JP2836353B2 - In-cylinder internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection internal combustion engine.

[0002]

2. Description of the Related Art A first fuel injection is performed during an engine intake stroke to form an air-fuel mixture dispersed throughout the combustion chamber using the injected fuel, and a second fuel injection is performed at the end of a compression stroke to perform this fuel injection. To form an air-fuel mixture in a limited area in the combustion chamber, and ignite the air-fuel mixture formed in the limited area with an ignition plug, and the air-fuel mixture dispersed throughout the combustion chamber as a kind of ignition. 2. Description of the Related Art There is known a direct injection internal combustion engine in which a fuel gas is combusted (see Japanese Patent Application Laid-Open No. 2-169834).

[0003]

However, in this direct injection internal combustion engine, the ratio of the second fuel injection amount to the total fuel injection amount (hereinafter referred to as "second fuel injection amount ratio"). The following problem arises because the temperature is not changed according to the intake air temperature. That is,
If the second fuel injection rate is fixed at a small value,
Since the air-fuel mixture around the ignition plug is relatively thin, when the intake air temperature is low, there arises a problem that good ignition cannot be ensured.

On the other hand, if the second fuel injection amount ratio is fixed at a large value, the difference between the air-fuel ratio of the air-fuel mixture in the richest part and the air-fuel ratio of the air-fuel mixture in the thinnest part becomes large. In other words, in order to increase the degree of stratification,
When the intake air temperature is high, the combustion temperature becomes high and a large amount of N
O _x cause the problem to generate.

[0005]

According to the present invention, in order to solve the above-mentioned problems, a first fuel injection is performed during an engine intake stroke to form an air-fuel mixture dispersed throughout the combustion chamber by the injected fuel. The second fuel injection is performed at the end of the compression stroke to form an air-fuel mixture in a limited area of the combustion chamber with the injected fuel, and the air-fuel mixture formed in this area is ignited by a spark plug and An in-cylinder injection-type internal combustion engine in which an air-fuel mixture is dispersed throughout the combustion chamber using an ignited air-fuel mixture as an ignition type is provided with an intake air temperature detecting means for detecting an intake air temperature. The ratio of the second fuel injection amount in the fuel injection amount is increased.

[0006]

The lower the intake air temperature, the greater the proportion of the second fuel injection amount. For this reason, when the intake air temperature is low, the proportion of the second fuel injection amount increases, and the mixture around the spark plug becomes rich, so that good ignition is ensured. On the other hand, when the intake air temperature is high, the proportion of the second fuel injection amount decreases, so that the degree of stratification decreases, and as a result, the generation of NO _x is reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG.
a. Each cylinder 1a has a corresponding intake branch pipe 2
Is connected to a common surge tank 3, and the surge tank 3 is connected to an air cleaner 6 via an intake duct 4 and an air flow meter 5. A throttle valve 8 connected to an accelerator pedal 7 is arranged in the intake duct 4. On the other hand, each cylinder 1a is connected to a common exhaust manifold 9, and this exhaust manifold 9 is connected to a three-way catalytic converter 10
Linked to Each cylinder 1a has a fuel injection valve 1
The fuel injection valves 11 are controlled based on the output signal of the electronic control unit 30.

The electronic control unit 30 is composed of a digital computer, and is connected to a random access memory (RAM) 32 and a ROM via a bidirectional bus 31.
(Read only memory) 33, CPU (microprocessor) 34, input port 35 and output port 36. The air flow meter 5 generates an output voltage proportional to the amount of intake air, and this output voltage is input to an input port 35 via an AD converter 37.

A water temperature sensor 12 for generating an output voltage proportional to the engine cooling water temperature is attached to the engine body 1, and the output voltage of the water temperature sensor 12 is input to an input port 35 via an AD converter 38. A load sensor 13 that generates an output voltage proportional to the amount of depression of the accelerator pedal 7 is connected to the accelerator pedal 7, and the output voltage of the load sensor 13 is input to an input port 35 via an AD converter 39. The input port 35 is connected to the rotation speed sensor 14 that generates an output pulse representing the engine rotation speed. An intake air temperature sensor 15 that generates an output voltage proportional to the intake air temperature is attached upstream of the air flow meter 5, and the output voltage of the intake air temperature sensor 15 is input to an input port 35 via an AD converter 41.

On the other hand, the output port 36 is connected to each fuel injection valve 11 via a corresponding drive circuit 40. 2 and 3 show the structure of the combustion chamber of each cylinder 1a. Referring to FIGS. 2 and 3, reference numeral 50 denotes a cylinder block;
Is a piston reciprocating in the cylinder block 50, 52
Represents a cylinder head fixed on the cylinder block 50, and 53 represents a combustion chamber formed between the piston 51 and the cylinder head 52, respectively. Although not shown in the drawing, an intake valve and an exhaust valve are arranged on the inner wall surface of the cylinder head 52, and the intake port is provided so that air flowing into the combustion chamber 53 generates a swirling flow around the cylinder axis. Is configured. As shown in FIG. 2, an ignition plug 54 is arranged at the center of the inner wall surface of the cylinder head 52, and the fuel injection valve 11 is arranged around the inner wall surface of the cylinder head 52.
As shown in FIGS. 2 and 3, a shallow plate portion 55 having a substantially circular contour extending from below the fuel injection valve 11 to below the spark plug 54 is formed on the top surface of the piston 51. A deep dish portion 56 having a substantially hemispherical shape is formed at the center of 55. Further, a shallow plate portion 55 below the ignition plug 54
A concave portion 57 having a substantially spherical shape is provided at a connection portion between the
Is formed.

In the embodiment according to the present invention, first, the target average air-fuel ratio (A / A /
F) ₀ is determined, and the intake air amount QA detected by the air flow meter 5 and the target average air-fuel ratio (A / F) ₀ are necessary for setting the entire air-fuel mixture to the target average air-fuel ratio (A / F) _0. The total fuel injection amount Qtotal is calculated. Next, from the total fuel injection amount Qtotal, it is determined whether to inject at the end of the compression stroke, to inject at the beginning of the intake stroke, or to inject both at the beginning of the intake stroke and at the end of the compression stroke.

FIG. 4 shows a combustion method at the time of low load operation of the engine, FIG. 5 shows a combustion method at the time of medium load operation of the engine, and FIG. 6 shows the injection of the intake stroke injection performed at the beginning of the intake stroke. The relationship between the amount Q ₁ , the injection amount Q ₂ of the compression stroke injection performed at the end of the compression stroke, and the total fuel injection amount Qtotal at the reference intake air temperature TA ₀ is shown. 6 is stored in the ROM 33 in advance.

In FIG. 6, the total fuel injection amount Qtotal is Qa
4A and 4B, at the end of the compression stroke, the fuel injection F is directed toward the peripheral wall surface of the deep dish portion 56. In the embodiment shown in FIG. 4, the gasoline injection is performed. Done. Fuel injection quantity Q ₂ at this time is equal to the total fuel injection quantity Qtotal As can be seen from FIG. 6, thus the fuel injection amount Q ₂ is increased as the total fuel injection quantity Qtotal increases. The fuel injected toward the peripheral wall surface of the deep dish portion 56 is diffused while being vaporized by the swirling flow S,
Thereby, an air-fuel mixture G is formed in the concave portion 57 and the deep dish portion 56 as shown in FIG. At this time, the inside of the combustion chamber 53 other than the concave portion 57 and the deep dish portion 56 is filled with air. Next, the mixture G is ignited by the spark plug 54.

On the other hand, in FIG. 6, the total fuel injection amount Qtotal
When the engine is in the middle-load operation where Qa is between Qa and Qb, the fuel injection is performed in two stages: the initial stage of the intake stroke and the final stage of the compression stroke. That is, first, as shown in FIGS. 5A and 5B, the injection amount Q ₁ is directed toward the shallow plate portion 55 at the beginning of the intake stroke.
Fuel injection F is performed, and the injected fuel
A lean air-fuel mixture is formed throughout the interior of the fuel cell 3. Next, FIG.
Peripheral fuel injection F of the injection quantity Q ₂ toward the wall surface is performed, the recess 57 and the deep dish by the injected fuel as shown in FIG. 5 (D) of the deep dish portion 56 in the end of the compression stroke as shown in An ignitable air-fuel mixture G serving as a fire is formed in the portion 56. The mixture G is ignited by the spark plug 54, and the ignition flame causes the lean mixture in the entire combustion chamber 53 to burn.

In FIG. 6, the total fuel injection amount Qtotal is Qb
When the engine is operated under a higher load, the fuel is injected toward the shallow plate portion 55 only once at the beginning of the intake stroke as shown in FIGS. 5 (A) and 5 (B).
A homogeneous air-fuel mixture is formed therein. Total fuel injection quantity Q as the time the beginning of the intake stroke of the fuel injection amount Q ₁ is seen from Figure 6
equal to total, thus the fuel injection amount Q ₁ is increased as the total fuel injection quantity Qtotal increases.

By the way, when the total fuel injection amount Qtotal is between Qa and Qb (see FIG. 6), when the fuel injection is performed in two stages of the initial stage of the intake stroke and the final stage of the compression stroke during the engine middle load operation, The ratio of the fuel injection amount in the compression stroke in the total fuel injection amount Qtotal (hereinafter referred to as “compression stroke injection amount ratio” (= second fuel injection amount ratio)) must be changed according to the intake air temperature. Such a problem arises.

That is, if the compression stroke injection amount ratio is fixed to a small value, the mixture G around the ignition plug 54 becomes relatively thin, so that good ignition is ensured when the intake air temperature is low. The problem arises that it is not possible. on the other hand,
If the compression stroke injection amount ratio is fixed to a large value, the difference between the air-fuel ratio of the air-fuel mixture in the richest part and the air-fuel ratio of the air-fuel mixture in the thinnest part in the combustion chamber 53 becomes large. for stratification degree is high, when the intake air temperature is high results in a problem of generating a large amount of the NO _x becomes higher combustion temperature.

Therefore, in this embodiment, as shown in FIG.
The compression stroke injection amount ratio f (Q ₂ ) is increased as the intake air temperature TA decreases. Thus, when the intake air temperature TA is low, the compression stroke injection amount ratio f (Q
₂ ) increases, the mixture G around the ignition plug 54 becomes rich, and as a result, good ignition can be ensured. On the other hand, when the intake air temperature TA is high, since the compression stroke injection amount ratio f (Q ₂ ) decreases, the air-fuel ratio of the air-fuel mixture in the richest portion and the air-fuel ratio in the thinnest portion in the combustion chamber 53 are reduced. the difference between the ratio decreases, i.e., stratification degree is lowered, it is possible capable of reducing the occurrence of this result NO _x.

FIG. 8 shows a main routine for controlling the fuel injection, and this routine is repeatedly executed. Referring to FIG. 8, first, at step 100, the intake air amount Q based on the output signal of the air flow meter 5 is determined.
A is detected. Next, at step 101, a target average air-fuel ratio (A / F) ₀ is calculated. The target average air-fuel ratio (A / F) ₀ is determined in advance in the form of a RO shown in FIG. 9 as a function of the depression amount L of the accelerator pedal 7 and the engine speed N.
It is stored in M33. Then the target average air fuel ratio (A / F) ₀ is corrected by multiplying the correction coefficient K in step 102 the target average air-fuel ratio (A / F) _0.
The correction coefficient K is provided for increasing the warm-up amount or the acceleration amount. For example, as shown in FIG. 10, the correction coefficient K is decreased as the engine cooling water temperature T decreases. When it is determined that the vehicle is accelerating from the rate of change in the amount of depression of the accelerator pedal 13, the correction coefficient K is decreased. Next, at step 103, the intake air amount Q
Total fuel injection quantity Qtotal necessary for A and the target average air fuel ratio (A / F) ₀ from the entire mixture the average air-fuel ratio the target average air fuel ratio (A / F) ₀ is calculated, followed by step 10
Proceed to 4.

In step 104, the total fuel injection amount Qtotal
Is greater than Qa. Qtotal ≤ Q
a, i.e., at the time of engine low load operation is willing total fuel injection quantity Qtotal in step 105 is the compression stroke injection amount Q _2.
Then the fuel injection amount Q ₂ is injected into the end of the compression stroke at step 106. On the other hand, in step 104, Qto
If it is determined that tal> Qa, the routine proceeds to step 107, where it is determined whether the total injection amount Qtotal is larger than Qb. When Qtotal ≦ Qb, that is, at the time of engine middle load operation, the routine proceeds to step 108, where the intake air temperature TA is detected based on the output signal of the intake air temperature sensor 15. Then step 109
In the compression stroke injection amount Q ₂ at the reference intake air temperature TA ₀ is calculated based on the total fuel injection quantity Qtotal from the relationship shown in FIG. Then the compression stroke injection amount Q ₂ based on the following equation at step 110 is corrected by the intake air temperature TA.

Q ₂ · {1−α · (TA−TA ₀ )} where α is a coefficient and TA ₀ is a reference intake air temperature. The coefficient α may be a fixed value, or the engine speed N _e
And a function of the total fuel injection amount Qtotal. The coefficient α is a value such that α · (TA−TA ₀ ) is a positive or negative number of 1 or less in absolute value. The compression stroke injection amount ratio f (Q ₂ ) of the compression stroke injection amount Q ₂ corrected by this equation is as shown in FIG.

Next, at step 111, the total fuel injection amount Q
intake stroke injection amount Q ₁ is calculated by subtracting the compression stroke injection amount Q ₂ from total. Then step 11
In 2, fuel is injected twice. That is, the fuel injection quantity Q ₁ is being injected into the intake stroke initial injection end of the compression stroke amount Q ₂
Of fuel is injected. On the other hand, in step 107, Q
If it is determined that total> Qb, that is, during high engine load operation, the routine proceeds to step 113, where the total fuel injection amount Qtotal
There is the intake stroke injection amount Q _1. Then step 114
In the fuel injection quantity Q ₁ is being injected into the intake stroke initial.

[0023]

With a good ignition even when the intake air temperature is low according to the present invention can be secured, even when the intake air temperature is high can be capable of reducing the occurrence of even NO _x.

[Brief description of the drawings]

FIG. 1 is an overall view of an internal combustion engine.

FIG. 2 is a side sectional view of a combustion chamber.

FIG. 3 is a plan view of a piston top surface.

FIG. 4 is a diagram for explaining a combustion method during low-load operation.

FIG. 5 is a diagram for explaining a combustion method during a medium load operation.

FIG. 6 is a diagram showing a fuel injection amount.

FIG. 7 is a diagram showing a ratio f (Q ₂ ) occupied by a compression stroke injection amount Q ₂ .

FIG. 8 is a flowchart for executing a main routine.

FIG. 9 is a diagram showing a fuel injection amount.

FIG. 10 is a diagram showing a correction coefficient K;

[Explanation of symbols]

 11: fuel injection valve 15: intake air temperature sensor

Claims (1)

(57) [Claims] 1. A first fuel injection is performed during an engine intake stroke to form an air-fuel mixture dispersed throughout the combustion chamber using the injected fuel, and a second fuel injection is performed at the end of a compression stroke to perform this fuel injection. To form an air-fuel mixture in a limited area in the combustion chamber, and ignite the air-fuel mixture formed in the area with an ignition plug, and burn the air-fuel mixture dispersed throughout the combustion chamber using the ignited air-fuel mixture as a fire. The in-cylinder injection internal combustion engine is provided with an intake air temperature detecting means for detecting the intake air temperature, and the lower the intake air temperature, the more the second fuel injection amount out of the total fuel injection amount A direct injection internal combustion engine with an increased ratio.