JP2000018071A - Fuel injection controller of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly distribute each cylinder with injection fuel out of an auxiliary fuel injection valve by installing this auxiliary fuel injection valve capable of injecting fuel in an inlet manifold in common with all cylinders, and in the case where a fuel supply to an engine is shared to a main fuel injection valve and this auxiliary fuel injection valve, respectively. SOLUTION: This device is so constituted that an auxiliary fuel injection valve 5 is arranged at the inlet side of a collector 3a of an intake manifold 3, whereby it is made so as to inject (two turns and one injection) a portion of fuel for all cylinders at one time injection, while injection timing of the auxiliary fuel injection valve 5 is variably set up according to engine speed. In the concrete, the injection timing is delayed at the low speed side, while it is advanced at the high speed side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a direct injection spark ignition type internal combustion engine having a main fuel injection valve for directly injecting fuel into a combustion chamber for each cylinder.
An auxiliary fuel injection valve capable of injecting fuel into the intake manifold common to all cylinders is provided, and fuel injection is performed when fuel supply to the engine is shared between the main fuel injection valve and the auxiliary fuel injection valve under predetermined operating conditions. It relates to a control device.

[0002]

2. Description of the Related Art In recent years, a direct injection spark ignition type internal combustion engine has attracted attention. In this type, a combustion system is switched according to engine operating conditions, that is, by injecting fuel in an intake stroke. Homogeneous combustion, in which fuel is diffused into the combustion chamber to form a homogeneous mixture, and stratified combustion, in which fuel is injected in the compression stroke to form a layered mixture intensively around the spark plug, (See JP-A-59-37236).

[0003]

Incidentally, in such a direct injection spark ignition type internal combustion engine, apart from the main fuel injection valve which injects fuel directly into the combustion chamber for each cylinder, the intake manifold is common to all cylinders. Auxiliary fuel injection valve capable of injecting fuel is provided at predetermined operating conditions (at least during homogeneous combustion)
It has been considered that the auxiliary fuel injection valve is operated so that the fuel supply to the engine is shared between the main fuel injection valve and the auxiliary fuel injection valve.

[0004] This aims at the following effects. (1) Elimination of the region of insufficient fuel injection represented by high rotation and high load (2) Improvement of combustion by homogeneous intake (in the high rotation and high load region, the time from in-cylinder injection to ignition (evaporation time) (3) Improve the volumetric efficiency by cooling the intake air (takes latent heat of vaporization in the intake passage because the fuel is shortened, so that the fuel homogenized (homogenized mixture and vaporized) in the intake passage is supplied in advance to homogenize the cylinder) , Improve inhalation efficiency).

[0005] However, when the auxiliary fuel injection valve is arranged on the collector inlet side of the intake manifold to inject fuel for all cylinders in one injection (injection once for every two revolutions of the engine), it is not always necessary to use each cylinder. Cannot distribute fuel evenly,
In some cases, the air-fuel ratio variation between the cylinders increases, leading to deterioration of the exhaust performance and impairment of the stability of the engine.

The present invention has been made in view of the above circumstances, and has as its object to reduce the variation in air-fuel ratio between cylinders by distributing the injected fuel from the auxiliary fuel injection valve to each cylinder as uniformly as possible.

[0007]

Therefore, in the present invention,
As shown in FIG. 1, a fuel injection control device for a direct injection spark ignition type internal combustion engine including a main fuel injection valve for directly injecting fuel into a combustion chamber for each cylinder, separately from the main fuel injection valve, An auxiliary fuel injection valve capable of injecting fuel into the intake manifold is provided for all cylinders, and the auxiliary fuel injection valve is operated under predetermined operating conditions to supply fuel to the engine with the main fuel injection valve and the auxiliary fuel injection valve. In the apparatus provided with the switching control means for sharing with the valve, the auxiliary fuel injection valve is arranged on the collector inlet side of the intake manifold, and the fuel for all cylinders is injected by one injection, An injection timing variable setting means for variably setting an injection timing of the auxiliary fuel injection valve according to an engine rotation speed is provided (claim 1).

More specifically, the variable injection timing setting means delays the injection timing on the low rotation speed side and advances the injection timing on the high rotation speed side.
According to the experiments of the present inventors, the air-fuel ratio variation between the cylinders changes for each engine speed, but by selecting the injection timing of the auxiliary fuel injection valve, it is possible to minimize the air-fuel ratio variation between the cylinders. it can. In view of this fact, by setting the injection timing of the auxiliary fuel injection valve variably according to the engine speed, the fuel injected from the auxiliary fuel injection valve can be distributed as uniformly as possible to each cylinder, and the air space between the cylinders is reduced. It reduces the fuel ratio variation.

[0009]

According to the present invention, the injection timing of the auxiliary fuel injection valve is variably set in accordance with the engine rotational speed. In particular, the injection timing is delayed on the low rotation side and advanced on the high rotation side. The fuel injected from the auxiliary fuel injection valve can be relatively uniformly distributed to the cylinders, thereby reducing the variation in the air-fuel ratio between the cylinders and thereby improving the exhaust performance and stability. .

[0010]

Embodiments of the present invention will be described below. FIG. 2 is a system diagram of a four-cylinder internal combustion engine showing one embodiment. First, this will be described. Under the control of the throttle valve 2, air is sucked into the combustion chamber of each cylinder of the internal combustion engine 1 mounted on the vehicle from the intake manifold 3 (collector 3a and branch pipe 3b).

An electromagnetic main fuel injection valve 4 is provided for each cylinder so as to directly inject fuel (gasoline) into the combustion chamber. In addition, an electromagnetic auxiliary fuel injection valve 5 is provided on the inlet side of the collector 3a of the intake manifold 3 for all cylinders. The auxiliary fuel injection valve 5
Is also referred to as a fifth valve in the case of four cylinders.

The main fuel injection valve 4 is energized by a solenoid by an injection pulse signal output from the control unit 6 in the intake stroke or the compression stroke of each cylinder in synchronization with the engine rotation, and is opened to a predetermined high pressure. The fuel whose pressure has been adjusted is injected. The injected fuel diffuses into the combustion chamber in the case of the intake stroke injection to form a homogeneous mixture, and in the case of the compression stroke injection, forms a layered mixture intensively around the spark plug, It is ignited by the spark plug and burns (homogeneous combustion or stratified combustion).

The auxiliary fuel injection valve 5 is an injection pulse output once every two revolutions of the engine from the control unit 6 in a specific region during homogeneous combustion or during homogeneous combustion in synchronization with switching between stratified combustion and homogeneous combustion. The solenoid is energized by a signal to open the valve and inject fuel adjusted to a predetermined low pressure. The injected fuel is homogenized to some extent in the intake manifold 3 and distributed to each cylinder.

The main fuel injection valve 4 and the auxiliary fuel injection valve 5
A low-pressure fuel pump 8 that sucks and discharges the fuel in the fuel tank 7, a low-pressure regulator 9 that regulates the discharge pressure of the low-pressure fuel pump 8, and further pressurizes the fuel from the low-pressure fuel pump 8. A high-pressure fuel pump 10 and a high-pressure regulator 11 for regulating the discharge pressure of the high-pressure fuel pump
And supplies the high-pressure fuel regulated by the high-pressure regulator 11 to the main fuel injection valve 4 through the fuel gallery 12, and supplies the low-pressure fuel regulated by the low-pressure regulator 9 to the auxiliary fuel injection valve 5. Supply.

The control unit 6 includes a CPU, an RO,
A microcomputer including an M, a RAM, an A / D converter, an input / output interface, and the like is provided. The microcomputer receives input signals from various sensors, performs arithmetic processing based on the signals, and performs processing based on the input signals. The operation of the fuel injection valve 5 and the like is controlled. Although the various sensors are not shown, the crankshaft or camshaft rotation of the engine 1 is detected, whereby a crank angle sensor capable of detecting the engine rotation speed Ne and the intake air amount Qa upstream of the throttle valve 2 are detected. An air flow meter, a throttle sensor for detecting an opening degree Tvo of the throttle valve 2, a water temperature sensor for detecting a cooling water temperature Tw of the engine 1, and the like are provided.

Next, the fuel injection control performed by the control unit 6 will be described with reference to the flowcharts of FIGS. FIG. 3 shows a fuel injection control routine, which is executed every predetermined time (or every predetermined rotation). This routine corresponds to the switching control means. In step 1 (referred to as S1 in the figure, the same applies hereinafter), a fuel injection amount QF per cylinder (one combustion) required by the engine is calculated based on the engine operating conditions. Specifically, the engine operation conditions are set to homogeneous combustion or stratified combustion, and based on the intake air amount Qa and the engine speed Ne, the target air-fuel ratio (generally stoichiometric for homogeneous combustion, lean for stratified combustion) The required fuel injection amount QF is calculated so that

In step 2, it is determined whether or not it is within the operating range (ON range) of the auxiliary fuel injection valve. In step 3, the sharing ratio P between the main fuel injection valve and the auxiliary fuel injection valve (the sharing ratio on the auxiliary fuel injection valve side) is set. This sharing ratio P may be variable depending on the load of the engine.

In step 4, the required fuel injection amount QF is multiplied by the sharing ratio P to calculate the fuel injection amount QF5 of the auxiliary fuel injection valve according to the following equation. QF5 = 4.times.QF.times.P is multiplied by 4 because the auxiliary fuel injection valve is set to inject once every two rotations, that is, to inject once for all cylinders (four cylinders).

In step 5, the calculated fuel injection amount QF5 of the auxiliary fuel injection valve is converted into an injection pulse width (injection time) in consideration of the fuel pressure (set pressure of the low pressure regulator) and set in a predetermined register. . Accordingly, when the injection timing set by the injection timing variable setting routine of the auxiliary fuel injection valve shown in FIG. 4 described later is reached, the auxiliary fuel injection valve is driven by the signal of the injection pulse width, and the fuel is injected into the intake manifold. Done.

In step 6, the required fuel injection amount QF is multiplied by the share ratio (1-P) of the main fuel injection valve by the following equation to calculate the fuel injection amount QF1-4 of the main fuel injection valve. QF1-4 = QF × (1-P) Then, the process proceeds to step 8. In step 8, the calculated fuel injection amount QF1-4 of the main fuel injection valve is converted into an injection pulse width (injection time) in consideration of the fuel pressure (set pressure of the high-pressure regulator) and set in a predetermined register. Thus, at a predetermined injection timing of the main fuel injection valve, the signal of this injection pulse width drives the main fuel injection valve, and fuel is injected directly into the combustion chamber.

If the auxiliary fuel injection valve is in the OFF region, the process proceeds to step S7. In this case, fuel injection is performed only by the main fuel injection valve. In step 7, the required fuel injection amount QF is directly used as the fuel injection amount QF1-4 of the main fuel injection valve by the following equation. QF1-4 = QF Then, the process proceeds to step 8.

In step 8, as described above, the calculated fuel injection amount QF1-4 of the main fuel injection valve is converted into an injection pulse width in consideration of the fuel pressure and set in a predetermined register. Thus, at a predetermined injection timing of the main fuel injection valve, the signal of this injection pulse width drives the main fuel injection valve, and fuel is injected directly into the combustion chamber. FIG. 4 shows an injection timing variable setting routine of the auxiliary fuel injection valve, which is executed at every predetermined time (or every predetermined rotation). This routine corresponds to injection timing variable setting means.

In step 11, it is determined whether or not it is in the operating range (ON range) of the auxiliary fuel injection valve. In step 12, the engine speed Ne
Is read, and the injection timing of the auxiliary fuel injection valve is set with reference to a table as shown in FIG. 5 in which the injection timing of the auxiliary fuel injection valve is determined in advance according to the engine speed Ne. Specifically, the injection timing is delayed on the low rotation side, and the injection timing is advanced on the high rotation side.

Next, the optimum injection timing of the auxiliary fuel injection valve will be described. In this example, as shown in FIG. 2, a branch pipe 3b branching from the most downstream side in the flow direction in the collector 3a of the intake manifold 3 corresponds to the # 1 cylinder, and has four cylinders, as shown in FIG. The branch pipe 3b that is more branched is # 4
Corresponds to cylinder. The ignition order is # 1 → # 3 → # 4 →
# 2.

FIG. 6 shows 6000 rpm and 5000 rpm
m, 4000rpm, 2000rpm engine speed N
Injection timing (injection start timing) of the auxiliary fuel injection valve for each e
With the crank angle of -180 deg (# 1 cylinder intake TD
C), 0 deg (# 3 cylinder intake TDC), 180 deg
(# 4 cylinder intake TDC), 360 deg (# 2 cylinder intake TDC), etc., to see the air-fuel ratio variation between cylinders at each setting,
It shows the result of measuring the emission (%).

From these results, at 6000 rpm, when the injection timing is set to 180 deg (# 4 cylinder intake TDC), the variation in the CO emission (%) between the cylinders is minimized. At 5000 rpm, the injection timing is 360 de
When g (# 2 cylinder intake TDC) is set, the variation in the CO emission (%) between the cylinders becomes the smallest. 400
At 0 rpm, when the injection timing is set to 450 deg (between the # 2 cylinder intake TDC and the # 1 cylinder intake TDC), the variation in the CO emission (%) between the cylinders is minimized. At 2000 rpm, the injection timing is -180 deg.
(= 540 deg; # 1 cylinder intake TDC), the variation in the CO emission (%) between the cylinders is minimized.

Accordingly, it is understood that it is better to advance the injection timing on the high rotation side and delay the injection timing on the low rotation side. FIG.
Is based on the experimental results as shown in FIG. 6, and the variation ΔCO (%) of the CO emission between cylinders is plotted on a map with the injection timing (crank angle) on the horizontal axis and the engine speed Ne on the vertical axis. It is shown by. In the figure, a line of ΔCO = 1%, a line of ΔCO = 2%,...
7% line.

Therefore, based on this map, it is preferable to set the injection timing (injection start timing) to a timing at which ΔCO becomes the minimum for each engine speed Ne. More specifically, as shown by hatching in the injection period at each engine speed Ne, the injection start timing is set to 180 de at 6000 rpm.
g (= -540 deg; # 4 cylinder intake TDC). At 5000 rpm, the injection start timing is set to -360.
deg (# 2 cylinder intake TDC). 400
At 0 rpm, the injection start timing is set near -270 deg (between the # 2 intake cylinder TDC and the # 1 intake cylinder TDC). At 2000 rpm, the injection start timing is set to -180d
eg (# 1 cylinder intake TDC).

[Brief description of the drawings]

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

FIG. 2 is a system diagram of an internal combustion engine showing an embodiment of the present invention.

FIG. 3 is a flowchart of a fuel injection control routine.

FIG. 4 is a flowchart of an injection timing variable setting routine of an auxiliary fuel injection valve;

FIG. 5 is a diagram showing an injection timing table of an auxiliary fuel injection valve;

FIG. 6 shows C of each cylinder according to the injection timing for each engine speed.
Diagram showing O emissions

FIG. 7 is a diagram showing a variation map of CO emissions.

[Explanation of symbols]

 Reference Signs List 1 internal combustion engine 2 throttle valve 3 intake manifold 4 main fuel injection valve 5 auxiliary fuel injection valve 6 control unit

Continued on front page F term (reference) 3G066 AA02 AA05 AB02 BA16 BA21 CD26 CE22 CE29 DA04 DA09 DB12 DB13 DC04 DC05 DC09 DC14 DC24 3G301 HA04 HA16 JA01 JA05 KA24 KA25 LB04 LB07 MA01 MA19 MA23 NC02 ND01 NE11 NE12 NE15 PA01Z PA03ZPD01 PE08Z

Claims (2)

[Claims] 1. A fuel injection control device for a direct injection spark ignition type internal combustion engine having a main fuel injection valve for injecting fuel directly into a combustion chamber for each cylinder, wherein all the cylinders are provided separately from the main fuel injection valve. An auxiliary fuel injection valve capable of injecting fuel is provided in the intake manifold in common, and the auxiliary fuel injection valve is operated under predetermined operating conditions to supply fuel to the engine with the main fuel injection valve and the auxiliary fuel injection valve. The auxiliary fuel injection valve is arranged on the collector inlet side of the intake manifold to inject fuel for all cylinders in one injection, A fuel injection control device for an internal combustion engine, comprising: injection timing variable setting means for variably setting an injection timing of a fuel injection valve according to an engine rotation speed. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein said variable injection timing setting means delays the injection timing on a low rotation speed side and advances the injection timing on a high rotation speed side. .