JP2000018137A - Fuel injection control system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control system of an internal combustion engine so as to make fuel supply to each cylinder from an auxiliary fuel injection valve uniform and prevent dispersion in the air/fuel ratios of the respective cylinders by appropriately positioning the auxiliary fuel injection valve. SOLUTION: An intake manifold 3 is provided with a throttle valve 2, an upstream end flange portion 13, four branch portions 21a to 21d, which are arranged in a row. An auxiliary fuel injection valve 5 is disposed in the intake manifold 3 at the position upstream from an intermediate point between the upstream end flange portion 13 and the branch portion 21a at the most upstream side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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, and injecting fuel into an intake passage separately from the main fuel injection valve. A fuel injection control device for providing a possible auxiliary fuel injection valve, operating the auxiliary fuel injection valve under predetermined operating conditions, and sharing fuel supply to the engine between the main fuel injection valve and the auxiliary fuel injection valve .

[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 fuel system is switched according to engine operating conditions, that is, by injecting fuel in an intake process. Homogeneous combustion is performed by diffusing fuel into the combustion chamber to form a homogeneous mixture, and stratified combustion is performed by forming a stratified mixture around the spark plug by injecting fuel in the compression process. (See JP-A-59-37236).

In such a direct injection spark ignition type internal combustion engine, an auxiliary fuel injection valve capable of injecting fuel into an intake passage is provided separately from a main fuel injection valve which directly injects fuel into a combustion chamber. It has been considered that the auxiliary fuel injection valve is operated under the above operating conditions (at least at the time of homogeneous combustion) so that 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]

Incidentally, the auxiliary fuel injection valve injects fuel into the intake passage to supply fuel to all cylinders by one, so that it is necessary to distribute fuel equally to each cylinder. There is. In particular, in the case of an intake manifold having a branch portion that sequentially branches from the upstream side to the downstream side of the linear intake passage and reaches each cylinder, since the distance from the auxiliary fuel injection valve to each branch portion is different, uniform distribution is achieved. There is a problem that it is difficult.

The present invention has been made in view of the above-described problems, and by appropriately setting the arrangement of the auxiliary fuel injection valve, the supply of fuel from the auxiliary fuel injection valve to each cylinder is made uniform, and the air-fuel ratio between the cylinders is improved. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine capable of suppressing variations in the fuel injection.

[0007]

Therefore, in the present invention,
A direct injection spark ignition type internal combustion engine including a main fuel injection valve for directly injecting fuel into a combustion chamber, wherein an auxiliary fuel injection valve capable of injecting fuel into an intake passage is provided separately from the main fuel injection valve. A switching control means for operating the auxiliary fuel injection valve under predetermined operating conditions to share the fuel supply to the engine with the main fuel injection valve and the auxiliary fuel injection valve, from upstream to downstream. An intake manifold having a branch portion that branches sequentially to each cylinder is provided, and an auxiliary position is provided at a position upstream of an intermediate point between an upstream end flange portion of the intake manifold and a junction portion of the most upstream branch portion. A fuel injection valve is provided.

[0008]

According to the present invention, in the direct injection spark ignition type internal combustion engine, the auxiliary fuel injection is provided at a position upstream of the intermediate point between the upstream end flange portion of the intake manifold and the junction of the most upstream branch portion. By installing the valve, fuel is injected sufficiently upstream also to the branch section on the most upstream side, so that the fuel spray can be evenly distributed to each cylinder while being carried on the airflow, and thus the cylinder can be evenly distributed. This has the effect of suppressing variations in the air-fuel ratio between the two.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of an internal combustion engine showing an embodiment of the present invention, and FIG. 2 is an enlarged view showing an installation position of an auxiliary fuel injection valve. First, FIG. 1 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 from an intake passage (intake manifold) 3. And for each cylinder,
An electromagnetic main fuel injection valve 4 is provided to inject fuel (gasoline) directly into the combustion chamber. An electromagnetic auxiliary fuel injection valve 5 is provided commonly to all cylinders so as to inject fuel into a collecting portion (collector) of the intake manifold 3 and distribute the fuel to each cylinder.

The main fuel injection valve 4 is energized by a solenoid in response to an injection pulse signal output from the control unit 6 in the intake stroke or the compression stroke of each cylinder in synchronism with the engine rotation, and is opened to a predetermined high pressure. The fuel whose pressure has been adjusted is injected. Then, in the case of the intake stroke injection, the injected fuel diffuses into the combustion chamber to form a homogeneous mixture, and is ignited by point electrification to burn (homogeneous combustion or stratified combustion).

The auxiliary fuel injector 5 is controlled by the control unit 6 in synchronism with the engine rotation 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 the output injection pulse signal, opens the valve, and injects 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,
The microcomputer includes a microcomputer including an M, a RAM, an A / D converter, an input / output interface, and the like. The microcomputer receives input signals from various sensors and performs arithmetic processing based on the input signals. The operation of the auxiliary fuel injection valve 5 and the like is controlled. Although illustration of the various sensors is omitted, rotation of the crankshaft or camshaft of the engine 1 is detected,
This allows the crank angle sensor to detect the engine speed,
An air flow meter for detecting an intake air amount upstream of the throttle valve 2, a throttle sensor for detecting an opening degree of the throttle valve 2, a water temperature sensor for detecting a cooling water temperature of the engine 1, an intake air temperature sensor for detecting an intake air temperature, and the like are provided. I have.

Next, FIG. 2 will be described. The intake manifold 3 is connected to a throttle chamber via the throttle valve 2 via an upstream end flange portion 13, and four branch portions 21a to 21d are arranged in a line from the upstream side to the downstream side. . The auxiliary fuel injection valve 5 is installed in the intake manifold 3 at a position upstream of an intermediate point between the upstream end flange portion 13 of the intake manifold 3 and the most upstream branch portion 21a. By installing the auxiliary fuel injection valve 5 at the position, the air whose suction amount is adjusted by the throttle valve 2 is mixed with the fuel injected by the auxiliary fuel injection valve 5 at a constant rate, and It flows uniformly into each branch part 21a-21d,
An injection amount shortage region of the main fuel injection valve 4 represented by a high load region is eliminated.

Here, in the configuration according to the present invention, the installation position of the auxiliary fuel injection valve 5 is limited to the above position, so that fuel injection is performed sufficiently upstream from the most upstream branch portion 21a, so that air and fuel are injected. The air-fuel mixture is evenly distributed to each cylinder while the air-fuel mixture is sufficiently mixed. In addition, if it is installed at a position that is too upstream (near the upstream end flange portion 13 of the intake manifold 3), the fuel adheres to the wall surface and reaches a wall flow before reaching the branch portions 21a to 21d, and is supplied in a liquid state. In addition, since a response delay may occur, it is preferable to keep the distance from the upstream end flange portion 13 too low.

Further, the injection axis of the auxiliary fuel injection valve 5 is injected at an angle as close as possible to the passage axis of the intake manifold 3 from the upstream to the downstream so that the fuel spray hardly forms a wall flow. . As a result, the variation in the air-fuel ratio among the cylinders is reduced, so that the correction of the main fuel injection valve 4 becomes unnecessary, and the air-fuel ratio can be set without considering the influence of the injection of the auxiliary fuel injection valve 5.

[Brief description of the drawings]

FIG. 1 is a system diagram of an internal combustion engine showing an embodiment of the present invention.

FIG. 2 is an enlarged view showing an installation position of an auxiliary fuel injection valve;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 10 High pressure fuel pump 2 Throttle valve 11 High pressure regulator 3 Intake manifold 12 Fuel gallery 4 Main fuel injection valve 13 Upstream end flange part 5 Auxiliary fuel injection valve 21a Branch part 6 Control unit 21b Branch part 7 Fuel tank 21c Branch part 8 Low pressure fuel pump 21d Branch 9 Low pressure regulator

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 3G066 AA02 AA05 AB02 AD10 AD12 BA02 BA03 BA12 BA16 CC06U CD26 CE22 DB09 DB13 DC04 DC05 DC09 DC11 DC13 DC14 3G301 HA01 HA04 HA06 HA16 JA01 JA05 KA09 KA25 LA01 LB04 LB05 LC01 MA03 MA03 PA01Z PA10Z PA11Z PE01Z PE03Z PE08Z

Claims (1)

[Claims] 1. A direct injection spark ignition type internal combustion engine having a main fuel injection valve for directly injecting fuel into a combustion chamber, wherein an auxiliary fuel capable of injecting fuel into an intake passage separately from the main fuel injection valve. An injection valve, and switching control means for operating the auxiliary fuel injection valve under predetermined operating conditions to share fuel supply to the engine between the main fuel injection valve and the auxiliary fuel injection valve, While the intake manifold provided with a branch portion that branches sequentially from the side to the downstream side and reaches each cylinder, the upstream portion is provided at an intermediate point between an upstream end flange portion of the intake manifold and a junction of the most upstream branch portion. A fuel injection control device for an internal combustion engine, wherein an auxiliary fuel injection valve is installed at a position on the side of the fuel injection valve.