the exhaust valve is opened and during an intake stroke when the intake valve is opened, a load sensor that detects an engine load is provided, and intake air is increased as the engine load increases. The fuel injection control device for an internal combustion engine according to claim 2, wherein the fuel injection amount during the stroke is increased with respect to the fuel injection amount during the exhaust stroke.

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