JPH0455259Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a fuel injection control device for an internal combustion engine that atomizes fuel spray from an injector through collision.

[Conventional technology]

In fuel-injected internal combustion engines, fuel from an injector is usually injected into an intake pipe in the form of a conical spray. In this case, there is a problem in that the fuel adheres to the wall surface of the intake pipe in liquid form. As a result, fuel becomes insufficient during transient operations such as during acceleration, and so-called increase correction becomes necessary. Therefore, there is a known method in which the spray from the injector is made to directly collide with the umbrella portion of the intake valve during the intake stroke to improve the atomization of the fuel. For example, see Utility Model Application No. 60-97374. That is, the spray from the injector collides with the umbrella portion of the intake valve, thereby becoming atomized, and there is little fuel adhesion to the wall surface of the intake pipe, which is a problem with normal injectors. Moreover, due to the high temperature of the combustion chamber, it evaporates, becomes well atomized, and is introduced into the fuel chamber, particularly near the spark plug. Such stratification improves combustion efficiency, reduces the required amount of acceleration correction, and is advantageous in terms of fuel consumption and emissions reduction.

[Problem that the invention attempts to solve]

In the conventional technology, fuel is injected in the latter half of the intake stroke to achieve stratified combustion. In this case, fuel mixability naturally deteriorates, combustion deteriorates, torque decreases, and fuel consumption rate becomes poor. Conversely, if fuel is injected at the beginning of the intake stroke to improve the mixing of fuel and air, the degree of stratification will be insufficient and the amount of nitrogen oxide components emitted will increase.

This idea achieves good stratification and also prevents deterioration of the mixing condition of fuel and air.

[Problem that the invention attempts to solve]

According to this invention, as shown in FIG. 1, in a fuel-injected internal combustion engine that atomizes the injection F by colliding with it from the injector 34, the first half and the second half of the intake stroke are provided at least in the low-load operating range of the internal combustion engine. A fuel injection control device for an internal combustion engine is provided, characterized in that it comprises means 1 for detecting two injection timings, and means for forming a fuel injection signal for driving an injector 34 at each timing.

〔Example〕

In FIG. 2, 10 is a cylinder block, 1
2 is a piston, 14 is a connecting rod, 1
6 is a combustion chamber, 18 is a cylinder head, 19 is a distributor, 20 is a throttle valve, and 21 is an air cleaner. In FIG. 3, two intake ports are installed as 22a and 22b, and two exhaust ports are similarly installed as 24a and 24b. The first intake port 22 among the intake ports
In the embodiment, a is configured as a so-called helical port, but it may also be a straight port. Respective intake ports 22a, 22b, exhaust port 24
Intake valves 26a, 26b and exhaust valves 28a, 28b are installed to open and close valves a and 24b, forming a so-called four-valve engine. The spark plug 30 is provided between the intake valve and the exhaust valve. The injector 34 is the first
The fuel tank 38 is installed at the intake port 22a of the engine and connected to the fuel tank 38 via a pipe 36. 40 is a fuel pump, and 42 is a pressure regulator. An intake control valve 44 is provided at the second intake port 22b. This intake control valve 44 is connected to an actuator 46 and is opened and closed depending on the load conditions of the engine. That is,
When the load is low, the intake control valve 44 is closed and air is introduced only from the first intake port 22a, and when the load is high, the intake control valve 44 is opened and air is introduced from the first and second intake ports 22a and 22b. be introduced.

In FIG. 3, the injector 34 is the nozzle 34
-1, and a spray like F is formed. This spray F hardly spreads and has a substantially columnar shape. As shown in FIG. 2, a protrusion 70 is installed integrally or separately on the bottom surface of the cylinder head 18 at a substantially central portion so as to extend toward the piston crown. The columnar spray F from the injector 34 is injected toward the protrusion 70 through the gap between the umbrella portion of the intake valve 26a and the valve seat. The shape is selected so that the reflected fuel is evenly diffused toward the center of the combustion chamber. The protrusion 72 becomes a heat spot within the combustion chamber 16,
Collision atomization occurs at a point of high temperature, resulting in good atomization and shortening the time until evaporation. The direction of reflection of the injection from the injector 34 is restricted by the protrusion 70 and does not collide with the other intake valve 26b. This eliminates uneven wear on the face of the intake valve due to uneven temperature distribution, improving the durability of the intake valve. can be improved.

In FIG. 2, a control circuit 50 performs fuel injection control in this invention, and is configured as, for example, a microcomputer system. The control circuit 50 includes an input section (not shown) that receives signals from each sensor, and the sensors include a crank angle sensor 52 that detects the angular position of the crankshaft, and an intake pipe pressure sensor that detects the intake pipe pressure PM. 54, and a cooling water temperature sensor 56 for detecting the temperature THW of the cooling water in the water jacket 10-1 of the cylinder block 10. Further, the control circuit 50 includes an output section (not shown), and outputs the injector 34 and the actuator 46.
is connected to. Further, the control circuit 50 includes a central processing unit, and performs arithmetic processing in the usual manner according to programs and data stored in the memory, thereby performing fuel injection control of this invention. According to this invention, the fuel injection timing is set separately for the first half and the second half of the intake stroke, at least when the load is low.

The operation will be explained below according to the flowchart shown in FIG. The routine shown in FIG. 5 is executed every time a signal from the crank angle sensor 52 arrives every 30°A. In step 60, it is determined whether it is set timing 1 or not. Set timing 1, as shown in (b) in Figure 6, is a position set near the intake top dead center of the cylinder where fuel will be injected from now on, and is a position that enables fuel injection in the first half of the intake stroke. . In step 61, the cylinder to which fuel will be injected is determined. In step 62, the fuel injection time τ of this cycle is calculated based on operating condition factors such as the load represented by the intake pipe pressure PM and the rotational speed. In step 64, the fuel injection amount τ is obtained by subtracting the predetermined value τ ₀ from the fuel injection amount τ, and the injection amount in the first half of the intake stroke is calculated. Predetermined value τ ₀
can be selected in various ways depending on the operating conditions. In step 70, the fuel injection end time _te is calculated from map 1. Map 1 is the fuel injection end time so that fuel injection is performed in the first half of the intake stroke.
The set value of t _e is stored according to the load and rotation speed, and the fuel injection timing is calculated by interpolation based on the current load, rotation speed, etc. In step 72, the fuel injection start time _ti is calculated from the fuel injection end time calculated based on the fuel injection time calculated in step 62. That is, the fuel injection end time is known from step 70, and the timing before the fuel injection time τ calculated at step 62 becomes the fuel injection start time _ti .

In step 74, the fuel injection signal is output at the time t _i calculated in step 72, and a signal is formed from the output section of the control circuit so that the fuel injection signal is stopped at the fuel injection end time t _e (this itself is public knowledge) will be carried out.

If the set timing is not 1, step 60
The process then proceeds to step 76, where it is determined whether it is set timing 2 or not. Set timing 2, as shown in (c) in Figure 6, is a position that is set near the compression bottom dead center of the cylinder where fuel is to be injected, and allows fuel injection in the latter half of the intake stroke. . That is, in this invention, the injection is divided into the first half and the second half of the intake stroke. In step 78, the cylinder to which fuel will be injected is determined. In step 80, the remaining injection quantity to be injected in this cycle is entered into τ. In step 82, the injection end time _te is map 2.
Calculated from Map 2 stores the fuel injection end time according to the load and rotation speed so that fuel injection is performed in the latter half of the intake stroke, and the fuel injection timing is calculated by interpolation based on the current load and rotation speed. . Proceed to step 72 and proceed to step 8 in the same manner as above.
The fuel injection start time t _i is calculated from the fuel injection end time calculated in step 2, and the fuel injection signal is output at time _{t i} , and the fuel injection end time t _e
A process is performed to form a signal from the output section of the control circuit so that the fuel injection signal is stopped.

FIG. 6 is a timing diagram illustrating the operation of this invention. (a) indicates the crank angle. (b) shows set timing 1, and (c) shows set timing 2. At set timing 1, a fuel injection signal for the first half of the intake stroke is calculated. At set timing 2, injection in the latter half of the intake stroke is set.

The fuel injection control of this invention described above will be explained with reference to FIG. 5. The first injection is performed in the first half of the intake stroke, and the columnar spray F from the injector 34 collides with the protrusion 70 and becomes atomized. Since fuel injection is not performed in the middle of the intake stroke, fuel is uniformly diffused into the cylinder bore and forms a lean mixture. At a timing in the second half of the intake stroke, a columnar spray F is again formed from the injector, forming a rich part of the air-fuel mixture in the vicinity of the ignition column that collided with the projection 70, and stratification is performed. Therefore, ignition at the timing and subsequent combustion can be performed satisfactorily.

The above embodiment has a protrusion 7 on the lower surface of the cylinder head.
0, and the spray from the injector 34 collides with this protrusion 70 to atomize it. However, this invention does not have such a protrusion, and instead of using an intake valve as in Japanese Patent Application Laid-Open No. 60-97374. It can also be applied to objects that collide with the umbrella part. That is, in FIG. 7, indicates the timing of the first half of the intake stroke, and the columnar spray from the injector 34 is atomized by colliding with the umbrella portion of the intake valve 26a. At this timing, fuel injection is temporarily stopped and the fuel is diffused. Injection is performed again from the injector 34 at the timing of , collides with the umbrella portion of the intake valve 26a, and forms a rich part of the air-fuel mixture near the ignition column electrode. Ignition occurs at the timing of

[Effect of idea]

In this invention, at least in the intake stroke, the injection is divided into two parts, the first half and the second half, so it is possible to harmonize the requirements for both mixing and stratification of the air-fuel mixture, especially at low loads where lean combustion is performed.

By appropriately controlling the sharing ratio of the fuel injection amount between the first half and the second half of the intake stroke, it is possible to optimally control the ratio of the rich layer and lean layer and the difference in air-fuel ratio thereof.

Since it is possible to improve the mixing of the lean layer in lean combustion, torque fluctuations are suppressed.

Since the fuel is injected twice, the amount of fuel injected per time is reduced, and even if fuel adheres to the ignition column electrode, smoldering is less likely to occur.

In order to improve the mixing, an improvement has been proposed in which fuel is injected while the intake valve is closed, but this provides better transient characteristics.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of this invention. FIG. 2 is an overall schematic configuration diagram of the embodiment. Figure 3 is a cross-sectional view of the combustion chamber. FIG. 4 is a flowchart explaining the operation of the control circuit. FIG. 5 is a series of schematic vertical cross-sectional views of the combustion chamber during one intake stroke for explaining the operation of the control circuit in order. FIG. 6 is a timing diagram illustrating the operation of the control circuit. FIG. 7 is a diagram similar to FIG. 5 in the second embodiment. 16... Combustion chamber, 22a, 22b... Intake port, 24a, 24b... Exhaust port, 26a, 2
6b...Intake valve, 28a, 28b...Exhaust valve, 3
0...Spark plug, 34...Injector, 44...
Intake control valve, 50...control circuit, 52...crank angle sensor, 70...protrusion.

Claims (1)

[Scope of utility model registration request] In a fuel-injected internal combustion engine that atomizes injection by colliding injections from an injector, means for detecting two injection timings, the first half and the second half of the intake stroke, at least in a low-load operating range of the internal combustion engine; 1. A fuel injection control device for an internal combustion engine, comprising means for forming a fuel injection signal for driving an internal combustion engine.