JPH0579337A - Inter-cylinder injection type internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a proper combustion in spite of lean air-mixture by increasing the intensity of a swirl stream when an engine load stays between the first set load and the second set load in comparison with the intensity of a swirl stream when the engine load is lower than the first set load or higher than the second set load. CONSTITUTION:A shallow dish part 12 which has a circular contour shape extending from the bottom of a fuel injection valve 11 to the bottom of an ignition plug 10 is formed on the top face of a piston 3, and a deep dish part 13 in approximately semi-sphere shape is formed in the central part of the shallow dish part 12. A spherical concave part 14 is formed at the connection part between the shallow dish part 12 and the deep dish part 13 below the ignition plug 10. A fuel injection quantity is small and air-mixture occupying the whole inside of a combustion chamber 5 becomes lean at the time of middle load operation of the engine. Since an intake air control valve is fully closed and strong swirl is generated inside the combustion chamber 5, the air-mixture inside the combustion chamber 5 formed by a first fuel injection becomes considerably lean, but flame is rapidly propagated by strong swirl, and thereby proper combustion is obtained.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A fuel injection valve is arranged in a combustion chamber and a groove is formed on the top surface of a piston so that the engine load is lower than a preset load when the engine is under low load. When the engine load is higher than the set load, the fuel is injected into the region other than the groove to inject the fuel into the region other than the groove to inject the fuel into the region inside the groove to ignite the mixture formed in the groove. A cylinder injection type internal combustion engine is known which is designed to form a uniform mixture to be filled (Japanese Patent Laid-Open No. 2-169834).
(See the official gazette).

[0003]

However, since the fuel injection amount decreases as the engine load decreases, forming a uniform mixture that fills the entire combustion chamber when the engine load is higher than the set load as described above. Qi becomes leaner as the engine load becomes lower. As a result, in the operating region where the engine load is higher than the set load, the air-fuel mixture becomes considerably lean in the region where the engine load is low, so the ignition flame does not propagate well, and thus good combustion can be obtained. There is a problem that you can not.

[0004]

According to the present invention, in order to solve the above problems, a fuel injection valve is arranged in a combustion chamber and a groove is formed on the top surface of a piston, so that an engine load is predetermined. During engine low load operation lower than the first set load, fuel is injected into the groove at the end of the compression stroke, and the fuel injected into the groove is ignited by the spark plug, so that the engine load is lower than the first set load. In a cylinder injection internal combustion engine in which fuel is injected during the intake stroke when is too high, the strength of the swirl flow generated in the combustion chamber by the intake air flow flowing into the combustion chamber is controlled according to the engine load. A swirling flow control device is provided, and the engine load is first
Of the swirling flow between the second set load higher than the first set load and the second set load higher than the first set load when the engine load is lower than the first set load and when the engine load is the second set load. It is designed to be stronger than the strength of the swirling flow when it is higher than the set load.

[0005]

When the engine load is between the first set load and the second set load, the swirl flow is maximized and the propagation speed of the combustion flame is increased.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an engine body 1 has four cylinders 1.
2 to 5, the combustion chamber structure of each cylinder 1a is shown. 2 to 5, 2 is a cylinder block, 3 is a reciprocating piston in the cylinder block 2, 4 is a cylinder head fixed on the cylinder block 2, and 5 is between the piston 3 and the cylinder head 4. The formed combustion chamber, 6a is a first intake valve, 6b is a second intake valve, 7a is a first intake port, 7b is a second intake port,
Reference numeral 8 indicates a pair of exhaust valves, and 9 indicates a pair of exhaust ports.
As shown in FIG. 2, the first intake port 7a is a helical intake port, and the second intake port 7b is a straight port that extends almost straight. Further, as shown in FIG. 2, a spark plug 10 is arranged at the center of the inner wall surface of the cylinder head 4, and fuel is injected to the peripheral portion of the inner wall surface of the cylinder head 4 near the first intake valve 6a and the second intake valve 6b. The valve 11 is arranged. As shown in FIGS. 3 and 4, on the top surface of the piston 3, there is formed a shallow dish portion 12 having a substantially circular contour shape extending from below the fuel injection valve 11 to below the spark plug 10. A basin portion 13 having a substantially hemispherical shape is formed in the central portion of 12. Also, the spark plug 1
A concave portion 14 having a substantially spherical shape is formed at a connecting portion between the shallow dish portion 12 and the deep dish portion 13 below 0.

As shown in FIG. 1, the first intake port 7a and the second intake port 7b of each cylinder 1a are respectively provided with a first intake passage 15a and a second intake passage 15a formed in each intake branch pipe 15, respectively.
The surge tank 16 is connected through the intake passage 15b, and the intake control valves 17 are arranged in the respective second intake passages 15b. These intake control valves 17 are connected via a common shaft 18 to an actuator 19 composed of, for example, a step motor. The step motor 19 is controlled based on the output signal of the electronic control unit 30. The surge tank 16 receives the air cleaner 2 through the intake duct 20.
1, the step motor 2 is installed in the intake duct 20.
A throttle valve 23 driven by 2 is arranged.
The throttle valve 23 is closed to some extent only when the engine load is extremely low, and is kept fully open when the engine load is slightly higher. On the other hand, the exhaust port 9 of each cylinder 1a is connected to the exhaust manifold 24.

The electronic control unit 30 comprises a digital computer, and a RAM (random access memory) 32 and a ROM connected to each other via a bidirectional bus 31.
A (read only memory) 33, a CPU (microprocessor) 34, an input port 35 and an output port 36 are provided. The accelerator pedal 25 includes a load sensor 26 that generates an output voltage proportional to the depression amount of the accelerator pedal 25.
Is connected, and the output voltage of the load sensor 26 is the AD converter 3
It is input to the input port 35 via 7. The top dead center sensor 27 generates an output pulse, for example, when the first cylinder 1a reaches the intake top dead center, and this output pulse is input to the input port 35.
Entered in. The crank angle sensor 28 generates an output pulse each time the crankshaft rotates 30 degrees, for example, and this output pulse is input to the input port 35. CPU3
In 4, the current crank angle is calculated from the output pulse of the top dead center sensor 27 and the output pulse of the crank angle sensor 28,
The engine speed is calculated from the output pulse of the crank angle sensor 28. On the other hand, the output port 36 has a corresponding drive rotation 3
8 through each fuel injection valve 11 and each step motor 1
9 and 22 are connected.

In the embodiment according to the present invention, fuel is injected from the fuel injection valve 11 in three directions as shown by F ₁ , F ₂ and F ₃ in FIGS. 2 and 3. Figure 6
Indicates the fuel injection amount from the fuel injection valve 11 and the fuel injection timing. In addition, in FIG. 6, L indicates the depression amount of the accelerator pedal 25. As can be seen from FIG. 6, during the engine low load operation in which the depression amount L of the accelerator pedal 25 is smaller than L _1, fuel is injected by the injection amount Q _{2 at the} end of the compression stroke. On the other hand, at the time of engine medium load operation in which the depression amount L of the accelerator pedal 25 is between L ₁ and L ₂ , fuel is injected by the injection amount Q ₁ during the intake stroke, and fuel is injected by the injection amount Q _{2 at the} end of the compression stroke. To be done. That is, at the time of engine medium load operation, fuel injection is performed in two times, the intake stroke and the end of the compression stroke. Further, during the engine high load operation in which the depression amount L of the accelerator pedal 25 is larger than L _{2, the} fuel is injected by the injection amount Q ₁ during the intake stroke. In addition, in FIG.
S1 and θE1 are fuel injection Q ₁ performed during the intake stroke
The injection start timing and the injection completion timing of
2 and θE2 respectively indicate the injection start timing and the injection completion timing of the fuel injection Q ₂ performed at the end of the compression stroke.

By the way, the injected fuel charge F ₁ from the fuel injection valve 11 as shown in FIG. 2 in the embodiment according to the present invention F
₂ is flying below the first intake valve 6a, the injected fuel F ₃ fuel to fly below the second intake valve 6b is injected,
The injected fuels F ₁ and F ₂ collide with the back surface of the bulkhead portion of the first intake valve 6a during the first injection during the engine medium load operation, that is, during the intake stroke injection, and during the intake stroke injection during the engine high load operation. The injected fuel F ₃ is caused to collide with the back surface of the bulkhead portion of the second intake valve 6b. Next, regarding this,
And it demonstrates with reference to FIG.

FIG. 7 shows the valve lift X of the first intake valve 6a and the second intake valve 6b and the valve lift Y of the exhaust valve 8. As can be seen from FIG. 7, the first intake valve 6a and the second intake valve 6
The valve lift X of b becomes the largest in the central part of the intake stroke. FIG. 8 shows the relationship between the first intake valve 6a and the injected fuel F ₁ . As shown in FIG. 8, the injected fuel F ₁ is injected slightly downward from the horizontal plane. Although not shown in FIG. 8, the injected fuels F ₂ and F ₃ are also injected slightly downward from the horizontal plane like the fuel injection F ₁ . As can be seen from FIG. 8, when the lift amount of the first intake valve 6a is small as shown in FIG. 8A, the injected fuel F ₁ does not collide with the first intake valve 6a, and as shown in FIG. When the lift amount of the first intake valve 6a increases, the injected fuel F ₁ collides with the back surface of the bulkhead of the first intake valve 6a so that the first intake valve 6a and the fuel injection valve 11
The relative position and the fuel injection direction from the fuel injection valve 11 are determined. Z in FIG. 7 shows a crank angle region where the injected fuel F ₁ collides with the rear surface of the first intake valve 6a at the bulge portion. Although not shown in FIG. 8, the injected fuel F ₂ also collides with the back surface of the bulge portion of the first intake valve 6a in the crank angle region Z, and the injected fuel F ₃ also in the crank angle region Z in the second intake valve 6b. It collides with the back of the umbrella.

If the fuel is injected from the fuel injection valve 11 in the crank angle region Z shown in FIG. 7 as described above, FIG.
As shown in (B), the injected fuel F ₁ collides with the back surface of the bulkhead portion of the first intake valve 6a. At this time, if the flow velocity of the injected fuel F ₁ is slow, the injected fuel F ₁ collides with the back surface of the bulge portion of the first intake valve 6a and then burns on the side opposite to the fuel injection valve 11 along the back surface of the bulge portion of the first intake valve 6a. Toward the periphery of chamber 5 but injected fuel F
_When the flow velocity of ₁ is high, the injected fuel F ₁ collides with the back surface of the bulge portion of the intake valve 6a and then is reflected and travels into the first intake port 7a as shown in FIG. 8 (B). Similarly injected injected fuel F ₂ if the flow velocity is fast in the fuel F ₂ is directed into the first intake port 7a is reflected after having collided with the rear bevel portion of the first intake valve 6a, if the flow rate of the injected fuel F ₃ is fast The injected fuel F ₃ is the second
After colliding with the rear surface of the bulge portion of the intake valve 6b, it is reflected and travels into the second intake port 7b. In the embodiment according to the present invention, after each of the injected fuels F ₁ , F ₂ , F ₃ is reflected on the back surface of the corresponding air intake valve 6 a, 6 b, the corresponding intake port 7 a,
The flow velocity of each of the injected fuels F ₁ , F ₂ and F ₃ is set so as to be directed to the inside of 7b. The flow velocity is mainly determined by the fuel injection pressure, and in the embodiment of the present invention, the fuel injection pressure is set to 70 kg / cm ² or more.

FIG. 9 shows the target opening S of the intake control valve 17 and the actuation.
The relationship with the depression amount L of the cell pedal 25 is shown. Figure
As shown in 9, the depression amount L of the accelerator pedal 25 is
L₁Intake control valve 17 during engine low load operation smaller than
Is opened only slightly and the accelerator pedal 25
Depression amount L is L₁And L₂During engine load operation between
The intake control valve 17 is fully closed in the
The stepping amount L of 25 is L ₂Larger engine under heavy load operation
The intake control valve 17 is fully opened. The engine is low
Intake control valve 17 when shifting from load operation to medium load operation
The target opening S of can be set as shown by the solid line.
However, it can also be set as shown by a broken line.

When the intake control valve 17 is fully closed as in the engine medium load operation, intake air is supplied into the combustion chamber 5 only from the first intake port 7a having a helical shape. At this time, the intake air flows into the combustion chamber 5 while swirling from the first intake port 7a, and thus, the combustion air in the combustion chamber 5 is changed to that shown in FIG.
At, a strong swirl flow is generated as shown by the arrow S. On the other hand, at the time of low load operation, the intake control valve 17 is opened slightly so that a small amount of air flows into the combustion chamber 5 from the second intake port 17b. At this time, the swirling flow generated in the combustion chamber 5 is weakened as compared with the case of the medium load operation, but the flow passage cross-sectional area of the intake air is increased, so that the pumping loss is reduced. On the other hand, during engine high load operation, the intake control valve 17 is fully opened, so at this time almost no swirl flow is generated in the combustion chamber 5. The relationship between the target opening degree S of the intake control valve 17 and the depression amount L of the accelerator pedal 25 shown in FIG.
It is stored in 3.

Returning to FIG. 6 again, FIG. 6 shows the crank angle region Z shown in FIG. As shown in FIG. 6, in the embodiment according to the present invention, both the _first fuel injection Q ₁ during the engine medium load operation and the fuel injection Q ₁ during the engine high load operation may be performed within the crank angle range Z. Recognize. Therefore, in the embodiment according to the present invention, all the fuel injected from the fuel injection valve 11 during the intake stroke must flow into the corresponding intake ports 7a, 7b after colliding with the back surface of the corresponding intake valve 6a, 6b. become.

Next, a combustion method will be described with reference to FIGS. 10 to 12 while referring to FIG. It should be noted that FIG. 10 shows a combustion method during engine low load operation.
Shows the combustion method during engine medium load operation, and FIG. 12 shows the combustion method during engine high load operation. As shown in FIG. 6, during the engine low load operation in which the depression amount L of the accelerator pedal 25 is smaller than L ₁ , fuel is injected at the end of the compression stroke. At this time, each injected fuel F ₁ , F
₂ and F ₃ collide with the peripheral wall surface of the basin 13 as shown in FIGS. 10 (A) and 10 (B). Injection amount Q _{2 at} this time
6 increases as the depression amount L of the accelerator pedal 25 increases, as shown in FIG. The fuel that has collided with the peripheral wall surface of the deep dish portion 13 is diffused while being vaporized by the swirling flow S, thereby forming the air-fuel mixture G in the recess 14 and the deep dish portion 13 as shown in FIG. It
At this time, the inside of the combustion chamber 5 other than the concave portion 14 and the deep plate portion 13 is filled with air. Next, the air-fuel mixture G is ignited by the spark plug 10.

On the other hand, in FIG. 6, the first fuel injection Q ₁ is performed in the crank angle region Z during the intake stroke during engine medium load operation in which the depression amount L of the accelerator pedal 25 is between L ₁ and L _2. Then, the second fuel injection Q ₂ is performed at the end of the compression stroke. That is, first, in FIG.
As shown in (A), the fuel is injected toward the back surface of the bulge portion of the corner intake valves 6a and 6b, and the injected fuel is reflected by the back surface of the bulge portion of the intake valves 6a and 6b, so that each intake port 7a,
It flows into 7b. Next, these injected fuels flow into the combustion chamber 5 again together with the intake air, and the injected fuel forms a lean mixture in the combustion chambers 5.

Next, the second fuel injection is performed at the end of the compression stroke. As can be seen from FIG. 6, the injection timing of the compression stroke injection Q ₂ during the engine medium load operation is slightly advanced as compared with the engine low load operation. Therefore, at this time, as shown in FIG. 11B, the fuel is injected toward both the deep pan portion 13 and the shallow pan portion 12, and as shown in FIG. An ignitable air-fuel mixture G is formed in the plate portion 13 as the ignition source. The air-fuel mixture G is ignited by the spark plug 10, and the lean flame ignites the lean air-fuel mixture occupying the entire combustion chamber 5.

By the way, the amount of fuel injection during the engine medium load operation is smaller than that during the engine high load operation, so that the air-fuel mixture occupying the entire combustion chamber 5 becomes considerably lean. However, at this time, the intake control valve 17 is fully closed as shown in FIG. 9, so that a strong swirling flow is generated in the combustion chamber 5. In this way, the first
The air-fuel mixture formed by the fuel injection of the first time and occupying the entire interior of the combustion chamber 5 becomes considerably lean, but since a powerful swirling flow is generated, the flame rapidly propagates in the lean air-fuel mixture, and thus the air-fuel mixture Even if it is lean, good combustion can be obtained. In this case, since it is sufficient to generate a spark for the fuel injected at the end of the compression stroke, as shown in FIG. 6, during the engine medium load operation, the fuel at the end of the compression stroke is irrespective of the depression amount L of the accelerator pedal 25. The injection amount Q ₂ is maintained constant. On the other hand, the fuel injection amount Q _{1 at the} beginning of the intake stroke increases as the depression amount L of the accelerator pedal 25 increases.

In FIG. 6, during the engine high load operation in which the depression amount L of the accelerator pedal 25 is larger than L ₂ , the fuel is injected in the crank angle region Z during the intake stroke. Therefore, at this time, as shown in FIG. 12, each intake valve 6
Fuel injection is performed toward the rear surface of the bulk portions of a and 6b, and the injected fuel is reflected by the rear surface of the bulk portions of the intake valves 6a and 6b and flows into the intake ports 7a and 7b. Next, these injected fuels flow into the combustion chamber 5 again together with the intake air, and the injected fuel forms a uniform air-fuel mixture in the combustion chambers 5. The fuel injection amount Q _{1 at} this time increases as the depression amount L of the accelerator pedal 25 increases as shown in FIG.

As shown in FIGS. 11A and 12, the injected fuel reflected by the intake valves 6a and 6b is transferred to the intake ports 7a and 7b.
When injected into the combustion chamber 5, the injected fuel is mixed with the intake air in the intake ports 7a and 7b, and then the injection fuel and the intake air that are sufficiently mixed are supplied into the combustion chamber 5. That is, since the premixed air is supplied to the combustion chamber 5 via the intake valves 6a and 6b, the injected fuel is uniformly dispersed in the combustion chamber 5. Further, when the flow velocity of the injected fuel is increased so that the injected fuel flows into the intake ports 7a, 7b after being reflected by the intake valves 6a, 6b, the injected fuel has a high velocity on the rear surface of the cap portion of the intake valves 6a, 6b. The fuel is atomized at the time of collision, and the atomized fuel advances into the intake ports 7a and 7b. At this time, since the advancing direction of the fuel and the inflow direction of the intake air flow are opposite to each other, the fuel is subjected to a strong shearing force by the intake air, and thus the fuel is further atomized. Thus, the injected fuel is atomized at the time of collision and then atomized by a strong shearing force, so that the injected fuel is vaporized well. In this way, the injected fuel is vaporized well, and moreover, it is evenly dispersed in the combustion chamber 5, so that the air-fuel mixture is burned well.

In the embodiment of the present invention, the injection start timing θS1 of the intake stroke injection Q _{1 and} the injection start timing θS2 of the compression stroke injection Q ₂ are predetermined in FIG. 6, and these injection start timings θS1 and θS2 are the accelerator pedal. Two
It is stored in advance in the ROM 33 in the form of a function of the depression amount L of 5. Therefore, the injection completion timings θE1 and θE2 are controlled based on the injection amounts Q ₁ and Q ₂ .

FIG. 13 shows a routine for controlling fuel injection, and this routine is repeatedly executed. Referring to FIG. 13, first, at step 40, the fuel injection amount Q is calculated. This fuel injection amount Q is stored in advance in the ROM 33 as a function of the engine speed N and the depression amount L of the accelerator pedal 25, as shown in FIG. Next, at step 41, it is judged if the depression amount L of the accelerator pedal 25 is smaller than L ₁ , that is, if it is during low load operation. When L <L _1, the routine proceeds to step 42, where the injection start timing θS2 of the compression stroke injection is calculated. Next, at step 43, the injection start timing θS2,
Injection completion timing θE from the fuel injection amount Q and the engine speed N
2 is calculated, and then the process proceeds to step 52.

On the other hand, if it is judged at step 41 that L ≧ L ₁ , then the routine proceeds to step 44, at which it is judged whether or not the depression amount L of the accelerator pedal 25 is smaller than L ₂ , that is, at the time of medium load operation. Is determined. During medium load operation, the routine proceeds to step 45, where the intake stroke injection amount Q ₁ and the compression stroke injection amount Q ₂ are calculated. Next, at step 46, the injection start timing θS1 of the intake stroke injection is calculated. Next, at step 47, the injection completion timing θE1 is calculated from the injection start timing θS1, the intake stroke injection amount Q ₁ and the engine speed N. Next, at step 48, the injection start timing θS2 of the compression stroke injection is calculated. Next, at step 49, the injection completion timing θE2 is calculated from the injection start timing θS2, the compression stroke injection amount Q ₂ and the engine speed N, and then the routine proceeds to step 52.

When it is judged in step 44 that L ≧ L _2, that is, when the engine is under high load operation, step 50
Then, the injection start timing θS1 of the intake stroke injection is calculated. Next, at step 51, the injection completion timing θE1 is calculated from the injection start timing θS1, the fuel injection amount Q and the engine speed N, and then the routine proceeds to step 52. Each fuel injection valve 1
From 1, the injection start timing θS calculated in this way
1, θS2 and fuel injection completion timings θE1, θE2.

In step 52, the depression amount L of the accelerator pedal 25 is calculated from the relationship shown in FIG. 9 stored in the ROM 33.
The target opening degree S of the intake control valve 17 is calculated according to Next, at step 53, the step motor 19 is driven so that the opening degree of the intake control valve 17 becomes the target opening degree S.

[0027]

When the engine load is between the first set load and the second set load, a strong swirling flow is generated in the combustion chamber, so that the fuel injected during the intake stroke enters the combustion chamber. Even if a lean air-fuel mixture is formed, the ignition flame rapidly propagates in this lean air-fuel mixture, and thus good combustion can be obtained.

[Brief description of drawings]

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

FIG. 2 is a plan sectional view of a cylinder head.

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

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a cross-sectional view taken along line VV in FIG.

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

FIG. 7 is a diagram showing lift amounts of an intake valve and an exhaust valve.

FIG. 8 is a side sectional view taken along the same section as FIG.

FIG. 9 is a diagram showing an opening of an intake control valve.

FIG. 10 is a diagram for explaining a combustion method during low load operation.

FIG. 11 is a diagram for explaining a combustion method during medium load operation.

FIG. 12 is a diagram for explaining a combustion method during high load operation.

FIG. 13 is a flowchart for executing a main routine.

FIG. 14 is a diagram showing a fuel injection amount.

[Explanation of reference numerals] 6a, 6b ... Intake valves 7a, 7b ... Intake port 11 ... Fuel injection valve 17 ... Intake control valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location F02D 45/00 310 H 8109-3G

Claims (1)

[Claims] 1. A fuel injection valve is arranged in the combustion chamber, a groove is formed on the top surface of the piston, and the engine load is lower than a predetermined first set load during engine low load operation at the end of the compression stroke. A cylinder in which fuel is injected into the groove and the fuel injected into the groove is ignited by a spark plug, and fuel is injected during an intake stroke when the engine load is higher than a first set load An injection type internal combustion engine is equipped with a swirl flow control device for controlling the strength of a swirl flow generated in a combustion chamber by an intake air flow flowing into the combustion chamber according to the engine load, and the swirl flow control device controls the engine load. Is the first
Of the swirling flow when the engine load is lower than the first set load and the engine load is the second set load higher than the first set load. An in-cylinder injection internal combustion engine in which the swirl flow is made stronger than the second set load when the load is higher than the second set load.