JP2987925B2 - In-cylinder direct injection spark ignition engine - Google Patents

Description

The present invention relates to a direct injection type spark ignition engine.

[Prior art] A fuel injection valve for linearly injecting fuel into a cylinder is provided. At low load, the ignition plug is directed in the second half of the compression stroke to inject fuel to perform stratified fuel, and at medium / high load, intake air is taken. An in-cylinder direct injection spark ignition engine has been disclosed in which fuel is injected in a stroke and a latter half of a compression stroke to perform weak stratified combustion (see Japanese Patent Application Laid-Open No. 2-169834).

[Problems to be solved by the invention]

However, in this internal combustion engine, when the engine is cold, the temperature in the cylinder, for example, the wall temperature of the combustion chamber is low, so that the evaporation of the fuel injected into the cylinder deteriorates. However, the formation of a suitable air-fuel mixture is insufficient, so that good ignition and combustion cannot be obtained.

[Means for Solving the Problems] An in-cylinder linear injection type spark ignition engine according to the present invention includes a fuel injection valve for directly injecting fuel into a cylinder and an ignition plug, wherein the fuel injection valve is an engine. A compression stroke fuel injection for forming an air-fuel mixture only around the spark plug and an intake air for forming a homogeneous air-fuel mixture in a cylinder based on a fuel injection amount ratio determined for every fuel injection amount according to an operation state. In a direct injection type spark ignition engine that performs stroke fuel injection, the fuel injection ratio is changed so that the fuel injection amount in the compression stroke fuel injection is increased when the engine is cold.

[Operation] When the engine is cold, the fuel injection ratio determined for each fuel injection amount according to the engine operating state is changed so as to increase the fuel injection amount in the compression stroke fuel injection.

〔Example〕

Referring to FIG. 1, 1 is a cylinder block, 2 is a cylinder head, 3 is a piston, 4 is a cylinder chamber, 5 is an intake pipe, and 6 is an exhaust pipe. A linkless throttle valve 7 is arranged in the intake pipe 5. The throttle valve 7 is controlled to be opened and closed by a step motor 8, and is almost fully opened except during idle operation and during deceleration operation. The tip of the fuel injection valve 9 extends to the cylinder chamber 4 and can directly inject fuel into the cylinder chamber 4. The fuel injection valves 9 of the respective cylinders are connected to a pressure accumulation chamber 10 common to the fuel injection valves 9, and the pressure accumulation chamber 10 is filled with a high-pressure fuel having a substantially constant pressure by a fuel pump 11. Spark plug
12 is connected to an igniter 14 via a distributor 13.

The electronic control unit 30 is composed of a digital computer, and a ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, an input port 35 interconnected by a bidirectional bus 31.
And an output port 36. The crank angle sensor 25 for detecting the engine speed is built in the distributor 13, and the output signal of the crank angle sensor 25 is supplied to the input port 35.
Is input to A water temperature sensor 26 for detecting the engine cooling water temperature is connected to an input port 35 via an AD converter 37.
An accelerator opening sensor 27 for detecting the amount of depression of an accelerator pedal (not shown) is connected to an input port via an AD converter 38.
Connected to 35.

On the other hand, the output port 36 is connected to the fuel injection valve 9, the igniter 14, and the step motor 8 via the respective drive circuits 39, 40, 41.

FIG. 2 is an enlarged sectional view of the engine body of FIG. Referring to FIG. 2, the concave combustion chamber 20 formed at the top of the piston includes a large-diameter shallow dish 21 on the upper side, and a lower deep dish 22 formed at the center of the shallow dish 21. The deep plate portion 22 is formed to have a smaller diameter than the shallow plate portion 21.

The intake port (not shown) is a swirl port, and the fuel injection valve 9 has a multi-hole hole nozzle. Therefore, the fuel injection valve 9 injects rod-shaped fuel which has a relatively large penetration force and a small spread angle. The fuel injection valve 9 is disposed at the top of the cylinder chamber 4 so as to face diagonally downward. The fuel injection direction and fuel injection timing of the fuel injection valve 9 are as follows:
It is determined that the injected fuel is directed into the combustion chamber 20. At the top dead center of the piston 3, the ignition plug 12 is
It is arranged to be located inside.

FIG. 3 shows a control pattern of the compression stroke injection and the intake stroke injection. Referring to FIG. 3, the horizontal axis represents the engine load. In FIG. 3, the fuel injection amount Q is taken as the load.
The vertical axis represents the fuel injection amount Q. Until the load region corresponding to the fuel injection amount Q _S, the fuel only during the compression stroke is injected. Compression stroke fuel injection amount is made to gradually increase up to Q _S. In the fuel injection amount Q _S, the compression stroke fuel injection amount is
Intake stroke fuel injection amount with used to lower rapidly to Q _D is caused to abruptly increase to Q _P. Q _S is the fuel injection amount near the medium load, as the sum of the Q _D and Q _P shown by the following equation.

Here _{Q S = Q D + Q P} , Q D is the least compression stroke fuel injection amount capable of forming a ignitable mixture by the spark plugs 12, Q _P is fuel cylinder chamber which is injected in the intake stroke This is the minimum intake stroke fuel injection amount that allows the ignition flame from the spark plug 12 to propagate when it is uniformly diffused into the fuel cell 4.

In a load region in which the fuel injection amount is larger than Q _S and smaller than Q _H , the entire fuel injection amount Q is divided into a compression stroke and an intake stroke, and the fuel is injected. The stroke fuel injection amount is increased as the load increases.

In the fuel injection amount Q _H greater load range, because the concentration of the premixed gas in the cylinder chamber formed by the intake stroke injection for the fuel injection amount is large deep enough to ignition, the compression stroke injection for the ignition And the entire required fuel injection amount is injected in the air stroke.
Q _H is minimal intake stroke fuel injection amount that can form a uniform mixture which can be ignited by a spark plug even when the fuel is homogeneously diffused in the cylinder chamber.

FIG. 4 is a diagram showing the fuel injection control pattern of FIG. 3 in the relationship between load and crank angle.

Referring to FIG. 2 again, in the lower load range than the near medium load Q _S, the total amount of the required injection quantity toward the combustion chamber 20 from the fuel injection valve 9 is injected in the compression stroke later. The fuel injection timing is delayed so that most of the fuel is injected into the deep dish 22. The fuel adhering to the inner wall surface of the deep dish portion 22 evaporates and atomizes, and forms a dense and mixed gas layer including a combustible region in the combustion chamber 20. A part of the air-fuel mixture layer is ignited by the ignition plug 12, and good combustion is completed mainly in the deep dish portion 22.

In a load region higher than Q _{S and} lower than Q _H near the middle load, as shown in FIG. 5, the intake stroke injection is executed at the beginning of the intake stroke (FIG. 5 (a)), Fuel is injected toward the chamber 20. The fuel injection F mainly collides with the shallow plate portion 21, a part of which is reflected into the cylinder chamber 4, and another portion adheres to the wall surface of the shallow plate portion 21 and is evaporated and atomized by heating from the wall surface. In these fuels, a premixed gas P is formed during the period from the intake stroke to the compression stroke due to the intake swirl flow SW and the turbulence R of the intake flow (FIG. 5 (b)). The air-fuel ratio of the premixed air P is set to such an extent that the ignition flame can propagate. If the suction swirl SW is strong, the cylinder chamber 4
A premixed gas is formed such that the area around the periphery is dark and the area near the center is thin.

If the fuel is injected when the piston 3 is located closer to the top dead center when the intake stroke injection timing is advanced, most of the fuel is injected into the deep dish portion 22, and most of the fuel is injected into the deep dish portion 22. It is premixed and vaporized in the section 22.

Subsequently, compression stroke injection is performed in the latter half of the compression stroke (FIG. 5 (c)), and most of the fuel is injected into the deep dish portion 22.
The fuel adhering to the inner wall surface of the deep dish portion 22 is vaporized by heating from the wall surface and the compressed air, and is diffused and mixed by the vortex SW to form a heterogeneous mixed gas layer including a combustible region. A part of the air-fuel mixture layer is ignited by the ignition plug 12, and the combustion of the heterogeneous air-fuel mixture proceeds (FIG. 5 (d)). In the process of developing the flame B formed by this combustion in the deep dish portion 22,
Propagation to the surrounding premixed gas, and furthermore, combustion proceeds to the outside of the deep dish portion 22 by the reverse squish flow S.

When the compression stroke injection timing is advanced and fuel is injected into both the shallow plate portion 21 and the deep plate portion 22, the flame is widely distributed in the shallow plate portion 21 and the deep plate portion 22, and the flame is diffused into the premixed gas. Flame propagation can be made easier.

By the way, in such an internal combustion engine, when the engine is cold, the temperature in the cylinder, for example, the wall temperature of the combustion chamber 20 is low, so that the evaporation of the fuel injected into the cylinder is deteriorated. However, the formation of an air-fuel mixture necessary for the combustion becomes insufficient, so that good ignition and combustion cannot be obtained.

Therefore, in the present embodiment, the compression stroke fuel injection amount is increased when the engine is cold such as before the engine is warmed up.
The increase in the compression stroke fuel injection amount includes an increase in the load region in which the compression stroke is to be injected.

This makes it possible to form an air-fuel mixture necessary for ignition, and to obtain good ignition even when the temperature in the cylinder is low. Further, the evaporation of the fuel can be promoted by the heat transfer from the generated flame, whereby good combustion can be obtained.

FIG. 6 shows a first embodiment of the fuel injection pattern when the temperature in the cylinder is low. Compared to the fuel injection pattern in the normal time (see FIG. 4), as shown by the shaded portion, also in the Q _H above the load area is executed compression stroke injection, compression stroke injection amount in Q _H above the load area Has been increased. The injection amount of the intake stroke injection is reduced by the increased amount of the compression stroke injection amount. Note the compression stroke fuel injection amount Q _H above the load region is equal to the compression stroke fuel injection amount of the load region less than Q _S or Q _H.

FIG. 7 shows a routine for executing the injection pattern of the first embodiment. This routine is executed by interruption every fixed crank angle. Referring to FIG. 7, first, at step 60, the total fuel injection amount Q is calculated from a map of the accelerator depression amount and the engine speed. Then the compression stroke fuel injection amount Q _C from the map of the total fuel injection amount Q and the engine speed at step 61 is calculated. Step 62 In the compression stroke fuel injection Q _C is 0 whether, i.e. the total fuel injection amount is determined whether or Q _H. If Q _C ≠ 0, ie Q
<In the case of Q _H, the process proceeds to step 67, the intake stroke fuel injection amount Q _I is calculated from the following equation, the routine ends.

Q _I = Q-Q _C side, Q _C = 0, that is, when Q ≧ Q _H, the step 63
Then, it is determined whether or not the engine cooling water temperature TW is 70 ° C. or higher, that is, whether or not the engine is cold. For TW <70 ° C., i.e. at the time of engine cold, is the compression stroke fuel injection amount Q _C, for example, 5 mm ³ proceeds to step 66. That is, if there is also a engine coolant temperature _{TW <70 ℃ Q ≧ Q H} , the compression stroke injection is performed. Next, at step 67, the intake stroke fuel injection amount Q _I
Is calculated.

FIG. 8 shows a second embodiment of the fuel injection pattern when the engine is cold. In this embodiment, as shown by oblique lines, in the engine cold, the compression stroke injection is executed in the load region below Q _H or Q _M. Others are the same as the fuel injection pattern shown in FIG.

FIG. 9 shows a routine for executing the injection pattern of the second embodiment. This routine is almost the same as the routine shown in FIG. 7, and the same steps are denoted by the same step numbers and description thereof is omitted. In step 70, it is determined whether the total fuel injection amount Q is less than Q _M , for example, 40 mm ³ . In the case of Q <Q _M, the process proceeds to step 63 below, the compression stroke injection and is determined to be the engine cold it is executed.
If Q ≧ Q _M, no compression stroke injection is performed.

FIG. 10 shows a third embodiment of the fuel injection pattern when the engine is cold. Compared to the first embodiment of the fuel injection pattern shown in FIG. 6, as indicated by hatching, load range by the compression stroke injection is performed is extended to Q _S or more Q _N.

FIG. 11 shows a routine for executing the injection pattern of the third embodiment. This routine is executed by interruption every fixed crank angle. Referring to FIG. 11, first, at step 80, the total fuel injection amount Q is calculated from a map of the accelerator depression amount and the engine speed. Next, at step 81, the compression stroke fuel injection amount is calculated from a map of the total fuel injection amount Q and the engine speed. In step 82, it is determined whether or not the engine cooling water temperature TW is 70 ° C. or higher, that is, whether or not the engine is cold. When TW <70 ° C., that is, when the engine is cold, the routine proceeds to step 85, where the compression stroke fuel injection amount Q _C
There 0 whether, i.e. the total fuel injection amount is determined whether or Q _H. If Q _C = 0, that is, if Q ≧ Q _H , step 88
It proceeds to be the compression stroke fuel injection amount Q _C, for example, 5 mm ^3.
That is, if the engine coolant temperature TW <70 ° C., the compression stroke injection is executed in the Q ≧ Q _H. In step 89, the intake stroke fuel injection amount Q _I is calculated from the following equation, the routine ends.

Meanwhile Q _I = Q-Q _C, in step 85, if not Qc = 0, ie Q <proceeds to step 86 if it is determined that the Q _H Q <
It is determined whether Q _N (see FIG. 10) or not, for example, less than 25 mm ³ . For Q <Q _N proceeds to step 87, the total fuel injection amount Q is set to the compression stroke fuel injection amount Q _C. For Q ≧ Q _N, Q _C calculated in step 81 it is used as it is, step
Intake stroke fuel injection amount Q _I is calculated by 89.

On the other hand, in step 82, if it is determined that TW ≧ 70 ℃, Q _C calculated in step 81 is used as it is.

FIG. 12 shows a fourth embodiment of the fuel injection pattern when the engine is cold. Compared to the third embodiment of the fuel injection pattern shown in FIG. 10, a compression stroke fuel injection amount between the Q _N and Q _H are caused to increase.

FIG. 13 shows a routine for executing the injection pattern of the fourth embodiment. This routine is substantially the same as the routine shown in FIG. 11, and the same steps are denoted by the same step numbers and description thereof is omitted. The compression stroke fuel injection amount Q _C If it is determined that the Q ≧ Q _N in step 86
Only 4mm ³ is caused to increase. Thus, the compression stroke fuel injection amount between Q _N and Q _H is made to increase.

In this embodiment, one fuel injection valve 9 performs the ball stroke injection and the compression stroke injection. However, the fuel injection valve 9 has two fuel injection valves, and one fuel injection valve executes the intake stroke injection. At the same time, the compression stroke injection may be executed by the other fuel injection valve.

〔The invention's effect〕

Since the air-fuel mixture required for ignition can be formed even when the engine is cold, good ignition and combustion can be obtained.

[Brief description of the drawings]

1 is an overall view of an internal combustion engine, FIG. 2 is a longitudinal sectional view of an engine body, FIG. 3 is a diagram showing an example of a control pattern of compression stroke injection and intake stroke injection, and FIG. FIG. 5 is a diagram showing a control pattern as a relationship between load and crank angle, FIG. 5 is an explanatory diagram showing a state of fuel injection, and FIG. 6 is a diagram showing a first embodiment of a fuel injection pattern when the engine is cold. FIG. 7, FIG. 7 is a flowchart for executing the injection pattern of the first embodiment, FIG. 8 is a diagram showing a second embodiment of the fuel injection pattern when the engine is cold, and FIG. FIG. 10 is a flow chart for executing the injection pattern of the third embodiment, FIG. 10 is a diagram showing a third embodiment of the fuel injection pattern when the engine is cold, and FIG. 11 is an execution of the injection pattern of the third embodiment. FIG. 12 shows a fuel injection pattern when the engine is cold. Diagram showing a fourth embodiment of the thirteenth
FIG. 11 is a flowchart for executing the injection pattern of the fourth embodiment. 4 ... cylinder chamber, 9 ... fuel injection valve, 12 ... spark plug, 26 ... water temperature sensor.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02D 41/04 330

Claims (1)

(57) [Claims] 1. A fuel injection valve for directly injecting fuel into a cylinder and an ignition plug, wherein the fuel injection valve has a fuel injection amount determined for every fuel injection amount according to an engine operating state. In a direct injection type spark ignition engine that performs a compression stroke fuel injection for forming a mixture only around the spark plug and an intake stroke fuel injection for forming a homogeneous mixture in a cylinder based on the ratio, An in-cylinder direct injection spark ignition engine, wherein the fuel injection ratio is changed to increase the fuel injection amount in the compression stroke fuel injection during a cold period.